rolling aluminum: from the mine through the mill

Rolling Aluminum:From the MineThrough the Mill

ACKNOWLEDGEMENTSThis manual has been prepared with information and assistancefrom The Aluminum Association and member companies representedon the Sheet and Plate Division’s Technology Committee.

SHEET & PLATE DIVISION MEMBER COMPANIES

USE OF INFORMATIONThe use of any information contained herein by any member or non-member of The Aluminum Association isentirely voluntary. The Aluminum Association has used its best efforts in compiling the information containedin this book. While the Association believes that its compilation procedures are reliable, it does not warrant,either expressly or implied, the accuracy or completeness of this information. The Aluminum Associationassumes no responsibility or liability for the use of the information herein.

All Aluminum Association published standards, data, specifications and other technical materials arereviewed and revised, reaffirmed or withdrawn on a periodic basis. Users are advised to contact TheAluminum Association to ascertain whether the information in this publication has been superseded in theinterim between publication and proposed use.

The Aluminum Association, Inc.1525 Wilson Blvd.

Suite 600Arlington, VA 22209

www.aluminum.org

© Copyright 2008. Unauthorized reproduction byphotocopy or any other method is illegal.

First Printing June 1990Third Edition December 2007

Alcoa Inc.Aleris Rolled ProductsALSCO Metals Corp.AMAG Rolling GmbHARCO Aluminum, Inc.Golden AluminmGulf Aluminium Rolling

Mill Co.Impol Aluminum Corp.Jupiter Aluminum Corporation

JW AluminumKaiser Aluminum and

Chemical CorporationKoenig & Vits, Inc.Logan Aluminum, Inc.Nichols AluminumNovelis Inc.Rio Tinto AlcanUnited Aluminum CorporationWise Metals Group

Rolling Aluminum:From the Mine Through the MillHOW TO USE THIS PUBLICATION

This publication enlarges upon the information presented in The Aluminum AssociationDVD “Rolling Aluminum: From the Mine Through the Mill”.The expanded explanations of various aspects of aluminum production and rolling

appear where they are mentioned in the DVD.The user who wants to learn the general features of aluminum production and rolling

will find them summarized in the DVD and the early paragraphs of each section of themanual and in its Self-Test Questions and Answers.For readers who want to understand these subjects more thoroughly, the full text of

the manual provides more detailed explanations.The manual may also be used as a ready-reference, by consulting its subheaded

Table of Contents and / or alphabetical index.Metric values of the US customary units in the manual have been included for the

convenience of the reader and are not intended as precise arithmetic conversions.Where the products (foil / sheet / plate) are defined by their thickness range, theactual metric gauge definition has also been included for reference.Finally, the loose-leaf format permits the easy insertion of product information,

additional notes or future informational updates.

ABOUT THE ALUMINUM ASSOCIATION

The Aluminum Association is an industry-wide trade organization representing US andforeign producers of aluminum, leading manufacturers of semi-fabricated aluminum

products, secondary smelters and suppliers to the aluminum industry.The Association’s aims are to increase public and industrial understanding of alu-

minum and the aluminum industry and — through its technical, statistical, marketingand information activities — to serve industries, consumers, financial analysts, educa-tors, government agencies and the public generally.For the aluminum industry and those industries that use aluminum, The Association

helps develop standards and designation systems, helps prepare codes and specifica-tions involving aluminum products and studies technical problems of the industry.The Association maintains and periodically issues industry-wide statistics and records

which are used as an authoritative source.Association members also join together on a number of commodity and end-market

committees to conduct industry-wide market development programs.

Section-Page

INTRODUCTIONAdvantages of Aluminum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1Flat-Rolled Aluminum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2Aluminum Sheet Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2Aluminum Plate Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2Aluminum Foil Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2Specialty Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2Definitions: Plate, Sheet, Foil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4Rolling Aluminum: General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4Technological Advances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7

PRODUCTION OF ALUMINUM AND ITS ALLOYSBauxite Mining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1Alumina Refining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1Aluminum Reduction: The Hall-Heroult Process . . . . . . . . . . . . . . . . . . . . . .2-2Alloying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5Aluminum Alloy Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5Heat-Treatable Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6Non-Heat-Treatable Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6Recycled Aluminum Scrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-7Addition of Alloying Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-7Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

PREPARATION OF ALUMINUM ALLOYS FOR ROLLINGMetal Cleaning: Fluxing and Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1Fluxing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1Alloy Sample Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2Additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3Continuous Casting of Sheet or Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3DC Ingot Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-6Electromagnetic Casting (EMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-7Scalping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-7Pre-Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-8Purposes of Pre-Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-8Pre-Heating Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-8Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-9

Rolling Aluminum:From the Mine through the Mill

CONTENTS

1

2

3

CONTENTS 6

THE ALUMINUM ROLLING MILLDescription and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1Single-Stand and Tandem Mills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3Mill Rolls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3Roll Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4Hot or Cold Rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6Hot Rolling: Metallurgical Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7Cold Rolling: Metallurgical Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-9

SHEET ROLLING OPERATIONSBreakdown Mill Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1Breakdown Coolant/Lubricant Applications . . . . . . . . . . . . . . . . . . . . . . . .5-2Breakdown Rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3Intermediate Hot Rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3Sheet Hot Rolling: The Tandem Mill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-4Coiling and Edge Trimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-5Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6Purposes of Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6Full Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6Partial Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7Stabilization Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7Annealing Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7Batch Annealing/Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7Sheet Annealing/Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7Cold Rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8Gauge and Profile Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8Texturing and Embossing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-10Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-11

SHEET FINISHINGSolution Heat Treating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1Metallurgical Function of Solution Heat Treating . . . . . . . . . . . . . . . . . . . . .6-1Solution Heat Treatment: “Soaking” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-2Quenching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-2Natural Aging (Precipitation Hardening) . . . . . . . . . . . . . . . . . . . . . . . . . . .6-3Artificial Aging (Precipitation Heat Treatment) . . . . . . . . . . . . . . . . . . . . . .6-3Slitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-4Tension-Leveling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-4Surface Finishes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-4Oiling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5Degreasing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5Coatings and Markings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5Cutting to Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5Stretcher-Leveling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6Packaging and Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-7

4

5

6

PLATE ROLLING AND FINISHINGPlate Rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1Slab Reheating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1Intermediate Edge Trimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1Plate Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1Solution Heat Treating and Quenching . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2Plate Stretching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2Ultrasonic Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2Artificial Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3Plate Edge Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3Inspection, Superficial Defect Removal and Storage . . . . . . . . . . . . . . . . .7-3Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

QUALITY AND PROCESS CONTROLTesting and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1Tensile Strength Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1Microscopic Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1Porosity Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1Coolant / Lubrication Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-2Anodizing and Bright-Dipping Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-2Dimensional Tolerance Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-2Surface Quality Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-2Computerized and Centralized Controls . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-7

TECHNICAL APPENDICESAppendix A: Aluminum Alloy Designation System . . . . . . . . . . . . . . . . . . . .10A-1Appendix B: Aluminum Temper Designation System . . . . . . . . . . . . . . . . .10B-1Appendix C: Typical Aluminum Alloy Properties . . . . . . . . . . . . . . . . . . . . .10C-1Appendix D: Aluminum Sheet & Plate Standards and Tolerances . . . . . .10D-1Appendix E: Self-Test Questions (Technical Appendices) . . . . . . . . . . . . .10E-1Appendix F: Answers to All Self-Test Questions . . . . . . . . . . . . . . . . . . . . . . .10F-1

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-1

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-1

CONTENTS 7

7

8

9

10

1112

Advantages of Aluminum

The properties of aluminum make it one of themost advantageous and versatile materials in

use today. Aluminum is:

� Lightweight—Aluminum and its alloys weighonly about one-third as much as equal volumes ofiron, steel or copper.

� Strong—Given appropriate tempers, somealuminum alloys equal or surpass the strength ofsome steels. Strong aluminum alloys can be asmuch as two or three times stronger than steel forthe same weight.

� Cryo-tolerant—In contrast to steel, titaniumand many other materials that become brittle atvery low (cryogenic) temperatures, aluminumremains ductile and even gains strength as temper-ature is reduced. This property makes aluminumhighly useful in very cold climates and for trans-porting extremely cold materials such as liquefiednatural gas (-260°F [-162°C]).

� Ductile and workable—Aluminum alloyscan be readily formed and fabricated by all stan-dard metalworking methods.

� Joinable—Aluminum alloys can be joined byall appropriate major methods, including welding,mechanical connections, and adhesive bonding.

� Reflective—Aluminum alloys with standardcommercial finishes typically reflect more than 80percent of visible light and more than 90 percentof infrared radiation, making aluminum an effec-tive reflector of, or shield against, light, radiowaves and radiant heat.

� Heat-conducting—Aluminum is an excel-lent heat conductor suitable for cooking ware andfor heat exchangers; it is more efficient, pound forpound, than copper.

� Electrical conductivity—Aluminum is alsoan excellent conductor of electricity, commonlyused in such heavy-duty applications as high-volt-age transmission lines, bus bars and local andbuilding distribution systems.

� Corrosion resistant—Aluminum, exposed toair, forms a transparent natural oxide film whichseals its surface against further reactions andprotects it from corrosion from normal weatherexposure. Specific aluminum alloys, treatmentsand/or coatings may be selected to maximizecorrosion resistance in particular applications.

� Non-toxic—Rolled aluminum alloys are non-toxic, easily cleaned, and non-absorbent. For thesereasons, they are widely used in food preparationand packaging.

� Non-combustible—Rolled aluminum doesnot burn, and it generates no hazardous emissionswhen exposed to heat. It is safer than many othermaterials where fire is a potential hazard.

� Recyclable—Aluminum’s resistance to cor-rosion and to reaction with most common materi-als keeps it in good condition throughout the life-time of most products. Scrap aluminum is widelyrecycled, reducing demands for waste disposaland the environmental impacts of new materialproduction.

INTRODUCTIONAPPLICATIONS

In aircraft and spacecraft...in railcars, autos, trucks, trailers and boats...on skyscrapers and homes...in cans and cooking utensils...strong, lightweight aluminum plate, sheet and foil arevital materials of modern society.

1Rolling Aluminum:From the Mine through the Mill

� INTRODUCTION 1-2

Flat-Rolled Aluminum

Flat-rolled products — sheet, plate and foil —have, for many years, made up by far the

largest volume of aluminum products shippedannually in the United States, outstripping otherforms such as castings, extrusions, wire, rod andbar, forgings and impacts, and powders and paste.

Consumption of aluminum sheet and plate inNorth America has generally increased over thepast 45 years. In 1960, sheet and plate consump-tion in domestic markets added up to 1.42 billionpounds (645 million metric tons), or about 34.6%of total aluminum product shipments.

By 1980, in a rapidly growing market for alu-minum, sheet and plate consumption was 5.56 bil-lion pounds (2,523 million MT) or 46.7%.

In 2005, domestic consumption of sheet andplate was 9.59 billion pounds (4,349 million MT),41.5% of the total; including foil, flat-roll prod-ucts accounted for just under half (47.7%) of allaluminum products shipped that year.

Aluminum Sheet Applications

Aluminum sheet is a remarkably versatilematerial, not only because of the custom-

tailored characteristics that it can be given in therolling mill, but also because of its suitability toa wide range of finishing, fabrication and joiningprocesses.

It can be given a wide variety of surfaces: pat-terned, painted, plated, polished, colored, coated,laminated, anodized, etched or textured. It can bemachined in different ways: sheared, sawed anddrilled. It can be easily formed: bent, corrugated,drawn or stamped. It can be readily joined to itselfor to other materials: riveted, bolted, clinched,brazed, soldered, welded and adhesively bonded.

Its applications are too many to list completely.They include such familiar products as: light bulbbases, beverage and food cans, cooking utensils;home appliances; awnings and Venetian blinds;siding, roofing, flashing, gutters and curtainwallpanels for residential, commercial, industrial andutility buildings; highway signs, license plates;heat exchangers; automobile structures and exteri-ors; truck, trailer and van panels; small boat hullsand aircraft skins.

Aluminum Plate Applications

Aluminum plate can be formed directly intostrong shapes with uniform thickness. It can

also serve as a “blank” from which complex large-area parts can be machined, such as the ribbedwing plates of advanced aircraft. It can be weldedinto large, strong, durable structures.

Among many other applications, aluminumplate is used to make railroad gondola and tankcars, battle armor for military tanks and vehicles,superstructures of large merchant and militaryships and offshore oil rigs, tanks for storing andtransporting super-cold liquefied natural gas, air-craft structural parts, and spacecraft components.

Aluminum Foil Applications

Aluminum foil is familiar to most people in thepopular form of soft, very thin (0.00065 inch

[0.0165 mm] thick) household kitchen foil: it’seasy to fold, impenetrable by water and vapor, fireresistant, both heat-conductive and heat-reflective,and inhospitable to molds.

But aluminum foil is also made of harder,stronger alloys whose strength may approach thatof steel.

The variety of properties available in aluminumfoils make them useful in applications rangingfrom the protective packaging of foods, pharma-ceuticals and many other consumer products, tolaminated vapor-barriers and insulation-backingin buildings, to artificial Christmas trees, soundtransducer/receiver diaphragms, rigid containersand adhesive-bonded structural honeycomb.

Specialty ProductsSpecial types of sheet and plate may be pro-

duced for particular applications. Some examplesinclude:

Anodizing sheetArmor plateBrazing sheetDecorative panel

sheetIndustrial roofing

sheetLithography sheetPainted sheetPatterned sheet

Porcelain enamelingsheet

Reflector sheetRural roofing sheetTapered sheet and

plateTooling plateTrailer roof sheetTread plateVinyl-coated sheet


Just a few of the hundreds of applications ofrolled aluminum.

� Plate is aluminum rolled one-quarter inch(6.3 mm) thick or more.Aluminum plate is a product that is rectangular incross-section and form, and 0.250 inch (6.3 mm)or more thick. It may have sheared or sawededges. It is usually produced in flat form (but canbe coiled) or in a variety of special shapes orfabrications. Some aluminum plate producers canperform additional processing or apply specialsurface treatments so that the plate product issuitable for the desired application. (Note: Whenproducts are ordered to metric specifications usingmetric dimensions, plate is defined as being > 6mm thick; however, the common US customaryreference thickness for 0.250" is 6.3 mm.)

� Under one-quarter inch (6.3 mm) downto eight-thousandths of an inch (0.20 mm)thick, it’s called “sheet.”Aluminum sheet is a product that is rectangular incross-section and form, and of > 0.0079" (0.20 mm)thickness through 0.249" (6.3 mm) thickness. Itmay have sheared, slit or sawed edges. It may be

produced in coiled or flat form, or in avariety of special shapes or fabrications. Somealuminum sheet producers can perform additionalprocessing or apply special surface treatments sothat the sheet product is suitable for the desiredapplication. (Notes: When products are orderedto metric specifications using metric dimensions,sheet is defined as being > 0.20 mm to ≤ 6 mmthick. Sheet was previously defined as ≥ 0.006"(0.15 mm) through 0.249" (6.3 mm).)

� Thinner than that, it’s “foil.”Plain aluminum foil is a rolled product that isrectangular in cross section and ≤ to .0079 inch(0.20 mm) thick. It is available in coiled form or inflat sheets. Some aluminum foil producers can per-form additional processing or apply special surfacetreatments so that the foil product is suitable for thedesired application. (Notes: When products areordered to metric specifications using metricdimensions, foil is defined as being ≤ 0.20 mmthick. Foil was previously defined as < 0.006"(0.15 mm) thick.)


DEFINITIONSAll three are aluminum products that arerolled flat with a rectangular cross-section.They differ mainly in thickness.

The actual passage of aluminum through arolling mill is only one step — although the

central one — in a comprehensive sequence. Eachflat-rolled product owes its final properties notjust to the rolling process itself but to its vitalinteractions with: the preparatory steps of alloy-ing, casting, scalping and pre-heating; intermedi-ate annealing; and such later finishing steps assolution heat treatment or final annealing, stretch-ing, leveling, slitting, edge trimming and aging.

Modern aluminum rolling plants conduct many,or all, of these operations, selecting, adjusting andcoordinating them scientifically to produce flat-rolled products with the precise dimensions, prop-

erties and other characteristics specified by eachcustomer.

Aluminum Rolling:A Capsule History

Aluminum is a modern metal — discovered in1807, first isolated in 1825, produced in tiny

amounts as a precious metal in 1845, and widelycommercialized only after the invention of theHall-Heroult production process in 1886. Sincethen, aluminum has rapidly grown to become thesecond most heavily used metal in the world afteriron/steel.

ROLLING ALUMINUM: GENERAL DESCRIPTIONSheet, plate and foil are usually made by rolling thickaluminum between rolls that reduce the thickness andlengthen it, the way a baker rolls out pie crust. But rollingaluminum is a lot more complicated than rolling dough.

By the time aluminum arrived on the scene,mankind had thousands of years’ experience cast-ing and forging metals and several hundred yearsof learning to roll them into sheets, plates andeven foils. Metal rolling may have been practicedin developed countries as early as the beginningof the 16th century. These familiar metal workingtechniques were all adapted and applied to alu-minum.

The first aluminum stew pan was stamped in1890, and most of the aluminum produced before1900 was used in cooking utensils.

Aluminum hulled boats were built in the 1890s,including the U.S. racing yacht “Defender”, withaluminum plates, in 1895.

By 1903, some 6.5 million pounds (3 millionkg) of aluminum was consumed annually, aboutone-third of it in the form of sheet.

In that same year aluminum foil was first rolled,in France; aluminum foil-rolling in the UnitedStates began in 1913, for wrapping candy andchewing gum

Thin aluminum skins appeared on aircraft as

early as 1917 (on the Junkers J-4 monoplane andthe Dornier DO-1 biplane, forerunner of today’s“stressed-skin” aircraft structures).

A practical method to produce Alclad sheet —strong aluminum alloy clad with a thin layer of adifferent aluminum alloy for enhanced corrosionresistance — was developed, in the United States,in 1926. Since then, many other clad aluminumproducts have been developed for such purposesas corrosion protection, surface appearances, orease of brazing.

Technological Advances

The fundamental principles and designs of metalrolling mills had been established by the end of

the 19th century, but improvements in theirtechnology and metallurgy have continuedthroughout the 20th century.

Aluminum rolling has gained steadily in bothquality and efficiency through advances in its ownspecific technology as well as improvementsapplied to metal rolling in general.


Floor plan, typical aluminum smelting plant

Hot and cold continuous sheet rolling millscame into operation in the United States in 1926.The maximum speed of the first U.S. cold “strip”mill was reported to be only about 200 feet perminute (60 m/min.); modern cold mills operateabout 35 times faster!

The rolling industry switched from steamengines to electric power; it built specialty mills,and bigger multi-purpose mills.

The standard “two-high” and “four-high” millconfigurations that were brought into early use,with mill rolls “stacked” vertically, are still basicto the rolling industry. They were later supple-mented, however, by various “cluster” designswith work rolls supported by two or more back-uprolls each, as explained in Section 4.

Over the decades, safety, efficiency, cost andproduct quality were improved by the introductionof automatic material handling devices, manipula-tors, guides, guards, lifting and tilting tables; auto-matic roll changers, compact load-measuring cellson roll bearings, gauge control feedbacks, loadequalization and overload protection; programmed

coolant/lubricant application; and many othertechnical advances.

In recent years, aluminum rolling mills havebeen introducing computerized process control,quality control and inventory tracking, andadvanced gauge and shape controls, to achieveeven higher product quality and consistency.Computerization, in turn, is pointing the way tosuch further developments as Computer IntegratedManufacturing (CIM), Statistical Process Control(SPC), and Just-In-Time (JIT) production sched-ules. These recent advances are designed toincrease product quality and delivery reliabilityand to reduce production costs.

Aluminum that starts out two feet (0.6 m)thick may travel a mile (1.6 km) throughlarge rolling mills, furnaces, cutters andstretchers, to emerge as thin sheet onlya few hundredths of an inch (a fewtenths of millimeters) thick... And it’s hada long journey before it even reachesthe rolling mill.


Floor plan, typical aluminum rolling plant.

SELF-TEST QUESTIONSSECTION 1: INTRODUCTION

1.1 Name any five important advantages ofrolled aluminum products.

1.2 Aluminum resists atmospheric corrosionbecause:a. It is always painted or coated.b. It has a naturally stable oxide film.c. It is a good heat conductor.d. It is non-combustible.

1.3 Aluminum weighs about as much as anequal volume of iron, steel or copper.a. Three-quarters.b. One-half.c. One-third.d. One-quarter.

1.4 High-strength aluminum alloy can be...a. up to half as strong asb. up to 90% as strong asc. just about as strong asd. stronger than

…an equal weight of steel.

1.5 As temperature is reduced, the strengthof aluminum...a. decreases.b. remains the same.c. increases.

1.6 The largest volume of aluminum productsshipped annually in the United Statesconsists of…a. castings.b. rolled products.c. forgings and impacts.d. wire, rod and bar.

1.7 Name five applications of aluminumsheet.

1.8 Name five applications of aluminum plate.

1.9a In US customary units “plate” means arolled product…a. less than 6 inches thick.b. greater than one-tenth inch thick.c. greater than or equal to one-quarterinch thick.d. exactly 0.250 inch thick.

1.9b In metric units “plate” means a rolledproduct…a. greater than 6 mm thick.b. greater than 2.5 mm thick.c. less than 150 mm thick.d. exactly 6 mm thick.

1.10a In US customary units “sheet" means arolled product...a. from .010 to .200 inch thick.b. from .008 to .249 inch thick.c. from .001 to .249 inch thick.d. from .006 to .490 inch thick.

1.10b In metric units “sheet” means a rolledproduct...a. from 0.25 to 5 mm thick.b. from 0.025 through 6 mm thick.c. from 0.20 through 6 mm thick.d. greater than 0.20 up to 12 mm thick.

1.11 Air conditioner fin stock produced as acoil product, for example, .0045-inch(0.115 mm) thick falls into the categoryof...a. sheet.b. plate.c. foil.

Why?



1.12 The existence of aluminum as a metalwas first discovered...a. in prehistoric times.b. around 700 B.C.c. in 1725 (A.D.).d. in 1807.e. in 1903.

1.13 The Hall-Heroult process wasinvented...a. in 1807.b. in 1825.c. in 1845.d. in 1886.

1.14 Most of the aluminum producedbefore 1900 was used in:a. Military armor.b. Vehicles.c. Cooking utensils.d. Architecture.e. Boat hulls.

1.15 Aircraft skins made of aluminumsheet appeared as early as...a. 1903.b. 1917.c. 1931.d. 1942.

1.16 The basic principles and designs ofmetal rolling mills had beenestablished by...a. the end of the Roman Empire.b. the end of the Renaissance.c. the end of the 19th century.d. the middle of the 20th century.

Aluminum is one of the most abundant ele-ments on earth. It is estimated that the solid

portion of the earth's crust to a depth of ten milesis about 8% aluminum, surpassed only by oxygen(47%) and silicon (28%). Aluminum is a majorconstituent of clay and almost all common rocks.

Aluminum is never found as a pure metal innature, but only in chemical compounds withother elements — and especially with oxygen,with which it combines strongly.

Feldspars, micas and clay contain aluminum ox-ide (A1203), also known as alumina, in concentra-tions ranging roughly between 15 and 40 percentby weight.

Most aluminum is produced from an ore calledbauxite (named after the town of Les Baux insouthern France where it was discovered in 1821),

which may contain 40 to 60 percent impurehydrated aluminum oxide — that is, aluminumoxide to which water molecules have becomeattached. The other components of bauxite typi-cally include various amounts of iron oxide, sili-con oxide, titanium oxide and water. Its texturecan range from crumbly to something like lime-stone, and its color varies from off-white to rusty-red, depending on its iron oxide (rust) content.

The richest and most economical bauxite oresare often found close to the earth’s surface in trop-ical and subtropical areas. Worldwide reserves ofbauxite ore are estimated to be very large: enoughhigh grade ore to last perhaps 300 to 500 years,and enough lower-grade ore for another 500 yearsat recent consumption rates. Clays and other min-erals could, if necessary, provide an almost limit-less source of alumina.

Mining methods may vary, but most bauxite ismined in open pits by conventional digging machin-ery, and then is crushed, washed and dried in prepa-ration for separation of the alumina from the other,undesirable components. Subsequent to the miningoperation, the aluminum industry spends consider-able effort to the restore the land and its flora andfauna back to their original condition.

ALUMINUM REFINING

Most alumina is refined from bauxite by theBayer process, patented in Germany by Karl

Josef Bayer in 1888. This process is carried out infour steps:

1. The crushed, washed and dried bauxite is“digested” with caustic soda (sodium hydroxide)at high temperatures and under steam pressure,dissolving the alumina in a mixture with undis-solved impurities called “red mud.”

PRODUCTIONof Aluminum Alloys: From Mine to Mill

BAUXITE MININGAluminum ore, the mineral bauxite, is minedin many countries around the world, and is crushedand refined to yield alumina — nearly purealuminum oxide.


*Others includes 2.1% Magnesium, 2.6% Potassium,2.8% Sodium, 3.6% Calcium, 5% Iron, and 0.14%Titanium, Manganese, Nickel, Copper, Zinc and Lead.

Main elements found in the earth’s crust.

2. This mixture is fil-tered to remove the redmud, which is discard-ed. The clarified alumi-na solution is trans-ferred to tall tankscalled “precipitators.”

3. In the precipitatortank, the hot solutionis allowed to cool withthe addition of a littlealuminum hydroxide to“seed”—that is, stimu-late — the precipitationof solid crystals of alu-minum hydroxide andsodium hydroxide. Thealuminum hydroxidesettles to the bottomand is removed fromthe tank.

4. The separated aluminum hydroxide is washedto remove residues of caustic soda and then isheated to drive off excess water in long rotatingkilns called “calciners.” Aluminum oxide (alumi-na) emerges as a fine white powder that looks like

granulated sugar but is hard enough to scratchglass. The widely-used abrasives corundum andemery are forms of alumina.

Refined alumina consists of about equal weightsof aluminum and oxygen, which must be separat-ed in order to produce aluminum metal.

� PRODUCTION 2-2

Bauxite mining.

ALUMINUM REDUCTION: THE HALL-HEROULT PROCESSA practical way of breaking down the aluminum oxide — theHall-Heroult process — was invented in 1886. Another mineral,cryolite, is melted, and the aluminum oxide is dissolved in it.

Electric current passed through the bath attracts the oxygento carbon anodes. The carbon and oxygen form carbon dioxide,which bubbles out of the bath.

Molten aluminum is left behind at the bottom of the reducingcell, or “pot.” It is siphoned into a crucible for transport to thecasting foundry.

The process is continuous, and a typical pot may produceabout 1400 pounds of aluminum daily. Hundreds ofcells on the same electrical circuit form a potline.

Aluminum and oxygen form such a strongchemical bond that it takes a very large

amount of energy to separate them by “bruteforce” methods like heating. Although aluminumas a pure metal melts at about 1220°F (660°C);aluminum oxide requires a temperature of about3660°F (2015°C) before it will melt.

Chemical methods of breaking down aluminumoxide were developed in the mid-19th century butwere so expensive that metallic aluminum cost asmuch as silver. The small amounts of aluminumthat were produced were used mainly for jewelryand other luxury items.

Early researchers thought of using electricity to

separate aluminum from its oxide in solution butwere frustrated by seemingly high energy require-ments; the inadequacy of their only sources of elec-tricity — batteries; and the insolubility of aluminain water.

The invention of the rotary electric generator, thedynamo, in 1866 solved part of that problem. Theother part was not solved until 1886 when CharlesMartin Hall in the United States and Paul L.T.Heroult in France discovered the answer almostsimultaneously. Hall and Heroult found that alumi-na would dissolve in a molten mineral called cryo-lite (a sodium aluminum fluoride salt) at about1742°F (950°C). In solution, the aluminum oxideis readily separated into aluminum and oxygen byelectric current.

Other solvents might have worked in theory. Cry-olite, however, has the practical advantages of sta-bility under process conditions and a density lowerthan that of aluminum, allowing the newly-formingmetal to sink to the bottom of the “reduction cell.”

The Hall-Heroult process takes a lot of electricitybut only a low voltage, so it is practical to connectmany reduction cells, or “pots”, in series along onelong electrical circuit, forming a “potline.” Moderncells are operated with currents of around 250,000amperes but at only four or five volts each. Suchcells use about six or seven kilowatts of electricityper pound of aluminum produced.

The heat generated by electrical resistance keeps

the solution molten.Oxygen atoms, separated from aluminum oxide,

carry a negative electrical charge and are attractedto the positive poles in each pot. These poles, oranodes, are made of carbon which immediatelycombines with the oxygen, forming the gases car-bon dioxide and carbon monoxide. These gasesbubble free of the melt, leaving behind the alu-minum which collects at the bottom of the pot.

The process, therefore, steadily consumes thecarbon anodes, which must be renewed either byregular replacement or by continuous feeding of aself baking paste (Soderberg anode). About one-half pound (225 g) of carbon is consumed for everypound (455 g) of aluminum produced. Most alu-minum reduction plants include their own facilitiesto manufacture carbon anodes, each of which mayweigh 600 - 700 pounds (270 - 320 kg) and mustbe replaced after about 14 days of service.

The negative electric pole, or cathode, forms theinner lining of each pot. It is also made of carbon.As a cathode it does not react with the melt, so ithas a long service life.

As alumina is reduced to aluminum and oxygen,fresh alumina is added to the molten bath to contin-ue the process. Aluminum fluoride is also addedwhen necessary to maintain the bath's chemicalcomposition, replacing aluminum fluoride lost byreactions with caustic soda residues and airbornemoisture. Modern smelters capture and recycle flu-orides and other emissions.

When sufficient molten aluminum has collectedat the bottom of a pot, it is siphoned into a cruciblefor transport to alloying and casting facilities. Thealuminum produced by the Hall-Heroult process ismore than 99 percent pure.

� PRODUCTION 2-3

Potline

Charles Martin Hall (left) and Paul L.T. Heroult.They found the key to modern aluminumproduction.

� PRODUCTION 2-4

Main steps in the Bayer alumina-refining process and the Hall-Heroult aluminum-reduction process.

Alloying requires the thorough mixing ofaluminum with other elements in liquid —

molten — form. This may be done in differentways, depending on the sources of aluminumused.

Newly-produced aluminum may be transferred,still liquid, from the Hall-Heroult reduction cellsinto a “holder” or reservoir furnace where solidalloying elements are added, to dissolve and mixinto the melt.

Solid scrap aluminum, from fabrication opera-tions or recycled products, must be melted in a“remelt” furnace before its alloy composition isadjusted as necessary. Then the recycled, re-alloyed scrap is transferred to a holder.

Often, new aluminum is alloyed with scrap alu-minum of known composition. The solid scrap isadded to the molten new aluminum, and then fur-ther alloying elements are added to the mixture asneeded to adjust its final composition.

Most melting furnaces are large (capacity asmuch as 200,000 pounds (90,000 kg) or more)and are oil- or gas-fired. They can accept moltenmetal and alloying ingredients in addition to scrapat a temperature around 1400°F (760°C). Forcertain melting needs, the furnace is smaller, has alower melting rate and may be electrically heatedto minimize oxidation of light gauge (thin) scrapor to control emissions. The molten metal is thentransferred to a holder.

After alloying, the molten metal is cleaned andfluxed to remove impurities and hydrogen gasbefore being transferred to the casting pit.

Aluminum Alloy Series

Aluminum alloys are registered according totheir composition. For most of the world, alu-

minum alloy formulations are registered with theAluminum Association under a numerical classifi-cation system.

Each alloy is assigned a four-digit number, inwhich the first digit identifies a general class,or “series”, characterized by its main alloyingelements:

� 1xxx Series alloys include aluminum of99 percent or higher purity. They have excellentcorrosion resistance and thermal and electricalconductivity.

� 2xxx Series alloys have copper as their princi-pal alloying element, often with smaller amountsof manganese and magnesium, and can bestrengthened substantially by heat treatment.

� 3xxx Series alloys have manganese as theirmajor alloying element, sometimes with smalleramounts of magnesium, and are generally non-heat-treatable.

� 4xxx Series alloys, alloyed mainly by silicon,are usually non-heat-treatable.

� 5xxx Series alloys contain magnesium astheir main alloying element, often with smalleramounts of manganese and/or chromium. Thesealloys are generally non-heat-treatable.

� 6xxx Series alloys contain silicon and magne-sium in proportions that will form magnesium sili-cide and are heat-treatable.

� 7xxx Series alloys are alloyed mainly by zinc,often with smaller amounts of magnesium andsometimes copper, resulting in heat-treatablealloys of very high strength.

� The 8xxx Series of alloy numbers is reservedfor alloys of various other compositions.

The aluminum alloy designation system is ex-plained in greater detail in Section 10, AppendixA. Section 10, Appendix C contains tables of typi-cal mechanical properties, physical properties, andcomparative characteristics and applications.

� PRODUCTION 2-5

ALLOYINGIn the melt house, the aluminum is poured into a remeltfurnace for alloying and fluxing.

Adding small amounts of other elements to pure aluminumproduces strong alloys, which can be further conditioned byheating, cooling and deformation treatments called “tempering.”

Some aluminum alloys can be significantlyhardened and strengthened by controlled heat-

ing and quenching sequences known as “heattreatment” followed by natural or artificial aging(“precipitation hardening”). Such alloys are called“heat-treatable.”

Most heat-treatable aluminum alloys containmagnesium, plus one or more other alloying ele-ments such as copper, silicon and zinc. In thepresence of those elements, even small amountsof magnesium promote precipitation hardening.

These alloys respond to heat treatment becausetheir key alloying elements show increasing solid

solubility in aluminum with increasing temperature.The increase of strength induced by heat treat-

ment can be dramatic. For example, in the fullyannealed O-temper, aluminum alloy 2024 has anultimate yield strength of about 27,000 pounds persquare inch (185 MPa). Heat treatment and coldworking followed by natural aging (T3 temper)increases its strength 2 1/2 times, to 70,000pounds per square inch (480 MPa). As strength isincreased by heat-treating, formability is affectedin the other direction: for example, alloy in the T3temper is less formable than “fully soft” alloy inthe O-temper.

� PRODUCTION 2-6

HEAT-TREATABLE ALLOYSSome alloys, usually in the 2xxx, 6xxx, and 7xxx series, are“solution heat treatable”. They can be strengthened by heat-ing and then quenching, or rapid cooling. They may be fur-ther strengthened by “cold working” controlled deformationat room temperature.

NON-HEAT-TREATABLE ALLOYS“Non-heat-treatable” alloys can be tempered only bycold working and annealing operations.

Alloys which will not gain strength and hard-ness from heat treatment are called “non-heat-

treatable.”The initial strength of these alloys, usually in

the 1xxx, 3xxx, 4xxx, and 5xxx series, is providedby the hardening effect of their alloying elements.Additional strengthening can be created by coldworking — deformation which induces strain-hardening, denoted by the “H” tempers. Strain-hardened alloys containing appreciable amountsof magnesium are usually given a final elevatedtemperature treatment to stabilize their properties.

Cold-working can increase strength significantly

in non-heat-treatable alloys. For example, the ulti-mate tensile strength of alloy 3003 is increasedfrom about 16,000 pounds per square inch (110MPa) in the O-temper to 29,000 pounds persquare inch (200 MPa) in the H18 strain hardenedtemper. The ultimate tensile strength of alloy 3004is increased from about 26,000 psi (180 MPa) inits O-temper to about 41,000 psi (280 MPa)in theH38 temper (strain-hardened and stabilizationheated).

Both heat-treatable and non-heat-treatable alloysmay be deliberately softened and made moreformable by annealing.

Aluminum for rolling must be alloyed to exacting specifications.It must be suitable for the planned rolling, for tempering, and forits intended end use.

Equally important is freedom from impurities that might weakenthe alloy, cause mechanical defects, or damage mill rolls.

Recycled beverage cans are not only a largesource of aluminum scrap but also a particular-

ly convenient one because of the known uniformi-ty of their alloy composition. They can be recy-cled right back into new sheet ingot for canstock,as well as other products. Some specialized plantsproduce aluminum sheet ingot only from used alu-minum beverage cans, providing very efficient,energy-saving “closed-loop” recycling.

Aluminum scrap generated within the rollingplant itself is also returned to the melting hearths;this in-house scrap is also very convenientbecause its alloy composition is exactly known.Similarly, scrap returned from fabricators oftenconsists of uniform loads of identified alloys.

Other scrap from various recycled products isalso used for alloying, taking into account its alloycomposition, determined by testing.

� PRODUCTION 2-7

RECYCLED ALUMINUM SCRAPIn the remelt furnace compatible aluminum scrap is added to thepure aluminum, from “charge buckets” moved by overhead cranes.

Recycled scrap makes up more than half of the aluminumalloy processed in the United States; and recycling uses95 percent less energy than making new aluminum.

ADDITION OF ALLOYING ELEMENTSNext, selected elements — such as magnesium, silicon,manganese, zinc or copper — are mixed in to achieve thecorrect alloy composition.

Magnesium, silicon and zinc are usually addedas pure ingredients. Chromium, manganese

and iron are usually added as briquettes contain-ing up to 85% pure metal, balance being alu-minum foil and binders, to facilitate mixing with

the melt. Copper is added in either pure (shot /chopped wire / etc.) or alloyed forms. Titaniumand zirconium are typically added as either 5-10%alloy or as compacted, 95% pure “hockey pucks”.

NOTES

� PRODUCTION 2-8

SELF-TEST QUESTIONSSECTION 2: PRODUCTION

2.1 Aluminum makes up about_____of theearth’s crust.a.8%.b.15%c. 28%d.47%

2.2 Aluminum is_____found as a pure metalin nature.a.alwaysb.sometimesc. never

2.3 Economically mined bauxite containswhat percentage of aluminum oxide?a. 40-60%b. 25-40%c. 15-25%

2.4 Most bauxite is mined...a. in deep tunnels.b. in open pits.c. in rock quarries.d. in shallow river bottoms.

2.5 “Alumina” is another name for...a. aluminum.b. bauxite.c. aluminum oxide.d. aluminum alloy.

2.6 Most alumina is refined by…a. the Karl process.b. the Hall processc. the Heroult process.d. the Hall-Heroult process.e. the Bayer process.

2.7 Refined alumina contains what propor-tion of aluminum by weight?a. about two-thirdsb. about one-halfc. about one-quarterd. None.

2.8 Pure aluminum melts at about…a. 660°Fb. 660°Cc.1220°Fd.1220°C

2.9 Aluminum oxide melts at about…a. 212°F (100°C).b. 660°F (350°C).c. l000°F (540°C).d. 3660°F (2015°C).

2.10 The main factor which induces therelease of metallic aluminum fromaluminum oxide is…a. heat.b. electricity.c. water.d. None of the above.

2.11 The modern Hall-Heroult reductionprocess utilizes...a. heat.b. dissolving medium.c. electric current.d. a, ce. b, cf. a, b, and c.

2.12 In the Hall-Heroult reduction process,what substance combines with theoxygen in Al2O3 to leave moltenaluminum?a. Feldsparb. Cathodec. Carbond. Hydrogen

2.13 Cryolite is…a. a popular aluminum alloy.b. a sodium aluminum fluoride salt.c. the material of aluminum reductionanodes.d. None of the above.

2.14 A typical modern Hall-Heroult cell usesabout how many kilowatts of electricityto produce one pound (455 g) of alu-minum?a. One or twob. Six or sevenc. Ten or twentyd. Trick question: no electricity.

� PRODUCTION 2-9

2.15 The cathodic lining of an aluminumreduction pot has a long service lifebecause…a. it is made of brick.b. it is not in direct contact with themelt.c. it does not react with the melt.d. it plays no role in the reductionprocess.

2.16 Molten aluminum is removed from areduction “pot” by…a. siphoning.b. pouring.c. ladling.d. pumping.

2.17 Aluminum produced by the Hall-Heroultprocess is…a. a high-strength alloy.b. about 75% pure aluminum.c. exactly 89% pure aluminum.d. more than 99% pure aluminum.

2.18 “The most important reason for havingremelt furnaces in a rolling facility is torecycle generated process scrap.”This statement is:a. True.b. False.

2.19 What is the approximate temperature ina melting furnace?a.1000°F (540°C).b.1400°F (760°C).c.1800°F (980°C).

2.20 Wrought aluminum alloy series numbersalways have how many digits?a. Three.b. Four.c. Five.d. As many as necessary.

2.21 The different aluminum alloy series arecharacterized by…a. alloy strength.b. aluminum content.c. alloy composition.d. (None of the above).

2.22 “Solution heat-treatable” alloys arethose which…a.can stand high temperatures without

melting.b.can be brightened by heating.c.can be dissolved at high tempera-

tures.d.can be strengthened by heating and

quenching.

2.23 Solution heat-treatable alloys are usuallyin the…a. 2xxx, 6xxx and 7xxx series.b. 2xxx, 4xxx and 5xxx series.c. 1xxx, 5xxx and 6xxx series.d. 2xxx series only.

2.24 “Non-heat-treatable” alloys are thosewhich…a. can be strengthened only by lowtemperatures.b. can be strengthened only by coldworking.c. can be strengthened by annealing.d. risk cracking when heated.

2.25 Non-heat-treatable alloys are usually inthe…a. 1xxx series.b. 3xxx series.c. 4xxx series.d. 5xxx series.e. All of the above.

2.26 An element which never plays a majorpart in the preciptiation hardening ofheat-treatable aluminum alloys is…a. copper.b. manganese.c. zinc.d. silicon.e. magnesium.

2.27 “Only solution-heat-treatable alloys canbe made more formable by annealing.”This statement is:a. True.b. False.

� PRODUCTION 2-10

2.28 Remelting and alloying scrap aluminumuses about as much energy as smeltingnew aluminum.a. 5%b. 50%c. 100%d. 150%

2.29 The melt is transferred into a holdingfurnace before casting in order to…a. add more scrap.b. adjust alloy composition.c. remove hydrogen.d. a and b.e. b and c.f. a and c.

� PRODUCTION 2-11

Materials charged into an alloying furnaceoften carry with them some unavoidable for-

eign matter, and other non-metallic materials maybe generated by chemical reactions. These sub-stances, which could otherwise cause problems inlater operations and impair product quality, areremoved from the alloy by fluxing and filtration.

Fluxing

“Fluxing” refers primarily to the removalof dissolved hydrogen gas from molten

aluminum alloy by bubbling gases through it.However, the bubbling gases also “sweep” somesolid impurities to the surface where they collectas a frothy dross which is removed.

Hydrogen gas — derived from airborne watervapor, from materials added to the melt, or fromfurnace walls, tools, or anything else that comesin contact with the melt — dissolves readily inmolten aluminum. But it is only about 5% assoluble in solid aluminum. If it were allowed toremain while the molten metal is cast, it wouldemerge during solidification to form tiny bubbles:blisters which mar the surface, or internal poreswhich weaken the product.

Before casting, dissolved hydrogen is removedby bubbling dry, hydrogen-free gases through themolten aluminum. Hydrogen dissolved in the alu-minum diffuses into these other gases and is car-ried out of the melt by the rising bubbles. Inert(nonreactive) gases, chiefly nitrogen, are used for

this purpose to avoid altering the chemical com-position of the alloy. However, small amounts ofchlorine or other reactive gases, typically less than10 percent, may be mixed with the inert gasesin order to react with certain impurities such assodium, calcium or lithium and form compoundswhich can be removed by skimming or filtration.Even though chlorine will have a tendency toreact and preferentially remove magnesium, itdoes offer the most efficient way to removehydrogen through a chemical reaction in contrastto a much slower diffusion process inherent toinert gases. Due to environmental and other con-cerns the use of chlorine is being reduced, and insome regions its use is prohibited.

Typical fluxing techniques include porous plugslocated in the bottom of the furnace, spinningrotors and fluxing wands (ceramic coated metaltubes which incorporate porous plugs at the end ofthe tube). All of these techniques are designed topromote uniform distribution of fine bubbles whichenhance diffusion and chemical reaction processes.

Fluxing may be done in the holding furnace or ina special in-line device between the furnace and thecasting station, separately or in conjunction withfiltration.

In-line degassing can be used as the only meansof hydrogen removal, or it can be a part of a com-prehensive approach which includes furnace fluxingand ceramic foam or other rigid media filtration.

PREPARATIONof Aluminum Alloys for Rolling

METAL CLEANING: FLUXING AND FILTRATIONThen the molten alloy is “fluxed”: nitrogen and chlorinegases are injected, and their bubbles bring impurities tothe surface to be skimmed off by a furnace operator.

ALLOY SAMPLE ANALYSISNow a small sample of the alloy is cast and is analyzedwithin minutes by the lab.

At the holding hearth and during casting, asmall amount of molten alloy is scooped up

with a ladle and poured into a small mold where itcools and hardens in about 15 to 20 seconds into a

solid disk about two inches (50mm) in diameter,called a “button”.

This “button” is identified with the number ofits alloy batch and is sent to the plant laboratory


for analysis. Laboratory analysis may be doneautomatically by a device called a spectrometeror quantometer. The alloy button is placed in achamber in the device. Then a high-voltage sparkinstantly vaporizes a tiny amount of material fromthe surface of the sample and momentarilyexcites, or energizes, the atoms in this alloy vapor.The excited atoms immediately radiate away theexcess energy, returning to their normal state.Each atom radiates excess energy in a pattern, aspectrum, unique to its element. By detecting andmeasuring the emitted energy patterns, the spec-trometer identifies each element present and itsproportion in the alloy sample.

A single “shot” in the high voltage spark spec-trometer is usually completed in about 25 secondsincluding the set-up time. A series of four shots onone sample can be completed in two or three min-utes.

The analyzer may be linked with a computerwhich automatically registers the batch numberand its specified alloy composition, compares itwith the actual sample analysis, and issues a“pass” message when the alloy is within specifica-tions or an “off-analysis” message if it is not.

The results may be returned automatically tothe hearth operator by instantaneous electroniccommunication. Thus, a “rush” request for analy-sis can be answered within a few minutes fromthe time the button sample leaves the hearth area.

If the alloy is found to be “off analysis”, ele-ments may be added to correct its composition. Itwill then be retested for approval. If batch correc-tion is not practical, off analysis alloy is recycled.

If its composition is correct, the alloymoves to a holding furnace for cast-ing; if not, if is corrected and retested.

� PREPARATION 3-2

FILTRATIONBefore casting, aluminum flows through a filter to removeany remaining particles.

Any foreign particles or inclusions that haveescaped the fluxing process or have devel-

oped afterward must be removed from the moltenaluminum alloy before it is cast into rolling ingot.Inclusions, hard or soft, might weaken the finalproduct, show up as streaks or flaws in its surface,or damage work roll surfaces. Filtration is per-formed to remove these potentially harmful parti-cles. Filtration is sometimes performed in combi-nation with the fluxing step, within the sameprocess unit.

Filtration may utilize deep bed filters which areused for multiple casts and typically consist of5 to 15" (125 – 380 mm) layers of media such assintered high density alumina flakes or sphereswith diameters in the range of .25 to .75" (6 – 19mm). Molten aluminum flows through the deepbed which captures and retains nonmetallic andsimilar fine particulates.

Another method utilizes disposable rigid mediafilters which have the morphology of a sponge.

They are typically 16" (400 mm), 20" (500 mm)or 24" (600 mm) square and approximately 2"(50 mm) thick. These filters have pore sizes whichrange from 20 per inch (8 per cm) for capturingcoarse impurities to 70 per inch (30 per cm) forremoval of very fine particulates.

During the past 25 years another group of filterswas developed. They use spinning nozzle technol-ogy. Each of these filters consists of two or threechambers. Each chamber is equipped with aspinning nozzle which delivers a fine dispersionof gas bubbles. It is very similar to the fluxingprocess in the holding furnace except that argonwith up to approximately 3% chlorine is used forflotation (removal) of small particulates andhydrogen. While the material is flowing throughthe chambers, particulates are captured and floatto the surface while at the same time hydrogen isalso removed. Some of the more commonly usedtypes are SNIF, ALPUR and LARS.

The addition of small amounts of titanium(usually in combination with either boron

or carbon) to molten aluminum alloy as a grain-refiner is widely practiced in the rolling industry.Dissolved in the alloy, titanium carbide or titani-um diboride particles provide numerous “nucle-ation points” where solidification begins duringcooling. This enhances uniformity, dispersesstresses throughout the solidifying aluminum,and reduces stress-induced cracking.

From its holding hearth, molten aluminum ispoured through a trough into the ingot-castingmold. The grain refiner is usually added immedi-

ately before casting, and the most commonly usedadditive form is 3/8" (10 mm) diameter rod.Typical grain refiners are 5%Ti /0.3% Boron or5% Ti/0.15% C alloys. For example, a solid rod ofthese grain refiners may be fed into the moltenstream of aluminum at a controlled rate en routeto casting. The addition levels are quite low,typically less than 0.01 weight percent.

Grain refiner is added “at the last minute”because it is most effective if its first five minutesin the aluminum alloy take place during alloysolidification. Longer residence in molten alloywould give the grain refiner time to coalesce intolarger particles, reducing its effectiveness.

� PREPARATION 3-3

ADDITIVESAlong the way, additional elements may be fed in; titaniumis often added to help prevent cracking during solidificationor for grain refinement.

CONTINUOUS CASTING OF SHEET OR PLATEAluminum sheet can be continuously cast for a variety ofapplications. This production method reduces the steps toproduce the sheet. The continuous casting process is usedfor a variety of common aluminum applications. Currentlyabout 20% of the North American sheet and plate productionis produced by this method.

Continuous casting takes molten metal andsolidifies it into a continuous strip. A vari-

ety of methods are used to solidify the metal,including roll casters, belt casters and block cast-ers. The common feature for all of these methodsis that sheet is taken directly from molten metal,solidified, and coiled in one operation. In manycases, the strip is run through a hot mill (whichmay have more than one stand).

Three significant differences between continu-ous casting and the more traditional DC ingotcasting (see next section) are:

� Significantly reduced hot working in continu-ous casting compared to DC ingot casting.

� No homogenization between casting and hotrolling.

� No scalping between casting and hot rolling.

The reduction in hot working is a result of thereduced casting thicknesses seen in continuouscasting. Although actual thicknesses vary bymethod and producer, “as-cast” continuous caststrip is less than 1 inch (25 mm) thick, comparedto the 30+ inch (760+ mm) thick ingot producedvia the DC ingot process.

Because it is much thinner than ingot, continu-ously cast strip cools and solidifies much fasterthan DC ingot; this may produce greater supersat-uration of alloying elements and less segregationof these elements within metal grains. In effect,continuously cast strip is partly pre-homogenized.

In addition, the rapid cooling of continuouslycast strip minimizes the tendency of alloyingelements to concentrate at the surfaces and makesscalping unnecessary, so these products can movedirectly to rolling.

The lack of homogenization and reduced hotworking does result in different metallurgicalstructures even in similar alloys. As a result,

continuously cast alloys may have differentcapabilities than their DC counterparts.

Producers of continuous cast sheet have estab-lished practices to ensure comparable performancein their chosen markets. In some applications,however, efforts to make continuous cast productsas formable as their DC ingot counterparts maysignificantly reduce the advantages of the continu-ous casting process.

There are many markets where continuous castproducts are found, including (but not limited to):

� Building and Construction Applications

� Foil and Fin Stock

� Food and Beverage Containers

� Truck and Trailer applications

� General Distribution

Types of Continuous Casters

Continuous casters are generally described bythe type of product they yield (“strip” or

“slab” casters), or by the type of equipment used(for example — roll, belt or block casters).

Both strip (continuous sheet) and slab (continu-ous plate) casters have been in use since the1950s. They are less versatile in product thick-nesses and characteristics than conventional millswhich flat-roll aluminum ingot, but they requirelower capital investment and have found economi-cal application primarily in conjunction with lim-ited-purpose “minimills.” There, one of their mainadvantages — particularly in slab casting — is theability to produce a continuous band, which canmove immediately through a hot-rolling mill fortransformation into thinner wrought products in anunbroken flow.

Continuous casting processes are undergoingfurther technical development aimed at increasingtheir speed and versatility.

Strip (Continuous Sheet) Casters

Strip casters can produce continuous aluminumsheet thin enough to be coiled immediately

after casting, without additional rolling. Thiscoiled sheet may be re-rolled later into thinnersheet gauges. Alternatively, the cast sheet maybe fed immediately through a hot-rolling mill forthickness reduction before the product is coiled.

Roll Casters

The roll caster is the most common form of stripcasting: molten aluminum flows from nozzles

between a pair of water-cooled rolls. In contactwith the rolls, it solidifies at a cooling ratebetween 100 and 1,000°F per second (55 –555°C/sec.). In addition, the newly solidifiedmetal undergoes some hot deformation as it passesthrough the roll gap.

Typical roll casters can produce continuoussheet in the range of 30 to 80 inches (760 – 2030mm) wide, at linear speeds ranging from about6 to 10 feet per minute (2 – 3 m/min.). Their pro-ductivity rates are generally in the range of 60 to100 pounds of product per hour, per inch of width(10 – 18 kg per hour per cm of width).

Slab Casters

Slab casters produce continuous aluminum prod-ucts in the plate thickness range. These prod-

ucts do not undergo any hot deformation in thecaster. They emerge with as-cast metallurgicalcharacteristics and must be rolled by hot mills toachieve wrought aluminum properties and a sheetgauge that can be coiled.

They produce slab typically between 10 and 80inches (255 – 2030 mm) wide, at linear speedsaround 20 feet per minute (6 m/min.), yieldingproductivities in the range of 1,000 to 1,300pounds per hour, per inch of width (180-225 kgper hour per cm of width).

Slab casters cool and solidify molten aluminumat rates ranging from 1 to 10°F per second (1/2 to5°C); solid slab emerges at a temperature of about1,000°F (540°C), requiring little or no reheatingbefore hot rolling.

The two main commercial types of slab castersare belt and block casters.

Belt Casters

In the belt caster, molten aluminum flowsbetween two almost-horizontal, continuous, thin

metal belts that are in constant motion. Metal sidedams moving with the belts contain the aluminumwhile it solidifies. The belts are usually inclined atan angle of 5 to 9 degrees from horizontal, to min-imize turbulence in the pool of molten aluminum,and belt speed is synchronized with the metalflow rate.

The hot metal transfers its heat through films of

� PREPARATION 3-4

lubricant to the metal belts, which are water-cooledon their outer sides, producing slabs typically inthe range of 1/2 to one inch (12 – 25 mm) thick.

This continuous slab is usually fed directly intolow-speed in-line rolling mills which reduce it tocoils of thinner sheet stock for eventual re-rolling.

Block Casters

The block caster operates on the same generalprinciple as the belt caster: that is, the alu-

minum slab is formed between upper and lowertraveling walls. In place of continuous flat belts,however, the block caster’s traveling walls consistof thick blocks of metal lined up side-by-side sothat the exposed surfaces which contact the alu-minum form flat walls about six feet long. Thesides of the blocks away from the aluminum areattached to a jointed loop belt, like “caterpillar”vehicle treads.

As this loop belt rotates around its drive gears,each block takes its turn lining up with its neigh-bors to contain the flow of molten aluminum froma nozzle. The blocks above and below the alu-minum absorb enough heat to solidify the alloy asthey travel along with it. Then, as they reach thefarther drive gears, each block lifts away from thealuminum and moves around to the far side of itsloop where a cooling system removes the heatbefore the block swings back for another turn inthe traveling mold wall.

As with belt casters, the continuous slab pro-duced by the block caster is usually hot-rolledimmediately into thinner sheet stock.

� PREPARATION 3-5

Belt Caster

Block Caster

“Hot metal” (molten aluminum alloy) isstored before casting in a holding hearth

at a temperature ranging from ~1290 to 1345°F(~700 – 730°C). Its temperature decreases byabout 40 to 50°F (22 – 28°C) upon transfer to thecasting pit or station.

Direct-chill ingot casting takes place in a “DCcasting pit” and each casting of ingot(s) is called a“drop”. Modern casting operations utilize multiple,commonly 4 – 6, rectangular DC molds typically16 to 30" (40 – 75 mm) thick and 45-80" (1.1 –2 m) wide.

The walls of the mold collar are water cooledto speed the solidification of the ingot shell. Thesolid shell cools to a temperature in a range ofabout 570 to 930°F (300 – 500°C) and contractsas it cools, separating from the mold wall beforeit emerges. The cooling rate is sharply reducedwhere wall contact is interrupted by this separa-tion, called the shrinkage gap. This effect maypermit an unwanted enrichment of alloyingelements in a narrow zone near the surface.The enrichment zone is usually removed beforerolling, a procedure called “scalping.”

As the bottom block is lowered and the solidify-ing ingot emerges from the mold, the surface isfurther cooled by water from openings aroundthe inside of the mold. The water is recirculatedthrough cooling towers to maintain a correcttemperature for effective ingot cooling.

Sensors linked to a computer coordinate the rateof water flow, molten metal levels, the rate ofmolten metal addition, and the bottom block speed.Casting speeds may range from one-and-a-half tofour inches per minute (37 to 100 mm/min.),

� PREPARATION 3-6

DC INGOT CASTINGBut most sheet and plate is rolled from thick slabs called“Ingots”, cast by the “direct chill” or DC method.Aluminum is poured into a mold that is only about six inches(150 mm) deep. Progressive cooling while in contact with themold and bottom block provides a solidified shell around thestill-molten core of the ingot.Once this solid shell forms, the bottom block is lowered alongwith the aluminum shell, while more aluminum is poured in,hardening at the walls and extending the shell.The ingot emerges at about a speed of 1 1/2 to 4 inches perminute (40-100 mm/min.) and is chilled by a water spray tocomplete its cooling.This direct-chill method permits mold walls only six inches(150 mm) deep to produce a retangular ingot over30 feet (9 m) long, seven-and-a-half feet (2300 mm) wideand over two-and-a-half feet (760 mm) thick, weighingabout 30 tons(27 metric tons).

Direct-chill ingot casting (schematic)

depending on the aluminum alloy and mold sizeinvolved.

Since it is very important to provide a continu-ous distribution of molten metal, fiberglass socks,screens and distribution bags are placed in theingot head within the confines of the mold. Theseprovide uniform molten metal distribution andtemperature through the entire perimeter of themold thus minimizing surfaces defects such ascold folds or molten metal breakouts.

At two inches per minute (50 mm/min.), it takesabout 2-1/2 hours to cast a 290-inch (7365 mm)long ingot. An aluminum ingot 24 inches thick,55 inches wide and 290 inches long (about 2 x 4.5x 24 feet [610 x 1400 x 7365 mm]) weighs about20 tons (18 metric tons) and contains enoughaluminum, for example, to produce more than1.5 million beverage can bodies.

DC casting has been used to produce ingots asmuch as 37 feet (11.25 m) long or longer.

Electromagnetic Casting

Electromagnetic casting (EMC) is a DC ingotcasting variation in which a strong magnetic

field confines the molten aluminum while its shellinitially solidifies. Continuous cooling and elimi-nation of the liquated zone inherent to the DCprocess eliminates the zone of enrichment thusminimizing the need for scalping. The aluminumdoes not contact mold walls, so there is no“shrinkage gap” effect and surface enrichment ofalloying elements is avoided

Therefore, EMC casting can produce ingotswith smoother, metallurgically more homogenoussurfaces that need little or no scalping and/or edgetrimming on the hot line. A number of sheet prod-ucts, such as 3xxx and 5xxx beverage stockalloys, have been cast and rolled without the needfor scalping

� PREPARATION 3-7

Temperature Distribution in an ingot during direct-chill casting.

SCALPINGTo create high qualify surfaces for rolling, the broadest sidesof the ingot are shaved by a machine with rotating bladescalled a “scalper.”

Sometimes all four of the sides are scalped.

Scalping is performed on an ingot to remove anyirregularities or undesirable chemical composi-

tions, such as excess oxides or concentrated alloy-ing elements, left in its surface by the castingprocess. By providing smooth, metallurgicallyhomogenous surfaces, scalping promotes highquality rolling and avoids the rolling of “slivers”into the surface of plate or sheet.

The scalper itself is a specialized millingmachine with horizontal blades spanning about fivefeet (1.5 m) or more and rotating on a vertical axle.

The scalper generally mills the rolling faces ofthe ingot-that is, its widest surfaces, scalping oneside and then turning the ingot over to scalp theother side. Some operations utilize two sets ofcutters permitting simultaneous scalping of both

rolling surfaces. Edges and ends which aretrimmed during the rolling operation need not bescalped. Recently, more emphasis is being placedon minimizing downstream operations such as

intermediate trimming. Therefore, based on ingotprofile, edges may also be scalped, thus eliminat-ing the need for intermediate trims or sawingoperations.

� PREPARATION 3-8

PREHEATINGThe scalped ingot must be preheated for hot rolling.The temperature and time is controlled to promotespecified ingot properties. There are a variety of methodsof preheating ingots. These include “walking-beam” or“pusher” furnaces, car-bottom furnaces and soaking pits.

Purposes of preheating

Preheating the ingot before hot rolling servesseveral important purposes, including:

1. Raising the alloy’s temperature above therecrystallization temperature to prevent cold-working (strain-hardening) from taking place dur-ing rolling. This avoidance of strain-hardening isthe key characteristic which differentiates hotrolling from cold rolling.

2. Homogenization — that is, putting all solublealloy constituents into a more complete and uni-form solid solution. During direct-chill castingsolidification alloying elements tend to segregateinside alloy grains, in low concentrations at graincenters and increasing concentrations toward grainboundaries. This concentric stratification is alsoknown as “coring.” At elevated pre-heating tem-peratures, these alloying elements redistributethemselves more uniformly within grains by diffu-sion, reducing segregation and coring.

3. Spheroidizing insoluble constituents.Homogenization pre-heating causes undissolvedprecipitates to coalesce into fewer particles and tolose their sharp comers and take on rounder, morecompact shapes which significantly improve thealloy’s formability.

4. Softening the ingot and thereby minimizing themechanical force necessary to reduce its thicknessby rolling.

5. Relieving stresses in the ingot.

Preheating methods

Ingots are preheated in temperature-controlledfurnaces. Several variations of preheating proce-

dure are available to serve different ingot dimen-sions or treatment requirements:

� Ingots may be stacked up, lying flat and sepa-rated by spacers, on cars which convey them intoand out of the furnace (“car-bottom” furnace).

� They may be stood on their long edge andpushed through the furnace on a slide (“pusher”furnace) or carried through it by “walking beams.”

� They may be inserted, standing on end, into afurnace called a soaking pit.

The temperature inside the furnace follows a con-trolled cycle which governs the rate of tempera-ture increase; the stabilized temperature; the timespent at each temperature level; the rate of tem-perature decrease; and the final temperature atwhich the ingot is delivered for rolling.

Temperature cycles vary according to alloys andintended metallurgical results. For example, inone case, ingot temperature may be raised directlyto a rolling temperature of perhaps 850°F (455°C)and held at that level right through to ingot deliv-ery. In a different case, the temperature might beraised above rolling temperature, held there for aspecified time, and then reduced by the use ofcooling fans to the rolling temperature.

Then the hot ingot is laid flat on aconveyor and checked.If its temperature is within the desiredrange, the carefully engineered ingotis sent to the rolling line.

SELF-TEST QUESTIONSSECTION 3: PREPARATION

3.1 “Fluxing” means...a.pouring molten aluminum.b. removing impurities from molten

aluminum.c.mixing in alloying elements.d.cleaning the walls of a reduction cell.

3.2 The main target of fluxing is...a. solid impurities.b. water vapor.c. dissolved hydrogen gas.d. undissolved aluminum particles.

3.3 The gases usually used for fluxing are...a. hydrogen and chlorine.b. nitrogen, argon and chlorine.c. oxygen and carbon dioxide.d. All of the above.

3.4 In a modern aluminum rolling plant, asample of alloy can be sent to the laband analyzed and the results reportedback to the mill operators within…a. a few seconds.b. a few minutes.c. a few hours.d. a few days.

3.5 Aluminum alloy which is found to be“off analysis” is…a. rolled into product more carefully.b. thrown away,c.corrected or recycled.d.stored to await a matching customer

order.

3.6 If inclusions are not removed frommolten aluminum alloy before it is castand rolled, they might...a.weaken the final product.b.cause streaks or flaws in the product

surface.c.damage work roll surfaces.d.None of the above.e.All of the above.

3.7 “Final filtration of molten metal is doneonly when the end user demands mini-mal inclusions.” This statement is:a. True.b. False.

3.8 Name a grain refining element used inaluminum alloys.

3.9 Grain refiner is added to aluminumalloy…a. in the Hall-Heroult reduction cell.b. with the other alloying elements.c. just before ingot casting.d. during solution heat-treating.

3.10 “Continuous casters”…a.produce ingots two feet (610 mm)

thick and 24 feet (7.3 m) long.b.operate 24 hours a day.c.produce unbroken slabs or strips.d.are used to cast large volume parts.

3.11 A roll caster…a.produces high-precision work rolls.b. solidifies molten metal between

chilled rolls.c. applies absolutely no hot deformation.d.None of the above.

3.12 The product emerging from belt castersor block casters is usually…a.set aside to cool slowly before rolling.b.used, as-is, in commercial products.c. chilled quickly for immediate cold

rolling,d.hot-rolled immediately into sheet

stock.

3.13 In casting, the term DC or Direct Chillrefers to the fact that…a.the molten metal comes in contact

with the mold directly.b. there is water circulating inside the

mold.c.water flows over the emerging slab or

billet.

3.14 In DC casting, the mold…a. is the size of a finished ingot cross

section.b.consists of two parts, one stationary

and one moveable.c.must be discarded after one use.d.a and b.e.b and c.f. a and c.

� PREPARATION 3-9

3.15 “Electromagnetic casting is capable ofproducing ingots which, for some prod-ucts, need no scalping and no hot milledge trim.” This statement is:a. True.b. False.

3.16 Scalping is applied…a. to remove the enrichment zone.b. to remove surface irregularities.c. to obtain uniform slab thickness.d. a and be. a and cf. a, b and c.

3.17 Scalping equipment can be describedaccurately as…a. a grinder.b. a lathe.c. a vertical or horizontal millingmachine.

3.18 Pre-heating ingot for hot rolling servesseveral purposes. One is to soften theingot for hot rolling. Another is…a. to oxidize the surface.b. to homogenize the alloy.c. to anneal the metal.

� PREPARATION 3-10

The work rolls, which actually contact and shapethe aluminum, lie at the heart of a massive assem-bly of scientifically designed and precision manu-factured parts that make up a modem rolling mill.

The mill’s main mechanical components alsoinclude:

� The mill stand: the strong structure whichsupports various parts and withstands the enormoustensions imposed by rolling.

� Back-up rolls, whose function is to supportthe work rolls against excessive flexing andvibration.

� Drive motors, which provide the power thatturns work rolls and forces aluminum through theroll gap.

� Gearboxes, which convert the rotation ratesof the motors into the appropriate rotation ratesand torque (turning force) for the work rolls.

� Drive spindles, which transmit the turningforce of the motors to the work rolls.

� Roll bending machinery, capable of induc-ing slight, controlled flexing in the rolls to com-pensate for thermal expansion or other distortionand, thereby, control product flatness.

� Gap adjustment machinery, to set the gapbetween work rolls accurately and then to main-tain it against the resistance of the alloy undergo-ing thickness reduct1on.

� Coolant systems, to apply liquidcoolant/lubricant to the rolls.

And, for sheet mills, coil and core handlingmachinery to install, remove and transport heavycoils of rolled sheet.

The components which directly apply the mechan-ical force that reduces the aluminum thicknessmust be both strong and precise, capable of apply-ing forces up to millions of pounds with uniformaccuracy of a few hundredths or thousandths ofan inch.

Rolls with appropriate diameters and surfacesmust be used. Automatic roll-changing machinerymakes it relatively easy to adapt a mill to chang-ing product requirements.

No less important than the large mechanical com-ponents are the control systems, which senseproduct thickness and shape, and the computerswhich analyze the data and control the mill’sadjustment systems to maintain product toleranceswhile the mill is running.

THE ROLLING MILLDESCRIPTION AND FEATURES

The rolling process must produce plate or sheet with not onlyaccurate dimensions, but such other attributes as: flatness,edge quality and correct thickness profile; specified physicalproperties; and freedom from surface defects.

So, before we follow an ingot down the rolling line, let’s takea look at the rolling mill itself.

The most basic parts of a rolling mill are two motor-drivencylinders called “work rolls.” These rotating rolls drawaluminum through, and reduce its thickness to the widthof the gap between them. The gap is variable. A thick ingotcan be reduced to thin sheet either by passing it repeatedlybetween the same work rolls and narrowing the gap eachtime, or by passing it through a series of rolls with progressivelysmaller gaps.


� THE ROLLING MILL 4-2

A number of rolling mill parameters are con-trolled, either by the operator or by computer.They may include: roll gap, roll force, roll torque,roll cooling, roll bending, roll tilting and sheettensions.

At many mills today, the operator may presetsuch parameters and then let the computer auto-matically run the mill through the prescribedprocess.

Main features of a four-high rolling mill.

Amill roll is basically just a long smooth steelcylinder with an axle shaped to be gripped

and rotated by powerful motors. The apparentsimplicity of its shape masks a lot of complexengineering.

It must be a near-perfect cylinder with a smoothbut hard surface. It must also be stiff enough notto bend excessively with the high force needed toflatten an ingot or plate of aluminum alloy.

The aluminum product receives its specifiedsurface directly from contact with the work rolls,which must therefore have the intended type ofsurface. Roll surface finish is also very importantboth for rolling efficiency and for product quality.Depending on specifications, flat rolled aluminummay be produced with a relatively rough “mill fin-ish” surface, or with smoother surfaces up to andincluding “bright sheet” with a mirror-smoothness.At the same time, the roll’s degree of roughnesslargely determines how effectively it can “bite”into the aluminum and, by friction, force it throughthe roll gap. A rougher roll applies more frictionand a stronger bite than a smoother roll, so therougher roll can apply greater thickness reductionper pass — an important factor in mill efficiency.In order to provide sufficient friction with asmooth roll surface, it may be necessary to reducethe application of coolant/lubricant. This, in turn,reduces the rate of heat removal and necessitatescompensating changes in the rolling plan.

Because of such considerations, it is economi-cally important to use rolls with surfaces appropri-ate to the type of product to be produced. A cus-tomer who would be satisfied with mill finish alu-minum might be just as satisfied with a smoothfinish. The unnecessarily smooth rolls, however,might impose equally unnecessary penalties onthe mill operation.

It is also important to maintain work roll surfacequality in service. On hot work rolls, even thesmallest blemishes must be avoided, to preventaluminum from sticking locally and creating sur-face flaws in the rolled product. Hot work rollsoften pick up tiny amounts of aluminum oxide oreven aluminum metal, a phenomenon known as“roll coating.” Within limits, this can be advanta-geous because it tends to increase friction andmake the rolls more efficient. Care must be takento avoid excessive build-up, which can result inproduct surface flaws through imprinting or oxidedetachment.

Work roll surface quality is closely monitoredfor excessive wear, deterioration or damage, toassure high quality products. Chrome plating ofthe work rolls was adopted to improve surfacehardness, improve surface finish and extend thelife of the work rolls.

Rolling solution, roll coolants or oil emulsionsis another closely controlled parameter. Computercontrols provide optimum addition of the coolant


SINGLE-STAND AND TANDEM MILLSA mill with one set of work rolls is a “single-stand” rolling mill;several sets of work rolls in a coordinated series form a“multiple-stand” or “tandem” mill.

MILL ROLLSThe hard steel rolls are precision-engineered. Depending onthe product, roll surface may range from a dull “mill finish” tomirror bright.

Roll diameter must not vary from specifications by more thantwo and a half ten-thousandths of an inch.To compensate for flexing and heat distortion, a work rollmay be crowned or concaved — the roll being thicker orthinner by a few thousandths of an inch around the middlethan at the ends.

to the work rolls. Controlled application ofcoolant improves control of the work roll temper-ature, thus improving shape control and ultimatelyyielding a flatter plate or sheet.

In addition, roll design is intimately connectedwith total mill design, because important trade-offsoccur when roll size and properties are varied.

Roll diameter and roll stiffness are two of themost important factors. Other things being equal,a mill’s efficiency in reducing product thicknessdepends on work roll diameter. Product flatnessdepends largely on roll stiffness which, in turn,depends on both the diameter of the roll and thesteel from which it is made.

Work rolls with a relatively small diameter canreduce aluminum thickness by a greater propor-tion in one pass than rolls with a larger diameter.On the other hand, smaller-diameter rolls bendmore easily than those with larger diameters, mak-ing it harder to maintain uniform, accurate productflatness. Overall roll flexibility increases withlength. The wider the rolled product must be, thelonger the roll must be and the more the roll islikely to deflect without support.

Roll deflection can be counteracted to someextent by “crowning" the roll: i.e., making itslightly larger in diameter by a few thousandths ofan inch (tenths of a millimeter) at the middle thanat the ends. Because crowning is a fixed dimen-sion, it can compensate accurately only for amatching, fixed amount of roll deflection. Thisimplies that any one crowned roll is fully suitable

only for specific rolling regimes with appropriatealloys and thickness reductions. It will not haveexactly the right shape for other rolling tasks.Moreover, it will fail to compensate or can evendistort the product, if roll deflection is allowed tobecome greater or smaller than intended.

Alternatively, in some circumstances work rollsmay be “concaved” — made slightly smaller indiameter at the center than at the ends — to com-pensate for anticipated thermal expansion whichwould otherwise cause undesired crowning.

Smaller-diameter rolls are also more vulnerableto horizontal deflection in the pass-through direc-tion. The friction of the aluminum passingbetween rolls tends to drag them in the samedirection and may cause a roll to deflect until itselasticity overcomes the friction and snaps itstraight again. Such deflections must be preventedby appropriate choice of roll size, and/or provisionof horizontally stabilizing back-up rolls.

Because of their larger mass, larger work rollscan absorb or surrender a given amount of heatwith less overall change in temperature thansmaller ones. Thus larger-diameter rolls havegreater thermal stability.

Larger, more massive work rolls also have morephysical inertia — more resistance to changes ofmotion. Therefore, it takes more energy to accel-erate and decelerate their rotation, a considerationthat may substantially affect mill design and eco-nomics, especially for reversing mills and otherstart-stop rolling mills.


ROLL CONFIGURATIONSBut most aluminum plate and sheet rolling requires so muchforce that it is difficult to avoid excessive flexing with only thetwo work rolls. So each work roll is backed up by a larger roll,pressing against it to keep it straight.Rolls are positioned one above the other. A stand with tworolls is called a “two-high” mill. A stand with two work rollsplus two back-up rolls is called a “four-high.”Some two-highs are used, mostly to roll foil or in laboratories.And mills with three-, five- or six-roll combinations are alsooperated. But the four-high mill is the most widely used forrolling aluminum.Some mills are designed to roll in only one direction; others,called “reversing mills” can roll aluminum back and forth.


Common roll configurations: a) two-high, b) four high, c) cluster.

In principle, it takes only two work rolls toreduce aluminum to any desired thickness.

In commercial practice, however, work rolls areusually supported by “back-up rolls” that pressagainst the work rolls and turn with them butnever touch the product. Either the work roll orthe back-up roll may be driven directly by themill's motors. The other roll becomes an idler,turned by the friction of the driven roll.

The most common arrangement is the “four-high” mill in which the two work rolls are placedone above the other and each is supported by abackup roll, above the top work roll and below thebottom one, in a vertically stacked configuration“four (rolls) high.”

In this configuration, the chief purpose of thebackup rolls is to maintain accurate, uniformproduct flatness by preventing excessive verticaldeflection in the work rolls. Thus, the mainrequirement of a back-up roll is strength, achievedby sufficient diameter to withstand the “separatingforce” applied by the aluminum’s resistance todeformation.

A larger-diameter back-up roll can permit theuse of a smaller-diameter work roll and, at thesame time, increase the thermal stability of theunit by acting as a heat sink or source for thework roll. However, a more massive backup rollalso increases the inertia of the rolling mill anddemands more energy for acceleration and decel-eration.

Thermal stability and inertia may influencebackup roll selection, but the dominant considera-

tion is always its ability to control work rolldeflection.

Backup rolls are also applied in other configura-tions to combat horizontal work roll deflection aswell as vertical deflection. This is accomplishedby positioning the back-up rolls off the verticalaxis of the work roll stack, so that their forceagainst the work rolls is directed both verticallyand horizontally.

Configurations using multiple back-up rolls aregenerally termed “cluster mills” and are usuallyused to roll thin products.

The combination of work rolls and back-up rollsin forceful contact with each other introduces thepossibility that the very small variations from per-fect roundness which would be acceptable ineither roll alone could add up to an unacceptabledeviation for the entire stack. In addition, smallacceptable amounts of “give” in the bearingswhich support each roll can also add up to unac-ceptable deviations from perfect rotation as morerolls (and more bearings) are involved.

So roll grinding and roll bearings must be pre-cise enough to keep the “eccentricity” (off centerdeviations) of the entire roll stack, as a unit, with-in the limits required for accurate, smooth productthickness.

Roll diameters must be accurate to within 2.5ten-thousandths of an inch (0.006 mm). Total roll-stack eccentricity may be held within limits assmall as 4 ten-thousandths of an inch (0.01 mm)or less.


HOT OR COLD ROLLINGRolling is done either “hot”— with hot, softened aluminum —or “cold”, with aluminum at room temperature.

In aluminum rolling terms, “hot” and “cold” havemore technical definitions than their common

meaning. “Hot” rolling means rolling at a metaltemperature high enough to avoid strain-hardening(work-hardening) as the metal is deformed.

“Cold” rolling means rolling the metal at a tem-perature low enough for strain-hardening to occur,even if the alloy would feel hot to human senses.

In practice, hot-rolling temperatures maydecline enough during rolling to permit somestrain-hardening to occur.

It takes more energy, of course, to roll coldmetal than metal which is softened by a highenough temperature. Cold rolling can provide asmoother final surface and different tempers thanhot rolling. The thinnest products must be coldrolled to their final thickness.

Hot mills currently roll sheet at rates approaching2,000 feet per minute (600 m/min).

Cold mills can roll sheet at rates up to 7,000feet per minute (2135 m/min) or more.

Hot Rolling – Metallurgical Effects

Hot rolling has at least two significant metallur-gical effects:

1. It welds pores left by casting, creating a denser,stronger metal.

2. It breaks up and distributes hard constituentsof iron and silicon which have formed at grainboundaries. This action transforms brittle castalloy into ductile wrought alloy, because frag-mented and distributed constituents offer lessresistance to the internal metal flow necessary toductility. Reduction schedule or reduction per passand directionality of rolling has a very importantimpact on some of the damage characteristics ofthe high strength aircraft alloys.

Rolling temperature also influences the appear-ance and structure of the final product. Lower hot-rolling temperatures yield relatively brighter prod-uct surfaces and elongated alloy grains, whilehigher hot-rolling temperatures can induce recrys-tallization in the metal. The rolling temperature isselected according to the product properties thatare to be achieved.

Too high a temperature can weaken grainboundaries and cause boundary cracking.Consequently, rolling temperature is kept 20 to90°F (10 to 50°C) below a certain limit — the“solidus” or solidification temperature — of eachalloy.

Cold Rolling – Metallurgical Effects

On the atomic level, solid metals have a “crys-tal lattice” structure: its atoms are arranged

in a regular pattern which can be considered,ideally, as a stack of flat planes.

When the metal is deformed, as it is in flat rolling,regions of the crystal “slip” past each other along

these “glide planes”; such “slip lines” are some-times visible on the metal surface. The latticeplanes are never ideal. There are breaks and off-sets in them, called “dislocations”, which tend toblock slippage and so resist deformation.

Rolling, or other cold deformation, tends to breakand offset the lattice planes, thereby increasing thenumber of dislocations which resist force andmaking the metal stronger and harder. This effectis deliberately induced as “~ hardening” (workhardening) to strengthen aluminum alloy products.Various applications of strain hardening areincluded in the “H-tempers” and some of the“T-tempers” of aluminum.

The same hardening effect can occur prematurely,before rolling is completed; it is undesirable if asoft product is ordered. In such cases, annealing isperformed to undo the work hardening that hasoccurred.

Work hardening has a natural limit for each alloybecause it is, in fact, straining the alloy toward itsstrength limit. The number of dislocations which acrystal lattice can develop is limited and, therefore,so is its maximum strength. As work hardeningincreases, the metal can withstand increasing forcewithout breaking; but it retains less reserveagainst additional force.

Metal cold worked to its maximum limit can bebroken by only a slight additional deformation.

Thus, cold working, or strain-hardening, is appliedto the degree required by product specificationswhich involves a trade-off between maximumstrength and maximum ductility.

The heat of annealing relieves the distorted, dislo-cated lattice structure and allows it to reform inrelatively undislocated planes again, restoringductility at the cost of the acquired strength.


NOTES


SELF-TEST QUESTIONSSECTION 4: ROLLING MILL

4.1 The parts of a rolling mill that applythickness reductions by direct contactwith the product are called…a. the mill stand.b. the drive spindles.c. the work rolls.d. the backup rolls.e. the gap adjustment machinery.

4.2 “The purpose of backup rolls is to permitthe use of smaller-diameter work rolls.”This statement is:a. true.b. false.

4.3 What type of work roll surface can beused efficiently for all rolled productsand specifications?a. mirror-smooth.b. smooth.c. mill finish.d. extra rough.e. none of the above.

4.4 Which of the following factors affect theamount of roll deflection during rolling?a. roll width.b. roll diameter.c.product width.d.product ductility.e.amount of applied thickness

reduction.f. all of the above.

4.5 The most common roll-configuration forrolling aluminum is the...a. two-high.b. four-high.

4.6 Which of the following affects the rollgap?a. roll crown.b. roll bending.c. coolant/lubricant sprays.d. all of the above.

4.7 Roll bending is the equivalent of...a. smoother finish.b. changing the roll crown.c. more reduction.

4.8 “Hot rolling” means rolling aluminum...a. when it is too hot to touch bare-handed.b. with pre-heated work rolls.c. hot enough to avoid strain-hardening.d. hot enough to induce full annealing.

4.9 Which, if any, of the following are signifi-cant effects of hot rolling:a. making the metal smoother.b. making the metal more dense.c. making the metal more ductile.d. making the metal more weldable.e. none of the above.

4.10 “Cold rolling” means rolling aluminum...a. at or near room temperature.b. after refrigeration.c. at any temperature which avoidsstrain hardening.

4.11 In general, cold deformation of alu-minum...a. increases its strength.b. decreases its strength.c. does not affect its strength.d. changes its strength unpredictably.e. causes it to break immediately.

4.12 Cold deformation of aluminum is effec-tive because...a. it twists the shape of the crystal

lattice.b. it makes lattice planes slip past each

other.c. it breaks and offsets lattice planes.d. it rearranges alloying elements in the

lattice.

4.13 In general, as strain-hardening increas-es, a metal’s ductility...a. increases.b. stays the same.c. becomes unstable.d. decreases.

4.14 The amount of strain-hardening that canbe achieved in aluminum alloy...a. is the same for all alloys.b. is unlimited.c. has a natural limit depending on the

alloy.d.has a limit depending on product

thickness.


The first rolling mill encountered by an alu-minum ingot entering the rolling line is called

the “breakdown mill.” It is usually a single-standfour-high reversing hot rolling mill.

Its main function is to “break down” the ingot,reducing its thickness to the dimensions of plate.

For some purposes the breakdown mill alonecan produce final product thickness. For others,the product of the breakdown mill is fed throughadditional rolling mills (hot or cold) for furtherthickness reduction and/or surface finishing.

In a breakdown mill, the work rolls are poweredand their back-up rolls are turned by contact with

the work rolls. A typical breakdown mill mayapply 5,000 horsepower (3730 kilowatts) to eachwork roll, for a total of 10,000 working horsepow-er (7460 kilowatts) to drive the ingot through thegap, where it undergoes a compression force ofabout 8 million pounds (3,635 metric tons) alongthe contact line.

Breakdown mills are often described by thelength of the work rolls they can accommodate(and consequently the maximum width of productthey can roll): for example, a “120-inch mill”(“3-meter mill”) or a “168-inch mill” (“4.25-metermill”).

SHEET ROLLING OPERATIONSNow let’s follow that preheated ingot through the rolling andfinishing processes that convert it into a coil of thin sheet.The first stage is the “breakdown mill,” a massive single-stand, four-high, reversing, hot-rolling mill.

BREAKDOWN MILL PARAMETERSIts operator, in an elevated control room called the pulpit,raises the upper rolls from their last setting and sets the gapfor the first pass — perhaps two or three inches (50-75mm)less than the ingot thickness.

Since it must reduce an ingot as much as 30inches thick (760 mm), the typical breakdown

mill is a large, powerful assembly. Its lower workroll and back-up roll are fixed in position. Itsupper work roll and back-up roll are raised orlowered by screw-threaded or hydraulic mount-ings in the mill stand’s side columns, so the opera-tor can continuously vary the gap between theworking rolls.

As indicated previously, the roll gap for eachpass is only one of several mill parameters thatare set to achieve the desired product properties.Rolls with appropriate diameters and surfacesmust be in place. Roll acceleration and speed arecontrolled as required for the alloy and the intend-ed reduction. In many modern mills the entirerolling sequence is computer-controlled, once theoperator feeds in appropriate instructions.

An aluminum-rolling mill operator in thecontrol pulpit.


Aprepared ingot is sent into the mill at a care-fully adjusted rolling temperature. The rolling

process itself generates additional heat: from fric-tion between the ingot and the work rolls; andfrom the severe deformation of the metal — ineffect, internal friction — as its thickness isreduced.

This additional heat must be removed to main-tain temperature control. This is necessary not onlyto prevent excessive thermal distor-tion of the mill rolls but also to con-trol alloy temper throughout therolling sequence.

In addition, the work rolls must belubricated, to prevent the hot alu-minum from sticking to the rolls andcausing surface flaws on the product.Both the quantity and application pat-tern of lubrication must be appropri-ately controlled.

Therefore, a system of hoses feedsliquid coolant/lubricant through thenozzles of spray bars installed in frontof the rolls.

Lubricant is generally suppressedwhen the ingot enters the workrollgap, to promote a good friction “bite”by the rolls, and then is applied whilethe ingot passes through. There mustbe enough lubricant to prevent stick-ing but not too much. Either too littleor too much lubricant can impair theproduct surface.

Both of these functions — heat removal andlubrication — are performed in a breakdown millby application of a single liquid coolant/lubricant,typically an emulsion of water with about fivepercent oil which is continuously filtered andrecirculated.

Other types of rolling mills may use differentcoolant/lubricant formulations suited to theirfunctions and products.

� SHEET ROLLING OPERATIONS 5-2

BREAKDOWN COOLANT/LUBRICANT APPLICATIONHe also sets an appropriate pattern for applying liquidcoolant. It may seem odd to preheat an ingot to the righttemperature, and then apply coolant when you roll it,but there are two good reasons for doing this.The coolant doubles as a lubricant to prevent aluminumfrom sticking to the rollsAnd the ingot undergoes both friction and a compressionforce of about 4,000 tons as the rolls reduce its thickness.Those forces generate extra heat which must be carriedaway to maintain a correct temperature.As we mentioned earlier, heating, cooling and reshaping allcontribute to the final temper of rolled aluminum, and thosefactors are carefully controlled throughout the process.

A rolling mill coolant/lubricant system (schematic drawing).

The ingot is positioned and fed to the work rollsby a set of conveyor rollers in the “feed table”

divided into right and left segments (table rolls)which are independently powered and controlled.By matching or varying the right and left convey-or speeds, the mill operator can maintain ingotalignment or turn the ingot to reposition it. Thus,ingot can be “cross-rolled”, i.e., run through thework rolls “sideways”, instead of in its normallengthwise orientation, to roll it into a productwider than the original ingot.

The table rolls push the ingot into contact withthe work rolls, but it is the work rolls themselvesthat “bite” the ingot by friction and force itthrough their gap.

The ingot is reduced in a number of passes to aslab a few inches (centimeters) thick. For exam-ple, a 15-inch-thick (380 mm) ingot may bereduced to about 13 inches (330 mm) on the firstpass. Then the roll gap is reset, the direction isreversed, and the ingot is passed through again

and is reduced to perhaps 11 inches (280 mm).The gap is repeatedly narrowed for each pass untilthe desired breakdown thickness is reached.

The operator in the control pulpit may read theroll separation directly from a digital displayinside his booth, or he may monitor the roll gapsettings from a large dial or indicator atop themill. In some modern mills the rolling sequencesare controlled automatically with sensors provid-ing feedback to the rolling program while theoperator monitors the operation.

When the ingot is rolled in its usual lengthwiseposition, the reduction in its thickness is compen-sated almost entirely by a corresponding increasein its length. Friction along the line of contactbetween the work rolls and the ingot is generallyenough to prevent the ingot from widening signif-icantly.

The edges of the ingot may also be rolled by workrolls on vertical axles at one end of the roll tables, toprevent edge cracking and control width spread.


BREAKDOWN ROLLINGOnce the breakdown mill is “set up”, the operator manip-ulates the table rolls — two sets of rollers independentlycontrolled — to position the ingot and start it between the workrolls. Cross rolling is sometimes needed to achieve a specificwidth.The work rolls draw the ingot through and reduce its thickness.Then the operator narrows the gap a few more inches (centi-meters), reverses the mill, and sends the ingot back through it.The ingot is rolled back and forth until if becomes a long slab,four to five inches (100-125 mm) thick.

INTERMEDIATE HOT ROLLINGIf it is to be made into sheet, it is usually conveyed toanother single-stand hot mill and is rolled down to aplate thickness of about one inch (25 mm).

Some rolling mills apply intermediate hotrolling, but most of the newer rolling mills

transfer plate-thickness slabs directly from thebreakdown mill to a tandem sheet-rolling mill.

In a multiple-stand mill, roll power relationships,roll gaps and sheet tension are all interrelated

and must be coordinated.When plate or sheet is reduced in thickness, the

total volume of metal, of course, remains the samebut is redistributed. Since the width of the piece is

essentially unchanged, any reduction in thicknessmust be compensated by a proportional lengthen-ing to maintain constant volume. For example, if aplate 1.2 inches (30 mm) thick is rolled down tosheet 0.2 inch (5 mm) thick, it is reduced in thick-ness by a factor of six. This product emerges from

the rolls six timeslonger and, there-fore, six timesfaster than itentered.

This principleapplies to eachstand in a tandemmill. Since eachstand except the lastfeeds its output intothe next stand, theroll speeds must beprogressively higherfrom stand to stand,

SHEET HOT ROLLING: THE SINGLESTAND REVERSING MILL

Some mills utilize a single stand reversing hotmill. This type of hot mill also includes one or

two coilers, one on each side of the mill. Startingwith a standard size ingot, the metal is rolled back

and forth through the reversing mill. Once thestrip is rolled to the desired thickness, generallyless than .500” (12 mm), the metal can then becoiled. The mill has rewind capabilities on bothsides, and the slab is generally coiled one or threetimes before the rolling is completed.


SHEET HOT ROLLING: THE TANDEM MILLThe plate is rolled down to sheet thickness in a tandem,or multiple-stand, hot-rolling mill. There, several thicknessreductions take place simultaneously as the sheet passesbetween several sets of work rolls with smaller and smallergaps.The stands of a tandem mill must be closely coordinated.From each stand, the sheet emerges thinner and longer —and so, faster — than it went in. Multiple-stand rolling speedsmust be coordinated to accommodate sheet acceleration.In fact, some sets of rolls must have a little extra power andspeed, to keep just the right amount of tension on the sheet.Too little tension would let the sheet buckle; too much wouldtear it.A modern multi-stand hot-rolling mill is computer-controlledto meet batch specifications. Sensors automatically measuresheet tensions, roll speeds and roll power relationships, andthe computer adjusts them.

A four-stand tandem rolling mill with take-up coil (schematic drawing).

to accommodate the accelerating sheet. Eachspeed increase must be large enough to keep ten-sion on the sheet and prevent buckling, but notlarge enough to tear the sheet.

Furthermore, the larger the reduction of thick-ness imposed by any single stand, the more turn-ing power it requires. Power differentials betweenstands also affect sheet tension, so roll speeds andturning power must be coordinated.

The roll gap is another influence which can be

adjusted to maintain correct sheettension. Since gap changes are rela-tively slow, tension is controlledmore quickly by adjusting roll speed.

Tension-measuring devices arelocated between the stands of a tan-dem mill. The rolled sheet passesover each device at a slight angle,generating a downward force whichis measured by load-cells in the bear-ing supports. An automatic feedbacksystem adjusts roll speeds and gapsas necessary to maintain correct sheettension.

Proper composition and applicationof coolant/lubricant is also crucial to tandem millsheet-rolling to remove excess heat; avoid dullingthe product surface or causing undesirable reduc-tion marks or “herringbone” and prevent alu-minum from sticking to work rolls. Mill lubricantsmay include various additives which increase theirload-bearing capacity — their ability to preventdirect contact between the aluminum and the steeleven under high pressures.

Also, the coolant/lubricant formulation mustremain chemically stable under rolling conditions.


COILING AND EDGETRIMMING

As sheet emerges from thehot mill, it is rolled up intoa coil which may be as muchas 8 feet (2.4 m) in diameter.

After rolling, this sheet is edge-trimmed on itsway to coiling.

A tension reel wraps the emerging sheet into atight coil, typically with an inside diameter ofabout 20 or 24 inches (500-600 mm) and an out-side diameter in excess of 90 inches (2285 mm).Sometimes the ends of the sheet are secured bywelding at the inside and outside of the coil.Otherwise, the coil is wrapped with a confiningband. The mandrel on which the coil is woundcontracts for removal of a full reel.

Coils of rolled aluminum awaiting furtherprocessing (right).

A tandem aluminum-rolling mill.

Purposes of Annealing

Aluminum alloys may be hardened by hot orcold rolling procedures to a degree that is not

desired in the finished product or that would inter-fere with further rolling and the achievement of adesired temper.

Heat-treatable alloys may be sufficiently heatedand cooled during hot-rolling to undergo somepartial solution heat treatment and precipitationhardening.

Cold rolling, on the other hand, elongates grainsand sets up internal stresses and strain. Thesechanges create resistance to further deformation:the cold-rolled plate or sheet is said to become“work-hardened.”

Unwanted precipitation hardening or work hard-ening is removed before further rolling or productfinishing by annealing — that is, by heating thealuminum alloy above its recrystallization temper-ature and holding it there long enough for thegrain structures created earlier to re-crystallizeand relieve the internal stresses.

Annealing can be applied at any stage in therolling process.

Full Annealing

Full annealing heats the alloy hot enough, longenough, to soften the product completely —

that is, to achieve full recrystallization.“Recrystallization temperature” is not a preciseterm. Recrystallization does not occur suddenly ata sharply defined temperature; instead, it beginsgradually as the temperature rises into an effectiverange, and it progresses to completion over anextended time. The effective recrystallization tem-perature depends on the alloy and on the deforma-tion and treatment it has previously undergone, aswell as the annealing “soak” time.

Full annealing converts both heat-treatable andnon-heat-treatable wrought alloys into their soft-est, most ductile, most workable condition, desig-nated as the “O-temper.”

For full annealing of heat treatable wrought alu-minum alloys, the metal is typically “soaked” forabout two hours at a temperature in the range of635 to 700ºF (335-370ºC) to remove cold work,or 750 to 800ºF (400-425ºC) to counteract heattreatment.

Then the metal is cooled slowly, at a closelycontrolled rate appropriate to the alloy. This per-


ANNEALINGIf additional rolling is needed, it may be done at room tem-perature in single- or multiple-stand cold rolling mills. Theyoperate on the same basic principles as hot rolling mills.Before, after, or between cold rolling operations, the sheetmay be fully or partially annealed for various reasons byheating and slow cooling, to soften it and counteract thetempering that has already taken place.Applied before or between cold rolling operations, annealingprepares the metal for rolling.Partial annealing may be applied after rolling is completed,to stabilize some tempered properties.Full or partial annealing may be used to prepare the sheet forlater mechanical forming in product fabrication.Or the annealed condition may simply be the final temperrequested by the customer.

mits maximum coalescence of precipitating parti-cles, minimizing hardness.

Non-heat-treatable alloys are annealed by heat-ing for one-half hour to two hours (most oftenabout one hour) at a temperature in the range of635 to 765ºF (335-405ºC). Then they are cooled ata controlled rate.

Annealing also provides the conditions forstress-relief and may even be applied specificallyfor that purpose if furnace schedules and productrequirements permit.

The “H1” and “H3” aluminum alloy tempers arecreated by applying specific amounts of strain-hardening to fully-annealed metal. These arecalled “rolled-to-temper” products.

Partial Annealing

As its name suggests, partial annealing stopsshort of full annealing and, instead, applies

patterns of temperature and time to strain-hard-ened, non-heat-treatable wrought alloys in order todevelop properties in between fully soft and fullywork hardened. It is typically performed after thecompletion of cold rolling.

These intermediate tempers are formally desig-nated as “H2X tempers”: strain-hardened and par-tially annealed.

A quality partially-annealed product requiressophisticated process control.

Stabilization Annealing

Certain non-heat-treatable aluminum-magne-sium alloys, such as 5052, 5456, 5083 and

5086 and also alloy 3004 develop high strengthsbecause of their high internal stresses after rolling.However, because of a tendency for magnesium tocome out of solid solution, the initial temper ofthese alloys is unstable and they may suffer “age-softening” — a gradual loss of some strength overtime, at room temperature. Such alloys may alsoundergo dimensional changes, unless stabilized.

Further age-softening is prevented and themechanical and dimensional properties of thesealloys are stabilized by heating them to a relative-ly low temperature, usually about 350ºF (180ºC).After stabilization, the strength, hardness anddimensions do not change at room temperature.

Annealing Methods

Annealing applies heat by convection throughthe atmosphere inside an annealing furnace.

To avoid oxidizing any unevaporated lubricantresidues or forming magnesium oxide on magne-sium-bearing alloys, annealing may be carried outin a dry, inert (low-oxygen) atmosphere such asnitrogen gas. A large integrated aluminum rollingplant may have its own nitrogen generating plantfor this purpose.

Annealing methods may be divided broadly intotwo general approaches: batch annealing and sheetannealing.

Batch Annealing/Treatment

Batch annealing means loading a furnace with abatch of metal, usually coiled sheet, and hold-

ing it there until the annealing process is com-plete. Coils of aluminum sheet are annealed as asingle batch, depending on the size of the coilsand the size and shape of the furnace.

In batch annealing, heat conveyed by the fur-nace atmosphere to the outside surfaces of thecoils must be conducted through the metal to theinnermost layers, and sufficient time must beallowed for all parts of each coil to absorb enoughheat to achieve the planned anneal.

Batch annealing is an efficient approach and isthe most commonly used method in high-produc-tion sheet mills.

Sheet Annealing/Treatment

In sheet annealing, uncoiled sheet is passedthrough a furnace so that its entire surface con-

tacts and is heated by the hot furnace atmosphere.This heats the sheet rapidly, permitting the devel-opment of a finer alloy grain structure.

Uncoiled sheet may be annealed either as con-tinuous sheet passed through the furnace from coilto coil or as cut sheet transported through by aconveyor.


Aluminum alloys can be cold rolled down tothicknesses of around 0.002 inch (0.05 mm).

Pure (low-alloy) aluminum can be cold rolled intofoil as thin as 0.0001 inch (0.0025 mm).

The first pass through a single-stand cold rollingmill may reduce the material thickness by about50 percent. Subsequent passes may reduce thethickness by similar or smaller amounts.

Sheet destined for cold rolling to thicknessesunder about 0.040 inch (1 mm) is usually hotrolled to about 0.120 to 0.240 inch (3-6 mm)before cold rolling begins.

As the work hardening increases, it takes morepower to roll the sheet thinner. Beyond a certaindegree of hardness, the metal may crack if it isrolled again. This imposes practical limits on theamount of cold rolled thickness reduction that canbe achieved in an uninterrupted series of passes.When further thickness reduction is necessary, thesheet must be annealed as described above to soft-en the metal for further cold rolling.

The degree of cold rolling performed after(or without) annealing is calculated to producedesired properties in the rolled sheet: either itsfinal temper or the condition required to achieveits final temper.

To produce a reflective surface on cold rolledsheet, smaller thickness reductions are rolled dur-ing the final passes. The brightest surfaces areproduced by the use of highly polished work rolls.

A typical single-stand cold mill can roll sheet ata rate of about 5,000 to 6,000 feet per minute(1525 to 1830 m/min) on each pass.

Although the sheet enters the mill “cold”, atroom temperature, the friction and pressure ofrolling may raise its temperature to about 180ºF(80ºC) or more. This excess heat must be removedby an appropriate coolant/lubricant.

Cold rolling in a tandem (multiple-stand) mill isgoverned by the same general principles as single-

stand cold rolling. The tandem mill applies severalthickness reductions in a single pass and readilymatches or surpasses the productivity of thesingle-stand.

Lubricants used for cold rolling are usuallycomposed of a load bearing additive in a lightpetroleum distillate oil. Lower-viscosity oils trans-fer heat more efficiently and improve rolling per-formance. A lower limit on viscosity is imposedby oil evaporation, flash and fire points at rollingtemperatures. Oil-water emulsions have beendeveloped for high speed cold rolling and havebeen adopted at some mills. Rolling lubricantsare filtered to remove rolling wear debris, thenrecirculated.

The length of sheet wrapped in a single coildepends on the coil’s diameter and on the sheetthickness. The 38 inches (965 mm) distancebetween an inner radius of 10 inches (255 mm)and an outer radius of 48 inches (1220 mm)(20-96-inch [510-2440 mm] coil diameters), canaccommodate 760 1ayers of sheet rolled to a typi-cal thickness of 0.05 inch (1.25 mm). One suchcoil could hold a strip of aluminum sheet over twomiles (3.25 kilometers) long which started from24 inch thick by 24-foot long (610 x 7315 mm)ingot.

(Flat-rolled metal more than one-quarter inch[6.3 mm] thick is not usually coiled but is deliv-ered to a run-out table and is cut to specifiedlengths.)

Gauge and Profile Control

As technology has progressed, the requirementsplaced on flat-rolled aluminum products for

accuracy of thickness (gauge), flatness and cross-sectional shape have become more demanding,and rolling technology has advanced to keep pace.

Initially, rolling technology concentrated mainlyon achieving uniform thickness throughout the


COLD ROLLINGCold rolling is used to give aluminum sheet a desired strength and temper;or to provide a final surface finish; or to reduce sheet to very small thicknesses.For example, aluminum beverage can stock is cold-rolled from sheet aboutone-tenth of an inch (2.5 mm) thick down to about one-hundredth of an inch(.25 mm). This may be done in four or five passes through a single-stand mill orin one pass through a multiple-stand mill.

length of the rolled product. In recent years, it hasadded a more sophisticated ability to controltransverse (cross-width) thickness.

The cross-width thickness variation is calledprofile, and it can be controlled during the hotrolling process. Profile can be further describedas having two main components, namely crownand wedge.

For most alloys, the edges of the sheet will beslightly thinner than the center (positive crown),as a result of slight bending or bowing of thework rolls as they work to reduce the slab thick-ness. The higher the rolling load, the greater thedegree of bending of the work rolls, and the high-er the crown. More dilute alloys (softer) are some-times prone to having thicker edges than center,or negative crown, a condition which can have anadverse effect on flatness during subsequent coldrolling passes.

Wedge is the difference in the thicknesses of thetwo edges where the sheet increases in thicknessacross the strip, and can be caused either by workrolls that are not parallel or by an uneven temper-ature distribution across the roll gap.

Many applications of sheet and plate require theflattest possible cross-sectional profile, with con-stant thickness across the strip. On the other hand,some applications require a positive profile, a lit-tle thicker toward the middle than toward theedges.

The formation of a required strip profile ismost readily achieved on thick, hot metal: that is,during single-stand hot rolling or in the entry andmiddle rolls of a hot-rolling tandem mill.

The flatness of the final product depends moreheavily on the rolling applied by the last millstand it passes through, its exit stand. Achievingthe best possible flatness is usually one of themain objectives of cold rolling.

Thickness control, of course, is practiced atevery rolling step; but it is most critical in the lastreduction stand which gives the product its finalthickness.

In order for thickness and profile to be effec-tively controlled, they must be both accuratelymeasured and accurately corrected. Modern com-puterized rolling technology makes it possible tomeasure the thickness, flatness and profile of aproduct as it comes out of the mill stand, comparethem with specified values, and adjust the rolling

mill to make appropriate corrections while therolling continues. Such measurement/control feed-back loops make it possible to produce sheet andplate with more accurate profiles than ever before.

In some cases, feedback loops may be augment-ed by “feed-forward” loops in which the productis measured both approaching and leaving thework rolls, and the two measurements can signalautomatic mill adjustments in time to correct therolling of the product as it enters the work rolls.

Product thickness (gauge) may be measuredduring rolling by contact rolls or by non-contactsensing of X-rays or other radiation beamedthrough the metal.

Surface flatness may be measured by segmentedcontact rolls or by laser beams.

Instantaneous thickness corrections duringrolling may be made by activating hydraulicpistons which move the rolls slightly upwardor downward to adjust the roll gap as needed.

Thickness and profile considerations overlapwhen the separating force applied by the rolledproduct causes work rolls to deflect. A variety oftechniques (called “actuators”) are available tocontrol gauge and/or profile during rolling. Theyinclude:

� Roll tilting: Work rolls may be tilted out ofparallel vertically to counteract and correct prod-uct surfaces which are non-parallel in the oppositedirection.

� Roll crossing:Work rolls may be “crossed”(made slightly non-parallel horizontally) by mov-ing their end-mountings, to alter the distributionof rolling forces. This type of adjustment is madebetween rolling passes.

� Localized roll cooling: Controlled increasesor decreases of cooling application to localizedsegments of rolls may be used to control thermalexpansion and contraction, and so control rollshape during rolling. This can be a significantcontrol technique for cold rolling.

� Roll-bending:Work rolls or backup rolls maybe bent in either the vertical or the horizontalplane, to compensate for rolling forces or tocorrect an incoming profile. Roll-bending can becontrolled dynamically, during rolling.

� Stepped backup rolls: Backup rolls may beinstalled with larger-diameter cylindrical center


sections and smaller-diameter ends, to concentratetheir pressure on the work rolls just over the widthof the rolled product. The “step” width may be aground-in fixed feature of the back-up roll, or itmay be adjustable, created by shrink-fittingremovable outer sleeves or sleeve segments on thecore roll. Stepped rolls are installed or adjustedbetween rolling passes.

� Axial shifting of sleeved backup rolls: Asleeve fitted on a backup roll may be moved fromside to side by sliding the sleeve along the roll,shifting the area of pressure against the work roll.The sleeves of upper and lower backup rolls maybe moved in the same, or in opposite, directionsdepending on the type of correction needed.Because these sleeves are shrink-fitted on theircores, they can be shifted only between rollingpasses.

� Axial shifting of cylindrical work rolls:Conventional cylindrical work rolls may, them-selves, be shifted from side to side to redistributetheir pressure against the product. The upper andlower work rolls may be shifted in the same or inopposite directions. Shifting is carried outbetween rolling passes.

� Axial shifting of non-cylindrical work rolls:Instead of the conventional straight cylinder, workrolls may be made with a wave-shaped profilefrom end to end; that is, a slightly convex formtoward one end, changing smoothly into a slightlyconcave form toward the other. When two such

work rolls are used together, the shape of the gapbetween them can be varied by shifting them axi-ally in opposite directions. Moving the two con-cave segments opposite each other allows theproduct passing between them to bulge in themiddle, either forming a crowned profile orcorrecting an undesired concavity. Moving twoconvex segments into opposition squeezes middleof the product and forms a concave profile orcorrects unwanted crowning. Placing convexand concave segments into opposition creates aproduct with constant transverse thickness but a“wavy” profile which may require flattening bysubsequent rolling.

� Flexible backup rolls: Backup rolls havebeen made available which can be expandedhydraulically at the center or at the ends to inducecrowning or concaving dynamically duringrolling, in response to sensor/computer feed-backloops. In addition, a “self compensating” backuproll, more flexible at its ends than at its middle,combats unwanted product crowning by offeringelastic resistance roughly in proportion to the vari-ous degrees of separating force all across the rollgap. Flexible backup rolls also extend the effec-tive range of work roll bending.

Some of these techniques may be applied in com-bination with others. The choice of measurementsystems, feedback loops, and actuator systems forany specific rolling mill depends on that mill’sown products and operating conditions.


TEXTURING AND EMBOSSINGSome products — such as the aluminum tread platesof decks and steps — call for texturing or embossingduring the final rolling. Instead of the usual smoothsurfaces, one or both work rolls will have a patternwhich is transferred to the sheet as it passes through,during rolling or subsequent finishing operations,and often by the last stand of a tandem mill.

� Embossing: Coiled sheet is run through set ofrolls with the purpose of transferring a special pat-tern from engraved rolls onto surface of the coil.Unlike during the fabricating of tread plate wherea deeper pattern is extruded on one side of the

metal, embossing does not appreciably reduce themetal thickness. Embossed aluminum sheet withspecific patterns such as “wood grain” or “dia-mond” is widely used in architectural applications.

SELF-TEST QUESTIONSSECTION 5: SHEET ROLLING

5.1 A breakdown mill…a. is of a vastly different design from

non-breakdown mills.b. is the first mill to apply rolling where

there are more mills than one.

5.2 The purpose of a coolant/lubricantspray system is to:a. remove excess heat generated during

the thickness reduction.b.control flatness.c.minimize variation in the roll gap

along its length.d.all of the above.

5.3 During ingot breakdown, a reduction inthickness of ____ per pass is not extraor-dinary.a. 0.02" (0.5 mm)b. 0.2" (5 mm)c. 2.0" (50 mm)

5.4 In a breakdown mill, the ingot or slab ispositioned for rolling by the…a. work rolls.b. backup rolls.c. table rolls.d. roll gap.

5.5 When a slab is rolled normally,its width…a. increases by about 10x.b. changes little.c. decreases.

Why?

5.6 If an ingot is rolled to 1/2 of its originalthickness, its length...a.becomes half the original length.b. remains unchanged.c.becomes 50% longer than the original

length.d.becomes twice as long as the original

length.

5.7 “Cross-rolling” means rolling an ingot...a. faster.b. sideways.c. thinner.

5.8 Cross-rolling rolling is done to increase...a. productivity.b. speed.c. width.

5.9 A group of two or more mill stands orranged so that the aluminum plate orsheet is successively rolled by eachstand during the same pass is called...a. a cold mill.b. a hot mill.c. a cluster mill.d. a tandem mill.e. a breakdown mill.

5.10 Which, if any, of these factors affectssheet tension between the stands of atandem mill?a. Sheet thickness.b. Roll power relationships.c. Take-up coil diameter.d. Roll gaps.e. None of the above.

5.11 Annealing is performed for which, if any,of these reasons?a.To remove precipitation hardening.b.To strengthen the alloy.c. To remove impurities.d.To remove work hardening.e. To remove recrystallization.f. None of the above.


5.12 Recrystallization occurs…a. suddenly at a precise temperature.b. gradually over an effective tempera-ture range.c. in sharp steps at several different tem-peratures.d. only after remelting.

5.13 What is the term used to signify thatmetal has been heated above itsrecrystallization temperature?

5.14 “Some recrystallization or annealing cantake place during hot rolling.” This state-ment is:a. true.b. false.

5.15 “Full anneal”, “partial anneal”, and“stabilize” are the thermal process termsrelated to…a. the alloy.b. the type of furnace.c. the purpose and practice.

5.16 The purpose of controlled atmosphereannealing is to avoid...a. oxidation of the residual oils.b. oxidation of the Mg in some alloys.c. a and b.d. Neither.

5.17 The primary reason for stabilizing 5xxx-series alloys is to…a. prevent age softening.b. improve corrosion resistance.c, optimize finishing characteristics.d. all of the above.

5.18 Some heat-treatable alloys are sold inO-temper because...a. the government requires it.b. forming requirement is severe.c. the cost is lower.

5.19 Brightness of final as-rolled surface finishis most affected by…a. the amount of reduction.b. the alloy.c. the finish of the work roll.

5.20 The main purpose of the coolant systemin the cold rolling mill is to...a. maintain the work roll dimensions.b. achieve the temper in the sheet.c. both.d. neither.

5.21 Llist five product characteristics that areaffected by cold rolling.

5.22 The fastest cold rolling mills reachspeeds of more than…a. 3000 ft./min. (915 m)b. 5000 ft./min. (1525 m)c. 7000 ft./min. (2135 m)

5.23 Name at least four techniques or“actuators” available to control gaugeand/or profile during rolling.

5.24 Tread plate is usually produced by…a. hot rolling.b. cold rolling.c. a finishing operation.


Metallurgical Functionof Solution Heat Treating

The atoms of every solid metal are naturallyarranged in regular, repeating patterns that form

crystals. Aluminum atoms tend to form repeatedjoined cubes that share their boundaries, just asrooms in an apartment building share walls, floorsand ceilings. This arrangement of joined cubes iscalled the crystal’s “lattice.” Cube walls that lineup with one another in any direction are said to liein the same lattice plane.

When the shape of solid metal is changed byforce — that is, deformed — its atomic lattice isrearranged. Normally, this means that parallellattice planes are forced to slip past each other.

Any condition that resists the slipping of latticeplanes stiffens the whole lattice and makes themetal mechanically stronger.

In practical metal products, crystal lattices arenever perfect and their planes are not smooth andunbroken. Here and there, the repeated patterngets out of step and the plane is “dislocated.”

Dislocations hinder lattice planes from slippingpast each other, creating resistance to deformationin the bulk metal. Alloying elements are introducedto create just that effect, strengthening the alloyby further distorting the crystallographic lattice.

But a dislocation itself, if it is not locked inplace, can be pushed along its plane by an appliedforce, like a hump in a rug that simply movessomeplace else if you step on it. A dislocation canblock plane slippage only if it stays in place andresists the slip instead of moving along with it.

When a molten aluminum alloy solidifies duringcasting, the atoms of its dissolved alloying ele-ments tend to cluster (precipitate) into relativelylarge particles visible under a microscope.

Large particles are essentially separate from themetal’s crystal lattice. Dislocations can travelaround them, much as waves in water can detouraround an isolated rock and continue past it.

Smaller, submicroscopic particles or individualalloying atoms, however, become closely integrat-ed with the aluminum crystal lattice. Their pres-ence tends to “pin down” lattice dislocations intwo ways.

Because they don’t fit in as neatly as the crys-tal’s natural element, aluminum, other elementscreate stressed areas that resist the movement ofdislocations, because it takes more energy tomove dislocations around stressed areas.

It also takes more energy to force a dislocationthrough a stressed area instead of around it. Bothways, dislocation migration is strongly impeded,and the metal is strengthened against deformation.

SHEET FINISHINGWhen rolling is completed, the coiled sheet goes throughselected finishing processes.

SOLUTION HEAT TREATINGHeat-treatable alloys may, at this point, be solution heat-treated. The sheet is conveyed through a furnace at the righttemperature, for the right amount of time, to dissolve alloyingelements more completely.At the exit of the furnace, the sheet is rapidly cooled i.e.“quenched” to retain the microstructure that existed at thehigh temperature.Solution heat treating should not be confused with annealing.Although both processes apply heat, annealing softens themetal; solution heat treating and quenching strengthens it.


The purpose of solution heat treating, then,is to dissolve large particles and disperse them assmaller precipitates or dissolved atoms capable ofpinning down dislocations and strengthening theproduct.

Solution Heat Treatment: “Soaking”

“Solution heat treatment” usually refers to athree-stage process in which solution heat-

ing is the first step. That is followed by quenchingand then aging.

Solution heating consists of raising the alloy tothe desired temperature and then holding it at thattemperature — “soaking” it — for the necessaryamount of time to dissolve alloying elements.

This dissolving (solutionizing) must take placein solid metal. Melting the alloy would only repeatthe casting conditions that form large particles.The degree to which solid aluminum can holdunprecipitated elements in solution is called its“solid solubility”. When solid aluminum is heated,the solid solubility of important alloying elementsin it is increased and precipitated elements canredissolve.

Therefore, the alloy is held at a temperaturebelow its melting point but high enough to producea nearly homogenous solid solution. The solutionheat treating temperature must be selected andcarefully controlled for each aluminum alloy,because the range between the solutiontemperature and the melting point may be quitenarrow, as illustrated by these examples of threealloys, all in the 2xxx series:

Alloy Solution Treating Eutectic MeltingTemperature, °F (°C) Temperature, °F (°C)

2014 925-945 (496-507) 945 (507)2017 925-950 (496-510) 955 (513)2024 910-930 (488-499) 935 (502)

In these examples, the lowest effective solutiontemperature is only 20 to 25°F (11-14°C) short ofthe melting point. One of these alloys soaked at atemperature in the middle of its solution rangewould be only 15°F (8°C) below the melting tem-perature. Thus, temperatures must be strictly con-trolled during solution heat treatment.

The “soak time” required for adequate solutionvaries depending on the thickness of the metal andits initial microstructure. It can range from min-utes to hours after the metal has reached solutiontemperature.

Quenching

Dissolved elements can move more freelythrough an alloy when its lattice structure is

absent (in the molten state), incomplete or weak,at high temperatures, than they can once the lat-tice is fully formed, cool and rigid.

If a solutionaized alloy were allowed to coolslowly, its dissolved, dispersed elements would bepartially squeezed out of the forming crystal lat-tice and would cluster together in large particleswith little strengthening influence.

This is prevented by “quenching” the hot alloy;that is, cooling it in a time too short for the dis-solved elements to migrate. This, in effect, freezesdissolved elements where they are, still dispersedin what becomes a “supersaturated” solid solutionholding more alloying elements in solution atroom temperature than would otherwise occurwith a slow cool down.

To achieve this condition, the alloy must becooled very quickly through the temperature rangein which particle precipitation would otherwiseoccur. The aim is to retain the “supersaturated” solidsolution all the way down to room temperature.

Quenching is usually accomplished by plungingheat-soaked metal into cold water or flushingwater over it at high flow rates.

Milder quenching methods, such as water spray,hot or boiling water, air blast or water-mist “fog”,may be used on some alloys whose heat treatedproperties are less sensitive to the quenching rate.Milder quenching may minimize distortion andresidual stress in the metal, reducing the need forstraightening operations.

Immediately after quenching, when alloying ele-ments are still in solution and have not had timeto form small dislocation-pinning precipitates,most aluminum alloys are almost as ductile as inthe annealed condition. Therefore, straighteningoperations are often carried out as soon as possi-ble after quenching to take advantage of this soft-ened condition.

Rolling or other cold working in this conditionmay further improve the properties of some heattreated alloys.

Modern mills use “continuous strip” heating andquenching. In this system, uncut sheet runs con-tinuously through a tunnel-type furnace and anadjacent quenching station.

� SHEET FINISHING 6-2

Natural Aging(Precipitation Hardening)

The increased strength which is the usual pur-pose of solution heat treating develops only

during its final step, aging or “precipitationhardening.”

The elements dissolved in a supersaturated,solid solution can still migrate through cool metal,even at room temperature, but not as fast or as faras they could at high temperatures. As a result,atoms of dissolved alloying elements can slowlygather to form tiny precipitates with relativelyshort distances between them, but not large, wide-ly-spaced particles. The large number and highdensity of small dislocation-pinning precipitatesgives the alloy its strength and hardness.

Aging means allowing enough time for this tohappen before the metal is used for its intendedapplications. Solution heat-treatment and quench-ing have established the necessary conditions fordislocation pinning to occur; aging allows it totake place.

This may occur during “natural aging” at roomtemperature. Some alloys, particularly those in thecopper-alloyed 2xxx series, reach virtually maxi-mum strength by natural aging in a short time—afew days or weeks—while others continue to gainstrength appreciably by precipitation hardeningfor years. In alloy 2024, for example, precipitationhardening is essentially complete after about fourdays at room temperature, achieving the T3 or T4temper. Alloys 2014 and 6061, sometimes used inthe T4 temper, reach fairly stable precipitationconditions after about one month at roomtemperature.

Artificial Aging(Precipitation Heat Treatment)

Many other alloys, however, harden slowly atroom temperature, continuing to strengthen

appreciably for years. Those alloys are treated toaccelerate precipitation by “artificial aging”:holding them for a limited time at a moderatelyraised temperature, which increases the mobilityof dissolved elements and allows them to precipi-tate more rapidly than at room temperature.This process is also called “precipitation heattreatment”.

Even alloys which naturally age rapidly maybe artificially aged to assure the development ofmaximum strength. The strength of some alloyscan be maximized by applying a combination oftreatments: a small amount of cold working, fol-lowed by artificial aging.

Precipitation heat treatment temperatures gener-ally range between 240 to 375°F (115-190°C), andsoak times vary from about 5 hours to 48 hours.The time/temperature cycle for each alloy isselected to achieve the most suitable compromisebetween the conflicting demands of productstrength and ductility, and other required charac-teristics such as corrosion resistance.

Artificial aging can be deliberately carriedbeyond the point of maximum alloy strength. Bypromoting the controlled growth of somewhatlarger precipitates and thus reducing strength andhardness, certain specified product properties areachieved. This procedure is called “over-aging.”

These variations in treatment are reflected in thedifferent definitions of the T3, T4, T6, T7, T8 andT9 aluminum alloy tempers, and the progressivelyaging “W” tempers.

It should be noted that precipitation hardeningcan also be slowed down to some extent by reduc-ing temperature. For some purposes and in somealloys, aging can be slowed or delayed for severaldays by refrigerating the metal at zero°F (-18°C)or lower.

Forming or straightening may induce desirableproperty changes if performed before significantaging (precipitation) has occurred. When theseprocedures cannot be carried out immediatelyafter quenching, the alloy may be refrigerated toretard aging until the metal can be worked moreconveniently.


The slitter may be used not only to trim theedges of wide sheet, but it may also cut sheet

into narrower strips down to widths as small as1/4 inch (6.3 mm) according to the customer'sspecifications. The slit sheet is recoiled as it

emerges from the slitter.A high-speed slitter applying a surface lubricant

electrostatically may process sheet at a rate up to4000 feet per minute (1220 m/min.). A laser scan-ner simultaneously checks for surface defects.


SLITTINGCoiled sheet is then run through a high-speed slitter,whose circular knives trim the edges straight.The slitter may also divide wide sheet into narrowercoils of specified widths.

TENSION-LEVELINGBefore or after slitting, the sheet may also go through atension-leveler. There, it passes over sets of rolls that flexand stretch the metal to remove any buckling and giveit a uniform flatness.

The tension-leveler flattens rolled strip bystretching it to a predetermined, exactly con-

trolled percentage of elongation. The sheet is keptin tension by the grip of entry and exit bridle rolls.In between the entry and exit bridle rolls, thesheet passes over and under a series of steel rolls.This bends and works the sheet beyond its elasticlimit and produces permanent elongation whichcounteracts any remaining curvature and com-pletes the straightening process, producing analloy strip which is flat and stress-equalized.

Surface FinishesAluminum sheet and plate emerge from rolling

with a surface largely determined by the smooth-ness of the work rolls employed. Various othersurface finishing operations may be performedafter rolling is completed, to enhance productappearance, improve surface characteristics, orincrease corrosion resistance.

Most surface finishing methods fall under oneof three general categories: mechanical finishes,chemical finishes, and coatings.

Configuration of tension leveler rolls (schematic drawing).

Mechanical Finishes for sheet and plate include:BuffingPolishingSandingScratchingGrindingBurnishingEmbossing

Chemical Finishes for sheet and plate include:EtchingAnodizingChemical brighteningConversion coatingZincate coating

Coatings for sheet and plate include:PrimingPaintingPorcelain enameling

Finishes and coatings may be applied singly or incombination as required for the intended product.

Oiling

Sheet and plate products may be coated withoil to prevent oxidation, water staining and

scratching during handling, storage and shipping(unless they have been given a specific surfacefinish which should not be oiled). Sheet and plateproducts destined for overseas shipment are usual-ly oiled. Customers purchasing sheet and platesometimes request that it be given a uniformcoating of oil which will ease later metal formingoperations. The oils used for these purposes usual-ly have a mineral oil base and are formulated toprovide high resistance to water while avoidingskin irritation among handlers.

Degreasing

Just the opposite procedure, degreasing,is applied to remove any oils remaining

on sheet or plate from the rolling operation,when a customer orders an oil-free product.


COATINGS AND MARKINGSCoatings or decorations may also be applied. Paint, enamelor other liquids are usually sprayed or rolled on. Paper, plasticor other films may be applied using adhesives, pressure andheat. Some aluminum rolling mills have their own coatinglines, but this type of finishing is often done elsewhere.

Stenciling

When ready identification of finished sheet isessential, codes identifying the product’s

specifications, alloy, temper, gauge, and manufac-turer may be stenciled on it by inked rollers orother marking devices. Stenciled markings may

also be required by federal or militaryspecifications.

In recent years, systems have been developedfor marking aluminum sheet and plate with barcodes that can be read automatically by computer-linked laser scanners.

CUTTING TO LENGTHWhen separate flat sheets are required, coiled sheet is sentto a “cut-to-length” line. There, it is uncoiled and cut to thespecified lengths.

Coiled sheet may be cut to length in one of twoways:

1. Sheet unrolled from a coil may be momentarilystopped and cut to a pre-set length by stationaryshears.

2. It may unroll from the coil and be cut to lengthby “flying shears” that travel with the movingsheet while they cut it.

A mechanical stacker using forced air or vacuumlifters lowers cut sheets onto the stack gently, toavoid scratching.

STRETCHER-LEVELINGIf necessary, cut sheets are stretchedto flatten them.

Cut sheet may be further flattened by a sheetstretcher. This device clamps the ends of the

sheet between pneumatically activated jaws. Thenthese stretcher heads are hydraulically separated,stretching the sheet to a preset amount. Stretcher-leveled sheet is important to many applications,such as smooth truck body panels whose wideexpanses would make any irregularity morenoticeable.


PACKAGING AND STORAGEFinally, the finished sheet is packaged and stored for shipping.The ends of coiled sheet are sometimes welded to the insideand outside of the coil to prevent uncoiling.Then the coils are wrapped in plastic to keep out moisture andare banded.

Coiled sheet is usually wrapped and sealedagainst moisture as a unit. Flat sheet is also

protected, usually by separating stacked sheets(“interleaving”) with an anti-tarnish, noncorrosivecraft paper.

Flat sheet surfaces may also be protectedtemporarily by gummed tape, which should beremoved within 90 days after its application.

Another protection method for some sheet prod-ucts is a thin transparent vinyl film which can be

readily removed by hand or by air blown betweenthe coating and the metal surface. This filmshould be removed within ~90 days or as recom-mended by the supplier. Leaving the film on forlonger periods can result in problems with itsremoval.

Flat sheet may be packaged for shipping in avariety of ways, such as: bare metal in a strappedbundle; a paper-wrapped bundle; or inside a fiberor wood box or a reusable shipping container.

SELF-TEST QUESTIONSSECTION 6: SHEET FINISHING

6.1 Solution heat treating involves dissolving...a. copper.b. lattice dislocations.c. alloying elements.

6.2 In solution heat treating, “soaking”means...a.wetting the alloy before heat-treat-

ment.b.heating the alloy long enough to

dissolve its alloying elements.c.quenching heated alloy in cold

water.d. remelting the alloy to add new

elements.

6.3 Solution heat treatment temperaturemay be critical because...a. precipitation may occur.b. melting temperature is close.c. solid solubility is limited.

6.4 The purpose of quenching is…a.to freeze dissolved elements where

they are.b. to make dissolved elements cluster

into large particles.c. to cool heat-treated metal to room

temperature for ease of handling.d. to establish the right temperature for

further rolling.

6.5 The purpose of aging after solution-treating and quenching is...a. to achieve specific length and width

dimensions.b. to achieve stable precipitation

conditions.c. to thicken aluminum's natural oxide

film.d. to produce a specified surface finish.

6.6 Maximum strength is not achieved in aheat treatable alloy unless it is...a. formed.b. artificially aged.c. naturally aged.

6.7 Tension leveling uses both tension andbending or flexing for flattening and toa. prevent scratches.b. equalize stresses.c. remove coil set.

6.8 Most aluminum surface finishing meth-ods fall under one of three general cat-egories. Name them.

6.9 In recent years, systems have beendeveloped to mark aluminum sheet andplate with…a. photo-engraved symbols.b. coded magnetic stripes.c. laser-scanned bar codes.d. laser-burned engraving.


Slab Reheating

After its initial breakdown reduction, the slab isadvanced on a run-out table where its ends

are trimmed square. Occasionally, slabs destinedfor further rolling into plate are then transferred toa furnace for reheating which may take from twoto 24 hours, depending on the alloy. Restored torolling temperature, they are moved to the inter-mediate rolling mill.

Intermediate Edge Trimming

Plates of some alloys may crack along the edgesduring rolling. Such cracks would invade the

product during subsequent rolling if they wereallowed to remain. Therefore, after intermediaterolling the plate’s edges are trimmed to removesuch cracks, leaving it wide enough for trimmingto final size when rolling is completed. Both endsare also trimmed square.

PLATE ROLLING & FINISHINGAluminum plate and sheet products are rolled and finished byessentially similar procedures.

PLATE ROLLINGA slab rolled in the breakdown mill to four to five inches (100-125 mm) is already thick plate. For some applications it issent straight to the finishing line. Thick plate is machined bycustomers into more elaborate shapes.Otherwise, the breakdown mill may continue rolling thickplate down to a thinner gauge.Final thickness may be achieved in a second hot-rollingstand, for closer control or simply for efficiency.Sometimes plate is also cold-rolled to increase its strengthor improve flatness. Plate for boat structures or military armormay be reduced 30 percent in thickness by cold-rolling, toincrease its strength.Plate remains uncoiled and flat all through its processing.It is often transported between work stations by a craneequipped with vacuum pads.

PLATE FINISHINGAlter rolling, heat-treatable plate goes through a horizontalor vertical furnace for solution heat treating and quenching.


Solution Heat Treatingand Quenching

The solution heat treating, quenching, and pre-cipitation hardening of aluminum plate follows

the same physical laws and practical proceduresas for aluminum sheet. The procedures may haveto be adapted to take into account the greaterthickness of plate.

Because the rate of heat transfer through metalis limited, it takes time for cooling applied at the

surface of hot plate to reach its center. During thattime large temperature differences can develop,setting up mechanical expansion/contractionstresses between surface and core which becomefrozen into the cooled plate and are permanentunless relieved by further operations.

Tests on two-inch-thick (50 mm) plate (alloy7075) have found as much as 350ºF (195ºC) dif-ference between surface and core, four secondsafter the start of quenching.

� PLATE ROLLING & FINISHING 7-2

PLATE STRETCHINGThick plate is stretched between the gripping jaws of ahydraulic machine, to flatten it, work-harden it, and relievestresses created by rolling and heat-treating. A large stretch-er can apply as much as 15,000 tons (133 meganewtons) ormore of tension!Thinner heat-treated plate is often stretched as well.But non-heat-treated thin plate is not usually stretchedunless it’s necessary for flatness.Plate may be stretched by as little as one percent,or as much as 15 percent of its original length.The stretcher’s grip imprints the ends of the plate,so they are sawed off and recycled.

Stretching has proven to be an effective meansof relieving stresses introduced into plate by

quenching.For the alloys, tempers and applications that

account for almost all rolled plate production,stretching is typically within the range of one tothree percent. In some specialized cases, such asalloys 2024 and 2219 in the T86 and T87 work-hardened tempers produced to meet demandingaerospace requirements, stretching of as much as15 percent may be applied.

A stretcher applying 6 million pounds (27meganewtons) of tension can relieve and levelaluminum plate up to three inches (75 mm) thick.A stretcher with 30 million pounds (133meganewtons) capacity can stress-relieve alu-minum plate up to six inches (150 mm) thick orlarger.

Stress-relief stretching has made it possible tomachine thick plate into complex structural air-craft parts with integral stiffeners, without thedistortion that might occur if the stresses werenot first relieved.

ULTRASONIC INSPECTIONAt this point, aluminum plate may be ultrasonically inspect-ed. It is submerged in water and sound waves are beamedinto it. They will bounce back from hidden flaws, revealingtheir presence and their location. Flawed plate, of course,is not shipped but is held back for correction or recycling.

Ultrasonic testing may be required for someproducts, particularly under certain military

specifications. On less critical products it may beused to spot-check samples for production quality.

For ultrasonic testing, a slab or plate is sub-merged in water in a large shallow tank nick-named the “swimming pool.” The water serves asan efficient coupling agent which aids in transmit-ting sound waves at frequencies above humanhearing (ultrasonic) from a transducer into thetested metal.

The ultrasonic waves are reflected back to adetector from both surfaces of the plate. Since thespeed of sound through the aluminum alloy isknown, the time difference between the arrival ofreflected waves from the two surfaces can be usedto calculate the distance between them and thethickness of the plate.

Hidden flaws within the metal will distort orreflect the sound waves as well. These flaws canbe revealed and even located by the reflectedpatterns.


ARTIFICIAL AGINGAfter stretching and inspection, some plate is further hard-ened by undergoing a moderately raised temperature toaccelerate its natural aging. The process is called “artificialaging.”

The natural aging and artificial aging of aluminumalloys are discussed above in the “Solution Heat

Treating” section under “Sheet Finishing.”The principles of aging (precipitation hardening)

are the same for sheet and plate and the proceduresand temperature/time cycles are governed primarilyby alloy composition and property specificationsrather than product form.

PLATE EDGE CUTTINGAt some convenient stage, plateedges are trimmed straight bycircular saws.

Plate edges are usually trimmed square andflat. Customers may, however, specify specialedge preparations such as: rabbeted, routed,machined or anodized.

PLATE INSPECTION, SUPERFICIAL DEFECT REMOVALAND STORAGE

Finally, the finished plate is inspected; any minor surfacedefects are removed, and the plate is stacked and stored forshipment—protected by plasticized paper and often separat-ed by wooden spacers.

NOTES


SELF-TEST QUESTIONSSECTION 7: PLATE ROLLING ANDFINISHING

7.1 Plate is cold rolled in order to…a. increase its strength.b. achieve special thickness tolerance.c. improve its flatness.d. all of the above.

7.2 Plate solution heat treating is normallydone...a. in a horizontal or vertical furnace.b. to improve flatness.c. using air quench.

7.3 The quenching of solution-heated platecan set up internal stresses because theplate…a.cools faster on one side than the

other.b.cools faster at the interior than at the

surfaces.c.cools faster at the surfaces than at

the interior.d.cools faster at the ends than at the

middle.

7.4 Stretching relieves stresses by…a.allowing all the grains to line up.b. raising unequal stresses to a higher,

more equal level.c. cold working the metal.

7.5 Plate is typically stretched…a. less than one percent.b.1-3%c. 5-1O%d.12-16%

7.6 A hydraulic stretcher…a. leaves no marks on stretched plate.b.makes the plate ends smoother than

the rest.c. leaves end imprints which become

part of the finished product.d. leaves end imprints which are sawed

off.

7.7 In some products, trimming is donebefore final rolling in order to…a.make the final trim easier to

dispose of.b. remove edge cracks.c. inspect the product as early as

possible.

7.8 Ultrasonic testing is done to…a. detect inclusions.b. satisfy OSHA requirements.c. check hardness or strength.

7.9 The principles of natural and artificialaging of aluminum plate…a.are essentially the same as for sheet.b.are entirely different than for sheet.c.depend on the shape of the finished

product.d.None of the above.


Sheet and plate products are routinely tested andinspected in accordance with certain govern-

ment and society specifications and good businesspractice. The testing routinely performed isfrequently sufficient to ensure the quality requiredby the customer.

Additional tests or inspections may be arrangedby agreement between the customer and theproducer.

Some of the additional tests which may beordered include:� Squareness inspection� Electrical conductivity testing� Fracture toughness testing

And, for plate:� Ultrasonic inspection� Ballistic testing

Tensile Strength Testing

In the rolling mill laboratory, the tensile strengthof an aluminum alloy is tested by stretching a

sample, of standard thickness and shape, in amachine which measures the force required todeform and then break it. A computer automatical-ly records these measured yield and tensilestrengths and reports the results. In a computer-ized rolling mill, the control center may alreadyhave entered the alloy batch specifications into the

computer, which immediately compares the testedstrength with the specifications. If the sample iswithin specifications, the computer automaticallytransmits an alloy clearance to the appropriateplant operator. If not, it reports that the sample isout of specifications.

Microscopic Inspection

The surface of an alloy sample is polished, chem-ically etched to enhance grain boundaries and

other metallurgical features, and then inspectedvisually under a light microscope. Such inspectioncan reveal grain sizes, inclusions, defect identifi-cation and other features of alloy structure, andcladding thickness.

If necessary, samples can be subjected to magni-fications as high as 100,000 times or more byelectron microscopy at appropriate facilities.

Porosity Testing

Porosity can be observed and estimated byapplying to the surface of an alloy sample

a penetrating liquid dye which concentrates inpores. This dye contains chemicals which fluo-resce — that is, emit visible light — whenexposed to invisible ultraviolet light. Thus, thetreated sample reveals its porosity when inspectedunder UV light in a darkroom.

QUALITY & PROCESSCONTROLTESTING AND INSPECTION

At every major step of aluminum sheet and plate rolling,product quality is checked—not only in general, but againstthe specifications required for each batch. Orders are rolledto each customer's specification… that is, custom made.A large aluminum rolling mill will have a well-equippedlaboratory which can routinely analyze alloy compositionwithin minutes…Test the strength of product samples…Inspect metallurgical structure microscopically…Detect porosity with a dye that glows under ultraviolet tight…And analyze rolling coolants and lubricants.


Coolant / Lubricant Analysis

The liquid coolants / lubricants used in rollingaluminum can be chemically analyzed automat-

ically. In as little as five to ten minutes, suchdevices can detect and measure the presence ofesters, acids, soaps and contaminants. They canprovide information about conditions prevalent inthe rolling process. In addition, viscosity and dis-tillation curves can be determined. Such factorsexert important influences on rolling speed andproduct surface quality.

Anodizing and Bright-Dipping Tests

If a batch of flat-rolled aluminum is eventually tobe anodized or bright-dipped, samples may be

given these treatments in small laboratory facili-ties to confirm that the metal will perform asintended.

Dimensional Tolerance Control

Standard dimensional tolerances for aluminumsheet and plate are promulgated by the

American National Standards Institute and pub-lished in ANSI H35.2 (and H35.2M, the metricversion).

ANSI H35.2 includes dimensional tolerances forthickness, width, length, lateral bow, squarenessand flatness, and other tolerances applicable tospecific types of products.

Sheet and plate are produced within these ANSItolerances unless other tolerances are specified.

Producers may publish their own standard toler-ances, which govern where they differ from theANSI tolerances.

Nonstandard tolerance specifications may beadopted by mutual agreement between the cus-tomer and the producer.

The ANSI tolerances usually applied imposelimits on dimensional deviations, which vary withalloy and with specified product thickness andwidth

For example, sheet rolled from alloy 5052 or anumber of other specific alloys to a specifiedthickness of 0.030 inch (0.75 mm) at a sheetwidth up through 39.37 inches (1000 mm) maydeviate from its nominal thickness by no morethan 0.0020 inch (0.045 mm) under the ANSIStandard Tolerance table.

If the same sheet is more than 39.37 inches

(1000 mm) wide, up to 59.06 inches (1500 mm),the standard tolerance is increased to a permittedthickness deviation of no more than .0025 inch(0.06 mm) .

Surface Quality Characteristics

Flat-rolled aluminum may be produced with oneof a number of common types of surface quali-

ties, including:

Mill finish:The general-purpose surface finish, which meetsmost customer needs, produced by work rolls sur-faced mainly for effective thickness reduction.

Skin-quality finish:High surface quality on one side of the flat-rolledproduct, with mill finish on the other side.

One-side-bright mill finish:Moderately “bright” (reflective) surface on oneside, with mill finish on the other side.

Standard one-side-bright finish:Uniformly bright surface on one side, with millfinish on the other side.

Standard bright finish:A relatively bright surface on both sides.

Other aspects of flat-rolled aluminum surfacesare discussed and illustrated in The AluminumAssociation's publication, “Visual QualityCharacteristics of Aluminum Sheet and Plate”(QCA-1;2002).

This booklet identifies more than 90 characteris-tics of bare and Alclad sheet and plate, groupedunder five general headings:

Flatness CharacteristicsMetallurgical CharacteristicsSurface CharacteristicsOther CharacteristicsCoated Sheet Characteristics.

The booklet describes and illustrates the visualappearances of various flaws which may becaused by deviations from optimal rolling condi-tions or by handling and storage conditions.

� QUALITY & PROCESS CONTROL 8-2

As computerization spreads and develops,modern aluminum rolling plants are increas-

ingly adopting such techniques as “computer-inte-grated manufacturing”, “just-in-time production”,and “statistical process control” to improve effi-ciency, customer service and product quality.

Computer-Integrated Manufacturing (CIM)systems use the computer, connected to sensorsand other information-inputs, to organize and con-trol the flow of materials through the rolling plantand to automate rolling operations, improvingplant efficiency and product uniformity.

Just-In-Time (JIT) systems coordinate plant uti-lization and production schedules with customerorders and product delivery timetables to reduceor eliminate unnecessary stockpiling and unantici-pated production changes, and guarantee productdelivery when the customer needs it.

Statistical Process Control (SPC) systems regu-larly measure key product and process characteris-tics; automatically analyze them in relation toproduct specifications; identify trends if changesstart to occur; and feed back these findings toprocess controllers which make the necessaryadjustments to keep processes and products withinspecifications.


COMPUTERIZED AND CENTRALIZED CONTROLSIn a modern mill, each rolling stand and many finishingoperations may be computer-controlled for high qualityand uniformity.And operators at a control center direct alloying on the basisof lab tests, and coordinate movements of scrap, alloy, androlled products throughout the plant.The aluminum rolling industry is moving increasingly towardcomputerized process coordination and the tracking ofmaterials and products by automatic bar-code reading.

Aluminum plate, sheet and foil look so simple—and it’s soeasy to make so many things out of them—that it’s hard toimagine how much technology, power, and care has goneinto them.The modern rolling mill applies massive physical force withfine precision, producing flat aluminum products with accu-rate dimensions and with properties tailor-made to meet thecustomer's needs.In the race for product versatility, durability, performance,economy, and ease of fabrication, it’s hard to beat aluminumplate, sheet and foil—they’re really rolling!

NOTES


SELF-TEST QUESTIONSSECTION 8: QUALITY AND PROCESSCONTROL8.1 Every ingot “drop”, when finished into

rolled product, is tested for dimensions,mechanical properties, and…a.anisotropy.b.hardness.c.alloy composition.d.all of the above.e.b and c.

8.2 “Analysis of used coolant / lubricantcan detect contaminants, but it can notreveal anything about the rollingprocess itself.” This statement is:a. true.b. false.c.a “trick question”.

8.3 “Standard dimensional tolerances” areapplied to aluminum sheet and plateproducts…a. in all cases.b.only when required by government

specifications.c.only when required by individual

purchasers.d.unless special tolerances are

specified.

8.4 Among recent rolling mill developments,the acronym “CIM” stands for;a.Comprehensive Inventory

Management.b.Computer-Intensive Mechanics.c.Complex-Intelligence Machines.d.Computer-Integrated Manufacturing.

8.5 A “JIT” system…a.coordinates production and delivery

time tables.b. stockpiles product for potential future

orders.c.automatically audits employee

work-hours.d. forecasts market trends for rolled

products.

8.6 “Statistical Process Control” (SPC)…a. improves the accuracy of company

record-keeping.b.monitors rolling industry business

statistics.c. heads off potential rolling-process

problems.d.matches ingot production with orders

for rolled products


Aging—Precipitation from solid solution result-ing in a change in properties of an alloy, usuallyoccurring slowly at room temperature (naturalaging) or more rapidly at elevated temperatures(artificial aging).

Alclad sheet—Composite sheet consisting of analuminum alloy core having on both surfaces (ifon one side only, Alclad One Side Sheet) a metal-lurgically bonded aluminum or aluminum alloylayer that is anodic to the core, thus electrolytical-ly protecting the core against corrosion.

Alloy, aluminum—Aluminum to which metallicadditions, known as alloying elements, have beenmade to impart certain properties. The mostimportant alloying elements for aluminum includemagnesium, copper, silicon, manganese and zinc.

Alumina—Aluminum oxide, A1203, an interme-diate product extracted from bauxite and fromwhich aluminum metal is separated by the Hall-Heroult reduction process; aluminum oxide, avery hard material, is also widely used as an abra-sive.

Annealing—A thermal treatment to soften metalby removal of stress resulting from cold workingor by coalescing precipitates from solid solution.See also “Full Annealing”, “Partial Annealing”and “Stabilization Annealing.”

Anode—A positive electrical pole: in the Hall-Heroult process, the positively-charged carbonpole which attracts and reacts with the oxygenfrom dissolved aluminum oxide.

Anodizing—A process for artificially increasingthe thickness of the oxide layer on aluminum byapplying a direct current while the piece is sus-pended in an electrolyte. The aluminum work-piece itself serves as the electrical anode; hence,the name “anodizing.”

ANSI—American National Standards Institute;verifies industry standard-setting procedures andaccredits industry-adopted standards.

ANSI-H35.2—“American National StandardDimensional Tolerances for Aluminum Mill

Products”, published by the AluminumAssociation; also published as ANSI-H35.2(M) inmetric units.

Artificial aging—Precipitation from solid solu-tion resulting in a change in properties of an alloy,accelerated by application of a moderately elevat-ed temperature.

Backup rolls—In a rolling mill, supporting rollswhich press against the work rolls to counteractdeflection forces.

Bauxite—Aluminum ore: a mineral first discov-ered at Les Baux, France, containing about 40-55% alumina (aluminum oxide), with impuritiessuch as iron oxide, silicon oxide, titanium oxideand water.

Bayer process—The process, patented in 1888,commonly used to extract alumina from bauxiteas an intermediate stage in the production of alu-minum metal.

Belt caster—A device which casts metal directlyand continuously into the form of plate or sheetby allowing molten metal to solidify betweencooled traveling belts which serve as local moldwalls.

Bite—The initial contact friction from work rollswhich draws the material being rolled into the rollgap.

Block caster—A device which casts metaldirectly in the form of plate or sheet by allowingmolten metal to solidify in contact with travelingcold blocks which serve as heat-sinks and as localmold walls.

Breakdown mill—A rolling mill which firstreduces aluminum ingot to slab, plate or sheetthickness.

Bright-dipping—Chemical treatment of alu-minum in a special dip solution to produce diffusebright or highly specular (mirror-bright) finishes.

Casting—Allowing a liquid material to solidifyinside a shaping form; a product formed by cast-ing.

GLOSSARY9Rolling Aluminum:From the Mine through the Mill

� GLOSSARY 9-2

Cold rolling—Rolling performed on metal at atemperature sufficiently low that strain-hardening(work hardening) occurs. Cold rolling may be per-formed at room temperature or at a moderatelyraised temperature.

Cold working—Plastic deformation of metal atsuch temperature and rate that strain hardeningoccurs.

Concaved roll—A work roll made to be of slight-ly smaller diameter toward the center than towardits ends at room temperature, to compensate foranticipated thermal expansion during rolling.

Continuous casting—Any process capable ofcasting a material into a continuously elongatingform without interruptions as long as the processis continued. See, also, Direct Casting.

Controlled-atmosphere annealing—Annealing carried out in a dry inert atmosphere,often nitrogen gas.

Cross rolling—Rolling ingot by feeding it intothe roll gap with its longest dimension parallel tothe roll axes; sometimes performed to widen thematerial before rolling it to its intended thicknessand length.

Crowned roll—A work roll made to be of slight-ly larger diameter toward the center than toward theends, to compensate for anticipated roll deflectionduring rolling.

Cryolite—The main component and solvent ofthe electrolytic bath in which aluminum oxide isdissolved in the Hall-Heroult aluminum produc-tion process; a mineral containing sodium alu-minum fluoride (Na3AlF6). It occurs naturally inGreenland, but most of the cryolite in commercialuse is produced synthetically.

Direct casting—In the context of plate and sheetproduction, any process in which molten metal iscast directly into a flat form, of sheet or platethickness; see also, “Roll Casting”, “Belt Casting”and “Block Casting.” Also known as “continuouscasting.”

Direct-chill (D-C) casting—A process for cast-ing ingots by pouring molten metal into a water-cooled mold collar whose floor is slowly with-drawn as the metal forms a solid shell, permittingthe casting of large, elongated ingots without thecomplete enclosure of a full-sized mold.

Drop—The shop term for the direct-chill castingof one or more rolling ingots in a set; that is, theresult of one lowering or “drop” of the hydrauliccylinder in the casting pit.

Ductility—The degree to which a metal or othermaterial may be deformed without breaking, aproperty important for forming during fabricationand for impact resistance in service; the oppositeof brittleness.

Electromagnetic casting—Metal casting inwhich an electromagnetic field is applied to con-tain molten metal and prevent it from physicallytouching mold walls while it solidifies; sometimesused in conjunction with “Direct-Chill Casting” toproduce ingots with particularly smooth, uniform-ly alloyed surfaces.

Flat rolling—A general term for the rolling of allflat products with uniform thickness, includingplate, sheet and foil.

Foil—A flat-rolled product rectangular in crosssection and form of thickness ≤ 0.0079 inch(<0.20 mm). (Note: Foil was previously definedas being <0.006 inch (0.15 mm thick.))

Four-high mill—A rolling mill which employsfour rolls: two work rolls, each supported by abackup roll.

Full annealing—Annealing performed above therecrystallization temperature for a long enoughtime to convert an alloy into its softest, mostductile, most workable condition, designated the“O-temper.”

Grain—A small region of solid metal withinwhich the atoms are arranged in a continuousuniform “lattice.”

“As-cast” grains form during crystallizationwhen molten metal solidifies.

“Deformed” grains, usually elongated,are formed during hot or cold working.

“Recrystallized” grains form duringannealing.

Hall-Heroult reduction process—The commoncommercial method of separating aluminum metalfrom its oxide (alumina). Invented in 1886 byCharles Martin Hall in the United States and PaulL.T. Heroult in France, it is based on the principleof dissolving aluminum oxide in molten cryolite

and separating the aluminum from oxygen byapplication of electric current.

Heat-treating—Heating and cooling a solidmetal or alloy in such a way as to obtain desiredconditions or properties. Commonly used as ashop term to denote a thermal treatment toincrease strength. Heating for the sole purposeof hot working (preheating) is excluded from themeaning of this definition. (See also, “Aging”,“Annealing”, “Partial Annealing”, “Stress Relief”and “Solution Heat Treating.”

Heat-treatable alloy—An alloy which may bestrengthened by a suitable thermal treatment.

Hot rolling—Rolling performed on metal at atemperature high enough to avoid strain-hardening.

Hot working—Plastic deformation of metal atsuch temperature and rate that strain hardeningdoes not occur.

Inclusion—Foreign material in the metal orimpressed into the surface.

Ingot, rolling—A thick cast form suitable forrolling.

Leveling—The application of controlled mechan-ical force to remove edge waves, pockets or otherflatness irregularities, yielding plate or sheetwhich is essentially flat.

Mill finish—The general-purpose surface finish,which meets most customer needs, produced bywork rolls surfaced mainly for effective thicknessreduction.

Mill, rolling—An installation consisting of a rollstand and its rolls and related equipment.

Natural aging—Precipitation from solid solutionat room temperature, resulting in a change inproperties of an alloy.

Non-heat-treatable alloy—An alloy which canbe strengthened only by cold work.

Nucleation—The formation of aggregates ofatoms which are stable enough to grow and formnew grains upon heating following deformation;the first stage in the process of recrystallization.

Partial annealing—Thermal treatment givencold worked metal to reduce strain-hardening toa controlled level.

Plate—A rolled product rectangular in cross sec-tion and form of thickness 0.250 inch (6.3 mm) ormore, with either sheared or sawed edges. (Note:When products are ordered to metric specifica-tions using metric dimensions, plate is definedas being > 6 mm thick.)

Pot—A single Hall-Heroult process “cell”: arefractory container holding alumina dissolved inmolten cryolite, through which electric current ispassed to produce aluminum metal.

Potline—A number of Hall-Heroult “pots”connected in series on the same electrical circuit.

Precipitation hardening—See “Aging.”

Pre-heating—A high temperature soaking treat-ment to provide a desired metallurgical structurein preparation for rolling. Homogenizing is a formof preheating.

Pure aluminum—In common industry parlance,“pure” aluminum refers to metal which is at least99.00 percent aluminum, as produced by standardcommercial methods. Aluminum of higher puritycan be produced by special processes.

Quenching—Cooling of a metal from an elevat-ed temperature by contact with a liquid, a gas, ora solid.

Recrystallization—The transformation of a cold-worked grain structure, at sufficiently high tem-peratures, into a soft metal structure with newgrains.

Recrystallization temperature—A temperatureabove which the formation of new grains within adeformed structure takes place; it is dependent onboth the amount of previous cold working and onthe annealing time.

Refined aluminum—Aluminum of very highpurity (99.950 percent or higher) obtained byspecial metallurgical treatments.

Reheating—Heating metal to hot-working tem-perature. In general no changes in metallurgicalstructure are intended by simple reheating.

� GLOSSARY 9-3

Reversing mill—A rolling mill which can rollplate or sheet on both directions by reversing therotation of its rolls between passes.

Roll caster—A device which directly producesplate or sheet by pouring molten metal into thegap between two cooled rolls where it solidifiesbefore emerging as a flat product. Some hot work-ing takes place as the solidified metal is rolledthrough the gap, but the product thickness isachieved mainly by the casting, not the rolling,process.

Roll gap—The space between work rolls whichdetermines the thickness of the rolled product.

Rolling—Passing a solid, ductile material betweentwo work rolls to reduce its thickness and/orimpart a desired surface finish.

Rolls—The round metal cylinders used for rolling.

Scalping—Machining the surface of an ingot toremove physical and/or metallurgical irregulari-ties.

Series, alloy—In most of the world, aluminumalloys are assigned four-digit identifying numberswhich group them in “series” according to theirmain alloying elements. Each series is identifiedby the first digit of the alloy number. For exam-ple, the “1xxx” (or “1000”) series includes alu-minum of 99 percent or higher purity; the “2xxx”series includes aluminum alloys in which copperis the principal alloying element; and so on.The alloy series are explained in “AluminumStandards and Data”, published by The AluminumAssociation. Other alloy identification systemsmay be used in some other countries. (See also,Technical Appendix A.)

Sheet—A rolled product rectangular in crosssection and form of thickness >0.0079 inch(over 0.20 mm) through 0.249 inch (6.3 mm), withsheared, slit or sawed edges. (Notes: When productsare ordered to metric specifications using metricdimensions, sheet is defined as being > 0.20 mmto ≤ 6 mm thick. Sheet was previously defined asbeing .006 to .249 inch (.15 to 6.3 mm) in thick-ness.)

Single-stand mill—A rolling mill with only one“stand” of rolls.

Slab—A semifinished product of rectangular

cross-section hot rolled from ingot to about fourinches thickness, suitable for further rolling.

Soak—In metallurgy, to maintain metal at a con-trolled elevated temperature for a sufficient timeto achieve the purposes of a thermal treatment.

Solution heat-treating—Heating an alloy at asuitable elevated temperature for sufficient time toallow soluble constituents to enter into solid solu-tion where they are retained in a supersaturatedstate after quenching.

Special tolerance—A tolerance other than“Standard.”

Stabilization annealing—Moderate-temperatureheating of certain non-heat-treatable aluminum-magnesium alloys to stabilize their cold-workedmechanical and dimensional properties.

Stand, rolling—A structure which supports andcontrols a set of rolls.

Standard Tolerances—Tolerances broadlyaccepted by the aluminum industry and users ofaluminum products as limits on acceptable devia-tions from nominal dimensions or other parame-ters. Standard tolerances are routinely appliedunless non-standard tolerances are specified byagreement between supplier and purchaser.Standard tolerances for aluminum rolled productsare presented in ANSI-H35.2, “American NationalStandard Dimensional Tolerances for AluminumMill Products”, and in “Aluminum Standards andData”, both published by The AluminumAssociation. (See also Technical Appendix D.)

Strain—A measure of the change in size or shapeof a body under stress, referred to its original sizeor shape.

Strain-hardening—Modification of a metalstructure by cold working resulting in an increasein strength and hardness with a corresponding lossof ductility.

Stress—Force per unit of area.

Stress relief—The reduction, by thermal ormechanical means, of internal residual stresses.

Stretcher-leveling—Flattening sheet or plate bymechanically gripping its ends and applying acontrolled amount of stretching.

Strip—Continuous sheet.

� GLOSSARY 9-4

Table rolls—motor-driven horizontal rollerswhich position an aluminum ingot or slab andtransport it to a mill’s work rolls.

Tandem mill—Multiple rolling stands arrangedin sequence and coordinated to apply successivethickness reductions to aluminum sheet during asingle pass through.

Temper—The combination of mechanical proper-ties, particularly strength, hardness and ductility,induced in a metal product by the thermal and/ormechanical treatments applied during its prepara-tion.

Tension leveling—Flattening sheet by controlledflexing: usually by passing it in tension over anadjustable roll.

Thermal treatment—A very general term mean-ing any treatment in which heat is applied, usuallyto alter the mechanical properties of solid metal; itincludes homogenizing or precipitation treatmentof ingots to affect finished grain size or someother property.

Tolerance—Allowable deviation from a nominalor specified dimension or other parameter: themaximum deviation that may be expected in anyindividual piece.

Two-high mill—A rolling mill employing only itstwo work rolls.

Ultrasonic inspection—The non-destructivetesting of rolled plate (or other products) by trans-mitting ultrasonic sound waves (frequencies abovehuman hearing) through the tested product.Electronic comparison of the time differencesbetween reflected waves can reveal internal flaws.

Work-harden—See “Strain-harden.”

Work rolls—In a rolling mill, the metal cylinderswhich grip the product, roll it between them andreduce its thickness.

Work—In metallurgy, to deform metal sufficient-ly to alter its metallurgical structure and conse-quently its mechanical properties.

Wrought product—A product which has beensubjected to mechanical working. Rolling produceswrought products.

� GLOSSARY 9-5

NOTES

� GLOSSARY 9-6GLOSSARY 9-6

� GLOSSARY 9-7

SELF-TEST QUESTIONSSECTION 9: GLOSSARY

9.1 An anode is…a.a negative electrical pole.b.a positive electric pole.c.a type of natural mineral formation.d.an alloy which has been annealed.

9.2 In aluminum rolling, “bite” means…a.the clamping action of a stretcher-

leveler.b. the cutting action of a slitter.c. the action of work rolls pulling metal

into the roll gap.d. the amount of thickness reduction

applied by a single mill stand.

9.3 “Controlled-atmosphere” annealingmeans carrying out the process…a. in a filtered natural-air atmosphere.b. in an oxygen-rich atmosphere.c. in a corrosive-gas atmosphere.d. in an inert-gas atmosphere.

9.4 “Ductility” means, roughly…a.tensile strength.b.ease of deformation.c.corrosion resistance.d.scratch-resistance.

9.5 In metallurgy, “grain” means…a.a hard particle trapped in an alloy.b.a rough pattern produced by

improper rolling.c.a small region of uniform crystalline

structure.d.a speck of metal that sticks to a work

roll.

9.6 In rolling, “mill finish” is…a.the final condition of all rolled prod-

ucts.b.a general-purpose surface that meets

most needs.c.a special surface finish requiring extra

steps.d. rolling by a five-stand tandem mill.

9.7 “Strain” means…a.amount of force applied.b.percentage of thickness reduction.c.percentage of elongation.d.amount of change in shape per unit

of stress.

9.8 “Stress” means…a.total amount of force applied.b.maximum force applied at any point.c. force applied per unit of area.d. force applied in tension.e. twisting force.

9.9 “Wrought” aluminum means a productwhich has been…a.cast under high pressure.b. solution heat treated and quenched.c.annealed in a controlled atmosphere.d.subjected to mechanical working.e. none of the above.

� GLOSSARY 9-8

� GLOSSARY 9-9

� GLOSSARY 9-10


Appendix A:Alloy and Temper Designation System

Alloy and Temper Designation Systems for Aluminum (ANSI H35.1-2006)

1. ScopeThis standard provides systems for designating

wrought aluminum and wrought aluminum alloys,aluminum and aluminum alloys in the form of castings and foundry ingot, and the tempers in whichaluminum and aluminum alloy wrought products andaluminum alloy castings are pro duced. Specific lim-its for chemical compositions and for mechanical andphysical properties to which conformance is requiredare provided by applicable product standards.

NOTE: A numerical designation assigned in con-formance with this stan dard should only be used toindicate an aluminum or an aluminum alloy havingchemical composition limits identical to those regis-tered with The Aluminum Association and, forwrought aluminum and wrought aluminum alloys,with the signatories of the Declaration of Accordon an International Alloy Designation System forWrought Aluminum and Wrought Aluminum Alloys.1

2. Wrought Aluminum and AluminumAlloy Designation System1

A system of four-digit numerical designations isused to identify wrought aluminum and wroughtaluminum alloys. The first digit indicates the alloygroup as follows:Aluminum, 99.00 percent and greater . . . . . . . . . . . . .1xxxAluminum alloys grouped bymajor alloying elements 2 3 4

Copper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2xxxManganese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3xxxSilicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4xxxMagnesium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5xxxMagnesium and silicon . . . . . . . . . . . . . . . . . . . . . . .6xxxZinc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7xxxOther element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8xxxUnused series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9xxx

The designation assigned shall be in the 1xxxgroup whenever the minimum aluminum content isspecified as 99.00 percent or higher. The alloy desig-nation in the 2xxx through 8xxx groups is deter-

mined by the alloying element (Mg2Si for 6xxxalloys) present in the greatest mean percentage,except in cases in which the alloy being registeredqualifi es as a modification or national variation ofa previously registered alloy. If the greatest meanpercentage is common to more than one alloyingelement, choice of group will be in order of groupsequence Cu, Mn, Si, Mg, Mg2Si, Zn or others.

The last two digits identify the aluminum alloy orindicate the aluminum purity. The second digit indicates modifications of the original alloy or impuritylimits.

1 Chemical composition limits and designations conforming to this standardfor wrought aluminum and wrought aluminum alloys, and aluminum andaluminum alloy castings and foundry ingot may be registered with TheAluminum Association provided: (1) the aluminum or aluminum alloy is offeredfor sale, (2) the complete chemical composition limits are registered, and(3) the composition is signifi cantly different from that of any aluminumor aluminum alloy for which a numerical designation already has beenassigned.2 For codification purposes an alloying element is any element that is inten-tionally added for any purpose other than grain refi nement and for whichminimum and maximum limits are specifi ed.3 Standard limits for alloying elements and impurities are expressed to thefollowing places:

Less than .001 percent . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.000X.001 but less than .01 percent . . . . . . . . . . . . . . . . . . . . . . 0.00X.01 but less than .10 percent

Unalloyed aluminum made by a refi ning process . . . . . 0.0XXAlloys and unalloyed aluminum not made by arefining process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.0X

.10 through .55 percent . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.XX(It is customary to express limits of 0.30 percent through 0.55 percent as 0.X0 or0.X5)

Over .55 percent 0.X, X.X, etc.(except that combined Si + Fe limits for 1xxx designations must be expressedas 0.XX or 1.XX)

4 Standard limits for alloying elements and impurities are expressed in the fol-lowing sequence: Silicon; Iron; Copper; Manganese; Magnesium; Chromium;Nickel; Zinc; Titanium (see Note 1); Other (see Note 2) Elements, Each; Other(see Note 2) Elements, Total; Aluminum (see Note 3).Note 1—Additional specifi ed elements having limits are inserted in alphabeti-cal order according to their chemical symbols between Titanium and OtherElements, Each, or are listed in footnotes.Note 2—“Other” includes listed elements for which no specifi c limit is shown aswell as unlisted metallic elements. The producer may analyze samples fortrace elements not specifi ed in the registration or specification. However,such analysis is not required and may not cover all metallic “other” elements.Should any analysis by the producer or the purchaser establish that an “other”element exceeds the limit of “Each” or that the aggregate of several “other”elements exceeds the limit of “Total”, the material shall be considered non-conforming.Note 3—Aluminum is specifi ed as minimum for unalloyed alu-minum, and as a remainder for aluminum alloys.

� APPENDIX A 10A-2

2.1 AluminumIn the 1xxx group for minimum aluminum puritiesof 99.00 percent and greater, the last two of the fourdigits in the designation indicate the minimum alu-minumpercentage.5 These digits are the same as thetwo digits to the right of the decimal point in theminimum aluminum percentage when it is expressedto the nearest 0.01 percent. The second digit in thedesignation indicates modifications in impurity limitsor alloying elements. If the second digit in the designa-tion is zero, it indicates unalloyed aluminum havingnatural impurity limits; integers 1 through 9, which areassigned con secutively as needed, indicate specialcontrol of one or more individual impurities or alloy-ing elements.

2.2 Aluminum AlloysIn the 2xxx through 8xxx alloy groups the last two ofthe four digits in the designation have no special sig-nificance but serve only to identify the different aluminum alloys in the group. The second digit in thealloy designation indicates alloy modifications. If thesecond digit in the designation is zero, it indicates theoriginal alloy; integers 1 through 9, which are assigned consecutively, indicate alloy modifications.A modification of the original alloy is limited to anyone or a combination of the following:

(a) Change of not more than the following amountsin arithmetic mean of the limits for an individualalloying element or combination of elementsexpressed as an alloying element or both.

Arithmetic Mean ofLimits for Alloying Maximum

Elements in Original Alloy ChangeUp thru 1.0 percent . . . . . . . . . . . . . . . 0.15Over 1.0 thru 2.0 percent . . . . . . . . . . 0.20Over 2.0 thru 3.0 percent . . . . . . . . . . 0.25Over 3.0 thru 4.0 percent . . . . . . . . . . 0.30Over 4.0 thru 5.0 percent . . . . . . . . . . 0.35Over 5.0 thru 6.0 percent . . . . . . . . . . 0.40Over 6.0 percent . . . . . . . . . . . . . . . . . 0.50

To determine compliance when maximum and mini-mum limits are specifi ed for a combination of twoor more elements in one alloy composition, the arith-metic mean of such a combination is compared to thesum of the mean values of the same individual ele-ments, or any combination thereof, in another alloycomposition.

(b) Addition or deletion of not more than one alloy-ing element with limits having an arithmetic meanof not more than 0.30 percent or addition or deletionof not more than one combination of elementsexpressed as an alloying element with limits havinga combined arithmetic mean of not more than 0.40percent.

(c) Substitution of one alloying element for anotherelement serving the same purpose.

(d) Change in limits for impurities expressed singlyor as a combination.

(e) Change in limits for grain refi ning elements.

(f ) Maximum iron or silicon limits of 0.12 percentand 0.10 percent, or less, respectively, reflecting useof high purity base metal.

An alloy shall not be registered as a modification if itmeets the requirements for a national variation.

2.3 Experimental AlloysExperimental alloys are also designated in accor-dance with this system, but they are indicated by theprefix X. The prefix is dropped when the alloy is nolonger experimental.

During development and before they are designatedas experimental, new alloys are identifi ed by serialnumbers assigned by their originators. Use of theserial number is discontinued when the X numberis assigned.

2.4 National VariationsNational variations of wrought aluminum andwrought aluminum alloys registered by another country in accordance with this system are identified by aserial letter following the numerical designation. Theserial letters are assigned internationally in alphabetical sequence starting with A but omitting I, O and Q.

A national variation has composition limits that aresimilar but not identical to those registered by another country, with differences such as:

5 The aluminum content for unalloyed aluminum made by a refining processis the difference between 100.00 percent and the sum of all other metallicelements plus silicon present in amounts of 0.0010 percent or more, eachexpressed to the third decimal before determining the sum, which is round-ed to the second decimal before subtracting; for unalloyed aluminum notmade by a refi ning process it is the difference between 100.00 percent andthe sum of all other analyzed metallic elements plus silicon present inamounts of 0.010 percent or more, each expressed to the second decimalbefore determining the sum. For unalloyed aluminum made by a refi ningprocess, when the specifi ed maximum limit is 0.0XX, an observed value or acalculated value greater than 0.0005 but less than 0.0010% is rounded offand shown as “less than 0.001”; for alloys and unalloyed aluminum notmade by a refi ning process, when the specifi ed maximum limit is 0.XX,an observed value or a calculated value greater than 0.005 but less than0.010% is rounded off and shown as “less than 0.01”.

(a) Change of not more than the following amountsin arithmetic mean of the limits for an individualalloying element or combination of elementsexpressed as an alloying element, or both:

Arithmetic Mean ofLimits for Alloying

Elements in Original MaximumAlloy or Modification Change

Up thru 1.0 percent . . . . . . . . . . . . . . . 0.15Up thru 1.0 percent.. . . . . . . . . . . . . . . 0.15Over 1.0 thru 2.0 percent . . . . . . . . . . 0.20Over 2.0 thru 3.0 percent . . . . . . . . . . 0.25Over 3.0 thru 4.0 percent . . . . . . . . . . 0.30Over 4.0 thru 5.0 percent . . . . . . . . . . 0.35Over 5.0 thru 6.0 percent . . . . . . . . . . 0.40Over 6.0 percent . . . . . . . . . . . . . . . . . 0.50

To determine compliance when maximum and mini-mum limits are specifi ed for a combination of twoor more elements in one alloy composition, thearithmetic mean of such a combination is comparedto the sum of the mean values of the same individualelements, or any combination thereof, in anotheralloy compo sition.

(b) Substitution of one alloying element for anotherelement serving the same purpose.

(c) Different limits on impurities except for low iron.Iron maximum of 0.12 percent, or less, reflectinghigh purity base metal, should be considered as analloy modification.

(d) Different limits on grain refining elements.

(e) Inclusion of a minimum limit for iron or silicon,or both.

Wrought aluminum and wrought aluminum alloysmeeting these requirements shall not be registered asa new alloy or alloy modification.

3. Cast Aluminum and AluminumAlloy Designation System 1

A system of four digit numerical designations isused to identify aluminum and aluminum alloys inthe form of castings and foundry ingot. The firstdigit indicates the alloy group as follows:

Aluminum, 99.00 percent minimum and greater . . .1xx.xAluminum alloys grouped by majoralloying elements 2 3 4

Copper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2xx.xSilicon, with added copper and/or magnesium .3xx.xSilicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4xx.xMagnesium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5xx.xZinc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7xx.xTin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8xx.xOther element. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9xx.x

Unused series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6xx.x

The alloy group in the 2xx.x through 9xx.x exclud-ing 6xx.x alloys is determined by the alloying ele-ment present in the greatest mean percentage, exceptin cases in which the alloy being registered qualified as a modifi cation of a previously registeredalloy. If the greatest mean percentage is common tomore than one alloying element, the alloy group willbe deter mined by the sequence shown above.

The second two digits identify the aluminum alloyor indicate the aluminum purity. The last digit,which is separated from the others by a decimalpoint, indicates the product form: that is, castings oringot. A modification of the original alloy or impuri-ty limits is indicated by a serial letter before thenumerical designation. The serial letters are assignedin alphabet ical sequence starting with A but omit-ting I, O, Q and X, the X being reserved for experimental alloys.

A modification of the original alloy is limited to anyone or a combination of the following:

(a) Change of not more than the following amountsin the arithmetic mean of the limits for an individualalloying element or combination of elementsexpressed as an alloying element or both:

Arithmetic Mean ofLimits for Alloying Maximum

Elements in Original Alloy ChangeUp thru 1.0 percent . . . . . . . . . . . . . . . . . .0.15Over 1.0 thru 2.0 percent . . . . . . . . . . . . .0.20Over 2.0 thru 3.0 percent . . . . . . . . . . . . .0.25Over 3.0 thru 4.0 percent . . . . . . . . . . . . .0.30Over 4.0 thru 5.0 percent . . . . . . . . . . . . .0.35Over 5.0 thru 6.0 percent . . . . . . . . . . . . .0.40Over 6.0 percent . . . . . . . . . . . . . . . . . . . .0.50

To determine compliance when maximum and minimum limits are specifi ed for a combination of twoor more elements in one alloy composition, thearithmetic mean of such a combination is compared


to the sum of the mean values of the same individualelements, or any combination thereof, in anotheralloy composition.

(b) Addition or deletion of not more than one alloy-ing element with limits having an arithmetic meanof not more than 0.30 percent or addition or deletionof not more than one combination of elementsexpressed as an alloying element with limits havinga combined arithmetic mean of not more than 0.40per cent.

(c) Substitution of one alloying element for anotherelement serving the same purpose.

(d) Change in limits for impurities expressed singlyor as a combination.

(e) Change in limits for grain refining elements.

(f ) Iron or silicon maximum limits of 0.12 percentand 0.10 percent, or less, respectively, reflecting useof high purity base metal.

3.1 Aluminum Castings and IngotIn the 1xx.x group for minimum aluminum puritiesof 99.00 percent and greater, the second two of thefour digits in the designation indicate the minimumaluminum percentage.5 These digits are the same asthe two digits to the right of the decimal point in theminimum aluminum percentage when it is expressedto the nearest 0.01 percent. The last digit, which is tothe right of the decimal point, indicates the productform: 1xx.0 indicates castings, and 1xx.1 indicatesingot.

3.2 Aluminum Alloy Castings and IngotIn the 2xx.x through 9xx.x alloy groups the secondtwo of the four digits in the designation have no special significance but serve only to identify the differ-ent aluminum alloys in the group. The last digit,which is to the right of the decimal point, indicatesthe product form: xxx.0 indicates castings, xxx.1indicates ingot that has chemical composition limitsconforming to 3.2.1, and xxx.2 indicates ingot thathas chemical composition limits that differ but fallwithin the limits of xxx.1 ingot.

3.2.1 Limits for alloying elements and impuritiesfor xxx.1 ingot are the same as for the alloy in theform of castings, except for the following:

Maximum Iron Percentage:For Sand and PermanentMold Castings For IngotUp thru 0.15 . . . . . . . . . . 0.03 less than castingsOver 0.15 thru 0.25. . . . . 0.05 less than castingsOver 0.25 thru 0.6. . . . . . 0.10 less than castingsOver 0.6 thru 1.0. . . . . . . 0.2 less than castingsOver 1.0 . . . . . . . . . . . . . 0.3 less than castings

For Die Castings For IngotUp thru 1.3 . . . . . . . . . . . 0.3 less than castingsOver 1.3 . . . . . . . . . . . . . 1.1 maximum

Minimum Magnesium Percentage:For All Castings For IngotLess than 0.50 . . . . . . . . . 0.05 more than castings*0.50 and greater . . . . . . . 0.1 more than castings*

Maximum Zinc Percentage:For Die Castings For IngotOver 0.25 thru 0.6. . . . . . 0.10 less than castingsOver 0.6 . . . . . . . . . . . . . 0.1 less than castings*Applicable only if the resulting magnesium range is 0.15 percent orgreater.

3.3 Experimental AlloysExperimental alloys are also designated in accor

dance with this system, but they are indicated by theprefix X. The prefix is dropped when the alloy is nolonger experimental.

During development and before they are designat-ed as experimental, new alloys are identified by seri-al numbers assigned by their originators. Use of theserial number is discontinued when the X number isassigned.


4. Temper Designation System6

The temper designation system is used for all formsof wrought and cast aluminum and aluminum alloysexcept ingot. It is based on the sequences of basictreatments used to produce the various tempers. Thetemper designation follows the alloy designation, thetwo being separated by a hyphen. Basic temper desig-nations consist of letters. Subdivisions of the basictempers, where required, are indicated by one or moredigits following the letter. These designate specificsequences of basic treatments, but only operationsrecognized as significantly influencing the character-istics of the product are indicated. Should some othervariation of the same sequence of basic operations beapplied to the same alloy, resulting in different char-acteristics, then additional digits are added to thedesignation.

4.1 Basic Temper DesignationsF as fabricated. Applies to the products of shap-

ing processes in which no special control overthermal conditions or strain hardening isemployed. For wrought products, there are nomechanical property limits.

O annealed. Applies to wrought products that areannealed to obtain the lowest strength temper,and to cast products that are annealed to improveductility and dimensional stability. The O may befollowed by a digit other than zero.

H strain-hardened (wrought products only).Applies to products that have their strengthincreased by strain-hardening, with or withoutsupplementary thermal treatments to producesome reduction in strength. The H is alwaysfollowed by two or more digits.

W solution heat-treated. An unstable temper

applicable only to alloys that spontaneously ageat room temperature after solution heat-treatment. This designation is specific only whenthe period of natural aging is indicated; forexample: W 1/2 hr.

T thermally treated to produce stabletempers other than F, O, or H. Applies toproducts that are thermally treated, with or withoutsupplementary strain-hardening, to produce stabletempers. The T is always followed by one ormore digits.

4.2 Subdivisions of Basic Tempers4.2.1 Subdivision of H Temper: Strain-hardened

4.2.1.1 The first digit following the H indi-cates the specific combination of basicoperations, as follows:

H1 strain-hardened only. Applies to productsthat are strain-hardened to obtain the desiredstrength without supplementary thermal treat-ment. The number following this designationindicates the degree of strain-hardening.

H2 strain-hardened and partially annealed.Applies to products that are strain-hardened morethan the desired final amount and then reduced instrength to the desired level by partial annealing.For alloys that age-soften at room temperature,the H2 tempers have the same minimum ultimatetensile strength as the corresponding H3 tempers.For other alloys, the H2 tempers have the sameminimum ultimate tensile strength as the corre-sponding H1 tempers and slightly higher elonga-tion. The number following this designation indi-cates the degree of strain-hardening remainingafter the product has been partially annealed.

H3 strain-hardened and stabilized. Appliesto products that are strain-hardened and whosemechanical properties are stabilized either by alow temperature thermal treatment or as a resultof heat introduced during fabrication.Stabilization usually improves ductility. This

Appendix BAluminum Temper Designation System

6 Temper designations conforming to this standard for wrought aluminumand wrought aluminum alloys, and aluminum alloy castings may be regis-tered with the Aluminum Association provided: (1) the temper is used or isavail able for use by more than one user, (2) mechanical property limits areregis tered, (3) the characteristics of the temper are significantly differentfrom those of all other tempers that have the same sequence of basic treat-ments and for which designations already have been assigned for the samealloy and product, and (4) the following are also registered if characteristicsother than mechanical properties are considered significant: (a) test meth-ods and limits for the characteristics or (b) the specific practices used to pro-duce the temper.


designation is applicable only to those alloysthat, unless stabilized, gradually age-soften atroom temperature. The number following thisdesignation indicates the degree of strainhardeningremaining after the stabilization treatment.

H4 strain-hardened and lacquered or paint-ed. Applies to products which are strain-hard-ened and which are subjected to some thermaloperation during the subsequent painting or lac-quering operation. The number following thisdesignation indicates the degree of strain-harden-ing remaining after the product has been thermal-ly treated, as part of painting/lacquering cureoperation. The corresponding H2X or H3Xmechanical property limits apply.

4.2.1.2 The digit following the designation H1, H2,H3, and H4 indicates the degree of strain-hardeningas identified by the minimum value of the ultimatetensile strength. Numeral 8 has been assigned to thehardest tempers normally produced. The minimumtensile strength of tempers HX8 may be determinedfrom Table 1 and is based on the minimum tensilestrength of the alloy in the annealed temper.However, temper registrations prior to 1992 that donot conform to the requirements of Table 1 shall notbe revised and registrations of intermediate or modi-fied tempers for such alloy/temper systems shallconform to the registration requirements that existedprior to 1992.

Table 1

US Customary UnitsMinimum tensile strength Increase in tensile strength

in annealed temper to HX8 temperksi ksi

up to 6 87 to 9 9

10 to 12 1013 to 15 1116 to 18 1219 to 24 1325 to 30 1431 to 36 1537 to 42 16

43 and over 17

Metric UnitsMinimum tensile strength Increase in tensile strength

in annealed temper to HX8 temperMPa MPa

up to 40 5545 to 60 6565 to 80 7585 to 100 85105 to 120 90125 to 160 95165 to 200 100205 to 240 105245 to 280 110285 to 320 115

325 and over 120

Tempers between O (annealed) and HX8 are desig-nated by numerals 1 through 7.

—Numeral 4 designates tempers whose ultimatetensile strength is approximately midwaybetween that of the O temper and that of theHX8 tempers;

—Numeral 2 designates tempers whose ultimatetensile strength is approximately midwaybetween that of the O temper and that of theHX4 tempers;

—Numeral 6 designates tempers whose ultimatetensile strength is approximately midwaybetween that of the HX4 tempers and that of theHX8 tempers;

—Numerals 1, 3, 5 and 7 designate, similarly,tempers intermediate between those definedabove.

—Numeral 9 designates tempers whose mini-mum ultimate tensile strength exceeds that of theHX8 tempers by 2 ksi or more. (For Metric Unitsby 10 MPa or more).

The ultimate tensile strength of the odd numberedintermediate (-HX1, -HX3, -HX5, and HX7) tem-pers, determined as described above, shall be round-ed to the nearest multiple of 0.5 ksi. (For MetricUnits when not ending in 0 or 5, shall be rounded tothe next higher 0 or 5 MPa.)

4.2.1.3 The third digit,7 when used, indicates a vari-ation of a two-digit temper. It is used when the degree of control of temper or the mechanical properties or both differ from, but are close to, that (orthose) for the two-digit H temper designation to

� APPENDIX B 10B-2

which it is added, or when some other characteristicis signifi cantly affected. (See Appendix for assignedthree-digit H tempers.) NOTE: The minimum ulti-mate tensile strength of a three-digit H temper mustbe at least as close to that of the corresponding two-digit H temper as it is to the adjacent two-digit Htempers. Products in the H temper whose mechani-cal properties are below H__1 shall be variations ofH__1.

4.2.2 Subdivision of T Temper:Thermally Treated4.2.2.1 Numerals 1 through 10 following the Tindicate specific sequences of basic treatments,as follows:8

T1 cooled from an elevated temperatureshaping process and nat urally aged toa substantially stable condition. Applies toprod ucts that are not cold worked after coolingfrom an elevated temperature shaping process, orin which the effect of cold work in flattening orstraightening may not be recognized in mechani-cal property limits.

T2 cooled from an elevated temperatureshaping process, cold worked, and nat-urally aged to a substantially stable con-dition. Applies to products that are cold workedto improve strength after cooling from an elevat-ed temperature shaping process, or in which theeffect of cold work in flattening or straighteningis recognized in mechanical property limits.

T3 solution heat-treated,9 cold worked, andnaturally aged to a substantially stablecondition. Applies to products that are coldworked to improve strength after solution heat-treatment, or in which the effect of cold work inflattening or straightening is recognized inmechanical property limits.

T4 solution heat-treated9 and naturally agedto a substantially stable condition. Appliesto products that are not cold worked after solu-tion heat-treatment, or in which the effect of coldwork in flattening or straightening may not berecognized in mechanical property limits.

T5 cooled from an elevated temperatureshaping process and then artificiallyaged. Applies to products that are not coldworked after cooling from an elevated tempera-

ture shaping process, or in which the effect ofcold work in flattening or straightening may notbe recognized in mechanical property limits.

T6 solution heat-treated9 and then artificiallyaged. Applies to products that are not coldworked after solution heat-treatment, or in whichthe effect of cold work in flattening or straight-ening may not be recognized in mechanicalproperty limits.

T7 solution heat-treated9 and overaged/stabi-lized. Applies to wrought products that are artificially aged after solution heat treatment to carrythem beyond a point of maximum strength toprovide control of some significantcharacteristic10. Applies to cast products that areartifi cially aged after solution heat-treatment toprovide dimensional and strength stability.

T8 solution heat-treated,9 cold worked, andthen artificially aged. Applies to productsthat are cold worked to improve strength, or inwhich the effect of cold work in flattening orstraightening is recognized in mechanical prop-erty limits.

T9 solution heat-treated,9 artificially aged,and then cold worked. Applies to productsthat are cold worked to improve strength.

T10cooled from an elevated temperatureshaping process, cold worked, and thenartificially aged. Applies to products that arecold worked to improve strength, or in which theeffect of cold work in flattening or straighteningis recognized in mechanical property limits.


7 Numerals 1 through 9 may be arbitrarily assigned as the third digit and reg-istered with the Aluminum Association for an alloy and product to indicate avariation of a two-digit H temper (see note Y).

8 A period of natural aging at room temperature may occur between orafter the operations listed for the T tempers. Control of this period is exercisedwhen it is metallurgically important.

9 Solution heat treatment is achieved by heating cast or wrought productsto a suitable temperature, holding at that temperature long enough to allowconstituents to enter into solid solution and cooling rapidly enough to holdthe con stituents in solution. Some 6xxx series alloys attain the same specifiedmechanical properties whether furnace solution heat treated or cooled froman elevated temperature shaping process at a rate rapid enough to holdcon stituents in solution. In such cases the temper designa tions T3, T4, T6, T7,T8, and T9 are used to apply to either process and are appropriate designa-tions.

10 For this purpose, characteristic is something other than mechanical prop-erties. The test method and limit used to evaluate material for this character-istic are specifi ed at the time of the temper registration

4.2.2.2 Additional digits,11 the first of which shallnot be zero, may be added to designations T1through T10 to indicate a variation in treatmentthat significantly alters the product characteristicsthat are or would be obtained using the basictreatment. (See Appendix for specific additionaldigits for T tempers.)

4.3 Variations of O Temper: Annealed4.3.1 A digit following the O, when used, indi-cates a product in the annealed condition havingspecial characteristics.

NOTE: As the O temper is not part of the strain-hardened (H) series, variations of O temper shallnot apply to products that are strain-hardened afterannealing and in which the effect of strain-harden-ing is recognized in the mechanical properties orother characteristics.

A1 Three-Digit H TempersA1.1 The following three-digit H temper designa-tions have been assigned for wrought products inall alloys:H_11 Applies to products that incur sufficient strain

hardening after the final anneal that they failto qualify as annealed but not so much or soconsistent an amount of strain hardening thatthey qualify as H_1.

H112 Applies to products that may acquire sometemper from working at an elevated tempera-ture and for which there are mechanical prop-erty limits.

A1.2 The following three-digit H temper designa-tions have been assigned forpattern or

embossed sheet fabricated fromH114 O temperH124, H224, H324 H11, H21, H31 temper, respectivelyH134, H234, H334 H12, H22, H32 temper, respectivelyH144, H244, H344 H13, H23, H33 temper, respectivelyH154, H254, H354 H14, H24, H34 temper, respectivelyH164, H264, H364 H15, H25, H35 temper, respectivelyH174, H274, H374 H16, H26, H36 temper, respectivelyH184, H284, H384 H17, H27, H37 temper, respectivelyH194, H294, H394 H18, H28, H38 temper, respectivelyH195, H295, H395 H19, H29, H39 temper, respectively

A1.3 The following three-digit H temper designa-tions have been assigned only for wrought prod-ucts in the 5xxx series, for which the magnesiumcontent is 3% nominal or more:

H116 Applies to products manufactured from alloysin the 5xxx series, for which the magnesiumcontent is 3% nominal or more. Products arestrain hardened at the last operation to specified stable tensile property limits and meetspecified levels of corrosion resistance inaccelerated type corrosion tests. They are suit-able for continuous service at temperature nogreater than 150°F (66°C). Corrosion testsinclude inter-granular and exfoliation.

H321 Applies to products from alloys in the 5xxxseries, for which the magnesium content is 3%nominal or more. Products are thermally stabi-lized at the last operation to specified stabletensile property limits and meet specified lev-els of corrosion resistance in accelerated typecorrosion tests. They are suitable for continu-ous service at temperatures no greater than150°F (66°C). Corrosion tests include inter-granular and exfoliation.

A2 Additional Digits for T TempersA2.1 The following specific additional digits havebeen assigned for stress-relieved tempers ofwrought products:Stress relieved by stretching.T_51 Applies to plate and rolled or cold-finished

rod or bar, die or ring forgings and rolled ringswhen stretched the indicated amounts aftersolution heat treatment or after cooling froman elevated temperature shaping process. Theproducts receive no further straightening afterstretching.Plate . . . . . . . . . . .1.5% to 3% permanent set.Rolled orCold-FinishedRod and Bar . . . . . .1% to 3% permanent set.Die or RingForgings andRolled Rings . . . . . .1% to 5% permanent set.

T_510 Applies to extruded rod, bar, profiles (shapes)and tube and to drawn tube when stretched theindicated amounts after solution heat treatmentor after cooling from an elevated temperatureshaping process. These products receive no fur-ther straightening after stretching.Extruded RodBar, Profiles (Shapes)and Tube . . . . . . . . .1% to 3% permanent set.Drawn Tube . . . . .1/2% to 3% permanent set.


11Additional digits may be arbitrarily assigned and registered with TheAluminum Association for an alloy and product to indicate a variation oftempers T1 through T10 even though the temper representing the basic treat-ment has not been registered (see note 6). Variations in treatment that donot alter the characteristics of the product are considered alternate treat-ments for which additional digits are not assigned.

T_511 Applies to extruded rod, bar, profiles (shapes)and tube and to drawn tube when stretched theindicated amounts after solution heat treat-ment or after cooling from an elevated tem-perature shaping process. These products mayreceive minor straightening after stretching tocomply with standard tolerances.Extruded Rod,Bar, Profiles (Shapes)and Tube . . . . . . . . .1% to 3% permanent set.Drawn Tube . . . . .1/2% to 3% permanent set.

Stress relieved by compressing.

T_52 Applies to products that are stress-relieved bycom pressing after solution heat treatment orcooling from an elevated temperature shapingprocess to produce a per manent set of 1 per-cent to 5 percent.

Stress relieved by combined stretching andcompressing.

T_54 Applies to die forgings that are stress relievedby restriking cold in the finish die.

NOTE: The same digits (51, 510, 511, 52, 54) may beadded to the designation W to indicate unsta-ble solution heat-treated and stress-relievedtempers.

A2.2 Temper Designations forProducer/Supplier LaboratoryDemonstration of Response toHeat-treatment:The following temper designations have been assigned for wrought products test material, furnaceheat-treated from annealed (O, O1, etc.) or F tem-per, to demonstrate response to heat-treatment.

T42 Solution heat-treated from annealed or Ftemper and naturally aged to a substantial-ly stable condition.

T62 Solution heat-treated from annealed or Ftemper and artificially aged.

T7_2 Solution heat-treated from annealed or Ftemper and artificially overaged to meetthe mechanical properties and corrosionresistance limits of the T7_ temper.

A2.3 Temper Designations forProducer/Supplier Demonstration ofResponse to Temper Conversion:Temper designation T2 shall be used to indicatewrought product test material, which has under-gone furnace heat-treatment for capability demon-stration of temper conversion. When the purchaserrequires capability demonstrations from T-temper,the seller shall note “Capabilitiy Demonstration”adjacent to the specified and ending tempers.Some examples are:

• “-T3 to -T82 Capability Demonstration forresponse to aging”;

• “-T4 to -T62 Capability Demonstration forresponse to aging”;

• “-T4 to -T762 Capability Demonstration forresponse to overaging”;

• “-T6 to -T732 Capability Demonstration forresponse to overaging”;

• “-T351 to -T42 Capability Demonstration forresponse to re-solution heat-treatment”.

A2.4 Temper Designation forPurchaser/User Heat-treatmentTemper designation T2 should also be applied towrought products heat-treated by the purchaser/user, in accordance with the applicable heattreatment specification, to achieve the propertiesapplicable to the final temper.

A3 Assigned O Temper VariationsA3.1 The following temper designation has beenassigned for wrought products high temperatureannealed to accentuate ultrasonic response andprovide dimensional stability.

O1 Thermally treated at approximately same timeand temperature required for solution heat treatmentand slow cooled to room temperature. Applicableto products that are to be machined prior tosolution heat treatment by the user. Mechanicalproperty limits are not applicable.


A4 Designation of UnregisteredTempersA4.1 The letter P has been assigned to denote H,T and O temper variations that are negotiatedbetween manufacturer and purchaser. The letter Pimmediately follows the temper designation thatmost nearly pertains. Specific examples wheresuch designation may be applied include the fol-lowing:

A4.1.1 The use of the temper is sufficiently limit-ed so as to preclude its registration. (Negotiated Htemper variations were formerly indicated by thethird digit zero.)

A4.1.2 The test conditions (sampling location,number of samples, test specimen configuration,etc.) are different from those required for registra-tion with The Aluminum Association.

A4.1.3 The mechanical property limits are notestablished on the same basis as required for reg-istration with The Aluminum Association.

A4.1.4 For products such as Aluminum MetalMatrix Composites which are not included in anyregistration records.


� APPENDIX A 10B-7

� APPENDIX A 10B-8

Metallurgical AspectsIn high-purity form aluminum is soft and ductile.Most commercial uses, however, require greaterstrength than pure aluminum affords. This isachieved in aluminum first by the addition ofother elements to produce various alloys, whichsingly or in combination impart strength to themetal. Further strength ening is possible by meansthat classify the alloys roughly into two cate-gories, non-heattreatable and heat-treatable.

Non-heat-treatable alloys—The initialstrength of alloys in this group depends upon thehardening effect of elements such as manganese,silicon, iron and mag nesium, singly or in variouscombinations. The non-heat-treatable alloys areusually designated, there fore, in the 1xxx, 3xxx,4xxx, or 5xxx series. Since these alloys are work-hard enable, further strength ening is made possi-ble by various degrees of cold working, denotedby the “H” series of tempers. Alloys containingappreciable amounts of magnesium when suppliedin strain-hardened tempers are usually given afinal elevated-temperature treatment called stabi-lizing to ensure stability of properties.

Heat-treatable alloys—The initial strength ofalloys in this group is enhanced by the additionof alloying elements such as copper, magnesium,zinc, and silicon. Since these elements singly or invarious combinations show increasing solid solu-bility in aluminum with increasing temperature,it is possible to subject them to thermal treatmentsthat will impart pronounced strengthening.

The first step, called heat treatment or solutionheat treatment, is an elevated-temperature processde signed to put the soluble element or elementsin solid solution. This is followed by rapidquenching, usually in water, which momentarily“freezes” the structure and for a short time rendersthe alloy very workable. It is at this stage thatsome fabricators retain this more workable struc-ture by storing the alloys at be low freezing tem-peratures until they are ready to form them. Atroom or elevated temperatures the alloys are notstable after quenching, however, and precipitationof the constituents from the super-saturated solu-

tion begins. After a period of several days at roomtemperature, termed aging or room-temperatureprecipita tion, the alloy is considerably stronger.Many alloys approach a stable condition at roomtemperature, but some alloys, particularly thosecontaining magnesium and silicon or magnesiumand zinc, continue to age-harden for long periodsof time at room temperature.

By heating for a controlled time at slightly elevat-ed temperatures, even further strengthening is pos-sible and properties are stabilized. This process iscalled artificial aging or precipitation hardening.By the proper combina tion of solution heat treat-ment, quenching, cold working and artificialaging, the highest strengths are obtained.

Clad alloys—The heat-treatable alloys in whichcopper or zinc are major alloying constituents areless resistant to corrosive attack than the majorityof non-heat-treatable alloys. To increase the corro-sion resis tance of these alloys in sheet and plateform, they are often clad with highpurity alu-minum, a low magnesium-silicon alloy, or analloy containing 1 percent zinc. The cladding,usually from 2.5 percent to 5 percent of the totalthickness on each side, not only protects the com-posite due to its own inherently excellent corro-sion resistance but also exerts a galvanic effect,which further protects the core material.

Special composites may be obtained such asclad nonheat-treatable alloys for extra corrosionprotection, for brazing purposes, or for specialsurface finishes. Some alloys in wire and tubularform are clad for similar reasons, and on an exper-imental basis extrusions also have been clad.

Annealing characteristics—All wrought alu-minum alloys are available in annealed form. Inaddition, it may be desirable to anneal an alloyfrom any other initial temper, after working, orbetween successive stages of working such as indeep drawing.

Effect of Alloying Elements1xxx series—Aluminum of 99 percent or higherpurity has many applications, especially in the


Appendix C:Typical Aluminum Alloy Properties

electrical and chemical fields. These compositionsare characterized by excellent corrosionresistance, high thermal and electrical conductivi-ty, low mechanical properties and excellent work-ability. Moderate increases in strength may beobtained by strain-hardening. Iron and silicon arethe major impurities.

2xxx series—Copper is the principal alloyingelement in this group. These alloys require solu-tion heat-treatment to obtain optimum properties;in the heat treated condition mechanical propertiesare similar to, and sometimes exceed, those ofmild steel. In some instances artificial aging isemployed to further increase the mechanical prop-erties. This treatment materially increases yieldstrength, with attendant loss in elongation; itseffect on tensile (ultimate) strength is not so great.The alloys in the 2xxx series do not have as goodcorrosion resistance as most other aluminumalloys, and under certain conditions they may besubject to intergranular corrosion. Therefore, thesealloys in the form of sheet are usually clad with ahigh-purity alloy or a magnesium-silicon alloy ofthe 6xxx series, which provides galvanic protec-tion to the core material and thus greatly increasesresistance to corrosion. Alloy 2024 is perhaps thebest known and most widely used aircraft alloy.

3xxx series—Manganese is the major alloyingele ment of alloys in this group, which are gener-ally non-heattreatable. Because only a limitedpercentage of manganese, up to about 1.5 percent,can be effectively added to aluminum, it is used asa major element in only a few instances. One ofthese, however, is the popular 3003, which iswidely used as a general purpose alloy for moder-ate-strength applications re quiring good worka-bility.

4xxx series—The major alloying element of thisgroup is silicon, which can be added in sufficientquantities to cause substantial lowering of themelting point without producing brittleness in theresulting alloys. For these reasons aluminum-sili-con alloys are used in welding wire and as brazingalloys where a lower melting point than that of theparent metal is required. Most alloys in this seriesare non-heat-treatable, but when used in weldingheattreatable alloys they will pick up some of the

alloying constituents of the latter and so respondto heat treatment to a limited extent. The alloyscontaining appreciable amounts of silicon becomedark grey when anodic oxide finishes are applied,and hence are in demand for architectural applica-tions.

5xxx series—Magnesium is one of the mosteffective and widely used alloying elements foraluminum. When it is used as the major alloyingelement or with manganese, the result is a moder-ate to high strength non-heat-treatable alloy.Magnesium is considerably more effective thanmanganese as a hardener, about 0.8 percent mag-nesium being equal to 1.25 percent manganese,and it can be added in considerably higher quanti-ties. Alloys in this series possess good weldingcharacteristics and good resistance to corrosion inmarine atmosphere. However, certain limitationsshould be placed on the amount of cold work andon the safe operating temperatures permissible forthe higher magnesium content alloys (over about3.5 percent for operating temperatures aboveabout 150°F) to avoid susceptibility to stresscorrosion.

6xxx series—Alloys in this group contain siliconand magnesium in approximate proportions toform magnesium silicide, thus making them heat-treatable. The major alloy in this series is 6061,one of the most versatile of the heat-treatablealloys. Though less strong than most of the 2xxxor 7xxx alloys, the magnesium-silicon (or magne-sium-silicide) alloys possess good formability andcorrosion resistance, with medium strength.Alloys in this heat-treatable group may be formedin the T4 temper (solution heat-treated but notartificially aged) and then reach full T6 propertiesby artificial aging.

7xxx series—Zinc is the major alloying elementin this group, and when coupled with a smallerpercentage of magnesium results in heat-treatablealloys of very high strength. Usually other ele-ments such as copper and chromium are alsoadded in small quantities. The outstanding mem-ber of this group is 7075, which is among thehighest strength alloys available and is used inair-frame structures and for highly stressed parts.

APPENDIX C 10C-2

The following typical properties are not guaran-teed, since in most cases they are averages forvarious sizes, product forms and methods of man-ufacture and may not be exactly representative of

any particular product or size. These data areintended only as a basis for comparing alloys andtempers and should not be specified as engineer-ing requirements or used for design purposes.

� APPENDIX C 10C-3

2. Typical Properties

TABLE 2.1 Typical U.S. Mechanical Properties1,2

For all numbered footnotes, see page 10C-6.




TABLE 2.1 Typical U.S. Mechanical Properties1,2 (continued)


� APPENDIX A 10C-5





TABLE 2.1 Typical U.S. Mechanical Properties1,2 (continued)






TABLE 2.1 Typical Mechanical Properties1,2 (concluded)

� APPENDIX A 10C-8 � APPENDIX C 10C-8



TABLE 2.3 Typical Physical Properties


� APPENDIX A 10C-9� APPENDIX C 10C-9



TABLE 2.3 Typical Physical Properties (concluded)




TABLE 2.1m Typical Metric Mechanical Properties1,2





TABLE 2.1m Typical Metric Mechanical Properties1,2 (continued)





TABLE 2.3m Typical Metric Physical Properties1,2





TABLE 2.3m Typical Metric Physical Properties1,2 (concluded)


TABLE 3.3 Comparative Characteristics and Applications



TABLE 3.3 Comparative Characteristics and Applications (continued)



TABLE 3.3 Comparative Characteristics and Applications (concluded)

To ensure high-quality products with dependableproperties and dimensions, the aluminum indus-

try has developed and adheres to standard limitsand tolerances which are routinely applied to alu-minum plate, sheet and foil (and other wroughtproducts).

These standards represent, for each of thetoleranced characteristics, the range within whichthe relevant product is to be produced. In mostinstances, actual deviation from nominal dimen-sions is even smaller than the standard toleranceswould allow.

If non-standard tolerances are desired, theymust be negotiated specifically between vendorand purchaser.

Adherence to these product standards is volun-tary, but they are broadly accepted by both the alu-minum industry and its customers and often formthe basis of tolerances incorporated in government,technical society and other specifications.

Standard Dimensional Tolerances

The Aluminum Association developed the indus-try's first standard dimensional tolerances, for

extruded and tubular products, in 1949 and thenexpanded its efforts, publishing its first standardsfor aluminum mill products in 1955.

In 1970, at the request of the AluminumAssociation, the American National StandardsInstitute (ANSI) authorized establishment ofStandards Committee H35 on Aluminum andAluminum Alloys, which was redesignated in1983 as the Accredited Standards Committee onAluminum and Aluminum Alloys H35. It includesrepresentatives of various branches of the alu-minum industry, aluminum-using industries andthe United States Government.

ANSI itself does not develop or interpret suchstandards; it accredits standards and revisionsafter verifying that they have been developedthrough appropriate consensus procedures.

The standard dimensional tolerances applied toaluminum sheet and plate include:

� Thickness.

� Width, sheared flat sheet and plate.

� Width and length, sawed flat sheet and plate.

� Length, sheared flat sheet and plate.

� Width, slit coiled sheet.

� Lateral bow, coiled sheet.

� Lateral bow, flat sheet and plate.

� Squareness, flat sheet and plate.

� Diameter, sheared or blanked sheet andplate circles.

� Diameter, sawed sheet and plate circles.

� Flatness, flat sheet.

� Flatness, sawed or sheared plate.

� Thickness, for sheet and plate for aerospacealloys.

Standard tolerances are also provided foraluminum duct sheet, commercial roofing andsiding, tread plate, and foil.

These tolerance tables are presented in:“American National Standard DimensionalTolerances for Aluminum Mill Products”,ANSI-H35.2 and “American National StandardDimensional Tolerances for Aluminum MillProducts (Metric)”, ANSI-H35.2M, TheAluminum Association.

Standard limits on Non-DimensionalProperties

The Aluminum Association also issues “StandardLimits” applied voluntarily to non-dimensional

properties of aluminum sheet, plate, and otherwrought products, in its publications “AluminumStandards and Data” and “Aluminum Standardsand Data Metric SI”(Technical Publication #1).

These standards include:

� Chemical composition limits of wroughtaluminum alloys.

� Ultrasonic discontinuity limits.

� Lot acceptance criteria for corrosion resistanttempers.

� Location for electrical conductivity measurements.

APPENDIX D:Aluminum Sheet & Plate Tolerances


� Fracture toughness limits.

� Corrosion resistance test criteria.

� Mechanical property limits- non-heat-treatablealloys (sheet and plate).

� Mechanical property limits- heat-treatablealloys (sheet and plate).

� Mechanical property limits- brazing sheet.

� Weights per square foot (by sheet thickness).

� Weight (/density) conversion factors (by alloy)

� Recommended minimum bend radii for 90-degree cold forming of sheet and plate.

Always Refer toMost Recent Revisions

Both the US customary and metric editions of“Aluminum Standards and Data” (ASD) are

periodically updated, revised and republished byThe Aluminum Association. In addition to TheAluminum Association’s non-dimensional stan-dards for wrought aluminum, ASD reprints theANSI standard dimensional tolerances which may,however, be revised between updates of ASD; inthose circumstances, the latest official ANSI-H35standards take precedence over any earlier ver-sions still in circulation.

Therefore, readers who wish to make use of thestandards currently in effect are advised to refer tothe most recent editions of “American NationalStandard Dimensional Tolerances for AluminumMill Products (ANSI-H35.2)” (or the metric ver-sion ANSI-H35.2M) for sheet, plate and foildimensional tolerances; and “AluminumStandards and Data” for non-dimensional wroughtaluminum standards.

These publications are available from TheAluminum Association’s on-linebookstore atwww.aluminum.org .

� APPENDIX D 10D-2

10.1 “Wrought aluminum alloys and castaluminum alloys share the same alloydesignation numbering system.” Thisstatement is:a. true.b. false.

10.2 The aluminum temper designationsystem uses…a.only letters of the alphabet.b.only numbers.c. letters followed by numbers.d.numbers followed by letters.

10.3 The initial symbols of aluminum temperdesignations are…a.1, 2, 3, 4, 5b.A, B, C,D,Ec.A,S,D,F,Gd.F,O,H,W,Te. the last line of a doctor’s eye chart.

10.4 Alloy 1199 contains a minimum of…a.99.00% aluminum.b.99.90% aluminum.c. 99.99% aluminum.

10.5 Typical yield strength of alloy 2024-O is…a.11 ksi (76 MPa)b.20 ksi (138 MPa)c. 26 ksi (179 MPa)

10.6 Name five Standard DimensionalTolerances applied to aluminum sheetand plate.

APPENDIX E: SELF-TESTQuestions for Technical Appendices


SECTION 1: INTRODUCTION1.1 Lightweight; strong; cold-resistant;

ductile and workable; joinable; reflec-tive; heat-conducting; electricallyconducting; corrosion resistant; non-toxic; noncombustible; recyclable.

1.2 b.1.3 c.1.4 d.1.5 c.1.6 b.1.7 See Sec.11.8 See Sec.11.9a c.1.9b a.1.10a b.1.10b c.1.11 c.Because flat-rolled aluminum

products less than .008-inch thickare defined as foil.

1.12 d.1.13 d.1,14 c.1.15 b.1.16 c.

SECTION 2: PRODUCTION2.1 a.2.2 c.2.3 a.2.4 b.2.5 c.2.6 c.2.7 b.2.8 b and/or c.2.9 d.2.10 b.

2.11 f.2.12 c.2.13 b.2.14 b.2.15 c.2.16 a.2.17 d.2.18 a.2.19 b.2.20 b.2.21 c.2.22 d.2.23 a.2.24 b.2.25 e.2.26 b.2.27 b.2.28 a.2.29 e.

SECTION 3: PREPARATION3.1 b.3.2 c.3.3 b.3.4 b.3.5 c.3.6 e.3.7 b.3.8 Titanium, or boron salts.3.9 c.3.10 c.3.11 b.3.12 d.3.13 c.3.14 d.

APPENDIX F: ANSWERSTo Self-Test Question


3.15 a.3.16 f.3.17 c.3.18 b.

SECTION 4: ROLLING MILL4.1 c.4.2 a.4.3 e.4.4 f.4.5 b.4.6 d.4.7 b.4.8 c.4.9 b and c.4.10 a.4.11 a.4.12 c.4.13 d.4.14 c.

SECTION 5: SHEET ROLLING5.1 b.5.2 d.5.3 c.5.4 c.5.5 b. Because friction in the roll gap

prevents the slab from spreading.5.6 d.5.7 b.5.8 c.5.9 d.5.10 b and d.5.11 a and d.5.12 b.5.13 Annealed.5.14 a.5.15 c.5.16 c.5.17 a.

5.18 b.5.19 c.5.20 a.5.21 Strength, temper, thickness, finish,

flatness, and profile.5.22 c.5.23 Roll tilting; roll crossing; localized roll

cooling; roll-bending; stepped backuprolls; axial shifting of sleeved backuprolls; axial shifting of cylindrical workrolls; axial shifting of non-cylindricalwork rolls; flexible backup rolls.

5.24 a.

SECTION 6: SHEET FINISHING6.1 c.6.2 b.6.3 b.6.4 a.6.5 b.6.6 b.6.7 b.6.8 Mechanical finishes, chemical finishes,

and coatings.6.9 c.

SECTION 7: PLATE ROLLING ANDFINISHING7.1 d.7.2 a.7.3 c.7.4 b.7.5 b.7.6 d.7.7 b.7.8 a.7.9 a.

SECTION 8: QUALITY AND PROCESSCONTROL8.1 c.8.2 b.

� APPENDIX F 10F-2

8.3 d.8.4 d.8.5 a.8.6 c.

SECTION 9: GLOSSARY9.1 b.9.2 c.9.3 d.9.4 b.9.5 c.9.6 b.9.7 d.9.8 e.9.9 d.

SECTION 10:TECHNICALAPPENDICES10.1 b.10.2 c.10.3 d.10.4 c.10.5 a.10.6 See Appendix D.

� APPENDIX F 10F-3

Altenpohl, D., “Aluminum: Technology,Applications and Environment”, 1998.

“Aluminum Statistical Review for 2005”, TheAluminum Association, Arlington, VA, 2005.

“Aluminum Standards and Data 2006”, TheAluminum Association, Arlington, VA, 2006.

“Aluminum Standards and Data 2006 MetricSI”, The Aluminum Association, Arlington, VA,2006.

“American National Standard DimensionalTolerances for Aluminum Mill Products”,ANSI-H35.2-2006, The Aluminum Association,Arlington, VA.

“American National Standard DimensionalTolerances for Aluminum Mill Products(Metric)”, ANSI-H35.2M-2006, The AluminumAssociation, Arlington, VA.

Anderson, M., Bruski, R., Groszkiewicz, D. andWagstaff, R.B., “NetCast Shape Casting tech-nology: A Technological Breakthrough thatEnhances the Cost Effectiveness of AluminumForgings,” Light Metals 2001, TMS, pp. 847-853.

ASM, Metals Handbook, 9th ed., 1981,vol. 4, pp. 675...

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Atack, P.A., Round, P.F., and Wright, L.C., “AnAdaptive Scheduling and Control System fora Single Stand Reversing Mill for Hot Rolling ofAluminum”, Proceedings of the Seminar onRolling Mill Gauge Shape/Profile, June 8-9,1988, Atlanta, Ga., The Aluminum Association.

Bachowiski, Ronald; O' Mally, R.J.; andMohajery, M.M., “Continuous Casters forAluminum Mini-Sheet Mills-an AlcoaPerspective”, Light Metal Age, August 1989.

Barten, Axel E., “Experience With Optiroll MillControl Systems”, Proceedings of the Seminaron Rolling Mill Gauge Shape/Profile, June 8-9,1988, Atlanta, GA, The AluminumAssociation.

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Black, Philip B., “Laser Flatness Gauging Hotand Cold Mills”, Proceedings of the Seminaron Rolling Mill Gauge/Shape Profile, June 8-9,1988, Atlanta, Ga., The AluminumAssociation.

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the Fourth Int’l Aluminum Extrusion TechnologySeminar, 1988, pp. 79-84.Church, Fred L., “Rolling mill improvementsgroomed for quality not tons”, ModernMetals, April 1989.Davis, J.L., and Levy, S.A., “Sub-SurfaceStructure of As-Cast LHC Slabs,” Alumitech1997, pp. 730-744, The Aluminum Association.Davis, J.L., Wagstaff, R.B. and Shaber, C.,“Developments in LHC Casting of WroughtAlloys,” Proceedings of the Fifth AustralasianPacific Conference on Aluminum Cast HouseTechnology, Theory and Practice, 1997, pp.253-269.Dunn, J. H., and Sewell, L.S., Jr., “HistoricalDevelopment of Aluminum Production andApplication”, in “Aluminum”, vol. 2, ed. DentR. Van Horn, American Society for Metals,1967.Emond, C., and Weaver, C., “An AluminumPlug with Multiple Holes for Self-Draining SheetIngot Stoolcaps,” Light Metals 1994, pp. 821-825.Farley, T.W.D., Nardini, D., Rogers, S. andWright, D.S., “An Approach to UnderstandingMill Vibrations”, Aluminum 2002 – Proceedingsof the TMS 2002 Annual Meeting: AutomotiveAlloys and Aluminum Sheet and Plate Rollingand Finishing Technology Symposia, TMS, 2002Forster, B.J., and Tucker, D., “ Advances in Hotand Cold Rolling Flatness Control ThroughEffective Roll Cooling Processes”, Aluminum2002 – Proceedings of the TMS 2002 AnnualMeeting: Automotive Alloys and AluminumSheet and Plate Rolling and FinishingTechnology Symposia, TMS, 2002Fusada, Tamotsu, “The Advanced QualityRolls for Aluminum Rolling Mills”, inProceedings, Seminar on Rolling AssemblyTechnology, Nov. 4-5, 1987, Chicago, TheAluminum Association.Ginzburg, Vladimir B., Bakhtar, Fereidoon,Tabone, Charles J., “Strip Profile and FlatnessAnalysis in Application to Rolling of Aluminumand Steel”, Proceedings of the Seminar onRolling Mill Gauge Shape/Profile, June 8-9,1988, Atlanta, GA, The Aluminum Association.Grealy, G.P., Davis, J.L., Jensen, K., Tøndel,P.A. and Moritz, J., “ Advances for DC IngotCasting: Part 1 - Introduction and Metal

Distribution,” Light Metals 2001, pp. 805-811.Grealy, G.P., Davis, J.L., Jensen, K., Tøndel,P.A. and Moritz, J., “ Advances for DC IngotCasting: Part 2 – Heat Transfer and CastingResults,” Light Metals 2001, pp. 813-821.Hegmann, W., “Aluminum WorkshopPractice”, English ed., edited and revised byA.W. Brace; Techicopy Limited, Gloucester,England, 1978.“Kaiser Aluminum Sheet and Plate ProductInformation”, 2nd ed., 1953; Kaiser Aluminum& Chemical Sales, Inc., Chicago, Ill.Keevil, David J., “Aluminum”, WorldResources, 1980.Kumar, Surinder, “Overview of a Rolling Mill”,in Proceedings, Workshop onCharacterization and Control of AluminumCold Rolling Mill Emissions, Nov. 16-17, 1983,Clarksville, IN, The Aluminum Association.Nirtanda, Masao: “High Crown Control Millwith Taper Piston Roll”, Proceedings of theSeminar on Rolling Mill Gauge/Shape Profile,June 8-9,1988, Atlanta, GA, The AluminumAssociation.Odok, Adnan M., and Gyongyos, Ivan:“Alusuisse Caster I and Caster II”, Light MetalAge, Dec. 1975.Outhwaite, Stephen J.; and Gouel, Roland:“Radiation Thickness Gauging of Aluminum”,Proceedings of the Seminar on Rolling MillGauge/Shape Profile, June 8-9, 1988, Atlanta,GA, The Aluminum Association.Petry, C.J., “The Hazelett Twin Belt Caster”,Light Metal Age, Dec.1975.Petry, Charles J. and Szczypiorski, Wojtek:“Update on Continuous Casting of AluminumAlloys by the Twin-Belt Process”, Light MetalAge, Aug, 1986.Platek, Stanley and Desautels, S. Jerry, “TheContinuous Casting and Direct Rolling ofWide, Thin Slab into Hot Band by BarmetAluminum Corporation using SecondaryOperations and Hazelett Technology”, AIME –February 1990 – Anaheim, CARitzmann, Henry W., “Cleaning of AluminumHot Mill Work Rolls With Cylindrical Brushes”, inProceedings, Seminar of Rolling AssemblyTechnology, Nov, 4-5, 1987. Chicago; TheAluminum Association.

� REFERENCES 11-2

“Rolling Mills, Rolls, and Roll Making”,Mackintosh-Hemphill Company, Pittsburgh,PA, 1953.Schmiedberg, W.F., “Developments inEquipment to Improve Gauge, Shape andProfile Control for Aluminum Mills (Hot &Cold)”, Proceedings of the Seminar on RollingMill Gauge/Shape Profile, June 8-9, 1988,Atlanta, GA, The Aluminum Association.Shaber, C. and Spilker, D., “Wagstaff EpsilonIngot Casting Technology: IngotCharacteristics and Metallurgical Structure,”Aluminium Cast House Technology – EighthAustralasian Conference, TMS, 2003, pp. 285-299.Shaber, C., “Wagstaff Epsilon Ingot CastingTechnology: Making Casting Easier,” 3rdInternational Melt Quality Workshop, 2005.Steer, David E. and Adams, Neil, “TorringtonBack-up Bearings for Precision Rolling Mills”,in Proceedings, Seminar on Rolling AssemblyTechnology, Nov. 4-5, 1987, Chicago; TheAluminum Association.Szczypiorski, Wojtek and Szczypiorski, Renata,“The Mechanical and MetallurgicalCharacteristics of Twin-Belt Cast AluminumStrip using current Hazelett Technology”,AIME – February, 1991 – New OrleansSzczypiorski, Wojtek, “Importance of Hazelettcaster Belt Coatings”, Light Metals 1994, TMSSzczypiorski, Wojtek and Szczypiorski, Renata,“Elimination of Surface Streaking on FinishedSheet Cast on Hazelett Casters”, The RollingTechnology Sessions at Alumitech ’94, TheAluminum Association 1994Vasily, George, “The Hunter ContinuousCasting Process”, Light Metal Age, Oct, 1975.“Visual Quality Characteristics of AluminumSheet and Plate” (QCA-1), 2002, TheAluminum Association, Arlington, VA.von Gal, Reed, “Twin-Belt Aluminum Casting-A Technology Which Has Come of Age”,Light Metal Age, April 1989.von Gal, Reed, “The Aluminium Sheet Mill forthe New Millennium”, ALUMINIUM, Vol. 76(2000) 12Wagstaff, F.E., “An Enhanced CoolingTechnique for Air Cushion Hot Top BilletCasting,” Proceedings of the 4th Int’l

Aluminum Extrusion Technology Seminar, 1988,pp. 75-78Wagstaff, R.B., and Ekenes, J.M., “Innovationsin Hard Alloy Hot Top Casting Systems,”Proceedings of the 5th Int’l AluminiumExtrusion Technology Seminar, 1992, pp. 39-48.Wagstaff, R.B., Bowles, K.D., and Allen,Jeff,“Enhanced Cooling Technique for Rollingand Extrusion Ingot,” Proceedings of 4thAustralasian Asian Pacific Conference onAluminium Cast House Technology,” TMS,1995, pp. 317-330.Wagstaff, R.B. and Bowles, K.D., “PracticalLow Head Casting (LHC) Mold for AluminiumIngot Casting,” Light Metals 1995, TMS, pp.1071-1075.

� REFERENCES 11-3

Actuators 5-9Additives (pre-casting) 3-3Age-softening 5-7Aging 2-6, 6-3, 9-1, 9-3, 10B-1, 10b-3, 10B-5,10C-1, 10C-2Alclad 1-5, 8-2, 9-1Alloys 1-1, 1-2, 2-1, 2-5, 2-6, 2-7, 2-10, 3-1, 3-3,3-4, 3-7, 3-8, 3-9, 4-4, 4-7, 4-9, 5-6, 5-7, 5-8, 5-9,5-12, 6-1, 6-2, 6-3, 7-1, 7-2, 7-3, 8-2, 9-4, 10A-1,10B-1, 10B-2, 10B-4, 10C-1-19, 10D-1-2, 10E-1,11-1-2, 12-1-3Alloy designations 2-5, 10A, 10BAlloy series 2-5, 2-10, 9-4Alloy structure, metallurgy 6-1Alloy analysis 3-1Alloying 2-5, 2-7Alumina 2-1, 2-2, 2-3, 2-9, 3-2, 9-1-4Aluminum oxide 2-1-3, 2-9, 4-3, 9-1-3Aluminum, properties of:See “Properties of aluminum”Annealing 1-4, 2-6, 2-10, 4-7, 4-9, 5-6, 5-8, 5-11-12, 6-1-7, 9-1-4, 9-7, 10B-1, 10B-4, 10C-1Anode 2-3, 9-1, 9-7Anodizing 1-2, 8-2, 9-1ANSI 8-2, 9-1, 9-4, 10A-1, 10D-1-2, 11-1Applications (of sheet, plate and foil) 1-1, 1-2Artificial aging 2-6, 6-3, 7-3, 9-1Back-up rolls 4-1, 4-2, 4-4, 4-6, 5-1, 5-2, 5-9, 9-1Bar-coding (of sheet and plate) 6-5Batch annealing/treatment 5-7Bauxite 2-1, 2-9, 9-1Bayer Process 2-1, 2-9, 9-1Belt caster 3-4, 9-1Bite 4-3, 5-2, 5-3, 9-1, 9-7Block caster 3-5, 9-1Brazeability 10C-15Breakdown mill 5-1--3, 7-1, 9-1Bright-dipping 8-2, 9-1Casting 3-3, 9-1Centralized controls 8-3Chemical (surface) finishes 6-4Chlorine (fluxing) 3-1Cluster mill 4-5-6, 5-11

Coatings (sheet and plate) 6-5Coiling 4-1, 5-5Cold rolling 3-8, 4-6, 5-8, 7-1, 9-2Cold rolling, metallurgy 4-7Cold strength: See “Cryongenic”Cold-working 9-2Computer 3-2, 4-2, 8-3Computer Integrated Manufacturing (CIM)1-6, 8-3, 8-5Concaved roll 4-4, 9-2Conductivity, electrical 1-1, 10C-7Conductivity, thermal 1-1, 10C-7Continuous casting 3-3, 9-2Controlled-atmosphere annealing 5-7, 9-2Coolant/lubricant 4-1-4, 5-2, 5-5, 5-8, 5-9Coolant/lubricant analysis 8-2Coring (of alloy grains) 3-8Corrosion resistance 1-1, 1-5, 2-5, 5-12, 6-3-4,10B-4, 10C-15Cross-rolling 5-3, 5-11, 9-2Crowned roll 4-3--4, 9-2Cryogenic 1-1Cryolite 2-2, 2-3, 2-9, 9-2, 9-3Cutting-to-length 6-5DC casting: See “Direct-chill casting”Degreasing (of sheet and plate) 6-5Direct-chill (DC) casting 3-3, 3-4, 3-6-8, 9-2Dislocation, lattice 4-7, 6-1Drive motors 4-1Drive spindles 4-1, 4-9Drop 3-6, 8-5, 9-2Ductility 1-1, 4-7, 6-3, 9-2, 9-4-5, 9-7, 10C-3Edge-trimming 3-7, 5-5, 7-1, 7-3Electrical resistivity 10C-7Electromagnetic casting (EMC) 3-7, 9-2Embossing 5-10, 6-5EMC: See “Electromagnetic casting”Enrichment zone 3-6Fatigue strength 10C-3Filtration 3-1--2, 3-9Finishes, surface 6-4Finishing (sheet) 6-1

INDEX12Rolling Aluminum:From the Mine through the Mill

Finishing, plate 7-1Flatness 4-1, 4-4, 5-9, 6-4, 7-1-2, 8-2Flat-rolled products 1-2, 1-4Flat-rolled shipments 1-2Flat-rolling 9-2Fluxing 3-1Flying shears 6-5Foil applications 1-2Foil definition 1-4, 9-2Foil 1-2, 1-4, 1-5, 1-7, 2-7, 3-4, 5-8, 8-3, 9-2Four-high mill 1-6, 4-2, 4-4, 4-5, 5-1, 9-2Full annealing 5-6, 9-2Gauge control 1-6, 5-8Gearboxes 4-1, 4-2Glide planes 4-7Grain 3-8-9, 4-7, 5-7, 8-1, 9-2Grain refiner (additive) 3-3Hall-Heroult Process 1-4, 1-8, 2-2, 2-4, 2-9, 9-2Hardness 2-6, 4-3, 5-7, 6-3, 7-5, 8-5, 9-4, 10C-3Heat-treatable alloys 2-5-6, 5-6, 6-1, 9-3, 10C-1Heat-treatment 2-6, 6-1, 6-3, 9-3High-voltage spark spectrometer 3-2Homogenization 3-3, 3-8, 9-3Hot rolling metallurgy 4-7Hot rolling 3-3-4, 3-8, 3-10, 4-7, 4-9, 5-3, 9-3Hot working 3-3, 9-3-4Hydrogen (gas) 2-5, 2-9, 2-11, 3-1-2, 3-9Inclusions 3-2, 3-9, 7-5, 8-1Ingot 2-7, 3-2-4, 3-6-8, 5-1, 5-3, 8-5, 9-3Ingot casting 3-3, 3-4Intermediate edge trimming 7-1Intermediate hot-rolling 5-3Joinability 1-1Just-In-Time (JIT) 1-6, 8-3Lattice, crystal 4-7, 6-1Leveling 1-4, 6-4, 6-6, 9-3Lubricant: See “Coolant/lubricant”Machinability 10C-15Mechanical 10C-3Mechanical (surface) finishes 6-4Melting point (and solution heat treatment)6-2Melting ranges 10C-7Microscopic inspection 8-1Mill, rolling 9-3Mill finish 4-3, 4-9, 8-2, 9-3

Mill stand 4-1, 5-1, 5-9. 9-7Mining 2-1, 2-2Modulus of elasticity 10C-3Multiple-stand mill: See “Tandem mill”Natural aging (See also “Aging”) 2-6, 6-3, 7-3,9-3Nitrogen (fluxing) 3-1Nitrogen (gas) 5-7Non-combustibility 1-1Non-heat-treatable alloys 2-6, 9-3, 10C-1Non-toxicity 1-1Nucleation 3-3, 9-3Oiling (of sheet and plate) 6-5One-side-bright mill finish 8-2Ore (of aluminum): See “Bauxite”Over-aging 6-3Packaging 1-1, 1-2, 6-6Partial annealing 5-6, 5-7, 9-3Pinning (of lattice dislocations) 6-2, 6-3Plate finishing 7-1Plate rolling 7-1Plate definition 1-4, 9-3Plate 1-2, 1-4Plate applications 1-2Porosity testing 8-1Pot (Hall-Heroult process) 2-2, 2-3, 9-3Potline 2-2, 2-3, 9-3Precipitates 3-8, 6-2-3, 9-1Precipitation hardening: See “Aging” 9-3Precipitation heat treatment:

See “Artificial aging”Pre-heating (of ingot) 3-5, 9-3Process control 1-6, 5-7. 8-1, 8-3, 8-5Profiles 5-9Properties, typical, of aluminum alloys 10C-1Physical 2-5, 4-1, 4-4, 7-2, 8-3, 9-4, 10C-7Property tables 10C, 10C-3Pure aluminum 2-5, 2-7, 2-9, 5-8, 9-3, 10C-1Quality control 1-6, 8-1Quenching (plate) 7-2Quenching 6-1, 6-2, 7-2, 9-3Recrystallization 5-6, 9-3Recrystallization temperature 3-8, 5-6, 5-12, 9-3Recyclability 1-1Recycling 2-5, 2-7Reduction (of alumina):

� INDEX 12-2

See “Hall-Heroult Process”Refined aluminum 9-3Reflectivity 1-1Reheating 3-4, 7-1, 9-3Reversing mill 4-4, 5-1, 5-4, 9-4, 11-1Roll 1-5, 1-6, 4-3, 5-9, 9-4Roll caster 3-4, 3-9, 9-4Roll gap 3-4, 4-1-3, 4-9, 5-1, 5-3, 5-5, 5-9-11, 9-3Roll coating 4-3Roll configurations 4-4Roll benders 4-1, 5-9Rolled-to-temper 5-7Rolling (general description) 1-4, 9-3Rolling aluminum, history 1-4Rolling aluminum, technological advances 1-5Rolling mill, general 4-1, 5-1Scalping 1-4, 3-3, 3-6-7, 3-10, 9-4Segregation 3-3, 3-8Series (alloy) 2-5, 10C-1Shear strength 10C-3Strength 1-1, 4-7Sheet applications 1-2Sheet rolling 1-6, 4-4, 5-1-11, 10F-2Sheet definition 1-4, 9-4Sheet hot rolling 5-4Sheet annealing/treatment 5-7Sheet 1-2, 1-4Shrinkage gap 3-6-7Single-stand mill 4-3, 5-1, 5-8, 9-4Skin-quality finish 8-2Slab 9-4Slab reheating 7-1Slab casting 3-4Slitting 1-4, 6-4Soak (definition) 9-4Soaking (solution heat treatment) 6-2Soaking (heat) 3-5Soaking pit 3-8Solid solubility 2-6, 6-2, 6-7,10C-1Solid solution 3-8, 5-7, 6-3, 9-1, 9-3, 9-4Solution heat treatment 1-4, 5-6, 6-2, 6-7, 7-2,9-4Special tolerance 9-4Spheroidizing 3-8Stabilization (anneal) 5-7, 9-4

Stand, rolling 9-4Standard bright finish 8-2Standard Tolerances: See “Tolerances” 9-4Statistical Process Control (SPC) 1-6, 8-3, 8-5Stenciling (of sheet and plate) 6-5Storage 6-5-6, 7-3, 8-2Strain-hardening 2-6, 3-8, 4-6-7, 4-9, 5-7, 9-4Strength 1-1, 4-7Stress-relief 5-7, 7-2, 9-4Stress-relief (stretching) 7-2Stretcher-leveling 6-6, 9-4Stretching (plate) 7-2Strip 1-6, 3-3-4, 5-4, 5-8, 5-9, 6-3, 6-4, 9-4Strip casters 3-4Surface quality 4-3, 8-2Surface finishes 5-8, 6-4, 10C-1Table rolls 5-3, 5-11, 9-5Tandem mill 4-3, 5-4, 5-5, 5-8-11, 9-5, 9-7Temper 2-6, 4-7, 5-2, 5-6-8, 5-12, 6-3, 6-5,9-2, 9-5, 10A-1, 10B-1Temper designations 10B-4, 10C-1, 10E-1Tensile strength testing 8-1Tensile strength 2-6, 8-1, 9-7, 10B-1-3, 10C-3Thermal expansion coefficients 10C-7Tension-leveler 6-4, 9-5Testing/Inspection 7-2-3, 8-1Texturing 5-10Thermal treatment 9-1, 9-3, 9-4, 9-5, 10B-1Titanium (titanium diboride) additive 3-3Tolerances 4-1, 8-2, 8-5, 9-1, 9-4, 9-5, 10B-5,10D-1-2, 11-1Two-high mill 1-6, 4-4, 4-5, 9-5Typical Properties, tables (aluminum alloys)10CUltrasonic inspection 7-2, 8-1, 9-5Weight 1-1, 1-7, 2-1, 2-9, 3-3, 10D-2Weldability 10C-15Workability 1-1, 10C-2, 10C-15Walking-beam furnace 3-8Work (definition) 9-5Work hardening 4-7, 5-6, 5-8, 5-11, 9-2Work rolls 1-6, 3-9, 4-1-4, 4-6, 4-9, 5-1-3, 5-8-11,6-4, 8-2, 9-5, 9-7, 10F-2, 11-2Wrought product (definition) 9-5

� INDEX 12-3

� INDEX 12-4

rolling aluminum: from the mine through the mill

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