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THE ALUMINUM EXTRUSION PROCESSBEGINS WITH ALUMINUMAluminum is the most abundant mineral in the earth's crust. In nature, however, it does not occurin its pure form, so must be extractedand refined to be put to use.

Although its use has been traced to300 B.C., it was not until 1886 that aneconomically feasible process wasdeveloped for commercial production of aluminum. Withindays of each other, two inventors--

Aluminum Extrusion Manual 3-1

THE ALUMINUM EXTRUSIONPROCESS

Section

3

The extrusion process allows designers andengineers an almost limitless number ofconfigurations and complex shapes, includ -ing this awning bracket (above left) whichreplaced a three-piece assembly. Aluminumextrusion was also chosen for this modular ,demountable interior wall system (aboveright) because it offers a noncor rosive natural finish, as well as nonmagnetic properties. Aluminum's lightweightstrength, durability, and cor rosion resistanceoffer the transportation industry manyadvantages, as seen in the aluminum bodyshell (below) for Danish inter-city trains.

3-2Section 3 Extrusion Process

Charles Martin Hall in the U.S. andPaul Heroult in France--working inde-pendently and completely unaware ofone another's work, each discoveredthe basic process by which aluminumis still produced today.

Aluminum is the lightweight, high-strength metal of choice for thousands of products. This recyclable, environmentally friendlymaterial is refined from bauxite toproduce alumina. It is then "smelted"through an electrolytic and chemicalprocess that generates heat and pro-duces molten aluminum. Other ele-ments are mixed with the aluminumto produce alloys required for mostapplications. It is then cast into ingotor log form.

Aluminum extrusion is the most inno-vative forming process for this versa-tile metal, allowing designers to exer-cise their creativity and stretch theirimaginations to design profiles thatmeet their exact, specialized needs.

Like toothpaste, the aluminum is notliquid, but rather a malleable solid atthe time of extrusion.

Unlike a simple tube of toothpaste, an aluminum extrusion press is comprised of many different partswhich function together .

THE ALUMINUM EXTRUSION PRESSThe basic principle of extrusion is assimple--and complex--as squeezingtoothpaste out of a tube.

Pressure applied at the closed end ofthe toothpaste tube forces the paste toflow through the open end.

The shape, or profile, of the paste as itemerges reflects the shape of theopening through which it has beenforced. Simple openings produce sim-ple shapes; complex openings pro-duce complex shapes.

The pressure in an extrusion press isapplied by a hydraulic ram, which usesfrom 100 tons to 15,000 tons or moreof force to push heated aluminumthrough the container and out thedie. The amount of force an extrusion press is able to exert dictatesthe size of the profiles it is capable ofproducing. The higher the tonnageof the press, the larger the possibleextrusion. The container of the extru-sion press is a hollow chamber con-structed of steel and generally fittedwith a removable liner. The containerhas an inside diameter just slightlylarger than the billet to be extruded,and holds and confines the billet dur-ing the extrusion cycle.

The die is a steel disk at the end ofthe container; aluminum is forcedthrough the opening(s) in the die tocreate the extruded product.

Aluminum extrusion dies are availablein three basic categories: solid, semi-hollow, and hollow. The namesdescribe the shape of the extruded profiles, and each category has specif-ic applications and advantages. (For amore detailed explanation of dies anddie categories, refer to Section 5,Extrusion Dies.)

3-3Aluminum Extrusion Manual

Solid dies have one or more openings, and produce extrusions without anyenclosed internal voids. The opening in a solid die has the exact cross-sectional profile of the extruded shape. Solid dies are used primarily inthe production of bars, channels and angles, as well as many customshapes.

Semihollow dies produce shapes that include partially enclosed voids with"open" profiles. The void has an area which is generally in a ratio ofthree-to-one larger than the tongue of the die. (See Section 5 for a mor edetailed explanation of semihollow dies.) Semihollow dies are used mostoften in the production of atypical channels and other custom shapes.

Hollow dies produce shapes that include an entirely enclosed internalvoid and have "closed" profiles. Hollow dies require two components, adie cap and a mandrel section, in order to produce required shapes.Hollow dies produce tubes and many custom hollow shapes.

AluminumBillet

Die Plate

Mandrel Section

Cap Section

AluminumBillet

Semi-Hollow

Backer

Solid

ExtrudingDirection

AluminumBillet

Mandrel Section

Cap Section

Hollow

ExtrudingDirection

ExtrudingDirection

INTRODUCTIONThere are three basic types of extrusion dies: solid dies, semihollowdies, and hollow dies, which producesolid profiles, semihollow profiles,and hollow profiles, respectively.

Extrusion dies are essentially thick,circular steel disks containing one ormore orifices of the desired profile.They are normally constructed fromH-13 tool steel and heat-treated tothe desired condition.

In a typical extrusion operation, theextrusion die will be placed in theextrusion press along with severalsupporting tools. These tools, alsomade from hardened tool steel, areknown as backers, bolsters and sub-bolsters. The backer, bolster, andsub-bolster provide support for thedie during the extrusion process andcontribute to improved tolerancecontrols and extrusion speeds.

A tool stack for a hollow die is similarto that used for a solid die. A hollowdie is a two-piece construction, onepiece forming the inside of the hollow profile and the other pieceforming the outside of the profile. It likewise requires the use of additional support tools.


EXTRUSION DIES

Section

5

A Solid Profile

A HollowProfile

A SemihollowProfile

5-2

SOLID DIESSolid dies are used to produce profiles that do not contain anyvoids. Various styles of solid dies areused, depending on the equipmentand manufacturing philosophy of theextruder. Some prefer to use flat-facestyle dies while others prefer to userecessed pocket or weld-plate styledies. A pocket die has a cavity slight-ly larger than the profile itself,approximately to deep. Thiscavity helps control the metal flowand allows the billets to be weldedtogether to facilitate the use of apuller. Both pocket and weld-platetype dies provide for additional metalflow control, compared to that of the flat-face type die.

Section 5 Extrusion Dies

A Typical Die Tooling Arrangement

This six-hole solid die will extrude six separate profiles simultaneously .

Bolster

Platen

ExtrusionBacker

Die

Die Ring

Billet

Stem

Liner

Die SlidePressure

RingContainer

Horse Shoe

Backer

Die

Direction ofExtrusion

Die Slide

Dummy Block

A weld plate is a steel disk that isplaced (often pinned and/or bolted)in front of a solid die. It has an orifice that controls the flow of aluminum to the die orifice. Weld orfeeder plates serve to provide continuous extrusion from one billetto the next, and/or control contour,and/or spread the aluminum.


Four-Hole Pocket Die

Solid Die with Feeder Plate (Typical Die Tooling Arrangement)



Backer

Die

Pocket

Bolster

Backer

Die

Feeder

A feeder plate, such as this, is used to spread the aluminum toneeded areas when the circle size of a profile is larger than 90 per -cent of the billet diameter .

A feeder plate,in this example, is used tocontrol contour for dies that requir especial dimensional tolerances.

5-4Section 5 Extrusion Dies

10-DegTaper

30-DegRelief

FeederPlate

Die Plate

Section A-A

Section A-A

5-DegRelief

5-DegRelief

FeederPlate

.500 Deep Pocket

Bearing

Die Plate

EntranceSide

Direction of Extrusion

A

A A

A

Cross Sectionof Web

Weld Chamberhalf in feederhalf in dieplate

A feeder plate, as shown, is used to weld billets together. The first billet is pushedthrough the die stack. All subsequent billetsweld together, allowing continuous extrusion,which facilitates the use of modern materialhandling equipment.

15-DegRelief

FeederPlate

Die Plate


AA

Section A-A


HOLLOW DIESA hollow die produces profiles withone or more voids. The profile couldbe as simple as a tube with one voidor as complex as a profile with manydetailed voids.

The most common type of hollow dieis the porthole die, which consists ofa mandrel and cap section; it may ormay not have a backer.

The mandrel, also known as the core,generates the internal features of theprofile. The mandrel has two ormore ports; the aluminum billet sepa-rates into each port and rejoins inthe weld chamber prior to enteringthe bearing area. The ports are separated by webs, also known aslegs, which support the core or mandrel section.

The cap, which creates the externalfeatures of the profile, is assembledwith the mandrel.

The backer, when used, provides critical tool support and is immedi-ately adjacent to, and in direct contact with, the exit side of the cap.

A pancake hollow die makes use of a backer in the tool stack, while aporthole die may not.

A porthole hollow die.

Bolster

Backer

Die Cap w/pocket

Die MandrelDie CapBacker

Die Mandrel

Bolster

Die Cap w/pocket

Die Mandrel Direction ofExtrusion


5-6Section 5 Extrusion Dies

In this example of porthole-type design, the die“tongue” is bolted to the weld plate for additionalsupport.

SEMIHOLLOW DIESA semihollow die is used to produceprofiles having semihollow character-istics as defined in AluminumStandards and Data(published by TheAluminum Association, Inc.). Briefly,a semihollow profile partially enclos-es a void; however, a solid shape alsomay partially enclose a void, and thedistinction may not be obvious. Thesemihollow classification derives froma mathematical comparison betweenthe area of the partially-enclosed voidand the mathematical square of thesize of the gap. This ratio(Area/Gap2) is called the tongueratio.

Depending on the tongue ratio, semihollow dies can be constructedas flat, recessed-pocket, weld-plate, orporthole design. Porthole dies aremore prevalent in the production of semihollow profiles.

A

A

Entrance Side

5-DegRelief

FeederPlate

Weld Chamber

Bearing

DiePlate


Section A-A

PracticesTo ensure high levels of quality control and product performance,the design should incorporate thepractices that best meet the eco-nomic and critical specifica-tions of the product.AssemblyThe aluminum profileis normally a part ofa more complexstructure, offer-ing theopportunityfor efficientassembly applica-tions in the design.

FabricationAluminum extru-sions adaptthemselvesto a variety offabricationprocesses which cantake advantage of theinherent characteristics ofaluminum and the designadvantages of the extrusionprocess to meet the criteriarequired for the final product.

EconomicsBoth on a direct and indirect basis,economics of the finished productcan be enhanced through creativedesigns utilizing aluminum extru-sions. Aluminum is readily recycled,thus reducing life-cycle costs;aluminum is lightweight, thus reducing shipping costs.

DESIGN DECISION -- WHY USE ALUMINUMEXTRUSION?

When there is no limit except your imagination, just think of the possibilities.

By offering designers a near netshape of their choice, in a timelymanner, through a relatively low-costprocess, aluminum extrusions areunrivaled among structural materialsfor design selection. From ideathrough design, to the production ofthe die ...through extrusion, fabrica-tion, and final finish... by providingthe end product with aluminumextrusion, you can design exactly theshape you need and let the produc-tion process serve you. Consider themany valuable characteristics of alu-minum and the versatility of theextrusion process.

FunctionThe first consideration in design,function is the key to successful formand fit within the component's actualuse.

AdvantagesAluminum profiles offer a number ofdesign advantages by virtue of theextrusion process itself.

ParametersThe design must dictate the envelopewithin which the aluminum extrusioncan provide the greatest benefit.


DESIGNING WITHALUMINUM EXTRUSIONS

Section

6

Function

Practices

Parameters

Assembly

Advantages

Economics

Fabrication

DESIGN DECISION --FUNCTIONDesigners are encouraged to explorethe vast opportunities availablethrough the use of aluminum extrusions and to set high expectations for the performance ofextruded aluminum components andend products. Of course, it is thenthe designer's challenge to figure outwhat it takes to meet these key criteria. From a functional perspective, it is important to askwhat it is you want the part to do, notwhat the part should look like. Inconsidering function, prepare a listof the following:

•What are the parts' essential functions?

•What essential shapes and dimensions do these functions require?

•How do these essential elements relate to each other?

•What secondary functional elements are necessary to connect, support, or strengthen the overall component?

•What other critical elements exist that may effect the final product?

Modeling Programs to Assist in DesignFinite Element Analysis is a modelingmethod for optimizing a design tohave minimal weight and cost, whilefully understanding how the designbehaves in operation.

Thermal Analysis is a modelingmethod by which to pre-determinejunction temperature based on sur-roundings to develop the optimumplan for heat transfer.

Structural Analysis is a modelingmethod used to identify the points ofstress and strain based on materialused, the supporting points, the loadapplied, and the contact points. 6-2Section 6 Designing

Gold 14.7 $4,767.28 0.003Silver 20.2 74.21 0.272Zinc 5.4 .795 6.792 ALUMINUM 9.7 .762 12.733Copper 18.7 .988 18.927

Note: * Cost may vary depending on the metal market values.

Thermal Conductivity for Various Metals

Pure Metal Thermal

Conductivity Est

Cost/PoundRelative

Performance

Through Finite Element Analysis, designers can getthe design right the first time, reduce material costs,and execute their designs through the product'seventual functions.


Function

This diagram shows several components in an electronic assembly .Thermal analysis is used to predict the junction temperature (at center ofdiagram). Cooling occurs, due to the natural thermal conductivity of aluminum, through the extruded heat sink at the top of the assembly .

For thermal analysis, the thermal model of theheatsink as shown is used to determine thespecific point of highest heat concentration (as shown in red) and how the design will dissipate the temperature throughout theextruded profile.

For structural analysis, the structural model ofthe extruded profile as shown displays thestress on the section in its application and atwhich specific point (as shown in red) theshape has its most stress or weakest point interms of structural strength.

The key determining factors of structural analysis are stress and strain.Significant parameters include: materials, supports, loading, and contact points.

6-4Section 6 Designing

DESIGN DECISION --ADVANTAGES WITH ALUMINUM EXTRUSIONSThere are any number of ways inwhich extruded aluminum can beapplied to meet design challengesmore effectively, more efficiently, ormore economically than alternativemethods of manufacture. The following illustrations offer just a fewcommon examples.

1. As shown, several rolled shapes,riveted together, can be replaced by asingle extruded profile, resulting inhigher strength while eliminatingjoining costs.

2. Machining costs often can bereduced by extruding the desiredcomponent to exact size and shaperequirements.

3. Weight can be greatly decreasedby putting the metal only whereneeded. The extrusion process canput the metal exactly where needed.

1

2

3


Advantages

4. Welded assemblies frequently canbe eliminated by designing an appro-priate extrusion. In this way, costscan be reduced while both strengthand accuracy are increased.

5. Sturdy multi-void hollow profilesare available to replace roll-formedalternatives, often at reduced set-upcosts and shortened lead times.

6. Improved stiffness and strengthcan be achieved through extrusion.Here, a detailed hollow profilereplaces a crimped tubular section, ata reduced manufacturing cost.

5

6

4

Tolerances. Section 8 offers detaileddiscussion of standard dimensional tolerances and geometric tolerancing.

Surface Finish. Surfaces can be finished in a variety of ways, as discussed in Section 4.

Alloy. There are a number of aluminum extrusion alloys, each with distinct characteristics and properties. They are discussed inSection 7.

Circumscribing Circle Size. Sometimesreferred to as the circumscribing circle diameter (CCD), this is themost common industry measurementof a profile's diameter.

Shape (Profile) ConfigurationA solid extruded profile is any profilethat is not a hollow or semihollow.

This covers a wide range including,for example, compact cross-sectionswith or without projections, angularor curved shapes, and those wrap-around shapes whose tongue ratiosare too low for the semihollow class.

Extruded rod is a solid product with around cross-section at least 0.375-inch in diameter.

Extruded bar is a solid product whosecross-section is square, rectangular,hexagonal or octagonal, and whosewidth between parallel faces is 0.375-inch or greater.

If the dimension across any of theseproducts is less than 0.375-inch, it isclassified as wire.


DESIGN DECISION -- PARAMETERSIn the detailed development of analuminum extrusion design, the following five factors (each of whichis described in detail over the nextfew pages) should be considered:

Shape (Profile) Configuration.Extruded profiles are described inthree general categories: solid, semi-hollow, and hollow.

A solid profile is the least complex.It may assume a variety of forms, aslong as its cross-section has no voids.

A semihollow profile partially enclos-es a void. It is defined by its tongueratio, and further categorized according to standard industryclassification tables.

A hollow profile completely enclosesa void. A single profile may containmultiple voids.

A solid profile.

A hollow profile is simply an extrudedprofile which, anywhere in its cross-sec-tion, completely encloses a void. Thevoid itself may have any sort of shape,and the complete profile may includea variety of other forms; but if any partof it encloses a void, it's classified as ahollow profile.

Hollow profiles are further classified asClass 1, Class 2, or Class 3 based on

analysis of the voidand the overallprofile geometry.

A Class 1 hollow profile.

Tube and Pipe are specific productforms.

Tubeis a hollow section that is long incomparison to its cross-sectional size.It is symmetrical and has uniform wallthickness, except as affected by cor-ners. It may be round or elliptical,or square, rectangular, hexago-nal, or octagonal. "Extrudedtube," as the name indicates, istube produced by hot extrusion;"drawn tube" is produced by drawingthrough a die.

A semihollow profile is one that partially encloses a void--for example,a circle or rectangle with a gap inone side; but a solid profile can alsopartially enclose a void, and the difference may not be obvious. It isdefined mathematically, by compar-ing the area of the partially-enclosedvoid to the square of the gap size.This ratio (Area/Gap2) is called thetongue ratio.

A Class 2 semihollowprofile.

If the tongueratio is largerthan a certainnumber, the pro-

file is classified as semihollow; if theratio is smaller, the profile is consid-ered a solid. Semihollow profiles arefurther classified as "Class 1" or"Class 2" according to standardindustry tables, such as the oneshown here.

Class1

Class 1 Class 2Gap Width Group A Group B Group A Group B(Inches) Alloys1 Alloys2 Alloys1 Alloys2

Ratio0.040-0.062 2.0 1.5 2.0 1.00.063-0.124 3.0 2.0 2.5 1.50.125-0.249 3.5 2.5 3.0 2.00.250-0.499 4.0 3.0 3.5 2.50.500-0.999 4.0 3.5 3.5 2.51.000-1.999 3.5 3.0 3.0 2.02.000 and more 3.0 2.5 3.0 2.0

1. Group A alloys are 1060, 1100, 1350, 3003, 5454, 6061, 60632. Group B alloys are 2011, 2014, 2024, 5083, 5086, 5456, 5066, 7001, 7075, 7178, 7079


Parameters

Classification--Semihollow Extruded Profiles


Pipeis a tube with certain standard-ized combinations of outside diame-ter and wall thickness. These arecommonly designated by "NominalPipe Sizes" and by "ANSI (AmericanNational Standards Institute)Schedule Numbers."

Dimensional TolerancesFor many applications, in which theextrusion will be part of an assemblyof components, dimensional toler-ances are critical. A designer shouldbe aware of the standard dimensionaltolerances to which extrusions arecommercially produced. Thesedimensional tolerances generallycover such characteristics as straight-ness, flatness, and twist, and suchcross-sectional dimensions as thick-ness, angles, contours, and corner orfillet radii.

The published standard dimensionaltolerances may be very easy toachieve or very difficult, dependingon the profile. The complexity ofprofile possibilities makes it impossi-ble to publish standard dimensionaltolerances that meet all situations.

Aluminum extrusions are oftendesigned to minimize or eliminatethe need for machining. If desired,extrusions can be produced to closer-than-standard dimensional tolerances, generating cost savings insecondary operations; such savingsmay range from modest to verysignificant, depending on circum-stances. The designer should carefully consider the requirementsof the application and specify specialtolerances only where they are reallyneeded.

If extruded parts are to interlock inany manner, the designer shouldwork with the supplier to make surethat dimensional tolerances willaccommodate a proper fit.

For more on standard dimensional tolerances, as well as an introductionto geometric tolerancing, pleaserefer to Section 8.

Surface FinishOne advantage of aluminumextrusions is the variety of ways thesurface can be finished, and thisoffers another range of choices tothe designer.

As-extruded, or mill finish can rangefrom structural, on which minor sur-face imperfections are acceptable, toarchitectural, presenting uniformlygood appearance. It should beunderstood that under normal circumstances aluminum may bemarred during routine handlingbecause it is a soft metal, especiallywhen it first leaves the die, at hightemperature. Special care isrequired if a blemish-free surface isdesired. This should be discussedwith the extruder and specificationsmade as necessary.

Finishes other than mill finishinclude scratch finishing, satin finish-ing, and buffing. Aluminum canalso be finished by clear or coloredanodizing, or by painting, enamel-ing, or other coatings.

Alloy 6063 is used for production ofa broad range of solid and hollowprofiles. It is easily welded, and ithas a pleasing natural finish andexcellent corrosion resistance. Alloy6063 is used in architecture and inmany moderate-stress applications.

Alloy 6061 is a good all-purposeextrusion alloy, combining relativityhigh tensile properties with goodcorrosion resistance, weldability, andmachining characteristics. In the T6temper, 6061 typically has a yieldstrength of 35,000 to 40,000 PSI, astrength comparable to structuralsteel. Alloy 6061 is used in manystructural applications.

Many other alloys are used for extrusions, to meet particularrequirements. For example, to mention only a few:

For further details, please refer toSection 7. New alloys are introducedoccasionally, so the designer shouldconsult current alloy and tempertables and discuss specific needs withthe extruder.


If a product will have surfaces thatare exposed in use, where normalprocessing marks may be objection-able, the extruder should be toldwhich surfaces are critical. Dies canbe designed to orient the shape toprotect those surfaces during theextrusion process; selection of theappropriate packaging can protectthe product during shipment.

For more on Finishing, please referto Section 4.

Alloy SelectionAluminum extrusions are made in awide variety of alloys and tempers tomeet a broad spectrum of needs.Selection is made to meet the specificrequirements in strength, weldability,forming characteristics, finish, corro-sion resistance, machinability, andsometimes other properties.

The complete list of registered alu-minum alloys is quite long, but inpractice a few alloys are chosenrepeatedly for extrusion because oftheir versatility and characteristics.Extruders generally stock the mostfrequently used alloys. When theirspecialized markets justify it, individ-ual companies include in their inven-tories additional alloys, which willvary with the needs of their majorcustomers. Many extrusion alloys areregularly available.

The 6xxx-series aluminum alloys(those whose four-digit registrationnumbers begin with a 6) are selectedfor nearly 75 percent of extrusionapplications. Alloys 6063 and 6061are used most frequently.

Characteristics AlloysHigh strength 7075, 2014High corrosion resistance 1100, 3003High electrical conductivity 6101

Parameters


Most common profiles are less than18 inches in diameter, but a fewextruders are capable of producingextrusions with a much larger circumscribing circle diameter(CCD), some as large as 32 inches.

Circumscribing Circle SizeOne common measurement of thesize of an extrusion is the diameter of the smallest circle that will entirelyenclose its cross-section--its circumscribing circle.

This dimension is one factor in theeconomics of an extrusion. In general, extrusions are most economical when they fit within amedium-sized circumscribing circle:that is, one with a diameter betweenone and ten inches.

The example shown here would be classifiedas a 3-to-4-inch circle-size shape.

2”

4”

5”6”

8”

9”10”

18”+

7”

3”

Not to scale

Keep Metal Thickness As UniformAs PossibleExtrusion allows you to put extrametal where it is needed--in high-stress areas, for example--and stillsave material by using normal dimensions elsewhere in the samepiece. Adjacent-wall thickness ratiosof less than two-to-one are extrudedwithout difficulty, but large differ-ences between thick and thin areasmay create dimensional control prob-lems during extrusion. It is best tomaintain near uniform metal thick-ness throughout a shape if possible.When a design combines thick andthin dimensions, streamline the tran-sitions with a radius (a curve, ratherthan a sharp angle) at junctionswhere the thickness changes sharply.


Practices

DESIGN DECISION --PRACTICESTo develop a good extrusion design,the following key characteristicsshould be addressed:

• Specify the appropriate metal thickness

• Keep metal thickness as uniform as possible

• Use metal dimensions for tolerances

• Design with surface finish in mind• Smooth transitions• Use webs where possible• Use ribs to straighten• Round corners wherever possible,

avoiding sharp edges• Incorporate indexing marks.

Specify the Most Appropriate Metal ThicknessesSpecify metal thicknesses that are justheavy enough to meet your structuralrequirements. Even in low stressareas, however, keep sufficient thick-ness to avoid risking distortion ordamage. Some shapes tend to invitedistortion during the extrusionprocess (such as an asymmetric pro-file or thin details at the end of along flange); such tendencies exertmore influence on thin-walled shapesthan on those with typical metalthickness.

Metal thicknesses should be appropriate.

Rounded corners ease the flow of metal.


Use Metal Dimensions for BestToleranceDimensions measured across solidmetal are easier to produce to closetolerances than those measuredacross a gap or angle. So rely on so-called metal dimensions as much aspossible when designing close-fittedmating parts or other shapes requir-ing closer tolerances. Standardindustry dimensional tolerances areentirely adequate for many applica-tions, but special tolerances can bespecified if necessary.

Design with Surface Finish in MindAlways indicate "exposed surfaces" on your design drawing so theextruder can give them special attention and protect their finishduring both extrusion and post-extrusion handling.

As a general rule, the narrower theexposed surface, the more uniformits finish.

Webs, flanges, and abrupt changes in metal thickness may show up asmarks on the opposite surface of an extrusion, particularly on thin sections. The marking of exposedsurfaces can be minimized bythoughtful design.

A "Metal Dimension"can be extruded toclose tolerances.

An "Open SpaceDimension" is mor edifficult to hold toclose tolerances.

Modifying the shapeby rounding the transitions reducesthe chance of oppo -site-side streaking.

This shape, with sharpangular transitions,risks show-throughstreaks on the oppositesurface.

3.00±.024

3.00±.057


Smooth All Transitions in ThicknessTransitions should be streamlined bya generous radius at any thick-thinjunction.

Web Gives Better DimensionalControlMetal dimensions are more easilyheld than gap or angle dimensions.The web also allows thinner wall sec-tions in this example.

Ribs Help Straightening OperationWide, thin sections can be hard tostraighten after extrusion. Ribs helpto reduce twisting, and to improveflatness.

Rounded Corner Strengthens TongueThe die tongue is less likely to snapoff when the corners of the profileare rounded at the narrowest area ofthe void.

Built-In Indexing MarkShallow extruded grooves makedrilling, punching, and assembly easier by eliminating the need forcenter-punching. An index groovecan also be used to help identifypieces that are similar in appearance,or to distinguish an inside (ratherthan an outside) surface.

Smooth transitionscan be achievedthrough rounding corners.

The hollow conditionof the part can beavoided by makingthe component in twopieces as shown bythe dotted line.

Rounded corners ar estronger corners.

An extruded groovecould eliminate theneed for center -punching.

Ribs reduce twisting.

EXTRUSION ALLOYSAn aluminum extrusion alloy is simply a mixed metal, made from apredetermined mixture of one ormore elements together with aluminum. Some of the commonelements alloyed with aluminuminclude copper, magnesium, man-ganese, chromium, silicon, iron, nick-el, and zinc. These alloying elementsare usually added to aluminum inamounts ranging from 0.05 to 7.0percent. Product performance isdetermined in part by the alloy com-position and in part by the method ofproduction. The productionmethod, in turn, strongly influencesthe final temper of the alloy, which isobtained through various types ofmechanical and thermal treatments.Structural and certain physical properties are influenced significantly by the choice of alloyand temper.

Alloying aluminum with elementssuch as manganese, magnesium, cop-per, silicon, and/or zinc, produces avariety of desirable characteristics,including corrosion-resistance,increased strength, or improvedformability. The proper balance ofalloying material depends on theintended application of the finishedpiece. For example, aluminumalloyed in the 5xxx and 6xxx series isparticularly suitable for application inbridge design.


ALUMINUM EXTRUSIONALLOYS

Section

7

Principal Alloying Element Designation

>99% pure Aluminum (Al) 1xxx

Copper (Cu) 2xxx

Manganese (Mn) 3xxx

Silicon (Si) 4xxx

Magnesium (Mg) 5xxx

Magnesium and Silicon (Mg and Si) 6xxx

Zinc (Zn) 7xxx

Other 8xxx

Alloy Series and Their Constituents

Various properties may make certain alloys particularlydesirable:

• Very light weight (one-third the density of steel and concrete)

• High strength (comparable to steel and steel/concrete composites)

• Excellent low-temperature performance (strength andductility as high or higher at sub-zero temperatures as at room temperature)

• Exceptional corrosion resistance (aluminum won’trust like common steel)

• Ease of fabrication by many techniques, (readily assumes unique structural configurations, has excellent weldability, good machinability).

MAJOR ALLOYING ELEMENTSThe following table represents themajor aluminum alloy series andtheir principal constituents.Aluminum alloys are grouped bymajor alloying elements; each seriesexhibits a unique set of propertiesand characteristics.

EFFECTS OF ALLOYING ELEMENTSThe addition of alloying elementsmodifies the properties and charac-teristics of aluminum. Such aspectsas density, electrical and thermal conductivity, thermal expansion,mechanical properties, ability to finish and harden, and corrosionresistance are all affected by combining the alloying elements withaluminum.

Manganese, for example, increasesthe mechanical strength of alloys inthe 3xxx group. Zinc, in combinationwith magnesium and copper, pro-duces a material that can be age-hardened, as in alloy 7075. Hardalloys such as 7075 must be thermallytreated away from the extrusion pressin a separate furnace. Alloys vary intheir relative ease of extrudability.Many extrude easily, others are con-sidered relatively easy, while a few arequite difficult to extrude and requireprocedures that slow the process. Alloys 6063, 6101, and 6463, forexample, are rated as having excellent extrudability, while 7075and 7178 are categorized as difficultto extrude.

7-2Section 7 Alloys

Wrought Alloy Major Alloying Elements andDesignation Typical Alloy Characteristics

1xxx Series Minimum 99% aluminumHigh Corrosion resistance. Excellent finishability. Easily joined by all methods. Low strength. Poor machinability. Excellent work-ability. High electrical and thermal conductivity.

2xxx Series CopperHigh strength. Relatively low corrosion resistance. Excellent machinability.Heat treatable.

3xxx Series ManganeseLow to medium strength. Good corrosion resistance. Poor machinability.Good workability.

4xxx Series SiliconNot available as extruded products.

5xxx Series MagnesiumLow to moderate strength. Excellent marine corrosion resistance. Very good weldability.

6xxx Series Magnesium & SiliconMost popular extrusion alloy class. Good extrudability. Good strength. Good corrosion resistance. Good machinability.Good weldability. Good formability.Heat treatable.

7xxx Series ZincVery high strength. Good machinability.Heat treatable.


Because of its adaptability to a number of large-volume uses, itsmany favorable characteristics, and itsease of extrudability, 6063 is used toproduce a large percentage of alu-minum profiles. New, cutting-edgealuminum alloys are being developedto produce even stronger, lighterextrusions for use in aviation anddeep-space vehicles. Aluminum-lithium is one of the new alloy classes.Lithium, one of the lightest metalsknown, is about one-fifth as dense asaluminum. When combined with aluminum into a new alloy, it’s 7 to 10percent lighter and up to 30 percentstiffer than conventional aircraftalloys.

New alloys are periodically intro-duced to satisfy the changing needsof the marketplace. Designers andspecifiers are encouraged to discusswith extruders the best-suited alloysfor any given application.

TEMPERSAll aluminum alloys, regardless ofproduct form, are classified as eitherheat-treatable or nonheat-treatable.Those alloys classified as nonheat-treatable develop maximum strengthcharacteristics through cold workafter extruding, if section shape permits. Nonheat-treatable alloys arefound in the 1xxx, 3xxx, and 5xxxseries.

Heat-treatable alloys attain their maxi-mum strength through controlledheat treatment. This group has thehighest strength of all aluminumalloys and includes the 2xxx, 6xxx,and 7xxx series.

F As Extruded: No special control over thermal conditions or strain-hardening; no mechanical property limits.

O Annealed: Thermally treated to obtain the lowest strength temper.

H Strain-hardened: Cold working used to increase strength and hardness.

T Thermally Treated: Thermally treated to produce stable tempers other than F, O, or H.

The Temper Designation System liststhe modification methods applied toheat-treatable and nonheat-treatablealloys:

O Fully annealed.H112 Strain-hardened; used for

nonheat-treatable alloys.T1 Cooled from an elevated

temperature and naturally aged.

T4 Solution heat-treated and naturally aged.

T5 Cooled from an elevated temperature and artificially aged.

T6 Solution heat-treated1 and artificially aged.

A complete alloy-temper designationreads like this: “6063-T5.” This designation indicates a particular alloy of the 6xxx series(Mg and Si), which is thermally treated by being cooled from an elevated temperature and artificiallyaged.

Typical Tempers for Extrusions

1. For some alloys, this may be accom-plished in-line at the extrusion press.

6101High strength bus conductors; Si 0.30-0.7 -H111 0.250 - 2.000 12.0 .. 8.0 .. ..good extrudability, weldability, Mg0.35-0.8 -T6 0.125 - 0.500 29.0 .. 25.0 .. 15brazeability, good resistance to 0.125 - 0.749 20.0 .. 15.0 ..stress corrosion cracking with -T61 0.750 - 1.499 18.0 .. 11.0 .. 19average machinability. 1.500 - 2.000 15.0 .. 8.0 ..

-T63 0.125 - 1.000 27.0 .. 22.0 .. 17-T64 0.125 - 1.000 15.0 .. 8.0 .. 20-T65 0.125 - 0.749 25.0 32.0 20.0 27.0 ..

6105Good medium to high strength Si 0.60-1.0 -T1 Up thru .500 25.0 .. 15.0 .. 16with average machinability and Mg0.45-0.8 -T5 Up thru .500 38.0 .. 35.0 .. 8good corrosion resistance.

6262Best machining of all extrusion Mg0.8 - 1.2 -T6,T62,[4,8] T6510[5] All 38.0 .. 35.0 .. 10alloys. Good corrosion Si 0.40-0.8 and T6511[5]

resistance. Pb 0.40-0.7Bi 0.40-0.7Cu0.15-0.4Cr 0.04-0.14

6351Mechanical properties similar Si 0.7 - 1.3 -T1 Up thru 0.499 [17] 26.0 .. 13.0 .. 15to 6061. Used in structural Mg0.40 -0.8 -T4 Up thru 0.749 [17] 32.0 .. 19.0 .. 16applications. Will take Mn0.40 -0.8 -T5 Up thru 0.249 [17] 38.0 .. 35.0 .. 8considerable forming in T4. 0.250-1.000[17] 38.0 .. 35.0 .. 10Good corrosion resistance. -T51 0.125-1.00[17] 36.0 .. 33.0 .. 10Used in transportation and -T54 Up thru 0.500 [17] 30.0 .. 20.0 .. 10general structures. -T6 Up thru 0.124 42.0 .. 37.0 .. 8

0.125-0.749 42.0 .. 37.0 .. 10

6463Designed to accept a bright Mg0.45-0.9 -T1 Up thru 0.500 [17] 17.0 .. 9.0 .. 12finish through anodizing or Si 0.20-0.6 -T5 Up thru 0.500 [17] 22.0 .. 16.0 .. 8polishing. Decorative trim Up thru 0.124 [17] 30.0 .. 25.0 .. 8applications; machinable High purity -T6 and T62[4,8] 0.125-0.500[17] 30.0 .. 25.0 .. 10and heat-treatable. version of 6063

7005Used in automotive and Zn 4.0 - 5.0other transportation Mg1.0 - 1.8 -T53 All 50.0 .. 44.0 .. 10applications where Mn0.20-0.7added strength is required. Cr 0.06-0.20

Zr 0.08-0.20Ti 0.01-0.06

7050Used in applications Zn 5.7-6.7 -T73510 [9] & up thru 5.000 [13] 70.0 .. 60.0 .. 8requiring high strength Mg1.9-2.6 T73511 [9]

and stress corrosion Cu2.0-2.6 -T74510 [20] & up thru 5.000 [13] 73.0 .. 63.0 .. 7resistance. Zr 0.08-0.15 T74511 [20]

-T76510 [21] & up thru 0.499 [13] 77.0 .. 68.0 .. 7T76511 [21]

-T76510 [21] & 0.500-5.000[13] 79.0 .. 69.0 .. 7T76511 [21]

7-6Section 7 Alloys

Aluminum Extrusion Alloys:

Number and Characteristics Temper and Thickness [1]-in.

Tensile Strength-ksi

Ultimatemin minmax max

Elongation[2]

percent minin 2 in. or

4D[3]

Yield

MajorAlloyingElements(Percent)


Aluminum Extrusion Alloys:

Number and Characteristics Temper and Thickness [1]-in.

Tensile Strength-ksi

Ultimatemin minmax max

Elongation[2]

percent minin 2 in. or

4D[3]

Yield

MajorAlloyingElements(Percent)

7075Used for aircraft structural Zn 5.1 - 6.1 -0 All .. 40.0 .. 24.0 10members, when extra strength Mg2.1 - 2.9is required. Can be spot welded. Cu1.2 - 2.0 -T6, T62,[4,8] T6510[5] Up thru 0.249 78.0 .. 70.0 .. 7

Cr 0.18-0.28 & T6511[5] 0.250 - 0.499 81.0 .. 73.0 .. 70.500 - 1.499 81.0 .. 72.0 .. 71.500 - 2.999 81.0 .. 72.0 .. 73.000 - 4.499[17] 81.0 .. 71.0 .. 73.000 - 4.499[18] 78.0 .. 70.0 .. 64.500 - 5.000[13] 78.0 .. 68.0 .. 6

-T73,[9] T73510[5,9] 0.062-0.249[17] 68.0 .. 58.0 .. 7& T73511[5,9] 0.250-1.499[11] 70.0 .. 61.0 .. 8

1.500-2.999[11] 69.0 .. 59.0 .. 83.000-4.499[17] 68.0 .. 57.0 .. 73.000-4.499[18] 65.0 .. 55.0 .. 7

-T76,[10] T76510[5,10] Up thru 0.249 73.0 .. 63.0 .. 7& T76511[5,10] 0.050-0.124 74.0 .. 64.0 .. 7

0.125-0.249[17] 74.0 .. 64.0 .. 70.250-0.499[17] 75.0 .. 65.0 .. 70.500-1.000[17] 75.0 .. 65.0 .. 71.001-2.000[17] 75.0 .. 65.0 .. 72.001-3.000[17] 74.0 .. 64.0 .. 73.001-4.000[17] 74.0 .. 63.0 .. 7

7178Used primarily for aircraft Zn 6.3-7.3 -0 [13] All [13] .. 40.0 .. 24.0 10structural members where high Mg 2.4-3.1strength is required but where Cu 1.6-2.4 -T6,T6510[5] & Up thru 0.061 [17] 82.0 .. 76.0 .. ..impact loading is not Cr 0.18-0.28 T6511[5] 0.062-0.249 [17] 84.0 .. 76.0 .. 5experienced. 0.250-1.499 [11] 87.0 .. 78.0 .. 5

1.500-2.499 [11] 86.0 .. 77.0 .. 51.500-2.499 [12] 84.0 .. 75.0 .. 52.500-2.999 [13] 82.0 .. 71.0 .. 5

-T62[4,8] Up thru 0.061 [17] 79.0 .. 73.0 .. ..0.062-0.249 [17] 82.0 .. 74.0 .. 50.250-1.499 [11] 86.0 .. 77.0 .. 51.500-2.499 [11] 86.0 .. 77.0 .. 51.500-2.499 [12] 84.0 .. 75.0 .. 52.500-2.999 [13] 82.0 .. 71.0 .. 5

-T76,[10] T76510[5,10] 0.125-0.249 [17] 76.0 .. 66.0 .. 7& T76511[5,10] 0.250-0.499 [17] 77.0 .. 67.0 .. 7

0.500-1.000 [17] 77.0 .. 67.0 .. 7

7475Typically used for shell casings, Zn 5.7 -T62 1.001-2.000 75.0 .. 66.0 .. 7aircraft, and structures. Mg 2.2

Cu 1.6Cr 0.22

Section 7 Alloys

5086-O A[4] A[4] A D D C A BH32, H116 A[4] A[4] B D D C A AH34 A[4] B[4] B C D C A AH36 A[4] B[4] C C D C A AH38 A[4] B[4] C C D C A AH111 A[4] A[4] B D D C A A

5154-O A[4] A[4] A D D C A BH32 A[4] A[4] B D D C A AH34 A[4] A[4] B C D C A AH36 A[4] A[4] C C D C A AH38 A[4] A[4] C C D C A A

5454-O A A A D D C A BH32 A A B D D C A AH34 A A B C D C A AH111 A A B D D C A A

6005-T1,T5 .. .. .. .. A A A A

6060-T1, T4 A A B D A A A AT5 A A B C A A A AT6 A A C C A A A A

6061-O B A A D A A A BT4, T451, T4510, T4511 B B B C A A A AT6, T651, T652, T6510, T6511 B A C C A A A A

6063-T1 A A B D A A A AT4 A A B D A A A AT5, T452 A A B C A A A AT6 A A C C A A A AT83, T831, T832 A A C C A A A A

6066-O C A B D D D B BT4, T4510, T4511 C B C C D D B BT6, T6510, T6511 C B C B D D B B

6070-T4, T4511 B B B C D A A AT6 B B C C D A A A

6101-T6, T63 A A C C A A A AT61, T64 A A B D A A A A

6105-T1, T5 B A C C A A B A

6262-T6, T651, T6510, T6511 B A C B B B B AT9 B A D B B B B A

6351-T1 .. .. C C C B A BT4 A .. C C C B A BT5 A .. C C C B A AT6 A .. C C C B A A

Extrusion Alloy Characteristics and Applications (continued)

RESISTANCETO

CORROSION

ALLOY AND TEMPER SOME APPLICATIONS

OF ALLOYS

WELDABILITY[6]

Unfired, welded pressure vessels,marine, auto, aircraft, cryogenics,TV towers, drilling rigs, transportation equipment, missilecomponents

Welded structures, storage tanks,pressure vessels, salt water service

Welded structures, pressure vessels, marine service

Structural applications

General purposes, architecturalapplications

Heavy-duty structures requiringgood corrosion resistance, truckand marine, railroad cars, furniture, pipelines

Pipe railing, furniture, architectural extrusions

Forgings and extrusions for welded structures

Heavy-duty welded structures,pipelines

High-strength bus conductors

General purposes, architectural

Screw machine products

Extruded shapes, structural, pipeand tube

7-10


Notes for table[1] Ratings A through E are relative ratings in decreasing orderof merit, based on exposures to sodium chloride solution byintermittent spraying or immersion. Alloys with A and B ratingscan be used in industrial and seacoast atmospheres withoutprotection. Alloys with C, D, and E ratings generally should beprotected at least on faying surfaces.

[2] Stress-corrosion cracking ratings are based on serviceexperience and on laboratory tests of specimens exposed tothe 3.5% sodium chloride alternate immersion test.A = No known instance of failure in service or in laboratorytests.B = No known instance of failure in service; limited failures inlaboratory tests of short transverse specimens.C = Service failures with sustained tension stress acting inshort transverse direction relative to grain structure; limited fail-ures in laboratory tests of long transverse specimens.D = Limited service failures with sustained longitudinal or longtransverse areas.

These ratings are neither product specific nor test directionspecific and therefore indicate only the general level of stress-corrosion cracking resistance. For more specific information oncertain alloys, see ASTM G64.

[3] In relatively thick sections the rating would be E.

[4] This rating may be different for material held at elevatedtemperature for long periods.

[5] Ratings A through D for Workability (cold), and A through Efor Machinability, are relative ratings in decreasing order ofmerit.

[6] Ratings A through D for Weldability and Brazeability are relative ratings defined as follows:A = Generally weldable by all commercial procedures andmethods.B = Weldable with special techniques or for specific applications that justify preliminary trials or testing to developwelding procedure and weld performance.C = Limited weldability because of crack sensitivity or loss inresistance to corrosion and mechanical properties.D = No commonly used welding methods have been developed.

[7] T74 type tempers, although not previously registered, haveappeared in various literature and specifications as T736 typetempers.

Except for alloys 6060 and 6105, reproduced from Aluminum Standards and Data, 1997, Table 3.3.

6463-T1 A A B D A A A AT5 A A B C A A A AT6 A A C C A A A A

7005-T53 .. .. .. .. B C A A

7050-T73510, T73511, C B D B D D D BT74[7], T7451[7], T74510[7],T74511[7], T7452[7], T7651,T76510, T76511

7075-O .. .. .. D D D D BT6, T651, T652, T6510,T6511 C[3] C D B D D D BT73, T7351 C B D B D D D B

7178-O .. .. .. .. D D D BT6, T651, T6510, T6511 C[3] C D B D D D B

Extrusion Alloy Characteristics and Applications (continued)

RESISTANCETO

CORROSION

ALLOY AND TEMPER SOME APPLICATIONS

OF ALLOYS

WELDABILITY[6]

Extruded architectural and trimsections

Aircraft and other structures



UNDERSTANDING TOLERANCES

What Are Tolerances?Ask any engineering student to makea critical measurement, and his firstquestion may be, “Accurate to howmany decimal places?”

He's just recognizing a basic fact ofnature: that dimensions, whethermeasured or produced, are neverabsolutely exact; they are only as precise as we and our equipment canmake them--or need to make them.Every manufacturing process haslimits of accuracy, imposed by tech-nology or economics, which are rou-tinely taken into account in designand production.

Most manufacturers and customersexpect to provide, or receive, prod-ucts whose dimensions are reliablewithin mutually acceptable limits ofdeviation. Those agreed-upon limitsare called tolerances, and at the timeof ordering, a clear consensusregarding those tolerances benefitsboth the extrusion supplier and theuser. It protects the user by ensuringthat the extruded product will besuitable for his use; it protects theextruder from having products reject-ed by a customer with unreasonableexpectations; it's good business forboth of them.


TOLERANCESSTANDARD DIMENSIONALTOLERANCES

Section

8

A

Note 8Note 6

Length

Cross-section/wall thickness

8-2

Where Are Dimensional TolerancesApplied?The shape of an aluminum profile isdescribed by specifying the dimen-sions of its cross-section on an engi-neering drawing, and by specifyingthe delivered length.

The allowed tolerances are usuallyexpressed in plus-or-minus (decimal)fractions of an inch or percentages ofa dimension, applied to zones wherethe dimensions are to be held withinthese specified limits.

Unless otherwise specified, standardindustry tolerances are applied.Special tolerances may be specified inconsultation with the extruder.

Extrusion tolerances are applied to avariety of physical dimensions.

Section 8 Tolerances

Y

D

D

Straightness

Twist


C

SurfaceRoughness

Corner & FilletRadii

Contour (Curved Surfaces)

End Cut Squareness(Vertical & Transverse

Angularity

Flatness

A

A

8-4Section 8 Tolerances

Mean

A

AB

B

At any one point

B

B

Wall thickness

A

AB

A

B

B BA

Extruded tube has additional standard tolerances:


Width and depth

B

B

AA

A

A

A

A

A

A

A

A

A

A

BB

A

A

8-6Section 8 Tolerances

Special TolerancesEven tighter dimensional tolerancesthan the Industry Standard can bespecified when necessary. To achievethem, however, requires moreinvolved die corrections, slower extru-sion rates, increased inspections, andsometimes a higher rejection rate.All that special care adds up, ofcourse, to higher costs to the extrud-er and higher prices to the customer.

In rare instances, a desired dimen-sional tolerance may not be possibleto achieve, but an experienced extru-sion supplier may be able to suggest adesign change that solves the prob-lem and still meets the purchaser'seconomic and functional requirements.

The purchaser and the vendor shouldagree on any special tolerancesbefore an order is entered, andshould specify them on the order andengineering drawing.

The published standard tolerancesmay be very easy to achieve, or verydifficult, depending on the profile. It may be practical and economicallydesirable to specify tolerances thatare broader than the standard.

Remember: If no special dimensionaltolerances are specified, standarddimensional tolerances will beapplied.

Standard Dimensional TolerancesThe industry's standard toleranceswere developed by technical commit-tees of The Aluminum Associationand the American National StandardsInstitute, taking into account boththe capabilities of extruders and theneeds of extrusion users.

These Industry Standards are pub-lished in National StandardDimensional Tolerances for AluminumMill Products(ANSI H35.2) andAluminum Standards and Data (ASD).Both publications are updated peri-odically to reflect improvements inextruder capabilities and changes inuser needs.

Standard tolerances are not simple,uniform fractional formulas. They incorporate many different spe-cific numbers or formulas publishedin tables. The various tolerances areestablished to match the variousdegrees of difficulty an extruder facesin controlling different toleranceddimensions. As a result, tolerancesvary with cross-sectional size (as mea-sured by the profile's fit within a cir-cumscribing circle--see Section 6),and even with the location of eachdimension on a complex shape.Alloy composition and temper alsoinfluence certain tolerances, and arereflected in the standard tolerancetables.

Because of all these important con-siderations, tolerancing tables arecomplex. But their significance issimple and important: under stan-dard tolerances, aluminum extru-sions are routinely produced withdimensions accurate within hun-dredths or thousandths of an inch.For most purposes, that's a more-than-ample degree of precision.

The choice isyours: throughstandard toler-ances or specialtolerances,aluminum extru-sions give youthe precision youneed--where youneed it.

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