2012 steelmaking ch12

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Steelmaking

Fabrication of SteelBudinski Chapter 12Study Unit 1

Science of MaterialsMTK 3A11



Study division goals

To develop

Insight into South Africa's role in global metal

production

An understanding of how steel is made

A knowledge of the steel products that are

commercially available

An understanding of steel terminology and steel

specification procedures

2MTK 3A 11 Steelmaking Ch12



Study division goals

To develop

An understanding of the metallurgical

reactions that occur in heat treatment

A knowledge of the common heat

treatments used on steels

Guidelines on how to specify heattreatments on engineering drawings




Describe the process of fabricating steel

and the workings of a typical steel mill

Discuss the processes involved in steelrefining

List the steel products that are

commercially availableDefine certain steel terminology and

specifications


H a v i n g c

o m p l e t e d

s t u d y

u n i t 1 y o u s h o u l d b e a b l e t o



GLOBAL METAL PRODUCTIONSouth Africa's role in

MTK 3A 11 Steelmaking Ch12 5



SA mineral production


The world’s

largest turnover of

platinum-group-

metals*



*Chromium


Cr

Corrosion and oxidation resistance

Mild hardenability agent

Improves wear resistancePromotes the retention of useful

strength levels at elevated

temperaturesChromium is an irreplaceable

constituent in all stainless steels



*Manganese


Desulfuriser and deoxidiserFlat rolled carbon and HSLA steelscontain up to 2% Mn formicrostructural refinement

Manganese may be substituted forpart of the nickel content in austeniticSS

Tool and die steels rely onmanganese for deep hardening

Farm equipment – PloughMg



* Vanadium


Approximately 80% of vanadiumproduced is used asferrovanadium or as a steeladditive

- specialty stainless steel, e.g. foruse in surgical instruments andtools- rust resistant and high speed

tool steels- mixed with aluminium in titaniumalloys used in jet engines andhigh-speed airframes

Va



Bushveld Igneous Complex


The largest known deposit of

platinum group metals (PGMs)

platinum, palladium, rhodium,

ruthenium, osmium and iridium arerecovered, as well as small amounts

of gold, nickel, copper and cobalt.

Largest resources of chromium and vanadium in the world



TYPICAL STEEL MILLFabricating steel and the workings of a




Steelmaking


Iron ore, coke &

limestone

Blast furnace &oxygen

Molten iron

Refine

Solidify & form



Iron ore


Alloy of Fe & C

Iron ore

Coke

Sinter



Integrated steel mill


• A coke plant

• A blast furnace

• Various steel-refining processes

• A number of product lines



Blast furnace




Blast furnace process


• Coke + Charge introduced into the furnace at

the top

• Blasts of heated air are injected into the

furnace through openings at the bottom of theshaft

• Coke is burned along with the injected fuels,producing the necessary heat and reducing gas to

remove oxygen from the ore in the

reduction process



Blast furnace process


• Carbon combines with oxygen in the ore

• As the iron melts, it descends and accumulates in

the crucible

• Molten pig iron (±5%C) and slag are drained

from the crucible through different tapping holes

• Gas that exits from the top of the furnace goes

through a cleaning process



Blast furnace




Direct reduction process


Iron ore, coal and oxygen are reactedin a single melting vessel → steel

Steel → an alloy of iron and a

restricted amount of carbon C < 0.005% is considered pure iron

C > 0.06% lower limit commercial steel

C > 2.00% cast ironMore C → brittle



Steel refining


Turning pig iron into

steel• Basic oxygen furnace (BOF)

• Electric arc furnace (EAF)



Basic oxygen steelmaking




Basic oxygen furnace (BOF)


Cr

converts the molten

iron from the blast

furnace into refined

steel



31



Electric arc furnace (EAF)


Cr

Reduce iron from iron ore

Heat is generated from an electric arc

Oxygen is blown into the furnace, and lime andother materials are added to combine with theimpurities and form slag

Molten iron is extracted and poured out via a

tapping spoutCan then be processed again in an electric arcfurnace to make steel (special quality steel)



33



Secondary Steelmaking


Speciality steels

→ alter chemical composition

→ reduce non-metallic inclusions

• Vacuum degassing

• Ladle stirring injection

• Ladle furnace heating



Special refining processes


Cr

VAR – Super alloys

VIM – Specialty AlloysEBR – To purify specialty alloys

ESR – Tool steel and special purpose steels



Continuous casting


Refinement of the casting process for the

continuous, high-volumeproduction of metal sections with a

constant cross-section



Continuous casting




Stand casting process and shapes produced

MTK 3A 11 Steelmaking Ch12



MTK 3A 11 Steelmaking Ch12



Standard shapes


Square & rectangulartubing

L-Shape

C-ShapeT-ShapeRail

S-ShapeW-Shape



Hot and cold finishing




Hot rolling




Cold rolling




On your own


Steel terminology• Familiarise yourself with the terms used to describe

mill processing operations

Steel specifications• Regardless of the identification system used,

essential items need to be addressed in purchasing

a steel. Discuss these characteristics



Next

Phase diagramsStudy unit 2

2012 steelmaking ch12

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