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

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

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

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)

converts the molten

iron from the blast

furnace into refined

Electric arc furnace (EAF)

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)

Secondary Steelmaking

Speciality steels

→ alter chemical composition

→ reduce non-metallic inclusions

• Vacuum degassing

• Ladle stirring injection

• Ladle furnace heating

Special refining processes

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

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

Phase diagramsStudy unit 2

2012 steelmaking ch12

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