2012 steelmaking ch12
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8/3/2019 2012 Steelmaking Ch12
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Steelmaking
Fabrication of SteelBudinski Chapter 12Study Unit 1
Science of MaterialsMTK 3A11
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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
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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
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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
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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
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GLOBAL METAL PRODUCTIONSouth Africa's role in
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SA mineral production
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The world’s
largest turnover of
platinum-group-
metals*
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*Chromium
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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
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*Manganese
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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
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* Vanadium
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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
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Bushveld Igneous Complex
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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
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TYPICAL STEEL MILLFabricating steel and the workings of a
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Steelmaking
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Iron ore, coke &
limestone
Blast furnace &oxygen
Molten iron
Refine
Solidify & form
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Iron ore
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Alloy of Fe & C
Iron ore
Coke
Sinter
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Integrated steel mill
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• A coke plant
• A blast furnace
• Various steel-refining processes
• A number of product lines
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Blast furnace
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Blast furnace process
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• 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
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Blast furnace process
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• 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
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Blast furnace
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Direct reduction process
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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
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Steel refining
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Turning pig iron into
steel• Basic oxygen furnace (BOF)
• Electric arc furnace (EAF)
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Basic oxygen steelmaking
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Basic oxygen furnace (BOF)
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Cr
converts the molten
iron from the blast
furnace into refined
steel
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Electric arc furnace (EAF)
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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)
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Secondary Steelmaking
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Speciality steels
→ alter chemical composition
→ reduce non-metallic inclusions
• Vacuum degassing
• Ladle stirring injection
• Ladle furnace heating
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Special refining processes
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Cr
VAR – Super alloys
VIM – Specialty AlloysEBR – To purify specialty alloys
ESR – Tool steel and special purpose steels
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Continuous casting
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Refinement of the casting process for the
continuous, high-volumeproduction of metal sections with a
constant cross-section
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Continuous casting
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Stand casting process and shapes produced
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Standard shapes
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Square & rectangulartubing
L-Shape
C-ShapeT-ShapeRail
S-ShapeW-Shape
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Hot and cold finishing
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Hot rolling
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Cold rolling
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On your own
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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
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