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Introducing steels EF 420 Lecture 5 John Taylor

Pig iron production ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Pig iron composition ,[object Object],[object Object],[object Object],[object Object]

Steel ,[object Object],[object Object],[object Object],[object Object],[object Object]

Other alloy elements ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Steelmaking ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Oxygen in Argon in

Ladle metallurgy ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Lance Cored Wire Argon stirring

Deoxidation & degassing ,[object Object],[object Object],[object Object],[object Object],[object Object],Vacuum Mould

Ingot casting ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Killed Semi-killed Rimming

Continuous casting ,[object Object],[object Object],[object Object],[object Object]

Remelting and refining ,[object Object],[object Object],[object Object],[object Object],Transformer Consumable electrode Water cooled Moveable mould ESR steel Slag pool

Processing structural steel ,[object Object],[object Object],[object Object],[object Object],[object Object]

Forms of delivery ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Classification by composition ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Classification by application ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Phase ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Equilibrium phase diagram ,[object Object],[object Object],Temperature Pressure 100 kPa 100˚C 0˚C SOLID LIQUID GAS Isotherm Isobar

Phases in iron 910˚C 1390˚C 1535˚C AUSTENITE (gamma) LIQUID FERRITE (delta) FERRITE (alpha) FERRITE Body centred cubic (bcc) AUSTENITE Face centred cubic (fcc)

Iron-carbon diagram Percentage Carbon Temperature Liquid Austenite + liquid Austenite Austenite + Fe 3 C Ferrite + Fe 3 C Alpha ferrite Delta ferrite A+F 1535˚C 1390˚C 1130˚C 723˚C 4.3% 0.83% 0.02% 1.7% 910˚C

Iron-iron carbide diagram    + Fe 3 C   + Fe 3 C 910°C 723°C 0.02% 0.83% Temperature Percent Carbon

Transformation to pearlite ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Structure of pearlite Ferrite (0.02% C) Cementite (6.67% C) Pearlite (0.8% C average)

Pearlite microstructure Alternate plates of carbide and ferrite. Normally the structure cannot be resolved. Particularly slow cooling has been used. 10  m

Iron-iron carbide diagram    + Fe 3 C   + Fe 3 C A 3 A 1 910°C 723°C 0.02% 0.83% Temperature Percent Carbon Hypoeutectoid Hypereutectoid

Hypoeutectoid steel ,[object Object],[object Object],[object Object],[object Object],[object Object]

Hypoeutectoid steel microstructure Ferrite + Austenite (yellow) Ferrite (white) + pearlite (black)

0.5% Carbon Steel Pearlite islands surrounded by ferrite. The ferrite shows the prior austenite grain boundaries

Annealing and normalising ,[object Object],[object Object],[object Object],[object Object],[object Object]

Sub-critical or process anneal ,[object Object],[object Object],[object Object],[object Object]

Process annealed steel Cold worked steel Process annealed steel

Effect of pearlite on properties 0 0.2 0.4 0.6 0.8 1.0 1.2 % pearlite % ferrite 0% 100% % carbon 300 MPa 900 MPa 500 MPa 700 MPa UTS (R m ) UTS cementite Elongation Elongation (A 5 ) 0% 10% 20% 30% 40%

Effect of rapid cooling of austenite

Isothermal transformation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Time Temp Deg C

Isothermal transformations ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Isothermal transformation diagram Martensite Upper bainite Lower bainite A + F + P A + B Austenite A + M Time (Seconds) Temperature (Deg C) 1 10 100 1000 M s M f Pearlite (+ ferrite) 100% Ac 1 0%

Formation of martensite ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Martensite Martensite formed by shear transformation in an austenite grain Martensite Retained austenite

Martensite Martensite is created when austenite transforms by a shear mechanism instead of by nucleation and growth. The shear transformation products are acicular. In this case, because of high carbon (1.2%) there is retained austenite.

Martensite properties ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Factors promoting martensite ,[object Object],[object Object],[object Object],[object Object]

Cooling rate depends on ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Hardenability measurement ,[object Object],[object Object],[object Object],[object Object],[object Object]

Hardenability determination ,[object Object],[object Object],[object Object],[object Object],[object Object]

Tempering ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Effect of tempering ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Constituents of Steel s ,[object Object],[object Object]

[object Object],[object Object]

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