Uncoated Plain Carbon SteelsSteel Production

Steel Production

Lesson ObjectivesWhen you finish this lesson you will understand:• The principles of basic steel making and casting•The principles of steel rolling • Factors effecting steel properties

Learning Activities1. Look up Keywords2. View Slides; 3. Read Notes, 4. Listen to lecture5. Do on-line

workbook6. Do homework

KeywordsHot Rolling, Cold Rolling, Interstitial Free Steels, Mild Steel, Rephosphorized Steel, High Strength Low Alloy Steels, Transformation Hardened Steels, Recovery Annealed Steels, Basic Oxygen Steel Making, Casting, Continuous Casting, Vacuum Arc Remelting, Dynamic Recrystallization, Grain Refinement, Tempering

Classification of Sheet Steels

Steel Type

Interstitial-Free Steel

Mild Steel

Rephosphorized Steel

PPN Hardened/GrainRefined Steel (HSLA)

Transformation Hardened Steel

Chemistry

C < 0.01%Boron & Ti additions

C: 0.02 - 0.08%Mn: 0.3%

P: 0.07%

Cb & V: 0.02%

C: 0.05 - 0.15%Mn: 0.5 - 1.5 % + Si

TS. < 30 ksiElongation: 50%

TS. < 40 ksiElongation: 30%

TS. > 40 ksiElongation > 20%

TS.: 50 - 80 ksi

TS.: 50 - 150 ksi

Mechanical PropertiesHot Rolled

ColdRolled

RecoveryAnnealed

Steel Melting and Casting

Making, Shaping & Treating of Steel,USS, 1964

C+O=CO2

Alloy Additions

A Few Melting Practice ProblemsWhich Can Result in Weld Problems

• Porosity• Loss of Intended Alloy Addition• Intermetallic Inclusions• Stringers or Banded Material• Poor Ingot Surface Carried Over to Strip

Steel refining - IF Steels

Making, Shaping & Treating of Steel,USS, 1964

Classification of Sheet Steels

Steel Type

Interstitial-Free Steel

Mild Steel

Rephosphorized Steel

PPN Hardened/GrainRefined Steel (HSLA)

Transformation Hardened Steel

Chemistry

C < 0.01%Boron & Ti additions

C: 0.02 - 0.08%Mn: 0.3%

P: 0.07%

Cb & V: 0.02%

C: 0.05 - 0.15%Mn: 0.5 - 1.5 % + Si

TS. < 30 ksiElongation: 50%

TS. < 40 ksiElongation: 30%

TS. > 40 ksiElongation > 20%

TS.: 50 - 80 ksi

TS.: 50 - 150 ksi

Mechanical PropertiesHot Rolled

ColdRolled

RecoveryAnnealed

Hot Rolling of Strip

Dynamic RecrystallizationFollowed by Grain Growth

Large GrainAustenite

Large GrainAustenite

TransformsFerrite/Pearlite

TIME

TEM

PE

RA

TUR

E

Martensite

Ferrite +Pearlite

Fine = Higher Strength

Coarse = Lower Strength

CQ, DQ & IF Steels

Rephosphorized Steel

Controlled Hot Rolled Strip Processing

Dynamic RecrystallizationPinned Grain Boundaries

Grain Size(fine)

Str

eng

th

ppt

Grain Refinement

HSLA Steels

Solid Solid SolutionSolution(Rephos)(Rephos)HSLA

SteelDual Phase Steel

TRIPSteel

Turn to the person sitting next to you and discuss (1 min.):• The particles that pin the grain boundaries during hot rolling are carbides and carbonitrides of niobium, vanadium and titanium. These each have their own dissolution temperature where they go back into solution in the steel. What happens if the temperature of the strip is just below this dissolution temperature (I.e. the particle have precipitated and are available for pinning grains) just before the strip goes through a hot rolling mill? Why might steel makers select a combination of these elements for their chemistry formulation?

Classification of Sheet Steels

Steel Type

Interstitial-Free Steel

Mild Steel

Rephosphorized Steel

PPN Hardened/GrainRefined Steel (HSLA)

Transformation Hardened Steel

Chemistry

C < 0.01%Boron & Ti additions

C: 0.02 - 0.08%Mn: 0.3%

P: 0.07%

Cb & V: 0.02%

C: 0.05 - 0.15%Mn: 0.5 - 1.5 % + Si

TS. < 30 ksiElongation: 50%

TS. < 40 ksiElongation: 30%

TS. > 40 ksiElongation > 20%

TS.: 50 - 80 ksi

TS.: 50 - 150 ksi

Mechanical PropertiesHot Rolled

ColdRolled

RecoveryAnnealed

Cold Rolling and Annealing

Str

eng

th

% Cold Reduction

Str

en

gth

Anneal Temperature

Recovery

Recrystallization

1

2

3

4

Cold Worked Structure

Classification of Sheet Steels

Steel Type

Interstitial-Free Steel

Mild Steel

Rephosphorized Steel

PPN Hardened/GrainRefined Steel (HSLA)

Transformation Hardened Steel

Chemistry

C < 0.01%Boron & Ti additions

C: 0.02 - 0.08%Mn: 0.3%

P: 0.07%

Cb & V: 0.02%

C: 0.05 - 0.15%Mn: 0.5 - 1.5 % + Si

TS. < 30 ksiElongation: 50%

TS. < 40 ksiElongation: 30%

TS. > 40 ksiElongation > 20%

TS.: 50 - 80 ksi

TS.: 50 - 150 ksi

Mechanical PropertiesHot Rolled

ColdRolled

RecoveryAnnealed

Transformation Hardened Steels

H2O

H2O

TIME

TEM

PE

RA

TUR

E

Martensite

Ferrite +Pearlite

Martensitic Structure

% Carbon

Har

dnes

s

Tempering

Tempering Temperature - 1 hr.

Hard

ness

12

3

4

Spot Weldability(Production of Welds Fit for Service)

Process Variables(Things Manufacturers Control)

Material Variables(Things Steel Makers Control)

Module 3 Module 4

Assignment 2