ZUBAIR AHMAD UNITED GULF STEEL ZUBAIR AHMAD UNITED GULF STEEL.

ZUBAIR AHMAD

UNITED GULF STEEL

ZUBAIR AHMAD

UNITED GULF STEEL

Rolling (Hot/Cold)

MechanicalWorking=

Permanent Deformation =

Mechanical WorkingIs a permanent deformation to which metal is

subjected to change its shape and/or properties.

Reheating Roughing Finishing Cooling Coiling•Grain Refinement•Recrystallization

•Grain Refinement•Precipitation

•Austenite Decomposition

•Accelerated Cooling

•Precipitation•Phase transformation

•> 1200 °C•Austenitizing

Slab Chemistry

Thickness & TemperatureReduction

Chemistry

(C, Mn, Ni, Cu, MAE)

Strength

Ductility

Toughness

Weldability

Sour Resistance

…etc

SteelMechanicalProperties

•CVN•DWTT

PSL2:•YS (min/max)•UTS (min/max)•YS/UTS

•CEPcm

•HIC•SSCC

5

SteelMechanicalProperties

Ch

emistry

Processing Processing ParametersParameters

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Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy

1- Meteoric Iron (5 – 30 % nickel) LimitedLimited

RareRare(Grains or nodules of Iron in basalt that erupted through beds of coal) (Grains or nodules of Iron in basalt that erupted through beds of coal)

(Use charcoal to reduce iron from its oxides)(Use charcoal to reduce iron from its oxides)

3- Man-made Ferrous Metals.

2- Telluric (Native) Iron

Fe2O3 + 3CO → 2Fe + 3 CO2

Iron is so important that primitive societies are measured by the point at which they learn how to refine iron and enter the iron age!

Gold is for the mistress ….

silver for the maid

Copper for the craftsman cunning at his trade.

"But IronIron … Cold Iron … is master of them all !“

Rudyard Kipling, 1910


• Strong materialStrong material

• Easy to shape Easy to shape

• Conduct heat and Conduct heat and electricityelectricity

• Unique magnetic Unique magnetic propertiesproperties

• Iron is plentiful (5% of the Iron is plentiful (5% of the Earth's crust)Earth's crust)

• Relatively easy to refineRelatively easy to refine

Iron


Iron oresIron ores are rocks that contain a high concentration of iron

• Hematite - Fe2O3 - 70 % iron

• Magnetite - Fe3O4 - 72 % iron

• Limonite - Fe2O3 + H2O - 50 % to 66 % iron

• Siderite - FeCO3 - 48 % iron

HematiteHematite


GrainsGrains

Crystal StructureCrystal Structure


X

Y

Z

Space Lattice: A collection of points that divided space into smaller sized segments.

Unit Cell: A subdivision of the lattice that still retains the overall characteristics of the entire lattice.

Crystal Structure(Atomic Arrangement)


AtomAtom

Formation of Polycrystalline Material

Liquid

a b

c d

Solid (Unit Cell)

Grain Boundaries

a) Small crystalline nuclei b) Growth of Crystals

c) Irregular grain shapes formed upon completion of solidification

d) Final grain structure

Grain Boundary: The zone of crystalline mismatch between adjacent grains. The lattice has different orientation on either side of the grain boundary


Grain Boundary

BCC - Delta Iron ()

FCC - Gamma Iron ()

BCC - Alpha Iron ()

Tem

pera

ture

1540 oC

1400 oC

910 oC

Atomic Packing in Iron (Allotropic)


Body Centered Cubic (BCC)

Alpha & Delta Iron (Alpha & Delta Iron ( , , ))Total 2 Atoms/Unit Cell

α Lattice Parameter (a) = 0.287 nm

δ Lattice Parameter (a) = 0.293 nm

a

Squared Packed Layer


Face Centered Cubic (FCC)

Gamma Iron (Gamma Iron ())Total 4 Atoms/Unit Cell

Lattice Parameter (a) = 0.359 nm

a

Close Packed Layer


High Dense Atomic Packing

Slip Distance

Effect of the Atomic Packing in Deformation Behavior

Dis

plac

emen

t

Slip Distance

Dis

plac

emen

t

Low Dense Atomic Packing

Slip occurs easily on closest packed plane (high atomic packing density) along the closest packed direction where the slip distance is minimum.


Smooth Surface Easy to slip with minimum power Example of closed Packed planes

Uneven Surface Relatively high energy is required for limited slip

Example of squared packed plans

Rough Surface Extremely hard to slip

Example of squared packed plans with high inter-atom

spaces

Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic MetallurgyEffect of the Atomic Packing in Deformation Behavior

STEEL = IRON + Alloying Elements ( C + Mn, Si, Ni, …)

IRON + < 2 % Carbon = STEEL

IRON + > 2 % Carbon = CAST IRON

What is the difference between “STEEL” and “CAST IRON” ?


Liquid (L)

( +Fe3C)

( +L)

Austenite ()

1540

1495

1150 °C

727 °C

910

0.5%

0.18%

0.1%

Cementite (Fe3C)+ Pearlite

( + )

( +L)

Steel Cast Iron

4.3%

2.1%Eutectic

Ferrite + Pearlite

Ferrite ()

Weight Percentage Carbon

Tem

pera

ture

(o

C)

1000 -

1200 -

1400 -

1600 -

1.0

800 -

4.03.02.0 6.67

400 -

600 -

200 -

0 -

Hypoeutectoid Hypereutectoid HypereutecticHypoeutectic

0.8%

Eutectoid

Delta Ferrite ( )

( )

Peritectic

Iron Carbon Phase Diagram

Atomic Packing in Iron (Allotropic)

BCC - Delta Iron ()

FCC - Gamma Iron ()

BCC - Alpha Iron ()



Weight Percentage Carbon

Tem

pera

ture

(o

C)

( +Fe3C)

( +L)

Austenite ()

Liquid (L)1540

1495

727 °C

910

Cementite (Fe3C)+ Pearlite

( + )

Ferrite + Pearlite

Ferrite ()

1000 -

1200 -

1400 -

1600 -

1.0

800 -

2.0

400 -

600 -

200 -

0 -0.8%

Eutectoid

Delta Ferrite ( )

( )

Peritectic

( +L)

1150 °C

Ferrite

Cementite

~0% C~0% C

0.2% C0.2% C

0.35% C0.35% C

0. 5% C0. 5% C

0. 7% C0. 7% C

0. 8% C0. 8% C

1.2% C1.2% C

• Strength: Ability to withstand loads (Tensile & Compressive Strength)

• Ductility:Ability to deform under tensile loads without rupture

• Bending AbilityAbility to bend without Fracture

• ToughnessAbility to absorb energy in shock loading (Impact Strength)

• HardnessResistance to penetration

• WeldabilityAbility to be welded without cracking

Fundamental Mechanical PropertiesFundamental Mechanical Properties


Carbon (C):

Strength & Hardness Ductility, Malleability & Weldability

Silicon (Si):

Manganese (Mn):

De-oxidizer, Strength, Hardenability & Impact Strength

De-oxidizer, Strength & Toughness Hardenability

Aluminum (Al):

Strong De-oxidizer, Grain Refinement Strength & Toughness

MAE (V, Ti & Nb):

Sulfur (S):

Harmful Ductility, Weldability Strength & Impact Strength

Grain Refinement Strength, Hardenability & Toughness


Effect of Alloying ElementsEffect of Alloying Elements

Stress – Vs - StrainStress – Vs - Strain

L1

F

L1

Force (F)

Lo

= F/Ao = F/Ao

Stress: Force per unit area

Measuring the internal resistance of the body.

Strain: Unit deformation

Measuring the change in dimensions of the body = (L1 – Lo)/Lo = (L1 – Lo)/Lo


Elastic Def.

Plastic DeformationO

P

Strain

Str

ess P: Elastic Limit

Y: Yield Point

S: Max. Load Value

B: Breaking Point

P: Elastic Limit

Y: Yield Point

S: Max. Load Value

B: Breaking Point

Y

S

B


Stress – Vs - StrainStress – Vs - Strain

Elastic & Plastic DeformationElastic & Plastic Deformation

Elastic Deformation:

Deformation of a material that recovered when the applied load is removed. This type of deformation involves stretching of the bonds without permanent atomic displacement.

Plastic Deformation:

Permanent deformation of a material that is not recovered when the applied load is removed. This Type of deformation involves breaking of a limited number of atomic bonds.


Microstructural DefectsMicrostructural Defects

Theoretical yield strength predicted for perfect crystals is much greater than the measured strength. The existence of defects explains the difference.

Which is easier to cut?


Braking all atomic bonds at once requires grater energy in perfect crystal


1) Point defects: a) vacancies, b) interstitial atoms, c) small substitional atoms, d) large substitional atoms, … etc.

2) Surface defects: Imperfections, such as grain boundaries, that form a two-dimensional plane within the crystal.



3) Line defects: dislocations (edge, screw, mixed)

Dislocation: A line imperfection in the lattice or crystalline material

Movement of dislocations helps to explain how materials deform. Interface with movement of dislocations helps explain how materials are strengthened.

They are typically introduced into the lattice during solidification of the material or when the material is deformed.



Motion of DislocationMotion of Dislocation

When a shear stress is applied to the dislocation in (a), the atoms displaced, causing the dislocation to move one step (Burger’s vector) in the slip (b). Continued movement of the dislocation eventually creates a step (deformation) direction (C)


ZUBAIR AHMAD UNITED GULF STEEL ZUBAIR AHMAD UNITED GULF STEEL.

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