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
د�يد� س� ش� �أ ح�د�يد� ف�يه� ب �ا ال ن ل ز� �ن و�أ
�اس� �لن �اف�ع� ل و�م�ن
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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
• 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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
GrainsGrains
Crystal StructureCrystal Structure
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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)
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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)
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
Face Centered Cubic (FCC)
Gamma Iron (Gamma Iron ())Total 4 Atoms/Unit Cell
Lattice Parameter (a) = 0.359 nm
a
Close Packed Layer
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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.
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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” ?
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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 ()
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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.
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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?
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
Braking all atomic bonds at once requires grater energy in perfect crystal
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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.
Microstructural DefectsMicrostructural Defects
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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.
Microstructural DefectsMicrostructural Defects
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
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)
Basic MetallurgyBasic MetallurgyBasic MetallurgyBasic Metallurgy
35