Basic Metallurgy 15-4-2008

8/13/2019 Basic Metallurgy 15-4-2008

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ZUBAIR AHMAD

UNITED GULF STEEL


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Rolling (Hot/Cold)

MechanicalWorking =

PermanentDeformation =

Mechanical WorkingIs a permanent deformation to which metal is

subjected to change its shape and/or properties .


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Reheating Roughing Finishing Cooling Coiling Grain Refinement Recrystallization

Grain Refinement Precipitation

AusteniteDecomposition

Accelerated Cooling

Precipitation Phase

transformation

> 1200

C Austenitizing

Slab Chemistry

Thickness & TemperatureReduction

Chemistry(C, Mn, Ni, Cu, MAE)


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Strength

Ductility

Toughness

Weldability

Sour Resistance

etc

SteelMechanicalProperties

CVN DWTT

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

CE Pcm

HIC SSCC


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5

SteelMechanicalProperties

C h

emi s

t r y

ProcessingParameters


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Basic Metallurgy

1- Meteoric Iron (5 30 % nickel) Limited

Rare(Grains or nodules of Iron in basalt that eruptedthrough beds of coal)

(Use charcoal to reduce iron from its oxides)3- Man-made Ferrous Metals.

2- Telluric (Native) Iron

Fe 2O3 + 3CO 2Fe + 3 CO 2


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Iron is so important that primitive societies aremeasured by the point at which they learn how torefine iron and enter the iron age !

Gold is for the mistress . silver for the maid

Copper for the craftsman cunning at his trade.

"But Iron Cold Iron is master of them all ! Rudyard Kipling, 1910

Basic Metallurgy
http://en.wikipedia.org/wiki/Image:Kiplingcropped.jpg


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Strong material Easy to shape Conduct heat and

electricity Unique magnetic properties Iron is plentiful (5% of the

Earth's crust)

Relatively easy to refine

Iron

Basic Metallurgy


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Iron ores are rocks that contain a high concentration of iron

Hematite - Fe 2O3 - 70 % iron Magnetite - Fe 3O 4 - 72 % iron Limonite - Fe 2O 3 + H 2O - 50 % to 66 % iron

Siderite - FeCO 3 - 48 % iron

Hematite

Basic Metallurgy


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Grains

Crystal

Structure

Basic Metallurgy


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X

Y

Z

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

Unit Cell: A subdivision of thelattice that still retains the overallcharacteristics of the entire lattice.

Crystal Structure(Atomic Arrangement)

Basic Metallurgy

Atom


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Formation of Polycrystalline Material

Liquid

a b

c d

Solid (Unit Cell)

a) Small crystalline nuclei b) Growth of Crystalsc) Irregular grain shapesformed upon completionof solidification

d) Final grain structure

Grain Boundary: The zone ofcrystalline mismatch betweenadjacent grains. The lattice hasdifferent orientation on eitherside of the grain boundary

Basic Metallurgy


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Grain Boundary


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BCC - Delta Iron ( d)

FCC - Gamma Iron (g)

BCC - Alpha Iron (a )

1540 oC

1400 oC

910 oC

Atomic Packing in Iron (Allotropic)Basic Metallurgy


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Body Centered Cubic (BCC)

Alpha & Delta Iron (a

,d)Total 2 Atoms/Unit Cell

Lattice Parameter (a) = 0.287 nm Lattice Parameter (a) = 0.293 nm

a

Squared Packed Layer

Basic Metallurgy


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Face Centered Cubic (FCC)

Gamma Iron (g)Total 4 Atoms/Unit Cell

g Lattice Parameter (a) = 0.359 nm

a

Close Packed Layer

Basic Metallurgy


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High Dense Atomic Packing

SlipDistance

Effect of the Atomic Packing in Deformation Behavior

D i s p

l a c e m e n

t

SlipDistance

D i s p

l a c e m e n

t

Low Dense Atomic Packing

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

Basic Metallurgy


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Smooth Surface Easy to slip with minimum powerExample of closed Packed planes

Uneven Surface Relatively high energy isrequired for limited slip

Example of squared packed plans

Rough Surface Extremely hard to slip

Example of squared packed planswith high inter-atom spaces

Basic Metallurgy

Effect of the Atomic Packing in Deformation Behavior


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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 Metallurgy


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Liquid (L)

( g + Fe 3C )

( g + L )

Austenite (g )

1540

1495

1150 C

727 C

910

0.5%

0.18%

0.1%

Cementite (F e 3C)+ Pearlite

( a + g )

( d + L )

Steel Cast Iron

4.3%

2.1%Eutectic

Ferrite + Pearlite

Ferrite (a )

Weight Percentage Carbon

T e m p e r a

t u r e

( 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 ( d )

( d g )

Peritectic

Iron Carbon Phase Diagram


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Atomic Packing in Iron (Allotropic)

BCC - Delta Iron ( d)

FCC - Gamma Iron (g)

BCC - Alpha Iron (a )

Basic Metallurgy


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Basic Metallurgy

Weight Percentage Carbon

T e m p e r a

t u r e

( o C )

( g + Fe 3C )

( g + L )

Austenite (g )

Liquid (L)15401495

727 C

910

Cementite (Fe 3C)+ Pearlite

( a + g )

Ferrite + Pearlite

Ferrite (a )

1000 -

1200 -

1400 -

1600 -

1.0

800 -

2.0

400 -

600 -

200 -

0 -0.8%

Eutectoid

Delta Ferrite ( d )

( d g ) Peritectic

( d + L )

1150 C

Ferrite

Cementite

~0% C

0.2% C

0.35% C

0. 5% C

0. 7% C

0. 8% C

1.2% C


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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 Weldability

Ability to be welded without cracking

Fundamental Mechanical Properties

Basic Metallurgy


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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 Metallurgy

Effect of Alloying Elements


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Stress Vs - Strain

L1

F

L1

Force (F)

Lo

s = F/A oStress: Force per unit area

Measuring the internal resistance of the body.

Strain: Unit deformation

Measuring the change in dimensions of the body e = (L 1 L o)/L o

Basic Metallurgy


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ElasticDef.

Plastic DeformationO

P

Strain

S t r e s s P: Elastic Limit

Y: Yield PointS: Max. Load Value

B: Breaking Point

Y

S

B

Basic Metallurgy

Stress Vs - Strain


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Elastic & Plastic Deformation

Elastic Deformation:

Deformation of a material that recoveredwhen the applied load is removed. Thistype of deformation involves stretching of

the bonds without permanent atomicdisplacement.

Plastic Deformation:

Permanent deformation of a material thatis not recovered when the applied load isremoved. This Type of deformationinvolves breaking of a limited number ofatomic bonds.

Basic Metallurgy


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Microstructural DefectsTheoretical yield strength predicted for perfect crystals is muchgreater than the measured strength. The existence of defectsexplains the difference.

Which is easier to cut?

Basic Metallurgy


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Braking all atomic bonds at once requires graterenergy in perfect crystal

Basic Metallurgy


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

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

Microstructural DefectsBasic Metallurgy


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

Dislocation: A line imperfection inthe lattice or crystalline material

Movement of dislocations helps toexplain how materials deform.Interface with movement ofdislocations helps explain howmaterials are strengthened.

They are typically introduced intothe lattice during solidification ofthe material or when the material isdeformed.

Microstructural DefectsBasic Metallurgy


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Motion of Dislocation

When a shear stress is applied to the dislocation in (a), the atomsdisplaced, causing the dislocation to move one step (Burgers vector) inthe slip (b). Continued movement of the dislocation eventually creates astep (deformation) direction (C)

Basic Metallurgy


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Basic Metallurgy 15-4-2008