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DIFFERNCE BETWEEN HOT ROLLING

AND COLD ROLLING

PARAMETERS HOT ROLLING COLD

ROLLING

% Reduction VERY HIGH Comparatively

low

Dimensional

Tolerance

WIDE CLOSE

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DIFFERNCE BETWEEN HOT ROLLING

AND COLD ROLLING

PARAMETERS HOT ROLLING COLD

ROLLING

Surface finish inferior superior

Properties Cannot be

controlledwithin narrow

band

Can be

controlledwithin narrow

band

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APPLICATIONS

AUTOMOBILES

WHITE GOODS GENERAL ENGINEERING

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AUTOMOBILE

APPLICATIONS

SKIN PANEL

INTERNAL PANELS

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SKIN PANEL

RECENT DEVELOPENTS

IF STEELS DENT RESISTANCE STEELS

- BH STEEL

- RE PHOSPHORISED STEEL

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PROPERTIES OF STEEL

CHEMISTRY(WELDABILITY , CARBON

EQUIVALENT)

MECHANICAL PROPERTIES(STRENGTH

AND FORMING)

YIELD STRENGTH

ULTIMATE TENSILE STRENGTH

ELONGATION

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PROPERTIES OF STEEL

HARDNESS

CUPPING VALUE

SURFACECHARACTERISTICS(LUBRICATION

AND PAINTABILITY) Ra

PEAKS PER INCH (PPI)

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CHEMISRTY SPECTROVACUUM

ULTIMATE TENSILE STRENGTH -UTM

HARDNESS

SURFACE RA AND PPI

PROPERTIES

DETERMINATION

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MECHANICAL PROPERTIES

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RECENT PROPERTIES

R-BAR

N - VALUE

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R bar

Strain ratio ( r ) =

Width strain /

Thickness Strain r bar = r0 + 2r45

+r90 / 4

Delta r = r0 2r45 +

r90 / 2

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n - Value

Related to uniform

elongation

Power law

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FORMABILITY

DRAWING

STRETCHING

BEDNING

FLANGING

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DRAWING

Property :

R bar

Ideally no increase in

surface area

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DRAWING VERTICAL

SECTION OF A CUP

Flange area =

Tendency to wrinkle

Wall area = Severe

stretching

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STRETCHING

Property :

n value

The surface area increase

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BENDING

Property :

% Elongation

Spring Back : Yield

Strength ,

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FLANGING

SHRINK FLANGING

STRETCH FLANGING

HOLE EXPANSION

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SHRINK FLANGING

PROPERTY

THICKNESS

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STRETCH FLANGING PROPERTY

% ELONGATION

Inclusion free

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HOLE EXPANSION Property

% Elongation

Inclusion free