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Rolling

Rolling is a metal forming process where metal is passed through rotating rolls to reduce thickness and alter the cross-sectional shape. It can be classified as hot or cold rolling depending on if the temperature is above or below the metal's recrystallization point. Hot rolling allows for larger deformations with fewer passes and does not require annealing, while cold rolling introduces defects that work harden the metal. Rolling mills use pairs of rolls to shape the metal, and products include sheets, plates, foils, and structural items.

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339 views3 pages

Rolling

Rolling is a metal forming process where metal is passed through rotating rolls to reduce thickness and alter the cross-sectional shape. It can be classified as hot or cold rolling depending on if the temperature is above or below the metal's recrystallization point. Hot rolling allows for larger deformations with fewer passes and does not require annealing, while cold rolling introduces defects that work harden the metal. Rolling mills use pairs of rolls to shape the metal, and products include sheets, plates, foils, and structural items.

Uploaded by

Ahmad Anwar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Rolling (Deformation

Process)
Rolling:
Rolling is plastic deformation of the metal by passing
between rolls to give it the desired shape.
 Metal is passed between two rolls that rotate in opposite
directions.
 Gap between the rolls being somewhat less than the
thickness of the entering metal.

Process:
• In the process of rolling the workpiece is fed from one side
into the rolls
• Reduces in thickness according to the section and gap
between the rolls.
• The reduction ratios have maximum allowable values for
different metals beyond which reduction is not practicable
in a single process.
Classification:
Rolling is classified according to the temperature of the metal
rolled:
 Cold Rolling
 Hot Rolling

Hot Rolling:
If the temperature of the metal is above its recrystallization
temperature, then the process is termed as hot rolling.
In hot rolling;
• Hot rolling permits large deformations of the metal to be
achieved with low number of rolling cycles.
• As the hot rolling process breaks up the grains, they
recrystallize and preventing the metal from hardening.
• Hot rolled material typically does not require annealing.
• Hot rolling is primarily concerned with manipulating
material shape and geometry rather than mechanical
properties.

Cold Rolling:
If the temperature of the metal is below its recrystallization
temperature, the process is termed as cold rolling.
In cold rolling;
• Cold rolling increases the yield strength and hardness of a
metal by introducing defects into the metal’s crystal
structure (dislocation density).
• These defects prevent further slip and can reduce the
grain size of the metal, resulting in hardening.
• Cold rolling is most often used to decrease the thickness
of plate and sheet metal.
• In cold rolling, high densities of imperfections are
introduced throughout the deformed area.
• These defects can be either point defects (a vacancy on
the crystal lattice) or a line defect

Rolling Mills:
A rolling mill is a machine or factory for shaping metal by
passing it between a pair of work rolls.

Classification:
There are fundamentally two types of rolls:
 Supporting rolls
 Driving rolls
Rolling mills can be conventionally classified with respect to the
number and arrangement of the rolls:
 Two-high mills
 Two-high reversing mills
 Three-high mills
 Four-high mills
 Cluster mills
 Continuous mills
 Planetary mills

Rolled Products:
 Bloom (First breakdown product of ingots)
 Billet (Reduction of bloom by rolling)
 Slab (Hot rolled ingot)
 Plate (thickness greater than ¼ in.)
 Sheet & strip (thickness less than ¼ in.)
 Foil (very Small thickness just 0.002 in.)
Advantages:
 For large reduction in cross sectional area. (Hot rolling
carried out)
 Hot rolling doesn’t require annealing.
 For high strength. (Cold rolling carried out.)
 It reduces ductility of metals.
 In cold rolling, there is no need to control temperature.
 Good surface finish.

Applications
 Bars, Rods, Rails.
 To produce sheets & strips.
 Piping
 Parts for airplane

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