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Astronuc
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Feb26-07, 06:37 AM
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Cold Working processes include

Cold Rolling - a billet or strip is passed between two rollers with a smaller gap (obviously) than the thickness of the billet or strip. The rolling compress the metals and elongation occurs in the rolling direction.

Drawing - barstock is passed through a die, which is how wire is made.

Pressing - a metal (e.g. copper or copper alloy) sheet is pressed onto a shaped die or mould to form an intricate shape.

Stamping - a punch is passed through a sheet of metal (e.g. copper or copper alloy)

Cold working, the permanent (plastic) deformation of a metal below its recrystallization temperature (and usually below its annealing temperature), produces additional dislocations within the metal's crystal lattice. Cold working induces Work Hardening

When two or more dislocations meet, the movement of one tends to interfere with the movement of the other. The more dislocations there are, the more they will hinder each other's movement.

Initially the dislocations produced by cold working can move through the metal structure and the shape of the material will change. As the working continues, however, the movement of the dislocations becomes more difficult. This increases the strength of the metal and also makes it stiffer. Therefore it becomes less malleable and ductile. That is, it is more difficult to change its shape. We say that the metal has become work hardened.

To make it more malleable and ductile again, the metal can be annealed.
See also - Annealing, Hot Working, Quenching - http://learningzone.coruseducation.c...eelch2pg3.html