Cold working operation

Hi friends,
Cold working does not necessarily mean literally what it says, it is true that many metal working processes are carried out at ambient temperature and these can certainly be termed cold working. However, metal working that is carried out at a temperature much higher than that revealing on the shop floor can also be described as cold working. The upper temperature limit of cold working varies with the metal and its metallurgical condition before working, but for steels cold working is generally considered to be between ambient and about 300 c. Significant work hardening takes place, and this severely limits the amount of plastic deformation that can occur before the material ruptures. To overcome this, if all the desired geometric changes cannot be achieved in one operation, the material must be partly changed and then annealed to eliminate the stress introduced by the work hardening. After annealing the work piece can then be safely subjected to a second cold working operation that will, hopefully, permit reduction to the final desired geometry. Cold working processes generally produce repeatable accurate components with a good surface finish. Unfortunately, cold working forces are very much higher than those required for hot working and unwanted residual stress are usually present after the final stages of working. If they are significant they tend to be released during subsequent machining of the part needs to be annealed before machining to remove these locked – in stresses. Any distortion that occurs during annealing is of no consequence as its geometrical effects will, of course, be removed during machining of the part. Thank you.