Forging

This is a squeezing/hammering technique, which is intended to achieve large deformation/shaping of the material. The process is usually carried out hot (i.e. above the re-crystallisation temperature), so that these large deformations can be attained without being accompanied by any massive, residual stresses.

Sometimes, a cold forging operation may be necessary. But, the material will be harder, stronger and pre-stressed (i.e. still containing unrelieved internal stresses).

Forging ranges from the simplest form of the hand operations, conducted by the blacksmith, to the massive, mechanical, powered rams, used for very large forgings. The forging hammer will often have a relatively low strike rate, but sometimes high-speed, pneumatic hammers are used for High-Energy-Rate Forming.

Forging not only shapes the metal, but also reduces grain size and produces a directional control of grain flow. Both of these are desirable features for many engineering applications, particularly for highly-stressed components, such as crankshafts and especially if they are subject to a mechanical fatigue environment.