hot forming

Deforming metal cold will cause workhardening that reduces the achievable deformation before the workpiece cracks. This is caused by deformation of the crystal strukture in the metal.

Higher deformations can be achieved with a proper heat treatment. For this there are two ways:

1- Forming the metal hot

2- Soft annealing between forming passes

Hot forming or forging has the advantage that the needed force to deform the metal is reduced. This is because the energy that was introduced into the workpiece by heating it up and the deformation force are combined in interconnection between the atoms.

In addition some metals like iron change there crystal structure by higher temperatures. Sometimes this structures are easier to be deformed (iron and steel is forming a crystal structure named austenit somewhere between 900-1000°C).

When forming cold the workhardening can be removed with a recrystailzation temper. For this the workpiece is brought up to temperature where the crystals can reform there normal inner structure and all inner tentions are loosened.

The specific process and temperatures are depending on the used metal.

Steel

Messing

Aluminium