When a piece of metal is hot forged it must be heated significantly. The average forging temperature necessary for hot forging of different metals is: 

Up to 1150°C for Steel

360 to 520°C for Al-Alloys

700 to 800°C for Cu-Alloys

During hot forging, the billet or bloom is heated either inductively or in a forging furnace or oven to a temperature above the recrystallization point of the metal. This kind of extreme heat is necessary in avoiding strain hardening of the metal during deformation. Because the metal is in a plastic state, fairly intricate shapes can be made. The metal remains ductile and malleable.

In order to forge certain metals like super alloys, a type of hot forging called isothermal forging is employed. Here, the die is heated to approximately the temperature of the billet to avoid surface cooling of the part during forging. Forging is also done sometimes in controlled atmospheres to minimize scale formation.

Traditionally, manufacturers choose hot forging for the fabrication of parts because it allows for the deformation of the material in its plastic state where the metal is easier to work. Hot forging is also recommended for the deformation of metal that features a high formability ratio, a measure of how much deformation a metal can undergo without developing defects. Other considerations for hot forging include:

• Production of discrete parts

• Low to medium accuracy

• Low stresses or low work hardening

• Homogenized grain structure

• Increased ductility

• Elimination of chemical incongruities and porosity

Possible disadvantages of hot forging include: 

• Less precise tolerances

• Possible warping of the material during the cooling process

• Varying metal grain structure

• Possible reactions between the surrounding atmosphere and the metal (scale formation)