Hot forging
Hot forging is defined as working a metal above its recrystallisation temperature. The main advantage of hot forging is that as the metal is deformed the strain-hardening effects are negated by the recrystallisation process.
Other advantages include:
- Decrease in yield strength, therefore it is easier to work and takes less energy (force)
- Increase in ductility
- Elevated temperatures increase diffusion which can remove or reduce chemical inhomogeneities
- Pores may reduce in size or close completely during deformation
- In steel, the weak, ductile, FCC (face-centered-cubic) austenite is deformed instead of the strong BCC (body-centered-cubic) ferrite at lower temperatures
The disadvantages of hot forging are:
- Undesirable reactions between the metal and the surrounding atmosphere
- Less precise tolerances due to thermal contraction and warping from uneven cooling
- Grain structure may vary throughout the metal for various reasons