Hot forging process is to press and form the metal at temperature above recrystallization temperature. The steel or alloy steel which is hard to be formed at warm or cold forging process will be done at hot forging process. The complex structure parts which is not easy to be formed in cold forging or warm forging process is normally forged in hot forging process. Hot forging process can normally get refined grain and improved mechanical properties.
 
Cold forging process is suitable for the low carbon or low carbon alloy steel, aluminum alloy material, copper alloy and some of middle carbon steel. Cold forging process can get good dimensional precision and good surface quality.
 
Warm forging process is to be done at temperature around recrystallization temperature.
This process can get good surface quality and dimensional precision under low forming press with comparison to cold forging process. Middle Carbon steel and middle carbon alloy steel are suitable to be formed by this kind of process.