Hot Forging

Hot forging is a forging performed at a metal recrystallization temperature or higher. Increasing the temperature can improve the plasticity of the metal, which is beneficial to improve the intrinsic quality of the workpiece and make it less prone to cracking. The high temperature also reduces the deformation resistance of the metal and reduces the tonnage of the required forging machinery. However, there are many hot forging processes, the workpiece precision is poor, the surface is not smooth, and the forgings are prone to oxidation, decarburization and burning. When the workpiece is large and thick, the material strength is high, and the plasticity is low (such as the bending of the thick plate, the elongation of the high carbon steel bar, etc.), hot forging is used.

Increasing the temperature improves the plasticity of the metal and makes it less susceptible to cracking. The high temperature also reduces the deformation resistance of the metal and reduces the tonnage of the required forging machinery. High temperature deformation is beneficial to improve the intrinsic quality of the workpiece. However, there are many hot forging processes, the workpiece precision is poor, the surface is not smooth, and the forgings are prone to oxidation, decarburization and burning. When metal (such as lead, tin, zinc, copper, aluminum, etc.) has sufficient plasticity and deformation (such as in most stamping processes), or the total amount of deformation is used for the forging process (such as extrusion, When radial forging, etc., is advantageous for plastic deformation of metal, hot forging is often not used, and cold forging is used instead. In order to complete as much forging work as possible for one heating, the temperature range between the initial forging temperature and the final forging temperature of the hot forging should be as large as possible. However, if the initial forging temperature is too high, the metal grain growth will be too large to form an overheating phenomenon, which will reduce the quality of the forging. When the temperature is close to the melting point of the metal, intergranular low melting point melting and intergranular oxidation occur, resulting in over-burning. Overfired billets tend to chip when forged. The hot forging temperature generally used is: carbon steel 800 ~ 1250 °C; alloy structural steel 850 ~ 1150 °C; high speed steel 900 ~ 1100 °C; commonly used aluminum alloy 380 ~ 500 °C; titanium alloy 850 ~ 1000 °C; brass 700 ~900 °C.