Hot forging is the forging process above the metal recrystallization temperature. Increasing the temperature can improve the plasticity of the metal, help to improve the internal quality of the workpiece, so that it is not easy to crack. High temperature can also reduce the deformation resistance of metal and the tonnage of forging machinery required. However, there are many hot forging processes, the workpiece precision is poor, the surface is not smooth, and the forgings are easy to be oxidized, decarburized, and burned. When the machined parts are large, thick, with high material strength and low plasticity (such as rolling bending of extra thick plates, stretching of high carbon steel bars, etc.), hot forging is used. When metal (such as lead, tin, zinc, copper, aluminum, etc.) has sufficient plasticity and deformation, or forging process (such as extrusion, radial forging, etc.). In favor of plastic deformation of metal, cold forging is often used instead of hot forging. In order to heat and complete as much forging work as possible, the temperature range between the initial forging temperature and the final forging temperature of hot forging should be as large as possible. However, when the initial forging temperature is too high, the overheating of metal particles will lead to overheating of metal particles. When the temperature is close to the metal melting point, the low melting point materials between crystals will melt and oxidize, forming overheating. Superheated billets often break during forging. General hot forging temperature: 800~1250 ℃ for carbon steel; Alloy structural steel 850~1150 ℃; High speed steel 900~100 ℃; Common aluminum alloy 380~500 ℃; Titanium alloy 850~1000 ℃; Brass 700~900 ℃.