What are the differences between cold forging and hot forging of flanges

　　The cold forging of flange is forged at low temperature, and the size change of flange is very small. When forging below 700 ℃, the formation of oxide scale is less, and there is no decarburization on the surface. Therefore, as long as the deformation energy is within the forming energy range, cold forging is easy to obtain good dimensional accuracy and surface finish. As long as the temperature and lubrication cooling are well controlled, the warm forging below 700 ℃ can also obtain good accuracy. Cold die forging, cold extrusion, cold heading and other plastic processing. Cold forging is the forming process of materials below the recrystallization temperature and forging below the recovery temperature. In production, forging without heating blank is used to be called cold forging. Cold forging materials are mostly aluminum and some alloys, copper and some alloys, low carbon steel, medium carbon steel and low alloy structural steel with low deformation resistance and good plasticity at room temperature. Cold forging has good surface quality and high dimensional accuracy, which can replace some cutting. Cold forging can strengthen the metal and improve the strength of the flange.

　　The development of cold forging technology is mainly to develop high value-added products and reduce production costs. At the same time, it is constantly infiltrating or replacing in the fields of cutting, powder metallurgy, casting, hot forging, sheet metal forming process and so on. It can also be combined with these processes to form a composite process.

　　The hot forging of flange is: during hot forging, large flange with complex shape can be forged because the deformation energy and deformation resistance are very small. The flange with high dimensional accuracy can be hot forged in the temperature range of 900-1000 ℃. In addition, attention should be paid to improving the working environment of hot forging. The service life of forging die is shorter than that of forging in other temperature ranges, but it has large degree of freedom and low cost. The purpose of hot forging flange is mainly to reduce the deformation resistance of metal, so as to reduce the forging pressure required for bad material deformation and greatly reduce the tonnage of forging equipment; Change the as cast structure of the flange material ingot. After recrystallization in the hot forging process, the coarse as cast structure becomes a new structure of fine grains, reduce the defects of as cast structure and improve the mechanical properties of the steel.