Cold precision forging is a (near) net forming process. The parts formed by this method have high strength and precision, and the surface quality is good. At present, the total amount of cold forgings used in a foreign ordinary car is 40~45kg, and the total number of tooth-shaped parts is more than 10kg. The weight of the cold forged gear can reach more than 1kg and the tooth profile can reach 7th.
Continuous process innovation has promoted the development of cold extrusion technology. Since the 1980s, precision forging experts at home and abroad have begun to apply split forging theory to cold forging of spur gears and helical gears. The main principle of split forging is to create a material split or split channel in the forming portion of the blank or mold. During the forging process, while the material is filled with the cavity, part of the material flows to the split or split channel. The application of the split forging technology has enabled the production of high-precision gears to be small and without cutting to quickly reach the industrial scale. For extrusions with a length to diameter ratio of 5, such as piston pins, a wide axial splitting of the axial residual mass can be used for cold extrusion once, and the stability of the punch is good; for flat spur gears Forming, the use of radial residual block can also achieve cold extrusion of the product.
The occlusion forging is a one-way or opposite-direction extrusion of the metal in one or two punches in the closed die to obtain a near net shape precision forging without flash. Some car precision parts such as planetary and semi-axle gears, star sleeves, cross bearings, etc., if the cutting method is used, not only the material utilization rate is very low (average less than 40%), but also takes a lot of man-hours and the production cost is extremely high. Foreign countries use occlusion forging technology to produce these net forgings, eliminating most of the cutting processing, and the cost is greatly reduced.