Cold precision forging is a (near) net shape forming process. The parts formed by this method have high strength and precision and good surface quality. At present, the total amount of cold forgings used in an ordinary foreign car is 40~45kg, of which the total amount of tooth-shaped parts is more than 10kg. The weight of a single piece of cold forged gear can reach more than 1kg, and the tooth shape precision can reach grade 7.
Continuous technological innovation has promoted the development of cold extrusion technology. Since the 1980s, precision forging experts at home and abroad have begun to apply the split forging theory to the cold forging of spur gears and helical gears. The main principle of split forging is to establish a split cavity or channel of material in the forming part of the blank or mold. During the forging process, while the material fills the cavity, part of the material flows to the distribution cavity or distribution channel. The application of split forging technology has enabled the less-cut and no-cut machining of higher-precision gears to quickly reach an industrial scale. For extrusion parts with a length-to-diameter ratio of 5, such as piston pins, one-time cold extrusion can be achieved by using the axial residual material block to pass through the axial diversion, and the stability of the punch is very good; for flat spur gears Forming, the cold extrusion forming of the product can also be realized by using the radial residual material block.
Closed forging is one-time extrusion of metal by one or two punches in a closed die to obtain near-net-shape precision forgings without flash. Some car precision parts such as planetary and side shaft gears, star sleeves, cross bearings, etc., if cutting is used, not only the material utilization rate is very low (less than 40% on average), but also it takes a lot of man-hours and the production cost is extremely high. Foreign countries use closed forging technology to produce these net-shape forgings, which saves most of the cutting process and greatly reduces the cost.
Skills requirement:
The forming accuracy of cold forging technology is higher than that of warm forging and hot forging, and has its unique advantages in the field of precision forming. The use of cold forging technology improves the smoothness of the inner bore, dimensional accuracy, and surface strength, prolongs the life of the barrel, improves the shooting accuracy of the gun, and facilitates the processing of tapered barrels, which can reduce the mass. The cold forging process was first proposed by Steyr, and later many countries in the world used Steyr's cold forging machine tools to process gun barrels.
