Gear forging can improve the utilization of materials, improve productivity, improve the mechanical properties of gears, reduce costs and enhance market competitiveness. Gear forging has greater benefits and potential for large-scale production in automobile industry.
If the forging can be carried out at room temperature, the shape and size of the gear can be easily controlled and the error caused by high temperature can be avoided. At present, many bevel gears and small cylindrical gears have been made by this method. When the overall size is suitable, the cold extrusion process can also be used to manufacture cylindrical spur and helical gears. However, most of the gears used in automobile transmission have large diameter and height, so they are not suitable for extrusion process. If closed die forging is used, high pressure is required to make the metal material flow and fill the die cavity, so this kind of gear needs hot forging or warm forging process. High temperature will lead to material oxidation, die distortion, and affect the accuracy and surface quality of forgings. It is difficult to correct these errors with additional machining, and the cost should be increased. When the subsequent grinding process is used to correct the error on the tooth profile, in addition to increasing the cost and prolonging the working hours, there is also the problem of gear positioning in the grinding process.