The purpose of precision gear forging is to directly produce gears without subsequent cutting. If forging can be carried out at room temperature, the shape and size of the gear can be easily controlled, and errors caused by high temperature can also be avoided. At present, many bevel gears and small cylindrical gears are manufactured in this way. When the overall size is appropriate, cylindrical spur gears and helical gears can also be manufactured by cold extrusion. However, high temperature will cause material oxidation and mold deformation, thereby affecting the accuracy and surface quality of the forging. It is difficult to correct these errors with additional cutting, which also increases costs.
In recent decades, great progress has been made in precision gear forging. More and more manufacturers and users pay attention to gear forging. It is generally believed that the forging method can increase material utilization, increase productivity, improve the mechanical properties of gears, reduce costs, and enhance market competitiveness. Especially for mass production in the automotive industry, precision gear forging has greater benefits and potential. Precision gear forging has many advantages and has been used in the mass production of bevel gears, but there is still a long way to go before the mass production of certain cylindrical spur gears and helical gears. Especially for automobile power transmission gears, a set of practical and reliable production processes must be established before they are accepted by manufacturers.
Especially when the error on the tooth profile is corrected by the subsequent grinding process, in addition to increasing the cost and prolonging the man-hour, there is also the problem of gear positioning during the grinding process. At present, the generally accepted process method is a combination of hot forging, warm forging and cold forging. Hot forging and warm forging can achieve high efficiency and high material utilization, while cold forging can correct the errors of hot forging and warm forging and improve the surface quality. At the same time, the cold treatment process can also obtain residual compressive stress on the tooth surface and increase the service life of the gear.