Warm precision forging process is a precision forging process with forming temperature between 650 ~ 900 ℃. It has the advantages of hot precision forging and cold precision forging at the same time. It can not only avoid the problems of serious oxidation and poor quality of forging surface after hot forging, but also solve the problems of large forming force of cold forging and complex process before cold extrusion.
Warm precision forging of spur gear has been widely carried out abroad. ThyssenKrupp company of the United States has produced a large number of warm precision forged automobile gears, and its warm forging products account for about 50% of all forging products. Komatsu company of Japan applies the warm forging process to the precision forming of various auto parts, and the warm precision forging process production line developed by its company occupies a place in the world.
The domestic research on the warm precision forging process of spur gears is also very rich. Xiejin city of Hefei University of technology adopts the warm forging cold shaping compound forming process to form large module spur gears. The effects of initial forging temperature, friction coefficient, forming speed and die temperature on the warm forging quality of spur gears are studied respectively, The optimal combination of process parameters for warm forging of spur gear is obtained, and the effects of finishing quantity and finishing passes on the forming accuracy of spur gear are studied. Yang Yongshun of Henan University of science and technology optimized the die entry angle of the warm extrusion tooth profile concave die of spur gear. The numerical simulation results show that the die entry angle is small, the blank center flows faster, the tooth top is not easy to fill, and the forming effect is the best when the die entry angle is 180 °. Professor Zhang Zhimin and Professor Zhang Baohong of Zhongbei university put forward the two-step forming process of constrained split warm extrusion of spur gear. As shown in the figure, the new process schemes of closed cold extrusion and warm extrusion are simulated with SuperForge software. The new process scheme of warm extrusion can greatly reduce the forming load and improve the service life of the die, At the same time, the two-step forming is conducive to the flow of excess metal from the tooth root to the tooth top and improve the filling of the corner of spur gear. However, the process scheme requires a special guide cone, which is troublesome in design and processing.