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在生产扁平状的螺旋伞齿轮时,如汽车后桥从动锥齿轮(材料20CrMnTi)由于渗碳后直接淬火变形量大,底平面的平面度严重超差,所以长期以来,传统的热处理工艺均采用渗碳→缓冷→重新加热→压床加压淬火的方法。这种工艺基本可以解决扁平状零件的淬火变形问题,但该方法生产周期长,效率低,消耗能源多。我们通过渗碳夹具的设计和淬火工艺的改进,经过工艺试验和生产实践,解决了这一问题,使平面度的合格率达90％以上。其他指标也均达到技术要求。我们的作法是: 1.渗碳工艺采用最常规的方法,即井式气体渗碳炉,用煤油作渗碳剂,渗碳温度930℃,降温保温后,将夹具和工件一起吊入流动机油中淬火。 2.降温的温度也就是出炉淬火温度,一定要严格控制好,否则会造成金相组织不合格。一般在840～850℃为宜,温度偏高时,容易引起马氏体和残余奥氏体级别超差。
In the production of flat helical bevel gear, such as automotive rear axle driven bevel gear (material 20CrMnTi) due to direct quenching after carburizing large deformation, the flatness of the bottom plane seriously out of tolerance, so for a long time, the traditional heat treatment process are Adopting carburizing → slow cooling → reheating → press quenching method. This process can basically solve the flat parts of the quenching deformation problems, but the production cycle of the long, low efficiency, energy consumption and more. Through the design of the carburizing fixture and the improvement of the quenching process, we solved this problem through the process test and production practice so that the passing rate of the flatness is more than 90%. Other indicators have also met the technical requirements. Our approach is: 1. Carburizing process using the most conventional method, that is, gas-type gas carburizing furnace, with kerosene as a carburizing agent, carburizing temperature of 930 ℃, cooling and holding, the fixture and the workpiece hanging together with mobile oil Quenching. 2 cooling temperature is released quenching temperature, must be strictly controlled, otherwise it will result in unacceptable microstructure. Generally 840 ~ 850 ℃ is appropriate, the temperature is high, easily lead to martensite and residual austenite grade tolerance.