减速小锥齿轮组件裂纹原因分析

Analysis on Cracks of Reduction Bevel Gears Assembly

减速小锥齿轮组件在加工完成后进行磁粉检测时,发现在轴颈内表面位置有多条裂纹。经宏微观观察、金相组织检查、硬度测试、残余应力测试、氢含量分析等手段,对裂纹性质和原因进行分析。结果表明:零件裂纹性质为氢致裂纹,氢的来源为轴径表面镀铬工序;外在原因为轴颈惯性摩擦焊位置加工方式由抛光改为车削加工,导致残余拉应力存在,两者综合因素导致该位置产生裂纹。后续通过控制镀铬的时间、及时除氢和消除应力、焊接位置严格执行抛光工序等工艺改进并进行验证,可有效防止类似故障的再次发生。

Reduction bevel gears were found to have cracks on the inner surface of the axle journal during magnetic powder inspection after processing.The property and cause of the cracks were analyzed by macro and micro observation,metallographic examination,hardness test,residual stress test and hydrogen content analysis.The results show that the cracks of the gears are hydrogen-induced cracks.The hydrogen mainly came from the chrome plating process of the surface of the axle journal.The external reason is that the machining method of the inertia friction welding position of the axle journal was changed from polishing to turning,resulting in the existence of residual tensile stress.Under the co-effect of hydrogen and residual tensile stress,cracks formed at this position.It is verified that controlling the time of chrome plating,timely hydrogen removal and stress relief,and strict implementation of polishing procedures at the welding position can effectively prevent such failure from happening again.