某厂精轧机在试运行一个月后电机轴发生断裂,采用金相检验、化学成分分析、力学性能测试及慢应变试验等方法对该轴断裂原因进行了分析.结果表明:电机轴断裂性质为解理断裂;其尺寸较大、热处理滞后以及热处理工艺不正常造成电机轴心部存在较大的残余热应力(残余拉应力)是导致电机轴断裂的主要原因,电机轴锻件心部组织偏析严重区域韧性较差对裂纹的萌生和扩展起到了一定的促进作用.

The motor shaft of a finishing mill was broken when plunged into test-run for one month.The fracture causes were analyzed by means of metallographic examination,chemical composition analysis,mechanical property test and slow strain rate test,etc.The results show that the crack feature was cleavage fracture,and the existing residual thermal stress(residual tensile stress) in the motor shaft center resulted from large size,delayed heat treatment and abnormal heat treatment processing was the main cause inducing the motor shaft fracture.On the other hand,the poor toughness in serions composition segregation zone of the motor shaft forging center played a certain promotion role in crack initiation and propagation.