硅油风扇离合器转轴在装配时发生断裂, 通过对断裂的风扇转轴进行宏观分析发现, 断裂起源于转轴中心的孔洞, 并且在未断裂转轴的底部中心同样存在孔洞。通过金相方法进一步确认了风扇转轴内部孔洞的存在, 并分析了孔洞缺陷的性质, 从而找到了风扇转轴早期断裂失效与零件内部存在严重的铸造缩孔缺陷有直接关系。另外转轴显微组织异常粗大有过热现象, 加剧了转轴早期断裂失效的发生。最后针对导致转轴断裂的原因提出了预防改进措施。

Fracture failure occurred to a silicone oil fan clutch shaft when assembling. Through macro analysis of the fractured shaft, it was found that the fracture originated from the hole at center of the shaft, and a hole was also found at bottom center of the unbroken shaft. The existence of internal holes of the shaft was further confirmed by metallographic examination method and the nature of the holes defects was analyzed. It was found that the early fracture of the shaft had direct relation with the serious internal casting shrinkage of the shaft. In addition, the abnormal coarse overheating microstructure exacerbated early fracture of the shaft. Finally, preventive and improvement measures were put forward according to the fracture reasons of the shaft.