汽车差速器用高强度螺栓断裂失效分析

Failure analysis of the high strength bolt fracture on an auto differential

某汽车差速器用高强度螺栓在装配后短期内发生了多起断裂失效。文章采用扫描电镜、硬度检测及化学成分分析等手段对失效螺栓断裂的主要原因进行了分析。结果表明:螺栓失效模式为典型的延迟断裂,主要原因是螺栓在热处理过程中表面增碳,导致其表面硬度偏高,从而增加了延迟敏感性。根据螺栓生产工艺,调整了回火温度,并对淬火加热炉内保护气氛进行了调整,降低了螺栓的延迟断裂敏感性。实践结果表明,工艺调整后的螺栓未发现延迟开裂现象。

xxx Many fracture failures occurred in the high strength bolts on the differentials of an automobile.The paper analyzes the main reasons for the bolt failure by applying SEM,hardness test and chemical component analysis.The results indicate that the bolt failure mode is the typical delayed fracture,which is mainly attributable to the surface recarburization of the bolts during their heat treatment,resulting in their high surface hardness and subsequently the increase of their sensitivity of fracture delay.Based on the production process,tempering temperature and the protective atmosphere in the quenching furnace is adjusted to reduce the sensitivity of the delayed fracture of the bolt.Test results show that there is no longer any delayed cracking in the bolts after the process adjustment.