油动机底座连接螺栓断裂原因

Fracture Causes of Connecting Bolts of Oil Motor Base

某电厂检修时发现油动机底座的连接螺栓发生了断裂,采用宏观分析、化学成分分析、力学性能试验、金相检验、扫描电镜分析、螺纹根部检查等方法对连接螺栓的断裂原因进行了分析。结果表明:该油动机底座连接螺栓的断裂类型为高周疲劳断裂,属于疲劳引起的脆性断裂。连接螺栓倒角处存在的微小裂纹缺陷,使得该处应力集中从而产生多处裂纹源,且连接螺栓显微组织中块状铁素体的存在降低了连接螺栓的疲劳强度,最终导致连接螺栓断裂。

During the maintenance of a power plant,it was found that the connecting bolts of the oil motor base fractured.The fracture causes of the connecting bolts were analyzed by means of macro analysis,chemical composition analysis,mechanical property test,metallographic examination,scanning electron microscope analysis and thread root inspection.The results show that the fracture type of the connecting bolts of the oil motor base was high cycle fatigue fracture,which belongs to brittle fracture caused by fatigue.The small crack defects in the chamfer of the connecting bolts made the stress concentrated and produced many crack sources.The existence of granular ferrite in the connecting bolts microstructure reduced the fatigue strength of the connecting bolts and finally led to the connecting bolts fracture.