起重机高强度螺栓和标准节断裂原因分析

针对某起重机的高强度紧固螺栓和标准节的断裂,从断口宏、微观特征和显微组织的角度分析了断裂原因。研究表明:螺栓热处理工艺存在缺陷,螺栓调质组织中存在明显的贝氏体和网状铁素体组织,螺栓丝口根部存在较多的铁素体,这种组织的差异导致螺栓疲劳强度降低。在工作过程中的高应力作用下,应力集中的螺栓丝口根部逐渐萌生微裂纹,疲劳扩展,最终导致标准节整体断裂。

Analysis on the fracture of fox bolt and standard node of an abutment crane

In view of fracture of fox bolt and standard node of an abutment crane,the reasons to result in the fracture were analyzed based on the fractography,micro-fractography and microstructure of the bolt and standard node.The investigation showed that due to some deflection in the heat treatment process there were a few of bainite and ferrite network in the microstructure of the fox bolt center,and there were a few of ferrite in the root of thread.The above-mentioned microstructure difference brought about the decrease of the fatigue strength,and then under the higher work stress the fatigue microcrack started up from the root of thread,and finally the breakdown of standard node took place.