油缸用35钢销轴断裂的原因

摘要

某型铣刨机摆臂油缸用35钢销轴在使用约2 a时发生断裂,采用化学成分分析、硬度检测、显微组织和表面形貌观察、有限元模拟、断口分析等方法探讨了销轴断裂的原因.结果表明:此销轴为多源疲劳断裂,断口平整,裂纹源位于销轴表面加工刀痕的根部;造成销轴断裂的原因是其加工表面粗糙,刀痕根部应力集中,在工作载荷的作用下销轴中部的刀痕根部形成了裂纹源;同时销轴未按要求进行调质热处理,导致其显微组织粗大,疲劳裂纹容易扩展.%The 35 steel pin for an oscillating arm oil cylinder of one type milling machine fractured after service for around 2 a.The reason for the pin fracture was studied by the methods such as chemical composition analysis,hardness test,microstructure and surface topography observation,finite element simulation and fracture analysis.The results show that the batch of pins had a multi-source fatigue fracture.The fracture surface was smooth and the crack source was located in the root of the turning tool mark on pin surface.The main reason for the pin fracture was that the machining surface of the pin was rough and the stresses were concentrated in the root of tool mark,leading to the formation of crack source in the tool mark root of the central pin under the working load. Meanwhile the pin was not subj ected to quenching and tempering as required,resulting in the coarse microstructure and the easy propagation of fatigue cracks.