钢轨在卸车过程中发生断裂。采用金相检验的方法对钢轨轨底角部位的弧形凹坑断口和凹坑四周的熔融状凸出物进行了检验分析。结果表明,手工电弧焊时意外在钢轨底部产生瞬时接触电流,随即产生的高温在轨底电弧区形成凹坑缺口并发生马氏体相变。凹坑缺口成为应力集中点,当钢轨从1.5 m高的平板车摔(落)下即从缺口处发生断裂。

The rail has fractured in discharging. Metallographic examination is used to check and analyze the arc-pitting fracture of rail base′s corner and the melted bulge around rail pit. The results showed that the temporal contant current in rail base was produced unexpectedly in electrode welding,and rail base arc zone formed arc-pitting by produceing high temperature and formed martensite. The pit became the stress comcentration point,the rail was fractured at the pit when disburdened from 1.5 m height.