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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。
Rail breaks during unloading. The method of metallographic examination was used to test the arc-shaped dimples at the corners of the rail track and the molten bulges around the dimples. The results show that when the manual arc welding accidentally produces instantaneous contact current at the bottom of the rail, the high temperature generated at the bottom of the rail forms a pit gap and undergoes martensitic transformation. The indentation of the dimples becomes the stress concentration point and breaks when the rails fall (fall) from a 1.5 m-high flatbed truck.