采用体视显微镜、光学显微镜和扫描电镜等仪器分析了PG4热处理钢轨母材落锤试验不合格的原因。结果表明:落锤断裂钢轨的断裂均起源于轨底角圆弧过渡处的表面薄层马氏体组织区域; 由于钢轨在输送过程中其轨底角与输送辊道轮缘根部磨损台阶接触形成滑动摩擦, 摩擦热导致局部金属温度瞬时升高并达到奥氏体化温度, 随后快速冷却生成了硬而脆的马氏体组织, 致使钢轨母材在锤重1 000 kg和锤高6.4 m条件下落锤1锤即发生断裂。

Instruments such as stereo microscope, optical microscope and scanning electron microscope were used to analyzing the falling weight fracture reason of PG4 heat treatment rails. The results show that when falling weight test, all rails fractured from the arc transition area of the rail base where there was a layer of martensite microstructure on the surface. During the rail transporting process, glide friction was formed between the rail base angle and the rim root of the transporting roller, and the friction heat resulted in the temperature instantaneous rising to the austenitizing temperature of the rail metal and formation of hard and brittle martensite microstructure after subsequent quick cooling. So the rail fractured only for a hammer under the condition of hammer mass of 1 000 kg and hammer height of 6.4 m.