60 kg/m U75V钢轨固定闪光焊接头断裂原因分析

Fracture Analysis on Fixed Flash Butt Welded Joint of 60 kg/m U75V Rail

针对断裂60 kg/m U75V钢轨固定闪光焊接头进行了宏观形貌观察、断口扫描电镜观察、显微组织观察和材质分析试验,分析认为闪光焊接头为疲劳断裂,轨底侧表面和下表面经过打磨形成了尖锐直角而成为应力集中点,在拉应力作用下由应力集中处萌生疲劳裂纹并扩展,最终导致钢轨断裂。建议控制焊接接头的表面打磨量,保证型式尺寸满足标准要求。

In this paper,the macroscopic morphology observation,scanning electron microscope observation,microstructure observation and material analysis test were carried out for the fracture on 60 kg/m U75V rail fixed flash butt welded joint.The analysis shows that the fracture of the flash butt welded joint is a fatigue fracture,and the stress concentration points are formed on the sharp right angles which are formed on the rail bottom surface and lower surface after grinding.Under the action of tensile stress,the fatigue crack initiates and expands from the stress concentration point,and finally lead to rail fracture.It is recommended to control the surface grinding amount of welded joints to ensure that the type and size meet the standard requirements.