U75V(N)淬火钢轨闪光焊接头失效分析

Failure analysis of flash welding joint of U75V rail

某线路钢轨闪光焊焊接接头处发现伤损,为找到伤损的客观原因,将接头下道后用探伤定位,采用静弯的方法将接头压断,找到接头缺陷。对接头断口采用宏观体视观察、扫描电镜观察(SEM)和能谱分析(EDS)、微观组织观察等手段对其进行了失效分析。结果表明:钢轨闪光焊焊接接头的伤损主要是由于接头熔合线处的夹杂物以及成分偏析引起的;夹杂物的存在使得接头内部出现应力集中,在钢轨运行过程中的动载荷作用下,缺陷在应力集中位置萌生并进一步扩展,最终导致接头的疲劳裂纹扩展。

The damage was found in the flash welded joint of a certain line.In order to find the objective cause of the damage,the damage was located by the nondestructive test after the joint was decommission,and the joint was crushed by the static bending method to find the joint defect.The fractures of the joints were analyzed by microscopic stereoscopic observation,scanning electron microscopy(SEM)and energy spectrum analysis(EDS),and microstructure observation.The results showed that the damage of the rail flash welding joint was mainly caused by the inclusions at the weld line of the joint and the segregation of components.The presence of inclusions caused stress concentration inside the joint.Under the dynamic load during the operation of the rail,the defects were initiated and further expanded at the stress concentration position,which eventually led to fatigue crack growth of the joint.