U71Mn钢轨闪光焊对接接头断裂原因分析

Analysis of fracture of U71Mn rail welded butt jioints on flash welding

随着列车行车速度的提高,钢轨的损坏由过去的磨损转变为各种形式的疲劳损坏,而夹杂物往往被视为显微裂纹的发源地,疲劳裂纹与夹杂物的存在关系密切。非金属夹杂物降低了钢轨的塑性、韧性和疲劳寿命。夹杂物对钢轨疲劳性能影响的具体程度取决于一系列因素,如夹杂物的数量、颗粒大小、形态及分布等。应用肉眼观察、光镜、电镜和能谱分析等方法从宏观和微观两个方面分析成昆线闪光对焊U71Mn钢轨断件的断裂原因。结果表明,本钢轨断件的破坏是由于疲劳裂纹扩展引起的横向断裂,即钢轨核伤;而疲劳裂纹是由闪光焊后残留在焊缝中的硅酸盐非金属夹杂物引起的。

As the train speed increased,damage to rail is changed from wear to various forms of fatigue.Inclusions are often seen as the birthplace of micro cracks,fatigue cracks and inclusions have a close relationship.The inclusions can reduce the plasticity,toughness and fatigue life of the rail.The concrete influence intensity that the performance of the inclusion to rail are decided by a series of factors,such as quantity,particle magnitude,shape and distribution and so on.The fracture of U71Mn rail welded butt jioints was analyzed by visual observation, metallographic microscope,SEM and EDS from macro and micro.The results show that：the cracking of the rail is fatigue-crack propagation,fatigue cracking is caused by silicate-non-metallic inclusions which are residues in the weld after flash welding.