基本轨铝热焊接头裂纹原因分析

Cause Analysis of Cracks in Thermit Welded Joint of Stock Rail

对一客运专线探伤检查发现的重伤基本轨铝热焊接头进行磁粉探伤复核时,在钢轨踏面发现了横向贯穿裂纹。为分析裂纹产生的原因,对裂纹处断口进行了宏观形貌观察、扫描电镜微观分析、显微组织观察、显微维氏硬度测试。结果表明:铝热焊接头踏面横向裂纹属于焊接缺陷;焊接接头焊缝熔合线一侧踏面经过焊补,在焊补热影响区存在马氏体组织,列车通过时在轮轨接触应力作用下由马氏体组织处萌生裂纹并进一步扩展。铝热焊接时应严格按照规范执行,焊缝和新钢轨不应焊补。

A transverse through crack was found on the rail tread during the magnetic particle flaw detection review of the thermit welded joint of the seriously injured stock rail found in the flaw detection of a passenger dedicated line.In order to analyze the cause of the crack,the macro morphology observation,SEM micro analysis,microstructure observation and micro Vickers hardness test were carried out.The results show that the transverse crack on the tread of thermit welded joint belongs to welding defect.The tread on one side of the welded seam fusion line of the welded joint is repaired by welding,and there is Martensite in the heat affected zone of the welding repair.When the train passes through,cracks are initiated and further expanded from the Martensite under the wheel rail contact stress.The thermit welding shall be carried out in accordance with the specifications strictly,and the welded seam and new rail shall not be repaired by welding.