高强度热处理钢轨闪光焊接头断裂原因分析

Fracture Cause Analysis of Flash-butt Welded Joints of High Strength Heat Treatment Rail

国内一重载铁路服役过程中高强度热处理钢轨闪光焊接头发生断裂。采用体视显微镜、光学显微镜和扫描电镜对断口宏微观形貌、金相组织等进行检验,分析接头断裂原因。结果表明:接头断裂是在循环载荷作用下的疲劳断裂,接头轨底脚严重氧化的黑色区域是裂纹源区;由于顶锻量过大,焊接流线升角达到71.5°,在车轮的循环载荷作用下,接头轨底脚沿流线逐渐开裂氧化,并以此为疲劳源向轨底中心区缓慢疲劳扩展,最后导致接头瞬间脆性断裂。

The flash-butt welded joints of high strength heat treatment rail fractured in the service process of a heavy haul railway in domestic.To analyze the macro appearance and micro appearance and metallographic structure of the fracture,instruments such as stereo microscope,optical microscope and scanning electron microscope were used,and the fracture causes were found.The results show that fatigue fractures of joints occur under the cyclic loading and the black heavily oxidized area on the foot of the rail is crack source area.The rise angle of stream-line reaches 71.5°due to the excessive upset force.The main reason for the transient brittle fracture of the joint is the gradual cracking and oxidation along the stream-line and the slow fatigue expansion to the center of the rail foot from this fatigue source.