某地铁列车车钩钩头法兰部位在磁粉探伤过程中发现磁粉聚集现象, 通过对磁粉聚集区域切片进行剖面宏观分析、硬度测试、化学成分分析、金相检验、扫描电镜分析以及能谱分析, 对磁粉聚集原因进行了分析。结果表明: 钩头法兰磁粉聚集区域存在焊接特征, 且焊缝中存在气孔、夹渣等焊接缺陷, 靠近焊接熔合线的热影响区存在疏松铸造缺陷; 在磁粉探伤时, 这些缺陷位置会形成漏磁场, 使磁粉在漏磁场处聚集, 从而形成磁粉聚集。

Magnetic powders aggregation phenomenon was found at the hook-head flange of the coupler for subway train when magnetic powders inspection. Cross-section of magnetic powders aggregation area was analyzed by means of macro analysis, metallographic examination, SEM morphology analysis and energy spectrum analysis to find the magnetic powders aggregation reasons. The results show that welding character and lots of defects were found at the magnetic powder aggregation area. Welding defects such as holes and slag inclusions were found at the weld, and cast porosity defect was found at the heat-affected zone near the weld bond. These above defects would form leakage magnetic field, make the magnetic powders aggregate here, and produce magnetic powders aggregation phenomenon when magnetic powders inspection.