地铁列车转向架构架由St52-3钢板焊接而成, 在列车运行大约5 a后转向架构架发生了开裂; 利用光学显微镜、扫描电子显微镜、万能材料试验机等对开裂件进行了宏微观形貌、化学成分、拉伸和疲劳性能分析, 以找到其失效的原因。结果表明: 转向架构架发生了疲劳开裂, 开裂起源于焊接连接部位的焊接缺陷处; 提出了提高焊接质量和改变转向架构架结构的措施, 经过近10 a的实际运行, 再也没有出现过开裂现象。

The subway train bogie frame was mainly welded by St52-3 steel plate. The bogie frame fractured after the subway train run for about 5 years. The macro/micro structure, chemical composition, tensile and fatigue properties were analyzed by optical microscopy, scanning electron microscopy, materials testing and so on. The results show that fatigue cracking occurred on the bogie frame which initiated in the welding defects of solder connection part. The subway train never occured fatigue cracking during nearly 10 years′ operation after improving welding quality and changing the stress structure of bogie frame.