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地铁列车转向架是由钢板焊接而成 ,在服役一年后断裂。对断裂件进行了断口形貌、金相组织、化学成分分析及硬度测定。结果表明 ,断口显示出疲劳断裂痕迹 ,焊接缺陷是引起疲劳裂纹萌生及扩展的主要原因 ,而热影响区粗大的贝氏体及低碳马氏体组织的存在加速了疲劳断裂过程 ,最终导致转向架早期疲劳断裂
Subway train bogies are welded steel plate, broken after one year of service. Fracture parts were analyzed by fracture surface morphology, microstructure, chemical composition analysis and hardness measurement. The results show that the fractures show the signs of fatigue fracture and the welding defects are the main causes of fatigue crack initiation and propagation. The presence of coarse bainite and low-carbon martensite in the heat-affected zone accelerates the fatigue fracture process and eventually leads to steering Early fatigue fracture