某型列车运载量增大后,列车车钩尾销孔牵引弧面位置大量出现裂纹。本文车钩尾销孔的化学成分和机械性能进行了检测,观察了车钩钩尾销孔裂纹的宏微观形貌,并对裂纹位置的金相组织进行了检测。结果表明,车钩钩尾销孔裂纹在径向上为脆性断裂特征,而周向上为疲劳断裂特征。分析认为,由于列车运载量增大,车钩尾销孔位置的工作应力增大,同时由于车钩尾销孔处淬硬层与基体的性能差异较大且无明显的过渡层,在工作应力作用下淬硬层首先发生脆性断裂并沿径向扩展,至淬硬层与基体界面处则沿着性能较弱的界面疲劳扩展。 After a certain type of train carrying capacity increases, a large number of cracks appear in the position of the traction arc of the tail hole of the train coupler. In this paper, the chemical composition and mechanical properties of the coupler pin hole were tested. The macroscopic and micro-morphology of the coupler pin hole was observed and the microstructure of the coupler at the crack location was tested. The results show that the crack in the coupler pin hole is characterized by brittle fracture in the radial direction and fatigue fracture in the circumferential direction. The analysis shows that due to the increase of train carrying capacity, the working stress of the coupler pin hole increases, and at the same time, due to the large difference in the performance of the hardened layer and the base at the coupler pin hole, there is no obvious transition layer. The hardened layer first brittle fracture and radial expansion, to the hardened layer and the substrate at the interface along the weak performance of the interface fatigue expansion.