某汽车厂焊装车间的空中积放式推杆悬挂牵引链节在使用过程中有两节断裂，其中一节为使用1 a（年）后两侧均出现断裂，另一节为使用10 a后在链节一侧出现断裂。采用宏观观察、化学成分分析、硬度测试、金相检验、宏微观断口形貌分析等方法，对链节断裂失效的原因进行了分析。结果表明：1 a断裂失效链节是由于疲劳及受力不均导致的过载断裂；10 a断裂失效链节整个断口上几乎都是疲劳扩展区，为疲劳断裂。

Two drag chains of aerial power and free push type suspension conveyer in an automotive welding workshop fractured during applications. One of the drag chains fractured on both sides after using 1 a (annum) time, the other fractured on one side after using 10 a time. The failure fracture reasons were analyzed by methods of macroscopic observation, chemical composition analysis, hardness test, metallographic examination, macro and micro fracture morphology analysis. The results show that the 1 a failure part overload fractured caused by fatigue and unequal stress; the fatigue expansion area almost completely covers the whole fracture of 10 a failure parts, which was fatigue fracture.