天车吊钩断裂失效分析

Failure analysis of crane hook fracture

吊钩在使用过程中断裂,采用金相显微镜和扫描电镜等对吊钩断裂件进行了观察和分析。结果表明,吊钩断裂部位由3块钢板焊接而成,焊缝区域有较多的未熔合和未焊透等焊接缺陷,焊缝区域组织有粗大的魏氏组织存在;分析认为焊缝区域的焊接缺陷处萌生裂纹,粗大的魏氏组织导致吊钩的综合力学性能下降,在天车起吊重物的应力作用下导致裂纹扩展至断裂。

The sample of the crane hook was observed and analyzed by means of optical microscope and scanning electron microscope to find out the causes for the fracture.The results show that the hook fracture part is welding together by three steel plates,and there are some welding defects such as lack of penetration and lack of fusion in the weld area,where the thick widmanstatten structure was observed.The observations and analysis conclude that the weld defects and the thick widmanstatten structure lead to a decline in the mechanical properties of the hook,which results in the hook fracture under the action of fatigue stress.