某挖掘机动臂焊缝开裂原因

Cracking reason of welding seam of excavator boom

某大型液压挖掘机的动臂在使用过程中发生开裂现象,采用宏观观察、化学成分分析、扫描电镜分析、力学性能测试、金相检验、有限元分析等方法对动臂开裂原因进行分析。结果表明:开裂的主要原因是内部焊缝的底部与母材存在未熔合缺陷,使焊接区域尖角应力集中,同时非标大负载铲斗使焊缝表面的应力明显加大,最终在循环大载荷的作用下,焊缝发生疲劳开裂。

The boom of a large hydraulic excavator cracked during use.The causes of boom cracking were analyzed by means of macroscopic observation,chemical composition analysis,scanning electron microscope analysis,mechanical property test,metallographic examination and finite element analysis.The results show that the main reason for cracking was that there were unfused defects between the bottom of the internal weld and the base metal,which caused the sharp corner stress concentration in the welding area.At the same time,the nonstandard large load bucket significantly increased the stress on the weld surface,and finally led to the fatigue cracking of the weld under the action of cyclic large load.