Cracking reason of welding seam of excavator boom

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 non－standard 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.