Experimental study on the effect of laser remelting on the performance of Q355 butt-welded joints

Welding stands as a crucial method for connecting steel structures, with the performance of welded joints directly influencing structural safety. Numerous post-weld treatment techniques aimed at enhancing joint properties have been developed; however, despite being a highly stable technology, application of laser in weld post-processing has rarely been studied. Thus, this paper introduces the surface treatment technique known as laser remelting (LR), which serves as an effective post-treatment for enhancing the lifecycle performance of welded joints. In this study, a range of tests were performed to examine the impact of LR treatment on the lifecycle performance of Q355 butt-welded joints, encompassing mechanical properties, microstructure, microhardness, corrosion resistance, and fatigue characteristics. The results demonstrated that LR technology is capable of reducing stress concentration at the weld toe while effectively enhancing the mechanical properties of welded joints. Macroscopic and microscopic experimental findings reveal that LR technology can smooth out the geometry of the weld toe, refine the grain structure within the remelted zone, and elevate microhardness levels. Furthermore, the corrosion resistance exhibited by remelted welded joints surpasses that of as-welded joints. The results of fatigue testing revealed that LR treatment modifies the fatigue fracture location and markedly enhances fatigue property, with the fatigue life of Q355 butt-welded joints undergoing LR treatment experiencing an increase ranging from 244% to 499%, accompanied by a 21.26% improvement in fatigue strength (FAT). • Utilizing LR process as a surface treatment technique to the Q355 butt-welded joints. • Remelted Q355 butt-welded joints exhibit enhanced tensile, microhardness, and corrosion resistance properties. • LR smooths the weld toe and reduces the stress concentration in butt-welded joints. • LR treatment significantly enhances the fatigue life of the welded joints.