Effect of laser remelting on the microstructure and mechanical properties of meta inert gas welded low carbon mild steel

Abstract

In this study, laser remelting has been performed on the Metal Inert Gas welded (MIG) low carbon mild steel at varying laser power inputs (400 W & 600 W). To investigate the influence of laser remelting on the joint properties, optical microscope observation, scanning electron microscope observation, microhardness measurement and mechanical tests have been conducted. The experimental results revealed that the surface appearance of the laser remelted MIG welded joints have been found to be smooth and the microstructure of its fusion zone possesses fine equiaxed dendrites as compared with that of the MIG welded joints. In addition, the fracture surface of the laser melting carried at low power (400 W) on the MIG welded joint has exhibited a ductile fracture whereas, the MIG welded joint has undergone brittle fracture. The laser remelting carried out at 400 W on the MIG welded joint has resulted in 12% increase in both the ultimate tensile strength and percentage of elongation as compared to that of the MIG welded joint and this has been ascribed to the presence of equiaxed grains in the microstructure.