Pulsed Laser Welding Process of SUS304 Stainless Steel Sheet and Microstructure and Mechanical Properties of Joint

Pulsed laser lap welding was conducted on SUS304 stainless steel sheets (0.2 mm thick), at different laser power (140-420 W) and welding velocities (10-30 mm·s^-1), namely different heat input. The influence of heat input on the weld formation was studied, and the microstructure and mechanical properties of the joint with optimal formability were analyzed. The results show that a well-formed weld can be obtained when the heat input was in the range of 9-20 J·mm^-1; the forming performance was the best at laser power of 320 W and welding velocity of 20 mm·s^-1 (heat input of 16 J·mm^-1). The microstructure in the weld center of the joint with optimal formability consisted of equiaxed grains, in the fusion line consisted of fine columnar grains, and in the weld near fusion line of cellular dendrites. The hardness at the fusion line of the welded joint with optirnal formability was the highest, followed by the weld zone. The joints obtained at different laser power and welding velocities all fractured in the heat-affected zone. The tensile strength of the joint with optinal formability was the highest of 790.1 MPa, which was close to that of the base metal, and the tesile fracture mode was ductile.