Effect of Laser Welding Process on Microstructure and Properties of Submicron-Grained 304 Stainless Steel Welded Joints
摘要
Laser welding was conducted on submicron-grained 304 austenitic stainless steel prepared through rapid annealing after cold rolling. Microstructural characterization, tensile properties, and microhardness testing of the laser-welded joints were performed using optical microscopy (OM), electron backscatter diffraction (EBSD), and tensile experiments. The study explored the influence of laser power, welding speed, and defocusing distance on the microstructure and mechanical properties of the welded joints of submicron-grained 304 austenitic stainless steel. Experimental results indicated that welding speed and defocusing distance significantly impacted the weld formation. The weld microstructure at room temperature consisted of austenite and flocculent ferrite. Under the conditions of 1060 W laser power, 20 mm s−1 welding speed, and + 2 mm defocusing distance, the welded joint achieved the highest tensile strength of 885 MPa, which is about 85.8% of the base metal. The hardness values across all regions of the welded joint were lower than that of the base material, with the average hardness in the heat-affected zone ranging from 196.3 to 315.4 HV and that in the weld zone ranging from 183.9 to 204.4 HV.