Forming Rules and Performances of Laser-MAG Hybrid Welding Joints of SUS301L-MT Stainless Steel

This study focusses on 6 mm-thick SUS301L-MT austenitic stainless steel, which will be used for the manufacture of next-generation city rail trains. In order to establish the technical foundation for the manufacture of city rail trains, the forming rules and performances of 6 mm-thick SUS301L-MT austenitic stainless steel laser-MAG (metal active gas welding) hybrid welding T-joints were studied using weld cross-section analysis, metallographic observation, X-ray diffraction residual stress tests, etc. The increase of laser power and defocusing distance can improve the width of the weld top surface. When welding speed increases, the widths of the weld middle section and weld bottom surface significantly decrease. The width of the weld cross-section increases significantly with the increase in defocusing distance. The microstructure of the weld zone is austenite mixed with ferrite. The maximum longitudinal residual stress appears at the center of the joint, with a value of 330 MPa.