Effects of different laser power and welding speed on the microstructure and mechanical properties of TRIP joints in laser-TIG arc hybrid lap filler wire welding

The TRIP steel applied in the automotive application was welded successfully by hybrid low-power laser-TIG arc lap welding method with the Fe-based filler wire. The influence of different laser powers and different welding speeds on the forming properties of joints was studied. The introduction of the laser increased the heat input and the weld depth of the joint. The pulse laser stirred the weld seam and improved the formation of the joint. At a welding speed of 1500 mm/min, the defect-free lap joint of TRIP steels was obtained. The fracture occurred on the base metal. Compared with low current TIG welding, with the introduction of laser, the fracture form changes from brittle fracture characteristic to ductile fracture characteristic. The microstructure was mainly composed of pearlite, bainite, ferrite, and cementite. Pearlite and bainite are the strengthening phases. The microstructure evolution model of joints that varied with laser power and welding speed was established.