Effects of temperature on microstructure and fracture position of MIG welded joints using circled wire-feeding mode

Based on the circled wire-feeding mode, the temperature distribution during the MIG welding process was studied by numerical simulation and experimental investigation and the effect of the peak temperature on the microstructure and fracture position was discussed. Results showed that for the circled weaving welding process, the materials in the left side of the weld and thermo-affected zone experience higher peak temperature because the material in the left side of the molten pool underwent periodic reheating process. The temperature of the molten pool using the weaving welding process is higher than that of the linear welding process. Compared with linear wire-feeding mode, the equiaxed grains in the weld bead using the weaving welding process are larger, while the columnar grains at the interface of the adjacent weld bead are smaller. The fracture position of the tensile samples under these two processes is closely related to the heat cycle in the weld zone.