Numerical simulation and testing of laser-MIG hybrid-welding angle-structure sheets

Numerical simulation and experimental investigation of laser-MIG hybrid angle-welding low-carbon 1.5-mm-thin SPCC steel sheets are presented in this work. The transient simulation analysis provides an access to the thermal-fluid phenomena prediction by employing a hybrid three-dimensional heat source model. Special attention is paid to the melt dynamic behaviors within the triangular molten pool affected by the Marangoni convection. The simulation results show that the temperature and its gradient distribution are symmetrical with respect to the laser beam, which is validated well by the experimental study. The microstructure of the welded joints was analyzed by scanning electron microscopy and transmission electron microscopy. The results show that the cross-section microstructures of welded joint are mainly composed of the weld zone, narrow heat-affected zone, and substrate. The semielliptic-like molten pool shape is consistent with that of the simulated results. The finer microstructure in the weld bead results from the rapid cooling rate of laser welding confirmed by the FEM calculation. The columnar and equiaxed dendrites are formed in the peripheral and central region of the molten pool, which is beneficial for the improvement of the microhardness.