Numerical and experimental investigation of thermal field and residual stress in laser-MIG hybrid welded NV E690 steel plates

A numerical simulation with sequential coupled thermal-mechanical finite element model has been performed for analyzing the temperature field, residual stresses and distortions in NV E690 weldment fabricated by hybrid laser-arc welding (HLAW). For the detailed validation of applicability of the proposed model, simulated and experimentally measured weld pool shape, residual stresses and distortions were compared. The comparison results showed that decent agreement was realized between the predicted weld pool dimension and measured weld bead geometry, suggesting the utility of the combined heat source model for predicting the transient temperature distribution during HLAW. Besides, the simulation results denoted that higher tensile stress distributed in the fusion zone and the surrounding heat affected zone. There was a qualitative agreement in terms of the numerical and experimental results of longitudinal stress and transverse stress. Additionally, the relative error of angular distortion between the experimental and numerical results was 28.18% and the absolute error value was 0.217°. In addition, increasing the heat input increased the peak temperature, residual stresses, and distortions in the weldment. Comparison of the numerical and experimental results suggested that the developed model can be effectively used to estimate welding residual stresses and distortions in hybrid welded steel plates. What is more, the effect of welding thermal cycles on microstructure evolution of the weld bead was also evaluated.