Computational fluid dynamics simulation of hybrid laser-MIG welding of 316 LN stainless steel using hybrid heat source

Abstract

Hybrid laser-MIG welding (HLMW) process is preferred for welding thick sections (>10 mm) to achieve faster and full penetration weld displaying enhanced productivity due to the synergistic effect of the laser and MIG heat sources in the weld pool. An optimum heat source model combining the effect of the laser and MIG heat source needs to be determined first for the accurate simulation of the weld pool development and temperature distribution during HLMW process. The current study first aims to determine the right hybrid heat source model for welding a 0.01 m thick 316 LN SS plate and then to study its effect on the weld pool dynamics. For this purpose, a three-dimensional (3D) transient model with ANSYS Fluent V.19.2 was designed by hybridizing laser and arc heat sources. Goldak's double-ellipsoidal mode of heat source was favoured for the arc source. A 3D conical, combined 3D conical-cylindrical and rotary Gaussian heat source model were considered for the laser source. The simulated weld pool profile and temperature distribution data obtained for the three hybrid heat sources were validated by carrying out experiments employing HLMW process with optimized welding parameters that achieve full penetration. The numerical modelling has shown that the double-ellipsoidal rotary Gaussian heat source as the appropriate model for HLMW simulation of 316 LN SS. There was good agreement between the simulated weld bead shape, size and the temperature with the experimental result. The synergy effect of the laser and MIG heat sources based on their separation distance was demonstrated using the optimized heat source model to get further insight on the weld pool dynamics and the keyhole penetration.