Numerical study on effect of laser position and joint gap on full penetration Laser-GMAW-P hybrid welding

The Laser-GMA hybrid welding experiments are carried out for GMA-trailing hybrid welding in full penetration. High power fiber laser welding of 10 kW with 4 mm defocusing inside the work piece is used along with pulsed Gas Metal Arc Welding. Different concentration of Cr in base metal and filler wire are used to see the mixing behavior in Laser-GMA hybrid welding. Numerical simulations are carried out using the same power, defocusing, GMAW current and voltage pulse parameters and Cr concentrations as in experiments. The laser simulations used real time multiple reflection inside keyhole and continuity, momentum, energy conservation equations are solved using volume of Fluid (VOF) model. Simulation results for GMA-trailing configuration are presented for mixing and fluid flow behavior and it found that GMA-trailing configuration is giving comparatively uniform mixing and longer pool length is found at root surface. The results for simulation and experiments are compared. The results are in fair agreement in terms of upper bead shape but the molten metal is dropping down due to gravity in simulations, thus forming undercut which is not observed in experiments. This may be due to the fact that assist gas effect is not considered in simulations.