A study on laser keyhole welding in vacuum by computational fluid dynamics simulations with plume effect models

A vacuum environment results in a deep penetration depth in laser keyhole welding. In this study, the numerical simulations of laser keyhole welding in various vacuum conditions were performed with consideration for multiphysics phenomena. To consider the vacuum environment in numerical simulations, a modified recoil pressure model with the change in pressure and vaporization temperature according to ambient pressure and a laser power attenuation model by scattering and absorption due to the nanoparticles in the laser-induced plume was considered. For the scattering and absorption calculations, artificial coefficients obtained for a 1 atm condition were used, and then the coefficients in the other pressure conditions were calculated under assumptions suggested in this study. The simulation results using the models based on the assumptions could depict a deeper penetration in vacuum conditions considered in this study, and they were in good agreement with the experimental results in terms of weld cross section.