Pore formation and prevention in deep penetration pulsed laser welding

Pores are often observed in deep welds by pulsed laser welding process. This article develops a mathematical model to understand the physical phenomena related to pore formation and, subsequently, to seek solutions for pore prevention. Our simulation results reveal that, in keyhole laser welding, there are two competing mechanisms contributing to pore formation: one is the solidification rate of the molten metal and the other is the speed that molten metal backfills the keyhole after the termination of laser power. Our model has demonstrated that by controlling the laser beam profile (which in turn controls the solidification rate) or by applying an electromagnetic force after irradiation termination (which in turn controls the molten metal flow), pores can be reduced or even eliminated in the weld.