Mathematical modeling of heat transfer, fluid flow, and solidification during linear welding with a pulsed laser beam

The evolution of temperature and velocity fields during welding of 304 stainless steel with a pulsed laser beam was simulated using a three dimensional numerical heat transfer and fluid flow model. The weld pool solidified between pulses and regions of the weld bead melted and solidified several times during welding. Short laser pulses restricted the width of the weld track and velocities in the weld pool. However, convection still remained an important mechanism of heat transfer in the weld pool. The computed high cooling rates during linear welding with neodymium-doped yttrium aluminum garnet pulsed laser operated at 140 W average power, 20 Hz frequency, and 5 ms pulse duration were consistent with those observed in typical laser welding. After the laser beam was switched off, the mushy zone expanded, reaching its maximum size when no pure liquid region remained. Calculations of solidification parameters indicated that the criterion for plane front solidification was not satisfied. The results demonstrate that the application of numerical transport phenomena can significantly improve the current understanding of linear welding with a pulsed laser beam. (c) 2006 American Institute of Physics.