Numerical analysis of weld pool behaviors in plasma arc welding with the lattice Boltzmann method

The lattice Boltzmann method (LBM) is first applied to both simulate and analyze the heat transfer and fluid flow with phase change in a workpiece of stationary plasma arc welding (PAW). The heating and key-holing effects are considered with a modified heat source model. The total enthalpy lattice Boltzmann model is employed to investigate the phase change process in the weld pool. The predicted weld pool geometry agrees well with the experimental results and average relative errors remain below 12%. It seems that LBM is more intuitive to display the fluid flow in the weld pool, e.g. circulations, than the finite volume method. However, the effect of fluid flow on the PAW process is indicated to be non-negligible, and particularly responsible for the upper shape of the weld pool. Mechanisms of the formation of the hump in the fusion line are further analyzed from the perspective of fluid motion. Finally, the sulfur activity of workpiece and welding current is discussed, showing that sulfur activity only affects pool geometry. High welding current accelerates the penetration with low time consumption and high energy efficiency; however, the optimum current is a better choice to ensure high weld quality.