Abstract
A fully coupled plasma arc-keyhole-weld pool model was developed to investigate the keyhole behaviors and
thermal fluid flow in high current plasma arc welding. The relationship between the forces distribution and fluid flow patterns was revealed. Owing to a constraint effect of the water cooling nozzle, the plasma arc flows downward with high energy and momentum, so a large keyhole forms. Inside the keyhole, the plasma arc mainly flows downward, and very few plasma arc flows upward along the keyhole wall. At the top surface of the keyhole, the plasma arc flows outward. The dominant downward plasma shear stress and negative arc pressure in the z direction cause a dominant anti-clockwise eddy in the weld pool. The outward plasma arc shear stress on the top weld pool surface causes a small clockwise eddy in the weld pool.
