Numerical Study on the Multi-physics Coupling Process of Pulsed GTAW

Pulsed gas tungsten arc welding (GTAW) is widely used in the welding of thin plates and heat-sensitive materials because of its low welding heat input and high welding quality. However, its dynamic characteristics related to the transient behavior are not clear causes of the complex mass and heat transfer processes. In this study, a multi-physics coupled mathematical model was established to solve the conservation equations of mass, momentum, and energy. Meanwhile, the arc-molten pool coupling heat transfer and flow behavior of unsteady pulsed GTAW were studied considering the metal vapor component transport, electromagnetic induction, and turbulence effects. In the pulsed GTAW welding process with a low pulse frequency of 50 Hz, the maximum arc temperature of the peak current reached over 20000 K, and dropped below 14000 K at the base current moment. The arc voltage decreased from 12.0 V to 8.7 V simultaneously. It took 2 ms for all physical fields to recover stability when the current increased to the peak value. The weld pool width changed following the pulse current periodic oscillation, and the weld pool depth increased monotonically under the pulse current impact. By analyzing the shear force distribution of the upper surface of the molten pool in the base and peak current half-circles, it was found that the range of the negative shear force on the upper surface of the molten pool in the base current half-circle was wider than that of the peak half-circle, and there was an inward flow at the edge of the molten pool, which was also the cause of the larger melting weld pool width amplitude under the pulse current. This study proposes a reasonable multi-physics coupling model for unsteady pulsed GTAW to reveal the complex arc welding physics process.