Numerical and experimental study of TIG welding arc in high frequency longitudinal magnetic field

The phenomenon of arc compression in TIG welding with high-frequency longitudinal magnetic field (HF-LMF) has been observed. However, its mechanism remains unclear, and there is a lack of numerical investigation. This work presents a two-dimension axisymmetrical model of arc plasma in high-frequency longitudinal magnetic field based on the magnetohydrodynamics (MHD). The distributions of temperature, velocity and pressure of arc plasma in HF-LMF are investigated at different applied LMF frequencies ranging from 0 to 5000 Hz. In order to make the simulation results more convincing, the induced current and the electric force were considered. The results show that the HF-LMF could generate a circumferential electric field, causing particles rotating. However, since HF-LMF is variable, the direction of the electric field also changes, which causes the arc to rotate back and forth. When the frequency of HF-LMF reaches 2000 Hz, the negative pressure zone above the center of the anode disappeared and the arc was compressed. Thus, as the frequency of LMF increases, the distribution of current density, anodic heat flux, and arc pressure changes from a bimodal distribution to a unimodal distribution, and the peak value increases. The theoretical predictions were in good agreement with the experimental results.