Numerical investigation of coupled arc and electrode for GTAW with a longitudinal electromagnetic field

Abstract

Due to the good conductivity of ions and free electrons in the arc column, arc plasma possesses a remarkable magnetic controllability. Thus, a new technique of electromagnetic stirring has been developed which is of great interest during welding process by applying superimposed external magnetic field. However, few researches have focused on arc behavior with a coupled electrode under a magnetic field. In this paper, a three-dimensional plasma arc model coupled cathode was developed, and the distributions of current density, electric potential, magnetic field, pressure, velocity and temperature of plasma arc were obtained by solving the conservation equations of momentum, mass and energy coupled Maxwell’s equations. By applying finite volume method, when the intensity of applied electromagnetic field exceeded a threshold value, it reveals that arc contraction near cathode and arc divergence near anode are induced resulting in mutation phenomenon. The distributions of arc temperature and pressure deviate from the axis of tungsten and exhibit a bimodal shape. This is distinctly different from that of the free arc under natural combustion condition. In addition, the maximum velocity of the plasma flow appears on both sides of the arc symmetry axis. Moreover, arc plasma presents a behavior of heavy reflow and eddy, and a low-temperature area and a negative pressure zone appear in the central axis of arc plasma.