COMPARISON OF TWO MAGNETIC FIELD APPROACHES ON THE HEAT TRANSFER AND FLUID FLOW IN PLASMA ARC WELDING
Plasma arc welding (PAW) is superior to other arc welding technologies in deep penetration welding. Much experimental and theoretical research has been conducted to study the heat transfer mechanism and weld pool formation during the welding process. However, the electro-thermal conversion and electromagnetic effects in PAW are less concerned, in which the induced magnetic field is an important issue. At present, only Maxwell-Ampere method and Magnetic vector potential formulation are used to calculate the magnetic intensity in PAW models. Hence, a unified model of plasma arc and workpiece was developed to compare the differences by the two methods. Temperature field, velocity field, current density and electromagnetic force are all presented. The arc temperature can be above 20000 K, and the arc velocity above 950 m/s. It is found that the heat flux, arc velocity, current density and electromagnetic force calculated by the Maxwell-Ampere method are all higher than that by the Magnetic vector potential formulation. The temperature difference and velocity difference are relatively small, while the maximum differences of the heat flux, current density and electromagnetic force may reach up to 40%, 16% and 69%, respectively. Different magnetic field approaches may cause much high differences, and the Magnetic vector potential formulation may be better in PAW models.