Numerical study on arc-droplet coupled behavior in magnetic field controlled GMAW process

Abstract

The metal transfer behavior is one of the most pivotal links of gas metal arc welding (GMAW) for improving the welding quality. Arc impacts the current path and heat input on the droplet surface, in reverse, the metal droplet detachment makes the arc to flicker. It is hard to make the metal transfer process clear with only experimental methods since the limited measuring space and high temperature in the welding region. In this work, with the help of computational fluid dynamics software ANSYS FLUENT, a magnetohydrodynamic model including argon arc plasma and steel wire and the droplet is constructed by using two independent governing equations of gas and metal phase for the mass, momentum, and energy balance. Comparing the magnetic field controlled GMAW with conventional GMAW, the temperature field, current density distribution, electric potential field, static pressure field and also metal vapor mass fraction distribution are highlighted. It is shown that the metal transfer frequency decreases and droplet diameter increases with 180 A welding current when applying an external constant axial magnetic field 0.002 T. So, the arc length decreases before the detaching moment, the current density expands in the arc region and the voltage decreases. The centrifugal movement impedes the downward flow and transfers heat from the droplet center to the outside region.