Numerical analysis of heat transfer and fluid flow in swing arc narrow gap GMA welding

A three-dimensional model is developed for swing arc narrow gap welding process considering the effect of moving trajectory of arc and joint geometric shape, which can calculate the temperature field and fluid flow in transient state. The arc heat source model also allows for the inclination of arc in the plane perpendicular to weld beam and the variation of the arc moving direction through coordinate system transformation, its distribution parameters being determined based the arc behavior captured by a high speed video system. The droplet heat transfer is assumed as the process of liquid metal with high temperature flowing into the weld pool from the certain area above it. The major forces acing on liquid molten pool, including arc pressure, arc plasma drag force, electromagnetic force, surface tension, Marangoni stress and buoyancy force are taken into account in this model. The characteristics of weld pool dynamic behavior and temperature profile are analyzed and the effect of different welding parameters on them is discussed. In swing arc narrow gap GMA welding, there exists a large vortex in the whole weld pool cross section and fluid flow pattern is beneficial to the growth of sidewall penetration depth. The width of high-temperature region outside weld pool is smaller than that of non-swing arc welding process. The arc swing frequency has minor influence on the cooling rate.