Numerical simulation of effects of activating flux on flow patterns and weld penetration in ATIG welding

摘要

A mathematical model to describe molten pool of three-dimensional gas tungsten arc welding due to a moving arc has been developed considering the surface tension temperature gradient as a function of temperature and oxygen concentration to simulate the effect of activating flux on flow patterns and weld penetration. The effect of oxygen content and arc constriction on the fluid flows and temperature fields of weld pool has been simulated by the Phoenics software. The effect of activating flux on the penetration has been considered in the model by changing the oxygen content in the surface tension equation and the arc heat flux distribution parameter in Gauss source and magnetic force equations. It is shown that oxygen, which changes the temperature dependence of surface tension gradient ∂γ/∂T from a negative value to a positive value, can cause a significant change in weld penetration. The change in the surface tension gradient in the molten pool is considered to be the principal mechanism for increased penetration in ATIG welding. An arc constriction and increase in voltage can cause the width of weld narrower and the penetration deeper, but not the main mechanism for increased penetration.