Numerical simulation of molten pool behavior and bead formation in Al-alloy GMAW bead-on-plate welding

A transient 3D numerical model was established to investigate the multi-coupling transport phenomena in the Al-alloy GMAW bead-on-plate welding process. An integrated self-adaptive distribution mode of “arc current density-arc pressure-electromagnetic force-arc heat” was proposed to adapt to the evolution of the surface morphology of the molten pool. The heat and force state of the molten pool was analyzed to investigate its influence on the bead formation. The results showed that the arc pressure and droplet impingement promoted the backward flow of the liquid metal, thus forming the gouging region. It decreased the concentration of the arc current density, thereby reducing the superheat of the liquid metal and facilitating the filling of the weld toe. Based on the characteristics of the temperature and velocity fields, the characteristics of weld formation in the three stages of arc preheating, melting, and solidification were analyzed. This study revealed the relationship between molten pool behavior and bead formation, promoting the implementation of Al-alloy GMAW in welding and additive manufacturing.