Stirring effect of the rotating arc on the molten pool during non-axisymmetric tungsten NG-GTAW

ABSTRACT The stirring effect of the rotating arc during non-axisymmetric tungsten narrow-gap GTAW (NT-NG-GTAW) on the molten pool is investigated. Tracer particles are embedded in the groove and plate metal surface, respectively. During welding, the floating tracer particles are captured with a high-speed camera to reflect the flow characteristics of the liquid metal. Compared with conventional GTAW processes, mechanical force (Fc) and inertial centrifugal force (Fl) in NT-NG-GTAW have more significant effect on the molten pool. They are the main driving forces to change the flow pattern of the molten pool under the rotating arc. As the arc rotate to the boundary of the molten pool, liquid metal layer on molten pool surface forms a vortex at the other edge to impact on the sidewall. When the arc rotates clockwise, the molten pool in bead-on-plate rotates counterclockwise, whereas the molten pool in the narrow gap rotates clockwise with the same rotation frequency as the arc.