Coupled mechanisms of arc, weld pool and weld microstructures in high speed tandem TIG welding

A novel high speed tandem TIG welding process was introduced to join pure titanium thin plates with high efficiency and high quality. In order to reveal coupled mechanisms of arc, weld pool and microstructure in this novel welding process, coupled electrode, arc and weld pool numerical models were developed for both the single TIG welding and high speed tandem TIG welding processes, to study the arc and weld pool behaviors in a similar line energy input condition. In the high speed tandem TIG welding, the arc interaction causes expansions of arcs, and decreases of current densities; therefore, the maximum arc temperature, arc velocity, and energy fluxes on the top weld pool surface decrease to the values similar to these in the single TIG welding. Owing to a Pull-Push flow pattern caused by the Marangoni force and arc shear stress on the top weld pool surface between two arcs, the fluid flow and energy propagation of the weld pool become much stronger. The existence time of high temperature is shorter, and the stirring effect of the weld pool is stronger, so finer weld microstructures can be obtained in the high speed tandem TIG welding. (C) 2020 Elsevier Ltd. All rights reserved.