Gas tungsten arc welding of magnesium alloy using activated flux-coated wire

Five-millimeter-thick plates of wrought magnesium AZ31B alloy was gas tungsten arc welded (GTAW) with mixture-activated fluxes by two methods. One is welded feeding flux-coated (FC) wires; the other is welded feeding normal wires after pasting the fluxes onto the base material. The same phenomenon was found with both methods: with an increase of MnCl2 content in the flux paste, the depth/width ratio of weld bead increased gradually. Arc spectroscopy revealed that the temperature of the arc in the FC wire weld process was higher than that in the normal wire with flux pasted onto plate weld process. Droplet transfer was analyzed and the difference in the surface tension between the droplet and the molten pool was considered to be the main factor that influenced the weld seam surface appearance.