Abstract: For aluminum alloys, a new type activating TIG welding called flux zoned TIG(FZ-TIG)welding is proposed, it simultaneously increases weld penetration dramatically and improves weld surface forming. A series of experiments are carried out to study the mechanism of activating fluxes increasing weld penetration of AC FZ-TIG welding for aluminum alloys. TIG welding with helium shielding gas is used to observe the change of arc behavior. The change of welding voltage with arc length is studied to find the pattern of activating fluxes influencing arc. The weld deviation experiment is carried out to analyze the effects of activating fluxes on current channel resistance. The potential chemical reactions between the activating fluxes and the weld surface oxide film or the welding pool metal are studied by X-ray diffraction analysis of weld surface slag and thermodynamic calculation. It is believed that the fluxes including outer region flux SiO2, central region insulating flux FZ108 simultaneously constricting arc root and arc column dramatically are the main mechanism of fluxes increasing weld penetration of AC FZ-TIG welding for aluminum alloys.

Key words: Activating flux, Aluminum alloy, Arc, FZ-TIG welding, Mechanism, Weld penetration