Study On Mechanism Of Oxide And Chloride In Activating Tungsten Inert Gas Welding

Comparing with the conventional TIG (Tungsten Inert Gas) welding, A-TIG (Active Tungsten Inert Gas) welding has many advantages, e.g. augmenting the penetration, refining the weld and increasing the production. Owning to the broad application prospects, A-TIG welding has attracted the popular attentions of people, since it has been developed. Regarding to the mechanism of increase of weld penetration for A-TIG welding, the mechanisms that has been recognized by the researchers are the arc constriction and the change of surface tension for different fluxes. However, up to now, there is no unified mechanism for the A-TIG welding, and there is no report on the detail way for different fluxes during A-TIG welding process.Based on the proposed mechanism for flux, chlorides and oxides are selected as activating fluxes to study the effect of flux on the penetration depth during A-TIG welding process. Furthermore, the regularity of weld penetration is summarized. Meanwhile, based on the property of the flux, the mechanism for flux is analyzed and discussed.In this study, it is observed that the weld penetrations are augmented when the metal oxides are applied. Moreover, the penetrations with fluxes are of little variation. The results indicate that, under the effects of oxides, the arc voltage and the electron density increase during A-TIG welding process; however, the electron temperature decrease. In addition, the phenomenon of arc constriction is not observed when the oxides are applied, which means the variation of the arc state is not the main mehcanism for the increase of weld penetration. When different metal chlorides are used, the pentetration with fluxes are different. Furthermore, it is observed that the penetrations of the three base metals are of the same regularity that increases firstly and then decreases with the increase of the metal first ionization potential. The results indicate that, when the metal chlorides are employed, the arc voltage and the electron temperature increase; however, the electron density decreases. Moreover, when the MnC12and ZnC12are applied, the phenomenon of arc constriction is observed; however, the phenomenon of arc constriction does not occur under the effects of KC1flux. The results obtained indicate that the effect on the welding plasma is the main mechanism for chlorides during A-TIG welding process.Base on the result obtained this paper has unified the mechanism of fluxes from the points of heat-input. We propose that when the oxides or chlorides are used, the increase of heat-input is the basic mechanism for the augment of weld penetration. When the oxides are applied, the constriction of conduction channel and the increase of ionization of arc plasma are the basic reason for the increase of arc voltage and the weld penetration. When the chlorides are applied, both the metal element and the chloride element will affect the welding arc plasma. The metal element will vary the temperature of the arc plasma to different extent, and the chloride element would absorb the electron of the outside of the arc plasma to form ions, which will constriction the welding plasma. The contribution of the metal elements and the chloride elements are the basic reason for the increase of weld penetration.