Study Of Arc Behavior Under The Magnetic Field And Activating Fluxes

The magnesium alloy because of light mass, high intensity, good heat has beenextensively used in car manufacturing industry, while other electronic products industry ofcomputers, mobile phones, cameras, and players also have very broad developmentalprospects. Comparing with TIG weld, A-TIG weld not only has advantages of TIG weld, butalso can increase the weld depth and clean welds to improve production efficiency. SinceA-TIG weld technology was made, it has been much attention. Welding involves physicalmetallurgy, solid phase transition, melt and crystallization of the welding metal. Flow state ofwelding liquid metal, the heat distribution of arc and mass and heat transfer of welding metalsare affecting welding quality.In the paper, by theoretical analysis, the math model of TIG weld arc had been simplifiedand successfully established. The math model of weld arc was applied to analyze thetemperature field and magnetic field of weld arc, to analyze weld arc shapes and temperaturefield distribution, potential distribution, the field current density and magnetic flux densitydistribution. It had important and profound significance to improve mechanization of weldingprocess. Two oxides active fluxes were chosen (TiO2、Cr2O3). Single active flux was coated onthe surface of the magnesium alloys, respectively, and then magnesium alloys were welded byA-TIG under magnetic field. The A-TIG weld arc shapes under magnetic field were shot andrecorded with high-speed cameras. Weld arc shapes coated with single active fluxes were got.The changing mechanism of arc shapes was analyzed.Experimental results show that: through numerical simulation and analysis of temperaturefield distribution of A-TIG weld arc, the simulated arc shape is basically consistent with thereal arc and the weld arc shape shows "bell" shape. The A-TIG weld arc shapes of AZ91magnesium alloys are shot and recorded with high-speed cameras. When it is not coated withactive fluxes under no magnetic field, weld arc presents cone. When it is coated with activefluxe, weld arc presents state of constraction. In addition, the constriction degree of weld arc ismost obvious with TiO2, Cr2O3is followed. Finally, based on theoretical analysis, arccontraction theory and the "anode spot" theory is the main reasons of weld depth increased byoxides active fluxes. When a magnetic field is applied in the welding process, the arc column shows in contraction state and rotates in the clockwise direction. When the welding parametersremain unchanged, the contraction degree of arc column increases with the magnetic fieldstrengthening. Based on theoretical formulas of magnetic field, it can be derived that under theaction of applied magnetic field, the rotation radius of arc and magnetic induction areinversely proportional.