| Activating welding has been drawing the people’s widespread attention since itcomes to world, because it significantly increases weld penetration and improveswelding production efficiency. The research of activating welding focuses on thedevelopment and application of the active flux, new highly active welding technologyand the mechanism of increasing penetration of active flux. At present, the research onthe mechanism of increasing the weld penetration of active welding shows that theactive agent plays different role due to welding materials, namely for iron-based alloysand stainless steel, the surface tension temperature coefficient of the molten pool rangefrom negative to positive and the inward flow motion dominates in molten pool, thusthe penetration increased significantly, for light metal such as aluminum, magnesiumand their alloys, the constriction of arc is the main reason for the increase of itspenetration depth.AA-TIG welding (Arc assisted Activating TIG welding) is proposed on the basisof the A-TIG welding. A pre-melt surface oxide layer is formed in this process byassisted arc before welding, which plays the role of increasing welding penetration asactive flux used in the A-TIG welding. Compared to A-TIG welding, AA-TIG weldingnot only avoids development of active agents, but also realizes welding atomization,thus welding efficiency is improved obviously. In the article, SUS304austeniticstainless steel (0Cr18Ni9) is selected as the base metal, Ar+O2is used as activeprotective gas in assisted arc, the effects of assisted arc parameters on the thickness ofpre-melting oxide and AA-TIG weld morphology were studied, influence law of thewelding parameters on pre-melting oxide thickness and weld depth to width ratio isobtained, and the pre-melting oxide composition and oxygen element in the moltenpool were analyzed. Transition model of the oxygen element from the arc atmosphereto the pre-melting oxide and then to the molten pool was established.Experimental results show that the oxygen gas flow rate in the assisted arc, theassisted arc current and the speed of the assisted arc have a great effect on weld D/Wratio, with the increase of oxygen flow rate in the assisted arc and the heat inputincreased, the weld depth to width ratio increase firstly and then decrease. Thecomposition of pre-melting oxide layer was analyzed by EPMA and XRD. The resultsindicate that pre-melting oxide layer is mainly consisted of oxides of Silicon,Manganese and Chromium, while the FeO mainly existed in the pre-molten metal.In terms of the mechanism of AA-TIG welding increasing weld depth, thecomparison experiment is carried out to verify the role of pre-melting oxide layer on increasing the weld penetration, and the effect of pre-melting surface oxide layer onthe main arc voltage and weld penetration is studied. The results show that the surfaceoxide layer has not obvious role on the increased AA-TIG welding penetration, theFeO in the pre-melting metal is the major factor which remarkably increasedpenetration of the AA-TIG welding.Oxygen content in the AA-TIG weld was measured, the results present the oxygencontent in the weld seam is of lower level, AA-TIG welding method does not lead to asubstantial increase of oxygen content in the weld. The method is of wide rangedapplication field, high welding manufacturing efficiency, and can realize automation aswell as obtaining high quality weld joint. AA-TIG is a new high efficient weldingprocess and takes on a development potential and applied value. |
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