Study Of Arc Assisted Activating TIG Welding Process

Recently,study of high efficiency and energy saving new welding processes has become one hot topic of the international welding fields.Recent study of A-TIG welding showed that,the temperature coefficient of surface tension was changed by Oxygen or other activating elements was the main mechanism of increasing weld penetration for mild steel,stainless steel and other steel products。In this paper,a new activating welding process has been put forward by changing the way of adding activating elements—AA-TIG welding(Arc assisted Activating TIG Welding). Before the TIG welding,using the assisted arc to prepare a thin oxide layer instead of coating activating flux,the weld penetration also can increase.Using the SUS304 austenitic stainless steel as the base metal,the effect of welding conditions of AA-TIG on weld penetration and width was studied with CO₂+Ar as the mixed activating shielding gas of the assisted arc,and the best welding conditions with good surface appearance and deeper weld depth were obtained.The effect of oxide layer on weld microstructure was studied by metallographic analysis,and the low-temperature impact toughness,corrosion resistance and hardness were also tested.Through the weld chemical composition analysis,the chemical composition differences between the traditional TIG welding and AA-TIG welding were studied.The results showed that the mechanical properties and chemical compositions of AA-TIG welding were very close to traditional TIG welding,and the oxide layer had little effect on the microstructure and performance of AA-TIG weld.Meanwhile,the effects of O₂+Ar,CO₂+Ar,N₂+Ar or the air of assisted arc on weld depth and microstructure of AA-TIG welding were studied,and the feasibility of double arcs assisted activating TIG welding was studied preliminarily.The results indicated that when the assisted arc contained O₂+Ar,CO₂+Ar or the air,weld penetration increased,but when assisted arc contained N₂+Ar,the weld penetration almost did not change.Therefore,oxygen had important effect on increasing weld penetration.The weld depth of double arcs assisted activating TIG welding increased dramatically,the ratio of weld depth reached 2.4,and the weld width contracted obviously,and this process will play significant role in fully automated production of AA-TIG.In terms of the mechanism of increasing weld depth,first,the effect of arc contraction on weld depth was studied through the analysis of arc shape and welding voltage.Second,the effect of oxides in oxide layer on surface tension was studied by XPS test.Third,the relationship between the weld penetration and oxygen content was studied by calculating the oxygen content of the surface of welding pool.The results showed that arc contraction was not the main reason for increasing weld penetration,the oxygen in oxide layer as the activating element can change the temperature coefficient of surface tension was the main mechanism.AA-TIG welding had broad applicability,it not only can use different mixed gases as the shielding gas,such as CO₂+Ar,O₂+Ar,even the air,but also can be applied to several kinds of steel products.The new welding method can realize fully-automated production with the advantages of higher efficiency and high-quality, which was a kind of new welding technology with huge developed potential.