Investigation On Formulation Design For A-TIG Welding Of Aluminum Alloy

Aluminum alloys have a diversified range of successful applications in aerospace,shipping vehicles, power generation and other industries due to its low density, highstrengths and good ability of corrosion resistance. AC TIG welding is one of the mostcommon welding processes used for Aluminum alloy. However, comparing to other arcwelding processes, this kind of process has lots of disadvantages, such as shallowpenetration and low deposition efficiency. Thereby, it increases the welding difficulty andreduces the welding efficiency. Recently, many researchers have focused on a new TIGprocess, namely, A-TIG (Activating Flux TIG Welding). A-TIG welding is a kind ofwelding with a thin layer of fine flux covered on the surface of the base material beforewelding and thus greatly increasing weld penetration with good mechanical property. In thisstudy, A-TIG welding is introduced in the welding for Aluminum alloy and the formationdesign of activating flux is investigated.A-TIG welding experiments for6061aluminum alloy were made using11species ofsingle-component activating fluxes. And six components were taken as basic activatingfluxes for the complex formulation applied in this experiment. The appropriate ratio ofcomposition is designed by means of the uniform design method and effective activatingflux is developed. And the effect of welding parameters such as welding current,weldingvelocity,arc length and coating quantity on weld penetration and width has been studied. arcshapes were captured using a high-speed camera system and arc spectrum were observed byspectrum device when the arc moves from non-flux zone to flux zone. Thus the mechanismof the increasing of A-TIG welding penetration can be analyzed.The experimental results indicate that good surface performance can be obtained whenthe flux is TiO2、Cr2O3、Al2O3、MnO2、MgO and CaF2. While poor surface performance isgotten when parent metal is coated with SiO2、NaCl、NaF、MnCl2and BaCl2. SiO2flux canincrease weld penetration substantially but cause modest increase in weld width. TiO2andCr2O3can also improve weld penetration obviously, and the effect of improvement changeslittle with fluctuation of welding current. When the value of current exceeds140A, MnCl2and BaCl2can notably increase weld penetration, But the other fluxes have little effect onweld penetration.The best range of each single component of complex formulation is determined through uniform design experiment. And the best formula YG304is developed throughoptimization design and trial adjustment, and its penetration is more than3times as that ofconventional TIG welding under the same circumstance. The experimental results show thatthe penetration of A-TIG welding is greater than that of conventional TIG welding.With technologies of high-speed photograph, It is found that arc contraction can beobserved obviously when using TiO2、Cr2O3、MnO2and MnCl2, when the flux is SiO2andBaCl2, arc experiences an obvious expansion process, the phenomenon of arc contraction isnot remarkable when using the other fluxes. Through observing the change tendency of arcvoltage, it is considered that resistance of conducting channel which consist of arc andactivating flux and molten pool make great effects on weld penetration, The significantimprovement of weld penetration may be the result of increase in heat input caused by thechange of resistance of conducting channel. Through the comparative analysis of arcspectrum of TIG welding and A-TIG welding, the increase of penetration may be attributedto the recombination of positive ion such as Si4+、Ti4+、Cr3+and electron that generates fromAr arc, thus increase the arc temperature and arc force and ultimately increase the weldpenetration, and the effect of increase penetration is different due to various physicalproperties of positive ion.