Transition Behavior Of Activating Flux Powders In The PPCA-TIG Alternating Current Arc Of Aluminum Alloys

A-TIG(Activating TIG)welding is an efficient welding method that can not only ensure the welding quality,but also significantly increase the penetration depth.However,it is difficult to ensure the coating quality and is not conducive to automation by manual coating of activating flux.For aluminum alloys,the previous welding method by introducing activating gas into O is not suitable for such metal welding.In view of the above problems,our research group proposed Powder Pool Coupled Activating TIG welding(PPCA-TIG welding).By selecting different activating flux powders,welding of various metals can be realized,which is conducive to mechanized and automatic production.In this paper,AC PPCA-TIG welding was used for 3003 aluminum alloy.On the basis of process research,the transition process of activating flux powders in arc was analyzed by electrostatic probe powder capture technology combined with SEM / EDS and thermodynamic calculation,and the influence law and mechanism of activating flux powders transition on arc were studied by electrostatic probe and spectroscopy.This is of great significance to enhance people's understanding of the interaction between activating flux powders and AC PPCA-TIG arc and the periodic evolution of AC arc,promote the development of this new AC activating welding method and equipment,and realize the automation,high penetration,low cost and green welding of activating metals such as aluminum and magnesium.When the welding current is 160 A,the welding speed is 100 mm·min^-1,the arc length is 3 mm,the inner gas flow rate is 12 L·min^-1,the outer gas flow rate is 8 L·min^-1,The motor speed is 30 r·min^-1 and the activating flux powders is 100 to 200 meshes.When the activating flux powder is SiO₂,it can weld through an 8 mm thick 3003 aluminum alloy at one time.When the activating flux powder is MnCl₂,the penetration increase ability 2.4 times that of traditional TIG welding,the weld formation when using MnCl₂ is better than when using SiO₂.After the activating flux powder enters the arc with the outer gas,with the increase of arc heating time,the physical processes of heating,melting,evaporation,crushing,collision and melting of the powders occur successively.This process is verified by thermodynamic calculation.The difference is that the physical and chemical changes of MnCl₂ in the arc are much faster than those of SiO₂ due to its low melting boiling point and chemical bond energy.The arc temperature was calculated based on the saturation ion zone and transition zone of the volt-ampere characteristic curve of the electrostatic probe,and compared with the temperature calculated by Boltzmann plot method.The error source of the plasma temperature measurement of the electrostatic probe was analyzed.It was found that the measurement model of the saturation ion zone was more suitable for the TIG arc plasma temperature measurement at atmospheric pressure.The experimental results of AC TIG and PPCA-TIG arc characteristics measured by probe saturated ion zone show that the axial temperature of arc center can be increased by adding activating flux powders.SiO₂ increases the temperature of PPCATIG arc near the tungsten electrode by 1825 K,increases the temperature near the base metal by 311 K,and makes the arc root shrink by 0.13 mm.MnCl₂ increased the temperature of PPCA-TIG arc near the tungsten electrode by 1025 K,and the temperature near the plate by 159 K,while the arc radius did not change significantly.The spectral test results show that the activating flux powder is dissociated under the action of arc high temperature and strong electric field,the gaseous elements generated after the dissociation of the surfactant promote the ionization of Ar and Al elements in the arc plasma.The temperature change of AC arc was characterized by Boltzmann plot method.The arc spectral intensity in EN period was higher than that in EP period,the arc voltage in EN period was less than that in EP period,and the arc temperature in EN period was lower than that in EP period.After adding activating flux powders,the arc center was higher than 1 mm of the plate.The arc temperature and arc voltage of PPCA-TIG were higher than those of traditional AC TIG arc in EN and EP periods.The average increase of PPCA-TIG-SiO₂ was 834 K,and the average increase of PPCA-TIG-MnCl₂ was 333 K.