Numerical Simulation Of Arc Characteristics About Double Layer Path Of Gas Tungsten Arc Welding

Gas Tungsten Arc Weld?GTAW for short?often use argon or helium as welding protection gas,also known as tungsten argon arc welding or tungsten helium arc welding.Argon arc is soft and the welding process is stable,but its low energy density and stiffness lead to shallow weld penetration and low welding efficiency.Helium arc has the advantages of high energy density and deep weld penetration,but the high cost of helium limits its application.Therefore,the Double layer path of Gas Tungsten Arc Welding?D-GTAW for short?is proposed in this paper.By changing the welding protective gas supply mode and type of the traditional GTAW to alleviate the problems of the traditional GTAW.As welding arc is the carrier of arc welding energy,it has a direct impact on the welding quality,so it is necessary to study the arc characteristics of D-GTAW.The numerical simulation technology overcomes the difficulties in the measurement and detection of arc characteristics caused by the high temperature and instantaneity.Based on the basic theory of magnetohydrodynamics and with the help of CFD?Computational Fluid Dynamics?software,two-dimensional axisymmetric simulation models including tungsten,arc region and workpiece are established for GTAW and D-GTAW.By combining the characteristics of the thermodynamic and transport properties of the welding protection gas,the article analyzes the reasons for the difference of the arc characteristics between the two welding methods,which can provide theoretical guidance for the practical application of the D-GTAW.The results indicate that,Compared with the traditional tungsten argon arc welding,the arc voltage of D-GTAW(CO₂ 10 L·min^-1+Ar 5 L·min^-1)increases by 31%,the current density in the center of the molten pool increases by 25%,and the total heat transferred to the molten pool increases by 19%.The molar mass fraction of CO₂ is below 1.0%in the tungsten tip region of D-GTAW?CO₂+Ar?,and the tungsten will not be burned obviously.When welding current is 150 A,the depth-width ratio of D-GTAW(CO₂ 10 L·min^-1+Ar 5L·min^-1)is 0.19,and the penetration reaches 1.1 mm,which is significantly higher than that of GTAW protected by pure argon.The arc of D-GTAW?Ar+He?gradually possesses the helium arc characteristics with the increase of the flow rate of He in the inner layer.When the molar volume of He in the inner layer accounts for 41%of the total gas,the total heat transferred to the molten pool can reach 76%of the tungsten helium arc welding,which exceeds the level of helium-argon hybrid shielded welding when the proportion of He in the helium-argon mixture is 70%.Under the same welding parameters,D-GTAW(Ar 10 L·min^-1+He3 L·min^-1)can penetrate 2219 aluminum alloy?6 mm?as that of GTAW of pure helium protection(He 10 L·min^-1).