Numerical Slimulation Of Arc-droplet Behavior In TIG-MIG Hybrid Welding

TIG-MIG hybrid welding combines the advantages of TIG and MIG,so that even under the protection of pure argon gas,it can efficiently obtain weld joints with small deformation and high quality,which is in line with modern manufacturing quality and efficiency requirements.In the process of hybrid welding,there is a strong interaction between the two arcs of TIG and MIG.This effect has an important influence on the arc behavior of the hybrid welding,the droplet transition,and the thermo-mechanical balance of the molten pool.However,the current research on arc-droplet of TIG-MIG hybrid welding is still mainly based on experimental results through the use of high-speed camera and spectral analysis to qualitatively or semi-quantitatively explore the thermo-mechanical law of arc-droplet.There are few studies on the coupling mechanism between arc-droplet.So,this paper uses a combination of simulation calculation and craft experimental to study the thermo-mechanical characteristics of the arc-droplet in TIG-MIG hybrid welding and the coupling mechanism between TIG and MIG,to analysis the difference of arc-droplet behavior between single MIG and TIG-MIG hybrid welding,revealing the physical characteristics of arc-droplet in TIG-MIG hybrid welding.Above study could provide the necessary theoretical basis and data support for further optimization of the welding process,and it has important research significance and engineering value.In this paper,based on the TIG-MIG hybrid welding process experimental platform,high-speed camera and laser background light source are used to obtain arc shape and droplet transition shape,which provides verification data for simulation calculation.Based on the theoretical basis of heat transfer,fluid dynamics and electromagnetics,a three-dimensional coupled transient model of arc-droplet in TIG-MIG hybrid welding is established.Analyze the parameters of temperature field,flow field,electromagnetic force,pressure and current density in the arc space,and reveal the mechanism of the TIG welding on the MIG arc initially.Meanwhile change the TIG current and the filament spacing,quantitatively analyze the influence of TIG arc(DCEP)on MIG arc(DCEN)and droplet dynamic behavior.The results show that introducing the TIG welding,a repulsive force is generated between the two arcs,which pushes the hybrid arc to deflect,the TIG arc deflects forward to preheat the workpiece,and the MIG arc deflects backward to extend the molten pool heating range.When the TIG current increases(80A,100A,120A),the coupling effect of the hybrid arc is enhanced;the swing angle of the MIG arc-droplet increases and the swing angle of the TIG arc decreases gradually;the droplet transition period increase first and then decrease.The flow speed of the liquid metal in the droplet at the end of the welding wire increases gradually,and the flow velocity in the droplet entering the workpiece increases first and then decreases.With the distance between wire and tungsten increasing(5mm,7mm,9mm),the MIG arc-droplet swing angle increase first and then decrease;the MIG arc swing angle decrease;and the droplet transition period decreases first and then increases.The flow rate of liquid metal in the droplet at the end of the wire decrease first and then increase,and the flow velocity in the droplet entering the workpiece decrease first and then increase.The simulated MIG arc-droplet swing angle and droplet transition frequency are compared with the experimental results,and the results are in good agreement.