Research On Droplet Transfer During Rotating TIG Filler Wire Welding Process Based On Numerical Simulation

As a real-time sensor,rotating arc sensor has the advantages those others sensors are difficult to replace.The application of rotating arc sensor to TIG Welding(Tungsten Inert Gas Arc Welding)is of great significance for promoting TIG welding automation.Due to the influence of centrifugal force,the heat field and flow field of the rotating arc are different from ordinary welding methods.In the welding process,the droplets are wrapped in welding arc,and the change of the arc properties will affect the droplet transfer.Therefore,in the study of droplet transfer,it is necessary to precede a thorough study about the welding arc.In the process of TIG welding,the welding wire can supplement the melting loss of elements caused by the high temperature burning arc.Because of the transition frequency and the transition form of droplet influence the welding formation and the quality of weld seam,the droplet transfer is studied in this paper.In order to have a deeply understand of the flow field distribution inside the arc and the influence of the welding parameters on the transition period and transition form of the droplet.The numerical simulation method is used to study the characteristics of the arc and the droplet transition.In this paper,the rotating arc and droplet transfer are numerically simulated separately by using the commercial computational fluid dynamics software FLUENT.Based on the theory of magnetohydrodynamics,a mathematical model of rotating TIG welding arc is established,and the numerical simulation of rotating arc under different welding current,rotating frequency and protective gas flow rate is carried out.Then a mathematical model of droplet transfer is established.The VOF method is used to track the free surface of the droplet.The droplet transition form under different welding voltages,different arc rotating frequencies and different welding current is simulated.When simulating arc and droplet,it is necessary to use UDF to communicate with internal data of FLUENT,so as to add the equation needed by the model.In order to verify the reasonableness of numerical simulation,the arc shape and the droplet transfer characteristics of corresponding welding parameters were respectively captured by high-speed camera.For arc simulation,in the range of selected parameters,the degree of arc deviating from the center line and the deflection range decrease with the increase of welding current.With the increase of rotating frequency,the welding arc,especially in the low temperature region of the arc,have a greater deflection angle.With the increase of protective gas flow rate,the isothermal line of the anode area has an outward expansion trend,that is,the arc bell shape is more obvious.For droplet simulation,with the increase of welding voltage,the droplet transition form change from globular transfer to free transfer.The distance between the end of welding wire and the molten pool is the most important factor which can affect the transition form of droplet.With the increase of arc rotational frequency,droplet transfer frequency increases slightly.When the welding current increases,the droplet transfer frequency increases significantly.The simulation results are compared with the results of high speed camera.Both of them are in good agreement and the simulation results are reasonable.This paper provides a theoretical basis for the welding process of setting the welding parameters of rotating arc TIG filler welding.