Numerical Simulation Of Droplet Transition In Plasma-MIG Hybrid Welding

Nowadays,in the era of rapid development of science and technology,welding technology has become the most important connection technology in the manufacturing field.With the continuous development of welding technology,more and more high-quality,high-efficiency welding methods have emerged.Plasma-MIG hybrid welding is a new welding method that combines plasma arc welding with MIG welding to form a coupling process of two arc interactions.In this method,the advantages of the two welding methods can be combined into one,so that the plasma-MIG hybrid welding has the characteristics of energy concentration,deep penetration,stable welding process,no spatter,less welding fumes,and high joint quality.This paper studies the droplet transition behavior of plasma-MIG hybrid welding.Because the welding droplet transition process is a very complex process involving fluid mechanics,electromagnetism and other theories,it is difficult to perform detailed analysis in actual welding experiments.Therefore,this paper uses computer numerical calculation method to simulate the droplet transfer process through FLUENT software combined with fluid dynamics theory.According to the other of studying MIG welding and plasma-MIG hybrid welding,compare the effect of plasma arc on the droplet transition of MIG welding.According to the three conservation equations of fluid mechanics,Maxwell equations,computational fluid dynamics theory(CFD)and multiphase flow theory(VOF),establish the two-dimensional model of MIG welding droplet transition and three-dimensional model of plasma-MIG hybrid welding droplet transition.Use the HYPERMESH software to mesh the calculation areas separately.Then determine the relevant material parameters and boundary conditions required for the simulation calculation and choose the PISO algorithm to calculate.By changing the welding current,compare the change of droplet morphology and droplet transition mode,and conclude the critical current.Then the influence of plasma arc on the droplet transition of MIG welding can be obtained.In the MIG welding two-dimensional model,the entire process of droplet formation,growth,and shedding is simulated.Combined with the force conditions of the droplets,analyze the process of forming elliptical droplets under the action of gravity,electromagnetic force and surface tension.Among them,gravity and electromagnetic force promote the droplet transition,and the surface tension hinders the droplet transition.As the welding current increases,the droplet size changes.The radial width decreases,the axial length increases,and the dropwise transition mode changes into the spray transition mode.The critical current of transition is about 230A.In the simulation results of the three-dimensional model of the plasma-MIG hybrid welding,the shape of the droplets is irregular,and when dropped,it is attracted by the plasma arc and shifts between the two arcs.With the increase of MIG current,the radial width of the droplet decreases,and the axial length increases,and the droplet transition mode changes from dropwise to spray.The critical current of the transition is about 190A.The influence of plasma arc on the droplet transfer of MIG welding was concluded through the comparison of two-dimensional and three-dimensional models.Finally,the accuracy of the simulation results was verified by actual welding tests.