Numerical Simulation Of Low Current Pulsed GMA Assisted High-power Solid Laser Welding Process

Laser+ pulsed GMAW(Pulsed Gas Metal Arc Welding,GMAW-P)hybrid welding,as one type of high-quality and efficient welding technologies,which combines the advantages of laser welding and GMAW,and has the energy synergy effect of "1+1>2",and great industrial applications potential.Compared with a single welding method,the low current pulsed GMA(Pulsed Gas Metal Arc)assisted high-power solid laser welding process can give full play to the advantages of laser welding,and can make up for its shortcomings of high assembly accuracy,poor bridging ability,and so on,to achieve low heat input and high efficient welding;While the coupling of low current pulsed arc and high-power laser has an important influence on the welding process stability and welding quality.In this paper,by establishing a numerical simulation model,the numerical simulation and process experiment verification of the low current pulsed GMA assisted high-power solid laser welding process were carried out to analyze and show the influence of the thermo-mechanical distribution in the molten pool on the flow behavior of molten liquid metal,which can understand in-depth the physical mechanism of low current pulsed GMA assisted high-power solid laser welding process,and provide some guidance and optimization of low current pulsed GMA assisted high-power solid laser welding.There are great theoretical significance and practical value to achieve high quality,high efficiency,low heat input welding.Arc images,arc voltage and welding current signals were collected in the low current pulsed GMA assisted high-power solid laser welding experiments.Based on the experimental results,the pulsed arc heat source model and the laser heat source model were optimized respectively,the effects of the molten pool surface deformation,the interaction of the laser and the arc on the arc heat flow distribution were comprehensively considered,and the droplet transfer and arc pressure models were optimized.Then,a three-dimensional transient computational fluid dynamic(CFD)model was founded to quantitatively analyze the difference of molten pool temperature field and flow field between laser welding and low current pulsed GMA assisted high-power solid laser welding.The model of hybrid welding was verified by the experimental results.The results show that,compared with single laser welding,the top surface of the molten pool of low current pulsed GMA assisted high-power solid laser welding is impacted by pulsed arc and droplets,which periodically interferes with the size of the keyhole opening and indirectly affects the eruption direction of metal vapor.And the pulsed GMA can effectively reduce the cooling rate of the top surface of the molten pool,the length of the molten pool is increased by 50%,the heat distribution on the surface of the molten pool is more uniform,the backward flow of liquid metal on the top surface of the molten pool becomes more complicated,and horizontal spreading trend of liquid metal is increased.The width of the molten pool is significantly increased,and the depth of the molten pool is not significantly changed.The evolution characteristics of the temperature field and flow field in the molten pool of full penetration welding were analyzed.The results show that,there are two major flow trends in the molten pool:clockwise flow in the upper part of the molten pool and small counterclockwise flow near the keyhole in the bottom of the molten pool.In the stable welding process,the maximum melting width of the back surface of the molten pool is about 1/3 of the top surface,and the length of the molten pool on the back surface of the molten pool is about 1/4 of the top surface.After the cooling of the back surface of the molten pool,a residual height of about 0.5mm formes,and the weld seam formed is relatively regular and beautiful.