Numerical Analysis Of Thermal And Force Characteristics Of MIG Arc Under Externally Applied Magnetic Field

Molten gas welding has become one of the most widely used welding techniques in the equipment manufacturing industry due to its low cost,high efficiency,simple equipment operation and easy realization of mechanical intelligent production.Increasing the welding speed is one of the important ways to improve the productivity of molten gas shielded welding.However,for high-speed MIG welding,excessive welding speed can lead to poor weld formation,and even lead to weld forming defects such as undercuts and hump welds,preventing further increase in welding speed and production efficiency.In the early stage,the research group developed a MIG welding process with additional magnetic field assisted.The experimental study verified that the applied composite magnetic field can effectively suppress the undercut and hump weld defects of high-speed MIG welding and greatly improve the welding speed.However,there is still no essential theoretical research on the intrinsic mechanism of the composite magnetic field affecting the thermal characteristics of the MIG arc and improving the weld formation.Therefore,according to the actual external excitation device type,the numerical model of the external composite magnetic field three-dimensional model and MIG arc simulation calculation is established.The finite element software was used to simulate the static MIG arc,the MIG magnetron arc without considering the droplet transfer,and the MIG magnetron arc considering the droplet transition.The thermodynamic characteristics of the MIG arc are analyzed.The influence of the applied composite magnetic field on the temperature field,flow field and electromagnetic field of the MIG arc is mainly studied.Changes in arc thermal characteristics during droplet flight were also investigated.The mechanism of the external magnetic field to control the MIG arc is preliminarily revealed.The influences ofthe excitation current and welding current on the MIG arc temperature,current density,fluid velocity,arc pressure and electromagnetic force are explored.The calculation results show that the applied composite magnetic field can deflect the MIG arc in the direction of the vertical weld and the forward tilt occurs in the forward direction of the weld.The deflection angle and forward rake angle of the MIG arc increase with increasing excitation current and decrease with increasing welding current.The high-speed magnetic control MIG welding experiment was carried out by using the composite magnetron welding experimental platform.The MIG arc shape under the control of the applied composite magnetic field was collected by the dual high-speed camera,and compared with the deflection angle and the forw ard tilt angle of the simulated arc.It is verified that the simulation results of the MIG arc deflection angle and the forward tilt angle are slightly larger than the experimental results when the droplet transfer is not considered?After considering the droplet transfer,the simulation results of the MIG arc deflection angle and the forward tilt angle are basically consistent with the experimental results.