Numerical Simulation Of TIG Welding Arc Behavior And The Welding Pool Flow Field With High Frequency Magnetic Field

The external magnetic field can influence the welding arc behavior,change the arc heat source distribution and further affect the weld pool flow.It is an effective method to control the quality of the welding process by improving the shape of the welding arc and the flow pattern of the welding pool.Exploring the arc shape and heat source distribution under different magnetic field conditions,establishing the movement laws of welding arc under different current and magnetic fields,providing theoretical and practical guidance for welding process control.Based on magnetohydrodynamics,a two-dimensional axisymmetric TIG welding arc numerical model and a three-dimensional TIG welding pool numerical model are constructed.The anode surface heat flux density and current density in the arc simulation results are added as boundary conditions to the welding pool numerical model to realize the arc-melting pool unidirectional coupling calculation.According to the numerical simulation results of arc and welding pool with the static or alternating longitudinal magnetic field,it is found that the longitudinal magnetic field will affect the arc shape and the flow of molten metal in the welding pool.For low-current TIG welding,when the static longitudinal magnetic field intensity is 0.03 T,the arc will shrink.With forward magnetic field,the arc shrinking is more pronounced and the arc near the surface of the anode has an expansion tendency,which is beneficial to improve the heat transfer efficiency during the welding process.The molten metal in the welding pool will rotate counterclockwise or clockwise depending on the direction of the magnetic field,so that the molten metal in the high temperature region is thoroughly mixed.When the forward magnetic field is applied,the ratio of depth to width of the welding pool is reduced by about 10% compared with no-external magnetic field.When the negative magnetic field is applied,the ratio of depth to width of the welding pool is similar or even increased compared with no-external magnetic field.When the alternating longitudinal magnetic field frequency is 1000 Hz,the arc will change periodically in a certain range with the change of magnetic field direction.The external alternating magnetic field can restrain the deformation of the welding pool contour due to electromagnetic stirring.And the width of welding pool expands rapidly,but the depth of welding pool does not change obviously,which makes the ratio of depth to width greatly reduced.However,when the pulse current is used for welding,the expansion of welding pool width can be inhibited when the external alternating magnetic field is applied,and the inhibition will change obviously with the difference of the current pulse waveform and the external magnetic field waveform.