Study On Arc Shape And Weld Forming Mechanism Of Longitudinal Magnetron High Speed Mag Welding

As a very important and common welding method,MAG welding has the characteristics of simple welding metallurgy process,fast deposition efficiency,high weld purity and beautiful appearance,and it is widely used in various industrial manufacturing fields.However,in order to achieve the purpose of improving production efficiency and enhancing market competitiveness,when the MAG reaches high-speed welding,the arc cathode drift phenomenon often occurs,and a series of weld defects such as hump weld bead,undercut and discontinuous weld are generated.Therefore,by adding a longitudinal magnetic field,the energy distribution of the arc,the flow and heat transfer process of the molten pool are changed,thereby eliminating weld defects and improving weld formation.In this paper,the 1.2mm ER50-6 welding wire is used,and the welding current of230A is explored by the pre-test process parameters.The welding arc voltage of 36V is82%Ar+18%CO₂,and the gas flow rate is 20L/min.The magnetron high-speed MAG welding test was carried out on a 4mm Q235 ordinary carbon structural steel plate to achieve a welding speed of 35mm/s.By changing the excitation parameters and capturing the welding arc shape change and the molten pool flow change process under the high-speed camera and welding video monitoring system,the weld forming effect is observed,and the mechanism of the magnetron high-speed MAG welding is explained and analyzed,and the welding arc can be selected.The excitation parameters of stable rotation and weld formation are good,and the mechanical properties of the weld and the metallographic structure of the weld are observed and compared.The research results show that when high-speed MAG welding is carried out,under the control of longitudinal DC magnetic field,when the excitation current is 2A,4A,6A,the welding arc rotation speed increases with the increase of the excitation current,but the arc shape is extremely unstable.The welding spatter is large and the weld forming effect is poor.Under the control of the longitudinal AC magnetic field,when the excitation current is 4A and the excitation frequency is 50Hz,the arc shape is bell-shaped and stably rotates.When the excitation current and the excitation frequency are 4A50Hz,4A70Hz and 6A50Hz,respectively,the weld bead forming effect is better,and no weld defects are found on the macroscopic.Under the control of the longitudinal alternating magnetic field,the radial motion component of the charged particles in the arc is affected by the Lorentz force,causing the welding arc to rotate clockwise and counterclockwise along the axial direction.As the excitation current increases,the magnetic induction intensity increases.The radius of rotation of the charged particles is reduced,and the degree of contraction of the arc shape is increased.At the same excitation current,as the excitation frequency increases,the edge of the compressed arc undergoes a slight expansion.Longitudinal magnetron can change the flow characteristics of the molten pool,effectively suppress undercuts and improve defects such as hump welds.In the mechanical properties test of the weld,the tensile strength and hardness of the weld have a certain tendency to decrease when the excitation parameters are from 4A50Hz,4A70Hz to 6A50Hz.In the microstructure observation,at4A70 Hz and 6A50 Hz,defects of many pores and unfused were observed and respectively.When the excitation parameter is 4A50Hz,the microstructure is most uniform and dense,and there is no defect.Therefore,in the longitudinal magnetron high-speed MAG welding,by changing the excitation parameters,the weld bead formation can be effectively improved,thereby realizing the magnetron high-speed MAG welding,thereby achieving the purpose of improving production efficiency and enhancing market competitiveness.