Study On Indirect Arc And Droplet Transition Behavior Of Gas Shielded Twin Wire Indirect Arc Welding Under Controlled Magnetic Field

Gas shielded twin wire indirect arc welding(hereinafter referred to as twin wire indirect arc welding)is a new type of welding method with high efficiency and energy saving.The two wires are respectively connected to the positive and negative electrodes of the welding power source,and the arc burns between the ends of the two wires.The workpiece is not connected to the power source during the welding process.This method has the advantages of energy saving,high efficiency,small fusion ratio,and the like.It is a new kind of welding method with a good application prospect.However,it also has its own shortcomings.Due to the low heat input,it is easy to produce defects such as insufficient penetration and unreasonable weld shape.It is limited to increase the heat input to the workpiece and improve the weld formation with adjusting the welding parameters.The addition of an external magnetic field during the welding process can change the arc shape and the droplet transfer behavior.It can adjust the heat input without changing the welding parameters,and promote the practical application of the new arc welding method in engineering.This paper summarizes the arc shape,droplet transfer behavior and weld formation law under the action of external magnetic field.The influence of external magnetic field on the heat input of double wire indirect arc welding and its internal mechanism are analyzed.Research indicates:The applied magnetic field affects the shape of the arc.The arc deflects negative toward the x-axis,the arc deflection angle increases as the magnetic induction increases under the negative magnetic field.The arc deflects in the negative direction of the x-axis,the deflection angle increases as the magnetic induction increases under the negative magneticfield.The applied magnetic field loading angle affects the arc deflection angle.As the applied magnetic field loading angle increases,the increase of the arc deflection angle decreases when the applied magnetic induction intensity increases from 0 mT to 5 mT.The larger the loading angle,the more significant reduction.The Lorentz force in arc plasma under external magnetic field is simply analyzed.It is found that different applied magnetic fields affect the magnitude of the Lorentz force of the electrons,which in turn affects the arc deflection angle.The change in arc shape ultimately affects the heat input of the arc to the workpiece.The arc width increases under the negative magnetic field,the arc increases the heating area of the workpiece,and the melting width is larger.The arc is more concentrated on the heating area of the workpiece under the negative magnetic field,and a greater penetration is obtained.Under the action of the negative magnetic field,the cathode droplet and the anode droplet are deflected toward the z-axis.The forward magnetic field causes the cathode droplet and the anode droplet to move away from the z-axis.The applied magnetic field induction has an important influence on the droplet transfer behavior.As the magnetic induction intensity increases,the cathodic arc and the anode arc approach and eventually contact each other,causing a short circuit and the arc is broken under the negative magnetic field,.Under the forward magnetic field,as the magnetic induction intensity increases,the cathode arc and the anode arc are separated from each other,and the welding is relatively stable.However,if the distance between the two droplets is too large,the arc will be broken,which will affect the welding heat input.According to the mass-spring model of water droplets,the droplet mass-spring model under the action of magnetic field is established.The droplet's gravity position is basically consistent with the actual center of gravity of the droplet during the welding process.It can be used to analyze the change of droplet shape under the action of magnetic field.The effect of the applied magnetic field on the arc shape and the droplet transfer ultimately affects the weld formation.The weld penetration decreases with the increase of the magnetic induction intensity under the negative magnetic field,and the melt width increases with the increase of the applied magnetic induction.The weld penetration in theforward magnetic field increases with the increase of the applied magnetic induction intensity,and the melt width decreases as the applied magnetic induction increases.The effect of the forward magnetic field on the weld formation is more pronounced than the negative magnetic field.The weld formation is best under the action of 3mT forward magnetic field,and the weld penetration is the largest,and the weld seam is the strongest bond with the base metal.