Study Of Arc Characters In Twin-wire Indirect Arc Welding

Twin-wire indirect arc gas-shielded welding is a novelty welding method, which is different from the traditional welding processes as the twin-wire are connected to the negative and positive plates of the power source respectively. In this process, the arc burns between the twin wires, and the workpiece isn't connected to the unit. As all of the penetration ratio, stress and deformation are low, the twin-wire indirect arc welding will be developed with positive foreground.The characters of the indirect arc play an important influence in the droplets' transition, the formation of weld and the stabilization of the process. Based on the existing results, numerical simulation and experiments are both used in the research. Besides the structures of the welding gun are optimized, the processing parameters' influence in the arc characters are studied.The results of numerical simulation adicated, when the shape of shielded cap is circular column, the speed of the gas flow is too slow, and the stiffness of the arc is in poor condition, as a result, the shielding effect changes little. Besides, the reachability of the welding gun decreases. When the shape of nozzle is changed to shrinking, the stiffness of the arc is in much better condition, but, the gas flow near the nozzle is too turbulent, and the shielding result is in low degree. At last, the shape of the shielded cap is changed to variable cross-section, the shielding result improves a lot. After further study, we found that when the circular column in the variable cross-section is 20mm long and the grade angle of the shrinking place is 45°, the integrated result is better.Following the continuty of the flow (conservation of mass), conservation of momentum and conservation of energy, we associate the fluid mechanics and the electromagnetics, establishing the numerical model of twin-wire indirect arc in three dimensions. The mathematic equations are solved in coupled electric field, magnetic field and flow field using ANSYS.At last, the distribution of temperature,arc voltage,current density and the velocity of arc plasma were obtained. The shape of free burning twin-wire indirect arc is similar to the flame in torch welding. It is the result of the movement of charged particles in the arc because of electromagnetic compression and flow compression. The including angleα, the distance from the meeting point to the basepiece H and the components of the shielding gas play important roles in the influence of the arc shapes. It is better when the angle a is 20～30°, the distance H is 8～10mm, and the shielding gas is 75% Ar+25%CO2.