Reduction of Spatter Generation in High Speed Pulsed MAG Welding

Abstract

If an arc length in high speed pulsed MAG welding is too long, undercuts and/or humping are generated and if it is too short, spatters are generated. As for the contradictory problem above, by refining the droplets from a wire and maintaining one droplet transfer per pulse at the same time, the short-circuiting in a short arc could be avoided and then, the prevention of spatters and high speed & high efficient welding became compatible with each other. As the basic means to refine droplets, the increase of two factors such as an electromagnetic pinch force to be applied to droplets and deformability of droplets with the same degree of an electromagnetic pinch force was examined. As the result of setting the simple rectangular wave pulse of high peak current in a short time using an inverter type pulsed power source under the constant diameter of a wire in order to increase an electromagnetic pinch force, one droplet transfer per pulse became possible upon condition that the volume of droplets decreases by about 30% than that in case of using the conventional power source with the secondary side chopping transistor. Furthermore, for the sake of increasing the deformability of droplets, the chemical compositions of the wire possible to transfer one droplet per pulse on condition that the volume of droplets decreases by 20% were found among those of various prototype-wires. Moreover, the droplets above showed the same surface tension as that of the conventional droplets and lower coefficient of viscosity. By the combination of pulsed current wave form and the improvement of wire physical properties, it is possible to decrease the volume of droplets to about a half of that of the conventional droplets. As the results, the increase of welding speed limit by more than 20% for no generation of both spatters and weld defects was shown and the achievement above was immediately applied to the actual mass-production line.