Research on properties of arcs interaction for plasma-MIG hybrid arc welding process

The coupling of plasma arc and MIG arc makes plasma-MIG hybrid arc welding to be a unique method with the merits such as high deposition rate, good arc stability and high weld quality. In the paper, a plasma-MIG hybrid arc welding system is developed. On the basis of the system, the effects of the compression extent as well as the current density of outer plasma arc on the droplet transfer modes and droplet size are studied, and furthermore, the features of droplet transfer with the use of filler metals with various electrical resistivity and melting heat are described. The results show that an increase in droplet size and decrease in droplet transfer frequency occur by introducing plasma arc, but the droplet size and droplet transfer frequency hardly change by further increasing the plasma arc current. An increase in the compression extent of outer plasma arc can promote droplet transfer, and also result in the changes in droplet transfer modes. Filler metals with low electrical resistivity and melting heat are heated mainly by the plasma arc, and in contrast, resistive heat from MIG arc is the unique heat source for filler metals with electrical resistivity and melting heat higher than the thresholds, and heat saturation also happens in this situation. The coupling mechanism and its welding characteristic will not only enrich theories of hybrid arc leaded high efficiency welding technology, but also promote its development.