A novel arc plasma generating method by coaxial hybrid a ring arc to constraint arc: Principle and progress

Controlling of arc pressure in an arcing system is a critical and basic issue for welding application. A novel arcing torch is proposed to improve the controllability, a ring tungsten cathode is coaxial embedded into the water-cooling copper plasma arc nozzle. In the arcing process, the arc current flows into a single arc after it heats the anode and breaks into two branches to earth into the two separated cathodes: the center path works as the ordinary plasma arc and flows into the inner tungsten, the outer bypass free arc surrounds the center arc and flows into the ring tungsten. In this way, a coaxial hybrid arc forms based on a high-density plasma arc and a less-density ring free arc. Serial experiments were done to observe and measure the arc properties, including the arc column shape, arc pressure and anode state. It is observed that the outer arc can be fully absorbed into the inner arc to form a stable single hybrid arc. The hybrid arc properties are related to the two paths of arc current; the outer ring arc current has smaller pressure/current ratio than the central constraint plasma arc current. With such a version torch model, the employing current level of the ring arc is limited and lower than 40A to obtain stable hybrid arc. The results show the proposed arcing torch model is promising to control the output arc pressure with increased accuracy.