Plasma arc welding

From GAWDAwiki

Plasma arc welding is a welding process in which an arc is formed between a tungsten electrode and a work-piece, similar to TIG welding. However, in plasma arc welding, the entire electrode is housed within the torch, allowing the plasma arc and the shielding gas envelope to be separated. Plasma is forced through a fine-bored copper nozzle, constricting the arc.

Applications

Various bore diameters and plasma flows can create three different methods of plasma arc welding.

1. Microplasma welding can be used at very low welding currents (0.1 to 15A). The needle-like, columnar arc minimizes arc wander and distortion and remains stable at arc lengths as high as 20mm. This process is commonly used to weld wire and mesh sections, in addition to sheets as thin as 0.1mm.
2. Medium-current welding uses arcs that operate at currents from 15 to 200A. These plasma arcs are similar to their TIG counterparts, but since they are constricted, they are stiffer. Increased plasma flow rates can improve weld pool penetration, but excessive turbulence in the gas shield could lead to air and shielding gas entrainment.
3. Keyhole plasma welding uses arcs that operate at currents of 100A and greater. High welding currents and plasma gas flows create a powerful plasma beam capable of full penetration. Keyhole plasma welding can be used to weld up to 10mm of stainless steel in a single pass.

References

1. http://www.twi.co.uk/content/jk7.html