| A number of different plasma welding methods are used in the metal fabrication industry. Plasma welding is very similar to TIG welding. An arc is formed between a tungsten electrode and the workpiece.
However, the electrode is positioned within the torch body, which means that the electrical plasma arc can be separated from the shielding gas flow. As a result, the plasma is forced through a fine hole in the copper nozzle, which constricts the arc and leads to higher energy density in the arc.
There are three operating modes depending on the bore diameters and plasma gas flow rates.
Micro plasma operates between 0.1 and 15A. The arc is operated at very low welding currents, which gives the operator great versatility when welding very thin materials.
Medium plasma uses currents between 15 and 200A. This process is very similar to TIG welding, except the plasma is constricted, resulting in better penetration characteristics.
Keyhole plasma operates above 100A. A very powerful plasma can be produced by increasing plasma gas flow and welding current, thus enabling full penetration of the workpiece (similar to laser welding). The keyhole progressively cuts through the metal, with the molten weld pool flowing behind the hole and forming the weld bead. The keyhole process is used to weld thicker materials in one single pass (e.g. 10mm-thick stainless steel plates). |
