Plasma WeldingPlasma welding uses the heat and pressure generated by a constricted electric arc to fuse the joint area and produce a keyhole or melting. It is similar to TIG welding but with plasma welding the arc is formed between the tip of the non-consumable electrode and either the workpiece or the constricting nozzle. The process may be operated with or without filler and a wide range of plasma gases and shielding gases are used. The process may be operated in one of two basic modes, namely 'transferred arc' in which the arc is maintained between the electrode and the workpiece or 'non-transferred arc', in which it is maintained between the electrode and a constricting orifice. It may also be used to 'melt-in', as with TIG, or 'keyhole' giving greater penetration. The features of the process are excellent arc stability, high welding speeds and excellent fusion and penetration characteristics. It can be used for a wide range of ferrous and non-ferrous alloys. Plasma gases are usually argon or helium, as are shielding gases, although these may contain small additions of hydrogen. Welding fume is generally low.
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