PAW – Plasma Arc Welding plasma welding (compressed arc welding) or PTAW – Plasma Transferred-Arc Welding plasma welding with a direct action arc. Plasma welding is welding using a directed flow of a plasma arc.
PAW plasma welding
Also, the abbreviations of plasma welding can be supplemented with designations identical to TIG welding:
- PAW-CW Cold Wire plasma welding with neutral (cold) filler wire
- PAW-HW Hot Wire plasma welding with the supply of electrically conductive (heated) filler wire
- PAW-DC Direct Current Plasma DC Welding
- PAW-AC Alternating Current Plasma AC Welding
Plasma Welding Technology
Methods of using the flow of ionized plasma as an energy source during welding began to be introduced in the 50s of the last century, but only recently have they found their wide application. The process is based on the ionization of the plasma gas using an electric arc and its focusing using a special design of the tip of the plasma torch. This focus allows for a more intense, concentrated flow of energy in the welding zone.
There are designs with a direct and indirect arc. Straight arc plasma welding predominates in metal welding and can be generally characterized as an advanced TIG welding technique. The plasma gas is ionized in the plasma torch and creates a stable discharge in the working area even at low energy. Due to this, plasma welding, for example, can be used for microobjects. For thicknesses up to 3 mm. plasma welding and TIG welding are comparable. But for larger thicknesses, due to the greater energy density in the arc, plasma welding allows for deeper penetration and greater welding speed, and the residual deformation (warping) of parts is less compared to TIG welding.
In plasma welding, gases are used for 3 different purposes:
- Plasma gas. This is the carrier that forms the plasma flow between the electrode and the working area of welding. Argon or argon-hydrogen welding mixtures are often used as a plasma gas for stainless steels, and argon and helium mixtures for non-ferrous metals.
- Shielding gas. A separate insulating medium is required to protect the welding pool and the seam area. The shielding gas is supplied through a separate (external) nozzle of the welding torch and borders the plasma gas flow as a protective shell. Depending on the type of gas used, the energy density in the arc can even be increased by means of a protective shell. Usually, the same gas is used both as a protective and as a plasma gas.
- Secondary shielding gas. Separately, the protective gas is fed into the zone of the root of the seam from the reverse side of the parts, if the heating zone on the reverse side must also be protected. As a secondary gas, high-purity argon or special welding mixtures are used. To ensure the supply of gas from one cylinder both to the welding torch and to protect the root of the seam, it is recommended to use special gearboxes with a T-connector and two flowmeters.
