Procedural Principle Plasma Welding

Schematic diagram plasma welding
Procedural principle of plasma welding

With plasma welding the weld or main arc burns between tungsten electrode and workpiece, just like it does with TIG-short time welding.
While with the TIG-method the arc burns freely, with plasma welding it is narrowed by an additional water-cooled plasma nozzle. Between tungsten electrode and plasma nozzle a Information über Schutzgase zum SchweißenPlasmagas - mostly 100 % Argon - conducted. The narrowing effect of the plasma arc results from the cooling effect of the nozzle (thermal pinch effect), which amplifies the narrowing effect of the electro-magnetic pinch effect.

With plasma welding there is a pilot arc additionally burning between the tungsten electrode and the plasma nozzle. The rated current is mostly between 3 to 15 A. The plasmagas forces the pilot arc faintly out of the plasma nozzle so that here a bright point of light is visible. The pilot arc ionizes the arc path, which leads to a extraordinary high ignition liability which is characteristic for plasma welding.

The protection of the molten pool is effected by Information über Schutzgase zum Schweißeninert gas being led between the outer inert gas nozzle and the plasma nozzle. As inert gas pure Ar or Ar-rich gas mixtures with hydrogen or helium are used.

Compared to the other conventional arc welding processes the narrowed plasma arc has a much higher energy density and a lower beam divergence. While the diameter of the TIG-arc increases very much from electrode tip to workpiece, the diameter of the plasma arc increases only slightly.