The Plasma Arc Torch or welding head is the main component of a PTA equipment for powder hardfacing.
Within its inner parts, a transformation of the electric power into heat occurs, and this energy at high enthalpy content (plasma) is transferred to the powders and piece to be welded.The torch is an energy converter from an electric arc (Pilot Arc) to a plasmagenic gas (usually Argon).
A second arc is transferred to the
workplace, thus creating the fusion bath and the welded deposit.
The conversion efficiency of plasma torch is about 50% : the balance is dissipated as radiation energy (light) and sound.
Fig. 1 - Plasma Torch is an Energy Converter.
A plasma is a gas which is heated to an extremely high temperature and ionized so that it becomes
electrically conductive. Similar to GTAW (TIG), the plasma arc welding process uses this plasma to transfer an
electric arc to a workpiece. The metal to be welded is melted by the intense heat of the arc and fuses together.
In the plasma welding torch, a Tungsten electrode is located
within a copper anodic nozzle having a small constricting orifice at the tip. The pilot arc is initiated between the torch electrode and the nozzle tip. This arc is then transferred to the
metal to be welded.
By forcing the plasma gas and arc through a constricted orifice, the torch delivers a high concentration of heat to a
small area. With high performance welding equipment, the plasma process produces exceptionally high quality welds.
Plasma gases are normally argon. The torch also uses a
secondary gas, argon, which assists in shielding the molten weld deposit thus minimizing pollution of the deposit.
