Manual keyhole plasma arc welding system

A manual key hole plasma arc welding system, comprising:

• (a) a power source for providing a sinewave alternating current;
• (b) a manual plasma arc welding torch assembly, including,
• (i) a shield cup having a terminal edge having a centrally disposed longitudinal axis,
• (ii) a orifice subassembly concentrically disposed within said shield cup, said orifice subassembly having a terminal end, a shield gas discharge annulus being formed between the terminal edge of the shield cup and the terminal end of the hollow orifice subassembly,
• (iii) an electrode, being connected to a first terminal of said power source, said electrode being concentrically disposed within said orifice subassembly, a plasma gas discharge annulus being formed between the terminal end of the hollow orifice subassembly and a terminus of said electrode,
• said terminal edge of the shield cup being extended beyond the terminal end of the orifice subassembly and so constructed to produce a laminar shield gas discharge flow through said discharge annulus providing cooling of the orifice subassembly;
• (c) a shield gas source in fluid communication with said shield gas discharge annulus, for providing a flow of an inert shield gas through said shield gas discharge annulus to said workpiece;
• (d) a plasma gas source in fluid communication with said plasma gas discharge annulus, for providing a flow of inert plasma gas through said plasma gas discharge annulus, said flow being substantially collimated;
• a second terminal of said power source being connected to the workpiece so as to provide a transferred arc between said electrode and said workpiece, the power density being sufficient to provide keyhole welding, the reversing sinewave polarities providing simultaneous keyhole penetration and cathodic cleaning eliminating the requirement of substantial workpiece surface preparation and/or removal of internal workpiece defects.