It’s a pity that the majority of potential users of the many keyhole TIG systems on the market are completely unaware of their major drawbacks compared to a real plasma keyhole welding setup.
They are seduced by the slick marketing and very impressive claims of weldable thicknesses at very high speeds but don’t know that these systems are not at all suited for real industrial applications. A real industrial application is when typical part tolerances and fit-up are encountered on a daily basis… the keyhole TIG systems just can’t cope with this.
Why? The keyhole produced has a very large volume compared to a real plasma keyhole system which uses a much higher arc concentration due to the plasma arc being constricted mechanically using a small diameter orifice, part of the plasma nozzle design. The keyhole Tig systems can only produce a keyhole by using g a very high arc concentration… this keyhole is then more sensitive to gravity and hence much less tolerant of gaps… The weld bead produced by keyhole TIG is always at the limit if producing undercut on the surface as no wire is usually utilized…if a wire is used then additional problems arise… added weight of the pool due to the wire, higher chance of collapse due to gravity… as well as disturbance of the keyhole due to the wire.
Finally, what’s better: to produce excellent x ray quality welds in stainless steel 10mm thickness using a plasma current of 210A at 20 cm/minute day in, day out in industrial situations or to have the promise of 2 x higher speed at more than 500A to 700A but using a process that’s just not practical industrially.
I have been involved in several cases where Keyhole TIG has been chosen over a real plasma keyhole system and has proved to be unworkable outside of a lab and where the customer has fitted a system such as that designed and developed, and used for over 40 years successfully in industries worldwide, by SAF (La Soudure Autogene Francaise), which became Air Liquide Welding which became Lincoln Electric….
For assistance in making the right choice in such applications- the full penetration welding of stainless steel tanks and vessels please feel free to message me… benefit from my experience…