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Plasma keyhole welding

Plasma keyhole welding is mainly found in stainless steel construction, tank, pipeline and chemical apparatus construction. The wall thicknesses to be joined are generally in the range between 3.0 mm and 10.0 mm. Typical applications here are I-butt welding of longitudinal and circular seams of "thick-walled" pipes, vessels and bottoms. For material thicknesses> 10mm, plasma welding is often used to weld the root.

How does plasma keyhole welding work?

In case of plasma keyhole welding a “keyhole” is formed at the beginning of the seam by very high plasma gas pressure, where the material in its total depth is melted. In that way, it is possible to weld high-alloy and unalloyed material up to 8 mm sheet thickness in one pass, by square butt joint. For filling up the keyhole and levelling up the root sag mostly a cold wire becomes necessary.

What are the advantages against other welding procedures?

Due to the technological conditions of plasma welding, there are a number of advantages against other welding procedures:

  • High productivity
  • Low energy input (= low distortion)
  • Lowest operating costs per meter of weld seam due to reduction of the side times and saving of additional material
  • No seam preparation up to 10mm
  • Single-layer welding up to 8mm

The low operating costs compared to the MAG, UP or TIG welding are mainly due to lower side times (chamfering) and the considerably lower addition of filler wire, since in the case of theplasma keyhole welding usually no chamfering of the sheets is necessary and the "filling volume" of the seam is very small . Typical wire feeding rates of 80-140 cm / min (wire strength 1.2 mm) are obtained at a welding speed of 20-40 cm / min.

How do I use the process in my production?

Several different manufacturing processes have become established in the production of containers, eg. The manufacturing in upright position, lying production on a reel stand, the welding on a bench or the seam welding. In the case of the application, there is no "royal road", so each method has its advantages and disadvantages.

The company MIG-O-MAT offers custom-made welding solutions with an intuitive control concept.
We would be pleased to advise you on the application and choice of the procedure for you.


  • Flexible, customer-oriented solutions for plasma welding
  • Intuitive control concept, industry 4.0 oriented system
  • Own production
  • Turnkey delivery

Production in vertical position

  • Easy observation of welding process in sight of the worker
  • No camera necessary
  • Good working economy
  • Formation of the root is very easy to realize

Production in horizontal position

  • Forming must be adapted to the production process
  • Welding via camera or lift platform
  • Welding process in PA position

Vertikal-Down with seamer

  • Easy prefabrication of the segments
  • Exact cold wire adjustement necessary
  • Easy handling of the segmentse

Welding of plane plates on a seamer

  • For the prefabrication of segments from standard form sheets or from the coil
  • Also as a height-adjustable version for welding round segments
  • High productivity and quality
  • Sheet feeding via tables and chain conveyors possible
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