Narrow gap welding processes

  • The single filler wires used most commonly have diameters in the range 3.2–4.8 mm; smaller wires are prone to cause random arc wander, particularly with the relatively long electrical stick-outs that are used, and larger diameter wires are more difficult to feed. welding processes

  • Although it is possible to use standard fluxes, special flux formulations with improved slag release characteristics have been devised for narrow-gap SAW.
  • The power used is DC electrode positive or AC; AC gives greater resistance to magnetic arc blow and square wave AC power supplies have also been used to improve control of the process.

narrow-gap-welding

Developments

Increased productivity and improved process control may be achieved by applying the techniques normally applied to conventional submerged arc welding to the narrow-gap process, i.e.:

  •  extended stick-out;
  •  twin wire;
  •  hot wire;
  •  metal powder addition;
  •  flux-cored consumables

These techniques are not widely used at present although some development work has been reported.

Applications

  • The standard NGSAW process has been in use in many commercial applications since the early 1980s.
  • Some of these are summarized in Table above; they range from nuclear reactor containment vessels in 600 mm thick Ni/Cr/Mo alloy steels to the welding of 60 mm material for offshore tubular.

See more information at Hong Ky welding machine

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