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Need
Status: Need is Closed

Control of Weld Start/Stops in Pulsed Gas Metal Arc Welding

Request Number

NG_2017_0006_N_021
Point of Contact
Need was closed on
Nov 5
Description

Subsea 7 invites proposals or technologies from organisations and experts to improve the quality of weld start/stops in Pulsed Gas Metal Arc Welding (PGMAW).

The proposed welding technology (or augmented secondary source) would be able to improve the control of arc stability and weld geometry, thereby reducing the risk of weld flaws at weld starts and stops.

Background

Currently, Pulsed Gas Metal Arc Welding (PGMAW) is utilised to weld pipes together in a multi-pass process. Initiation of the weld starts at the top of the pipe but because of the synergistic nature of the PGMAW, the arc initiation and the filler metal addition cannot be controlled separately. Therefore, following arc initiation, a weld pool is formed prior to the weld torch traversing round the pipe circumference and subsequently a crater is formed as the arc is terminated at the end of the weld pass at the bottom of the pipe. These start/stops require mechanical grinding to a smooth and tapered geometry to enable subsequent weld passes to form the final welded structure. Typically welding is performed using discrete passes of weld metal of about 3mm in height.

The following characteristics should be considered in the final technology offering:

  • Elimination of grinding
  • Suitable for fully automatic deployment
  • Required equipment should be compact and non-intrusive as far as is practical
  • Should not increase welding time

 

Key success Criteria
  • Suitable for carbon steel, clad and Corrosion Resistant Alloy (CRA) metallic materials in wall thicknesses 6-45mm and diameters 150-500mm
  • Minimal susceptibility to weld flaws in start/stop locations
  • Elimination of mechanical grinding
Possible Approaches
  • Augmented secondary heat source
    • Laser
    • Tungsten or plasma arc
  • Synchronised wire feeding
Approaches not of Interest
  • Welding processes other than GMAW/PGMAW
Due Date
Oct 30
Gallery Moderator(s)
Oliver Worsfold
Request Number
NG_2017_0006_N_021
Area of Interest