Evolving arc welding processes and control technologies for nuclear repair

TWI is currently carrying out research and development into application of processes which have the potential of offering a number of benefits for more effective remote automated repair. Examples of these are:

A-TIG

The principle of the technique is that by applying a thin coating of the flux to the surface of the material, the arc is constricted which increases the current density at the anode root and the arc force acting on the weld pool. Arc constriction significantly increases weld pool penetration producing a deep narrower weld compared with a wide, shallow weld bead with the conventional TIG process. This has potential advantages for remote repair operations in that it provides a one-shot welding solution with existing and proven welding technology.

Conventional TIG weld

Conventional TIG weld
Increased penetration A-TIG weld

Increased penetration A-TIG weld
Fully penetrating orbital A-TIG weld

Fully penetrating orbital A-TIG weld

Plasma powder arc welding

Plasma powder arc welding

Plasma powder arc welding

Plasma powder arc welding offers a number of advantages over existing arc welding technologies:

  • Powder filler providing simple remote fill capability in either keyhole or melt mode and good torch movement
  • Compact welding torch giving improved torch accessibility
  • Higher welding speeds and lower distortion claimed compared to TIG
  • Suitable for robot welding
  • Will cope with variable arc lengths
  • No HF interference

Arc welding in-process control

Top face penetration control

There are a number of options for in-process control and TWI has recently carried out work investigated both top face monitoring and through-arc welding process control. The top face monitoring system developed at TWI views the weld pool from the arc side using infra red or CCD cameras and provides adaptive control to maintain weld penetration for thickness or cast to cast variation and will also act as a seam tracking device. Weld print will monitor weld parameters and provide information on weld bead shape and position. Although this system currently only warns when quality limits are being exceeded, it also has the potential for adaptive control. Development of both of these systems will have benefits for implementation of remote automated repair techniques.


For further information, please contact us at: power@twi.co.uk

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