Power

TWI's advanced manufacturing techniques aimed at thermonuclear fusion experiment applications

Principal techniques

TWI has expertise in a wide range of joining techniques that have application in thermonuclear fusion experimental applications. These range from thick section welding techniques for installation fabrication to low heat input fusion processes for welding attachments during refurbishment or repair. In addition to the primary joining processes, TWI has wide experience of remote operation in cutting and welding along with associated offline programming, real time sensing, monitoring, seam tracking and post weld inspection techniques.

Laser welding

Advantages: Nd:YAG laser welding offers a remote, non-contact deep penetration process for in-situ repair and refurbishment of contaminated areas with restricted personnel access. The light is transmitted to the workpiece by flexible optical fibre which is then expanded, collimated and focused to a point locally by the processing head to give the intensity of light necessary to produce the welds. An example of robotic processing for a structural application at TWI with 4kW of laser power is shown in this video clip on tack welding. (File size: 4.68MB)
Facilities: CO ₂ (100W - 20 kW), Nd:YAG (30W - 10kW), excimer laser
Technologies/services: welding, procedure development, heat treatment, component and joint design, feasibility studies, prototype and small batch welding production.

Electron beam welding

Advantages: Although electron beam welding can be used at reduced pressure with local vacuum sealing for very deep penetration welding in situ, it is probably of greatest interest for primary fabrication. The process is capable of very deep penetration welding in a single pass, with low distortion and, due to being carried out in vacuum, no oxide contamination.
Facilities: 100kW EB facilities, 150m ³ vacuum chamber, five EB welding machines
Technologies/services: welding, procedure development, heat treatment, evaporation, reduced pressure EB welding, out of vacuum EB, demagnetisation, finite element analysis of electromagnetic and electrostatic fields, component and joint design, feasibility studies, prototype equipment design and manufacture, prototype and small batch welding production.

Arc welding

Advantages: TWI has experience of all arc welding processes that are used in fusion experiments. Arc welding offers a relatively low capital expenditure method of producing welded joints and although the processing time is slower than either electron beam or laser, for remote processing, productivity is still acceptable in relative terms. TWI has experience in developing procedures and designing equipment for remote operation in both fusion experiments and also within nuclear power generation and oil and gas industrial sectors.
Facilities: MIG, TIG, MMA, plasma, hot wire TIG, orbital TIG, flux cored, SAW (single and twin wire and narrow gap), robotic MIG & TIG, MicroTIG, keyhole plasma, novel processes (including A-TIG, microwave plasma and moving contact arc welding).
Technologies/services: process selection and procedures, procedure development, equipment development, consumables evaluation, weld monitoring, repair welding, manufacture of prototype fabrications, on-site consultancy and welding services.

Subsidiary techniques

Friction welding

Facilities: rotary, radial, orbital and linear friction welding, friction stir and friction plunge welding, friction hydropillar processing and friction extrusions, third body friction welding, friction taper stitch and seam welding, underwater friction stud welding and transformation hardening.
Technologies/services: welding, procedure development, component and joint design, feasibility studies, prototype and small batch welding production.

Brazing

Facilities: vacuum and inert gas furnaces at temperatures up to 1850°C
Technologies/services: reactive and diffusion brazing, joint design, interlayer design, materials section, joint design, training, troubleshooting

Diffusion bonding

Facilities: vacuum and inert gas vessels, radiant and induction heating, temperatures to 1850°C
Technologies/services: uniaxial pressing, hot isostatic pressing, interlayers

TWI has additional expertise in other aspects of materials joining technology. These include:

Robotic welding

Facilities: robotic welding cells including laser, arc and resistance welding
Technologies/services: Computer Integrated Manufacturing (CIM), robotic handling, portable robots, simulation and off-line programming, equipment specification and selection, pre-production trials, simulation, performance optimisation, integration

Manufacturing

Services: strategy development and analysis, facilities planning, simulation, process improvement, equipment selection, problem solving, design and manufacturing reviews, 'Just in Time' (JIT), lean and agile manufacturing, independent technology monitoring.

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