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TWI publishes ground breaking developments for friction stir welding of steel

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Stephen Cater, a researcher at TWI Technology Centre at the Advanced Manufacturing Park, Sheffield, has presented ground-breaking results on friction stir welding of steel at the recent 9th International Conference on Trends in Welding Research, Chicago, USA. Friction stir welding was initially invented by TWI for welding aluminium and has quickly become the process of choice for world-leading manufacturers such as Boeing, SpaceX, Hitachi, Mazda and Volvo for the fabrication of strong, stiff, lightweight aluminium structures.

Following its widespread acceptance by the aerospace, shipbuilding, train making and automotive industries for manufacturing aluminium structures, TWI is developing the process for application to steel. The work undertaken at TWI Technology Centre in Yorkshire has shown that welds in steel made by friction stir welding have considerably better mechanical properties than those made by conventional arc welding, for example significantly improved toughness and fatigue lives. The lack of melting and thus low heat input which are characteristic of the friction stir welding process also reduces distortion in the welded structures.

Results just published show that for 6mm thick, high strength shipbuilding steel, FSW reduces distortion along the length of a 2m welded plate from 115mm to 15mm while tripling weld toughness and increasing fatigue life compared to submerged arc welding. As up to 40% of the costs of building a ship are associated with correcting distortion of welded plates, this new technique has potential to introduce considerable cost savings during manufacture.

Process advantages:

Unlike conventional welding techniques, FSW does not melt the metal being welded and results in strong, defect-free welds without fear of health and safety concerns from any of molten metal, fumes or ultra-violet light. The process also offers cost savings when compared with conventional arc welding of aluminium.

Industry benefits:

  • Stronger welds than currently possible using existing techniques
  • Very low distortion, making significant savings on rework and post-weld straightening
  • Improved fatigue and toughness, leading to better in-service performance
  • Improved Health and Safety conditions in the welding environment.

For further information, please contact Stephen Cater, stephen.cater@twi.co.uk or see the Friction Stir Welding section of our website: http://www.twi.co.uk/technologies/welding-coating-and-material-processing/friction-stir-welding/

Photo caption: Friction stir welding presents new opportunities for steel processing

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