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Friction Stir Welding

This is a welding process invented by TWI in 1991. The process involves a spinning tool, in contact with the material to be welded, with sufficient down force to create frictional heat in the material (about 80% of the material's melting point). This causes the material to become soft, allowing the spinning tool to create the weld.

Friction stir welding is now widely used in the aerospace, automotive, rail and ship building industries.

LowStir Friction Stir Welder

Unlike other friction stir welders, the LowStir friction stir welding system includes a unit that attaches to most standard milling machines via an ISO taper, making it an affordable option to smaller enterprises. It is supplied with software to calibrate the system, monitor the welding process and log welding parameters for later analysis. The product, developed following a European funded research project involving TWI, Applied Measurements Ltd, Fatronik, Sigmapi Systems Ltd and Suffolk Precision Ltd, is now manufactured and marketed by the LowStir Consortium (the latter four companies listed - see Who We Are).

Diagrammatic representation of a friction stir weld

LowStir unit in action

Benefits of friction stir welding include:

• Improved weld properties (e.g. strength, fatigue) compared to arc welding or riveting. Joint efficiencies of 75-96% have been reported depending on materials
• Because it is a solid phase process (where the materials are joined without melting), no shielding gases or filler materials are required. Furthermore, there is almost complete elimination of weld distortion and solidification defects.
• Operators do not need special qualifications or certification. There’s no arc welding, gas emissions or weld spatter involved.
• Vastly reduced preparation and reworking time reduces costs, time and labour requirements
• Low power consumption. The only energy required is to rotate the tool and apply force to it to create the frictional heat. Without the large current requirements of arc welding, energy consumption can be reduced by 80% plus.