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Small joints make a big difference

Connect, no. 143, July - August 2006, p.1

Micro friction stir welding in action
Micro friction stir welding in action

TWI has developed a technique that enables ultra-thin aluminium alloy sheet to be joined by a process that uses neither glue nor welding filler wire.

This new technique, called micro-friction stir welding (µFSW), has achieved perfect and permanent lap-welded and spot-welded joints in less than 0.3mm material thickness and butt welds in little more than 0.5mm thickness. Welding speeds have been in the range of 100 - 500mm/min.

The process applies pressure to the joint through a rotating tool. Friction causes the temperature to rise, enabling the metal sheets to become soft enough to be stirred together. TWI is the inventor and owner of the technology.

Dr Nee Joo Teh, the project leader, said: 'The process uses no glues, chemicals or welding fillers, fluxes or wires and a minimum amount of energy'. 'Environmentally, this process is a major breakthrough', he added.

A micro friction stir butt weld in 0.5mm aluminium alloy
A micro friction stir butt weld in 0.5mm aluminium alloy

Potential applications include sealing packages within the electronics and photonics industry and welding aluminium foil for use in the aerospace industry. Applications also exist in other industries, including medical devices, consumer goods and food packaging.

These welds, some of the smallest of their kind in the world, were achieved using equipment that was specially designed and adapted at TWI.

'We are now at the stage of finding the limits for the process and seeing how small our welds can be', said Dr Teh. 'We already see many exciting commercial applications for this technology.'

Since its invention in the early 1990s Friction Stir Welding (FSW) has come to prominence in many industrial sectors. It is revolutionising the way aeroplanes, ships and trains are built and is proving to be useful in the construction industry. It is a versatile technology capable of joining most grades of aluminium alloys as well as other materials such as copper, steel and titanium.

For more information please see Joining Technologies or please contact us.

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