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Stirring things up on the London rail network

Connect, no. 136, May/June 2005, p.1

Inside the new friction stir welded London Underground carbody
Inside the new friction stir welded London Underground carbody

One of the world's most famous transport systems is to herald the latest application of a globally renowned TWI invention. Friction stir welding is being used to build replacement stock for London Underground.

No fewer than 376 friction stir welded vehicles have been ordered from the TWI Industrial Member Bombardier for the latest Victoria Line upgrade.

The process is being used to join stiff longitudinal extrusions which constitute the carbody's sidewalls. The welding is sub-contracted to Swedish supplier Sapa Profiler, who hold a TWI friction stir welding licence.

'Friction stir welding is likely to be used on future contracts for over 2200 more new trains in the next decade' Bombardier's welding engineer Mick Wood told Connect. 'This work stems from the successful introduction, some time ago, of friction stir welding on the lower bodyside panels of mainline trains. The technological and commercial advantages of the process were studied and deemed favourable by ourselves and London Underground.'

Bombardier first showed interest in friction stir welding 11 years ago. In those days the welding process showed enormous promise but little was known about its capability to join thick plate or materials other than aluminium.

Bombardier became a member of the very first TWI Group Sponsored Project on friction stir welding and has subscribed to several similar projects since then. After a three year process review by Bombardier, between 2001 and 2004, in which TWI played a major part, the manufacturer introduced friction stir welding onto its Electrostar range of vehicles for the UK market in October 2003.

It is now pursuing its research into friction stir welding through both internal and European projects such as ALJOIN which are geared towards improving the crashworthiness of today's rail vehicles throughout Europe.

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