Fabrication of pipe strings using friction stir welding

摘要

A method of fabricating a metal pipeline by friction stir welding (FSW) along a circumferential interface comprises spinning first and second FSW tools about respective axes of rotation in contact with a pipe wall to heat, plasticise and stir respective zones of plasticised metal at the interface. The zone of plasticised metal produced by the second FSW tool extends deeper into the pipe wall than the zone of plasticised metal produced by the first FSW tool. Relative circumferential movement of the FSW tools along the interface is controlled such that the second FSW tool following the first FSW tool enters the zone of plasticised metal produced by the first FSW tool while the metal in that zone remains plastic.