ROTARY FRICTION WELDING

A method for welding together pieces which form a curved or angled end product using a friction welding process is described. The method comprises; providing first and second pieces which together define the end product geometry, each piece comprising an end product geometry portion and a sacrificial weld portion, the sacrificial weld portion forming a dog-leg relative to the end product geometry portion and terminating in a planar weld interface surface. The pieces are arranged with their planar weld interface surfaces together at a weld surface interface and the sacrificial weld portions in coaxial alignment. Mechanical friction is applied between the planar weld interface surfaces sufficient to plasticly deform the sacrificial weld portions. An axial force is applied along the co-axis of the sacrificial weld portions sufficient to upset the sacrificial weld portions and bring together the end product geometry portions. The sacrificial geometry portions are removed to provide the end product.