METHOD FOR MANUFACTURE OF WELDED TUBES WITH LONGITUDINAL SEAM Russian patent published in 1995 - IPC

FIELD: plastic working of metals. SUBSTANCE: method involves feeding strips for forming; conducting multiple-pass forming of uniform radius trough-shaped strips in gages oriented along axis of forming and simultaneously applying transverse compressive forces to strip edge end surface: in m-th roughing pass at the side adjacent to convex edge of basic billet, and in mSSS-th roughing pass at the side adjacent to concave edge of basic billet, with strip being moved in tangential direction: in m-th roughing pass towards concave edge of basic billet and in mSSS-th roughing pass towards convex edge of basic billet till symmetrically arranged cross-section of billet relative to axis of forming is obtained; welding strip edges along longitudinal seam. Transverse compressive force is applied in m-1 -th roughing pass to strip edge at the side adjacent to convex edge of basic billet, with strip being moved tangentially relative to its cross-section curvature center till strip edge adjacent to convex edge of basic billet is arranged in position defined by dependence recited in Specification. EFFECT: improved quality of welded tubes with longitudinal seam by preventing strip edges from loosing local local loss of stability of stability to provide parallelism of edge ends in the process of welding seams. 2 dwg