A METHOD FOR FORMING AN ELECTRIC RESISTANCE WELDED STEEL PIPE

摘要

A method of forming a skelp into a rounded tubular form in the preparation of an electric resistance welded steel pipe. Different from conventional methods, the skelp is bent in the initial and intermediate forming stages within a limited region alone along the centerline thereof to have a U-shaped forming flower. Thereafter, the edge portions of the bent skelp are bent in the upstream fin pass rolls to have a curvature of at least 80% of the final curvature with simultaneous over bending in the boundary regions on both sides of the side portions of the rounded skelp. Finally, the rounded skelp is pressed down in the direction to decrease the vertical diameter to bulge out in the transverse direction with simultaneous unbending the over-bent portions into the final curvature.