(57) The invention provides an improvement in the 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 in 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
overbending 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 overbent portions into the final curvature.
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