Abstract: A method and apparatus for manufacturing metal pipe. The edges of a metal plate are bent up slightly, and the thus bent plate is then bent into a U-shape cross-section blank. The U-shape blank is finish-formed into an O-shaped blank with the longitudinal edges opposed to each other in a position for welding by placing one end of the U-shaped blank into at least one two-part die the parts of which are movable toward and away from each other.

Abstract: In a method and an apparatus for manufacturing a metal pipe wherein a flat strip or skelp is formed into a cylindrical pipe while being fed in its longitudinal direction by a forming mill having a prefinishing stand, a train of forming stands for forming the skelp with a U-shaped cross section, and a train of finishing stands, the improvement wherein both edge surfaces of the skelp are caused to contact in substantially point contact recess-defining surfaces of concave V-shaped recess in pairs of forming rolls, the respective rolls which are disposed symmetrically in a plane normal to the pass line as the skelp moves through the train of forming stands along the line, and the skelp has a bending load applied by the forming rolls so as to form the skelp into a U-shaped skelp.