MATRIX AND METHOD OF MAKING STEEL PIPE Russian patent published in 2020 - IPC B21D5/01 

FIELD: metal forming.

SUBSTANCE: group of inventions relates to metal forming and can be used for production of steel welded pipes of flexible sheet. Preform of a U-shaped section is formed by bending sheet material, an open pipe is formed with a gap for welding and form a pipe by connection of a gap section for welding. Workpiece of preliminary shape during pressure processing takes shape, central angles in which within appropriate arcs, having diameter equal to or substantially equal to outer diameter of steel pipe, are 70 degrees or more and 150 degrees or less, and the sum of the central angles within the arcs having the diameter equal to or substantially equal to the outer diameter of the steel pipe is less than 360 degrees. At that, pressure treatment is performed by means of a pair of semi-female dies having arc-shaped sections with radii of 0.96–1.04 of external radius of steel pipe.

EFFECT: upgraded quality of welded pipes.

7 cl, 10 tbl, 17 dwg