METHOD FOR PRODUCING WELDED STEEL PIPE Russian patent published in 2017 - IPC B21D5/01 B21C37/08 

FIELD: technological processes.

SUBSTANCE: pipe is produced by the method of press bending by means of three-point bending of a thick steel sheet by means of two matrix elements and a punch capable of moving entering the space between the two matrix elements, forming the open pipe. Further opposite edges of the steel pipe are welded to produce a welded steel pipe. First, the first sheet half is pressed from one edge to the sheet center in the sheet width direction, in which the central portion is left unpressed. Then, the second sheet half is pressed from the opposite sheet edge to the sheet center in the sheet width direction, in which the central portion is left unpressed. Then final press moulding is carried out at central portion of the steel sheet.

EFFECT: small offset value is provided of the steel pipe opposing welded edges.

2 cl, 8 dwg, 4 tbl, 4 ex