METHOD FOR PRODUCING STEEL PIPE Russian patent published in 2017 - IPC B21D39/20 B21D5/01 

FIELD: machine engineering.

SUBSTANCE: steel sheet is formed into a cylindrical shape by press bending. Pressing of the steel sheet is performed by the punch providing the edge location in the transverse direction of the steel sheet opposite to each other. Then docking and welding of the opposed edges in the transverse direction of the steel sheet, are performed . Thereafter expansion of the steel pipe is performed from the inside by the expanding device. Herewith the expansion ratio of the R pipe, which is the ratio of the outer peripheral surface curvature radius of each dispensing element to the predetermined radius of the inner steel pipe surface, and the punch ratio R being the ratio of the outer curvature peripheral surface radius of the front punch end to the predetermined radius of the inner steel pipe surface, are less than 1, and they satisfy the relation: the expansion ratio of the R pipe ≥ -0.3 × the punch ratio R+1.18.

EFFECT: ensuring the possibily of manufacturing a steel tube with high roundness without the cracking risk of the distributing elements.

2 cl, 7 dwg