METHOD FOR PRODUCTION OF WELDED LONGITUDINAL PIPES OF LARGE DIAMETER FOR MAIN PIPELINES Russian patent published in 2018 - IPC B21C37/06 

FIELD: technological processes.

SUBSTANCE: invention relates to the field of production of steel welded longitudinal pipes for main pipelines. Method includes welding the process strips to the initial workpiece, processing its longitudinal edges, bending the longitudinal edges of the workpiece, forming the tube blank, assembly of the workpiece and welding of its edges with technological, internal and external seams, expansion and hydrotest of the pipe. Increasing the stability of the geometric parameters of the pipe billet, reducing the amount of edge displacement, ovality, the size of the gap between the edges is ensured by the fact that forming of the pipe blank is performed by means of a multi-transverse bending by a single-radius punch in two stages: in the first molding step, the deformation is carried out along the inner surface of the blank in the direction from the longitudinal edges to the axis of the preform, the rim portions being formed with a curvature exceeding the curvature of the finished pipe by 1–5 % side portions of the preform are formed with curvature, less than the curvature of the finished pipe by 1–3 %, the central portion of the preform is formed with a curvature equal to the curvature of the finished pipe, in the second molding step, the workpiece is deformed along its outer surface in the edge areas, while for positioning the tubular blank relative to the vertical plane of the deformation tool, it is alternately rotated about its axis in a counterclockwise direction and deformed after each rotation by moving the deformation tool vertically downward, angles of rotation for each step of deformation and the magnitude of the tool stroke for each of the ends of the pipe blank are regulated by mathematical dependencies.

EFFECT: method for the production of welded, straight-through large diameter pipes for main pipelines is proposed.

1 cl, 2 dwg, 5 tbl