METHOD FOR PRODUCTION OF SEAMLESS PIPES OF LARGE DIAMETER FROM STRUCTURAL STEELS Russian patent published in 2020 - IPC B21B21/00 

FIELD: technological processes.

SUBSTANCE: invention relates to pipe rolling. In the casting centrifugal machine, a large-sized thick-wall hollow billet is obtained, the ratio of the outer diameter to the wall thickness of which is 4.0–10, with a dense structure caused by directed crystallization of the metal. After removal of the workpiece, the billet is put into a thermos flask for slow cooling. Surface of workpiece is cleaned and directed for forging by hydraulic press with four-hammer forging device with subsequent drawing and calibration. Extending on mandrel with conical surface geometry, with uniform value of reduction at temperature of 1,180–1,200 °C. Said rod is calibrated without mandrel at 850–900 °C with 180° turn for uniform heating with successive pressing of the press with billet feeding 0.6–0.8 of the striker width along the drawing axis till forging end at temperature not higher than 800 °C with drawing coefficients of μ₁=1.8 and μ₂=1.4.

EFFECT: higher quality of pipe metal due to provision of dense structure without gas-shrinking and liquation defects.

1 cl, 2 tbl