PIPE WITH HIGH DEFORMATION CAPACITY AND HIGH VISCOSITY OF WELDING JOINT AND METHOD OF ITS MANUFACTURE Russian patent published in 2018 - IPC C21D8/10 C22C38/00 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to the production of electrically welded, longitudinal-welded pipes of large diameter. To provide increased deformability and high viscosity of the welded joint of pipes intended for the transportation of natural gas, a pipe with a wall thickness of 15–40 mm is obtained from a steel sheet having a yield strength of more than 480 MPa, containing, % by weight: carbon — 0.04–0.08, silicon — 0.10–0.30, manganese — 1.60–1.85, chromium — no more than 0.30, nickel — 0.20–0.40, molybdenum — 0.10–0.25, copper — no more than 0.30, aluminum — no more than 0.05, niobium — 0.03–0.06, titanium — 0.010–0.020, vanadium — no more than 0.01, sulfur — no more than 0.003, phosphorus — not more than 0.013, the rest — iron and unavoidable impurities, by forming a steel sheet into a pipe billet, submerged multiarc welding of the longitudinal edges of the pipe billet from the inner and outer surfaces and expansion.

EFFECT: welding is carried out according to the regimes providing formation of a microstructure in the heat affected zone consisting of at least 60% of finely divided lower and rack bainite.

2 cl, 3 tbl