STEEL MATERIAL FOR MAIN PIPES, METHOD FOR ITS PRODUCTION AND METHOD FOR MANUFACTURING THE MAIN PIPE Russian patent published in 2021 - IPC C21D8/02 B21B3/00 B21C37/08 C22C38/58 

FIELD: oil and gas transportation; underwater pipelines.

SUBSTANCE: group of inventions relates to steel material for main pipes, a method for producing steel material for main pipes and a method for manufacturing main pipes; it can be used in the manufacture of main pipes used for the transportation of oil and natural gas, as well as for underwater pipelines. A method for producing a steel material in the form of a plate for main pipes having a thickness of 30 mm or more, a tensile strength of 570 MPa or more, a compressive strength of 440 MPa or more, includes: heating of steel containing, wt.%: C from 0.030 to 0.10, Si from 0.01 to 0.30, Mn from 1.0 to 2.0, Nb from 0.005 to 0.050, Ti from 0.005 to 0.025, Al 0.08 or less, one or more elements selected from: Cu 0.5 or less, Ni 1.0 or less, Cr 1.0 or less, Mo 0.5 or less, V 0.1 or less, Fe and unavoidable impurities - the rest, up to a temperature in the range of 1000 to 1200℃; hot rolling, wherein the final rolling temperature is the average temperature of the steel plate and is equal to the transformation temperature Ar3 or higher and 790℃ or lower; accelerated cooling from the transformation temperature Ar3 or higher to the cooling stop temperature; and reheating to ensure the surface temperature of the steel plate from 350 to 550℃ and the center temperature of the steel plate below 550℃.

EFFECT: steel material is obtained for main pipes having a wall thickness of 30 mm or more, high strength.

7 cl, 3 tbl, 26 ex