SHEET OF HIGH-STRENGTH STEEL HAVING EXCELLENT LOW-TEMPERATURE FRACTURE TOUGHNESS AND ELONGATION COEFFICIENT, AND THE METHOD FOR ITS MANUFACTURE Russian patent published in 2022 - IPC C22C38/58 C22C38/50 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to a sheet of high-strength steel with a thickness of less than 20 mm, having excellent low-temperature fracture toughness and elongation coefficient, used for the manufacture of pipelines. The sheet contains, wt. %: 0.05-0.1 carbon (C), 0.05-0.5 silicon (Si), 1.4-2.0 manganese (Mn), 0.01-0.05 aluminum (Al), 0.005-0.02 titanium (Ti), 0.002-0.01 nitrogen (N), 0.04–0.07 niobium (Nb), 0.05-0.3 chromium (Cr), 0.05-0.4 nickel (Ni), 0.02 or less phosphorus (P), 0.005 or less sulfur (S), 0.0005-0.004 calcium (Ca), if necessary 0.3 or less molybdenum (Mo), the rest is iron (Fe) and the inevitable impurities. The microstructure of the sheet contains from 20 to 60% of the area of ferrite, from 35 to 75% of the area of bainite and 4.5% or less of the area of the martensitic-austenitic component. More than 80% of grains with high-angle boundaries of 15° in the central part of the sheet, which is an area located from the surface at a distance from t/4 to 3t/4, where t is the thickness of the sheet, have a grain size of 70 microns or less. The sheet has a total elongation coefficient of 28% or more, a uniform elongation coefficient in the direction perpendicular to the rolling direction of 9% or more, and a percentage of viscous shear during the falling load test (DWTT) at -30 °C in the direction perpendicular to the rolling direction of 85% or more.

EFFECT: expansion of the range of solutions for pipeline engineering.

7 cl, 4 dwg, 4 tbl, 1 ex