HIGH-STRENGTH STEEL MATERIAL AND METHOD OF ITS PRODUCTION Russian patent published in 2019 - IPC C22C38/04 C22C38/38 C22C38/58 C21D8/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to high-strength steel material used for production of oil and gas well pipes. Material has the following chemical composition, wt. %: C: from 0.30 to 1.0, Si: from 0.05 to 1.0, Mn: from 16.0 to 35.0, P: 0.030 or less, S: 0.030 or less, Al: from 0.003 to 0.06, N: 0.1 or less, V: from 0 to 3.0, Ti: from 0 to 1.5, Nb: from 0 to 1.5, Cr: from 0 to 5.0, Mo: from 0 to 3.0, Cu: from 0 to 1.0, Ni: from 0 to 1.0, B: from 0 to 0.02, Zr: from 0 to 0.5, Ta: from 0 to 0.5, Ca: from 0 up to 0.005, Mg: from 0 to 0.005, rest is Fe and impurities. Composition of the material satisfies the condition V + Ti + Nb > 2.0, wherein the numerical density of carbides/carbonitrides released in steel having an equivalent diameter of circle of 5–30 nm is 50–700/mcm², and the numerical density of carbides/carbonitrides released in steel having an equivalent diameter of a circle greater than 100 nm is less than 10/mcm².

EFFECT: material has stable guaranteed yield point YS value equal to 758 MPa or more, for which value of fracture viscosity K_ISSC in DCB test is 33,7 MPa×m^0,5 or more.

4 cl, 3 dwg, 3 tbl