COLD-ROLLED AND ANNEALED STEEL SHEET AND METHOD OF ITS PRODUCTION Russian patent published in 2020 - IPC C21D1/25 C21D1/26 C21D8/04 C21D9/48 C22C38/14 

FIELD: metallurgy.

SUBSTANCE: group of inventions relates to metallurgy, particularly to cold-rolled and heat-treated steel sheet and method of its production. Cold-rolled and heat-treated steel sheet of steel, characterized by composition, wt.%: C: 0.03–0.25; Mn: 3.5–8; Si: 0.1–2.0; Al: 0.03–2.0; Ti < 0.080; Nb ≤ 0.080; V < 0.2; V + Ti + Nb > 0.01; S < 0.010; P < 0.020; N < 0.008 and optionally containing one or more of following elements: Mo: 0.1–0.5, Cr: 0.01–1, B: 0.0005–0.004, balance – iron and unavoidable impurities. Sheet has a microstructure consisting of, in parts of surface: from 10 % to 30 % residual austenite, wherein said residual austenite is present in form of films having an aspect ratio of at least 3, and in form of martensite-austenite islands, wherein less than 8 % of such martensite-austenite islands have a size of more than 0.5 mcm, not more than 10 % of fresh martensite and reduced martensite, which includes release of at least one element from among niobium, titanium and vanadium.

EFFECT: higher yield point and ultimate tensile strength; sheet is also characterized by high plasticity and good deformability.

17 cl, 4 tbl, 17 ex