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

FIELD: metallurgy.

SUBSTANCE: group of inventions relates to metallurgy, namely to cold-rolled and heat-treated steel sheet and method of its production. Cold-rolled and heat-treated steel sheet obtained from steel has composition, wt.%: C: 0.03 – 0.25; Mn: 3.5–8; Si: 0.5–2.0; 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 one or more following elements, wt%: Mo: 0.1–0.5, Cr: 0.01–1, B: 0.0005–0.004, balance – iron and unavoidable impurities. Microstructure of sheet consists of, in parts of surface: from 10 to 30 % of residual austenite, wherein said residual austenite is present in form of films, characterized by aspect ratio of at least 3, and in form of martensite-austenitic islands, wherein less than 8 % of such martensite-austenite islands have a size of more than 0.5 mcm, not more than 1 % of fresh martensite, not more than 50 % of tempered martensite and reduced martensite, comprising extraction of at least one element selected from niobium, titanium and vanadium, characterized by improved tensile yield strength and tensile strength.

EFFECT: sheets are characterized by high plasticity and deformability.

17 cl, 4 tbl, 6 ex