COLD-ROLLED AND HEAT-TREATED STEEL SHEET AND METHOD FOR ITS MANUFACTURING Russian patent published in 2023 - IPC C21D8/02 C22C38/02 C22C38/04 C22C38/06 C22C38/12 C22C38/14 

FIELD: metallurgy.

SUBSTANCE: invention is related to cold-rolled and heat-treated steel sheet used in the automotive industry. The sheet is made of steel having the following composition, in wt.%: С: 0.12-0.25, Mn: 3.0-8.0, Si: 0.70-1.50, Al: 0.3-1.2 V: 0.0002-0.004, S ≤ 0.010, P ≤ 0.020, N ≤ 0.008, optionally one or more elements selected from: Mo ≤ 0,5, V ≤ 0,2, Nb ≤ 0,06 и Ti ≤ 0,05, the rest is iron and inevitable impurities resulting from smelting. The sheet has a microstructure with surface consisting of the following fractions: 5-45% ferrite, 25-85% redistribution martensite having a carbide density strictly less than 2×10⁶/mm², 10-30% residual austenite and less than 8% fresh martensite. Part of said fresh martensite is combined with residual austenite in form of martensitic-austenite (MA) islands with a total surface fraction of less than 10%.

EFFECT: enables obtaining sheets with the required mechanical characteristics.

11 cl, 5 tbl