METHOD FOR PRODUCING A HIGH-STRENGTH STEEL SHEET, HAVING IMPROVED FORMABILITY AND DUCTILITY, AND OBTAINED SHEET Russian patent published in 2019 - IPC C21D9/46 C21D8/02 C21D6/04 C22C38/02 C22C38/04 C22C38/06 C23C2/02 

FIELD: metallurgy.

SUBSTANCE: method for producing a high-strength sheet with improved formability and ductility, the chemical composition of the steel which contains, in percent by weight: 0.25<C≤0.4; 2.3≤Mn≤3.5; 2.3≤Si≤3; Al≤0.040, rest are Fe and unavoidable impurities. Method includes the steps of hot rolling a sheet, annealing a rolled sheet in a chamber furnace, cold rolling the hot rolled and annealed sheet, annealing the cold rolled sheet with an annealing time higher than the steel transformation temperature Ac₃, quenching with cooling to quenching temperature QT from Ms – 65 °C to Ms – 115 °C to obtain a final structure containing at least 65 % of martensite and at least 15 % of residual austenite, with the sum of ferrite and bainite less than 10 %, while Ms is the transformation temperature of steel Ms in accordance with the Andrews formula, heating the sheet to the overageing temperature PT 360 °C–500 °C with exposure at the specified temperature and cooling the sheet to room temperature. Before cooling, hot coating can be carried out on the steel sheet at 450 °C–490 °C.

EFFECT: resulting sheet has improved ductility and formability, in particular, has a yield strength above 1050 MPa, a uniform elongation of at least 10 % and is suitable for the production of different equipment, such as automobile parts, trailers, trucks.

18 cl, 2 tbl