METHOD FOR PRODUCING HIGH-STRENGTH STEEL SHEET Russian patent published in 2024 - IPC C21D8/02 C21D9/46 C22C38/22 C22C38/24 C22C38/26 C22C38/28 C22C38/32 

FIELD: metallurgy.

SUBSTANCE: invention relates to a method for producing high-strength steel sheets and can be used for the manufacture of critical elements of agricultural earth-moving equipment. A method for producing a high-strength steel sheet with a tensile yield strength of at least 1200 MPa, a tensile strength of at least 1560 MPa and an elongation of at least 22% from steel containing, wt.%: carbon 0.30-0.46, silicon 1.50-2.0, manganese 1.00-1.40, chromium 0.80-1.20, molybdenum 0.20-0.50, if necessary, at least one component: niobium up to 0.10, vanadium up to 0.20, titanium up to 0.04 and boron up to 0.005, iron and inevitable impurities - the rest, characterized by the fact that the steel billet is heated to a temperature of 1100-1080°C and kept at this temperature for at least 1 hour for homogenization. Rolling is carried out from a temperature of 1100-1050°C to a temperature of at least 900°C with a compression ratio of 60% and subsequent cooling in air, then reheated to a temperature of A_C3+(30-50)°C, but not lower than 900°C, until complete austenitization, cooled to the quenching temperature in molten salt, preheated to a temperature of 30-50°C below the temperature of the onset of martensitic transformation Ms, with a cooling rate of 210-250°C per second in the range 900-300°C for 30-180 seconds, ensuring that at least 60% retained austenite is obtained in the structure. Then the sheet is heated in molten salt to a temperature that is higher than the temperature of the onset of martensitic transformation Ms and is 350-410° C, carbon is distributed between martensite and retained austenite for 60-300 seconds to prevent the formation of bainite in an amount of more than 15%, followed by the subsequent cooling of the sheet in air for self-tempering.

EFFECT: obtaining steel sheet with high strength and ductility.

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