METHOD FOR PRODUCING HIGH-STRENGTH STEEL SHEET Russian patent published in 2024 - IPC C21D8/02 C21D9/46 C22C38/18 C22C38/22 

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 from it. The method for producing high-strength steel sheet includes thermomechanical treatment, which produces a steel billet comprising, 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, aluminium up to 0.02, iron and inevitable impurities the rest, which 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 compression of at least 60% and subsequent cooling in air. Then the sheet is reheated to temperature A_C3 + (30-50)°C, but not lower than 900°C, until complete austenitization. Cooling to the quenching temperature is done in molten salt preheated to a temperature of 30-50°C below the temperature of the onset of martensitic transformation Ms, at a cooling rate of 210-250°C per second in the temperature range 900-300°C for 200-500 seconds, ensuring that at least 60% retained austenite is obtained in the structure. The sheet is heated in molten salt to a temperature of 350-410°C and carbon is distributed between martensite and retained austenite for 500-2000 seconds, ensuring the formation of bainite in the structure, and then final cooling in air is done.

EFFECT: high strength and ductility in the steel sheet.

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