METHOD FOR PRODUCTION OF LOW-ALLOY ROLLED PRODUCTS OF STRENGTH CATEGORY S390P Russian patent published in 2022 - IPC C21D8/02 C22C38/50 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to a method for the production of low-alloy rolled products of the strength category S390P. The method includes smelting in a steelmaking unit of low-alloy low-carbon steel, micro-alloying of the melt with titanium and aluminum, out-of-furnace treatment in a ladle, obtaining a continuously cast billet, austenization of the resulting billet, rough rolling to the thickness of the intermediate roll, its cooling, finishing rolling with a regulated temperature of the end of rolling and laminar cooling with water to the temperature of winding into a roll. A continuous cast billet is obtained from steel containing, wt. %: carbon 0.05-0.10, manganese 0.4-1.0, silicon 0.1-0.5, chromium 0.4-1.0, copper no more than 0.15, nickel no more than 0.25, aluminum no more than 0.10, vanadium 0.03-0.2, titanium 0.001-0.04, niobium 0.01-0.15, sulfur no more than 0.010, phosphorus no more than 0.015, nitrogen no more than 0.010, iron and unavoidable impurities the rest, and the titanium content is no more than 0.5 of the vanadium content, the total content of niobium, vanadium and titanium is no more than 0.25 wt. %, and the carbon equivalent of Ce does not exceed 0.36. Austenization of a continuously cast billet is carried out with an exposure at a given temperature of at least 4 hours. The subsequent rough rolling of the billet is carried out at a value of a single relative compression in the first pass of at least 30% and at least 20% in the last pass, and the thickness of the intermediate roll is set to be 3-5 of the thickness of the finished rolled product. Finishing rolling is carried out at a value of a single relative compression in the first pass of at least 20% and no more than 12% in the last pass, and the temperature of the end of finishing rolling is set depending on the thickness of the finished rolled product from the ratio Tfr = (920-k*h), °C, where h is the thickness of the finished rolled product, mm, k is an empirical coefficient ranging from 3 to 6. The laminar cooling rate of the finished rolled products on the discharge roller is 8-20°C/sec, and the strip is wound into a roll in the temperature range 450-520°C.

EFFECT: method ensures the production of rolled products with a fire resistance index of σ_t⁺⁶⁰⁰/σ_t⁺²⁰, amounting to at least 0.6, while maintaining the required level of strength and plastic characteristics.

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