METHOD FOR MANUFACTURING HOT-ROLLED SHEETS FROM CRYOGENIC STEEL (VARIANTS) Russian patent published in 2021 - IPC C21D8/02 B21B1/26 C22C38/54 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to manufacture of thick sheets from extra cold-resistant structural steels used for manufacturing equipment intended for storage and transportation of liquefied natural gas. The method for manufacturing hot-rolled sheets from cryogenic steel includes heating of continuously cast workpieces, rough rolling thereof, finishing rolling and cooling. The continuously cast workpieces are produced from steel containing, wt.%: C 0.03 to 0.10, Si no more than 0.45, Mn 0.20 to 0.80, Al 0.02 to 0.06, Cr no more than 0.20, Ni 6.5 to 11.0, Cu no more than 0.20, Nb no more than 0.020, Ti no more than 0.020, V no more than 0.02, Mo no more than 0.30, S no more than 0.005, P no more than 0.010, N no more than 0.010, B no more than 0.008, Sn no more than 0.015, Sb no more than 0.015, As up to 0.005, Ca up to 0.003 and/or REM up to 0.005, Fe and unavoidable impurities the rest. The continuously cast workpieces are heated to a temperature of 1,100 to 1,250°C, rough rolling thereof is executed at a temperature not lower than 950°C to a thickness of at least 2 thicknesses of the finished sheet with relative reduction per pass of at least 10%, finishing rolling begins at a temperature of the rolling product of 850 to 920°C and finished at a temperature of 760 to 830°C, subsequent accelerated cooling is executed, followed by heating the sheets to a temperature of 520 to 620°C and cooling in air to room temperature. In the second variant of implementation of the method, after rolling, the subsequent cooling from a temperature of 760 to 830°C is executed in air, then the sheets are heated to a temperature of 770 to 830°C and subjected to accelerated cooling, followed by heating the sheets to a temperature of 520 to 620°C and cooling in air to room temperature.

EFFECT: production of high-strength cryogenic steel with an improved complex of mechanical properties characterised by high values of impact strength in the temperature range down to minus 196°C with the maintained high strength characteristics is provided.

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