METHOD FOR PRODUCTION OF CRYOGENIC STRUCTURAL STEEL SHEETS Russian patent published in 2019 - IPC C21D8/02 C22C38/08 C22C38/40 B21B1/26 

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy, in particular, to production of new high-efficiency type of metal products – sheet steel from cryogenic structural steel for production, transportation and storage of liquefied natural gas. To ensure high cold resistance of steel at simultaneous combination of increased strength and sufficient resource of plasticity steel workpieces are heated to temperature of hot deformation, rolled and twice quenched in water at temperatures of 770–930 °C and 640–730 °C. After double quenching, high tempering is performed at temperature range of 540–630 °C with cooling in air; at that, slabs are made of steel of the following chemical composition, wt%: 0.02–0.06 C; 0.10–0.30 Si; 0.20–0.60 Mn; not more than 0.15 Cr; 8.50–10.00 Ni; 0.01–0.20 Mo; 0.001–0.015 V; 0.02–0.08 Al; 0.001–0.008 N; 0.002–0.03 Nb; 0.002–0.03 Ti; 0.01–0.20 Cu; not more than 0.003 S; not more than 0.010 P, Fe is the rest.

EFFECT: after heat treatment, sheets from cryogenic structural steel have the following complex of mechanical properties: yield stress of not less than 585 MPa, tensile strength of not less than 680 MPa, relative elongation δ₅ not less than 18 % and impact viscosity KCV at minus 196 °C not less than 100 J/cm².

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