STRUCTURAL CRYOGENIC AUSTENITE HIGH-STRENGTH CORROSION-RESISTANT WELDABLE STEEL AND ITS TREATMENT METHOD Russian patent published in 2018 - IPC C22C38/58 C21D8/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely, to the production of ingots from structural cryogenic austenitic high-strength corrosion-resistant welded steel, for production of used in the liquefied gases transportation and storage high-strength welded cryogenic structures. Said steel contains, wt%: C 0.05–0.07, Cr 18.0–20.0, Ni 5.0–7.0, Mn 9.0–11.0, Mo 1.8–2.2, Si 0.25–0.35, N 0.30–0.38, Cu 0.6–1.4, B from more than 0.01 to 0.015, Al 0.015-0.035, S≤0.0025, P≤0.015, Sn≤0.005, Pb≤0.005, Bi≤0.005, As≤0.005, Fe – the rest. Produces ingots are heated to the temperature of 1,250–1,050 °C, forged into blanks with the total degree of deformation of at least 50 % and cooled down in air. Blanks are heated-up to the temperature of 1,180–1,080 °C with subsequent rolling with the total reduction rate of at least 40 % and air cooling with the rolled products production. Rolled products heated to the temperature of 1,150–1,080 °C and performing the final rolling in 2-3 passes with the total reduction rate of 30–80 % and the rolling completion temperature of 1,050–1,080 °C, after which performing the accelerated cooling down at a rate of 20–100 °C/s until the room temperature.

EFFECT: enabling the strength and viscosity required values in the cryogenic temperatures range, weldability and corrosion resistance in the acidic environment and sea water.

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