Cryogenic steel plate and method for manufacturing same
AssigneePosco
InventorHak-Cheol LEE
Life of this patent
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Abstract
Provided are a cryogenic steel plate and a method for manufacturing the same, the cryogenic steel plate comprising, in wt %, 0.04 to 0.08% carbon (C), 8.9 to 9.3% nickel (Ni), 0.6 to 0.7% manganese (Mn), and 0.2 to 0.3% silicon (Si), and 50 ppm or less of P, 10 ppm or less of S, and the remainder in iron (Fe) and various unavoidable impurities, and the microstructure at a ¼t location of the steel plate, where t is a thickness of the steel plate, comprising, in % surface area, 10% or more of tempered bainite, 10% or less of residual austenite, and the remainder of tempered martensite.
Claims16
A cryogenic steel plate comprising, in wt %:
- 0.04 to 0.08% of carbon (C), 8.9 to 9.3% of nickel (Ni), 0.6 to 0.7% of manganese (Mn), 0.2 to 0.3% of silicon (Si), 50 ppm or less of P, 10 ppm or less of S, and a remainder in iron (Fe) and various unavoidable impurities,
- wherein a microstructure at a ¼t location of the steel plate, where t is a thickness of the steel plate, includes, in % surface area, 10% or more of tempered bainite, 10% or less of residual austenite, and a remainder of tempered martensite.
A method for manufacturing a cryogenic steel plate comprising operations of:
- heating a steel slab including, in wt %, 0.04 to 0.08% of carbon (C), 8.9 to 9.3% of nickel (Ni), 0.6 to 0.7% of manganese (Mn), 0.2 to 0.3% of silicon (Si), 50 ppm or less of P, 10 ppm or less of S, and a remainder in iron (Fe) and various unavoidable impurities, and then finish hot rolling at a temperature of 900° C. or less to obtain a steel plate;
- direct quenching of cooling the steel plate at a cooling rate of 10 to 40° C./sec;
- and
- tempering the steel plate directly quenched as described above at a temperature of 580 to 600° C.,
- wherein a microstructure of the steel plate prior to the tempering operation after the direct quenching operation comprises, in surface area %, 10% or more of bainite in a martensite matrix.
Dependencies are inferred from the claim text.