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WO2023157897A1 - Matériau en acier approprié pour une utilisation en environnements acides - Google Patents

Matériau en acier approprié pour une utilisation en environnements acides Download PDF

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WO2023157897A1
WO2023157897A1 PCT/JP2023/005359 JP2023005359W WO2023157897A1 WO 2023157897 A1 WO2023157897 A1 WO 2023157897A1 JP 2023005359 W JP2023005359 W JP 2023005359W WO 2023157897 A1 WO2023157897 A1 WO 2023157897A1
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steel
content
test
steel material
ssc resistance
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English (en)
Japanese (ja)
Inventor
裕紀 神谷
勇次 荒井
陣 川▲崎▼
桂一 近藤
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Nippon Steel Corp
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Nippon Steel Corp
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Priority to US18/724,764 priority Critical patent/US20250066891A1/en
Priority to JP2023532799A priority patent/JP7406177B1/ja
Priority to MX2024009724A priority patent/MX2024009724A/es
Priority to EP23756422.4A priority patent/EP4481062A1/fr
Publication of WO2023157897A1 publication Critical patent/WO2023157897A1/fr
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium

Definitions

  • the present disclosure relates to steel, and more particularly to steel suitable for use in sour environments.
  • oil wells Due to the deepening of oil wells and gas wells (hereinafter collectively referred to as "oil wells"), there is a demand for higher strength steel materials for oil wells, represented by steel pipes for oil wells.
  • oil well steel pipes of 80 ksi class yield strength of 80 to less than 95 ksi, that is, 552 to 655 MPa
  • 95 ksi class yield strength of 95 to less than 110 ksi, that is, 655 to 758 MPa
  • yield strength of 758 MPa yield strength of 758 MPa or more.
  • a sour environment means an acidified environment containing hydrogen sulfide.
  • the sour environment may contain carbon dioxide.
  • Oil well steel pipes used in such a sour environment are required to have not only high strength but also sulfide stress cracking resistance (hereinafter referred to as SSC resistance). Thus, steel materials with high strength and excellent SSC resistance are beginning to be demanded.
  • Patent Document 1 JP-A-2000-297344
  • Patent Document 2 JP-A-2001-271134
  • Patent Document 3 International Publication No. 2008/ No. 123422
  • the oil well steel disclosed in Patent Document 1 contains, in mass %, C: 0.15 to 0.3%, Cr: 0.2 to 1.5%, Mo: 0.1 to 1%, V: 0.05-0.3%, Nb: 0.003-0.1%.
  • the total amount of precipitated carbides is 1.5 to 4% by mass
  • the proportion of MC type carbides in the total amount of carbides is 5 to 45% by mass
  • M 23 C 6 type carbides are The ratio is not more than (200/t) mass % when the thickness of the product is t (mm).
  • Patent Document 1 describes that this oil well steel has excellent SSC resistance.
  • the low-alloy steel material disclosed in Patent Document 2 has, in mass %, C: 0.2 to 0.35%, Si: 0.05 to 0.5%, Mn: 0.1 to 1%, P: 0.025% or less, S: 0.01% or less, Cr: 0.1-1.2%, Mo: 0.1-1%, B: 0.0001-0.005%, Al: 0.005 ⁇ 0.1%, N: 0.01% or less, V: 0.05-0.5%, Ni: 0.1% or less, W: 1.0% or less, O: 0.01% or less
  • the remainder is composed of Fe and impurities, satisfies the formula (0.03 ⁇ Mo x V ⁇ 0.3) and the formula (0.5 x Mo-V + GS / 10 ⁇ 1), and has a yield strength of 1060 MPa or more .
  • GS in the formula means the ASTM grain size number of prior austenite grains. Patent Document 2 describes that this low-alloy steel material has excellent SSC resistance.
  • This low-alloy steel has 0.1/mm 2 or less of M 23 C 6 type precipitates with a grain size of 1 ⁇ m or more. Patent Document 3 describes that this low-alloy steel has improved SSC resistance.
  • An object of the present disclosure is to provide a steel material that has high strength and excellent SSC resistance in a sour environment.
  • the steel according to the present disclosure is in % by mass, C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.05-0.30%, P: 0.030% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.10%, Mo: 0.40-2.00%, Ti: 0.002 to 0.020%, Nb: 0.002 to 0.100%, B: 0.0005 to 0.0040%, N: 0.0100% or less, O: less than 0.0040%, V: 0 to 0.30%, Cu: 0-0.50%, Ni: 0 to 0.50%, W: 0 to 1.50%, Ca: 0 to 0.0100%, Mg: 0-0.0100%, Zr: 0 to 0.0100%, Rare earth element: 0 to 0.0100%, and The balance consists of Fe and impurities, Yield strength is 862 MPa or more, In the steel material, In mass %, the Si content is 20% or more, the O content is
  • the steel material according to the present disclosure has high strength and excellent SSC resistance in sour environments.
  • FIG. 1 shows the number density (pieces/100 mm 2 ) of coarse Si oxides with a major axis of 5.0 ⁇ m or more in steel materials with a yield strength of less than 862 to 931 MPa, and the occurrence of SSC in the SSC resistance test. It is a figure which shows the relationship with the number (book).
  • FIG. 2 shows the number density (pieces/200 mm 2 ) of coarse Si oxides having a major axis of 5.0 ⁇ m or more and the number of SSCs generated in the SSC resistance test ( It is a diagram showing the relationship with the book).
  • the inventors considered obtaining a steel material having a yield strength of 125 ksi (862 MPa) or more as high strength.
  • the present inventors investigated and examined methods for obtaining a yield strength of 125 ksi or more and excellent SSC resistance in sour environments in steel materials that are assumed to be used in sour environments. As a result, the inventors obtained the following knowledge.
  • the inventors focused on the chemical composition and studied obtaining a steel material having a yield strength of 125 ksi or more and excellent SSC resistance in a sour environment.
  • Mn manganese
  • S sulfur
  • Mn sulfide is easily stretched by rolling, and tends to become inclusions having a long major diameter.
  • Mn sulfides with long major diameters tend to be starting points of destruction in sour environments. Therefore, by reducing the Mn content to 0.30% or less, it is possible to suppress the formation of Mn sulfides and improve the SSC resistance of the steel material.
  • the present inventors in mass%, C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.05 to 0.30%, P: 0.030 % or less, S: 0.0050% or less, Al: 0.005-0.100%, Cr: 0.30-1.10%, Mo: 0.40-2.00%, Ti: 0.002- 0.020%, Nb: 0.002-0.100%, B: 0.0005-0.0040%, N: 0.0100% or less, O: less than 0.0040%, V: 0-0.30 %, Cu: 0-0.50%, Ni: 0-0.50%, W: 0-1.50%, Ca: 0-0.0100%, Mg: 0-0.0100%, Zr: 0
  • a steel material consisting of up to 0.0100%, rare earth elements: 0 to 0.0100%, and the balance being Fe and impurities has a yield strength of 125 ksi or more, and furthermore, excellent SSC resistance in a sour environment. I thought it might be possible.
  • the present inventors have made a detailed study of the factors that reduce the SSC resistance of the steel material having the chemical composition described above and a yield strength of 125 ksi or more. As a result, it became clear that there is a concern that coarse Si oxides may be contained in the steel material having the chemical composition described above. If the steel material contains coarse Si oxides, the SSC resistance of the steel material may decrease.
  • a Si oxide having a Si content of 20% or more, an O content of 10% or more, and a major axis of 5.0 ⁇ m or more is also referred to as a "coarse Si oxide".
  • the inventors of the present invention have further studied in detail the factors that reduce the SSC resistance for each yield strength of the steel material having the chemical composition described above. As a result, the present inventors obtained the following findings.
  • the number density of coarse Si oxides is set to 5/100 mm 2 or less, so that a high yield strength of 125 ksi or more and excellent SSC resistance can be compatible. This point will be specifically described with reference to the drawings.
  • FIG. 1 shows the number density (pieces/100 mm 2 ) of coarse Si oxides (Si oxides having a major axis of 5.0 ⁇ m or more) and the SSC resistance in steel materials with a yield strength of less than 125 to 135 ksi in this example.
  • FIG. 2 is a diagram showing the relationship with the number of SSCs (lines) generated in a sex test.
  • FIG. 1 shows the number density of coarse Si oxides obtained by the method described later and the number density of coarse Si oxides obtained by the method described later for the steel material having the above chemical composition and the yield strength of less than 125 to 135 ksi among the examples described later. As a result of the SSC resistance test, it was created using the number of SSCs generated.
  • steel materials with a yield strength of 125 ksi or more steel materials with a yield strength of 135 ksi or more (931 MPa or more) have excellent SSC resistance in a sour environment even if the number density of coarse Si oxides is 5 pieces/100 mm 2 or less. Sometimes it wasn't.
  • steel materials with a yield strength of 135 ksi or more by further reducing the number density of coarse Si oxides to 5 pieces/200 mm 2 or less, high yield strength and excellent It became clear that both the SSC resistance and the SSC resistance can be achieved. This point will be specifically described with reference to the drawings.
  • FIG. 2 shows the number density (pieces/200 mm 2 ) of coarse Si oxides (Si oxides having a major axis of 5.0 ⁇ m or more) in steel materials with a yield strength of 135 ksi or more in this example, and the SSC resistance test.
  • FIG. 10 is a diagram showing the relationship between the number of SSCs (lines) generated in .
  • FIG. 2 shows the number density of coarse Si oxides obtained by the method described later, and the number density of coarse Si oxides obtained by the method described later, and the endurance It was created using the number of SSC generated as a result of the SSC property test.
  • the steel material according to the present embodiment has the chemical composition described above, a yield strength of 862 MPa or more, a number density of coarse Si oxides in the steel material of 5 pieces/100 mm 2 or less, and a yield strength of 931 MPa or more.
  • the number density of coarse Si oxides in the steel material is 5 pieces/200 mm 2 or less.
  • the gist of the steel material according to this embodiment completed based on the above knowledge is as follows.
  • [1] is steel, in % by mass, C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.05-0.30%, P: 0.030% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.10%, Mo: 0.40-2.00%, Ti: 0.002 to 0.020%, Nb: 0.002 to 0.100%, B: 0.0005 to 0.0040%, N: 0.0100% or less, O: less than 0.0040%, V: 0 to 0.30%, Cu: 0-0.50%, Ni: 0 to 0.50%, W: 0 to 1.50%, Ca: 0 to 0.0100%, Mg: 0-0.0100%, Zr: 0 to 0.0100%, Rare earth element: 0 to 0.0100%, and The balance consists of Fe and impurities, Yield strength is 862 MPa or more, In the steel material, In mass %, the Si content is 20% or more, the O content is 10% or
  • the steel material according to [1] or [2] is an oil well steel pipe, steel.
  • oil country tubular goods may be oil country tubular goods.
  • the oil well steel pipe may be a seamless steel pipe or a welded steel pipe.
  • Oil country tubular goods are, for example, steel pipes used for casing and tubing applications.
  • the oil well steel pipe according to this embodiment is preferably a seamless steel pipe. If the oil well steel pipe according to the present embodiment is a seamless steel pipe, it has a yield strength of 125 ksi or more and excellent SSC resistance in a sour environment even if the wall thickness is 15 mm or more.
  • the shape of the steel material according to this embodiment is not particularly limited. That is, the steel material according to the present embodiment may be a steel pipe, a round steel (solid material), or a steel plate.
  • the round steel means a bar having a circular cross section perpendicular to the axial direction.
  • the steel pipe may be a seamless steel pipe or a welded steel pipe.
  • C 0.15-0.45% Carbon (C) enhances the hardenability of the steel material and enhances the strength of the steel material. Further, C promotes spheroidization of carbides during tempering during the manufacturing process and enhances the SSC resistance of the steel material. Dispersed carbides further increase the strength of the steel material. If the C content is too low, the above effect cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the C content is too high, even if the contents of the other elements are within the ranges of the present embodiment, the amount of carbides will be too large and the toughness of the steel material will be lowered. If the C content is too high, quench cracks may easily occur during quenching during the manufacturing process.
  • the C content is 0.15-0.45%.
  • the lower limit of the C content is preferably 0.18%, more preferably 0.20%, still more preferably 0.22%, still more preferably 0.25%.
  • a preferable upper limit of the C content is 0.40%, more preferably 0.38%, and still more preferably 0.35%.
  • Si 0.05-1.00% Silicon (Si) deoxidizes steel. If the Si content is too low, the above effect cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the Si content is too high, the SSC resistance of the steel deteriorates even if the content of other elements is within the range of the present embodiment. Therefore, the Si content is 0.05-1.00%.
  • the lower limit of the Si content is preferably 0.10%, more preferably 0.15%, still more preferably 0.20%.
  • the preferred upper limit of the Si content is 0.85%, more preferably 0.75%, still more preferably 0.60%, still more preferably 0.50%, still more preferably 0.40 %.
  • Mn 0.05-0.30%
  • Manganese (Mn) deoxidizes steel. Mn further enhances the hardenability of the steel material. If the Mn content is too low, the above effect cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the Mn content is too high, coarse sulfide-based inclusions are formed even if the contents of other elements are within the ranges of the present embodiment, and the SSC resistance of the steel is lowered. Therefore, the Mn content is 0.05-0.30%. A preferable lower limit of the Mn content is 0.06%, more preferably 0.08%, and still more preferably 0.10%. A preferable upper limit of the Mn content is 0.28%, more preferably 0.25%, and still more preferably 0.20%.
  • Phosphorus (P) is an impurity. That is, the lower limit of the P content is over 0%. If the P content is too high, even if the content of other elements is within the range of the present embodiment, P will segregate at the grain boundaries and the SSC resistance of the steel material will decrease. Therefore, the P content is 0.030% or less.
  • a preferable upper limit of the P content is 0.025%, more preferably 0.020%, and still more preferably 0.015%. The lower the P content is, the better. However, an extreme reduction in the P content greatly increases manufacturing costs. Therefore, considering industrial production, the preferable lower limit of the P content is 0.001%, more preferably 0.002%, and still more preferably 0.003%.
  • S 0.0050% or less Sulfur (S) is an impurity. That is, the lower limit of the S content is over 0%. If the S content is too high, even if the contents of other elements are within the range of the present embodiment, S will segregate at the grain boundaries and the SSC resistance of the steel material will decrease. Therefore, the S content is 0.0050% or less.
  • a preferable upper limit of the S content is 0.0040%, more preferably 0.0030%, and still more preferably 0.0020%. It is preferable that the S content is as low as possible. However, an extreme reduction in the S content greatly increases manufacturing costs. Therefore, considering industrial production, the preferred lower limit of the S content is 0.0001%, more preferably 0.0002%, and still more preferably 0.0003%.
  • Al 0.005-0.100%
  • Aluminum (Al) deoxidizes steel. If the Al content is too low, even if the content of other elements is within the range of the present embodiment, the above effects cannot be obtained sufficiently, and the SSC resistance of the steel material is lowered. On the other hand, if the Al content is too high, even if the contents of other elements are within the ranges of the present embodiment, coarse oxide-based inclusions are formed, and the SSC resistance of the steel is lowered. Therefore, the Al content is 0.005-0.100%.
  • a preferable lower limit of the Al content is 0.010%, more preferably 0.015%, and still more preferably 0.020%.
  • a preferable upper limit of the Al content is 0.080%, more preferably 0.060%, and still more preferably 0.040%.
  • the "Al" content referred to in this specification means the content of "acid-soluble Al", that is, "sol. Al".
  • Chromium (Cr) enhances the hardenability of steel materials. Cr also increases the resistance to temper softening of the steel and enables high temperature tempering. As a result, the SSC resistance of the steel is enhanced. If the Cr content is too low, the above effect cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the Cr content is too high, the SSC resistance of the steel deteriorates even if the content of other elements is within the range of the present embodiment. Therefore, the Cr content is 0.30-1.10%. A preferable lower limit of the Cr content is 0.35%, more preferably 0.40%, and still more preferably 0.50%. A preferable upper limit of the Cr content is 1.00%, more preferably 0.90%, and still more preferably 0.80%.
  • Mo 0.40-2.00%
  • Molybdenum (Mo) enhances the hardenability of steel materials. Mo also increases the resistance to temper softening of the steel material and enables high temperature tempering. As a result, the SSC resistance of the steel is enhanced. If the Mo content is too low, the above effect cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the Mo content is too high, the above effects are saturated. Therefore, the Mo content is 0.40-2.00%.
  • a preferable lower limit of the Mo content is 0.45%, more preferably 0.50%, and still more preferably 0.60%.
  • a preferable upper limit of the Mo content is 1.80%, more preferably 1.60%, and still more preferably 1.40%.
  • Ti 0.002-0.020% Titanium (Ti) combines with N to form nitrides, and refines the crystal grains of the steel due to the pinning effect. As a result, the strength of the steel material increases. If the Ti content is too low, the above effect cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the Ti content is too high, even if the contents of other elements are within the ranges of the present embodiment, Ti nitrides will coarsen and the SSC resistance of the steel material will deteriorate. Therefore, the Ti content is 0.002-0.020%. A preferable lower limit of the Ti content is 0.003%, more preferably 0.004%. A preferable upper limit of the Ti content is 0.018%, more preferably 0.015%, and still more preferably 0.010%.
  • Niobium combines with C and/or N to form carbides, nitrides, or carbonitrides (hereinafter referred to as “carbonitrides, etc.”). Carbonitrides and the like refine the crystal grains of the steel due to the pinning effect, and improve the low-temperature toughness and SSC resistance of the steel. Nb also forms fine carbides during tempering to increase the resistance to temper softening of the steel material and increase the strength of the steel material. If the Nb content is too low, the above effect cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment.
  • the Nb content is 0.002-0.100%.
  • the lower limit of the Nb content is preferably 0.005%, more preferably 0.010%, still more preferably 0.015%, still more preferably 0.020%.
  • a preferable upper limit of the Nb content is 0.080%, more preferably 0.060%, and still more preferably 0.040%.
  • B 0.0005 to 0.0040% Boron (B) forms a solid solution in steel to enhance the hardenability of the steel and increase the strength of the steel. If the B content is too low, the above effect cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the B content is too high, even if the content of other elements is within the range of the present embodiment, coarse nitrides are formed and the SSC resistance of the steel material is lowered. Therefore, the B content is 0.0005-0.0040%. A preferable lower limit of the B content is 0.0006%, more preferably 0.0008%. The preferred upper limit of the B content is 0.0035%, more preferably 0.0030%, still more preferably 0.0025%, still more preferably 0.0020%.
  • N Nitrogen (N) is inevitably contained. That is, the lower limit of the N content is over 0%. N combines with Ti to form nitrides, and refines the crystal grains of the steel due to the pinning effect. As a result, the strength of the steel material increases. However, if the N content is too high, coarse nitrides are formed even if the content of other elements is within the range of the present embodiment, and the SSC resistance of the steel is lowered. Therefore, the N content is 0.0100% or less. A preferable upper limit of the N content is 0.0080%, more preferably 0.0060%, and still more preferably 0.0040%. A preferable lower limit of the N content for obtaining the above effect more effectively is 0.0005%, more preferably 0.0010%, still more preferably 0.0015%, still more preferably 0.0020% is.
  • Oxygen (O) is an impurity. That is, the lower limit of the O content is over 0%. If the O content is too high, coarse oxides are formed even if the content of other elements is within the range of the present embodiment, and the SSC resistance of the steel is lowered. Therefore, the O content is less than 0.0040%.
  • the upper limit of the O content is preferably 0.0035%, more preferably 0.0030%, still more preferably 0.0025%, still more preferably 0.0020%. It is preferable that the O content is as low as possible. However, the drastic reduction of the O content greatly increases the manufacturing cost. Therefore, considering industrial production, the lower limit of the O content is preferably 0.0001%, more preferably 0.0002%, and still more preferably 0.0003%.
  • the remainder of the chemical composition of the steel material according to this embodiment consists of Fe and impurities.
  • the impurities are those that are mixed from ore, scrap, or the manufacturing environment as raw materials when the steel material is industrially manufactured, and are within a range that does not adversely affect the steel material according to the present embodiment. means acceptable.
  • V 0-0.30% Vanadium (V) is an optional element and may not be contained. That is, the V content may be 0%.
  • V forms carbonitrides and the like. Carbonitrides and the like refine the crystal grains of the steel due to the pinning effect, and improve the SSC resistance of the steel. V also forms fine carbides during tempering to increase the resistance to temper softening of the steel material and increase the strength of the steel material. If even a small amount of V is contained, the above effect can be obtained to some extent. However, if the V content is too high, carbonitrides and the like are excessively formed even if the content of other elements is within the range of the present embodiment, and the SSC resistance of the steel material is lowered.
  • the V content is 0-0.30%.
  • the preferred lower limit of the V content is more than 0%, more preferably 0.01%, more preferably 0.02%, still more preferably 0.05%, still more preferably 0.07% is.
  • a preferable upper limit of the V content is 0.25%, more preferably 0.20%, and still more preferably 0.15%.
  • the chemical composition of the steel material described above may further contain one or more elements selected from the group consisting of Cu and Ni in place of part of Fe. All of these elements are optional elements and enhance the hardenability of the steel material.
  • Cu 0-0.50% Copper (Cu) is an optional element and may not be contained. That is, the Cu content may be 0%. When contained, Cu enhances the hardenability of the steel material and enhances the strength of the steel material. If even a small amount of Cu is contained, the above effects can be obtained to some extent. However, if the Cu content is too high, the hardenability of the steel becomes too high and the SSC resistance of the steel deteriorates even if the content of other elements is within the range of the present embodiment. Therefore, the Cu content is 0-0.50%.
  • the lower limit of the Cu content is preferably over 0%, more preferably 0.01%, still more preferably 0.02%, still more preferably 0.05%.
  • a preferred upper limit of the Cu content is 0.35%, more preferably 0.25%, still more preferably 0.15%, still more preferably 0.10%.
  • Ni 0-0.50%
  • Nickel (Ni) is an optional element and may not be contained. That is, the Ni content may be 0%. When contained, Ni enhances the hardenability of the steel material and enhances the strength of the steel material. Furthermore, Ni dissolves in steel and enhances the low-temperature toughness of the steel material. These effects can be obtained to some extent if even a small amount of Ni is contained. However, if the Ni content is too high, even if the content of the other elements is within the range of the present embodiment, local corrosion is promoted and the SSC resistance of the steel is lowered. Therefore, the Ni content is 0-0.50%. A preferable lower limit of the Ni content is more than 0%, more preferably 0.01%, and still more preferably 0.02%. A preferable upper limit of the Ni content is 0.30%, more preferably 0.20%, and still more preferably 0.10%.
  • the chemical composition of the steel material described above may further contain W instead of part of Fe.
  • W 0-1.50% Tungsten (W) is an optional element and may not be contained. That is, the W content may be 0%. When included, W forms a protective corrosion film in a sour environment and inhibits the penetration of hydrogen into the steel material. This enhances the SSC resistance of the steel material. If even a small amount of W is contained, the above effect can be obtained to some extent. However, if the W content is too high, coarse carbides are formed in the steel material even if the content of other elements is within the range of the present embodiment, and the low temperature toughness and SSC resistance of the steel material are lowered. Therefore, the W content is 0-1.50%.
  • the lower limit of the W content is preferably over 0%, more preferably 0.01%, still more preferably 0.03%, still more preferably 0.05%.
  • a preferable upper limit of the W content is 1.30%, more preferably 1.10%.
  • the chemical composition of the steel material described above may further contain one or more elements selected from the group consisting of Ca, Mg, Zr, and rare earth elements instead of part of Fe. All of these elements are optional elements, and detoxify S in the steel material as sulfides. As a result, these elements enhance the SSC resistance of the steel.
  • Ca 0-0.0100% Calcium (Ca) is an optional element and may not be contained. That is, the Ca content may be 0%. When Ca is contained, it detoxifies S in the steel material as sulfide, and enhances the SSC resistance of the steel material. If even a little Ca is contained, the above effect can be obtained to some extent. However, if the Ca content is too high, even if the contents of other elements are within the range of the present embodiment, the oxides in the steel material will coarsen and the SSC resistance of the steel material will decrease. Therefore, the Ca content is 0-0.0100%.
  • the lower limit of the Ca content is preferably over 0%, more preferably 0.0001%, still more preferably 0.0003%, still more preferably 0.0006%.
  • a preferable upper limit of the Ca content is 0.0040%, more preferably 0.0025%, and still more preferably 0.0020%.
  • Mg 0-0.0100%
  • Mg Magnesium (Mg) is an optional element and may not be contained. That is, the Mg content may be 0%. When contained, Mg detoxifies S in the steel material as sulfide and enhances the SSC resistance of the steel material. If even a small amount of Mg is contained, the above effect can be obtained to some extent. However, if the Mg content is too high, even if the contents of other elements are within the range of the present embodiment, the oxides in the steel material will coarsen and the SSC resistance of the steel material will decrease. Therefore, the Mg content is 0-0.0100%.
  • a preferable lower limit of the Mg content is more than 0%, more preferably 0.0001%, still more preferably 0.0003%, still more preferably 0.0006%.
  • a preferable upper limit of the Mg content is 0.0040%, more preferably 0.0025%, and still more preferably 0.0020%.
  • Zr Zirconium
  • Zr Zirconium
  • Zr is an optional element and may not be contained. That is, the Zr content may be 0%.
  • Zr detoxifies S in the steel material as sulfides and enhances the SSC resistance of the steel material. If even a small amount of Zr is contained, the above effect can be obtained to some extent. However, if the Zr content is too high, even if the contents of other elements are within the ranges of the present embodiment, the oxides in the steel material will coarsen, and the SSC resistance of the steel material will decrease. Therefore, the Zr content is 0-0.0100%.
  • a preferable lower limit of the Zr content is more than 0%, more preferably 0.0001%, still more preferably 0.0003%, still more preferably 0.0006%.
  • a preferable upper limit of the Zr content is 0.0040%, more preferably 0.0025%, and still more preferably 0.0020%.
  • Rare earth element 0-0.0100%
  • a rare earth element (REM) is an optional element and may not be contained. That is, the REM content may be 0%.
  • REM detoxifies S in the steel material as sulfides and enhances the SSC resistance of the steel material.
  • REM further binds with P in the steel material and suppresses the segregation of P at grain boundaries. Therefore, deterioration of the SSC resistance of the steel due to the segregation of P is suppressed.
  • the above effect can be obtained to some extent even if the content of other elements is within the range of the present embodiment.
  • the REM content is 0-0.0100%.
  • a preferable lower limit of the REM content is more than 0%, more preferably 0.0001%, more preferably 0.0003%, still more preferably 0.0006%.
  • a preferable upper limit of the REM content is 0.0040%, more preferably 0.0025%, and still more preferably 0.0020%.
  • REM refers to scandium (Sc) with atomic number 21, yttrium (Y) with atomic number 39, and lanthanoid (La) with atomic number 57 to atomic number 71. It means one or more elements selected from the group consisting of lutetium (Lu). Moreover, the REM content in this specification means the total content of these elements.
  • yield strength of the steel material according to this embodiment is 862 MPa or more. Yield strength as used herein means the stress at 0.65% elongation (0.65% proof stress) obtained in a tensile test.
  • the steel material according to the present embodiment has the chemical composition described above and satisfies the number density of coarse Si oxides described later, so that even if the yield strength is 862 MPa or more, it has excellent SSC resistance in a sour environment.
  • the upper limit of the yield strength of the steel material is not particularly limited, but is, for example, 1069 MPa (155 ksi), preferably 1034 MPa (150 ksi).
  • the yield strength of the steel material according to this embodiment can be obtained by the following method. Specifically, a tensile test is performed by a method conforming to ASTM E8/E8M (2021). A round bar test piece is produced from the steel material according to the present embodiment. When the steel material is a steel plate, a round bar test piece is produced from the central portion of the plate thickness. In this case, the axial direction of the round bar test piece is parallel to the rolling direction of the steel plate. When the steel material is a steel pipe, a round bar test piece is produced from the center of the wall thickness. In this case, the axial direction of the round bar test piece is parallel to the axial direction of the steel pipe.
  • the steel material is a round bar
  • a round bar specimen is produced from the R/2 position.
  • the R/2 position means the center position of the radius R in the cross section perpendicular to the axial direction of the round bar.
  • the axial direction of the round bar test piece is parallel to the axial direction of the round bar.
  • the size of the round bar test piece is, for example, a parallel portion diameter of 8.9 mm and a gauge length of 35.6 mm.
  • yield strength (MPa) is obtained by rounding off the obtained numerical value to the first decimal place.
  • the steel material according to the present embodiment has the above-described chemical composition and the above-described yield strength, and further has a Si content of 20% or more and an O content of 10% or more in terms of mass% in the steel material.
  • the number density of Si oxides (coarse Si oxides) having a major axis of 5.0 ⁇ m or more is 5 pieces/100 mm 2 or less. Further, in the steel material according to the present embodiment, when the yield strength is 931 MPa or more, the number density of coarse Si oxides is 5 pieces/200 mm 2 or less.
  • the steel material according to the present embodiment when the yield strength is less than 862 to 931 MPa, the number density of coarse Si oxides is 5/100 mm 2 or less (that is, 10/200 mm 2 or less), and the yield strength is In the case of 931 MPa or more, the number density of coarse Si oxides is 5 pieces/200 mm 2 or less.
  • the steel material according to this embodiment can achieve both a yield strength of 125 ksi or more and excellent SSC resistance.
  • the upper limit of the number density of coarse Si oxides is preferably 4/100 mm 2 , more preferably 3/100 mm 2 .
  • the upper limit of the number density of coarse Si oxides is preferably 4/200 mm 2 , more preferably 3/200 mm 2 .
  • the lower limit of the number density of coarse Si oxides is not particularly limited, and may be 0/100 mm 2 , that is, 0/200 mm 2 .
  • the number density of coarse Si oxides in the steel material can be obtained by the following method.
  • a test piece having a surface including the rolling direction and the rolling direction as an observation surface is produced.
  • the steel material is a steel plate
  • a test piece is prepared from the central portion of the plate thickness, the observation surface being a plane including the rolling direction and the plate thickness direction.
  • the steel material is a steel pipe
  • a test piece is prepared from the center of the wall thickness, the observation surface being a plane including the pipe axial direction and the pipe radial direction.
  • the steel material is a round bar
  • a test piece is prepared whose observation surface is a plane including the R/2 position in the center and including the axial direction and the radial direction.
  • the measurement is performed.
  • the area of the viewing surface is not limited, it is assumed to be 300 mm 2 (20 mm ⁇ 15 mm), for example.
  • the number of Si oxides having a major axis of 5.0 ⁇ m or more on the observed surface is determined.
  • the particles on the observation plane are identified from the contrast.
  • An elemental concentration analysis (EDS analysis) is performed on each identified particle.
  • EDS analysis the acceleration voltage is set to 20 kV, and the target elements are quantified as N, O, Mg, Al, Si, P, S, Ca, Ti, Cr, Mn, Fe, Cu, Zr, and Nb. Based on the EDS analysis results of each particle, if the Si content is 20% or more and the O content is 10% or more in mass %, the particle is specified as "Si oxide".
  • Si oxides (coarse Si oxides) having a major axis of 5.0 ⁇ m or more are identified, and the total number of coarse Si oxides is determined.
  • the major axis of the Si oxide can be determined by a well-known method.
  • the major axis of the Si oxide means the largest line segment ( ⁇ m) among the line segments connecting any two points on the outer periphery of the Si oxide on the viewing surface. Based on the total number of coarse Si oxides and the total area of the observation surface, the number density of coarse Si oxides (pieces/100 mm 2 or pieces/200 mm 2 ) is obtained.
  • the number density of coarse Si oxides is obtained by rounding off the obtained numerical value to the first decimal place.
  • the number density of coarse Si oxides can be measured using a scanning electron microscope equipped with a composition analysis function (SEM-EDS apparatus).
  • SEM-EDS apparatus for example, an automatic analyzer manufactured by FEI (ASPEX) under the trade name of Metals Quality Analyzer can be used.
  • the SSC resistance of the steel material according to this embodiment can be evaluated by an SSC resistance test carried out in accordance with NACE TM0177-2016 Method A. Specifically, it can be evaluated by the following method.
  • a mixed aqueous solution of 5.0% by mass sodium chloride and 0.4% by mass sodium acetate (NACE solution B) adjusted to pH 3.5 with acetic acid is used as the test solution.
  • a round bar test piece is produced from the steel material according to the present embodiment.
  • the steel material is a steel plate
  • a round bar test piece is produced from the central portion of the plate thickness. In this case, the axial direction of the round bar test piece is parallel to the rolling direction of the steel plate.
  • the steel material is a steel pipe
  • a round bar test piece is produced from the center of the wall thickness. In this case, the axial direction of the round bar test piece is parallel to the axial direction of the steel pipe. If the steel material is a round bar, a round bar specimen is produced from the R/2 position.
  • the axial direction of the round bar test piece is parallel to the axial direction of the round bar.
  • the size of the round bar test piece is, for example, a diameter of 6.35 mm and a parallel portion length of 25.4 mm.
  • the axial direction of the round bar test piece is parallel to the rolling direction of the steel material.
  • the total volume fraction of tempered martensite and tempered bainite is 90% or more.
  • the remainder of the microstructure is for example ferrite or perlite. If the microstructure of the steel material having the above chemical composition contains 90% or more of the total volume fraction of tempered martensite and tempered bainite, it is excellent in a sour environment on the condition that other configurations of the present embodiment are satisfied. It shows SSC resistance. That is, in the present embodiment, if the steel material has excellent SSC resistance, the microstructure is judged to have a total volume fraction of tempered martensite and tempered bainite of 90% or more.
  • a test piece having an observation surface is produced from the steel material according to the present embodiment.
  • the steel material is a steel plate
  • a test piece is prepared from the central portion of the plate thickness, the observation surface being a plane including the rolling direction and the plate thickness direction.
  • the steel material is a steel pipe
  • a test piece is prepared from the center of the wall thickness, the observation surface being a plane including the pipe axial direction and the pipe radial direction.
  • the steel material is a round bar
  • a test piece is prepared whose observation surface is a plane including the R/2 position in the center and including the axial direction and the radial direction.
  • the etched observation surface is observed in 10 fields of view with secondary electron images using a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the visual field area is, for example, 0.01 mm 2 (1000 times magnification).
  • Tempered martensite and tempered bainite are identified from the contrast in each field.
  • the area ratios of the specified tempered martensite and tempered bainite are determined.
  • a method for obtaining the area ratio is not particularly limited, and a well-known method may be used.
  • image analysis can determine the area ratio of tempered martensite and tempered bainite.
  • the arithmetic average value of the area ratios of tempered martensite and tempered bainite obtained in all fields of view is defined as the volume ratio of tempered martensite and tempered bainite.
  • the shape of the steel material according to this embodiment is not particularly limited.
  • Steel materials are, for example, steel pipes, steel plates, and round steel.
  • the wall thickness is preferably 9 to 60 mm. More preferably, the steel material according to this embodiment is a seamless steel pipe.
  • the steel material according to the present embodiment is a seamless steel pipe, even a thick seamless steel pipe having a wall thickness of 15 mm or more has a yield strength of 125 ksi or more and excellent SSC resistance in a sour environment.
  • a method for manufacturing a steel material according to this embodiment will be described.
  • a method for manufacturing a seamless steel pipe will be described below as an example of the steel material according to the present embodiment.
  • the manufacturing method of seamless steel pipes consists of a process of preparing materials (steelmaking process), a process of hot working the materials to manufacture mother pipes (hot working process), and performing quenching and tempering of the mother pipes. and a process (quenching process and tempering process) to form a seamless steel pipe.
  • the manufacturing method according to the present embodiment is not limited to the manufacturing method described below. Each step will be described in detail below.
  • Stepmaking process In the steelmaking process, first, molten iron manufactured by a known method is subjected to refining (primary refining) in a converter. Secondary refining is performed on the primary refined molten steel. In secondary refining, addition of alloying elements for component adjustment is performed to produce molten steel that satisfies the chemical composition described above.
  • RH Rasterstahl-Hausen vacuum degassing
  • VAD Vauum Arc Degassing
  • Materials are manufactured using molten steel that has undergone secondary refining.
  • a slab (slab, bloom, or billet) is produced by a continuous casting method using molten steel that has undergone secondary refining.
  • the continuous casting method first, molten steel is poured from a ladle into a tundish. At this time, in order to seal the nozzle of the ladle, the nozzle is usually filled with packing sand. Therefore, packing sand may be mixed with the molten steel from the ladle to the tundish.
  • Si oxide may be used as packing sand when manufacturing a material having the chemical composition described above. In this case, there is a concern that Si oxide may be introduced into the manufactured material.
  • the molten steel and the Si oxide are separated in order to prevent the Si oxide enclosed in the nozzle of the ladle from being introduced into the tundish.
  • the method for separating the Si oxide is not particularly limited, the following method can be used, for example.
  • a beveled metal plate is placed below the nozzle of the ladle and above the opening of the tundish.
  • Si oxide is discharged from the nozzle first, and then molten steel is discharged.
  • Si oxide is lighter than molten steel. Therefore, the Si oxide discharged from the nozzle is guided out of the opening of the tundish along the slope of the metal plate.
  • the inclination of the metal plate may be provided, for example, by arranging a metal plate processed into a conical shape without a bottom so that the apex is directly below the nozzle of the ladle, or provided by other methods. good too. Also, one metal plate may be used, or a plurality of metal plates may be stacked and used. Furthermore, although the thickness of the metal plate is not particularly limited, it is, for example, about 1 to 10 mm.
  • the metal plate in the present embodiment is preferably a metal plate made of an alloying element contained in molten steel.
  • an aluminum plate can be used as the metal plate made of an alloy element contained in molten steel.
  • the aluminum plate means a metal plate composed of aluminum and impurities.
  • the metal plate is removed from below the nozzle after the Si oxide is discharged from the nozzle and before the molten steel is discharged.
  • the number density of coarse Si oxides can sometimes be reduced to 5 pieces/200 mm 2 or less. Therefore, in this embodiment, it is preferable to remove the metal plate from below the nozzle after the Si oxide is discharged from the nozzle and before the molten steel is discharged.
  • the method of removing the metal plate from below the nozzle is not particularly limited, but for example, a hole may be formed in a part of the metal plate and a rod having a hook formed at the tip thereof may be used to remove the metal plate.
  • the metal plate can be removed by hooking the hook at the tip of the rod to the hole in the metal plate and pulling the rod.
  • the Si oxide can be separated from the molten steel and the molten steel can be introduced into the tundish.
  • the method for separating Si oxide from molten steel is not limited to the method described above.
  • molten steel is cast to manufacture materials.
  • the material is preferably a billet with a circular cross section (round billet).
  • a method for manufacturing the material is not particularly limited. For example, a continuous casting process may be used to cast molten steel into round billets. Alternatively, a billet having a rectangular cross section may be produced by casting molten steel, or a bloom may be produced. In these cases, blooming is preferably performed to produce a round billet from a billet having a rectangular cross section or a bloom.
  • the prepared material is hot worked to produce an intermediate steel material. If the steel material is a seamless steel pipe, the intermediate steel material corresponds to the base pipe.
  • the billet is heated in a heating furnace.
  • the heating temperature is not particularly limited, it is, for example, 1100 to 1300.degree.
  • a billet extracted from a heating furnace is subjected to hot working to produce a blank pipe (seamless steel pipe).
  • the method of hot working is not particularly limited, and a known method may be used.
  • the Mannesmann method may be carried out as hot working to produce a mother tube.
  • the round billet is pierced and rolled by a piercing machine.
  • the piercing ratio is not particularly limited, but is, for example, 1.0 to 4.0.
  • the pierced-rolled round billet is further hot-rolled by a mandrel mill, a reducer, a sizing mill, or the like to form a mother pipe.
  • the cumulative area reduction rate in the hot working process is, for example, 20 to 70%.
  • a blank tube may be manufactured from a billet by implementing other hot working methods.
  • a blank pipe may be manufactured by forging such as the Ehrhardt method.
  • a blank pipe is manufactured by the above steps.
  • the wall thickness of the blank tube is not particularly limited, it is, for example, 9 to 60 mm.
  • the blank tube manufactured by hot working may be air-cooled (As-Rolled).
  • a mother tube manufactured by hot working may be quenched directly after hot working without cooling to room temperature, or may be quenched after supplementary heating (reheating) after hot working. good.
  • SR stress relief annealing
  • the material is first heated in a heating furnace.
  • the heating temperature is not particularly limited, it is, for example, 1100 to 1300.degree.
  • the raw material extracted from the heating furnace is subjected to hot working to produce an intermediate steel material having a circular cross section perpendicular to the axial direction.
  • Hot working is, for example, blooming by a blooming mill or hot rolling by a continuous rolling mill.
  • a horizontal stand having a pair of grooved rolls arranged vertically and a vertical stand having a pair of grooved rolls arranged horizontally are arranged alternately.
  • the material is first heated in a heating furnace.
  • the heating temperature is not particularly limited, it is, for example, 1100 to 1300.degree.
  • the raw material extracted from the heating furnace is subjected to hot rolling using a blooming mill and a continuous rolling mill to produce an intermediate steel material in the form of a steel plate.
  • the prepared materials are hot worked to produce intermediate steel materials.
  • the hardening process will be described in detail below.
  • quenching means quenching an intermediate steel material having a point of A3 or higher.
  • a preferred quenching temperature is 800-1000°C. If the quenching temperature is too high, the crystal grains of the prior ⁇ grains become coarse, and the SSC resistance of the steel material may deteriorate. Therefore, the quenching temperature is preferably 800-1000°C.
  • the quenching temperature is the surface temperature of the intermediate steel measured by a thermometer installed on the delivery side of the device that performs the final hot working when quenching is performed directly after hot working. Equivalent to.
  • the quenching temperature further corresponds to the temperature of the furnace in which the supplementary heating or reheating is carried out when the quenching is carried out after supplementary heating or reheating after hot working.
  • the intermediate steel material (base pipe) is continuously cooled from the quenching start temperature, and the surface temperature of the base pipe is continuously lowered.
  • a method of continuous cooling treatment is not particularly limited, and a known method may be used.
  • the method of continuous cooling treatment includes, for example, a method of cooling the tube by immersing it in a water tank, and a method of accelerating cooling the tube by shower water cooling or mist cooling.
  • the microstructure will not be mainly composed of martensite and bainite, and the mechanical properties specified in this embodiment (yield strength of 125 ksi or more) cannot be obtained. Furthermore, good low temperature toughness and good SSC resistance are not obtained in this case.
  • the intermediate steel is rapidly cooled during quenching.
  • the average cooling rate when the surface temperature of the intermediate steel material (base tube) during quenching is in the range of 800 to 500° C. is defined as the cooling rate during quenching CR 800-500 .
  • the cooling rate during quenching, CR 800-500 is the slowest cooling part in the cross section of the intermediate steel material to be quenched (for example, when forced cooling is performed on both surfaces, the central part of the intermediate steel thickness) determined from the temperature measured at
  • a preferable cooling rate during quenching CR 800-500 is 300° C./min or more.
  • a more preferable lower limit of the cooling rate during quenching CR 800-500 is 450°C/min, more preferably 600°C/min.
  • the upper limit of the cooling rate CR 800-500 during quenching is not specified, it is, for example, 60000° C./min.
  • the blank pipe is heated in the austenitic region multiple times, and then quenched.
  • the SSC resistance of the steel is enhanced.
  • heating in the austenite region may be repeated multiple times, and by performing normalizing and quenching, heating in the austenite region may be repeated multiple times.
  • quenching and tempering which will be described later, may be combined and performed multiple times. That is, quenching and tempering may be performed multiple times. In this case, the SSC resistance of the steel is further enhanced.
  • the tempering process will be described in detail below.
  • tempering is performed on the shell that has been quenched as described above.
  • the term "tempering” means reheating the intermediate steel material after quenching at a temperature lower than the Ac1 point and maintaining it.
  • the tempering temperature corresponds to the temperature of the furnace when the intermediate steel material after quenching is heated and held.
  • the tempering time means the time from when the temperature of the intermediate steel material reaches a predetermined tempering temperature to when it is extracted from the heat treatment furnace.
  • the tempering temperature is appropriately adjusted according to the chemical composition of the seamless steel pipe and the desired yield strength. That is, the yield strength of the seamless steel pipe is adjusted to 862 MPa or more by adjusting the tempering temperature for the mother pipe having the chemical composition of the present embodiment.
  • a person skilled in the art can naturally adjust the tempering temperature to adjust the yield strength of the seamless steel pipe to 862 MPa or more and 931 MPa or more.
  • the preferred tempering temperature is 650-690°C.
  • a more preferable lower limit of the tempering temperature is 655°C.
  • a more preferable upper limit of the tempering temperature is 685°C.
  • the tempering time is preferably 10 to 90 minutes.
  • a more preferable lower limit of the tempering time is 15 minutes.
  • a more preferable upper limit of the tempering time is 80 minutes.
  • the steel material according to this embodiment can be manufactured by the manufacturing method described above.
  • the method for manufacturing a seamless steel pipe has been described as an example.
  • the steel material according to this embodiment may be a steel plate or other shapes.
  • a method of manufacturing a steel sheet or other shape may also comprise, for example, a preparation step, a quenching step, and a tempering step, similar to the manufacturing method described above.
  • the manufacturing method described above is merely an example, and other manufacturing methods may be used.
  • Example 1 steel materials with a yield strength of less than 862 to 931 MPa were evaluated. Specifically, first, molten steel having chemical compositions shown in Tables 1-1 and 1-2 was produced. "-" in Table 1-2 means that the content of each element is at the impurity level. Specifically, it means that the V content, Cu content, Ni content, and W content of Steel A were 0% after rounding off to the third decimal place. Furthermore, the Ca content, Mg content, Zr content, and rare earth element (REM) content of Steel A were rounded off to the fifth decimal place, meaning that they were 0%.
  • REM rare earth element
  • a round billet was manufactured by continuous casting.
  • a metal plate processed into a conical shape with no bottom is placed above the opening of the tundish so that the apex is directly below the nozzle of the ladle. placed.
  • Table 2 shows whether or not the metal plate having the above shape was placed above the opening of the tundish. Specifically, when a metal plate having the above shape is arranged above the opening of the tundish, it is indicated as "A" in the "metal plate” column of Table 2. When the metal plate having the above shape was not arranged above the opening of the tundish, "B" is shown in the "metal plate” column of Table 2.
  • the metal plate having the shape described above and placed above the opening of the tundish was an aluminum plate. Specifically, three aluminum plates with a thickness of 2 mm were stacked and used. In test numbers 3, 8 to 10, and 12, after the Si oxide was discharged from the nozzle and before the molten steel was discharged, a rod with a hook formed at the tip was used to pour metal from below the nozzle. Removed the plate.
  • test numbers 1 to 19 After holding the produced round billets of test numbers 1 to 19 at 1250° C. for 1 hour, hot rolling was performed by the Mannesmann-mandrel system to produce blank pipes (seamless steel pipes) of test numbers 1 to 19. Further, quenching was performed on the obtained blank pipes of test numbers 1 to 19. Specifically, the blank pipes of test numbers 1 to 19 were held at the quenching temperature (°C) listed in the "quenching" column of Table 2 for the quenching time (minutes), and then quenched by shower water cooling. In test numbers 1 to 19, the cooling rate CR 800-500 during quenching was all within the range of 480 to 30000° C./min.
  • the quenching temperature (°C) described in Table 2 was the temperature (°C) of the heat treatment furnace in which the mother tube was heated. Furthermore, the quenching time (minutes) listed in Table 2 was the time (minutes) during which the blank tube was held at the quenching temperature.
  • Tempering was performed on the obtained blank pipes of test numbers 1 to 19. Specifically, the blank pipes of test numbers 1 to 19 were tempered at the tempering temperature (°C) listed in the "Tempering" column of Table 2 for the tempering time (minutes).
  • the tempering temperature (°C) described in Table 2 was the temperature (°C) of the tempering furnace in which the tube was heated.
  • the tempering time (minutes) listed in Table 2 was the time (minutes) during which the tube was held at the tempering temperature. Seamless steel pipes of test numbers 1 to 19 were obtained through the above manufacturing process.
  • the SSC resistance test was performed on the seamless steel pipes of test numbers 1 to 19 by a method conforming to NACE TM0177-2016 Method A to evaluate the SSC resistance. Specifically, a round bar test piece having a diameter of 6.35 mm and a parallel portion length of 25.4 mm was prepared from the thickness central portion of the seamless steel pipes of test numbers 1 to 19. An SSC resistance test was performed on three of the prepared test pieces. The axial direction of the test piece was parallel to the tube axial direction.
  • a tensile stress was applied in the axial direction of the round bar test pieces of test numbers 1 to 19. At this time, the applied stress was adjusted to 90% of the actual yield stress of each steel plate.
  • the test solution used was a mixed aqueous solution of 5.0% by mass sodium chloride and 0.4% by mass sodium acetate adjusted to pH 3.5 with acetic acid (NACE solution B).
  • a test solution at 24° C. was poured into each of three test containers to form a test bath. Three stressed round bar specimens were immersed in test baths of different test containers. After degassing each test bath, a mixed gas of 0.1 atm H 2 S gas and 0.9 atm CO 2 gas was blown into the test bath to saturate it. A test bath saturated with a mixed gas of 0.01 atm H 2 S gas and 0.99 atm CO 2 gas was held at 24° C. for 1440 hours.
  • SSC sulfide stress cracking
  • the Mn content of the seamless steel pipe of test number 15 was too high. As a result, SSC occurred in the test piece in the SSC resistance test. That is, the seamless steel pipe of test number 15 did not have excellent SSC resistance.
  • the Mo content of the seamless steel pipe of test number 16 was too low. As a result, SSC occurred in the test piece in the SSC resistance test. That is, the seamless steel pipe of test number 16 did not have excellent SSC resistance.
  • the S content of the seamless steel pipe of test number 17 was too high. As a result, SSC occurred in the test piece in the SSC resistance test. That is, the seamless steel pipe of test number 17 did not have excellent SSC resistance.
  • the P content of the seamless steel pipe of test number 18 was too high. As a result, SSC occurred in the test piece in the SSC resistance test. That is, the seamless steel pipe of test number 18 did not have excellent SSC resistance.
  • the seamless steel pipe of test number 19 had too high an O content. As a result, SSC occurred in the test piece in the SSC resistance test. That is, the seamless steel pipe of test number 19 did not have excellent SSC resistance.
  • Example 2 steel materials with a yield strength of 931 MPa or more were evaluated. Specifically, first, molten steel having chemical compositions shown in Tables 3-1 and 3-2 was produced. "-" in Table 3-2 means that the content of each element is at the impurity level. Specifically, it means that the Cu content, Ni content, and W content of Steel R were 0% after rounding off to the third decimal place. Furthermore, the Ca content, Mg content, Zr content, and rare earth element (REM) content of steel R were rounded to the fifth decimal place, meaning that they were 0%.
  • REM rare earth element
  • a round billet was manufactured by continuous casting.
  • a metal plate processed into a conical shape with no bottom is placed above the opening of the tundish so that the apex is directly below the nozzle of the ladle. placed.
  • Table 4 shows whether or not the metal plate having the above shape was placed above the opening of the tundish. Specifically, when a metal plate having the above shape is arranged above the opening of the tundish, it is shown as "A" in the "metal plate” column of Table 4. When the metal plate having the above shape was not arranged above the opening of the tundish, "B" is indicated in the "metal plate” column of Table 4.
  • the metal plate having the shape described above and placed above the opening of the tundish was an aluminum plate. Specifically, three aluminum plates with a thickness of 2 mm were stacked and used.
  • a rod having a hook formed at the tip is used to push the metal plate from below the nozzle. removed.
  • test numbers 20 to 40 After holding the manufactured round billets of test numbers 20 to 40 at 1250° C. for 1 hour, hot rolling was performed by the Mannesmann-mandrel system to manufacture blank pipes (seamless steel pipes) of test numbers 20 to 40. Furthermore, hardening was performed on the obtained blank pipes of test numbers 20 to 40. Specifically, the blank pipes of test numbers 20 to 40 were held at the quenching temperature (°C) listed in the "quenching" column of Table 4 for the quenching time (minutes), and then quenched by shower water cooling. In test numbers 20 to 40, the cooling rates CR 800 to 500 during quenching were all within the range of 480 to 30000°C/min.
  • the quenching temperature (°C) described in Table 4 was the temperature (°C) of the heat treatment furnace in which the mother tube was heated. Furthermore, the quenching time (minutes) shown in Table 4 was the time (minutes) during which the tube was held at the quenching temperature.
  • the second quenching was performed on the blank pipe of test number 22.
  • the blank pipe of Test No. 3 was held in a heat treatment furnace at 900° C. for 10 minutes, and then quenched by shower water cooling.
  • the cooling rates CR800-500 during quenching were all within the range of 480 to 30000°C/min.
  • Tempering was performed on the obtained blank pipes with test numbers 20 to 40. Specifically, the blank pipes of test numbers 20 to 40 were tempered at the tempering temperature (°C) listed in the "Tempering" column of Table 4 for the tempering time (minutes).
  • the tempering temperature (°C) described in Table 4 was the temperature (°C) of the tempering furnace in which the tube was heated.
  • the tempering time (minutes) listed in Table 4 was the time (minutes) during which the tube was held at the tempering temperature. Seamless steel pipes with test numbers 20 to 40 were obtained through the above manufacturing process.
  • the SSC resistance test was performed on the seamless steel pipes of test numbers 20 to 40 by a method conforming to NACE TM0177-2016 Method A to evaluate the SSC resistance. Specifically, a round bar test piece having a diameter of 6.35 mm and a parallel portion length of 25.4 mm was prepared from the thickness central portion of the seamless steel pipes of test numbers 20 to 40. An SSC resistance test was performed on three of the prepared test pieces. The axial direction of the test piece was parallel to the tube axial direction.
  • Tensile stress was applied in the axial direction of round bar test pieces of test numbers 20 to 40. At this time, the applied stress was adjusted to 90% of the actual yield stress of each steel plate.
  • the test solution used was a mixed aqueous solution of 5.0% by mass sodium chloride and 0.4% by mass sodium acetate adjusted to pH 3.5 with acetic acid (NACE solution B).
  • a test solution at 24° C. was poured into each of three test containers to form a test bath. Three stressed round bar specimens were immersed in test baths of different test containers. After degassing each test bath, a mixed gas of 0.01 atm H 2 S gas and 0.99 atm CO 2 gas was blown into the test bath to saturate it. A test bath saturated with a mixed gas of 0.01 atm H 2 S gas and 0.99 atm CO 2 gas was held at 24° C. for 1440 hours.
  • SSC sulfide stress cracking
  • the O content of the seamless steel pipe of test number 38 was too high. As a result, SSC occurred in the test piece in the SSC resistance test. That is, the seamless steel pipe of Test No. 38 did not have excellent SSC resistance.
  • the Mo content of the seamless steel pipe of test number 39 was too low. As a result, SSC occurred in the test piece in the SSC resistance test. That is, the seamless steel pipe of Test No. 39 did not have excellent SSC resistance.
  • the S content of the seamless steel pipe of test number 40 was too high. As a result, SSC occurred in the test piece in the SSC resistance test. That is, the seamless steel pipe of test number 40 did not have excellent SSC resistance.

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Abstract

L'invention concerne un matériau en acier à haute résistance qui présente une excellente résistance SSC (fissuration sous contrainte due au sulfure) en environnements acides. Le matériau en acier selon la présente divulgation comprend, en % en masse, C : de 0,15 % à 0,45 %, Si : de 0,05 % à 1,00 %, Mn : de 0,05 % à 0,30 %, P : pas plus de 0,030 %, S : pas plus de 0,0050 %, Al : de 0,005 % à 0,100 %, Cr : de 0,30 % à 1,10 %, Mo : de 0,40 % à 2,00 %, Ti : de 0,002 % à 0,020 %, Nb : de 0,002 % à 0,100 %, B : de 0,0005 % à 0,0040 %, N : pas plus de 0,0100 %, et O : moins de 0,0040 %, le reste étant du Fe et des impuretés, et a une limite d'élasticité d'au moins 862 MPa. La densité en nombre dans le matériau en acier d'oxyde de Si ayant une teneur en Si d'au moins 20 % en masse, une teneur en O d'au moins 10 % en masse, et un diamètre côté longueur d'au moins 5,0 µm, n'est pas supérieure à 5/100 mm2 ; lorsque la limite d'élasticité est de 931 MPa ou plus, la densité en nombre d'oxyde de Si n'est pas supérieure à 5/200 mm2.
PCT/JP2023/005359 2022-02-17 2023-02-16 Matériau en acier approprié pour une utilisation en environnements acides Ceased WO2023157897A1 (fr)

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US18/724,764 US20250066891A1 (en) 2022-02-17 2023-02-16 Steel material suitable for use in sour environment
JP2023532799A JP7406177B1 (ja) 2022-02-17 2023-02-16 サワー環境での使用に適した鋼材
MX2024009724A MX2024009724A (es) 2022-02-17 2023-02-16 Material de acero adecuado para su uso en entornos amargos.
EP23756422.4A EP4481062A1 (fr) 2022-02-17 2023-02-16 Matériau en acier approprié pour une utilisation en environnements acides

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WO2024209921A1 (fr) * 2023-04-06 2024-10-10 日本製鉄株式会社 Matériau d'acier
WO2025033003A1 (fr) * 2023-08-07 2025-02-13 日本製鉄株式会社 Matériau d'acier
WO2025033002A1 (fr) * 2023-08-07 2025-02-13 日本製鉄株式会社 Matériau d'acier

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WO2025169959A1 (fr) * 2024-02-05 2025-08-14 日本製鉄株式会社 Matériau d'acier et composant pour structure mécanique

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JP2001271134A (ja) 2000-03-24 2001-10-02 Sumitomo Metal Ind Ltd 耐硫化物応力割れ性と靱性に優れた低合金鋼材
WO2008123422A1 (fr) 2007-03-30 2008-10-16 Sumitomo Metal Industries, Ltd. Acier faiblement allié, conduit en acier sans soudure pour puits de pétrole et procédé de fabrication d'un conduit en acier sans soudure
JP2008254051A (ja) * 2007-04-06 2008-10-23 Nippon Steel Corp 連続鋳造方法
CN106399862A (zh) * 2016-09-28 2017-02-15 睿智钢业有限公司 一种高强防腐钢材及其制备方法和应用
WO2018074109A1 (fr) * 2016-10-17 2018-04-26 Ｊｆｅスチール株式会社 Tuyau d'acier sans soudure de résistance élevée pour puits de pétrole et procédé pour sa production
WO2021039431A1 (fr) * 2019-08-27 2021-03-04 日本製鉄株式会社 Matériau en acier approprié pour être utilisé dans un environnement acide

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Publication number Priority date Publication date Assignee Title
JP2000297344A (ja) 1999-04-09 2000-10-24 Sumitomo Metal Ind Ltd 靭性と耐硫化物応力腐食割れ性に優れる油井用鋼およびその製造方法
JP2001271134A (ja) 2000-03-24 2001-10-02 Sumitomo Metal Ind Ltd 耐硫化物応力割れ性と靱性に優れた低合金鋼材
WO2008123422A1 (fr) 2007-03-30 2008-10-16 Sumitomo Metal Industries, Ltd. Acier faiblement allié, conduit en acier sans soudure pour puits de pétrole et procédé de fabrication d'un conduit en acier sans soudure
JP2008254051A (ja) * 2007-04-06 2008-10-23 Nippon Steel Corp 連続鋳造方法
CN106399862A (zh) * 2016-09-28 2017-02-15 睿智钢业有限公司 一种高强防腐钢材及其制备方法和应用
WO2018074109A1 (fr) * 2016-10-17 2018-04-26 Ｊｆｅスチール株式会社 Tuyau d'acier sans soudure de résistance élevée pour puits de pétrole et procédé pour sa production
WO2021039431A1 (fr) * 2019-08-27 2021-03-04 日本製鉄株式会社 Matériau en acier approprié pour être utilisé dans un environnement acide

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Publication number Priority date Publication date Assignee Title
WO2024209921A1 (fr) * 2023-04-06 2024-10-10 日本製鉄株式会社 Matériau d'acier
WO2025033003A1 (fr) * 2023-08-07 2025-02-13 日本製鉄株式会社 Matériau d'acier
WO2025033002A1 (fr) * 2023-08-07 2025-02-13 日本製鉄株式会社 Matériau d'acier

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JPWO2023157897A1 (fr) 2023-08-24

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