WO2024058278A1 - Austenite alloy material - Google Patents

Austenite alloy material Download PDF

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Publication number
WO2024058278A1
WO2024058278A1 PCT/JP2023/033809 JP2023033809W WO2024058278A1 WO 2024058278 A1 WO2024058278 A1 WO 2024058278A1 JP 2023033809 W JP2023033809 W JP 2023033809W WO 2024058278 A1 WO2024058278 A1 WO 2024058278A1
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content
alloy material
still
temperature ammonia
ammonia environment
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PCT/JP2023/033809
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French (fr)
Japanese (ja)
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礼文 河内
孝裕 小薄
伸之佑 栗原
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日本製鉄株式会社
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C22C30/04—Alloys containing less than 50% by weight of each constituent containing tin or lead
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C22C30/06—Alloys containing less than 50% by weight of each constituent containing zinc
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon

Definitions

  • the present disclosure relates to alloy materials, and more specifically, to austenitic alloy materials.
  • Hydrogen is a gas at normal temperature and pressure, and when it is liquefied for transportation, it needs to be brought to an extremely low temperature of -253°C or lower. Therefore, it is difficult to transport hydrogen alone.
  • ammonia as a hydrogen carrier is being considered.
  • Ammonia contains about 18% hydrogen by mass and liquefies at -33°C, which is higher than the boiling point of hydrogen. Therefore, studies are underway to utilize hydrogen as energy by transporting ammonia, which is a hydrogen carrier, and desorbing hydrogen from the ammonia at the transport destination.
  • ammonia is decomposed using a catalyst in a high temperature environment of about 600°C at normal pressure.
  • a catalyst in a high temperature environment of about 600°C at normal pressure.
  • an environment with a high temperature of about 600° C., normal pressure, and an ammonia atmosphere will be referred to as a "high-temperature ammonia environment.” Therefore, there is a need for alloy materials that can withstand use in high-temperature ammonia environments.
  • Austenitic alloy materials used in chemical plants are considered as alloy materials that can be applied to high-temperature ammonia environments for hydrogen production. This is because chemical plants have high-temperature environments equivalent to high-temperature ammonia environments.
  • An austenitic alloy material for chemical plants is disclosed in, for example, Japanese Patent Application Publication No. 2017-088957 (Patent Document 1).
  • the alloy material disclosed in this document has a chemical composition in mass % of C: 0.02 to 0.12%, Si: 0.1 to 2%, Mn: 0.1 to 3%, and P: 0.
  • Patent Document 1 describes that the above-mentioned austenitic alloy material has excellent creep strength when used in a high-temperature environment.
  • An object of the present disclosure is to provide an austenitic alloy material that has excellent nitriding resistance in a high-temperature ammonia environment.
  • the austenitic alloy material of the present disclosure is The chemical composition is in mass%, C: more than 0 to 0.200%, Si: more than 0 to 3.00%, Mn: more than 0 to 3.00%, P: more than 0 to 0.050%, S: more than 0 to 0.050%, Ni: 40.00 to 80.00%, and Contains Cr: 10.00 to 35.00%, moreover, Sn: more than 0 to 0.1000%, Zn: more than 0 to 0.0100%, Pb: more than 0 to 0.0100%, Sb: more than 0 to 0.0100%, As: more than 0 to 0.0010%, and Bi: contains one or more selected from the group consisting of more than 0 to 0.0010%, moreover, Cu: more than 0 to 5.00%, Mo: more than 0 to 20.00%, Co: more than 0 to 3.00%, W: more than 0 to 7.00%, Ti: more than 0 to 1.00%, Nb: more than 0 to
  • Fn1 177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
  • Fn2 (Sn+Zn+Pb+Sb+As+Bi) ⁇ 10 3 (2)
  • the content in mass % of the corresponding element is substituted for the element symbol in the formula, and if the element is not contained, "0" is substituted for the corresponding element symbol.
  • the austenitic alloy material of the present disclosure has excellent nitriding resistance in a high-temperature ammonia environment.
  • Figure 1 shows Fn1 and nitrided layer depth ( ⁇ m ) is a graph showing the relationship between
  • the present inventors investigated alloy materials that can provide excellent nitriding resistance when used in a high-temperature ammonia environment.
  • the present inventors investigated elements that enhance nitriding resistance in a high-temperature ammonia environment.
  • Mn, Cu, Cr, Ni, and Mo increase the nitriding resistance of the alloy material in a high-temperature ammonia environment, while Si decreases the nitriding resistance of the alloy material in a high-temperature ammonia environment. found out.
  • alloy materials were investigated from the viewpoint of chemical composition, taking into consideration the nitriding resistance improving elements (Mn, Cu, Cr, Ni, and Mo) and the nitriding resistance decreasing element (Si) mentioned above.
  • the present inventors found that, in mass %, C: more than 0 to 0.200%, Si: more than 0 to 3.00%, Mn: more than 0 to 3.00%, P: more than 0 to 0. 050%, S: more than 0 to 0.050%, Ni: 40.00 to 80.00%, Cr: 10.00 to 35.00%, and further Sn: more than 0 to 0.1000%.
  • the present inventors discovered that the content of the above-mentioned nitriding resistance improving elements (Mn, Cu, Cr, Ni, and Mo) and the content of the nitriding resistance decreasing element (Si) have a predetermined relationship. We thought that nitriding resistance in a high-temperature ammonia environment would be improved if the conditions were met. Therefore, the present inventors determined that the content of nitriding resistance improving elements (Mn, Cu, Cr, Ni, and Mo) and nitriding resistance decreasing elements (Si) in an austenitic alloy material satisfying the above chemical composition, The relationship between the depth of the nitrided layer in a high-temperature ammonia environment was investigated.
  • Figure 1 shows Fn1 and nitrided layer depth ( ⁇ m ) is a graph showing the relationship between FIG. 1 was created based on data obtained in Examples described below.
  • the alloy material is held at 600°C for 25 hours in an atmosphere of 100% ammonia.
  • the depth of the nitrided layer in this case exceeds 30.0 ⁇ m.
  • Fn1 is less than 20
  • the depth of the nitrided layer is 15.0 ⁇ m or less when held at 600° C. for 25 hours in a 100% ammonia atmosphere, and the nitriding resistance is significantly increased.
  • an austenitic alloy material having the above-mentioned chemical composition and Fn1 of less than 20 can provide excellent nitriding resistance in a high-temperature ammonia environment.
  • an austenitic alloy material having the above-mentioned chemical composition and Fn1 of less than 20 intergranular cracking may occur in the surface layer of the alloy material in a high-temperature ammonia environment, as a new problem.
  • the present inventors further investigated means for suppressing the occurrence of intergranular cracking in a high-temperature ammonia environment in an austenitic alloy material having the above-mentioned chemical composition and Fn1 of less than 20.
  • Fn2 defined by formula (2) is higher than 21 and less than 50, it can be used in a high-temperature ammonia environment. It has been found that excellent nitriding resistance can be obtained and that the occurrence of intergranular cracking in the surface layer can be sufficiently suppressed.
  • Fn2 (Sn+Zn+Pb+Sb+As+Bi) ⁇ 10 3 (2)
  • the content in mass % of the corresponding element is substituted for the element symbol in the formula, and if the element is not contained, "0" is substituted for the corresponding element symbol.
  • Fn2 is higher than 21 and less than 50, on the premise that Fn1 is less than 20, it is possible to sufficiently suppress the occurrence of intergranular cracking in the surface layer of the austenitic alloy material in a high-temperature ammonia environment.
  • intergranular cracking in the surface layer is suppressed by a mechanism different from the one described above.
  • Fn1 is less than 20
  • Fn2 is higher than 21 and less than 50
  • grain boundary cracking in the surface layer is sufficiently suppressed in a high-temperature ammonia environment, as shown in the examples described below. It has been proven.
  • the austenitic alloy material of this embodiment was completed.
  • the austenitic alloy material of this embodiment has the following configuration.
  • the austenitic alloy material with the first configuration is The chemical composition is in mass%, C: more than 0 to 0.200%, Si: more than 0 to 3.00%, Mn: more than 0 to 3.00%, P: more than 0 to 0.050%, S: more than 0 to 0.050%, Ni: 40.00 to 80.00%, and Contains Cr: 10.00 to 35.00%, moreover, Sn: more than 0 to 0.1000%, Zn: more than 0 to 0.0100%, Pb: more than 0 to 0.0100%, Sb: more than 0 to 0.0100%, As: more than 0 to 0.0010%, and Bi: contains one or more selected from the group consisting of more than 0 to 0.0010%, moreover, Cu: more than 0 to 5.00%, Mo: more than 0 to 20.00%, Co: more than 0 to 3.00%, W: more than 0 to 7.00%, Ti: more than 0 to 1.00%, Nb: more than 0 to
  • Fn1 177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
  • Fn2 (Sn+Zn+Pb+Sb+As+Bi) ⁇ 10 3 (2)
  • the content in mass % of the corresponding element is substituted for the element symbol in the formula, and if the element is not contained, "0" is substituted for the corresponding element symbol.
  • the austenitic alloy material with the second configuration is An austenitic alloy material having a first configuration
  • Fn3 defined by formula (3) is higher than 0.20
  • Fn4 defined by formula (4) is 1000 to 5000.
  • Fn3 Fn2/D ave (3)
  • Fn4 Fn2 ⁇ D ave (4)
  • the austenitic alloy material with the third configuration is An austenitic alloy material having a first configuration or a second configuration,
  • the chemical composition is in mass%, C: more than 0 to 0.050%, Si: more than 0 to 0.50%, Mn: more than 0 to 0.50%, P: more than 0 to 0.025%, S: more than 0 to 0.010%, Cu: 2.00-4.00%, Ni: 44.00-50.00%, Cr: 20.00-25.00%, Mo: 5.00-7.00%, W: 2.00 to 5.00%, and Contains Fe: 12.00 to 20.00%.
  • the austenitic alloy material with the fourth configuration is An austenitic alloy material having a first configuration or a second configuration,
  • the chemical composition is in mass%, C: more than 0 to 0.150%, Si: 1.00-2.50%, Mn: more than 0 to 1.00%, P: more than 0 to 0.010%, S: more than 0 to 0.010%, Cu: 1.50-3.00%, Cr: 28.00-32.00%, Mo: 1.00-3.00%, Ti: more than 0 to 1.00%, and Contains Fe: 2.00 to 6.00%.
  • the austenitic alloy material with the fifth configuration is An austenitic alloy material having a first configuration or a second configuration,
  • the chemical composition is in mass%, C: more than 0 to 0.050%, Si: more than 0 to 0.50%, Mn: more than 0 to 0.50%, P: more than 0 to 0.030%, S: more than 0 to 0.015%, Cu: more than 0 to 0.50%, Cr: 27.00-31.00%, Fe: 7.00 to 15.00%, and Contains Ni: 58.00 to 80.00%.
  • the austenitic alloy material of this embodiment will be described in detail. Note that “%” regarding elements means mass % unless otherwise specified. In the following description, the austenitic alloy material is also simply referred to as "alloy material.”
  • the austenitic alloy material of this embodiment includes the following features.
  • Feature 1 The chemical composition is in mass%, C: more than 0 to 0.200%, Si: more than 0 to 3.00%, Mn: more than 0 to 3.00%, P: more than 0 to 0.050%, S: Contains more than 0 to 0.050%, Ni: 40.00 to 80.00%, Cr: 10.00 to 35.00%, and further contains Sn: more than 0 to 0.1000%, Zn: more than 0.
  • Fn1 defined by formula (1) is less than 20.
  • Fn1 177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
  • the content in mass % of the corresponding element is substituted for the element symbol in formula (1). If an element is not contained, "0" is assigned to the corresponding element symbol.
  • Fn2 defined by formula (2) is higher than 21 and lower than 50.
  • Fn2 (Sn+Zn+Pb+Sb+As+Bi) ⁇ 10 3 (2)
  • the content in mass % of the corresponding element is substituted for the element symbol in formula (2). If an element is not contained, "0" is assigned to the corresponding element symbol.
  • the chemical composition of the austenitic alloy material according to this embodiment contains the following elements.
  • C More than 0 to 0.200% Carbon (C) generates fine carbides during use of alloy materials in a high-temperature ammonia environment, increasing creep strength. However, if the C content exceeds 0.200%, carbides are excessively generated at grain boundaries in a high-temperature ammonia environment. In this case, even if the contents of other elements are within the range of this embodiment, intergranular cracks are likely to occur on the surface of the alloy material. Therefore, the C content is greater than 0 to 0.200%.
  • the preferable lower limit of the C content is 0.001%, more preferably 0.005%, still more preferably 0.010%, and still more preferably 0.020%.
  • a preferable upper limit of the C content is 0.180%, more preferably 0.160%, and still more preferably 0.150%.
  • the preferable range of the C content is, for example, 0.001 to 0.180%, more preferably 0.005 to 0.160%, even more preferably 0.010 to 0.150%, and even more preferably is 0.020 to 0.150%.
  • Si more than 0 to 3.00% Silicon (Si) deoxidizes the alloy. Si further increases the oxidation resistance of the alloy material in a high temperature ammonia environment. However, if the Si content exceeds 3.00%, intergranular cracking may occur in a high-temperature ammonia environment even if the contents of other elements are within the range of this embodiment. Therefore, the Si content is greater than 0 to 3.00%.
  • the preferable lower limit of the Si content is 0.01%, more preferably 0.05%, still more preferably 0.10%, and still more preferably 0.30%.
  • a preferable upper limit of the Si content is 2.80%, more preferably 2.70%, and still more preferably 2.60%.
  • the preferable range of the Si content is, for example, 0.01 to 2.80%, more preferably 0.05 to 2.70%, still more preferably 0.10 to 2.60%, and even more preferably is 0.30 to 2.60%.
  • Mn more than 0 to 3.00%
  • Manganese (Mn) increases the nitriding resistance of alloy materials in high-temperature ammonia environments. However, if the Mn content exceeds 3.00%, the creep ductility of the alloy material decreases in a high-temperature ammonia environment even if the other element contents are within the ranges of this embodiment. Furthermore, the toughness of the alloy material decreases. Therefore, the Mn content is greater than 0 to 3.00%.
  • the preferable lower limit of the Mn content is 0.01%, more preferably 0.05%, still more preferably 0.10%, and still more preferably 0.30%.
  • a preferable upper limit of the Mn content is 2.80%, more preferably 2.50%, still more preferably 2.00%, and still more preferably 1.50%.
  • the preferable range of the Mn content is, for example, 0.01 to 2.80%, more preferably 0.05 to 2.50%, even more preferably 0.10 to 2.00%, and even more preferably is 0.30 to 1.50%.
  • Phosphorus (P) is an impurity. If the P content exceeds 0.050%, P segregates at grain boundaries in a high-temperature ammonia environment. Therefore, even if the contents of other elements are within the range of this embodiment, intergranular cracking may occur in the alloy material in a high-temperature ammonia environment. Therefore, the P content is greater than 0 to 0.050%. It is preferable that the P content is as low as possible. However, excessive reduction in P content significantly increases manufacturing costs. Therefore, when considering industrial production, the preferable lower limit of the P content is 0.001%, more preferably 0.002%, and still more preferably 0.005%.
  • a preferable upper limit of the P content is 0.045%, more preferably 0.042%, and still more preferably 0.040%.
  • the preferable range of the P content is, for example, 0.001 to 0.045%, more preferably 0.002 to 0.042%, and still more preferably 0.005 to 0.040%.
  • S More than 0 to 0.050% Sulfur (S) is an impurity. If the S content exceeds 0.050%, S will segregate at grain boundaries in a high-temperature ammonia environment. Therefore, even if the contents of other elements are within the range of this embodiment, intergranular cracking may occur in the alloy material in a high-temperature ammonia environment. Therefore, the S content is greater than 0 to 0.050%. It is preferable that the S content is as low as possible. However, excessive reduction in S content significantly increases manufacturing costs. Therefore, when considering industrial production, the preferable lower limit of the S content is 0.001%, more preferably 0.002%, and still more preferably 0.005%.
  • a preferable upper limit of the S content is 0.045%, more preferably 0.040%, and still more preferably 0.035%.
  • the preferable range of the S content is, for example, 0.001 to 0.045%, more preferably 0.002 to 0.040%, and still more preferably 0.005 to 0.035%.
  • Ni 40.00-80.00%
  • Nickel (Ni) increases the nitriding resistance of the alloy material in a high-temperature ammonia environment. If the Ni content is less than 40.00%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment. On the other hand, if the Ni content exceeds 80.00%, intergranular cracking may occur in a high-temperature ammonia environment even if the contents of other elements are within the range of this embodiment. Therefore, the Ni content is 40.00 to 80.00%.
  • the preferable lower limit of the Ni content is 43.00%, more preferably 45.00%, still more preferably 50.00%, and even more preferably 55.00%.
  • a preferable upper limit of the Ni content is 75.00%, more preferably 70.00%, still more preferably 65.00%, and still more preferably 60.00%.
  • the preferable range of the Ni content is, for example, 43.00 to 75.00%, more preferably 45.00 to 70.00%, still more preferably 50.00 to 65.00%, and even more preferably is 55.00 to 60.00%.
  • Chromium (Cr) increases the nitriding resistance of the alloy material in a high-temperature ammonia environment. If the Cr content is less than 10.00%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment. On the other hand, if the Cr content exceeds 35.00%, the creep strength of the alloy material in a high-temperature ammonia environment will decrease even if the contents of other elements are within the ranges of this embodiment. Therefore, the Cr content is between 10.00 and 35.00%.
  • the lower limit of the Cr content is preferably 12.00%, more preferably 15.00%, and still more preferably 18.00%.
  • a preferable upper limit of the Cr content is 33.00%, more preferably 32.00%, still more preferably 31.00%, and still more preferably 30.00%.
  • the preferred range of the Cr content is, for example, 12.00 to 33.00%, more preferably 15.00 to 32.00%, even more preferably 18.00 to 31.00%, even more preferably is 18.00 to 30.00%.
  • the austenitic alloy material of this embodiment further contains the first group.
  • Sn more than 0 to 0.1000%
  • Zn more than 0 to 0.0100%
  • Pb more than 0 to 0.0100%
  • Sb more than 0 to 0.0100%
  • Bi one or more selected from the group consisting of more than 0 to 0.0010% Sn, Zn, Pb, Sb, As, and Bi all cause intergranular cracking near the surface layer of the alloy material in a high-temperature ammonia environment. suppress.
  • Each element of the first group will be explained below.
  • Tin (Sn) may not be contained. That is, the Sn content may be 0%.
  • Sn segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment.
  • the segregated Sn suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Sn is contained, the above effects can be obtained to some extent.
  • the Sn content is greater than 0 to 0.1000%.
  • the preferable lower limit of the Sn content is 0.0001%, more preferably 0.0002%, and still more preferably 0.0003%.
  • a preferable upper limit of the Sn content is 0.0700%, more preferably 0.0500%, and still more preferably 0.0450%.
  • the preferable range of Sn content is, for example, 0.0001 to 0.0700%, more preferably 0.0002 to 0.0500%, and still more preferably 0.0003 to 0.0450%.
  • Zinc (Zn) may not be contained. That is, the Zn content may be 0%.
  • Zn When Zn is contained, that is, when the Zn content is more than 0%, Zn segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment. The segregated Zn suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Zn is contained, the above effects can be obtained to some extent.
  • the Zn content is greater than 0 to 0.0100%.
  • the lower limit of the Zn content is preferably 0.0001%, more preferably 0.0010%, and still more preferably 0.0020%.
  • a preferable upper limit of the Zn content is 0.0095%, more preferably 0.0090%, and still more preferably 0.0080%.
  • the preferred range of Zn content is, for example, 0.0001 to 0.0095%, more preferably 0.0010 to 0.0090%, and even more preferably 0.0020 to 0.0080%.
  • Pb more than 0 to 0.0100%
  • Lead (Pb) may not be contained. That is, the Pb content may be 0%.
  • Pb segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment.
  • the segregated Pb suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Pb is contained, the above effects can be obtained to some extent.
  • the Pb content is greater than 0 to 0.0100%.
  • the preferable lower limit of the Pb content is 0.0001%, more preferably 0.0010%, and still more preferably 0.0020%.
  • a preferable upper limit of the Pb content is 0.0090%, more preferably 0.0080%, and still more preferably 0.0070%.
  • the preferred range of the Pb content is, for example, 0.0001 to 0.0090%, more preferably 0.0010 to 0.0080%, and still more preferably 0.0020 to 0.0070%.
  • Sb more than 0 to 0.0100%
  • Antimony (Sb) may not be contained. That is, the Sb content may be 0%.
  • Sb segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment.
  • the segregated Sb suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Sb is contained, the above effects can be obtained to some extent.
  • the Sb content is greater than 0 to 0.0100%.
  • the preferable lower limit of the Sb content is 0.0001%, more preferably 0.0010%, and still more preferably 0.0015%.
  • a preferable upper limit of the Sb content is 0.0090%, more preferably 0.0080%, and still more preferably 0.0070%.
  • the preferable range of the Sb content is, for example, 0.0001 to 0.0090%, more preferably 0.0010 to 0.0080%, and still more preferably 0.0015 to 0.0070%.
  • Arsenic (As) may not be contained. That is, the As content may be 0%. When it is contained, that is, when the As content is more than 0%, As is segregated at grain boundaries during use of the alloy material in a high-temperature ammonia environment. The segregated As suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of As is contained, the above effects can be obtained to some extent.
  • the As content is greater than 0 to 0.0010%.
  • the lower limit of the As content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.
  • a preferable upper limit of the As content is 0.0009%, more preferably 0.0008%, and even more preferably 0.0007%.
  • the preferable range of the As content is, for example, 0.0001 to 0.0009%, more preferably 0.0002 to 0.0008%, and still more preferably 0.0003 to 0.0007%.
  • Bi more than 0 to 0.0010% Bismuth (Bi) may not be contained. That is, the Bi content may be 0%.
  • Bi When Bi is contained, that is, when the Bi content exceeds 0%, Bi segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment.
  • the segregated Bi suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Bi is contained, the above effects can be obtained to some extent.
  • the Bi content is greater than 0 to 0.0010%.
  • the preferable lower limit of the Bi content is 0.0001%, more preferably 0.0002%, and still more preferably 0.0003%.
  • a preferable upper limit of the Bi content is 0.0009%, more preferably 0.0008%, and still more preferably 0.0007%.
  • the preferred range of Bi content is, for example, 0.0001 to 0.0009%, more preferably 0.0002 to 0.0008%, and even more preferably 0.0003 to 0.0007%.
  • the austenitic alloy material of this embodiment further contains one or more selected from the group consisting of the second group to the fourth group.
  • Cu more than 0 to 5.00% Copper (Cu) may not be contained. That is, the Cu content may be 0%. When contained, that is, when the Cu content is more than 0%, Cu increases the nitriding resistance of the alloy material in a high-temperature ammonia environment. If even a small amount of Cu is contained, the above effects can be obtained to some extent. However, if the Cu content exceeds 5.00%, the creep ductility of the alloy material in a high-temperature ammonia environment decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Cu content is greater than 0 to 5.00%.
  • the preferable lower limit of the Cu content is 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.50%, and even more preferably 1.00%. %, more preferably 1.50%.
  • the upper limit of the Cu content is preferably 4.50%, more preferably 4.00%, even more preferably 3.50%, still more preferably 3.00%, and even more preferably 2.50%. %.
  • the preferable range of the Cu content is, for example, 0.01 to 4.50%, more preferably 0.05 to 4.00%, still more preferably 0.10 to 3.50%, and even more preferably is 0.50 to 3.00%, more preferably 1.00 to 2.50%, even more preferably 1.50 to 2.50%.
  • Mo more than 0 to 20.00% Molybdenum (Mo) may not be contained. That is, the Mo content may be 0%. When contained, that is, when the Mo content is more than 0%, Mo increases the nitriding resistance of the alloy material in a high-temperature ammonia environment. If even a small amount of Mo is contained, the above effects can be obtained to some extent. However, if the Mo content exceeds 20.00%, the hot workability of the alloy material will decrease even if the contents of other elements are within the ranges of this embodiment. Therefore, the Mo content is greater than 0 to 20.00%.
  • the lower limit of the Mo content is preferably 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.50%, and still more preferably 1.00%. %, more preferably 1.50%, further preferably 3.00%, still more preferably 5.00%, still more preferably 8.00%.
  • a preferable upper limit of the Mo content is 18.00%, more preferably 16.00%, and still more preferably 14.00%.
  • the preferred range of Mo content is, for example, 0.01 to 18.00%, more preferably 0.05 to 16.00%, even more preferably 0.10 to 14.00%, and even more preferably is 0.50 to 14.00%, more preferably 1.00 to 14.00%, even more preferably 1.50 to 14.00%, even more preferably 3.00 to 14.00%. %, more preferably 5.00 to 14.00%, even more preferably 8.00 to 14.00%.
  • Co, W, Ti, Nb, V, B, N, and rare earth elements Co, W, Ti, Nb, V, B, N, and rare earth elements (REM) all increase the creep strength of the alloy material in a high temperature ammonia environment. Each element will be explained below.
  • Co more than 0 to 3.00% Cobalt (Co) may not be contained. That is, the Co content may be 0%.
  • Co When Co is contained, that is, when the Co content is more than 0%, Co dissolves in the alloy material and increases the creep strength of the alloy material in a high-temperature ammonia environment. If even a small amount of Co is contained, the above effects can be obtained to some extent. However, if the Co content exceeds 3.00%, the effect will be saturated and the manufacturing cost will increase. Therefore, the Co content is greater than 0 to 3.00%.
  • the preferable lower limit of the Co content is 0.01%, more preferably 0.05%, still more preferably 0.10%, and still more preferably 0.15%.
  • a preferable upper limit of the Co content is 2.80%, more preferably 2.50%, and still more preferably 2.00%.
  • the preferable range of the Co content is, for example, 0.01 to 2.80%, more preferably 0.05 to 2.50%, still more preferably 0.10 to 2.00%, even more preferably is 0.15 to 2.00%.
  • W More than 0 to 7.00% Tungsten (W) may not be contained. That is, the W content may be 0%.
  • W When W is contained, that is, when the W content is more than 0%, W is dissolved in the alloy material and increases the creep strength of the alloy material in a high-temperature ammonia environment. W also forms precipitates during use of the alloy material in a high temperature ammonia environment, increasing the creep strength of the alloy material in a high temperature ammonia environment. If even a small amount of W is contained, the above effects can be obtained to some extent. However, if the W content exceeds 7.00%, the hot workability of the alloy material decreases even if the contents of other elements are within the ranges of this embodiment.
  • the W content is greater than 0 to 7.00%.
  • the lower limit of the W content is preferably 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.50%, and still more preferably 1.00%. %, more preferably 2.00%.
  • the upper limit of the W content is preferably 6.50%, more preferably 6.00%, even more preferably 5.50%, even more preferably 5.00%, and still more preferably 4.50%. %, more preferably 4.00%, still more preferably 3.50%.
  • the preferable range of the W content is, for example, 0.01 to 6.50%, more preferably 0.05 to 6.00%, still more preferably 0.10 to 5.50%, and even more preferably is 0.50 to 5.00%, more preferably 1.00 to 4.50%, even more preferably 2.00 to 4.00%, even more preferably 2.00 to 3.50%. %.
  • Titanium (Ti) may not be contained. That is, the Ti content may be 0%. When contained, that is, when the Ti content is more than 0%, Ti generates precipitates during use of the alloy material in a high-temperature ammonia environment, increasing the creep strength of the alloy material in a high-temperature ammonia environment. . If even a small amount of Ti is contained, the above effects can be obtained to some extent. However, if the Ti content exceeds 1.00%, the Ti precipitates will become coarse even if the contents of other elements are within the range of this embodiment. In this case, the creep strength and toughness of the alloy material decrease. Therefore, the Ti content is greater than 0 to 1.00%.
  • the lower limit of the Ti content is preferably 0.01%, more preferably 0.02%, even more preferably 0.05%, and still more preferably 0.10%.
  • the preferable upper limit of the Ti content is 0.90%, more preferably 0.80%, even more preferably 0.70%, still more preferably 0.60%, and even more preferably 0.50%. %, more preferably 0.45%, still more preferably 0.40%, still more preferably 0.35%, still more preferably 0.30%.
  • the preferable range of the Ti content is, for example, 0.01 to 0.90%, more preferably 0.02 to 0.80%, still more preferably 0.05 to 0.70%, and even more preferably is 0.10 to 0.60%, more preferably 0.10 to 0.50%, even more preferably 0.10 to 0.45%, even more preferably 0.10 to 0.40 %, more preferably 0.10 to 0.35%, even more preferably 0.10 to 0.30%.
  • Niobium (Nb) may not be contained. That is, the Nb content may be 0%. When contained, that is, when the Nb content is more than 0%, Nb generates precipitates during use of the alloy material in a high-temperature ammonia environment, increasing the creep strength of the alloy material in a high-temperature ammonia environment. . If even a small amount of Nb is contained, the above effects can be obtained to some extent. However, if the Nb content exceeds 0.10%, Nb precipitates become coarse. In this case, even if the content of other elements is within the range of this embodiment, the creep strength and toughness of the alloy material decrease. Therefore, the Nb content is greater than 0 to 0.10%.
  • the lower limit of the Nb content is preferably 0.01%, more preferably 0.02%, and still more preferably 0.03%.
  • a preferable upper limit of the Nb content is 0.09%, more preferably 0.08%, and still more preferably 0.07%.
  • the preferred range of the Nb content is, for example, 0.01 to 0.09%, more preferably 0.02 to 0.08%, and still more preferably 0.03 to 0.07%.
  • V More than 0 to 0.50% Vanadium (V) may not be contained. That is, the V content may be 0%. When contained, that is, when the V content is more than 0%, V generates precipitates during use of the alloy material in a high-temperature ammonia environment, increasing the creep strength of the alloy material in a high-temperature ammonia environment. . If even a small amount of V is contained, the above effects can be obtained to some extent. However, if the V content exceeds 0.50%, V precipitates become coarse. In this case, even if the content of other elements is within the range of this embodiment, the creep strength and toughness of the alloy material decrease. Therefore, the V content is greater than 0 to 0.50.
  • the lower limit of the V content is preferably 0.01%, more preferably 0.05%, and even more preferably 0.10%.
  • a preferable upper limit of the V content is 0.45%, more preferably 0.40%, and still more preferably 0.35%.
  • the preferable range of the V content is, for example, 0.01 to 0.45%, more preferably 0.05 to 0.40%, and still more preferably 0.10 to 0.35%.
  • B More than 0 to 0.0050% Boron (B) may not be contained. That is, the B content may be 0%.
  • B When B is contained, that is, when the B content is more than 0%, B segregates to the grain boundaries in a high-temperature ammonia environment and strengthens the grain boundaries. Therefore, the creep strength of the alloy material increases in a high-temperature ammonia environment. If even a small amount of B is contained, the above effects can be obtained to some extent. However, if the B content exceeds 0.0050%, the hot workability and weldability of the alloy material will deteriorate even if the contents of other elements are within the ranges of this embodiment. Therefore, the B content is greater than 0 to 0.0050%.
  • the preferable lower limit of the B content is 0.0001%, more preferably 0.0002%, and still more preferably 0.0005%.
  • a preferable upper limit of the B content is 0.0045%, more preferably 0.0040%, and still more preferably 0.0035%.
  • the preferable range of the B content is, for example, 0.0001 to 0.0045%, more preferably 0.0002 to 0.0040%, and still more preferably 0.0005 to 0.0035%.
  • N More than 0 to 0.200% Nitrogen (N) may not be contained. In other words, it does not need to be contained. That is, the N content may be 0%.
  • N When N is contained, that is, when the N content is more than 0%, N is dissolved in the alloy material and increases the creep strength of the alloy material in a high-temperature ammonia environment. Furthermore, N forms precipitates during use of the alloy material in a high temperature ammonia environment, increasing the creep strength of the alloy material in a high temperature ammonia environment. If even a small amount of N is contained, the above effects can be obtained to some extent.
  • the N content is greater than 0 to 0.200%.
  • the preferable lower limit of the N content is 0.001%, more preferably 0.005%, and still more preferably 0.010%.
  • a preferable upper limit of the N content is 0.190%, more preferably 0.160%, still more preferably 0.140%, and still more preferably 0.120%.
  • the preferred range of the N content is, for example, 0.001 to 0.190%, more preferably 0.005 to 0.160%, even more preferably 0.010 to 0.140%, and even more preferably is 0.010 to 0.120%.
  • Rare earth elements more than 0 to 0.100%
  • Rare earth elements (REM) may not be contained. That is, the REM content may be 0%. When contained, that is, when the REM content is more than 0%, REM segregates to the grain boundaries in a high-temperature ammonia environment and strengthens the grain boundaries. Therefore, the creep strength of the alloy material increases in a high-temperature ammonia environment. If even a small amount of REM is contained, the above effects can be obtained to some extent. However, if the REM content exceeds 0.100%, inclusions such as oxides will be formed in the alloy material. Therefore, even if the contents of other elements are within the range of this embodiment, the creep strength of the alloy material decreases.
  • the REM content is greater than 0 to 0.100%.
  • the lower limit of the REM content is preferably 0.001%, more preferably 0.005%, and still more preferably 0.010%.
  • a preferable upper limit of the REM content is 0.090%, more preferably 0.070%, and still more preferably 0.055%.
  • the preferable range of the REM content is, for example, 0.001 to 0.090%, more preferably 0.005 to 0.070%, and still more preferably 0.010 to 0.055%.
  • REM in this specification contains one or more selected from the group consisting of Sc, Y, and lanthanoids (La with atomic number 57 to Lu with atomic number 71), and the REM content is defined as the content of these elements. Means total content (mass%).
  • Al more than 0 to 0.500%
  • Aluminum (Al) may not be contained. That is, the Al content may be 0%.
  • Al When Al is contained, that is, when the Al content is more than 0%, Al deoxidizes the alloy in the manufacturing process of the alloy material. If even a small amount of Al is contained, the above effects can be obtained to some extent. However, if the Al content exceeds 0.500%, even if the contents of other elements are within the ranges of this embodiment, inclusions will be excessively generated and the creep strength and toughness of the alloy material will be reduced. Therefore, the Al content is greater than 0 to 0.500%.
  • the lower limit of the Al content is preferably 0.001%, more preferably 0.005%, and still more preferably 0.010%.
  • a preferable upper limit of the Al content is 0.450%, more preferably 0.400%, still more preferably 0.350%, and still more preferably 0.300%.
  • the preferable range of the Al content is, for example, 0.001 to 0.450%, more preferably 0.005 to 0.400%, still more preferably 0.010 to 0.350%, and even more preferably is 0.010 to 0.300%.
  • Ca more than 0 to 0.0100% Calcium (Ca) may not be contained. That is, the Ca content may be 0%. When contained, that is, when the Ca content is more than 0%, Ca deoxidizes the alloy in the manufacturing process of the alloy material. If even a small amount of Ca is contained, the above effects can be obtained to some extent. However, if the Ca content exceeds 0.0100%, even if the contents of other elements are within the ranges of this embodiment, inclusions will be excessively generated and the creep strength and toughness of the alloy material will be reduced. Therefore, the Ca content is greater than 0 to 0.0100%.
  • the lower limit of the Ca content is preferably 0.0001%, more preferably 0.0005%, and still more preferably 0.0010%.
  • a preferable upper limit of the Ca content is 0.0090%, more preferably 0.0080%, still more preferably 0.0070%, and still more preferably 0.0060%.
  • the preferred range of Ca content is, for example, 0.0001 to 0.0090%, more preferably 0.0005 to 0.0080%, still more preferably 0.0010 to 0.0070%, and even more preferably is 0.0010 to 0.0060%.
  • Mg more than 0 to 0.0150%
  • Magnesium (Mg) may not be contained. That is, the Mg content may be 0%.
  • Mg deoxidizes the alloy in the manufacturing process of the alloy material. If even a small amount of Mg is contained, the above effects can be obtained to some extent.
  • the Mg content exceeds 0.0150%, even if the contents of other elements are within the ranges of this embodiment, inclusions will be excessively generated and the creep strength and toughness of the alloy material will be reduced. Therefore, the Mg content is greater than 0 to 0.0150%.
  • the preferable lower limit of the Mg content is 0.0001%, more preferably 0.0005%, and still more preferably 0.0010%.
  • a preferable upper limit of the Mg content is 0.0140%, more preferably 0.0120%, still more preferably 0.0100%, and still more preferably 0.0080%.
  • the preferred range of Mg content is, for example, 0.0001 to 0.0140%, more preferably 0.0005 to 0.0120%, still more preferably 0.0010 to 0.0100%, and even more preferably is 0.0010 to 0.0080%.
  • the remainder of the chemical composition of the austenitic alloy material according to this embodiment consists of Fe and impurities.
  • impurities in the chemical composition are those that are mixed in from raw materials such as ore, scrap, or the manufacturing environment when industrially manufacturing austenitic alloy materials, and are unintentionally contained. This means an acceptable value within a range that does not adversely affect the austenitic alloy material according to the present embodiment.
  • the Fe content is greater than 0 to 30.00%. Specifically, Fe improves the hot workability of Ni-based alloys. If the Fe content is too low, the above effects cannot be sufficiently obtained. On the other hand, if the Fe content is too high, the corrosion resistance of the Ni-based alloy will decrease. Therefore, preferably the Fe content is greater than 0 to 30.00%.
  • the preferable lower limit of the Fe content is 0.01%, more preferably 0.20%, even more preferably 0.40%, and still more preferably 0.50%.
  • the preferable upper limit of the Fe content is 29.00%, more preferably 27.00%, still more preferably 25.00%, and still more preferably 23.00%.
  • the preferred range of Fe content is, for example, 0.01 to 29.00%, more preferably 0.20 to 27.00%, even more preferably 0.40 to 25.00%, and even more preferably It is 0.50 to 23.00%.
  • the chemical composition of the austenitic alloy material of this embodiment is one of the following first to third chemical compositions.
  • First chemical composition A chemical composition that satisfies characteristic 1, and C: 0.050% or less, Si: 0.01 to 0.50%, Mn: 0.01 to 0.50%, P: 0.025% or less, S: 0.010% or less, Cu: 2.00 to 4.00%, Ni: 44.00 to 50.00%, Cr: 20.00 to 25.00%, Mo: 5.00 to 7.00 %, W: 2.00 to 5.00%, and Fe: 12.00 to 20.00%
  • second chemical composition A chemical composition that satisfies characteristic 1, and C: 0.150% or less, Si: 1.00 to 2.50%, Mn: 0.01 to 1.00%, P: 0.010% or less, S: 0.010% or less, Cu: 1.50 to 3.00%, Cr: 28.00 to 32.00%, Mo: 1.00 to 3.00%, Ti: 0.01 to 1.00 % and
  • Fn1 defined by formula (1) is less than 20.
  • Fn1 177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
  • the content in mass % of the corresponding element is substituted for the element symbol in formula (1). If an element is not contained, "0" is assigned to the corresponding element symbol.
  • Fn1 is an index regarding the nitriding resistance of the alloy material in a high-temperature ammonia environment.
  • Mn, Cu, Cr, Ni, and Mo improve the nitriding resistance of the austenitic alloy material in a high-temperature ammonia environment.
  • Si reduces the nitriding resistance of the austenitic alloy material in a high-temperature ammonia environment.
  • Fn1 is less than 20
  • the depth of the nitrided layer will be 15.0 ⁇ m or less when held at 600° C. for 25 hours in a 100% ammonia atmosphere. Therefore, when Fn1 is less than 20, excellent nitriding resistance can be obtained in an austenitic alloy material used in a high-temperature ammonia environment.
  • the upper limit of Fn1 is preferably 19, more preferably 18, even more preferably 17, even more preferably 16, still more preferably 13, and still more preferably 10.
  • Fn1 is 10 or less, the depth of the nitrided layer can be significantly reduced, and even better nitriding resistance can be obtained.
  • the lower limit of Fn1 is not particularly limited.
  • the lower limit of Fn1 is, for example, 1, and is, for example, 2.
  • Fn1 is, for example, 1 to 19, more preferably 2 to 18, even more preferably 2 to 17, still more preferably 2 to 16, still more preferably 2 to 13, and Preferably, it is 2 to 10.
  • the Fn1 value is an integer. That is, the Fn1 value is an integer obtained by rounding off the obtained value to the first decimal place.
  • Fn2 defined by formula (2) is higher than 21 and less than 50.
  • Fn2 (Sn+Zn+Pb+Sb+As+Bi) ⁇ 10 3 (2)
  • the content in mass % of the corresponding element is substituted for the element symbol in the formula. If an element is not contained, "0" is assigned to the corresponding element symbol.
  • Fn2 is an index related to intergranular cracking in the surface layer of an alloy material in a high-temperature ammonia environment. If Fn2 is 21 or less, intergranular cracking is likely to occur in the surface layer of the alloy material in a high-temperature ammonia environment even if the alloy material satisfies Features 1 and 2. On the other hand, if Fn2 is 50 or more, Sn, Zn, Pb, Sb, As, and Bi are excessively segregated at grain boundaries, and the grain boundary strength is rather reduced. Therefore, even if the alloy material satisfies Features 1 and 2, intergranular cracking is likely to occur in the surface layer of the alloy material in a high-temperature ammonia environment.
  • Fn2 is higher than 21 and less than 50, it is possible to sufficiently suppress the occurrence of intergranular cracking in the surface layer of the alloy material in a high-temperature ammonia environment, provided that the alloy material satisfies Features 1 and 2. .
  • the lower limit of Fn2 is preferably 22, more preferably 24, and still more preferably 26.
  • the lower limit of Fn2 is preferably 48, more preferably 46, and still more preferably 44.
  • the preferred range of Fn2 is, for example, 22-48, more preferably 24-46, and even more preferably 26-44.
  • the Fn2 value is an integer. That is, the Fn2 value is an integer obtained by rounding off the obtained value to the first decimal place.
  • the austenitic alloy material of this embodiment satisfies Features 1 to 3. Therefore, in the austenitic alloy material of this embodiment, excellent nitriding resistance is obtained during use in a high-temperature ammonia environment, and occurrence of intergranular cracking in the surface layer is sufficiently suppressed.
  • the shape of the austenitic alloy material of this embodiment is not particularly limited.
  • the austenitic alloy material of this embodiment may be an alloy tube, a rod-shaped solid material, or an alloy plate.
  • the alloy pipe may be a seamless pipe or a welded pipe.
  • the austenitic alloy material of this embodiment can be widely applied to applications where nitriding resistance is required.
  • the austenitic alloy material of this embodiment is suitable for high-temperature ammonia environments.
  • the austenitic alloy material of this embodiment can also be applied to other uses than the high-temperature ammonia environment.
  • the austenitic alloy material of this embodiment satisfies Features 1 to 3, and further satisfies the following Feature 4. (Feature 4)
  • Feature 4 When the average grain size in ⁇ m of the surface layer of the austenitic alloy material is defined as D ave , Fn3 defined by formula (3) is higher than 0.20, Fn4 defined by formula (4) is 1000 to 5000.
  • Fn3 Fn2/D ave (3)
  • Fn3 and Fn4 are indicators regarding intergranular cracking in the surface layer of the alloy material in a high-temperature ammonia environment.
  • the lower limit of Fn3 is preferably 0.21, more preferably 0.22, and still more preferably 0.23.
  • the upper limit of Fn3 is not particularly limited. However, when the austenitic alloy material satisfies Features 1 to 3, the upper limit of Fn3 is, for example, preferably 0.90, more preferably 0.85, and even more preferably 0.82.
  • the preferred range of Fn3 is, for example, 0.21 to 0.90, more preferably 0.22 to 0.85, and still more preferably 0.23 to 0.82.
  • the Fn3 value is the value obtained by rounding off the third decimal place of the obtained value to the second decimal place.
  • the lower limit of Fn4 is preferably 1100, more preferably 1200.
  • the upper limit of Fn4 is preferably 4,900, more preferably 4,600, and even more preferably 4,200.
  • the preferred range of Fn4 is, for example, 1,100 to 4,900, more preferably 1,200 to 4,600, and even more preferably 1,200 to 4,200. Note that the Fn4 value is an integer.
  • the average grain size D ave of the surface layer of the austenitic alloy material is measured by the following method.
  • a test piece is taken from a cross section (L cross section) parallel to the rolling direction of the austenitic alloy material.
  • the test piece has a rectangular observation surface consisting of a side with a length of 5 mm corresponding to the surface of the alloy material and a side with a length of 5 mm from the surface in the depth direction. That is, the observation surface is a 5 mm x 5 mm rectangle.
  • the size of the test piece other than the observation surface is not particularly limited.
  • the observation surface after mirror polishing is etched using a mixed acid of hydrochloric acid and nitric acid to reveal the microstructure.
  • Ten arbitrary visual fields of the observation surface after etching are observed using a 300x optical microscope. Each field of view is 1000 ⁇ m ⁇ 1000 ⁇ m.
  • the crystal grain size ( ⁇ m) is determined according to the cutting method described in JIS G 0551:2020.
  • the arithmetic mean value of the crystal grain sizes of the obtained 10 fields of view is defined as the average crystal grain size D ave ( ⁇ m) of the surface layer of the austenitic alloy material.
  • An example of the method for manufacturing the austenitic alloy material of this embodiment will be described.
  • An example of the method for manufacturing an austenitic alloy material according to the present embodiment includes a material preparation step, a hot working step, and a solution treatment step. Each process will be explained in detail.
  • an alloy satisfying Features 1 to 3 or Features 1 to 4 is melted.
  • the alloy may be melted by an electric furnace, an Ar-O 2 mixed gas bottom blowing decarburization furnace (AOD furnace), or a vacuum decarburization furnace (VOD furnace). good.
  • the melted alloy may be made into an ingot by an ingot method, or a slab, bloom, or billet by a continuous casting method. If necessary, the slab, bloom, or ingot may be bloomed and rolled to produce a billet.
  • a material (slab, bloom, or billet) is manufactured through the above steps.
  • Hot processing process In the hot working step, a well-known hot working is performed on the produced material to produce an intermediate alloy material.
  • the hot working may be hot forging, hot extrusion, or hot rolling.
  • the hot working method is not particularly limited, and may be any known method.
  • the Mannesmann method may be performed as hot working to produce a blank tube, which is an intermediate alloy material.
  • the Eugene-Séjournet method or the Erhardt push bench method (namely, hot extrusion) may be implemented as the hot processing to produce the raw pipe.
  • the produced raw pipe may be hot rolled using a mandrel mill, a reducer, a sizing mill, or the like.
  • solution treatment process a well-known solution treatment is performed on the intermediate alloy material manufactured in the hot working step.
  • the intermediate alloy material is charged into a heat treatment furnace, maintained at a desired temperature, and then rapidly cooled.
  • the solution treatment temperature is, for example, 1000 to 1300°C.
  • the crystal grain size can be adjusted by adjusting the rolling reduction rate in the hot working step and the solution treatment temperature in the solution treatment step.
  • the austenitic alloy material of this embodiment is manufactured by the above manufacturing method.
  • the method for manufacturing an austenitic alloy material according to the present embodiment may include steps other than those described above.
  • a cold working step may be performed on the intermediate alloy material after the hot working step and before the solution treatment step.
  • cold working is performed on the intermediate alloy material.
  • Cold working may be cold rolling or cold drawing. In this case, it can be processed into desired dimensions.
  • cold working may be performed on the intermediate alloy material after the solution treatment step. In this case, the strength of the austenitic alloy material increases.
  • the manufacturing method of an alloy tube was explained as an example of an austenitic alloy material.
  • the austenitic alloy material of this embodiment may have other shapes such as a rod shape or a plate shape.
  • the rod-shaped or plate-shaped manufacturing method includes, for example, a material preparation step, a hot working step, and a solution treatment step, and may further include a cold working step.
  • the above-described manufacturing method is just an example, and the austenitic alloy material of the present embodiment that satisfies Features 1 to 3 or Features 1 to 4 may be produced by other manufacturing methods.
  • the austenitic alloy material of this embodiment will be explained in more detail with examples.
  • the conditions in the following examples are examples of conditions adopted to confirm the feasibility and effects of the austenitic alloy material of this embodiment. Therefore, the austenitic alloy material of this embodiment is not limited to this one example condition.
  • the alloys of each test number were melted by high frequency vacuum melting method. Using the melted alloy, a 30 kg ingot was manufactured by an ingot forming method. The ingots of each test number were heated at 1200°C for 2 hours. Hot forging was performed on the heated ingot to produce a square material with a cross section of 50 mm x 55 mm. The obtained square material was heated at 1200° C. for 30 minutes and then hot rolled to produce a hot rolled material with a plate thickness of 15 mm. The obtained hot rolled material was cold rolled to produce an intermediate alloy material (alloy plate) with a thickness of 10.5 mm. The intermediate alloy material was subjected to solution treatment at a solution treatment temperature of 1150° C. for 10 minutes. Note that water cooling was used as the cooling method after being maintained at the solution treatment temperature. Through the above manufacturing process, austenitic alloy materials (alloy plates) of each test number were manufactured.
  • a test piece with a thickness of 3 mm, width of 15 mm, and length of 20 mm was cut out from the austenitic alloy material (alloy plate) of each test number. Buffing was performed on the surface of the test piece, and then the surface of the test piece was degreased.
  • the degreased test piece was suspended from a quartz jig using a stainless steel wire and placed in a box-shaped furnace. After charging the test piece, the furnace was maintained at 600° C. for 25 hours while atmospheric gas was passed through the furnace. The atmospheric gas was 100% ammonia. The flow rate of the atmospheric gas was 500 mL/min.
  • a test piece for tissue observation was prepared, including a cross section perpendicular to the longitudinal direction of the test piece and the surface of the test piece.
  • the above-mentioned cross section was used as the observation surface.
  • SEM scanning electron microscope
  • EDS analysis was performed in a rectangular field of view using an EDS device attached to the SEM device. Specifically, EDS analysis was performed in the depth direction from an arbitrary point corresponding to the surface of the test piece in a rectangular field of view.
  • nitrided layer depth ⁇ m
  • the obtained nitrided layer depth is shown in the "Nitrided layer depth ( ⁇ m)" column in Table 2.
  • the length of the void is the total length of the void along the grain boundary.
  • Test results The test results are shown in Table 1 (Table 1-1, Table 1-2) and Table 2. Referring to each table, the austenitic alloy materials of test numbers 1 to 43 satisfied characteristics 1 to 3. Therefore, the depth of the nitrided layer was 15.0 ⁇ m or less, and sufficient nitriding resistance was obtained in a high-temperature ammonia environment. Furthermore, intergranular cracking was suppressed in a high-temperature ammonia environment.
  • the austenitic alloy materials of test numbers 1 to 18 and test numbers 25 to 43 satisfied not only features 1 to 3 but also feature 4. Therefore, grain boundary cracking was sufficiently suppressed compared to Test Nos. 19 to 24, which did not satisfy Feature 4.
  • test number 44 the Si content was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
  • test number 45 the Ni content was too low. Therefore, in a high-temperature ammonia environment, the depth of the nitrided layer exceeded 15.0 ⁇ m, and sufficient nitriding resistance could not be obtained.
  • test number 46 the Ni content was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
  • test number 47 the Cr content was too low. As a result, in the high-temperature ammonia environment, the nitrided layer depth exceeded 15.0 ⁇ m, and sufficient nitridation resistance was not obtained.
  • test numbers 48 and 50 the Sb content was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
  • test number 49 the Pb content was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
  • test numbers 51 to 53 Fn1 was too high. Therefore, in a high-temperature ammonia environment, the depth of the nitrided layer exceeded 15.0 ⁇ m, and sufficient nitriding resistance could not be obtained.
  • test numbers 54 and 55 Fn2 was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
  • test numbers 56 to 58 Fn2 was too low. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.

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Abstract

Provided is an austenite alloy material having excellent nitriding resistance in a high-temperature ammonia environment. The austenite alloy material of the present disclosure contains, in mass%, C: more than 0 to 0.200%, Si: more than 0 to 3.00%, Mn: more than 0 to 3.00%, P: more than 0 to 0.050%, S: more than 0 to 0.050%, Ni: 40.00 to 80.00%, and Cr: 10.00 to 35.00%, also contains one or more selected from the group consisting of Sn, Zn, Pb, Sb, As, and Bi, also contains one or more selected from the group consisting of Cu, Mo, Co, W, Ti, Nb, V, B, N, rare earth elements, Al, Ca, and Mg, with the remainder comprising Fe and impurities. Fn1 is less than 20, and Fn2 is higher than 21 and less than 50.　Fn1=177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo Fn2=(Sn+Zn+Pb+Sb+As+Bi)×103

Description

オーステナイト系合金材Austenitic alloy material
　本開示は、合金材に関し、さらに詳しくは、オーステナイト系合金材に関する。 The present disclosure relates to alloy materials, and more specifically, to austenitic alloy materials.
　最近、二酸化炭素を発生しないクリーンエネルギーとして、水素が注目されている。水素は常温常圧下において気体であり、搬送するために液化する場合、－２５３℃以下の極低温状態にする必要がある。そのため、水素単体で搬送することは困難である。 Recently, hydrogen has been attracting attention as a clean energy source that does not generate carbon dioxide. Hydrogen is a gas at normal temperature and pressure, and when it is liquefied for transportation, it needs to be brought to an extremely low temperature of -253°C or lower. Therefore, it is difficult to transport hydrogen alone.
　そこで、アンモニアを水素のキャリアとして利用することが検討されている。アンモニアは質量％で１８％程度の水素を含有し、水素の沸点よりも高い－３３℃で液化する。そのため、水素キャリアであるアンモニアを搬送し、搬送先でアンモニアから水素を脱離することで、水素をエネルギーとして利用する検討が進められている。 Therefore, the use of ammonia as a hydrogen carrier is being considered. Ammonia contains about 18% hydrogen by mass and liquefies at -33°C, which is higher than the boiling point of hydrogen. Therefore, studies are underway to utilize hydrogen as energy by transporting ammonia, which is a hydrogen carrier, and desorbing hydrogen from the ammonia at the transport destination.
　アンモニアから水素を脱離するには、触媒を用いて、常圧で６００℃程度の高温環境でアンモニアを分解する。以降の説明では、６００℃程度の高温、常圧であって、アンモニア雰囲気の環境を、「高温アンモニア環境」という。そこで、高温アンモニア環境での使用に耐えうる合金材が求められている。 To remove hydrogen from ammonia, ammonia is decomposed using a catalyst in a high temperature environment of about 600°C at normal pressure. In the following description, an environment with a high temperature of about 600° C., normal pressure, and an ammonia atmosphere will be referred to as a "high-temperature ammonia environment." Therefore, there is a need for alloy materials that can withstand use in high-temperature ammonia environments.
　水素製造用の高温アンモニア環境に適用可能な合金材として、化学プラントで使用されているオーステナイト系合金材が考えられる。化学プラントは、高温アンモニア環境と同等の高温環境であるためである。化学プラント用のオーステナイト系合金材は例えば、特開２０１７－０８８９５７号公報（特許文献１）に開示されている。この文献に開示された合金材は、化学組成が、質量％で、Ｃ：０．０２～０．１２％、Ｓｉ：０．１～２％、Ｍｎ：０．１～３％、Ｐ：０．０４％以下、Ｓ：０．０２％以下、Ｃｒ：２０～２６％、Ｎｉ：２６％を超え３５％以下、Ｗ：１～５．５％、Ｖ：０．０１～１％、Ｎｂ：０．０１～１％、Ｂ：０．０００５～０．００８％、Ｍｏ：０．３％以下、Ａｌ：０．００１～０．３％、Ｃｕ：０．３％以下、Ｔｉ：０．０１％以下、Ｎ：０．１３％を超え０．３５％以下、ＲＥＭ：０．００３～０．１０％等を含有する。上述のオーステナイト系合金材では、高温環境での使用において、優れたクリープ強度が得られる、と特許文献１には記載されている。 Austenitic alloy materials used in chemical plants are considered as alloy materials that can be applied to high-temperature ammonia environments for hydrogen production. This is because chemical plants have high-temperature environments equivalent to high-temperature ammonia environments. An austenitic alloy material for chemical plants is disclosed in, for example, Japanese Patent Application Publication No. 2017-088957 (Patent Document 1). The alloy material disclosed in this document has a chemical composition in mass % of C: 0.02 to 0.12%, Si: 0.1 to 2%, Mn: 0.1 to 3%, and P: 0. .04% or less, S: 0.02% or less, Cr: 20-26%, Ni: more than 26% and 35% or less, W: 1-5.5%, V: 0.01-1%, Nb: 0.01-1%, B: 0.0005-0.008%, Mo: 0.3% or less, Al: 0.001-0.3%, Cu: 0.3% or less, Ti: 0.01 % or less, N: more than 0.13% and 0.35% or less, REM: 0.003 to 0.10%, etc. Patent Document 1 describes that the above-mentioned austenitic alloy material has excellent creep strength when used in a high-temperature environment.
特開２０１７－０８８９５７号公報JP2017-088957A
　ところで、上述の高温アンモニア環境でオーステナイト系合金材を使用する場合、合金材の表層で窒化が促進されてしまうことが新たに判明した。形成される窒化層が厚くなれば、窒化層以外の合金部分が薄くなる。この場合、高温でのクリープ強度が低下してしまう。したがって、高温アンモニア環境で使用されるオーステナイト系合金材では、優れた耐窒化性が求められる。 By the way, it has been newly found that when an austenitic alloy material is used in the above-mentioned high-temperature ammonia environment, nitridation is promoted in the surface layer of the alloy material. As the nitrided layer formed becomes thicker, the alloy portion other than the nitrided layer becomes thinner. In this case, the creep strength at high temperatures decreases. Therefore, an austenitic alloy material used in a high-temperature ammonia environment is required to have excellent nitriding resistance.
　本開示の目的は、高温アンモニア環境において優れた耐窒化性を有するオーステナイト系合金材を提供することである。 An object of the present disclosure is to provide an austenitic alloy material that has excellent nitriding resistance in a high-temperature ammonia environment.
　本開示のオーステナイト系合金材は、
　化学組成が、質量％で、
　Ｃ：０超～０．２００％、
　Ｓｉ：０超～３．００％、
　Ｍｎ：０超～３．００％、
　Ｐ：０超～０．０５０％、
　Ｓ：０超～０．０５０％、
　Ｎｉ：４０．００～８０．００％、及び、
　Ｃｒ：１０．００～３５．００％、を含有し、
　さらに、
　Ｓｎ：０超～０．１０００％、
　Ｚｎ：０超～０．０１００％、
　Ｐｂ：０超～０．０１００％、
　Ｓｂ：０超～０．０１００％、
　Ａｓ：０超～０．００１０％、及び、
　Ｂｉ：０超～０．００１０％、からなる群から選択される１種以上を含有し、
　さらに、
　Ｃｕ：０超～５．００％、
　Ｍｏ：０超～２０．００％、
　Ｃｏ：０超～３．００％、
　Ｗ：０超～７．００％、
　Ｔｉ：０超～１．００％、
　Ｎｂ：０超～０．１０％、
　Ｖ：０超～０．５０％、
　Ｂ：０超～０．００５０％、
　Ｎ：０超～０．２００％、
　希土類元素：０超～０．１００％、
　Ａｌ：０超～０．５００％、
　Ｃａ：０超～０．０１００％、及び、
　Ｍｇ：０超～０．０１５０％、からなる群から選択される１種以上を含有し、
　残部はＦｅ及び不純物からなり、
　式（１）で定義されるＦｎ１が２０未満であり、
　式（２）で定義されるＦｎ２が２１よりも高く５０未満である。
　Ｆｎ１＝１７７．８４＋１１．１２Ｓｉ－２４．３６Ｍｎ－８．１１Ｃｕ－１．６１Ｃｒ－１．７８Ｎｉ－２．６８Ｍｏ　（１）
　Ｆｎ２＝（Ｓｎ＋Ｚｎ＋Ｐｂ＋Ｓｂ＋Ａｓ＋Ｂｉ）×１０３　（２）
　ここで、式中の元素記号には、対応する元素の質量％での含有量が代入され、元素が含有されていない場合、対応する元素記号には「０」が代入される。 The austenitic alloy material of the present disclosure is
The chemical composition is in mass%,
C: more than 0 to 0.200%,
Si: more than 0 to 3.00%,
Mn: more than 0 to 3.00%,
P: more than 0 to 0.050%,
S: more than 0 to 0.050%,
Ni: 40.00 to 80.00%, and
Contains Cr: 10.00 to 35.00%,
moreover,
Sn: more than 0 to 0.1000%,
Zn: more than 0 to 0.0100%,
Pb: more than 0 to 0.0100%,
Sb: more than 0 to 0.0100%,
As: more than 0 to 0.0010%, and
Bi: contains one or more selected from the group consisting of more than 0 to 0.0010%,
moreover,
Cu: more than 0 to 5.00%,
Mo: more than 0 to 20.00%,
Co: more than 0 to 3.00%,
W: more than 0 to 7.00%,
Ti: more than 0 to 1.00%,
Nb: more than 0 to 0.10%,
V: more than 0 to 0.50%,
B: more than 0 to 0.0050%,
N: more than 0 to 0.200%,
Rare earth elements: more than 0 to 0.100%,
Al: more than 0 to 0.500%,
Ca: more than 0 to 0.0100%, and
Contains one or more selected from the group consisting of Mg: more than 0 to 0.0150%,
The remainder consists of Fe and impurities,
Fn1 defined by formula (1) is less than 20,
Fn2 defined by formula (2) is higher than 21 and lower than 50.
Fn1=177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
Fn2=(Sn+Zn+Pb+Sb+As+Bi)×10 3 (2)
Here, the content in mass % of the corresponding element is substituted for the element symbol in the formula, and if the element is not contained, "0" is substituted for the corresponding element symbol.
　本開示のオーステナイト系合金材は、高温アンモニア環境において優れた耐窒化性を有する。 The austenitic alloy material of the present disclosure has excellent nitriding resistance in a high-temperature ammonia environment.
図１は、化学組成中の各元素含有量が本実施形態の範囲内である合金材において、１００％アンモニアの雰囲気下で６００℃、２５時間保持した場合の、Ｆｎ１と窒化層深さ（μｍ）との関係を示すグラフである。Figure 1 shows Fn1 and nitrided layer depth (μm ) is a graph showing the relationship between
　本発明者らは、高温アンモニア環境で使用した場合に優れた耐窒化性が得られる合金材について、検討を行った。初めに、本発明者らは、高温アンモニア環境において、耐窒化性を高める元素について検討を行った。その結果、Ｍｎ、Ｃｕ、Ｃｒ、Ｎｉ及びＭｏは高温アンモニア環境において合金材の耐窒化性を高め、一方で、Ｓｉは高温アンモニア環境において合金材の耐窒化性を低下させることを、本発明者らは見出した。 The present inventors investigated alloy materials that can provide excellent nitriding resistance when used in a high-temperature ammonia environment. First, the present inventors investigated elements that enhance nitriding resistance in a high-temperature ammonia environment. As a result, the inventors found that Mn, Cu, Cr, Ni, and Mo increase the nitriding resistance of the alloy material in a high-temperature ammonia environment, while Si decreases the nitriding resistance of the alloy material in a high-temperature ammonia environment. found out.
　そこで、上述の耐窒化性向上元素（Ｍｎ、Ｃｕ、Ｃｒ、Ｎｉ及びＭｏ）、及び、耐窒化性低下元素（Ｓｉ）を考慮して、化学組成の観点から、合金材の検討を行った。その結果、本発明者らは、質量％で、Ｃ：０超～０．２００％、Ｓｉ：０超～３．００％、Ｍｎ：０超～３．００％、Ｐ：０超～０．０５０％、Ｓ：０超～０．０５０％、Ｎｉ：４０．００～８０．００％、Ｃｒ：１０．００～３５．００％、を含有し、さらに、Ｓｎ：０超～０．１０００％、Ｚｎ：０超～０．０１００％、Ｐｂ：０超～０．０１００％、Ｓｂ：０超～０．０１００％、Ａｓ：０超～０．００１０％、及び、Ｂｉ：０超～０．００１０％、からなる群から選択される１種以上を含有し、さらに、Ｃｕ：０超～５．００％、Ｍｏ：０超～２０．００％、Ｃｏ：０超～３．００％、Ｗ：０超～７．００％、Ｔｉ：０超～１．００％、Ｎｂ：０超～０．１０％、Ｖ：０超～０．５０％、Ｂ：０超～０．００５０％、Ｎ：０超～０．２００％、希土類元素：０超～０．１００％、Ａｌ：０超～０．５００％、Ｃａ：０超～０．０１００％、及び、Ｍｇ：０超～０．０１５０％、からなる群から選択される１種以上を含有し、残部はＦｅ及び不純物からなるオーステナイト系合金材であれば、高温アンモニア環境においても優れた耐窒化性が得られる可能性があると考えた。 Therefore, alloy materials were investigated from the viewpoint of chemical composition, taking into consideration the nitriding resistance improving elements (Mn, Cu, Cr, Ni, and Mo) and the nitriding resistance decreasing element (Si) mentioned above. As a result, the present inventors found that, in mass %, C: more than 0 to 0.200%, Si: more than 0 to 3.00%, Mn: more than 0 to 3.00%, P: more than 0 to 0. 050%, S: more than 0 to 0.050%, Ni: 40.00 to 80.00%, Cr: 10.00 to 35.00%, and further Sn: more than 0 to 0.1000%. , Zn: more than 0 to 0.0100%, Pb: more than 0 to 0.0100%, Sb: more than 0 to 0.0100%, As: more than 0 to 0.0010%, and Bi: more than 0 to 0. 0010%, furthermore, Cu: more than 0 to 5.00%, Mo: more than 0 to 20.00%, Co: more than 0 to 3.00%, W : more than 0 to 7.00%, Ti: more than 0 to 1.00%, Nb: more than 0 to 0.10%, V: more than 0 to 0.50%, B: more than 0 to 0.0050%, N : more than 0 to 0.200%, rare earth elements: more than 0 to 0.100%, Al: more than 0 to 0.500%, Ca: more than 0 to 0.0100%, and Mg: more than 0 to 0.0150 It is believed that an austenitic alloy material containing one or more selected from the group consisting of Ta.
　しかしながら、上記化学組成を有するオーステナイト系合金材であっても、依然として、高温アンモニア環境において十分な耐窒化性が得られない場合があった。そこで、本発明者らはさらに検討を行った。 However, even with an austenitic alloy material having the above chemical composition, sufficient nitriding resistance may still not be obtained in a high-temperature ammonia environment. Therefore, the present inventors conducted further investigation.
　ここで、本発明者らは、上述の耐窒化性向上元素（Ｍｎ、Ｃｕ、Ｃｒ、Ｎｉ及びＭｏ）の含有量と、耐窒化性低下元素（Ｓｉ）の含有量とが、所定の関係を満たす場合に、高温アンモニア環境での耐窒化性が高まるのではないかと考えた。そこで、本発明者らは、上述の化学組成を満たすオーステナイト系合金材において、耐窒化性向上元素（Ｍｎ、Ｃｕ、Ｃｒ、Ｎｉ及びＭｏ）及び耐窒化性低下元素（Ｓｉ）の含有量と、高温アンモニア環境での窒化層深さとの関係を調査した。その結果、本発明者らは、耐窒化性向上元素（Ｍｎ、Ｃｕ、Ｃｒ、Ｎｉ及びＭｏ）の各々の含有量と、耐窒化性低下元素（Ｓｉ）の含有量とに基づいて式（１）で定義されるＦｎ１が２０未満であれば、高温アンモニア環境において、優れた耐窒化性が得られることを見出した。
　Ｆｎ１＝１７７．８４＋１１．１２Ｓｉ－２４．３６Ｍｎ－８．１１Ｃｕ－１．６１Ｃｒ－１．７８Ｎｉ－２．６８Ｍｏ　（１）
　ここで、式中の元素記号には、対応する元素の質量％での含有量が代入され、元素が含有されていない場合、対応する元素記号には「０」が代入される。 Here, the present inventors discovered that the content of the above-mentioned nitriding resistance improving elements (Mn, Cu, Cr, Ni, and Mo) and the content of the nitriding resistance decreasing element (Si) have a predetermined relationship. We thought that nitriding resistance in a high-temperature ammonia environment would be improved if the conditions were met. Therefore, the present inventors determined that the content of nitriding resistance improving elements (Mn, Cu, Cr, Ni, and Mo) and nitriding resistance decreasing elements (Si) in an austenitic alloy material satisfying the above chemical composition, The relationship between the depth of the nitrided layer in a high-temperature ammonia environment was investigated. As a result, the present inventors found that the formula (1) It has been found that when Fn1 defined by ) is less than 20, excellent nitriding resistance can be obtained in a high-temperature ammonia environment.
Fn1=177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
Here, the content in mass % of the corresponding element is substituted for the element symbol in the formula, and if the element is not contained, "0" is substituted for the corresponding element symbol.
　図１は、化学組成中の各元素含有量が本実施形態の範囲内である合金材において、１００％アンモニアの雰囲気下で６００℃、２５時間保持した場合の、Ｆｎ１と窒化層深さ（μｍ）との関係を示すグラフである。図１は後述の実施例により得られたデータに基づいて作成した。図１を参照して、化学組成中の各元素含有量が本実施形態の範囲内である合金材において、Ｆｎ１が２０以上である場合、１００％アンモニアの雰囲気下で６００℃、２５時間保持した場合の窒化層深さは３０．０μｍを超える。一方、Ｆｎ１が２０未満である場合、１００％アンモニアの雰囲気下で６００℃、２５時間保持した場合の窒化層深さが１５．０μｍ以下となり、耐窒化性が顕著に高まる。 Figure 1 shows Fn1 and nitrided layer depth (μm ) is a graph showing the relationship between FIG. 1 was created based on data obtained in Examples described below. Referring to FIG. 1, in the case where the content of each element in the chemical composition is within the range of this embodiment, and Fn1 is 20 or more, the alloy material is held at 600°C for 25 hours in an atmosphere of 100% ammonia. The depth of the nitrided layer in this case exceeds 30.0 μm. On the other hand, when Fn1 is less than 20, the depth of the nitrided layer is 15.0 μm or less when held at 600° C. for 25 hours in a 100% ammonia atmosphere, and the nitriding resistance is significantly increased.
　以上のとおり、上述の化学組成を有し、Ｆｎ１が２０未満であるオーステナイト系合金材であれば、高温アンモニア環境において優れた耐窒化性が得られることを、本発明者らは見出した。しかしながら、上述の化学組成を有し、Ｆｎ１が２０未満であるオーステナイト系合金材では、新たな課題として、高温アンモニア環境において合金材の表層に粒界割れが発生する場合があることが判明した。 As described above, the present inventors have discovered that an austenitic alloy material having the above-mentioned chemical composition and Fn1 of less than 20 can provide excellent nitriding resistance in a high-temperature ammonia environment. However, it has been found that in an austenitic alloy material having the above-mentioned chemical composition and Fn1 of less than 20, intergranular cracking may occur in the surface layer of the alloy material in a high-temperature ammonia environment, as a new problem.
　そこで、本発明者らは、上述の化学組成を有し、Ｆｎ１が２０未満であるオーステナイト系合金材において、高温アンモニア環境での粒界割れの発生を抑制する手段について、さらに検討を行った。その結果、上述の化学組成を有し、Ｆｎ１が２０未満であるオーステナイト系合金材において、さらに、式（２）で定義されるＦｎ２が２１よりも高く、５０未満であれば、高温アンモニア環境において、優れた耐窒化性が得られ、かつ、表層での粒界割れの発生も十分に抑制できることを見出した。
　Ｆｎ２＝（Ｓｎ＋Ｚｎ＋Ｐｂ＋Ｓｂ＋Ａｓ＋Ｂｉ）×１０３　（２）
　ここで、式中の元素記号には、対応する元素の質量％での含有量が代入され、元素が含有されていない場合、対応する元素記号には「０」が代入される。 Therefore, the present inventors further investigated means for suppressing the occurrence of intergranular cracking in a high-temperature ammonia environment in an austenitic alloy material having the above-mentioned chemical composition and Fn1 of less than 20. As a result, in an austenitic alloy material having the above-mentioned chemical composition and Fn1 of less than 20, if Fn2 defined by formula (2) is higher than 21 and less than 50, it can be used in a high-temperature ammonia environment. It has been found that excellent nitriding resistance can be obtained and that the occurrence of intergranular cracking in the surface layer can be sufficiently suppressed.
Fn2=(Sn+Zn+Pb+Sb+As+Bi)×10 3 (2)
Here, the content in mass % of the corresponding element is substituted for the element symbol in the formula, and if the element is not contained, "0" is substituted for the corresponding element symbol.
　Ｆｎ２が２１よりも高く５０未満であれば、高温アンモニア環境において表層の粒界割れを抑制できる理由は定かではないが、本発明者らは、次のとおり考えている。上述の化学組成を有するオーステナイト系合金材において、Ｓｎ、Ｚｎ、Ｐｂ、Ｓｂ、Ａｓ及びＢｉはいずれも、微量に含有されることにより、高温アンモニア環境での合金材の粒界に偏析する。そのため、これらの元素は、粒界に析出物が生成したり、粒界にＰ、Ｓが偏析したりするのを抑制する。その結果、粒界が強化され、高温アンモニア環境での合金材の表層近傍での粒界割れが抑制される。Ｆｎ２が２１以下であれば、上記効果が十分に得られない。 Although it is not clear why grain boundary cracking in the surface layer can be suppressed in a high-temperature ammonia environment when Fn2 is higher than 21 and less than 50, the present inventors believe as follows. In the austenitic alloy material having the above-mentioned chemical composition, Sn, Zn, Pb, Sb, As, and Bi are all contained in trace amounts and segregate at the grain boundaries of the alloy material in a high-temperature ammonia environment. Therefore, these elements suppress the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. As a result, grain boundaries are strengthened, and grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment is suppressed. If Fn2 is 21 or less, the above effects cannot be sufficiently obtained.
　一方、Ｆｎ２が５０以上となれば、Ｓｎ、Ｚｎ、Ｐｂ、Ｓｂ、Ａｓ及びＢｉが粒界に過剰に偏析し、粒界強度がかえって低下する。そのため、高温アンモニア環境において、合金材の表層で粒界割れが発生しやすくなる。 On the other hand, if Fn2 is 50 or more, Sn, Zn, Pb, Sb, As, and Bi will segregate excessively at the grain boundaries, and the grain boundary strength will instead decrease. Therefore, intergranular cracking is likely to occur in the surface layer of the alloy material in a high-temperature ammonia environment.
　Ｆｎ２が２１よりも高く、５０未満であれば、Ｆｎ１が２０未満であることを前提として、高温アンモニア環境でのオーステナイト系合金材の表層において、粒界割れが発生するのを十分に抑制できる。 If Fn2 is higher than 21 and less than 50, on the premise that Fn1 is less than 20, it is possible to sufficiently suppress the occurrence of intergranular cracking in the surface layer of the austenitic alloy material in a high-temperature ammonia environment.
　上記メカニズムと異なるメカニズムで表層の粒界割れが抑制されている可能性もある。しかしながら、Ｆｎ１が２０未満であることを前提として、Ｆｎ２が２１よりも高く、５０未満であれば、高温アンモニア環境において表層での粒界割れが十分に抑制されることは、後述の実施例で証明されている。 It is also possible that intergranular cracking in the surface layer is suppressed by a mechanism different from the one described above. However, assuming that Fn1 is less than 20, if Fn2 is higher than 21 and less than 50, grain boundary cracking in the surface layer is sufficiently suppressed in a high-temperature ammonia environment, as shown in the examples described below. It has been proven.
　以上の技術思想に基づいて、本実施形態のオーステナイト系合金材は完成した。本実施形態のオーステナイト系合金材は次の構成を有する。 Based on the above technical idea, the austenitic alloy material of this embodiment was completed. The austenitic alloy material of this embodiment has the following configuration.
　第１の構成のオーステナイト系合金材は、
　化学組成が、質量％で、
　Ｃ：０超～０．２００％、
　Ｓｉ：０超～３．００％、
　Ｍｎ：０超～３．００％、
　Ｐ：０超～０．０５０％、
　Ｓ：０超～０．０５０％、
　Ｎｉ：４０．００～８０．００％、及び、
　Ｃｒ：１０．００～３５．００％、を含有し、
　さらに、
　Ｓｎ：０超～０．１０００％、
　Ｚｎ：０超～０．０１００％、
　Ｐｂ：０超～０．０１００％、
　Ｓｂ：０超～０．０１００％、
　Ａｓ：０超～０．００１０％、及び、
　Ｂｉ：０超～０．００１０％、からなる群から選択される１種以上を含有し、
　さらに、
　Ｃｕ：０超～５．００％、
　Ｍｏ：０超～２０．００％、
　Ｃｏ：０超～３．００％、
　Ｗ：０超～７．００％、
　Ｔｉ：０超～１．００％、
　Ｎｂ：０超～０．１０％、
　Ｖ：０超～０．５０％、
　Ｂ：０超～０．００５０％、
　Ｎ：０超～０．２００％、
　希土類元素：０超～０．１００％、
　Ａｌ：０超～０．５００％、
　Ｃａ：０超～０．０１００％、及び、
　Ｍｇ：０超～０．０１５０％、からなる群から選択される１種以上を含有し、
　残部はＦｅ及び不純物からなり、
　式（１）で定義されるＦｎ１が２０未満であり、
　式（２）で定義されるＦｎ２が２１よりも高く５０未満である。
　Ｆｎ１＝１７７．８４＋１１．１２Ｓｉ－２４．３６Ｍｎ－８．１１Ｃｕ－１．６１Ｃｒ－１．７８Ｎｉ－２．６８Ｍｏ　（１）
　Ｆｎ２＝（Ｓｎ＋Ｚｎ＋Ｐｂ＋Ｓｂ＋Ａｓ＋Ｂｉ）×１０３　（２）
　ここで、式中の元素記号には、対応する元素の質量％での含有量が代入され、元素が含有されていない場合、対応する元素記号には「０」が代入される。 The austenitic alloy material with the first configuration is
The chemical composition is in mass%,
C: more than 0 to 0.200%,
Si: more than 0 to 3.00%,
Mn: more than 0 to 3.00%,
P: more than 0 to 0.050%,
S: more than 0 to 0.050%,
Ni: 40.00 to 80.00%, and
Contains Cr: 10.00 to 35.00%,
moreover,
Sn: more than 0 to 0.1000%,
Zn: more than 0 to 0.0100%,
Pb: more than 0 to 0.0100%,
Sb: more than 0 to 0.0100%,
As: more than 0 to 0.0010%, and
Bi: contains one or more selected from the group consisting of more than 0 to 0.0010%,
moreover,
Cu: more than 0 to 5.00%,
Mo: more than 0 to 20.00%,
Co: more than 0 to 3.00%,
W: more than 0 to 7.00%,
Ti: more than 0 to 1.00%,
Nb: more than 0 to 0.10%,
V: more than 0 to 0.50%,
B: more than 0 to 0.0050%,
N: more than 0 to 0.200%,
Rare earth elements: more than 0 to 0.100%,
Al: more than 0 to 0.500%,
Ca: more than 0 to 0.0100%, and
Contains one or more selected from the group consisting of Mg: more than 0 to 0.0150%,
The remainder consists of Fe and impurities,
Fn1 defined by formula (1) is less than 20,
Fn2 defined by formula (2) is higher than 21 and lower than 50.
Fn1=177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
Fn2=(Sn+Zn+Pb+Sb+As+Bi)×10 3 (2)
Here, the content in mass % of the corresponding element is substituted for the element symbol in the formula, and if the element is not contained, "0" is substituted for the corresponding element symbol.
　第２の構成のオーステナイト系合金材は、
　第１の構成のオーステナイト系合金材であって、
　オーステナイト系合金材の表層のμｍ単位での平均結晶粒径をＤａｖｅと定義したとき、
　式（３）で定義されるＦｎ３が０．２０よりも高く、
　式（４）で定義されるＦｎ４が１０００～５０００である。
　Ｆｎ３＝Ｆｎ２／Ｄａｖｅ　（３）
　Ｆｎ４＝Ｆｎ２×Ｄａｖｅ　（４） The austenitic alloy material with the second configuration is
An austenitic alloy material having a first configuration,
When the average grain size in μm of the surface layer of the austenitic alloy material is defined as D ave ,
Fn3 defined by formula (3) is higher than 0.20,
Fn4 defined by formula (4) is 1000 to 5000.
Fn3=Fn2/D ave (3)
Fn4=Fn2×D ave (4)
　第３の構成のオーステナイト系合金材は、
　第１の構成又は第２の構成のオーステナイト系合金材であって、
　化学組成が、質量％で、
　Ｃ：０超～０．０５０％、
　Ｓｉ：０超～０．５０％、
　Ｍｎ：０超～０．５０％、
　Ｐ：０超～０．０２５％、
　Ｓ：０超～０．０１０％、
　Ｃｕ：２．００～４．００％、
　Ｎｉ：４４．００～５０．００％、
　Ｃｒ：２０．００～２５．００％、
　Ｍｏ：５．００～７．００％、
　Ｗ：２．００～５．００％、及び、
　Ｆｅ：１２．００～２０．００％、を含有する。 The austenitic alloy material with the third configuration is
An austenitic alloy material having a first configuration or a second configuration,
The chemical composition is in mass%,
C: more than 0 to 0.050%,
Si: more than 0 to 0.50%,
Mn: more than 0 to 0.50%,
P: more than 0 to 0.025%,
S: more than 0 to 0.010%,
Cu: 2.00-4.00%,
Ni: 44.00-50.00%,
Cr: 20.00-25.00%,
Mo: 5.00-7.00%,
W: 2.00 to 5.00%, and
Contains Fe: 12.00 to 20.00%.
　第４の構成のオーステナイト系合金材は、
　第１の構成又は第２の構成のオーステナイト系合金材であって、
　化学組成が、質量％で、
　Ｃ：０超～０．１５０％、
　Ｓｉ：１．００～２．５０％、
　Ｍｎ：０超～１．００％、
　Ｐ：０超～０．０１０％、
　Ｓ：０超～０．０１０％、
　Ｃｕ：１．５０～３．００％、
　Ｃｒ：２８．００～３２．００％、
　Ｍｏ：１．００～３．００％、
　Ｔｉ：０超～１．００％、及び、
　Ｆｅ：２．００～６．００％、を含有する。 The austenitic alloy material with the fourth configuration is
An austenitic alloy material having a first configuration or a second configuration,
The chemical composition is in mass%,
C: more than 0 to 0.150%,
Si: 1.00-2.50%,
Mn: more than 0 to 1.00%,
P: more than 0 to 0.010%,
S: more than 0 to 0.010%,
Cu: 1.50-3.00%,
Cr: 28.00-32.00%,
Mo: 1.00-3.00%,
Ti: more than 0 to 1.00%, and
Contains Fe: 2.00 to 6.00%.
　第５の構成のオーステナイト系合金材は、
　第１の構成又は第２の構成のオーステナイト系合金材であって、
　化学組成が、質量％で、
　Ｃ：０超～０．０５０％、
　Ｓｉ：０超～０．５０％、
　Ｍｎ：０超～０．５０％、
　Ｐ：０超～０．０３０％、
　Ｓ：０超～０．０１５％、
　Ｃｕ：０超～０．５０％、
　Ｃｒ：２７．００～３１．００％、
　Ｆｅ：７．００～１５．００％、及び、
　Ｎｉ：５８．００～８０．００％、を含有する。 The austenitic alloy material with the fifth configuration is
An austenitic alloy material having a first configuration or a second configuration,
The chemical composition is in mass%,
C: more than 0 to 0.050%,
Si: more than 0 to 0.50%,
Mn: more than 0 to 0.50%,
P: more than 0 to 0.030%,
S: more than 0 to 0.015%,
Cu: more than 0 to 0.50%,
Cr: 27.00-31.00%,
Fe: 7.00 to 15.00%, and
Contains Ni: 58.00 to 80.00%.
　以下、本実施形態のオーステナイト系合金材について詳述する。なお、元素に関する「％」は、特に断りがない限り、質量％を意味する。以降の説明では、オーステナイト系合金材を単に「合金材」ともいう。 Hereinafter, the austenitic alloy material of this embodiment will be described in detail. Note that "%" regarding elements means mass % unless otherwise specified. In the following description, the austenitic alloy material is also simply referred to as "alloy material."
　［本実施形態のオーステナイト系合金材の特徴］
　本実施形態のオーステナイト系合金材は、次の特徴を含む。
　（特徴１）
　化学組成が、質量％で、Ｃ：０超～０．２００％、Ｓｉ：０超～３．００％、Ｍｎ：０超～３．００％、Ｐ：０超～０．０５０％、Ｓ：０超～０．０５０％、Ｎｉ：４０．００～８０．００％、Ｃｒ：１０．００～３５．００％、を含有し、さらに、Ｓｎ：０超～０．１０００％、Ｚｎ：０超～０．０１００％、Ｐｂ：０超～０．０１００％、Ｓｂ：０超～０．０１００％、Ａｓ：０超～０．００１０％、及び、Ｂｉ：０超～０．００１０％、からなる群から選択される１種以上を含有し、さらに、Ｃｕ：０超～５．００％、Ｍｏ：０超～２０．００％、Ｃｏ：０超～３．００％、Ｗ：０超～７．００％、Ｔｉ：０超～１．００％、Ｎｂ：０超～０．１０％、Ｖ：０超～０．５０％、Ｂ：０超～０．００５０％、Ｎ：０超～０．２００％、希土類元素：０超～０．１００％、Ａｌ：０超～０．５００％、Ｃａ：０超～０．０１００％、及び、Ｍｇ：０超～０．０１５０％、からなる群から選択される１種以上を含有し、残部はＦｅ及び不純物からなる。
　（特徴２）
　式（１）で定義されるＦｎ１が２０未満である。
　Ｆｎ１＝１７７．８４＋１１．１２Ｓｉ－２４．３６Ｍｎ－８．１１Ｃｕ－１．６１Ｃｒ－１．７８Ｎｉ－２．６８Ｍｏ　（１）
　ここで、式（１）中の元素記号には、対応する元素の質量％での含有量が代入される。元素が含有されていない場合、対応する元素記号には「０」が代入される。
　（特徴３）
　式（２）で定義されるＦｎ２が２１よりも高く、５０未満である。
　Ｆｎ２＝（Ｓｎ＋Ｚｎ＋Ｐｂ＋Ｓｂ＋Ａｓ＋Ｂｉ）×１０３　（２）
　ここで、式（２）中の元素記号には、対応する元素の質量％での含有量が代入される。元素が含有されていない場合、対応する元素記号には「０」が代入される。
　以下、各特徴について説明する。 [Characteristics of the austenitic alloy material of this embodiment]
The austenitic alloy material of this embodiment includes the following features.
(Feature 1)
The chemical composition is in mass%, C: more than 0 to 0.200%, Si: more than 0 to 3.00%, Mn: more than 0 to 3.00%, P: more than 0 to 0.050%, S: Contains more than 0 to 0.050%, Ni: 40.00 to 80.00%, Cr: 10.00 to 35.00%, and further contains Sn: more than 0 to 0.1000%, Zn: more than 0. ~0.0100%, Pb: more than 0 ~ 0.0100%, Sb: more than 0 ~ 0.0100%, As: more than 0 ~ 0.0010%, and Bi: more than 0 ~ 0.0010%. Contains one or more selected from the group, further Cu: more than 0 to 5.00%, Mo: more than 0 to 20.00%, Co: more than 0 to 3.00%, W: more than 0 to 7 .00%, Ti: more than 0 to 1.00%, Nb: more than 0 to 0.10%, V: more than 0 to 0.50%, B: more than 0 to 0.0050%, N: more than 0 to 0 .200%, rare earth elements: more than 0 to 0.100%, Al: more than 0 to 0.500%, Ca: more than 0 to 0.0100%, and Mg: more than 0 to 0.0150%. The remainder consists of Fe and impurities.
(Feature 2)
Fn1 defined by formula (1) is less than 20.
Fn1=177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
Here, the content in mass % of the corresponding element is substituted for the element symbol in formula (1). If an element is not contained, "0" is assigned to the corresponding element symbol.
(Feature 3)
Fn2 defined by formula (2) is higher than 21 and lower than 50.
Fn2=(Sn+Zn+Pb+Sb+As+Bi)×10 3 (2)
Here, the content in mass % of the corresponding element is substituted for the element symbol in formula (2). If an element is not contained, "0" is assigned to the corresponding element symbol.
Each feature will be explained below.
　［（特徴１）化学組成について］
　本実施形態によるオーステナイト系合金材の化学組成は、次の元素を含有する。 [(Feature 1) Regarding chemical composition]
The chemical composition of the austenitic alloy material according to this embodiment contains the following elements.
　Ｃ：０超～０．２００％
　炭素（Ｃ）は高温アンモニア環境で合金材を使用中に、微細な炭化物を生成して、クリープ強度を高める。しかしながら、Ｃ含有量が０．２００％を超えれば、高温アンモニア環境において、炭化物が粒界に過剰に生成する。この場合、他の元素含有量が本実施形態の範囲内であっても、合金材の表面で粒界割れが発生しやすくなる。
　したがって、Ｃ含有量は０超～０．２００％である。
　Ｃ含有量の好ましい下限は０．００１％であり、さらに好ましくは０．００５％であり、さらに好ましくは０．０１０％であり、さらに好ましくは０．０２０％である。
　Ｃ含有量の好ましい上限は０．１８０％であり、さらに好ましくは０．１６０％であり、さらに好ましくは０．１５０％である。
　Ｃ含有量の好ましい範囲は例えば、０．００１～０．１８０％であり、さらに好ましくは０．００５～０．１６０％であり、さらに好ましくは０．０１０～０．１５０％であり、さらに好ましくは０．０２０～０．１５０％である。 C: More than 0 to 0.200%
Carbon (C) generates fine carbides during use of alloy materials in a high-temperature ammonia environment, increasing creep strength. However, if the C content exceeds 0.200%, carbides are excessively generated at grain boundaries in a high-temperature ammonia environment. In this case, even if the contents of other elements are within the range of this embodiment, intergranular cracks are likely to occur on the surface of the alloy material.
Therefore, the C content is greater than 0 to 0.200%.
The preferable lower limit of the C content is 0.001%, more preferably 0.005%, still more preferably 0.010%, and still more preferably 0.020%.
A preferable upper limit of the C content is 0.180%, more preferably 0.160%, and still more preferably 0.150%.
The preferable range of the C content is, for example, 0.001 to 0.180%, more preferably 0.005 to 0.160%, even more preferably 0.010 to 0.150%, and even more preferably is 0.020 to 0.150%.
　Ｓｉ：０超～３．００％
　シリコン（Ｓｉ）は合金を脱酸する。Ｓｉはさらに、高温アンモニア環境での合金材の耐酸化性を高める。しかしながら、Ｓｉ含有量が３．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境において、粒界割れが発生する場合がある。
　したがって、Ｓｉ含有量は０超～３．００％である。
　Ｓｉ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％であり、さらに好ましくは０．３０％である。
　Ｓｉ含有量の好ましい上限は２．８０％であり、さらに好ましくは２．７０％であり、さらに好ましくは２．６０％である。
　Ｓｉ含有量の好ましい範囲は例えば、０．０１～２．８０％であり、さらに好ましくは０．０５～２．７０％であり、さらに好ましくは０．１０～２．６０％であり、さらに好ましくは０．３０～２．６０％である。 Si: more than 0 to 3.00%
Silicon (Si) deoxidizes the alloy. Si further increases the oxidation resistance of the alloy material in a high temperature ammonia environment. However, if the Si content exceeds 3.00%, intergranular cracking may occur in a high-temperature ammonia environment even if the contents of other elements are within the range of this embodiment.
Therefore, the Si content is greater than 0 to 3.00%.
The preferable lower limit of the Si content is 0.01%, more preferably 0.05%, still more preferably 0.10%, and still more preferably 0.30%.
A preferable upper limit of the Si content is 2.80%, more preferably 2.70%, and still more preferably 2.60%.
The preferable range of the Si content is, for example, 0.01 to 2.80%, more preferably 0.05 to 2.70%, still more preferably 0.10 to 2.60%, and even more preferably is 0.30 to 2.60%.
　Ｍｎ：０超～３．００％
　マンガン（Ｍｎ）は高温アンモニア環境での合金材の耐窒化性を高める。しかしながら、Ｍｎ含有量が３．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境において、合金材のクリープ延性が低下する。さらに、合金材の靱性が低下する。
　したがって、Ｍｎ含有量は０超～３．００％である。
　Ｍｎ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％であり、さらに好ましくは０．３０％である。
　Ｍｎ含有量の好ましい上限は２．８０％であり、さらに好ましくは２．５０％であり、さらに好ましくは２．００％であり、さらに好ましくは１．５０％である。
　Ｍｎ含有量の好ましい範囲は例えば、０．０１～２．８０％であり、さらに好ましくは０．０５～２．５０％であり、さらに好ましくは０．１０～２．００％であり、さらに好ましくは０．３０～１．５０％である。 Mn: more than 0 to 3.00%
Manganese (Mn) increases the nitriding resistance of alloy materials in high-temperature ammonia environments. However, if the Mn content exceeds 3.00%, the creep ductility of the alloy material decreases in a high-temperature ammonia environment even if the other element contents are within the ranges of this embodiment. Furthermore, the toughness of the alloy material decreases.
Therefore, the Mn content is greater than 0 to 3.00%.
The preferable lower limit of the Mn content is 0.01%, more preferably 0.05%, still more preferably 0.10%, and still more preferably 0.30%.
A preferable upper limit of the Mn content is 2.80%, more preferably 2.50%, still more preferably 2.00%, and still more preferably 1.50%.
The preferable range of the Mn content is, for example, 0.01 to 2.80%, more preferably 0.05 to 2.50%, even more preferably 0.10 to 2.00%, and even more preferably is 0.30 to 1.50%.
　Ｐ：０超～０．０５０％
　りん（Ｐ）は不純物である。Ｐ含有量が０．０５０％を超えれば、高温アンモニア環境において、Ｐが粒界に偏析する。そのため、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材において粒界割れが発生する場合がある。
　したがって、Ｐ含有量は０超～０．０５０％である。
　Ｐ含有量はなるべく低い方が好ましい。しかしながら、Ｐ含有量の過度の低減は、製造コストを大幅に高める。したがって、工業生産を考慮した場合、Ｐ含有量の好ましい下限は０．００１％であり、さらに好ましくは０．００２％であり、さらに好ましくは０．００５％である。
　Ｐ含有量の好ましい上限は０．０４５％であり、さらに好ましくは０．０４２％であり、さらに好ましくは０．０４０％である。
　Ｐ含有量の好ましい範囲は例えば、０．００１～０．０４５％であり、さらに好ましくは０．００２～０．０４２％であり、さらに好ましくは０．００５～０．０４０％である。 P: More than 0 to 0.050%
Phosphorus (P) is an impurity. If the P content exceeds 0.050%, P segregates at grain boundaries in a high-temperature ammonia environment. Therefore, even if the contents of other elements are within the range of this embodiment, intergranular cracking may occur in the alloy material in a high-temperature ammonia environment.
Therefore, the P content is greater than 0 to 0.050%.
It is preferable that the P content is as low as possible. However, excessive reduction in P content significantly increases manufacturing costs. Therefore, when considering industrial production, the preferable lower limit of the P content is 0.001%, more preferably 0.002%, and still more preferably 0.005%.
A preferable upper limit of the P content is 0.045%, more preferably 0.042%, and still more preferably 0.040%.
The preferable range of the P content is, for example, 0.001 to 0.045%, more preferably 0.002 to 0.042%, and still more preferably 0.005 to 0.040%.
　Ｓ：０超～０．０５０％
　硫黄（Ｓ）は不純物である。Ｓ含有量が０．０５０％を超えれば、高温アンモニア環境において、Ｓが粒界に偏析する。そのため、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材において粒界割れが発生する場合がある。
　したがって、Ｓ含有量は０超～０．０５０％である。
　Ｓ含有量はなるべく低い方が好ましい。しかしながら、Ｓ含有量の過度の低減は、製造コストを大幅に高める。したがって、工業生産を考慮した場合、Ｓ含有量の好ましい下限は０．００１％であり、さらに好ましくは０．００２％であり、さらに好ましくは０．００５％である。
　Ｓ含有量の好ましい上限は０．０４５％であり、さらに好ましくは０．０４０％であり、さらに好ましくは０．０３５％である。
　Ｓ含有量の好ましい範囲は例えば、０．００１～０．０４５％であり、さらに好ましくは０．００２～０．０４０％であり、さらに好ましくは０．００５～０．０３５％である。 S: More than 0 to 0.050%
Sulfur (S) is an impurity. If the S content exceeds 0.050%, S will segregate at grain boundaries in a high-temperature ammonia environment. Therefore, even if the contents of other elements are within the range of this embodiment, intergranular cracking may occur in the alloy material in a high-temperature ammonia environment.
Therefore, the S content is greater than 0 to 0.050%.
It is preferable that the S content is as low as possible. However, excessive reduction in S content significantly increases manufacturing costs. Therefore, when considering industrial production, the preferable lower limit of the S content is 0.001%, more preferably 0.002%, and still more preferably 0.005%.
A preferable upper limit of the S content is 0.045%, more preferably 0.040%, and still more preferably 0.035%.
The preferable range of the S content is, for example, 0.001 to 0.045%, more preferably 0.002 to 0.040%, and still more preferably 0.005 to 0.035%.
　Ｎｉ：４０．００～８０．００％
　ニッケル（Ｎｉ）は、高温アンモニア環境での合金材の耐窒化性を高める。Ｎｉ含有量が４０．００％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｎｉ含有量が８０．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境において、粒界割れが発生する場合がある。
　したがって、Ｎｉ含有量は４０．００～８０．００％である。
　Ｎｉ含有量の好ましい下限は４３．００％であり、さらに好ましくは４５．００％であり、さらに好ましくは５０．００％であり、さらに好ましくは５５．００％である。
　Ｎｉ含有量の好ましい上限は７５．００％であり、さらに好ましくは７０．００％であり、さらに好ましくは６５．００％であり、さらに好ましくは６０．００％である。
　Ｎｉ含有量の好ましい範囲は例えば、４３．００～７５．００％であり、さらに好ましくは４５．００～７０．００％であり、さらに好ましくは５０．００～６５．００％であり、さらに好ましくは５５．００～６０．００％である。 Ni: 40.00-80.00%
Nickel (Ni) increases the nitriding resistance of the alloy material in a high-temperature ammonia environment. If the Ni content is less than 40.00%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Ni content exceeds 80.00%, intergranular cracking may occur in a high-temperature ammonia environment even if the contents of other elements are within the range of this embodiment.
Therefore, the Ni content is 40.00 to 80.00%.
The preferable lower limit of the Ni content is 43.00%, more preferably 45.00%, still more preferably 50.00%, and even more preferably 55.00%.
A preferable upper limit of the Ni content is 75.00%, more preferably 70.00%, still more preferably 65.00%, and still more preferably 60.00%.
The preferable range of the Ni content is, for example, 43.00 to 75.00%, more preferably 45.00 to 70.00%, still more preferably 50.00 to 65.00%, and even more preferably is 55.00 to 60.00%.
　Ｃｒ：１０．００～３５．００％
　クロム（Ｃｒ）は、高温アンモニア環境での合金材の耐窒化性を高める。Ｃｒ含有量が１０．００％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｃｒ含有量が３５．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材のクリープ強度が低下する。
　したがって、Ｃｒ含有量は１０．００～３５．００％である。
　Ｃｒ含有量の好ましい下限は１２．００％であり、さらに好ましくは１５．００％であり、さらに好ましくは１８．００％である。
　Ｃｒ含有量の好ましい上限は３３．００％であり、さらに好ましくは３２．００％であり、さらに好ましくは３１．００％であり、さらに好ましくは３０．００％である。
　Ｃｒ含有量の好ましい範囲は例えば、１２．００～３３．００％であり、さらに好ましくは１５．００～３２．００％であり、さらに好ましくは１８．００～３１．００％であり、さらに好ましくは１８．００～３０．００％である。 Cr:10.00~35.00%
Chromium (Cr) increases the nitriding resistance of the alloy material in a high-temperature ammonia environment. If the Cr content is less than 10.00%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Cr content exceeds 35.00%, the creep strength of the alloy material in a high-temperature ammonia environment will decrease even if the contents of other elements are within the ranges of this embodiment.
Therefore, the Cr content is between 10.00 and 35.00%.
The lower limit of the Cr content is preferably 12.00%, more preferably 15.00%, and still more preferably 18.00%.
A preferable upper limit of the Cr content is 33.00%, more preferably 32.00%, still more preferably 31.00%, and still more preferably 30.00%.
The preferred range of the Cr content is, for example, 12.00 to 33.00%, more preferably 15.00 to 32.00%, even more preferably 18.00 to 31.00%, even more preferably is 18.00 to 30.00%.
　本実施形態のオーステナイト系合金材はさらに、第１群を含有する。
　［第１群］
　Ｓｎ：０超～０．１０００％、
　Ｚｎ：０超～０．０１００％、
　Ｐｂ：０超～０．０１００％、
　Ｓｂ：０超～０．０１００％、
　Ａｓ：０超～０．００１０％、及び、
　Ｂｉ：０超～０．００１０％、からなる群から選択される１種以上
　Ｓｎ、Ｚｎ、Ｐｂ、Ｓｂ、Ａｓ及びＢｉはいずれも、高温アンモニア環境での合金材の表層近傍での粒界割れを抑制する。以下、第１群の各元素について説明する。 The austenitic alloy material of this embodiment further contains the first group.
[Group 1]
Sn: more than 0 to 0.1000%,
Zn: more than 0 to 0.0100%,
Pb: more than 0 to 0.0100%,
Sb: more than 0 to 0.0100%,
As: more than 0 to 0.0010%, and
Bi: one or more selected from the group consisting of more than 0 to 0.0010% Sn, Zn, Pb, Sb, As, and Bi all cause intergranular cracking near the surface layer of the alloy material in a high-temperature ammonia environment. suppress. Each element of the first group will be explained below.
　Ｓｎ：０超～０．１０００％
　すず（Ｓｎ）は含有されなくてもよい。つまり、Ｓｎ含有量は０％であってもよい。
　含有される場合、つまり、Ｓｎ含有量が０％超である場合、Ｓｎは高温アンモニア環境での合金材の使用中において粒界に偏析する。偏析したＳｎは、粒界に析出物が生成したり、粒界にＰ及びＳが偏析したりするのを抑制する。これにより、粒界が強化され、高温アンモニア環境での合金材の表層近傍での粒界割れが抑制される。Ｓｎが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｓｎ含有量が０．１０００％を超えれば、高温アンモニア環境での合金材の使用中において、Ｓｎが粒界に過剰に偏析する。この場合、粒界の強度がかえって低下する。そのため、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材の表層近傍での粒界割れが促進されてしまう。
　したがって、Ｓｎ含有量は０超～０．１０００％である。
　Ｓｎ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．０００２％であり、さらに好ましくは０．０００３％である。
　Ｓｎ含有量の好ましい上限は０．０７００％であり、さらに好ましくは０．０５００％であり、さらに好ましくは０．０４５０％である。
　Ｓｎ含有量の好ましい範囲は例えば、０．０００１～０．０７００％であり、さらに好ましくは０．０００２～０．０５００％であり、さらに好ましくは０．０００３～０．０４５０％である。 Sn: more than 0 to 0.1000%
Tin (Sn) may not be contained. That is, the Sn content may be 0%.
When Sn is contained, that is, when the Sn content is more than 0%, Sn segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment. The segregated Sn suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Sn is contained, the above effects can be obtained to some extent.
However, if the Sn content exceeds 0.1000%, Sn will segregate excessively at grain boundaries during use of the alloy material in a high-temperature ammonia environment. In this case, the strength of the grain boundaries is rather reduced. Therefore, even if the content of other elements is within the range of this embodiment, intergranular cracking will be promoted near the surface layer of the alloy material in a high-temperature ammonia environment.
Therefore, the Sn content is greater than 0 to 0.1000%.
The preferable lower limit of the Sn content is 0.0001%, more preferably 0.0002%, and still more preferably 0.0003%.
A preferable upper limit of the Sn content is 0.0700%, more preferably 0.0500%, and still more preferably 0.0450%.
The preferable range of Sn content is, for example, 0.0001 to 0.0700%, more preferably 0.0002 to 0.0500%, and still more preferably 0.0003 to 0.0450%.
　Ｚｎ：０超～０．０１００％
　亜鉛（Ｚｎ）は含有されなくてもよい。つまり、Ｚｎ含有量は０％であってもよい。
　含有される場合、つまり、Ｚｎ含有量が０％超である場合、Ｚｎは高温アンモニア環境での合金材の使用中において粒界に偏析する。偏析したＺｎは、粒界に析出物が生成したり、粒界にＰ及びＳが偏析したりするのを抑制する。これにより、粒界が強化され、高温アンモニア環境での合金材の表層近傍での粒界割れが抑制される。Ｚｎが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｚｎ含有量が０．０１００％を超えれば、高温アンモニア環境での合金材の使用中において、Ｚｎが粒界に過剰に偏析する。この場合、粒界の強度がかえって低下する。そのため、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材の表層近傍での粒界割れが促進されてしまう。
　したがって、Ｚｎ含有量は０超～０．０１００％である。
　Ｚｎ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．００１０％であり、さらに好ましくは０．００２０％である。
　Ｚｎ含有量の好ましい上限は０．００９５％であり、さらに好ましくは０．００９０％であり、さらに好ましくは０．００８０％である。
　Ｚｎ含有量の好ましい範囲は例えば、０．０００１～０．００９５％であり、さらに好ましくは０．００１０～０．００９０％であり、さらに好ましくは０．００２０～０．００８０％である。 Zn: more than 0 to 0.0100%
Zinc (Zn) may not be contained. That is, the Zn content may be 0%.
When Zn is contained, that is, when the Zn content is more than 0%, Zn segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment. The segregated Zn suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Zn is contained, the above effects can be obtained to some extent.
However, if the Zn content exceeds 0.0100%, Zn will segregate excessively at grain boundaries during use of the alloy material in a high-temperature ammonia environment. In this case, the strength of the grain boundaries is rather reduced. Therefore, even if the content of other elements is within the range of this embodiment, intergranular cracking will be promoted near the surface layer of the alloy material in a high-temperature ammonia environment.
Therefore, the Zn content is greater than 0 to 0.0100%.
The lower limit of the Zn content is preferably 0.0001%, more preferably 0.0010%, and still more preferably 0.0020%.
A preferable upper limit of the Zn content is 0.0095%, more preferably 0.0090%, and still more preferably 0.0080%.
The preferred range of Zn content is, for example, 0.0001 to 0.0095%, more preferably 0.0010 to 0.0090%, and even more preferably 0.0020 to 0.0080%.
　Ｐｂ：０超～０．０１００％
　鉛（Ｐｂ）は含有されなくてもよい。つまり、Ｐｂ含有量は０％であってもよい。
　含有される場合、つまり、Ｐｂ含有量が０％超である場合、Ｐｂは高温アンモニア環境での合金材の使用中において粒界に偏析する。偏析したＰｂは、粒界に析出物が生成したり、粒界にＰ及びＳが偏析したりするのを抑制する。これにより、粒界が強化され、高温アンモニア環境での合金材の表層近傍での粒界割れが抑制される。Ｐｂが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｐｂ含有量が０．０１００％を超えれば、高温アンモニア環境での合金材の使用中において、Ｐｂが粒界に過剰に偏析する。この場合、粒界の強度がかえって低下する。そのため、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材の表層近傍での粒界割れが促進されてしまう。
　したがって、Ｐｂ含有量は０超～０．０１００％である。
　Ｐｂ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．００１０％であり、さらに好ましくは０．００２０％である。
　Ｐｂ含有量の好ましい上限は０．００９０％であり、さらに好ましくは０．００８０％であり、さらに好ましくは０．００７０％である。
　Ｐｂ含有量の好ましい範囲は例えば、０．０００１～０．００９０％であり、さらに好ましくは０．００１０～０．００８０％であり、さらに好ましくは０．００２０～０．００７０％である。 Pb: more than 0 to 0.0100%
Lead (Pb) may not be contained. That is, the Pb content may be 0%.
When contained, that is, when the Pb content is more than 0%, Pb segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment. The segregated Pb suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Pb is contained, the above effects can be obtained to some extent.
However, if the Pb content exceeds 0.0100%, Pb will segregate excessively at grain boundaries during use of the alloy material in a high-temperature ammonia environment. In this case, the strength of the grain boundaries is rather reduced. Therefore, even if the content of other elements is within the range of this embodiment, intergranular cracking will be promoted near the surface layer of the alloy material in a high-temperature ammonia environment.
Therefore, the Pb content is greater than 0 to 0.0100%.
The preferable lower limit of the Pb content is 0.0001%, more preferably 0.0010%, and still more preferably 0.0020%.
A preferable upper limit of the Pb content is 0.0090%, more preferably 0.0080%, and still more preferably 0.0070%.
The preferred range of the Pb content is, for example, 0.0001 to 0.0090%, more preferably 0.0010 to 0.0080%, and still more preferably 0.0020 to 0.0070%.
　Ｓｂ：０超～０．０１００％
　アンチモン（Ｓｂ）は含有されなくてもよい。つまり、Ｓｂ含有量は０％であってもよい。
　含有される場合、つまり、Ｓｂ含有量が０％超である場合、Ｓｂは高温アンモニア環境での合金材の使用中において粒界に偏析する。偏析したＳｂは、粒界に析出物が生成したり、粒界にＰ及びＳが偏析したりするのを抑制する。これにより、粒界が強化され、高温アンモニア環境での合金材の表層近傍での粒界割れが抑制される。Ｓｂが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｓｂ含有量が０．０１００％を超えれば、高温アンモニア環境での合金材の使用中において、Ｓｂが粒界に過剰に偏析する。この場合、粒界の強度がかえって低下する。そのため、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材の表層近傍での粒界割れが促進されてしまう。
　したがって、Ｓｂ含有量は０超～０．０１００％である。
　Ｓｂ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．００１０％であり、さらに好ましくは０．００１５％である。
　Ｓｂ含有量の好ましい上限は０．００９０％であり、さらに好ましくは０．００８０％であり、さらに好ましくは０．００７０％である。
　Ｓｂ含有量の好ましい範囲は例えば、０．０００１～０．００９０％であり、さらに好ましくは０．００１０～０．００８０％であり、さらに好ましくは０．００１５～０．００７０％である。 Sb: more than 0 to 0.0100%
Antimony (Sb) may not be contained. That is, the Sb content may be 0%.
When Sb is contained, that is, when the Sb content is more than 0%, Sb segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment. The segregated Sb suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Sb is contained, the above effects can be obtained to some extent.
However, if the Sb content exceeds 0.0100%, Sb will excessively segregate at grain boundaries during use of the alloy material in a high-temperature ammonia environment. In this case, the strength of the grain boundaries is rather reduced. Therefore, even if the content of other elements is within the range of this embodiment, intergranular cracking will be promoted near the surface layer of the alloy material in a high-temperature ammonia environment.
Therefore, the Sb content is greater than 0 to 0.0100%.
The preferable lower limit of the Sb content is 0.0001%, more preferably 0.0010%, and still more preferably 0.0015%.
A preferable upper limit of the Sb content is 0.0090%, more preferably 0.0080%, and still more preferably 0.0070%.
The preferable range of the Sb content is, for example, 0.0001 to 0.0090%, more preferably 0.0010 to 0.0080%, and still more preferably 0.0015 to 0.0070%.
　Ａｓ：０超～０．００１０％
　砒素（Ａｓ）は含有されなくてもよい。つまり、Ａｓ含有量は０％であってもよい。
　含有される場合、つまり、Ａｓ含有量が０％超である場合、Ａｓは高温アンモニア環境での合金材の使用中において粒界に偏析する。偏析したＡｓは、粒界に析出物が生成したり、粒界にＰ及びＳが偏析したりするのを抑制する。これにより、粒界が強化され、高温アンモニア環境での合金材の表層近傍での粒界割れが抑制される。Ａｓが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ａｓ含有量が０．００１０％を超えれば、高温アンモニア環境での合金材の使用中において、Ａｓが粒界に過剰に偏析する。この場合、粒界の強度がかえって低下する。そのため、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材の表層近傍での粒界割れが促進されてしまう。
　したがって、Ａｓ含有量は０超～０．００１０％である。
　Ａｓ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．０００２％であり、さらに好ましくは０．０００３％である。
　Ａｓ含有量の好ましい上限は０．０００９％であり、さらに好ましくは０．０００８％であり、さらに好ましくは０．０００７％である。
　Ａｓ含有量の好ましい範囲は例えば、０．０００１～０．０００９％であり、さらに好ましくは０．０００２～０．０００８％であり、さらに好ましくは０．０００３～０．０００７％である。 As: more than 0 to 0.0010%
Arsenic (As) may not be contained. That is, the As content may be 0%.
When it is contained, that is, when the As content is more than 0%, As is segregated at grain boundaries during use of the alloy material in a high-temperature ammonia environment. The segregated As suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of As is contained, the above effects can be obtained to some extent.
However, when the As content exceeds 0.0010%, As is excessively segregated at grain boundaries during use of the alloy material in a high-temperature ammonia environment. In this case, the strength of the grain boundaries is rather reduced. Therefore, even if the content of other elements is within the range of this embodiment, intergranular cracking will be promoted near the surface layer of the alloy material in a high-temperature ammonia environment.
Therefore, the As content is greater than 0 to 0.0010%.
The lower limit of the As content is preferably 0.0001%, more preferably 0.0002%, and even more preferably 0.0003%.
A preferable upper limit of the As content is 0.0009%, more preferably 0.0008%, and even more preferably 0.0007%.
The preferable range of the As content is, for example, 0.0001 to 0.0009%, more preferably 0.0002 to 0.0008%, and still more preferably 0.0003 to 0.0007%.
　Ｂｉ：０超～０．００１０％
　ビスマス（Ｂｉ）は含有されなくてもよい。つまり、Ｂｉ含有量は０％であってもよい。
　含有される場合、つまり、Ｂｉ含有量が０％超である場合、Ｂｉは高温アンモニア環境での合金材の使用中において粒界に偏析する。偏析したＢｉは、粒界に析出物が生成したり、粒界にＰ、Ｓが偏析したりするのを抑制する。これにより、粒界が強化され、高温アンモニア環境での合金材の表層近傍での粒界割れが抑制される。Ｂｉが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｂｉ含有量が０．００１０％を超えれば、高温アンモニア環境での合金材の使用中において、Ｂｉが粒界に過剰に偏析する。この場合、粒界の強度がかえって低下する。そのため、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材の表層近傍での粒界割れが促進されてしまう。
　したがって、Ｂｉ含有量は０超～０．００１０％である。
　Ｂｉ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．０００２％であり、さらに好ましくは０．０００３％である。
　Ｂｉ含有量の好ましい上限は０．０００９％であり、さらに好ましくは０．０００８％であり、さらに好ましくは０．０００７％である。
　Ｂｉ含有量の好ましい範囲は例えば、０．０００１～０．０００９％であり、さらに好ましくは０．０００２～０．０００８％であり、さらに好ましくは０．０００３～０．０００７％である。 Bi: more than 0 to 0.0010%
Bismuth (Bi) may not be contained. That is, the Bi content may be 0%.
When Bi is contained, that is, when the Bi content exceeds 0%, Bi segregates at grain boundaries during use of the alloy material in a high-temperature ammonia environment. The segregated Bi suppresses the formation of precipitates at grain boundaries and the segregation of P and S at grain boundaries. This strengthens grain boundaries and suppresses grain boundary cracking near the surface layer of the alloy material in a high-temperature ammonia environment. If even a small amount of Bi is contained, the above effects can be obtained to some extent.
However, if the Bi content exceeds 0.0010%, Bi will segregate excessively at grain boundaries during use of the alloy material in a high-temperature ammonia environment. In this case, the strength of the grain boundaries is rather reduced. Therefore, even if the content of other elements is within the range of this embodiment, intergranular cracking will be promoted near the surface layer of the alloy material in a high-temperature ammonia environment.
Therefore, the Bi content is greater than 0 to 0.0010%.
The preferable lower limit of the Bi content is 0.0001%, more preferably 0.0002%, and still more preferably 0.0003%.
A preferable upper limit of the Bi content is 0.0009%, more preferably 0.0008%, and still more preferably 0.0007%.
The preferred range of Bi content is, for example, 0.0001 to 0.0009%, more preferably 0.0002 to 0.0008%, and even more preferably 0.0003 to 0.0007%.
　本実施形態のオーステナイト系合金材はさらに、第２群～第４群からなる群から選択される１種以上を含有する。
　［第２群］
　Ｃｕ：０超～５．００％、及び、
　Ｍｏ：０超～２０．００％、からなる群から選択される１種以上
　［第３群］
　Ｃｏ：０超～３．００％、
　Ｗ：０超～７．００％、
　Ｔｉ：０超～１．００％、
　Ｎｂ：０超～０．１０％、
　Ｖ：０超～０．５０％、
　Ｂ：０超～０．００５０％、
　Ｎ：０超～０．２００％、及び、
　希土類元素：０超～０．１００％、からなる群から選択される１種以上
　［第４群］
　Ａｌ：０超～０．５００％、
　Ｃａ：０超～０．０１００％、及び、
　Ｍｇ：０超～０．０１５０％、からなる群から選択される１種以上
　以下、第２群～第４群の各元素について説明する。 The austenitic alloy material of this embodiment further contains one or more selected from the group consisting of the second group to the fourth group.
[Group 2]
Cu: more than 0 to 5.00%, and
Mo: more than 0 to 20.00%, one or more types selected from the group consisting of [Group 3]
Co: more than 0 to 3.00%,
W: more than 0 to 7.00%,
Ti: more than 0 to 1.00%,
Nb: more than 0 to 0.10%,
V: more than 0 to 0.50%,
B: more than 0 to 0.0050%,
N: more than 0 to 0.200%, and
Rare earth elements: one or more selected from the group consisting of more than 0 to 0.100% [Group 4]
Al: more than 0 to 0.500%,
Ca: more than 0 to 0.0100%, and
Mg: one or more selected from the group consisting of more than 0% to 0.0150% Each element of the second to fourth groups will be explained below.
　［（第２群）Ｃｕ及びＭｏ］
　Ｃｕ及びＭｏはいずれも、高温アンモニア環境での合金材の耐窒化性を高める。以下、各元素について説明する。 [(2nd group) Cu and Mo]
Both Cu and Mo improve the nitriding resistance of the alloy material in a high temperature ammonia environment. Each element will be explained below.
　Ｃｕ：０超～５．００％
　銅（Ｃｕ）は含有されなくてもよい。つまり、Ｃｕ含有量は０％であってもよい。
　含有される場合、つまり、Ｃｕ含有量が０％超である場合、Ｃｕは、高温アンモニア環境での合金材の耐窒化性を高める。Ｃｕが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｃｕ含有量が５．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材のクリープ延性が低下する。
　したがって、Ｃｕ含有量は、０超～５．００％である。
　Ｃｕ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％であり、さらに好ましくは０．５０％であり、さらに好ましくは１．００％であり、さらに好ましくは１．５０％である。
　Ｃｕ含有量の好ましい上限は４．５０％であり、さらに好ましくは４．００％であり、さらに好ましくは３．５０％であり、さらに好ましくは３．００％であり、さらに好ましくは２．５０％である。
　Ｃｕ含有量の好ましい範囲は例えば、０．０１～４．５０％であり、さらに好ましくは０．０５～４．００％であり、さらに好ましくは０．１０～３．５０％であり、さらに好ましくは０．５０～３．００％であり、さらに好ましくは１．００～２．５０％であり、さらに好ましくは１．５０～２．５０％である。 Cu: more than 0 to 5.00%
Copper (Cu) may not be contained. That is, the Cu content may be 0%.
When contained, that is, when the Cu content is more than 0%, Cu increases the nitriding resistance of the alloy material in a high-temperature ammonia environment. If even a small amount of Cu is contained, the above effects can be obtained to some extent.
However, if the Cu content exceeds 5.00%, the creep ductility of the alloy material in a high-temperature ammonia environment decreases even if the contents of other elements are within the ranges of this embodiment.
Therefore, the Cu content is greater than 0 to 5.00%.
The preferable lower limit of the Cu content is 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.50%, and even more preferably 1.00%. %, more preferably 1.50%.
The upper limit of the Cu content is preferably 4.50%, more preferably 4.00%, even more preferably 3.50%, still more preferably 3.00%, and even more preferably 2.50%. %.
The preferable range of the Cu content is, for example, 0.01 to 4.50%, more preferably 0.05 to 4.00%, still more preferably 0.10 to 3.50%, and even more preferably is 0.50 to 3.00%, more preferably 1.00 to 2.50%, even more preferably 1.50 to 2.50%.
　Ｍｏ：０超～２０．００％
　モリブデン（Ｍｏ）は含有されなくてもよい。つまり、Ｍｏ含有量は０％であってもよい。
　含有される場合、つまり、Ｍｏ含有量が０％超である場合、Ｍｏは、高温アンモニア環境での合金材の耐窒化性を高める。Ｍｏが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｍｏ含有量が２０．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、合金材の熱間加工性が低下する。
　したがって、Ｍｏ含有量は、０超～２０．００％である。
　Ｍｏ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％であり、さらに好ましくは０．５０％であり、さらに好ましくは１．００％であり、さらに好ましくは１．５０％であり、さらに好ましくは３．００％であり、さらに好ましくは５．００％であり、さらに好ましくは８．００％である。
　Ｍｏ含有量の好ましい上限は１８．００％であり、さらに好ましくは１６．００％であり、さらに好ましくは１４．００％である。
　Ｍｏ含有量の好ましい範囲は例えば、０．０１～１８．００％であり、さらに好ましくは０．０５～１６．００％であり、さらに好ましくは０．１０～１４．００％であり、さらに好ましくは０．５０～１４．００％であり、さらに好ましくは１．００～１４．００％であり、さらに好ましくは１．５０～１４．００％であり、さらに好ましくは３．００～１４．００％であり、さらに好ましくは５．００～１４．００％であり、さらに好ましくは８．００～１４．００％である。 Mo: more than 0 to 20.00%
Molybdenum (Mo) may not be contained. That is, the Mo content may be 0%.
When contained, that is, when the Mo content is more than 0%, Mo increases the nitriding resistance of the alloy material in a high-temperature ammonia environment. If even a small amount of Mo is contained, the above effects can be obtained to some extent.
However, if the Mo content exceeds 20.00%, the hot workability of the alloy material will decrease even if the contents of other elements are within the ranges of this embodiment.
Therefore, the Mo content is greater than 0 to 20.00%.
The lower limit of the Mo content is preferably 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.50%, and still more preferably 1.00%. %, more preferably 1.50%, further preferably 3.00%, still more preferably 5.00%, still more preferably 8.00%.
A preferable upper limit of the Mo content is 18.00%, more preferably 16.00%, and still more preferably 14.00%.
The preferred range of Mo content is, for example, 0.01 to 18.00%, more preferably 0.05 to 16.00%, even more preferably 0.10 to 14.00%, and even more preferably is 0.50 to 14.00%, more preferably 1.00 to 14.00%, even more preferably 1.50 to 14.00%, even more preferably 3.00 to 14.00%. %, more preferably 5.00 to 14.00%, even more preferably 8.00 to 14.00%.
　［（第３群）Ｃｏ、Ｗ、Ｔｉ、Ｎｂ、Ｖ、Ｂ、Ｎ、及び、希土類元素］
　Ｃｏ、Ｗ、Ｔｉ、Ｎｂ、Ｖ、Ｂ、Ｎ、及び、希土類元素（ＲＥＭ）はいずれも、高温アンモニア環境での合金材のクリープ強度を高める。以下、各元素について説明する。 [(Group 3) Co, W, Ti, Nb, V, B, N, and rare earth elements]
Co, W, Ti, Nb, V, B, N, and rare earth elements (REM) all increase the creep strength of the alloy material in a high temperature ammonia environment. Each element will be explained below.
　Ｃｏ：０超～３．００％
　コバルト（Ｃｏ）は含有されなくてもよい。つまり、Ｃｏ含有量は０％であってもよい。
　含有される場合、つまり、Ｃｏ含有量が０％超である場合、Ｃｏは合金材に固溶して、高温アンモニア環境での合金材のクリープ強度を高める。Ｃｏが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｃｏ含有量が３．００％を超えれば、効果が飽和し、製造コストが高くなる。
　したがって、Ｃｏ含有量は０超～３．００％である。
　Ｃｏ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％であり、さらに好ましくは０．１５％である。
　Ｃｏ含有量の好ましい上限は２．８０％であり、さらに好ましくは２．５０％であり、さらに好ましくは２．００％である。
　Ｃｏ含有量の好ましい範囲は例えば、０．０１～２．８０％であり、さらに好ましくは０．０５～２．５０％であり、さらに好ましくは０．１０～２．００％であり、さらに好ましくは０．１５～２．００％である。 Co: more than 0 to 3.00%
Cobalt (Co) may not be contained. That is, the Co content may be 0%.
When Co is contained, that is, when the Co content is more than 0%, Co dissolves in the alloy material and increases the creep strength of the alloy material in a high-temperature ammonia environment. If even a small amount of Co is contained, the above effects can be obtained to some extent.
However, if the Co content exceeds 3.00%, the effect will be saturated and the manufacturing cost will increase.
Therefore, the Co content is greater than 0 to 3.00%.
The preferable lower limit of the Co content is 0.01%, more preferably 0.05%, still more preferably 0.10%, and still more preferably 0.15%.
A preferable upper limit of the Co content is 2.80%, more preferably 2.50%, and still more preferably 2.00%.
The preferable range of the Co content is, for example, 0.01 to 2.80%, more preferably 0.05 to 2.50%, still more preferably 0.10 to 2.00%, even more preferably is 0.15 to 2.00%.
　Ｗ：０超～７．００％
　タングステン（Ｗ）は含有されなくてもよい。つまり、Ｗ含有量は０％であってもよい。
　含有される場合、つまり、Ｗ含有量が０％超である場合、Ｗは合金材に固溶して、高温アンモニア環境での合金材のクリープ強度を高める。Ｗはさらに、高温アンモニア環境での合金材の使用中において析出物を生成し、高温アンモニア環境での合金材のクリープ強度を高める。Ｗが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｗ含有量が７．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、合金材の熱間加工性が低下する。
　したがって、Ｗ含有量は０超～７．００％である。
　Ｗ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％であり、さらに好ましくは０．５０％であり、さらに好ましくは１．００％であり、さらに好ましくは２．００％である。
　Ｗ含有量の好ましい上限は６．５０％であり、さらに好ましくは６．００％であり、さらに好ましくは５．５０％であり、さらに好ましくは５．００％であり、さらに好ましくは４．５０％であり、さらに好ましくは４．００％であり、さらに好ましくは３．５０％である。
　Ｗ含有量の好ましい範囲は例えば、０．０１～６．５０％であり、さらに好ましくは０．０５～６．００％であり、さらに好ましくは０．１０～５．５０％であり、さらに好ましくは０．５０～５．００％であり、さらに好ましくは１．００～４．５０％であり、さらに好ましくは２．００～４．００％であり、さらに好ましくは２．００～３．５０％である。 W: More than 0 to 7.00%
Tungsten (W) may not be contained. That is, the W content may be 0%.
When W is contained, that is, when the W content is more than 0%, W is dissolved in the alloy material and increases the creep strength of the alloy material in a high-temperature ammonia environment. W also forms precipitates during use of the alloy material in a high temperature ammonia environment, increasing the creep strength of the alloy material in a high temperature ammonia environment. If even a small amount of W is contained, the above effects can be obtained to some extent.
However, if the W content exceeds 7.00%, the hot workability of the alloy material decreases even if the contents of other elements are within the ranges of this embodiment.
Therefore, the W content is greater than 0 to 7.00%.
The lower limit of the W content is preferably 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.50%, and still more preferably 1.00%. %, more preferably 2.00%.
The upper limit of the W content is preferably 6.50%, more preferably 6.00%, even more preferably 5.50%, even more preferably 5.00%, and still more preferably 4.50%. %, more preferably 4.00%, still more preferably 3.50%.
The preferable range of the W content is, for example, 0.01 to 6.50%, more preferably 0.05 to 6.00%, still more preferably 0.10 to 5.50%, and even more preferably is 0.50 to 5.00%, more preferably 1.00 to 4.50%, even more preferably 2.00 to 4.00%, even more preferably 2.00 to 3.50%. %.
　Ｔｉ：０超～１．００％
　チタン（Ｔｉ）は含有されなくてもよい。つまり、Ｔｉ含有量は０％であってもよい。
　含有される場合、つまり、Ｔｉ含有量が０％超である場合、Ｔｉは、高温アンモニア環境での合金材の使用中において析出物を生成し、高温アンモニア環境での合金材のクリープ強度を高める。Ｔｉが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｔｉ含有量が１．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、Ｔｉ析出物が粗大となる。この場合、合金材のクリープ強度及び靱性が低下する。
　したがって、Ｔｉ含有量は０超～１．００％である。
　Ｔｉ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０２％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％である。
　Ｔｉ含有量の好ましい上限は０．９０％であり、さらに好ましくは０．８０％であり、さらに好ましくは０．７０％であり、さらに好ましくは０．６０％であり、さらに好ましくは０．５０％であり、さらに好ましくは０．４５％であり、さらに好ましくは０．４０％であり、さらに好ましくは０．３５％であり、さらに好ましくは０．３０％である。
　Ｔｉ含有量の好ましい範囲は例えば、０．０１～０．９０％であり、さらに好ましくは０．０２～０．８０％であり、さらに好ましくは０．０５～０．７０％であり、さらに好ましくは０．１０～０．６０％であり、さらに好ましくは０．１０～０．５０％であり、さらに好ましくは０．１０～０．４５％であり、さらに好ましくは０．１０～０．４０％であり、さらに好ましくは０．１０～０．３５％であり、さらに好ましくは０．１０～０．３０％である。 Ti: more than 0 to 1.00%
Titanium (Ti) may not be contained. That is, the Ti content may be 0%.
When contained, that is, when the Ti content is more than 0%, Ti generates precipitates during use of the alloy material in a high-temperature ammonia environment, increasing the creep strength of the alloy material in a high-temperature ammonia environment. . If even a small amount of Ti is contained, the above effects can be obtained to some extent.
However, if the Ti content exceeds 1.00%, the Ti precipitates will become coarse even if the contents of other elements are within the range of this embodiment. In this case, the creep strength and toughness of the alloy material decrease.
Therefore, the Ti content is greater than 0 to 1.00%.
The lower limit of the Ti content is preferably 0.01%, more preferably 0.02%, even more preferably 0.05%, and still more preferably 0.10%.
The preferable upper limit of the Ti content is 0.90%, more preferably 0.80%, even more preferably 0.70%, still more preferably 0.60%, and even more preferably 0.50%. %, more preferably 0.45%, still more preferably 0.40%, still more preferably 0.35%, still more preferably 0.30%.
The preferable range of the Ti content is, for example, 0.01 to 0.90%, more preferably 0.02 to 0.80%, still more preferably 0.05 to 0.70%, and even more preferably is 0.10 to 0.60%, more preferably 0.10 to 0.50%, even more preferably 0.10 to 0.45%, even more preferably 0.10 to 0.40 %, more preferably 0.10 to 0.35%, even more preferably 0.10 to 0.30%.
　Ｎｂ：０超～０．１０％
　ニオブ（Ｎｂ）は含有されなくてもよい。つまり、Ｎｂ含有量は０％であってもよい。
　含有される場合、つまり、Ｎｂ含有量が０％超である場合、Ｎｂは、高温アンモニア環境での合金材の使用中において析出物を生成し、高温アンモニア環境での合金材のクリープ強度を高める。Ｎｂが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｎｂ含有量が０．１０％を超えれば、Ｎｂ析出物が粗大となる。この場合、他の元素含有量が本実施形態の範囲内であっても、合金材のクリープ強度及び靱性が低下する。
　したがって、Ｎｂ含有量は０超～０．１０％である。
　Ｎｂ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０２％であり、さらに好ましくは０．０３％である。
　Ｎｂ含有量の好ましい上限は０．０９％であり、さらに好ましくは０．０８％であり、さらに好ましくは０．０７％である。
　Ｎｂ含有量の好ましい範囲は例えば、０．０１～０．０９％であり、さらに好ましくは０．０２～０．０８％であり、さらに好ましくは０．０３～０．０７％である。 Nb: more than 0 to 0.10%
Niobium (Nb) may not be contained. That is, the Nb content may be 0%.
When contained, that is, when the Nb content is more than 0%, Nb generates precipitates during use of the alloy material in a high-temperature ammonia environment, increasing the creep strength of the alloy material in a high-temperature ammonia environment. . If even a small amount of Nb is contained, the above effects can be obtained to some extent.
However, if the Nb content exceeds 0.10%, Nb precipitates become coarse. In this case, even if the content of other elements is within the range of this embodiment, the creep strength and toughness of the alloy material decrease.
Therefore, the Nb content is greater than 0 to 0.10%.
The lower limit of the Nb content is preferably 0.01%, more preferably 0.02%, and still more preferably 0.03%.
A preferable upper limit of the Nb content is 0.09%, more preferably 0.08%, and still more preferably 0.07%.
The preferred range of the Nb content is, for example, 0.01 to 0.09%, more preferably 0.02 to 0.08%, and still more preferably 0.03 to 0.07%.
　Ｖ：０超～０．５０％
　バナジウム（Ｖ）は含有されなくてもよい。つまり、Ｖ含有量は０％であってもよい。
　含有される場合、つまり、Ｖ含有量が０％超である場合、Ｖは、高温アンモニア環境での合金材の使用中において析出物を生成し、高温アンモニア環境での合金材のクリープ強度を高める。Ｖが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｖ含有量が０．５０％を超えれば、Ｖ析出物が粗大となる。この場合、他の元素含有量が本実施形態の範囲内であっても、合金材のクリープ強度及び靱性が低下する。
　したがって、Ｖ含有量は０超～０．５０である。
　Ｖ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％である。
　Ｖ含有量の好ましい上限は０．４５％であり、さらに好ましくは０．４０％であり、さらに好ましくは０．３５％である。
　Ｖ含有量の好ましい範囲は例えば、０．０１～０．４５％であり、さらに好ましくは０．０５～０．４０％であり、さらに好ましくは０．１０～０．３５％である。 V: More than 0 to 0.50%
Vanadium (V) may not be contained. That is, the V content may be 0%.
When contained, that is, when the V content is more than 0%, V generates precipitates during use of the alloy material in a high-temperature ammonia environment, increasing the creep strength of the alloy material in a high-temperature ammonia environment. . If even a small amount of V is contained, the above effects can be obtained to some extent.
However, if the V content exceeds 0.50%, V precipitates become coarse. In this case, even if the content of other elements is within the range of this embodiment, the creep strength and toughness of the alloy material decrease.
Therefore, the V content is greater than 0 to 0.50.
The lower limit of the V content is preferably 0.01%, more preferably 0.05%, and even more preferably 0.10%.
A preferable upper limit of the V content is 0.45%, more preferably 0.40%, and still more preferably 0.35%.
The preferable range of the V content is, for example, 0.01 to 0.45%, more preferably 0.05 to 0.40%, and still more preferably 0.10 to 0.35%.
　Ｂ：０超～０．００５０％
　ボロン（Ｂ）は含有されなくてもよい。つまり、Ｂ含有量は０％であってもよい。
　含有される場合、つまり、Ｂ含有量が０％超である場合、Ｂは、高温アンモニア環境で粒界に偏析して粒界を強化する。そのため、高温アンモニア環境での合金材のクリープ強度が高まる。Ｂが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｂ含有量が０．００５０％を超えれば、他の元素含有量が本実施形態の範囲内であっても、合金材の熱間加工性及び溶接性が低下する。
　したがって、Ｂ含有量は０超～０．００５０％である。
　Ｂ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．０００２％であり、さらに好ましくは０．０００５％である。
　Ｂ含有量の好ましい上限は０．００４５％であり、さらに好ましくは０．００４０％であり、さらに好ましくは０．００３５％である。
　Ｂ含有量の好ましい範囲は例えば、０．０００１～０．００４５％であり、さらに好ましくは０．０００２～０．００４０％であり、さらに好ましくは０．０００５～０．００３５％である。 B: More than 0 to 0.0050%
Boron (B) may not be contained. That is, the B content may be 0%.
When B is contained, that is, when the B content is more than 0%, B segregates to the grain boundaries in a high-temperature ammonia environment and strengthens the grain boundaries. Therefore, the creep strength of the alloy material increases in a high-temperature ammonia environment. If even a small amount of B is contained, the above effects can be obtained to some extent.
However, if the B content exceeds 0.0050%, the hot workability and weldability of the alloy material will deteriorate even if the contents of other elements are within the ranges of this embodiment.
Therefore, the B content is greater than 0 to 0.0050%.
The preferable lower limit of the B content is 0.0001%, more preferably 0.0002%, and still more preferably 0.0005%.
A preferable upper limit of the B content is 0.0045%, more preferably 0.0040%, and still more preferably 0.0035%.
The preferable range of the B content is, for example, 0.0001 to 0.0045%, more preferably 0.0002 to 0.0040%, and still more preferably 0.0005 to 0.0035%.
　Ｎ：０超～０．２００％
　窒素（Ｎ）は含有されなくてもよい。つまり、含有されなくてもよい。つまり、Ｎ含有量は０％であってもよい。
　含有される場合、つまり、Ｎ含有量が０％超である場合、Ｎは合金材に固溶して、高温アンモニア環境での合金材のクリープ強度を高める。Ｎはさらに、高温アンモニア環境での合金材の使用中において析出物を生成し、高温アンモニア環境での合金材のクリープ強度を高める。Ｎが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｎ含有量が０．２００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、高温アンモニア環境での合金材の使用中において窒化物が過剰に生成する。この場合、合金材のクリープ延性又は靱性が低下する。
　したがって、Ｎ含有量は０超～０．２００％である。
　Ｎ含有量の好ましい下限は０．００１％であり、さらに好ましくは０．００５％であり、さらに好ましくは０．０１０％である。
　Ｎ含有量の好ましい上限は０．１９０％であり、さらに好ましくは０．１６０％であり、さらに好ましくは０．１４０％であり、さらに好ましくは０．１２０％である。
　Ｎ含有量の好ましい範囲は例えば、０．００１～０．１９０％であり、さらに好ましくは０．００５～０．１６０％であり、さらに好ましくは０．０１０～０．１４０％であり、さらに好ましくは０．０１０～０．１２０％である。 N: More than 0 to 0.200%
Nitrogen (N) may not be contained. In other words, it does not need to be contained. That is, the N content may be 0%.
When N is contained, that is, when the N content is more than 0%, N is dissolved in the alloy material and increases the creep strength of the alloy material in a high-temperature ammonia environment. Furthermore, N forms precipitates during use of the alloy material in a high temperature ammonia environment, increasing the creep strength of the alloy material in a high temperature ammonia environment. If even a small amount of N is contained, the above effects can be obtained to some extent.
However, if the N content exceeds 0.200%, nitrides will be excessively produced during use of the alloy material in a high-temperature ammonia environment even if the contents of other elements are within the range of this embodiment. In this case, the creep ductility or toughness of the alloy material decreases.
Therefore, the N content is greater than 0 to 0.200%.
The preferable lower limit of the N content is 0.001%, more preferably 0.005%, and still more preferably 0.010%.
A preferable upper limit of the N content is 0.190%, more preferably 0.160%, still more preferably 0.140%, and still more preferably 0.120%.
The preferred range of the N content is, for example, 0.001 to 0.190%, more preferably 0.005 to 0.160%, even more preferably 0.010 to 0.140%, and even more preferably is 0.010 to 0.120%.
　希土類元素：０超～０．１００％
　希土類元素（ＲＥＭ）は含有されなくてもよい。つまり、ＲＥＭ含有量は０％であってもよい。
　含有される場合、つまり、ＲＥＭ含有量が０％超である場合、ＲＥＭは、高温アンモニア環境で粒界に偏析して粒界を強化する。そのため、高温アンモニア環境での合金材のクリープ強度が高まる。ＲＥＭが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、ＲＥＭ含有量が０．１００％を超えれば、合金材中に酸化物等の介在物が形成される。そのため、他の元素含有量が本実施形態の範囲内であっても、合金材のクリープ強度が低下する。
　したがって、ＲＥＭ含有量は０超～０．１００％である。
　ＲＥＭ含有量の好ましい下限は０．００１％であり、さらに好ましくは０．００５％であり、さらに好ましくは０．０１０％である。
　ＲＥＭ含有量の好ましい上限は０．０９０％であり、さらに好ましくは０．０７０％であり、さらに好ましくは０．０５５％である。
　ＲＥＭ含有量の好ましい範囲は例えば、０．００１～０．０９０％であり、さらに好ましくは０．００５～０．０７０％であり、さらに好ましくは０．０１０～０．０５５％である。 Rare earth elements: more than 0 to 0.100%
Rare earth elements (REM) may not be contained. That is, the REM content may be 0%.
When contained, that is, when the REM content is more than 0%, REM segregates to the grain boundaries in a high-temperature ammonia environment and strengthens the grain boundaries. Therefore, the creep strength of the alloy material increases in a high-temperature ammonia environment. If even a small amount of REM is contained, the above effects can be obtained to some extent.
However, if the REM content exceeds 0.100%, inclusions such as oxides will be formed in the alloy material. Therefore, even if the contents of other elements are within the range of this embodiment, the creep strength of the alloy material decreases.
Therefore, the REM content is greater than 0 to 0.100%.
The lower limit of the REM content is preferably 0.001%, more preferably 0.005%, and still more preferably 0.010%.
A preferable upper limit of the REM content is 0.090%, more preferably 0.070%, and still more preferably 0.055%.
The preferable range of the REM content is, for example, 0.001 to 0.090%, more preferably 0.005 to 0.070%, and still more preferably 0.010 to 0.055%.
　本明細書におけるＲＥＭは、Ｓｃ、Ｙ、及び、ランタノイド（原子番号５７番のＬａ～７１番のＬｕ）からなる群から選択される１種以上を含有し、ＲＥＭ含有量は、これらの元素の合計含有量（質量％）を意味する。 REM in this specification contains one or more selected from the group consisting of Sc, Y, and lanthanoids (La with atomic number 57 to Lu with atomic number 71), and the REM content is defined as the content of these elements. Means total content (mass%).
　［（第４群）Ａｌ、Ｃａ及びＭｇ］
　Ａｌ、Ｃａ及びＭｇはいずれも、合金材の製造工程において、合金を脱酸する。以下、各元素について説明する。 [(Group 4) Al, Ca and Mg]
Al, Ca, and Mg all deoxidize the alloy in the manufacturing process of the alloy material. Each element will be explained below.
　Ａｌ：０超～０．５００％
　アルミニウム（Ａｌ）は含有されなくてもよい。つまり、Ａｌ含有量は０％であってもよい。
　含有される場合、つまり、Ａｌ含有量が０％超である場合、Ａｌは合金材の製造工程において、合金を脱酸する。Ａｌが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ａｌ含有量が０．５００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、介在物が過剰に生成して合金材のクリープ強度及び靱性を低下する。
　したがって、Ａｌ含有量は０超～０．５００％である。
　Ａｌ含有量の好ましい下限は０．００１％であり、さらに好ましくは０．００５％であり、さらに好ましくは０．０１０％である。
　Ａｌ含有量の好ましい上限は０．４５０％であり、さらに好ましくは０．４００％であり、さらに好ましくは０．３５０％であり、さらに好ましくは０．３００％である。
　Ａｌ含有量の好ましい範囲は例えば、０．００１～０．４５０％であり、さらに好ましくは０．００５～０．４００％であり、さらに好ましくは０．０１０～０．３５０％であり、さらに好ましくは０．０１０～０．３００％である。 Al: more than 0 to 0.500%
Aluminum (Al) may not be contained. That is, the Al content may be 0%.
When Al is contained, that is, when the Al content is more than 0%, Al deoxidizes the alloy in the manufacturing process of the alloy material. If even a small amount of Al is contained, the above effects can be obtained to some extent.
However, if the Al content exceeds 0.500%, even if the contents of other elements are within the ranges of this embodiment, inclusions will be excessively generated and the creep strength and toughness of the alloy material will be reduced.
Therefore, the Al content is greater than 0 to 0.500%.
The lower limit of the Al content is preferably 0.001%, more preferably 0.005%, and still more preferably 0.010%.
A preferable upper limit of the Al content is 0.450%, more preferably 0.400%, still more preferably 0.350%, and still more preferably 0.300%.
The preferable range of the Al content is, for example, 0.001 to 0.450%, more preferably 0.005 to 0.400%, still more preferably 0.010 to 0.350%, and even more preferably is 0.010 to 0.300%.
　Ｃａ：０超～０．０１００％
　カルシウム（Ｃａ）は含有されなくてもよい。つまり、Ｃａ含有量は０％であってもよい。
　含有される場合、つまり、Ｃａ含有量が０％超である場合、Ｃａは合金材の製造工程において、合金を脱酸する。Ｃａが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｃａ含有量が０．０１００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、介在物が過剰に生成して合金材のクリープ強度及び靱性を低下する。
　したがって、Ｃａ含有量は０超～０．０１００％である。
　Ｃａ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．０００５％であり、さらに好ましくは０．００１０％である。
　Ｃａ含有量の好ましい上限は０．００９０％であり、さらに好ましくは０．００８０％であり、さらに好ましくは０．００７０％であり、さらに好ましくは０．００６０％である。
　Ｃａ含有量の好ましい範囲は例えば、０．０００１～０．００９０％であり、さらに好ましくは０．０００５～０．００８０％であり、さらに好ましくは０．００１０～０．００７０％であり、さらに好ましくは０．００１０～０．００６０％である。 Ca: more than 0 to 0.0100%
Calcium (Ca) may not be contained. That is, the Ca content may be 0%.
When contained, that is, when the Ca content is more than 0%, Ca deoxidizes the alloy in the manufacturing process of the alloy material. If even a small amount of Ca is contained, the above effects can be obtained to some extent.
However, if the Ca content exceeds 0.0100%, even if the contents of other elements are within the ranges of this embodiment, inclusions will be excessively generated and the creep strength and toughness of the alloy material will be reduced.
Therefore, the Ca content is greater than 0 to 0.0100%.
The lower limit of the Ca content is preferably 0.0001%, more preferably 0.0005%, and still more preferably 0.0010%.
A preferable upper limit of the Ca content is 0.0090%, more preferably 0.0080%, still more preferably 0.0070%, and still more preferably 0.0060%.
The preferred range of Ca content is, for example, 0.0001 to 0.0090%, more preferably 0.0005 to 0.0080%, still more preferably 0.0010 to 0.0070%, and even more preferably is 0.0010 to 0.0060%.
　Ｍｇ：０超～０．０１５０％
　マグネシウム（Ｍｇ）は含有されなくてもよい。つまり、Ｍｇ含有量は０％であってもよい。
　含有される場合、つまり、Ｍｇ含有量が０％超である場合、Ｍｇは合金材の製造工程において、合金を脱酸する。Ｍｇが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｍｇ含有量が０．０１５０％を超えれば、他の元素含有量が本実施形態の範囲内であっても、介在物が過剰に生成して合金材のクリープ強度及び靱性を低下する。
　したがって、Ｍｇ含有量は０超～０．０１５０％である。
　Ｍｇ含有量の好ましい下限は０．０００１％であり、さらに好ましくは０．０００５％であり、さらに好ましくは０．００１０％である。
　Ｍｇ含有量の好ましい上限は０．０１４０％であり、さらに好ましくは０．０１２０％であり、さらに好ましくは０．０１００％であり、さらに好ましくは０．００８０％である。
　Ｍｇ含有量の好ましい範囲は例えば、０．０００１～０．０１４０％であり、さらに好ましくは０．０００５～０．０１２０％であり、さらに好ましくは０．００１０～０．０１００％であり、さらに好ましくは０．００１０～０．００８０％である。 Mg: more than 0 to 0.0150%
Magnesium (Mg) may not be contained. That is, the Mg content may be 0%.
When contained, that is, when the Mg content is more than 0%, Mg deoxidizes the alloy in the manufacturing process of the alloy material. If even a small amount of Mg is contained, the above effects can be obtained to some extent.
However, if the Mg content exceeds 0.0150%, even if the contents of other elements are within the ranges of this embodiment, inclusions will be excessively generated and the creep strength and toughness of the alloy material will be reduced.
Therefore, the Mg content is greater than 0 to 0.0150%.
The preferable lower limit of the Mg content is 0.0001%, more preferably 0.0005%, and still more preferably 0.0010%.
A preferable upper limit of the Mg content is 0.0140%, more preferably 0.0120%, still more preferably 0.0100%, and still more preferably 0.0080%.
The preferred range of Mg content is, for example, 0.0001 to 0.0140%, more preferably 0.0005 to 0.0120%, still more preferably 0.0010 to 0.0100%, and even more preferably is 0.0010 to 0.0080%.
　本実施形態によるオーステナイト系合金材の化学組成の残部は、Ｆｅ及び不純物からなる。ここで、化学組成における不純物とは、オーステナイト系合金材を工業的に製造する際に、原料としての鉱石、スクラップ、又は製造環境等から混入されるものであって、意図せずに含有されるものであり、本実施形態によるオーステナイト系合金材に悪影響を与えない範囲で許容されるものを意味する。 The remainder of the chemical composition of the austenitic alloy material according to this embodiment consists of Fe and impurities. Here, impurities in the chemical composition are those that are mixed in from raw materials such as ore, scrap, or the manufacturing environment when industrially manufacturing austenitic alloy materials, and are unintentionally contained. This means an acceptable value within a range that does not adversely affect the austenitic alloy material according to the present embodiment.
　好ましくは、Ｆｅ含有量は０超～３０．００％である。具体的には、ＦｅはＮｉ基合金の熱間加工性を高める。Ｆｅ含有量が低すぎれば、上記効果が十分に得られない。一方、Ｆｅ含有量が高すぎれば、Ｎｉ基合金の耐食性が低下する。したがって、好ましくは、Ｆｅ含有量は０超～３０．００％である。
　Ｆｅ含有量の好ましい下限は０．０１％であり、さらに好ましくは０．２０％であり、さらに好ましくは０．４０％であり、さらに好ましくは０．５０％である。
　Ｆｅ含有量の好ましい上限は２９．００％であり、さらに好ましくは２７．００％であり、さらに好ましくは２５．００％であり、さらに好ましくは２３．００％である。
　Ｆｅ含有量の好ましい範囲は例えば０．０１～２９．００％であり、さらに好ましくは０．２０～２７．００％であり、さらに好ましくは０．４０～２５．００％であり、さらに好ましくは０．５０～２３．００％である。 Preferably, the Fe content is greater than 0 to 30.00%. Specifically, Fe improves the hot workability of Ni-based alloys. If the Fe content is too low, the above effects cannot be sufficiently obtained. On the other hand, if the Fe content is too high, the corrosion resistance of the Ni-based alloy will decrease. Therefore, preferably the Fe content is greater than 0 to 30.00%.
The preferable lower limit of the Fe content is 0.01%, more preferably 0.20%, even more preferably 0.40%, and still more preferably 0.50%.
The preferable upper limit of the Fe content is 29.00%, more preferably 27.00%, still more preferably 25.00%, and still more preferably 23.00%.
The preferred range of Fe content is, for example, 0.01 to 29.00%, more preferably 0.20 to 27.00%, even more preferably 0.40 to 25.00%, and even more preferably It is 0.50 to 23.00%.
　［オーステナイト系合金材の好ましい化学組成について］
　好ましくは、本実施形態のオーステナイト系合金材の化学組成は、次の第１化学組成～第３化学組成のいずれかである。
　（第１化学組成）
　特徴１を満たす化学組成であって、かつ、Ｃ：０．０５０％以下、Ｓｉ：０．０１～０．５０％、Ｍｎ：０．０１～０．５０％、Ｐ：０．０２５％以下、Ｓ：０．０１０％以下、Ｃｕ：２．００～４．００％、Ｎｉ：４４．００～５０．００％、Ｃｒ：２０．００～２５．００％、Ｍｏ：５．００～７．００％、Ｗ：２．００～５．００％、及び、Ｆｅ：１２．００～２０．００％、を含有する化学組成
　（第２化学組成）
　特徴１を満たす化学組成であって、かつ、Ｃ：０．１５０％以下、Ｓｉ：１．００～２．５０％、Ｍｎ：０．０１～１．００％、Ｐ：０．０１０％以下、Ｓ：０．０１０％以下、Ｃｕ：１．５０～３．００％、Ｃｒ：２８．００～３２．００％、Ｍｏ：１．００～３．００％、Ｔｉ：０．０１～１．００％、及び、Ｆｅ：２．００～６．００％、を含有する化学組成
　（第３化学組成）
　特徴１を満たす化学組成であって、かつ、Ｃ：０．０５０％以下、Ｓｉ：０．０１～０．５０％、Ｍｎ：０．０１～０．５０％、Ｐ：０．０３０％以下、Ｓ：０．０１５％以下、Ｃｕ：０．０１～０．５０％、Ｃｒ：２７．００～３１．００％、Ｆｅ：７．００～１５．００％、及び、Ｎｉ：５８．００～８０．００％、を含有する化学組成 [About preferred chemical composition of austenitic alloy material]
Preferably, the chemical composition of the austenitic alloy material of this embodiment is one of the following first to third chemical compositions.
(First chemical composition)
A chemical composition that satisfies characteristic 1, and C: 0.050% or less, Si: 0.01 to 0.50%, Mn: 0.01 to 0.50%, P: 0.025% or less, S: 0.010% or less, Cu: 2.00 to 4.00%, Ni: 44.00 to 50.00%, Cr: 20.00 to 25.00%, Mo: 5.00 to 7.00 %, W: 2.00 to 5.00%, and Fe: 12.00 to 20.00% (second chemical composition)
A chemical composition that satisfies characteristic 1, and C: 0.150% or less, Si: 1.00 to 2.50%, Mn: 0.01 to 1.00%, P: 0.010% or less, S: 0.010% or less, Cu: 1.50 to 3.00%, Cr: 28.00 to 32.00%, Mo: 1.00 to 3.00%, Ti: 0.01 to 1.00 % and Fe: 2.00 to 6.00% (third chemical composition)
A chemical composition that satisfies characteristic 1, and C: 0.050% or less, Si: 0.01 to 0.50%, Mn: 0.01 to 0.50%, P: 0.030% or less, S: 0.015% or less, Cu: 0.01 to 0.50%, Cr: 27.00 to 31.00%, Fe: 7.00 to 15.00%, and Ni: 58.00 to 80 Chemical composition containing .00%
　［（特徴２）Ｆｎ１について］
　本実施形態のオーステナイト系合金材ではさらに、式（１）で定義されるＦｎ１が２０未満である。
　Ｆｎ１＝１７７．８４＋１１．１２Ｓｉ－２４．３６Ｍｎ－８．１１Ｃｕ－１．６１Ｃｒ－１．７８Ｎｉ－２．６８Ｍｏ　（１）
　ここで、式（１）中の元素記号には、対応する元素の質量％での含有量が代入される。元素が含有されていない場合、対応する元素記号には「０」が代入される。 [(Feature 2) About Fn1]
Furthermore, in the austenitic alloy material of this embodiment, Fn1 defined by formula (1) is less than 20.
Fn1=177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
Here, the content in mass % of the corresponding element is substituted for the element symbol in formula (1). If an element is not contained, "0" is assigned to the corresponding element symbol.
　Ｆｎ１は、高温アンモニア環境での合金材の耐窒化性に関する指標である。上述の化学組成中の元素のうち、Ｍｎ、Ｃｕ、Ｃｒ、Ｎｉ及びＭｏは、高温アンモニア環境でのオーステナイト系合金材の耐窒化性を高める。一方で、Ｓｉは、高温アンモニア環境でのオーステナイト系合金材の耐窒化性を低下する。図１に示すとおり、Ｆｎ１が２０未満であれば、１００％アンモニアの雰囲気下で６００℃、２５時間保持した場合の窒化層深さが１５．０μｍ以下となる。したがって、Ｆｎ１が２０未満であれば、高温アンモニア環境で使用するオーステナイト系合金材において、優れた耐窒化性が得られる。 Fn1 is an index regarding the nitriding resistance of the alloy material in a high-temperature ammonia environment. Among the elements in the above chemical composition, Mn, Cu, Cr, Ni, and Mo improve the nitriding resistance of the austenitic alloy material in a high-temperature ammonia environment. On the other hand, Si reduces the nitriding resistance of the austenitic alloy material in a high-temperature ammonia environment. As shown in FIG. 1, if Fn1 is less than 20, the depth of the nitrided layer will be 15.0 μm or less when held at 600° C. for 25 hours in a 100% ammonia atmosphere. Therefore, when Fn1 is less than 20, excellent nitriding resistance can be obtained in an austenitic alloy material used in a high-temperature ammonia environment.
　Ｆｎ１の好ましい上限は１９であり、さらに好ましくは１８であり、さらに好ましくは１７であり、さらに好ましくは１６であり、さらに好ましくは１３であり、さらに好ましくは１０である。Ｆｎ１が１０以下であれば、窒化層深さを顕著に低減することができ、さらに優れた耐窒化性が得られる。 The upper limit of Fn1 is preferably 19, more preferably 18, even more preferably 17, even more preferably 16, still more preferably 13, and still more preferably 10. When Fn1 is 10 or less, the depth of the nitrided layer can be significantly reduced, and even better nitriding resistance can be obtained.
　Ｆｎ１の下限は特に限定されない。Ｆｎ１の下限は例えば、１であり、例えば、２である。 The lower limit of Fn1 is not particularly limited. The lower limit of Fn1 is, for example, 1, and is, for example, 2.
　Ｆｎ１の好ましい範囲は例えば、１～１９であり、さらに好ましくは２～１８であり、さらに好ましくは２～１７であり、さらに好ましくは２～１６であり、さらに好ましくは２～１３であり、さらに好ましくは、２～１０である。 The preferred range of Fn1 is, for example, 1 to 19, more preferably 2 to 18, even more preferably 2 to 17, still more preferably 2 to 16, still more preferably 2 to 13, and Preferably, it is 2 to 10.
　なお、Ｆｎ１値は整数とする。つまり、Ｆｎ１値は、得られた値の小数第一位を四捨五入した整数とする。 Note that the Fn1 value is an integer. That is, the Fn1 value is an integer obtained by rounding off the obtained value to the first decimal place.
　［（特徴３）Ｆｎ２について］
　本実施形態のオーステナイト系合金材ではさらに、式（２）で定義されるＦｎ２が２１よりも高く５０未満である。
　Ｆｎ２＝（Ｓｎ＋Ｚｎ＋Ｐｂ＋Ｓｂ＋Ａｓ＋Ｂｉ）×１０３　（２）
　ここで、式中の元素記号には、対応する元素の質量％での含有量が代入される。元素が含有されていない場合、対応する元素記号には「０」が代入される。 [(Feature 3) About Fn2]
Furthermore, in the austenitic alloy material of this embodiment, Fn2 defined by formula (2) is higher than 21 and less than 50.
Fn2=(Sn+Zn+Pb+Sb+As+Bi)×10 3 (2)
Here, the content in mass % of the corresponding element is substituted for the element symbol in the formula. If an element is not contained, "0" is assigned to the corresponding element symbol.
　Ｆｎ２は、高温アンモニア環境での合金材の表層の粒界割れに関する指標である。Ｆｎ２が２１以下であれば、合金材が特徴１及び特徴２を満たしていても、高温アンモニア環境での合金材の表層において、粒界割れが発生しやすい。一方、Ｆｎ２が５０以上となれば、Ｓｎ、Ｚｎ、Ｐｂ、Ｓｂ、Ａｓ及びＢｉが粒界に過剰に偏析し、粒界強度がかえって低下する。そのため、合金材が特徴１及び特徴２を満たしていても、高温アンモニア環境での合金材の表層で粒界割れが発生しやすい。 Fn2 is an index related to intergranular cracking in the surface layer of an alloy material in a high-temperature ammonia environment. If Fn2 is 21 or less, intergranular cracking is likely to occur in the surface layer of the alloy material in a high-temperature ammonia environment even if the alloy material satisfies Features 1 and 2. On the other hand, if Fn2 is 50 or more, Sn, Zn, Pb, Sb, As, and Bi are excessively segregated at grain boundaries, and the grain boundary strength is rather reduced. Therefore, even if the alloy material satisfies Features 1 and 2, intergranular cracking is likely to occur in the surface layer of the alloy material in a high-temperature ammonia environment.
　Ｆｎ２が２１よりも高く５０未満であれば、合金材が特徴１及び特徴２を満たすことを前提として、高温アンモニア環境での合金材の表層において、粒界割れが発生するのを十分に抑制できる。
　Ｆｎ２の好ましい下限は２２であり、さらに好ましくは２４であり、さらに好ましくは２６である。
　Ｆｎ２の好ましい下限は４８であり、さらに好ましくは４６であり、さらに好ましくは４４である。
　Ｆｎ２の好ましい範囲は例えば、２２～４８であり、さらに好ましくは２４～４６であり、さらに好ましくは２６～４４である。 If Fn2 is higher than 21 and less than 50, it is possible to sufficiently suppress the occurrence of intergranular cracking in the surface layer of the alloy material in a high-temperature ammonia environment, provided that the alloy material satisfies Features 1 and 2. .
The lower limit of Fn2 is preferably 22, more preferably 24, and still more preferably 26.
The lower limit of Fn2 is preferably 48, more preferably 46, and still more preferably 44.
The preferred range of Fn2 is, for example, 22-48, more preferably 24-46, and even more preferably 26-44.
　なお、Ｆｎ２値は整数とする。つまり、Ｆｎ２値は、得られた値の小数第一位を四捨五入した整数とする。 Note that the Fn2 value is an integer. That is, the Fn2 value is an integer obtained by rounding off the obtained value to the first decimal place.
　［本実施形態のオーステナイト系合金材の効果］
　以上のとおり、本実施形態のオーステナイト系合金材は、特徴１～特徴３を満たす。そのため、本実施形態のオーステナイト系合金材では、高温アンモニア環境での使用中において、優れた耐窒化性が得られ、かつ、表層での粒界割れの発生が十分に抑制される。 [Effects of the austenitic alloy material of this embodiment]
As described above, the austenitic alloy material of this embodiment satisfies Features 1 to 3. Therefore, in the austenitic alloy material of this embodiment, excellent nitriding resistance is obtained during use in a high-temperature ammonia environment, and occurrence of intergranular cracking in the surface layer is sufficiently suppressed.
　［形状及び用途］
　本実施形態のオーステナイト系合金材の形状は特に限定されない。本実施形態のオーステナイト系合金材は、合金管であってもよく、棒状の中実材であってもよく、合金板であってもよい。また、合金管は継目無管であってもよく、溶接管であってもよい。 [Shape and usage]
The shape of the austenitic alloy material of this embodiment is not particularly limited. The austenitic alloy material of this embodiment may be an alloy tube, a rod-shaped solid material, or an alloy plate. Further, the alloy pipe may be a seamless pipe or a welded pipe.
　本実施形態のオーステナイト系合金材は、耐窒化性が求められる用途に広く適用可能である。特に、本実施形態のオーステナイト系合金材は、高温アンモニア環境に好適である。ただし、本実施形態のオーステナイト系合金材は、高温アンモニア環境以外の他の用途にも適用可能である。 The austenitic alloy material of this embodiment can be widely applied to applications where nitriding resistance is required. In particular, the austenitic alloy material of this embodiment is suitable for high-temperature ammonia environments. However, the austenitic alloy material of this embodiment can also be applied to other uses than the high-temperature ammonia environment.
　［本実施形態のオーステナイト系合金材の好ましい形態］
　好ましくは、本実施形態のオーステナイト系合金材は、特徴１～特徴３を満たし、さらに、次の特徴４を満たす。
　（特徴４）
　オーステナイト系合金材の表層のμｍ単位での平均結晶粒径をＤａｖｅと定義したとき、
　式（３）で定義されるＦｎ３が０．２０よりも高く、
　式（４）で定義されるＦｎ４が１０００～５０００である。
　Ｆｎ３＝Ｆｎ２／Ｄａｖｅ　（３）
　Ｆｎ４＝Ｆｎ２×Ｄａｖｅ　（４）
　以下、特徴４について説明する。 [Preferred form of austenitic alloy material of this embodiment]
Preferably, the austenitic alloy material of this embodiment satisfies Features 1 to 3, and further satisfies the following Feature 4.
(Feature 4)
When the average grain size in μm of the surface layer of the austenitic alloy material is defined as D ave ,
Fn3 defined by formula (3) is higher than 0.20,
Fn4 defined by formula (4) is 1000 to 5000.
Fn3=Fn2/D ave (3)
Fn4=Fn2×D ave (4)
Feature 4 will be explained below.
　Ｆｎ３及びＦｎ４は、高温アンモニア環境での合金材の表層の粒界割れに関する指標である。 Fn3 and Fn4 are indicators regarding intergranular cracking in the surface layer of the alloy material in a high-temperature ammonia environment.
　Ｓｎ、Ｚｎ、Ｐｂ、Ｓｂ、Ａｓ及びＢｉの総含有量（つまりＦｎ２）と、合金材の平均結晶粒径Ｄａｖｅ（μｍ）とが適切な関係を満たした場合に、高温アンモニア環境での粒界割れはさらに抑制される。以下、Ｆｎ３及びＦｎ４について説明する。 When the total content of Sn, Zn, Pb, Sb, As, and Bi (that is, Fn2) and the average grain size D ave (μm) of the alloy material satisfy an appropriate relationship, the grain size in a high-temperature ammonia environment Boundary cracking is further suppressed. Fn3 and Fn4 will be explained below.
　［Ｆｎ３について］
　Ｆｎ２が式（２）を満たす場合においてさらに、Ｆｎ３が０．２０超であれば、単位粒界面積当たりに含まれるＳｎ、Ｚｎ、Ｐｂ、Ｓｂ、Ａｓ及びＢｉの総含有量がさらに適切となる。そのため、高温アンモニア環境での粒界割れがさらに抑制される。
　したがって、好ましくは、Ｆｎ３は０．２０超である。 [About Fn3]
In the case where Fn2 satisfies formula (2), if Fn3 exceeds 0.20, the total content of Sn, Zn, Pb, Sb, As, and Bi contained per unit grain boundary area becomes more appropriate. . Therefore, grain boundary cracking in a high-temperature ammonia environment is further suppressed.
Therefore, preferably Fn3 is greater than 0.20.
　Ｆｎ３の好ましい下限は０．２１であり、さらに好ましくは０．２２であり、さらに好ましくは０．２３である。
　Ｆｎ３の上限は特に限定されない。しかしながら、オーステナイト系合金材が特徴１～特徴３を満たす場合、Ｆｎ３の上限は例えば、好ましくは０．９０であり、さらに好ましくは０．８５であり、さらに好ましくは０．８２である。
　Ｆｎ３の好ましい範囲は例えば、０．２１～０．９０であり、さらに好ましくは０．２２～０．８５であり、さらに好ましくは０．２３～０．８２である。 The lower limit of Fn3 is preferably 0.21, more preferably 0.22, and still more preferably 0.23.
The upper limit of Fn3 is not particularly limited. However, when the austenitic alloy material satisfies Features 1 to 3, the upper limit of Fn3 is, for example, preferably 0.90, more preferably 0.85, and even more preferably 0.82.
The preferred range of Fn3 is, for example, 0.21 to 0.90, more preferably 0.22 to 0.85, and still more preferably 0.23 to 0.82.
　なお、Ｆｎ３値は、得られた値の小数第三位を四捨五入した小数第二位の値とする。 Note that the Fn3 value is the value obtained by rounding off the third decimal place of the obtained value to the second decimal place.
　［Ｆｎ４について］
　さらに、Ｆｎ２が式（２）を満たす場合において、Ｆｎ４が１０００～５０００であれば、粒界面積が適切な大きさであり、かつ、Ｓｎ、Ｚｎ、Ｐｂ、Ｓｂ、Ａｓ及びＢｉの総含有量が適切な量となっている。この場合、き裂の発生だけでなく、き裂の伝播もより有効に抑制することができる。その結果、高温アンモニア環境での粒界割れがさらに抑制される。
　したがって、好ましくは、Ｆｎ４は１０００～５０００である。 [About Fn4]
Furthermore, when Fn2 satisfies formula (2), if Fn4 is 1000 to 5000, the grain boundary area is an appropriate size, and the total content of Sn, Zn, Pb, Sb, As, and Bi is is the appropriate amount. In this case, not only the occurrence of cracks but also the propagation of cracks can be more effectively suppressed. As a result, grain boundary cracking in a high-temperature ammonia environment is further suppressed.
Therefore, Fn4 is preferably 1000 to 5000.
　Ｆｎ４の好ましい下限は１１００であり、さらに好ましくは１２００である。
　Ｆｎ４の好ましい上限は４９００であり、さらに好ましくは４６００であり、さらに好ましくは４２００である。
　Ｆｎ４の好ましい範囲は例えば、１１００～４９００であり、さらに好ましくは１２００～４６００であり、さらに好ましくは１２００～４２００である。
　なお、Ｆｎ４値は整数である。 The lower limit of Fn4 is preferably 1100, more preferably 1200.
The upper limit of Fn4 is preferably 4,900, more preferably 4,600, and even more preferably 4,200.
The preferred range of Fn4 is, for example, 1,100 to 4,900, more preferably 1,200 to 4,600, and even more preferably 1,200 to 4,200.
Note that the Fn4 value is an integer.
　［オーステナイト系合金材の表層の平均結晶粒径の測定方法］
　オーステナイト系合金材の表層の平均結晶粒径Ｄａｖｅは、次の方法で測定する。
　オーステナイト系合金材の圧延方向に平行な断面（Ｌ断面）から、試験片を採取する。試験片は、合金材の表面に相当する長さ５ｍｍの辺と、当該表面から深さ方向に５ｍｍの辺とで構成される矩形の観察面を有する。つまり、観察面は５ｍｍ×５ｍｍの矩形である。観察面以外の試験片のサイズは特に限定されない。 [Method for measuring the average grain size of the surface layer of austenitic alloy material]
The average grain size D ave of the surface layer of the austenitic alloy material is measured by the following method.
A test piece is taken from a cross section (L cross section) parallel to the rolling direction of the austenitic alloy material. The test piece has a rectangular observation surface consisting of a side with a length of 5 mm corresponding to the surface of the alloy material and a side with a length of 5 mm from the surface in the depth direction. That is, the observation surface is a 5 mm x 5 mm rectangle. The size of the test piece other than the observation surface is not particularly limited.
　試験片をミクロ組織観察用樹脂に埋め込む。樹脂埋めされた試験片の観察面を鏡面研磨する。鏡面研磨後の観察面に対して、塩酸と硝酸との混酸を用いたエッチングを実施して、ミクロ組織を現出させる。エッチング後の観察面の任意の１０視野を、３００倍の光学顕微鏡で観察する。各視野は１０００μｍ×１０００μｍとする。各視野において、ＪＩＳ　Ｇ　０５５１：２０２０に記載の切断法に準拠して、結晶粒径（μｍ）を求める。得られた１０視野の結晶粒径の算術平均値を、オーステナイト系合金材の表層の平均結晶粒径Ｄａｖｅ（μｍ）とする。 Embed the test piece in resin for microstructure observation. Mirror-polish the observation surface of the resin-filled test piece. The observation surface after mirror polishing is etched using a mixed acid of hydrochloric acid and nitric acid to reveal the microstructure. Ten arbitrary visual fields of the observation surface after etching are observed using a 300x optical microscope. Each field of view is 1000 μm×1000 μm. In each field of view, the crystal grain size (μm) is determined according to the cutting method described in JIS G 0551:2020. The arithmetic mean value of the crystal grain sizes of the obtained 10 fields of view is defined as the average crystal grain size D ave (μm) of the surface layer of the austenitic alloy material.
　［本実施形態のオーステナイト系合金材の製造方法］
　本実施形態のオーステナイト系合金材の製造方法の一例を説明する。本実施形態のオーステナイト系合金材の製造方法の一例は、素材準備工程と、熱間加工工程と、溶体化処理工程と、を含む。各工程について詳述する。 [Method for manufacturing austenitic alloy material of this embodiment]
An example of the method for manufacturing the austenitic alloy material of this embodiment will be described. An example of the method for manufacturing an austenitic alloy material according to the present embodiment includes a material preparation step, a hot working step, and a solution treatment step. Each process will be explained in detail.
　［素材準備工程］
　素材準備工程では、特徴１～特徴３又は特徴１～特徴４を満たす合金を溶製する。合金は、電気炉によって溶製してもよく、Ａｒ－Ｏ２混合ガス底吹き脱炭炉（ＡＯＤ炉）によって溶製してもよく、真空脱炭炉（ＶＯＤ炉）によって溶製してもよい。溶製した合金は、造塊法によってインゴットにしてもよく、連続鋳造法によってスラブ、ブルーム、又はビレットにしてもよい。必要に応じて、スラブ、ブルーム又はインゴットを分塊圧延して、ビレットを製造してもよい。以上の工程により素材（スラブ、ブルーム、又は、ビレット）を製造する。 [Material preparation process]
In the material preparation step, an alloy satisfying Features 1 to 3 or Features 1 to 4 is melted. The alloy may be melted by an electric furnace, an Ar-O 2 mixed gas bottom blowing decarburization furnace (AOD furnace), or a vacuum decarburization furnace (VOD furnace). good. The melted alloy may be made into an ingot by an ingot method, or a slab, bloom, or billet by a continuous casting method. If necessary, the slab, bloom, or ingot may be bloomed and rolled to produce a billet. A material (slab, bloom, or billet) is manufactured through the above steps.
　［熱間加工工程］
　熱間加工工程では、製造された素材に対して周知の熱間加工を実施して、中間合金材を製造する。熱間加工は、熱間鍛造であってもよく、熱間押出であってもよく、熱間圧延であってもよい。熱間加工の方法は、特に限定されず、周知の方法でよい。 [Hot processing process]
In the hot working step, a well-known hot working is performed on the produced material to produce an intermediate alloy material. The hot working may be hot forging, hot extrusion, or hot rolling. The hot working method is not particularly limited, and may be any known method.
　最終製品が合金管である場合、例えば、熱間加工としてマンネスマン法を実施して、中間合金材である素管を製造してもよい。また、熱間加工としてユジーン・セジュルネ法、又は、エルハルトプッシュベンチ法（すなわち、熱間押出）を実施して、素管を製造してもよい。また、製造された素管に対して、マンドレルミル、レデューサー、サイジングミル等による熱間圧延を実施してもよい。 When the final product is an alloy tube, for example, the Mannesmann method may be performed as hot working to produce a blank tube, which is an intermediate alloy material. Moreover, the Eugene-Séjournet method or the Erhardt push bench method (namely, hot extrusion) may be implemented as the hot processing to produce the raw pipe. Further, the produced raw pipe may be hot rolled using a mandrel mill, a reducer, a sizing mill, or the like.
　［溶体化処理工程］
　溶体化処理工程では、熱間加工工程で製造された中間合金材に対して、周知の溶体化処理を実施する。例えば、中間合金材を熱処理炉に装入し、所望の温度で保持した後、急冷する。溶体化処理温度は例えば、１０００～１３００℃である。 [Solution treatment process]
In the solution treatment step, a well-known solution treatment is performed on the intermediate alloy material manufactured in the hot working step. For example, the intermediate alloy material is charged into a heat treatment furnace, maintained at a desired temperature, and then rapidly cooled. The solution treatment temperature is, for example, 1000 to 1300°C.
　なお、熱間加工工程での圧下率及び溶体化処理工程での溶体化処理温度を調整することにより、結晶粒径を調整することができる。以上の製造方法により、本実施形態のオーステナイト系合金材が製造される。 Note that the crystal grain size can be adjusted by adjusting the rolling reduction rate in the hot working step and the solution treatment temperature in the solution treatment step. The austenitic alloy material of this embodiment is manufactured by the above manufacturing method.
　［その他の工程について］
　本実施形態のオーステナイト系合金材の製造方法は、上述の工程以外の工程を含んでもよい。例えば、熱間加工工程後であって、溶体化処理工程前の中間合金材に対して、冷間加工工程を実施してもよい。冷間加工工程では、中間合金材に対して、冷間加工を実施する。冷間加工は、冷間圧延であってもよく、冷間引抜であってもよい。この場合、所望の寸法に加工することができる。例えば、溶体化処理工程後の中間合金材に対して、冷間加工を実施してもよい。この場合、オーステナイト系合金材の強度が高まる。 [About other processes]
The method for manufacturing an austenitic alloy material according to the present embodiment may include steps other than those described above. For example, a cold working step may be performed on the intermediate alloy material after the hot working step and before the solution treatment step. In the cold working step, cold working is performed on the intermediate alloy material. Cold working may be cold rolling or cold drawing. In this case, it can be processed into desired dimensions. For example, cold working may be performed on the intermediate alloy material after the solution treatment step. In this case, the strength of the austenitic alloy material increases.
　なお、上述の製造方法では、オーステナイト系合金材の一例として合金管の製造方法を説明した。しかしながら、本実施形態のオーステナイト系合金材は、棒状や板状等、他の形状であってもよい。棒状又は板状の製造方法も、上述の製造方法と同様に、例えば、素材準備工程と、熱間加工工程と、溶体化処理工程を備え、さらに、冷間加工工程を実施してもよい。さらに、上述の製造方法は一例であり、他の製造方法によって特徴１～特徴３又は特徴１～特徴４を満たす本実施形態のオーステナイト系合金材が製造されてもよい。 In addition, in the above-mentioned manufacturing method, the manufacturing method of an alloy tube was explained as an example of an austenitic alloy material. However, the austenitic alloy material of this embodiment may have other shapes such as a rod shape or a plate shape. Similarly to the above-mentioned manufacturing method, the rod-shaped or plate-shaped manufacturing method includes, for example, a material preparation step, a hot working step, and a solution treatment step, and may further include a cold working step. Furthermore, the above-described manufacturing method is just an example, and the austenitic alloy material of the present embodiment that satisfies Features 1 to 3 or Features 1 to 4 may be produced by other manufacturing methods.
　実施例により本実施形態のオーステナイト系合金材の効果をさらに具体的に説明する。以下の実施例での条件は、本実施形態のオーステナイト系合金材の実施可能性及び効果を確認するために採用した一条件例である。したがって、本実施形態のオーステナイト系合金材はこの一条件例に限定されない。 The effects of the austenitic alloy material of this embodiment will be explained in more detail with examples. The conditions in the following examples are examples of conditions adopted to confirm the feasibility and effects of the austenitic alloy material of this embodiment. Therefore, the austenitic alloy material of this embodiment is not limited to this one example condition.
　表１（表１－１及び表１－２）に示す化学組成を有するオーステナイト系合金材を製造した。なお、表１中の「－」は対応する元素含有量が不純物レベル以下であることを示す。 An austenitic alloy material having a chemical composition shown in Table 1 (Table 1-1 and Table 1-2) was manufactured. Note that "-" in Table 1 indicates that the content of the corresponding element is below the impurity level.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　各試験番号の合金を高周波真空溶解法により溶製した。溶製された合金を用いて、造塊法により３０ｋｇのインゴットを製造した。各試験番号のインゴットを１２００℃で２時間加熱した。加熱後のインゴットに対して熱間鍛造を実施して、断面が５０ｍｍ×５５ｍｍの角材を製造した。得られた角材を１２００℃で３０分加熱した後、熱間圧延して、板厚１５ｍｍの熱間圧延材を製造した。得られた熱間圧延材に対して冷間圧延を実施して、板厚１０．５ｍｍの中間合金材（合金板）を製造した。中間合金材に対して、１１５０℃の溶体化処理温度で１０分保持する溶体化処理を実施した。なお、溶体化処理温度で保持した後の冷却方法は水冷とした。以上の製造工程により、各試験番号のオーステナイト系合金材（合金板）を製造した。 The alloys of each test number were melted by high frequency vacuum melting method. Using the melted alloy, a 30 kg ingot was manufactured by an ingot forming method. The ingots of each test number were heated at 1200°C for 2 hours. Hot forging was performed on the heated ingot to produce a square material with a cross section of 50 mm x 55 mm. The obtained square material was heated at 1200° C. for 30 minutes and then hot rolled to produce a hot rolled material with a plate thickness of 15 mm. The obtained hot rolled material was cold rolled to produce an intermediate alloy material (alloy plate) with a thickness of 10.5 mm. The intermediate alloy material was subjected to solution treatment at a solution treatment temperature of 1150° C. for 10 minutes. Note that water cooling was used as the cooling method after being maintained at the solution treatment temperature. Through the above manufacturing process, austenitic alloy materials (alloy plates) of each test number were manufactured.
　［評価試験］
　製造された各試験番号のオーステナイト系合金材に対して、次の評価試験を実施した。 [Evaluation test]
The following evaluation tests were conducted on the manufactured austenitic alloy materials of each test number.
　［耐窒化性及び表層粒界割れ評価試験］
　各試験番号のオーステナイト系合金材の耐窒化性及び表層粒界割れについて、次の方法で評価した。 [Nitriding resistance and surface grain boundary cracking evaluation test]
The nitriding resistance and surface intergranular cracking of the austenitic alloy materials of each test number were evaluated by the following method.
　各試験番号のオーステナイト系合金材（合金板）から、厚さ３ｍｍ、幅１５ｍｍ、長さ２０ｍｍの試験片を切り出した。試験片の表面に対してバフ研磨を実施し、その後、試験片の表面を脱脂仕上げした。脱脂仕上げ後の試験片を、ステンレス線を用いて石英製治具に吊り下げ、ボックス状炉内に装入した。試験片を装入後の炉内に雰囲気ガスを通気しながら、６００℃で２５時間保持した。雰囲気ガスは、１００％アンモニアとした。雰囲気ガスの流量は、５００ｍＬ／分とした。 A test piece with a thickness of 3 mm, width of 15 mm, and length of 20 mm was cut out from the austenitic alloy material (alloy plate) of each test number. Buffing was performed on the surface of the test piece, and then the surface of the test piece was degreased. The degreased test piece was suspended from a quartz jig using a stainless steel wire and placed in a box-shaped furnace. After charging the test piece, the furnace was maintained at 600° C. for 25 hours while atmospheric gas was passed through the furnace. The atmospheric gas was 100% ammonia. The flow rate of the atmospheric gas was 500 mL/min.
　２５時間経過後の試験片の長手方向に垂直な断面と、試験片の表面とを含む組織観察用試験片を作製した。組織観察用試験片では、上記断面を観察面とした。観察面のうち、試験片の表面を含み、表面からの深さが６００μｍ、幅方向に８００μｍの矩形視野を、走査型電子顕微鏡（ＳＥＭ）にて３００倍の倍率で観察し、写真画像（反射電子像）を得た。さらに、矩形視野においてＳＥＭ装置に付属したＥＤＳ装置を用いて、ＥＤＳ分析を実施した。具体的には、矩形視野の試験片表面に相当する任意の点から深さ方向にＥＤＳ分析を実施した。分析結果のうち、母材のＮ含有量（質量％）と比較して、Ｎ含有量（質量％）の２倍以上となった領域を、窒化層と認定した。窒化層と認定した領域の試験片表面からの深さを、窒化層深さ（μｍ）と定義した。得られた窒化層深さを、表２中の「窒化層深さ（μｍ）」欄に示す。 After 25 hours had elapsed, a test piece for tissue observation was prepared, including a cross section perpendicular to the longitudinal direction of the test piece and the surface of the test piece. In the specimen for tissue observation, the above-mentioned cross section was used as the observation surface. A rectangular field of view including the surface of the test piece, with a depth of 600 μm from the surface and 800 μm in the width direction, was observed with a scanning electron microscope (SEM) at a magnification of 300 times. An electronic image) was obtained. Furthermore, EDS analysis was performed in a rectangular field of view using an EDS device attached to the SEM device. Specifically, EDS analysis was performed in the depth direction from an arbitrary point corresponding to the surface of the test piece in a rectangular field of view. Among the analysis results, a region where the N content (mass %) was twice or more as compared to the N content (mass %) of the base material was recognized as a nitrided layer. The depth of the region recognized as a nitrided layer from the surface of the test piece was defined as the nitrided layer depth (μm). The obtained nitrided layer depth is shown in the "Nitrided layer depth (μm)" column in Table 2.
　さらに、各試験番号の矩形視野の写真画像中の試験片の表層部分で、粒界割れの有無を確認した。粒界上に０．５μｍ以上の長さの空隙が確認される領域が存在しない場合、粒界割れが十分に抑制されたと判断した（表２中の「粒界割れ」で「Ｅ」（Ｅｘｃｅｌｌｅｎｔ）と表示）。粒界上に０．５μｍ以上の長さの空隙が確認される領域が存在するが、１．０μｍ未満の長さの空隙が確認される領域が存在しない場合、粒界割れが抑制されたと判断した（表２中の「粒界割れ」で「Ｇ」（Ｇｏｏｄ）と表示）。粒界上に１μｍ以上の長さの空隙が確認される領域が存在する場合、粒界割れが十分に抑制されなかったと判断した（表２中の「粒界割れ」で「Ｂ」（Ｂａｄ）と表記）。なお、空隙の長さとは、粒界に沿った空隙の総長さのことである。 Furthermore, the presence or absence of intergranular cracks was confirmed in the surface layer portion of the test piece in the rectangular field photographic image of each test number. It was judged that grain boundary cracking was sufficiently suppressed when there was no region where voids with a length of 0.5 μm or more were confirmed on the grain boundaries ("E" (Excellent) for "grain boundary cracking" in Table 2). ). If there is a region where voids with a length of 0.5 μm or more are confirmed on the grain boundary, but there is no region where voids with a length of less than 1.0 μm are confirmed, it is determined that intergranular cracking has been suppressed. (Displayed as "G" (Good) for "grain boundary cracking" in Table 2). If there was a region on the grain boundary where voids with a length of 1 μm or more were confirmed, it was determined that grain boundary cracking was not sufficiently suppressed ("B" (Bad) for "grain boundary cracking" in Table 2). ). Note that the length of the void is the total length of the void along the grain boundary.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　［試験結果］
　試験結果を表１（表１－１、表１－２）及び表２に示す。各表を参照して、試験番号１～４３のオーステナイト系合金材は、特徴１～特徴３を満たした。そのため、窒化層深さは１５．０μｍ以下であり、高温アンモニア環境において十分な耐窒化性が得られた。さらに、高温アンモニア環境において、粒界割れが抑制された。 [Test results]
The test results are shown in Table 1 (Table 1-1, Table 1-2) and Table 2. Referring to each table, the austenitic alloy materials of test numbers 1 to 43 satisfied characteristics 1 to 3. Therefore, the depth of the nitrided layer was 15.0 μm or less, and sufficient nitriding resistance was obtained in a high-temperature ammonia environment. Furthermore, intergranular cracking was suppressed in a high-temperature ammonia environment.
　特に、試験番号１～１８及び試験番号２５～４３のオーステナイト系合金材は、特徴１～特徴３だけでなく、特徴４を満たした。そのため、特徴４を満たさなかった試験番号１９～２４と比較して、粒界割れが十分に抑制された。 In particular, the austenitic alloy materials of test numbers 1 to 18 and test numbers 25 to 43 satisfied not only features 1 to 3 but also feature 4. Therefore, grain boundary cracking was sufficiently suppressed compared to Test Nos. 19 to 24, which did not satisfy Feature 4.
　一方、試験番号４４では、Ｓｉ含有量が高すぎた。そのため、高温アンモニア環境において、粒界割れが十分に抑制されなかった。 On the other hand, in test number 44, the Si content was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
　試験番号４５では、Ｎｉ含有量が低すぎた。そのため、高温アンモニア環境において、窒化層深さが１５．０μｍを超え、十分な耐窒化性が得られなかった。 In test number 45, the Ni content was too low. Therefore, in a high-temperature ammonia environment, the depth of the nitrided layer exceeded 15.0 μm, and sufficient nitriding resistance could not be obtained.
　試験番号４６では、Ｎｉ含有量が高すぎた。そのため、高温アンモニア環境において、粒界割れが十分に抑制されなかった。 In test number 46, the Ni content was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
　試験番号４７では、Ｃｒ含有量が低すぎた。そのため、高温アンモニア環境において、窒化層深さが１５．０μｍを超え、十分な耐窒化性が得られなかった。 In test number 47, the Cr content was too low. As a result, in the high-temperature ammonia environment, the nitrided layer depth exceeded 15.0 μm, and sufficient nitridation resistance was not obtained.
　試験番号４８及び５０では、Ｓｂ含有量が高すぎた。そのため、高温アンモニア環境において、粒界割れが十分に抑制されなかった。 In test numbers 48 and 50, the Sb content was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
　試験番号４９では、Ｐｂ含有量が高すぎた。そのため、高温アンモニア環境において、粒界割れが十分に抑制されなかった。 In test number 49, the Pb content was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
　試験番号５１～５３では、Ｆｎ１が高すぎた。そのため、高温アンモニア環境において、窒化層深さが１５．０μｍを超え、十分な耐窒化性が得られなかった。 In test numbers 51 to 53, Fn1 was too high. Therefore, in a high-temperature ammonia environment, the depth of the nitrided layer exceeded 15.0 μm, and sufficient nitriding resistance could not be obtained.
　試験番号５４及び５５では、Ｆｎ２が高すぎた。そのため、高温アンモニア環境において、粒界割れが十分に抑制されなかった。 In test numbers 54 and 55, Fn2 was too high. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
　試験番号５６～５８では、Ｆｎ２が低すぎた。そのため、高温アンモニア環境において、粒界割れが十分に抑制されなかった。 In test numbers 56 to 58, Fn2 was too low. Therefore, intergranular cracking was not sufficiently suppressed in a high-temperature ammonia environment.
　以上、本開示の実施の形態を説明した。しかしながら、上述した実施の形態は本開示を実施するための例示に過ぎない。したがって、本開示は上述した実施の形態に限定されることなく、その趣旨を逸脱しない範囲内で上述した実施の形態を適宜変更して実施することができる。
  The embodiments of the present disclosure have been described above. However, the embodiments described above are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the embodiments described above, and the embodiments described above can be modified and implemented as appropriate without departing from the spirit thereof.

Claims (5)

  1. 　化学組成が、質量％で、
    　Ｃ：０超～０．２００％、
    　Ｓｉ：０超～３．００％、
    　Ｍｎ：０超～３．００％、
    　Ｐ：０超～０．０５０％、
    　Ｓ：０超～０．０５０％、
    　Ｎｉ：４０．００～８０．００％、及び、
    　Ｃｒ：１０．００～３５．００％、を含有し、
    　さらに、
    　Ｓｎ：０超～０．１０００％、
    　Ｚｎ：０超～０．０１００％、
    　Ｐｂ：０超～０．０１００％、
    　Ｓｂ：０超～０．０１００％、
    　Ａｓ：０超～０．００１０％、及び、
    　Ｂｉ：０超～０．００１０％、からなる群から選択される１種以上を含有し、
    　さらに、
    　Ｃｕ：０超～５．００％、
    　Ｍｏ：０超～２０．００％、
    　Ｃｏ：０超～３．００％、
    　Ｗ：０超～７．００％、
    　Ｔｉ：０超～１．００％、
    　Ｎｂ：０超～０．１０％、
    　Ｖ：０超～０．５０％、
    　Ｂ：０超～０．００５０％、
    　Ｎ：０超～０．２００％、
    　希土類元素：０超～０．１００％、
    　Ａｌ：０超～０．５００％、
    　Ｃａ：０超～０．０１００％、及び、
    　Ｍｇ：０超～０．０１５０％、からなる群から選択される１種以上を含有し、
    　残部はＦｅ及び不純物からなり、
    　式（１）で定義されるＦｎ１が２０未満であり、
    　式（２）で定義されるＦｎ２が２１よりも高く５０未満である、
    　オーステナイト系合金材。
    　Ｆｎ１＝１７７．８４＋１１．１２Ｓｉ－２４．３６Ｍｎ－８．１１Ｃｕ－１．６１Ｃｒ－１．７８Ｎｉ－２．６８Ｍｏ　（１）
    　Ｆｎ２＝（Ｓｎ＋Ｚｎ＋Ｐｂ＋Ｓｂ＋Ａｓ＋Ｂｉ）×１０３　（２）
    　ここで、式中の元素記号には、対応する元素の質量％での含有量が代入され、元素が含有されていない場合、対応する元素記号には「０」が代入される。     The chemical composition is in mass%,
    C: more than 0 to 0.200%,
    Si: more than 0 to 3.00%,
    Mn: more than 0 to 3.00%,
    P: more than 0 to 0.050%,
    S: more than 0 to 0.050%,
    Ni: 40.00 to 80.00%, and
    Contains Cr: 10.00 to 35.00%,
    moreover,
    Sn: more than 0 to 0.1000%,
    Zn: more than 0 to 0.0100%,
    Pb: more than 0 to 0.0100%,
    Sb: more than 0 to 0.0100%,
    As: more than 0 to 0.0010%, and
    Bi: contains one or more selected from the group consisting of more than 0 to 0.0010%,
    moreover,
    Cu: more than 0 to 5.00%,
    Mo: more than 0 to 20.00%,
    Co: more than 0 to 3.00%,
    W: more than 0 to 7.00%,
    Ti: more than 0 to 1.00%,
    Nb: more than 0 to 0.10%,
    V: more than 0 to 0.50%,
    B: more than 0 to 0.0050%,
    N: more than 0 to 0.200%,
    Rare earth elements: more than 0 to 0.100%,
    Al: more than 0 to 0.500%,
    Ca: more than 0 to 0.0100%, and
    Contains one or more selected from the group consisting of Mg: more than 0 to 0.0150%,
    The remainder consists of Fe and impurities,
    Fn1 defined by formula (1) is less than 20,
    Fn2 defined by formula (2) is higher than 21 and less than 50,
    Austenitic alloy material.
    Fn1=177.84+11.12Si-24.36Mn-8.11Cu-1.61Cr-1.78Ni-2.68Mo (1)
    Fn2=(Sn+Zn+Pb+Sb+As+Bi)×10 3 (2)
    Here, the content in mass % of the corresponding element is substituted for the element symbol in the formula, and if the element is not contained, "0" is substituted for the corresponding element symbol.
  2. 　請求項１に記載のオーステナイト系合金材であって、
    　前記オーステナイト系合金材の表層のμｍ単位での平均結晶粒径をＤａｖｅと定義したとき、
    　式（３）で定義されるＦｎ３が０．２０よりも高く、
    　式（４）で定義されるＦｎ４が１０００～５０００である、
    　オーステナイト系合金材。
    　Ｆｎ３＝Ｆｎ２／Ｄａｖｅ　（３）
    　Ｆｎ４＝Ｆｎ２×Ｄａｖｅ　（４）     The austenitic alloy material according to claim 1,
    When the average grain size in μm of the surface layer of the austenitic alloy material is defined as Da ,
    Fn3 defined by formula (3) is higher than 0.20,
    Fn4 defined by formula (4) is 1000 to 5000,
    Austenitic alloy material.
    Fn3=Fn2/D ave (3)
    Fn4=Fn2×D ave (4)
  3. 　請求項１又は請求項２に記載のオーステナイト系合金材であって、
    　化学組成が、質量％で、
    　Ｃ：０超～０．０５０％、
    　Ｓｉ：０超～０．５０％、
    　Ｍｎ：０超～０．５０％、
    　Ｐ：０超～０．０２５％、
    　Ｓ：０超～０．０１０％、
    　Ｃｕ：２．００～４．００％、
    　Ｎｉ：４４．００～５０．００％、
    　Ｃｒ：２０．００～２５．００％、
    　Ｍｏ：５．００～７．００％、
    　Ｗ：２．００～５．００％、及び、
    　Ｆｅ：１２．００～２０．００％、を含有する、
    　オーステナイト系合金材。     The austenitic alloy material according to claim 1 or claim 2,
    The chemical composition is in mass%,
    C: more than 0 to 0.050%,
    Si: more than 0 to 0.50%,
    Mn: more than 0 to 0.50%,
    P: more than 0 to 0.025%,
    S: more than 0 to 0.010%,
    Cu: 2.00-4.00%,
    Ni: 44.00-50.00%,
    Cr: 20.00-25.00%,
    Mo: 5.00-7.00%,
    W: 2.00 to 5.00%, and
    Contains Fe: 12.00 to 20.00%,
    Austenitic alloy material.
  4. 　請求項１又は請求項２に記載のオーステナイト系合金材であって、
    　化学組成が、質量％で、
    　Ｃ：０超～０．１５０％、
    　Ｓｉ：１．００～２．５０％、
    　Ｍｎ：０超～１．００％、
    　Ｐ：０超～０．０１０％、
    　Ｓ：０超～０．０１０％、
    　Ｃｕ：１．５０～３．００％、
    　Ｃｒ：２８．００～３２．００％、
    　Ｍｏ：１．００～３．００％、
    　Ｔｉ：０超～１．００％、及び、
    　Ｆｅ：２．００～６．００％、を含有する、
    　オーステナイト系合金材。     The austenitic alloy material according to claim 1 or claim 2,
    The chemical composition is in mass%,
    C: more than 0 to 0.150%,
    Si: 1.00-2.50%,
    Mn: more than 0 to 1.00%,
    P: more than 0 to 0.010%,
    S: more than 0 to 0.010%,
    Cu: 1.50-3.00%,
    Cr: 28.00-32.00%,
    Mo: 1.00-3.00%,
    Ti: more than 0 to 1.00%, and
    Contains Fe: 2.00 to 6.00%,
    Austenitic alloy material.
  5. 　請求項１又は請求項２に記載のオーステナイト系合金材であって、
    　化学組成が、質量％で、
    　Ｃ：０超～０．０５０％、
    　Ｓｉ：０超～０．５０％、
    　Ｍｎ：０超～０．５０％、
    　Ｐ：０超～０．０３０％、
    　Ｓ：０超～０．０１５％、
    　Ｃｕ：０超～０．５０％、
    　Ｃｒ：２７．００～３１．００％、
    　Ｆｅ：７．００～１５．００％、及び、
    　Ｎｉ：５８．００～８０．００％、を含有する、
    　オーステナイト系合金材。     The austenitic alloy material according to claim 1 or claim 2,
    The chemical composition is in mass%,
    C: more than 0 to 0.050%,
    Si: more than 0 to 0.50%,
    Mn: more than 0 to 0.50%,
    P: more than 0 to 0.030%,
    S: more than 0 to 0.015%,
    Cu: more than 0 to 0.50%,
    Cr: 27.00-31.00%,
    Fe: 7.00 to 15.00%, and
    Contains Ni: 58.00 to 80.00%,
    Austenitic alloy material.
PCT/JP2023/033809 2022-09-16 2023-09-15 Austenite alloy material WO2024058278A1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH073369A (en) * 1993-04-21 1995-01-06 Sumitomo Metal Ind Ltd High ni base alloy excellent in hydrogen embrittlement resistance and production thereof
JP2010150593A (en) * 2008-12-25 2010-07-08 Sumitomo Metal Ind Ltd Austenitic heat-resistant alloy
WO2020067444A1 (en) * 2018-09-27 2020-04-02 日本製鉄株式会社 Austenitic alloy
JP2021183721A (en) * 2020-05-22 2021-12-02 日本製鉄株式会社 Ni-BASED ALLOY TUBE AND WELDED JOINT
WO2021256128A1 (en) * 2020-06-19 2021-12-23 Ｊｆｅスチール株式会社 Alloy pipe and method for manufacturing same

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH073369A (en) * 1993-04-21 1995-01-06 Sumitomo Metal Ind Ltd High ni base alloy excellent in hydrogen embrittlement resistance and production thereof
JP2010150593A (en) * 2008-12-25 2010-07-08 Sumitomo Metal Ind Ltd Austenitic heat-resistant alloy
WO2020067444A1 (en) * 2018-09-27 2020-04-02 日本製鉄株式会社 Austenitic alloy
JP2021183721A (en) * 2020-05-22 2021-12-02 日本製鉄株式会社 Ni-BASED ALLOY TUBE AND WELDED JOINT
WO2021256128A1 (en) * 2020-06-19 2021-12-23 Ｊｆｅスチール株式会社 Alloy pipe and method for manufacturing same

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