WO2020067444A1 - Alliage austénitique - Google Patents

Alliage austénitique Download PDF

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Publication number
WO2020067444A1
WO2020067444A1 PCT/JP2019/038198 JP2019038198W WO2020067444A1 WO 2020067444 A1 WO2020067444 A1 WO 2020067444A1 JP 2019038198 W JP2019038198 W JP 2019038198W WO 2020067444 A1 WO2020067444 A1 WO 2020067444A1
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content
alloy
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austenitic alloy
austenitic
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PCT/JP2019/038198
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Japanese (ja)
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礼文 河内
孝裕 小薄
佳奈 浄▲徳▼
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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
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • 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 an austenitic stainless steel or a Ni-based alloy containing Cr.
  • facilities such as thermal power generation boilers and chemical plants used in a high-temperature carburizing environment include, as heat-resistant alloys, austenitic stainless steel with an increased Cr content and Ni content, or a Ni-based alloy with an increased Cr content. Alloys are used. These heat-resistant alloys are austenitic alloys containing about 10 to 40% by mass of Cr and about 20 to 70% by mass of Ni.
  • Austenitic alloys used in facilities such as thermal power boilers and chemical plants are manufactured into a predetermined shape by hot working. Therefore, high hot workability is required for the austenitic alloys described above.
  • austenitic alloys generally have high deformation resistance at high temperatures and low ductility. Therefore, an austenitic alloy having excellent hot workability in addition to the above-described excellent carburization resistance is required.
  • Austenitic alloys that can be used in a high-temperature carburizing environment include, for example, WO2017 / 119415 (Patent Document 1), WO2018 / 003823 (Patent Document 2), and WO2010 / 113830 (Patent Document 1). 3) is proposed.
  • the austenitic heat-resistant alloy disclosed in Patent Document 1 is, by mass%, C: 0.03 to less than 0.25%, Si: 0.01 to 2.0%, Mn: 2.0% or less, Cr: 10 to less than 30%, Ni: more than 25 to 45%, Al: more than 2.5 to less than 4.5%, Nb: 0.2 to 3.5%, N: 0.025% or less, Ti: 0 to Less than 0.2%, W: 0-6%, Mo: 0-4%, Zr: 0-0.1%, B: 0-0.01%, Cu: 0-5%, rare earth element: 0- 0.1%, Ca: 0 to 0.05%, and Mg: 0 to 0.05%, with the balance being Fe and impurities, where P and S in the impurities are respectively P: 0.04 % And S: 0.01% or less, and the total volume ratio of precipitates having an equivalent circle diameter of 6 ⁇ m or more in the structure is 5% or less.
  • the austenitic stainless steel disclosed in Patent Document 2 is, by mass%, C: 0.03 to less than 0.25%, Si: 0.01 to 2.0%, Mn: 2.0% or less, P: 0.04% or less, S: 0.01% or less, Cr: 10 to less than 22%, Ni: more than 30.0% to 40.0%, Al: more than 2.5% to less than 4.5%, Nb : 0.01 to 3.5%, N: 0.03% or less, Ca: 0.0005 to 0.05%, Mg: 0.0005 to 0.05%, Ti: 0 to less than 0.2%, Mo: 0 to 0.5%, W: 0 to 0.5%, Cu: 0 to 0.5%, V: 0 to 0.2%, and B: 0 to 0.01%,
  • the balance has a chemical composition consisting of Fe and impurities, and satisfies Expression (1).
  • the cast product disclosed in Patent Document 3 has a C content of 0.05 to 0.7%, a Si content of more than 0% and 2.5% or less, and a Mn content of more than 0% and 3.0% by mass%.
  • Cr 15 to 50%
  • Ni 18 to 70%
  • Al 2 to 4%
  • rare earth element 0.005 to 0.4%
  • W 0.5 to 10% and / or Mo:
  • It has a cast of a heat-resistant alloy containing 0.1 to 5%, the balance being Fe and unavoidable impurities, and a barrier layer is formed on the surface of the cast in contact with a high-temperature atmosphere.
  • the barrier layer is an Al 2 O 3 layer having a thickness of 0.5 ⁇ m or more.
  • Al 2 O 3 accounts for 80% by area or more of the outermost surface of the barrier layer, and Cr-based particles having a higher Cr concentration than the alloy base are dispersed at the interface between the Al 2 O 3 layer and the casting.
  • An austenitic alloy usable in a high-temperature carburizing environment can be obtained by the techniques disclosed in Patent Documents 1 to 3 described above.
  • an austenitic alloy having excellent carburization resistance and excellent hot workability can be obtained.
  • An object of the present disclosure is to provide an austenitic alloy having excellent carburization resistance and hot workability.
  • the austenitic alloy of the present disclosure In mass%, C: 0.030 to less than 0.250%, Si: 0.01-2.00%, Mn: 2.00% or less, P: 0.040% or less, S: 0.010% or less, Cr: 10.00 to less than 25.00%, Ni: 30.00 to 60.00%, Al: more than 2.50% to 3.50%, Nb: 0.20 to 3.50%, Zr: selected from the group consisting of 0.0001 to 0.1000%, Hf: 0.0001 to 0.1000%, Sn: 0.0001 to 0.1000%, and As: 0.0001 to 0.1000%.
  • the austenitic alloy of the present disclosure has excellent carburization resistance and hot workability.
  • FIG. 1 is a diagram showing the F1 value, carburizing resistance, and hot workability of an austenitic alloy in which the content of each element in the chemical composition is within the range of the element content of the present embodiment. .
  • a high-temperature carburizing environment refers to an environment of 1000 ° C. or higher in a hydrocarbon gas atmosphere.
  • the austenitic alloy means austenitic stainless steel or a Ni-based alloy containing Cr.
  • the austenitic alloy contains Al.
  • an Al 2 O 3 film is formed on the surface of the alloy instead of the Cr 2 O 3 film.
  • Al 2 O 3 acts as a protective film.
  • Al 2 O 3 is more thermodynamically stable than Cr 2 O 3 in a high temperature carburizing environment. That is, with Al 2 O 3 , the carburization resistance of the austenitic alloy can be increased even in an environment of 1000 ° C. or higher.
  • the Al content in the austenitic alloy is excessively high, a gamma prime phase ( ⁇ ′ phase: Ni 3 Al) is likely to precipitate in the austenitic alloy manufacturing process. If the ⁇ 'phase precipitates, precipitation strengthening occurs. In this case, hot workability is significantly reduced. For this reason, the Al content needs to be limited to a certain amount or less.
  • the present inventors found that, by mass%, C: 0.030 to less than 0.250%, Si: 0.01 to 2.00%, Mn: 2.00% or less, P: : 0.040% or less, S: 0.010% or less, Cr: 10.00 to less than 25.00%, Ni: 30.00 to 60.00%, Al: more than 2.50% to 3.50% , Nb: 0.20 to 3.50%, Ti: 0 to less than 0.20%, Mo: 0 to 0.10%, W: 0 to 0.20%, B: 0 to 0.1000%, V : 0 to 0.500%, Cu: 0 to 5.0%, Ca: 0 to 0.0500%, Mg: 0 to 0.0500%, REM: 0 to 0.1000%, N: 0 to 0. 030%, and the balance is considered to be an austenitic alloy composed of Fe and impurities, which can enhance the carburization resistance while maintaining the hot workability. .
  • the Al 2 O 3 film may not be sufficiently formed in a high-temperature carburizing environment. Therefore, the present inventors have studied a method of promoting the formation of an Al 2 O 3 film in a high-temperature carburizing environment while suppressing the Al content to more than 2.50% to 3.50%. As a result, Zr: 0.0001 to 0.1000%, Hf: 0.0001 to 0.1000%, Sn: 0.0001 to 0.1000%, and As: By containing one or more members selected from the group consisting of 0.0001 to 0.1000%, the formation of an Al 2 O 3 film is promoted in a high-temperature carburizing environment to ensure carburization resistance. It was found that a sufficient Al 2 O 3 film could be formed.
  • Zr, Hf, Sn and As promote the uniform formation of the Al 2 O 3 film in the austenitic alloy having the above-mentioned chemical composition is not clear. However, the following reasons are considered. Zr, Hf, Sn and As promote external Al oxidation in a high-temperature carburizing environment. As a result, it is considered that uniform formation of the Al 2 O 3 film is promoted.
  • C 0.030 to less than 0.250%
  • Si 0.01 to 2.00%
  • Mn 2.00% or less
  • P 0.040% or less
  • S 0.010% or less
  • Cr 10.00 to less than 25.00%
  • Al more than 2.50% to 3.50%
  • Nb 0.20 From 3.50%
  • Zr 0.0001 to 0.1000%
  • Hf 0.0001 to 0.1000%
  • Sn 0.0001 to 0.1000%
  • Ti 0 to less than 0.20%
  • Mo 0 to 0.10%
  • W 0 to 0.20%
  • B 0 to 0.1000%
  • V 0 to 0.500%
  • Cu 0 to 5.0%
  • Ca 0 to 0.0500%
  • Mg 0 to 0.0500%
  • REM 0 to 0.1000%
  • N 0 to 0.030%
  • the balance is excellent if the contents of
  • the austenitic alloy of this embodiment has been completed based on the above findings.
  • the austenitic alloy of the present embodiment has the following configuration.
  • the austenitic alloy of [2] An austenitic alloy according to [1], In mass%, Ti: 0.01 to less than 0.20%, Mo: 0.01 to 0.10%, W: 0.01 to 0.20%, B: 0.0001 to 0.1000%, V: 0.001 to 0.500%, and Cu: contains one or more members selected from the group consisting of 0.1 to 5.0%.
  • the austenitic alloy of [3] An austenitic alloy according to [1] or [2], In mass%, Ca: 0.0001 to 0.0500% One or more selected from the group consisting of Mg: 0.0001 to 0.0500% and REM: 0.0005 to 0.1000%.
  • the austenitic alloy of [4] The austenitic alloy according to any one of [1] to [3], In mass%, N: contains 0.001 to 0.030%.
  • the austenitic alloy of [5] The austenitic alloy according to any one of [1] to [4],
  • the average grain size of the austenite crystal grains measured according to JIS G 0551 (2013) is 60 to 130 ⁇ m.
  • the austenitic alloy not only achieves excellent carburization resistance and excellent hot workability, but also obtains high creep strength.
  • the chemical composition of the austenitic alloy according to the present embodiment contains the following elements.
  • C 0.030 to less than 0.250%
  • Carbon (C) mainly combines with Cr to form a Cr carbide.
  • Cr carbide increases the creep strength of the alloy when used in a high temperature carburizing environment. If the C content is less than 0.030%, the above effects cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the C content is 0.250% or more, a large number of coarse eutectic carbides are generated in the solidified structure of the alloy after casting even if the other element contents are within the range of the present embodiment. . Therefore, the toughness of the alloy decreases. Therefore, the C content is less than 0.030 to 0.250%.
  • a preferred lower limit of the C content is 0.040%, more preferably 0.050%, further preferably 0.060% or more, further preferably 0.070%, and still more preferably 0.1%. 080%.
  • a preferred upper limit of the C content is 0.240%, more preferably 0.230%, further preferably 0.220%, more preferably 0.210%, and still more preferably 0.200%. %.
  • Si 0.01 to 2.00%
  • Silicon (Si) deoxidizes the alloy. If deoxidation can be sufficiently performed with another element, the content of Si may be as small as possible. However, excessive reduction of the Si content increases the manufacturing cost. Therefore, the lower limit of the Si content is 0.01%.
  • the Si content exceeds 2.00%, the hot workability of the alloy is reduced even if the content of other elements is within the range of the present embodiment. Therefore, the Si content is 0.01 to 2.00%.
  • a preferred lower limit of the Si content is 0.02%, more preferably 0.03%, further preferably 0.05%, more preferably 0.10%, and still more preferably 0.20%. %.
  • the preferable upper limit of the Si content is 1.80%, more preferably 1.65%, further preferably 1.50%, further preferably 1.20%, and still more preferably 1.00. %.
  • Mn 2.00% or less Manganese (Mn) is inevitably contained. That is, the Mn content is more than 0%. Mn combines with S contained in the alloy to form MnS. MnS enhances the hot workability of the alloy. However, if the Mn content exceeds 2.00%, the alloy becomes too hard even if the content of other elements is within the range of the present embodiment. As a result, the hot workability and weldability of the alloy decrease. Therefore, the Mn content is 2.00% or less.
  • a preferable lower limit of the Mn content is 0.10%, more preferably 0.20%, further preferably 0.30%, and further preferably 0.40%.
  • the preferable upper limit of the Mn content is 1.80%, more preferably 1.70%, further preferably 1.60%, further preferably 1.50%, and further preferably 1.40%. %, And more preferably 1.30%.
  • Phosphorus (P) is an unavoidable impurity. That is, the P content is more than 0%. P reduces the weldability and hot workability of the alloy. Therefore, the P content is 0.040% or less.
  • the preferable upper limit of the P content is 0.035%, more preferably 0.030%, and still more preferably 0.025%.
  • the P content is preferably as low as possible. However, reducing the P content excessively increases costs. Therefore, the preferable lower limit of the P content is 0.001%, and more preferably 0.002%.
  • S 0.010% or less Sulfur (S) is an impurity.
  • the S content may be 0%. S reduces the weldability and hot workability of the alloy. Therefore, the S content is 0.010% or less.
  • the preferable upper limit of the S content is 0.009%, more preferably 0.008%, and further preferably 0.007%.
  • the S content is preferably as low as possible. However, reducing the S content excessively increases costs. Therefore, the lower limit of the S content is, for example, 0.001%.
  • Chromium (Cr) promotes the formation of an Al 2 O 3 film when used in a high-temperature carburizing environment. Cr further combines with C in the alloy to form Cr carbides in the alloy, increasing creep strength. If the Cr content is less than 10.00%, the above effects cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment. On the other hand, if the Cr content is 25.00% or more, even if the other element contents are within the range of the present embodiment, in a high-temperature carburizing environment, Cr and C derived from an atmospheric gas (hydrocarbon gas) are not used. Bond to form Cr carbide on the alloy surface.
  • an atmospheric gas hydrocarbon gas
  • the Cr content is 25.00% or more, Cr carbide on the alloy surface physically inhibits formation of a uniform Al 2 O 3 film. Therefore, the Cr content is less than 10.00 to less than 25.00%.
  • a preferable lower limit of the Cr content is 11.00%, more preferably 12.00%, further preferably 13.00%, and further preferably 14.00%.
  • a preferred upper limit of the Cr content is 24.00%, more preferably 23.00%, further preferably 22.00%, more preferably 21.00%, and further preferably 20.00%. %.
  • Ni 30.00% to 60.00%
  • Nickel (Ni) stabilizes austenite and increases creep strength. Ni further enhances the carburization resistance of the alloy. If the Ni content is less than 30.00%, the above effects cannot be sufficiently obtained even if other element contents are within the range of the present embodiment. On the other hand, if the Ni content exceeds 60.00%, the hot workability of the alloy decreases. Therefore, the Ni content is 30.00% to 60.00%.
  • a preferred lower limit of the Ni content is 31.00%, more preferably 32.00%, further preferably 35.00%, more preferably 38.00%, and further preferably 40.00%. %.
  • the preferable upper limit of the Ni content is 58.00%, more preferably 56.00%, further preferably 54.00%, and further preferably 50.00%.
  • Al more than 2.50% to 3.50%
  • Aluminum (Al) forms an Al 2 O 3 coating on the alloy surface during use in a high temperature carburizing environment.
  • Al enhances the carburization resistance of the alloy during use in a high temperature carburizing environment.
  • the Al content is 2.50% or less, the above effects cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment.
  • the Al content exceeds 3.50%, the ⁇ ′ phase (Ni 3 Al) is typified during the manufacturing process of the alloy even if other element contents are within the range of the present embodiment.
  • the intermetallic compound containing Al significantly reduces the hot workability of the alloy. Therefore, the Al content is more than 2.50% to 3.50%.
  • a preferred lower limit of the Al content is 2.55%, more preferably 2.60%, further preferably 2.65%, and further preferably 2.70%.
  • the preferable upper limit of the Al content is 3.45%, more preferably 3.40%, further preferably 3.35%, and further preferably 3.30%.
  • the Al content means the total amount of Al contained in the alloy.
  • Nb 0.20 to 3.50% Niobium (Nb), during use at a high temperature carburizing environment, to form an intermetallic compound serving as a precipitation strengthening phase (Laves phase and Ni 3 Nb-phase).
  • the Laves phase and the Ni 3 Nb phase strengthen the precipitation at the grain boundaries and inside the grains, thereby increasing the creep strength of the alloy.
  • the Nb content is less than 0.20%, the above effects cannot be sufficiently obtained even if other element contents are within the range of the present embodiment.
  • the Nb content exceeds 3.50%, the Laves phase and the Ni 3 Nb phase are excessively generated and the toughness of the alloy is reduced even if the other element contents are within the range of the present embodiment. I do.
  • the Nb content is 0.20 to 3.50%.
  • the preferable lower limit of the Nb content is 0.25%, more preferably 0.30%, further preferably 0.35%, and further preferably 0.40%.
  • the preferable upper limit of the Nb content is 3.40%, more preferably 3.30%, further preferably less than 3.20%, further preferably 3.10%, and still more preferably 3.10%. 00%.
  • Zr selected from the group consisting of 0.0001 to 0.1000%, Hf: 0.0001 to 0.1000%, Sn: 0.0001 to 0.1000%, and As: 0.0001 to 0.1000%.
  • the chemical composition of the austenitic alloy of the present embodiment is one or more kinds selected from the group consisting of zirconium (Zr), hafnium (Hf), tin (Sn) and arsenic (As). It contains.
  • Zr, Hf, Sn and As when contained are as follows. Further, the contents of Zr, Hf, Sn, and As satisfy the following expression (1).
  • Zr 0.0001 to 0.1000%
  • Zirconium (Zr) promotes the formation of Al 2 O 3 coatings on alloy surfaces during use in high temperature carburizing environments.
  • the Zr content exceeds 0.1000%, the intermetallic compound is excessively generated during the alloy manufacturing process even if the other element content is within the range of the present embodiment. As a result, the hot workability of the alloy decreases. Therefore, the Zr content is 0.0001 to 0.1000%.
  • a preferred lower limit of the Zr content is 0.0005%, more preferably 0.0010%, and further preferably 0.0020%.
  • the preferable upper limit of the Zr content is 0.0800%, more preferably 0.0700%, further preferably 0.0600%, and further preferably 0.0500%.
  • Hf 0.0001 to 0.1000%
  • Hafnium (Hf) promotes the formation of an Al 2 O 3 coating on the alloy surface during use in a high temperature carburizing environment.
  • the Hf content is 0.0001 to 0.1000%.
  • a preferred lower limit of the Hf content is 0.0005%, more preferably 0.0010%, and further preferably 0.0020%.
  • a preferable upper limit of the Hf content is 0.0800%, more preferably 0.0700%, further preferably 0.0600%, and further preferably 0.0500%.
  • Tin (Sn) promotes the formation of an Al 2 O 3 coating on the alloy surface during use in a high temperature carburizing environment.
  • Sn content is 0.0001 to 0.1000%.
  • a preferred lower limit of the Sn content is 0.0005%, more preferably 0.0010%, and further preferably 0.0020%.
  • the preferable upper limit of the Sn content is 0.0800%, more preferably 0.0700%, further preferably 0.0600%, further preferably 0.0500%, and still more preferably 0.0400%. %, And more preferably 0.0100%.
  • Arsenic (As) promotes the formation of Al 2 O 3 coatings on alloy surfaces during use in high temperature carburizing environments.
  • the As content exceeds 0.1000%, the intermetallic compound is excessively generated during the alloy manufacturing process even if the other element content is within the range of the present embodiment. As a result, the hot workability of the alloy decreases. Therefore, the As content is 0.0001 to 0.1000%.
  • a preferred lower limit of the As content is 0.0005%, more preferably 0.0010%, and still more preferably 0.0020%.
  • the preferable upper limit of the As content is 0.0800%, more preferably 0.0700%, further preferably 0.0600%, further preferably 0.0500%, and still more preferably 0.0400%. %, And more preferably 0.0100%.
  • the austenitic alloy of the present embodiment may contain one or more selected from the group consisting of Zr, Hf, Sn and As.
  • the remainder of the chemical composition of the austenitic alloy of the present embodiment is composed of Fe and impurities.
  • the impurities are those that are mixed in from an ore, scrap, or a production environment as a raw material when the austenitic alloy is manufactured industrially, and adversely affect the austenitic alloy of the present embodiment. Means that it is acceptable within a certain range.
  • the chemical composition of the austenitic alloy described above may further include one or more selected from the group consisting of Ti, Mo, W, B, V, and Cu instead of part of Fe. These elements are all optional elements, and all increase the creep strength of the alloy.
  • Titanium (Ti) is an optional element and may not be contained. That is, the Ti content may be 0%.
  • Ti forms intermetallic compounds (Laves phase and Ni 3 Ti phase) that become precipitation strengthening phases during use in a high temperature carburizing environment. These intermetallic compounds increase the creep strength of the alloy by precipitation strengthening. The above effect can be obtained to some extent if Ti is contained even a little. However, if the Ti content is 0.20% or more, these intermetallic compounds are excessively generated even if other element contents are within the range of the present embodiment. As a result, the hot ductility and hot workability of the alloy are reduced.
  • the Ti content is 0.20% or more, the toughness of the alloy is further reduced during long-time use in a high-temperature carburizing environment. Therefore, the Ti content is 0 to less than 0.20%.
  • a preferred lower limit of the Ti content is 0.01%, more preferably 0.02%, and even more preferably 0.05%.
  • the preferable upper limit of the Ti content is 0.19%, more preferably 0.18%, and further preferably 0.17%.
  • Mo Molybdenum
  • Mo is an optional element and may not be contained. That is, the Mo content may be 0%. When contained, Mo dissolves in austenite, which is the parent phase. The solid solution Mo increases the creep strength in a high-temperature carburizing environment by solid solution strengthening. The above effect can be obtained to some extent if Mo is contained at all. However, if the Mo content exceeds 0.10%, the hot workability of the alloy decreases even if the content of other elements is within the range of the present embodiment. Therefore, the Mo content is 0 to 0.10%.
  • a preferred lower limit of the Mo content is 0.01%, more preferably 0.02%, and still more preferably 0.03%.
  • a preferable upper limit of the Mo content is 0.09%, more preferably 0.08%, further preferably 0.07%, and further preferably 0.05%.
  • Tungsten (W) is an optional element and need not be contained. That is, the W content may be 0%.
  • W forms a solid solution in austenite which is a parent phase.
  • the solid solution W enhances the creep strength in a high-temperature carburizing environment by solid solution strengthening. The above effect can be obtained to some extent if W is contained at all. However, if the W content exceeds 0.20%, the hot workability of the alloy decreases. Therefore, the W content is 0 to 0.20%.
  • a preferred lower limit of the W content is 0.01%, more preferably 0.02%, and still more preferably 0.03%.
  • a preferred upper limit of the W content is 0.19%, more preferably 0.18%, further preferably 0.17%, further preferably 0.15%, and still more preferably 0.10%. %.
  • B 0 to 0.1000%
  • Boron (B) is an optional element and need not be contained. That is, the B content may be 0%. When contained, B segregates at the grain boundaries and promotes precipitation of intermetallic compounds at the grain boundaries. Thereby, B increases the creep strength of the alloy in a high temperature carburizing environment. The above effect can be obtained to some extent if B is contained at all. However, if the B content exceeds 0.1000%, the weldability and hot workability of the alloy are reduced even if the content of other elements is within the range of the present embodiment. Therefore, the B content is 0 to 0.1000%.
  • a preferable lower limit of the B content is 0.0001%, more preferably 0.0005%, further preferably 0.0010%, more preferably 0.0020%, and further preferably 0.0030%. %, More preferably 0.0050%, further preferably 0.0070%, and still more preferably 0.0100%.
  • the preferable upper limit of the B content is 0.0800%, and more preferably 0.0600%.
  • V 0 to 0.500%
  • Vanadium (V) is an optional element and may not be contained. That is, the V content may be 0%. When included, V forms an intermetallic compound, similar to Ti, and increases the creep strength of the alloy in a high temperature carburizing environment. The above effect can be obtained to some extent if V is contained at all. However, if the V content exceeds 0.500%, the intermetallic compound is excessively generated and the hot workability of the alloy is reduced even if the content of other elements is within the range of the present embodiment. . Therefore, the V content is 0 to 0.500%.
  • a preferable lower limit of the V content is 0.001%, more preferably 0.010%, further preferably 0.030%, and further preferably 0.050%.
  • the preferable upper limit of the V content is 0.400%, more preferably 0.350%, further preferably 0.300%, more preferably 0.250%, and still more preferably 0.100%. %.
  • Cu 0 to 5.0% Copper (Cu) is an optional element and need not be contained. That is, the Cu content may be 0%. When included, Cu stabilizes austenite. Cu further precipitates in a high temperature carburizing environment, increasing the creep strength of the alloy by precipitation strengthening. The above effect can be obtained to some extent if Cu is contained even a little. However, if the Cu content exceeds 5.0%, the ductility and hot workability of the alloy decrease. Therefore, the Cu content is 0 to 5.0%. A preferred lower limit of the Cu content is 0.1%, more preferably 0.2%, and still more preferably 0.3%. A preferable upper limit of the Cu content is 4.5%, more preferably 4.0%, further preferably 3.5%, and further preferably 3.0%.
  • the chemical composition of the austenitic alloy described above may further include one or more selected from the group consisting of Ca, Mg, and REM instead of a part of Fe. These elements are all optional elements and enhance the hot workability of the alloy.
  • Ca 0 to 0.0500%
  • Calcium (Ca) is an optional element and may not be contained. That is, the Ca content may be 0%. When contained, Ca fixes S as sulfide and enhances the hot workability of the alloy. The above effect can be obtained to some extent if Ca is contained even a little. However, if the Ca content exceeds 0.0500%, the toughness and ductility of the alloy are reduced and the hot workability of the alloy is reduced even if the content of other elements is within the range of the present embodiment. I do. If the Ca content exceeds 0.0500%, the cleanliness of the alloy further decreases. Therefore, the Ca content is 0 to 0.0500%.
  • a preferable lower limit of Ca is 0.0001%, more preferably 0.0005%, further preferably 0.0010%, and further preferably 0.0050%.
  • the preferable upper limit of the Ca content is 0.0400%, more preferably 0.0350%, further preferably 0.0300%, further preferably 0.0250%, and still more preferably 0.0200%. %.
  • Mg 0 to 0.0500%
  • Magnesium (Mg) is an optional element and may not be contained. That is, the Mg content may be 0%. When contained, Mg fixes S as a sulfide and enhances the hot workability of the alloy. The above effect can be obtained to some extent if Mg is contained at all. However, if the Mg content exceeds 0.0500%, the toughness and ductility of the alloy are reduced and the hot workability of the alloy is reduced even if the content of other elements is within the range of the present embodiment. I do. If the Mg content exceeds 0.0500%, the cleanliness of the alloy is further reduced. Therefore, the Mg content is 0-0.0500%.
  • a preferred lower limit of Mg is 0.0001%, more preferably 0.0005%, further preferably 0.0010%, more preferably 0.0050%, and still more preferably 0.0080%. is there.
  • a preferable upper limit of the Mg content is 0.0400%, more preferably 0.0350%, further preferably 0.0300%, and further preferably 0.0250%.
  • the rare earth element (REM) is an optional element and may not be contained. That is, the REM content may be 0%. When included, REM fixes S as sulfide and enhances the hot workability of the alloy. REM also forms oxides to increase the corrosion resistance, creep strength, and creep ductility of the alloy. The above effect can be obtained to some extent if REM is contained even a little. However, if the REM content exceeds 0.1000%, even if the content of other elements is within the range of the present embodiment, the amount of inclusions such as oxides becomes excessively large. In this case, the hot workability and weldability of the alloy decrease. Therefore, the REM content is 0-0.1000%.
  • a preferable lower limit of the REM content is 0.0005%, more preferably 0.0010%, further preferably 0.0050%, further preferably 0.0080%, and further preferably 0.0100%. %.
  • a preferred upper limit of the REM content is 0.0950%, more preferably 0.0900%, further preferably 0.0850%, and still more preferably 0.0800%.
  • REM is a general term for a total of 17 elements of Sc, Y and lanthanoids.
  • the REM content means the content of the element when the REM contained in the austenitic alloy is one of these elements.
  • the REM content means the total content of those elements.
  • the chemical composition of the austenitic alloy described above may further contain N instead of part of Fe.
  • N is an optional element and stabilizes austenite.
  • N 0 to 0.030%
  • Nitrogen (N) is an optional element and need not be contained. That is, the N content may be 0%. When included, N stabilizes austenite. The above effect can be obtained to some extent if N is contained at all. However, if the N content exceeds 0.030%, coarse nitrides and / or carbonitrides are generated even if other element contents are within the range of the present embodiment. The coarse nitrides and / or carbonitrides remain undissolved even after heat treatment during the manufacturing process. Coarse nitrides and / or carbonitrides reduce the toughness of the alloy. Therefore, the N content is 0 to 0.030%.
  • a preferred lower limit of N is 0.001%, more preferably 0.002%, and still more preferably 0.005%.
  • a preferred upper limit of the N content is 0.029%, more preferably 0.026%, and still more preferably 0.024%.
  • the austenitic alloy of the present embodiment satisfies the above chemical composition and further satisfies the formula (1). 0.07 ⁇ 1.96 ⁇ Zr + Hf + 1.50 ⁇ Sn + 2.38 ⁇ As ⁇ 0.50 (1) Here, the content (% by mass) of the corresponding element is substituted for the element symbol in the formula (1).
  • the austenitic alloy of the present embodiment In a high-temperature carburizing environment, it is extremely effective to form an Al 2 O 3 coating on the alloy surface as a protective coating in order to enhance the carburization resistance of the austenitic alloy. If the Al content in the austenitic alloy is increased, the formation of an Al 2 O 3 film is promoted. However, in the above-described austenitic alloy chemical composition, if the Al content exceeds 3.50%, the hot workability of the alloy is significantly reduced. Therefore, in the austenitic alloy of the present embodiment, the Al content is set to more than 2.50% to 3.50%, and Zr: 0.0001 to Zr is used as an accelerating element for the Al 2 O 3 film in a high-temperature carburizing environment.
  • FIG. 1 is a diagram showing the F1 value, carburizing resistance, and hot workability of an austenitic alloy in which the content of each element in the chemical composition is within the range of the element content of the present embodiment.
  • the vertical axis indicates the average amount of invading C (% by mass), which is an index of carburization resistance.
  • the method for measuring the average intrusion C amount will be described later.
  • the symbol “•” (Solid @ circle) in FIG. 1 indicates that the drawing value at 900 ° C. was 60% or more, indicating that excellent hot workability was exhibited.
  • the symbol “1” (Solid @ triangle) in FIG. 1 indicates that the drawing value at 900 ° C. was less than 60% and the hot workability was low.
  • F1 is set to 0.07 to 0.50.
  • a preferred lower limit of ⁇ F1 is 0.08, more preferably 0.09, and still more preferably 0.10.
  • a preferred upper limit of F1 is 0.48, more preferably 0.46, further preferably 0.44, and still more preferably 0.42.
  • the F1 value is a value obtained by rounding off the third decimal place of the obtained value (that is, the value of the second decimal place).
  • the shape of the austenitic alloy according to the present embodiment is not particularly limited.
  • the austenitic alloy is, for example, a tube.
  • the austenitic alloy is used, for example, for chemical plant applications.
  • austenitic alloys are used, for example, as reaction tubes for chemical plants.
  • Austenitic alloys are not limited to tubes.
  • the austenitic alloy may be a plate or a rod.
  • the microstructure of the austenitic alloy substantially consists of austenite. That is, the microstructure of the austenitic alloy is substantially an austenitic single phase structure.
  • substantially composed of austenite means that the microstructure is composed of austenite except for inclusions and precipitates. The total area ratio of inclusions and precipitates in the microstructure is so small as to be negligible as compared with the area ratio of austenite in the microstructure.
  • the austenitic alloy of the present embodiment has the above chemical composition and satisfies the formula (1). Therefore, it has excellent carburization resistance. Specifically, after a high-temperature carburizing test in which a high-temperature carburizing gas atmosphere containing 67% by volume of H 2 gas, 30% by volume of CH 4 gas, and 3% by volume of CO 2 gas is maintained at 1100 ° C. for 96 hours. The average infiltration C amount (% by mass) obtained by subtracting the C content (% by mass) of the surface layer of the austenitic alloy before the high-temperature carburizing test from the C content (% by mass) of the surface layer of the austenitic alloy is 0. .25% or less.
  • the average intrusion C amount is measured by the following method.
  • a test specimen is collected from the austenitic alloy.
  • the austenitic alloy is a tube
  • a test piece is taken from the center of the wall thickness.
  • the austenitic alloy is a plate
  • a test piece is taken from the center of the width and from the center of the plate thickness.
  • the austenitic alloy is a rod
  • a test piece is taken from a center position in a cross section perpendicular to the longitudinal direction.
  • the size of the test piece is not particularly limited.
  • the following high-temperature carburizing test is performed on the test specimen.
  • a high-temperature carburizing gas atmosphere containing 67% by volume of H 2 gas, 30% by volume of CH 4 gas, and 3% by volume of CO 2 gas was tested in a heat treatment furnace at 1100 ° C. Load the pieces. The specimen is kept in a heat treatment furnace at 1100 ° C. for 96 hours. Thereafter, the temperature in the furnace of the heat treatment furnace is reduced to room temperature. After lowering the furnace temperature to room temperature, the test piece is extracted from the heat treatment furnace. The oxide film on the test piece after the above-described high-temperature carburizing test is subjected to dry polishing with # 600 abrasive paper to remove the oxide film.
  • the C content (% by mass) of each layer is determined by performing a high-frequency combustion infrared absorption method based on JIS G1211-3 (2013) using the swarf for analysis in each layer. Further, the C content of the test piece before the high-temperature carburizing test (hereinafter, referred to as base material C content) is measured in advance by a high-frequency combustion infrared absorption method in accordance with JIS G1211-3 (2013).
  • the difference between the C content of each layer after the high-temperature carburizing test and the C content of the base material is defined as the intrusion C amount of each layer.
  • the arithmetic mean value of the obtained four intrusion C amounts is defined as an average intrusion C amount (% by mass).
  • the austenitic alloy of the present embodiment further has excellent hot workability together with excellent carburization resistance. Specifically, in the austenitic alloy according to the present embodiment, the reduction obtained by performing a tensile test at 900 ° C. at a strain rate of 10 / sec according to JIS G 0567 (2012) is 60% or more. It is.
  • the drawing at 900 ° C. is measured by the following method.
  • An ingot of an austenitic alloy having the above-described chemical composition is prepared.
  • a tensile test piece is collected from the prepared ingot.
  • the diameter of the parallel part of the tensile test piece is 10 mm, and the length of the parallel part is 130 mm.
  • a tensile test is performed at 900 ° C. at a strain rate of 10 / sec in accordance with JIS G 0567 (2012).
  • the original cross-sectional area of the parallel part of the tensile test piece before the tensile test is defined as S o (mm 2 ).
  • the minimum cross-sectional area of the tensile test piece after fracture is defined as S u (mm 2 ).
  • the preferred average grain size of austenite crystal grains measured according to JIS G 0551 (2013) is 60 to 130 ⁇ m.
  • the content of each element in the chemical composition is within the range of the present embodiment and the average grain size of the austenite crystal grains in the austenitic alloy in which F1 satisfies the formula (1) is 60 ⁇ m or more, high temperature Excellent creep strength in carburizing environment.
  • the rupture time is 1.0 ⁇ 10 3 hours. That is all.
  • the average particle size of the austenite crystal grains is 130 ⁇ m or less, the average amount of intrusion C can be further suppressed, and more excellent carburization resistance can be obtained.
  • the average infiltration C amount (% by mass) obtained by subtracting the C content (% by mass) of the surface layer of the austenitic alloy before the high-temperature carburizing test from the C content (% by mass) of the surface layer of the austenitic alloy is 0. 0.22% or less, preferably 0.21% or less.
  • a preferred lower limit of the average grain size of the austenite crystal grains is 65 ⁇ m, more preferably 70 ⁇ m, and further preferably 73 ⁇ m.
  • the preferred upper limit of the average grain size of the austenite crystal grains is 125 ⁇ m, more preferably 120 ⁇ m, further preferably 115 ⁇ m, and further preferably 110 ⁇ m.
  • the average particle size of austenite crystal grains is measured by the following method.
  • a test specimen is collected from the austenitic alloy.
  • the austenitic alloy is a tube
  • a test piece is taken from the center of the wall thickness.
  • the austenitic alloy is a plate
  • a test piece is taken from the center of the width and from the center of the plate thickness.
  • the austenitic alloy is a rod
  • a test piece is taken from a center position in a cross section perpendicular to the longitudinal direction.
  • the size of the test piece is not particularly limited.
  • the size of the test piece is, for example, 15 mm in the longitudinal direction L (rolling direction), 5 mm in the thickness direction t (thickness direction in a tube, thickness direction in a plate, radial direction in a bar), and in the thickness direction and the longitudinal direction. It is 20 mm in a vertical direction (hereinafter, referred to as a width direction W, which corresponds to a circumferential direction in a pipe, a width direction in a plate, and a direction perpendicular to a radial direction in a rod).
  • Creep strength is measured by the following method.
  • a round bar test piece is collected from the austenitic alloy.
  • the austenitic alloy is a tube
  • a round bar specimen is collected from the center of the wall thickness.
  • the austenitic alloy is a plate
  • a round bar test piece is collected from the center position in the width and from the center position in the plate thickness.
  • the austenitic alloy is a rod
  • a round bar test piece is collected from a center position in a cross section perpendicular to the longitudinal direction.
  • the diameter of the parallel portion of the round bar test piece is 6 mm
  • the length of the parallel portion is 30 mm.
  • the parallel portion is parallel to the longitudinal direction (rolling direction) of the austenitic alloy.
  • a creep rupture test according to JIS Z2271 (2010) is performed using the manufactured round bar test piece.
  • the creep rupture test is performed by applying a tensile load (test stress) of 15 MPa to a round bar test piece in an air atmosphere at 1000 ° C. to determine a rupture time.
  • the austenitic alloy of the present embodiment has the above-described chemical composition, and F1 satisfies the formula (1). Therefore, both excellent carburization resistance and excellent hot workability can be achieved.
  • the austenite crystal grains of the austenitic alloy of the present embodiment have an average grain size of 60 to 130 ⁇ m. In this case, the austenitic alloy of the present embodiment has excellent creep strength and also shows excellent carburization resistance.
  • the austenitic alloy of the present embodiment will be described.
  • the method for manufacturing an austenitic alloy described below is an example of the austenitic alloy of the present embodiment. Therefore, the austenitic alloy having the above-described configuration may be manufactured by another manufacturing method other than the manufacturing method described below.
  • the manufacturing method described below is a preferable example of the method for manufacturing an austenitic alloy of the present embodiment.
  • the method of manufacturing an austenitic alloy according to the present embodiment includes a preparation step, a hot working step, a cold working step, and a solution treatment step. Hereinafter, each step will be described.
  • a material having the above-described chemical composition is prepared.
  • the material may be supplied from a third party or may be manufactured.
  • the material may be an ingot, a slab, a bloom, or a billet.
  • the material is produced by the following method.
  • a melt (alloy) having the above chemical composition is manufactured.
  • an ingot is produced by an ingot-making method.
  • Slabs, blooms, and billets may be manufactured by a continuous casting method using the manufactured molten metal. Hot working may be performed on the manufactured ingot, slab, and bloom to produce a billet.
  • hot forging may be performed on an ingot to produce a cylindrical billet, and this billet may be used as a material (column material).
  • the temperature of the raw material immediately before the start of hot forging is not particularly limited, but is, for example, 900 to 1300 ° C.
  • the method of cooling the material after hot forging is not particularly limited.
  • the hot working step is performed as needed. That is, the hot working step may not be performed.
  • hot working is performed on the material prepared in the preparing step to produce an intermediate material.
  • the intermediate material may be, for example, a tube, a plate, or a rod.
  • the intermediate material is a pipe
  • the following processing is performed in the hot working process.
  • a column material is prepared.
  • a through hole is formed along the central axis of the cylindrical material by machining.
  • Hot extrusion typified by the Eugene Sejournet method is performed on the columnar material in which the through-holes are formed to produce an intermediate material (pipe).
  • the temperature of the raw material immediately before hot extrusion is not particularly limited.
  • the temperature of the raw material immediately before hot extrusion is, for example, 900 to 1300 ° C.
  • a hot-punched tube may be implemented.
  • piercing and rolling by the Mannesmann method may be performed to produce a tube.
  • a raw material column material
  • a piercing machine to produce a raw tube.
  • the piercing ratio is not particularly limited, but is, for example, 1.0 to 4.0.
  • the raw tube manufactured by piercing rolling is further hot-rolled by a mandrel mill, a reducer, a sizing mill, or the like.
  • the cumulative area reduction rate in the hot working step is not particularly limited, but is, for example, 20 to 80%.
  • the pipe temperature (finish temperature) immediately after the completion of the hot working is preferably 900 ° C. or more.
  • the hot working step uses, for example, one or more rolling mills.
  • the rolling mill includes a pair of work rolls. Hot rolling is performed on a material such as a slab using a rolling mill to produce a plate. The material is heated before hot rolling. Hot rolling is performed on the heated material.
  • the temperature of the raw material immediately before hot rolling is, for example, 900 to 1300 ° C.
  • the plate temperature (finish temperature) immediately after the completion of the hot working is preferably 900 ° C. or more.
  • the hot working step includes, for example, a rough rolling step and a finish rolling step.
  • the material is hot-worked to produce a billet.
  • a slab rolling mill is used. The material is subjected to slab rolling by a sizing mill to produce a billet.
  • a continuous rolling mill is installed downstream of the bulk rolling mill, the billet after the bulk rolling is further subjected to hot rolling using a continuous rolling mill to produce a smaller billet. You may.
  • a continuous rolling mill for example, a horizontal stand having a pair of horizontal rolls and a vertical stand having a pair of vertical rolls are alternately arranged in a line.
  • a material such as bloom is manufactured into a billet.
  • the raw material temperature immediately before the rough rolling step is not particularly limited, but is, for example, 900 to 1300 ° C.
  • the finish rolling step the billet is first heated.
  • the billet after heating is subjected to hot rolling using a continuous rolling mill to produce a bar.
  • the heating temperature in the heating furnace in the finish rolling step is not particularly limited, but is, for example, 900 to 1300 ° C.
  • the temperature (finish temperature) of the bar immediately after the completion of hot working is preferably 900 ° C. or more.
  • the cold working step is performed as needed. That is, the cold working step need not be performed.
  • cold working is performed.
  • the intermediate material is a tube or a rod
  • the cold working is, for example, cold drawing.
  • the intermediate material is a plate
  • the cold working is, for example, cold rolling.
  • strain is imparted to the intermediate material before the solution treatment step. Thereby, at the time of the solution treatment step of the next step, recrystallization can be exhibited and the grain size can be adjusted.
  • the area reduction rate in the cold working step is not particularly limited, but is, for example, 10 to 90%.
  • the solution treatment step is an essential step.
  • a solution treatment is performed on the raw material prepared in the preparation step, the intermediate material after the hot working step, or the intermediate material after the cold working step.
  • precipitates in the raw material or the intermediate material are dissolved. Further, recrystallization is caused to change the metal structure to a sized structure.
  • the solution treatment is performed by the following method.
  • a raw material or an intermediate material is charged into a heat treatment furnace in which the furnace atmosphere is an air atmosphere.
  • the air atmosphere here means, for example, an atmosphere containing 78% or more by volume of nitrogen, which is a gas constituting the atmosphere, and 20% or more by volume of oxygen.
  • the raw material or the intermediate material is heated to a solution treatment temperature in a furnace in an air atmosphere, and the raw material or the intermediate material is held at the solution treatment temperature.
  • the holding time is, for example, 1 to 60 minutes.
  • the material or intermediate material after holding is rapidly cooled.
  • the quenching method may be water cooling or oil cooling.
  • the preferred solution treatment temperature is 1230 to 1300 ° C. If the solution treatment temperature is 1230 ° C. or higher, the average grain size of austenite crystal grains of the austenitic alloy becomes 60 ⁇ m or more. If the solution treatment temperature is 1300 ° C. or less, the average grain size of austenite crystal grains of the austenitic alloy becomes 130 ⁇ m or less.
  • the preferred lower limit of the solution treatment temperature is 1235 ° C, more preferably 1240 ° C.
  • the preferable upper limit of the solution treatment temperature is 1295 ° C, more preferably 1290 ° C, and further preferably 1285 ° C.
  • a scale removing step of removing scale formed on the surface may be performed on the material or intermediate material after the solution treatment.
  • the scale removing step is performed by, for example, pickling and / or shot processing.
  • the pickling conditions are not particularly limited.
  • pickling for example, a mixed acid solution of nitric acid and hydrochloric acid is used.
  • the pickling time is, for example, 30 minutes to 60 minutes.
  • the shot processing can further impart distortion to the alloy surface.
  • Shot processing conditions material, shape, and processing conditions of shot grains
  • the austenitic alloy of the present embodiment can be manufactured.
  • the above-described manufacturing method is an example of the method for manufacturing the austenitic alloy of the present embodiment. Therefore, the manufacturing method of the austenitic alloy of the present embodiment is not limited to the above-described manufacturing method.
  • the austenitic alloy of the present embodiment is not particularly limited to the above-described manufacturing method as long as it has the above-described chemical composition and F1 satisfies the formula (1).
  • the effects of the austenitic alloy of this embodiment will be described more specifically by way of examples.
  • the conditions in the following examples are one example of conditions adopted to confirm the feasibility and effects of the austenitic alloy of the present embodiment. Therefore, the austenitic alloy of the present embodiment is not limited to this one condition example.
  • the “REM” column is the total sum (% by mass) of the detection amounts of the La content, the Ce content, and the Nd content. Blank columns in the chemical composition column in Table 1 mean that the corresponding element content was below the detection limit.
  • a columnar ingot was manufactured using the above molten metal. Hot forging was performed on the ingot to produce a billet. The manufactured billet was allowed to cool to room temperature. The heating temperature of the ingot was 1220 ° C.
  • the solution treatment temperature was the temperature shown in the column of “solution treatment temperature (° C.)” in Table 2.
  • the retention time at the solution treatment temperature was 10 minutes for all test numbers.
  • the intermediate material after the elapse of the holding time was rapidly cooled. Specifically, the intermediate material after the elapse of the holding time was water-cooled.
  • Test pieces were collected from the center of the sheet width and the center of the sheet thickness of the austenitic alloy of each test number.
  • the size of the test piece was 8 mm in the thickness direction t, 20 mm in the width direction W, and 30 mm in the rolling direction (longitudinal direction) L.
  • # 600 emery wet abrasive paper the surface of the collected test piece was polished and finished. The polished test piece was immersed in acetone to perform ultrasonic degreasing.
  • a high-temperature carburizing test was performed on the degreased test piece. Specifically, a high-temperature carburizing gas atmosphere containing 67% by volume of H 2 gas, 30% by volume of CH 4 gas, and 3% by volume of CO 2 gas was tested in a heat treatment furnace at 1100 ° C. A piece was charged. The test piece was kept at 1100 ° C. for 96 hours in a heat treatment furnace. Thereafter, the furnace temperature of the heat treatment furnace was lowered to room temperature. After the furnace temperature was lowered to room temperature, the test piece was extracted from the heat treatment furnace. The oxide film on the test piece after the above-described high-temperature carburizing test was subjected to dry polishing using # 600 abrasive paper to remove the oxide film.
  • the difference between the C content in each layer after the high-temperature carburizing test and the C content of the base material was defined as the intrusion C amount of each layer.
  • the arithmetic average value of the obtained four intrusion C amounts was defined as the average intrusion C amount (% by mass).
  • the obtained average penetration C amount is shown in "Average penetration C amount (% by mass)" in Table 2.
  • a tensile test was performed at 900 ° C. at a strain rate of 10 / sec in accordance with JIS G 0567 (2012).
  • the original cross-sectional area of the parallel portion of the tensile test piece before the tensile test was defined as S o (mm 2 ).
  • the minimum cross-sectional area of the tensile test piece after breaking was defined as S u (mm 2 ).
  • the average grain size of the austenite crystal grains of the austenitic alloy of each test number was measured by the following method. Test pieces were collected from the austenitic alloys of each test number. Specifically, test pieces were collected from the center of the plate width and the center of the plate thickness of the austenitic alloy (plate) of each test number. The size of the test piece was 15 mm in the longitudinal direction L (rolling direction), 5 mm in the sheet thickness direction t, and 20 mm in the sheet width direction W.
  • the collected test piece was embedded in a resin for microstructure observation. Then, of the surfaces of the test pieces, a surface including the thickness direction t and the width direction W was defined as an observation surface. Buffing was performed on the observation surface of the test piece embedded with the resin. The observation surface after the buff polishing was etched using a mixed acid of hydrochloric acid and nitric acid to reveal a microstructure. The average grain size ( ⁇ m) of austenite crystal grains was determined for the observation surface after etching according to JIS G 0551 (2013). The obtained average particle size is shown in the column of “Average particle size ( ⁇ m)” in Table 2.
  • the creep strength of the austenitic alloy of each test number was determined by the following method.
  • a round bar test piece was collected from the austenitic alloy. Specifically, a round bar test piece was collected from the center of the sheet width and the center of the sheet thickness of the austenitic alloy (sheet) of each test number.
  • the diameter of the parallel part of the round bar test piece was 6 mm, and the length of the parallel part was 30 mm.
  • the parallel part was parallel to the longitudinal direction (rolling direction) of the austenitic alloy.
  • a creep rupture test based on JIS Z2271 (2010) was performed using the produced round bar test piece. The creep rupture test was performed by applying a tensile load (test stress) of 15 MPa to a round bar test piece in an air atmosphere at 1000 ° C., and the rupture time was determined.
  • Test Nos. 1 to 6 8 to 20 and 34 further had a solution treatment temperature in the range of 1230 to 1300 ° C. Therefore, in Test Nos. 1 to 6, 8 to 20, and 34, the austenite crystal grains were 60 to 130 ⁇ m. Therefore, the breaking time in the creep rupture test at 1000 ° C. was 1.0 ⁇ 10 3 hours or more, and a high creep strength was obtained. Furthermore, the average penetration C amount was 0.22% or less in each case.
  • test number 24 the Ni content was too high. As a result, the drawing at 900 ° C. was less than 60%, and the hot workability was low.
  • Test Nos. 31, 32 and 35 although the content of each element was appropriate, the F1 value was less than the lower limit of the formula (1). As a result, the average penetration C amount of Test No. 31 was 0.28%, the average penetration C amount of Test No. 32 was 0.41%, and the average penetration C amount of Test No. 35 was 0.32%. , All had low carburization resistance.

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Abstract

L'invention concerne un alliage austénitique ayant une excellente résistance à la carburation et une excellente aptitude au façonnage à chaud. L'alliage austénitique contient, en % en masse, de 0,030 à moins de 0,250 % de C, de 0,01 à 2,00 % de Si, 2,00 % ou moins de Mn, 0,040 % ou moins de P, 0,010 % ou moins de S, de 10,00 à moins de 25,00 % de Cr, de 30,00 à 60,00 % de Ni, de plus de 2,50 % à 3,50 % d'Al, et de 0,20 à 3,00 % de Nb, et contient également un ou plusieurs constituants choisis parmi un groupe constitué de Zr à hauteur de 0,0001 à 0,1000 %, de Hf à hauteur de 0,0001 à 0,1000 %, de Sn à hauteur de 0,0001 à 0,1000 % et d'As à hauteur de 0,0001 à 0,1000 %, le reste étant du Fe et des impuretés. La composition chimique dudit alliage satisfait à l'expression (1). 0,07 ≤ 1,96 × Zr + Hf +1,50 × Sn + 2,38 × As ≤ 0,50 (1)
PCT/JP2019/038198 2018-09-27 2019-09-27 Alliage austénitique WO2020067444A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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WO2024058278A1 (fr) * 2022-09-16 2024-03-21 日本製鉄株式会社 Matériau en alliage austénitique

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JP2007518879A (ja) * 2003-12-30 2007-07-12 サンドビック インテレクチュアル プロパティー アクティエボラーグ オーステナイト合金製品の製造方法およびその使用
WO2017119415A1 (fr) * 2016-01-05 2017-07-13 新日鐵住金株式会社 Alliage austénitique résistant à la chaleur et procédé pour la fabrication de ce dernier
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WO2005078148A1 (fr) * 2004-02-12 2005-08-25 Sumitomo Metal Industries, Ltd. Tube en métal destiné à être utilisé dans une atmosphère de gaz de cémentation
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WO2023170935A1 (fr) * 2022-03-11 2023-09-14 日本製鉄株式会社 Matériau d'acier inoxydable austénitique
WO2024058278A1 (fr) * 2022-09-16 2024-03-21 日本製鉄株式会社 Matériau en alliage austénitique

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