Ni-based alloy tube

Abstract

Provided is an Ni-based alloy tube with which it is possible to obtain exceptional corrosion resistance. A Ni-based alloy tube according to the present disclosure has a chemical composition containing, by mass, 0.200% or less of C, 3.00% or less of Si, 3.00% or less of Mn, 0.050% or less of P, 0.050% or less of S, 5.00% or less of Cu, 20.00-35.00% of Cr, and 40.00-80.00% of Ni, the chemical composition furthermore containing one or more selected from the group consisting of 0.60-10.00% of Mo and 0.60-2.00% of Al, the balance including Fe and impurities. The half-value width F200(°) of the peak of the {200} plane obtained through concentration X-ray diffraction measurement on the inner surface of the Ni-based alloy tube satisfies relationship (1).　Relationship 1: 30 ≤ (100 + 20Mo + 45Al) × F200 ≤ 130

Description

Ni-based alloy tube

[0001] The present disclosure relates to Ni-based alloy materials, and more particularly to Ni-based alloy pipes.

[0002] Recently, hydrogen has been attracting attention as a clean energy source that does not produce carbon dioxide. Hydrogen is a gas at room temperature and pressure, and when liquefied for transportation, it must be kept at an extremely low temperature of -253°C or below. This makes it difficult to transport hydrogen alone.

[0003] 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 melting point of hydrogen. Therefore, studies are underway to transport ammonia as a hydrogen carrier and desorb hydrogen from the ammonia at the destination to use hydrogen as energy.

[0004] To desorb hydrogen from ammonia, ammonia is decomposed in a high-temperature environment using a catalyst. This process can produce ammonium chloride. Ammonium chloride is acidic and highly corrosive to metal materials typically used in plant components (e.g., reactor tubes and piping). Therefore, plant components used in such corrosive environments must have excellent corrosion resistance.

[0005] As a plant component having excellent corrosion resistance, for example, a Ni-based alloy pipe made of a Ni-based alloy material is known. A technology relating to a Ni-based alloy material that can obtain excellent corrosion resistance is proposed, for example, in JP 2014-001413 A (Patent Document 1).

[0006] The Ni-based alloy material disclosed in Patent Document 1 contains, in mass %, C: 0.03% or less, Si: 0.01 to 0.5%, Mn: 0.01 to 1.0%, P: 0.03% or less, S: 0.003% or less, Cr: 20% or more and less than 30%, Ni: more than 40% and 50% or less, Cu: more than 2.5% and 5.0% or less, Mo: 5.0 to 10%, W: 3 to 10%, Al: 0.005 to 0.5%, N: more than 0.08% and 0.3% or less, and rare earth elements (REM): 0.001 to 0.20%, satisfying formula (1), with the remainder consisting of Fe and impurities. Cu+Cr+6Mo+3W+20N-20REM≧75 (1) Patent Document 1 describes that this Ni-based alloy material has excellent corrosion resistance by satisfying the above-mentioned chemical composition and further satisfying formula (1).

[0007] JP 2014-001413 A

[0008] However, the corrosion resistance of the Ni-based alloy pipe may be improved by a means other than the Ni-based alloy material disclosed in Patent Document 1.

[0009] An object of the present disclosure is to provide a Ni-based alloy pipe that provides excellent corrosion resistance.

[0010] The Ni-based alloy pipe of the present disclosure has a chemical composition, in mass%, of C: 0.200% or less, Si: 3.00% or less, Mn: 3.00% or less, P: 0.050% or less, S: 0.050% or less, Cu: 5.00% or less, Cr: 20.00 to 35.00%, Ni: 40.00 to 80.00%, Co: 0 to 1.00%, W: 0 to 10.00%, N: 0 to 0.20%, V: 0 to 0.50%, Nb: 0 to 5.00%, Ti: 0 to 1.00%, Ca: 0 to 0.0100%, Mg: 0 to 0.0100%, B: 0 to 0.0050%, and REM: 0 to 0.100%, and further containing one or more selected from the group consisting of Mo: 0.60 to 10.00%, and Al: 0.60 to 2.00%, with the balance consisting of Fe and impurities, wherein the half width F of the peak of the {200} plane obtained by focusing X-ray diffraction measurement on the inner surface of the Ni-based alloy tube is ２００(°) satisfies formula (1). 30≦(100+20Mo+45Al)×F ２００ ≦130 (1) Here, the contents of the corresponding elements in mass% are substituted for Mo and Al in formula (1). When the corresponding element is not contained, "0" is substituted for the element symbol.

[0011] The Ni-based alloy pipe of the present disclosure provides excellent corrosion resistance.

[0012] The present inventors first investigated the chemical composition of Ni-based alloy pipes that offer excellent corrosion resistance, and found that the composition is, in mass %, C: 0.200% or less, Si: 3.00% or less, Mn: 3.00% or less, P: 0.050% or less, S: 0.050% or less, Cu: 5.00% or less, Cr: 20.00 to 35.00%, Ni: 40.00 to 80.00%, Co: 0 to 1.00%, W: 0 to 10.00%, N: 0 to 0.20%, V: 0 to 0.50%, Nb: 0 to 5.00%, Ti: The inventors considered that excellent corrosion resistance could be obtained with a Ni-based alloy pipe containing the following elements: 0.0 to 1.00%, Ca: 0 to 0.0100%, Mg: 0 to 0.0100%, B: 0 to 0.0050%, and REM: 0 to 0.100%, and further containing one or more elements selected from the group consisting of Mo: 0.60 to 10.00% and Al: 0.60 to 2.00%, with the balance consisting of Fe and impurities.

[0013] The alloy pipe having the above-mentioned chemical composition has a sufficiently high Cr content. Cr forms a passive film mainly composed of Cr oxides on the surface of the alloy pipe, thereby enhancing the corrosion resistance of the alloy pipe. The alloy pipe having the above-mentioned chemical composition also contains a sufficient amount of at least one of Mo and Al. Mo concentrates at damaged portions of the passive film, enhancing the self-repairing ability of the passive film. Furthermore, Al forms an additional film composed of Al oxides inside the passive film composed of Cr oxides. In this way, the corrosion resistance of the alloy pipe is further enhanced.

[0014] However, even with alloy pipes having the above-mentioned chemical composition, there are cases where excellent corrosion resistance cannot be obtained. Therefore, the present inventors have conducted research into means for further improving the corrosion resistance of alloy pipes having the above-mentioned chemical composition, focusing on dislocations contained in the alloy pipe. As a result, the inventors have obtained the following findings.

[0015] The aforementioned effect of Mo and Al in improving corrosion resistance is realized by the diffusion of Mo and Al, which are dissolved in the alloy pipe, to the surface of the alloy pipe. Dislocations contained in the alloy pipe act as diffusion paths for solute elements such as Mo and Al. Therefore, if the dislocation density is high on the surface of the alloy pipe, particularly near the inner surface (hereinafter also referred to as the "surface layer"), which is likely to be exposed to a corrosive environment, the diffusion of Mo and Al to the inner surface is promoted. As a result, the corrosion resistance-improving effect of Mo and Al can be enhanced without increasing the Mo and Al contents. In other words, increasing the dislocation density in the surface layer of the alloy pipe is effective in improving the corrosion resistance of the alloy pipe.

[0016] On the other hand, if the dislocation density in the surface layer of the alloy pipe becomes excessively high, the strength of the surface layer becomes excessive. In this case, the toughness of the alloy pipe is significantly reduced. In other words, in an alloy pipe having the above-mentioned chemical composition, in order to obtain excellent corrosion resistance while maintaining sufficient toughness, it is necessary to appropriately adjust the dislocation density in the surface layer of the alloy pipe according to the content of Mo or Al.

[0017] The dislocation density in the surface layer of an alloy pipe can be evaluated by quantifying the non-uniform lattice strain, which is an index of dislocation density, using focusing X-ray diffraction measurement. The larger the non-uniform lattice strain in the surface layer, the larger the half-width of the peak of each lattice plane in the diffraction profile obtained by focusing X-ray diffraction measurement of the inner surface. In other words, the dislocation density in the surface layer can be adjusted by adjusting the half-width of the peak obtained by focusing X-ray diffraction measurement.

[0018] Based on the above findings, for Ni-based alloy pipes that can obtain excellent corrosion resistance, the Mo and Al contents and the half-width F of the {200} plane peak obtained by focusing X-ray diffraction measurement on the inner surface were ２００The inventors further investigated the relationship between the half-width F ２００ The present inventors have found that excellent corrosion resistance can be obtained while maintaining sufficient toughness if the Mo content (°) satisfies the following formula (1): 30≦(100+20Mo+45Al)×F ２００ ≦130 (1) Here, the contents of the corresponding elements in mass% are substituted for Mo and Al in formula (1). When the corresponding element is not contained, "0" is substituted for the element symbol.

[0019] The Ni-based alloy pipe of this embodiment was completed based on the above technical concept and has the following configuration. Note that the above mechanism is a presumption. Therefore, the Ni-based alloy pipe of this embodiment may achieve excellent corrosion resistance through a mechanism different from that described above. However, as will be shown in the examples described later, a Ni-based alloy pipe having the following configuration can achieve excellent corrosion resistance.

[0020] The Ni-based alloy pipe of the first configuration has a chemical composition, in mass %, of C: 0.200% or less, Si: 3.00% or less, Mn: 3.00% or less, P: 0.050% or less, S: 0.050% or less, Cu: 5.00% or less, Cr: 20.00 to 35.00%, Ni: 40.00 to 80.00%, Co: 0 to 1.00%, W: 0 to 10.00%, N: 0 to 0.20%, V: 0 to 0.50%, Nb: 0 to 5.00%, Ti: 0 to 1.00%, Ca: 0 to 0.0100%, Mg: 0 to 0.0100%, B: 0 to 0.0050%, and REM: 0 to 0.100%, and further containing one or more selected from the group consisting of Mo: 0.60 to 10.00%, and Al: 0.60 to 2.00%, with the balance consisting of Fe and impurities, wherein the half width F of the peak of the {200} plane obtained by focusing X-ray diffraction measurement on the inner surface of the Ni-based alloy tube is ２００ (°) satisfies formula (1). 30≦(100+20Mo+45Al)×F ２００≦130 (1) Here, the contents of the corresponding elements in mass% are substituted for Mo and Al in formula (1). When the corresponding element is not contained, "0" is substituted for the element symbol.

[0021] The Ni-based alloy pipe of the second configuration is the Ni-based alloy pipe of the first configuration, wherein the chemical composition contains, in mass %, one or more elements selected from the group consisting of Co: 0.01 to 1.00%, W: 0.01 to 10.00%, N: 0.01 to 0.20%, V: 0.01 to 0.50%, Nb: 0.01 to 5.00%, Ti: 0.01 to 1.00%, Ca: 0.0001 to 0.0100%, Mg: 0.0001 to 0.0100%, B: 0.0001 to 0.0050%, and REM: 0.001 to 0.100%.

[0022] The Ni-based alloy pipe according to this embodiment will be described in detail below. Note that "%" for elements means mass % unless otherwise specified.

[0023] [Features of the Ni-based alloy pipe of this embodiment] The Ni-based alloy pipe of this embodiment has the following features: (Feature 1) The chemical composition, in mass %, is: C: 0.200% or less, Si: 3.00% or less, Mn: 3.00% or less, P: 0.050% or less, S: 0.050% or less, Cu: 5.00% or less, Cr: 20.00 to 35.00%, Ni: 40.00 to 80.00%, Co: 0 to 1.00%, W: 0 to 10.00%, N: 0 to 0.20%, V: 0 to 0.50%, N b: 0-5.00%, Ti: 0-1.00%, Ca: 0-0.0100%, Mg: 0-0.0100%, B: 0-0.0050%, and REM: 0-0.100%, and further contains one or more elements selected from the group consisting of Mo: 0.60-10.00% and Al: 0.60-2.00%, with the balance consisting of Fe and impurities. (Feature 2) The half width F of the peak of the {200} plane obtained by focusing X-ray diffraction measurement on the inner surface of the Ni-based alloy tube is ２００ (°) satisfies formula (1). 30≦(100+20Mo+45Al)×F ２００≦130 (1) Here, the contents of the corresponding elements in mass% are substituted for Mo and Al in formula (1). When the corresponding element is not contained, "0" is substituted for the element symbol. Each feature will be described below.

[0024] [(Feature 1) Chemical Composition] The chemical composition of the Ni-based alloy pipe of this embodiment contains the following elements.

[0025] C: 0.200% or less Carbon (C) deoxidizes the alloy used to make the alloy pipe. C also increases the strength of the alloy pipe. Even if even a small amount of C is contained, the above effect can be achieved to some extent. Therefore, the C content is greater than 0%. On the other hand, if the C content exceeds 0.200%, excessive carbides are formed at grain boundaries. Therefore, even if the contents of other elements are within the ranges of this embodiment, the toughness of the alloy pipe decreases. Therefore, the C content is 0.200% or less. The preferred lower limit of the C content is 0.001%, more preferably 0.005%, even more preferably 0.010%, even more preferably 0.020%, and even more preferably 0.030%. The preferred upper limit of the C content is 0.180%, even more preferably 0.160%, even more preferably 0.150%, even more preferably 0.130%, and even more preferably 0.100%.

[0026] Si: 3.00% or less Silicon (Si) deoxidizes the alloy used to make the alloy pipe. Even if even a small amount of Si is contained, the above effect can be obtained to some extent. Therefore, the Si content is greater than 0%. On the other hand, if the Si content exceeds 3.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Si content is 3.00% or less. The preferred lower limit of the Si content is 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.20%, and even more preferably 0.30%. The preferred upper limit of the Si content is 2.80%, even more preferably 2.60%, and even more preferably 2.40%.

[0027] Mn: 3.00% or less Manganese (Mn) deoxidizes the alloy used to make the alloy pipe. Even if even a small amount of Mn is contained, the above effect can be obtained to some extent. Therefore, the Mn content is greater than 0%. On the other hand, if the Mn content exceeds 3.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Mn content is 3.00% or less. The preferred lower limit of the Mn content is 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.20%, and even more preferably 0.30%. The preferred upper limit of the Mn content is 2.80%, even more preferably 2.60%, and even more preferably 2.40%.

[0028] P: 0.050% or less Phosphorus (P) is an impurity. That is, the lower limit of the P content is greater than 0%. If the P content exceeds 0.050%, P segregates excessively at grain boundaries, reducing grain boundary strength. Therefore, even if the contents of other elements are within the ranges of this embodiment, the toughness of the alloy pipe decreases. Therefore, the P content is 0.050% or less. The lower the P content, the more preferable it is. However, excessive reduction of the P content increases manufacturing costs. Therefore, considering normal industrial production, the lower limit of the P content is preferably 0.001%, more preferably 0.005%, and even more preferably 0.010%. The upper limit of the P content is preferably 0.040%, more preferably 0.030%, and even more preferably 0.020%.

[0029] S: 0.050% or less Sulfur (S) is an impurity. That is, the lower limit of the S content is greater than 0%. If the S content exceeds 0.050%, S segregates excessively at grain boundaries, reducing grain boundary strength. Therefore, even if the contents of other elements are within the ranges of this embodiment, the toughness of the alloy pipe decreases. Therefore, the S content is 0.050% or less. The lower the S content, the more preferable it is. However, excessive reduction of the S content increases manufacturing costs. Therefore, considering normal industrial production, the lower limit of the S content is preferably 0.001%, more preferably 0.005%, and even more preferably 0.010%. The upper limit of the S content is preferably 0.040%, more preferably 0.030%, and even more preferably 0.020%.

[0030] Cu: 5.00% or less Copper (Cu) improves the corrosion resistance of alloy pipes. Cu also increases the strength of alloy pipes. Even if even a small amount of Cu is contained, the above effects can be obtained to some extent. Therefore, the Cu content is greater than 0%. On the other hand, if the Cu content exceeds 5.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Cu content is 5.00% or less. The preferred lower limit of the Cu content is 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.20%, and even more preferably 0.30%. The preferred upper limit of the Cu content is 4.50%, even more preferably 4.00%, and even more preferably 3.00%.

[0031] Cr: 20.00 to 35.00% Chromium (Cr) forms a passive film, primarily composed of Cr oxides, on the surface of the alloy pipe, enhancing the corrosion resistance of the alloy pipe. If the Cr content is less than 20.00%, the above effect cannot be fully achieved, even if the contents of other elements are within the ranges of this embodiment. On the other hand, if the Cr content exceeds 35.00%, even if the contents of other elements are within the ranges of this embodiment, intermetallic compounds, such as the σ phase, are more likely to form, thereby reducing the corrosion resistance of the alloy pipe. This further reduces the toughness of the alloy pipe. Therefore, the Cr content is 20.00 to 35.00%. The preferred lower limit of the Cr content is 21.00%, more preferably 23.00%, and even more preferably 25.00%. The preferred upper limit of the Cr content is 34.00%, more preferably 33.00%, and even more preferably 32.00%.

[0032] Ni: 40.00 to 80.00% Nickel (Ni) is an austenite-forming element and stabilizes austenite in the alloy pipe. Ni also enhances the corrosion resistance of the alloy pipe. If the Ni content is less than 40.00%, the above effects cannot be sufficiently achieved even if the contents of other elements are within the ranges of this embodiment. On the other hand, if the Ni content exceeds 80.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Ni content is 40.00 to 80.00%. The preferred lower limit of the Fe content is 41.00%, more preferably 42.00%, even more preferably 45.00%, and even more preferably 50.00%. The preferred upper limit of the Fe content is 78.00%, even more preferably 75.00%, and even more preferably 70.00%.

[0033] The chemical composition of the alloy pipe of this embodiment further contains one or more elements selected from the group consisting of Mo: 0.60 to 10.00% and Al: 0.60 to 2.00%.

[0034] Mo: 0.60 to 10.00% Molybdenum (Mo) enhances the self-repairing ability of the passive film and improves the corrosion resistance of the alloy pipe. If the Mo content is less than 0.60%, the above effect cannot be sufficiently obtained even if the contents of other elements are within the ranges of this embodiment. On the other hand, if the Mo content exceeds 10.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Mo content is 0.60 to 10.00%. The preferred lower limit of the Mo content is 0.80%, more preferably 1.00%, even more preferably 1.50%, and even more preferably 2.00%. The preferred upper limit of the Mo content is 9.00%, even more preferably 8.80%, even more preferably 8.00%, and even more preferably 7.00%.

[0035] Al: 0.60 to 2.00% Aluminum (Al) forms a passive film, primarily composed of Al oxides, on the surface of the alloy pipe, improving the corrosion resistance of the alloy pipe. If the Al content is less than 0.60%, the above effect cannot be fully achieved, even if the contents of other elements are within the ranges of this embodiment. On the other hand, if the Al content exceeds 2.00%, coarse inclusions form in the alloy pipe. As a result, the toughness of the alloy pipe decreases, even if the contents of other elements are within the ranges of this embodiment. Therefore, the Al content is 0.60 to 2.00%. The preferred lower limit of the Al content is 0.65%, more preferably 0.70%, even more preferably 0.80%, and even more preferably 1.00%. The preferred upper limit of the Al content is 1.90%, even more preferably 1.80%, even more preferably 1.70%, and even more preferably 1.50%.

[0036] The balance of the chemical composition of the alloy pipe of this embodiment is Fe and impurities. The Fe content is, for example, 2.00 to 20.00%. The impurities in the chemical composition refer to substances that are mixed in from raw materials or the manufacturing environment during industrial manufacturing of the alloy pipe, and are acceptable within a range that does not adversely affect the alloy pipe of this embodiment.

[0037] [Optional Elements] The chemical composition of the alloy pipe of this embodiment may further contain, in place of a portion of Fe, one or more elements selected from the group consisting of Co: 0-1.00%, W: 0-10.00%, N: 0-0.20%, V: 0-0.50%, Nb: 0-5.00%, Ti: 0-1.00%, Ca: 0-0.0100%, Mg: 0-0.0100%, B: 0-0.0050%, and REM: 0-0.100%. All of these elements are optional elements and may not be included. These optional elements will be described below.

[0038] [First Group: Co, W, N, V, Nb, and Ti] The chemical composition of the alloy tube of this embodiment may further contain elements from the first group described above in place of a portion of Fe. All of these elements increase the strength of the alloy tube. Each element in the first group will be described below.

[0039] Cobalt (Co) is an optional element and does not necessarily need to be contained. That is, the Co content may be 0%. When Co is contained, that is, when Co exceeds 0%, Co dissolves in the alloy pipe and increases the strength of the alloy pipe. Even if even a small amount of Co is contained, the above effect can be obtained to some extent. On the other hand, if the Co content exceeds 1.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Co content is 0 to 1.00%. The preferred lower limit of the Co content is 0.01%, more preferably 0.10%, and even more preferably 0.20%. The preferred upper limit of the Co content is 0.80%, more preferably 0.60%, and even more preferably 0.40%.

[0040] W: 0 to 10.00% Tungsten (W) is an optional element and does not necessarily need to be included. In other words, the W content may be 0%. When W is included, that is, when the W content exceeds 0%, W dissolves in the alloy pipe and increases the strength of the alloy pipe. Even if even a small amount of W is included, the above effect can be achieved to some extent. On the other hand, if the W content exceeds 10.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the W content is 0 to 10.00%. The preferred lower limit of the W content is 0.01%, more preferably 0.50%, even more preferably 1.00%, even more preferably 2.00%, even more preferably 3.00%, and even more preferably 4.00%. The preferred upper limit of the W content is 8.00%, even more preferably 7.00%, even more preferably 6.80%, even more preferably 6.00%, and even more preferably 5.00%.

[0041] N: 0 to 0.20% Nitrogen (N) is an optional element and does not necessarily need to be contained. In other words, the N content may be 0%. When N is contained, that is, when the N content exceeds 0%, N dissolves in the alloy pipe, increasing the strength of the alloy pipe. Even if even a small amount of N is contained, the above effect can be achieved to some extent. On the other hand, when the N content exceeds 0.20%, coarse nitrides are formed in the alloy pipe. Therefore, even if the contents of other elements are within the ranges of this embodiment, the toughness of the alloy pipe decreases. Therefore, the N content is 0 to 0.20%. The preferred lower limit of the N content is 0.01%, more preferably 0.03%, and even more preferably 0.05%. The preferred upper limit of the N content is 0.19%, more preferably 0.17%, and even more preferably 0.15%.

[0042] V: 0 to 0.50% Vanadium (V) is an optional element and does not necessarily need to be contained. That is, the V content may be 0%. When vanadium (V) is contained, that is, when the V content exceeds 0%, V forms precipitates and increases the strength of the alloy pipe. Even if even a small amount of V is contained, the above effect can be obtained to some extent. On the other hand, when the V content exceeds 0.50%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the V content is 0 to 0.50%. The preferred lower limit of the V content is 0.01%, more preferably 0.03%, even more preferably 0.05%, and even more preferably 0.10%. The preferred upper limit of the V content is 0.40%, even more preferably 0.30%, and even more preferably 0.20%.

[0043] Nb: 0 to 5.00% Niobium (Nb) is an optional element and does not necessarily need to be contained. That is, the Nb content may be 0%. When Nb is contained, that is, when the Nb content exceeds 0%, Nb forms precipitates and increases the strength of the alloy pipe. Even if even a small amount of Nb is contained, the above effect can be obtained to some extent. On the other hand, when the Nb content exceeds 5.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Nb content is 0 to 5.00%. The preferred lower limit of the Nb content is 0.01%, more preferably 0.03%, even more preferably 0.05%, even more preferably 0.10%, even more preferably 0.50%, and even more preferably 1.00%. The preferred upper limit of the Nb content is 4.50%, even more preferably 4.00%, even more preferably 3.00%, and even more preferably 2.60%.

[0044] Ti: 0 to 1.00% Titanium (Ti) is an optional element and does not necessarily need to be contained. In other words, the Ti content may be 0%. When titanium is contained, that is, when the Ti content exceeds 0%, Ti forms precipitates and increases the strength of the alloy pipe. Even if even a small amount of Ti is contained, the above effect can be achieved to some extent. On the other hand, if the Ti content exceeds 1.00%, the toughness of the alloy pipe decreases even if the contents of other elements are within the ranges of this embodiment. Therefore, the Ti content is 0 to 1.00%. The preferred lower limit of the Ti content is 0.01%, more preferably 0.03%, and even more preferably 0.05%. The preferred upper limit of the Ti content is 0.80%, more preferably 0.60%, even more preferably 0.50%, even more preferably 0.40%, and even more preferably 0.30%.

[0045] [Second Group: Ca, Mg, B, and REM] The chemical composition of the alloy pipe of this embodiment may further contain elements of the second group described above in place of a portion of Fe. All of these elements increase the toughness of the alloy pipe. Each element of the second group will be described below.

[0046] Ca: 0 to 0.0100% Calcium (Ca) is an optional element and does not necessarily need to be contained. In other words, the Ca content may be 0%. When contained, that is, when the Ca content exceeds 0%, Ca neutralizes the S in the alloy pipe by fixing it as sulfide, thereby increasing the toughness of the alloy pipe. Even if even a small amount of Ca is contained, the above effect can be achieved to some extent. On the other hand, when the Ca content exceeds 0.0100%, coarse oxides are formed in the alloy pipe. Therefore, even if the contents of other elements are within the ranges of this embodiment, the toughness of the alloy pipe will actually decrease. Therefore, the Ca content is 0 to 0.0100%. The preferred lower limit of the Ca content is 0.0001%, more preferably 0.0010%, and even more preferably 0.0020%. The upper limit of the Ca content is preferably 0.0090%, more preferably 0.0070%, further preferably 0.0060%, and still further preferably 0.0050%.

[0047] Mg: 0 to 0.0100% Magnesium (Mg) is an optional element and does not necessarily need to be contained. In other words, the Mg content may be 0%. When magnesium is contained, that is, when the Mg content exceeds 0%, Mg neutralizes the S in the alloy pipe by fixing it as sulfide, thereby increasing the toughness of the alloy pipe. Even if even a small amount of Mg is contained, the above effect can be achieved to some extent. On the other hand, when the Mg content exceeds 0.0100%, coarse oxides are formed in the alloy pipe. Therefore, even if the contents of other elements are within the ranges of this embodiment, the toughness of the alloy pipe decreases. Therefore, the Mg content is 0 to 0.0100%. The preferred lower limit of the Mg content is 0.0001%, more preferably 0.0010%, and even more preferably 0.0020%. The upper limit of the Mg content is preferably 0.0090%, more preferably 0.0070%, even more preferably 0.0065%, and still more preferably 0.0050%.

[0048] B: 0 to 0.0050% Boron (B) is an optional element and does not necessarily need to be contained. In other words, the B content may be 0%. When contained, that is, when the B content exceeds 0%, B segregates at grain boundaries, strengthening the grain boundaries and thereby increasing the toughness of the alloy pipe. Even if even a small amount of B is contained, the above effect can be achieved to some extent. On the other hand, when the B content exceeds 0.0050%, coarse oxides are formed in the alloy pipe. Therefore, even if the contents of other elements are within the ranges of this embodiment, the toughness of the alloy pipe decreases. Therefore, the B content is 0 to 0.0050%. The preferred lower limit of the B content is 0.0001%, more preferably 0.0003%, even more preferably 0.0005%, and even more preferably 0.0010%. The preferred upper limit of the B content is 0.0045%, even more preferably 0.0040%, even more preferably 0.0030%, and even more preferably 0.0020%.

[0049] REM: 0 to 0.100% Rare earth elements (REM) are optional elements and do not necessarily need to be present. In other words, the REM content may be 0%. When present, that is, when the REM content exceeds 0%, the REM neutralizes the S in the alloy pipe by fixing it as sulfides, thereby increasing the toughness of the alloy pipe. Even if even a small amount of REM is present, the above effect can be achieved to some extent. On the other hand, when the REM content exceeds 0.100%, coarse oxides are formed in the alloy pipe. Therefore, even if the contents of other elements are within the ranges of this embodiment, the toughness of the alloy pipe will actually decrease. Therefore, the REM content is 0 to 0.100%. The preferred lower limit of the REM content is 0.001%, more preferably 0.010%, and even more preferably 0.020%. The upper limit of the REM content is preferably 0.090%, more preferably 0.070%, even more preferably 0.060%, even more preferably 0.055%, and still more preferably 0.050%.

[0050] In this specification, REM refers to one or more elements selected from the group consisting of scandium (Sc) with atomic number 21, yttrium (Y) with atomic number 39, and lanthanoids lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71. In addition, the REM content in this specification refers to the total content of these elements.

[0051] [(Feature 2) Regarding Formula (1)] In the Ni-based alloy pipe of this embodiment, the half-width F of the peak of the {200} plane obtained by focusing X-ray diffraction measurement on the inner surface of the Ni-based alloy pipe is further ２００ (°) satisfies formula (1). 30≦(100+20Mo+45Al)×F ２００ ≦130 (1) Here, the contents of the corresponding elements in mass% are substituted for Mo and Al in formula (1). When the corresponding element is not contained, "0" is substituted for the element symbol. Formula (1) will be explained below.

[0052] F1 is defined as follows: F1 = (100 + 20Mo + 45Al) x F ２００As described above, Mo and Al contained in the alloy pipe enhance the corrosion resistance of the alloy pipe. In addition, the higher the dislocation density in the surface layer of the alloy pipe, the more Mo and Al are diffused to the inner surface of the alloy pipe, and therefore the corrosion resistance is improved. The dislocation density in the surface layer of the alloy pipe can be determined by the half-width F of the {200} plane peak obtained by focusing X-ray diffraction measurement on the inner surface of the alloy pipe. ２００ (°) can be used as an index. ２００ The larger F1 is, the higher the dislocation density in the surface layer. In other words, the higher F1 is, the more the corrosion resistance of the alloy pipe is improved due to the synergistic effect of the dislocation density, Mo, and Al.

[0053] On the other hand, if the contents of Mo and Al are too high, the alloy pipe is excessively strengthened, resulting in a decrease in the toughness of the alloy pipe. Furthermore, if the dislocation density in the surface layer of the alloy pipe is too high, the strength of the surface layer becomes excessive, resulting in a decrease in the toughness of the alloy pipe. In other words, in order to ensure sufficient toughness in the alloy pipe, it is necessary to appropriately adjust F1 so that it does not become too high.

[0054] If F1 is less than 30, the dislocation density is not sufficient relative to the Mo and Al contents in the surface layer. Therefore, the diffusion of Mo and Al to the inner surface of the alloy pipe is suppressed, and the effect of Mo and Al in improving corrosion resistance is not sufficiently obtained. As a result, even if the alloy pipe satisfies Feature 1, excellent corrosion resistance cannot be obtained.

[0055] If F1 exceeds 130, the dislocation density is excessively high relative to the Mo and Al contents, resulting in an alloy pipe with excessive strength. As a result, even if an alloy pipe satisfies Feature 1, sufficient toughness cannot be obtained.

[0056] If F1 is 30 to 130, the diffusion of Mo and Al into the inner surface of the alloy pipe can be sufficiently promoted while preventing the strength of the alloy pipe from becoming excessively high. As a result, provided that the alloy pipe satisfies Feature 1, it is possible to obtain excellent corrosion resistance while maintaining sufficient toughness. Therefore, F1 satisfies Formula (1).

[0057] The lower limit of F1 is preferably 32, more preferably 35, even more preferably 38, and even more preferably 40. The upper limit of F1 is preferably 128, more preferably 125, and even more preferably 120. F1 is an integer value obtained by rounding off to one decimal place.

[0058] [Frequency width F ２００ Measurement method of the half-value width F of the {200} plane peak ２００ The angle (°) is determined by the following method. Three test pieces are taken, each having the inner surface of the alloy pipe as the observation surface. The size of the test piece is not particularly limited. X-ray diffraction measurement is performed on the observation surface of the test piece using an X-ray diffractometer to obtain a diffraction profile. The incident direction of the X-rays is parallel to a plane containing the longitudinal and radial directions of the alloy pipe. The radiation source of the X-ray diffractometer is Cu-Kα. The acceleration voltage in the X-ray diffraction measurement is 40 kV, the acceleration current is 40 mA, the divergence slit is 1 / 2°, the scan speed is 0.2° / min, and the sampling width is 0.02°. The measurement method is the focusing method. The peak of the {200} plane is identified from the obtained diffraction profile, and its half-width is determined. The arithmetic average value of the half-width of the peak of the {200} plane determined for the three test pieces is defined as the half-width F of the peak of the {200} plane. ２００ (°). The half-width F ２００ is a value rounded off to three decimal places.

[0059] [Effects of the Ni-based alloy pipe of this embodiment] As described above, the Ni-based alloy pipe of this embodiment satisfies Features 1 and 2. Therefore, the Ni-based alloy pipe of this embodiment can obtain excellent corrosion resistance.

[0060] [Microstructure of Ni-based alloy pipe of this embodiment] The microstructure of the Ni-based alloy pipe of this embodiment is made of austenite, excluding precipitates and inclusions.

[0061] [Shape of Ni-based alloy pipe of this embodiment] The shape of the Ni-based alloy pipe of this embodiment is not particularly limited as long as it is tubular. The Ni-based alloy pipe of this embodiment is, for example, a seamless alloy pipe.

[0062] [Uses of the Ni-base alloy tube of this embodiment] The Ni-base alloy tube of this embodiment is widely applicable to applications requiring excellent corrosion resistance. Therefore, it is suitable for reaction tubes and piping in ammonia decomposition plants for the purpose of hydrogen extraction, where highly corrosive ammonium chloride may be generated. However, the Ni-base alloy tube of this embodiment can also be applied to applications other than the above-mentioned applications.

[0063] [Method for manufacturing a Ni-base alloy pipe according to this embodiment] An example of a method for manufacturing a Ni-base alloy pipe according to this embodiment will be described. The method for manufacturing a Ni-base alloy pipe described below is one example for manufacturing a Ni-base alloy pipe according to this embodiment. Therefore, a Ni-base alloy pipe having the above-described configuration may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferred example of a method for manufacturing a Ni-base alloy pipe according to this embodiment. In this embodiment, a method for manufacturing a seamless pipe will be described as an example of a Ni-base alloy pipe.

[0064] An example of a method for manufacturing a Ni-based alloy pipe according to this embodiment includes the following steps: (Step 1) Material preparation step (Step 2) Hot working step (Step 3) Cold drawing step (Step 4) Solution treatment step Each step will be described below.

[0065] [(Step 1) Material Preparation Step] In the material preparation step, a material for the Ni-based alloy pipe of this embodiment is prepared. Specifically, an alloy having a chemical composition that satisfies Feature 1 is produced. The refining method is not particularly limited, and any known method may be used.

[0066] The refined alloy is used to produce a cylindrical material by a well-known casting method. For example, a cylindrical ingot is produced by an ingot casting method. Alternatively, a billet may be produced by a continuous casting method. The produced ingot may be subjected to hot working to produce a billet. The hot working may be hot rolling or hot forging. The heating temperature of the material during hot working in the material preparation step is not particularly limited, but is, for example, 1000 to 1300°C.

[0067] [(Step 2) Hot Working Step] In the hot working step, the produced material (cylindrical ingot or billet) is subjected to hot extrusion to produce an intermediate alloy pipe. Specifically, the produced material is first machined to form a through hole (guide hole) along the central axis of the material. The material with the through hole formed is heated. The heating temperature is not particularly limited and is, for example, 900 to 1300°C. The heated material is subjected to hot piercing using a plug to expand the inner diameter of the through hole in the material. The material after hot piercing may be subjected to hot piercing again. In this way, a hollow material having a through hole with a predetermined inner diameter is prepared.

[0068] Next, the produced hollow material is heated and subjected to hot extrusion, typically the Ugine-Séjournet process. Hot extrusion may be performed once or multiple times. The heating temperature in the hot extrusion is not particularly limited, and is, for example, 900 to 1300°C. The extrusion ratio in the hot extrusion is also not particularly limited, and is, for example, 20 to 40%. In this manner, an intermediate alloy pipe is produced.

[0069] [(Step 3) Cold Drawing Step] In the cold drawing step, the intermediate alloy pipe produced in the hot working step is cold drawn to work the intermediate alloy pipe into a predetermined size. Specifically, the intermediate alloy pipe, which has been subjected to a known lubricating treatment, is drawn through a known die and plug under atmospheric pressure. This step is repeated multiple times until the intermediate alloy pipe reaches the predetermined outer diameter and wall thickness.

[0070] [(Step 4) Solution Treatment Step] In the solution treatment step, the intermediate alloy pipe manufactured in the hot working step is subjected to solution treatment. For example, the intermediate alloy pipe is carried into a heat treatment furnace, maintained at a desired temperature, and then rapidly cooled. The solution treatment temperature is 1000 to 1300°C.

[0071] [Manufacturing Conditions in the Manufacturing Method of the Present Embodiment] In the manufacturing method described above, the maximum reduction in area in one pass in the cold drawing step is R ＭＡＸ (%), the average drawing speed in the cold drawing step is v (m / min), and the heating holding time in the solution treatment step is t (min), the formula (A) is satisfied. ＭＡＸ×v / t≦100 (A) This allows the amount of dislocations introduced into the surface layer of a Ni-based alloy pipe whose chemical composition satisfies characteristic 1 to be adjusted to a range that satisfies characteristic 2.

[0072] FA is defined by the following formula: FA = R ＭＡＸ ×v / t FA is an index of the amount of dislocations introduced into the surface layer of an alloy pipe that has been subjected to the cold drawing process and the solution treatment process.

[0073] A "pass" refers to the operation of drawing an intermediate alloy pipe through a die once. In the cold drawing process, cold drawing consisting of one or more passes is performed. The "maximum reduction in area in one pass R ＭＡＸ " is the maximum value of the area reduction rate in one pass among one or more passes performed in the cold drawing process. The maximum area reduction rate R ＭＡＸ The larger the value, the larger the amount of dislocations introduced into the surface layer of the intermediate alloy pipe during the cold drawing process.

[0074] The longitudinal length (m) of the intermediate alloy pipe after passing through the die divided by the time (min) elapsed for passing through the die is defined as the drawing speed (m / min) in each pass. The average drawing speed v (m / min) in the cold drawing process is the arithmetic mean value of the drawing speeds in all passes performed in the cold drawing process. The faster the average drawing speed v, the greater the amount of dislocations introduced into the surface layer of the intermediate alloy pipe during the cold drawing process. Considering the workability of an intermediate alloy pipe whose chemical composition satisfies Feature 1, the upper limit of the average drawing speed v is set to 20 m / min in order to sufficiently suppress the occurrence of surface defects in the produced alloy pipe.

[0075] In the solution treatment process, the elapsed time from when the intermediate alloy pipe is charged into the heat treatment furnace until it is extracted is defined as the heating holding time t (minutes). In the solution treatment process, dislocations introduced into the surface layer of the intermediate alloy pipe are reduced by annihilation promoted by heat. The shorter the heating holding time t in the solution treatment process, the more effectively the reduction of dislocations in the surface layer can be suppressed.

[0076] Here, the higher the FA defined by the formula (A), the higher the maximum cross-sectional area reduction rate R ＭＡＸis large, the average drawing speed v is fast, and the heating holding time t is short. Therefore, the amount of dislocations introduced into the surface layer of the alloy pipe that has been subjected to the cold drawing process and the solution treatment process is large.

[0077] If FA is less than 10, the amount of dislocations introduced into the surface layer of the alloy pipe after the cold drawing process and the solution treatment process is too small. ２００ As a result, the alloy pipe cannot satisfy feature 2 while satisfying feature 1.

[0078] On the other hand, if the FA is more than 100, the amount of dislocations introduced into the surface layer of the alloy pipe after the cold drawing process and the solution treatment process is too large. ２００ As a result, the alloy pipe cannot satisfy feature 2 while satisfying feature 1.

[0079] If FA is 10 to 100, the half-width F of the alloy pipe to be manufactured is ２００ can be adjusted to an appropriate range depending on the contents of Mo and Al. As a result, the alloy pipe can satisfy feature 1 and feature 2. Therefore, FA satisfies formula (A).

[0080] The Ni-based alloy pipe of this embodiment is manufactured by the above-described manufacturing method.

[0081] The effects of the Ni-based alloy pipe of this embodiment will be explained more specifically using examples. The conditions in the following examples are one example of conditions adopted to confirm the feasibility and effects of the Ni-based alloy pipe of this embodiment. Therefore, the Ni-based alloy pipe of this embodiment is not limited to this one example of conditions.

[0082] Alloy tubes were manufactured having the chemical compositions shown in Tables 1A and 1B.

[0083]

[0084]

[0085] Specifically, a molten metal having the chemical composition of each test number was melted using a vacuum melting furnace. The molten metal was then used to produce a cylindrical ingot by ingot casting. The ingot was heated at 1220°C for 3 hours. The heated ingot was then hot forged to produce a billet.

[0086] The produced billet was machined to form a through-hole along the central axis of the billet. The billet with the through-hole formed was heated to 1200°C. The heated billet was hot pierced once to produce a hollow blank. The produced hollow blank was heated again to 1200°C. The heated hollow blank was hot extruded by the Ugine-Séjournet method to produce an intermediate alloy pipe.

[0087] The intermediate alloy pipe after hot extrusion was subjected to cold drawing under normal pressure to be processed into a shape of the intermediate alloy pipe having a diameter of 60 mm and a wall thickness of 8.0 mm. ＭＡＸ The results of the test were as shown in Table 2.

[0088]

[0089] The intermediate alloy pipes after cold drawing were subjected to solution treatment. Specifically, the intermediate alloy pipes after cold drawing were charged into a heat treatment furnace heated to 1150°C. After a predetermined time had elapsed, the intermediate alloy pipes were removed from the heat treatment furnace and quenched to room temperature by oil quenching. The heating holding time t (minutes) for each test number was as shown in Table 2. Alloy pipes with a diameter of 60 mm and a wall thickness of 8.0 mm were produced for each test number using the above manufacturing process.

[0090] [Evaluation Tests] The following evaluation tests were carried out on the manufactured alloy pipes with each test number. (Test 1) Half-width F ２００ (Test 2) Toughness evaluation test (Test 3) Corrosion resistance evaluation test Each test will be explained below.

[0091] [(Test 1) Half-width F ２００ Measurement test of the above-mentioned [half width F ２００ Based on the measurement method of the {200} plane peak half-width F on the inner surface of the alloy pipe of each test number,２００ The results are shown in Table 2.

[0092] [(Test 2) Toughness Evaluation Test] The toughness of the alloy pipe of each test number was evaluated by the following method. V-notch test specimens conforming to JIS Z 2242:2018 were taken from a region of each alloy pipe of each test number, extending from the inner surface to a depth of 4.0 mm. The size of the V-notch test specimen was 10 mm × 2.5 mm × 55 mm. The longitudinal direction of the V-notch test specimen was parallel to the longitudinal direction of the alloy pipe. A V-notch perpendicular to the longitudinal direction was formed at the longitudinal center of one of the 2.5 mm × 55 mm surfaces of the V-notch test specimen. The V-notch had a depth of 2 mm, a V-notch angle of 45°, and a V-notch tip radius of 0.25 mm. Two V-notch test specimens were prepared for each test number.

[0093] Using V-notch test specimens, Charpy impact tests were performed in air at room temperature in accordance with JIS Z 2242:2018 to determine the absorbed energy (J). The arithmetic mean value of the absorbed energy per unit area of ​​the two obtained V-notch test specimens was defined as the toughness value (J) of the alloy pipe of that test number. If the toughness value was 20J or more, the test specimen was rated as "E (Excellent)" and was judged to have sufficient toughness (shown as "E" in the "Toughness" column in Table 2). If the toughness value was less than 20J, the test specimen was rated as "B (Bad)" and was judged to have insufficient toughness (shown as "B" in the "Toughness" column in Table 2). Note that for test numbers in which sufficient toughness was not obtained, the subsequent evaluation test (Test 3) was not performed.

[0094] [(Test 3) Corrosion Resistance Evaluation Test] The corrosion resistance of the alloy pipe of each test number was evaluated by the following method. Three test pieces having a surface consisting of the inner surface of the alloy pipe were taken from each alloy pipe of each test number. In the surface consisting of the inner surface of the alloy pipe, the side corresponding to the longitudinal direction of the alloy pipe was defined as the long side, and the side corresponding to the circumferential direction of the alloy pipe was defined as the short side. The long side of the surface consisting of the inner surface of the alloy pipe was 20 mm, and the short side was 15 mm. The normal direction (thickness direction) of the surface consisting of the inner surface of the alloy pipe was defined as the thickness direction of the test piece. The thickness of the test piece was 3 mm. The mass (mg) of the test piece before the corrosion test was measured.

[0095] A corrosion test was carried out using the collected test specimens. Specifically, the test specimens were sealed in an autoclave containing a 40% aqueous ammonium chloride solution as the test solution. The autoclave was heated to 200°C while stirring the test solution. Pressure was applied to the autoclave using a pressure regulator, and the gauge pressure (pressure difference from atmospheric pressure) inside the autoclave was adjusted to 10 atm. After 72 hours had passed since heating to 200°C, the pressure inside the autoclave was returned to atmospheric pressure, and the test specimens were removed from the autoclave. The test specimens were then washed with water and thoroughly dried.

[0096] The mass (mg) of the thoroughly dried test piece after the corrosion test was measured. The mass (mg) of the test piece after the corrosion test was subtracted from the mass (mg) of the test piece before the corrosion test to determine the mass loss (mg) of the test piece due to the corrosion test. Then, the surface area (8.10 cm) of the test piece before the corrosion test was measured. ２ ) to obtain the mass loss per unit area of ​​the test piece (mg / cm ２ The arithmetic mean value of the mass loss per unit area of ​​the three test pieces was calculated as the mass loss per unit area (mg / cm) of the alloy pipe of the test number. ２ )

[0097] Mass loss per unit area is 2.0 mg / cm ２ When the mass loss per unit area was 2.0 mg / cm or less, the evaluation was given as "E (Excellent)" and it was determined that excellent corrosion resistance was obtained (shown as "E" in the "Corrosion Resistance" column in Table 2). ２ When the corrosion resistance exceeded this value, the evaluation was rated as "B (Bad)" and it was determined that excellent corrosion resistance was not obtained (shown as "B" in the "Corrosion Resistance" column in Table 2).

[0098] [Test Results] Referring to Tables 1A, 1B and 2, the alloy pipes of test numbers 1 to 15 satisfied characteristics 1 and 2. Therefore, excellent corrosion resistance was obtained.

[0099] On the other hand, in test numbers 16 and 17, the Mo content was too low, and therefore excellent corrosion resistance was not obtained.

[0100] In test numbers 18 and 19, the Al content was too low, so excellent corrosion resistance was not obtained.

[0101] In test numbers 20 and 21, the FA in the manufacturing process was too low, and therefore the F1 was too low, resulting in failure to obtain excellent corrosion resistance.

[0102] In test numbers 22 and 23, the FA in the manufacturing process was too high. Therefore, F1 was too high. As a result, sufficient toughness was not obtained.

[0103] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

Claims

1. A Ni-based alloy pipe having a chemical composition, in mass%, of C: 0.200% or less, Si: 3.00% or less, Mn: 3.00% or less, P: 0.050% or less, S: 0.050% or less, Cu: 5.00% or less, Cr: 20.00 to 35.00%, Ni: 40.00 to 80.00%, Co: 0 to 1.00%, W: 0 to 10.00%, N: 0 to 0.20%, V: 0 to 0.50%, Nb: 0 to 5.00%, Ti: 0 to 1.00%, Ca: 0 to 0.0100%, Mg: 0 to 0.0100%, B: 0 to 0.0050%, and REM: 0 to 0.100%, and further containing one or more selected from the group consisting of Mo: 0.60 to 10.00%, and Al: 0.60 to 2.00%, with the balance consisting of Fe and impurities, wherein the half width F of the peak of the {200} plane obtained by focusing X-ray diffraction measurement on the inner surface of the Ni-based alloy tube is ２００ A Ni-based alloy pipe in which (°) satisfies formula (1). 30≦(100+20Mo+45Al)×F ２００ ≦130 (1) Here, the contents of the corresponding elements in mass% are substituted for Mo and Al in formula (1). When the corresponding element is not contained, "0" is substituted for the element symbol.

2. A Ni-based alloy pipe according to claim 1, wherein the chemical composition contains, in mass %, one or more elements selected from the group consisting of Co: 0.01 to 1.00%, W: 0.01 to 10.00%, N: 0.01 to 0.20%, V: 0.01 to 0.50%, Nb: 0.01 to 5.00%, Ti: 0.01 to 1.00%, Ca: 0.0001 to 0.0100%, Mg: 0.0001 to 0.0100%, B: 0.0001 to 0.0050%, and REM: 0.001 to 0.100%.

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