Hydrogen resistant material and hydrogen resistant structural component

Abstract

To provide a hydrogen resistant material with a high Young's modulus that allows coexistence of strength and fracture toughness demanded for a structural component operated in a hydrogen atmosphere, the material exhibiting no or little reduction in these characteristics under the hydrogen atmosphere.SOLUTION: There is provided a hydrogen resistant material to be processed into a hydrogen resistant structural component used for operation under a hydrogen atmosphere, the hydrogen resistant material being composed of a copper alloy comprising Ni: 13.0-30.0 mass%, Sn: 3.0-10.0 mass%, Mn: 0-0.5 mass%, and Fe: 0-0.5 mass%, the balance being Cu and inevitable impurities, wherein the hydrogen resistant material exhibits a tensile strength of 700 MPa or more in each of an atmospheric atmosphere and a hydrogen atmosphere of 90 MPa or more and 120 MPa or less in a low strain rate tensile test performed at a strain rate of 5×10-5 s-1 or less, exhibits a relative reduction of area (RRA) of 0.80 or more determined by the low strain rate tensile test, and exhibits a Young's modulus of 135 GPa or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydrogen-resistant material and a hydrogen-resistant structural component. [Background technology]

[0002] In recent years, the demand for hydrogen as a fuel for fuel cell vehicles, power plants, etc. has been rapidly increasing. Hydrogen as a fuel comes into direct contact with containers and equipment components during the production, transportation, storage, and use processes. However, hydrogen embrittlement occurs in many metallic materials, so care must be taken when using it. In particular, components that operate in hydrogen atmosphere require high strength and toughness, so there is a strong demand for consideration of hydrogen embrittlement resistance.

[0003] Components that operate under hydrogen include parts of hydrogen compressors, such as the pistons and cylinders of reciprocating compressors, the rotors and casings of rotary compressors, the impellers of axial compressors, and the impellers and shafts of centrifugal compressors. Currently, chromium-molybdenum steels such as SCM431 and SCM435 are often used for these structural components, especially for the operating parts, but in reality, they are only operated within a low load stress range due to consideration of hydrogen embrittlement.

[0004] Hydrogen compressors are required to achieve even higher performance to meet the rapidly increasing demand for hydrogen. For example, 1) as shafts and impellers rotate at higher speeds, higher performance is required, the number of connected hydrogen compressors must be reduced, and the number of impellers must be reduced. 2) To suppress vibration during high-speed rotation, shafts and impellers must maintain high rigidity. 3) Green hydrogen production applications require intermittent operation, such as daily start-stop (DSS), because energy supplies from solar and wind power are unstable. However, structural materials made of chromium-molybdenum steel are susceptible to hydrogen embrittlement and are therefore insufficient for high-speed rotation and intermittent operation.

[0005] On the other hand, it is known that beryllium copper alloys can exhibit hydrogen resistance. For example, Patent Document 1 (Japanese Patent No. 6755521) discloses a hydrogen-resistant component used in contact with hydrogen, and discloses that this heat exchange component is made of a beryllium copper alloy containing 0.20% by mass or more and 2.70% by mass or less of Be, a total content of Co, Ni, and Fe of 0.20 to 2.50% by mass, and a total content of Cu, Be, Co, Ni, and Fe of 99% by mass or more. Patent Document 2 (Japanese Patent Laid-Open No. 2021-115631) discloses a method for producing a hydrogen-resistant component with good hydrogen embrittlement resistance, which discloses a method in which the surfaces of first and second beryllium copper alloy members are immersed in an alkaline solution, the surfaces of the copper alloy members are boiled in an organic acid solution such as formic acid, and the first and second copper alloy members are joined by heating and pressurizing. Patent Document 3 (WO2022 / 149561) discloses a copper alloy joined body that is composed of a plurality of age-hardenable copper alloy members that are diffusion-bonded to each other and that has been subjected to a solution treatment and an aging treatment. This copper alloy joined body, including the joint, is said to have excellent hydrogen embrittlement resistance and high tensile strength. Specifically, Patent Document 3 discloses that a strain rate of 5×10 -5 s -1 Within the range below (e.g., 5×10 -5 s -1 The document discloses a copper alloy joint having a tensile strength of 520 MPa or more in a slow strain rate tensile (SSRT) test in hydrogen gas and an RRA (relative reduction of area) of 0.8 or more.

[0006] Therefore, using beryllium copper alloys, which have hydrogen resistance and superior strength to chromium-molybdenum steel, for parts operating in hydrogen atmospheres would be advantageous in expanding the range of operating conditions, such as high-speed operation and intermittent operation. However, the Young's modulus of materials, which affects the deflection of parts under load and radial expansion during high-speed rotation, is somewhat lower at 127 GPa compared to 200 GPa for chromium-molybdenum steel. For this reason, in order to increase the rotation speed of parts, especially in hydrogen atmospheres, there has been a demand for materials that exhibit hydrogen embrittlement resistance (such as high strength and high fracture toughness in hydrogen atmospheres) and also have a Young's modulus that is as high as possible.

[0007] Nickel-tin-copper alloys are known as alloys with strength comparable to that of beryllium-copper alloys. Patent Document 4 (Japanese Patent No. 6492057) discloses a spinodal alloy consisting of 5-20% by weight Ni, 5-10% by weight Sn, impurities, trace additives, and the remainder copper, which has a 0.2% offset yield strength of at least 517 MPa (75 ksi) and an impact toughness of at least 16 J (12 ft-lbs). Patent Document 5 (Japanese Patent No. 6651464) discloses a coupling for a sucker rod containing a spinodally hardened copper-nickel-tin alloy containing 9-15.5% by weight Ni, 6-9% by weight Sn, and the remainder copper. This alloy is said to have a 0.2% offset yield strength of at least 95 ksi and a Charpy V-notch impact energy of at least 22 ft-lbs at room temperature. Patent Documents 4 and 5 do not discuss hydrogen resistance. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6755521 [Patent Document 2] Patent Publication No. 2021-115631 [Patent Document 3] WO2022 / 149561 [Patent Document 4] Patent No. 6492057 [Patent Document 5] Patent No. 6651464 [Non-patent literature]

[0009] [Non-Patent Document 1] Matsunaga Hisao, Junichiro Yamabe, and Saburo Matsuoka, "Proposal of Strength Design Guidelines for Chromium-Molybdenum Steels Used in High-Pressure Hydrogen Gas Environments," Surface Science, Vol. 36, No. 11, pp. 562-567, 2015 Summary of the Invention

[0010] As mentioned above, structural materials made of chromium-molybdenum steel are susceptible to hydrogen embrittlement, making them inadequate for operation under high load stress in a hydrogen atmosphere, particularly in intermittent operation and high-speed rotation. For example, the currently used SCM435 steel exhibits excellent fracture toughness in air, but hydrogen degradation has been confirmed, making it unsuitable for intermittent operation that induces fatigue. Therefore, beryllium-copper alloys, which are less susceptible to degradation in a hydrogen atmosphere, are expected to be a candidate for replacing chromium-molybdenum steel. However, compared to the Young's modulus of approximately 200 GPa for chromium-molybdenum steel, the Young's modulus of beryllium-copper alloys is somewhat lower at approximately 133 GPa. Therefore, to increase the rotational speed of components, particularly in a hydrogen atmosphere, improvements have been required to maintain high strength in hydrogen while achieving a slightly higher Young's modulus. Furthermore, there is a trade-off between material strength and fracture toughness required for rotating structures such as shafts and impellers. For this reason, hydrogen-resistant materials are desired that combine the material strength and fracture toughness required for structural components operating in a hydrogen atmosphere, and that are less likely to lose these properties in a hydrogen atmosphere (i.e., have excellent hydrogen embrittlement resistance).

[0011] The present inventors have now discovered that by controlling the composition of a nickel-tin-copper alloy, which has strength comparable to that of a beryllium-copper alloy, and performing an overaging treatment, it is possible to provide a hydrogen-resistant material with a high Young's modulus that achieves both the material strength and fracture toughness required for structural components that operate in a hydrogen atmosphere, and in which these properties do not or are less likely to deteriorate in a hydrogen atmosphere (i.e., excellent hydrogen embrittlement resistance).

[0012] Therefore, an object of the present invention is to provide a hydrogen-resistant material with a high Young's modulus that satisfies both the material strength and fracture toughness required for structural components that operate in a hydrogen atmosphere, and in which these properties do not or are less likely to deteriorate in a hydrogen atmosphere (i.e., excellent resistance to hydrogen embrittlement).

[0013] According to the present invention, the following aspects are provided. [Aspect 1] A hydrogen-resistant material to be processed into a hydrogen-resistant structural component to be used while operating in a hydrogen atmosphere, the hydrogen-resistant material comprising: Ni: 13.0~30.0% by mass, Sn: 3.0~10.0% by mass, Mn: 0 to 0.5 mass%; and Fe: 0~0.5% by mass, and the remainder is a copper alloy containing Cu and unavoidable impurities, The hydrogen-resistant material has a strain rate of 5×10 in both an air atmosphere and a hydrogen atmosphere of 90 MPa or more and 120 MPa or less. -5 s -1 The slow strain rate tensile test performed below shows a tensile strength of 700 MPa or more. the hydrogen-resistant material exhibits a relative reduction of area (RRA) of 0.80 or greater as determined by the slow strain rate tensile test; The hydrogen-resistant material has a Young's modulus of 135 GPa or more. [Aspect 2] The hydrogen-resistant material has a thermal conductivity of 45 MPa·m in both an air atmosphere and a hydrogen atmosphere of 90 MPa or more and 120 MPa or less. 1 / 2 Fracture toughness value K IC2. The hydrogen resistant material of embodiment 1, wherein [Aspect 3] 3. The hydrogen-resistant material according to claim 1, wherein the copper alloy has a Ni content of more than 20.0% by mass and not more than 30.0% by mass, and the hydrogen-resistant material exhibits a Young's modulus of more than 140 GPa. [Aspect 4] A hydrogen-resistant material according to any one of aspects 1 to 3, wherein the hydrogen-resistant material exhibits a 0.2% proof stress of 520 M or more in both an air atmosphere and a hydrogen atmosphere of 90 MPa or more and 120 MPa or less. [Aspect 5] The hydrogen-resistant material has a resistance of 16 J / cm when measured by a V-notch Charpy impact test in an atmospheric environment. 2 A hydrogen-resistant material according to any one of aspects 1 to 4, which exhibits the above Charpy impact value. [Aspect 6] A hydrogen-resistant structural component manufactured from the hydrogen-resistant material according to any one of aspects 1 to 5. [Aspect 7] A hydrogen-resistant structural component according to aspect 6, wherein the hydrogen-resistant structural component is at least one selected from the group consisting of vessels, piping, valves, and joints, which are in direct contact with high-pressure hydrogen, and components of hydrogen compressors. [Aspect 8] A hydrogen-resistant structural part according to Aspect 7, wherein the hydrogen-resistant structural part is a component of the hydrogen compressor, and the component of the hydrogen compressor is at least one selected from the group consisting of a piston and cylinder of a reciprocating compressor, a rotor and casing of a rotary compressor, an impeller of an axial compressor, and an impeller and shaft of a centrifugal compressor. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hydrogen-resistant materials The hydrogen-resistant material according to the present invention is a material to be processed into hydrogen-resistant structural components used (particularly in operation) in a hydrogen atmosphere. Preferred examples of hydrogen-resistant structural components used in a hydrogen atmosphere include containers (e.g., containers for storing high-pressure hydrogen), piping, valves, and joints that come into direct contact with high-pressure hydrogen. Preferred examples of hydrogen-resistant structural components used in operation in a hydrogen atmosphere include, but are not limited to, various components of hydrogen compressors (e.g., pistons and cylinders of reciprocating compressors, rotors and casings of rotary compressors, impellers of axial compressors, and especially impellers and shafts of centrifugal compressors). The hydrogen-resistant material is made of a nickel-tin-copper alloy. This nickel-tin-copper alloy contains 13.0 to 30.0 mass% Ni, 3.0 to 10.0 mass% Sn, 0 to 0.5 mass% Mn, and 0 to 0.5 mass% Fe, with the remainder being Cu and unavoidable impurities. This hydrogen-resistant material has the following characteristics: (i) a strain rate of 5×10 in both an air atmosphere and a hydrogen atmosphere of 90 MPa or more and 120 MPa or less; -5 s -1 (ii) a relative reduction of area (RRA) of 0.80 or more as determined by the slow strain rate tensile test described above; (iii) a Young's modulus of 135 GPa or more; and preferably, (iv) a Young's modulus of 45 MPa m in air and in a hydrogen atmosphere of 90 MPa or more and 120 MPa or less. 1 / 2 Fracture toughness value K IC These properties are realized by controlling the nickel content of the nickel-tin-copper alloy of the above composition and by performing overaging treatment. That is, the strength of a spinodally decomposable nickel-tin-copper alloy increases as the spinodal treatment is performed, but if the spinodal treatment is continued even after the peak strength is reached and the alloy is brought into an overaging state, the strength decreases to some extent, but the Charpy impact value and fracture toughness value K ICThese properties are significantly improved. It has been confirmed that these properties are significantly reduced in hydrogen in other materials such as chromium-molybdenum steel. In contrast, the nickel-tin-copper alloy of the above composition, which the inventors have confirmed in tests does not reduce these properties even in a hydrogen atmosphere, can provide a hydrogen-resistant material with a high Young's modulus of 135 GPa or more that achieves both the material strength and fracture toughness required for structural parts that operate in a hydrogen atmosphere and that does not or is less likely to reduce these properties in a hydrogen atmosphere (i.e., has excellent hydrogen embrittlement resistance).

[0015] As mentioned above, structural materials made of chromium-molybdenum steel are susceptible to hydrogen embrittlement, and therefore, their use in hydrogen, particularly under conditions involving stress loading and unloading, is unsatisfactory because the reduction in strength and toughness significantly impacts component reliability. Therefore, aged beryllium copper alloys, which have been confirmed not to deteriorate in a hydrogen atmosphere in Patent Document 1 (Japanese Patent No. 6755521) and other publications, have been expected to be a candidate material to replace chromium-molybdenum steel. However, the Young's modulus of beryllium copper alloys is low, at approximately 133 MPa. Therefore, when beryllium copper alloys are used as rotating parts, radial expansion during high-speed rotation is large, which poses the inconvenience of requiring a sufficient clearance between the impeller and the case, for example. Furthermore, the material strength (e.g., tensile strength) and fracture toughness (e.g., fracture toughness value K IC ) are in a trade-off relationship. For this reason, it has been difficult to realize a hydrogen-resistant material that satisfies both the material strength and fracture toughness required for structural parts that operate in a hydrogen atmosphere, and that is resistant to deterioration of these properties in a hydrogen atmosphere (i.e., has excellent hydrogen embrittlement resistance). In this regard, the present invention advantageously solves this problem.

[0016] The nickel-tin-copper alloy constituting the hydrogen-resistant material of the present invention contains 13.0 to 30.0 mass% Ni, 3.0 to 10.0 mass% Sn, 0 to 0.5 mass% Mn, 0 to 0.5 mass% Fe, and the balance being Cu and unavoidable impurities. Preferred examples of nickel-tin-copper alloys satisfying this composition include nickel-tin-copper 158 alloy (hereinafter referred to as NiSnCu158), nickel-tin-copper 215 alloy (hereinafter referred to as NiSnCu215), and a nickel-increased alloy of nickel-tin-copper 215 alloy (hereinafter referred to as NiSnCu215 hiNi), and their compositions are as follows:

[0017] [Table 1]

[0018] Ni, together with Sn, contributes to the copper alloy's excellent basic performance as a nickel-tin-copper alloy (strength, workability, fatigue properties, heat resistance, corrosion resistance, hydrogen embrittlement resistance, etc.) through spinodal decomposition. The Ni content in the nickel-tin-copper alloy constituting the hydrogen-resistant material is 5.0 to 30.0 mass%. From the viewpoint of improving Young's modulus, the Ni content is preferably 13.0 to 30.0 mass%, more preferably 14.5 to 30.0 mass%, even more preferably more than 20.0 mass% and up to 30.0 mass%, particularly preferably 20.5 to 30.0 mass%, and most preferably 22.0 to 30.0 mass%. For example, when the Ni content in the copper alloy is more than 20.0 mass% and up to 30.0 mass%, the hydrogen-resistant material is likely to achieve a Young's modulus exceeding 140 GPa. When the Ni content is within the above-mentioned range, the above-mentioned basic performance can be effectively achieved through a synergistic effect with Sn, while the influence of an excessive amount of Ni on the deterioration of hydrogen resistance can be avoided.

[0019] As described above, Sn provides the above-mentioned basic performance through a synergistic effect with Ni. The Sn content in the nickel-tin-copper alloy constituting the hydrogen-resistant material is 3.0 to 10.0 mass%. (i) When the Ni content is 13.0 mass% or more and 17.0 mass% or less, the Sn content is preferably 6.0 to 10.0 mass%, more preferably 7.0 mass% to 9.0 mass%, and even more preferably 7.5 to 8.5 mass%. (ii) When the Ni content is more than 17.0 mass% and less than 25.0 mass%, the Sn content is preferably 3.0 to 7.2 mass%, more preferably 4.0 mass% to 6.2 mass%, and even more preferably 4.5 to 5.7 mass%. (iii) When the Ni content is 25.0 mass% or more and 30.0 mass% or less, the Sn content is preferably 4.0 to 9.1 mass%, more preferably 5.0 to 8.1 mass%, and even more preferably 5.5 to 7.6 mass%.

[0020] Mn and Fe are optional components that can be contained in trace amounts in nickel-tin-copper alloys, and they have the effect of keeping the Sn content stable when producing nickel-tin-copper castings without affecting basic performance. The nickel-tin-copper alloy that constitutes the hydrogen-resistant material contains 0 to 0.5 mass% of Mn and 0 to 0.5 mass% of Fe.

[0021] The nickel-tin-copper alloy constituting the hydrogen-resistant material of the present invention exhibits a high Young's modulus (preferably equal to or greater than that of a beryllium-copper alloy). Specifically, the Young's modulus of the hydrogen-resistant material of the present invention is 135 GPa or greater, preferably 137 GPa or greater, more preferably 139 GPa or greater, and even more preferably greater than 140 GPa, for example, 144 GPa or greater or 150 GPa or greater. The Young's modulus herein is a value obtained by measuring at 40°C using a resonance method with an elastic modulus measuring device, details of which will be described in the Examples below. Young's modulus is a physical property that affects the deflection of a component when stress is applied. For example, a slightly higher Young's modulus is preferable to minimize radial expansion when a structural component made of the hydrogen-resistant material of the present invention rotates at high speed. Therefore, the hydrogen-resistant material of the present invention can be said to have both excellent hydrogen embrittlement resistance and high rigidity, from the viewpoint of having a Young's modulus greater than that of a beryllium-copper alloy having similar high tensile strength and hydrogen embrittlement resistance. In this sense, the Young's modulus of the hydrogen-resistant material of the present invention should not have any particular upper limit, but is typically 175 GPa or less, and more typically 165 GPa or less.

[0022] The hydrogen-resistant material of the present invention has a strain rate of 5×10 in both an air atmosphere and a hydrogen atmosphere of 90 MPa or more and 120 MPa or less (for example, 95 MPa). -5 s -1 Less than (e.g., 5 × 10 -5 s -1 In a slow strain rate tensile (SSRT) test, the material exhibits a tensile strength of 700 MPa or more. Such a hydrogen-resistant material has high tensile strength not only in an air atmosphere but also in a hydrogen atmosphere, and exhibits a tensile strength of preferably 780 MPa or more, more preferably 850 MPa or more. The above tensile strength is (desirable fracture toughness value K ICSince it is desirable that the strain rate is as high as possible (as long as the strain rate is obtained), the upper limit should not be specified, but is typically 1150 MPa or less, more typically 1100 MPa or less, and even more typically 1000 MPa or less. This slow strain rate tensile test may be performed by preparing a test piece conforming to ASTM E8M Specimen 4 and following the procedure described in the Examples below in accordance with ASTM-G-142. Generally, in slow strain rate tensile tests, hydrogen sensitivity is evaluated using the relative reduction of area (RRA), which is the tensile strength or reduction of area in hydrogen gas divided by the tensile strength or reduction of area in a reference gas that is not affected by hydrogen. In slow strain rate tensile tests, for example, at a strain rate of 5 x 10 -5 s -1 The test may be performed at a hydrogen gas pressure of 90 MPa or more and 120 MPa or less (for example, 95 MPa) assuming that the component will be used in hydrogen. The higher the hydrogen gas pressure, the greater the amount of hydrogen that penetrates into the material, making the test piece more susceptible to the effects of hydrogen exposure, allowing for a more appropriate evaluation of hydrogen embrittlement. In the test related to this application, the hydrogen characteristics are evaluated by calculating the relative reduction of area (RRA) according to the procedure described in the examples below.

[0023] The hydrogen-resistant material of the present invention evaluated by the slow strain rate tensile test exhibits a relative reduction of area (RRA) of 0.80 or more, more preferably 0.90 or more. The upper limit of RRA is theoretically 1, but because errors or fluctuations in actual measurements can cause the value to exceed 1.0, it is typically 1.55 or less, more typically 1.20 or less. If the tensile strength of a hydrogen-resistant material is within the above range in air at room temperature or under a hydrogen gas pressure of 90 MPa to 120 MPa (e.g., 95 MPa), and if its RRA also satisfies the above range, this means that the hydrogen-resistant material has strength suitable for hydrogen-resistant structural components (especially rotating structures such as shafts and impellers) and is not likely to decrease in a hydrogen atmosphere (i.e., is not susceptible to hydrogen embrittlement). Therefore, the hydrogen-resistant material of the present invention can be said to have excellent resistance to hydrogen embrittlement from the standpoint of tensile strength.

[0024] Furthermore, the hydrogen-resistant material of the present invention has a resistance of 40 MPa m in both air and hydrogen atmospheres of 90 MPa or more and 120 MPa or less (e.g., 95 MPa). 1 / 2 or more, preferably 45 MPa m 1 / 2 More preferably, 47.5 MPa m 1 / 2 Fracture toughness value K IC Such hydrogen-resistant materials exhibit high fracture toughness values ​​K not only in air but also in hydrogen atmospheres. IC Fracture toughness value K IC It is desirable that the fracture toughness value K is as high as possible (as long as the desired tensile strength is obtained). IC is a static fracture toughness test in accordance with ASTM E-399-90. IC The test can be performed according to the procedure described in the Examples below. As mentioned above, the tensile strength and fracture toughness K required for rotating structures such as shafts and impellers are IC However, the hydrogen-resistant material of the present invention has a good fracture toughness value K while having an allowable tensile strength for hydrogen-resistant structural parts (especially rotating structures such as shafts and impellers) not only in air but also in hydrogen atmosphere. IC In other words, it exhibits a good fracture toughness value K IC does not or is unlikely to decrease in a hydrogen atmosphere (i.e., hydrogen embrittlement is unlikely to occur). Therefore, the hydrogen-resistant material of the present invention can be said to have excellent hydrogen embrittlement resistance not only in terms of the above-mentioned tensile strength but also in terms of fracture toughness.

[0025] The hydrogen-resistant material of the present invention has a resistance of 16 J / cm when measured by a V-notch Charpy impact test in an air atmosphere. 2 It is preferable that the Charpy impact value is 21 J / cm or more, and more preferably 21 J / cm 2 More preferably, 30 J / cm 2 Although the Charpy impact value cannot be measured in a hydrogen atmosphere, the fracture toughness value K ICIt has the advantage of being correlated with the strength of the material and can be measured inexpensively. Such a high Charpy impact value means that the hydrogen-resistant material has high fracture toughness, improving the reliability of hydrogen-resistant structural parts (especially rotating structures such as shafts and impellers). Therefore, although the upper limit of the Charpy impact value should not be specified, taking into account the balance with the material strength, it is typically set at 120 J / cm 2 less than, more typically, 100 J / cm 2 The V-notch Charpy impact test may be performed in accordance with JIS Z 2242:2018 according to the procedure described in the examples below.

[0026] The hydrogen-resistant material of the present invention preferably exhibits a 0.2% yield strength of 520 MPa or more in both air and a hydrogen atmosphere of 90 MPa to 120 MPa (e.g., 95 MPa), more preferably 700 MPa or more, even more preferably 900 MPa or more, and particularly preferably 1000 MPa or more. Having a high 0.2% yield strength in both air and hydrogen atmospheres means that the hydrogen-resistant material has high reliability and is not likely to deteriorate in a hydrogen atmosphere (i.e., is not susceptible to hydrogen embrittlement). Therefore, no upper limit should be specified, but considering the balance with the material strength, it is typically 1250 MPa or less, more typically 1150 MPa or less. The 0.2% yield strength can be measured by cutting a test piece from the hydrogen-resistant material in accordance with ASTM E8M standard and conducting a tensile test in air or a hydrogen atmosphere according to the procedure described in the Examples below.

[0027] Manufacturing method The hydrogen-resistant material according to the present invention can be preferably produced by preparing a nickel-tin-copper alloy having the above-described composition by a known production method and then subjecting it to spinodal treatment (including overaging treatment). For example, the hydrogen-resistant member can be produced through (1) a melting and casting process, (2) a homogenization process, (3) a hot forging process, a hot rolling process, and / or a hot extrusion process, (4) a solution treatment process, (5) a cold working process, and (6) a spinodal treatment process (including overaging treatment). Specifically, the process is as follows.

[0028] (1) Melting and Casting Process In this process, the raw materials are mixed, then melted in a high-frequency furnace and semi-continuously cast to produce a cast iron. Other methods that can be used include horizontal continuous casting, melting in an EREMA furnace, metal mold casting, and low-pressure casting; the casting method is not particularly limited. The mold used for casting can be made of pure copper, copper alloy, or alloy steel. The melting atmosphere can be air, or, if necessary, an inert atmosphere such as nitrogen, argon, or helium. In the melting and casting process, it is preferable to limit the content of various impurities (e.g., S and P) to less than 0.01% by mass.

[0029] (2) Homogenization process The purpose of this process is to homogenize the heterogeneous structure of the ingot by holding it at a high temperature. Homogenization conditions vary depending on the composition. For example, for NiSnCu158 (CDA72950), NiSnCu215 (CDA72900), and NiSnCu215hiNi, as listed in Table 1 above, a temperature holding time of 800–900°C for 4 hours or more but less than 48 hours is effective. In this case, treatment times of less than 4 hours at each temperature for each alloy are insufficient to promote the diffusion of atoms such as Sn. Furthermore, treatment times of more than 48 hours, once a certain degree of homogenization has been achieved, are unlikely to be effective.

[0030] (3) Hot forging process, hot rolling process and / or hot extrusion process These processes aim to destroy and recrystallize the cast structure of the ingot after homogenization treatment, improving mechanical properties such as material strength and elongation after subsequent annealing, solution treatment, and spinodal treatment (including overaging), or to simultaneously process the material into a desired shape. The cumulative forging ratio and reduction rate significantly affect the degree of destruction of the cast structure. Hot-forged materials typically undergo multiple upsetting and elongation processes. For example, the forging ratio is expressed as 3S for elongating to three times the length and 1 / 2U for elongating to half the length. The cumulative forging ratio is expressed by multiplying the value for elongation by the reciprocal of the value for upsetting. The higher the cumulative forging ratio, the more the cast structure is destroyed, resulting in a finer, more desirable forged structure. In hot rolling and hot extrusion, the reduction rate is the difference between the cross-sectional area of ​​the ingot and the cross-sectional area of ​​the rolled or extruded material after processing. In hot rolling and hot extrusion, the higher the processing rate, the more the cast structure is destroyed, resulting in a finer and more desirable forged structure. However, since the processing rate is limited by the final product shape, in order to obtain a finer structure, the ingot may be hot forged to destroy the cast structure, and then hot rolled or hot extruded again. In addition, the hot processing temperature rate of hot forging, hot rolling, and hot extrusion may be controlled to control the grain size during the subsequent solution treatment process. Alternatively, a similar effect can be achieved by performing heat treatment below the solution treatment temperature after these processes.

[0031] (4) Solution treatment In this process, hot-forged, hot-rolled, or hot-extruded materials are solution-treated to obtain a solution-treated material in which additives such as Ni and Sn are dissolved in the Cu matrix. Specifically, the hot-forged, hot-rolled, or hot-extruded materials are heated and held in a predetermined solution-treatment temperature range for a predetermined time, followed by water quenching to obtain the solution-treated material. For NiSnCu158 (CDA72950), NiSnCu215 (CDA72900), and NiSnCu215hiNi, a temperature range of 750 to 900°C is effective for the solution-treatment temperature range, with a holding time of substantially 30 minutes or more. Industrially, the material is typically held in a furnace at the set temperature for 2 to 5 hours, followed by water quenching.

[0032] (5) Cold working In this process, the solution-treated material is subjected to cold working to obtain a solution-treated cold-worked material. Specifically, cold forging is generally used for solution-treated forged materials, cold rolling is generally used for solution-treated rolled materials, and cold drawing is generally used for solution-treated extruded materials. Cold working increases the dislocation density after solution treatment, increasing the number of nuclei that serve as the starting points for aging precipitation. This not only increases the strength at the peak of the spinodal treatment, but also can be expected to improve the balance between strength and toughness during overaging. Note that, although cold working can be expected to particularly improve strength by applying cold working to solution-treated materials, applying cold working is not an essential process in the present invention.

[0033] (6) Spinodal treatment In this process, the solution-treated or solution-treated cold-worked material is held at a predetermined temperature for a certain period of time to undergo spinodal hardening. Spinodal treatment involves holding the alloy at temperatures between 260 and 600°C for 0.5 to 8 hours, which causes short-range diffusion (concentration fluctuations) and results in the formation of chemically heterogeneous regions with identical crystal structures throughout the matrix. Alloys strengthened by spinodal decomposition exhibit a characteristic modulated microstructure that can be confirmed by electron microscopy. The treatment temperatures for peak spinodal conditions that result in high strength and hardness are 300 to 470°C for NiSnCu158 (CDA72950) and 350 to 520°C for NiSnCu215 (CDA72900) and NiSnCu215hiNi. The spinodal treatment time at these treatment temperatures is preferably 1 to 8 hours.

[0034] Hydrogen-resistant structural parts The hydrogen-resistant material of the present invention is a material that combines the material strength and fracture toughness required for structural members used in a hydrogen atmosphere, particularly those operating in a hydrogen atmosphere, and in which these properties do not or are unlikely to deteriorate in a hydrogen atmosphere (i.e., has excellent hydrogen embrittlement resistance). Therefore, the hydrogen-resistant material of the present invention is suitable for processing into hydrogen-resistant structural parts that are used (particularly those that are operated) in a hydrogen atmosphere, and is particularly suitable for hydrogen-resistant structural parts that are used intermittently or at high speeds, which are prone to fatigue in a hydrogen atmosphere. Preferred examples of such hydrogen-resistant structural parts include, but are not limited to, containers (e.g., containers for storing high-pressure hydrogen), piping, valves, and joints that come into direct contact with high-pressure hydrogen, as well as various components of hydrogen compressors (e.g., pistons and cylinders of reciprocating compressors, rotors and casings of rotary compressors, impellers of axial compressors, and especially impellers and shafts of centrifugal compressors). [Example]

[0035] The present invention is further illustrated by the following examples.

[0036] Example 1 (1) Preparation of hydrogen-resistant materials Raw materials yielding the alloy composition of GMX215 (CDA C72950) shown in Table 2 were weighed, melted, and cast to produce a GMX215 alloy ingot. This ingot was subjected to soaking (homogenization annealing) at 880°C for 24 hours, followed by hot forging with a cumulative forging ratio of 18 to obtain a forged ingot. This forged ingot was water-cooled from 880°C to solutionize it, and then subjected to 65% cold working to produce a solution-treated cold-worked material. The resulting solution-treated cold-worked material was subjected to spinodal treatment at 450°C for 2 hours to produce a hydrogen-resistant material.

[0037] The forging ratio is expressed as 3S when stretched to three times its length, and 1 / 2U when set at half its length. The cumulative forging ratio is calculated by multiplying the value when stretched by the reciprocal of the value when set at half its length.

[0038] (2) Evaluation of hydrogen-resistant materials The hydrogen-resistant materials thus produced were subjected to various evaluations as follows, with the results shown in Table 3.

[0039] <Slow strain rate tensile test (SSRT)> The hydrogen-resistant material was cut out to prepare test specimens conforming to ASTM E8M Specimen 4. The slow strain rate tensile test was performed in accordance with ASTM-G-142, with a displacement rate of 0.001 mm / sec (strain rate 5 × 10 -5 s -1 ) and the test was carried out in air or in a 95 MPa hydrogen atmosphere at room temperature. In this way, the slow strain rate tensile strength was measured in each atmosphere. The reduction of area RA of the test piece obtained in the slow strain rate tensile test in each atmosphere was calculated using the following formula: RA=(A0-A1) / A0 (In the formula, A0 is the cross-sectional area of ​​the test piece before the slow strain rate tensile test, and A1 is the cross-sectional area of ​​the location where necking fractured after the slow strain rate tensile test.) The RRA (relative reduction of area) used as an index for evaluating hydrogen embrittlement properties was calculated using the cross-sectional reduction of area RA under a hydrogen atmosphere at 95 MPa. H2 RA under atmospheric conditions Air By dividing by (i.e., the ratio RA H2 / RA Air (by determining the

[0040] <Vickers hardness> To measure the Vickers hardness of the hydrogen-resistant material, a Vickers hardness test was conducted in accordance with JIS Z 2244: 2009. The test force selected was 4.9 N (hardness symbol HV0.5).

[0041] <Charpy impact test> To measure the Charpy impact value of the hydrogen-resistant material, a Charpy impact test was conducted in accordance with JIS Z 2242:2018. The hydrogen-resistant material was processed to prepare a V-notch test specimen (55 mm long, 10 mm square cross section, V-notch at the center of the length, notch angle 45°, notch depth 2 mm, and notch base radius 0.25 mm) as specified in JIS Z 2242:2018, and the Charpy impact value (absorbed energy) was measured at room temperature in an air atmosphere using a Charpy impact tester (Tokyo Koki Testing Instruments Co., Ltd., automatic Charpy impact tester CI-500D).

[0042] <Fracture toughness test> For hydrogen-resistant materials, the static fracture toughness test K is performed in air or in a 95 MPa hydrogen atmosphere at room temperature in accordance with ASTM E-399-90. IC The fracture toughness value K of the hydrogen-resistant material was determined by the test. IC was measured.

[0043] <0.2% yield strength> The 0.2% yield strength of hydrogen-resistant materials was measured from the stress-strain diagram obtained in the slow strain rate tensile test conducted at room temperature in air or a 95 MPa hydrogen atmosphere. Specifically, in the stress-strain diagram obtained in the tensile test in air or a 95 MPa hydrogen atmosphere, the slope (elastic modulus) of any point judged to be elastic was determined, a line was drawn, and the determined line was offset to 0.2% strain. The value at the intersection of the offset line and the stress-strain relationship was taken as the 0.2% yield strength.

[0044] <Young's modulus> The hydrogen-resistant material was heated to 800°C in an air atmosphere for two hours and then cooled in a furnace to remove processing strain. Measurement specimens measuring 60 mm x 10 mm x 1.5 mm were cut from the water-resistant material after processing strain had been removed. Using the cut specimens, Young's modulus was measured using the resonance method with a high-temperature elastic modulus measuring device (EG-HT model, manufactured by Nippon Technoplus Co., Ltd.) while maintaining the sample temperature at 40°C. The resonance method utilizes resonance to vibrate the sample with a very weak force and measure its natural frequency, allowing for highly accurate measurement of elastic modulus (Young's modulus and rigidity modulus). This method has the advantage of being capable of measuring from cryogenic temperatures (10 K) to high temperatures (1470 K). While Young's modulus can also be estimated from the slope of the stress-strain diagram in a tensile test, this method is not preferred due to its low measurement accuracy.

[0045] Example 2 Except for the fact that the solution-treated cold-worked material was subjected to spinodal treatment at 500°C for 3 hours to obtain an overaged material, the preparation of materials and various evaluations were carried out in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0046] Example 3 Except for the fact that the solution-treated cold-worked material was subjected to spinodal treatment at 520°C for 9 hours to obtain an overaged material, the preparation of materials and various evaluations were carried out in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0047] Example 4 Except for the fact that the solution-treated cold-worked material was subjected to spinodal treatment at 550°C for 1 hour to obtain an overaged material, the preparation of materials and various evaluations were carried out in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0048] Example 5 Except for the fact that the solution-treated cold-worked material was subjected to spinodal treatment at 550°C for 5 hours to obtain an overaged material, the preparation of materials and various evaluations were carried out in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0049] Example 6 Materials were prepared and various evaluations were carried out in the same manner as in Example 1, except that raw materials were used that resulted in the alloy composition of GMX215 HiNi1 shown in Table 2. The results are shown in Tables 3 and 4.

[0050] Example 7 Materials were prepared and various evaluations were carried out in the same manner as in Example 1, except that raw materials were used that resulted in the alloy composition of GMX215 HiNi2 shown in Table 2. The results are shown in Tables 3 and 4.

[0051] Example 8 Except for the fact that the solution-treated cold-worked material was subjected to spinodal treatment at 450°C for 12 hours to obtain an overaged material, the preparation of materials and various evaluations were carried out in the same manner as in Example 7. The results are shown in Tables 3 and 4.

[0052] Example 9 Using raw materials that yielded the alloy composition of GMX158 (CDA C72900) shown in Table 2, a solution-treated cold-worked material was obtained by the same process as in Example 1, and then an overaged material was obtained by spinodal treatment at 380°C for 6 hours. Various evaluations were carried out on the material thus obtained in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0053] Example 10 (comparison) Using raw materials that yielded the alloy composition of GMX96 (CDA C72700) shown in Table 2, a solution-treated cold-worked material was obtained by the same process as in Example 1, and then a spinodal treatment was carried out at 380°C for 2 hours to obtain an overaged material. The material thus obtained was subjected to various evaluations in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0054] Example 11 (comparison) Raw materials yielding the CuBe25 (JIS C1720) alloy composition shown in Table 2 were weighed, melted, and cast to produce a CuBe25 alloy ingot. The ingot was subjected to soaking (homogenization annealing) at 780°C for 8 hours, followed by hot forging with a cumulative forging ratio of 18 to obtain a forged ingot. The forged ingot was water-cooled from 780°C to solutionize it, and then subjected to 40% cold working to produce a solution-treated cold-worked material. The solution-treated cold-worked material was subjected to aging treatment at 315°C for 3 hours to produce a hydrogen-resistant material as a peak-aged material. The resulting material was subjected to various evaluations in the same manner as in Example 1, except that the hydrogen pressure used for slow strain rate tensile testing (measurements of tensile strength, RRA, and 0.2% proof stress) and fracture toughness testing was 115 MPa. The results are shown in Tables 3 and 4.

[0055] Example 12 (comparison) Materials were prepared and various evaluations were carried out in the same manner as in Example 11, except that the solution-treated cold-worked material was aged at 390°C for 3 hours to obtain an overaged material. The results are shown in Tables 3 and 4.

[0056] Example 13 (comparison) Materials were prepared and various evaluations were carried out in the same manner as in Example 11, except that the solution-treated cold-worked material was aged at 390°C for 9 hours to obtain an overaged material. The results are shown in Tables 3 and 4.

[0057] Example 14 (comparison) Raw materials yielding the CuBe11 (JIS C1751) alloy composition shown in Table 2 were weighed, melted, and cast to produce a CuBe11 alloy ingot. This ingot was subjected to the same process as in Example 1 to obtain a forged ingot. This forged ingot was water-cooled from 850°C to solutionize it, and then subjected to 40% cold working to obtain a solution-treated cold-worked material. The resulting material was subjected to various evaluations in the same manner as in Example 1, except that the hydrogen pressure used to perform slow strain rate tensile tests (measurements of tensile strength, RRA, and 0.2% proof stress) and fracture toughness tests was 115 MPa. The results are shown in Tables 3 and 4.

[0058] Example 15 (comparison) For comparison, the data for chromium-molybdenum steel (SCM435) are shown in Tables 3 and 4, which are the values ​​shown in Fig. 2(b) and Table 1 in Non-Patent Document 1 (Matsunaga Hisao, Yamabe Junichiro, and Matsuoka Saburo, "Proposal of Strength Design Guidelines for Using Chromium-Molybdenum Steel in High-Pressure Hydrogen Gas Environments," Surface Science, Vol. 36, No. 11, pp. 562-567, 2015).

[0059] [Table 2]

[0060] [Table 3]

[0061] [Table 4]

[0062] The evaluation items shown in Tables 3 and 4 are explained below.

[0063] Regarding the evaluation of fracture toughness tests, if the measured value under hydrogen is 20% or more lower than the measured value under air, it can be judged that deterioration has occurred under hydrogen. There are cases where the measured value under hydrogen exceeds the measured value under air, but in principle, the properties do not improve under hydrogen, so it is judged that there is no change in the hydrogen properties due to measurement variance.

[0064] Relative reduction of area (RRA) is the reduction of area of ​​the test material under hydrogen (the reduction in area of ​​the fractured part at fracture) RA H2 The reduction in area of ​​the test material under air (reduction in area of ​​the fractured part at the time of fracture) is RA Air In this case, RA H2 / RA AirRRA is defined as the ratio of the resistance to the strain, and if the RRA is 0.8 or less, the material is judged to be unusable in hydrogen because it will degrade in hydrogen. Although values ​​exceeding 1.0 are sometimes measured, this is not due to an improvement in properties under hydrogen, but rather to test variability, and it is judged that no hydrogen degradation has occurred.

Claims

1. A hydrogen-resistant material to be processed into a hydrogen-resistant structural component to be used while operating in a hydrogen atmosphere, the hydrogen-resistant material comprising: Ni: 13.0 to 30.0% by mass, Sn: 3.0 to 10.0% by mass, Mn: 0 to 0.5 mass%; and Fe: 0 to 0.5% by mass, and the remainder is a copper alloy containing Cu and unavoidable impurities, The hydrogen-resistant material has a strain rate of 5×10 in an air atmosphere and in a hydrogen atmosphere of 90 MPa or more and 120 MPa or less. －５ s －１ A slow strain rate tensile test performed as follows shows a tensile strength of 700 MPa or more, the hydrogen resistant material exhibits a relative reduction of area (RRA) of 0.80 or greater as determined by the slow strain rate tensile test; The hydrogen-resistant material has a Young's modulus of 135 GPa or more.

2. The hydrogen-resistant material has a resistance of 45 MPa m in both an air atmosphere and a hydrogen atmosphere of 90 MPa or more and 120 MPa or less. １／２ Fracture toughness value K ＩＣ 2. The hydrogen resistant material of claim 1, wherein:

3. 2. The hydrogen resistant material according to claim 1, wherein the copper alloy has a Ni content of more than 20.0 mass % and not more than 30.0 mass %, and the hydrogen resistant material exhibits a Young's modulus of more than 140 GPa.

4. 2. The hydrogen-resistant material according to claim 1, wherein the hydrogen-resistant material exhibits a 0.2% proof stress of 520 MPa or more in both an air atmosphere and a hydrogen atmosphere of 90 MPa or more and 120 MPa or less.

5. The hydrogen-resistant material has a resistance of 16 J / cm when measured by a V-notch Charpy impact test in an air atmosphere. ２ The hydrogen-resistant material according to claim 1, which exhibits a Charpy impact value of at least 100 kJ / cm2.

6. A hydrogen-resistant structural part manufactured from the hydrogen-resistant material according to any one of claims 1 to 5.

7. 7. The hydrogen-resistant structural part according to claim 6, wherein the hydrogen-resistant structural part is at least one selected from the group consisting of vessels, piping, valves, and joints, which are in direct contact with high-pressure hydrogen, and components of hydrogen compressors.

8. 8. The hydrogen-resistant structural part according to claim 7, wherein the hydrogen-resistant structural part is a component of the hydrogen compressor, and the component of the hydrogen compressor is at least one selected from the group consisting of a piston and a cylinder of a reciprocating compressor, a rotor and a casing of a rotary compressor, an impeller of an axial compressor, and an impeller and a shaft of a centrifugal compressor.

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