Hydrogen-resistant material and hydrogen-resistant structural member

Abstract

Provided is a hydrogen-resistant material which combines the material strength and fracture toughness required for a structural member that operates in a hydrogen atmosphere, and which does not deteriorate or does not easily deteriorate in the hydrogen atmosphere. The hydrogen-resistant material is used for processing a hydrogen-resistant structural member used for operating in a hydrogen atmosphere, and is composed of a beryllium-copper alloy containing 0.2-2.7 mass% of Be and 0.2-2.5 mass% in total of at least one element selected from the group consisting of Co, Ni and Fe, the remainder being Cu and unavoidable impurities, and the total content of Cu, Be, Co, Ni and Fe being 99.0 mass% or more of the beryllium-copper alloy. The hydrogen-resistant material exhibits a tensile strength of 700 MPa or more, a relative reduction in area (RRA) of 0.80 or more, and a fracture toughness value KIC of 50 MPa.m < 1 / 2 > or more, respectively, in an air atmosphere and a hydrogen atmosphere, respectively, by a low strain rate tensile test in the air atmosphere and the hydrogen atmosphere.

Description

Technical Field

[0001] The invention relates to hydrogen-resistant materials and hydrogen-resistant structural components. Background Art

[0002] In recent years, demand for hydrogen as a fuel for fuel cell vehicles, power plants, and other applications has rapidly increased. Hydrogen, as a fuel, comes into direct contact with containers and equipment components during production, transportation, storage, and use. Many metal materials are susceptible to hydrogen embrittlement, necessitating careful consideration during use. Components operating in the presence of hydrogen, in particular, require high strength and toughness, necessitating consideration of hydrogen embrittlement resistance.

[0003] Examples of components operating in the presence of hydrogen include components of hydrogen compressors, such as the pistons and cylinders of reciprocating compressors, the rotors and housings 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 commonly used for these structural components, especially the operating parts. However, due to hydrogen embrittlement, these components are typically operated within low stress ranges.

[0004] For hydrogen compressors, in order to cope with the rapid increase in demand for hydrogen, further high performance is required. For example, 1) with the high-speed rotation of the shaft and impeller, high performance, a reduction in the number of connections of the hydrogen compressor and a reduction in the number of impellers are required. In addition, 2) in order to suppress vibration during high-speed rotation, the shaft and impeller are required to maintain high rigidity. Furthermore, 3) in the use of green hydrogen production, in order to utilize the unstable energy supply of sunlight and wind power, intermittent operation such as DSS (Daily Start & Stop) is required. However, structural materials made of chromium-molybdenum steel have hydrogen embrittlement, and therefore are still insufficient from the perspective of 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 Gazette No. 6755521) discloses a hydrogen-resistant component used in a state of contact with hydrogen, and the heat exchange component discloses a beryllium copper alloy containing Be in an amount of 0.20% by mass or more and 2.70% by mass or less, and 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 Publication No. 2021-115631) discloses a method for manufacturing a hydrogen-resistant component with good hydrogen embrittlement resistance, and discloses a method of immersing the surfaces of first and second beryllium copper alloy components in an alkaline solution, boiling the surfaces of these copper alloy components in an organic acid solution such as formic acid, and heating and pressurizing the first and second copper alloy components to join them. Patent Document 3 (WO2022 / 149561) discloses a copper alloy joint body composed of a plurality of age-hardening copper alloy components that are diffusion-bonded to each other and subjected to solution treatment and aging treatment. This copper alloy joint body, including the joint portion, has excellent hydrogen embrittlement resistance and high tensile strength. Specifically, Patent Document 3 discloses a copper alloy joint body that has a strain rate of 5×10 -5 s -1 The following range (e.g. 5×10 -5 s -1 ) in a slow strain rate tensile (SSRT: Slow Strain Rate Tensile) test conducted in hydrogen, the tensile strength in hydrogen was 520 MPa or more, and the RRA (relative reduction of area) was 0.8 or more.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 6755521

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2021-115631

[0010] Patent Document 3: WO2022 / 149561

[0011] Non-patent literature

[0012] Non-Patent Document 1: Nagao Matsunaga, Junichiro Yamabe, and Saburo Matsuoka, “Proposal of Strength Design Guidelines for Chromium-Molybdenum Steel Used in High-Pressure Hydrogen Environments,” Surface Science, Vol. 36, No. 11, pp. 562-567, 2015

[0013] Non-Patent Document 2: Saburo Matsuoka, Nagaio Matsunaga, Junichiro Yamabe, Shigeru Hamada, and Takashi Iijima, “Various Strength Properties and Design Principles of Low-Alloy Steels SCM435 and SNCM439 in 115 MPa Hydrogen,” Proceedings of the Japan Society of Mechanical Engineers, Vol. 83, No. 854, pp. 1-20, 2017 [DOI: 10.1299 / transjsme.17-00264] Summary of the Invention

[0014] As mentioned above, structural materials made of chromium-molybdenum steel have hydrogen embrittlement, so they are not sufficient for working under high load stress in a hydrogen atmosphere, especially intermittent work and high-speed rotation. For example, the currently used SCM435 exhibits excellent fracture toughness in the atmosphere, but it has been confirmed that hydrogen degradation occurs and is not suitable for intermittent work that causes fatigue. Therefore, beryllium copper alloys that are not easily degraded in a hydrogen atmosphere are expected to be candidates for alternative materials to chromium-molybdenum steel. However, the raw material strength and fracture toughness required for rotating structures such as shafts and impellers are in a trade-off relationship. Therefore, it is desired to have a hydrogen-resistant material that takes into account both the raw material strength and fracture toughness required for structural components working in a hydrogen atmosphere, and these properties are not easily reduced in a hydrogen atmosphere (i.e., excellent hydrogen embrittlement resistance).

[0015] The present inventors have discovered that by overaging a beryllium copper alloy of a specified composition, it is possible to provide a hydrogen-resistant material that achieves both the raw material strength and fracture toughness required for structural members operating in a hydrogen atmosphere, and in which these properties are not or are unlikely to be degraded in a hydrogen atmosphere (i.e., exhibits excellent resistance to hydrogen embrittlement).

[0016] Therefore, an object of the present invention is to provide a hydrogen-resistant material that satisfies both the material strength and fracture toughness required for structural members operating in a hydrogen atmosphere and in which these properties are not degraded or are unlikely to degrade in a hydrogen atmosphere (i.e., have excellent hydrogen embrittlement resistance).

[0017] According to the present invention, the following aspects are provided.

[0018] [Method 1]

[0019] A hydrogen-resistant material for processing into a hydrogen-resistant structural component used in a hydrogen atmosphere, the hydrogen-resistant material comprising a beryllium copper alloy containing 0.20 to 2.70 mass% of Be and a total of 0.20 to 2.50 mass% of at least one selected from Co, Ni, and Fe, with the balance consisting of Cu and unavoidable impurities, wherein the total content of Cu, Be, Co, Ni, and Fe is not less than 99.0 mass% of the beryllium copper alloy;

[0020] The hydrogen resistant material was subjected to the conditions of atmospheric atmosphere and 115 MPa hydrogen atmosphere respectively by straining at a strain rate of 5×10 -5 s-1 The following low strain rate tensile test showed a tensile strength of more than 700 MPa;

[0021] The hydrogen resistant material exhibits a relative reduction of area (RRA) of 0.80 or greater as determined by the low strain rate tensile test;

[0022] The hydrogen resistant material exhibits a hydrogen resistance of 50 MPa·m in the air atmosphere and 115 MPa hydrogen atmosphere. 1 / 2 The fracture toughness value K above IC .

[0023] [Method 2]

[0024] The hydrogen-resistant material according to embodiment 1, wherein the beryllium copper alloy has a Be content of 1.60 to 2.70 mass%, a total Co and Ni content of 0.20 mass% or more, a total Cu, Ni, and Fe content of 0.60 mass% or less, and a total Cu, Be, Co, Ni, and Fe content of 99.5 mass% or more.

[0025] [Method 3]

[0026] The hydrogen resistant material according to embodiment 1 or 2, wherein the hydrogen resistant material exhibits a V-notch Charpy impact strength of 21 J / cm 2 Charpy impact values ​​above.

[0027] [Method 4]

[0028] The hydrogen resistant material according to embodiment 3, wherein the Charpy impact value is 30 J / cm 2 above.

[0029] [Method 5]

[0030] The hydrogen resistant material according to any one of aspects 1 to 4, wherein the hydrogen resistant material exhibits a 0.2% yield strength of 520 MPa or higher in both the air atmosphere and the hydrogen atmosphere at 115 MPa.

[0031] [Method 6]

[0032] A hydrogen-resistant structural component is made of the hydrogen-resistant material according to any one of aspects 1 to 5.

[0033] [Method 7]

[0034] The hydrogen-resistant structural component according to embodiment 6 is at least one selected from a container that comes into direct contact with high-pressure hydrogen (e.g., a container for storing high-pressure hydrogen), a pipe, a valve and a joint, and a component of a hydrogen compressor.

[0035] [Method 8]

[0036] A hydrogen-resistant structural component according to method 7, wherein the hydrogen-resistant structural component is a constituent component of the hydrogen compressor, and the constituent component of the hydrogen compressor is at least one selected from the piston and cylinder of a reciprocating compressor, the rotor and casing of a rotary compressor, the impeller of an axial compressor, and the impeller and shaft of a centrifugal compressor. DETAILED DESCRIPTION

[0037] Hydrogen-resistant materials

[0038] The hydrogen-resistant material of the present invention is a material for processing into hydrogen-resistant structural components for use in a hydrogen atmosphere (especially for use in operation). Preferred examples of hydrogen-resistant structural components for use in a hydrogen atmosphere include containers that are in direct contact with high-pressure hydrogen (for example, containers for storing high-pressure hydrogen), piping, valves, and joints. In addition, preferred examples of hydrogen-resistant structural components for use in operation in a hydrogen atmosphere include various components of hydrogen compressors (for example, pistons and cylinders of reciprocating compressors, rotors and housings of rotary compressors, impellers of axial compressors, and especially impellers and shafts of centrifugal compressors), but are not limited thereto. The hydrogen-resistant material is composed of a beryllium copper alloy. The beryllium copper alloy contains 0.20 to 2.70 mass% of Be and a total of 0.20 to 2.50 mass% of at least one selected from Co, Ni, and Fe, with the remainder being composed of Cu and unavoidable impurities, and the total content of Cu, Be, Co, Ni, and Fe is 99.0 mass% or more of the beryllium copper alloy. Furthermore, for the hydrogen resistant material, (i) the strain rate was 5×10 -5 s -1 The following low strain rate tensile test was conducted, and (ii) a tensile strength of 700 MPa or more was exhibited, and (iii) a relative reduction of area (RRA) of 0.80 or more was exhibited as determined by the above low strain rate tensile test, and (iv) a tensile strength of 50 MPa·m in air atmosphere and 115 MPa in hydrogen atmosphere. 1 / 2 The fracture toughness value K above IC These characteristics are achieved by overaging the beryllium copper alloy of the above composition. That is, the strength of the age-hardenable beryllium copper alloy increases with the aging treatment, but even if the peak strength is exceeded, if the aging treatment is continued and the alloy is in an overaged state, the strength will decrease to some extent, but the Charpy impact value and fracture toughness value K ICIt has been confirmed that these properties are significantly reduced in other materials such as chromium-molybdenum steel in the presence of hydrogen. In contrast, the present inventors have confirmed in experiments that the beryllium copper alloy of the above composition does not reduce these properties even in a hydrogen atmosphere. This beryllium copper alloy can provide a hydrogen-resistant material that achieves both the material strength and fracture toughness required for structural components operating in a hydrogen atmosphere, and in which these properties are not reduced or are unlikely to be reduced in a hydrogen atmosphere (i.e., has excellent hydrogen embrittlement resistance).

[0039] That is, as mentioned above, chromium-molybdenum steel structural materials have hydrogen embrittlement. Therefore, in the presence of hydrogen, especially when used under conditions such as stress load unloading, the reduction in strength and toughness has a greater impact on the reliability of the components. In this regard, it is insufficient. Therefore, in Patent Document 1 (Japanese Patent No. 6755521), beryllium copper alloy aging materials that do not deteriorate in hydrogen atmosphere are expected to be a candidate for chromium-molybdenum steel replacement. However, the material strength (e.g., tensile strength) and fracture toughness (e.g., fracture toughness value K) required for rotating structures such as shafts and impellers are not in good condition. IC ) are in a trade-off relationship. Therefore, it has been difficult to achieve a hydrogen-resistant material that achieves both the strength and fracture toughness required of components operating in a hydrogen atmosphere, while also stabilizing these properties in a hydrogen atmosphere (i.e., exhibiting excellent resistance to hydrogen embrittlement). The present invention effectively eliminates this problem.

[0040] The beryllium copper alloy constituting the hydrogen-resistant material of the present invention contains 0.20 to 2.70 mass% Be and a total of 0.20 to 2.50 mass% of at least one selected from Co, Ni, and Fe, with the balance consisting of Cu and unavoidable impurities. The total content of Cu, Be, Co, Ni, and Fe accounts for at least 99.0 mass% of the beryllium copper alloy. Preferred examples of beryllium alloys meeting this composition include beryllium copper 25 alloy (hereinafter referred to as CuBe25), beryllium copper 165 alloy (hereinafter referred to as CuBe165), and beryllium copper 11 alloy (hereinafter referred to as CuBe11), and their compositions are as follows.

[0041] [Table 1]

[0042] Table 1 Composition of various beryllium copper alloys (mass %)

[0043] Alloy Type Be Ni Co+Ni Co+Ni+Fe margin JIS alloy number CuBe25 1.80～2.00 - 0.20 and above Below 0.60 Cu C1720 CuBe165 1.60～1.79 - 0.20 and above Below 0.60 Cu C1700 CuBe11 0.20～0.60 1.40～2.20 - - Cu C1751

[0044] Be imparts excellent basic properties (strength, workability, fatigue properties, heat resistance, corrosion resistance, and hydrogen embrittlement resistance) to copper alloys. The Be content in beryllium copper alloys, which constitute hydrogen-resistant materials, is 0.20 to 2.70 mass%, preferably 0.20 to 2.20 mass%, more preferably 1.60 to 2.00 mass%, and even more preferably 1.80 to 2.00 mass%. Within this range, the basic properties described above can be effectively achieved while avoiding the cost impact of excessive Be.

[0045] In beryllium copper alloys, Co, Ni, and / or Fe primarily contribute to suppressing the premature overprecipitation of the γ phase at grain boundaries in the high-strength C1720 and C1700 alloys shown in Table 1, and primarily contribute to improving mechanical properties through precipitation as beryllium compounds in the highly conductive C1751 alloy shown in Table 1. The total content of at least one element selected from Co, Ni, and Fe in the beryllium copper alloy constituting the hydrogen-resistant material is 0.20 to 2.50 mass%, preferably 0.20 to 2.20 mass%, and more preferably 0.20 to 0.60 mass%. Co is particularly preferred among Co, Ni, and Fe for suppressing the premature overprecipitation of the γ phase at grain boundaries.

[0046] The total content of Cu, Be, Co, Ni, and Fe in the beryllium copper alloy constituting the hydrogen-resistant material is 99.0% by mass or greater, preferably 99.5% by mass or greater, of the beryllium copper alloy. Therefore, the beryllium copper alloy contains substantially no components other than Cu, Be, Co, Ni, and Fe. Therefore, the remainder of the beryllium copper alloy other than Be, Co, Ni, and Fe can be said to consist of Cu and unavoidable impurities.

[0047] A particularly preferred beryllium copper alloy has a Be content of 1.60-2.00% by mass, a combined Co and Ni content of 0.20% by mass or greater, a combined Cu, Ni, and Fe content of 0.60% by mass or less, and a combined Cu, Be, Co, Ni, and Fe content of 99.5% by mass or greater. Examples of alloys meeting this composition include CuBe25 and CuBe165.

[0048] The hydrogen resistant material of the present invention is subjected to the conditions of air atmosphere and 115 MPa hydrogen atmosphere at a strain rate of 5×10 -5 s -1 Below (e.g. 5×10 -5 s -1) in a slow strain rate tensile (SSRT) test, the tensile strength is 700 MPa or more, preferably 780 MPa or more, and more preferably 850 MPa or more. This hydrogen-resistant material has high tensile strength not only in air but also in hydrogen atmosphere. The above tensile strength (as long as the desired fracture toughness value K can be obtained) IC ) is expected to be high, so its upper limit should not be specified, but it is typically below 1100 MPa, more typically below 1000 MPa. For the low strain rate tensile test, a test piece according to ASTME8M Specimen 4 is prepared, and the test is carried out according to the steps described in the examples described later in accordance with ASTM-G-142. Usually, in the low strain rate tensile test, the relative reduction in area (RRA) obtained by dividing the tensile strength and reduction in area in hydrogen by the tensile strength and reduction in area in a reference gas without the influence of hydrogen is used to evaluate hydrogen sensitivity. In the low strain rate tensile test, for example, at a strain rate of 5×10 -5 s -1 The low strain rate tensile test was performed under a hydrogen pressure of 115 MPa, assuming that the component was used in the presence of hydrogen. If the hydrogen pressure is higher, the amount of hydrogen that penetrates the material increases, so the test piece is more susceptible to hydrogen exposure, and hydrogen embrittlement can be evaluated more appropriately. In the tests related to the present application, the hydrogen characteristics were evaluated by calculating the relative reduction of area (RRA) according to the procedures described in the examples described below.

[0049] The hydrogen-resistant material of the present invention evaluated by the above-mentioned low strain rate tensile test thus 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 sometimes exceeds 1.0 due to errors or fluctuations in the measured value, so it is typically 1.10 or less, more typically 1.05 or less. The tensile strength of the hydrogen-resistant material is a value within the above range at room temperature or at a hydrogen pressure of 115 MPa, and its RRA also satisfies the value within the above range, which means that the hydrogen-resistant material has a strength suitable for hydrogen-resistant structural parts (especially rotating structures such as shafts and impellers), which is not easily reduced in a hydrogen atmosphere (i.e., not easily hydrogen embrittled). Therefore, from the viewpoint of tensile strength, it can be said that the hydrogen-resistant material of the present invention has excellent hydrogen embrittlement resistance.

[0050] Furthermore, the hydrogen resistant material of the present invention exhibits a hydrogen resistance of 50 MPa·m in air atmosphere and 115 MPa in hydrogen atmosphere. 1 / 2 Above, preferably 60 MPa·m 1 / 2 More than 65 MPa·m 1 / 2 The fracture toughness value K above ICThe hydrogen resistant material not only has a high fracture toughness value K in atmospheric atmosphere IC , and also has high fracture toughness value K in hydrogen atmosphere IC . Fracture toughness value K IC The upper limit should not be specified (as long as the desired tensile strength can be obtained), but is typically 200 MPa·m 1 / 2 Below, more typically 150 MPa·m 1 / 2 Below. Fracture toughness value K IC The static fracture toughness test K is measured according to ASTM E-399-90 according to the procedure described in the examples below. IC As mentioned above, the tensile strength and fracture toughness value K required for rotating structures such as shafts and impellers IC In a trade-off relationship, the hydrogen-resistant material of the present invention has a tensile strength that can be tolerated as a hydrogen-resistant structural component (especially a rotating structure such as a shaft or impeller) not only in an atmospheric atmosphere but also in a hydrogen atmosphere, and exhibits a good fracture toughness value K IC That is, a good fracture toughness value K IC The hydrogen resistant material of the present invention does not decrease or is not easily decreased in a hydrogen atmosphere (i.e., is not easily hydrogen embrittled). Therefore, it can be said that it has excellent hydrogen embrittlement resistance not only from the perspective of the above-mentioned tensile strength, but also from the perspective of fracture toughness.

[0051] The hydrogen resistant material of the present invention preferably exhibits a V-notch Charpy impact strength of 21 J / cm 2 Charpy impact value of more than 30J / cm 2 Although the Charpy impact value cannot be measured in a hydrogen atmosphere, it is related to the fracture toughness value K IC There is a correlation, and it has the advantage of being able to be measured cheaply. Such a high Charpy impact value means that the hydrogen-resistant material has high fracture toughness, thus improving the reliability of hydrogen-resistant structural parts (especially rotating structures such as shafts and impellers). Therefore, the upper limit of the Charpy impact value should not be specified, but considering the balance with the strength of the raw material, it is typically 120 J / cm 2 Below, more typically 100 J / cm 2 The V-notch Charpy impact test may be carried out according to the procedure described in the Examples described later in JIS Z 2242:2018.

[0052] The hydrogen-resistant material of the present invention preferably exhibits a 0.2% yield strength of 520 MPa or more in an atmospheric atmosphere and a hydrogen atmosphere of 115 MPa, more preferably 700 MPa or more. Such a high 0.2% yield strength in both an atmospheric atmosphere and a hydrogen atmosphere means that the hydrogen-resistant material has high reliability, and it does not decrease or is not easily decreased in a hydrogen atmosphere (that is, it is not easy to cause hydrogen embrittlement). Therefore, its upper limit should not be specified, but if the balance with the strength of the raw material is taken into account, it is typically 1000 MPa or less, more typically 900 MPa or less. The 0.2% yield strength can be measured by cutting a test piece from the hydrogen-resistant material in accordance with the ASTM E8M standard and performing a tensile test in the atmosphere or hydrogen atmosphere according to the steps described in the examples described later.

[0053] Manufacturing method

[0054] The hydrogen-resistant material of the present invention can be preferably manufactured by preparing a beryllium copper alloy of the above-mentioned composition using a known manufacturing method (e.g., see Patent Document 1) and subjecting it to an overaging treatment. For example, the hydrogen-resistant component can be manufactured through (1) a melt casting process, (2) a homogenization treatment 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) an overaging treatment process. The specific process is as follows.

[0055] (1) Melting and casting process

[0056] In this operation, as industrial method, generally after allocating raw materials, in high frequency furnace, melt and manufacture ingot by semi-continuous casting.In addition, also can adopt the melting, die casting method, low pressure casting method etc. utilizing EREMA furnace, and casting method is not particularly limited.The casting mold used in casting can be the casting mold made of pure copper, copper alloy or alloy steel.Melting atmosphere can be atmosphere, also can be the inactive atmosphere such as nitrogen, argon, helium as required.In the melting casting process, preferably the content of various impurities (such as S, P) is limited to be less than 0.01 quality %.

[0057] (2) Homogenization process

[0058] The purpose of this process is to homogenize the heterogeneous structure of the ingot by maintaining it at a high temperature. The homogenization treatment conditions vary depending on the composition. For example, for C1720 and C1700 described in Table 1 above, it is effective to maintain the treatment at a temperature range of 750 to 850°C for more than 4 hours and less than 24 hours. On the other hand, for C1751, it is effective to maintain the treatment at a temperature of 900 to 1000°C for more than 4 hours and less than 24 hours. At this time, if the treatment time at each temperature for each alloy is less than 4 hours, it is not enough to promote the diffusion of atoms such as Be. In addition, in the treatment of more than 24 hours at which a certain homogenization effect ends, no effect beyond that can be expected.

[0059] (3) Hot forging process, hot rolling process and / or hot extrusion process

[0060] The purpose of these processes is to destroy the casting structure of the ingot that has undergone homogenization treatment and recrystallize it, thereby improving the mechanical properties such as strength and elongation of the raw material after annealing, solution treatment and aging treatment (including overaging treatment) in the subsequent process, or processing it into the desired shape. At this time, the cumulative forging ratio and processing rate have a great influence on the degree of destruction of the casting structure. Hot forging materials are usually repeatedly upset and stretched many times. For example, in the forging ratio marked as 3S when extended to 3 times the length and 1 / 2U when upset to 1 / 2 the length, the reciprocal of the value at the time of elongation and the value at the time of upset are accumulated to mark the cumulative forging ratio. The larger the cumulative forging ratio, the more the casting structure is destroyed, and a fine and preferred forging structure can be obtained. In hot rolling and hot extrusion, the difference between the cross-sectional area of ​​the ingot and the cross-sectional area of ​​the rolled material or extruded material after processing becomes the processing rate. In hot rolling and hot extrusion, the higher the processing rate, the more the cast structure is destroyed, and a fine and preferred forged structure can be obtained. However, depending on the final product shape, there are restrictions on the processing rate. Therefore, in order to obtain a finer structure, the ingot is sometimes temporarily hot forged to destroy the cast structure, and then hot rolled or hot extruded again. In addition, the hot working temperature and speed of hot forging, hot rolling and hot extrusion are sometimes controlled to manage the crystal grain size during the solid solution treatment in the subsequent process. Alternatively, the same effect can be achieved by performing a heat treatment below the solid solution temperature after these processes.

[0061] (4) Solution treatment

[0062] In this process, a hot forging block, hot rolled material or hot extruded material is subjected to a solid solution treatment to obtain a solid solution material in which additives such as Be and Co are dissolved in a Cu matrix. Specifically, the hot forging block, hot rolled material or hot extruded material is heated in a prescribed solid solution treatment temperature range, maintained at a prescribed solid solution treatment temperature, and then water-cooled to obtain a solid solution material. Regarding the solid solution treatment temperature range, for C1720 or C1700, it is effective to maintain the treatment at a temperature of 720 to 850°C for substantially more than 30 minutes. On the other hand, for C1751, it is effective to maintain the treatment at 900 to 1000°C for substantially more than 30 minutes. In industry, it is usually kept in a furnace that has reached the above-mentioned set temperature for about 2 to 5 hours before water cooling.

[0063] (5) Cold working

[0064] In this process, cold working is applied to the solid solution material to obtain a solid solution cold worked material. Specifically, in the case of a solid solution material of a forged material, cold forging is usually performed, in the case of a solid solution material of a rolled material, cold rolling is usually performed, and in the case of a solid solution material of an extruded material, cold drawing is usually performed. By performing cold working, the density of dislocations after solid solutionization increases, increasing the nuclei that become the starting point of aging precipitation. Thus, in addition to the increase in strength during peak aging, an improvement in the balance between strength and toughness can be expected during overaging.

[0065] (6) Over-aging treatment

[0066] In this step, the solution cold worked material is held at a predetermined age hardening temperature for a predetermined time to precipitate a precipitate phase and obtain an aged material. The precipitation phase of beryllium copper at this time changes as follows: (a) GP zone → (b) γ" phase (crystal structure: BCT (body-centered tetragonal)) → (c) γ1' phase (crystal structure: BCM (body-centered monoclinic)) → (d) γ1 phase (crystal structure: BCT (body-centered tetragonal)) → (e) γ' phase (crystal structure: BCT (body-centered tetragonal)) → (f) γ phase (crystal structure: BCC (body-centered cubic)). The treatment temperature for peak aging conditions to achieve high strength and hardness is 250-340°C for C1720 or C1700, and 430-500°C for C1751. The aging treatment time at these treatment temperatures is preferably 15 minutes to 24 hours or less. During this peak aging, the precipitated phase passes through the (a) GP zone and the (b) γ" phase, and the majority is almost exclusively the (c) γ1' phase. The tensile strength and hardness are highest in this precipitated phase, but the toughness is insufficient. However, if overaging is performed at a higher temperature, the phase changes to (d)γ1 phase → (e)γ' phase → (f)γ phase, and although the strength and hardness decrease, the toughness improves. The present inventors have previously confirmed that beryllium copper does not undergo hydrogen embrittlement during peak aging (see Patent Document 1), but the hydrogen characteristics of the (d)γ1 phase, (e)γ' phase, and (f)γ phase generated during overaging had not been confirmed at the time, and this is a new characteristic discovered by the present inventors.

[0067] Hydrogen-resistant structural components

[0068] The hydrogen-resistant material of the present invention has both the raw material strength and fracture toughness required for structural components used in a hydrogen atmosphere, especially structural components working in a hydrogen atmosphere, and these properties do not decrease or are not easily decreased in a hydrogen atmosphere (i.e., excellent hydrogen embrittlement resistance). Therefore, the hydrogen-resistant material of the present invention is suitable for processing into hydrogen-resistant structural components used in a hydrogen atmosphere (especially for working), and is particularly suitable for hydrogen-resistant structural components used for intermittent work and high-speed rotation that are prone to fatigue in a hydrogen atmosphere. As preferred examples of such hydrogen-resistant structural components, in addition to containers that are in direct contact with high-pressure hydrogen (such as containers for storing high-pressure hydrogen), piping, valves and joints, various components of hydrogen compressors (such as pistons and cylinders of reciprocating compressors, rotors and housings of rotary compressors, impellers of axial compressors, especially impellers and shafts of centrifugal compressors) can also be cited, but are not limited to these.

[0069] Example

[0070] The present invention is further described in detail by the following examples.

[0071] Examples 1a and 1b (Compare)

[0072] (1) Preparation of hydrogen-resistant materials

[0073] Raw materials of the CuBe25 (JIS C1720) alloy composition shown in Table 2 were weighed, melted, and cast to produce CuBe25 alloy ingots. After 8 hours of standing (homogenization annealing) at 780°C, the ingots were hot forged with a cumulative forging ratio of 18 to produce forged blocks. After solutionizing the forged blocks with water cooling from 780°C, they were cold worked 40% to produce solution-treated cold-worked materials. The resulting solution-treated cold-worked materials were aged at 315°C for 3 hours to produce hydrogen-resistant peak-aged materials.

[0074] The forging ratio is denoted as 3S when the length is extended to 3 times, and 1 / 2U when the length is upset. The cumulative forging ratio is calculated by accumulating the reciprocal of the values ​​at the time of extension and the values ​​at the time of upset.

[0075] (2) Evaluation of hydrogen-resistant materials

[0076] The prepared hydrogen-resistant material was subjected to various evaluations as follows. The results are shown in Table 3.

[0077] <Slow strain rate tensile test (SSRT)>

[0078] The hydrogen-resistant material was cut out and a test piece was made according to ASTM E8M Specimen 4. The low strain rate tensile test was carried out in accordance with ASTM-G-142 at a displacement speed of 0.001 mm / sec (strain rate of 0.00005 / sec) in an air atmosphere or a 115 MPa hydrogen atmosphere at room temperature. The low strain rate tensile strength was measured in each atmosphere in this manner. In addition, the cross-sectional reduction ratio RA of the test piece obtained in the low strain rate tensile test in each atmosphere was calculated by the following formula:

[0079] RA=(A0-A1) / A0

[0080] Where A0 is the cross-sectional area of ​​the test piece before the low strain rate tensile test, and A1 is the cross-sectional area of ​​the necking fracture site after the low strain rate tensile test.

[0081] By measuring the area reduction ratio RA under 115 MPa hydrogen atmosphere H2 Divide by the area reduction ratio RA under atmospheric atmosphere Air (That is, by finding the ratio RA H2 / RA Air ) is used to calculate RRA (relative reduction of area), which is an indicator for evaluating hydrogen embrittlement properties.

[0082] <Vickers Hardness>

[0083] To measure the Vickers hardness of the hydrogen-resistant material, a Vickers hardness test was performed in accordance with JIS Z 2244: 2009. The test force was 4.9 N (hardness symbol HV0.5).

[0084] <Charpy impact test>

[0085] To measure the Charpy impact value of hydrogen-resistant materials, a Charpy impact test in accordance with JIS Z 2242:2018 was conducted. The Charpy impact test was conducted by processing the hydrogen-resistant material to produce a V-notch test piece specified in JIS Z 2242:2018 (having a square cross-section of 55 mm in length and 10 mm on each side, with a V-notch at the center of the length, a notch angle of 45°, a notch depth of 2 mm, and a notch bottom radius of 0.25 mm). The Charpy impact value (absorbed energy) was measured in an air atmosphere at room temperature using a Charpy impact tester (Automatic Charpy Impact Tester CI-500D, manufactured by Tokyo Hyoki Testing Co., Ltd.).

[0086] <Fracture toughness test>

[0087] For hydrogen resistant materials, the K value is measured as a static fracture toughness test in accordance with ASTM E-399-90 in air atmosphere or 115 MPa hydrogen atmosphere at room temperature. IC Test to determine the fracture toughness value K of hydrogen resistant materials IC .

[0088] <0.2% yield strength>

[0089] The 0.2% yield strength of hydrogen-resistant materials is determined based on the stress-strain curve obtained from the aforementioned low-strain rate tensile test conducted in air or a 115 MPa hydrogen atmosphere at room temperature. Specifically, the slope (elastic modulus) of any point in the stress-strain curve obtained from the tensile test in air or a 115 MPa hydrogen atmosphere is determined, and a straight line is drawn. This straight line is then offset to 0.2% strain, and the value at the intersection of the offset line and the stress-strain relationship is used as the 0.2% yield strength.

[0090] Example 2 (Compare)

[0091] Materials were prepared and evaluated in the same manner as in Examples 1a and 1b, except that the solution cold worked material was aged at 340°C for 6 hours to obtain an overaged material. The results are shown in Table 3.

[0092] Example 3

[0093] Materials were prepared and evaluated in the same manner as in Examples 1a and 1b, except that the solution cold worked material was aged at 390°C for 3 hours to obtain an overaged material. The results are shown in Table 3.

[0094] Example 4

[0095] Materials were prepared and evaluated in the same manner as in Examples 1a and 1b, except that the solution cold worked material was aged at 390°C for 6 hours to obtain an overaged material. The results are shown in Table 3.

[0096] Example 5

[0097] Materials were prepared and evaluated in the same manner as in Examples 1a and 1b, except that the solution cold worked material was aged at 390°C for 9 hours to obtain an overaged material. The results are shown in Table 3.

[0098] Example 6

[0099] Materials were prepared and evaluated in the same manner as in Examples 1a and 1b, except that the solution cold worked material was aged at 430°C for 3 hours to obtain an overaged material. The results are shown in Table 3.

[0100] Example 7

[0101] Materials were prepared and evaluated in the same manner as in Examples 1a and 1b, except that the solution cold worked material was aged at 410°C for 18 hours to obtain an overaged material. The results are shown in Table 3.

[0102] Example 8 (Compare)

[0103] Using raw materials having the alloy composition of CuBe165 (JIS C1700) shown in Table 2, the same procedures as in Examples 1a and 1b were followed to obtain a solution cold worked material. This material was then aged at 315°C for 3 hours to obtain a peak aged material. The resulting material was subjected to various evaluations in the same manner as in Examples 1a and 1b. The results are shown in Table 3.

[0104] Example 9

[0105] Using raw materials having the alloy composition of CuBe165 (JIS C1700) shown in Table 2, the same procedures as in Examples 1a and 1b were followed to obtain a solution cold worked material. This material was then aged at 370°C for 21 hours to obtain an overaged material. The thus obtained material was subjected to various evaluations in the same manner as in Examples 1a and 1b. The results are shown in Table 3.

[0106] Example 10

[0107] Using raw materials having the alloy composition of CuBe165 (JIS C1700) shown in Table 2, the same procedures as in Examples 1a and 1b were followed to obtain a solution cold worked material. This material was then aged at 370°C for 27 hours to obtain an overaged material. The thus obtained material was subjected to various evaluations in the same manner as in Examples 1a and 1b. The results are shown in Table 3.

[0108] Example 11

[0109] Using raw materials having the alloy composition of CuBe165 (JIS C1700) shown in Table 2, the same procedures as in Examples 1a and 1b were followed to obtain a solution cold worked material. This material was then aged at 390°C for 9 hours to obtain an overaged material. The resulting material was subjected to various evaluations in the same manner as in Examples 1a and 1b. The results are shown in Table 3.

[0110] Example 12

[0111] Using raw materials having the alloy composition of CuBe165 (JIS C1700) shown in Table 2, the same procedures as in Examples 1a and 1b were followed to obtain a solution cold worked material. This material was then aged at 410°C for 6 hours to obtain an overaged material. The resulting material was subjected to various evaluations in the same manner as in Examples 1a and 1b. The results are shown in Table 3.

[0112] Example 13

[0113] Using raw materials having the alloy composition of CuBe165 (JIS C1700) shown in Table 2, the same procedures as in Examples 1a and 1b were followed to obtain a solution cold worked material. This material was then aged at 430°C for 9 hours to obtain an overaged material. The resulting material was subjected to various evaluations in the same manner as in Examples 1a and 1b. The results are shown in Table 3.

[0114] Example 14

[0115] Raw materials having the alloy composition of CuBe11 (JIS C1751) shown in Table 2 were weighed, melted, and cast to produce an ingot of CuBe11 alloy. This ingot was subjected to the same steps as in Examples 1a and 1b to obtain a forged block. This forged block was solution-finished by water cooling starting at 850°C and then subjected to 40% cold working to produce a solution-finished cold-worked material. The resulting material was subjected to various evaluations in the same manner as in Examples 1a and 1b. The results are shown in Table 3.

[0116] Examples 15a-15c (Compare)

[0117] For comparison, as data for chromium-molybdenum steel (SCM435), Figure 2(b) and Table 1 of Non-Patent Document 1 (Matsunosuke Matsunaga, Junichiro Yamabe, and Saburo Matsuoka, “Proposal of strength design guidelines for chromium-molybdenum steel for use in high-pressure hydrogen environments,” Surface Science, Vol. 36, No. 11, pp. 562-567, 2015) and Table 5 and the values ​​recorded in Figure 5 of Non-Patent Document 2 (Matsuoka Saburo, Matsunaga Matsunaga, Junichiro Yamabe, Shigeru Hamada, and Takashi Iijima, “Various strength characteristics and design guidelines for low-alloy steels SCM435 and SNCM439 in 115 MPa hydrogen,” Proceedings of the Japan Society of Mechanical Engineers, Vol. 83, No. 854, pp. 1-20, 2017 [DOI: 10.1299 / transjsme.17-00264]) are shown in Table 3.

[0118] Example 16 (Compare)

[0119] For comparison, Table 3 shows the numerical values ​​described in Table 5 and FIG. 5 of Non-Patent Document 2 as data for nickel-chromium-molybdenum steel (SNCM439).

[0120] [Table 2]

[0121] Table 2

[0122]

[0123] [Table 3]

[0124]

[0125] The following supplements the evaluation items shown in Table 3.

[0126] In fracture toughness testing, if the value measured in the presence of hydrogen is 20% or more lower than the value measured in the atmosphere, it is considered that deterioration has occurred in the presence of hydrogen. While there are cases where the value measured in the presence of hydrogen exceeds the value measured in the atmosphere, in principle, the properties do not improve in the presence of hydrogen, so this is considered to be a measurement error and no change in the hydrogen properties.

[0127] The relative reduction of area RRA is defined as the reduction of area of ​​the test material in the presence of hydrogen (% reduction in the area of ​​the fractured portion at the time of fracture) H2 The reduction in area of ​​the test material under the atmosphere (the percentage reduction in the area of ​​the fractured portion at the time of fracture) is defined as RA. Air When , it is defined as RA H2 / RA AirWhen the RRA is 0.8 or less, it is determined that degradation has occurred in hydrogen gas, and the material cannot be used in the presence of hydrogen. Sometimes a value exceeding 1.0 is measured, but this is not due to improved properties in the presence of hydrogen, but rather to test variations, indicating that hydrogen degradation has not occurred.

Claims

1. A hydrogen-resistant material for processing into a hydrogen-resistant structural component used in a hydrogen atmosphere. The hydrogen resistant material is made of beryllium copper alloy. The beryllium copper alloy contains 0.20 to 2.70 mass% of Be and a total of 0.20 to 2.50 mass% of at least one selected from Co, Ni, and Fe, with the balance being Cu and unavoidable impurities, and the total content of Cu, Be, Co, Ni, and Fe being 99.0 mass% or more of the beryllium copper alloy. The hydrogen resistant material was subjected to the conditions of atmospheric atmosphere and 115 MPa hydrogen atmosphere respectively by straining at a strain rate of 5×10 -5 s -1 The low strain rate tensile test conducted below showed a tensile strength of more than 700 MPa. The hydrogen resistant material exhibits a relative reduction of area (RRA) of 0.80 or greater as determined by the low strain rate tensile test, The hydrogen resistant material exhibits a hydrogen resistance of 50 MPa·m in the air atmosphere and 115 MPa hydrogen atmosphere. 1 / 2 The fracture toughness value K above IC .

2. The hydrogen resistant material according to claim 1, wherein The beryllium copper alloy has a Be content of 1.60 to 2.70 mass%, a total Co and Ni content of 0.20 mass% or more, a total Cu, Ni, and Fe content of 0.60 mass% or less, and a total Cu, Be, Co, Ni, and Fe content of 99.5 mass% or more.

3. The hydrogen resistant material according to claim 1, wherein The hydrogen resistant material exhibits a V-notch Charpy impact test under atmospheric conditions of 21 J / cm 2 Charpy impact values ​​above.

4. The hydrogen resistant material according to claim 3, wherein The Charpy impact value is 30 J / cm 2 above.

5. The hydrogen resistant material according to claim 1, wherein The hydrogen-resistant material exhibits a 0.2% yield strength of 520 MPa or more in an air atmosphere and in a hydrogen atmosphere at 115 MPa. A hydrogen-resistant structural component made of the hydrogen-resistant material according to any one of claims 1 to 5.

7. The hydrogen-resistant structural component according to claim 6, wherein: The hydrogen-resistant structural component is at least one selected from a container, a pipe, a valve, a joint, and a component of a hydrogen compressor that is in direct contact with high-pressure hydrogen.

8. The hydrogen-resistant structural component according to claim 7, wherein: The hydrogen-resistant structural component is a constituent member of the hydrogen compressor, and the constituent member 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 a housing of a rotary compressor, an impeller of an axial compressor, and an impeller and a shaft of a centrifugal compressor.

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