Copper alloy bonded body and method for producing same

Abstract

The invention provides a copper alloy bonded body and a method for manufacturing the same. The copper alloy bonded body is an age-hardening copper alloy bonded body which is resistant to solution treatment and aging treatment after bonding treatment and achieves extremely high bonding strength. The copper alloy bonded body is composed of a plurality of members made of an age-hardening copper alloy which are diffusion bonded to each other, the bonded body has been subjected to solution treatment and aging treatment, the beryllium content of the age-hardening copper alloy is 0.7 wt% or less, and (i) the bonding interface between the plurality of members disappears and the bonding interface between the plurality of members disappears. And / or (ii) the bonding interface of the plurality of members remains and the thickness of the oxide film at the bonding interface is 0-5.0 nm inclusive, and the tensile strength of the copper alloy bonded body including the bonding portion in hydrogen as measured in a low strain rate tensile test performed at a strain rate of 5 * 10 <-5 > s <-1 > or less is 520 MPa or more.

Description

[0001] This invention is a divisional application of application No. 202180071156.7 (international application No. PCT / JP2021 / 049009), filed on December 28, 2021, entitled "Copper Alloy Joint and Manufacturing Method Thereof". Technical Field

[0002] This invention relates to copper alloy joints and methods for manufacturing the same. Background Technology

[0003] Hydrogen refueling stations that supply hydrogen to fuel cell vehicles are equipped with precoolers for rapidly supplying high-pressure hydrogen cooled to approximately -45°C. That is, if hydrogen is rapidly filled into the tanks of fuel cell vehicles, the tank temperature will rise due to adiabatic compression, which is dangerous. Therefore, by precooling the hydrogen using a precooler during supply, high-pressure hydrogen can be safely and rapidly supplied to fuel cell vehicles. Therefore, in the heat exchanger, which is a key component of the precooler for hydrogen refueling stations, materials that obviously do not exhibit hydrogen embrittlement and possess tensile strength capable of withstanding high pressure and thermal conductivity capable of effective cooling are preferably used. Currently, high-pressure hydrogen stainless steel such as SUS316L (Ni equivalent material) is used in the heat exchanger of precoolers for hydrogen refueling stations to avoid hydrogen embrittlement, but there is still room for improvement from the viewpoint of tensile strength and thermal conductivity.

[0004] Beryllium copper, known for its high tensile strength and thermal conductivity, is suitable as a raw material for heat exchangers, and it has been confirmed that it does not undergo hydrogen embrittlement even under high-pressure hydrogen. For example, Patent Document 1 (Japanese Patent Application Publication No. 9-87780) discloses a beryllium copper alloy for heat exchangers, which, although not intended for hydrogen refueling stations, has a Be content of 1.0 to 2.5%, a combined Ni and Co content of 0.2 to 0.6%, and the balance consisting of Cu and unavoidable impurities. Furthermore, Patent Document 2 (Japanese Patent Application Publication No. 2017-145472) discloses a beryllium copper alloy with a Be content of 0.20 to 2.70 wt%, a combined Co, Ni, and Fe content of 0.20 to 2.50 wt%, and a combined Cu, Be, Co, Ni, and Fe content of 99 wt% or more, which is considered to have excellent resistance to hydrogen embrittlement, tensile strength, and thermal conductivity. In addition to not exhibiting hydrogen embrittlement (i.e., possessing hydrogen embrittlement resistance), beryllium copper alloys also have higher tensile strength (e.g., about 1.5 to 2.5 times) and higher thermal conductivity (e.g., about 7 to 16 times) than stainless steel for high-pressure hydrogen applications. Therefore, compared to stainless steel products, the size of heat exchangers for high-pressure hydrogen applications that cannot be achieved in low-purity, low-strength copper alloys can be significantly reduced (e.g., about one-quarter).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 9-87780

[0008] Patent Document 2: Japanese Patent Application Publication No. 2017-145472 Summary of the Invention

[0009] The heat exchanger of the precooler for hydrogen refueling stations has a structure formed by joining multiple layers of metal plates with slits or grooves to create a flow path for hydrogen supply and refrigerant passage. As a currently used method for joining stainless steel for high-pressure hydrogen, diffusion bonding is widely known: the surface oxide film is sublimated and removed during a depressurization and heating process towards the bonding temperature, and bonding pressure is applied to the joint at a high temperature below the melting point to bond the stainless steel plates together. However, for copper alloys, (i) a strong oxide film that is difficult to remove is easily formed under simple depressurization and heating, and / or (ii) even if the oxide film is removed before bonding, an oxide film easily reforms on the bonding surface (sealing surface) during the high vacuum heating process in the bonding process (and even at temperatures close to the bonding temperature, this oxide film is difficult to sublimate). When diffusion bonding is performed on this copper alloy using the same process, although a certain bonding strength is ensured, it is difficult to obtain a microstructure and strength equivalent to the base material. In particular, to achieve the extremely high strength of copper alloy components required for the aforementioned high-pressure heat exchanger applications, it is necessary to perform solution treatment and aging treatment on age-hardening copper alloys. However, diffusion joints of age-hardening copper alloys that do not ensure sufficient bond strength are prone to fracture at the joint due to their inability to withstand the severe thermal shock and dimensional changes accompanying solution treatment and aging treatment.

[0010] The inventors have obtained the following insight: by selectively using an age-hardening copper alloy with a beryllium content of 0.7% by weight or less, and after finishing the joint surface to a predetermined flatness and removing the oxide film, diffusion bonding (and homogenization treatment as needed) is performed, solution treatment and aging treatment can be carried out in a manner that makes the joint interface disappear (or even if not, makes the oxide film at the joint interface less than 5.0 nm thick), thereby providing a copper alloy joint with extremely high bonding strength.

[0011] Therefore, the object of the present invention is to provide a bonded body of an age-hardening copper alloy that achieves extremely high bond strength by resisting solution treatment and aging treatment after the bonding process.

[0012] According to one aspect of the present invention, a copper alloy joint is provided, comprising a plurality of age-hardening copper alloy components diffusely bonded together, wherein the copper alloy joint has undergone solution treatment and aging treatment.

[0013] The beryllium content of the aforementioned age-hardening copper alloy is less than 0.7% by weight, and

[0014] (i) The joint interface of the aforementioned components disappears, and / or

[0015] (ii) The joint interface of the above-mentioned components remains and the thickness of the oxide film at the joint interface is more than 0 nm and less than 5.0 nm.

[0016] According to another aspect of the present invention, a method for manufacturing a copper alloy joint is provided, the method comprising:

[0017] The process of preparing multiple components made of age-hardening copper alloy with a beryllium content of less than 0.7% by weight, whose surfaces to be joined are flat surfaces with a flatness of less than 0.1 mm and a ten-point average roughness Rzjis of less than 6.3 μm.

[0018] The process of removing the oxide film present on the surfaces to be joined of the above-mentioned components;

[0019] The process of forming an intermediate joint by hot pressing to diffusely join the above-mentioned multiple components;

[0020] The intermediate bond is subjected to a solution treatment process involving heating at 700-1100°C for 1 minute to 3 hours, followed by water cooling; and,

[0021] The intermediate bond that has undergone the above solution treatment is subjected to an aging treatment at 350~550°C for 30 minutes to 480 minutes.

[0022] According to another aspect of the invention, a hydrogen-resistant component made of Cothen copper (EN material numbers CW109C, CW111C; UNS alloy numbers C19010, C70250, AMPCO944, and AMPCO940) is provided. Alternatively, the application of Cothen copper in hydrogen-resistant components or a method for manufacturing hydrogen-resistant components using Cothen copper is provided. The inventors have confirmed that Cothen copper does not undergo hydrogen embrittlement even under high-pressure hydrogen. Attached Figure Description

[0023] Figure 1A This diagram illustrates the experimental steps for elemental analysis of oxide films formed on the surfaces of various copper alloys during heat treatment in a high-vacuum furnace. It conceptually represents the oxidation process and shows the locations of open and closed surfaces within the furnace where elemental analysis is performed, as well as the appearance of the samples.

[0024] Figure 1B According to Figure 1AThe experimental procedures shown illustrate the results of elemental analysis of oxide films formed on the surfaces (pickled surfaces, open surfaces, and / or sealed surfaces) of various copper alloys during heat treatment in a high-vacuum furnace. Specifically, XPS results are shown for beryllium copper 25 alloy, beryllium copper 165 alloy, beryllium copper 11 alloy, beryllium copper 10Zr alloy, beryllium copper 50 alloy, and chromium copper alloy.

[0025] Figure 1C According to Figure 1A The experimental procedures shown illustrate the results of elemental analysis of oxide films formed on the surfaces (pickled surfaces, open surfaces, and / or sealed surfaces) of various copper alloys during heat treatment in a high-vacuum furnace. Specifically, XPS results for Cohen copper AMPCO940 and Cohen copper AMPCO944 are presented.

[0026] Figure 2 These are optical microscope images at 200x, 500x, and 1000x magnification of the cross sections, including the joints, of the copper alloy joints of Examples 2, 30, 33, 43, and 46, which were prepared by solution treatment and aging treatment.

[0027] Figure 3 These are optical microscope images at 200x, 500x, and 1000x magnification of the cross sections including the joints of the copper alloy joints of Examples 26, 27, and 28, which were prepared by solution treatment and aging treatment.

[0028] Figure 4 These are optical microscope images at 200x, 500x, and 1000x magnification of the cross sections including the joints of the copper alloy joints of Examples 47 and 53, which were prepared by solution treatment and aging treatment.

[0029] Figure 5 The images show STEM images and EELS / EDX elemental distribution images of a cross-section including the joint surface of a copper alloy joint (CuBe11) in the diffusion-bonded state (without solution treatment or aging treatment) of Example 2.

[0030] Figure 6A The images show STEM images and EELS / EDX elemental distribution images of a cross section including the joint surface of a copper alloy joint (CuBe25) in the diffusion-bonded state (without solution treatment and aging treatment), Example 43 (Comparative).

[0031] Figure 6B yes Figure 6A STEM image (HAADF image) of a cross section including the joint surface of the copper alloy joint (CuBe25) shown.

[0032] Figure 6C yes Figure 6ASTEM image and EELS / EDX elemental distribution image of the cross section including the joint surface of the copper alloy joint (CuBe25).

[0033] Figure 7 The images show STEM images and EELS / EDX elemental distribution images of a cross section including the joint surface of a copper alloy joint (Coleon copper AMPCO940) of Example 47, which underwent solution treatment and aging treatment after diffusion bonding.

[0034] Figure 8 The images show STEM images and EELS / EDX elemental distribution images of a cross-section including the joint surface of a copper alloy joint (Coleon Copper AMPCO944) of Example 53, which underwent solution treatment and aging treatment after diffusion bonding.

[0035] Figure 9A This is a stress-stroke diagram of the low strain rate tensile test (SSRT) conducted in air or hydrogen on the copper alloy joint (CuBe11) of Example 2, which was prepared by solution treatment and aging treatment.

[0036] Figure 9B This is a stress-stroke diagram of the low strain rate tensile test (SSRT) conducted in air or hydrogen on the copper alloy joints (CuBe11) of Examples 17 and 18, which were prepared by solution treatment and aging treatment.

[0037] Figure 9C This is a stress-stroke diagram of a low strain rate tensile test (SSRT) conducted in air or hydrogen on beryllium copper 11 alloy or beryllium copper 25 alloy that has undergone solution aging treatment and is used as a bonding material.

[0038] Figure 9D This is a stress-stroke graph of Cohen copper AMPCO940, which has undergone solution aging treatment and is used as a bonding material, in air or hydrogen during a low strain rate tensile test (SSRT).

[0039] Figure 9E This is a stress-stroke graph of Cohen copper AMPCO944, which has undergone solution aging treatment and is used as a bonding material, in air or hydrogen during a low strain rate tensile test (SSRT).

[0040] Figure 10A This is a SEM image of the fracture surface of the copper alloy joint (CuBe11) of Example 17, which was prepared by solution treatment and aging treatment, after a low strain rate tensile test (SSRT) in air.

[0041] Figure 10B It is observation Figure 10AThe image shows a magnified SEM image of a specific location on the fracture surface.

[0042] Figure 11 This is an optical microscope image of a cross section including the joint of the joint sample of Example 62, which was prepared by homogenization at 980°C and has a flow path space. Detailed Implementation

[0043] Copper alloy joint

[0044] The copper alloy joint of the present invention comprises multiple age-hardening copper alloy components diffusely bonded together, and subjected to solution treatment and aging treatment. The beryllium content of the age-hardening copper alloy is 0.7% by weight or less. Furthermore, in this copper alloy joint, (i) the bonding interface of the multiple components disappears, and / or (ii) the bonding interface of the multiple components remains, and the thickness of the oxide film at the bonding interface is 0 nm or more and 5.0 nm or less. Thus, by selectively using an age-hardening copper alloy with a beryllium content of 0.7% by weight or less, and by performing solution treatment and aging treatment in a manner that makes the bonding interface disappear (or, even if not, makes the oxide film at the bonding interface 5.0 nm or less in thickness) (after homogenization treatment as needed), a copper alloy joint with extremely high bonding strength can be provided.

[0045] As described above, when diffusion bonding is performed on copper alloys that (i) easily develop a strong oxide film that is difficult to remove under simple reduced pressure and heating and / or (ii) reform an oxide film under high vacuum, although a certain bond strength is ensured, it is difficult to obtain the same microstructure and strength as the base material. In particular, in order to achieve the extremely high strength copper alloy components required for the aforementioned heat exchanger applications, it is necessary to perform solution treatment and aging treatment on age-hardening copper alloys. However, diffusion-bonded age-hardening copper alloys have the problem of being unable to withstand the severe thermal shock and dimensional changes accompanying solution treatment and aging treatment, resulting in fracture at the joint.

[0046] Regarding this, the above-described configuration according to the present invention effectively eliminates such problems, providing copper alloy joints with extremely high bonding strength. The reason for this is as explained in the inventors' verification tests described later, and is as follows: Specifically, by selectively using an age-hardening copper alloy with a beryllium content of 0.7% by weight or less, adjusting the flatness and surface roughness of the joint surface to suit diffusion bonding, and removing the oxide film from the joint surface, the joint interfaces of the copper alloy components are brought into close contact, and diffusion bonding is performed by pressurizing and heating. In this case, in age-hardening copper alloys with a beryllium content exceeding 0.7% by weight, the oxide film formed on the joint surface is either not formed or only very slightly formed, thus achieving a high-quality diffusion bond that can sufficiently withstand solution treatment and aging treatment.

[0047] However, it is known that stainless steel and pure copper can be bonded with high reliability via diffusion bonding. Stainless steel has a dense chromium oxide film forming on its surface under atmospheric conditions, providing strong weather resistance. However, this oxide film sublimates when heated to temperatures exceeding 700°C under high vacuum. Therefore, it is naturally removed during the heating process in diffusion bonding, easily resulting in an active stainless steel surface without an oxide film. Thus, good bonding without residual oxides or other foreign matter at the bonding interface can be achieved simply by applying pressure at the bonding temperature. Similarly, pure copper has a copper oxide (CuO) film on its surface, but this oxide decomposes during the holding period at the diffusion bonding temperature, allowing oxygen to diffuse into the copper matrix. Therefore, like stainless steel, good bonding without residual oxides or other foreign matter at the bonding interface is possible.

[0048] In experiments prior to completing this invention, the inventors confirmed that while conventional diffusion bonding of age-hardening copper alloys yields a certain bond strength, solution aging of the resulting bond often leads to bond strength deterioration and fracture. This phenomenon is particularly pronounced in beryllium copper 25 alloy (JIS C1720), known for achieving the highest strength among age-hardening copper alloys. The inventors hypothesize that this is due to residual oxide film on the bonding surface, which is not found in stainless steel or pure copper. To clarify the mechanism of this residual oxide film, further investigation was conducted... Figure 1A The following experiment is shown. Figure 1B and 1C Each alloy shown was machined into a plate with dimensions of 15mm × 15mm × 5mm. The top and bottom surfaces of the resulting test piece 10 (15mm × 15mm) were then polished to achieve a flatness of less than 0.1mm and a surface roughness Rzjis of less than 0.8μm. Before the test, the plate was cleaned with 30% nitric acid to remove the oxide film. Three test pieces 10 were prepared for each alloy. Figure 1A As shown, one of the test pieces 10 was placed in the bonding furnace while in contact with the vacuum atmosphere inside the furnace, and the remaining two test pieces 10 were placed in a stacked (as in the bonding surface in diffusion bonding) and tightly sealed state. After undergoing the same heat treatment as during bonding under various depressurization conditions inside the bonding furnace, they were removed. For the former, the surface in contact with the furnace atmosphere (hereinafter referred to as the furnace release surface) was argon etched, and for the latter, the surface of the test pieces that were tightly sealed together (hereinafter referred to as the sealing surface) was argon etched. At the same time, elemental analysis of the oxide film 12 on the surface was performed using an X-ray photoelectron spectroscopy analyzer (XPS, product name: Quantera SXM, manufactured by ULVAC-PHI).

[0049] Figure 1B and 1CThe results show the determination of the oxide film on each alloy after pickling, after heat treatment of the furnace release surface, and / or after heat treatment of the sealed surface. These results indicate that the oxide film on any alloy was completely removed by pickling, even at 5 × 10⁻⁶ mm. -5 Even under the high vacuum of Torr, a very thick oxide film forms. The degree of oxide film formation on the sealing surface, which is a problem in the bonding process, is confirmed as follows:

[0050] i) Alloys with a beryllium content of less than 0.7% by weight (beryllium copper 11 alloy, beryllium copper 50 alloy, beryllium copper 10Zr alloy, chromium copper alloy, Cohen copper AMPCO 940 and Cohen copper AMPCO 944) are subjected to a 5×10⁻⁶ molten metallurgy process. -5 When processed at the bonding temperature under the high vacuum of Torr (the vacuum achieved by continuous venting using a diffusion pump), no oxide film is formed, or only a very slight oxide film is formed.

[0051] ii) Even for alloys with a beryllium content of less than 0.7% by weight, at 1×10 -1 Even under a vacuum of around Torr, an oxide film can form due to oxygen penetrating the sealed surface; and

[0052] iii) Alloys with a beryllium content exceeding 0.7% by weight (beryllium copper 25 alloy and beryllium copper 165 alloy), even at 5×10 - 5 The process is carried out under high vacuum by Torr, and an oxide film is formed due to the oxygen penetrating the sealed surface.

[0053] The results above show that, due to the extremely high affinity of beryllium for oxygen, even with increased component tightness under high vacuum, it is difficult to suppress the formation of oxide film caused by oxygen intruding into the joint surface when the beryllium concentration is above a certain level. In order to prevent oxide film residue on the joint surface, the beryllium content must be considered when selecting raw materials.

[0054] The age-hardening copper alloy used in the copper alloy joints of the present invention is not particularly limited as long as the beryllium content is 0.7% by weight or less. Joints using beryllium copper alloys with a high Be content exceeding 0.7% by weight (e.g., beryllium copper 25 alloy (JIS alloy number C1720)) exhibit significant residual oxide film on the joint surface, making them unable to withstand solution treatment and aging treatment, and resulting in fracture at the joint after solution treatment or aging treatment. However, by selectively using age-hardening copper alloys with a low Be content of 0.7% by weight or less for diffusion bonding, copper alloy joints that are resistant to solution treatment and aging treatment and possess extremely high joint strength can be achieved. Examples of such age-hardening copper alloys include beryllium copper 11 alloy (JIS alloy number C1751, EN material number CW110C and UNS alloy number C17510), beryllium copper 10 alloy (EN material number CW104C and UNS alloy number C17500), beryllium copper CuCo1Ni1Be (EN material number CW103C), beryllium copper 14Z alloy, beryllium copper 50 alloy, beryllium copper 10Zr alloy, chromium copper (UNS alloy number C18200), and chromium zirconium copper (UNS alloy number C18200). The preferred age-hardening alloys are beryllium copper 11, beryllium copper 10, beryllium copper CuCo1Ni1Be, beryllium copper 14Z, beryllium copper 50, or beryllium copper 10Zr alloys, with beryllium copper 11 being the most preferred. These preferred age-hardening alloys not only achieve extremely high bond strength after solution aging, but also exhibit excellent resistance to hydrogen embrittlement and thermal conductivity, making them particularly advantageous as materials for heat exchangers in precoolers for hydrogen refueling stations. The compositions of the various copper alloys mentioned above are shown in Table 1 below.

[0055] [Table 1]

[0056]

[0057] As described above, the copper alloy joints of the present invention, which have undergone solution treatment and aging treatment, satisfy any one or both of the following conditions, which contributes to achieving high joint strength:

[0058] (i) The joint interface of multiple components disappears.

[0059] (ii) Residual oxide film at the interface of multiple components, wherein the thickness of the oxide film at the interface is greater than 0 nm and less than 5.0 nm.

[0060] The disappearance or presence of the joint interface is determined by observing the cross-section of the copper alloy joint, including the joint portion, using an optical microscope at 200-1000x magnification (e.g., refer to...). Figure 2 and Figure 3 The disappearance / residue of the bonding interface should be determined based on whether traces of the bonding surface of the copper alloy components before bonding remain. If grain boundary movement from the bonding surface occurs due to grain growth beyond the bonding interface, it is not considered a residual bonding interface. Therefore, in the case of residual bonding interfaces of multiple components, the thickness of the oxide film at the bonding interface is measured, and it is determined whether the thickness is greater than 0 nm and less than 5.0 nm. Regarding the thickness of the oxide film at the bonding interface, a cross-section containing the bonding interface can be observed using scanning transmission electron microscopy (STEM). An elemental distribution image of this cross-section is obtained using electron energy loss spectroscopy (EELS) / energy dispersive X-ray analysis (EDX). The oxide film and its thickness are determined by comparing the STEM image with the EELS / EDX elemental distribution image. It should be noted that the oxide film present at the bonding interface is not only a layered film but sometimes also a particle-like film (i.e., oxide particles). In this case, the height of the oxide particles is also included in the thickness of the oxide film. In summary, the presence or absence of a bonding interface can be confirmed using optical microscopy, which is relatively simple and inexpensive. On the other hand, STEM-EELS / EDX is a time-consuming and expensive analytical method. Therefore, when determining whether the above conditions (i) and / or (ii) are met, the following approach is preferred:

[0061] 1) Use an optical microscope to confirm whether the above condition (i) is met (if condition (i) is met, it is not necessary to confirm the oxide film).

[0062] 2) If the above condition (i) is not met, the thickness of the oxide film at the bonding interface is measured by STEM-EELS / EDX.

[0063] The thickness of the oxide film present at the bonding interface of the copper alloy joint of the present invention is 0 nm or more and 5.0 nm or less, preferably 0 nm or more and 4.0 nm or less, more preferably 0 nm or more and 3.0 nm or less, further preferably 0 nm or more and 2.0 nm or less, particularly preferably 0 nm or more and 1.5 nm or less, and most preferably 0 nm or more and 1.0 nm or less. If the oxide film is so thin, it can withstand solution aging treatment, similar to the case where the bonding interface disappears, and a copper alloy joint with extremely high bonding strength is obtained after aging treatment.

[0064] The copper alloy joint of the present invention may contain age-hardening copper alloy grains that have grown beyond the joint interface or at a location that was previously a joint interface (old joint interface). That is, it can be observed that the copper alloy joint of the present invention has a structure at the joint interface or old joint interface where the grains of the copper alloy component before jointing have reorganized and recrystallized after jointing, rather than being in the state of the initial joint interface. Because the copper alloy joint has such a joint microstructure, the joint strength becomes superior.

[0065] From the viewpoint of ensuring high bond strength and hydrogen resistance of the base material with equal strength, the copper alloy joint of the present invention preferably has no residual components from materials other than age-hardening copper alloy at the joint interface or at the former joint interface (old joint interface). Therefore, it is desirable that the copper alloy joint of the present invention does not contain solder or other bonding agents during the jointing process. That is, the copper alloy joint of the present invention is preferably composed only of age-hardening copper alloy.

[0066] The strength of the base material and the joint of the copper alloy joint after solution aging is preferably 520 MPa or more, more preferably 690 MPa or more. By achieving such strength, the copper alloy joint sufficiently meets the requirements for high-strength applications, primarily as a heat exchanger for a precooler in a hydrogen refueling station. Due to the high desired strength, an upper limit should not be specified, but the strength of the base material and the joint of the copper alloy joint of the present invention after solution aging, with a beryllium content of 0.7% by weight or less, is typically 895 MPa or less. The strength of the base material and the joint of the copper alloy joint before and after solution aging can be determined by preparing a test piece according to ASTM E8M Specimen 3 with the joint at the center of the test piece, and performing a tensile test on the test piece according to the procedure in ASTM E8M.

[0067] It is desirable for the base material of the joint containing the copper alloy joint to have a high thermal conductivity. Like electrical conduction, thermal conduction is based on the energy transfer of conduction electrons; therefore, there is a correlation between the two known as the Wiedemann-Frantz law, and thermal conductivity can be converted to electrical conductivity, which can be measured more easily. The thermal conductivity (and its equivalent electrical conductivity) of the base material of the joint containing the copper alloy joint is preferably 209 W / mK or higher (equivalent electrical conductivity of 50 IACS% or higher), more preferably 228 W / mK or higher (equivalent electrical conductivity of 55 IACS% or higher), and even more preferably 246 W / mK or higher (equivalent electrical conductivity of 60 IACS% or higher). Such a high thermal conductivity is advantageous for use in heat exchangers, resulting in extremely high heat exchange efficiency (for example, due to the excellent properties of hydrogen, the thermal conductivity of SUS316LNi equivalent used in current precooler heat exchangers is very low at 16 W / mK, leading to poor heat exchange efficiency, which is a challenge in its application). Because a high thermal conductivity is desired, its upper limit should not be specified. However, the thermal conductivity of the base material of the joint of the copper alloy joint containing the beryllium content of the present invention is typically 280 W / mK or less, i.e., the base material that can ensure the strength of the base material and the joint of 520 MPa or more.

[0068] The copper alloy joint including the joint is subjected to a strain rate of 5×10 -5 s -1 The following range (e.g., 5×10) -5 s -1 In the low strain rate tensile (SSRT) test conducted on the copper alloy, the tensile strength in hydrogen gas is preferably 520 MPa or higher, more preferably 690 MPa or higher. The copper alloy joint, including the joint, exhibits excellent resistance to hydrogen embrittlement and high tensile strength. This low strain rate tensile test is performed according to ASTM-G-142. For example, a shaped test piece (smooth test piece) can be used in the low strain rate tensile test. Typically, in the smooth test piece, hydrogen sensitivity is evaluated using the relative tensile strength (RTS) and relative reduction of area (RRA), which are obtained by dividing the tensile strength and reduction of area in hydrogen gas by the tensile strength and reduction of area in a reference gas without hydrogen influence. In the low strain rate tensile test of the smooth test piece, for example, a strain rate of 5 × 10⁻⁶ can be used. -5 s -1Measurements were performed. The experiment involved a 70 MPa-class FCV (fuel cell vehicle) and a hydrogen refueling station, with a low strain rate tensile test conducted at a hydrogen pressure exceeding 95 MPa. Higher hydrogen pressures resulted in increased hydrogen penetration into the material, making the test specimens more susceptible to the effects of hydrogen exposure and allowing for a more appropriate evaluation of hydrogen embrittlement. In the tests relevant to this application, shaped test specimens (smooth test specimens) were used, and relative tensile strength (RTS) and relative reduction of area (RRA) were used to evaluate hydrogen properties.

[0069] In the copper alloy joint including the joint, in the aforementioned low strain rate tensile test, when the tensile strength is 520 MPa or more, preferably 690 MPa or more, the relative reduction of area (RRA) is preferably 0.8 or more, more preferably 0.9 or more. Furthermore, the tensile strength (RTS) is preferably 0.8 or more, more preferably 0.9 or more. The tensile strength of the copper alloy joint including the joint is within the aforementioned range at ambient temperature or under hydrogen pressure of 95 MPa or more, and its RRA and RTS also satisfy the aforementioned range. This means that the copper alloy joint has high strength and excellent resistance to hydrogen embrittlement, and therefore is particularly suitable for use as a heat exchanger in a precooler for hydrogen refueling stations. Since high tensile strength is desirable, its upper limit should not be specified, but the tensile strength of the copper alloy joint of the present invention with a beryllium content of 0.7% by weight or less in the low strain rate tensile test at ambient temperature or under hydrogen pressure of 95 MPa or more is typically 895 MPa or less.

[0070] The copper alloy joint can also be configured to have a flow path space inside. In this case, the flow path space can be used as an internal space for the passage of media such as hydrogen and refrigerant. Therefore, the copper alloy joint with the flow path space is preferably used as a heat exchanger for a precooler in a hydrogen refueling station where multiple flow path spaces are desired for the passage of hydrogen and refrigerant respectively.

[0071] Manufacturing method

[0072] The copper alloy joint of the present invention can be manufactured by sequentially performing the following steps on multiple age-hardening copper alloy components: smoothing of the joint surface as needed (any step), removal of oxide film, hot pressing (diffusion bonding), homogenization treatment as needed (any step), solution treatment, and aging treatment. Details are as follows.

[0073] (a) Preparation of copper alloy components

[0074] First, multiple age-hardening copper alloy components for joining are prepared. The beryllium content of this age-hardening copper alloy is 0.7% by weight or less, and alloys as described above can be used. The uppermost and lowermost materials of the laminated joint manufactured as heat exchangers are preferably rolled or forged materials, and the multiple laminated materials other than the uppermost and lowermost materials, which may or may not have internal cooling water channels, are preferably rolled materials.

[0075] The copper alloy joint of the present invention preferably uses a copper alloy material that does not cause hydrogen degradation. Regarding copper alloy raw materials, it is known that, for example, in cupronickel (Cu-10%~30%), hydrogen degradation becomes significant when the Ni concentration is 20% or higher, and hydrogen degradation also occurs significantly in ductile copper (undeoxidized pure copper). Therefore, when selecting the copper alloy used in the copper alloy joint of the present invention, it is desirable to conduct low strain rate tensile tests (e.g., according to ASTM-G-142, setting the displacement velocity to 0.001 mm / sec (strain velocity 0.00005 / sec) in a smooth test piece) under both atmospheric and high-pressure hydrogen atmospheres (e.g., in 95 MPa hydrogen atmosphere), and to confirm a copper alloy material that does not cause hydrogen degradation by comparing the test results in atmospheric and high-pressure hydrogen atmospheres. For example, the copper alloy joint of the present invention preferably uses a copper alloy with a strain rate of 5 × 10⁻⁶ mm / sec. -5 s -1 The copper alloy component is manufactured with an RRA (relative reduction of area) of 0.8 or more in hydrogen, as measured in the low strain rate tensile test conducted below, and more preferably 0.9 or more.

[0076] Here, the multiple age-hardening copper alloy components used for joining need to have flat surfaces, the surfaces to be joined having a flatness of less than 0.1 mm and a ten-point average roughness Rzjis of less than 6.3 μm (preferably less than 2.0 μm). That is, as described above, in order to suppress re-oxidation of the joint surface during hot pressing (diffusion bonding) even after removing the oxide film on the surface of the joined components, it is necessary to ensure the tightness of the joint surface so that the oxygen atoms penetrating the joint surface under a high vacuum atmosphere are sufficiently reduced. This tightness can be ensured as long as the flatness and ten-point average roughness are within the above-mentioned range. When the joined components are rolled materials, the flatness and ten-point average roughness within the above-mentioned range are mostly satisfied, so no special smoothing process is required. On the other hand, when the flatness and ten-point average roughness within the above-mentioned range are not satisfied, a flat surface with the flatness and ten-point average roughness within the above-mentioned range is formed by grinding, machining and / or other methods. It should be noted that although the sheet metal may sometimes curl, as long as the sheet thickness accuracy is properly adjusted and the flatness is below 0.1 mm when the necessary load is applied during hot pressing (diffusion bonding), the target tightness can be ensured, and there will be no problem. It should also be noted that the ten-point average roughness Rzjis is the surface roughness specified in JIS B 0601-2001. Furthermore, in this specification, flatness is a parameter defined in JIS B 0621-1984 as "the magnitude of the deviation of a planar object from a geometrically correct plane (geometric plane)," referring to the value expressed by the width when an object is sandwiched between two planes.

[0077] Ideally, grooves that create flow path spaces after joining are formed on the surfaces of the multiple components to be joined, preferably before the removal of the oxide film in the next process. The grooves can be formed using various known methods such as etching, pressing, and machining. Thus, as described above, it is possible to manufacture copper alloy joints with internal flow path spaces. For example, by alternately stacking and joining grooved copper alloy plates and non-grooved copper alloy plates, a copper alloy laminate with multiple flow paths can be manufactured. Such multilayer joints are preferably used as heat exchangers in precoolers for hydrogen refueling stations where multiple flow path spaces are desired for the separate passage of hydrogen and refrigerant.

[0078] (b) Removal of oxidized film

[0079] As described above, an oxide film exists on the surface of the copper alloy component. Therefore, it is necessary to remove the oxide film present on the surfaces of the copper alloy component to be joined. From the perspective of effectively removing the oxide film, it is preferable to remove the oxide film by cleaning the surfaces of the copper alloy component to be joined with an inorganic acid solution. Examples of inorganic acid solutions include nitric acid, sulfuric acid, chemical polishing slurry, hydrochloric acid, tri-acid chemical polishing bath, hydrofluoric acid, etc., with nitric acid being particularly preferred. It should be noted that chemical polishing slurry is sulfuric acid with hydrogen peroxide added as an oxidant, and tri-acid chemical polishing bath is a mixture of sulfuric acid, nitric acid, and hydrochloric acid, sometimes with a small amount of sodium hydroxide added. Examples of preferred mixing ratios in tri-acid chemical polishing baths include sulfuric acid:nitric acid:hydrochloric acid = 61:4:4, 81:1:0.02, or 11:1:0.02, etc. Alternatively, the oxide film can be removed by mechanical polishing, or a combination of mechanical polishing and cleaning with an inorganic acid solution can be used.

[0080] (c) Hot-press bonding (diffusion bonding)

[0081] An intermediate joint is formed by joining multiple copper alloy components through hot pressing. This joining can be performed using a diffusion bonding method. For example, hot pressing is preferably performed using a bonding depth higher than 1.0 × 10⁻⁶. -2 Torr's vacuum level (i.e., below 1.0 × 10⁻⁶) -2 The process involves applying pressure (Torr) at 500–1050 °C for 30–480 minutes at a pressure exceeding 1.0 MPa within a furnace. However, in age-hardening copper alloys that do not contain Be (e.g., Cohen copper), hot pressing can be performed at pressures exceeding 1.0 × 10⁻⁶ MPa. -1 Torr's vacuum level (i.e., below 1.0 × 10⁻⁶) -1 The hot pressing is performed in a furnace at a temperature of 500–1050°C for 30–480 minutes and a pressure of 1.0 MPa or more. In summary, this hot pressing is performed such that the length deformation in the pressure direction during the joining of copper alloy components is preferably 0.5% or more and 30% or less, more preferably 1% or more and 20% or less, and even more preferably 2% or more and 8% or less. A suitable combination of hot pressing temperature and pressure is preferred, preferably 1 MPa or more and 16 MPa or less when the temperature exceeds 840°C but is below 1050°C, 2 MPa or more and 24 MPa or less when the temperature exceeds 720°C but is below 840°C, and 4 MPa or more and 50 MPa or less when the temperature exceeds 600°C but is below 720°C. The hot pressing time is preferably 15–480 minutes, more preferably 30–150 minutes, and even more preferably 30–60 minutes. It should be noted that, from the viewpoint of suppressing oxidation, the vacuum degree inside the furnace during hot pressing is preferably less than 1.0 × 10⁻⁶. -3 Torr, more preferably less than 1.0 × 10 -4Torr, more preferably less than 5.0 × 10 -5 Torr.

[0082] In particular, when grooves are formed on the surface of the copper alloy component to provide flow path space for the intermediate joint, it is preferable to perform the aforementioned hot pressing at a relatively low temperature and a relatively high pressure, from the perspective of controlling the flow path crushing caused by pressing to a slight degree. Specifically, the hot pressing in this method is performed at a pressure higher than 1.0 × 10⁻⁶. -2 Torr's vacuum level (i.e., below 1.0 × 10⁻⁶) -2 Torr pressure), preferably higher than 1.0 × 10 -4 Torr's vacuum level (i.e., below 1.0 × 10⁻⁶) -4 The pressure of Torr inside the furnace is controlled by the following method:

[0083] (i) Applying a pressure of 1 MPa or more and 4 MPa for 30 to 480 minutes (preferably 30 to 60 minutes) at a temperature exceeding 840°C and below 930°C, or

[0084] (ii) Applying a pressure of 2 MPa or more and 8 MPa or less at a temperature exceeding 720°C and below 840°C for 30 to 480 minutes (preferably 30 to 60 minutes), or

[0085] (iii) Apply pressure of 4 MPa or more and 30 MPa to a temperature of 600°C or more and 720°C or less for 30 to 480 minutes (preferably 30 to 60 minutes).

[0086] (d) Homogenization process (any step)

[0087] When a groove is formed on the surface of a copper alloy component to provide a flow path for the intermediate joint, and hot pressing is performed at a relatively low temperature and relatively high pressure, it is preferable that the intermediate joint is subjected to a pressure higher than 1.0 × 10⁻⁶ before solution treatment. -1 Torr's vacuum level (i.e., below 1.0 × 10⁻⁶) -1 Homogenization is performed at 900–1050 °C for 60–480 minutes in a furnace under a pressure of (Tor) or (at atmospheric or reduced pressure) nitrogen or other non-oxidizing gas atmosphere (inactive atmosphere). Homogenization is also known as homogenizing annealing, and the term "homogenization treatment" is used in this specification. That is, when hot pressing is performed at relatively low temperatures and relatively high pressures, the bonding interface is prone to remain, but by performing homogenization treatment, the bonding interface can be reduced or eliminated. Through subsequent solution treatment and aging treatment, extremely high bonding strength can be achieved. In other words, it is possible to achieve both suppression of flow path collapse and high bonding strength. To suppress oxidation, homogenization treatment is preferably performed at a pressure below 1.0 × 10⁻⁶.-1 Torr in atmospheric atmosphere, or at normal pressure or reduced to below 1.0 × 10⁻⁶. -1 The homogenization process is carried out in a non-reactive atmosphere such as nitrogen under pressure. The homogenization temperature is preferably 900-1050°C, more preferably 930-1000°C, and even more preferably 960-990°C. The holding time at the above homogenization temperature is 60-480 minutes, more preferably 60-360 minutes, and even more preferably 60-240 minutes. Of course, the above homogenization process can be performed as needed even if grooves are not formed on the surface of the copper alloy component.

[0088] It should be noted that (c) hot-pressing (diffusion bonding) and (d) homogenization are preferably performed continuously by releasing the pressurized load and raising the temperature without lowering the furnace temperature. Therefore, after hot-pressing (diffusion bonding) under temperature and pressurization conditions that do not excessively crush the flow path space, there is no need to pressurize again to crush the flow path space. Hot-pressing (diffusion bonding) and homogenization can be performed as a series of continuous operations at a temperature effective for homogenizing the microstructure. This not only improves the reliability of the joint but is also advantageous from an economic point of view.

[0089] (e) Solution treatment

[0090] Solution treatment is performed on the intermediate bond. This solution treatment is preferably performed by heating the intermediate bond at 700-1100°C in an atmospheric furnace, non-oxidizing atmosphere furnace, salt bath furnace, or similar furnace for 1-180 minutes, followed by water cooling. The copper alloy used in this invention is an age-hardening alloy. By eliminating the bonding interface or adjusting the thickness of the oxide film at the bonding interface to a certain level, solution treatment and subsequent aging treatment can achieve the desired tempering characteristics (e.g., high strength), particularly extremely high bond strength. The solution treatment temperature varies slightly depending on the alloy composition, but is preferably 700-1100°C, more preferably 800-1050°C, and even more preferably 900-1000°C. The effective holding time at the above solution treatment temperature is preferably 1-180 minutes, more preferably 5-90 minutes, and even more preferably 10-60 minutes.

[0091] (f) Timeliness processing

[0092] The intermediate bond that has undergone solution treatment is subjected to aging treatment. The aging treatment varies slightly depending on the alloy composition, but is preferably performed at 350–550°C for 30–480 minutes. As described above, age-hardening alloys such as beryllium copper alloys can exhibit desired tempering characteristics (e.g., high strength), particularly extremely high bond strength, through solution treatment and aging treatment. The aging treatment temperature is preferably 350–550°C, more preferably 400–500°C, and even more preferably 450–480°C. The holding time at the above aging treatment temperature is preferably 30–480 minutes, more preferably 30–300 minutes, even more preferably 60–240 minutes, and particularly preferably 90–180 minutes. From the viewpoint of suppressing oxidation, the aging treatment is preferably performed at a temperature higher than 1.0 × 10⁻⁶. -1 Torr's vacuum level (i.e., below 1.0 × 10⁻⁶) -1 The process is carried out in a furnace under a non-oxidizing atmosphere such as Torr pressure or nitrogen.

[0093] Hydrogen-resistant components

[0094] According to another aspect of the invention, a hydrogen-resistant component made of Cohen copper (EN material numbers CW109C, CW111C, UNS alloy numbers C19010, C70250, AMPCO944, and AMPCO940) is provided. The hydrogen-resistant component of this aspect is not limited to copper alloy joints as described above, but can be various forms of copper alloy articles. That is, as demonstrated in the embodiments described later, even Cohen copper has resistance to hydrogen embrittlement and therefore has value as a hydrogen-resistant component. In particular, Cohen copper has the advantage of being able to stably manufacture products with joints, thus being advantageous in terms of the ability to stably supply products made from hydrogen-resistant components. A hydrogen-resistant component is defined as a component used in contact with hydrogen. Examples of uses for hydrogen-resistant components include hydrogen-containing components, heat exchange components (e.g., heat exchangers) that allow hydrogen to flow and exchange heat, hydrogen-flowing piping components, valve components connected to hydrogen-flowing piping components, sealing components connected to hydrogen-flowing piping components, and combinations thereof. This hydrogen-resistant component can be used, for example, in contact with medium-pressure hydrogen (above 30 MPa and 45 MPa) and high-pressure hydrogen (above 70 MPa and 90 MPa). It can also be used in hydrogen refueling stations that handle high-pressure hydrogen and in fuel cell vehicles (FCVs).

[0095] [Example]

[0096] The invention is illustrated more specifically by the following examples.

[0097] Example 1~57

[0098] The copper alloy joint is fabricated through the following steps, and various evaluations are performed.

[0099] (1) Preparation of copper alloy

[0100] For each example, prepare multiple copper alloy round bars with a diameter of 32mm × length of 50mm or a diameter of 80mm × length of 50mm, as shown in Tables 2A, 3A, 4A and 5A, of the alloy types and compositions.

[0101] In Examples 1-40 and 43-57, the end faces (hereinafter referred to as mating faces) of the copper alloy round bars used for joining are made into flat surfaces with a ten-point average roughness Rzjis of less than 6.3 μm as measured according to JIS B 0601-2001 and a flatness of less than 0.1 mm as measured according to JIS B 0621-1984 by machining such as lathe machining and precision grinding.

[0102] On the other hand, in Example 41, the mating surfaces of the two copper alloy round bars were intentionally adjusted to be flat surfaces with a flatness of less than 0.1 mm as measured according to JIS B0621-1984, but with a ten-point average roughness Rzjis value greater than 6.3 μm. Furthermore, in Example 42, the mating surfaces of the two copper alloy round bars were intentionally adjusted to have a ten-point average roughness Rzjis value less than 6.3 μm as measured according to JIS B 0601-2001, but with a flatness value greater than 0.2 mm as measured according to JIS B 0621-1984.

[0103] (2) Removal of oxide film (except for example 36)

[0104] In Examples 1-35, 37-48, and 50-53, the joint surfaces of the two copper alloy round bars were cleaned with 30% nitric acid to remove the oxide film present on the joint surfaces. In Example 55, the joint surfaces of the two copper alloy round bars were cleaned with a chemical polishing solution (20% sulfuric acid containing 3% hydrogen peroxide water) to remove the oxide film present on the joint surfaces. In Examples 49, 54, and 56, the joint surfaces of the two copper alloy round bars were mechanically polished with #600 Emery paper to remove the oxide film present on the joint surfaces. In Example 57, the joint surfaces of the two copper alloy round bars were mechanically polished with a #320 polishing wheel (nylon-polyester nonwoven fabric) to remove the oxide film present on the joint surfaces. However, in Example 36 (Comparative Example), the oxide film was not removed.

[0105] (3) Hot pressing

[0106] Two copper alloy round bars, cleaned with nitric acid, were directly butted together (without brazing filler metal) at their joint surfaces. They were then hot-pressed in a vacuum furnace under the joining conditions shown in Tables 2A, 3A, 4A, and 5A to obtain a round bar-shaped intermediate joint. The deformation D during joining was calculated using the following formula: L0 is the cumulative length of the two samples in the joining direction before joining, and L1 is the length of the sample in the joining direction after joining. The results are shown in Tables 2A, 3A, 4A, and 5A.

[0107] D = [(L0-L1) / L0] × 100

[0108] To conduct various evaluations, for each case, multiple tensile test specimens were prepared, and tissue observation samples were prepared from adjacent locations before and after heat treatment.

[0109] (4) Solution treatment

[0110] The above intermediate joints were subjected to solution treatment. The solution treatment was carried out as follows: the copper alloy joints were held in a molten salt bath at 930°C for 5 minutes (Examples 1-42 and 47-57) or at 780°C for 5 hours (Examples 43-46), and then water-cooled.

[0111] (5) Timeliness processing

[0112] The intermediate joint after the above solution treatment was subjected to aging treatment. This aging treatment was carried out as follows: the copper alloy joint was subjected to aging at 1×10⁻⁶ ℃. -1 After being held at 450°C for 3 hours (Examples 1-42 and 55-57), 320°C for 3 hours (Examples 43-46), or 500°C for 2 hours (Examples 47-54) in a vacuum furnace with a Torr vacuum level, furnace cooling is performed. In this way, a round bar-shaped copper alloy joint that has been quenched and tempered by solution treatment and aging treatment is obtained.

[0113] (6) Evaluation

[0114] The following evaluation is performed on intermediate joints joined by hot pressing as described above, copper alloy joints in solution-treated state, copper alloy joints after solution treatment and aging treatment, and / or copper alloy joints after homogenization treatment of intermediate joints under various temperature and time conditions followed by solution treatment and aging treatment (hereinafter, they are collectively referred to as joint samples).

[0115] <Joint strength>

[0116] Each joint specimen was fabricated according to ASTM E8M Specimen 3, with the joint centered on the test piece. Tensile tests were then performed on each specimen according to ASTM E8M to determine the tensile strength (joint strength) and identify the fracture location. The results are shown in Tables 2A to 5C.

[0117] <Observation of the joint cross-section using an optical microscope>

[0118] The joint section of the specimen, including the joint portion, was cut out from the jointed specimen or from the jointed specimen after further solution treatment and aging treatment, and then ground. As an observation specimen, as described above, a specimen from the portion adjacent to where the tensile test piece was cut out and which underwent the same joint heat treatment process was used. The obtained cross-sections were observed using an optical microscope at magnifications of 200x, 500x, and 1000x to investigate whether the joint interface disappeared (in other words, whether the joint interface remained). The results are shown in Tables 2B, 3B, 4B, and 5B. Figure 2 The images show the cross-sectional photographs obtained in Examples 2, 30, 33, 43, and 46. Figure 3 This refers to the cross-sectional photographs obtained in Examples 26, 27, and 28. Figure 4 The figures show cross-sectional photographs obtained in Examples 47 and 53. As these figures show, the bonding interface of Examples 2 (CuBe11) and 30 (CuBe10Zr) as examples disappeared, indicating high bonding quality. On the other hand, the bonding samples of Examples 43 (CuBe25) and 46 (CuBe165) as comparative examples confirmed the presence of a residual bonding interface. However, although the bonding samples of Examples 33 (CuBe50), 26 (CuCr), 27 (CuCrZr), 28 and 47 (Colein Copper AMPCO940), and 53 (Colein Copper AMPCO944) as examples achieved high bonding strength, the presence of a residual bonding interface was confirmed. Thus, the disappearance of the bonding interface is effective in achieving the high bonding strength that is the object of the present invention, but it is not necessary. Based on the fact that the bonding samples of Examples 33, 26, 27, 28, 47, and 53, which confirmed the presence of a residual bonding interface, also achieved high bonding strength, it can be said that a good bonding state was achieved in the same way as in Examples 2 and 30.

[0119] <STEM observation and EELS / EDX elemental analysis of the interface>

[0120] Cross sections containing the bonding interface of the diffusely bonded specimens (Examples 2, 3, 26, 30, 33, 43, 46, 47, and 53) and / or the bonded specimens after solution treatment and aging treatment (hereinafter referred to as solution aging) were cut out and processed into thin sheets using a focused ion beam (FIB, product name: NB5000, Hitachi High Technology). The cross sections containing the bonding interface of the obtained bonded specimens were observed using a scanning transmission electron microscope (STEM, product name: HD-2700, Hitachi High Technology) with spherical aberration correction at an accelerating voltage of 200 kV to determine the presence or thickness of the oxide film at the bonding interface. Furthermore, elemental analysis of the bonding interface and its vicinity was performed using an electron energy loss spectrometer (EELS, trade name: Enfinium, Gatan) / energy dispersive X-ray analyzer (EDX, trade name: XMAXN 100TLE, Oxford) attached to the STEM. These results are shown in Tables 2B, 3B, 4B, and 5B, and Figures 5-8 And the following explanation is provided.

[0121] Examples 2 and 3 demonstrate the use of CuBe11 to withstand solution aging, resulting in welds with high bond strength (>690 Ma). While the bond surface in Examples 2 and 3 was not identified under an optical microscope, areas where the bond surface could be determined by STEM were present. However, due to… Figure 5 As shown in the STEM and EELS / EDX elemental distribution images, in Example 2, no residual oxide film was observed at the bonding surface (i.e., the oxide film thickness was 0 nm). No residual oxide film was also confirmed based on the EELS elemental distribution. However, in the bonding body (bonded body in the bonded state) of Example 3, an oxide film with a thickness of 0.7 nm was observed in a portion. The EELS elemental distribution also confirmed residual oxide film with a thickness of less than 1 nm. Therefore, it can be seen that an oxide film with a thickness of 0-1 nm exists in CuBe11, but as long as the oxide film is thin enough, good bonding strength can be ensured.

[0122] Example 30 demonstrates the use of CuBe10Zr to withstand solution aging, resulting in a bond with high bonding strength (>690 Ma). STEM observation and EELS / EDX elemental analysis, similar to Example 2 (CuBe11), showed no residual oxide film. Concentrated Zr was identified within the matrix, but not as oxide (ZrO) residue at the bonding interface; therefore, it did not affect the bonding quality.

[0123] Example 33 is an example of using CuBe50 to withstand solution aging, resulting in a bond with high bonding strength (>690 Ma). STEM observation and EELS / EDX elemental analysis showed no residual oxide film, similar to Examples 2 (CuBe11) and 19 (CuBe10Zr). These results are consistent with the mechanical behavior of a solution-resistant aging bond.

[0124] Example 26 illustrates the use of CuCr to withstand solution aging, resulting in a bond with high bond strength. STEM observation and EELS / EDX elemental analysis, similar to Examples 2 (CuBe11), 30 (CuBe10Zr), and 33 (CuBe50), showed no residual oxide film. Concentrated Cr deposits were identified within the matrix and at the bonding interface, but these were not residual oxides (CrO) at the interface and therefore did not affect the bond quality. These results are consistent with the mechanical behavior of a solution-resistant aging bond.

[0125] Example 43 (Comparative) is a comparative example of a bond that fractured during solution aging using CuBe25. STEM observation and EELS / EDX elemental analysis revealed a homogeneous oxide film of approximately 6 nm across the entire interface of the bond (in the bonded state). The oxide film thicknesses at two specific locations were 5.8 nm and 6.2 nm (see reference). Figure 6A Additionally, in Figure 6B In the diagram, areas with high BeO concentrations are indicated by black dots (emphasized by arrows), and spherical, thick oxide films are observed at various locations. Figure 6B In this process, the thickness of the oxide film on these spherical parts is determined according to... Figure 6C The ELLS elemental distribution shown is approximately 15~20nm.

[0126] Example 46 (Comparison) is a comparative example of a bond that fractured during solution aging using CuBe165. STEM observation and EELS / EDX elemental analysis revealed no homogeneous oxide film covering the entire bond surface, and localized areas lacking an oxide film. However, thick, spherical oxide films induced by high BeO concentrations were observed in various locations. The thickness of these spherical oxide films was estimated to be between approximately 20 nm and over 50 nm. The thickness of the oxide film, comprising both homogeneous and spherical oxide films, was determined to be in the range of 1–80 nm.

[0127] Examples 47 and 53 illustrate how Cosne copper AMPCO940 and Cosne copper AMPCO944, respectively, were used to withstand solution aging, resulting in welds with high bond strength. The weld specimens in Examples 47 and 53 show areas where the joint surface can be determined by STEM. However, due to… Figure 7 and 8 As shown in the STEM images and EELS / EDX elemental distribution images (corresponding to Examples 47 and 53 respectively), no residual oxide film was observed at the bonding surface in Examples 47 and 53 (i.e., the thickness of the oxide film was 0 nm). No residual oxide film was also confirmed based on the EELS elemental distribution.

[0128] <Determination of electrical conductivity and conversion of thermal conductivity>

[0129] The conductivity (IACS%) of the bonded sample was measured at room temperature using an eddy current conductivity meter (Hocking AutoSigma 3000DL, manufactured by GE Sensing & Inspection Technologies). The obtained conductivity was then converted using a correlation based on the Wiedeman-Fritz law to calculate the thermal conductivity (W / mK).

[0130] <Research on Homogenization Temperature>

[0131] Intermediate joints (intermediate joints before solution treatment) of Examples 1-3, 8-11, 16-25, 30, 32-35, 47, 48, 53, and 55-57, after being heated and pressurized, were subjected to homogenization treatment (high-temperature immersion) at different temperatures of 900°C, 930°C, 960°C, or 980°C for 8 hours, followed by furnace cooling, and then held at 930°C for 5 minutes and water-cooled (solution treatment). The resulting joints were then held at 450°C for 3 hours (Examples 1-3, 8-11, 16-25, 30, 32-35, and 55-57) or at 500°C for 2 hours (Examples 47, 48, and 53) followed by furnace cooling (aging treatment). Each joint specimen was machined to create a test piece according to ASTM E8M Specimen 3 with the joint at the center of the test piece. The test specimen was subjected to tensile testing according to ASTM E8M procedures. After determining the tensile strength (joint strength), the fracture location was identified. The results are shown in Tables 2C, 3C, 4C, and 5C. These results indicate that the higher the homogenization temperature, the more the joint interface disappears, and in the tensile test, the base material fails instead of the joint surface. (However, there are also joints where base material failure occurs even without homogenization. In grain growth beyond or at locations that were once joint interfaces, homogenization is not necessary, but it more completely eliminates the joint surface, resulting in base material failure at all locations.)

[0132] [Table 2A]

[0133]

[0134] [Table 2B]

[0135]

[0136] [Table 2C]

[0137]

[0138] [Table 3A]

[0139]

[0140] [Table 3B]

[0141]

[0142] [Table 3C]

[0143]

[0144] [Table 4A]

[0145]

[0146] [Table 4B]

[0147]

[0148] [Table 4C]

[0149]

[0150] [Table 5A]

[0151]

[0152] [Table 5B]

[0153]

[0154] [Table 5C]

[0155]

[0156] <Evaluation of Hydrogen Embrittlement Resistance Based on Low Strain Rate Tensile Test (SSRT)>

[0157] Cut out the copper alloy joints (CuBe11) prepared by joining and solution aging as in Examples 2, 17, and 18, and fabricate test specimens according to ASTM E8M Specimen 4 with the joint at the center. It should be noted that these test specimens were not homogenized. Low strain rate tensile tests were conducted according to ASTM-G-142, with a displacement velocity of 0.001 mm / sec (strain velocity of 0.00005 / sec) for smooth test specimens, in atmospheric or 95 MPa hydrogen atmosphere. It should be noted that in the low strain rate tensile tests of smooth test specimens, hydrogen embrittlement characteristics were evaluated by RRA (relative reduction of area). The test results are shown in Table 6A. Figure 9A and 9B The stress-stroke diagram is shown in the figure. Figure 10A and 10B The image shows a SEM image of the fracture surface of the test piece in Example 17. The tensile strength and reduction of area of ​​each test piece did not change under atmospheric or hydrogen conditions, and no hydrogen embrittlement was confirmed. Figure 10A and 10B The failure shown occurs in the base material, and its failure mode is cup-cone failure, with the fracture surface forming a characteristic pit shape of ductile failure. Therefore, the bonding material of the present invention exhibits excellent properties of high tensile strength and superior resistance to hydrogen embrittlement.

[0158] In addition, the hydrogen embrittlement resistance of the raw copper alloys used to make the copper alloy joints (not the copper alloy joints themselves) was evaluated. Specifically, solution-treated and aged raw materials of CuBe25 alloy (raw material 1), CuBe11 alloy (raw material 2), Cohen's copper AMPCO940 (raw material 3), and Cohen's copper AMPCO944 (raw material 4) used as joint raw materials were cut out and test pieces were made according to ASTM E8M Specimen 4. Low strain rate tensile tests were conducted according to ASTM-G-142. For smooth test pieces, the displacement velocity was 0.001 mm / sec (strain velocity 0.00005 / sec), and the tests were conducted in atmosphere or 95 MPa hydrogen gas. It should be noted that in the low strain rate tensile tests of smooth test pieces, the hydrogen embrittlement characteristics were evaluated by RRA (relative reduction of area). The test results are shown in Table 6B. Figures 9C-9E The stress-stroke diagram is shown. The tensile strength and reduction of area of ​​each test piece remained unchanged under atmospheric or hydrogen conditions, and no hydrogen embrittlement was confirmed. The failure mode was cup-cone fracture, with the fracture surface forming the characteristic pitted shape of ductile fracture. These results indicate that these raw materials, used as copper alloy raw materials in the fabrication of the copper alloy bonding material of this invention, exhibit excellent properties of high tensile strength after aging and superior resistance to hydrogen embrittlement.

[0159] [Table 6A]

[0160]

[0161] [Table 6B]

[0162]

[0163] Examples 58~67

[0164] The joint specimens with internal flow path spaces were prepared under various conditions and evaluated.

[0165] <Study on joint conditions for reducing flow path crushing>

[0166] Prepare multiple copper alloy plates (cast) with a thickness of 1.6 mm and dimensions of 50 mm × 50 mm, of the alloy types and compositions shown in Table 7. On the surface of half of these copper alloy plates, etch grooves with an arched cross-section of 2.4 mm width × 1.2 m depth are formed to create flow path spaces. After removing the oxide film on the bonding surfaces with 30% nitric acid, the grooved copper alloy plates are alternately stacked with ungrooved copper alloy plates, or grooved alloy plates with grooves on both sides are alternately stacked. Diffusion bonding is achieved through hot pressing under the bonding conditions and deformation amounts shown in Table 7. This yields an intermediate bond with flow path spaces. The crushing of the flow path and the bonding state of the obtained intermediate bond are evaluated by microscopic observation. Diffusion bonding is more favorable at higher temperatures, but according to the results shown in Table 7, in this example of a hollow body with flow paths, high temperature and high pressure lead to significant crushing, narrowing of the flow path, and a tendency to blockage. To reduce such crushing, it is considered preferable to use bonding conditions with a temperature below 840°C and a pressure above 5 MPa in the hollow body. Furthermore, microscopic observation of the bonding state of the intermediate bond revealed the disappearance of the bonding surface under high-temperature and high-pressure bonding conditions, but as the temperature decreased, the presence of a bonding surface remained regardless of the bonding pressure. However, as demonstrated in the above embodiments, the bonding surface can disappear during homogenization at high temperatures. Therefore, it can be said that performing high-load bonding at a slightly lower temperature followed by high-temperature homogenization, while suppressing flow path crushing, is advantageous in the manufacture of bonds with flow path spaces.

[0167] [Table 7]

[0168]

[0169] To demonstrate this, the following experiment was conducted, including a high-temperature homogenization treatment of the intermediate bond from Example 62. First, the intermediate bond with flow path space prepared in Example 62 (840°C, 3 Pa) was subjected to a homogenization treatment (high-temperature immersion) at 980°C for 8 hours. The intermediate bond was then water-cooled (solution treatment) at 930°C for 5 minutes. The resulting bond was then furnace-cooled (aging treatment) after being held at 450°C for 3 hours. Thus, a copper alloy bond (including flow path) that had undergone homogenization treatment and solution aging was obtained. Figure 11 The image shown is an optical microscope image obtained by observing a cross-section of the copper alloy joint near the flow path of Example 62. Figure 11 As shown, in the joint where homogenization treatment was performed, the disappearance of the joint interface was confirmed. If homogenization treatment is performed after diffusion bonding, the joint interface disappears and cannot be distinguished from the base material, resulting in complete homogenization (i.e., age-hardening copper alloy grains growing beyond the old joint interface exist at the joint). Therefore, in the case of tensile testing, the base material fails not at the joint interface but (however, there are also joints where the base material fails even without homogenization treatment, because the growth of grains beyond the old joint interface makes homogenization treatment unnecessary). Therefore, as described above, in the case of low-temperature, high-load bonding with low water channel collapse, although the joint interface remains, it can be made to disappear by performing high-temperature homogenization treatment.

Claims

1. A copper alloy joint comprising a plurality of age-hardening copper alloy components diffusely bonded together, wherein, The copper alloy joint underwent solution treatment and aging treatment. The beryllium content of the age-hardening copper alloy is less than 0.7% by weight, and, (i) The joint interface of the plurality of components disappears, and / or (ii) The bonding interface of the plurality of components remains, wherein the thickness of the oxide film at the bonding interface is 0 nm or more and 5.0 nm or less. At a strain rate of 5×10 -5 s -1 The tensile strength of the copper alloy joint including the joint, measured in hydrogen in the following low strain rate tensile test, is above 520 MPa.

2. The copper alloy joint according to claim 1, comprising grains of the age-hardening copper alloy grown beyond the joint interface or at a location that was once the joint interface.

3. The copper alloy joint according to claim 1 or 2, wherein, The thickness of the oxide film is greater than 0 nm and less than 1.0 nm.

4. The copper alloy joint according to claim 1 or 2, wherein, There are no residual components from materials other than the age-hardening copper alloy at the joint interface or at the location that was once the joint interface.

5. The copper alloy joint according to claim 1 or 2, wherein, The strength of the base material and the joint of the copper alloy joint is above 520 MPa.

6. The copper alloy joint according to claim 5, wherein, The strength of the base material and the joint of the copper alloy joint is above 690 MPa.

7. The copper alloy joint according to claim 1 or 2, wherein, The thermal conductivity of the base material containing the copper alloy joint is above 209 W / mK.

8. The copper alloy joint according to claim 1 or 2, wherein, The electrical conductivity of the base material comprising the copper alloy joint is 50 IACS% or higher.

9. The copper alloy joint according to claim 1 or 2, wherein, The age-hardening copper alloy is selected from at least one of the following copper alloys: Beryllium copper 11 alloy, namely JIS alloy number C1751, EN material number CW110C and UNS alloy number C17510; Beryllium copper 10 alloy, namely EN material number CW104C and UNS alloy number C17500; Beryllium copper CuCo1Ni1Be, also known as EN material number CW103C; Beryllium copper 14Z alloy, namely Be: 0.2~0.6 wt%, Ni: 1.4~2.4 wt%, Zr: 0~0.5 wt%, with the balance consisting of Cu and unavoidable impurities; Beryllium copper 50 alloy, namely Be: 0.2~0.6 wt%, Ni: 1.4~2.1 wt%, Ag: 0.1~0.3 wt%, Zr: 0~0.5 wt%, with the balance consisting of Cu and unavoidable impurities; The beryllium copper 10Zr alloy consists of Be: 0.4~0.7 wt%, Co: 2.0~2.8 wt%, Zr: 0~0.3 wt%, with the balance being Cu and unavoidable impurities. Chromium copper, also known as UNS alloy number C18200; Chromium-zirconium copper, namely UNS alloy number C18510 and EN material number CW106C; Zirconium copper, also known as UNS alloy number C15000 and EN material number CW120C; and Cosne copper, namely EN material numbers CW109C, CW111C, UNS alloy numbers C19010, C70250, AMPCO944 and AMPCO940, wherein AMPCO944 contains Ni: 6.5~7.5 wt%, Si: 1.5~2.5 wt%, Cr: 0.5~1.5 wt%, with the balance being Cu and unavoidable impurities, and AMPCO940 contains Ni: 1.5~3.0 wt%, Si: 0.5~1.5 wt%, Cr: 0.3~1.5 wt%, with the balance being Cu and unavoidable impurities.

10. The copper alloy joint according to claim 9, wherein, The age-hardening copper alloy is selected from at least one of the following copper alloys: Beryllium copper 11 alloy, namely JIS alloy number C1751, EN material number CW110C and UNS alloy number C17510; Beryllium copper 10 alloy, namely EN material number CW104C and UNS alloy number C17500; Beryllium copper CuCo1Ni1Be, also known as EN material number CW103C; Beryllium copper 14Z alloy, namely Be: 0.2~0.6 wt%, Ni: 1.4~2.4 wt%, Zr: 0~0.5 wt%, with the balance consisting of Cu and unavoidable impurities; Beryllium copper 50 alloy, namely Be: 0.2~0.6 wt%, Ni: 1.4~2.1 wt%, Ag: 0.1~0.3 wt%, Zr: 0~0.5 wt%, with the balance consisting of Cu and unavoidable impurities; and The beryllium copper 10Zr alloy consists of Be: 0.4~0.7 wt%, Co: 2.0~2.8 wt%, Zr: 0~0.3 wt%, with the balance being Cu and unavoidable impurities.

11. The copper alloy joint according to claim 1 or 2, used at a strain rate of 5 × 10⁻⁶. -5 s -1 The following copper alloy components were manufactured based on the RRA (relative reduction of area) of 0.8 or higher in hydrogen, as determined in the low strain rate tensile test.

12. The copper alloy joint according to claim 1 or 2, wherein, At a strain rate of 5×10 -5 s -1 The tensile strength of the copper alloy joint containing the joint, measured in hydrogen in the following low strain rate tensile test, is above 690 MPa.

13. The copper alloy joint according to claim 1 or 2, wherein, The copper alloy joint has a flow path space inside.

14. A method for manufacturing a copper alloy joint, which is the method for manufacturing a copper alloy joint according to any one of claims 1 to 13, comprising: The process of preparing multiple components made of age-hardening copper alloy, wherein the multiple components made of age-hardening copper alloy are flat surfaces with a flatness of less than 0.1 mm and a ten-point average roughness Rzjis of less than 6.3 μm, and a beryllium content of less than 0.7% by weight. The process of removing the oxide film present on the surfaces of the plurality of components to be joined. The process of forming an intermediate joint by hot pressing to diffusely join the multiple components. The intermediate joint is subjected to a solution treatment process involving heating at 700-1100°C for 1-180 minutes followed by water cooling. The process of aging the intermediate bond that has undergone the solution treatment at 350~550°C for 30~480 minutes.

15. The method according to claim 14, wherein, The oxide film is removed by cleaning the surfaces of the plurality of components to be joined with an inorganic acid solution.

16. The method according to claim 14 or 15, wherein, The hot pressing is performed under a vacuum degree higher than 1.0 × 10⁻⁶. -2 Torr is less than 1.0 × 10 -2 The pressure of Torr is achieved by applying a pressure of 1.0 MPa or higher to a furnace at a temperature of 500~1050℃ for 30~480 minutes.

17. The method according to claim 14 or 15, wherein, In the case where the age-hardening copper alloy does not contain Be, the hot pressing is performed under a vacuum degree higher than 1.0 × 10⁻⁶. -1 Torr is less than 1.0 × 10 -1 The process involves applying pressure of 1.0 MPa or higher to a furnace at a temperature of 500-1050°C for 30-480 minutes.

18. The method according to claim 14 or 15, wherein, The method further includes the following step: prior to the solution treatment, at a temperature higher than 1.0 × 10⁻⁶ -1 The vacuum level of Torr is less than 1.0 × 10⁻⁶. -1 The intermediate bond is homogenized for 60 to 480 minutes in a furnace under Torr pressure or in a nitrogen or other non-oxidizing gas atmosphere at a temperature of 900 to 1050°C.

19. The method according to claim 18, wherein, The hot pressing and homogenization processes are carried out continuously by raising the temperature by releasing the pressing load without lowering the furnace temperature.

20. The method according to claim 14 or 15, wherein, The method further includes a step of forming grooves on the surfaces of the plurality of components to be joined, which will create flow space after joining, before removing the oxide film.

21. The method according to claim 20, wherein, The hot pressing is above 1.0 × 10 -2 The vacuum level of Torr is less than 1.0 × 10⁻⁶. -2 The pressure of the Torr furnace is achieved by (i) applying a pressure of 1 MPa or more and 4 MPa or less for 30 to 480 minutes at a temperature exceeding 840°C and below 930°C, or (ii) applying a pressure of 2 MPa or more and 8 MPa or less for 30 to 480 minutes at a temperature exceeding 720°C and below 840°C, or (iii) applying a pressure of 4 MPa or more and 30 MPa or less for 30 to 480 minutes at a temperature exceeding 600°C and below 720°C. The method further includes the following step: prior to the solution treatment, at a temperature higher than 1.0 × 10⁻⁶ -1 The vacuum level of Torr is less than 1.0 × 10⁻⁶. -1 The intermediate bond is homogenized for 60 to 480 minutes in a furnace under Torr pressure or in a nitrogen or other non-oxidizing gas atmosphere at a temperature of 900 to 1050°C.

22. The method according to claim 21, wherein, The hot pressing and homogenization processes are carried out continuously by raising the temperature by releasing the pressing load without lowering the furnace temperature.

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