Integration structure of metal material and dissimilar metal material

Abstract

To provide a structure having a junction in which a metal material containing a group 5 element, which can provide an excellent hydrogen separation function and a dissimilar metal material which is different from the metal material are joined to each other.SOLUTION: A structure has a junction in which a metal material containing a group 5 element and a dissimilar metal material which is different from the metal material are joined to each other, where the metal material is used to separate hydrogen from mixed gas including hydrogen. The junction is formed by directly contacting the metal material with the dissimilar metal material, where a width in which the metal material contacts the dissimilar metal material in the junction is 0.5 mm or more and 3 mm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a structure having a joint where a metal material containing a Group 5 element is joined to a different metal material that is different from this metal material. [Background technology]

[0002] There is a separation technology for separating hydrogen (H) from a mixed gas stream. This separation technology uses a membrane-based separation technology, and the membrane (hydrogen-selective membrane) is a vanadium-based membrane (i.e., a vanadium or vanadium alloy-based membrane). A brazing technology is known in which the vanadium-based membrane is laser-welded to a different metal, preferably stainless steel (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-525270 A (paragraphs

[0005] ,

[0007] ,

[0013] ,

[0021] ,

[0087] to

[0090] , Figure 5(b)) Summary of the Invention [Problem to be solved by the invention]

[0004] When a hydrogen-permeable membrane made of a Group 5 metal, such as vanadium (V), niobium (Nb), or tantalum (Ta), or an alloy of these metals is used to separate hydrogen (H) from a mixed gas stream, the hydrogen-permeable membrane must be attached to the housing of the hydrogen separation device. The inventors investigated this issue and found that when the brazing technique using laser welding described in Patent Document 1 is used, impurities such as the brazing material dissolve into the hydrogen-permeable membrane, such as vanadium, at the welded joint. As a result, when hydrogen (H) is separated from a mixed gas stream using a hydrogen-permeable membrane, hydrogen embrittlement occurs at the joint where the impurities have dissolved, and the joint is destroyed over a long separation time.

[0005] The present invention was created in consideration of the above problems, and aims to provide a structure having a joint where a metal material containing a Group 5 element and a dissimilar metal material different from the metal material are joined, which can provide good hydrogen separation function. [Means for solving the problem]

[0006] In Comparative Example 1 of Patent Document 1, direct laser welding (welding without brazing filler metal) is performed, but large crystal grains present at the joint may cause cracking or fracture, and direct laser welding is not suitable for joining and sealing vanadium-based films to stainless steel or other metal joints.

[0007] However, according to the inventors' investigations, the reason why Patent Document 1 states that direct laser welding is not suitable is because the bonding area of ​​the bonding portion is insufficient (considering that Patent Document 1 states that a vanadium-based film thickness of 0.2 to 0.5 mm is more preferable, and looking at the cross-sectional photograph of Comparative Experimental Example 1 (FIG. 5(b)), the width of the bonding portion is considered to be 200 μm or less), and it was found that the size of the crystal grains is not the cause. Rather, the inventors' investigations have found that by ensuring a sufficient bonding area, the problem of hydrogen embrittlement due to the dissolution of impurities can be solved, while also solving the problems of cracking and shattering of the hydrogen-permeable film.

[0008] The present invention is a structure having a joint where a metal material containing a Group 5 element is joined to a dissimilar metal material different from the metal material, wherein the metal material is used to separate hydrogen from a mixed gas containing hydrogen, the joint is formed by directly contacting the metal material with the dissimilar metal material, and the width of contact between the metal material and the dissimilar metal material at the joint is 0.5 mm or more and 3 mm or less.

[0009] In the present invention, the metal material preferably has the form of a metal film.

[0010] In the present invention, the thickness of the metal film is preferably 0.05 mm or more and 5 mm or less.

[0011] In the present invention, the Group 5 metal is preferably at least one selected from the group consisting of vanadium, niobium, and tantalum.

[0012] In the present invention, the metal material containing the Group 5 element is preferably pure vanadium or a vanadium alloy.

[0013] In the present invention, the dissimilar metal material is preferably at least one selected from the group consisting of steel, stainless steel, and a nickel-chromium-iron alloy. [Effects of the Invention]

[0014] It is possible to provide a structure having a joint where a metal material containing a Group 5 element and a different metal material different from the metal material are joined, which can provide a good hydrogen separation function. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows a schematic diagram of an electron beam welding apparatus (left side) in Example 1, and a schematic diagram (right side) showing the state of a metal material (vanadium film with a diameter of 40 mm) and a dissimilar metal material (ring-shaped stainless steel plate with a diameter of 52 mm and an inner diameter of 30 mm) placed on a workpiece during electron beam welding. [Figure 2] FIG. 2 shows SEM observation images of the cross section of the joint in the three samples prepared in Example 1. [Figure 3]FIG. 3 shows the measurement results of the hydrogen permeation performance of a sample (effective diameter of the membrane: 30 mm) in which a vanadium membrane was electron-beam welded to the center of the donut-shaped stainless steel ring (diameter: 52 mm) shown in FIG. 1 in Example 1, and a normal vanadium membrane without this welding (the diameter of the vanadium membrane was 52 mm, but the data obtained in the experiment was converted so that the effective diameter of the membrane was 30 mm in order to compare with the electron-beam welded sample). [Figure 4] FIG. 4 is a schematic diagram of the experimental apparatus used in the hydrogen permeation test. [Figure 5] FIG. 5 shows a schematic diagram of a fiber welding apparatus (left side) in Example 2, and a schematic diagram (right side) showing the state of a metal material (vanadium film with a diameter of 40 mm) and a dissimilar metal material (ring-shaped stainless steel plate with a diameter of 52 mm and an inner diameter of 30 mm) placed on the workpiece during fiber welding. [Figure 6] FIG. 6 shows the measurement results of the hydrogen permeation performance of a sample (effective membrane diameter: 40 mm) in which a vanadium membrane was fiber-welded to the center of the doughnut-shaped stainless steel ring (diameter: 52 mm) shown in FIG. 5 in Example 2, and a normal vanadium membrane without this welding (the diameter of the vanadium membrane was 52 mm, but the data obtained in the experiment was converted so that the effective membrane diameter was 40 mm in order to compare with the electron-beam welded sample). DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments for carrying out the present invention will be described below. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. Furthermore, it goes without saying that the following embodiments may be modified as appropriate within the scope of the gist of the present invention.

[0017] The present invention provides a structure having a joint formed by joining a metallic material containing a Group 5 element to a dissimilar metallic material different from the metallic material. The metallic material is used to separate hydrogen from a hydrogen-containing mixed gas. The joint is formed by direct contact between the metallic material and the dissimilar metallic material, and the contact width between the metallic material and the dissimilar metallic material at the joint is 0.5 mm or more and 3 mm or less.

[0018] In the present invention, the joint is formed by directly contacting the metal material and the dissimilar metal material without using a third material (e.g., brazing filler metal) for joining the two materials. This makes it easier to prevent contamination of the joint surface by the third material and the third material from dissolving into the metal material, and also makes it less likely that hydrogen embrittlement will occur when hydrogen is extracted from a mixed gas or the like (when hydrogen diffuses through the metal material).

[0019] Furthermore, in the present invention, by ensuring the contact area (contact width between the metal material and the dissimilar metal material), the sealing performance between the metal material used to separate hydrogen from a hydrogen-containing mixed gas and the dissimilar metal material is ensured, making it easier to prevent leakage of hydrogen or the mixed gas from the joint. Furthermore, since the joint between the metal material and the dissimilar metal material is strong, the metal material is less likely to peel off from the dissimilar metal material that serves as the base material. As a result, when the dissimilar metal material is part of the housing of the hydrogen separation device, stable hydrogen separation is possible, making it easier to operate the hydrogen separation device for long periods of time.

[0020] The metal material of the present invention contains a Group 5 element. The metal material is used to separate hydrogen from a hydrogen-containing mixed gas. This is because metal materials containing a Group 5 element have excellent properties, such as the ability to selectively separate and transmit hydrogen from a mixed gas. The Group 5 element is preferably at least one selected from the group consisting of vanadium, niobium, and tantalum, with vanadium being more preferred. Group 5 elements, such as vanadium, particularly the so-called vanadium group elements, have similar chemical properties. Vanadium has the property of permeating hydrogen, so Group 5 elements other than vanadium, particularly vanadium group elements, also have similar properties. Although the present invention uses a Group 5 element for the metal membrane, as described above, Group 5 elements may be used in combination because their chemical properties are similar. For example, vanadium may coexist with niobium or tantalum, or an alloy thereof may be formed.

[0021] Furthermore, the metallic material of the present invention may contain elements other than Group 5 elements. The inclusion of such elements facilitates the imparting of various properties to the metallic material. Examples of such elements include iron (Fe), ruthenium (Ru), aluminum (Al), tungsten (W), molybdenum (Mo), chromium (Cr), and cobalt (Co). The use of these alloying elements facilitates the imparting of rigidity to metallic materials (e.g., hydrogen separation membranes) and suppresses the hydrogen solid solubility (also known as hydrogen solubility) in the alloy even under increased hydrogen pressure, thereby contributing to improved hydrogen embrittlement resistance. The content of elements other than Group 5 elements is typically 0.1 atomic % or more, preferably 1 atomic % or more, for each element. This range facilitates the imparting of the above-described properties to the metallic membrane. Meanwhile, the content of elements other than Group 5 elements is typically 50 atomic % or less, preferably 40 atomic % or less, and more preferably 11 atomic % or less, for each element. Within this range, the benefits of using a Group 5 element are not diminished and the required properties can be easily imparted.

[0022] In consideration of hydrogen permeability, the metal material of the present invention is preferably made of pure vanadium or a vanadium alloy containing a Group 5 element. In principle, pure vanadium refers to a metal material containing 100 atm% vanadium. However, the concept of "pure vanadium" also includes metal materials containing unavoidable impurities in vanadium.

[0023] The content of Group 5 elements and other elements in metallic materials can be analyzed using the following method: a scanning electron microscope equipped with EDS or WDS (SEM / EDS / WDS) or a field emission scanning electron microscope (FE-SEM / EDS / WDS) can be used to analyze the type and composition of contained elements by setting appropriate analytical conditions.

[0024] The metal material of the present invention preferably has the form of a metal film. In this case, the thickness of the metal film is preferably 0.05 mm or more. Generally, the thicker the metal film, the greater the mechanical strength, making it less susceptible to fracture and allowing hydrogen to permeate over a long period of time. On the other hand, increasing the thickness of the metal film tends to decrease the amount of hydrogen that can permeate per unit time. For this reason, the thickness of the metal film must be appropriately controlled. From the above perspectives, the thickness of the metal film is preferably 0.1 mm or more, more preferably 0.2 mm or more, even more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more, while typically 5 mm or less, preferably 1 mm or less. The thickness of the metal film may be measured using a known measuring device such as a finger, vernier caliper, micrometer, or 3D shape measuring device, depending on the thickness.

[0025] In the present invention, the metal material and dissimilar metal material have a joint. The "joint" refers to the interface between the metal material and dissimilar metal material, that is, the portion where the metal material and dissimilar metal material are joined. There are no particular limitations on the joining method, but in the present invention, welding is preferably used. This makes it easier to form a strong joint, ensuring mechanical strength, ensuring sealing properties, and suppressing hydrogen embrittlement. In the present invention, the joint is formed by direct contact between the metal material and dissimilar metal material. For this reason, welding is performed without using solder or brazing filler.

[0026] There are no particular limitations on the welding method. For example, there is pressure welding, which applies mechanical pressure to the joint between a metal material and a dissimilar metal material, and fusion welding, which heats the joint between a metal material and a dissimilar metal material to a temperature above the melting point to join them. Of these, fusion welding is preferred from an industrial perspective. Furthermore, among fusion welding methods, electron beam welding, laser welding, and TIG welding are preferred from the viewpoints of ensuring the mechanical strength of the joint, ensuring sealing properties, and suppressing hydrogen embrittlement. Furthermore, considering that thin plates such as hydrogen-permeable membranes are being welded, electron beam welding or laser welding is more preferred as the welding method. Furthermore, when using electron beam welding, it is preferable to perform welding in a vacuum. Welding in a vacuum makes it easier to suppress oxidation of the metal material or dissimilar metal material, thereby making it easier to suppress hydrogen embrittlement at the joint. Furthermore, when using laser welding, it is more preferable to use a solid-state laser from the viewpoint of achieving high-precision, high-density welding, and fiber welding using a fiber laser is preferred.

[0027] The detailed conditions for welding may be appropriately controlled from the viewpoints of ensuring the mechanical strength of the joint, ensuring sealing properties, and suppressing hydrogen embrittlement, with the aim of suppressing the generation of impurities or the incorporation of modified substances into the joint during welding.

[0028] In the present invention, the contact width between the metal material and the dissimilar metal material at the joint is set to 0.5 mm or more and 3 mm or less. Here, the "contact width between the metal material and the dissimilar metal material" is synonymous with the width of the joint between the metal material and the dissimilar metal material, and in this specification, the two terms are treated as synonymous. In addition, the contact width between the metal material and the dissimilar metal material at the joint is preferably determined by observing the cross section of the joint with a scanning electron microscope (SEM).

[0029] As described above, the term "joint" refers to the interface between a metal material and a dissimilar metal material, i.e., the portion where the metal material and the dissimilar metal material are joined. In practice, the metal material and the dissimilar metal material are brought into contact with each other, and then the contact portion is joined using welding or the like to form the joint. The cross-section of the joint is then observed, and the width of the joint between the two is set within the above-mentioned numerical range. Here, to observe the cross-section of the joint, the structure of the present invention is cut to expose the cross-section. Examples of cutting methods include mechanical machining and ion beam machining. More specifically, mechanical polishing, microtome, FIB (Focused Ion Beam), ion polisher (CP), and liquid nitrogen cooling fracture are examples of such methods. Among these, mechanical polishing after mechanical machining (wire EDM) is preferred from the viewpoint of enabling good observation of the cross-section and the state of the joint.

[0030] When using a scanning electron microscope (SEM), observations should be performed at a magnification that allows the joint to fit within the field of view and the width of the joint to be observed. The width of the joint observed within this field of view (the portion where the boundary between the metal material and the dissimilar metal material cannot be visually confirmed) should be measured appropriately. Scanning electron microscopes (SEMs) sold by analytical equipment manufacturers can be used. For example, the JSM-7100F manufactured by JEOL Ltd. can be used. When using this device, secondary electron images can be obtained at an accelerating voltage of 15 kV for SEM observations.

[0031] In the present invention, the contact width between the metal material and the dissimilar metal material at the joint is set to 0.5 mm or more and 3 mm or less. The reason for setting the width to 0.5 mm or more is to prevent defects such as peeling or tearing of the metal material containing a Group 5 element from the dissimilar metal material, taking into consideration the decrease in strength of the metal material containing a Group 5 element when separating hydrogen from a hydrogen-containing mixed gas. This will be explained using vanadium as the Group 5 element as an example. Hereinafter, in the explanation of the lower limit of the contact width between the metal material and the dissimilar metal material, significant figures may be used up to three digits.

[0032] Using a pure vanadium film as the metallic material containing a Group 5 element, we assume that this film will break due to shear deformation. First, we calculate the yield stress of the pure vanadium film from its Vickers hardness. It is generally known that there is a 1 / 3 relationship between Vickers hardness and yield stress, and since the Vickers hardness of pure vanadium is 120 HV (1180 MPa in MPa), we can infer that the yield stress of the pure vanadium film is approximately 400 MPa.

[0033] When a pure vanadium membrane with a diameter of 43 mm and a thickness of 0.3 mm is used, the area subjected to shear stress on this membrane is 40.5 mm, which is the product of the circumference length of 135 mm (= 43 mm × π) and the membrane thickness of 0.3 mm. 2 If we consider shear stress to be the same as yield stress, the maximum load Patom that this membrane can withstand can be calculated from the yield stress and the area calculated above. Patom is then 1620 kgf (= 400 (MPa) x 40.5 (mm 2 ) / 9.8(gravitational acceleration, unit: m / s 2 This value is the maximum load that the membrane can withstand under atmospheric pressure.

[0034] On the other hand, experiments have shown that when a pure vanadium membrane of the above shape is pressurized in a hydrogen atmosphere, it will break at a pressure difference of approximately 10 atmospheres. At this time, the load acting on the pure vanadium membrane is PH = 148.0 kgf (= 1450 (membrane area, unit: mm 2) x 1 (pressure, unit: MPa) / 9.8 (gravitational acceleration, unit: m / s 2 )). It can be seen that PH is a much lower value than Patom. This difference can be considered to be the effect of hydrogen embrittlement. Therefore, PH / Patom = 0.09 is defined as the coefficient RH that takes into account the effect of hydrogen embrittlement. Based on the above, we determine the minimum weld width required between a pure vanadium film and a dissimilar metal material in a hydrogen atmosphere.

[0035] When operating a hydrogen permeation device using the above pure vanadium membrane, the pressure difference between the primary side (input side, in other words, the side where the hydrogen-containing mixed gas comes into contact with the pure vanadium membrane) and the secondary side (output side, in other words, the side where hydrogen is separated and permeates) is set to 0.3 MPa, in order to ensure stable operation without cracking the pure vanadium membrane. If a pure vanadium membrane with a diameter of 30 mm is used as the hydrogen separation membrane (when a stainless steel ring with an outer diameter of 52 mm and an inner diameter of 30 mm is concentrically welded to a pure vanadium membrane with an outer diameter of 43 mm, the vanadium membrane to which pressure is applied will be 30 mm), its area will be 707 mm. 2 As mentioned above, the pressure difference between the primary and secondary sides is set to 0.3 MPa, so the pressure difference for the pure vanadium membrane is 21.6 kgf (= 0.3 (pressure difference, unit: MPa) x 707 (membrane area, unit: mm 2 ) / 9.8(gravitational acceleration, unit: m / s 2 )) load is applied.

[0036] Next, we will determine the minimum welding area required under atmospheric pressure when welding a certain width inward from the diameter of a pure vanadium film of 30 mm. The minimum welding area in this case is calculated as follows: 21.6 (load, unit: kgf) x 9.8 (gravitational acceleration, unit: m / s 2 ) / minimum welding area = 400 (yield stress = shear strength, unit: MPa). Therefore, the minimum welding area is 0.53 mm 2 (=21.6 (load, unit: kgf) x 9.8 (gravitational acceleration, unit: m / s 2) / 400 (yield stress = shear strength, unit: MPa). Calculating the minimum weld width from this minimum weld area, the circumference of a 30 mm diameter is 94.2 mm, so the required weld width in air is Latom = 0.0056 mm (= 0.53 (required cross-sectional area, unit: mm 2 ) / 94.2 (circumferential length · unit: mm)). By correcting this Latom with the correction factor mentioned above, the required weld width in a hydrogen atmosphere is obtained as LH = 0.06 mm (= 0.0056 (Latom · unit: mm) / 0.09 (RH · correction factor)).

[0037] As described above, when calculations are performed under the given assumptions, a weld width (bead width) of 0.06 mm is sufficient. If this is converted into the weld width of an actual welding device, the lower limit of the bead width (the width where the metal material and dissimilar metal material come into contact) is 0.5 mm.

[0038] The width of the contact between the metal material and the dissimilar metal material is preferably 0.6 mm or more from the viewpoint of improving the mechanical strength of the joint. On the other hand, the wider the width of the contact between the metal material and the dissimilar metal material, the more preferable it is from the viewpoint of ensuring mechanical strength, but from the viewpoint of shortening the joining time and improving production efficiency, the width is preferably 2.5 mm or less, and more preferably 2 mm or less.

[0039] In the present invention, the hardness of the joint generally tends to be softer than that of the non-jointed portion of the metal material (the portion of the base metal material). This is because the joint melts during welding, resulting in an effect similar to annealing. However, from the viewpoint of the strength of the film itself, the Vickers hardness of the joint is preferably 30 HV or higher, more preferably 50 HV or higher, and particularly preferably 60 HV or higher.

[0040] On the other hand, the Vickers hardness of the non-jointed portion (the portion of the base metal material) is preferably 80 HV or higher. This range softens the metal material, making it easier to ensure toughness. On the other hand, from the viewpoint of hardening the metal material and ensuring mechanical strength, the Vickers hardness is preferably 100 HV or higher, more preferably 120 HV or higher, particularly preferably 130 HV or higher, and most preferably 150 HV or higher. The Vickers hardness of metal materials is generally 500 HV or lower, usually 300 HV or lower. The Vickers hardness may be measured using a commercially available Vickers hardness tester (for example, a micro Vickers hardness tester (for example, the HM-100 series from Mitutoyo Corporation)).

[0041] The dissimilar metal material used in the present invention refers to a metal material containing a major element different from the major element constituting the metal material. There are no particular limitations on this dissimilar metal material, but the dissimilar metal material often serves as a base material or substrate to support the metal material and also constitutes part of the housing of the hydrogen separation device. From this perspective, the dissimilar metal material is preferably at least one selected from the group consisting of steel, stainless steel, and a nickel-chromium-iron alloy. Furthermore, from the perspective of the housing of the hydrogen separation device, it is more industrially preferable that the dissimilar metal material be stainless steel.

[0042] [Variations] While the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the scope of the above-described embodiments. Various modifications and improvements can be made to the above-described embodiments. [Example]

[0043] [Example 1] (Electron Beam Welding) A disk-shaped pure vanadium film with a diameter of 40 mm and a thickness of 0.3 mm was prepared as the metallic material containing a Group 5 element. A ring-shaped stainless steel plate with an outer diameter of 52 mm, an inner diameter of 30 mm, and a thickness of 0.5 mm was prepared as the dissimilar metallic material. The two were then welded in a vacuum using an electron beam. Figure 1 shows a schematic diagram of the electron beam welding apparatus (left side) and a schematic diagram (right side) showing the metallic material (vanadium film with a diameter of 40 mm) and the dissimilar metallic material (ring-shaped stainless steel plate with a diameter of 52 mm and an inner diameter of 30 mm) placed on the workpiece during electron beam welding. Electron beam welding was performed in a vacuum chamber of the electron beam welding apparatus shown in the left side of Figure 1 under reduced pressure. The welding conditions were as follows: Electron beam processing machine: EBM-6LB-1VR (Mitsubishi Electric Corporation) Processing conditions: Cathode diameter φ2 mm, acceleration voltage 60 kV, WD 300 mm, beam current 15.5 mA

[0044] (SEM observation of the cross section of the joint) Three welded samples (n=3) of the disk-shaped pure vanadium film and ring-shaped stainless steel plate welded as described above were prepared, and the cross section of each joint (the test piece (cross section) was prepared by mechanically polishing after machining (wire electric discharge machine)) was observed with a scanning electron microscope (SEM). For SEM observation, a JEOL JSM-7100F was used to acquire secondary electron images at an accelerating voltage of 15 kV.

[0045] The observation results are shown in Figure 2. Figure 2 shows SEM observation images of the cross section of the joint in the three samples prepared. In the first sample (Figure 2(a)), the contact width between the metal material and the dissimilar metal material was 0.8 mm. In the second sample (Figure 2(b)), the contact width between the metal material and the dissimilar metal material was 1.1 mm. In the third sample (Figure 2(c)), the contact width between the metal material and the dissimilar metal material was 1.65 mm.

[0046] (Hydrogen permeation test) Figure 3 shows the measurement results of the hydrogen permeation performance of a sample (effective membrane diameter 30 mm) in which a vanadium membrane was electron-beam welded to the center of the doughnut-shaped stainless steel ring (diameter 52 mm) shown in Figure 1, and a normal vanadium membrane without this welding (the diameter of the vanadium membrane was 52 mm, but in order to compare with the electron-beam welded sample, the data obtained in the experiment was converted so that the effective membrane diameter was 30 mm). The hydrogen permeation test was carried out using the following procedure.

[0047] A standard vanadium film was RF sputtered for 6 minutes at a substrate temperature of 300°C using an RF sputtering device, and both sides of the film were coated with Pd-25 mol% Ag to impart hydrogen dissociation catalytic properties.For the sample in which the vanadium film was electron beam welded to the center of the donut-shaped stainless steel ring shown in Figure 1, the vanadium film before welding was RF sputtered for 6 minutes at a substrate temperature of 300°C using an RF sputtering device, and both sides of the film were coated with Pd-25 mol% Ag to impart hydrogen dissociation catalytic properties.

[0048] Figure 4 is a schematic diagram of the experimental equipment used in the hydrogen permeation test. In the area labeled "hydrogen permeable membrane" on this schematic diagram, either (1) a sample (membrane effective diameter 30 mm) in which a vanadium membrane was electron-beam welded to the center of a donut-shaped stainless steel ring (diameter 52 mm) as shown in Figure 1, which had been RF sputtered, or (2) a sample with a regular vanadium membrane was placed. The entire equipment was evacuated, and the amount of hydrogen permeated was measured with a flow meter while the mixed gas pressure on the primary side was adjusted appropriately.

[0049] When the samples (1) and (2) above were placed in the location marked "hydrogen-permeable membrane" in Figure 4, the vanadium membrane was exposed to the primary mixed gas flowing from left to right. The hydrogen permeation test was conducted at a test temperature of 350°C, with the hydrogen gas supply pressure ranging from 0.1 to 0.5 MPa abs. The hydrogen gas outlet pressure was controlled by vacuuming with a pump. In Figure 3, the vertical axis represents the hydrogen permeation rate per minute (L(SLM)), and the horizontal axis represents the hydrogen gas supply pressure on the input (primary) side.

[0050] The hydrogen permeation test for the above sample (1) was carried out using a sample welded under the same conditions as the above three prepared welded samples.

[0051] As can be seen from the graph in Figure 3, there was no cracking of the membrane or destruction or fracture of the welded joints up to an absolute pressure of 0.5 MPa on the primary side of the input gas. The amount of hydrogen permeation was also as good as that of a normal vanadium membrane that is not welded.

[0052] [Example 2] (Fiber welding) A disk-shaped pure vanadium film and a ring-shaped stainless steel plate were prepared, each of the same size as in Example 1. Then, the two were joined by fiber welding. Figure 5 shows a schematic diagram of the fiber welding apparatus (left side) and a schematic diagram (right side) showing the metallic material (vanadium film, diameter 40 mm) and dissimilar metallic material (ring-shaped stainless steel plate, diameter 52 mm, inner diameter 30 mm) placed on the workpiece during fiber welding. Fiber welding was performed in the atmosphere under appropriately set welding conditions. Visual inspection and measurement of the cross section revealed that the contact width between the metallic material and the dissimilar metallic material was 1 to 2 mm.

[0053] (Hydrogen permeation test) A hydrogen permeation test was carried out in the same manner as in Example 1. Figure 6 shows the measurement results of the hydrogen permeation performance of a sample (effective membrane diameter: 40 mm) in which a vanadium membrane was fiber-welded to the center of the doughnut-shaped stainless steel ring (diameter: 52 mm) shown in Figure 5, and a normal vanadium membrane without this welding (the diameter of the vanadium membrane was 52 mm, but the data obtained in the experiment was converted so that the effective membrane diameter was 40 mm in order to compare with the electron-beam welded sample).

[0054] As can be seen from the graph in Figure 6, there was no cracking of the membrane or destruction or fracture of the welded joints up to an absolute pressure of 0.5 MPa on the primary side of the input gas. The amount of hydrogen permeation was also as good as that of a normal vanadium membrane that is not welded. [Industrial Applicability]

[0055] The present invention provides a structure having a joint where a metal material containing a Group 5 element and a dissimilar metal material different from the metal material are joined, and which can provide a good hydrogen separation function.

Claims

1. A structure having a joint in which a metal material containing a Group 5 element and a dissimilar metal material different from the metal material are joined, The metallic material is used to separate hydrogen from a mixed gas containing hydrogen, the joint is formed by direct contact between the metal material and the dissimilar metal material, A structure characterized in that the width of the contact between the metal material and the dissimilar metal material at the joint is 0.5 mm or more and 3 mm or less.

2. The structure of claim 1 , wherein the metallic material is in the form of a metallic film.

3. 3. The structure of claim 2, wherein the thickness of the metal film is greater than or equal to 0.05 mm and less than or equal to 5 mm.

4. 10. The structure of claim 1, wherein the Group 5 metal is at least one selected from the group consisting of vanadium, niobium, or tantalum.

5. 10. The structure of claim 1, wherein the Group 5 element-containing metallic material is pure vanadium or a vanadium alloy.

6. 2. The structure of claim 1, wherein the dissimilar metal material is at least one selected from the group consisting of steel, stainless steel, and nickel-chromium-iron alloy.

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