Conductive connecting member

Abstract

To provide a conductive connection member that has a low volume resistivity, and has sufficient corrosion resistance at room temperature in the atmosphere, or desirably, mechanical strength (0.2% proof stress) and high-temperature corrosion resistance that can withstand long-term service at a high temperature of 600°C in the atmosphere.SOLUTION: A conductive connection member comprises a clad material comprising a first metal layer, a second metal layer, and a third metal layer that are laminated in this order and subjected to a cladding process. The first metal layer and the third metal layer are composed of a metal material comprising at least Cr. The second metal layer is composed of a metal material having a volume resistivity lower than those of the first metal layer and the third metal layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a conductive connecting member used for electrical connections, and more specifically, to a conductive connecting member composed of a clad material formed by rolling and joining dissimilar metals. [Background technology]

[0002] Conventionally, conductive connecting members used for electrical connections are known. Such conductive connecting members are disclosed, for example, in Patent Document 1 (Japanese Patent Publication No. 2016-162730) and Patent Document 2 (Japanese Patent Publication No. 2000-182653).

[0003] Patent Document 1 discloses an electrode lead wire member in which a corrosion-resistant protective layer is formed on the surface of a thin metal sheet made of one of the following materials: SUS (stainless steel), Ni (pure nickel), Cu (pure copper), or Al (pure aluminum) by a passivation treatment. Patent Document 2 discloses a conductive connecting rod in which an oxidation-resistant protective layer is formed on the surface of a conductive metal rod made of SUS or Ni by an oxidation-resistant treatment. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-162730 [Patent Document 2] Japanese Patent Publication No. 2000-182653 [Overview of the project] [Problems that the invention aims to solve]

[0005] The SUS disclosed in Patent Documents 1 and 2 is a metal material that has moderate corrosion resistance, workability, and conductivity, is relatively inexpensive and readily available, and can be used for electrical connections. The Ni disclosed in Patent Documents 1 and 2 has better conductivity than SUS, good corrosion resistance, moderate workability, and is more expensive than SUS, but is widely used for electrical connections. The Cu disclosed in Patent Document 1 has better conductivity than Ni, good workability, and is widely used for electrical connections. The Al disclosed in Patent Document 1, while not as good as Cu, has better conductivity than Ni, good workability, is widely used for lightweight applications, and is also used for electrical connections. In addition, Au (pure gold), which has better conductivity than Al, has good workability, and is a metal material widely used for electrical connections.

[0006] However, conductive connectors made of Cu or Al have sufficient conductivity, but their corrosion resistance is inferior to that of SUS and Ni, so corrosion progresses even in ambient air at room temperature, and they have the problem of not being able to withstand long-term use. Also, conductive connectors made of Ni have sufficient conductivity, but as is conventionally known, their mechanical strength decreases in high-temperature air environments of 500°C to 600°C, so they may not be able to withstand long-term use in high-temperature air environments exceeding 500°C. Furthermore, conductive connectors made of SUS have mechanical strength and high-temperature corrosion resistance that can withstand long-term use in high-temperature air environments better than Ni, but their volume resistivity is higher and their conductivity is inferior to that of Al, Cu, and Ni, so they have the problem of reduced electrical efficiency. Finally, conductive connectors made of Au have superior conductivity to Al and Ni, and superior corrosion resistance to Ag and Cu, but they are more expensive than any of the above materials, and are softer and have lower mechanical strength than Al, so they cannot withstand use in high-temperature air environments.

[0007] The objective of this invention is to provide a conductive connecting member with low volume resistivity and sufficient corrosion resistance in a normal temperature atmospheric environment. Furthermore, if possible, to provide a conductive connecting member with mechanical strength (0.2% yield strength) and high-temperature corrosion resistance that can withstand long-term use in a high-temperature atmospheric environment of 600°C. [Means for solving the problem]

[0008] The inventor came up with the idea of combining a highly corrosion-resistant material having corrosion resistance in a normal-temperature atmospheric environment so as to suppress the surface exposure of a highly conductive material having a small volume resistivity. Further, from the same perspective, the inventor came up with the idea of combining a heat-resistant material having mechanical strength (0.2% proof stress) and high-temperature corrosion resistance in a high-temperature atmospheric environment so as to suppress the surface exposure of a highly conductive material having a small volume resistivity. Then, through subsequent improvements, the inventor found that the above problems could be solved and conceived of this invention.

[0009] That is, the conductive connection member according to this invention is composed of a clad material in which a first metal layer, a second metal layer, and a third metal layer are laminated and roll-bonded in this order. The first metal layer and the third metal layer are made of a metal material containing at least Cr, and the second metal layer is made of a metal material having a smaller volume resistivity than the first metal layer and the third metal layer.

[0010] In this invention, it is preferable that the first metal layer and the third metal layer are made of a metal material containing 11 mass% or more of Cr (chromium).

[0011] In this invention, it is preferable that the second metal layer is made of a metal material having a volume resistivity of 20×10 -8 Ω·m or less.

[0012] In this invention, it is preferable that the first metal layer and the third metal layer are made of an Fe-based alloy or a Ni-based alloy.

[0013] In this invention, it is preferable that the first metal layer and the third metal layer are made of SUS (stainless steel).

[0014] In this invention, it is preferable that the second metal layer is made of any one of Ag (pure silver), an Ag-based alloy, Al (pure aluminum), an Al-based alloy, Cu (pure copper), a Cu-based alloy, Mo (pure molybdenum), a Mo-based alloy, Ni (pure nickel), and a Ni-based alloy.

[0015] In this invention, the second metal layer is preferably made of Cu (pure copper) or a Cu-based alloy. For example, the conductive connection part is made of a clad material in which the first metal layer made of SUS, the second metal layer made of Cu or a Cu-based alloy, and the third metal layer made of SUS are laminated in this order and roll-joined.

[0016] In this invention, the second metal layer is preferably made of Ni (pure nickel) or a Ni-based alloy. For example, the conductive connection part is made of a clad material in which the first metal layer made of SUS, the second metal layer made of Ni or a Ni-based alloy, and the third metal layer made of SUS are laminated in this order and roll-joined.

[0017] In this invention, the second metal layer is preferably made of Al (pure aluminum) or an Al-based alloy. For example, the conductive connection part is made of a clad material in which the first metal layer made of SUS, the second metal layer made of Al or an Al-based alloy, and the third metal layer made of SUS are laminated in this order and roll-joined. [Effects of the Invention]

[0018] According to this invention, by appropriately selecting a metal material according to the application and purpose, it is possible to provide a conductive connecting member with low volume resistivity and sufficient corrosion resistance, for example, in a normal temperature atmospheric environment. Furthermore, by more appropriately selecting the metal material, it is possible to provide a conductive connecting member with mechanical strength (0.2% yield strength) and high-temperature corrosion resistance that can withstand long-term use in a high-temperature atmospheric environment of 600°C. [Brief explanation of the drawing]

[0019] [Figure 1] This figure schematically shows the cross-sectional configuration of the conductive connecting member according to this invention. [Figure 2] This is a diagram (photograph) showing the cross-sectional configuration of a conductive connecting member, which is one embodiment of this invention. [Modes for carrying out the invention]

[0020] In this invention, by appropriately selecting a metal material according to its application and purpose, and by combining a metal layer made of a highly corrosion-resistant material that has corrosion resistance (room temperature corrosion resistance) in a normal temperature atmospheric environment, for example, in order to minimize the surface exposure of the metal layer made of a highly conductive material, a conductive connecting member according to this invention can be obtained that has low volume resistivity and sufficient corrosion resistance in a normal temperature atmospheric environment.

[0021] Furthermore, in this invention, by more appropriately selecting the metal material and suppressing the surface exposure of the metal layer made of a highly conductive material, for example by combining it with a heat-resistant material that has mechanical strength (0.2% yield strength) and high-temperature corrosion resistance in a high-temperature atmospheric environment, it is possible to obtain a conductive connecting member according to this invention that has low volume resistivity and mechanical strength (0.2% yield strength) and high-temperature corrosion resistance that can withstand long-term use in a high-temperature atmospheric environment of 600°C.

[0022] In other words, the conductive connecting member according to this invention is composed of a clad material in which a first metal layer, a second metal layer, and a third metal layer are laminated in this order and rolled and joined, the first metal layer and the third metal layer are made of a metallic material containing at least Cr, and the second metal layer is made of a metallic material with a lower volume resistivity compared to the first metal layer and the third metal layer.

[0023] Figure 1 is a schematic diagram showing the cross-sectional structure of the conductive connecting member according to this invention. The conductive connecting member 1 shown in Figure 1 is composed of a clad material 10 in which a first metal layer 11, a second metal layer 12, and a third metal layer 13 are laminated in this order. This clad material 10 can be manufactured by a dissimilar metal rolling joining method in which the first metal layer 11, the second metal layer 12, and the third metal layer 13 are laminated in this order and then roll-joined. The dissimilar metal rolling joining method applied to this invention includes manufacturing processes such as softening annealing and intermediate rolling before rolling joining, diffusion annealing and intermediate rolling after rolling joining, finish rolling to obtain the thickness, width, surface properties, and various characteristics of the target product, skin pass rolling, annealing, surface treatment, and stripping, and several manufacturing processes can be selected as needed. The conductive connecting member (conductive connecting member 1) according to this invention can be manufactured using the clad material 10 manufactured by such a manufacturing process. For example, by processing the clad material 10 into a desired shape, a conductive connecting member having a desired shape can be manufactured.

[0024] The clad material 10 shown in Figure 1 is made up of a first metal layer 11, a second metal layer 12, and a third metal layer 13, which are laminated in this order. The second metal layer 12 is located between the first metal layer 11 and the third metal layer 13, and a first joint 12a formed by rolling bonding is located between the first metal layer 11 and the second metal layer 12, and a second joint 12b formed by rolling bonding is located between the second metal layer 12 and the third metal layer 13. From the viewpoint of increasing the bonding strength, the first joint 12a and the second joint 12b are preferably joints formed by metal diffusion caused by annealing (metal diffusion layers).

[0025] The thickness t (total thickness) of the cladding material 10 constituting the conductive connecting member 1 is, for example, 0.05 mm to 2 mm, assuming that the conductive connecting member 1 is used as a lead (tab), terminal, connector (interconnector), or busbar. In this case, the ratio (layer ratio) of the thickness t1 of the first metal layer 11, the thickness t2 of the second metal layer 12, and the thickness t3 of the third metal layer 13 may be, for example, 1:1:1 to 1:4:1. If the conductivity of the conductive connecting member 1 is to be further improved, it is preferable to make the thickness t2 of the second metal layer 12 greater than the thickness t1 of the first metal layer 11 and the thickness t3 of the third metal layer 13. Also, if the room temperature corrosion resistance and high-temperature characteristics (0.2% yield strength, high-temperature corrosion resistance, etc.) of the conductive connecting member 1 are to be further improved, it is preferable to make the thickness t1 of the first metal layer 11 and the thickness t3 of the third metal layer 13 greater than the thickness t2 of the second metal layer 12. Furthermore, the thickness t1 of the first metal layer 11 and the thickness t3 of the third metal layer 13 may or may not be the same.

[0026] In the conductive connecting member 1 having such a clad structure, the surface exposure of the second metal layer 12, which is made of a metal material with low volume resistivity, is suppressed to a small extent by the first metal layer 11 and the third metal layer 13, which are made of a metal material containing Cr. As a result, highly efficient electrical connection can be made due to the conductivity of the second metal layer 12, and the progression of corrosion can be suppressed due to the corrosion resistance of the first metal layer 11 and the third metal layer 13. This makes it possible to obtain a conductive connecting member with low volume resistivity and sufficient corrosion resistance, for example, in a normal temperature atmospheric environment. Furthermore, by selecting a more appropriate metal material containing Cr, it is possible to obtain a conductive connecting member with low volume resistivity and mechanical strength (0.2% yield strength) and high-temperature corrosion resistance that can withstand long-term use in a high-temperature atmospheric environment of 600°C.

[0027] In the conductive connecting member according to this invention, the metal material constituting the first metal layer and the third metal layer, which contains at least Cr, is a highly corrosion-resistant material. Metal materials containing Cr that readily form a passivation film are generally metal materials with high corrosion resistance and oxidation resistance. The Cr-containing metal material applied to this invention may, for example, be a metal material that has corrosion resistance in a normal temperature atmospheric environment (a highly corrosion-resistant material at normal temperature), or a metal material that has mechanical strength (0.2% yield strength) and high-temperature corrosion resistance in a high-temperature atmospheric environment (a highly corrosion-resistant and heat-resistant material).

[0028] In this invention, as described above, the first metal layer and the third metal layer are made of a metal material such as a highly corrosion-resistant material or a highly corrosion-resistant and heat-resistant material containing at least Cr. Furthermore, if a conductive connecting member with even higher corrosion resistance is desired, the first metal layer and the third metal layer are preferably made of a metal material containing 11% by mass or more of Cr.

[0029] Specific examples of metal materials containing Cr, such as highly corrosion-resistant and highly corrosion-resistant / heat-resistant materials, include ferritic SUS such as SUS405, SUS410L, SUS430, and SUS444; austenitic SUS such as SUS301, SUS304, SUS310S, and SUS316L; and martensitic SUS such as SUS403, SUS410, and SUS410S. These SUS materials are specified in JIS-G4305:2021. Other examples include Fe-Cr-Mo (molybdenum) alloys, Fe-Cr-W (tungsten) alloys, and Ni-based heat-resistant alloys such as Alloy 718, Alloy 713C, and Alloy 713LC as specified by ASTM.

[0030] Preferably, such metallic materials are Fe-based alloys or Ni-based alloys. Among Fe-based alloys, SUS is relatively inexpensive and readily available, possessing moderate corrosion resistance. Various usage environments can be envisioned for conductive connecting members, but if they are to be used in particularly harsh high-temperature environments, it is advisable to select from SUS, Fe-Cr-Mo alloys, Fe-Cr-W alloys, or Ni-based heat-resistant alloys, which offer superior heat resistance.

[0031] In the conductive connecting member according to this invention, the metal material constituting the second metal layer, which has a lower volume resistivity than the first and third metal layers, is a highly conductive material. Highly conductive materials generally have excellent conductivity and are suitable for electrical connections, but their corrosion resistance in ambient air environments at room temperature may be unsatisfactory, as may their mechanical strength (0.2% yield strength) and corrosion resistance (high-temperature corrosion resistance) in high-temperature air environments. Therefore, in this invention, the first and third metal layers are made of a highly corrosion-resistant material at room temperature or a highly corrosion-resistant and heat-resistant material containing at least Cr, in order to minimize surface exposure of the second metal layer, which is made of a highly conductive material with low volume resistivity.

[0032] In this invention, as described above, the second metal layer is made of a metal material with low volume resistivity. The conductive connecting member according to this invention, which is composed of a clad material with at least three layers, is considered to have greater durability for long-term use as the thickness of the first metal layer and the third metal layer increases. Therefore, it is considered preferable to make the second metal layer, which is not expected to have the same durability as the first and third metal layers, thinner and to make its volume resistivity even lower. The volume resistivity of SUS, which is considered suitable as a metal material for the first and third metal layers, is, for example, 50 × 10⁻¹⁰ at room temperature. -8 It exceeds Ω·m and is 100 × 10 in high-temperature environments. -8 It exceeds Ω·m. From this perspective, if we want to obtain a conductive connecting member that has reasonable durability and higher conductivity, it is preferable that the second metal layer has a volume resistivity of 20 × 10 in an environment of 0°C to 100°C. -8 It shall consist of a metallic material with a value of Ω·m or less.

[0033] To give specific examples of metallic materials with relatively low volume resistivity, for instance, Ag (pure silver) such as 925, 835, and 800 has a volume resistivity of 1.59 × 10⁻⁶. -8 Approximately Ω·m (at 0°C), Cu (pure copper) such as C1020 is 1.68 × 10⁻⁶ -8 Approximately Ω·m (at 0°C), Al (pure aluminum) such as A1050 is 2.65 × 10 -8On the order of Ω·m (0 to 100 °C), Mo (pure molybdenum) is 5.00×10 -8 On the order of Ω·m (0 °C), Ni (pure nickel) is 6.99×10 -8 On the order of Ω·m (0 °C), Fe (pure iron) is 10.0×10 -8 On the order of Ω·m (0 to 200 °C), and Au (pure gold) is 2.44×10 -8 On the order of Ω·m (0 to 100 °C). Among these, Au is more conductive than Al and Ni, and more corrosion-resistant than Ag and Cu. On the other hand, it is more expensive than any of the materials mentioned above, softer than Al, and has a lower mechanical strength. The temperature or temperature range shown in the parentheses above is the measurement environmental temperature of the volume resistivity.

[0034] The metal material constituting the second metal layer may be any metal material having a smaller volume resistivity than the first metal layer and the third metal layer. When selecting a metal material to form the second metal layer, preferably, it is a metal material composed of any one of Ag, Cu, Au, Al, Mo, and Ni, or a metal material composed of an alloy based on one or more of Ag, Cu, Au, Al, Mo, and Ni that does not substantially contain Cr. Among these, Cu (pure copper) is cheaper than Ag, has a smaller volume resistivity and better conductivity than Mo and Ni, better heat resistance than Al, and is relatively easy to form a clad material due to its good workability. Cu-based alloys may also be more preferable than Ag-based alloys, Mo-based alloys, Ni-based alloys, and Al-based alloys for the same reasons as in the case of Cu. Ni (pure nickel) is cheaper than Ag and Mo, has better heat resistance, corrosion resistance, and mechanical strength than Cu, and is relatively easy to form a clad material due to its good workability. Ni-based alloys may also be more preferable than Ag-based alloys, Cu-based alloys, Mo-based alloys, and Al-based alloys for the same reasons as in the case of Ni. Al (pure aluminum) has a disadvantage in heat resistance compared to Cu and Ni, but is lightweight and has good workability, and is effective when shape freedom and weight reduction of the conductive connection member are desired. Al-based alloys may also be more preferable than Ag-based alloys, Cu-based alloys, Mo-based alloys, and Ni-based alloys for the same reasons as in the case of Al.

[0035] The conductive connecting member according to this invention has a second metal layer made of a metal material with low volume resistivity, and therefore the metal material can have a corresponding conductivity. At the same time, the conductive connecting member according to this invention has a first metal layer and a third metal layer made of a metal material containing at least Cr, and therefore the first and third metal layers can have corresponding properties (room temperature corrosion resistance, 0.2% yield strength, high temperature corrosion resistance, etc.). As a result, the conductive connecting member according to this invention can be applied to general electrical connections and at the same time has sufficient corrosion resistance in a room temperature atmospheric environment. Furthermore, it can have mechanical strength (0.2% yield strength) and high temperature corrosion resistance that can withstand long-term use in a high temperature atmospheric environment of, for example, 600°C. General electrical connections refer to connection structures that can be constructed by means such as screw fastening, fitting, crimping, compression, various types of welding (laser welding, ultrasonic welding, etc.), brazing, and diffusion bonding. Furthermore, the connecting partner to the conductive connecting member according to this invention is also a conductive member (connected member) that has a corresponding degree of conductivity.

[0036] The conductive connecting member according to this invention can be applied to, for example, leads (tabs), terminals, connectors (interconnectors), or busbars. The conductive connecting member according to this invention can be electrically connected to, for example, current collectors, metal separators, electrodes, or electrode terminals.

[0037] Figure 2 shows an example of a cross-sectional image (photograph) of a conductive connecting member that is one embodiment of the present invention and was actually manufactured. The cross-sectional image shown in Figure 2 was taken with multiple conductive connecting members 1 (1a, 1b, 1c, 1d) stacked in the thickness direction. The conductive connecting member 1 shown in Figure 2 is composed of a clad material 10 which is formed by laminating and rolling together a first metal layer 11 made of a metal material equivalent to SUS316L (JIS-G4305:2021) with a Cr content of 17.3 mass%, a second metal layer 12 made of a metal material equivalent to C1020 (JIS-H3100:2018) with a Cu content of 99.9 mass% or more, and a third metal layer 13 made of a metal material equivalent to SUS316L with a Cr content of 17.3 mass%, in this order.

[0038] The average thickness t (total thickness) of this clad material 10 is approximately 0.2 mm. The ratio (layer ratio) of the average thickness t1 of the first metal layer 11, the average thickness t2 of the second metal layer 12, and the average thickness t3 of the third metal layer 13 is approximately 1:2:1. The average thickness t1 of the first metal layer 11 and the average thickness t3 of the third metal layer 13 are almost equal.

[0039] C1020, which constitutes the second metal layer 12, is, as is well known, one of the well-known highly conductive materials. SUS316L, which constitutes the first metal layer 11 and the third metal layer 13, is, as is well known, one of the highly corrosion-resistant and heat-resistant materials that exhibits corrosion resistance in a normal temperature atmospheric environment and mechanical strength (0.2% yield strength) and corrosion resistance in a relatively high temperature atmospheric environment. The volume resistivity of C1020 constituting the second metal layer 12 is approximately 1.71 × 10⁻⁶ at normal temperature. -8 The conductivity is Ω·m (approximately 101% IACS). The volume resistivity of SUS316L constituting the first metal layer 11 and the third metal layer 13 is approximately 74 × 10⁻¹⁶ at room temperature. -8 The resistivity is Ω·m. Therefore, the second metal layer 12 has a lower volume resistivity than the first metal layer 11 and the third metal layer 13, which is approximately 2.3% of that of the first metal layer 11 and the third metal layer 13. Thus, this conductive connecting member 1 enables highly efficient electrical connection through the second metal layer 12 made of the highly conductive material C1020, and at the same time, it is possible to have corrosion resistance in a normal temperature atmospheric environment through the first metal layer 11 and the third metal layer 13 made of the highly corrosion-resistant and heat-resistant material SUS316L, and furthermore, it is possible to have mechanical strength (0.2% yield strength) and high-temperature corrosion resistance in a high-temperature atmospheric environment (for example, 600°C). [Examples]

[0040] Five types of cladding materials were prepared, and test specimens 1 to 5 (conductive connecting members) were fabricated from these cladding materials. In addition, seven types of veneers were prepared, and test specimens 6 to 12 were fabricated from these veneers. Test specimens 1 to 5 are examples of the present invention. Test specimens 6 to 12 are comparative examples.

[0041] As Test Specimen 1, a three-layer clad material (SUS430 / NW2201 / SUS430) with a thickness of 1.0 mm was prepared. Specifically, a stainless steel sheet made of SUS430 (JIS-G4305:2021) with a Cr content of 16.5 mass%, a Ni sheet made of NW2201 (JIS-G4902:2019) with a Ni content of 99.0 mass% or more, and a stainless steel sheet made of SUS430 with a Cr content of 16.5 mass% were laminated in this order and rolled and joined at a reduction ratio of approximately 62%. Next, diffusion annealing (held at 875°C for 5 minutes) was performed. Then, finish rolling was performed at a reduction ratio of approximately 38%. The total reduction ratio from rolling joining to finish rolling (total reduction ratio) was approximately 76%. Next, annealing (held at 900°C for 5 minutes) was performed to temper the material. Finally, a three-layer clad material with a total thickness of 1.0 mm was fabricated. The thickness ratio of each layer to the total thickness of the resulting clad material was approximately 33% for the stainless steel layer (SUS430 layer) on one surface corresponding to the first metal layer, approximately 34% for the intermediate Ni layer (NW2201 layer) corresponding to the second metal layer, and approximately 33% for the stainless steel layer (SUS430 layer) on the other surface corresponding to the third metal layer.

[0042] As test specimen 2, a three-layer clad material (SUS316L / C1020 / SUS316L) with a thickness of 0.20 mm was prepared. Specifically, a stainless steel sheet made of SUS316L (JIS-G4305:2021) with a Cr content of 17.2 mass%, a Cu sheet made of C1020 (JIS-H3100:2018) with a Cu content of 99.96 mass% or more, and a stainless steel sheet made of SUS316L with a Cr content of 17.2 mass% were laminated in this order and rolled and joined at a reduction ratio of approximately 56%, and then rolled again at a reduction ratio of approximately 29%. Next, diffusion annealing (held at 1000°C for 1.3 minutes) was performed. Then, finish rolling was performed at a reduction ratio of approximately 20%, and tempering was performed. The total reduction ratio from rolling and joining to finish rolling (total reduction ratio) was approximately 75%. Finally, a three-layer clad material with a total thickness of 0.20 mm was fabricated. The thickness ratio of each layer to the total thickness of the resulting clad material was approximately 25% for the stainless steel layer (SUS316L layer) on one surface corresponding to the first metal layer, approximately 50% for the intermediate Cu layer (C1020 layer) corresponding to the second metal layer, and approximately 25% for the stainless steel layer (SUS316L layer) on the other surface corresponding to the third metal layer.

[0043] As test specimen 3, a three-layer clad material (SUS304 / C1020 / SUS304) with a thickness of 0.20 mm was prepared. Specifically, a stainless steel sheet made of SUS304 (JIS-G4305:2021) with a Cr content of 18.1 mass%, a Cu sheet made of C1020 with a Cu content of 99.9 mass% or more, and a stainless steel sheet made of SUS304 with a Cr content of 18.1 mass% were laminated in this order and rolled at a reduction ratio of 59%, and then rolled and joined at a reduction ratio of 4%. Next, diffusion annealing (held at 1050°C for 1.5 minutes) was performed. Next, it was rolled at a reduction ratio of approximately 35% and annealed (held at 1050°C for 1.3 minutes). Next, it was finish rolled at a reduction ratio of approximately 13% and tempered. The total reduction ratio from rolling and joining to finish rolling was approximately 78%. Finally, a three-layer clad material with a total thickness of 0.20 mm was produced. The thickness ratio of each layer to the total thickness of the final clad material was approximately 33% for the stainless steel layer (SUS304 layer) on one surface corresponding to the first metal layer, approximately 34% for the intermediate Cu layer (C1020 layer) corresponding to the second metal layer, and approximately 33% for the stainless steel layer (SUS304 layer) on the other surface corresponding to the third metal layer.

[0044] As Test Specimen 4, a three-layer clad material (SUS301 / C1020 / SUS301) with a thickness of 0.20 mm was prepared. Specifically, a stainless steel sheet made of SUS301 (JIS-G4305:2021) with a Cr content of 17.5 mass%, a Cu sheet made of C1020 with a Cu content of 99.96 mass% or more, and a stainless steel sheet made of SUS301 with a Cr content of 17.5 mass% were laminated in this order and rolled and joined at a reduction ratio of 56%, and then rolled again at a reduction ratio of 33%. Next, diffusion annealing (held at 1050°C for 1.2 minutes) was performed. Then, finish rolling was performed at a reduction ratio of 15%, and tempering was performed. The total reduction ratio from rolling and joining to finish rolling (total reduction ratio) was approximately 75%. Finally, a three-layer clad material with a thickness (total thickness) of 0.20 mm was prepared. The thickness ratio of each layer to the final thickness of the clad material is approximately 25% for the stainless steel layer (SUS301 layer) on one surface corresponding to the first metal layer, approximately 50% for the intermediate Cu layer (C1020 layer) corresponding to the second metal layer, and approximately 25% for the stainless steel layer (SUS301 layer) on the other surface corresponding to the third metal layer.

[0045] As test specimen 5, a three-layer clad material (SUS304 / A1050 / SUS304) with a thickness of 0.20 mm was prepared. Specifically, a stainless steel sheet made of SUS304 with a Cr content of 18.4 mass%, an Al sheet made of A1050 (JIS-H4000:2014) with an Al content of 99.5 mass% or more, and a stainless steel sheet made of SUS304 with a Cr content of 18.4 mass% were laminated in this order and rolled and joined at a reduction ratio of 30%, and then finished rolled at a reduction ratio of 9%. The total reduction ratio from rolling and joining to finish rolling (total reduction ratio) was 36%. Next, diffusion annealing (held at 500°C for 0.6 minutes) was performed, which also served as tempering. Finally, a three-layer clad material with a total thickness of 0.20 mm was prepared. The thickness ratios of each layer to the final thickness of the clad material are as follows: the stainless steel layer on one surface corresponding to the first metal layer (SUS304 layer) accounts for approximately 13%, the intermediate Al layer (A1050 layer) corresponding to the second metal layer accounts for approximately 74%, and the stainless steel layer on the other surface corresponding to the third metal layer (SUS304 layer) accounts for approximately 13%.

[0046] As test specimen 6, a stainless steel sheet (SUS430 single sheet) with a thickness of 0.20 mm made of SUS430 was prepared. Specifically, a stainless steel sheet with a thickness of 0.8 mm made of SUS430 with a Cr content of 16.1 mass% was prepared. This stainless steel sheet was rolled to a reduction ratio of 38%, annealed (held at 900°C for 5 minutes), and then rolled to a reduction ratio of 60%. Next, it was tempered by annealing (held at 900°C for 5 minutes). Finally, a SUS430 single sheet with a thickness of 0.20 mm was prepared.

[0047] For test specimen 7, a 0.20 mm thick stainless steel sheet (SUS316L single sheet) made of SUS316L was prepared. Specifically, a 0.20 mm thick stainless steel sheet made of SUS316L with a Cr content of 17.3 mass% was purchased. From this stainless steel sheet, a 0.20 mm thick SUS316L single sheet was ultimately produced. The purchased stainless steel sheet used for test specimen 7 was annealed material that had been heated and held at approximately 850°C. This is for the following reasons: Regarding the 0.2% yield strength under high-temperature atmospheric conditions shown in Table 1 below, test specimen 7 is approximately 50% of that of test specimen 2. Also, regarding the oxidation loss shown in Table 1, test specimen 7 is approximately twice that of test specimen 2. Furthermore, as mentioned above, test specimen 2 underwent heating equivalent to solution heat treatment (diffusion annealing held at 1000°C) before rolling tempering. Considering these factors, it can be concluded that the stainless steel plate used in test specimen 7 underwent heating equivalent to stress relief heat treatment (generally held at approximately 850°C), but not heating equivalent to solution heat treatment (generally held at 1000°C to 1100°C and then rapidly cooled).

[0048] As test specimen 8, a stainless steel sheet (SUS304 single sheet) with a thickness of 0.20 mm made of SUS304 was prepared. Specifically, a 1.5 mm thick stainless steel sheet made of SUS304 with a Cr content of 18.3 mass% was prepared. This stainless steel sheet was subjected to rolling and annealing (held at 900°C for 5 minutes) with a reduction ratio of 67%, rolling and annealing (held at 900°C for 5 minutes) with a reduction ratio of 30%, and rolling with a reduction ratio of 43%. Next, it was tempered by annealing (held at 900°C for 5 minutes). Finally, a SUS304 single sheet with a thickness of 0.20 mm was prepared.

[0049] As test specimen 9, a stainless steel sheet (SUS301 single sheet) with a thickness of 0.22 mm made of SUS301 was prepared. Specifically, a 1.5 mm thick stainless steel sheet made of SUS301 with a Cr content of 17.1 mass% was prepared. This stainless steel sheet was subjected to rolling and annealing (held at 900°C for 5 minutes) at a reduction ratio of 33%, rolling and annealing (held at 900°C for 5 minutes) at a reduction ratio of 35%, rolling and annealing (held at 900°C for 5 minutes) at a reduction ratio of 33%, rolling and annealing (held at 900°C for 5 minutes) at a reduction ratio of 30%, and rolling at a reduction ratio of 27%. Next, it was tempered by annealing (held at 900°C for 5 minutes). Finally, a SUS301 single sheet with a thickness of 0.22 mm was prepared.

[0050] As test specimen 10, a 0.20 mm thick Ni veneer (NW2201 veneer) made of NW2201 was prepared. Specifically, a 1.17 mm thick Ni plate made of NW2201 with a Ni content of 99.0 mass% or more was prepared. This Ni plate was subjected to rolling and annealing (held at 900°C for 5 minutes) with a reduction ratio of 57%, and then rolling with a reduction ratio of 60%. Next, it was tempered by annealing (held at 900°C for 5 minutes). Finally, a 0.20 mm thick NW2201 veneer was prepared.

[0051] As test specimen 11, a 0.20 mm thick copper veneer (C1020 veneer) made of C1020 was prepared. Specifically, a 0.40 mm thick copper plate made of C1020 with a copper content of 99.96% by mass or more was prepared. This copper plate was rolled with a reduction ratio of 50%. Next, it was tempered by annealing (holding at 500°C for 5 minutes). Finally, a 0.20 mm thick C1020 veneer was prepared.

[0052] As test specimen 12, an Al veneer (A1050 veneer) with a thickness of 0.20 mm made of A1050 was prepared. Specifically, an Al plate with a thickness of 1.5 mm made of A1050 with an Al content of 99.50% by mass or more was prepared. This Al plate was rolled with a reduction ratio of 60%. Next, it was tempered by annealing (holding at 500°C for 5 minutes). Finally, an A1050 veneer with a thickness of 0.20 mm was prepared.

[0053] Next, the characteristics of test specimens 1-5, 6-11, and 12 described above were evaluated. The results are shown in Table 1.

[0054] [Table 1]

[0055] <Conductivity at room temperature> To evaluate the conductivity under ambient temperature and atmospheric conditions, the volume resistivity of each test specimen was measured under ambient temperature and atmospheric conditions. Specifically, the volume resistivity of each test specimen was measured in a room controlled at a predetermined set temperature (23°C) according to the four-terminal method of JIS-C2525:1999, using test pieces with a width of 10 mm and a length of 120 mm.

[0056] As a result, as shown in Table 1, the volume resistivity under normal temperature and atmospheric conditions was sufficiently low for test specimens 2-5, 11, and 12, at 10.0 × 10⁻⁶. -8 It was less than Ω·m. Next, test specimen 10 was small, 10.0 × 10 -8 It was less than Ω·m. Next, test specimen 1 was small, 20.0 × 10 -8The values ​​were less than Ω·m. In contrast, test specimens 6-9 were larger, measuring 50.0 × 10⁻⁶. -8 The value exceeded Ω·m. Thus, the volume resistivity of test specimens 1-5, which are made of clad material containing two metal layers made of stainless steel, under normal temperature and atmospheric conditions was significantly smaller than that of test specimens 6-9, which are made of single sheets of stainless steel. Furthermore, among test specimens 1-5, test specimen 1, which used Ni for the second metal layer, had a large resistivity, while test specimens 2-5, which used Cu or Al, which have higher conductivity than Ni, had a resistivity that was significantly smaller than that of test specimen 10 (NW2201 single sheet).

[0057] From this, it was found that even with a clad material having two metal layers (first metal layer and third metal layer) made of a metallic material such as stainless steel containing at least Cr, by having a metal layer (second metal layer) made of a metallic material such as Cu or Al with a lower volume resistivity than the two metal layers between the two metal layers, the volume resistivity under normal ambient temperature conditions is reduced, and a conductive connecting member with appropriate conductivity at ambient temperature can be obtained.

[0058] <Mechanical strength at room temperature> To evaluate the mechanical strength under normal temperature and atmospheric conditions, tensile tests were performed on each specimen under normal temperature and atmospheric conditions, and the 0.2% yield strength of each specimen was measured. Specifically, the 0.2% yield strength of each specimen was measured in a room controlled at a predetermined temperature (30°C) in accordance with JIS-Z2241:2011. Test pieces with a total length of 180 mm, a gripping section length of 45 mm, a shoulder radius of 25 mm, a base gauge length of 50 mm, a parallel section length of 70 mm, and a parallel section width of 12.5 mm were prepared.

[0059] As a result, as shown in Table 1, the 0.2% yield strength under normal temperature and atmospheric conditions was 450 MPa or higher for specimens 2-4, 400 MPa or higher for specimen 9, 300 MPa or higher for specimens 5 and 8, 200 MPa or higher for specimens 6 and 7, and 150 MPa or higher for specimen 1. Specimens 10-12 had a yield strength of less than 100 MPa. Specimens 9 (with a 0.2% yield strength of 400 MPa or higher), specimen 8 (with a yield strength of 300 MPa or higher), and specimens 6 and 7 (with a yield strength of 200 MPa or higher) are stainless steel veneers generally suitable for applications requiring both corrosion resistance and mechanical strength. Specimens 10-12, with a 0.2% yield strength of less than 100 MPa, are all veneers of high-purity metals with excellent conductivity, but are generally considered unsuitable for applications requiring mechanical strength.

[0060] In contrast, test specimens 2-4, which had a 0.2% yield strength of 450 MPa or higher under normal temperature and atmospheric conditions, were clad materials that had metal layers (first and third metal layers) made of austenitic stainless steel on both sides of a C1020 layer (second metal layer), which has lower mechanical strength than stainless steel, and were then tempered by rolling (reduction ratios of 15% and 20%). Test specimen 5, which had a 0.2% yield strength of 300 MPa or higher, was a clad material that had metal layers (first and third metal layers) made of austenitic stainless steel on both sides of an A1050 layer (second metal layer) with a 0.2% yield strength of about 50% of C1020, and was then tempered by annealing (held at 500°C). Furthermore, test specimen 1, which had a 0.2% yield strength of 150 MPa or higher, was a clad material having a 0.2% yield strength of approximately the same as C1020, with metal layers (first and third metal layers) made of SUS430, a ferritic stainless steel, on both sides, which was annealed (held at 900°C).

[0061] Furthermore, the 0.2% yield strength of test specimen 1 under normal temperature and atmospheric conditions was 196 MPa, which was the lowest among test specimens 1 to 5. However, considering the comparison between test specimens 1 and 10 and test specimens 5 and 12, it can be seen that, for example, by making the tempering conditions of test specimen 1 (annealing held at 900°C) equivalent to those of test specimen 5 (annealing held at 500°C), it is possible to achieve a 0.2% yield strength of 300 MPa or more under normal temperature and atmospheric conditions, even if the material and composition are the same as test specimen 1 (SUS430 / NW2201 / SUS430).

[0062] From this, it was found that even in a clad material having a metal layer (second metal layer) made of a metal material such as Cu or Al, which has a 0.2% yield strength lower than two metal layers (first metal layer and third metal layer) made of a metal material such as stainless steel containing at least Cr, by placing the metal layer between two metal layers with a higher 0.2% yield strength at room temperature and atmospheric conditions, a conductive connecting member with a correspondingly high room temperature mechanical strength (0.2% yield strength) can be obtained.

[0063] <Corrosion resistance at room temperature> To evaluate corrosion resistance under ambient temperature and atmospheric conditions, salt spray tests were conducted on each test specimen under ambient temperature and atmospheric conditions to assess the corrosion state of each specimen. Specifically, the salt spray test was performed using test pieces measuring 70 mm in width and 150 mm in length, controlled to the specified test conditions in accordance with the rating number method of JIS-Z2371:2015 (Annex JC). The salt spray chamber was controlled to a specified temperature (35°C), the salt concentration was 50 g / L ± 5 g / L, the compressed air pressure for salt spraying was 98 kPa ± 10 kPa, and the salt spraying time was 24 hours. The corrosion state was quantified using a rating number. Specifically, the central part of the test piece (area approximately 500 mm²) was used. 2 The surface condition of the material was compared with the standard diagrams described in Annex JC of the above JIS standard, and the number of the standard diagram that was determined to be the closest to the surface condition was assigned. The rating number is, for example, 10 if the presence or absence of corrosion cannot be determined with the naked eye, and 0 if corrosion is confirmed throughout the surface.

[0064] As a result, as shown in Table 1, the rating numbers for the salt spray test under ambient temperature conditions were 10 for test specimens 1-10 and 0 for test specimens 11 and 12. Thus, test specimens 1-10, whose surfaces are made of stainless steel or Ni, which are considered to have relatively high corrosion resistance at ambient temperature, all received a rating number of 10. In contrast, test specimens 11 and 12, whose surfaces are made of Cu or Al, which are considered to have relatively low corrosion resistance at ambient temperature, received a rating number of 0. However, test specimens 1-5, which are made of clad material containing a metal layer (second metal layer) made of Cu or Al, which are considered to have relatively low corrosion resistance at ambient temperature, received a rating number of 10, not 0. This is thought to be because both sides of the metal layer made of Cu or Al, which are considered to have relatively low corrosion resistance at ambient temperature, are coated with stainless steel, which is considered to have relatively high corrosion resistance at ambient temperature.

[0065] From this, it was found that even in a clad material having a metal layer (second metal layer) made of a metal material such as Cu or Al, which has inferior corrosion resistance at room temperature compared to two metal layers (first metal layer and third metal layer) made of a metal material such as stainless steel containing at least Cr, by placing the metal layer with inferior corrosion resistance at room temperature between two metal layers with high corrosion resistance at room temperature, a conductive connecting member with a rating number of 10 in a salt spray test under room temperature atmospheric conditions can be obtained, thus possessing a reasonable level of corrosion resistance at room temperature.

[0066] <High-temperature conductivity> To evaluate the conductivity under high-temperature atmospheric conditions, the volume resistivity of test specimens 1 to 12 at high temperatures (around 600°C) was determined. Specifically, the volume resistivity of test specimens 1 to 5 was calculated using the formula described in (4) below, with the volume resistivity of each metal constituting each layer of test specimens 1 to 5 at around 600°C as described in the literature (1) to (3) below. Furthermore, the high-temperature volume resistivity of test specimens 6 to 12 was calculated using the volume resistivity of each metal constituting test specimens 6 to 12 at around 600°C as described in the literature (1) to (3) below. (1) Stainless Steel Handbook, Third Edition, edited by the Stainless Steel Association, published by Nikkan Kogyo Shimbun, 1995, ISBN: 4-526-03618-8 (2) Japan Stainless Steel Association (https: / / www.jssa.gr.jp / contents / ), HOME > About Stainless Steel > Q&A > Physical properties of stainless steel such as conductivity, magnetic permeability, and thermal expansion coefficient (https: / / www.jssa.gr.jp / contents / faq-article / q6 / ) (3) Aluminum Handbook, edited by the Japan Light Metals Association, published by Kalos Publishing in 1996, ISBN: 4-87432-010-4 (4) Volume resistivity of clad material around 600°C = 1 / (A+B+C), where A = ratio of thickness of the first metal layer / volume resistivity of the first metal layer around 600°C, B = ratio of thickness of the second metal layer / volume resistivity of the second metal layer around 600°C, C = ratio of thickness of the third metal layer / volume resistivity of the third metal layer around 600°C

[0067] As a result, as shown in Table 1, the volume resistivity under high-temperature atmospheric conditions was sufficiently low for test specimens 2-5, 11, and 12, at 20.0 × 10⁻⁶. -8 It was less than Ω·m. Next, test specimen 10 was small, 50.0 × 10 -8 It was less than Ω·m. Next, test specimen 1 was small, 100.0 × 10 -8 The values ​​were less than Ω·m. In contrast, test specimens 6-9 were larger, measuring 100.0 × 10⁻⁶. -8 The value exceeded Ω·m. Thus, the volume resistivity of test specimens 1-5, which are made of clad material containing two metal layers made of stainless steel, under high-temperature atmospheric conditions was significantly smaller than that of test specimens 6-9, which are made of single sheets of stainless steel. Furthermore, among test specimens 1-5, test specimen 1, which used Ni for the second metal layer, had a large resistivity, while test specimens 2-5, which used Cu or Al, which have higher conductivity than Ni, had a resistivity that was significantly smaller than that of test specimen 10 (NW2201 single sheet).

[0068] From this, it was found that even in a clad material having two metal layers (first metal layer and third metal layer) made of a metallic material such as stainless steel containing at least Cr, by having a metal layer (second metal layer) made of a metallic material such as Cu or Al, which has a lower volume resistivity in a high-temperature atmospheric environment compared to the two metal layers, between the two metal layers, the volume resistivity in a high-temperature atmospheric environment is reduced, and a conductive connecting member with appropriate high-temperature conductivity can be obtained.

[0069] <Mechanical strength at high temperatures> To evaluate the mechanical strength under high-temperature atmospheric conditions, tensile tests were conducted on each specimen under high-temperature atmospheric conditions, and the 0.2% yield strength of each specimen was measured. Specifically, the 0.2% yield strength of each specimen was measured by preparing a test piece with a total length of 175 mm, a gripping section length of 40 mm, a shoulder radius of 20 mm, a gauge length of 50 mm, a parallel section length of 57 mm, and a parallel section width of 12.5 mm. The specimen was heated and held at a predetermined set temperature (600°C) in accordance with JIS-G0567:2020. However, specimens 5 and 12, which used A1050 with a melting point of approximately 660°C, fractured during the tensile test due to softening of A1050 caused by heating and rising temperatures, and therefore could not be measured.

[0070] As a result, as shown in Table 1, the 0.2% yield strength under high-temperature atmospheric conditions was 200 MPa or higher for specimens 2, 3, 8, and 9, 150 MPa or higher for specimen 4, 100 MPa or higher for specimen 7, and 50 MPa or higher for specimens 1 and 6. Specimens 10 and 11 were below 50 MPa. Specimens 7-9, which had a 0.2% yield strength of 100 MPa or higher, are generally austenitic stainless steel veneers suitable for applications requiring both heat resistance (mechanical strength) and high-temperature corrosion resistance. Specimen 6, which had a 0.2% yield strength of 50 MPa or higher, is a ferritic stainless steel veneer (SUS430) which is inferior to austenitic stainless steel but is also used in applications requiring heat resistance (mechanical strength). Furthermore, although test specimens 10 and 11, which had a 0.2% proof stress of less than 50 MPa, are both single sheets of high-purity metal with excellent conductivity, both NW2201 and C1020 soften at 600°C, and are generally considered unsuitable for applications requiring heat resistance (mechanical strength).

[0071] In contrast, test specimens 2 and 3, which had a 0.2% yield strength of 200 MPa or higher, and test specimen 4, which had a yield strength of 150 MPa or higher, were made of clad material having metal layers (first and third metal layers) made of austenitic stainless steel on both sides of a C1020 layer (second metal layer) which has inferior heat resistance (mechanical strength), and were rolled (reduction ratio 15%, 20%) and tempered. Furthermore, test specimen 4, which had a yield strength of 150 MPa or higher, was made of clad material having metal layers (first and third metal layers) made of austenitic stainless steel (SUS301) on both sides of a C1020 layer (second metal layer), and was rolled (reduction ratio 15%) and tempered. Furthermore, specimen 1, which measured over 50 MPa, is a clad material having a metal layer (first and third metal layers) made of ferritic stainless steel (SUS430) on both sides of an NW2201 layer (second metal layer) that is about twice as thick as C1020, and has been tempered by annealing (held at 900°C). In addition, the 0.2% proof stress of specimen 1 in a high-temperature atmospheric environment was 69 MPa, which was the lowest among specimens 1 to 4 for which the 0.2% proof stress could be measured. However, although specimen 1 is composed of a clad material having a metal layer (second metal layer) made of NW2201 (see specimen 10), which is inferior to SUS430 (see specimen 6), it was able to measure over 60 MPa and have a 0.2% proof stress of about 70% of that of specimen 6.

[0072] From this, it was found that even in a clad material having a metal layer (second metal layer) made of a metal material such as Cu or Ni, which has a 0.2% yield strength lower under high temperature atmospheric conditions (600°C) compared to two metal layers (first metal layer and third metal layer) made of a metal material such as stainless steel containing at least Cr, by placing the metal layer between two metal layers that have a high 0.2% yield strength under high temperature atmospheric conditions (600°C), a conductive connecting member with a correspondingly high high-temperature mechanical strength (0.2% yield strength) can be obtained.

[0073] <High-temperature corrosion resistance> To evaluate corrosion resistance in a high-temperature atmospheric environment, the high-temperature continuous oxidation test method for metallic materials specified in JIS-Z2281:1993 was used. Each test specimen was subjected to a high-temperature holding treatment under predetermined conditions, and the oxidation loss of each specimen was measured. Specifically, test pieces with a width of 20 mm and a length of 30 mm were prepared. The surface area (A0) of each test piece was calculated and its mass (W0) was measured before the high-temperature holding treatment. Next, each test piece was subjected to a high-temperature holding treatment under predetermined conditions. The high-temperature holding treatment involved placing the test piece in a crucible and arranging it in a constant-temperature bath (width 260 mm, height 180 mm, depth 300 mm) under an atmospheric atmosphere. The bath was heated to a predetermined set temperature (600°C), held at the predetermined set temperature (600°C) for 100 hours, and then cooled to room temperature. Next, the mass (W1) of each test piece after the high-temperature holding treatment was measured. Finally, the oxidation loss (b0) was calculated. In this invention, the oxidation loss (b0) is calculated using the formula b0 = (W1 - W0) / A0. When b0 ≈ 0, it means that no substantial oxide scale is formed on the surface of the test piece, indicating high-temperature corrosion resistance. When b0 < 0, it means that the oxide scale is peeling off, and when b0 > 0, it means that the oxide scale is growing. In either case, the high-temperature corrosion resistance is low, depending on the absolute value of b0.

[0074] As a result, as shown in Table 1, the oxidation loss due to high-temperature holding treatment in a high-temperature atmospheric environment was smallest in absolute value of b0 for test specimens 5, 8, and 12, at 0.3 g / m². 2 The results were as follows: Next, test specimens 4 and 9 were sufficiently small, at 0.5 g / m². 2 The results were as follows. Next, test specimens 1 and 2 were small, at 1.0 g / m². 2 The results were as follows. Next, test specimens 3 and 6 were small, at 1.5 g / m². 2 The results were as follows. In contrast, test specimens 7 and 10 had a concentration of 1.5 g / m². 2 Exceeding this limit, test specimen 11 was the largest at 400 g / m². 2 This exceeded the limit. Thus, test specimens 1-6, 8, and 9, whose surfaces are made of stainless steel, which is considered to have relatively high high-temperature corrosion resistance, had an oxidation loss of 1.5 g / m². 2The results were as follows. In contrast, test specimen 11, whose surface is made of Cu (see test specimen 11), which has low high-temperature corrosion resistance, had an oxidation loss of 1.5 g / m². 2 This was significantly exceeded. This is thought to be because both sides of the metal layer, which consists of Cu (a material with low high-temperature corrosion resistance), are coated with stainless steel, which has high high-temperature corrosion resistance.

[0075] Furthermore, test specimens 5 and 12, which contained A1050 and were thought to have relatively low high-temperature corrosion resistance, had an oxidation loss of 0.3 g / m². 2 The results were as follows. In the case of test specimen 12 (A1050 single sheet), it is thought that a surface oxide film was formed in the initial stages of heating, and this surface oxide film acted as a barrier, preventing oxidation from progressing. In the case of test specimen 5 (SUS304 / A1050 / SUS304), it is thought that the A1050 layer had SUS304 layers on both the front and back surfaces, which have high high-temperature corrosion resistance, and that the surface oxide film formed on the exposed edge of the A1050 layer acted as a barrier, preventing oxidation from progressing.

[0076] The oxidation loss for test specimen 7 (SUS316L single sheet) was 2.08 g / m². 2 However, the oxidation loss for test specimen 2 (SUS316L / C1020 / SUS316L) was 0.75 g / m². 2 Considering this, for example, by making the tempering conditions of test specimen 7 (annealing held at approximately 850°C) equivalent to those of test specimen 2 (rolling with a reduction ratio of 20%), the oxidation loss would be 1.0 g / m². 2 The following is possible:

[0077] Therefore, even in a clad material having a metal layer (second metal layer) made of a metal material such as Cu, which has inferior high-temperature corrosion resistance compared to two metal layers (first metal layer and third metal layer) made of a metal material such as stainless steel containing at least Cr, by placing the metal layer with inferior high-temperature corrosion resistance between the two metal layers with high high-temperature corrosion resistance, the oxidation loss due to the above high-temperature holding treatment in a high-temperature atmospheric environment is 1.5 g / m². 2 Preferably 1.0 g / m 2 More preferably, 0.5 g / m 2 More preferably, 0.3 g / m 2The results were as follows, and it was found that a conductive connecting member with reasonable corrosion resistance at high temperatures can be obtained.

[0078] As described above, it was confirmed that Test specimen 1, a conductive connecting member composed of a clad material in which a SUS430 layer, an NW2201 layer, and a SUS430 layer are laminated and roll-bonded in that order, has a low volume resistivity, sufficient corrosion resistance and mechanical strength (0.2% yield stress) in a normal temperature atmospheric environment, and furthermore, can withstand long-term use in a high-temperature atmospheric environment of 600°C with mechanical strength (0.2% yield stress) and high-temperature corrosion resistance.

[0079] Furthermore, it was confirmed that Test Specimen 2, a conductive connecting member composed of a clad material in which a SUS316L layer, a C1020 layer, and a SUS316L layer are laminated and roll-bonded in that order, has a low volume resistivity, sufficient corrosion resistance and mechanical strength (0.2% yield stress) in a normal temperature atmospheric environment, and can also withstand long-term use in a high-temperature atmospheric environment of 600°C, possessing mechanical strength (0.2% yield stress) and high-temperature corrosion resistance.

[0080] Furthermore, it was confirmed that test specimen 3, a conductive connecting member composed of a clad material in which a SUS304 layer, a C1020 layer, and a SUS304 layer are laminated and roll-bonded in that order, has a low volume resistivity, sufficient corrosion resistance and mechanical strength (0.2% yield stress) in a normal temperature atmospheric environment, and can also withstand long-term use in a high-temperature atmospheric environment of 600°C, possessing mechanical strength (0.2% yield stress) and high-temperature corrosion resistance.

[0081] Furthermore, it was confirmed that test specimen 4, a conductive connecting member composed of a clad material in which a SUS301 layer, a C1020 layer, and a SUS301 layer are laminated and roll-bonded in that order, has a low volume resistivity, sufficient corrosion resistance and mechanical strength (0.2% yield stress) in a normal temperature atmospheric environment, and can also withstand long-term use in a high-temperature atmospheric environment of 600°C, possessing mechanical strength (0.2% yield stress) and high-temperature corrosion resistance.

[0082] Furthermore, it was confirmed that test specimen 5, a conductive connecting member composed of a clad material in which a SUS304 layer, an A1050 layer, and another SUS304 layer are laminated and roll-bonded in that order, has a low volume resistivity and can possess sufficient corrosion resistance and mechanical strength (0.2% yield strength) under normal temperature and atmospheric conditions. Although the conductive connecting member of test specimen 5, which can possess desirable properties under normal temperature and atmospheric conditions, is thought to have high-temperature corrosion resistance due to its small oxidation loss under high-temperature atmospheric conditions of 600°C, it is considered difficult to obtain mechanical strength sufficient for long-term use because the 0.2% yield strength at high temperatures could not be measured.

[0083] As described above, according to this invention, by appropriately selecting the material and tempering conditions of each layer constituting the clad material according to the application and purpose, it is possible to provide a conductive connecting member with low volume resistivity and sufficient corrosion resistance in a normal temperature atmospheric environment. Furthermore, by more appropriately selecting the material and tempering conditions of each layer constituting the clad material, it is possible to provide a conductive connecting member with mechanical strength (0.2% yield strength) and high-temperature corrosion resistance that can withstand long-term use in a high-temperature atmospheric environment of 600°C. [Explanation of symbols]

[0084] 1: Conductive connecting member 10: Clad material 11: 1st metal layer 12: Second metal layer 12a: 1st joint 12b:Second joint 13: Third metal layer t: Thickness of the clad material (total thickness) t1: Thickness of the first metal layer t2: Thickness of the second metal layer t3: Thickness of the third metal layer

Claims

1. The clad material is composed of a first metal layer, a second metal layer, and a third metal layer, which are laminated and rolled together in this order. The first metal layer and the third metal layer are made of an Fe-based alloy or Ni-based alloy containing at least Cr. The conductive connecting member comprises a second metal layer made of Ni or a Ni-based alloy, and having a lower volume resistivity compared to the first and third metal layers.

2. The conductive connecting member according to claim 1, wherein the first metal layer and the third metal layer are made of a metallic material containing 11% by mass or more of Cr.

3. The second metal layer has a volume resistivity of 20 × 10 －８ A conductive connecting member according to claim 1 or 2, comprising a metallic material with an Ω·m or less.

4. The conductive connecting member according to claim 1, wherein the first metal layer and the third metal layer are made of stainless steel.

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