A method for joining stainless steel to copper or a copper alloy, and a joined body of stainless steel to copper or a copper alloy and a method for manufacturing the same.

Abstract

The present invention provides a simple method for joining stainless steel and copper or a copper alloy at low cost, the method being able to be carried out in the atmosphere. According to the present invention, Sn or an Sn alloy having an Sn content of 40% by mass or more is used as a joining metal. In the joining step, the copper or the copper alloy is heated by a heating device, and the stainless steel and the copper or the copper alloy are joined with each other by melting the joining metal while heating the stainless steel by means of heat transfer from the copper or the copper alloy. The highest temperature reached by the stainless steel is 350°C or less, and the residence time in the temperature range of 150°C or higher of the stainless steel is 5 seconds to 5 minutes inclusive.

Description

Technical Field

[0001] The present invention relates to a method for joining stainless steel and copper or a copper alloy, as well as a joined body of stainless steel and copper or a copper alloy and a method for producing the same.

Background Art

[0002] Stainless steel is a material with excellent corrosion resistance and is widely used as steel plates and steel pipes in various heat exchangers for automobiles, air conditioners, etc. Also, copper is a material with excellent thermal conductivity and is widely used as copper plates and copper pipes in various heat exchangers.

[0003] In recent years, with the soaring price of copper, there has been a trend to change the materials from copper and copper alloys to stainless steel in copper-made and even copper alloy-made heat exchangers. However, it is difficult to change all the materials from copper and copper alloys to stainless steel, and copper-made and copper alloy-made parts remain partially. In this case, since products are manufactured by combining stainless steel parts and copper or copper alloy parts, joining of stainless steel and copper or a copper alloy is required.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, brazing is often used as a method of joining parts together in the manufacture of heat exchangers. In the manufacturing process of heat exchangers, two main types of brazing are used: furnace brazing, which involves heating the components in an atmospheric furnace to perform multi-point simultaneous joining, and torch brazing, which involves heating the joint with a torch in the open air to perform single-point joining. The appropriate brazing method is selected from these methods depending on the product part and the stage of assembly.

[0006] In brazing copper or copper alloys, phosphorus copper solder is commonly used as the joining metal (brazing material). However, when phosphorus copper solder is used as the joining metal for brazing stainless steel with copper or copper alloys, an embrittlement layer forms at the interface between the stainless steel and the joining metal. As a result, the joining metal peels off from the stainless steel, and a joint between stainless steel and copper or copper alloy cannot be obtained.

[0007] Therefore, silver solder is commonly used as the joining metal when brazing stainless steel with copper or copper alloys. However, silver solder is expensive. In addition, in torch brazing, which is performed in the open air, the stainless steel is exposed to high temperatures due to the heating by the torch. This causes a thick oxide film to form on the surface of the stainless steel, and this oxide film inhibits the wetting and spreading of the solder.

[0008] Furthermore, Patent 1 includes, "A method for joining copper or a copper alloy and an austenitic steel alloy, comprising placing at least one intermediate layer between the joining surfaces of objects to be joined, pressing the joining surfaces including each intermediate layer together, and heating at least the joining region to create a diffusion bond, wherein the method is characterized by placing a first intermediate layer (3) in contact with or against the joining surface of the steel object (2) to primarily prevent nickel loss from the steel object (2), and placing at least one second intermediate layer (4) in contact with or against the joining surface of the copper object (1) to activate the formation of a diffusion bond." This has been disclosed.

[0009] Patent Document 2 contains: "A method for joining stainless steel and an object to be joined to the stainless steel, comprising the steps of: bringing a bonding agent consisting of solder and a joining metal into contact between the stainless steel and the object to be joined; and performing a heat treatment while the bonding agent is in contact with the stainless steel and the object to be joined." This has been disclosed.

[0010] Here, the technology described in Patent Document 1 involves providing an intermediate layer, such as nickel, between the joining surfaces of stainless steel and copper or a copper alloy. The technology described in Patent Document 2 involves providing a joining metal, specifically nickel foil or nickel particles, in addition to solder, between the joining surfaces of stainless steel and copper or a copper alloy. In other words, both the technologies in Patent Documents 1 and 2 require the use of expensive nickel. Furthermore, the increased manufacturing process reduces productivity.

[0011] Thus, it cannot be said that a low-cost and simple method for joining stainless steel to copper or copper alloys that can be carried out in the atmosphere has been developed. Therefore, there is a current need for the development of such a joining method for stainless steel to copper or copper alloys.

[0012] This invention was developed in view of the above-mentioned circumstances, and aims to provide a simple and low-cost method for joining stainless steel with copper or a copper alloy that can be implemented in the atmosphere. Furthermore, the present invention aims to provide a joint made of stainless steel and copper or a copper alloy, and a method for manufacturing the same. [Means for solving the problem]

[0013] Now, in order to achieve the above objective, the inventors conducted extensive research and came to the conclusion that, when joining stainless steel and copper or copper alloys in the atmosphere, it is desirable to use Sn and Sn alloys such as solder (hereinafter also simply referred to as Sn alloys) as the joining metals.

[0014] In other words, one of the factors that makes brazing stainless steel with copper or copper alloys difficult is the formation of an oxide film on the surface of the stainless steel. This oxide film reduces the wettability of the joining metals. In brazing, joining occurs when the constituent elements of the joining metals diffuse slightly at the interface of the base metals and bond together. However, the aforementioned oxide film hinders the diffusion of the constituent elements of the joining metals.

[0015] Therefore, when brazing stainless steel with copper or copper alloys, it is necessary to prevent the formation of the aforementioned oxide film. Here, the oxide film is more likely to form at higher temperatures. On the other hand, Sn alloys have a lower melting point than silver solder, etc. They are also advantageous in terms of cost. For these reasons, the inventors have concluded that it is desirable to use Sn alloy as the joining metal when joining stainless steel with copper or copper alloys in the atmosphere.

[0016] Based on the above idea, the inventors used a Sn alloy as the joining metal and performed joining of stainless steel with copper or copper alloys under various conditions in the atmosphere, obtaining the following findings. (1) In torch brazing, when the area near the joint to be joined (the copper end in Figure 1 or the stainless steel end in Figure 2) of the materials to be joined, which consists of stainless steel and copper or a copper alloy, is heated with a torch, the temperature of the stainless steel rises preferentially over that of the copper or copper alloy in the heated area. In addition, heat diffusion to the unheated area is more likely to occur in copper or copper alloy. That is, because copper or copper alloy has a higher thermal conductivity than stainless steel, the temperature rise of the stainless steel rises preferentially over that of copper or copper alloy. (2) As a result, even if the temperature of the stainless steel is raised above the melting point of the joining metal (Sn alloy), the temperature of the copper remains below the melting point of the joining metal. This leads to a phenomenon where the joining metal does not wet sufficiently. (3) On the other hand, if the parts to be joined are heated so that the temperature of the copper or copper alloy exceeds the melting point of the joining metal, the stainless steel will become even hotter. This causes a thick oxide film to form on the surface of the stainless steel, and the joining metal to detach from the stainless steel. For this reason, it has been difficult to join stainless steel with copper or copper alloy.

[0017] Based on the above findings, the inventors conducted further investigations. As a result, the inventors obtained the following findings. The joining metal is Sn or an Sn alloy with a Sn content of 40% by mass or more. The copper or copper alloy among the materials to be joined is heated, and the joining metal is melted while the stainless steel is heated by heat transfer from the copper or copper alloy. At this time, the maximum temperature reached by the stainless steel is kept below 350°C, and the residence time of the stainless steel in the temperature range above 150°C is controlled to be between 5 seconds and 5 minutes. This ensures that the joining metal spreads sufficiently and prevents the formation of a thick oxide film on the surface of the stainless steel, thus joining the stainless steel and copper or copper alloy.

[0018] Furthermore, the inventors attempted, as an alternative to torch brazing, to heat and melt the Sn alloy, which is the joining metal, using a heating device with a heating element such as a soldering iron, to join stainless steel with copper or a copper alloy. However, depending on the joining conditions, particularly the type of copper or copper alloy used for the materials to be joined, the Sn alloy may not wet sufficiently, making it impossible to join the stainless steel with copper or the copper alloy. In addition, a thick oxide film may form on the surface of the stainless steel, making it impossible to join the stainless steel with copper or the copper alloy.

[0019] Therefore, the inventors conducted further experiments and studies, and obtained the following findings. That is, according to the thermal conductivity of the copper or copper alloy used for the joined material, it is important to appropriately control the heating position, particularly the contact position in the direction perpendicular to the joint between the heat generating part of the heating device and the joined material (hereinafter simply referred to as the contact position). Specifically, taking the overlapping end, which is the starting point of pouring the joining metal onto the overlapping surface of the joined material, as the reference position (0 mm), with the stainless steel side as + and the copper or copper alloy side as -, when the thermal conductivity of the copper or copper alloy is 250 W / mK or more, the range is more than 0 mm to +15 mm, when the thermal conductivity of the copper or copper alloy is less than 250 W / mK, it is important that the range is -15 mm to +15 mm. Also, at this time, it is important to control the maximum temperature reached by the stainless steel to 250 °C or less and the residence time of the stainless steel in the temperature range of 100 °C or more to 5 seconds or more and 5 minutes or less. By simultaneously satisfying these conditions, the joining metal is sufficiently wetted and spread, and it is also possible to prevent the formation of a thick oxide film on the surface of the stainless steel, and the stainless steel and the copper or copper alloy are joined. The present invention has been completed through further study based on the above findings.

[0020] That is, the gist configuration of the present invention is as follows. 1. A joining method having a joining step of joining a joined material in which stainless steel and copper or a copper alloy are overlapped with a joining metal, wherein the joining metal is Sn or a Sn alloy having a Sn content of 40 mass% or more, in the joining step, heating the copper with a heating device, and while heating the stainless steel by heat transfer from the copper or copper alloy, melting the joining metal to join the stainless steel and the copper or copper alloy, wherein the maximum temperature reached by the stainless steel is 350 °C or less, and the residence time of the stainless steel in the temperature range of 150 °C or more is 5 seconds or more and 5 minutes or less, A joining method for stainless steel and copper or a copper alloy.

[0021] 2. The method for joining stainless steel and copper or a copper alloy as described in 1, wherein the heating device is a torch.

[0022] 3. The joining process involves joining a material consisting of stainless steel and copper or a copper alloy, using a joining metal. The joining metal is Sn or an Sn alloy with a Sn content of 40% by mass or more. In the aforementioned joining process, By using a heating device having a heating element, the heating element is brought into contact with the material to be joined, thereby melting the joining metals and joining the stainless steel and the copper or copper alloy. The contact position between the heating element and the material to be joined in the direction perpendicular to the joining is such that the overlapping end, which is the starting point for the pouring of the joining metal into the overlapping surface of the material to be joined, is set as the reference position (0 mm), with the stainless steel side being + and the copper or copper alloy side being -. If the thermal conductivity of the copper or copper alloy is 250 W / mK or higher, the range is greater than 0 mm to +15 mm. If the thermal conductivity of the copper or copper alloy is less than 250 W / mK, the range is -15 mm to +15 mm. The maximum temperature that the aforementioned stainless steel can reach is 250°C or less, and The residence time of the aforementioned stainless steel in a temperature range of 100°C or higher is 5 seconds or more and 5 minutes or less. A method for joining stainless steel to copper or copper alloys.

[0023] 4. The method for joining stainless steel and copper or a copper alloy as described in 3, wherein the heating device is a soldering iron.

[0024] 5. A joint of stainless steel and copper or copper alloy, obtained by joining stainless steel and copper or copper alloy using the joining method of stainless steel and copper or copper alloy described in any of 1 to 4 above.

[0025] 6. A method for manufacturing a stainless steel and copper or copper alloy joint, comprising joining stainless steel and copper or copper alloy by the joining method for stainless steel and copper or copper alloy described in any of items 1 to 4 above. [Effects of the Invention]

[0026] According to the present invention, a low-cost and simple method for joining stainless steel and copper or copper alloys can be obtained, which can be carried out in the atmosphere. Furthermore, since the joined body obtained using the joining method of the present invention can be manufactured at a lower cost than when silver brazing is performed, it is extremely advantageous to apply it to the joining targets of stainless steel and copper or copper alloys in various devices, such as gas water heaters and water supply / hot water piping. [Brief explanation of the drawing]

[0027] [Figure 1] This is a schematic diagram showing an example of a positional relationship in a joining method according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing an example of a positional relationship in a joining method according to one embodiment of the present invention. [Figure 3] This is a schematic diagram showing an example of a joint according to one embodiment of the present invention. [Figure 4] This is a schematic diagram showing an example of a joint according to one embodiment of the present invention. [Figure 5] This is an example of an optical microscope image of the cross-section of the joint in a jointed body (an example of the cross-section of the joint in Test No. 1-2 of Example 1). [Figure 6] This is an example of an optical microscope image of a cross-section of a joint in a jointed body (an example of a cross-section of the joint in Test No. 3-2 of Example 3). [Modes for carrying out the invention]

[0028] The present invention will be described based on the following embodiments. [1] Method of joining stainless steel to copper or copper alloy First, a method for joining stainless steel and copper or a copper alloy according to one embodiment of the present invention (hereinafter also simply referred to as the joining method) will be described.

[0029] A joining method according to the first embodiment is: The joining process involves joining materials, which consist of stainless steel and copper or a copper alloy, with a joining metal. The joining metal is Sn or an Sn alloy with a Sn content of 40% by mass or more. In the aforementioned joining process, The copper or copper alloy is heated by a heating device, and the stainless steel is heated by heat transfer from the copper or copper alloy, while the joining metal is melted to join the stainless steel and the copper or copper alloy. The maximum temperature that the aforementioned stainless steel can reach is 350°C or less, and The residence time of the aforementioned stainless steel in a temperature range of 150°C or higher is 5 seconds or more and 5 minutes or less. It is.

[0030] A joining method according to the second embodiment is: The joining process involves joining materials, which consist of stainless steel and copper or a copper alloy, with a joining metal. The joining metal is Sn or an Sn alloy with a Sn content of 40% by mass or more. In the aforementioned joining process, By using a heating device having a heating element, the heating element is brought into contact with the material to be joined, thereby melting the joining metals and joining the stainless steel and the copper or copper alloy. The contact position between the heating element and the material to be joined in the direction perpendicular to the joining is such that the overlapping end, which is the starting point for the pouring of the joining metal into the overlapping surface of the material to be joined, is set as the reference position (0 mm), with the stainless steel side being + and the copper or copper alloy side being -. If the thermal conductivity of the copper or copper alloy is 250 W / mK or higher, the range is greater than 0 mm to +15 mm. If the thermal conductivity of the copper or copper alloy is less than 250 W / mK, the range is -15 mm to +15 mm. The maximum temperature that the aforementioned stainless steel can reach is 250°C or less, and The residence time of the aforementioned stainless steel in a temperature range of 100°C or higher is 5 seconds or more and 5 minutes or less. It is.

[0031] Here, as shown in Figure 1, when the starting point for pouring the joining metal (in the direction perpendicular to the joining) onto the overlapping surfaces of the materials to be joined is the copper or copper alloy end (hereinafter also referred to as the copper end), the reference position is the copper end. As shown in Figure 2, when the starting point for pouring the joining metal (in the direction perpendicular to the joining) onto the overlapping surfaces of the materials to be joined is the stainless steel end, the reference position is the stainless steel end.

[0032] Furthermore, in the joining method according to the second embodiment, as shown in Figure 1, when the reference position is a copper end, the contact position is the surface on the side of the material to be joined where the copper or copper alloy is located (the upper surface of the material to be joined in Figure 1, hereinafter also referred to as the copper-side surface of the material to be joined). As shown in Figure 2, when the reference position is a stainless steel end, the contact position is the surface on the side of the material to be joined where the stainless steel is located (the upper surface of the material to be joined in Figure 2, hereinafter also referred to as the stainless steel-side surface of the material to be joined).

[0033] The X, Y, and Z directions in Figures 1-6 are as follows: X direction: joining direction Y direction: Direction perpendicular to the joint (a direction perpendicular to the joint progression direction (X direction) and also perpendicular to the thickness direction (Z direction), which will be described later). Z-direction: The thickness direction of the joined materials (jointed body) (hereinafter also simply referred to as the thickness direction).

[0034] The joining methods according to the first and second embodiments will be described in detail below. In the following description, any description that does not specifically specify whether it is the joining method according to the first or second embodiment applies to both the joining methods according to the first and second embodiments.

[0035] (1) Stainless steel The material to be joined (the base material of the joined body after joining) is stainless steel, and its shape is either plate-shaped (stainless steel plate) or tubular (stainless steel pipe). Note that "plate-shaped" here includes not only flat plates but also curved plates. The thickness of the stainless steel (plate thickness or pipe thickness) is not particularly limited, but from the viewpoint of heat transfer during joining, it is preferable to have a thickness of 0.1 mm or more. Furthermore, the thickness of the stainless steel is preferably 2.0 mm or less. More preferably, the thickness of the stainless steel is 0.2 mm or more, and even more preferably 0.3 mm or more. Furthermore, the thickness of the stainless steel is preferably 1.0 mm or less.

[0036] When the stainless steel is in the form of a plate, there are no particular limitations on the size of the plate. For example, from the viewpoint of heat dissipation after joining, it is preferable that the size be 10 mm square or larger. More preferably, it is 30 mm square or larger.

[0037] When the stainless steel base material is tubular, there are no particular limitations on the size of the tube (outer diameter and length). For example, from the viewpoint of heat dissipation after joining, the outer diameter of the tube is preferably four times or more the thickness (wall thickness) of the tube. Also, an outer diameter of 5 mm or more is preferable. An outer diameter of 500 mm or less is preferable. The length of the tube is preferably 10 mm or more, more preferably 30 mm or more.

[0038] Furthermore, the composition of the stainless steel is not particularly limited and can be any composition common to stainless steel. For example, an iron-based alloy containing 10.5% by mass or more of Cr and 50% by mass or more of Fe is acceptable. As an example, austenitic stainless steel sheets, austenitic-ferritic stainless steel sheets, ferritic stainless steel sheets, martensitic stainless steel sheets, and precipitation-hardening stainless steel sheets as specified in JIS G 4305:2021, as well as processed products thereof, can be used. In addition, stainless steel sanitary pipes, general-purpose stainless steel pipes, piping pipes, and boiler / heat exchanger stainless steel pipes as specified in JIS G 3447:2015, JIS G 3448:2016, JIS G 3459:2021, JIS G 3463:2019, and JIS G 3468:2021, as well as processed products thereof, can be used. Furthermore, stainless steel sheets with various surface finishes can be used, including No. 2B finish (annealed pickled skin pass finish), No. 2D finish (annealed pickled finish), No. 4 finish (polished finish), No. 8 finish (mirror polished finish), BA finish (bright annealed finish), HL (hairline) finish, dull finish, embossed finish, and blast finish.

[0039] (2) Copper or copper alloy The material to be joined (the base material of the joined body after joining) is copper or a copper alloy, and its shape is either plate-shaped (copper plate or copper alloy plate) or tubular (copper tube or copper alloy tube). Note that "plate-shaped" here includes not only flat plates but also curved plates. The thickness of the copper or copper alloy (plate thickness or tube thickness) is not particularly limited, but from the viewpoint of heat transfer during joining, it is preferable to have a thickness of 0.1 mm or more. More preferably, the thickness of the copper or copper alloy is 0.3 mm or more, and even more preferably 0.5 mm or more. Furthermore, the thickness of the copper or copper alloy is preferably 4.0 mm or less, more preferably 2.0 mm or less, and even more preferably 1.0 mm or less. In particular, in the joining method according to the second embodiment, from the viewpoint of suppressing the inhibition of temperature rise of the material to be joined due to heat diffusion, the thickness of the copper or copper alloy is more preferably 2.0 mm or less, and even more preferably 1.0 mm or less.

[0040] When the copper or copper alloy is in the form of a plate, there are no particular limitations on the size of the plate. For example, from the viewpoint of heat dissipation after joining, it is preferable that the size be 10 mm square or larger. More preferably, it is 30 mm square or larger.

[0041] When the base material, copper or copper alloy, is tubular, there are no particular limitations on the size (outer diameter and length) of the tube. For example, from the viewpoint of heat dissipation after joining, the outer diameter of the tube is preferably four times or more the thickness (wall thickness) of the tube. Also, an outer diameter of 5 mm or more is preferable. An outer diameter of 500 mm or less is preferable. The length of the tube is preferably 10 mm or more, more preferably 30 mm or more.

[0042] The copper or copper alloy referred to here includes not only so-called pure copper consisting of Cu and unavoidable impurities, but also copper alloys containing 50% by mass or more of Cu. As an example, various copper or copper alloy sheets and tubes, as well as processed products thereof, can be used, including oxygen-free copper, tough pitch copper, phosphorus-deoxidized copper, brass, free-cutting brass, and red brass, as specified in JIS H 3100:2018. Furthermore, copper alloy sheets and tubes, as well as processed products thereof, such as phosphor bronze and nickel silver, as specified in JIS H 3110:2018, can also be used. For example, the thermal conductivity of oxygen-free copper and tough pitch copper is 391 W / mK. The thermal conductivity of phosphorus-deoxidized copper is 339-381 W / mK. The thermal conductivity of brass and free-cutting brass is 117-121 W / mK. The thermal conductivity of red brass is 138-234 W / mK. The thermal conductivity of phosphor bronze is 58-201 W / mK. The thermal conductivity of nickel silver is 29-46 W / mK. In the case of sheet metal, copper or copper alloy sheets with various surface finishes, such as HL (hairline) finish, matte finish, blast finish, and hammered finish, can be used. In the case of tubular metal, seamless and welded copper or copper alloy pipes, as specified in JIS H 3300:2018 and JIS H 3320:2006, and their processed products can be used.

[0043] (3) Joining metal: Sn or Sn alloy with a Sn content of 40% by mass or more To suppress excessive temperature rise of the stainless steel during joining and to ensure sufficient melting of the joining metal, the joining metal is Sn or a Sn alloy with a Sn content of 40% by mass or more. If the Sn content of the joining metal is less than 40% by mass, the amount of heat required to melt the joining metal increases. This results in insufficient melting of the joining metal, and the stainless steel and copper or copper alloy are not joined. Therefore, the joining metal is Sn or a Sn alloy with a Sn content of 40% by mass or more. The Sn content of the joining metal is preferably 90% by mass or more. Furthermore, from the viewpoint of suppressing the reduction of brittleness in extremely cold regions, the Sn content of the joining metal is preferably 99.5% by mass or less, more preferably 97% by mass or less.

[0044] Examples of Sn alloys with a Sn content of 40% by mass or more include solder. In particular, solders with a Sn content of 40% by mass or more, as described in JIS Z 3282:2017, can be suitably used. The joining metal may contain flux (so-called rosin-core solder is also acceptable).

[0045] Furthermore, examples of the above-mentioned Sn alloys are given below. (Sn-Ag alloy) It contains 4.5-5.5% by mass of Ag, with the remainder consisting of Sn and unavoidable impurities. (Sn-Cu alloy) It contains 2.0-4.0% by mass of Cu, with the remainder consisting of Sn and unavoidable impurities. (Sn-Sb alloy) It contains 4.0-6.0% by mass of Sb, with the remainder consisting of Sn and unavoidable impurities. (Sn-Ag-Cu alloy) It contains Ag: 0.5-4.5% by mass and Cu: 0.2-1.0% by mass, with the remainder consisting of Sn and unavoidable impurities. (Sn-Pb alloy) It contains 3.0 to 60.0% by mass of Pb, with the remainder consisting of Sn and unavoidable impurities. (Sn-Ag-Bi-Cu alloy) It contains Ag: 2.0-3.0 mass%, Bi: 0.5-1.5 mass%, and Cu: 0.2-1.0 mass%, with the remainder being Sn and unavoidable impurities. (Sn-In-Ag-Bi alloy) It contains In: 3.0-9.0% by mass, Ag: 3.0-4.0% by mass, and Bi: 0.2-1.0% by mass, with the remainder consisting of Sn and unavoidable impurities. (Sn-Zn alloy) It contains 8.0-10.0% by mass of Zn, with the remainder consisting of Sn and unavoidable impurities. (Sn-Zn-Bi alloy) It contains Zn: 7.0-9.0% by mass, Bi: 2.5-3.5% by mass, with the remainder consisting of Sn and unavoidable impurities. (Sn-Bi alloy) It contains Bi: 55.0-60.0% by mass, with the remainder consisting of Sn and unavoidable impurities. (Sn-In alloy) It contains 50.0-55.0% by mass of In, with the remainder consisting of Sn and unavoidable impurities.

[0046] Thus, the remainder of the bonded metal, excluding Sn, contains 60% by mass or less of metal elements such as Ag, Cu, Sb, Pb, Bi, In, and Zn (hereinafter also referred to as "metal elements other than Sn"). The content of metal elements other than Sn is preferably 10% by mass or less. However, Ni is not included in the metal elements other than Sn. Furthermore, the content of metal elements other than Sn is preferably 0.5% by mass or more, more preferably 3.0% by mass or more. Suitable content of each metal element other than Sn is, for example, Ag: 5.5% by mass or less, Cu: 4.0% by mass or less, Sb: 6.0% by mass or less, Pb: 60% by mass or less, Bi: 60% by mass or less, In: 55% by mass or less, and Zn: 10.0% by mass or less. More details are as described above.

[0047] Inevitable impurities in the joined metal include elements such as Pb, Sb, Bi, Cd, Cu, Au, In, Ag, Al, As, Cd, Fe, Ni, Zn, Ge, P, and Ga. These elements are acceptable if their total content is 2.0 mass% or less. Inevitable impurities may also be present at 0 mass%. Elements actively added to the joined metal are not treated as unavoidable impurities.

[0048] Furthermore, the melting point of the joined metal is preferably 100 to 320°C. Here, the melting point T (°C) of the joined metal is the temperature that can be determined from the solidus temperature Ts (°C) and the liquidus temperature Tl (°C) of the joined metal by the following formula. T = (Ts + Tl) / 2

[0049] In particular, in the joining method according to the first embodiment, the melting point of the joining metal is preferably 100°C or higher, more preferably 190°C or higher. Also, the melting point of the joining metal is preferably 320°C or lower, more preferably 300°C or lower.

[0050] Furthermore, in the joining method according to the second embodiment, the melting point of the joining metal is preferably 100°C or higher. The melting point of the joining metal is preferably 320°C or lower, more preferably 250°C or lower, and even more preferably 240°C or lower.

[0051] (4)Joining process (4-1) First Embodiment In the joining process of the joining method according to the first embodiment, for example, while moving the heating device in the direction of joining, the materials to be joined, which consist of stainless steel and copper or copper alloy (hereinafter, in the description of the joining process of the joining method according to the first and second embodiments, copper and copper alloy will be collectively referred to simply as copper) are joined with a joining metal, as shown in Figure 1 or Figure 2. At this time, the copper in the materials to be joined is heated, and the stainless steel is heated by heat transfer from the copper, while the joining metal is melted to join the stainless steel and copper.

[0052] Heating points by the heating device: Copper In the joining method according to the first embodiment, it is important to heat the copper of the materials to be joined using a heating device, and to heat the stainless steel through heat transfer from the copper, melt the joining metal and join the stainless steel and copper. This ensures that the joining metal spreads sufficiently and prevents the formation of a thick oxide film on the surface of the stainless steel, thus joining the stainless steel and copper. For this reason, the heating point (hereinafter also simply referred to as the heating point) is the copper of the materials to be joined. In the description of the heating point, copper and copper alloys will also be collectively referred to simply as copper in the embodiments described later.

[0053] Here, the fact that the heated area is copper means the following: (Joining Condition 1-a) As shown in Figure 1, when the part to be joined is near the copper end (the starting point for pouring the joining metal into the overlapping surface of the materials to be joined is the copper end, in other words, the supply (installation) position of the joining metal is on the copper end side of the materials to be joined), and the heating area by the heating device (for example, in the case of a torch, the area in contact with the gas flame, hereinafter also simply referred to as the heating area) is on the upper surface of the copper (the surface of the copper opposite to the side overlapping with the stainless steel) "The heated area is copper" means that, in the direction perpendicular to the joint, with the copper end as the reference position (0 mm), the stainless steel side as +, and the copper side as -, the heated position is less than 0 mm, and the heated area does not include stainless steel. (Joining condition 1-b) As shown in Figure 1, when the part to be joined is near the copper end, and the heating area by the heating device is the lower surface of the copper (the surface of the copper that overlaps with the stainless steel) "The heated area is copper" means that, in the direction perpendicular to the joint, with the copper end as the reference position (0 mm), the stainless steel side as +, and the copper side as -, the heated position is less than -L (overlap width) mm, and the heated area does not include stainless steel. (Joining condition 2-a) As shown in Figure 2, when the part to be joined is near the end of the stainless steel (the starting point for pouring the joining metal into the overlapping surface of the materials to be joined is the end of the stainless steel, in other words, the supply (installation) position of the joining metal is on the stainless steel end side of the materials to be joined), and the heating area is the upper surface of the copper (the surface of the copper on the side that overlaps with the stainless steel) "The heated area is copper" means that, in the direction perpendicular to the joint, with the stainless steel end as the reference position (0 mm), the stainless steel side as +, and the copper side as -, the heated position is less than 0 mm, and the heated area does not include stainless steel. (Joining condition 2-b) As shown in Figure 2, when the part to be joined is near the end of the stainless steel, and the heating area is the underside of the copper (the surface of the copper opposite to the side overlapping with the stainless steel) "The heated area is copper" means that, in the direction perpendicular to the joint, with the stainless steel end as the reference position (0 mm), the stainless steel side as +, and the copper side as -, the heated position is less than L (overlap width) mm, and the heated area does not include stainless steel. The heating position referred to here is the center position of the heating region in the direction perpendicular to the joint.

[0054] Furthermore, from the viewpoint of more reliably excluding stainless steel from the heating region and sufficiently melting the joining metals while heating the stainless steel through heat transfer from copper, it is preferable to set the heating position in the direction perpendicular to the joining as follows, depending on the above joining conditions. (Joining condition 1-a) With the copper end as the reference position (0 mm), the range on the upper surface of the copper is -(L+100) mm to -L mm. (Joining condition 1-b) With the copper end as the reference position (0 mm), the range on the underside of the copper is -(L+100) mm to -(L+10) mm. (Joining condition 2-a) With the stainless steel end as the reference position (0 mm), the range on the upper surface of the copper is -100 mm to -10 mm. (Joining condition 2-b) With the stainless steel end as the reference position (0 mm), the range on the underside of the copper is -100 mm to 0 mm.

[0055] Maximum temperature achievable by stainless steel: 350°C or less In the joining method according to the first embodiment, it is important to suppress the formation of an oxide film on the surface of the stainless steel. In particular, when heating with a torch or the like, if the maximum temperature reached by the stainless steel during joining exceeds 350°C, an oxide film rapidly forms on the surface of the stainless steel, and the joining metal detaches from the stainless steel. For this reason, the maximum temperature reached by the stainless steel should be 350°C or lower. Preferably, the maximum temperature reached by the stainless steel is 300°C or lower. The lower limit of the maximum temperature reached by the stainless steel is not particularly limited. For example, preferably 200°C or higher, more preferably 250°C or higher.

[0056] Residence time of stainless steel at temperatures above 150°C (hereinafter also referred to as residence time of stainless steel at temperatures above 150°C): 5 seconds to 5 minutes In the joining method according to the first embodiment, as described above, the copper of the materials to be joined is heated. Then, the joining metal is melted while the stainless steel is heated by heat transfer from the copper, and the joining metal flows into the overlapping surface of the materials to be joined. At this time, excessive heating of the stainless steel is prevented and the formation of an oxide film on the surface of the stainless steel is suppressed. If the residence time of the stainless steel at 150°C or above is less than 5 seconds, the joining metal will not flow sufficiently into the overlapping surface of the materials to be joined, and the joining of the stainless steel and copper will be hindered. On the other hand, if the residence time of the stainless steel at 150°C or above exceeds 5 minutes, a thick oxide film will be formed on the surface of the stainless steel, and the joining of the stainless steel and copper will be hindered. For this reason, the residence time of the stainless steel at 150°C or above is set to 5 seconds or more and 5 minutes (300 seconds) or less. Preferably, the residence time of the stainless steel at 150°C or above is 15 seconds or more. Preferably, the residence time of the stainless steel at 150°C or above is 3 minutes (180 seconds) or less, more preferably 1 minute (60 seconds) or less.

[0057] Furthermore, when measuring the temperature of stainless steel for the purpose of deriving the maximum temperature achievable and the residence time at 150°C or higher, the entire surface of the stainless steel may be measured, for example, using thermography. Alternatively, depending on the heating area of ​​the heating device, the surface temperature of the stainless steel near the heating area may be measured using a thermocouple.

[0058] For example, in the cases of (joining conditions 1-a) and (joining conditions 1-b) above, the copper end should be used as the reference position (0 mm), and the surface temperature of the first surface of the stainless steel (the top surface of the stainless steel in Figure 1) should be measured at a position from 0 mm (copper end) to +20 mm in the direction perpendicular to the joint. Also, in the cases of (joining conditions 2-a) and (joining conditions 2-b) above, the stainless steel end should be used as the reference position (0 mm), and the surface temperature of the second surface of the stainless steel (the top surface of the stainless steel in Figure 2) should be measured at a position from 0 mm (stainless steel end) to +20 mm in the direction perpendicular to the joint.

[0059] At the above locations, the temperature of the stainless steel during joining will be approximately the same. Therefore, the temperature measurement position should be determined from the above locations depending on the structure of the materials to be joined. Here, the first surface of the stainless steel is the surface of the stainless steel on the side that overlaps with the copper (where the copper is placed), and the second surface of the stainless steel is the surface of the stainless steel on the opposite side from the side that overlaps with the copper. Furthermore, the measurement interval for the temperature of the stainless steel in the direction of joining is preferably, for example, 3 to 10 mm.

[0060] Furthermore, the maximum temperature reached by the stainless steel during joining and the residence time of the stainless steel at 150°C or above can be controlled by adjusting, in addition to the heating position, the joining speed (the speed at which the heating device moves in the direction of joining), the distance between the heating device and the materials to be joined, and the output of the heating device. For example, when using a torch as the heating device, the maximum temperature reached by the stainless steel during joining and the residence time of the stainless steel at 150°C or above can be controlled within the above ranges by adjusting the joining speed in the range of 30 to 200 mm / min, the distance between the heating device and the materials to be joined in the range of 50 to 150 mm, and the output of the heating device in the range of 2000 to 3000 kcal / hour, depending on the type, size, and arrangement of the materials to be joined.

[0061] Furthermore, the heating device is not particularly limited as long as it can heat the stainless steel by heat transfer from copper, melt the joining metal, and control the maximum temperature and residence time of the stainless steel during joining to within the above range. Among these, a torch (for example, a heating device specified in JIS Z 3001-1:2018), and especially a torch that utilizes a gas flame (torch burner), is preferred.

[0062] The size of the heating area is not particularly limited. To ensure that stainless steel is excluded from the heating area, it is preferable that the heating area be contained within a 30mm square. For example, a torch with a nozzle diameter of φ10-20mm can be used.

[0063] (4-2) Second Embodiment In the joining process of the joining method according to the second embodiment, for example, the heating device is moved in the direction of joining, and the heating element of the heating device is brought into contact with the materials to be joined, which consist of stainless steel and copper stacked together as shown in Figure 1 or Figure 2. This melts the joining metals and joins the stainless steel and copper. At this time, it is important to appropriately control the contact position according to the thermal conductivity of the copper used in the materials to be joined.

[0064] Contact position when the thermal conductivity of copper is 250 W / mK or higher: greater than 0 mm to +15 mm If the thermal conductivity of copper is 250 W / mK or higher, setting the contact position to 0 mm or less, in other words, setting the contact position to copper, will cause most of the heat input from the heating element of the heating device to be transferred to the copper, preventing the stainless steel from being sufficiently heated. As a result, the joining metal will not flow sufficiently into the overlapping surface of the materials to be joined, hindering the bonding of stainless steel and copper. On the other hand, setting the contact position to more than +15 mm will prevent the joining metal and the stainless steel near the overlapping surface of the materials from being joined from being sufficiently heated. As a result, the joining metal will not flow sufficiently into the overlapping surface of the materials to be joined, hindering the bonding of stainless steel and copper. Therefore, if the thermal conductivity of copper is 250 W / mK or higher, the contact position should be in the range of more than 0 mm to +15 mm. Preferably, the contact position should be +1 mm or more. More preferably, the contact position should be +10 mm or less, and even more preferably +5 mm or less.

[0065] Contact position when the thermal conductivity of copper is less than 250 W / mK: -15 mm to +15 mm If the thermal conductivity of copper is less than 250 W / mK, stainless steel can be sufficiently heated even if the contact point is copper. However, if the contact point is less than -15 mm, the stainless steel will not be sufficiently heated. As a result, the joining metal will not flow sufficiently into the overlapping surface of the materials to be joined, hindering the bonding of stainless steel and copper. On the other hand, if the contact point exceeds +15 mm, the stainless steel near the overlapping surface of the materials to be joined will not be sufficiently heated. As a result, the joining metal will not flow sufficiently into the overlapping surface of the materials to be joined, hindering the bonding of stainless steel and copper. Therefore, if the thermal conductivity of copper is less than 250 W / mK, the contact point should be in the range of -15 mm to +15 mm. Preferably, the contact point is -5 mm or more. More preferably, the contact point is +5 mm or less.

[0066] As described above, the contact position is indicated with the overlapping end, which is the starting point for the joining metal to flow into the overlapping surfaces of the materials to be joined, as the reference position (0 mm), with the stainless steel side as + and the copper side as -. Furthermore, if the reference end is the copper end, the contact position is the copper surface of the materials to be joined. Furthermore, if the reference end is the stainless steel end, the contact position is the stainless steel surface of the materials to be joined.

[0067] For example, as shown in Figure 1, if the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is the copper end, or in other words, the supply (installation) position of the joining metal is on the copper end side of the materials to be joined, the reference position is the copper end of the materials to be joined. In this case, the contact position is the copper-side surface of the materials to be joined (the upper surface of the materials to be joined in Figure 1).

[0068] Furthermore, as shown in Figure 2, if the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is the stainless steel end, in other words, the supply (installation) position of the joining metal is on the stainless steel end side of the materials to be joined, the reference position shall be the stainless steel end. In this case, the contact position shall be the stainless steel side surface of the materials to be joined (the upper surface of the materials to be joined in Figure 2).

[0069] The contact position referred to here is the center position in the direction perpendicular to the joint where the heating element of the heating device and the material to be joined come into contact.

[0070] Furthermore, since the joining metal can be melted by heat transfer from the materials to be joined, the heating element of the heating device may or may not be in contact with the joining metal. Also, the heating element of the heating device may be in contact with the end face on the reference position side of the overlapping portion of the materials to be joined.

[0071] Maximum temperature achievable by stainless steel: 250℃ or less In the joining method according to the second embodiment, it is important to suppress the formation of an oxide film on the surface of the stainless steel. In particular, in joining by the heating method described above, if the maximum temperature reached by the stainless steel exceeds 250°C, an oxide film rapidly forms on the surface of the stainless steel, and the joining metal detaches from the stainless steel. Therefore, the maximum temperature reached by the stainless steel should be 250°C or lower. The lower limit of the maximum temperature reached by the stainless steel is not particularly limited. For example, the maximum temperature reached by the stainless steel is preferably 150°C or higher, more preferably 200°C or higher.

[0072] Residence time of stainless steel at temperatures above 100°C (hereinafter also referred to as residence time of stainless steel at temperatures above 100°C): 5 seconds to 5 minutes In the joining method according to the second embodiment, as described above, a heating device having a heating element is used to heat the material to be joined by bringing the heating element into contact with the material to be joined. This causes the joining metal to flow into the overlapping surface of the material to be joined. At this time, excessive heating of the stainless steel is prevented and the formation of an oxide film on the surface of the stainless steel is suppressed. If the residence time of the stainless steel at 100°C or above is less than 5 seconds, the joining metal will not flow sufficiently into the overlapping surface of the material to be joined, and the joining of the stainless steel and copper will be hindered. On the other hand, if the residence time of the stainless steel at 100°C or above exceeds 5 minutes, a thick oxide film will form on the surface of the stainless steel, and the joining of the stainless steel and copper will be hindered. Therefore, the residence time of the stainless steel at 100°C or above is set to 5 seconds or more and 5 minutes (300 seconds) or less. Preferably, the residence time of the stainless steel at 100°C or above is 15 seconds or more. Preferably, the residence time of the stainless steel at 100°C or above is 3 minutes (180 seconds) or less, more preferably 1 minute (60 seconds) or less.

[0073] Furthermore, when measuring the temperature of stainless steel for the purpose of deriving the maximum temperature achievable and the residence time of stainless steel at 100°C or above, the entire surface of the stainless steel may be measured, for example, using thermography. In addition, depending on the heating area (the contact area between the heating element of the heating device and the material to be joined), the surface temperature of the stainless steel near the heating area may be measured using a thermocouple.

[0074] For example, as shown in Figure 1, if the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is the copper end, the copper end should be used as the reference position (0 mm), and the surface temperature of the first surface of the stainless steel (the top surface of the stainless steel in Figure 1) should be measured at a position from 0 mm (copper end) to +20 mm in the direction perpendicular to the joint. Alternatively, as shown in Figure 2, if the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is the stainless steel end, the stainless steel end should be used as the reference position (0 mm), and the surface temperature of the second surface of the stainless steel (the top surface of the stainless steel in Figure 2) should be measured at a position from 0 mm (stainless steel end) to +20 mm in the direction perpendicular to the joint. In this case, the surface temperature of the end face of the stainless steel may also be measured.

[0075] At the above locations, the temperature of the stainless steel during joining will be approximately the same. Therefore, the temperature measurement position should be determined from the above locations depending on the structure of the materials to be joined. Here, the first surface of the stainless steel is the surface of the stainless steel on the side that overlaps with the copper (where the copper is placed), and the second surface of the stainless steel is the surface of the stainless steel on the opposite side from the side that overlaps with the copper. Furthermore, the measurement interval for the temperature of the stainless steel in the direction of joining is preferably, for example, 3 to 10 mm.

[0076] Furthermore, the maximum temperature reached by the stainless steel during joining and the residence time of the stainless steel at temperatures above 100°C can be controlled by adjusting, for example, the joining speed (the speed at which the heating device moves in the direction of joining) and the output of the heating device, in addition to the contact area between the heating element of the heating device and the materials to be joined. For example, when using a soldering iron as the heating device, the maximum temperature reached by the stainless steel during joining and the residence time of the stainless steel at temperatures above 100°C can be controlled within the above range by adjusting the joining speed within the range of 30 to 200 mm / min and the output (heat quantity) of the heating device within the range of 100 to 500 W, depending on the type, size, and arrangement of the materials to be joined.

[0077] Furthermore, the heating device is not particularly limited as long as it has a heating element as described above and can heat the material to be joined by bringing the heating element into contact with the material to be joined. An example of such a heating device is a soldering iron. Examples of heating methods in the heating element include electric heating (power supply type and battery type) and gas heating. The output (heat quantity) of the heating device is preferably 100W or more. In other words, if the amount of heat generated is small, the time required to heat the material to be joined will be long, which may lead to the formation of an oxide film on the surface of the stainless steel. Furthermore, the tip diameter of the heating element (in the case of a soldering iron, the tip diameter of the soldering iron) is preferably 1 to 5 mm. In addition, if the surface of the heating element oxidizes due to its own heat generation, it is preferable to polish it with a metal file or the like to remove the oxide before starting the joining process.

[0078] Other than the conditions mentioned above, the joining method according to the first and second embodiments is not particularly limited and may be any conventional method.

[0079] For example, as a method of supplying the joining metal, the joining metal may be applied or placed between the overlapping surfaces of the materials to be joined, on the copper ends or stainless steel ends, before heating. Alternatively, the materials to be joined may be continuously supplied during joining (by inserting the filler rods that will become the materials to be joined). In particular, it is preferable to place the joining metal on the copper ends or stainless steel ends of the materials to be joined before heating.

[0080] Furthermore, the overlap width L (width perpendicular to the weld) between the stainless steel and copper is preferably, for example, 5 to 20 mm. The gap at the overlapping portion between the stainless steel and copper (the distance between the stainless steel and copper, hereinafter simply referred to as the gap) is preferably, for example, 0.01 mm to 0.50 mm.

[0081] Furthermore, the maximum temperature reached by the copper during joining is preferably 500°C or lower, and more preferably 350°C or lower, from the viewpoint of avoiding a decrease in the strength and corrosion resistance of the copper. Also, the residence time of the copper in the temperature range of 200°C or higher is preferably 5 minutes or less, and more preferably 3 minutes or less, from the viewpoint of avoiding softening of the copper.

[0082] In addition, from the viewpoint of improving the wetting spread of the joining metals and improving workability, it is preferable to apply flux to the joining target area and its vicinity of the materials to be joined before the joining process. A general stainless steel flux is suitable as the flux. For example, it is preferable to use an aqueous solution containing zinc chloride: 30-50% by mass, ammonium chloride: 1-10% by mass, hydrogen chloride: 1-10% by mass, and water: 30-70% by mass, with the remainder being unavoidable impurities. The flux may be applied to the joining target area and its vicinity of both the stainless steel and copper materials to be joined, or to the joining target area and its vicinity of either one of them. Furthermore, the flux may be applied only to the joining target area, or only to a part of the joining target area.

[0083] [2] Joint of stainless steel and copper or copper alloy A joint of stainless steel and copper or copper alloy (hereinafter also simply referred to as a joint) according to one embodiment of the present invention has, as shown in Figure 3 or Figure 4, stainless steel, copper or copper alloy, and a joint between the stainless steel and copper or copper alloy. The joint is located between the stainless steel and copper or copper alloy at the overlapping portion where the stainless steel and copper or copper alloy overlap each other. Such a joint can be suitably obtained, for example, by the joining method described in [1] above.

[0084] The stainless steel and copper or copper alloy of the joint is derived from the stainless steel and copper or copper alloy of the materials to be joined, as described above [1].

[0085] The Sn content of the joint is preferably 40% by mass or more, more preferably 90% by mass or more. The Sn content of the joint is preferably 99.5% by mass or less, more preferably 97% by mass or less. The remainder may contain nonmetallic particles such as oxides. As for metal elements other than Sn and unavoidable impurities, they are the same as those described in (3) Joining Metal in [1] above, so their explanation is omitted here.

[0086] Furthermore, the average thickness of the joint is preferably 0.50 mm or less, more preferably 0.20 mm or less. Also, the average thickness of the joint is preferably 0.01 mm or more, more preferably 0.02 mm or more.

[0087] The average width of the joint (the average length of the joint in the direction perpendicular to the joint) is preferably 1.0 mm or more, more preferably 2.0 mm or more, and even more preferably 5.0 mm or more.

[0088] Furthermore, as shown in Figure 1, if the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is on the copper end side, a joined body can be obtained in which the joint contacts the copper end, as shown in Figure 3. Also, as shown in Figure 2, if the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is on the stainless steel end side, a joined body can be obtained in which the joint contacts the stainless steel end, as shown in Figure 4. The joint may also contact both the copper end and the stainless steel end. In addition, the width of the joint may be equal to the overlapping width L.

[0089] Here, the joint is defined, for example, as follows. First, a cross-sectional sample of the joint in the thickness direction (a sample with a cross-section perpendicular to the direction of joint propagation (X direction) (YZ plane)) is prepared with a mirror-polished finish, as shown in Figures 5 and 6. Next, the cross-sectional sample is observed with an optical microscope or SEM at a magnification of 100x. Then, the interface between the joint and the stainless steel (base material), and the interface between the joint and the copper or copper alloy (base material) are determined from the color (contrast) differences of each structure and the contrast of the interfaces observed in the obtained image, and the joint is defined. Then, based on the defined joint, the thickness and width of the joint in the cross-sectional sample are measured. This measurement is performed on four cross-sectional samples randomly cut from the jointed body, and the thickness and width of the joint in each cross-sectional sample are determined. Then, the average values ​​of these are calculated and used as the thickness and width of the joint in the jointed body.

[0090] Furthermore, in the above cross-sectional sample, if the thickness of the joint is not uniform, such as when there are non-parallel portions between the interface between the joint and the stainless steel, or between the joint and the copper or copper alloy, the thickness of the joint in that cross-section shall be calculated as follows: Specifically, in the joint defined as described above, the thickness of the joint shall be measured at five points, including both ends, at equal intervals. The average of the thicknesses of the five measured joint points shall then be taken as the thickness of the joint in that cross-section.

[0091] Furthermore, the Sn content of the joint is measured at a point halfway through the joint's thickness. For example, the Sn content of the joint can be measured as follows. First, a cross-sectional sample in the thickness direction (a sample with a cross-section perpendicular to the X direction, which is the direction of bonding (the YZ plane)) is prepared as shown in Figures 5 and 6. At this time, the cross-section is polished to a mirror finish, and then the cross-section is etched using an etching solution (5 mL of 38 mass% iron(II) chloride aqueous solution - 15 mL of 36 mass% hydrochloric acid - 120 mL of distilled water). Next, the obtained cross-sectional sample is observed by SEM at a magnification of 100x, and then SEM-EDS analysis is performed. In this analysis, an EDS point scan is performed on the bond portion of the cross-section, and the Sn content (mass%) is measured. The EDS scan points are 10 points randomly selected at a position half the thickness of the bond portion (a position away from the interface between copper or copper alloy and the bonding metal on the stainless steel side by a length obtained by dividing the thickness of the bond portion obtained from the above observation by 2). Then, the Sn content (mass%) measured at each point is averaged to determine the Sn content of the bond portion of the cross-sectional sample. This measurement is performed on four cross-sectional samples prepared by randomly taking samples from the joint, and the average value of the Sn content at the joint in each cross-sectional sample is taken as the Sn content of the joint.

[0092] Furthermore, if the overlapping surface side of the copper or stainless steel end is chamfered to facilitate the flow of the joining metal into the overlapping surface of the materials to be joined during joining, the thickness of the joint will not be uniform. In addition, when chamfering is performed, it is preferable that the angle between the chamfered surface and the surface of the other material to be joined be 5 to 10 degrees. In addition, it is preferable that the length of the chamfering be 1.0 to 3.0 mm in the direction perpendicular to the joint.

[0093] Furthermore, if the width of the joint is not uniform, such as when the width of the joint differs near stainless steel and near copper or copper alloy, meaning the width of the joint differs depending on the position in the thickness direction, the minimum length of the joint in the direction perpendicular to the joint at the position in the thickness direction between the overlapping surfaces of the joined materials shall be defined as the width of the joint.

[0094] Furthermore, a portion of the joint may protrude from the overlapping surface of the materials to be joined in the direction perpendicular to the joint. In this case, the thickness and width of the joint described above shall be measured excluding the portion that protrudes from the overlapping surface of the materials to be joined.

[0095] Furthermore, the joints may be connected by crimping or fitting, depending on the required strength and airtightness.

[0096] The joint according to one embodiment of the present invention may be either plate-shaped (including flat plates as well as curved plates) or tubular. If it is tubular, it is a joint between a stainless steel pipe and a copper pipe or copper alloy pipe. For example, the following combinations are possible. In these combinations, a part of the stainless steel pipe may be inserted into the copper pipe or copper alloy pipe, or a part of the copper pipe or copper alloy pipe may be inserted into the stainless steel pipe for joining. • A combination of a copper pipe or copper alloy pipe and a stainless steel pipe, where the outer diameter of the stainless steel pipe is approximately equal to the inner diameter of the copper pipe or copper alloy pipe. A combination of a stainless steel pipe and a copper or copper alloy pipe, where the ends have been expanded to be approximately equal to the outer diameter of the stainless steel pipe. - A combination of a stainless steel pipe with its ends tapered to be approximately equal in diameter to the inner diameter of the copper pipe or copper alloy pipe, and a copper pipe or copper alloy pipe, etc.

[0097] Furthermore, a joint according to one embodiment of the present invention includes a joint having a plurality of joints, at least one of which is the above-mentioned joint.

[0098] [3] Method for manufacturing a joint of stainless steel and copper or copper alloy Next, a method for manufacturing a joint made of stainless steel and copper or a copper alloy according to one embodiment of the present invention (hereinafter also referred to as the method for manufacturing the joint) will be described. A method for manufacturing a joint according to one embodiment of the present invention comprises the step of joining stainless steel and copper or a copper alloy by the joining method described in [1] above. The joint described in [2] above can be suitably manufactured by a method for manufacturing a joint according to one embodiment of the present invention. [Examples]

[0099] (Example 1) Stainless steel sheet (SUS443J1 as specified in JIS G 4305:2021) with a thickness of 1.0 mm and copper sheet (phosphorus deoxidized copper sheet (C1220) as specified in JIS H 3100:2018) or copper alloy sheet (C2680 as specified in JIS H 3100:2018) with a thickness of 1.0 mm were each cut to 120 mm square. Then, the copper sheet or copper alloy sheet was placed on the stainless steel sheet so that it overlapped with the overlap width L shown in Table 1 (arrangement shown in Figure 1) to obtain the material to be joined. At this time, spacers were placed between the stainless steel sheet and the copper sheet or copper alloy sheet at both ends in the direction of joining of the overlapping portion of the material to be joined so that the gap shown in Table 1 was formed, and then the material to be joined was clamped with clips. Furthermore, flux (BS-45, manufactured by Taiyo Electric Industries Co., Ltd.) was applied in advance to the surface of the stainless steel at the overlapping surfaces of the materials to be joined and in the vicinity thereof.

[0100] Next, as shown in Figure 1, thermocouples were attached to the surface (first surface) of the stainless steel at intervals of 5 mm in the direction of joining, at a position 10 mm away from the copper end of the material to be joined on the stainless steel side in the direction perpendicular to the joining (a position +10 mm from the copper end, which is the reference position (0 mm)).

[0101] Next, a φ2.0 rod of solder (Sn96.5Ag3Cu0.5 as specified in JIS Z 3282:2017) was placed near the copper end of the material to be joined.

[0102] Next, while moving the heating device in the direction of joining, the materials to be joined were heated from the upper surface of the copper plate or copper alloy plate to join the stainless steel plate and the copper plate or copper alloy plate, thereby obtaining a joined body of stainless steel and copper or copper alloy. The heating position was set at a position 20 mm away from the copper end, which was the reference position (-20 mm position). For tests No. 1-15 and No. 1-16 in Table 1, the materials to be joined were heated from the lower surface of the stainless steel, and the heating position was set at a position 20 mm away from the copper end, which was the reference position (+20 mm position) on the stainless steel side. Here, a gas torch, a so-called gas burner (manufactured by Shin-Fuji Burner Co., Ltd., RZ-820, heat output: 2300 kcal / hour, nozzle diameter: φ16 mm) was used as the heating device. In all conditions, joining was performed in an atmospheric environment. Furthermore, for conditions not specified, the general description above and conventional methods were followed. During the bonding process, the temperature of the stainless steel was measured and recorded at 0.1-second intervals using the thermocouple and temperature logger mentioned above, and the temperature history of the stainless steel was obtained from the output temperature logs. From the obtained temperature history of the stainless steel, (I) Maximum temperature reached in stainless steel (II) Residence time of stainless steel at temperatures above 150°C The result was derived. The results are shown in Table 1.

[0103] (I) and (II) were derived for each temperature measurement location where a thermocouple was installed. Table 1 shows only the maximum value of (I) and the minimum and maximum values ​​of (II) at each temperature measurement location as representative examples. Furthermore, in this example, (I) and (II) satisfied the above ranges at all temperature measurement locations. The same applies to Example 2, which will be described later.

[0104] From the resulting joint, four cross-sectional samples were cut out in the manner described above, and the thickness and width of the joint in each cross-sectional sample were measured. Furthermore, the feasibility of the joint was determined according to the following criteria. The results are shown in Table 1. Acceptable: In all four cross-sectional samples, the width of the joint is 1.0 mm or more. Unacceptable: In at least one cross-sectional sample, the width of the joint is less than 1.0 mm.

[0105] Next, from the thickness and width of the joint in each cross-sectional sample measured above, (III) Average value of the thickness of the joint (IV) Average value of the width of the joint The result was calculated. Also, following the above procedure, (V) Sn content of the joint (mass%) We measured it. The results are shown in Table 1. Note that calculations and measurements in (III) to (V) were not performed for those deemed unsuitable for joining. Furthermore, the fact that the average width of the joint is equal to the overlap width L means that the entire overlapping surface of the materials to be joined constitutes the joint.

[0106] Here, the thickness and width of the joint were measured using the DSX510 optical microscope manufactured by Olympus Corporation (now Evident Co., Ltd.). In addition, the Sn content (mass%) of the joint was measured using the Miniscope® TM3030plus scanning electron microscope (SEM) manufactured by Hitachi High-Tech Corporation, and the AZtecOne energy-dispersive X-ray spectrometer (EDS) manufactured by Oxford Instruments.

[0107] [Table 1]

[0108] As shown in Table 1, in all of the inventive examples, a jointed body of stainless steel and copper or copper alloy was obtained using a cost-effective Sn alloy as the joining metal, and by a simple joining method in an atmospheric environment.

[0109] On the other hand, in all of the comparative examples, the stainless steel and copper alloy were not properly joined. In other words, in the comparative example of Test No. 1-12, the maximum temperature reached by the stainless steel exceeded the appropriate range, making joining impossible. In the comparative example of Test No. 1-13, the residence time of the stainless steel at temperatures above 150°C exceeded the appropriate range, resulting in failure to bond. In the comparative example of Test No. 1-14, the residence time of the stainless steel at temperatures above 150°C fell below the appropriate range, resulting in failure to bond. In the comparative example of Test No. 1-15, joining was not possible because the heated area was made of stainless steel. In the comparative example of Test No. 1-16, the heating area was made of stainless steel, and the temperature of the stainless steel was raised excessively, resulting in failure to bond.

[0110] (Example 2) Stainless steel pipes having the outer diameter and thickness (wall thickness) listed in Table 2, and copper pipes (phosphorus deoxidized copper pipes (C1220T) as specified in JIS H 3300:2018) or copper alloy pipes (brass pipes (C2700T) as specified in JIS H 3100:2018) having the outer diameter and thickness (wall thickness) listed in Table 2, were cut to a length of 300 mm. The stainless steel pipes were inserted into the copper pipes or copper alloy pipes (as shown in Figure 1), or the copper pipes or copper alloy pipes were inserted into the stainless steel pipes (as shown in Figure 2), so that the overlap width L was 10 mm, and these were used as the materials to be joined. At this time, the outer circumference of the smaller diameter pipe end corresponding to the overlap portion was pre-ground or polished to adjust the gap between the stainless steel pipe and the copper pipe or copper alloy pipe to 0.05 mm. In addition, the same flux as in Example 1 was pre-applied to the outer surface of the smaller diameter pipe at the overlapping surface of the materials to be joined and in its vicinity.

[0111] Next, for materials to be joined in which a stainless steel pipe is inserted inside a copper pipe or copper alloy pipe, thermocouples were attached to the outer surface (first surface) of the stainless steel pipe at intervals of 4 mm in the direction of joining (circumferential direction), at a position 20 mm away from the copper end of the material to be joined on the stainless steel side in the direction perpendicular to the joining (a position +20 mm from the copper end which is the reference position (0 mm)). Furthermore, for materials to be joined in which a copper pipe or copper alloy pipe is inserted inside a stainless steel pipe, thermocouples were attached to the outer surface (second surface) of the stainless steel pipe at intervals of 4 mm in the direction of joining (circumferential direction), at a position 20 mm away from the stainless steel end of the material to be joined on the stainless steel side in the direction perpendicular to the joining (a position +20 mm from the stainless steel end which is the reference position (0 mm)).

[0112] Next, a φ1.0 rod-shaped solder (as specified in JIS Z 3282:2017) described in Table 2 was wrapped around the outer circumference of the smaller diameter pipe near the larger diameter pipe end of the material to be joined.

[0113] Next, the materials to be joined were heated from the outside of the pipe while moving the heating device in the direction of joining (circumferential direction), and the stainless steel pipe and the copper pipe or copper alloy pipe were joined to obtain a joined body of stainless steel and copper or copper alloy. The heating position was set at a position 20 mm away from the reference position (stainless steel end or copper end) on the copper side (-20 mm position). Here, a gas torch, a so-called gas burner, was used as the heating device. The gas burner used was the same as that used in Example 1 above. In all conditions, the joining was performed in an atmospheric environment. Furthermore, for conditions not specified, the general description above and conventional methods were followed. Then, from the temperature history of the stainless steel obtained in the same manner as in Example 1, (I) Maximum temperature reached in stainless steel (II) Residence time of stainless steel at temperatures above 150°C The result was derived. The results are shown in Table 2.

[0114] Furthermore, the feasibility of joining the obtained joints was determined in the same manner as in Example 1. (III) Average value of the thickness of the joint (IV) Average value of the width of the joint (V) Sn content of the joint (mass%) The following was calculated and measured. The results are shown in Table 2.

[0115] [Table 2]

[0116] As shown in Table 2, in all of the inventive examples, a jointed body of stainless steel and copper or copper alloy was obtained using a cost-effective Sn alloy as the joining metal, and by a simple joining method in an atmospheric environment.

[0117] On the other hand, in the comparative example of Test No. 2-13, the Sn content of the joining metal was below the appropriate range, resulting in insufficient melting of the joining metal and making joining impossible.

[0118] (Example 3) Stainless steel sheets with a thickness of 1.0 mm (SUS443J1 as specified in JIS G 4305:2021) and copper sheets with a thickness of 1.0 mm (phosphorus deoxidized copper sheets (C1220) as specified in JIS H 3100:2018, thermal conductivity: 339 W / mK) or copper alloy sheets (brass sheets (C2680) as specified in JIS H 3100:2018, thermal conductivity: 117 W / mK) were each cut to 120 mm square. Then, the copper sheets or copper alloy sheets were placed on the stainless steel sheet so that they overlapped with the overlap width L shown in Table 3, thereby obtaining the materials to be joined. At this time, spacers were placed between the stainless steel sheet and the copper sheets or copper alloy sheets at both ends in the direction of joining of the overlapping portion of the materials to be joined so that the gap shown in Table 3 was formed, and then the stainless steel sheet and the copper sheets or copper alloy sheets were clamped together with clips. Furthermore, flux (BS-45, manufactured by Taiyo Electric Industries Co., Ltd.) was applied in advance to the surface of the stainless steel at the overlapping surfaces of the materials to be joined and in the vicinity thereof.

[0119] Next, as shown in Figure 1, thermocouples were attached to the surface (first surface) of the stainless steel at intervals of 5 mm in the direction of joining, at a position 10 mm away from the copper end of the material to be joined on the stainless steel side in the direction perpendicular to the joining (a position +10 mm from the copper end, which is the reference position (0 mm)).

[0120] Next, a φ2.0 rod of solder (Sn96.5Ag3Cu0.5 as specified in JIS Z 3282:2017) was placed near the copper end of the material to be joined.

[0121] Next, the heating device was moved in the direction of joining while the heating element of the heating device was brought into contact with the materials to be joined at the contact positions shown in Table 3. This melted the joining metals, joining the stainless steel and copper or copper alloy to obtain a joined body. Here, a soldering iron (SS-152J (150W) sheet metal soldering iron from Ishizaki Electric Works Co., Ltd.) was used as the heating device. In all conditions, joining was performed in an atmospheric environment. Furthermore, for conditions not specified, the general description above and conventional methods were followed. During joining, the temperature of the stainless steel was measured and recorded at 0.1-second intervals using the thermocouple and temperature logger, and the temperature history of the stainless steel was obtained from the output temperature log. From the obtained temperature history of the stainless steel, (I) Maximum temperature reached in stainless steel (II) Residence time of stainless steel at temperatures above 100°C The result was derived. The results are shown in Table 3.

[0122] (I) and (II) were derived for each temperature measurement location where a thermocouple was installed. Table 3 shows only the maximum value of (I) and the minimum and maximum values ​​of (II) at each temperature measurement location as representative examples. Furthermore, in this example, (I) and (II) satisfied the above ranges at all temperature measurement locations. The same applies to Example 4, which will be described later.

[0123] Furthermore, the feasibility of joining the obtained joints was determined in the same manner as in Example 1. (III) Average value of the thickness of the joint (IV) Average value of the width of the joint (V) Sn content of the joint (mass%) The following was calculated and measured. The results are shown in Table 3.

[0124] [Table 3]

[0125] As shown in Table 3, in all of the inventive examples, a joint between stainless steel and copper or copper alloy was obtained using a cost-effective Sn alloy as the joining metal, and through a simple joining method in an atmospheric environment. Furthermore, no discoloration (temper color) of the stainless steel surface was observed.

[0126] On the other hand, in all of the comparative examples, the stainless steel and copper or copper alloy were not properly joined. In other words, in the comparative example of test No. 3-12, the residence time of the stainless steel at temperatures above 100°C exceeded the appropriate range, making joining impossible. In the comparative example of Test No. 3-13, the contact position was outside the appropriate range, the stainless steel did not reach a temperature of 100°C or higher, and the residence time at 100°C or higher was not within the appropriate range, resulting in failure to bond. In the comparative example of Test No. 3-14, the contact position was outside the appropriate range, the stainless steel did not reach a temperature of 100°C or higher, and the residence time at 100°C or higher was not within the appropriate range, resulting in failure to bond. In the comparative example of test No. 3-15, the maximum temperature reached by the stainless steel exceeded the appropriate range, making joining impossible. In the comparative example of Test No. 3-16, the residence time of the stainless steel at temperatures above 100°C fell below the appropriate range, making joining impossible. In the comparative example of Test No. 3-17, the contact position was outside the appropriate range, the stainless steel did not reach a temperature of 100°C or higher, and the residence time at 100°C or higher was not within the appropriate range, resulting in failure to bond. In the comparative example of Test No. 3-18, the contact position was outside the appropriate range, the stainless steel did not reach a temperature of 100°C or higher, and the residence time at 100°C or higher was not within the appropriate range, resulting in failure to bond.

[0127] (Example 4) Stainless steel pipes having the outer diameter and thickness (wall thickness) listed in Table 4, and copper pipes (phosphorus deoxidized copper pipes (C1220T) as specified in JIS H 3300:2018) or copper alloy pipes (brass pipes (C2700T) as specified in JIS H 3100:2018) having the outer diameter and thickness (wall thickness) listed in Table 4, were cut to a length of 300 mm. The stainless steel pipes were inserted into the copper pipes or copper alloy pipes (as shown in Figure 1), or the copper pipes or copper alloy pipes were inserted into the stainless steel pipes (as shown in Figure 2), so that the overlap width L was 10 mm, and these were used as the joined materials. At this time, the outer circumference of the smaller diameter pipe end corresponding to the overlap portion was pre-ground or polished to adjust the gap between the stainless steel pipe and the copper pipe or copper alloy pipe to 0.05 mm. In addition, the same flux as in Example 3 was pre-applied to the outer surface of the smaller diameter pipe at the overlapping surface of the joined materials and in its vicinity.

[0128] Next, for materials to be joined in which a stainless steel pipe is inserted inside a copper pipe or copper alloy pipe, thermocouples were attached to the outer surface (first surface) of the stainless steel pipe at intervals of 4 mm in the direction of joining (circumferential direction), at a position 15 mm away from the copper end of the material to be joined on the stainless steel side in the direction perpendicular to the joining (a position +15 mm from the copper end which is the reference position (0 mm)). Furthermore, for materials to be joined in which a copper pipe or copper alloy pipe is inserted inside a stainless steel pipe, thermocouples were attached to the outer surface (second surface) of the stainless steel pipe at intervals of 4 mm in the direction of joining (circumferential direction), at a position 15 mm away from the stainless steel end of the material to be joined on the stainless steel side in the direction perpendicular to the joining (a position +15 mm from the stainless steel end which is the reference position (0 mm)).

[0129] Next, a φ1.0 rod-shaped solder (as specified in JIS Z 3282:2017) described in Table 4 was wrapped around the outer circumference of the smaller diameter pipe near the larger diameter pipe end of the material to be joined.

[0130] Next, the heating device was moved in the direction of bonding (circumferential direction) while the heating element of the heating device was brought into contact with the materials to be joined. The contact positions are as shown in Table 4. This melted the joining metals and joined the stainless steel and copper or copper alloy to obtain a joined body. Here, the same soldering iron as in Example 3 was used as the heating device. In all conditions, the bonding was performed in an atmospheric environment. Furthermore, for conditions not specified, the general description above and conventional methods were followed. Then, from the temperature history of the stainless steel obtained in the same manner as in Example 3, (I) Maximum temperature reached in stainless steel (II) Residence time of stainless steel at temperatures above 100°C The result was derived. The results are shown in Table 2.

[0131] Furthermore, the feasibility of joining the obtained joints was determined in the same manner as in Example 1. (III) Average value of the thickness of the joint (IV) Average value of the width of the joint (V) Sn content of the joint (mass%) The following was calculated and measured. The results are shown in Table 4.

[0132] [Table 4]

[0133] As shown in Table 4, in all of the inventive examples, a joint between stainless steel and copper or copper alloy was obtained using a cost-effective Sn alloy as the joining metal, and by a simple joining method in an atmospheric environment. Furthermore, no discoloration (temper color) of the stainless steel surface was observed.

[0134] On the other hand, in the comparative example of test No. 4-13, the Sn content of the joining metal was below the appropriate range, resulting in insufficient melting of the joining metal and making joining impossible. [Industrial applicability]

[0135] A joint according to one embodiment of the present invention is suitable for application to various products, including heat exchanger piping, hot water supply piping, cold water supply piping, gas water heater piping, air conditioning equipment piping, residential equipment piping, electronic equipment components, and household electrical appliances.

Claims

1. The joining process involves joining materials, which consist of stainless steel and copper or a copper alloy, with a joining metal. The joining metal is Sn or an Sn alloy with a Sn content of 40% by mass or more. In the aforementioned joining process, The copper or copper alloy is heated by a heating device, and the stainless steel is heated by heat transfer from the copper or copper alloy, while the joining metal is melted to join the stainless steel and the copper or copper alloy. The maximum temperature that the aforementioned stainless steel can reach is 350°C or less, The residence time of the aforementioned stainless steel in a temperature range of 150°C or higher is 5 seconds or more and 5 minutes or less. The heating device is a torch. A method for joining stainless steel to copper or copper alloys. Here, the temperature of the stainless steel relating to the maximum temperature reached and the residence time in the temperature range of 150°C or higher is: When the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is the end of a copper or copper alloy, the surface temperature of the first surface of the stainless steel is defined as the position between 0 mm and +20 mm in the direction perpendicular to the joining, with the copper or copper alloy end as the reference position (0 mm), the stainless steel side as +, and the copper or copper alloy side as -. When the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is the end of the stainless steel, the surface temperature of the second surface of the stainless steel is defined as the position between 0 mm and +20 mm in the direction perpendicular to the joining, with the stainless steel end as the reference position (0 mm), the stainless steel side as +, and the copper or copper alloy side as -. Furthermore, the first surface of the stainless steel is the surface of the stainless steel that overlaps with the copper or copper alloy, and the second surface of the stainless steel is the surface of the stainless steel opposite to the side that overlaps with the copper or copper alloy.

2. The joining process involves joining materials, which consist of stainless steel and copper or a copper alloy, with a joining metal. The joining metal is Sn or an Sn alloy with a Sn content of 40% by mass or more. In the aforementioned joining process, By using a heating device having a heating element, the heating element is brought into contact with the material to be joined, thereby melting the joining metals and joining the stainless steel and the copper or copper alloy. The contact position between the heating element and the material to be joined in the direction perpendicular to the joining is such that the overlapping end, which is the starting point for the pouring of the joining metal into the overlapping surface of the material to be joined, is the reference position (0 mm), with the stainless steel side being + and the copper or copper alloy side being -. When the thermal conductivity of the copper or copper alloy is 250 W / mK or higher, the range is greater than 0 mm to +15 mm. If the thermal conductivity of the copper or copper alloy is less than 250 W / mK, the range is -15 mm to +15 mm. The maximum temperature that the aforementioned stainless steel can reach is 250°C or less, The residence time of the aforementioned stainless steel in a temperature range of 100°C or higher is 5 seconds or more and 5 minutes or less. The heating device is a soldering iron. A method for joining stainless steel to copper or copper alloys. Here, the temperature of the stainless steel relating to the maximum temperature reached and the residence time in the temperature range of 100°C or higher is: When the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is the end of a copper or copper alloy, the surface temperature of the first surface of the stainless steel is defined as the position between 0 mm and +20 mm in the direction perpendicular to the joining, with the copper or copper alloy end as the reference position (0 mm), the stainless steel side as +, and the copper or copper alloy side as -. When the starting point for pouring the joining metal into the overlapping surfaces of the materials to be joined is the end of the stainless steel, the surface temperature of the second surface of the stainless steel is defined as the position between 0 mm and +20 mm in the direction perpendicular to the joining, with the stainless steel end as the reference position (0 mm), the stainless steel side as +, and the copper or copper alloy side as -. Furthermore, the first surface of the stainless steel is the surface of the stainless steel that overlaps with the copper or copper alloy, and the second surface of the stainless steel is the surface of the stainless steel opposite to the side that overlaps with the copper or copper alloy.

3. A joined body of stainless steel and copper or copper alloy, formed by joining stainless steel and copper or copper alloy by the method of joining stainless steel and copper or copper alloy according to claim 1 or 2.

4. A method for manufacturing a stainless steel and copper or copper alloy bond, comprising joining stainless steel and copper or copper alloy by the joining method for stainless steel and copper or copper alloy described in claim 1 or 2.

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