Joint structure and manufacturing method of the same

Abstract

To provide a joint structure which can inhibit reduction of joint strength even when a brass which contains bismuth (Bi) in place of lead and stainless steel are brazed with a brazing material, and to provide a manufacturing method of the joint structure.SOLUTION: A joint structure in which a stainless member and a brass member are brazed, includes a layer structure in which the stainless member, a first brazing material layer, a Bi barrier layer, a second brazing material layer, and the brass member are sequentially arranged in a laminar manner. The brass member contains Bi, and the Bi barrier layer inhibits Bi in the brass member from being moved to the first brazing material layer by brazing of the stainless member and the brass member.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a joint structure and a method for manufacturing the joint structure, and more particularly to a joint structure between stainless steel and brass and a method for manufacturing the joint structure. [Background technology]

[0002] Conventionally, when joining dissimilar metals, such as stainless steel and brass, brazing has been performed (for example, Patent Document 1). Recently, the use of materials containing lead has become stricter from the viewpoint of environmental regulations, and there is a trend toward using bismuth (hereinafter sometimes referred to as "Bi") as a substitute for lead (hereinafter sometimes referred to as "Pb"). The same is true for brass, where lead has the effect of improving the machinability of brass, but bismuth is used instead of lead. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-276072 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-98685 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-42325 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when brass containing bismuth instead of lead is brazed to stainless steel using a brazing filler metal, the bonding strength between the stainless steel and the brazing filler metal may be reduced compared to when conventional lead-containing brass is brazed to stainless steel.

[0005] In view of the above problems, the present invention aims to provide a joining structure and a method for manufacturing a joining structure that can suppress a decrease in joining strength even when brass containing bismuth instead of lead and stainless steel are joined by brazing using a brazing filler metal. [Means for solving the problem]

[0006] In order to solve the above problems, the joining structure of the present invention is a joining structure in which a stainless steel member and a brass member are brazed together, and has a layered structure in which the stainless steel member, a first brazing material layer, a Bi shielding layer, a second brazing material layer, and the brass member are arranged in layered form by the brazing, in that order, the brass member contains Bi, and the Bi shielding layer is a layer that suppresses the migration of Bi in the brass member to the first brazing material layer by the brazing of the stainless steel member and the brass member.

[0007] The bonding strength between the stainless steel member and the brass member is 100 N / mm 2 It may be more than that.

[0008] The brass member may be a joint of a pressure sensor, and the stainless steel member may be a dish-shaped lid attached to the joint of the pressure sensor.

[0009] The brass member may be a joint of a pressure switch, and the stainless steel member may be a dish-shaped lid attached to the joint of the pressure switch.

[0010] The brass member may be the main body of the valve, and the stainless steel member may be a bottom cover member arranged around the opening of the main body.

[0011] The brass member may be a main body of the valve, and the stainless steel member may be a cylindrical member disposed in an opening of the main body.

[0012] In addition, in order to solve the above-mentioned problems, the manufacturing method of the joint structure of the present invention includes a first layer structure formation process in which the stainless steel member, the first brazing material, the Bi shielding layer, the second brazing material, and the brass member are arranged in layers to form a first layer structure; a first brazing process in which the first layer structure is heated to braze the stainless steel member and the brass member; and a first cooling process in which the first layer structure after the first brazing process is cooled to form a joint structure having a layer structure in which the stainless steel member, the first brazing material layer, the Bi shielding layer, the second brazing material layer, and the brass member are arranged in layers.

[0013] In the method for producing a brazed joint of the present invention, the first brazing filler metal and the second brazing filler metal may be brazing filler metals of the same composition.

[0014] The Bi shielding layer may be in the shape of a washer.

[0015] The Bi shielding layer may be cylindrical.

[0016] In addition, in order to solve the above-mentioned problems, the manufacturing method of the joint structure of the present invention includes a second layer structure formation process in which the stainless steel member, the Bi shielding layer, and the brass member are arranged in layers, and a brazing material is arranged between the stainless steel member and the Bi shielding layer, between the Bi shielding layer and the brass member, or on at least one of the sides of the Bi shielding layer to form a second layer structure; a second brazing process in which the second layer structure is heated to braze the stainless steel member and the brass member; and a second cooling process in which the second layer structure after the second brazing process is cooled to form a joint structure having a layer structure in which the stainless steel member, the first brazing material layer, the Bi shielding layer, the second brazing material layer, and the brass member are arranged in layers.

[0017] The Bi shielding layer may be in the shape of a washer.

[0018] The Bi shielding layer may be cylindrical. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a joining structure and a method for manufacturing a joining structure that can suppress a decrease in joining strength even when brass containing bismuth instead of lead and stainless steel are joined by brazing using a brazing filler metal. [Brief explanation of the drawings]

[0020] [Figure 1] These are SEM images taken with an SEM of a cross section of a joint structure in which a stainless steel member and a brass member are brazed together. Figure 1(A) shows a joint structure 200 of Conventional Example 1, which uses a conventional brass member containing lead. Figure 1(B) shows a joint structure 300 of Comparative Example 1, which uses a brass member containing bismuth instead of lead. Figure 1(C) shows a joint structure 100 of Example 1, which uses a brass member containing bismuth instead of lead and further has a barrier layer between the stainless steel member and the brass member. [Figure 2] 2(A) and 2(B) are side views of the test specimen used in the joining test and the jig used in the joining test, respectively. FIG. 2(A) shows the test specimen before assembly of the jig and the test specimen, FIG. 2(B) shows the test specimen after assembly of the jig and the test specimen, and FIG. 2(C) is an enlarged view of a portion of the joining portion of the circled area E of the brazed joint 200 shown in FIG. 2(A). [Figure 3] 1 is a cross-sectional view of a pressure sensor equipped with a bonding structure of the present invention. [Figure 4] 1 is a cross-sectional view of a pressure switch equipped with a joint structure of the present invention. [Figure 5] 5 is an enlarged cross-sectional view of a region A that is a portion of the joining structure in the pressure switch shown in FIG. 4. FIG. [Figure 6] 1 is a cross-sectional view of an electric valve equipped with a joining structure of the present invention. [Figure 7] 1 is a cross-sectional view of a regulating valve equipped with a joint structure of the present invention. [Figure 8] 1 is a cross-sectional view of an expansion valve equipped with the joining structure of the present invention. [Figure 9] 1 is a cross-sectional view of a solenoid valve equipped with a joining structure of the present invention. [Figure 10] 10 is an enlarged cross-sectional view of a region C that is a portion of the joining structure in the solenoid valve shown in FIG. 9. FIG. [Figure 11]FIG. 2 is a perspective view showing an example of each member constituting the first layer structure. [Figure 12] FIG. 2 is a partial cross-sectional view of a first layer structure. [Figure 13] FIG. 2 is a perspective view showing an example of each member constituting the second layer structure. [Figure 14] FIG. 2 is a partial cross-sectional view of a second layer structure. [Figure 15] FIG. 2 is a perspective view showing an example of each member constituting the second layer structure. [Figure 16] FIG. 2 is a partial cross-sectional view of a second layer structure. [Figure 17] FIG. 6 is a partial cross-sectional view of the solenoid valve 6000. [Figure 18] FIG. 2 is a partial cross-sectional view of a second layer structure. [Figure 19] FIG. 2 is a partial cross-sectional view of a second layer structure. [Figure 20] 20A and 20B are SEM images of a cross section of a portion of the joining structure 100 taken with an SEM and an EDS element mapping image of bismuth in the cross section corresponding to the SEM image. Fig. 20A is an image of a cross section of the layer structure consisting of the stainless steel 10, the first brazing filler metal layer 20, and the blocking layer 30, and Fig. 20B is an image of a cross section of the layer structure consisting of the blocking layer 30, the second brazing filler metal layer 40, and the brass member 50. [Figure 21] The figure shows an SEM image of a cross section of a layer structure consisting of stainless steel 10, brazing material layer 80, and brass member 50 of joint structure 300, taken with an SEM, and an image of bismuth element mapping by EDS of the cross section corresponding to the SEM image. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the joint structure and the method for manufacturing the joint structure of the present invention will be described, but the present invention is not limited to the following example.

[0022] [Joining structure] The joining structure of the present invention is a joining structure in which a stainless steel member and a brass member are brazed together, and has a layered structure in which the stainless steel member, a first brazing material layer, a Bi shielding layer, a second brazing material layer, and the brass member are arranged in layered form by the brazing, in that order.

[0023] The joining structure of the present invention is not particularly limited in shape as long as it has such a layer structure, and can be used for various applications as a part in which dissimilar metals, such as stainless steel and brass, are joined by brazing. Examples of parts include a brazed joint between a stainless steel cap and a brass joint in a pressure switch, a brazed joint between a stainless steel cap and a brass joint in a pressure sensor, a brazed joint between a stainless steel cap and a brass body in an electric valve, a brazed joint between a stainless steel tube and a brass body in an electromagnetic valve, a brazed joint between a stainless steel cap and a brass body in a regulating valve, and a brazed joint between a stainless steel cap and a brass body in an expansion valve. Specific examples of these parts will be described later.

[0024] 1A to 1C show SEM images of a cross section of a brazed joint structure in which a stainless steel member and a brass member are brazed together. Of these, Fig. 1C shows a joint structure 100 of Example 1 in Examples described later, which is an example of the joint structure of the present invention.

[0025] 1(C), the joining structure 100 has a layered structure in which a stainless steel member 10, a first brazing filler metal layer 20, a Bi shielding layer 30, a second brazing filler metal layer 40, and a brass member 50 are arranged in this order. That is, the stainless steel member 10 and the brass member 50 are brazed together, and in the present invention, the stainless steel member 10 and the Bi shielding layer 30 are brazed together, and the brass member 50 and the Bi shielding layer 30 are brazed together.

[0026] <Stainless steel material 10> The stainless steel member 10 is not particularly limited, and examples thereof include stainless steel members used in the above-mentioned components. Specifically, austenitic stainless steel such as SUS304, ferritic stainless steel, martensitic stainless steel, and any of these two-phase stainless steels can be used as the stainless steel member 10.

[0027] <Brass member 50> The brass member 50 is not particularly limited except that it uses brass containing Bi, and examples thereof include brass members used in the above-mentioned parts. Specifically, brass having a Cu content of 57.4 to 64.0 mass%, a Pb content of 0.1 mass% or less, and a Bi content of 0.50 to 4.00 mass% can be used as the brass member 50. More specifically, C6801B, C6802B, C6803B, C6804B, etc. can be used.

[0028] In the present invention, since brass containing bismuth is used instead of lead for the brass member 50, it is ideal to contain as little Pb as possible, and the lower limit of the Pb content is 0% by mass, and in consideration of analytical accuracy, the lower limit is preferably below the detection limit of Pb. However, there are cases where Pb is unavoidably contained, or where a small amount is not a problem, so it is important that the Pb content does not exceed 0.1% by mass.

[0029] <Bi shielding layer 30> The Bi shielding layer 30 is a layer that prevents Bi in the brass member 50 from migrating to the first brazing material layer 20 when the stainless steel member 10 and the brass member 50 are brazed together.

[0030] In the case of a conventional joint structure in which a brass member containing lead and a stainless steel member 10 are joined by brazing, there is no problem with the joint strength. For example, the joint strength, which is a guideline for the strength used for the above-mentioned parts, is 100 N / mm 2 It fully met the above criteria.

[0031] However, when the brass member 50 containing bismuth instead of lead is brazed to the stainless steel member 10, the bonding strength between the stainless steel and the brazing material decreases, and the bonding strength is 100 N / mm 2 In some cases, the bonding strength was less than 1 / 2. When the cause of this decrease in bonding strength was investigated, it was found that bismuth migrated from the brass member 50 to the brazing filler metal layer, forming a brazing filler metal layer containing bismuth, and that the bismuth segregated at the stainless steel interface, resulting in a decrease in the bonding strength between the brazing filler metal layer and the stainless steel member 10. Therefore, in order to ensure sufficient bonding strength, it is important that even if bismuth migrates from the brass member 50 to the brazing filler metal layer, the bismuth does not reach the vicinity of the bonding interface between the stainless steel member 10 and the brazing filler metal layer.

[0032] Therefore, in the present invention, the Bi shielding layer 30 is provided to prevent bismuth from reaching the vicinity of the joint interface with the stainless steel member 10. Although bismuth migrates from the brass member 50 to the second brazing filler metal layer 40 by brazing, the Bi shielding layer 30 blocks the migration of bismuth, thereby preventing the bismuth from migrating around the Bi shielding layer 30 to the first brazing filler metal layer 20, thereby preventing a decrease in the joint strength between the stainless steel member 10 and the first brazing filler metal layer 20. As a result, the stainless steel member 10 and the brass member 50 can be joined while maintaining sufficient strength.

[0033] It is important that the Bi shielding layer 30, which fulfills this role, can withstand the heating temperature during brazing and does not contain excessive amounts of lead or bismuth. Even if the stainless steel member 10, the first brazing filler metal layer 20, the second brazing filler metal layer 40, and the brass member 50 have sufficient strength, if the strength of the Bi shielding layer 30 is low, there is a risk of fracture at the Bi shielding layer 30. Therefore, to prevent fracture at the shielding layer, the tensile strength of the Bi shielding layer 30 itself is set to, for example, 400 N / mm 2 It is preferable that there is more than one.

[0034] Materials that satisfy these conditions and can be used for the Bi shielding layer 30 include the following brass and phosphor bronze, and at least one of these can be used alone or in combination.

[0035] (Brass for Bi shielding layer 30) The Bi shielding layer 30 can be made of brass with a Cu content of 59.0 to 71.5 mass% and a Pb content of 0.10 mass% or less. In the present invention, the Bi shielding layer 30 should ideally contain as little Pb and Bi as possible, with the lower limits of the Pb content and the Bi content being 0 mass%, and considering analytical accuracy, the lower limits are preferably below the detection limit for both Pb and Bi. However, there are cases where Pb and Bi are unavoidably contained, or where a small amount is not a problem. For example, it is important that the Pb content does not exceed 0.1 mass%.

[0036] As such brass, for example, C2680 and C2801 can be used.

[0037] (Phosphor bronze for Bi shielding layer 30) The Bi shielding layer 30 can be made of phosphor bronze containing 5.5 to 7.0 mass% Sn, 0.03 to 0.35 mass% P, 0.02 mass% or less Pb, 0.10 mass% or less Fe, 0.20 mass% or less Zn, and the remainder Cu, with the total of Cu, Sn, and P being 99.5 mass% or more. In the present invention, the Bi shielding layer 30 should ideally contain as little Pb and Bi as possible, with the lower limits for the Pb and Bi contents being 0 mass%. Considering analytical accuracy, these lower limits are preferably below the detection limit for both Pb and Bi. However, there are cases where Pb and Bi are unavoidably contained, or where a small amount is not a problem. For example, it is important that the Pb content does not exceed 0.1 mass%, and the above phosphor bronze can be used without any problems.

[0038] As such phosphor bronze, for example, C5191 can be used.

[0039] (Shape and thickness of Bi shielding layer 30) The Bi shielding layer 30 may be in the form of a plate or thin film with a uniform thickness, a ring shape such as a washer or nut, or a cylindrical shape. When using a Bi shielding layer 30 in such a shape, its dimensions can be adjusted appropriately depending on the shape of the stainless steel member 10 or the brass member 50. The thickness of the Bi shielding layer 30 may be, for example, 0.4 to 1.2 mm.

[0040] <First brazing filler metal layer 20> The brazing filler metal constituting the first brazing filler metal layer 20 is preferably in a liquid state at 680 to 800° C. By using a brazing filler metal that is liquid at this temperature, the stainless steel member 10 and the brass member 50 can be joined via the Bi shielding layer 30.

[0041] The brazing filler metal that can be used for the first brazing filler metal layer 20 preferably does not contain Pb or Bi, and furthermore, in consideration of environmental regulations, it is preferable that it does not contain Cd. Examples of such brazing filler metals include BAg-4, BAg-5, BAg-6, BAg-7, BAg-7A, BAg-7B, BAg-8, BAg-8A, BAg-8B, BAg-20, and BAg-24. These brazing filler metals can be used alone or in combination.

[0042] For example, when a member made by processing SUS304 is used as the stainless steel member 10, the first brazing filler metal layer 20 may be a layer of a brazing filler metal containing BAg-7.

[0043] <Second brazing filler layer 40> The brazing filler metal constituting the second brazing filler metal layer 40 is preferably in a liquid state at 680 to 800° C. By using a brazing filler metal that is liquid at this temperature, the stainless steel member 10 and the brass member 50 can be joined via the Bi shielding layer 30.

[0044] The brazing filler metal that can be used for the second brazing filler metal layer 40 preferably does not contain Pb or Bi, and furthermore, in consideration of environmental regulations, it is preferable that it does not contain Cd. Examples of such brazing filler metals include BAg-4, BAg-5, BAg-6, BAg-7, BAg-7A, BAg-7B, BAg-8, BAg-8A, BAg-8B, BAg-20, and BAg-24. These brazing filler metals can be used alone or in combination.

[0045] For example, when a member made by processing SUS304 is used as the stainless steel member 10, the second brazing filler metal layer 40 may be a layer of a brazing filler metal containing BAg-7.

[0046] The second brazing filler metal layer 40 may be formed by brazing the stainless steel member 10 and the brass member 50 using the same brazing filler metal as the first brazing filler metal layer 20, or a different brazing filler metal may be used. However, bismuth migrates from the brass member 50 to the second brazing filler metal layer 40 due to the heating for brazing. Therefore, the amount of bismuth in the second brazing filler metal layer 40 is greater than that in the first brazing filler metal layer 20.

[0047] <Joining strength> Pressure vessels such as pressure switches, pressure sensors, motor-operated valves, solenoid valves, regulating valves, and expansion valves have fluids such as refrigerants under high pressure inside them. Therefore, it is important that they have pressure resistance. When the joining structure 100 of the present invention is used as a component of these pressure vessels, the joining strength between the stainless steel member 10 and the brass member 50 must be 100 N / mm to prevent fluid leakage to the outside due to breakage caused by pressure. 2 It is preferable that this is equal to or greater than this.

[0048] However, the joint structure 100 of the present invention is 2 If the application does not require a bonding strength of 100 N / mm 2 It doesn't need to be more than that.

[0049] <Pressure Sensor 1000> The joining structure of the present invention can be used as a component in a pressure sensor (for example, Patent Document 2, etc.). In this case, the brass member is a joint of the pressure sensor, and the stainless steel member is a dish-shaped lid attached to the joint of the pressure sensor. As an example of a pressure sensor, a cross-sectional view of a pressure sensor 1000 equipped with the joining structure of the present invention is shown in FIG.

[0050] This pressure sensor 1000 has a cover 1030 connected to the tip of a joint 1020, which has an inlet passage 1010 for the fluid under pressure to be detected in the center. A metal header 1070 having an insulating member 1040 in the center is connected to this cover 1030. A sealant 1110 is filled into the space formed in a resin case 1100 to prevent moisture from entering the pressure sensor.

[0051] The insulating member 1040 is made of, for example, glass hermetic, and the header 1070, insulating member 1040, and diaphragm 1060 form a liquid-sealed chamber. The pressure detection element 1050 is disposed within the liquid-sealed chamber, and detects the pressure acting on the diaphragm 1060 via the sealed liquid within the liquid-sealed chamber. A plurality of lead pins 1090 that input and output signals to and from the pressure detection element 1050 and a stem 1080 that supports the pressure detection element 1050 are fixed by the insulating member 1040.

[0052] That is, in the pressure sensor 1000, the pressure acting on the diaphragm 1060 is transmitted via the enclosed liquid to the pressure detection element 1050 fixed on the stem 1080 arranged opposite the diaphragm 1060, and a detection output is obtained from the lead pin 1090 extending through the insulating member 1040.

[0053] In this pressure sensor 1000, the hexagonal column-shaped joint 1020 corresponds to the brass member, and the dish-shaped lid 1030 and header 1070 are each made of stainless steel, with the lid 1030 corresponding to the stainless steel member. The joint 1020 and the lid 1030 are brazed together with a brazing filler metal, sandwiching the washer-shaped Bi shielding layer 31 between them. One example of assembling these components in the pressure sensor 1000 is to first braze the joint 1020 (brass member) and the lid 1030 (stainless steel member) in a reducing atmosphere furnace with the Bi shielding layer 31 sandwiched between them, then cool them in the reducing atmosphere furnace and remove them from the furnace and allow them to cool at room temperature to form a joint structure. The header 1070 is then welded to the lid 1030 of the joint structure.

[0054] In the pressure sensor 1000, the Bi shielding layer 31 serves as a layer that prevents Bi in the joint 1020 from migrating to the first brazing material layer when the lid 1030, which is a stainless steel member, is brazed to the joint 1020, which is a brass member, and as a result, it is possible to prevent a decrease in the bonding strength between the lid 1030 and the joint 1020.

[0055] <Pressure Switch 2000> The joining structure of the present invention can be used as a component in a pressure switch. In this case, the brass member is a joint of the pressure switch, and the stainless steel member is a dish-shaped lid attached to the joint of the pressure switch. As an example of a pressure switch, Fig. 4 shows a cross-sectional view of a pressure switch 2000 equipped with the joining structure of the present invention.

[0056] This pressure switch 2000 turns on / off by moving one of a pair of contacts relative to the other by operating an operating rod in response to pressure fluctuations. This pressure switch 2000 uses a metal diaphragm 2010 made of a thin metal film, and metal diaphragm 2010, cover 2030, and outer periphery 2130 of stopper 2120 are welded together to form diaphragm unit 2140, which can completely block the permeation of refrigerant. This pressure switch 2000 has a dish-shaped cover 2030 that defines a pressure-sensing chamber 2020 on one side of a metal diaphragm 2010, a joint 2040 that is airtightly connected to this dish-shaped cover 2030 and that introduces a refrigerant (pressure) such as high-pressure gas or oil to the pressure-sensing chamber 2020, and a resin case member 2090 that protects a contact portion 2052 that includes a movable contact 2050 and a fixed contact 2051 that are switched by an operating rod 2150 in response to the displacement of the metal diaphragm 2010. In addition, connection terminal pieces 2100 and 2110 are attached to the case member 2090.

[0057] Metal holder member 2070 is a caulking material that can be plastically deformed by caulking to join and integrate two or more parts. By caulking holder member 2070, diaphragm unit 2140 including case member 2090, intermediate plate member 2080, rubber O-ring 2060, metal diaphragm 2010, cover 2030, and stopper 2120 can be integrated.

[0058] In such a pressure switch 2000, the joint 2040 corresponds to the brass member, and the dish-shaped lid 2030 corresponds to the stainless steel member. The joint 2040 and the lid 2030 are brazed with a brazing material, sandwiching a washer-shaped Bi shielding layer 32 therebetween.

[0059] As an example of assembling these in the pressure switch 2000, first, the joint 2040, which is a brass member, and the dish-shaped lid 2030, which is a stainless steel member, are brazed in a reducing atmosphere furnace with the Bi shielding layer 32 sandwiched between them, and then cooled in the reducing atmosphere furnace and removed from the furnace and allowed to cool at room temperature to form a joint structure. Then, the metal diaphragm 2010 is placed on the lid 2030 of the joint structure, and further the stopper 2120 is placed on top of that, and from this state the stopper 2120, the metal diaphragm 2010, and the outer periphery 2130 of the lid 2030 are joined together by welding.

[0060] Fig. 5 shows an enlarged cross-sectional view of region A, which is part of the joint structure 110 in the pressure switch 2000 shown in Fig. 4. Although the brazing filler metal layer is not shown in Fig. 4 because it is thin, as shown in Fig. 5, the joint structure 110 has a layered structure in which a cover 2030, which is a stainless steel member, a first brazing filler metal layer 21, a Bi shielding layer 32, a second brazing filler metal layer 41, and a joint 2040, which is a brass member, are arranged in this order. Although the motor-operated valve 3000, a regulating valve 4000, and an expansion valve 5000 shown in Figs. 6 to 8, which will be described later, are not shown in the drawings because their brazing filler metal layers are thin, they also have joint structures with similar layered structures.

[0061] The SEM image of the cross section of the joint structure 100 of Example 1 shown in Fig. 1(C) is an image obtained by photographing the cross section of the joint structure 110 shown in Fig. 5 with an SEM. The stainless steel member 10, the first brazing filler metal layer 20, the Bi shielding layer 30, the second brazing filler metal layer 40, and the brass member 50 in the joint structure 100 in Fig. 1(C) correspond to the lid body 2030, the first brazing filler metal layer 21, the Bi shielding layer 32, the second brazing filler metal layer 41, and the joint 2040 of the joint structure 110 in Fig. 5, respectively.

[0062] In the pressure switch 2000, the Bi shielding layer 32 serves as a layer that prevents Bi in the joint 2040 from migrating to the first brazing material layer 21 when the cover 2030, which is a stainless steel member, is brazed to the joint 2040, which is a brass member, and as a result, a decrease in the bonding strength between the cover 2030 and the joint 2040 can be prevented.

[0063] The joining structure of the pressure sensor 1000 shown in FIG. 3 also has a layer structure similar to the layer structure shown in FIG. 5, although the brazing material layer is not shown in FIG. 3 because it is thin.

[0064] <Motor valve 3000, regulating valve 4000, expansion valve 5000> The joining structure of the present invention can be used as a component in an electric valve (for example, Patent Document 3), a regulating valve, or an expansion valve. In this case, the brass member is the main body of the valve, and the stainless steel member is a bottom cover material placed around the opening of the main body. Examples of an electric valve, a regulating valve, and an expansion valve will be described below.

[0065] (Motor Valve 3000) 6 shows a cross-sectional view of a motor-operated valve 3000 equipped with the joining structure of the present invention. The motor-operated valve 3000 has a valve body 3010, which is formed with a valve chamber 3011, a pipe connection hole 3012 opening onto one inner circumferential surface of the valve chamber 3011, a pipe connection hole 3013 opening downward from the valve chamber 3011, and a valve port 3014 connecting the pipe connection hole 3013 to the valve chamber 3011. The pipe connection hole 3012 is formed as a horizontal hole, to which a first coupling pipe 3020 is fixed by brazing. The pipe connection hole 3013 is formed as a pilot hole, to which a second coupling pipe 3030 is fixed by brazing.

[0066] A dish-shaped lid case 3050 is hermetically secured by brazing to the top of the valve body 3010, and a coil 3101 is attached to a rotor case 3110 which is hermetically secured to the lid case 3050. The coil 3101 and the magnet 3230 form a stepping motor 3100. Lead wire 3102 is an electric wire that electrically connects the stepping motor 3100 to a power source (not shown). A rotor 3200 including a fixing member 3210, a female screw member 3220, a magnet 3230, and an operating shaft 3240 is rotatably disposed inside the rotor case 3110. When a pulse signal is given to the stepping motor 3100, the rotor 3200 rotates according to the number of pulses.

[0067] A stopper holding rod 3300 is fixed so as to hang down inside the rotor case 3110. A screw guide 3310 is attached to the stopper holding rod 3300, and a movable stopper 3320 is engaged with the screw guide 3310.

[0068] The valve element 3015 is formed integrally with the operating shaft 3240, and when the rotor 3200 is rotated by driving the stepping motor 3100, the rotation of the rotor 3200 is converted into linear motion of the operating shaft 3240 by thrust from the female screw member 3220, which rotates together with the rotor 3200, and the male screw member 3040, which is fixed by the valve body 3010 and fits into the female screw member 3220, and the valve element 3015 moves in the vertical direction in Figure 6 via the operating shaft 3240. In this way, the valve element 3015 adjusts the opening of the valve port 3014, and the flow rate of the refrigerant flowing in from the first joint pipe 3020 and flowing out from the second joint pipe 3030 is controlled.

[0069] In such an electric valve 3000, the valve body 3010, which is the main body of the valve, corresponds to the brass member, and the lid case 3050, which is the lower lid material arranged around the opening 3016 into which the valve element 3015 of the valve body 3010, which is the main body, is inserted, corresponds to the stainless steel member. The valve body 3010 and the lid case 3050 are brazed with a brazing material, sandwiching a washer-shaped Bi shielding layer 33. At this time, it is also possible to braze the first joint pipe 3020, the second joint pipe 3030, and the valve body 3010 simultaneously.

[0070] As an example of assembling these components in the motor-operated valve 3000, first, the valve body 3010, which is a brass member, and the lid case 3050, which is a stainless steel member, are brazed together in a reducing atmosphere furnace with the Bi shielding layer 33 sandwiched between them, and then cooled in the reducing atmosphere furnace and removed from the furnace and allowed to cool at room temperature to form a joined structure.

[0071] In the electric valve 3000, the Bi shielding layer 33 serves as a layer that prevents Bi in the valve body 3010 from migrating to the first brazing material layer when the lid case 3050, which is a stainless steel member, is brazed to the valve body 3010, which is a brass member, and as a result, a decrease in the bonding strength between the lid case 3050 and the valve body 3010 can be prevented.

[0072] (Regulating valve 4000) 7 shows a cross-sectional view of a regulating valve 4000 equipped with the joining structure of the present invention. The regulating valve 4000 has a valve body 4010 having a substantially cylindrical outer shape. The valve body 4010 is formed with a piping connection hole 4020, a piping connection hole 4030, a valve chamber 4040, a valve insertion hole 4050, a secondary side port 4060, a spring chamber 4070, and a valve port 4080. The piping connection hole 4020, the piping connection hole 4030, the valve chamber 4040, the valve insertion hole 4050, and the secondary side port 4060 are all cylindrical holes.

[0073] A first joint pipe 4100 through which fluid flows in as shown by the arrow is attached to the pipe connection hole 4020, and a second joint pipe 4200 through which fluid flows out as shown by the arrow is attached to the pipe connection hole 4030. The first joint pipe 4100 and the second joint pipe 4200 are integrally assembled to the valve body 4010 by brazing.

[0074] The first joint pipe 4100 is connected to the valve chamber 4040 via a valve port 4080, and the first joint pipe 4100, the valve chamber 4040, and the valve insertion hole 4050 are located on the central axis L of the valve port 4080. The second joint pipe 4200 is connected to the valve chamber 4040 via a secondary side port 4060. The valve port 4080 is a cylindrical hole centered on the central axis L.

[0075] A cylindrical valve element 4090 is disposed within the valve insertion hole 4050. The valve insertion hole 4050 is cylindrical and centered on a central axis L, and the valve element 4090 moves within the valve insertion hole 4050 in the direction of the central axis L, i.e., in the up-and-down direction in FIG. 7 . The spring chamber 4070 is formed as a deep, ring-shaped groove around the valve insertion hole 4050, and a coil spring 4071 is disposed within the spring chamber 4070. A flange-shaped spring retainer 4072 is fixed to the valve element 4090, and the coil spring 4071 is compressed between the spring retainer 4072 and a bottom 4073 of the spring chamber 4070. As a result, the coil spring 4071 biases the valve element 4090 toward a diaphragm 4300, which will be described later, and presses the valve element 4090 against the diaphragm 4300.

[0076] A ring-shaped bottom cover 4400 is integrally assembled to the valve body 4010 by brazing around the outer periphery of the spring chamber 4070 of the valve body 4010 via the Bi shielding layer 34. A diaphragm 4300 and a top cover 4500 are attached to the bottom cover 4400. The bottom cover 4400, the diaphragm 4300, and the top cover 4500 are welded together at the outer periphery B indicated by the dashed-dotted ellipse in Figure 7. As a result, a pressure chamber 4600 that applies pressure to the diaphragm 4300 is formed inside the bottom cover 4400.

[0077] Diaphragm 4300 is disc-shaped and rotates about central axis L, and is made of a metal leaf spring. When the pressure in pressure chamber 4600 exceeds a set pressure determined by the characteristics of diaphragm 4300, diaphragm 4300 deforms in the direction of central axis L, and mainly flat portion 4310 moves in the direction of central axis L, i.e., upward in FIG. 7.

[0078] In such a regulating valve 4000, the valve body 4010, which is the main body of the valve, corresponds to the brass member, and the bottom cover 4400, which is the bottom cover material arranged around the opening 4011 of the valve body 4010, which is the main body, corresponds to the stainless steel member. The valve body 4010 and the bottom cover 4400 are brazed together with a brazing material after the opening 4011 of the valve body 4010 is fixed by crimping with the washer-shaped Bi shielding layer 34 sandwiched therebetween.

[0079] As an example of assembling these in the regulating valve 4000, first, the valve body 4010, which is a brass member, and the bottom cover 4400, which is a stainless steel member, are brazed together in a reducing atmosphere furnace with the Bi shielding layer 34 sandwiched between them, and then cooled in the reducing atmosphere furnace and removed from the furnace and allowed to cool at room temperature to form a joint structure. At this time, it is also possible to braze the first joint pipe 4100, the second joint pipe 4200, and the valve body 4010 simultaneously.

[0080] In the regulating valve 4000, the Bi shielding layer 34 serves as a layer that prevents Bi in the valve body 4010 from migrating to the first brazing material layer when the lower cover 4400, which is a stainless steel member, is brazed to the valve body 4010, which is a brass member, and as a result, a decrease in the bonding strength between the lower cover 4400 and the valve body 4010 can be prevented.

[0081] (Expansion valve 5000) 8 shows a cross-sectional view of an expansion valve 5000 equipped with the joining structure of the present invention. The expansion valve 5000 has a metal valve body 5010. The valve body 5010 has a pipe connection hole 5020 and a pipe connection hole 5030, with a first joint pipe 5040 attached to the pipe connection hole 5020 and a second joint pipe 5050 attached to the pipe connection hole 5030. The first joint pipe 5040 and the second joint pipe 5050 are integrally assembled with the valve body 5010 by brazing or the like.

[0082] A diaphragm device 5100 is attached to the top of the valve body 5010. The diaphragm device 5100 has a case body formed by a thin, disk-shaped upper cover 5110 and a lower cover 5120, and in this case body, the lower cover 5120 is brazed to the valve body 5010 via a Bi shielding layer 35, thereby being fixed to the valve body 5010. A diaphragm 5130 is provided between the upper cover 5110 and the lower cover 5120, and this diaphragm 5130 defines a diaphragm chamber 5140 and a pressure chamber 5150. A metal abutment 5160 is disposed within the lower cover 5120, and an operating shaft 5200 abuts against this metal abutment 5160.

[0083] The diaphragm chamber 5140 is connected in communication with a temperature sensing bulb 5400 by a capillary tube 5300. Note that the capillary tube 5300 is partially omitted from illustration in Fig. 8. The temperature sensing bulb 5400 is filled with, for example, the same gas (or liquid) as the refrigerant of the refrigeration cycle, and is attached to the outlet piping of an indoor heat exchanger (evaporator) in the refrigeration cycle, as described below. In addition, the first joint pipe 5040 is connected to the outlet piping of a condenser of the refrigeration cycle, and the second joint pipe 5050 is connected to the inlet piping of the evaporator.

[0084] As a result, the internal pressure of the diaphragm chamber 5140 changes according to the temperature of the outlet-side piping of the evaporator sensed by the temperature sensing bulb 5400. Also, the pressure chamber 5150 is connected to the communication path 5500 and is applied with the inlet pressure of the evaporator.

[0085] The operating shaft 5200 abuts against abutment 5160 and spring receiver 5210, and the vertical movement of the valve element 5220 opens and closes the valve port 5230. The degree of superheat is controlled by adjusting the opening of the valve port through the balance between the diaphragm chamber 5140, pressure chamber 5150, and spring 5240.

[0086] In such an expansion valve 5000, the valve body 5010, which is the main body of the valve, corresponds to the brass member, and the bottom cover 5120, which is a bottom cover material arranged around the opening 5011 of the valve body 5010, which is the main body, corresponds to the stainless steel member. The valve body 5010 and the bottom cover 5120 are brazed with a brazing material, sandwiching a washer-shaped Bi shielding layer 35 therebetween. At this time, it is also possible to braze the first joint pipe 5040, the second joint pipe 5050, and the valve body 5010 simultaneously.

[0087] As an example of assembling these in the expansion valve 5000, first, the valve body 5010, which is a brass member, and the lower cover 5120, which is a stainless steel member, are brazed together in a reducing atmosphere furnace with the Bi shielding layer 35 sandwiched between them, and then cooled in the reducing atmosphere furnace and removed from the furnace and allowed to cool at room temperature to form a joined structure.

[0088] In the expansion valve 5000, the Bi shielding layer 35 serves as a layer that prevents Bi in the valve body 5010 from migrating to the first brazing material layer when the lower cover 5120, which is a stainless steel member, is brazed to the valve body 5010, which is a brass member, and as a result, it is possible to prevent a decrease in the bonding strength between the lower cover 5120 and the valve body 5010.

[0089] <Solenoid Valve 6000> The joining structure of the present invention can be used as a component in a solenoid valve. In this case, the brass member is the main body of the valve, and the stainless steel member is a tubular member placed in the opening of the main body. As an example of a solenoid valve, Figure 9 shows a cross-sectional view of a solenoid valve 6000 equipped with the joining structure of the present invention.

[0090] The solenoid valve 6000 is disposed in the refrigerant circulation cycle of, for example, a cooling / heating air conditioner, a refrigerator, etc. The solenoid valve 6000 includes a valve body 6010 constituting a valve body, and an electromagnetic operating coil 6020 connected to the valve body 6010 and controlling the movement of a valve element disposed inside the valve body 6010. The valve body 6010 has a valve chamber 6030, into which a first coupling pipe 6040 and a second coupling pipe 6050 are connected so as to communicate with each other via a valve seat 6060.

[0091] There is provided a valve element 6070 made of a ball or the like that opens and closes the fluid passage by moving in a direction toward and away from the valve seat 6060. There is also provided a plunger movement cylinder 6080 having one end connected to the valve main body 6010, and a plunger 6090 that is disposed within the plunger movement cylinder 6080 so as to be movable in the axial direction and has one end connected to the valve element 6070.

[0092] Furthermore, an aspirator 6100 is fixed to the other end of the plunger movement cylinder 6080 so as to face the other end of the plunger 6090. A biasing member 6110 made of a coil spring or the like that biases the plunger 6090 in a direction away from the aspirator 6100 is interposed between the plunger 6090 and the aspirator 6100. An electromagnetic actuating coil 6020 is fixed to the upper part of the aspirator 6100 via an outer casing member 6130 by a fastening member 6120 such as a bolt.

[0093] Furthermore, a coil member 6140 that generates magnetic flux when energized is disposed on the outer periphery of the plunger movement cylinder 6080. In FIG. 9, reference numeral 6150 denotes a bobbin case, and reference numeral 6160 denotes a lead wire. In the solenoid valve 6000 configured in this manner, energizing (applying voltage) the coil member 6140 generates magnetic flux in a direction that attracts the plunger 6090 to the attractor 6100, thereby generating an attractive force. As a result, the plunger 6090 is attracted to the attractor 6100, and the valve element 6070 moves in a direction away from the valve seat 6060, thereby opening the fluid passage, i.e., the valve opens.

[0094] On the other hand, by de-energizing the coil member 6140, the magnetic flux disappears and the attractive force acting between the plunger 6090 and the attractor 6100 also disappears. As a result, the urging force of the urging member 6110 moves the plunger 6090 away from the attractor 6100 and moves the valve body 6070 in the direction of seating it on the valve seat 6060, thereby closing the fluid passage, i.e., closing the valve.

[0095] Figure 10 shows an enlarged cross-sectional view of region C, which is a portion of the joint structure in the solenoid valve shown in Figure 9. Although the brazing filler metal layer is not shown in Figure 9 because it is thin, as shown in Figure 10, the joint structure 120 has a layered structure in which a plunger movement cylinder 6080, which is a stainless steel member, a first brazing filler metal layer 22, a Bi shielding layer 36, a second brazing filler metal layer 42, and a valve body 6010, which is a brass member, are arranged in this order.

[0096] In such a solenoid valve 6000, the valve body 6010, which is the main body of the valve, corresponds to the brass member, and the plunger movement cylinder 6080, which is a cylindrical member disposed in the opening 6011 of the valve body 6010, which is the main body, corresponds to the stainless steel member. The valve body 6010 and the plunger movement cylinder 6080 are brazed with a brazing material with the cylindrical Bi shielding layer 36 sandwiched therebetween.

[0097] As an example of assembling these components in the solenoid valve 6000, first, the valve body 6010, which is a brass member, and the plunger movement cylinder body 6080, which is a stainless steel member, are brazed together in a reducing atmosphere furnace with the Bi shielding layer 36 sandwiched therebetween, and then cooled within the reducing atmosphere furnace and removed from the furnace and allowed to cool at room temperature to form the joint structure 120. At this time, the first joint pipe 6040, the second joint pipe 6050, and the valve body 6010 can also be brazed simultaneously.

[0098] In the solenoid valve 6000, the Bi shielding layer 36 serves as a layer that prevents Bi in the valve body 6010 from migrating to the first brazing material 22 layer by brazing the plunger movement cylinder 6080, which is a stainless steel member, to the valve body 6010, which is a brass member, and as a result, it is possible to prevent a decrease in the bonding strength between the plunger movement cylinder 6080 and the valve body 6010.

[0099] [Method of manufacturing joint structure 1] Next, manufacturing method 1 will be described as an example of a manufacturing method for the joint structure of the present invention. This manufacturing method is a method capable of manufacturing the above-described joint structure of the present invention, and includes a first layer structure forming step, a first brazing step, and a first cooling step. Hereinafter, the joining structure 100 will be described as an example, with reference to a perspective view of an example of each member constituting the first layer structure 600 in FIG. 11 and a partial cross-sectional view of the first layer structure 600 in FIG. 12.

[0100] <First layer structure formation process> 11 are sequentially arranged in layers to form a first layer structure 600. For example, the stainless steel member 10 is disk-shaped like an open-bottomed dish, the first brazing filler metal 25, the Bi shielding layer 30, and the second brazing filler metal 45 are washer-shaped, and the brass member 50 is hexagonal prism-shaped.

[0101] The method for forming the first layer structure 600 is not particularly limited, and the first layer structure 600 may be formed by stacking the second brazing filler metal 45, the Bi shielding layer 30, the first brazing filler metal 25, and the stainless steel member 10 in this order on the brass member 50, or the first layer structure 600 may be formed by stacking the first brazing filler metal 25, the Bi shielding layer 30, the second brazing filler metal 45, and the brass member 50 in this order on the stainless steel member 10. Furthermore, in addition to forming the first layer structure in the vertical direction, a layer structure may also be formed in the horizontal direction.

[0102] The first layer structure may be formed manually or automatically using a device or the like, and may be formed, for example, at 0°C to 50°C under atmospheric pressure of about 1 atmosphere. However, it is not preferable to perform this process at a temperature of 680°C or higher, as this may cause the first brazing filler metal 25 and the second brazing filler metal 45 to melt.

[0103] The stainless steel member 10, brazing filler metal, Bi shielding layer 30, and brass member 50 that can be used to manufacture the joint structure are as described above, and therefore further description will be omitted. The first brazing filler metal 25 and the second brazing filler metal 45 may be brazing filler metals of the same composition.

[0104] <First brazing process> In this step, the first layer structure 600 is heated and brazed so that the temperatures of the first brazing filler metal 25 and the second brazing filler metal 45 are 680 to 800°C.

[0105] Heating may be performed under atmospheric pressure of about 1 atmosphere or under a reducing gas atmosphere such as hydrogen or ammonia, and specifically, this step may be performed by placing the first layer structure 600 in a heating device such as an oven, a heating furnace, a reducing atmosphere furnace, etc. The holding time for holding the temperatures of the first brazing filler metal and the second brazing filler metal at 680 to 800°C may be set to, for example, 5 to 10 minutes.

[0106] Alternatively, a burner may be used to heat the first layer structure 600 to braze the stainless steel member 10 and the brass member 50. The holding time for holding the temperatures of the first brazing filler metal and the second brazing filler metal at 680 to 800°C can be set to, for example, several tens of seconds.

[0107] <First cooling process> In this step, the first layer structure 600 after the first brazing step is cooled to form a joining structure 100 having a layer structure in which the stainless steel member 10, the first brazing filler metal layer 20, the Bi shielding layer 30, the second brazing filler metal layer 40, and the brass member 50 are arranged in layers. The liquid first brazing filler metal and second brazing filler metal solidify upon cooling to become the first brazing filler metal layer 20 and the second brazing filler metal layer 40, respectively, and the joining structure 100 is manufactured.

[0108] The method for cooling the first layer structure 600 in this process is not particularly limited, and for example, the first layer structure that was placed in the heating device during the brazing process may be removed from the heating device and allowed to cool in an atmospheric pressure atmosphere of, for example, 0°C to 50°C and approximately 1 atmosphere.

[0109] [Method of manufacturing joint structure 2] Next, manufacturing method 2 will be described as an example of a method for manufacturing the joint structure of the present invention. This manufacturing method is a method capable of manufacturing the joint structure of the present invention described above, and includes a second layer structure forming step, a second brazing step, and a second cooling step. Hereinafter, the manufacturing method will be described with reference to Figs. 13 to 19, taking joint structure 100 as an example.

[0110] <Second layer structure formation process> In this process, the stainless steel member 10, the Bi shielding layer 30, and the brass member 50 are arranged in layer form in this order. At the same time, a first brazing filler metal 25 is arranged between the stainless steel member 10 and the Bi shielding layer 30 (FIG. 13), thereby forming a second layer structure 700 (FIG. 14). Furthermore, a second brazing filler metal 46 is arranged between the Bi shielding layer 30 and the brass member 50 (FIG. 15), thereby forming a second layer structure 800 (FIG. 16).

[0111] The shapes of the respective members are, for example, such that the stainless steel member 10 is a disk-like shape like a dish with an open bottom, the Bi shielding layer 30 is a washer-shaped member, and the brass member 50 is a hexagonal column-shaped member.

[0112] 18 and 19 are partial cross-sectional views showing enlarged views of a portion of the area D surrounded by a dotted line in the partial cross-sectional view of the solenoid valve 6000 shown in FIG. 17. As shown in these figures, a plunger movement cylinder 6080 (corresponding to a stainless steel member), a Bi shielding layer 36, and a valve body 6010 (corresponding to a brass member) may be arranged in layers, with one third brazing filler metal 27 arranged on the side of the Bi shielding layer 36, to form a second layer structure 900 (FIG. 18). Alternatively, a second brazing filler metal 28 may be arranged between the Bi shielding layer 36 and the valve body 6010, and a third brazing filler metal 29 may be arranged on the side of the Bi shielding layer 36 to form a second layer structure 950 (FIG. 19). Furthermore, two or more third brazing filler metals may be arranged on the side of the Bi shielding layer 36.

[0113] From the viewpoint of simplifying the manufacturing process and managing the number of brazing material components, it is preferable to use one brazing material, that is, second layer structure 900 is preferable to second layer structure 950 from the above viewpoint.

[0114] 11, the third brazing filler metal 27 may have a spring washer shape similar to the first brazing filler metal 25, or may have a flat washer shape like the second brazing filler metal 45. The same applies to the shapes of the second brazing filler metal 46, the second brazing filler metal 28, and the third brazing filler metal 29.

[0115] The method for forming the second layer structures 700, 800 is not particularly limited, and the second layer structures 700, 800 may be formed by stacking the Bi shielding layer 30 and the stainless steel member 10 on the brass member 50, or the second layer structures 700, 800 may be formed by stacking the Bi shielding layer 30 and the brass member 50 on the stainless steel member 10. Furthermore, in addition to forming the second layer structures in the vertical direction, the layer structure may also be formed in the horizontal direction. The same applies to the second layer structures 900, 950, and the method for forming them is not particularly limited.

[0116] The second layer structures 700, 800, 900, and 950 may be formed manually or automatically using a device or the like, and may be performed, for example, at a temperature of 0°C to 50°C and atmospheric pressure of about 1 atmosphere. However, performing this step at a temperature of 680°C or higher is not preferable because the first brazing filler metal 25, the second brazing filler metal 46, the third brazing filler metal 27, the second brazing filler metal 28, and the third brazing filler metal 29 may melt.

[0117] The stainless steel member 10, brazing material, Bi shielding layer 30, and brass member 50 that can be used to manufacture the joint structure are as described above, and therefore a description thereof will be omitted.

[0118] <Second brazing process> In this step, the second layer structure 700 is heated and brazed so that the temperature of the first brazing filler metal 25 reaches 680 to 800° C. The same applies to the second layer structures 800, 900, and 950.

[0119] Heating may be performed under atmospheric pressure of about 1 atmosphere or under a reducing gas atmosphere such as hydrogen or ammonia, and specifically, this step may be performed by placing the second layer structure 700 in a heating device such as an oven, a heating furnace, or a reducing atmosphere furnace. The holding time for holding the temperature of the first brazing filler metal 25 at 680 to 800°C may be set to 5 to 10 minutes, for example. The same applies to the second layer structures 800, 900, and 950.

[0120] Alternatively, the stainless steel member 10 and the brass member 50 may be brazed together by heating the second layer structure 700 with a burner. The time for maintaining the temperature of the first brazing filler metal 25 at 680 to 800°C may be set to, for example, several tens of seconds. The same applies to the second layer structures 800, 900, and 950.

[0121] As explained in the second layer structure forming process, there are various ways to arrange the first brazing material 25, the second brazing material 46, the third brazing material 27, the second brazing material 28, and the third brazing material 29, but the first brazing material 25, the second brazing material 46, the third brazing material 27, the second brazing material 28, and the third brazing material 29 melt in the second brazing process, and by capillary action, the first brazing material 25, the second brazing material 46, the third brazing material 27, the second brazing material 28, and the third brazing material 29 penetrate between the stainless steel 10 and the blocking layer 30, and between the blocking layer 30 and the brass member 50, and between the plunger movement cylinder 6080 and the Bi shielding layer 36, and between the blocking layer 36 and the valve body 6010.

[0122] <Second cooling process> In this step, the second layer structure 700 after the second brazing step is cooled to form a joining structure 100 having a layer structure in which the stainless steel member 10, the first brazing filler metal layer 20, the Bi shielding layer 30, the second brazing filler metal layer 40, and the brass member 50 are arranged in layers. The liquid first brazing filler metal 25 solidifies upon cooling to become the first brazing filler metal layer 20 and the second brazing filler metal layer 40, respectively, thereby producing the joining structure 100. The same applies to the second layer structures 800, 900, 950.

[0123] The method for cooling the second layer structure 700, 800, 900, 950 in this step is not particularly limited, and for example, the second layer structure 700, 800, 900, 950 that was placed in the heating device in the second brazing step may be removed from the heating device and allowed to cool in an atmospheric pressure atmosphere, for example, at 0°C to 50°C and around 1 atmosphere.

[0124] <Other processes> The manufacturing methods 1 and 2 of the joining structure of the present invention may include methods other than those described above. For example, there may be a removal step of removing factors that inhibit brazing, such as dirt, deposits, and oxides, from the surfaces of the stainless steel member 10, the Bi shielding layer 30, and the brass member 50 that come into contact with the brazing filler metal, or a step of applying flux to improve the wettability of the brazing filler metal. The same applies to the plunger movement cylinder 6080, the Bi shielding layer 36, and the valve body 6010. [Example]

[0125] The present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples in any way.

[0126] [Preparation of test specimen] Example 1 1(C) (same as the joint structure 110 shown in FIG. 5) was fabricated as a test specimen. Specifically, a first layer structure was formed by stacking, in order, a washer-shaped second brazing filler metal (BAg-7) having an outer diameter of 15 mm and a thickness of 0.15 mm, a washer-shaped Bi shielding layer 30 (C2801) having an outer diameter of 15 mm and a thickness of 0.6 mm, a washer-shaped first brazing filler metal (BAg-7) having an outer diameter of 15 mm and a thickness of 0.15 mm, and a disk-shaped stainless steel 10 (same as the lid body 2030) (SUS304) having an outer diameter of 21 mm and a thickness of 0.8 mm on top of a brass member 50 (same as the joint 2040) (C6803, Pb content 0.01 mass% or less, Bi content 0.5 to 4.0 mass%) having a diagonal distance of 15 mm and a height of 18 mm and a hexagonal column shape. Then, this first layer structure was placed in a hydrogen atmosphere reduction furnace and held at a temperature range of 680°C to 720°C for 6 minutes (first brazing step). After the first brazing step, the first layer structure was cooled in the furnace, and then removed from the reduction furnace and allowed to cool at 25°C under atmospheric pressure (first cooling step), thereby producing a joint structure 100, which was used as the test specimen of Example 1. A plurality of test specimens were prepared for use in a test to confirm the joint strength and in SEM observation.

[0127] <Conventional Example 1> A layered structure was formed by stacking, in order, a washer-shaped brazing filler metal (BAg-7) with an outer diameter of 15 mm and a thickness of 0.15 mm and a disk-shaped stainless steel 10 (SUS304) with an outer diameter of 21 mm and a thickness of 0.8 mm, the same as in Example 1, on a brass member 60 (C3604, Pb content 1.8 to 3.7% by mass) having the same shape and dimensions as the joint 2040 of Example 1. This layered structure was then subjected to a first brazing step and a first cooling step as in Example 1, to produce a joint structure 200 in which the brass member 60 and the stainless steel 10 were brazed with a brazing filler metal layer 70, and this was used as a test specimen for Conventional Example 1. Multiple test specimens were prepared for use in a test to confirm the joint strength and for SEM observation.

[0128] Comparative Example 1 A layered structure was formed by stacking a brass member 50 (C6803, Pb content 0.01 mass% or less, Bi content 0.5 to 4.0 mass%) having the same shape as in Example 1 on top of a washer-shaped brazing filler metal (BAg-7) having an outer diameter of 15 mm and a thickness of 0.15 mm, the same as in Conventional Example 1, and a disk-shaped stainless steel 10 (SUS304) having an outer diameter of 21 mm and a thickness of 0.8 mm, the same as in Example 1. This layered structure was then subjected to a first brazing step and a first cooling step in the same manner as in Example 1, to produce a joint structure 300 in which the brass member 50 and the stainless steel 10 were brazed with a brazing filler metal layer 80. This was used as a test specimen for Comparative Example 1. A plurality of test specimens were prepared for use in a test to confirm the joining strength and for SEM observation.

[0129] [Verifying joint strength] In order to confirm the bond strength between brass and stainless steel, the tensile strength of the test specimen was measured using a tensile testing machine. Figure 2 shows a side view of the test specimen used in the bond strength confirmation test and the jig used in the bond strength confirmation test, with Figure 2(A) showing the state before the jig and test specimen were assembled, and Figure 2(B) showing the state after the jig and test specimen were assembled. Figure 2 shows a bonded structure 200, which is the test specimen of Conventional Example 1, as an example, and a bond strength confirmation test was conducted using an upper jig 400 and a lower jig 500.

[0130] The inner surface 510 of the lower jig 500 has a shape that corresponds to the outer shape of the joining structure 200, and the brass member 60 side of the joining structure 200 is inserted into the lower jig 500 so that the brass member 60 protrudes from under the lower jig 500. Next, the upper jig 400 is inserted into the inner surface 510 of the lower jig 500. Here, the side surface 410 of the upper jig 400 is threaded to form a male thread, and the side surface 520 of the inner surface 510 of the lower jig 500 is threaded to form a female thread shape that corresponds to the shape of the male thread on the side surface 410. Then, by inserting the upper jig 400 into the inner surface 510 of the lower jig 500 while rotating it to reach the state shown in assembly diagram 2(B), the upper jig 400 and the lower jig 500 can be placed in a state where they will not come off even if pulled in the vertical direction.

[0131] After achieving the state shown in Figure 2(B), a tensile testing machine was used to grip and fix the brass member 60 of the joint structure 200 around the area marked with the symbol 220 (gripping portion 220), and then the upper jig 400 was gripped around the area marked with the symbol 420 (gripping portion 420) and pulled the upper jig 400 vertically upward, thereby measuring the joint strength of the joint structure 200.

[0132] The joint strength of the joint structure 200, which is the test specimen of Conventional Example 1, is 100 N / mm 2 As described above, the strength was sufficient for use in the above-mentioned parts.

[0133] The joint strength of the joint structure 100, which is the specimen of Example 1, was also measured in the same manner, and the joint strength was 100 N / mm 2 More than 100N / mm 2 The strength was well above this, and therefore the strength was sufficient for use in the above-mentioned parts.

[0134] Furthermore, when the bonding strength of the bonded structure 300, which is the specimen of Comparative Example 1, was measured in the same manner, the bonding strength was 100 N / mm 2 Less than 100N / mm 2 Since the strength was significantly lower than that of the above-mentioned components, it was not possible to demonstrate sufficient strength for use in the above-mentioned components.

[0135] [SEM observation and elemental mapping] The cross sections of the test specimens (joint structures 100, 200, 300) of Example 1, Conventional Example 1, and Comparative Example 1 were photographed with a scanning electron microscope (SEM). These SEM images are shown in Fig. 1. As shown in Fig. 1(C), it was confirmed that the first brazing filler metal layer 20 and the second brazing filler metal layer 40 were shielded by the Bi shielding layer 30, and that the Bi shielding layer 30 was arranged in a way that could prevent the bismuth contained in the brass member 50 from migrating to the first brazing filler metal layer 20.

[0136] Furthermore, elemental mapping of bismuth was performed by energy dispersive X-ray spectroscopy (EDS) on the cross sections of the specimens of Example 1, Conventional Example 1, and Comparative Example 1. Fig. 20 shows an image of the specimen of Example 1 (joint structure 100), and Fig. 21 shows an image of the specimen of Comparative Example 1 (joint structure 300).

[0137] The element mapping results confirmed that bismuth was scattered in the second brazing filler metal layer 40 of the specimen of Example 1 (FIG. 20(B)), but no bismuth was present in the first brazing filler metal layer 20 (FIG. 20(A)). Furthermore, the brazing filler metal layer 80 of the specimen of Comparative Example 1 contained more bismuth than the second brazing filler metal layer 40, and planar segregation of bismuth was confirmed near the interface between the brazing filler metal layer 80 and the stainless steel 10. Note that, since the brass member 60 used in Conventional Example 1 did not contain bismuth, bismuth was not detected in the brazing filler metal layer 70.

[0138] [summary] From the above, it can be seen from the results of Comparative Example 1 that the bonding strength is reduced due to planar segregation of bismuth near the interface between the brazing material layer 80 and the stainless steel 10. And from the results of Example 1, it can be seen that by using the Bi shielding layer 30, even when a brass member 50 containing bismuth is used, the Bi shielding layer 30 can block bismuth migrating from the brass member 50, thereby preventing a reduction in bonding strength and providing sufficient bonding strength similar to that of Conventional Example 1.

[0139] Second bonded structures 700, 800, 900, and 950 were prepared by the method described in [Method for manufacturing bonded structure 2], and bonded structure 100 was manufactured based on the method for manufacturing the test specimen described in Example 1, using similar components and similar heating and cooling processes. Then, as in Example 1, confirmation of bond strength, SEM observation, and element mapping were performed.

[0140] As a result, all of the joint structures 100 had a joint strength of 100 N / mm 2 More than 100N / mm 2 The results of SEM observation and element mapping were also similar to those of the specimen in Example 1.

[0141] In other words, even when the joint structure 100 is manufactured by the method described in [Method for manufacturing joint structure 2], by using a Bi shielding layer 30, etc., even when a brass member 50, etc. containing bismuth is used, the bismuth migrating from the brass member 50, etc. can be blocked by the Bi shielding layer 30, etc., and it has been found that this prevents a decrease in joint strength and maintains sufficient joint strength.

[0142] As described above, the present invention is industrially useful because it can provide a joining structure and a method for manufacturing a joining structure that can suppress a decrease in joining strength even when brass containing bismuth instead of lead and stainless steel are joined by brazing using a brazing filler metal. [Explanation of symbols]

[0143] 10: Stainless steel member, 20: First brazing filler metal layer, 21: First brazing filler metal layer, 22: First brazing filler metal layer, 25: First brazing filler metal, 27: Third brazing filler metal, 28: Second brazing filler metal, 29: Third brazing filler metal, 30: Bi shielding layer, 31: Bi shielding layer, 32: Bi shielding layer, 33: Bi shielding layer, 34: Bi shielding layer, 35: Bi shielding layer, 36: Bi shielding layer, 40: Second brazing filler metal layer, 41: Second brazing filler metal layer, 42: Second brazing filler metal layer, 45: Second brazing filler metal, 46: Second brazing filler metal, 50: Brass member, 60: Brass member, 70: Brazing filler metal layer, 80: Brazing filler metal layer, 100: Joined structure, 110: Joined structure, 120: Joined structure, 2 00: Joint structure, 220: Grip portion, 300: Joint structure, 400: Upper jig, 410: Side surface, 420: Grip portion, 500: Lower jig, 510: Inner surface, 520: Side surface, 600: First layer structure, 700: Second layer structure, 800: Second layer structure, 900: Second layer structure, 950: Second layer structure, 1000: Pressure sensor, 1010: Inlet passage, 1020: Joint, 1030: Cover, 1040: Insulating member, 1050: Pressure detection element, 1060: Diaphragm, 1070: Header, 1080: Stem, 1090: Lead pin, 1100: Case, Sealing material: 1110, 2000: Pressure force switch, 2010: metal diaphragm, 2020: pressure sensing chamber, 2030: cover, 2040: joint, 2050: moving contact, 2051: fixed contact, 2052: contact portion, 2060: O-ring, 2070: holder member, 2080: intermediate plate member, 2090: case member, 2100: connection terminal piece, 2110: connection terminal piece, 2120: stopper, 2130: outer periphery, 2140: diaphragm unit, 2150: operating rod, 3000: motor-operated valve, 3010: valve body, 3011: valve chamber, 3012: piping connection hole, 3013: piping connection hole, 3014: valve port, 3015 : Valve body, 3016: Opening, 3020: First coupling pipe, 3030: Second coupling pipe, 3040: Male thread member, 3050: Cover case, 3100: Stepping motor, 3101: Coil, 3102: Lead wire, 3110: Rotor case, 3200: Rotor, 3210: Fixed member, 3220: Female thread member, 3230: Magnet, 3240: Operating shaft, 3300: Stopper holding rod, 3310: Spiral guide, 3320: Movable stopper, 4000: Adjusting valve, 4010: Valve body, 4011: Opening, 4020: Pipe connection hole, 4030: Pipe connection hole, 4040: Valve chamber,4050: Valve insertion hole, 4060: Secondary side port, 4070: Spring chamber, 4071: Coil spring, 4072: Spring holder, 4073: Bottom, 4080: Valve port, 4090: Valve body, 4100: First joint pipe, 4200: Second joint pipe, 4300: Diaphragm, 4310: Flat portion, 4400: Lower cover, 4500: Upper cover, 4600 : Pressure chamber, 5000: Expansion valve, 5010: Valve body, 5011: Opening, 5020: Pipe connection hole, 5030: Pipe connection hole, 5040: First joint pipe, 5050: Second joint pipe, 5100: Diaphragm device, 5110: Upper cover, 5120: Lower cover, 5130: Diaphragm, 5140: Diaphragm chamber, 5150: Pressure chamber, 51 60: retaining plate, 5200: operating shaft, 5210: spring bearing, 5220: valve body, 5230: valve port, 5240: spring, 5300: capillary tube, 5400: temperature sensing bulb, 5500: communication passage, 6000: solenoid valve, 6010: valve body, 6011: opening, 6020: electromagnetic operating coil, 6030: valve chamber, 6040: first coupling tube , 6050: second coupling pipe, 6060: valve seat, 6070: valve body, 6080: plunger movement cylinder, 6090: plunger, 6100: suction element, 6110: biasing member, 6120: fastening member, 6130: outer casing member, 6140: coil member, 6150: bobbin case, 6160: lead wire, A: region, B: outer periphery, C: region,

Claims

1. A joining structure in which a stainless steel member and a brass member are brazed, a layer structure in which the stainless steel member, a first brazing filler metal layer, a Bi shielding layer, a second brazing filler metal layer, and the brass member are arranged in layer form by the brazing, the brass member contains Bi, A joining structure in which the Bi shielding layer is a layer that suppresses the migration of Bi in the brass member to the first brazing material layer when the stainless steel member and the brass member are brazed.

2. The bonding strength between the stainless steel member and the brass member is 100 N / mm ２ The joining structure according to claim 1 .

3. 2. The joining structure according to claim 1, wherein the brass member is a joint of a pressure sensor, and the stainless steel member is a dish-shaped lid attached to the joint of the pressure sensor.

4. 2. The joining structure according to claim 1, wherein the brass member is a joint of a pressure switch, and the stainless steel member is a dish-shaped lid attached to the joint of the pressure switch.

5. 2. The joining structure according to claim 1, wherein the brass member is a main body of a valve, and the stainless steel member is a bottom cover material disposed around an opening of the main body.

6. 2. The joining structure according to claim 1, wherein the brass member is a main body of a valve, and the stainless steel member is a tubular member disposed in an opening of the main body.

7. A method for manufacturing the joint structure according to claim 1, a first layer structure forming step of forming a first layer structure by arranging the stainless steel member, the first brazing filler metal, the Bi shielding layer, the second brazing filler metal, and the brass member in layers, in this order; a first brazing step of heating the first layer structure to braze the stainless steel member and the brass member; a first cooling step of cooling the first layer structure after the first brazing step to form a joining structure having a layered structure in which the stainless steel member, the first brazing material layer, the Bi shielding layer, the second brazing material layer, and the brass member are arranged in layers; A method for manufacturing a joint structure, comprising:

8. The method for manufacturing a joint structure according to claim 7 , wherein the first brazing filler metal and the second brazing filler metal have the same composition.

9. The method for manufacturing a joint structure according to claim 7 , wherein the Bi shielding layer is in a washer shape.

10. The method for manufacturing a joint structure according to claim 7 , wherein the Bi shielding layer is cylindrical.

11. A method for manufacturing the joint structure according to claim 1, a second layer structure forming step of sequentially arranging the stainless steel member, the Bi shielding layer, and the brass member in layers, and disposing a brazing filler metal between the stainless steel member and the Bi shielding layer, between the Bi shielding layer and the brass member, or on a side surface of the Bi shielding layer to form a second layer structure; a second brazing step of heating the second layer structure to braze the stainless steel member and the brass member; a second cooling step of cooling the second layer structure after the second brazing step to form a joining structure having a layered structure in which the stainless steel member, the first brazing material layer, the Bi shielding layer, the second brazing material layer, and the brass member are arranged in layers; A method for manufacturing a joint structure, comprising:

12. The method for manufacturing a joint structure according to claim 11 , wherein the Bi shielding layer is in a washer shape.

13. The method for manufacturing a joint structure according to claim 11 , wherein the Bi shielding layer is cylindrical.

Images