Manufacturing method for pipe and metal component assemblies

Abstract

To provide a method for manufacturing an assembly product of a pipe and a metal component, which can integrate the pipe and the metal component well by soldering.SOLUTION: One end of a pipe 2 having an outer peripheral surface 2a coated with a flux F is fitted in a fitting recess 3a from the other end surface side of a head 3. One end surface 2b of the pipe 2 is brought into contact with an end surface 3b facing the fitting recess 3a. A soldering material W is disposed on the outer peripheral surface 2a adjacently to the other end surface of the head 3. A gas reservoir C is formed by a chamfering part 2c provided within the range of the outer peripheral surface 2a located in a closed space S formed by surrounding the outer peripheral surface 2a by the inner peripheral surface and the end surface 3b of the fitting recess 3a. The soldering material W is heated to melt and fills the closed space S. One end of the pipe 2 and the head 3 are integrated by means of the solidified soldering material W, and a gas g generated from the flux F is stored in the gas reservoir C.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an assembly of a pipe and a metal part, and more particularly, to a method for manufacturing an assembly that can satisfactorily integrate a pipe and a metal part by brazing.

Background Art

[0002] Various methods have been proposed for integrating a pipe and a metal part by brazing (see, for example, Patent Document 1). In order to remove the oxide film on the outer peripheral surface of the pipe to be brazed and improve the wettability of the brazing material, a flux is preliminarily applied to the outer peripheral surface of the pipe. When the brazing material is heated and melted and the flux reaches the activation temperature, gas is generated when the oxide film decomposes.

[0003] When brazing is performed with one end of the pipe fitted into the metal part, for example, one end of the pipe abuts against the opposing end surface of the metal part, and in some cases, the range where the flux is applied is surrounded by the fitting portion and it becomes difficult to communicate with the outside air. In such a structure, when the brazing material is heated and melted, there is no escape path for the gas generated from the flux, and it remains as voids (bubbles) in the brazed portion. The portion where voids exist becomes a defective portion where brazing has not been performed, which is an obstacle to sufficiently and firmly integrating the pipe and the metal part. Therefore, when integrating a pipe and a metal part by brazing, there is room for improvement in suppressing the voids generated in the brazed portion and achieving good integration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The object of the present invention is to provide a method for manufacturing an assembly of a pipe and a metal part that can be well integrated by brazing. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides a method for manufacturing an assembly of a pipe and a metal part in which the pipe and the metal part are integrated by brazing, wherein one end of the pipe, on which flux has been applied to the outer surface, is fitted into a fitting recess of the metal part from the other end face side of the metal part, the one end face of the pipe is brought into contact with the opposing end face of the fitting recess, a brazing material is placed on the outer surface of the pipe adjacent to the other end face of the metal part, and the outer surface of the one end of the pipe fitted into the fitting recess A closed space is formed by surrounding the surface with the opposing end faces and the inner circumferential surface of the fitting recess, and a gas reservoir is formed by a notch or recess provided in at least one of the outer circumferential surface of the pipe or the fitting recess of the metal part located inside the closed space, and the brazing material is heated and melted, filled into the closed space and solidified, thereby integrating the one end of the pipe and the metal part via the solidified brazing material, and the gas generated from the flux by the heating is stored in the gas reservoir. A method comprising: heating and melting the brazing material with one end of the pipe as the upper end, and the fitting recess fitted to this upper end. It is characterized by the following: Another method for manufacturing an assembly of a pipe and a metal part according to the present invention is a method for manufacturing an assembly of a pipe and a metal part in which the pipe and the metal part are integrated by brazing, wherein one end of the pipe, on which flux has been applied to the outer surface, is fitted into a fitting recess of the metal part from the other end face side of the metal part, the one end face of the pipe is brought into contact with the opposing end face of the fitting recess, brazing material is placed on the outer surface of the pipe adjacent to the other end face of the metal part, and the outer surface of the one end of the pipe fitted into the fitting recess is surrounded by the opposing end face and the inner surface of the fitting recess to form a closed space A method for forming a gas reservoir by forming a notch or recess in at least one of the outer circumferential surface of the pipe or the fitting recess of the metal part located inside the closed space, heating and melting the brazing material and filling it into the closed space to solidify, thereby integrating the one end of the pipe and the metal part via the solidified brazing material, and storing the gas generated from the flux by the heating in the gas reservoir, characterized in that the gas reservoir is formed by providing a circumferentially continuous annular groove on the outer circumferential surface of the pipe. [Effects of the Invention]

[0007] According to the present invention, even in a fitting structure between a pipe and a metal part such that the outer circumferential surface of one end of the pipe fitted into the fitting recess is surrounded by the opposing end face and the inner circumferential surface of the fitting recess to form a closed space, the gas reservoir is formed inside the closed space. Therefore, when the brazing material is heated and melted, the gas generated from the flux can be stored in the gas reservoir. That is, by storing the gas in the gas reservoir which is formed in advance at an intended location, it is possible to avoid the gas remaining at any location in the brazed portion due to the solidified brazing material. Therefore, this is advantageous for good integration of the pipe and the metal part by brazing. [Brief explanation of the drawing]

[0008] [Figure 1] This is an explanatory diagram illustrating an assembly product manufactured according to the present invention in a longitudinal cross-sectional view. [Figure 2] This is a cross-sectional view AA in Figure 1. [Figure 3] This is a cross-sectional view of BB in Figure 1. [Figure 4] This is an explanatory diagram illustrating the state of the individual components that make up the assembly shown in Figure 1 before they are integrated. [Figure 5] This is an explanatory diagram illustrating, in a vertical cross-sectional view, the state in which one end of the pipe shown in Figure 4 is fitted into the mating recess of the head section. [Figure 6] This is an enlarged explanatory diagram illustrating a state in which brazing material is placed on the outer surface of the pipe adjacent to the lower end surface of the head portion shown in Figure 5. [Figure 7] Figure 6 is an explanatory diagram illustrating the process of heating and melting the brazing material to fill the gap between the fitting recess of the head and the outer surface of the pipe. [Figure 8] Figure 7 is an explanatory diagram illustrating the state in which the head portion and the pipe are brazed together and integrated using the filled brazing material. [Figure 9] This is an explanatory diagram illustrating, in a longitudinal cross-sectional view, the state in which the other end of the pipe shown in Figure 4 is fitted into the mating recess of the nipple. [Figure 10]This is an explanatory diagram illustrating, in a longitudinal cross-sectional view, another embodiment of the manufacturing method of the assembled product, in which one end of the pipe is fitted into the mating recess of the head portion. [Figure 11] This is an explanatory diagram illustrating a state in which the brazing material is placed on the outer surface of the pipe adjacent to the lower end surface of the head portion shown in Figure 10. [Figure 12] Figure 11 is an explanatory diagram illustrating the state in which the head and pipe are brazed together and integrated using the brazing material shown. [Figure 13] This is an explanatory diagram illustrating another embodiment of the manufacturing method for an assembled product, in which brazing material is placed on the outer surface of the pipe adjacent to the lower end surface of the head portion, with one end of the pipe fitted into the fitting recess. [Figure 14] Figure 13 is an explanatory diagram illustrating the state in which the head and pipe are brazed together and integrated using the brazing material shown. [Modes for carrying out the invention]

[0009] The manufacturing method of the pipe and metal parts assembly according to the present invention will be described below based on the embodiment shown in the figure.

[0010] The present invention produces an assembly 1 consisting of a pipe 2 and metal parts 3 and 4, as illustrated in Figures 1 to 3. As illustrated in Figure 4, this assembly 1 has a pipe 2 and metal parts, a head portion 3 and a nipple 4, and the pipe 2, head portion 3 and nipple 4 are joined together by brazing. In this embodiment, the head portion 3 is joined to one end of the pipe 2 and the nipple 4 is joined to the other end of the pipe 2, but the assembly 1 can be any assembly in which metal parts 3 and 4 are joined to at least one of the ends of the pipe 2.

[0011] The pipe 2, the head portion 3, and the nipple 4 are each made of metal and are formed of general-purpose known materials such as carbon steel, stainless steel, and aluminum alloy. The pipe 2, the head portion 3, and the nipple 4 are brazed using a known brazing material W suitable for these joined materials. For example, the pipe 2, the head portion 3, and the nipple 4 are joined by silver brazing, copper brazing, or the like.

[0012] In this embodiment, the pipe 2 is a straight pipe with a constant inner diameter, but in the case of a bent pipe or a pipe with a changing inner diameter, the shape is not particularly limited. As illustrated in FIG. 4, this pipe 2 has chamfered portions 2c at both longitudinal ends. Therefore, the area of each annular end face 2b at both longitudinal ends of this pipe 2 is smaller than that in the case where the chamfered portions 2c are not provided.

[0013] The head portion 3 is a cylindrical body, and the inner diameter of one end portion (the left end portion in FIG. 4) is tapered and enlarged. The head portion 3 has a fitting recess 3a at the other end portion (the right end portion in FIG. 4) with an inner diameter approximately the same size (slightly larger) as the outer diameter of the pipe 2. A cylindrical portion with a smaller inner diameter is connected to one end portion side of this fitting recess 3a. Therefore, an annular end face 3b that protrudes to the inner peripheral side of the head portion 3 is formed on one end portion side of the fitting recess 3a.

[0014] In the assembly product 1, one end portion of the pipe 2 is inserted and fitted into the fitting recess 3a at the other end portion of the head portion 3. The gap between the inner peripheral surface of the fitting recess 3a and the outer peripheral surface 2a of one end portion of the pipe 2 is filled with the solidified brazing material W. This gap is, for example, 1 mm or less. The brazing material W joins the fitting recess 3a and one end portion of the pipe 2. One end portion of the head portion 3 is connected to various devices, joint parts, and the like.

[0015] The nipple 4 is a cylindrical body and has a mating recess 4a at one end (the left end in Figure 4) whose inner diameter is approximately the same as (slightly larger than) the outer diameter of the pipe 2. A cylindrical portion with a smaller inner diameter is connected to the other end (the right end in Figure 4) of this mating recess 4a. Therefore, an annular end face 4b is formed on the other end of the mating recess 4a, protruding towards the inner circumference of the nipple 4. Since a hose is fitted to the other end of the nipple 4, numerous retaining protrusions are formed on its outer surface.

[0016] In assembly 1, the other end of the pipe 2 is inserted and fitted into the mating recess 4a at one end of the nipple 4. The gap between the inner surface of the mating recess 4a and the outer surface 2a of the other end of the pipe 2 is filled with solidified brazing material W. This gap is, for example, 1 mm or less. The mating recess 4a and the other end of the pipe 2 are joined by this brazing material W. A hose is fitted to the other end of the nipple 4, and this hose is connected to various devices and joint parts.

[0017] The following describes an example of the manufacturing procedure of the present invention for producing this assembly 1.

[0018] As illustrated in Figure 5, one end of the pipe 2, on which flux F has been applied to its outer surface 2a, is inserted into the fitting recess 3a of the head portion 3 from the other end face side (the lower end face side in Figure 5) and fitted into place. The fitting depth h of one end of the pipe 2 into the fitting recess 3a is, for example, 15 mm or more. The flux F is used to remove the oxide film from the outer surface 2a of the pipe 2 to be brazed and to improve the wettability of the brazing material W, and any known flux may be used. The one end face 2b of the pipe 2 fitted into the fitting recess 3b is brought into contact with the opposing end face 3b of the fitting recess 3b. As a result, the outer surface 2a of one end of the pipe 2 fitted into the fitting recess 3a is surrounded by the inner surface and end face 3b of the fitting recess 3a, forming a closed space S that is a dead end.

[0019] Then, as illustrated in Figure 6, a known brazing material W is placed on the outer circumferential surface 2a of the pipe 2 adjacent to the other end face of the head portion 3 (the lower end face in Figure 6). The brazing material W is arranged in a ring shape along the outer circumferential surface 2a of the pipe 2. This makes it even more difficult for the cul-de-sac enclosed space S to communicate with the outside.

[0020] A chamfered portion 2c is formed at one end of the pipe 2. Therefore, the chamfered portion 2c is present on the outer circumferential surface 2a of the pipe 2 located inside the enclosed space S, and the volume of the enclosed space S is larger compared to the case where the chamfered portion 2c is not present. This region with increased volume functions as a gas reservoir C. In other words, in this embodiment, the region enclosed by the inner circumferential surface and end surface 3b of the mating recess 3a and the chamfered portion 2c is the gas reservoir C.

[0021] Next, the brazing material W is heated and melted by a known method, such as high-frequency heating. As illustrated in Figure 7, the molten brazing material W penetrates and diffuses into the gap between the inner surface of the mating recess 3a and the outer surface 2a of one end of the pipe 2 by capillary action, filling the closed space S. As the brazing material W filling the closed space S cools and solidifies, one end of the pipe 2 and the head portion 3 (matting recess 3a) are joined and integrated via the solidified brazing material W, as illustrated in Figure 8.

[0022] Here, as the brazing material W is heated, the flux F is also heated and reaches its activation temperature, generating gas g when the oxide film on the outer surface 2a decomposes. In this enclosed structure between one end of the pipe 2 and the head portion 3, a closed space S is formed, so the generated gas g cannot be discharged to the outside of the closed space S. However, since a gas reservoir C exists in the closed space S, the generated gas g can be stored in the gas reservoir C, as illustrated in Figure 8.

[0023] By storing the generated gas g in the gas reservoir C, it is possible to suppress the retention of gas g as voids in the brazed portion formed by the brazing material W solidified in the narrow gap between the inner circumferential surface of the mating recess 3a and the outer circumferential surface 2a of one end of the pipe 2. Consequently, the reduction in the brazing area in this narrow gap can be suppressed, which is advantageous for more firmly joining one end of the pipe 2 and the head portion 3 and achieving a good integrated structure.

[0024] Thus, in this invention, a gas reservoir C is formed in advance at an intended location (a location that has little effect on the joint strength) within the enclosed space S. Therefore, the generated gas g is prevented from remaining as a void at a location that would significantly affect the reduction in the joint strength between one end of the pipe 2 and the head portion 3 at the brazing portion, which is advantageous for good integration of the pipe 2 and the head portion 3 by brazing.

[0025] In conventional technology, when the fitting depth h of one end of the pipe 2 into the fitting recess 3a is 20 mm or more, the amount of gas g generated increases, and the proportion of gas g remaining in the closed space S also increases. Consequently, the generated gas g tends to remain in a position that significantly affects the reduction in the joint strength between the brazed end of the pipe 2 and the head portion 3, making it difficult to firmly join and integrate the end of the pipe 2 and the head portion 3. However, according to the present invention, by providing a gas reservoir C in the closed space S, it becomes possible to firmly join the end of the pipe 2 and the head portion 3 even when the fitting depth h is 20 mm or more.

[0026] As illustrated in Figures 6 to 8, in this embodiment, one end of the pipe 2 is made the upper end, and the fitting recess 3a is fitted into this upper end while the brazing material W is heated and melted. Therefore, the gas reservoir C is located above the closed space S. The generated gas g naturally moves upward towards the gas reservoir C, which is even more advantageous for smoothly storing the gas g in the gas reservoir C.

[0027] In the above explanation, the case in which one end of pipe 2 is fitted into the fitting recess 3a of head portion 3 and the two are brazed together was used as an example. However, as illustrated in Figure 9, the same procedure is followed when the other end of pipe 2 is fitted into the fitting recess 4a of nipple 4 and the two are brazed together. In this case as well, the area enclosed by the inner circumferential surface and end face 4b of fitting recess 4a and the chamfered portion 2c of the other end of pipe 2 becomes the gas reservoir C. By storing the generated gas g in the gas reservoir C, it is possible to suppress the retention of gas g as voids in the brazing material W solidified in the narrow gap between the inner circumferential surface of fitting recess 4a and the outer circumferential surface 2a of the other end of pipe 2. Consequently, the reduction in the brazing area in this narrow gap can be suppressed, which is advantageous for more firmly joining the other end of pipe 2 and nipple 4 and achieving a good integrated structure.

[0028] In the embodiment described above, the gas reservoir C is formed by providing chamfered portions 2c at both longitudinal ends of the pipe 2, so there is no need to process the head portion 3 for the gas reservoir C. The gas reservoir C is not limited to this form, and other forms can be adopted.

[0029] Figure 10 illustrates an embodiment of assembly 1 having a different form of gas reservoir C. In this embodiment, an annular groove 3c is provided on the end face 3b of the fitting recess 3a of the pipe 2 that faces one end face 2b, along the annular shape of one end face 2b of the pipe 2. This annular groove 3c facing one end face 2b forms the gas reservoir C. This pipe 2 is a simple straight pipe without a chamfered portion 2c at one end.

[0030] In this embodiment, one end of the pipe 2, on which flux F has been applied to the outer surface 2a, is fitted into the fitting recess 3a from the other end face side (the lower end face side in Figure 10) of the head portion 3, so that one end face 2b of the pipe 2 comes into contact with the opposing end face 3b. Next, as illustrated in Figure 11, brazing material W is placed on the outer surface 2a of the pipe 2 adjacent to the other end face (the lower end face in Figure 11) of the head portion 3, and the outer surface 2a of the end of the pipe 2 fitted into the fitting recess 3a is surrounded by the inner surface and end face 3b of the fitting recess 3a to form a closed space S.

[0031] An annular groove 3c is formed in the fitting recess 3a. Therefore, the annular groove 3c is present in the fitting recess 3a located inside the closed space S, and the volume of the closed space S is larger compared to the case where the annular groove 3c is not present. This region with increased volume functions as a gas reservoir C.

[0032] Next, the brazing material W is heated and melted, then filled into the closed space S and allowed to solidify, thereby integrating one end of the pipe 2 with the head portion 3 (fitting recess 3a) via the solidified brazing material W. As illustrated in Figure 12, the gas g generated from the flux F as the brazing material W is heated is stored in the gas reservoir C.

[0033] In this embodiment, since an annular groove 3c is formed in the head portion 3 to provide the gas reservoir C, there is no need to process the pipe 2 (provide a chamfered portion 2c) for the gas reservoir C. In addition to the gas reservoir C provided by the annular groove 3c, a gas reservoir C provided by the chamfered portion 2c described above may also be used.

[0034] Figure 13 illustrates an embodiment of assembly 1 having a different form of gas reservoir C.

[0035] In this embodiment, an annular groove 2d is provided on the outer circumferential surface 2a of one end of the pipe 2, which is continuous in the circumferential direction. This annular groove 2d forms a gas reservoir C.

[0036] In this embodiment, one end of the pipe 2, on which flux F has been applied to the outer surface 2a, is fitted into the fitting recess 3a from the other end face side (the lower end face side in Figure 13) of the head portion 3, so that one end face 2b of the pipe 2 comes into contact with the opposing end face 3b. Next, the brazing material W is placed on the outer surface 2a of the pipe 2 adjacent to the other end face (the lower end face in Figure 13) of the head portion 3, and the outer surface 2a of the end of the pipe 2 fitted into the fitting recess 3a is surrounded by the inner surface and end face 3b of the fitting recess 3a to form a closed space S.

[0037] An annular groove 2d is formed on the outer circumferential surface 2a of one end of pipe 2. Therefore, the annular groove 2d is present on the outer circumferential surface 2a of pipe 2 located inside the closed space S, and the volume of the closed space S is larger than in the case where the annular groove 2d is not present. This region with increased volume functions as a gas reservoir C.

[0038] Next, the brazing material W is heated and melted, then filled into the closed space S and allowed to solidify, thereby integrating one end of the pipe 2 with the head portion 3 (fitting recess 3a) via the solidified brazing material W. As illustrated in Figure 14, the gas g generated from the flux F as the brazing material W is heated is stored in the gas reservoir C.

[0039] In this embodiment, since an annular groove 2d is formed on the outer circumferential surface 2a of the pipe 2 to provide the gas reservoir C, there is no need to process the head portion 3 (provide a chamfered portion 2c) for the gas reservoir C. In addition to the gas reservoir C provided by the annular groove 2d, at least one of the gas reservoir C provided by the chamfered portion 2c and the gas reservoir C provided by the annular groove 3c described above may also be used. [Examples]

[0040] In the pipe-head joint structure illustrated in Figure 5, ten types of assemblies were manufactured by joining one end of a carbon steel pipe to a carbon steel head using silver brazing, with only the size of the chamfered portion at one end of the pipe differing as shown in Table 1, while all other conditions were kept the same. The outer surface of the pipe was coated with a flux mainly composed of potassium fluoride, boric acid, and water, and the joint depth h was 9 mm. Each manufactured assembly was disassembled, and the area of ​​voids remaining in the brazed portion between the outer surface of the pipe end and the inner surface of the joint recess of the head was measured, and the results are shown in Table 1.

[0041] In Table 1, the "brazing volume" is the volume of the portion (cylindrical portion) enclosed by the outer circumferential surface of one end of the mated pipe and the inner circumferential surface and end face of the mating recess in the head portion, and corresponds to the volume of the enclosed space S described above. For all assembled products, the "brazing volume" is 40.03 mm³. 3 The dimensions were standardized as follows: "Chamfered portion dimensions" are the dimensions of one side of the cut-out chamfered portion, with the corners of two perpendicular sides chamfered at a 45-degree angle. "Gap volume" is the volume increased by providing the chamfered portion in the portion (cylindrical portion) enclosed by the outer circumferential surface of one end of the fitted pipe and the inner circumferential surface and end face of the fitted recess of the head portion, compared to the case without the chamfered portion, and corresponds to the volume of the gas reservoir portion mentioned above. "Brazing area" is the area of ​​the brazed portion on the outer circumferential surface of one end of the pipe corresponding to the brazed volume. The void area is the total area of ​​voids in this brazed portion.

[0042] [Table 1]

[0043] From the results in Table 1, it can be seen that in order to suppress the proportion of voids remaining in the brazed area calculated by "void area / brazed area", it is desirable to set the "gap volume / brazed volume" to approximately 10% or more. Setting the "gap volume / brazed volume" to around 15% to 40% allows the "void area / brazed area" to be kept to a minimum, which is even more advantageous for firmly joining one end of the pipe to the head.

Claims

1. In a method for manufacturing an assembly of a pipe and a metal part, in which the pipe and the metal part are integrated by brazing, One end of the pipe, to which flux has been applied to the outer surface, is fitted into the fitting recess of the metal part from the other end face side of the metal part, so that the one end face of the pipe abuts against the opposing end face of the fitting recess, and brazing material is placed on the outer surface of the pipe adjacent to the other end face of the metal part, so that the outer surface of the one end of the pipe fitted into the fitting recess is surrounded by the opposing end face and the inner surface of the fitting recess to form a closed space, and a gas reservoir is formed by a notch or recess provided in at least one area of ​​the outer surface of the pipe or the fitting recess of the metal part located inside the closed space, A method for manufacturing an assembly of a pipe and a metal part, wherein the brazing material is heated and melted, and then filled into the closed space and solidified, thereby integrating the one end of the pipe and the metal part via the solidified brazing material, and the gas generated from the flux by the heating is stored in the gas reservoir, wherein the one end of the pipe is the upper end, and the fitting recess is fitted to this upper end, and the brazing material is heated and melted in this manner.

2. The method for manufacturing an assembly of a pipe and a metal part according to claim 1, wherein the gas reservoir is formed by providing an annular groove that is continuous in the circumferential direction on the outer surface of the pipe.

3. In a method for manufacturing an assembly of a pipe and a metal part, in which the pipe and the metal part are integrated by brazing, One end of the pipe, to which flux has been applied to the outer surface, is fitted into the fitting recess of the metal part from the other end face side of the metal part, so that the one end face of the pipe abuts against the opposing end face of the fitting recess, and brazing material is placed on the outer surface of the pipe adjacent to the other end face of the metal part, so that the outer surface of the one end of the pipe fitted into the fitting recess is surrounded by the opposing end face and the inner surface of the fitting recess to form a closed space, and a gas reservoir is formed by a notch or recess provided in at least one area of ​​the outer surface of the pipe or the fitting recess of the metal part located inside the closed space, A method for manufacturing an assembly of a pipe and a metal part, comprising heating and melting the brazing material, filling the closed space with it and allowing it to solidify, thereby integrating one end of the pipe and the metal part via the solidified brazing material, and storing the gas generated from the flux by the heating in the gas reservoir, wherein the gas reservoir is formed by providing an annular groove on the outer surface of the pipe that is continuous in the circumferential direction.

4. A method for manufacturing an assembly of a pipe and a metal part according to any one of claims 1 to 3, wherein the gas reservoir is formed by providing a chamfered portion at one end of the pipe.

5. A method for manufacturing an assembly of a pipe and a metal part according to any one of claims 1 to 4, wherein the gas reservoir is formed by providing an annular groove on the opposing end faces along the annular shape of one end face of the pipe.

6. A method for manufacturing an assembly of a pipe and a metal part according to any one of claims 1 to 5, wherein the fitting depth of one end of the pipe into the fitting recess is 20 mm or more.

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