Joining hardware, its manufacturing method, and joining structure

Abstract

To provide a joining fitting and its manufacturing method that can absorb earthquake energy from the initial deformation of the core material, as well as through friction between the core material and the inner wall of the pipe, and a joining structure in which wood material and other members are joined using this joining fitting. [Solution] The joining fitting 30 for joining a wood material 40 and another member 50 comprises a hollow 12 surrounded by an inner wall 13, a female screw 14 provided at one end of the hollow 12, and a first male screw 17 provided on the outer circumference 16, and a steel pipe 10 embedded inside the wood material 40, and a steel core material 20 having a second male screw 25 provided at least at one end, a part of the core material 20 being housed in the hollow 12, the second male screw 25 being screwed into the female screw 14, the core material 20 being spiral or coil spring shaped with a part of it in contact with the inner wall 13, a joining portion 27 for joining with another member provided at the other end of the core material 20, and a part or all of the joining portion 27 protruding from the end 15 of the pipe 10.

Description

Technical Field

[0001] The present invention relates to a joint fitting, a method for manufacturing the same, and a joint structure.

Background Art

[0002] When joining a wooden beam and a wooden column that are wooden members, or joining a wooden brace that is a wooden member and a steel frame, a joint fitting composed of a steel pipe and a steel core material may be applied. By screwing a male thread at one end of the core material into a female thread at one hollow end of the pipe, the two are integrated to form the joint fitting, the pipe is embedded in one wooden member to be joined, and the other end of the core material is joined to the other wooden member, steel member or the like to be joined, whereby a joint structure of two members via the joint fitting is formed.

[0003] Here, Patent Document 1 proposes a connection fitting for wooden buildings provided with a lag screw main body. This connection fitting for wooden buildings is a connection fitting consisting of a lag screw main body, and a connection screw shaft integrated with the lag screw main body and protruding concentrically from one end of the lag screw main body. The lag screw main body is formed of a pipe member in which a square shaft portion for rotational operation is provided on the outer periphery of one end, a bolt crimping and fixing region is provided on the other end, and a spiral ridge is formed on the outer peripheral surface between the square shaft portion for rotational operation and the bolt crimping and fixing region. The connection screw shaft is constituted by a rear end screw shaft portion of a bolt inserted into the lag screw main body, the other end portion of the bolt is provided with a tip screw shaft portion located inside the bolt crimping and fixing region of the lag screw main body, and the inner peripheral surface of the bolt crimping and fixing region is crimped to the tip screw shaft portion of the bolt so that the two are integrated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The core material placed inside the pipe that forms the conventional joint fitting is linear in shape. More specifically, a linear core material with a diameter smaller than the inner diameter of the hollow pipe is inserted into the hollow, and the male thread of the core material is screwed into the female thread at one end of the hollow, so that the two are integrated. In this state, a gap is provided between the inner wall of the hollow and the linear core material, forming the joint fitting. This configuration is the same as that of the connecting fitting for wooden buildings described in Patent Document 1.

[0006] Examples of joint structures formed by joining wood materials to each other or wood materials to steel members via connecting hardware include the joint structures between beams and columns that form the building frame, and the joint structures between braces and columns or beams. When the building frame deforms during an earthquake and compressive or tensile forces act on the core material of the connecting hardware, the core material is restrained from buckling by the surrounding pipes, and the earthquake energy is absorbed during the process of compressive and tensile deformation.

[0007] Incidentally, the inventors have experimentally confirmed that in a joint fitting in which a straight core material is arranged inside a pipe, when a compressive force is applied to the core material, the core material twists in a spiral shape while undergoing compression deformation. A portion of the spirally compressed core material slides against the inner wall of the pipe, and seismic energy is absorbed by the friction during this sliding motion.

[0008] In other words, the connecting fitting with the above configuration can absorb seismic energy not only through the compression and tensile deformation of the core material, but also through friction between the core material and the inner wall of the pipe. However, the absorption of seismic energy through friction is achieved after the core material has compressed and slid against the inner wall of the pipe, and it is not possible to expect seismic energy absorption through friction from the initial stage of core material deformation.

[0009] The present invention has been made in view of the above problems, and aims to provide a joining fitting having a core material disposed inside a pipe, which can absorb seismic energy from the initial deformation of the core material, in addition to the deformation of the core material, by friction between the core material and the inner wall of the pipe, as well as a joining structure in which a wooden material and other members are joined by this joining fitting. [Means for solving the problem]

[0010] To achieve the above objective, one embodiment of the joining fitting according to the present invention is: A joining metal fitting for joining wood material to other components, A steel pipe having a hollow structure enclosed by an inner wall, with a female thread at one end of the hollow structure and a first male thread on its outer circumference, and being embedded inside the end of the wooden material, It has a steel core material with a second male screw at at least one end, A portion of the core material is housed in the hollow, and the second male thread is screwed into the female thread. The core material has a spiral or coil spring shape, and a part of it is in contact with the inner wall. The other end of the core material is provided with a joint that connects to the other member, and part or all of the joint protrudes from the end of the pipe.

[0011] According to this embodiment, since the joining fitting is formed (manufactured) with a portion of the core material, which is spiral-shaped or coil spring-shaped, in contact with the inner wall of the pipe, it is possible to absorb earthquake energy from the initial deformation of the core material during an earthquake, in addition to the deformation of the core material, by friction between the core material and the inner wall of the pipe, resulting in a joining fitting with excellent earthquake energy absorption properties.

[0012] Here, "a portion of the core material is in contact with the inner wall" means that one or more points on the core material are in contact with the inner wall. An example of a steel pipe is a pipe plug screw, and an example of a steel core material is a steel rod having a second male thread at at least one end.

[0013] Joints that protrude from the end of a pipe, either partially or entirely, can take various forms, such as steel plates with bolt holes for bolting to other members (a form in which a steel plate is joined to the end of the core material) or male threads that are screwed into female threads on other members (a form in which male threads are provided at the end of the core material). If the protrusion of the joint from the end of the pipe is too long, the joint of the core material is more likely to break around the edge of the pipe end during an earthquake, so it is preferable that the protrusion length of the joint from the end of the pipe be as short as possible.

[0014] Furthermore, in another embodiment of the connecting fitting according to the present invention, The aforementioned joint is a third male screw, The third male screw is characterized in that it is screwed into the other member.

[0015] According to this embodiment, the joint portion protruding from the end of the pipe is a third male thread that is screwed into another member, allowing for a strong connection with another member using a relatively simple joint structure.

[0016] Furthermore, other embodiments of the connecting fitting according to the present invention are: The invention is characterized in that a lubricating layer is provided on the inner wall, and the friction coefficient between the core material and the inner wall is adjusted by the lubricating layer.

[0017] According to this embodiment, the friction coefficient between the core material and the inner wall is adjusted by the lubricating layer provided on the inner wall, thereby preventing excessive friction from hindering the deformation of the core material. Here, the lubricating layer can be formed by applying or spraying a lubricant to the inner wall of the pipe.

[0018] Furthermore, one embodiment of the joining structure according to the present invention is: The pipe forming the connecting fitting is embedded in the wood material, and the joint is connected to the other member.

[0019] According to this aspect, by joining the wood-based material and the other member via the joint fitting of the present invention, a joint structure with high joint strength and excellent seismic energy absorption performance can be formed.

[0020] Here, examples of the wood-based material forming the joint structure include wooden columns, wooden beams, wooden braces, wooden floors and the like. Further, examples of the other member forming the joint structure include another wood-based material, steel material, reinforced concrete member and the like.

[0021] Further, another aspect of the joint structure according to the present invention is characterized in that the other member is another wood-based material, a steel material, or a concrete member.

[0022] According to this aspect, since the other member is another wood-based material, steel material, or concrete member, it is possible to form a joint structure between wood-based materials or a joint structure between a wood-based material and a steel material, which has high joint strength and excellent seismic energy absorption performance.

[0023] Here, when the other member is another wood-based material, examples of the wood-based material to be joined and the another wood-based material include a configuration in which one is a wooden beam (including a foundation beam) and the other is a wooden column, a configuration in which one is a wooden column and the other is a wooden brace, a configuration in which one is a wooden beam and the other is a wooden brace, a configuration in which one is a wooden floor and the other is a wooden column or wooden beam, and the like. Further, the steel material includes steel beams, steel columns, steel floors, steel brackets fixed thereto, and the like. Furthermore, the concrete member includes reinforced concrete beams, reinforced concrete columns, reinforced concrete slabs, and the like.

[0024] Further, one aspect of the method for manufacturing a joint fitting according to the present invention is A method for manufacturing a joint fitting that joins a wood-based material and another member, the method comprising: preparing a steel pipe having a hollow surrounded by an inner wall, a female thread provided at one end of the hollow, and a first male thread on the outer periphery, and a steel core member having a second male thread at least at one end, The joining fitting is manufactured by housing a part of the core material in the hollow, screwing the second male thread into the female thread, causing the other end of the core material to protrude from the pipe, applying a compressive force to the other end of the core material in the direction of its material axis to cause the core material to be in a spiral shape, bringing a part of the core material into contact with the inner wall, and causing the joining portion at the other end of the core material that is joined to the other member to protrude from the pipe.

[0025] According to this embodiment, a portion of the core material is housed within the hollow of the pipe, and the other end of the core material is extended from the pipe. By applying a compressive force to the other end in the direction of its axial axis, the core material can be quickly transformed into a spiral shape, and a portion of it can be brought into contact with the inner wall. This manufacturing method ensures that the core material deforms into a spiral shape under compressive force during an earthquake.

[0026] Furthermore, other embodiments of the method for manufacturing the connecting fitting according to the present invention are: The compressive force is set within a range that is greater than or equal to the product of the cross-sectional area and yield strength of the core material, and less than or equal to the product of the cross-sectional area and yield strength of the pipe.

[0027] According to this embodiment, by setting the compressive force within a range that is greater than or equal to the product of the cross-sectional area of ​​the core material and the yield strength, and less than or equal to the product of the cross-sectional area of ​​the pipe and the yield strength, the pipe can be prevented from yielding by the applied compressive force, and the core material can be kept in a spiral shape.

[0028] Furthermore, other embodiments of the method for manufacturing the connecting fitting according to the present invention are: A method for manufacturing a joining fitting for joining wood material to other components, A steel pipe having a hollow enclosed by an inner wall, with a female thread at one end of the hollow and a first male thread on its outer circumference, A steel core material is prepared, having a second male screw at at least one end and exhibiting a coil spring shape. The method is characterized by housing the core material in the hollow while sliding a portion of the core material against the inner wall, screwing the second male screw into the female screw, and having the joint portion at the other end of the core material that connects to the other member protrude from the pipe to manufacture the connecting fitting.

[0029] According to this embodiment, by housing a portion of the steel core material, which has a coil spring shape, in a hollow space while sliding it against the inner wall of the pipe, a portion of the steel core material can be efficiently brought into contact with the inner wall of the pipe.

[0030] Furthermore, other embodiments of the method for manufacturing the connecting fitting according to the present invention are: The method is characterized by providing a lubricating layer on the inner wall, and then bringing a portion of the core material into contact with the inner wall.

[0031] According to this embodiment, by providing a lubricating layer on the inner wall of the pipe and bringing a portion of the core material into contact with the inner wall, seismic energy can be absorbed through friction between the core material and the inner wall of the pipe from the initial stage of deformation of the core material during an earthquake, thereby enabling the manufacture of a joint fitting with excellent seismic energy absorption properties. [Effects of the Invention]

[0032] As can be understood from the above explanation, the joint fitting of the present invention and the joint structure in which the wood material and other members are joined by this joint fitting allow the joint fitting to absorb seismic energy from the initial deformation of the core material, in addition to the deformation of the core material, by friction between the core material and the inner wall of the pipe, thereby forming a joint fitting and joint structure with excellent seismic energy absorption. Furthermore, the manufacturing method of the joint fitting of the present invention allows for the efficient manufacture of a joint fitting with excellent seismic energy absorption. [Brief explanation of the drawing]

[0033] [Figure 1] This figure shows an example of a connecting fitting according to an embodiment, and the inside of the pipe is visible through the diagram. [Figure 2] This figure shows an example of a joint structure according to an embodiment, and is a longitudinal cross-sectional view taken at the embedded position of the joint fitting. [Figure 3] This diagram shows an example of a connecting fitting according to an embodiment, in which a compressive force during an earthquake is applied, and the inside of the pipe is transparent. [Figure 4] (a) and (b) are diagrams showing an example of a connecting fitting according to the embodiment under the effect of tensile force during an earthquake, and the inside of the pipe is transparent. [Figure 5] This is a process diagram showing an example of a method for manufacturing a connecting fitting according to the embodiment. [Figure 6] Following Figure 5 is a process diagram showing an example of a method for manufacturing a connecting fitting according to the embodiment. [Figure 7] Following Figure 6 is a process diagram showing an example of a method for manufacturing a connecting fitting according to the embodiment. [Modes for carrying out the invention]

[0034] Hereinafter, an example of a joint fitting, its manufacturing method, and a joint structure according to the embodiment will be described with reference to the attached drawings. In this specification and the drawings, substantially identical components may be denoted by the same reference numerals to avoid redundant explanations.

[0035] [Joining fitting according to an embodiment, its manufacturing method, and joining structure] Referring to Figures 1 to 7, an example of a joint fitting according to an embodiment, its manufacturing method, and a joint structure will be described. Here, Figure 1 is a diagram showing an example of a joint fitting according to an embodiment, with the inside of the pipe visible, and Figure 2 is a diagram showing an example of a joint structure according to an embodiment, a longitudinal cross-sectional view cut at the buried position of the joint fitting. Figure 3 is a diagram showing an example of a joint fitting according to an embodiment under compressive force during an earthquake, with the inside of the pipe visible, and Figure 4, in order (a) and (b), shows an example of a joint fitting according to an embodiment under tensile force during an earthquake, with the inside of the pipe visible. Furthermore, Figures 5 to 7 are process diagrams showing an example of a manufacturing method for the joint fitting according to an embodiment, in order.

[0036] The connecting fitting 30 comprises a steel pipe 10 and a steel core material 20 inserted through the hollow 12 of the pipe 10.

[0037] The pipe 10 has a female thread 14 at one end of the hollow 12 and a first male thread 17, which is a machined thread, on its outer surface 16. The pipe 10 is, for example, a pipe plug screw.

[0038] The core material 20 has a body 22 made of round steel, with a second male thread 25, which is a rolled thread, provided at one end of the body 22, and a third male thread 27 (an example of a joint), which is also a rolled thread, provided at the other end of the body 22. The outer diameter of the body 22 is smaller than the inner diameter of the hollow 12 of the pipe 10. Here, the core material may be formed from materials other than round steel, such as deformed steel bars.

[0039] The core material 20 is inserted into the hollow 12 from the other end 15 of the pipe 10, and the second male thread 25 at one end is screwed into the female thread 14.

[0040] In this state, as explained below, a compressive force is applied to the other end 27 of the core material 20 in the direction of its material axis, causing the main body 22 of the core material 20 to deform into a spiral shape, with a portion 23 of it in contact with the inner wall 13 of the hollow 12. In the illustrated example, multiple (five in the illustrated example) spirally deformed peaks 23 are in contact with the inner wall 13.

[0041] The main body 22 of the core material 20 housed in the hollow 12 of the pipe 10 has a spiral shape, with a portion 23 of it in contact with the inner wall 13, and the third male screw 27 at the other end of the core material 20 protrudes from the other end 15 of the pipe 10, thereby forming the connecting fitting 30.

[0042] Here, although not shown in the diagram, a lubricating layer may be provided on the inner wall 13 of the pipe 10, and the friction coefficient between the main body 22 of the core material 20 and the inner wall 13 of the pipe 10 may be adjusted by the lubricating layer, thereby adjusting the seismic energy absorption capacity due to friction.

[0043] Furthermore, by adjusting the cross-sectional diameter of the core material 20, the seismic energy absorption capacity due to the compressive and tensile deformation of the core material 20 can be adjusted.

[0044] As shown in Figure 2, the pipe 10 is embedded inside the end 42 of the wood material 40. In this embedded position, the third male thread 27 protrudes from the side of the end 42 of the wood material 40.

[0045] On the other hand, a mating joint fitting 60 is embedded in the other member 50 that is joined to the wood material 40. The mating joint fitting 60 in the illustrated example is a fitting that has a male screw 64 on its outer circumference and a female screw 62 inside, and the joint structure 70 is formed when the third male screw 27 protruding from the end 42 of the wood material 40 is screwed into the female screw 62.

[0046] Here, the other member 50 in the illustrated example is made of wood. One of the wood members 40 and 50 is a wood column and the other is a wood beam. Alternatively, one is a wood floor and the other is a wood column or wood beam. In addition, one is a wood column or wood beam and the other is a wood brace.

[0047] Wood-based materials 40 and 50 are formed from laminated timber, solid wood, structural plywood, laminated veneer lumber (LVL), cross-laminated timber (CLT), and nail-laminated timber (NLT).

[0048] Here, the joining structure may be a joining structure between the wood material 40, in which the joining fitting 30 is embedded, and another member 50, which is also made of wood, or a joining structure between the wood material 40 and another member made of steel, or between the wood material 40 and another member made of concrete.

[0049] Furthermore, the joining structure between the connecting fitting 30 and the mating connecting fitting 60 shown in Figure 2 is just one example, and the joining portion may take a form other than the male screw (third male screw) shown in the example. For example, if the joining portion is made of steel material with bolt holes, the joining structure is formed by bolting the joining portion to a steel bracket or the like attached to another member.

[0050] Next, referring to Figures 3 and 4, we will explain the seismic energy absorption properties of the connecting fittings 30 when compressive and tensile forces are applied to the connecting structure 70 and the connecting fittings 30 during an earthquake.

[0051] As shown in Figure 3, when the compressive force Q1 during an earthquake acts from the joint 27 of the core material 20, the main body 22 of the core material 20 deforms further in the axial direction from its initial helical state shown in Figure 1. This compressive deformation causes the multiple peaks 23 that are in contact with the inner wall 13 of the pipe 10 to transform into flattened peaks 24, further increasing the contact area with the inner wall 13.

[0052] In the initial stage shown in Figure 1, the ridges 23 of the main body 22 of the core material 20 are in contact with the inner wall 13 of the pipe 10. Therefore, from the initial stage when the core material 20 receives a compressive force Q1 and deforms in the axial direction, the core material 20 absorbs not only seismic energy through compressive deformation but also through friction between the core material 20 and the inner wall 13 of the pipe 10. Consequently, compared to conventional general joint fittings, where the initial state of the core material is linear and only seismic energy absorption through compressive deformation is achieved in the initial stage when subjected to compressive force, the seismic energy absorption performance is improved.

[0053] On the other hand, as shown in Figure 4(a), when a tensile force Q2 during an earthquake acts on the joint 27 of the core material 20, the main body 22 of the core material 20 deforms in the direction of the material axis from its initial helical state shown in Figure 1, resulting in a linear shape in the direction of the material axis. Furthermore, as shown in Figure 4(b), the seismic energy absorption is achieved by further tensile deformation due to the acting tensile force Q2.

[0054] In this way, by joining the wooden material 40 and other members 50 with a connecting fitting 30 that has excellent seismic energy absorption properties, a connecting structure 70 with excellent seismic energy absorption properties is formed, and for example, a building frame equipped with such a connecting structure 70 becomes a building frame with excellent seismic energy absorption properties.

[0055] Next, an example of a method for manufacturing a connecting fitting will be described with reference to Figures 5 to 7.

[0056] As shown in Figure 5, a steel pipe 10, which is a pipe plug screw, and a steel core material 20, which has a second male thread 25 and a third male thread 27 at both ends of the main body 22, are prepared.

[0057] Next, as shown in Figure 6(a), the core material 20 is inserted into the hollow 12 in the X direction from the other end 15 of the pipe 10, and as shown in Figure 6(b), the second male thread 25 at one end is screwed into the female thread 14, so that the joint portion 27 protrudes from the other end 15 of the pipe 10.

[0058] Next, as shown in Figure 7, with the pipe 10 fixed to a fixing jig (not shown), a compressive force Q3 is applied to the other end 27 of the core material 20 in the direction of its material axis, causing the main body 22 of the core material 20 to take on a spiral shape, and a part 23 of the main body 22 is brought into contact with the inner wall 13 of the pipe 10 to produce the joint fitting 30.

[0059] Here, the compressive force Q3 applied to the core material 20 is set to be greater than or equal to the product of the cross-sectional area of ​​the core material 20 and its yield strength, and less than or equal to the product of the cross-sectional area of ​​the pipe 10 and its yield strength. By applying this set compressive force Q3 to the core material 20, the pipe 10 can be prevented from yielding by the applied compressive force, and the core material 20 can be made to transition to a spiral shape.

[0060] Furthermore, if a lubricating layer is provided on the inner wall 13 of the pipe 10 as described above, after applying or spraying the lubricant to the inner wall 13, a compressive force Q3 is applied to the core material 20 to bring a part 23 of the main body 22 into contact with the inner wall 13.

[0061] Although not shown in the diagram, instead of manufacturing the joint fitting using the method shown in the diagram, it is also possible to manufacture the joint fitting by preparing a steel core material having a coil spring shape and equipped with a second male thread at at least one end, housing the core material in the hollow while sliding a part of the core material against the inner wall, screwing the second male thread into the female thread, and causing the joint at the other end of the core material to protrude from the pipe.

[0062] Furthermore, other embodiments may be used in which other components are combined with the configurations listed in the above embodiments, and the present invention is not limited in any way to the configurations shown herein. In this regard, modifications can be made without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of Symbols]

[0063] 10: Pipe (Pipe Plug Screw) 12:Hollow 13:Inner wall 14 female thread 15: Other end 16: Outer surface (outer perimeter) 17: First male screw 20: Core material (round steel) 22: Main unit 23: Part (Yamabe) 24: Part (flat mountain area) 25: Second male screw 27: Joint (third male thread, other end) 30: Connecting hardware 40: Wood material 42: End 50: Other components (wood materials) 60: Mating connector 62: Female thread 64: Male screw 70:Joint structure Q1: Compression force Q2: Tensile force Q3: Compression force

Claims

1. A joining metal fitting for joining wood material to other components, A steel pipe having a hollow structure enclosed by an inner wall, with a female thread at one end of the hollow structure and a first male thread on its outer circumference, and being embedded inside the end of the wooden material, It has a steel core material with a second male screw at at least one end, A portion of the core material is housed in the hollow space, and the second male thread is screwed into the female thread. The core material has a spiral or coil spring shape, and a part of it is in contact with the inner wall. A connecting fitting characterized in that a connecting portion is provided at the other end of the core material for joining with the other member, and part or all of the connecting portion protrudes from the end of the pipe.

2. The aforementioned joint is a third male screw, The connecting fitting according to claim 1, characterized in that the third male screw is screwed into the other member.

3. The joining fitting according to claim 1 or 2, characterized in that a lubricating layer is provided on the inner wall, and the coefficient of friction between the core material and the inner wall is adjusted by the lubricating layer.

4. A joining structure characterized in that the pipe forming the joining fitting according to claim 1 or 2 is embedded in the wood material, and the joining portion is joined to the other member.

5. The joint structure according to claim 4, characterized in that the other member is a separate wood material, a steel material, or a concrete member.

6. A method for manufacturing a joining fitting for joining wood material to other components, A steel pipe is provided, having a hollow enclosed by an inner wall, with a female thread at one end of the hollow and a first male thread on its outer circumference; and a steel core material is provided, having a second male thread at at least one end. A method for manufacturing a connecting fitting, characterized in that a part of the core material is housed in the hollow, the second male thread is screwed into the female thread, the other end of the core material is made to protrude from the pipe, a compressive force is applied to the other end of the core material in the direction of its material axis to make the core material spiral, a part of the core material is brought into contact with the inner wall, and the connecting portion at the other end of the core material that is joined to the other member protrudes from the pipe to manufacture the connecting fitting.

7. The method for manufacturing a joint fitting according to claim 6, characterized in that the compressive force is set within a range that is greater than or equal to the product of the cross-sectional area of ​​the core material and the yield strength, and less than or equal to the product of the cross-sectional area of ​​the pipe and the yield strength.

8. A method for manufacturing a joining fitting for joining wood material to other components, A steel pipe having a hollow enclosed by an inner wall, with a female thread at one end of the hollow and a first male thread on its outer circumference, A steel core material is prepared, having a second male screw at at least one end and exhibiting a coil spring shape. A method for manufacturing a connecting fitting, characterized in that a part of the core material is brought into sliding contact with the inner wall while the core material is housed in the hollow, the second male screw is screwed into the female screw, and the connecting portion at the other end of the core material that is joined to the other member is extended from the pipe to manufacture the connecting fitting.

9. A method for manufacturing a joining fitting according to any one of claims 6 to 8, characterized in that a lubricating layer is provided on the inner wall, and then a part of the core material is brought into contact with the inner wall.

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