METHOD FOR MANUFACTURING METAL STRUCTURE, AND METAL STRUCTURE

Abstract

To provide a method for manufacturing a metal structure, which can ensure a design freedom while suppressing and even preventing generation of a defect in a joined part and complication of a manufacturing process.SOLUTION: In a metal structure manufacturing method, the metal structure includes two metal members stacked together in a perpendicular direction to be joined through friction agitation joining, the two metal members are stacked together in the perpendicular direction to form an assembly having an internal space between the two metal members, the assembly has a discontinuous part formed by the two metal members which are not joined but contact or come close to each other to be discontinuous at positions where they are exposed to the internal space therein, and a boundary formed between the two metal members in a manner that the two metal members are not joined but contact or come close to each other at positions where they are exposed to the internal space therein.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a metal structure and a metal structure.

Background Art

[0002] As a conventional metal structure, there is a metal structure including a main body portion and a lid portion. A lid groove is formed in the main body portion. A concave groove is further formed on the bottom surface of the lid groove of the main body portion. The lid portion is fitted into the lid groove. The main body portion and the lid portion around the lid groove are joined. Thereby, the space surrounded by the concave groove and the lid portion becomes an internal space and can be used as a flow path for a fluid. Such a metal structure can be used as a heat transfer metal structure. The heat transfer metal structure is arranged, for example, in contact with or close to an object to be heat-exchanged, heated or cooled. For example, when releasing heat from the object, a cooling medium is caused to flow through the flow path, and the heat of the object is transferred from the object to the metal main body portion and the cooling medium, whereby the heat of the object can be released.

[0003] Patent Document 1 discloses a technique for joining a main body portion and a lid portion around a lid groove by friction stir welding with respect to a metal structure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a method for manufacturing a metal structure and a metal structure that can secure a degree of design freedom while suppressing or preventing the occurrence of defects at a joining site and the complication of a manufacturing process.

Means for Solving the Problems

[0006] The inventor has studied the above-described problems and obtained the following findings.

[0007] Figs. 1(a) and (b) are cross-sectional views schematically showing the state of joining of the main body portion 101 and the lid portion 102 by friction stir welding. Here, the cross-sectional view refers to a cross-sectional view obtained by a plane orthogonal to the direction in which the internal space 103 as a fluid flow path extends.

[0008] As shown in Fig. 1(a), the horizontal distance GD between the joining portion (the passing position of the tip 105a of the tool 105) of the main body portion 101 and the lid portion 102 and the internal space 103 is ensured to be relatively large. As shown in Fig. 1(b), if the distance GD is short, during friction stir welding, the metal base material 103a may enter the internal space 103, and there is a risk of defects occurring in the joining portion. Therefore, either of the following (i) or (ii) is required. (i) The metal structure is designed so that the distance GD is sufficiently ensured. (ii) A joining method other than friction stir welding is adopted for a portion where it is difficult to ensure the distance GD.

[0009] When a design is made to sufficiently ensure the distance GD as in (i) above, for example, it is difficult to arrange the internal space 103 densely, and there arises a problem that the design freedom of the metal structure is restricted. On the other hand, when friction stir welding is combined with another joining method as in (ii) above, there is a problem that the manufacturing process becomes complicated.

[0010] Figs. 2(a) and (b) are longitudinal sectional views schematically showing the state of joining of the main body portion 101 and the lid portion 102 by friction stir welding. Here, the longitudinal sectional view refers to a sectional view obtained by a plane parallel to the direction in which the internal space 103 as a fluid flow path extends. However, since Figs. 2(a) and (b) are longitudinal sectional views based on the passing position of the tool 105, the internal space 103 is not shown.

[0011] In Fig. 2(a), a lid portion 102 is fitted into a lid groove (not shown) formed in a main body portion 101. The tool 105 of a friction stir apparatus (not shown) has a cylindrical shape and a thin tip portion 105a. The tool 105 is inclined with respect to the vertical direction VD such that the tip portion 105a is positioned more forward in the advancing direction of the tool 105. The inclination angle D (advancing angle) is preferably more than 0 degree and 5 degrees or less, and more preferably 1 degree or more and 4 degrees or less. However, when the tool 105 is moved in the advancing direction PD while the tool 105 has the inclination angle D, deformation such as floating may occur in the lid portion 102 in front of the advancing direction PD as shown in Fig. 2(b). The ease of such deformation and the amount of deformation increase in proportion to the size (i.e., load) of the tool 105. Therefore, when the thickness of the lid portion 102 is large, there has been a problem that the lid portion 102 is likely to be deformed during friction stir welding and the tool 105 of the friction stir apparatus is likely to be damaged. For this reason, it has been difficult to adopt the lid portion 102 having a large thickness, and the design freedom of the metal structure may be restricted. Further, when adopting the lid portion 102 having a large thickness, if the tool 105 is enlarged to ensure the mechanical strength of the tool 105, a larger joining portion has to be secured, so that the design freedom of the metal structure is further restricted. Further, since measures for preventing or suppressing the deformation of the lid portion 102 are required, there arises a problem that the manufacturing process becomes complicated.

[0012] Based on the above findings, the present inventor has completed the present invention. As an embodiment of the present invention, the following configuration can be adopted.

[0013] (1) A method for manufacturing a metal structure, wherein the metal structure includes two metal members joined by friction stir welding in a state of being stacked in directions perpendicular to each other, The two metal members are configured to form an assembly having an internal space between the two metal members by being overlapped with each other in the vertical direction. The assembly is configured such that at a position exposed to the internal space inside the assembly, the two metal members are non - continuous by contacting or approaching each other without being joined to each other, and at a position not exposed to the internal space inside the assembly, the two metal members are configured to have a boundary with each other by contacting or approaching each other without being joined to each other. The assembly has a non - continuous portion and a non - joined portion that is physically continuous with the non - continuous portion. The non - joined portion includes an upper portion where the two metal members contact or approach each other in the vertical direction without being joined to each other at a position shallower than the non - continuous portion with reference to the upper surface of the assembly when the assembly is viewed in the vertical direction. Each of the non - continuous portion and the upper portion is formed to surround the internal space when the assembly is viewed in the vertical direction. The manufacturing method is a preparation step of preparing the two metal members, an assembly step of forming the assembly by overlapping the two metal members in the vertical direction, a joining step of inserting a tool for friction stir joining from the upper surface of the assembly to a joining depth while rotating the tool and moving it along the upper portion as viewed in the vertical direction to form a joined portion where the two metal members are joined. The joined portion is formed such that the non - joined portion remains at an inner position communicating with the internal space through the non - continuous portion. and has The joining depth is a depth at which the friction stir joining reaches the upper portion but does not reach the depth of the non - continuous portion.

[0014] According to the manufacturing method of (1), in the joining step, the tool is inserted into the assembly such that friction stir welding reaches the upper part but does not reach the discontinuous part. The upper part is located at a position shallower than the discontinuous part. Since the formation of the joint is performed at a shallow position, the tool is not inserted to a deep position. It is possible to reduce the load applied to the metal structure during joining, and to suppress or prevent enlargement of the tool for friction stir welding. Deformation of the metal member can be suppressed or prevented. It becomes possible to employ a metal member with a large thickness. Since the distance between the insertion position of the tool and the internal space can be ensured, it is possible to suppress or prevent the occurrence of a situation where the metal base material flows into the internal space due to friction stir welding. In addition, since friction stir welding is performed on the upper part where the two metal members overlap in the vertical direction, a joint is formed. Therefore, the occurrence of defects in the joint can be prevented.

[0015] As described above, according to the manufacturing method of (1), it is possible to increase the design freedom of the metal structure while preventing the occurrence of defects. Further, according to the manufacturing method of (1), since joining at a shallow position is possible, it is easy to adopt friction stir welding. It is not necessary to combine friction stir welding with other joining methods, and a configuration that can be joined only by friction stir welding can be adopted. However, the joining of the two metal members in the metal structure of (1) is not necessarily limited to only friction stir welding. Other joining methods than friction stir welding may also be used together with friction stir welding. By adopting the manufacturing method of (1), the design freedom is improved, a structure in which the joining of two metal members is easy can be adopted, and the demerits due to the combination of joining methods can be reduced.

[0016] (2) The manufacturing method of (1), wherein in the joining step, the joint is formed such that the non-joined part has a portion extending in the vertical direction at the inner position.

[0017] According to the manufacturing method of (2), since the non-joint part has a portion extending vertically at the inner position, the distance between the discontinuous part and the joint part can be ensured in the vertical direction. Therefore, for example, even if the horizontal distance between the discontinuous part and the joint part is not sufficiently ensured, the distance between the discontinuous part and the joint part can be ensured. As a result, for example, it is possible to arrange the internal spaces more densely. It is possible to suppress the occurrence of defects, suppress or prevent the complication of the manufacturing process, and improve the design freedom.

[0018] (3) The manufacturing method of (1) or (2), wherein in the joining step, the joint part is formed so as to leave the non-joint part not only at the inner position but also at an outer position not communicating with the internal space.

[0019] According to the manufacturing method of (3), the joint part is formed so that the non-joint part remains on both sides of the joint part (that is, both the inner position and the outer position). The generation of voids in the joint part can be suppressed or prevented. As a result, it is possible to prevent the occurrence of defects in the metal structure, particularly defects in the internal space, avoid the complication of the manufacturing process, and improve the design freedom of the metal structure.

[0020] Note that since there is a joint part between the outer non-joint part (the non-joint part remaining at the outer position) and the internal space, the outer non-joint part does not communicate with the internal space. However, when the metal structure has another internal space, the outer non-joint part may communicate with the other internal space. The outer non-joint part corresponds to the inner non-joint part when viewed with respect to the other internal space. Also, the outer non-joint part may communicate with the outside of the metal structure.

[0021] (4) The manufacturing method according to any one of (1) to (3), wherein the upper part is formed so as to surround the internal space at a position where it does not overlap with the internal space when the assembly is viewed in the vertical direction, the discontinuous part is formed so as to surround the internal space along the outer peripheral edge of the internal space when the assembly is viewed in the vertical direction.

[0022] According to the manufacturing method of (4), it is possible to prevent the occurrence of defects in the metal structure, particularly defects in the internal space, avoid complicating the manufacturing process, and improve the design freedom of the metal structure.

[0023] (5) The manufacturing method according to any one of (1) to (4), the two metal members are a main body portion and a lid portion, the main body portion has a shoulder portion formed to protrude toward the upper surface of the assembly at a position corresponding to the upper portion when viewed in the vertical direction, the lid portion has a bottomed groove formed to receive the shoulder portion when the lid portion is overlapped with the main body portion, the joining depth is a depth at which the friction stir joining reaches the shoulder portion but does not reach the depth of the non - continuous portion.

[0024] According to the manufacturing method of (5), it is possible to prevent the occurrence of defects in the metal structure, particularly defects in the internal space, avoid complicating the manufacturing process, and improve the design freedom of the metal structure.

[0025] (6) The manufacturing method according to (5), the main body portion has a lid groove on the surface for fitting the lid portion, and the shoulder portion is formed to protrude from the bottom surface of the lid groove toward the upper surface of the assembly, the lid portion has a shape that can be fitted into the lid groove, and is configured such that the shoulder portion is received in the bottomed groove when the lid portion is fitted into the lid groove.

[0026] According to the manufacturing method of (6), it is possible to prevent the occurrence of defects in the metal structure, particularly defects in the internal space, avoid complicating the manufacturing process, and improve the design freedom of the metal structure.

[0027] (7) The manufacturing method according to any one of (1) to (6), The metal structure is a heat transfer metal structure installed in contact with or in proximity to an object to be heat-exchanged, heated, or cooled.

[0028] According to the manufacturing method of (7) above, it is possible to improve the design freedom of the metal structure, particularly the design freedom of the internal space, while preventing the occurrence of defects. By using the internal space as a flow path for a fluid, for example, a metal structure in which flow paths with excellent fluid tightness are densely arranged can be realized. That is, a metal structure having excellent heat transfer performance can be realized due to high tightness and design freedom. That is, according to the manufacturing method of (7), a metal structure suitable for heat transfer can be manufactured.

[0029] (8) A metal structure according to any one of (1) to (6), The metal structure is a hollow metal structure used in a state where the internal space is a cavity.

[0030] According to the manufacturing method of (8) above, it is possible to improve the design freedom of the metal structure, particularly the design freedom of the internal space, while preventing the occurrence of defects. By making the internal space a cavity, for example, a metal structure in which cavities are densely arranged can be realized. That is, a hollow metal structure with a high degree of design freedom regarding the combination of the mechanical strength, weight, and size of the structure can be realized.

[0031] (9) A metal structure, The metal structure, An internal space provided inside the metal structure, At positions where two metal parts constituting a metal wall portion defining the internal space are exposed to the internal space, they are configured not to be joined to each other but to be in contact or proximity to each other, so that a discontinuous portion is formed in which the two metal parts are discontinuous, At positions inside the metal structure that are not exposed to the internal space, the two metal parts are configured not to be joined to each other but to be in contact or proximity to each other so that the two metal parts have a boundary, and an inner non-joined portion is formed at an inner position communicating with the internal space through the discontinuous portion, A joint portion that closes one end of the inner non-joint portion so that the boundary between the two metal parts is indistinguishable or difficult to distinguish at a position not exposed to the internal space inside the metal structure, and has The joint portion is located in one or substantially one plane and is formed to surround the internal space when viewed in a vertical direction perpendicular or substantially perpendicular to the plane. The discontinuous portion is formed to surround the internal space when viewed in the vertical direction. The inner non-joint portion has a portion extending in the vertical direction such that the discontinuous portion and the joint portion are located at different heights in the vertical direction.

[0032] According to the metal structure of (9), it is possible to prevent the occurrence of defects in the metal structure, particularly defects in the internal space, avoid complication of the manufacturing process, and improve the design freedom of the metal structure.

[0033] (10) The metal structure of (9), wherein the metal structure further has At a position not exposed to the internal space inside the metal structure, the two metal parts are configured to have a boundary by contacting or approaching each other without being joined to each other, and are located at an outer position not communicating with the internal space, and have an outer non-joint portion whose one end is closed by the joint portion.

[0034] The metal structure of (10) above is manufactured such that the inner non-joint portion and the outer non-joint portion are located on both sides of the joint portion. Generation of voids at the joint portion during manufacturing can be suppressed or prevented.

[0035] (11) The metal structure of (9) or (10), wherein the metal structure is a heat transfer metal structure installed so as to be in contact with or close to an object to be heat-exchanged, heated, or cooled.

[0036] According to the metal structure of (11) above, while preventing the occurrence of defects, the degree of freedom in designing the metal structure, particularly the degree of freedom in designing the internal space, can be improved. By using the internal space as a flow path for a fluid, for example, a metal structure in which flow paths with excellent fluid tightness are densely arranged can be realized. That is, a metal structure having excellent heat transfer performance can be realized due to high tightness and design freedom. That is, the metal structure of (11) is suitable for heat transfer.

[0037] (12) A metal structure of (9) or (10), wherein the metal structure is a hollow metal structure used in a state where the internal space is a cavity.

[0038] According to the manufacturing method of (12) above, while preventing the occurrence of defects, the degree of freedom in designing the metal structure, particularly the degree of freedom in designing the internal space, can be improved. By making the internal space a cavity, for example, a metal structure in which cavities are densely arranged can be realized. That is, a hollow metal structure with a high degree of freedom in designing the combination of the mechanical strength, weight, and size of the structure can be realized.

Advantages of the Invention

[0039] According to the present invention, while suppressing or preventing the occurrence of defects at the joint part and the complication of the manufacturing process, the degree of freedom in design can be ensured.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0041] <<Metal Structure According to an Embodiment>> First, the metal structure 10 according to an embodiment will be described. FIG. 3(a) is a plan view schematically showing the metal structure 10. FIG. 3(b) is a cross-sectional view taken along line A-A in FIG. 3(a).

[0042] The metal structure 10 has an internal space 3, a discontinuous part 3c, an inner non-joined part 3d, a joined part 3f, and an outer non-joined part 3h.

[0043] The metal structure 10 is a plate-like body. As shown in Fig. 3(a), the metal structure 10 has a rectangular shape extending in the longitudinal direction (the vertical direction in Fig. 3(a)) in a plan view. As shown in Fig. 3(b), the metal structure 10 has a rectangular cross-sectional shape. The metal structure 10 is configured to include a metal portion 1a and a metal portion 2a. The metal portion 1a and the metal portion 2a are joined to each other at the joint portion 3f. The metal structure 10 is made of copper. That is, the metal portion 1a and the metal portion 2a are made of copper. The metal constituting the metal structure 10 is not particularly limited. Examples of the metal include copper, aluminum, or an alloy containing at least one of these. Further, the metal portion 1a and the metal portion 2a may be made of the same metal as each other, or may be made of different metals.

[0044] The internal space 3 is provided inside the metal structure 10. In a plan view, the internal space 3 has a shape extending in the longitudinal direction (the vertical direction in Fig. 3(a)). The shape of the internal space is not particularly limited. The internal space may be U-shaped or zigzag-shaped. The number of internal spaces in one metal structure is not particularly limited and may be one or more. The internal space 3 is defined by a metal wall portion 3b. The metal wall portion 3b is constituted by a portion of the metal structure 10 that is exposed to the internal space 3. The metal wall portion 3b is composed of a portion constituted by the metal portion 1a and a portion constituted by the metal portion 2a. The metal portion 1a corresponds to the main body portion 1 described later. The metal portion 2a corresponds to the lid portion 2 described later. The metal portion 1a and the metal portion 2a are integrated by being joined at the joint portion 3f.

[0045] The discontinuous portion 3c is a portion configured such that the metal portion 1a and the metal portion 2a are discontinuous by coming into contact or proximity without being joined to each other at the position where the metal portion 1a and the metal portion 2a are exposed to the internal space 3. The discontinuous portion 3c is formed so as to surround the internal space 3 when viewed in the vertical direction X.

[0046] The inner non-joint portion 3d is a portion configured such that the metal portion 1a and the metal portion 2a have a boundary by contacting or approaching each other without being joined to each other at a position not exposed to the internal space 3 of the metal structure 10, and is formed at an inner position communicating with the internal space 3 via the discontinuous portion 3c. That is, one end 3e of the inner non-joint portion 3d is closed by the joint portion 3f, and the discontinuous portion 3c corresponds to the other end of the inner non-joint portion 3d. The inner non-joint portion 3d has a portion extending in the vertical direction X such that the discontinuous portion 3c and the joint portion 3f are located at different heights in the vertical direction X. The inner non-joint portion 3d is located at an inner position of the joint portion 3f. Note that the inner position of the joint portion 3f is a position relatively close to the internal space 3 and refers to a position communicating with the inner space 3 via the discontinuous portion 3c. On the other hand, the outer position of the joint portion 3f is a position relatively far from the internal space 3 and refers to a position not communicating with the inner space 3.

[0047] The joint portion 3f is a portion that closes one end 3e of the inner non-joint portion 3d such that the boundary between the metal portion 1a and the metal portion 2a is indistinguishable or difficult to distinguish at a position not exposed to the internal space 3 of the metal structure 10. Note that it is not necessary to strictly distinguish whether the boundary is indistinguishable or difficult to distinguish. The entry and exit of fluid can be blocked between the inner position and the outer position of the joint portion 3f. The joint portion 3f is located within a single plane S. The plane S is a virtual plane. The vertical direction X refers to a direction perpendicular or substantially perpendicular to the plane S. That is, the joint portion 3f is located at the same or substantially the same height (depth) in the vertical direction X. The plane S may have a width in the vertical direction X. The plane S including the joint portion 3f is included in the metal portion 2a. In other words, the joint portion 3f is formed in the metal portion 2a. Further, when viewed in the vertical direction X, the joint portion 3f is formed so as to surround the internal space 3 as shown in FIG. 3(a).

[0048] The outer non-joint portion 3h is a portion configured such that the metal portion 1a and the metal portion 2a have a boundary by contacting or approaching each other without being joined to each other at a position not exposed to the internal space 3 of the metal structure 10. It is located at an outer position, and one end 3g is closed by the joint portion 3f. The other end of the outer non-joint portion 3h may communicate with the outside of the metal structure 10. When the metal structure 10 has another internal space 3, the other end of the outer non-joint portion 3h may communicate with the other internal space 3. Note that depending on the structure of the metal structure, there may be no outer non-joint portion at the outer position.

[0049] The internal space 3 communicates with the outside of the metal structure 10 through the through-hole 3a formed in the metal portion 2a. As shown in Fig. 3(a), two through-holes 3a are formed in the metal portion 2a. The through-hole 3a is used, for example, as an inlet or outlet for a fluid such as a refrigerant. Note that the number of through-holes 3a is not particularly limited. The through-hole 3a may be one or a plurality. The through-hole 3a is formed only in the metal portion 2a, but may be formed only in the metal portion 1a, or may be formed in both the metal portion 1a and the metal portion 2a.

[0050] The through-hole 3a is formed in the metal portion 2a. As described above, the joint portion 3f is also formed in the metal portion 2a. Thus, it is preferable that the through-hole 3a and the joint portion 3f are formed in one metal portion 2a and not in the other metal portion 1a. Thereby, the flow of fluid between the internal space 3 and the outside of the metal structure 10 is prevented through the metal portion 1a. For example, when a fluid such as a refrigerant flows through the internal space 3, leakage of the fluid from the metal portion 1a is prevented. Therefore, the metal portion 1a can be suitably used as a heat transfer surface that contacts or approaches an object to be heat-exchanged, heated, or cooled. In the present embodiment, the metal portion 1a has a heat transfer surface, but the metal portion 2a may have a heat transfer surface. Further, as shown in Fig. 3(a), it is preferable that the internal space 3 is sealed except for the through-hole 3a by forming the joint portion 3f over the entire circumference of the outer periphery of the internal space 3. Note that the through-hole 3a is not an essential component.

[0051] The use of the metal structure 10 is not particularly limited. The metal structure 10 may be, for example, a hollow metal structure used in a state where the internal space 3 is a cavity. Further, the metal structure 10 may be a heat transfer metal structure installed so as to be in contact with or close to an object to be heat-exchanged, heated, or cooled. The metal structure 10 has an internal space 3 with excellent airtightness. That is, the main body portion 1 and the lid portion 2 joined to each other at the joint portion 3f can block the inflow and outflow of fluid between the internal space 3 and the outside of the metal structure 10. The metal structure 10 can be suitably used so that the internal space 3 functions as a fluid flow path or a storage portion. The fluid is, for example, a gas or a liquid. When the metal structure 10 is used as a heat transfer metal structure, the fluid is, for example, a heat transfer fluid such as a refrigerant.

[0052] <<Method for manufacturing a metal structure according to an embodiment>> Next, a method for manufacturing the metal structure 10 according to an embodiment will be described with reference to FIGS. 4(a) to (c) and FIG. 5.

[0053] <Preparation step> First, in the preparation step, as shown in FIG. 4(a), the main body portion 1 is prepared, and as shown in FIG. 4(b), the lid portion 2 is prepared. The main body portion 1 and the lid portion 2 each correspond to a "metal member".

[0054] The main body portion 1 is made of a metal material. The metal material is not particularly limited as long as it is a metal material that can be plastically deformed by being softened by the frictional heat of friction stir welding. Examples of the metal material include copper, aluminum, or an alloy containing at least one of these. The main body portion 1 is a plate-like body. The main body portion 1 is a long plate-like body. The shape of the main body portion 1 is not limited to a plate-like body.

[0055] As shown in FIG. 4(a), the main body portion 1 has a first defining surface 1d for defining an internal space 3. In the present embodiment, the internal space 3 corresponds to the space within the groove formed in the main body portion 1. The first defining surface 1d corresponds to the surface of the groove formed in the main body portion 1. The internal space 3 is defined by the first defining surface 1d of the main body portion 1 and the second defining surface 2d of the lid portion 2 shown in FIG. 4(b). As shown in FIG. 4(a), a shoulder portion 4 is formed outside the first defining surface 1d.

[0056] The lid portion 2 is made of a metal material. The metal material is not particularly limited as long as it can be plastically flowed by being softened by the frictional heat of friction stir welding. Examples of the metal material include copper, aluminum, or an alloy containing at least one of these. The material of the lid portion 2 may be the same as or substantially the same as the material of the main body portion 1, or may be different from the material of the main body portion 1.

[0057] As shown in FIG. 4(b), the lid portion 2 has a second defining surface 2d that defines the internal space 3 together with the first defining surface 1d. As shown in FIG. 4(d), the lid portion 2 has a contact surface 2b that contacts the outer surface 1b of the main body portion 1 when the lid portion 2 is placed on the main body portion 1. A bottomed groove 6 for receiving the shoulder portion 4 is formed in the contact surface 2b. The bottomed groove 6 is a groove with a bottom. The cross-sectional shape of the bottomed groove 6 is rectangular. In the present embodiment, the first defining surface 1d forms a recess, and the second defining surface 2d is a flat surface. However, the first defining surface 1d may be a flat surface and the second defining surface 2d may form a recess. Also, both the first defining surface 1d and the second defining surface 2d may have recesses.

[0058] <Assembly Process> In the assembly process, as shown in FIG. 4(c), the lid portion 2 is placed on the main body portion 1 such that the shoulder portion 4 of the main body portion 1 is received in the bottomed groove 6 of the lid portion 2. Thereby, an assembly 10a having an internal space 3 is formed. In the assembly 10a, in the vertical direction, the main body portion 1 is located below and the lid portion 2 is located above. The assembly 10a has a discontinuous portion 3c and a non-joined portion 3n. The discontinuous portion 3c is a portion configured such that the main body portion 1 and the lid portion 2 have a mutual boundary by coming into contact or proximity without being joined to each other at a position exposed to the internal space 3 of the assembly 10a. The non-joined portion 3n is configured such that the main body portion 1 and the lid portion 2 have a mutual boundary by coming into contact or proximity without being joined to each other at a position not exposed to the internal space of the assembly 10. The non-joined portion 3n is the boundary between the main body portion 1 and the lid portion 2. The non-joined portion 3n physically communicates with the discontinuous portion 3c, which is also the boundary between the main body portion 1 and the lid portion 2. In the assembly 10a, the non-joined portion 3n includes an upper portion 8. The upper portion 8 is a portion where the main body portion 1 and the lid portion 2 come into contact or proximity in the vertical direction X without being joined to each other at a position shallower than the discontinuous portion 3c with reference to the upper surface 2c of the assembly 10a when the assembly 10a is viewed in the vertical direction X. The upper portion 8 is a portion where the shoulder portion 4 and the bottomed groove 6 overlap in the vertical direction X. The discontinuous portion 3c and the upper portion 8 are formed so as to surround the internal space 3 when the assembly 10a is viewed in the vertical direction X (see FIG. 3(a)).

[0059] <Joining Process> As shown in FIG. 5, the joining process is performed on the assembly 10a. In the joining process, the main body portion 1 and the lid portion 2 are joined by friction stir welding. A tool 5 of a friction stir welding apparatus (not shown) is used in this joining process. The tool 5 is formed of a material having high heat resistance and wear resistance. The tool 5 is a columnar body having a tapered tip portion 5a at its tip. The tool 5 is controlled by a driving device provided in the friction stir welding apparatus so as to move while rotating. Specifically, the tool 5 can perform relative lifting and lowering movement with respect to the main body portion 1 and the lid portion 2 and relative parallel movement with respect to the main body portion 1 and the lid portion 2 while rotating. The lifting and lowering movement is movement in the vertical direction X. The parallel movement is movement in a direction perpendicular to the vertical direction X. A spiral thread groove (not shown) is provided on the outer peripheral surface of the tip portion 5a of the tool 5.

[0060] In the joining process, while rotating the tool 5, it is inserted from the upper surface 2c of the assembly 10a to the joining depth inside the lid portion 2. The upper surface 2c of the assembly 10a corresponds to the surface on the opposite side of the contact surface 2b in the lid portion 2. FIG. 5 shows a state in which the tool 5 is inserted to the joining depth while rotating. The joining depth is such that the depth WD of the friction stir welding reaches the shoulder portion 4 received in the bottomed groove 6 but does not reach the outer surface 1b (non - continuous portion 3c). In other words, the joining depth is set so that the depth WD of the friction stir welding satisfies the condition of depth SD ≦ WD < depth OD. As shown in FIG. 5, the depth SD is the depth from the upper surface 2c of the lid portion 2 to the shoulder portion 4. The depth OD is the depth from the upper surface 2c of the lid portion 2 to the outer surface 1b (non - continuous portion 3c). At this time, the joint portion 3f is formed so as to leave the non - joint portion 3n at an inner position communicating with the internal space 3 through the non - continuous portion 3c. As a result, the non - joint portion 3n remains as an inner non - joint portion 3d (see FIG. 3(b)). Further, the non - joint portion 3n also remains as an outer non - joint portion 3h (see FIG. 3(b)). Note that the width of the shoulder portion 4 (upper portion 8) is not particularly limited and may be equal to or greater than the width of the tip 5a of the tool 5, or may be equal to or less than the width. The shoulder portion 4 protrudes upward from the outer surface 1b and has a height that does not reach the surface 1s of the main body portion 1.

[0061] With the tool 5 rotating and inserted to the joining depth WD in this way, the tool 5 is moved along the shoulder 4 (see Fig. 3(a)) in a plan view. The metal material between the top of the shoulder 4 and the bottom of the bottomed groove 6 is stirred while being fluidized in a solid state by frictional heat and integrated. As a result, the top of the shoulder 4 and the bottom of the bottomed groove 6 are joined. As a result, the main body portion 1 and the lid portion 2 are joined. Thus, a metal structure 10 configured by friction stir joining the main body portion 1 and the lid portion 2 is manufactured. In the present embodiment, since the tool 5 does not reach the depth of the internal space 3, the horizontal distance GD between the upper portion 8 (the passing position of the tip portion 5c of the tool 5) and the internal space 3 can be shortened. The distance GD in the present embodiment is shorter than the distance GD in Fig. 1(a).

[0062] Note that the manufacturing method of the metal structure 10 may have steps other than the preparation step, the assembly step, and the joining step. For example, the manufacturing method of the metal structure 10 may have a step for positioning the main body portion 1 and the lid portion 2 between the assembly step and the joining step. The positioning may be performed by mechanical means such as clamping means. The positioning may be performed by forming a plurality of joining portions by friction stir joining with a space therebetween. The joining portion may be dot-shaped or linear having a predetermined length. Further, in the positioning step, a plurality of linear joining portions may be provided after a plurality of dot-shaped joining portions are provided. Further, after the joining step, a flattening process for removing burrs generated by the joining step may be performed. Furthermore, as described with reference to Fig. 2, the tool 5 may be inclined in the joining step.

[0063] <<Other Embodiments>> Next, other embodiments will also be described. Fig. 6(a) is a plan view schematically showing a metal structure 10 according to another embodiment, and Figs. 6(b) to (e) are cross-sectional views showing the manufacturing process thereof, corresponding to the cross-sectional view taken along the line B-B in Fig. 6(a). The same components as those included in the embodiments of Figs. 3 to 5 are denoted by the same reference numerals.

[0064] As shown in Fig. 6(a), in the metal structure 10 according to this embodiment, two lid portions 2 are provided for one main body portion 1. One main body portion 1 and two lid portions 2 correspond to "metal members". In this way, the metal structure may be configured to include three or more metal members. Further, in the metal structure 10 according to this embodiment, one lid portion 2 and one main body portion 1 correspond to "two metal members joined by friction stir welding in a state of being overlapped in a direction perpendicular to each other", and the other lid portion 2 and one main body portion 1 also correspond to "two metal members joined by friction stir welding in a state of being overlapped in a direction perpendicular to each other". In this way, the metal structure may have a plurality of combinations corresponding to "two metal members".

[0065] As shown in Fig. 6(a), the metal structure 10 is a rectangular plate-like body extending in the longitudinal direction (vertical direction in the figure). The metal structure 10 has a plurality (two) of internal spaces 3. Each internal space 3 is independent. Each internal space 3 has a shape extending in the longitudinal direction. Each internal space 3 is parallel to each other.

[0066] The manufacturing method of the embodiment will be described with reference to Figs. 6(a) to (e).

[0067] First, in the preparation step, as shown in Figs. 6(a) and (b), one main body portion 1 and two lid portions 2 are prepared.

[0068] The main body portion 1 has two lid grooves 7 on the surface 1s of the main body portion 1. The lid grooves 7 have a shape extending in the longitudinal direction as shown in Fig. 6(a). The bottom surface of the lid groove 7 corresponds to the outer surface 1b as shown in Fig. 6(b). A shoulder portion 4 is formed on the outer surface 1b. The shoulder portion 4 is formed along the side edge of the concave groove (internal space 3) and protruding from the surface (outer surface 1b) of the lid groove 7 as shown in Figs. 6(a) and (b). The bottom surface of the concave groove corresponds to the first defined surface 1d.

[0069] The two lid parts 2 each have a shape that can be fitted into the lid groove 7 as a whole, as shown in FIG. 6(c). The lid part 2 has a bottomed groove 6 on the contact surface 2b. The contact surface 2b refers to the surface of the lid part 2 that contacts the main body part 1 when the lid part 2 is fitted into the lid groove 7. The bottomed groove 6 has a shape that can receive the shoulder part 4. The bottomed groove 6 is preferably formed so that no gap is generated when the shoulder part 4 is received.

[0070] Next, in the assembly process, as shown in FIG. 6(d), each lid part 2 is placed on the main body part 1 so as to be respectively fitted into the lid groove 7 of the main body part 1. A plurality (two) of internal spaces 3 are defined by one main body part 1 and two lid parts 2. One internal space 3 is defined for each lid part 2. The numerical relationship among the main body part 1, the lid part 2, and the internal space 3 is not limited to these examples and can be set as appropriate. As a result, an upper part 8 in which the shoulder part 4 and the bottomed groove 6 overlap in the vertical direction X is formed between the main body part 1 and the lid part 2. The upper part 8 exists at a position shallower than the discontinuous part 3c in the vertical direction X.

[0071] Next, in the joining process, as shown in FIG. 6(e), friction stir joining is performed on the upper part 8, thereby forming a joined part 3f. The friction stir joining reaches the upper part 8 but does not reach the discontinuous part 3c.

[0072] Through the above steps, a metal structure 10 having two internal spaces 3 is manufactured.

[0073] According to the present embodiment, a plurality of internal spaces that are independent of each other and closely arranged can be formed in the metal structure, and a wide degree of design freedom can be ensured. Further, according to the present embodiment, even when a plate-like body with a large thickness is adopted as the lid part 2, a wide degree of design freedom can be ensured. This point will be described with reference to FIGS. 7(a) and 7(b).

[0074] In FIGS. 7(a) and (b), the thickness OD of the lid part 2 is large. Specifically, the thickness OD is larger than the thickness T of the main body part 1.

[0075] FIG. 7(a) is a cross-sectional view schematically showing a main body portion 1 and a lid portion 2 during joining of a conventional metal structure. The depth at which the tip 5a of the tool 5 is inserted, i.e., the joining depth, is set such that the friction stir joining depth WD satisfies WD ≧ the depth OD. Since the tip 5a of the tool 5 is inserted deeply, there is a risk of large deformation occurring in the lid portion 2. Also, in order to suppress or prevent a decrease in the airtightness of the internal space 3 due to such deformation, it is necessary to ensure a wide distance GD between the tip 5a of the tool 5 and the internal space 3 in the horizontal direction.

[0076] FIG. 7(b) is a cross-sectional view schematically showing a main body portion and a lid portion during joining according to the embodiment. The joining depth is set such that the friction stir joining depth WD satisfies the depth SD ≦ WD < the depth OD. Since the tip 5a of the tool 5 is not inserted deeply, the risk of large deformation occurring in the lid portion 2 can be reduced or prevented. As a result, the distance GD can be set narrow. Along with the design freedom of the internal space, the design freedom regarding the thickness of the metal member can also be widely ensured.

[0077] Next, the shape of the non-joined portion will be described with reference to FIGS. 8(a) to (d).

[0078] FIG. 8(a) is an explanatory view of a method for manufacturing a conventional metal structure. FIG. 8(b) is an explanatory view of a conventional metal structure. As shown in FIG. 8(a), in the assembly 110a, the contact surface between the main body portion 101 and the lid portion 102 is flat. The tip 105a of the tool 105 is inserted into the lid portion 102 and reaches the main body portion 101. After joining, as shown in FIG. 8(b), the discontinuous portion 103c, the inner non-joined portion 103d, the joined portion 103f, and the outer non-joined portion 103h are located at the same height.

[0079] FIG. 8(c) is an explanatory diagram of a method for manufacturing a metal structure according to an embodiment. FIG. 8(d) is an explanatory diagram of the metal structure according to the embodiment. As shown in FIG. 8(c), in the assembly 10a, the main body portion 1 has a shoulder portion 4. The lid portion 2 has a bottomed groove 6 for receiving the shoulder portion 4. Therefore, the upper portion 8 where the shoulder portion 4 and the bottomed groove 6 overlap in the vertical direction is located at a position higher than the non - continuous portion 3c in the vertical direction X. After joining, as shown in FIG. 8(d), the inner non - joined portion 3d and the outer non - joined portion 3h have portions extending in the vertical direction. As a result, the joined portion 3f is located at a position higher than the non - continuous portion 3c. As a result, the horizontal distance between the joined portion 3f and the internal space 3 in FIG. 8(d) is shorter than the horizontal distance between the joined portion 103f and the internal space 103 in FIG. 8(b).

[0080] FIG. 9 is a cross - sectional view schematically showing a metal structure 10 according to another embodiment. The metal structure 10 shown in FIG. 9 has a plurality of internal spaces 3. The main body portion 1 has a plurality of shoulder portions 4. The shoulder portions 4 are configured to separate adjacent internal spaces 3. The lid portion 2 has a plurality of bottomed grooves 6. Each bottomed groove 6 is configured to receive a shoulder portion 4.

[0081] In the metal structure 10 shown in FIG. 9, with reference to the central internal space 3, in order from the non - continuous portion 3c in the upper right, the inner non - joined portion 3d, the joined portion 3f, and the outer non - joined portion 3h are continuous. The outer non - joined portion 3h communicates with the non - continuous portion 3c located in the upper left of the right internal space 3. Here, the outer non - joined portion 3h does not communicate with the central internal space 3.

[0082] On the other hand, when referring to the right internal space 3, in order from the non - continuous portion 3c in the upper left, the inner non - joined portion 3d, the joined portion 3f, and the outer non - joined portion 3h are continuous. The outer non - joined portion 3h communicates with the non - continuous portion 3c located in the upper right of the central internal space 3. Here, the outer non - joined portion 3h does not communicate with the right internal space 3.

[0083] Thus, the outer non-joint portion 3h when viewed with respect to one internal space 3 may correspond to the inner non-joint portion 3d when viewed with respect to an adjacent internal space 3.

[0084] The metal structure 10 shown in FIG. 9 is configured to separate adjacent internal spaces 3 only by the shoulders 4. Thereby, the metal structure 10 can have a plurality of internal spaces 3 arranged more densely. A higher degree of design freedom can be achieved.

[0085] FIG. 10 is a cross-sectional view schematically showing a method of manufacturing the metal structure 10 according to another embodiment. In the assembly 10a shown in FIG. 10, the upper portion 8 is located at a position higher than the non-continuous portion 3c in the vertical direction X. The upper portion 8 is a portion where the main body portion 1 and the lid portion 2 overlap in the vertical direction. Inside the upper portion 8, the non-joint portion 3n extends downward and communicates with the internal space 3 through the non-continuous portion 3c. On the other hand, outside the upper portion 8, the non-joint portion 3n extends upward and communicates with the outside of the assembly 3c. Thus, the upper portion 8 forms a step.

[0086] In the example shown in FIG. 10, friction stir welding is performed by inserting the tip 5a of the tool 5 into the non-joint portion 3n extending upward together with the upper portion 8. Therefore, in the example shown in FIG. 10, no outer non-joint portion is generated. Thus, the outer non-joint portion does not necessarily have to be generated. By performing friction stir welding on the stepped upper portion 8, the airtightness can be improved. Further, when there is a non-joint portion extending upward as shown in FIG. 10, the airtightness can be further improved by performing friction stir welding so as to leave at least the non-joint portion as an outer non-joint portion.

[0087] Also, the numerical values, materials, structures, shapes, etc. given in the above-described embodiments and examples are merely examples, and different numerical values, materials, structures, shapes, etc. may be used as necessary.

Explanation of Reference Numerals

[0088] 1 Body part 1a Metal part 1b Outer surface 1d First drawn surface 2 Cover part 2a Metal part 2b Contact surface 2c Upper surface 2d Second drawn surface 3 Internal space (recess) 3a Through hole 3b Metal wall part 3c Discontinuous part 3d Inner non - joint part 3e One end (of the inner non - joint part) 3f Joint part 3g One end (of the outer non - joint part) 3h Outer non - joint part 3n Non - joint part 4 Shoulder 5 Tool 5a Tip part 6 Bottomed groove 7 Cover groove 10 Metal structure 10a Assembly

Claims

1. A metal structure, The metal structure is a plate-like body and includes a plate-like main body portion and a plate-like lid portion that are stacked vertically on each other, The plate-shaped body portion has an outer surface of the plate-shaped body portion, a shoulder portion protruding from the outer surface, and a first defining surface, The plate-shaped cover portion has a contact surface that contacts the outer surface, a bottomed groove formed to receive the shoulder portion, and a second defining surface, The metal structure is an internal space defined by the first boundary surface and the second boundary surface within the metal structure; a discontinuous portion in which the plate-shaped main body portion and the plate-shaped lid portion are in contact with or close to each other without being joined to each other at a position exposed to the internal space, and which is formed so as to surround the internal space when viewed in the vertical direction; an inner non-joined portion formed at an inner position communicating with the internal space via the discontinuous portion, the inner non-joined portion being configured such that the plate-shaped main body portion and the plate-shaped lid portion have a boundary by being in contact or close to each other without being joined at a position inside the metal structure that is not exposed to the internal space; a joining portion that closes one end of the inner non-joined portion at a position that is not exposed to the internal space inside the metal structure so that the boundary between the plate-shaped main body portion and the plate-shaped cover portion is indistinguishable or difficult to distinguish; having The joint is When viewed in the vertical direction, the shoulder protruding from the outer surface of the plate-shaped main body and the bottomed groove of the plate-shaped lid are formed in an upper portion where they overlap in the vertical direction so as to surround the internal space, and are located in one or substantially one plane at a depth that does not reach either the depth of the discontinuous portion or the depth of the internal space, so that the inner non-joint portion has a portion that extends in the vertical direction such that the joint portion is located at a position higher than the discontinuous portion in the vertical direction. A metal structure comprising:

2. The metal structure according to claim 1 , The metal structure further comprises: The plate-shaped main body and the plate-shaped lid are configured to have a boundary by being in contact or close to each other without being joined at a position not exposed to the internal space inside the metal structure, and have an outer non-joined portion located at an outer position not communicating with the internal space and one end of which is closed by the joint portion. A metal structure comprising:

3. The metal structure according to claim 1 , The first defining surface and the second defining surface are the first demarcated surface is concave and the second demarcated surface is flat; the first boundary surface is flat and the second boundary surface is recessed; or Both the first and second defining surfaces have a recess. A metal structure comprising:

4. The metal structure according to claim 1 or 2, The metal structure is a heat transfer metal structure that is placed in contact with or in close proximity to an object to be heat exchanged, heated, or cooled. A metal structure comprising:

5. The metal structure according to claim 1 or 2, The metal structure is a hollow metal structure used in a state where the internal space is hollow. A metal structure comprising:

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