Friction stir welding method, friction stir welding joining tool, and method for manufacturing friction stir welded joints

Abstract

To provide a friction stir welding method which enables acquisition of a friction stir welded junction having high junction strength between a first member formed of metal material and a second member formed of material different from the material of the first member.SOLUTION: A friction stir welding method comprises: an overlapping step of arranging a second member in a space between a lower aluminum plate (a first member) 11 formed of metal material and an upper aluminum plate (a joining assist member) 13 formed of material same as the material of the first member in such a manner that a through-hole 16 of a steel plate (the second member) 12 formed of material different from the material of the first member is covered; and a friction stir welding step of pushing at least either of the first member and the joining assist member into the through-hole 16 using a joining tool 18 to form a friction stir welded portion 15 between the first member and the joining assist member. In the joining tool 18, a space between a distal end surface 18e of a shoulder portion 18a and a side surface 18d of a joining pin 18b and a space between the side surface 18d of the joining pin 18b and a distal end surface 18c of the joining pin 18b are rounded.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present invention relates to a friction stir welding method, a joining tool for friction stir welding, and a friction stir welded joint.

Background Art

[0002] The weight reduction of transportation machines such as automobiles and trains is an eternal need expected to improve fuel efficiency, the accompanying CO2 reduction effect, and the steering performance. As one of the means to achieve this, material substitution that replaces a part of steel with lightweight materials such as aluminum alloys and CFRP (Carbon Fiber Reinforced Plastics) can be cited. However, so-called dissimilar material joining is required at the boundary between members. The dissimilar material joining methods are roughly classified into the fields of (1) welding systems, (2) mechanical fastening, and (3) adhesion. In the case of welding, for example, when iron and aluminum melt and mix, it is difficult to obtain high strength because brittle intermetallic compounds are generated. Therefore, mechanical fastening and adhesion are often used.

[0003] However, adhesion has large anisotropy in strength and characteristics of deterioration over time. Therefore, it lacks reliability for application to parts that require high strength. For this reason, adhesion is not used alone and is generally used as a combined measure. Mechanical fastening has high reliability and has many actual achievements as a dissimilar material joining method. Specifically, many use steel consumable members (rivets) such as bolts and nuts, SPR (Self-Piercing Rivet), FDS (Flow Drill Screw), and blind rivets.

[0004] However, due to various disadvantages such as (a) the high cost of consumables, (b) the need to drill through holes in some cases, (c) poor work efficiency in some cases, (d) the inability to apply when one of the materials to be joined is a hollow member, and (e) the inability to join linearly, limiting it to point joining, it has not been able to satisfy all needs. Therefore, there is still a strong desire for the emergence of a dissimilar material joining method that (I) has few limitations in terms of shape and material application, (II) is inexpensive, (III) is highly efficient, (IV) allows for linear joining, and (V) provides high strength and high reliability.

[0005] Friction stir welding (FSW) is known as a candidate that satisfies a relatively large number of the above conditions (I) to (V). This joining method involves rotating a stirring pin made of a high-strength material such as steel and pressing it into the joint of a soft material such as aluminum, thereby causing a portion of the base materials to be joined to plastically flow and eliminating the interface, thus joining them. Because this joining method is suitable for soft base materials, it has been used industrially for joining aluminum materials together, but recently, with the development of high-strength stirring pins, it has become possible to use it for joining steel materials together as well. Furthermore, recently, friction stir welding has attracted attention not only for joining metals of the same type, but also for joining dissimilar metals such as aluminum and iron, or between metals and non-metals such as metals and resins.

[0006] FSW (Friction Stir Spot Welding) can be broadly classified into two types: one that uses a rotating stirring pin to move in a planar direction to form a linear joint, and another that uses a rotating stirring pin to move only in the vertical direction to form a point-like joint (generally referred to more narrowly as FSJ (Friction Spot Joining) or FSSW (Friction Stir Spot Welding)). The former typically uses large gantry-type equipment, while the latter typically uses equipment equipped with articulated robots, resulting in significantly different forms of practical equipment.

[0007] It has been reported that dissimilar material joining of aluminum and steel is possible by selecting optimal conditions using these FSW devices. For example, Patent Document 1 describes a friction stir welding method in which a steel material having a through hole is sandwiched and stacked between a first workpiece and a second workpiece made of aluminum, and the material of the second workpiece, which has undergone plastic flow by passing a stirring pin of a friction stir welding tool through the through hole, is joined to the inner wall of the through hole and integrally friction stir-welded with the material of the first workpiece.

[0008] Furthermore, Patent Document 2 proposes a dissimilar material joining method for joining a metal member to be joined and a resin member to be joined using a joining metal member. The dissimilar material joining method described in Patent Document 2 involves preparing a resin member to be joined having a through hole, a metal member to be joined, and a joining metal member, and stacking the metal member to be joined, the resin member to be joined, and the joining metal member so that the through hole is covered by the metal member to be joined and also covered by the joining metal member, and then pushing the joining metal member into the through hole with a rotating joining tool to friction stir weld it to the metal member to be joined. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 4473713 [Patent Document 2] Japanese Patent Publication No. 2019-171460 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] However, when using the joining methods described in Patent Documents 1 and 2, cracks may occur due to high stress concentration on the joining metal members, making it impossible to obtain sufficiently high joint strength.

[0011] The present invention has been made in view of the aforementioned problems, and its object is to provide a friction stir welding method that can obtain a friction stir joint with high bonding strength between a first member made of a metal material and a second member made of a different material from the first member, a friction stir welding joining tool used in the method, and a friction stir joint obtained by the method. [Means for solving the problem]

[0012] Therefore, the above objective of the present invention is achieved by the configuration of the friction stir welding method described below [1].

[0013] [1] A friction stir welding method for joining a first member made of a metal material and a second member made of a different material from the first member and having at least one through hole, using a joining auxiliary member made of the same material as the first member, A superimposing step in which the first member, the second member, and the joining auxiliary member are superimposed in the order such that the through hole of the second member is covered by the first member and the joining auxiliary member, The process includes a friction stir welding step in which a rotating joining tool is used to push at least one of the first member and the joining auxiliary member into the through hole, thereby forming a friction stir joint between the first member and the joining auxiliary member, The joining tool comprises a rotating shoulder portion and a joining pin formed coaxially with the shoulder portion on the tip surface of the shoulder portion, which rotates together with the shoulder portion. The area between the tip surface of the shoulder portion and the side surface of the connecting pin is rounded, A friction stir welding method wherein the space between the side surface of the joining pin and the tip surface of the joining pin is rounded (R-shaped).

[0014] Furthermore, the above objective of the present invention is achieved by the configuration of the following [2] relating to a joining tool for friction stir welding. [2] A friction stir welding tool used in the friction stir welding method described in [1], It has a rotating shoulder portion and a joining pin formed coaxially with the shoulder portion on the tip surface of the shoulder portion and rotating together with the shoulder portion. An R process is performed between the tip surface of the shoulder portion and the side surface of the joining pin, and An R process is performed between the side surface of the joining pin and the tip surface of the joining pin. A joining tool for friction stir welding.

[0015] Further, the above object of the present invention is achieved by the configuration of the following [3] related to a friction stir welded joint. [3] A friction stir welded joint manufactured by the friction stir welding method described in [1], The second member is sandwiched by the first member and the joining auxiliary member, and at least one of the first member and the joining auxiliary member is pushed into the through hole of the second member, so that a friction stir welded joint is formed between the first member and the joining auxiliary member. A friction stir welded joint having a portion.

Effects of the Invention

[0016] According to the friction stir welding method of the present invention, a second member made of a metal material different from that of the first member is sandwiched between the first member and the joining auxiliary member made of the same kind of metal material, and a friction stir welded joint is formed between the first member and the joining auxiliary member. By doing so, a joint portion with high joint strength can be obtained. Further, by the friction stir welding method, a friction stir welded joint having a joint portion with high joint strength can be manufactured.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a perspective view of a friction stir welded joint according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory view showing a friction stir welding method of the friction stir welded joint shown in FIG. 1. [Figure 3A] FIG. 3A is a cross-sectional view showing a joining process of the friction stir welded joint of FIG. 1. [Figure 3B] FIG. 3B is a schematic view showing a part of the joining tool shown in FIG. 3A enlarged. [Figure 3C] FIG. 3C is a cross-sectional view showing a state where friction stir welding is performed using a conventional joining tool. [Figure 4] FIG. 4 is a schematic configuration diagram of a friction stir welding apparatus capable of forming the friction stir welded joint of FIG. 1. [Figure 5A] FIG. 5A is a perspective view showing a friction stir welding method according to a second embodiment of the present invention. [Figure 5B] FIG. 5B is a cross-sectional view taken along line VB-VB of FIG. 5A. [Figure 6] FIG. 6 is a cross-sectional view showing a joining step of the friction stir welding method of FIG. 5A. [Figure 7] FIG. 7 is a perspective view of a friction stir welded joint according to a third embodiment of the present invention. [Figure 8] FIG. 8 is a perspective view showing a friction stir welding method of the friction stir welded joint shown in FIG. 7. [Figure 9] FIG. 9 is a cross-sectional view showing a joining step of the friction stir welded joint shown in FIG. 7. [Figure 10] FIG. 10 is a perspective view showing a friction stir welding method according to a fourth embodiment of the present invention. [Figure 11] FIG. 11 is a cross-sectional view showing a joining step of the friction stir welded joint shown in FIG. 10. [Figure 12] FIG. 12 is a perspective view showing a friction stir welding method according to a fifth embodiment of the present invention. [Figure 13] FIG. 13 is an explanatory diagram for explaining the relationship between the number of joints and the joint strength. [Figure 14] FIG. 14 is a perspective view of a friction stir welded joint according to a sixth embodiment of the present invention. [Figure 15A] FIG. 15A is a perspective view showing the friction stir welding method shown in FIG. 14. [Figure 15B] FIG. 15B is a cross-sectional view taken along line XVB-XVB of FIG. 15A. [Figure 16] FIG. 16 is a perspective view showing a friction stir welding method according to a seventh embodiment of the present invention. [Figure 17] FIG. 17 is a cross-sectional view showing a joining step of the friction stir welding method shown in FIG. 16. [Figure 18A] Figure 18A is a perspective view showing a friction stir welding method according to the eighth embodiment of the present invention. [Figure 18B] Figure 18B is a perspective view showing a friction stir welding method according to a modified example of the eighth embodiment. [Figure 19] Figure 19 is a perspective view of a friction stir-welded joint according to the ninth embodiment of the present invention. [Figure 20] Figure 20 is a perspective view showing the joining method of the friction stir weld joint shown in Figure 19. [Figure 21] Figure 21 is a cross-sectional view showing the joining process of the friction stir welded joint shown in Figure 19. [Figure 22] Figure 22 is a perspective view showing a friction stir welding method according to a 10th embodiment of the present invention. [Figure 23] Figure 23 is a cross-sectional view showing the joining process of the friction stir welding method shown in Figure 22. [Figure 24] Figure 24 is a perspective view showing a friction stir welding method according to an 11th embodiment of the present invention. [Figure 25] Figure 25 is a cross-sectional view showing the joining process of the friction stir welding method shown in Figure 24. [Figure 26] Figure 26 is a perspective view showing a friction stir welding method according to a 12th embodiment of the present invention. [Figure 27] Figure 27 is a cross-sectional view showing the joining process of the friction stir welding method shown in Figure 26. [Figure 28] Figure 28 is a perspective view showing a friction stir welding method according to the 13th embodiment of the present invention. [Figure 29] Figure 29 is a cross-sectional view showing the joining process of the friction stir welding method shown in Figure 28. [Figure 30] Figure 30 is an explanatory diagram illustrating the relationship between the number of joints and joint strength. [Figure 31] Figure 31 is a perspective view of a friction stir-welded joint according to the 14th embodiment of the present invention. [Figure 32] Figure 32 is a perspective view showing the friction stir welding method for the friction stir welded joint shown in Figure 31. [Figure 33]Figure 33 is a perspective view of a friction stir-welded joint according to the 15th embodiment of the present invention. [Figure 34] Figure 34 is a perspective view showing the friction stir welding method for the friction stir welded joint shown in Figure 33. [Figure 35] Figure 35 is a cross-sectional view showing the joining process of the friction stir welding method shown in Figure 34. [Figure 36] Figure 36 is a perspective view of a friction stir-welded joint according to the 16th embodiment of the present invention. [Figure 37] Figure 37 is a perspective view showing the joining method of the friction stir weld joint shown in Figure 36. [Figure 38] Figure 38 is a cross-sectional view showing the joining process of the friction stir welding method shown in Figure 37. [Figure 39A] Figure 39A is a perspective view of an extruded product according to a modified example of the 16th embodiment. [Figure 39B] Figure 39B is a perspective view of an extruded product according to another modification of the 16th embodiment. [Figure 40A] Figure 40A is a cross-sectional view showing the joining process of a friction stir-welded joint according to the 17th embodiment of the present invention. [Figure 40B] Figure 40B is a cross-sectional view showing an enlarged portion of the steel plate in Figure 40A. [Figure 40C] Figure 40C is a cross-sectional view showing another example of Figure 40B. [Figure 41A] Figure 41A is a perspective view showing the test method for the cross tensile test. [Figure 41B] Figure 41B is a cross-sectional view showing the test method for the cross tensile test. [Modes for carrying out the invention]

[0018] Hereinafter, each embodiment of the friction stir welding method according to the present invention will be described in detail with reference to the drawings. The friction stir welding method according to this embodiment is a joining method that forms a friction stir joint by sandwiching a second member made of a different material from the first member between a first member made of the same type of metal material and a joining auxiliary member, and forming a friction stir joint between the first member and the joining auxiliary member.

[0019] The first member and joining auxiliary member to be joined by the friction stir welding method according to this embodiment can be any metal of the same type to which friction stir welding can be applied. Examples include aluminum, aluminum alloys, magnesium, magnesium alloys, titanium, titanium alloys, copper, copper alloys, iron, and steel. Here, "same type" includes not only completely identical materials but also metallic materials that share a common main component. On the other hand, the second member, which is made of a different material from the first member, can be any metal, as well as resin materials such as polyethylene (PE), polypropylene (PP), ethylene-acrylic acid copolymer (EAA), polytetrafluoroethylene (PTFE), composites in which fibers are mixed with these resins, such as carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP), and non-metallic materials such as wood, rubber, and ceramics.

[0020] Furthermore, if at least one of the first member, second member, and joining auxiliary member is made of metal, various plating, painting, or other treatments may be applied to its surface. This is because the plating or coating is physically removed and discharged during the friction stir welding process, allowing for bonding on a fresh surface. In the case of metal-to-metal bonding, if at least one of the members is treated with an electrically insulating surface treatment, it is possible to prevent galvanic corrosion, which is a problem in dissimilar metal bonding. Additionally, an adhesive may be applied between the first member, second member, and joining auxiliary member prior to the friction stir welding process. The friction stir welding may be performed before or after the adhesive has solidified.

[0021] (First Embodiment) A friction stir welding method according to the first embodiment of the present invention will be described with reference to Figures 1 to 4.

[0022] As shown in Figure 1, the friction stir joint 10 according to this embodiment comprises a lower aluminum plate 11 which is a first member, a steel plate 12 which is a second member, and an upper aluminum plate 13 which is a joining auxiliary member. The friction stir joint 10 is joined by a plurality of friction stir joints 15 (six in the embodiment shown in Figure 1) which are friction stir-bonded in a point-like manner, with the steel plate 12 sandwiched between the upper aluminum plate 13 and the lower aluminum plate 11.

[0023] Here, friction stir welding is a method of joining metal materials by pressing a joining tool against them while rotating it, softening the metal material with frictional heat, causing it to undergo plastic flow, and joining the metal materials together. The friction stir welding method according to this embodiment will be further explained with reference to Figures 2, 3A, and 3B.

[0024] First, the lower aluminum plate 11, the steel plate 12, and the upper aluminum plate 13 are prepared. Multiple through holes 16 are pre-formed in the steel plate 12 at the planned joining locations by machining such as pressing. Next, the steel plate 12 is sandwiched between the lower aluminum plate 11 and the upper aluminum plate 13 so as to cover the through holes 16 in the steel plate 12, and then placed on top of the backing plate 17.

[0025] Then, the joining tool 18 is brought into contact with the upper aluminum plate 13 (left diagram in Figure 3A), and the joining tool 18 is rotated to soften the upper aluminum plate 13 through frictional heat, pushing it into the through hole 16 of the steel plate 12. Further frictional heat causes plastic flow of the upper aluminum plate 13 and a portion of the lower aluminum plate 11, integrating them to form a friction stir joint 15, and the upper aluminum plate 13 and the lower aluminum plate 11 are friction stir bonded in a point-like manner (center diagram in Figure 3A). Finally, the joining tool 18 is removed to complete the friction stir joint 10 (right diagram in Figure 3A).

[0026] Here, the joining tool 18 for friction stir welding used in this embodiment will be described with reference to Figure 3B. Figure 3B is a schematic diagram showing an enlarged view of a part (region A1) of the joining tool shown in Figure 3A. The joining tool 18 has a rotating shoulder portion 18a and a joining pin 18b fixed to the tip surface of the shoulder portion 18a, formed coaxially with the shoulder portion 18a, and rotating together with the shoulder portion 18a. In the following description, when it is not necessary to distinguish between the shoulder portion 18a and the joining pin 18b, they will simply be referred to as the joining tool 18. In this embodiment, the corner r1 between the tip surface 18e of the shoulder portion 18a and the side surface 18d of the joining pin 18b is curved. Also, the corner r2 between the tip surface 18c of the joining pin 18b and the side surface 18d of the joining pin 18b is curved.

[0027] Let's consider the case where a joining tool without corner and edge rounding is used. In this embodiment, unlike general friction stir welding with two base materials, the upper aluminum plate 13 is softened and pushed into the through hole 16 of the steel plate 12, reaching the lower aluminum plate 11. As a result, the local deformation rate of the upper aluminum plate 13 becomes large. Therefore, as shown in Figure 3C, if a joining tool 48 is used where the area between the shoulder portion 48a and the joining pin 48b, and the tip edge of the joining pin 48b are not rounded, and the upper member is made of a material with poor local ductility, cracks 49 will occur as the joining pin 48b is pushed in, unable to withstand the deformation rate. As a result, sufficient joint strength cannot be obtained. In contrast, in this embodiment, as shown in Figure 3B, the corner portion r1 and the edge portion r2 are rounded, so cracks can be prevented during the joining process by friction stir welding.

[0028] The radius of curvature R1 of the corner r1 is not particularly limited, but if it is 20% or more of the thickness of the upper aluminum plate, it is possible to suppress the occurrence of cracks in the upper aluminum plate 13, which is a joining auxiliary member, and the joint strength can be further increased. Also, if the radius of curvature R1 of the corner r1 is 200% or less of the thickness of the upper aluminum plate, a sound friction stir joint 15 can be formed. Therefore, it is preferable that the radius of curvature R1 of the corner r1 be 20% or more and 200% or less of the thickness of the upper aluminum plate, and more preferably 50% or more and 100% or less of the thickness of the upper aluminum plate.

[0029] The size R2 of the corner r2 is not particularly limited, but if it is 10% or more and 50% or less of the hole diameter provided in the steel plate, a sound friction stir joint 15 can be formed. Therefore, it is preferable that the size R2 of the corner r2 be 10% or more and 50% or less of the hole diameter provided in the steel plate, and more preferably 25% or more and 40% or less of the hole diameter provided in the steel plate.

[0030] In the joining tool 18 shown in Figure 3B, the tip surface 18c of the joining pin 18b has a curved shape that protrudes gently towards the tip, but the tip surface 18c of the joining pin 18b may also be flat.

[0031] In this embodiment, the above-described joining process is repeated sequentially to join the lower aluminum plate 11 and the upper aluminum plate 13 that sandwich the steel plate 12 at six locations. Although friction stir welding may be performed at only one location, it is preferable to join at multiple locations because if a strong force is applied, the lower aluminum plate 11, the steel plate 12, and the upper aluminum plate 13 may shift relative to each other.

[0032] As a result, the steel plate 12 is restrained in the direction along the plane of the steel plate 12 by the friction stir joint 15 formed in the through hole 16, and is also restrained in the thickness direction by being sandwiched between the lower aluminum plate 11 and the upper aluminum plate 13.

[0033] Furthermore, it is preferable to use a 7000 series aluminum alloy for the lower aluminum plate 11 and the upper aluminum plate 13 from the viewpoint of ensuring strength. In addition, it is preferable that the diameter of the through hole 16 in the steel plate 12 be larger than the diameter of the joining pin 18b plus twice the thickness of the upper aluminum plate, and smaller than the diameter of the shoulder portion 18a. This ensures that the joining pin 18b can reliably push the softened upper aluminum plate 13 into the through hole 16. Also, when the upper aluminum plate 13 is pushed in by the joining pin 18b, the upper aluminum plate 13 tends to lift up due to the reaction force. However, by making the diameter of the shoulder portion 18a larger than the diameter of the through hole 16, it is possible to prevent the upper aluminum plate 13 from lifting up.

[0034] Furthermore, since the lower aluminum plate 11 and the upper aluminum plate 13 are made of the same aluminum material, no intermetallic compounds are formed at the joint interface, and the interface can be reliably eliminated by plastic flow, thereby improving the joint strength of the friction stir joint 15. In addition, compared to mechanical fastening methods using joining members such as rivets and bolts, the mass of the joining members can be reduced, resulting in a lighter construction.

[0035] When forming the friction stir joint 15 in a point-like manner, instead of the combination of the joining tool 18 and backing plate 17 described above, a friction stir welding apparatus 40 as shown in Figure 4 can also be used. This friction stir welding apparatus 40 comprises a frame 42 having a roughly C-shape in plan view, a pressing motor 43 provided at one end of the frame 42, a rotating motor (not shown), a joining pin 41 provided at the tip of the rotating shaft of the rotating motor, and a support base 44 provided at the end of the frame 42 facing the pressing motor 43.

[0036] Then, the joining pin 41 is rotated by the rotary motor and lowered by the pressing motor 43, contacting the upper aluminum plate 13 placed on the support base 44. The frictional heat softens the upper aluminum plate 13, causing it to be frictionally stir-bonded to the lower aluminum plate 11. As a result, the upper aluminum plate 13 and the lower aluminum plate 11 are joined at points at the frictionally stir-bonded joint 15. The support base 44 has strong rigidity so as not to deform under the pressing force of the pressing motor 43 during frictionally stir-bonding.

[0037] (Second Embodiment) A friction stir welding method according to a second embodiment of the present invention will be described with reference to Figures 5A, 5B, and 6. Note that parts identical to those in the first embodiment are denoted by the same or equivalent reference numerals, and their descriptions are simplified or omitted; the same applies to subsequent embodiments.

[0038] In this embodiment, the upper aluminum plate 13 has a protrusion 13a formed on it that corresponds to the through hole 16 of the steel plate 12 and can be fitted into the through hole 16. The lower aluminum plate 11, the steel plate 12, and the upper aluminum plate 13 are then placed on the backing plate 17 in this order. At that time, the protrusion 13a of the upper aluminum plate 13 is fitted into the through hole 16 of the steel plate 12 and stacked. By forming the protrusion 13a on the upper aluminum plate 13 in advance by press working or the like, the amount of deformation of the upper aluminum plate 13 during joining can be reduced, making the upper aluminum plate 13 less likely to break, and the joining position can be visually confirmed from the outside, improving work efficiency.

[0039] Then, as shown in Figure 6, the rotating joining tool 18 is brought into contact with the protrusion 13a, and the protrusion 13a, which has softened due to frictional heat with the upper aluminum plate 13, is pushed into the through hole 16 to form a friction stir joint 15, thereby frictionally stirring the upper aluminum plate 13 and the lower aluminum plate 11 in a point-like manner.

[0040] Note that the height H of the convex portion 13a should be slightly lower than the thickness t of the steel plate 12. Thereby, when the convex portion 13a is fitted into the through hole 16 of the steel plate 12, a slight gap is formed between the tip of the convex portion 13a and the upper surface of the lower aluminum plate 11. Therefore, when the rotating joining tool 18 is abutted against the convex portion 13a and pushed in, the upper aluminum plate 13 and the steel plate 12 are surely in close contact, so that the upper aluminum plate 13, the steel plate 12, and the lower aluminum plate 11 are joined in a state of being in close contact without a gap. For other parts other than the above-described content, since they are the same as those of the friction stir joint 10 of the first embodiment, the description thereof is omitted.

[0041] (Third Embodiment) The friction stir joint of the third embodiment of the present invention will be described with reference to FIGS. 7 to 9.

[0042] The first member of the present embodiment is different from those of the first and second embodiments in that it is made of an aluminum hollow material having a closed cross-section, for example, an extruded product 20 having a cross-sectional shape formed like a Chinese character "Ri". The extruded product 20 has an outer surface having a top surface 20a on which the steel plate 12 is overlapped, and an inner surface which is the surface opposite to the outer surface, and a void portion 20b surrounded by the inner surface is formed.

[0043] Also, the steel plate 12 and the upper aluminum plate 13 are provided with through holes 16 and convex portions 13a, respectively, in the same manner as in the second embodiment. Note that the void portion 20b of the extruded product 20 may be a void portion having an open cross-section such as a C-shape.

[0044] Then, the steel plate 12 and the upper aluminum plate 13 with the convex portion 13a fitted into the through hole 16 are overlapped and laminated on the top surface 20a of the extruded product 20, and by abutting the convex portion 13a while rotating the joining tool 18, the convex portion 13a is softened by frictional heat and pushed into the through hole 16, and a friction stir joint portion 15 is formed between the upper aluminum plate 13 and the top surface 20a of the extruded product 20, and friction stir joining is performed in a dot shape.

[0045] Furthermore, the top surface 20a of the extruded product 20 must have sufficient rigidity to prevent deformation by the pressing force of the joining tool 18. If the thickness of the top surface 20a is thin, there is a risk that frictional heat will be insufficient and the joining will be inadequate. Also, as shown in Figure 7, if the first member is an extruded product 20 and the lower part of the top surface 20a is not open to the outside (i.e., a closed space), the friction stir welding apparatus 40 shown in Figure 4 is difficult to use, and friction stir welding is performed using a combination of the joining tool 18 and the backing plate 17. Other aspects not covered above are the same as those of the friction stir joint 10 in the first and second embodiments, so their explanation will be omitted.

[0046] (Fourth Embodiment) A friction stir welding method according to a fourth embodiment of the present invention will be described with reference to Figures 10 and 11.

[0047] The configuration of the upper aluminum plate 13, the steel plate 12, and the aluminum extruded product 20 in this embodiment is the same as in the third embodiment, but it differs from the third embodiment in that a backing plate 17 is inserted into the void portion 20b of the extruded product 20 during friction stir welding.

[0048] The thickness of the backing plate 17 is approximately the same as the height of the void 20b, and it is preferable that the backing plate 17 is inserted so that there is virtually no gap in the void 20b, and especially no gap in the vertical direction. This allows the backing plate 17 to support the pressing force from the joining tool 18, preventing deformation of the top surface 20a and ensuring the frictional heat necessary for friction stir welding. After friction stir welding, the backing plate 17 is removed from the void 20b. Other aspects not covered above are the same as those of the friction stir joint 10 in the first to third embodiments, and therefore will not be explained.

[0049] (Fifth embodiment) A fifth embodiment of the present invention, a friction stir welding method, will be described with reference to Figure 12.

[0050] In the friction stir welding method of this embodiment, the thickness of the backing plate 17 inserted into the void 20b of the extruded product 20 is smaller than the vertical dimension of the void 20b. Below the backing plate 17 inserted into the void 20b, a tube 21 is positioned. The tube 21 is an inflatable non-metallic tube such as rubber or cloth. During welding, a pressurized fluid such as water, air, or oil is supplied into the tube 21 to inflate it, pushing up the backing plate 17 and causing the backing plate 17 to come into close contact with the inner surface of the top surface 20a of the extruded product 20 without any gaps, thereby increasing the rigidity of the top surface 20a.

[0051] This prevents deformation of the top surface 20a due to the pressing force of the joining tool 18, and ensures friction between the upper aluminum plate 13 and the joining tool 18. The thickness of the backing plate 17 only needs to be rigid enough not to deform due to the pressing force of the joining tool 18, and a thinner plate is preferable as it is easier to handle.

[0052] In the friction stir welding method of this embodiment, the backing plate 17 is pushed up by the expanding tube 21 and comes into contact with the inner surface of the top surface 20a, thereby improving the adhesion between the backing plate 17 and the top surface 20a. Furthermore, compared to the case where the tube 21 is not used, the backing plate 17 can be made thinner and lighter, making it easier to install the backing plate 17 in the gap 20b.

[0053] After joining the upper aluminum plate 13 and the extruded product 20, the backing plate 17 can be easily pulled out of the gap 20b by discharging the pressurized fluid from the tube 21, improving work efficiency. Furthermore, the deformation of the tube 21 allows it to easily accommodate even complex shapes in the gap 20b. Other aspects not mentioned above are the same as those of the friction stir joint 10 in the first to fourth embodiments, so their explanation will be omitted.

[0054] Incidentally, as shown in Figures 13(a) to 13(d), when the lower aluminum plate 11 and the upper aluminum plate 13 are friction stir welded in a point manner, there may be only one joint (see Figure 13(a)), but the steel plate 12, the upper aluminum plate 13, and the lower aluminum plate 11 may rotate relative to each other around the joint. Therefore, in order to improve the joint strength of the upper aluminum plate 13, the steel plate 12, and the lower aluminum plate 11, it is preferable to provide multiple joints in at least one of the X direction or the Y direction (see Figures 13(b) and 13(c)). Furthermore, it is even more preferable to provide multiple joints in both the X direction and the Y direction (see Figure 13(d)).

[0055] When forming multiple friction stir joints 15, they may be friction stir joined one by one in sequence, but they can also be formed simultaneously. This not only shortens the joining time but also prevents deformation and wrinkling of the upper aluminum plate 13 and the lower aluminum plate 11.

[0056] (Sixth Embodiment) A friction stir welding method according to a sixth embodiment of the present invention will be described with reference to Figures 14, 15A, and 15B.

[0057] In this embodiment, the steel plate 12 and upper aluminum plate 13 of the friction stir joint 10 are provided with linear groove-shaped through holes 22 and a protruding ridge portion 23 in the figure, instead of the through holes 16 and protrusions 13a provided in the steel plate 12 and upper aluminum plate 13 of the third embodiment (see Figure 8).

[0058] Specifically, the steel plate 12 has multiple groove-shaped through holes 22 pre-formed through it by machining such as pressing at the planned joining locations, and the upper aluminum plate 13 has multiple protrusions 23 that can be fitted into the groove-shaped through holes 22. The groove-shaped through holes 22 of the steel plate 12 shown in Figure 15A consist of four L-shaped holes 22a arranged in a rectangular shape facing each other, and a straight hole 22b located in the center of the rectangle. The protrusions 23 of the upper aluminum plate 13 consist of four L-shaped protrusions 23a and a straight protrusion 23b, which are formed to be similar in shape to the L-shaped holes 22a and straight hole 22b of the steel plate 12, respectively, and can be fitted into the L-shaped holes 22a and straight hole 22b of the steel plate 12, respectively.

[0059] Then, on the top surface 20a of the aluminum extruded product 20, which has a cross-sectional shape resembling the Japanese character for "sun," a steel plate 12 with a protruding portion 23 fitted into a groove-shaped through hole 22 and an upper aluminum plate 13 are stacked in order. A backing plate 17 and a tube 21 are placed in the gap 20b formed below the top surface 20a, and the joining tool 18 is rotated and moved linearly along the protruding portion 23 to push the upper aluminum plate 13 into the groove-shaped through hole 22. The protruding portion 23 of the upper aluminum plate 13 and the top surface 20a of the extruded product 20 are then joined by friction stir bonding by frictional heat.

[0060] Linear movement of the joining tool 18 along the shape of the pier section 23 can be achieved by mounting the joining tool 18 on a linear coordinate robot or an articulated robot. As a result, the steel plate 12 is sandwiched between the upper aluminum plate 13 and the top surface 20a of the extruded product 20, restricting relative movement in the vertical and horizontal directions.

[0061] The groove-shaped through-holes 22 in the steel plate 12 can be formed by press punching or laser cutting, and the protruding portion 23 of the upper aluminum plate 13 can be formed by press working. Furthermore, the upper aluminum plate 13 does not necessarily need to have the protruding portion 23, and may be a flat plate without the protruding portion 23. In addition, the first member can be the lower aluminum plate 11 instead of the extruded product 20. Other aspects not mentioned above are the same as those of the friction stir joint 10 in the first to fifth embodiments, so their explanation will be omitted.

[0062] (Seventh Embodiment) A friction stir welding method according to a seventh embodiment of the present invention will be described with reference to Figures 16 and 17.

[0063] The steel plate 12 of this embodiment has a substantially rectangular cutout hole 25 as a through hole. The cutout hole 25 has an area that allows for the formation of a friction stir joint 15, which will be described later, and a non-joint space 27 formed between the friction stir joint 15. The upper aluminum plate 13 has a loop-shaped rectangular frame-shaped protrusion 28 that can be fitted into the cutout hole 25. That is, the cutout hole 25 has an area larger than the area partitioned by the frame-shaped protrusion 28.

[0064] When the upper aluminum plate 13 is stacked on top of the steel plate 12 and laminated onto the top surface 20a of the extruded product 20, the lower surface of the frame-shaped protrusion 28 and the upper surface of the top surface 20a face each other with a small gap in between. In addition, the inner rectangular area enclosed by the frame-shaped protrusion 28 is spaced apart from the top surface 20a, forming a space 27.

[0065] The joining tool 18 rotates along the shape of the frame-shaped protrusion 28, connecting its starting point SP and ending point EP in a linear fashion, softening the upper aluminum plate 13 with frictional heat and pressing it in. Furthermore, the frame-shaped protrusion 28 of the upper aluminum plate 13 and the top surface 20a of the extruded product 20 are softened with frictional heat and friction stir bonded, forming a roughly rectangular frame-shaped friction stir bonded portion 15 as shown in the upper diagram of Figure 17.

[0066] Furthermore, as shown in the lower diagram of Figure 17, the rotating joining tool 18 may move linearly while pressing within the rectangular area inside the frame-shaped protrusion 28 to friction stir bond the upper aluminum plate 13 to the top surface 20a, thereby forming a linear friction stir bond 15. As a result, within the rectangular area inside the frame-shaped protrusion 28, a friction stir bond 15 and a non-jointed space 27 surrounded by the friction stir bond 15 are formed.

[0067] The space 27 enclosed by the friction stir joint 15 can be formed airtight or watertight and connected to an inlet and outlet of a fluid (not shown), allowing the space 27 to be used as a fluid channel. For example, by circulating a cooling medium through the space 27, a heat transfer function can be added to the upper aluminum plate 13, which can be used, for example, to cool a battery mounted in an automobile. The movement trajectory of the joining tool 18 inside the frame-shaped protrusion 28, i.e., the shape of the linear friction stir joint 15, can be formed into any shape, such as multiple linear friction stir joints 15, a single spiral friction stir joint 15, or a zigzag friction stir joint 15. Therefore, the shape of the space 27 as a channel is also arbitrary. Other aspects not mentioned above are the same as those of the friction stir joint 10 in the first to sixth embodiments, so their explanation will be omitted.

[0068] (Eighth embodiment) An eighth embodiment of the present invention, a friction stir welding method, will be described with reference to Figure 18A.

[0069] In this embodiment, the friction stir-welded joint 10 has an upper aluminum plate 13 and the top surface 20a of the aluminum extruded product 20 connected at a connecting portion 29 on one side of each, forming a U-shaped cross-section integrally. That is, a space S into which a steel plate 12 can be inserted is formed between the upper aluminum plate 13 and the top surface 20a. Such a shape can be easily formed, for example, by extruding aluminum. Then, the steel plate 12, which has a through hole 16 formed therein, is inserted into the space S between the upper aluminum plate 13 and the top surface 20a, and a rotating joining tool 18 is pressed against the upper aluminum plate 13, softening the upper aluminum plate 13 and the top surface 20a by frictional heat to perform friction stir welding. Note that the friction stir welding method according to this embodiment can also be similarly applied to cases where the aluminum extruded product 20 is replaced by a lower aluminum plate 11, as shown in Figure 18B. Other aspects not covered above are the same as those of the friction stir joint 10 in the first to seventh embodiments, and therefore will not be explained.

[0070] (Ninth Embodiment) A friction stir welding method according to the ninth embodiment of the present invention will be described with reference to Figures 19 to 21.

[0071] In this embodiment, the friction stir-welded joint 10 has the materials of the first member, second member, and joining auxiliary member reversed compared to the first embodiment. Specifically, the first member is an upper steel plate 31 made of steel, the second member is an aluminum plate 32 made of aluminum, and the joining auxiliary member is a lower steel plate 33 made of the same material as the first member. In other words, in this embodiment, the friction stir-welded joint 10 is formed by sandwiching the aluminum plate 32 between the upper steel plate 31 and the lower steel plate 33, and friction stir-welding the upper steel plate 31 and the lower steel plate 33. Furthermore, the materials of the first member, second member, and joining auxiliary member described above are the same in the 10th to 16th embodiments (including modified examples) described below.

[0072] The aluminum plate 32 has multiple through holes 16. The lower steel plate 33, the aluminum plate 32, and the upper steel plate 31 are then stacked and placed on the backing plate 17 in that order. The rotating joining tool 18 is brought into contact with the upper steel plate 31, and the frictional heat generated by the upper steel plate 31 softens the upper steel plate 31, pushing it into the through holes 16, thereby joining the upper steel plate 31 and the lower steel plate 33 in a point manner at the friction stir joint 15. Other parts not covered above are the same as those of the friction stir joint 10 of the first embodiment, so their explanation will be omitted.

[0073] (Tenth embodiment) A friction stir welding method according to the tenth embodiment of the present invention will be described with reference to Figures 22 and 23.

[0074] The upper steel plate 31 of the present embodiment has a convex portion 31a that can be fitted into the through hole 16 formed by press working or the like corresponding to the through hole 16 of the aluminum plate 32. By forming the convex portion 31a on the upper steel plate 31, the amount of deformation of the upper steel plate 31 during friction stir welding is reduced and it is difficult to break. In addition, the joining position can be visually confirmed from the outside, improving workability. Regarding other parts other than the above-described content, since they are the same as the friction stir welding joint 10 of the second embodiment of the present invention, the description is omitted.

[0075] (11th Embodiment) The friction stir welding method of the 11th embodiment of the present invention will be described with reference to FIGS. 24 and 25.

[0076] The second member of the present embodiment is an extruded product 20 made of aluminum having a cross-sectional shape formed like a Chinese character "ri", and a plurality of through holes 20c are formed in the top surface 20a. The top surface 20a functions in the same manner as the aluminum plate 32 in the 10th embodiment. That is, the lower steel plate 33 is inserted into the gap portion 20b of the extruded product 20, and the top surface 20a of the extruded product 20 is sandwiched between the upper steel plate 31 and the lower steel plate 33. Further, a backing metal 17 is inserted below the lower steel plate 33, and the rotating joining tool 18 is pressed against the upper steel plate 31 to friction stir weld the upper steel plate 31 and the lower steel plate 33 supported by the backing metal 17. According to the friction stir welding joint 10 of the present embodiment, since the lower steel plate 33 is inserted into the gap portion 20b of the extruded product 20 and becomes difficult to see, the appearance performance is improved. Regarding other parts other than the above-described content, since they are the same as the friction stir welding joint 10 of the fourth embodiment of the present invention, the description is omitted.

[0077] (12th Embodiment) The friction stir welding method of the 12th embodiment of the present invention will be described with reference to FIGS. 26 and 27.

[0078] First, the protrusion 31a of the upper steel plate 31 is fitted into the through hole 20c of the top surface 20a of the extruded product 20 and overlapped. Next, the lower steel plate 33 and the tube 21 (see Figure 26) are inserted in this order into the void 20b of the extruded product 20. Then, pressurized fluid is supplied into the tube 21 to inflate it and support the lower steel plate 33 from below. This allows the upper steel plate 31 and the lower steel plate 33 to be friction stir-bonded without using a backing plate 17. After bonding is complete, the pressurized fluid is discharged from the tube 21 to shrink it, allowing the tube 21 to be easily removed from the void 20b of the extruded product 20. Other parts not mentioned above are the same as those of the friction stir joint 10 of the fifth embodiment of the present invention, and therefore will not be described.

[0079] (13th Embodiment) A friction stir welding method according to the 13th embodiment of the present invention will be described with reference to Figures 28 and 29.

[0080] In this embodiment, the lower steel plate 33, backing plate 17, and tube 21 are inserted in this order into the void 20b of the extruded product 20. During friction stir welding, pressurized fluid is supplied into the tube 21 to raise the backing plate 17 until it contacts the inner surface of the top surface 20a of the extruded product 20, thereby supporting the top surface 20a. After the welding is complete, the pressurized fluid is discharged from the tube 21 and the backing plate 17 is lowered, allowing the backing plate 17 and tube 21 to be easily removed from the void 20b of the extruded product 20.

[0081] As shown in Figures 30(a) to 30(d), the joint strength of the upper steel plate 31, aluminum plate 32 (top surface 20a), and lower steel plate 33 improves with increasing number of joints; therefore, a larger number of joints is preferable. The number of joints should be determined according to the required joint strength and joint location for the friction stir joint 10. Other parts not mentioned above are the same as those of the friction stir joint 10 of the fifth embodiment of the present invention, and therefore will not be described.

[0082] (14th Embodiment) Next, the friction stir welding method of the 14th embodiment of the present invention will be described with reference to Figures 31 and 32.

[0083] In this embodiment, the friction stir-welded joint 10, formed by the friction stir welding method, sandwiches the top surface 20a of an aluminum extruded product 20 between an upper steel plate 31 and a lower steel plate 33, and the upper steel plate 31 and the lower steel plate 33 are friction stir-welded. The upper steel plate 31 and the top surface 20a are provided with a protrusion 23 and a groove-shaped through hole 22, respectively, similar to the upper aluminum plate 13 and steel plate 12 in the sixth embodiment (see Figure 15A). Furthermore, in this friction stir-welding method, only the tube 21 is inserted below the lower steel plate 33, which is inserted into the void 20b of the extruded product 20, and no backing plate 17 is used. Other parts not mentioned above are the same as those of the friction stir joint 10 of the sixth embodiment of the present invention, and therefore will not be described.

[0084] (15th Embodiment) A friction stir welding method according to the 15th embodiment of the present invention will be described with reference to Figures 33 to 35.

[0085] The extruded product 20 of this embodiment has a substantially rectangular cutout hole 25 on its top surface 20a. The upper steel plate 31 has a rectangular frame-shaped protrusion 28a that can be fitted into the cutout hole 25, and a pair of straight protrusions 28b extending from opposite sides of the frame-shaped protrusion 28a toward the other side.

[0086] The frame-shaped protrusion 28a of the upper steel plate 31 is fitted into the hollowed-out hole 25 of the extruded product 20, and the lower steel plate 33 and tube 21 are placed in the gap 20b below the top surface 20a. The tube 21 is inflated to sandwich the top surface 20a between the upper steel plate 31 and the lower steel plate 33. The joining tool 18 is then moved linearly along the frame-shaped protrusion 28a, connecting its starting point SP and ending point EP, and then linearly along the straight protrusion 28b to friction stir weld the upper steel plate 31 and the lower steel plate 33 in a linear manner. As a result, a space 27, which is a non-jointed area, is formed between the linear friction stir welded joint 15 formed along the frame-shaped protrusion 28a and the straight protrusion 28b. This space 27 can be used as a flow path for fluid, similar to the friction stir welded joint 10 of the seventh embodiment (see Figure 17). Other parts not mentioned above are the same as those of the friction stir joint 10 of the seventh embodiment of the present invention, and therefore will not be described.

[0087] (16th Embodiment) A friction stir welding method according to the 16th embodiment of the present invention will be described with reference to Figures 36 to 38.

[0088] In this embodiment, the extruded product 20 has a holding portion 26, capable of holding the lower steel plate 33, integrally molded with the top surface 20a within the void portion 20b. The holding portion 26 includes a flattened hollow portion 26a with a rectangular cross-section. The height of the flattened hollow portion 26a is slightly greater than the thickness of the lower steel plate 33, allowing the lower steel plate 33 to be inserted without any gaps.

[0089] Furthermore, by inserting the lower steel plate 33 into the flattened hollow section 26a, the top surface 20a is supported by the lower steel plate 33. Therefore, the upper steel plate 31 and the lower steel plate 33 can be friction stir-bonded with the joining tool 18 without the need to provide a backing plate 17 or tube 21 to support the top surface 20a. Other parts not mentioned above are the same as those of the friction stir joint 10 of the 11th embodiment of the present invention, and therefore will not be described.

[0090] Figure 39A is a perspective view of a modified extruded product 20 equipped with a holding portion 26, wherein the thickness of the top surface 20a is increased, and a flattened hollow portion 26a serving as the holding portion 26 is formed within the thickness of the top surface 20a.

[0091] Figure 39B is a perspective view of another modified extruded product 20 equipped with a holding portion 26, in which thick plate portions 20d are provided at both the left and right ends of the top surface 20a, and a pair of protrusions 20e extending from the lower surface of the thick plate portions 20d toward the opposing thick plate portions 20d are integrally molded. A pair of opposing L-shaped protrusions form a holding portion 26 that holds the lower steel plate 33.

[0092] Note that the extruded product 20 shown in Figures 39A and 39B is in its shape before the through-hole 20c (see Figure 37) is formed in the top surface 20a. If necessary, the through-hole 20c can be provided by machining or other means prior to friction stir welding.

[0093] (17th Embodiment) The friction stir welding method of the 17th embodiment of the present invention will be described with reference to Figures 40A to 40C, 41A, and 41B. The 17th embodiment is a modification of the first embodiment.

[0094] In this embodiment, the through hole 16 formed in the steel plate 12 is further processed. Specifically, the corner between the upper surface 12a of the steel plate 12, i.e., the surface facing the upper aluminum plate 13, and the inner wall surface 16a of the through hole 16 is chamfered to form a chamfered portion 16b. The shape of the chamfered portion 16b can be a C-chamfer, as shown in Figure 40B, in which the corner is removed at an angle of approximately 45° to the inner wall surface 16a of the through hole 16 and the upper surface 12a of the steel plate 12. Alternatively, as shown in Figure 40C, it can be a R-process, in which the corner is rounded by an arc of a predetermined radius. Methods for forming the chamfered portion 16b include forming the through hole 16 with a drill or end mill and then reaming the corner. Alternatively, the chamfered portion 16b can be formed after forming the through hole 16 by using a tapered end mill. Other parts not mentioned above are the same as those of the friction stir joint 10 of the first embodiment of the present invention, and therefore will not be described.

[0095] As described above, if a chamfered portion 16b is formed on the upper part of the inner wall surface 16a of the through hole 16, a sufficient thickness T can be secured in the region of the upper aluminum plate 13 above the chamfered portion 16b, as shown in the right-hand figure of Figure 40A. The strength of the joint can be evaluated, for example, by a cross tensile test as shown in Figures 41A and 41B. Specifically, a lower aluminum plate 11 formed with one side longer than the other and a steel plate 12 of similar size with a through hole having a chamfered portion are placed on top of each other so as to form a cross in plan view, and then the upper aluminum plate 13 is placed on top and friction stir welding is performed. After that, both longitudinal ends of the upper aluminum plate 13 and the lower aluminum plate 11 are pulled in the direction of the arrows, and the joint strength and stress concentration can be confirmed by measuring the tensile load until fracture and observing the location of fracture. As in this embodiment, by using a steel plate 12 with a through hole 16 having a chamfered portion 16b, it is possible to prevent stress from concentrating in the area of ​​the upper aluminum plate 13 on the chamfered portion 16b, preventing the upper aluminum plate 13 from easily breaking, and as a result, excellent joint strength can be obtained.

[0096] When the chamfered portion 16b is formed by R-processing, the radius of curvature R3 of the chamfered portion 16b is not particularly limited, but if it is 30% or more of the thickness of the steel plate, the thickness T of the upper aluminum plate 13 after joining can be secured to a sufficient thickness, and the joint strength can be further improved. On the other hand, even if R3 is increased, there is no particular adverse effect on the jointability, but if it exceeds 100% of the plate thickness, the effect saturates, and the amount of steel plate to be removed increases. Therefore, it is preferable that the radius of curvature R3 of the chamfered portion 16b be 30% or more and 100% or less of the thickness of the steel plate, and more preferably 50% or more and 100% or less of the thickness of the steel plate.

[0097] Furthermore, when the chamfered portion 16b is formed by C-chamfering, the depth D of the chamfered portion 16b on the inner wall surface 16a of the through hole 16 is not particularly limited, but if it is 30% or more of the thickness of the steel plate, the thickness T of the upper aluminum plate 13 after joining can be secured to be sufficiently thick, and the joint strength can be further improved. Also, even if the depth D of the chamfered portion 16b reaches the physical upper limit of 100% of the thickness of the steel plate, no adverse effects will occur. Therefore, it is preferable that the depth D of the chamfered portion 16b be 30% or more and 100% or less of the thickness of the steel plate, and more preferably 50% or more and 100% or less of the thickness of the steel plate.

[0098] Furthermore, the method of chamfering the corner between the inner wall surface 16a of the through hole 16 and the upper surface 12a of the steel plate 12 to form a chamfered portion 16b is not limited to the first embodiment described above, but can be applied to all forms of the first to sixteenth embodiments. However, the position in which the chamfered portion 16b is formed is appropriately selected from the upper aluminum plate 13 and the lower aluminum plate 11 depending on the member being pushed in by the joining tool. That is, for example, as shown in the seventeenth embodiment, when the upper aluminum plate 13, which is a joining auxiliary member, is pushed into the through hole 16 by the joining tool 18, chamfering is performed between the surface of the steel plate 12 facing the upper aluminum plate 13 and the inner wall surface 16a of the through hole 16. On the other hand, for example, as shown in the ninth embodiment, when the upper steel plate 31, which is the first member, is pushed into the through hole 16 by the joining tool 18, chamfering is performed between the surface of the aluminum plate 32 facing the upper steel plate 31 and the inner wall surface 16a of the through hole 16.

[0099] Although various embodiments have been described above with reference to the drawings, the present invention is not limited to the embodiments described above, and can be modified, improved, etc. as appropriate. For example, in the embodiments described above, the second member was described as an example of an aluminum plate or a steel plate, but the second member is not limited to an aluminum plate or a steel plate, and any material such as resin or wood can be used.

[0100] As described above, the following matters are disclosed in this specification:

[0101] (1) A friction stir welding method for joining a first member made of a metal material and a second member made of a different material from the first member and having at least one through hole, using a joining auxiliary member made of the same material as the first member, A superimposing step in which the first member, the second member, and the joining auxiliary member are superimposed in the order such that the through hole of the second member is covered by the first member and the joining auxiliary member, The process includes a friction stir welding step in which a rotating joining tool is used to push at least one of the first member and the joining auxiliary member into the through hole, thereby forming a friction stir joint between the first member and the joining auxiliary member, The joining tool comprises a rotating shoulder portion and a joining pin formed coaxially with the shoulder portion on the tip surface of the shoulder portion, which rotates together with the shoulder portion. The area between the tip surface of the shoulder portion and the side surface of the connecting pin is rounded, A friction stir welding method wherein the space between the side surface of the joining pin and the tip surface of the joining pin is rounded (R-shaped). According to this configuration, a second member made of a different material is sandwiched between a first member and a joining auxiliary member made of the same type of metal material, and a friction stir joint is formed between the first member and the joining auxiliary member, thereby enabling the joining of dissimilar materials at a friction stir joint with high joining strength.

[0102] (2) The friction stir welding method according to (1), wherein at least one of the first member and the joining auxiliary member is formed by punching and has a protrusion that can be inserted into the through hole corresponding to the through hole of the second member. This configuration reduces the deformation of the joining support members during friction stir welding, making them less prone to breakage. Furthermore, the joining position can be visually confirmed from the outside, improving work efficiency.

[0103] (3) The friction stir welding method according to (1) or (2), wherein the first member is made of a hollow material with a closed or open cross-section. With this configuration, a hollow material such as an extruded product can be used as the first component.

[0104] (4) The hollow material has an outer surface on which the second member is superimposed, and an inner surface which is the surface opposite to the outer surface, The friction stir welding method according to (3), wherein a backing plate is provided in the region of the inner surface corresponding to the region in which the friction stir welding portion is formed, the backing plate being inserted into the void surrounded by the inner surface and for suppressing deformation of the hollow material. With this configuration, the deformation of the hollow material is suppressed by the backing plate inserted into the void, thereby forming a good friction stir joint.

[0105] (5) In at least the friction stir welding process, the backing plate is in contact with the region of the inner surface corresponding to the region in which the friction stir weld is formed, The friction stir welding method according to (4), further comprising a removal step of removing the backing plate after the friction stir welding step. This configuration allows for the suppression of deformation of the hollow material during friction stir welding, while also enabling the removal of the backing plate inserted into the void after the friction stir welding process.

[0106] (6) The friction stir welding method according to (5), wherein the backing plate is inserted together with the backing plate into the void surrounded by the inner surface and is pressed by an expandable non-metallic tube that contains a fluid inside. This configuration allows the expansion of the non-metallic tube to press the backing plate against the hollow material, thereby suppressing the deformation of the hollow material. Furthermore, the backing plate can be made thinner and lighter, making it easier to handle.

[0107] (7) In at least the friction stir welding process, the backing plate is pressed by expanding the nonmetallic tube, The friction stir welding method according to (6), wherein after the friction stir welding step, the expansion of the non-metallic tube is released and the backing plate is removed. This configuration makes it easy to insert and remove the backing plate from the gap.

[0108] (8) The joining auxiliary member is formed integrally with the first member such that it has a space between the first member and the joining auxiliary member that allows the second member to be interposed between them. The friction stir welding method according to any one of (3) to (7), wherein the overlapping step is performed by interposing the second member between the first member and the joining auxiliary member. With this configuration, the overlapping process of the first member, the second member, and the joining auxiliary member is performed by inserting the second member between the first member and the joining auxiliary member, making the overlapping work easier.

[0109] (9) The friction stir welding method according to any one of (3) to (8), wherein a 7000 series aluminum alloy is used as the material for the first member and the joining auxiliary member. This configuration improves the strength of the first member and the joining auxiliary member.

[0110] (10) The second member is made of a hollow material with a closed or open cross-section, The hollow material has an outer surface on which the first member is superimposed, and an inner surface which is the surface opposite to the outer surface. The friction stir welding method according to (1) or (2), wherein a backing plate is provided in the region of the inner surface corresponding to the region in which the friction stir welding portion is formed, the backing plate is inserted into the void surrounded by the inner surface and is used to suppress deformation of the hollow material. With this configuration, a hollow material can be used as the second component, and the deformation of the hollow material can be suppressed by the backing plate.

[0111] (11) In at least the friction stir welding process, the backing plate is in contact with the region of the inner surface corresponding to the region in which the friction stir welding portion is formed, The friction stir welding method according to (10), further comprising a removal step of removing the backing plate after the friction stir welding step. With this configuration, deformation of the hollow material can be suppressed by the backing plate during friction stir welding, and the backing plate can be removed after the friction stir welding process.

[0112] (12) The friction stir welding method according to (11), wherein the backing plate is inserted together with the backing plate into a void surrounded by the inner surface and is pressed by an expandable non-metallic tube that contains a fluid inside. With this configuration, the backing plate can be pressed against the lower surface of the second member by the non-metallic tube inserted into the gap.

[0113] (13) In at least the friction stir welding process, the backing plate is pressed by expanding the nonmetallic tube, The friction stir welding method according to (12), wherein after the friction stir welding step, the expansion of the non-metallic tube is released and the backing plate is removed. With this configuration, the backing plate can be easily pressed by the expansion and deexpansion of the non-metallic tube, and the backing plate can be removed after the friction stir welding process.

[0114] (14) The second member is made of a hollow material with a closed or open cross-section, The hollow material has an outer surface on which the first member is superimposed, and an inner surface which is the surface opposite to the outer surface. The friction stir welding method according to (1) or (2), wherein an expandable non-metallic tube for containing a fluid is provided in a region of the inner surface corresponding to the region in which the friction stir welding portion is formed, the tube being inserted into the void surrounded by the inner surface and for suppressing deformation of the hollow material. This configuration allows for the deformation of the hollow material to be suppressed by expanding the non-metallic tube inserted into the void.

[0115] (15) The second member is made of a hollow material with a closed or open cross-section, The hollow material has an outer surface on which the first member is superimposed, and an inner surface which is the surface opposite to the outer surface. The friction stir welding method according to (1) or (2), wherein a holding portion capable of holding the joining auxiliary member is located within the void surrounded by the inner surface. With this configuration, the second member can hold the joining auxiliary member by inserting it into the holding portion formed within the void of the second member.

[0116] (16) The friction stir welding method according to any one of (1) to (15), wherein a plurality of friction stir welded portions are formed in the friction stir welding step. With this configuration, the joint strength is improved by the multiple friction stir joints formed between the first member and the joining auxiliary member.

[0117] (17) The friction stir welding method according to (16), wherein the plurality of friction stir welds are formed simultaneously. This configuration shortens the joining time and prevents deformation and wrinkling of the first member and the joining auxiliary member.

[0118] (18) The through hole of the second member is a linearly formed groove-shaped through hole, The friction stir welding method according to any one of (1) to (17), wherein the joining tool moves linearly along the groove-shaped through hole while rotating, pushing at least one of the first member and the joining auxiliary member into the through hole, and forming the friction stir joint between the first member and the joining auxiliary member. With this configuration, the first member and the joining auxiliary member can be friction stir-bonded at a linear joint of any shape.

[0119] (19) The through hole of the second member is sized to form the friction stir joint and the non-jointed portion other than the friction stir joint inside it. The friction stir welding method according to any one of (1) to (18), wherein the joining tool rotates and moves linearly around the through hole, connecting its starting and ending points, to push at least one of the first member and the joining auxiliary member into a portion of the through hole, thereby forming the friction stir joint between the first member and the joining auxiliary member, and creating a space that is airtight or watertight due to the unjointed portion surrounded by the friction stir joint. This configuration allows for the addition of a heat transfer function to the friction stir joint by circulating, for example, a cooling medium within the airtight or watertight space formed by the non-joint portion.

[0120] (20) The friction stir welding method according to any one of (1) to (19), wherein the second member has a chamfered surface between the surface of the first member and the joining auxiliary member that is pressed in by the joining tool and the inner surface of the through hole. This configuration makes it possible to manufacture friction stir-welded joints with even higher joint strength.

[0121] (21) A friction stir welding tool used in the friction stir welding method described in any one of (1) to (20), It has a rotating shoulder portion and a connecting pin formed coaxially with the shoulder portion on the tip surface of the shoulder portion, which rotates together with the shoulder portion. The area between the tip surface of the shoulder portion and the side surface of the connecting pin is rounded, A joining tool for friction stir welding, wherein the area between the side surface of the joining pin and the tip surface of the joining pin is rounded (R-shaped). This configuration makes it possible to manufacture friction stir-welded joints with even higher joint strength.

[0122] (22) A friction stir-welded joint manufactured by the friction stir-welding method described in any one of (1) to (20), A friction stir joint having a friction stir joint portion formed between the first member and the joining auxiliary member, wherein the second member is sandwiched between the first member and the joining auxiliary member, and at least one of the first member and the joining auxiliary member is pushed into the through hole of the second member. This configuration allows for the manufacture of a friction stir-welded joint with high joint strength, in which a second member made of a different material is sandwiched between a first member and a joining auxiliary member made of the same type of metal material. [Explanation of Symbols]

[0123] 10 Friction stir joints 11 Lower aluminum plate (first component) 12. Steel plate (second component) 13. Upper aluminum plate (joining support member) 13a Convex part 15 Friction stir welding 16 Through holes 16b Chamfered section 17. Backing metal 18 Joining Tools 20. Extruded products (hollow materials) 20a Top surface 20b Cavity 20c through hole 21 Tubes (non-metallic tubes) 22 Groove-shaped through hole 23 Pier 25 Holes 26 Holding part 27 Space (non-joint part) 28 Frame-shaped protruding section 31 Upper steel plate (first member) 31a Convex part 32. Aluminum plate (second component) 33 Lower steel plate (joining auxiliary member) EP terminus r1 corner r2 corner SP Starting point S space

Claims

1. A friction stir welding method for joining a first member made of a metal material and a second member made of a different material from the first member and having at least one through hole, using a joining auxiliary member made of the same material as the first member, A stacking step in which the first member, the second member, and the joining auxiliary member are stacked in the order such that the through hole of the second member is covered by the first member and the joining auxiliary member, The process includes a friction stir welding step in which a rotating joining tool is used to push at least one of the first member and the joining auxiliary member into the through hole, thereby forming a friction stir joint between the first member and the joining auxiliary member, The joining tool comprises a rotating shoulder portion and a joining pin formed coaxially with the shoulder portion on the tip surface of the shoulder portion, which rotates together with the shoulder portion. The area between the tip surface of the shoulder portion and the side surface of the connecting pin is rounded, The area between the side surface of the connecting pin and the tip surface of the connecting pin is rounded. A friction stir welding method wherein the radius of curvature of the R-processing between the tip surface of the shoulder portion and the side surface of the joining pin is 20% or more and 200% or less of the plate thickness of the joining auxiliary member.

2. The friction stir welding method according to Claim 1, wherein the radius of curvature of the R-processing between the side surface of the joining pin and the tip surface of the joining pin is 10% or more and 50% or less of the hole diameter of the through hole of the second member.

3. The friction stir welding method according to claim 1 or 2, wherein at least one of the first member and the joining auxiliary member is formed by punching and has a protrusion that can be inserted into the through hole corresponding to the through hole of the second member.

4. The friction stir welding method according to any one of claims 1 to 3, wherein the first member is made of a hollow material with a closed or open cross-section.

5. The hollow material has an outer surface on which the second member is superimposed, and an inner surface which is the surface opposite to the outer surface. The friction stir welding method according to claim 4, wherein a backing plate is provided in the region of the inner surface corresponding to the region in which the friction stir welding portion is formed, the backing plate is inserted into the void surrounded by the inner surface and is used to suppress deformation of the hollow material.

6. In at least the friction stir welding process, the backing plate is in contact with the region of the inner surface corresponding to the region where the friction stir welding portion is formed. The friction stir welding method according to claim 5, further comprising a removal step of removing the backing plate after the friction stir welding step.

7. The friction stir welding method according to claim 6, wherein the backing plate is inserted together with the backing plate into the void surrounded by the inner surface and is pressed by an expandable non-metallic tube that contains a fluid inside.

8. The joining auxiliary member is formed integrally with the first member such that it has a space between the first member and the joining auxiliary member that allows the second member to be interposed between them. The friction stir welding method according to any one of claims 4 to 7, wherein the overlapping step is performed by interposing the second member between the first member and the joining auxiliary member.

9. The friction stir welding method according to any one of claims 4 to 8, wherein a 7000 series aluminum alloy is used as the material for the first member and the joining auxiliary member.

10. The second member consists of a hollow material with a closed or open cross-section. The hollow material has an outer surface on which the first member is superimposed, and an inner surface which is the surface opposite to the outer surface. A friction stir welding method according to any one of claims 1 to 3, wherein a backing plate is provided in the region of the inner surface corresponding to the region in which the friction stir welding portion is formed, the backing plate is inserted into the void surrounded by the inner surface, and is used to suppress deformation of the hollow material.

11. In at least the friction stir welding process, the backing plate is in contact with the region of the inner surface corresponding to the region where the friction stir welding portion is formed. The friction stir welding method according to claim 10, further comprising a removal step of removing the backing plate after the friction stir welding step.

12. The friction stir welding method according to claim 11, wherein the backing plate is inserted together with the backing plate into a void surrounded by the inner surface and is pressed by an expandable non-metallic tube that contains a fluid inside.

13. The second member consists of a hollow material with a closed or open cross-section. The hollow material has an outer surface on which the first member is superimposed, and an inner surface which is the surface opposite to the outer surface. A friction stir welding method according to any one of claims 1 to 3, wherein an expandable non-metallic tube for containing a fluid is provided in a region of the inner surface corresponding to the region in which the friction stir welding portion is formed, the tube being inserted into the void surrounded by the inner surface and for suppressing deformation of the hollow material.

14. The second member consists of a hollow material with a closed or open cross-section. The hollow material has an outer surface on which the first member is superimposed, and an inner surface which is the surface opposite to the outer surface. A friction stir welding method according to any one of claims 1 to 3, wherein a holding portion capable of holding the joining auxiliary member is located within the void surrounded by the inner surface.

15. The friction stir welding method according to any one of claims 1 to 14, wherein a plurality of friction stir-welded portions are formed in the friction stir welding step.

16. The friction stir welding method according to claim 15, wherein the plurality of friction stir welds are formed simultaneously.

17. The through-hole of the second member is a linearly formed groove-shaped through-hole, The friction stir welding method according to any one of claims 1 to 16, wherein the joining tool rotates and moves linearly along the groove-shaped through hole to push at least one of the first member and the joining auxiliary member into the through hole, thereby forming the friction stir joint between the first member and the joining auxiliary member.

18. The through hole of the second member has a size that allows for the formation of the friction stir joint and the non-jointed portion other than the friction stir joint within its interior. The friction stir joining method according to any one of claims 1 to 17, wherein the joining tool rotates and moves linearly around the through hole, connecting its starting and ending points, to push at least one of the first member and the joining auxiliary member into a portion of the through hole, thereby forming the friction stir joint between the first member and the joining auxiliary member, and creating an airtight or watertight space surrounded by the non-jointed portion.

19. The second member has a chamfered surface between the surface facing the first member and the joining auxiliary member that is pressed in by the joining tool, and the inner surface of the through hole. A friction stir welding method according to any one of claims 1 to 18.

20. A friction stir welding tool used in the friction stir welding method according to any one of claims 1 to 19, It has a rotating shoulder portion and a connecting pin formed coaxially with the shoulder portion on the tip surface of the shoulder portion, which rotates together with the shoulder portion. The area between the tip surface of the shoulder portion and the side surface of the connecting pin is rounded, The area between the side surface of the connecting pin and the tip surface of the connecting pin is rounded. A joining tool for friction stir welding, wherein the radius of curvature of the R-processing between the tip surface of the shoulder portion and the side surface of the joining pin is 20% or more and 200% or less of the plate thickness of the joining auxiliary member.

21. The friction stir welding joining tool according to claim 20, wherein the radius of curvature of the R-processing between the side surface of the joining pin and the tip surface of the joining pin is 10% or more and 50% or less of the hole diameter of the through hole of the second member.

22. A method for manufacturing a friction stir-welded joint produced by the friction stir-welding method described in any one of claims 1 to 19, A method for manufacturing a friction stir joint, wherein the second member is sandwiched between the first member and the joining auxiliary member, and at least one of the first member and the joining auxiliary member is pushed into the through hole of the second member, thereby having a friction stir joint formed between the first member and the joining auxiliary member.

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