Friction stir welding method

Abstract

Comprising a joining step for joining a member to be joined by moving a rotating tool (F) along a movement path set on the member to be joined, the movement path being set to have a first movement path in which the member to be joined is friction-stirred by the movement of the rotating tool (F) to form a plasticized region, and a second movement path in which the plasticized region is formed by the movement of the rotating tool (F). And a second movement path in which the member to be joined is plastically fluidised again by friction-stirring the member to be joined in a state in which the rotating tool (F) is inserted from the same side as the first movement path into a part of a plasticization region (W (Wa)) formed in the first movement path. The insertion depth of the rotating tool (F) when the rotating tool (F) is plastically fluidised again in the second movement path is deeper than the insertion depth of the rotating tool (F) when the plasticized region (W (Wa)) is formed in the first movement path.

Description

Technical Field

[0001] The invention relates to a friction stir welding method. Background Art

[0002] When the moving path of the rotation tool is a closed shape or when friction stir welding is performed on a complex-shaped member to be joined, the moving path of the rotation tool is sometimes partially repeated to overlap a portion of the plasticized region (see Patent Document 1).

[0003] In friction stir welding, in order to make the joining state homogeneous and suppress the generation of defects and burrs, the insertion depth of the rotating tool is generally kept constant. Even when the moving path of the rotating tool is partially repeated as in Patent Document 1, friction stir welding is performed while the insertion depth of the rotating tool is kept constant at the joining portion. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2010-203395 Summary of the invention Technical problem to be solved by the invention

[0005] However, when the rotary tool is inserted into the member to be joined and friction stir welding is performed, a groove is formed in the moving track of the rotary tool. In other words, the material is thickened in the track after one movement of the rotary tool. Therefore, when the moving path of the rotary tool is repeated with the same insertion depth of the rotary tool and friction stir welding is performed, less material can be rolled in when the rotary tool performs friction stir welding for the second time. As a result, there is a problem that defects are easily generated on the front side of the member to be joined after friction stir welding.

[0006] From the above viewpoints, an object of the present invention is to provide a friction stir welding method that can suppress the generation of defects on the front surface of the members to be welded even when the movement path of the rotation tool is repeated. Technical solutions adopted to solve technical problems

[0007] In order to solve the aforementioned technical problems, the present invention is a method for friction stir joining of joined components using a rotating tool, which includes a joining process, in which the rotating tool is moved along a moving path set on the joined components to join the joined components, and the moving path is set to have: a first moving path in which the joined components are friction stirred to form a plasticized area by moving the rotating tool; and a second moving path in which the joined components are friction stirred and plastically fluidized again by moving the rotating tool while the rotating tool is inserted into a part of the plasticized area formed in the first moving path from the same side as the first moving path, and the insertion depth of the rotating tool in the second moving path when plastically fluidizing again is deeper than the insertion depth of the rotating tool when the plasticized area is formed in the first moving path.

[0008] Furthermore, preferably, the position of the rotation axis of the rotation tool in the second movement path is displaced in the left-right direction relative to the travel direction of the rotation tool when the position of the rotation axis in the first movement path is used as a reference.

[0009] Furthermore, preferably, when the insertion depth of the rotation tool in the second movement path is set to D2 and the insertion depth of the rotation tool in the first movement path is set to D1, D1×1.05<D2<D1×1.25 is satisfied.

[0010] Furthermore, preferably, after the rotary tool passes through the first movement path, the rotary tool passes through the second movement path in such a manner as to become the same direction as the traveling direction of the rotary tool in the first movement path.

[0011] Furthermore, preferably, after the rotary tool passes through the first movement path, the rotary tool passes through the second movement path in a manner that becomes a direction opposite to a traveling direction of the rotary tool in the first movement path.

[0012] Furthermore, preferably, after the rotary tool passes through the first movement path, the rotary tool passes through the second movement path in a manner intersecting with a travel direction of the rotary tool in the first movement path.

[0013] Furthermore, preferably, in the joining step, an overlapping portion formed by overlapping the joined members is joined, and the position of the front end of the rotation tool in the second movement path is lower than the overlapping portion.

[0014] In addition, preferably, the joined member includes a first joined member and a second joined member, the first joined member has an opening portion, the second joined member closes the opening portion, and the first joined member has: a bottom; a peripheral wall portion, the peripheral wall portion rises from the bottom and includes the opening portion; a first step portion, the first step portion has a first step bottom surface and a first step side surface rises from the first step bottom surface and is arranged on the inner peripheral edge of the end surface of the peripheral wall portion; and a first bottom surface, the first bottom surface is continuous with the first step bottom surface and is at approximately the same height position, and also includes a loading process, in which the second joined member is loaded on the first step bottom surface and the first bottom surface to overlap the first bottom surface with the back surface of the second joined member to form an overlapping portion, and the first step side surface is butted with the side surface of the second joined member to form a first butt joint. The part comprises: in the joining process, there is: in the overlapping part, by moving the rotating tool, at least the second joined member is frictionally stirred to form a plasticized area; in the first docking part, by moving the rotating tool, a third moving path is frictionally stirred to the first joined member and the second joined member; and in the overlapping part, by moving the rotating tool, the first joined member and the second joined member are frictionally stirred and plastically fluidized again in a state where the rotating tool is inserted into a part of the plasticized area formed in the first moving path from the same side as the first moving path, and the rotating tool is moved in the order of the first moving path, the third moving path and the second moving path to join the first joined member and the second joined member.

[0015] Furthermore, preferably, in the joining step, the rotating tool is in contact with only the second joined member when joining the first movement path.

[0016] Furthermore, preferably, in the joining process, in the third moving path, the front end of the rotating tool is positioned at the same height as the first step difference bottom surface, and in the second moving path, the front end of the rotating tool is positioned lower than the first bottom surface.

[0017] In addition, preferably, the first joined member comprises: a second step portion, the second step portion having a second step bottom surface that is continuous with and at approximately the same height as the first step bottom surface, and a second step side surface that stands up from the second step bottom surface; and a third step portion, the third step portion having a third step bottom surface that is continuous with and at approximately the same height as the first step bottom surface, and a third step side surface that stands up from the third step bottom surface, in the placing step, the second joined member is placed on the first step bottom surface, the second step bottom surface, the third step bottom surface, and the first bottom surface, so that the second step side surface is butted against the side surface of the second joined member to form a second butting portion, And the third step difference side is docked with the side of the second joined member to form a third docking portion. In the joining process, there are: in the second docking portion, a fourth moving path for frictionally stirring the first joined member and the second joined member by moving the rotating tool; and in the third docking portion, a fifth moving path for frictionally stirring the first joined member and the second joined member by moving the rotating tool. The rotating tool is moved in the order of the fourth moving path, the first moving path, the third moving path, the second moving path and the fifth moving path to join the first joined member and the second joined member.

[0018] In addition, preferably, in the joining process, in the third moving path, the position of the front end of the rotating tool is at the same height as the bottom surface of the first step difference, in the fourth moving path, the position of the front end of the rotating tool is at the same height as the bottom surface of the second step difference, in the fifth moving path, the position of the front end of the rotating tool is at the same height as the bottom surface of the third step difference, and in the second moving path, the position of the front end of the rotating tool is lower than the first bottom surface.

[0019] Furthermore, it is preferable that when entering the first movement path from the fourth movement path, the insertion depth of the rotation tool is reduced while the rotation tool is moved.

[0020] Furthermore, it is preferable that the thickness of the second joined member is larger than the height dimension of the first step side surface.

[0021] Furthermore, preferably, in the third movement path, the first and second members to be joined are friction stir welded in a state where the rotation axis of the rotation tool is located slightly closer to the second member to be joined than the first abutting portion.

[0022] Furthermore, preferably, the first joined member is formed of a first aluminum alloy, and the second joined member is formed of a second aluminum alloy, and the first aluminum alloy is a material type having a higher hardness than the second aluminum alloy.

[0023] In addition, the rotating tool includes a shoulder portion and a stirring pin hanging down from the center of the lower end surface of the shoulder portion. In the joining process, friction stir joining is performed with the lower end surface of the shoulder portion in contact with the front surface of the joined member.

[0024] In addition, preferably, the rotating tool includes a base and a stirring pin hanging down from the center of the lower end surface of the base, and in the joining process, friction stir joining is performed while the base is separated from the joined member and only the stirring pin is in contact with the joined member.

[0025] In addition, the rotating tool has a base and a stirring pin arranged on the base, the stirring pin includes a base end side pin continuous with the base and a front end side pin continuous with the base end side pin, the taper angle of the base end side pin is larger than the taper angle of the front end side pin, and a stepped pin step portion is formed on the outer peripheral surface of the base end side pin. In the joining process, friction stir joining is performed with the outer peripheral surface of the base end side pin in contact with the front surface of the joined component. Effects of the Invention

[0026] According to the friction stir welding method of the present invention, even when the movement path of the rotation tool is repeated, the generation of defects on the front surface of the members to be welded can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an exploded perspective view showing a joined body according to the first embodiment of the present invention. Figure 2 It is a perspective view showing a placing step of the friction stir welding method according to the first embodiment. Figure 3 yes Figure 2 Sectional view taken along the III-III direction. Figure 4 yes Figure 2 Sectional view taken along the IV-IV direction. Figure 5 yes Figure 2 V-V sectional view. Figure 6 yes Figure 2 Sectional view viewed in the direction VI-VI. Figure 7 yes Figure 2 Cross-sectional view taken along the VII-VII direction. Figure 8yes Figure 2 Sectional view taken along the VIII-VIII direction. Fig. 9 yes Figure 2 Sectional view taken along the IX-IX direction. Fig.10 It is a side view showing the rotation tool according to the first embodiment. Fig.11 This is an overall schematic diagram showing a movement path of the friction stir welding method according to the first embodiment. Fig.12 In the joining step of the friction stir welding method according to the first embodiment, Fig.11 Cross-sectional view taken along the XII-XII direction. Fig.13 This is an enlarged schematic diagram showing a fourth movement path of the friction stir welding method according to the first embodiment. Fig.14 In the joining step of the friction stir welding method according to the first embodiment, Fig.11 Cross-sectional view taken along the XIV-XIV direction. Fig.15 In the joining step of the friction stir welding method according to the first embodiment, Fig.11 Cross-sectional view taken along the XV-XV direction. Fig.16 This is an enlarged schematic diagram showing a third movement path of the friction stir welding method according to the first embodiment. Fig.17 In the first embodiment of the friction stir welding method, the welding step Fig.16 Cross-sectional view taken along the XVII-XVII direction. Fig.18 This is an enlarged schematic diagram showing a fifth movement path of the friction stir welding method according to the first embodiment. Fig.19 In the joining step of the friction stir welding method according to the first embodiment, Fig.18 Cross-sectional view taken along the XIX-XIX direction. Fig. 20 It is an exploded perspective view showing a joined body according to a second embodiment of the present invention. Fig.21 It is a perspective view showing a placing step of the friction stir welding method according to the second embodiment. Fig. 22 yes Fig.21 Cross-sectional view taken along the XXII-XXII direction. Fig.23 yes Fig.21 Sectional view from the XXIII-XXIII direction Fig.24This is an overall schematic diagram showing a movement path of the friction stir welding method according to the second embodiment. Fig.25 In the joining step of the friction stir welding method according to the second embodiment, Fig.24 Cross-sectional view taken along the XXV-XXV direction. Fig.26 In the joining step of the friction stir welding method according to the second embodiment, Fig.24 Cross-sectional view taken along the XXVI-XXVI direction. Fig. 27 In the joining step of the friction stir welding method according to the second embodiment, Fig.24 Cross-sectional view taken along the direction XXVII-XXVII. Fig.28 It is an exploded perspective view showing a joined body according to a third embodiment of the present invention. Fig.29 It is a perspective view showing a placing step of the friction stir welding method according to the third embodiment. Fig.30 In the joining step of the friction stir welding method according to the third embodiment, Fig.29 Sectional view taken in the direction of XXX-XXX. Fig.31 In the joining step of the friction stir welding method according to the third embodiment, Fig.29 A cross-sectional view taken along the XXXI-XXXI direction. Fig.32 It is a side view showing a rotation tool according to a first modification. Fig.33 It is a side view showing a rotation tool according to a second modification. Fig.34 It is an enlarged side view showing a rotation tool according to a second modification. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are described with reference to the accompanying drawings as appropriate. The present invention is not limited to the following embodiments. Some or all of the components in the embodiments and modifications can be appropriately combined. This direction is for the convenience of description and does not limit the present invention.

[0029] [1. First embodiment] [1-1. Members to be joined and joined body] In the friction stir welding method of the first embodiment of the present invention, Figure 1As shown, the case of forming a liquid cooling jacket (joined body 1) is illustrated. The liquid cooling jacket 1 is composed of a jacket body (first joined member) 2 and a closure member (second joined member) 3. The liquid cooling jacket 1 is a device for circulating a fluid inside and cooling a heat generating body arranged therein. The jacket body 2 and the closure member 3 are integrated by friction stir welding. The "front side" in the following description refers to the side opposite to the "back side".

[0030] The sleeve body (first joined member) 2 is mainly composed of a bottom 10, a peripheral wall portion 11, and a horizontal frame portion 15. The sleeve body 2 is not particularly limited as long as it is a metal that can be frictionally stirred, but in this embodiment, it is formed to mainly contain a first aluminum alloy. The first aluminum alloy uses, for example, an aluminum alloy casting material such as JIS H5302ADC12 (Al-Si-Cu series).

[0031] The bottom 10 is a rectangular plate-shaped member. The peripheral wall 11 is a wall portion that stands up in a frame shape from the peripheral edge of the bottom 10. A concave portion 16 as a hollow portion is formed inside the bottom 10 and the peripheral wall 11, and an opening portion 17 that opens upward is formed. The inside of the peripheral wall 11 is composed of inner side surfaces 11A, 11B, 11C, 11D, 11E, 11F, 11G, and 11H that stand up vertically relative to the bottom 10.

[0032] The inner side surface 11A faces the inner side surface 11G in parallel and is perpendicular to the inner side surfaces 11B and 11H respectively extending from both ends of the inner side surface 11A. The inner side surface 11B faces the inner side surface 11H in parallel and is perpendicular to the inner side surfaces 11A and 11C respectively extending from both ends of the inner side surface 11B. The inner side surface 11C faces the inner side surface 11E in parallel and is perpendicular to the inner side surfaces 11B and 11H respectively extending from both ends of the inner side surface 11C.

[0033] The inner side surface 11D faces the inner side surface 11H in parallel and is perpendicular to the inner side surfaces 11C and 11E respectively extending from both ends of the inner side surface 11D. The inner side surface 11E faces the inner side surface 11C in parallel and is perpendicular to the inner side surfaces 11D and 11F respectively extending from both ends of the inner side surface 11E. The inner side surface 11F faces the inner side surface 11H in parallel and is perpendicular to the inner side surfaces 11E and 11G respectively extending from both ends of the inner side surface 11F.

[0034] The inner side surface 11G faces the inner side surface 11A in parallel and is perpendicular to the inner side surfaces 11F and 11H respectively extending from both ends of the inner side surface 11G. The inner side surface 11H faces the inner side surface 11D in parallel and is perpendicular to the inner side surfaces 11A and 11G respectively extending from both ends of the inner side surface 11H.

[0035] Inner side surface 11B and inner side surface 11F are formed in the same plane. Inner side surfaces 11A, 11B, and 11C form a crank shape in a plan view. Inner side surfaces 11E, 11F, and 11G form a crank shape in a plan view.

[0036] The horizontal frame portion 15 is formed to be bridged between the inner side surface 11C and the inner side surface 11E. The horizontal frame portion 15 is a plate-shaped portion with a rectangular cross section. The surface (first bottom surface) 15a of the horizontal frame portion 15 is continuous and coplanar with the step bottom surface 12 described later. The side surface 15b of the horizontal frame portion 15 is coplanar with the inner side surfaces 11B and 11F, respectively. By providing the horizontal frame portion 15, the front side (one side) of the recessed portion 16 is partitioned into a smaller hollow portion, and the rear side (the other side) is partitioned into a larger hollow portion.

[0037] A step portion 14 is formed on the inner periphery of the peripheral portion 11 over the entire circumference. The step portion 14 is formed by a step bottom surface 12 and a step side surface 13 rising from the step bottom surface 12. The step bottom surface 12, the step side surface 13, and the step portion 14 are distinguished by marking the corresponding parts of the inner side surfaces 11A to 11H with numbers. Each step portion will be described in detail later, for example, Figure 1 As shown, the second step portion 14A at a location corresponding to the inner side surface 11A is composed of the second step bottom surface 12A and the second step side surface 13A.

[0038] In addition, the width dimension of each step bottom surface can be set appropriately, but in the present embodiment, all are the same. In addition, the height position of each step bottom surface can be set appropriately, and in the present embodiment, all are the same height position. In addition, the height dimension of each step side surface can be set appropriately, and in the present embodiment, all are the same. In addition, the sleeve body 2 of the present embodiment is formed in one piece, but for example, the peripheral wall portion 11 can also be formed as a split structure and integrated by joining with a sealing member.

[0039] The closure member (second joined member) 3 is a plate-shaped member that closes the opening 17 of the sleeve body 2. The closure member 3 is composed of a large plate portion 3A as a larger portion and a small plate portion 3B as a portion smaller than the large plate portion 3A. The large plate portion 3A is a portion that covers the cross frame portion 15 and the inner side surfaces 11A, 11B, 11F, 11G, and 11H. The small plate portion 3B is a portion that covers the inner side surfaces 11C, 11D, and 11E. The closure member 3 is formed in a shape that is substantially the same as the outer edge of the step portion 14 in a manner that is substantially free of gaps and is arranged on the step portion 14. The closure member 3 includes a front surface 3j, a back surface 3k, and side surfaces 3a to 3h.

[0040] The sealing member 3 is not particularly limited as long as it is a metal that can be frictionally stirred, but in the present embodiment, it is formed mainly of a second aluminum alloy. The second aluminum alloy is a material having a lower hardness than the first aluminum alloy. The second aluminum alloy is formed of an aluminum alloy ductile material such as JIS A1050, A1070, A1100, A6063, etc.

[0041] [1-2. Manufacturing method] Next, a method for manufacturing a joined body (friction stir welding method) according to the present embodiment will be described. In the friction stir welding method according to the present embodiment, a preparation step, a placement step, and a joining step are performed.

[0042] <Preparation process> The preparation step is a step of preparing the cover body 2 and the closure member 3. The cover body 2 and the closure member 3 are not particularly limited in the manufacturing method, but the cover body 2 is molded by, for example, casting, and the closure member 3 is molded by, for example, extrusion.

[0043] <Placing process> like Figure 2 As shown, the placing process is a process of placing the closure member 3 on the sleeve body 2 to form each docking portion and overlapping portion. In the present embodiment, a first docking overlapping portion J1, a second docking overlapping portion J2, a third docking overlapping portion J3 and a fourth overlapping portion U are formed. The first docking overlapping portion J1 corresponds to the inner side surfaces 11C, 11D, and 11E, and is roughly C-shaped when viewed from above as shown by the thick line. The second docking overlapping portion J2 corresponds to the inner side surfaces 11A and 11B, and is roughly L-shaped when viewed from above as shown by the dotted line. The third docking overlapping portion J3 corresponds to the inner side surfaces 11F, 11G, and 11H, and is roughly C-shaped when viewed from above and reversed left and right as shown by the dotted line. The fourth overlapping portion U is an elongated rectangle when viewed from above as shown by the imaginary line.

[0044] like Figure 3 As shown, the side surface 3e of the closure member 3 is butted against the first step side surface 13E to form a first butted portion J1A. In addition, the back surface 3k of the closure member 3 overlaps with the first step bottom surface 12E to form a first overlapped portion J1B. The front surface 3j of the closure member 3 is coplanar with the end surface 11a of the peripheral wall portion 11. The side surface 3c of the sealing member 3 butts against the first step side surface 13C to form a first butting portion J1A. The back surface 3k of the sealing member 3 overlaps against the first step bottom surface 12C to form a first overlapping portion J1B.

[0045] like Figure 4As shown, the side surface 3d of the closure member 3 is butted against the first step side surface 13D to form a first butted portion J1A. In addition, the back surface 3k of the closure member 3 overlaps with the first step bottom surface 12D to form a first overlapped portion J1B. The three first butted portions J1A and the three first overlapped portions J1B described above form a first butted overlapped portion J1.

[0046] like Figure 5 As shown, the side surface 3a of the closing member 3 is butted against the second step side surface 13A to form a second butted portion J2A. In addition, the back surface 3k of the closing member 3 is overlapped with the second step bottom surface 12A to form a second overlapped portion J2B.

[0047] like Figure 6 As shown, the side surface 3b of the closure member 3 is butted against the second step side surface 13B to form a second butted portion J2A. In addition, the back surface 3k of the closure member 3 overlaps with the second step bottom surface 12B to form a second overlapped portion J2B. The second butted overlapped portion J2 is formed by the two second butted portions J2A and the two second overlapped portions J2B described above.

[0048] like Figure 7 As shown, the side surface 3f of the closing member 3 is butted against the third step side surface 13F to form a third butted portion J3A. In addition, the back surface 3k of the closing member 3 is overlapped with the third step bottom surface 12F to form a third overlapped portion J3B. Furthermore, the side surface 3h of the closing member 3 butts against the third step side surface 13H to form a third butting portion J3A. Furthermore, the back surface 3k of the closing member 3 overlaps with the third step bottom surface 12H to form a third overlapping portion J3B.

[0049] like Figure 8 As shown, the side surface 3g of the closure member 3 is butted against the third step side surface 13G to form a third butted portion J3A. In addition, the back surface 3k of the closure member 3 overlaps with the third step bottom surface 12G to form a third overlapped portion J3B. The three third butted portions J3A and the three third overlapped portions J3B described above form a third butted overlapped portion J3.

[0050] like Fig. 9 As shown, the back surface 3k of the closing member 3 overlaps with the front surface (first bottom surface) 15a of the horizontal frame portion 15 to form a fourth overlapping portion U.

[0051] <Rotation tool> The rotating tool F used in manufacturing the joint body is described below. Fig.10As shown, the rotating tool F includes a shoulder portion F1 and a stirring pin F2. The rotating tool F is formed of, for example, tool steel. The shoulder portion F1 is a portion connected to the output shaft of the coupling device (not shown), and is columnar or frustoconical. The stirring pin F2 hangs down from the center of the lower end face F1a of the shoulder portion F1. The stirring pin F2 has the lower end face F1a side of the shoulder portion F1 as the base end, and is in the shape of a frustum of a cone that decreases in diameter as it moves toward the front end side. The lower end face F1a can be either flat or bowl-shaped that is concave upward (in the direction away from the stirring pin F2). The front end F2a of the stirring pin F2 is flat. A spiral groove is formed on the outer peripheral surface of the stirring pin F2 throughout the entire height direction. The spiral groove can also be either right-handed or left-handed, but in the present embodiment, it is left-handed (counterclockwise when viewed from above).

[0052] When the rotating tool F is rotated to the right while the spiral groove is rotated to the left, or when the rotating tool F is rotated to the left while the spiral groove is rotated to the right, the plastic flow material softened by friction stirring is guided by the spiral groove and flows toward the front end side of the stirring pin F2. As a result, the plastic flow material can be prevented from overflowing to the outside during friction stirring, and the generation of burrs can be suppressed. In addition, by making the lower end face F1a of the shoulder portion F1 contact with the joined member and performing friction stir joining, the softened plastic flow material can be squeezed in, thereby suppressing the generation of burrs.

[0053] <Joining process> like Fig.11 As shown in FIG. 1 , the joining process is a process of friction stir joining the sleeve body 2 and the sealing member 3 using a rotating tool F. In the joining process, the rotating tool F is rotated clockwise to perform friction stir joining. Fig.11 As shown, the rotation tool F is moved along each butt-jointed overlapped portion and the fourth overlapped portion U, and friction stir welding is continuously performed without disengaging the rotation tool F in the middle. In the welding process, after the rotation tool F is inserted into the starting position SP1 set at the end surface 11a of the peripheral wall portion 11, it is inserted into the middle position S1, and the second butt-jointed overlapped portion J2, the fourth overlapped portion U, the first butt-jointed overlapped portion J1, the fourth overlapped portion U, and the third butt-jointed overlapped portion J3 are friction stir welded, and the peripheral wall portion 11 is separated from the peripheral wall portion 11 at the end position EP1 set at the end surface 11a of the peripheral wall portion 11. In other words, while friction stir welding is performed twice on the fourth overlapped portion U that is repeated relative to the passage of the rotation tool F, the rotation tool F is moved in an 8-shaped shape to perform friction stir welding.

[0054] In addition, the intermediate position S1 is set near the position where the second butt overlap portion J2 and the third butt overlap portion J3 intersect on the front surface 3j of the closure member 3. In addition, the intermediate position S2 is set near the position that is the seam between the second butt overlap portion J2 and the fourth overlap portion U. In addition, the intermediate position S3 is set near the position that is the seam between the fourth overlap portion U and the first butt overlap portion J1 (and the third butt overlap portion J3).

[0055] <Second butting overlapping portion J2: fourth moving path L4> First, the starting position SP1 is set at the end surface 11a of the peripheral wall portion 11. The starting position SP1 may also be set at the front surface 3j of the closure member 3. After the rotary tool F is inserted to the starting position SP while rotating forward, it is moved toward the second butting overlap portion J2 while being pressed deeper and deeper. Fig.12 As shown, after reaching the second butt-jointed overlapping portion J2, the lower end face F1a of the shoulder portion F1 is slightly pressed into the end face 11a of the peripheral wall portion 11 and the front face 3j of the closure member 3, while being inserted to an insertion depth D4 set in such a way that the front end F2a of the stirring pin F2 becomes the same height position as the second step bottom face 12A. While maintaining the insertion depth D4, the second butt-jointed portion J2A and the second overlapping portion J2B are friction-stir-joined by moving the rotating tool F along the second butt-jointed overlapping portion J2. A plasticized region W is formed in the moving trajectory of the rotating tool F.

[0056] The rotation axis C of the rotating tool F may overlap with the second docking portion J2A, but in this embodiment, the friction stir welding is performed while the rotation axis C is shifted to the inner side (the side of the sealing member 3) than the second docking portion J2A. Fig.13 As shown, if the moving path (the path through which the rotation axis C passes) of the rotating tool F when performing friction stir welding on the second butt joint overlap portion J2 is set as the fourth moving path L4, the fourth moving path L4 is set along the second butt joint portion J2A and is slightly shifted to the inside of the second butt joint portion J2A. The displacement amount P1 from the second butt joint portion J2A to the fourth moving path L4 is preferably 0.1<P1(mm), more preferably 0.2<P1(mm), and preferably P1<0.5(mm), more preferably P1<0.4(mm). After the rotating tool F reaches the middle position S2, it enters the first friction stir welding of the fourth overlap portion U.

[0057] <Fourth overlapping portion U: First time: First moving path L1> like Fig.14As shown, in the first friction stir welding of the fourth overlapped portion U, the lower end face F1a of the shoulder portion F1 is brought into contact with the front face 3j of the closure member 3, and the insertion depth D1 is set so that the front end F2a of the stirring pin F2 does not reach the fourth overlapped portion U. Although the front end F2a of the stirring pin F2 does not reach the front face 15a of the cross frame portion 15, the plasticized region W reaches the front face 15a, and therefore, the fourth overlapped portion U can be friction stir welded. When friction stir welding is performed from the second butt overlap portion J2 to the fourth overlapped portion U, it is preferred to perform friction stir welding while gradually raising the height position of the rotating tool F (while becoming shallower) while moving the rotating tool F.

[0058] like Fig.14 As shown in FIG. 1 , if the moving path of the rotating tool F when the friction stir welding is performed on the fourth overlapped portion U for the first time is set as the first moving path L1, the first moving path L1 is set to the approximate center of the width direction of the fourth overlapped portion U. When the rotating tool F reaches the middle position S3 (refer to Fig.11 ) vicinity, the friction stir welding of the first butt overlap portion J1 is then entered.

[0059] <First butting overlap portion J1: third movement path L3> like Fig.15 As shown, after reaching the first butt-jointing overlap J1, the lower end face F1a of the shoulder portion F1 is slightly pressed into the end face 11a of the peripheral wall portion 11 and the front face 3j of the closure member 3, while being inserted to an insertion depth D3 set in such a way that the front end F2a of the stirring pin F2 becomes at the same height position as the first step difference bottom face 12E. While maintaining the insertion depth D3, the first butt-jointing portion J1A and the first overlapping portion J1B are frictionally stirred and joined by moving the rotating tool F along the first butt-jointing overlap J1. In addition, in order to make the shear side and the flow side of the rotating tool F constant on the sleeve body 2 side and the closure member 3 side, the rotation direction of the rotating tool F may also be reversed when friction stirring and joining the first butt-jointing overlap J1.

[0060] In addition, at the intermediate position S3, when the front end F2a of the stirring pin F2 is shallower than the first step difference bottom surface 12E, there is a possibility that it will become a cause of poor joining of the first butt overlap J1. Therefore, when entering the first butt overlap J1 from the fourth overlap U, it is sufficient to set the front end F2a of the stirring pin F2 to be at the same height as the first step difference bottom surface 12E when reaching the intermediate position S3. For example, when entering the first butt overlap J1 from the fourth overlap U, it is preferred to move the rotating tool F while gradually lowering the height position of the rotating tool F (while deepening) and perform friction stir joining.

[0061] The rotation axis C of the rotating tool F may overlap with the first docking portion J1A, but in this embodiment, the friction stir welding is performed while the rotation axis C is shifted to the inner side (the side of the sealing member 3) than the first docking portion J1A. Fig.16 As shown, if the moving path of the rotating tool F when performing friction stir welding on the first butt joint overlap portion J1 is set as the third moving path L3, the third moving path L3 is along the first butt joint portion J1A and is set at a position slightly shifted to the inside of the first butt joint portion J1A. The displacement amount P2 from the first butt joint portion J1A to the third moving path L3 is preferably 0.1<P2(mm), more preferably 0.2<P2(mm), and preferably P2<0.5(mm), more preferably P2<0.4(mm). After the rotating tool F reaches the vicinity of the middle position S2, it enters the second friction stir welding of the fourth overlap portion U.

[0062] <Fourth overlapping portion U: Second time: Second moving path L2> like Fig.17 As shown, in the second fourth overlap U, the lower end face F1a of the shoulder portion F1 is slightly pressed into the front face 3j of the closure member 3, and the insertion depth D2 is set so that the front end F2a of the stirring pin F2 reaches the cross frame portion 12 (fourth overlap U). When entering the fourth overlap U from the first butt overlap J1, it is preferred to perform friction stir welding while moving the rotating tool F and gradually lowering the height position of the rotating tool F (while deepening).

[0063] like Fig.17 and Fig.18 As shown, if the moving path of the rotating tool F during the second friction stirring of the fourth overlapped portion U is set as the second moving path L2, the second moving path L2 is slightly shifted to the left and right direction (here, to the left direction) relative to the moving direction of the rotating tool F when the first moving path L1 is used as a reference. As a result, the first plasticized area W (Wa) and the second plasticized area W (Wb) are slightly offset and formed. In the fourth overlapped portion U, it is sufficient to appropriately set the displacement amount P3 of the first moving path L1 (first time) and the second moving path L2 (second time), but it is preferably 0.1<P3 (mm), more preferably 0.2<P3 (mm), and further preferably 0.3<P3 (mm), and preferably P3<1.2 (mm), more preferably P3<1.0 (mm), and further preferably P3<0.8 (mm).

[0064] In addition, when the insertion depth of the rotating tool F in the second moving path L2 (second time) is set to D2 and the insertion depth of the rotating tool F in the first moving path L1 (first time) is set to D1, preferably, D1×1.05<D2<D1×1.25. The upper limit value is preferably D2<D1×1.25, more preferably D2<D1×1.20, and further preferably D2<D1×1.15. The insertion depth refers to the distance from the front face of the joined component (here, the front face 3j of the closure 3) to the front end F2a of the stirring pin F2. As Fig.18 As shown, after the rotary tool F reaches the vicinity of the intermediate position S3, the friction stir welding of the third butting overlap portion J3 is started.

[0065] <Third butting overlap portion J3: fifth movement path L5> like Fig.19 As shown, after the rotary tool F reaches the middle position S3, the lower end face F1a of the shoulder portion F1 is slightly pressed into the end face 11a of the peripheral wall portion 11 and the front face 3j of the closure member 3, while being inserted to an insertion depth D5 set in such a way that the front end F2a of the stirring pin F2 becomes the same height position as the third step difference bottom surface 12F. While maintaining the insertion depth D5, the third docking portion J3A and the third overlap portion J3B are frictionally stirred and joined by moving the rotary tool F along the third docking portion J3A. When entering the third docking overlap portion J3 from the second fourth overlap portion U, it is sufficient to set the front end F2a of the stirring pin F2 to be at the same height as the first step difference bottom surface 12E at the moment when the rotary tool F reaches the middle position S3 of entering the third docking overlap portion J3. For example, it is preferred to perform friction stirring and joining while gradually raising the height position of the rotary tool F (while becoming shallower) while moving the rotary tool F.

[0066] The rotation axis C of the rotating tool F may overlap with the third docking portion J3A, but in this embodiment, the friction stir welding is performed while the rotation axis C is shifted to the inner side (the side of the sealing member 3) than the third docking portion J3A. Fig.18 and Fig.19As shown, if the moving path of the rotating tool F when performing friction stir welding on the third butting overlap portion J3 is set as the fifth moving path L5, the fifth moving path L5 is along the third butting portion J3A and is set at a position slightly shifted to the inside of the third butting portion J3A. The displacement amount P4 from the third butting portion J3A to the fifth moving path L5 is preferably 0.1<P4(mm), more preferably 0.2<P4(mm), and preferably P4<0.5(mm), more preferably P4<0.4(mm). After the rotating tool F reaches the intermediate position S1, while gradually raising the height position of the rotating tool F, the rotating tool F is separated from the peripheral wall portion 11 at the end position EP1. Through the above steps, the sleeve body 2 and the closure 3 are friction stir welded to form an integrated body.

[0067] [1-3. Effects] In the friction stir welding of the present embodiment described above, in the area (the fourth overlapping portion U) where the rotating tool F repeatedly causes the joined components to be plastically fluidized, the insertion depth D2 of the rotating tool F when causing the joined components to be plastically fluidized again is set deeper than the insertion depth D1 of the rotating tool F when causing the joined components to be plastically fluidized for the first time. Thus, the material is drawn in from the area of ​​the joined component that has not been plastically fluidized, especially the area of ​​the joined component that has not been plastically fluidized in the depth direction, and friction stir welding is performed again, so that the thickness reduction on the front side of the material caused by the first friction stir can be compensated. As a result, even if the rotating tool F repeatedly adopts the moving trajectory that causes the joined component to be plastically fluidized, defects on the front side of the joined component can be suppressed, so that good joining can be performed. In addition, the degree of freedom of the moving path and the degree of freedom of the design of the joined component can be increased, and the moving path can be made efficient and the time required for joining can be shortened, so that productivity can be improved.

[0068] In addition, in the fourth overlapped portion U, the first moving path L1 and the second moving path L2 may also be at the same position, but in this embodiment, they are staggered in the left-right direction relative to the traveling direction. By staggering the positions of the rotating tool F in the first friction stir welding and the second friction stir welding relative to the traveling direction (in the horizontal direction), it is possible to supplement materials not only from the top and bottom directions but also from the left and right directions, thereby suppressing defects on the front side of the joined member. In addition, the increased joining width can increase the joining strength.

[0069] In addition, as long as the insertion depth during friction stir welding is appropriately set in the first moving path L1 and the second moving path L2, if the rotary tool F enters too deeply in the second moving path L2, there is a possibility that the joining mark of the groove generated on the front side of the joined member will become larger. In this regard, in the present embodiment, when the insertion depth of the rotary tool F in the second moving path L2 is set to D2 and the insertion depth of the rotary tool F in the first moving path L1 is set to D1, it is set to D1×1.05<D2<D1×1.25. Thus, it is possible to prevent the joining mark of the groove generated on the front side of the joined member caused by the rotary tool F entering too deeply in the second moving path L2 from becoming larger.

[0070] In addition, in the present embodiment, the fourth overlapping portion U is friction stir welded twice from the same side (the front surface 3j side of the sealing member 3), but even in the above case, defects can be prevented from occurring on the front surface of the joined member.

[0071] In addition, it is sufficient to set the insertion depth of the rotating tool F appropriately within the range in which the joined members can be joined. However, in the present embodiment, the position of the front end F2a of the rotating tool F in the second moving path L2 for joining the fourth overlapping portion U formed by overlapping the joined members is lower than the position of the fourth overlapping portion U. Thus, the sleeve body 2 and the closing body 3 can be reliably joined, and the joining strength between the sleeve body 2 and the closing body 3 can be improved. On the other hand, by making the position of the front end F2a of the rotating tool F in the first moving path L1 higher than the fourth overlapping portion U, it is possible to ensure a margin (margin) for lowering the height of the rotating tool F in the second moving path L2. Thus, the insertion amount of the rotating tool F in the second moving path L2 can be suppressed, and therefore, the joining marks of the grooves generated on the front surface of the joined members and the excessive inflow of materials from the closing member 3 can be suppressed.

[0072] Furthermore, in the joining process of the present embodiment, when the fourth overlapping portion U is joined in the first moving path L1, the rotating tool F does not contact the horizontal frame portion 15 but only contacts the closure 3 (the second joined member). Even in the above case, since the first plasticized area W (Wa) reaches the fourth overlapping portion, the fourth overlapping portion U can be joined. Furthermore, even in the case where the plasticized area W does not reach the fourth overlapping portion U, when the closure 3 and the sleeve body 2 are interlocked by the action of the rotating tool F and the concave and convex parts are formed, the oxide film between the closure 3 and the sleeve body 2 is destroyed, so that the base materials of the two are partially mixed, and therefore, crimping can be performed. Thus, the load acting on the joining device (not shown) can be reduced.

[0073] In addition, in the joining process of the present embodiment, the insertion depth of the rotating tool F only needs to be appropriately set within the range in which the joined members can be joined, but in the third moving path L3, the height position of the front end F2a of the stirring pin F2 is set to the same height as the first step bottom surface 12C, 12D, 12E, and in the second moving path L2, the height position of the front end F2a of the rotating tool F is set to be lower than the front surface (first bottom surface) 15a of the horizontal frame portion 15. Thus, the rolling up of the oxide film in the third butt overlap portion J3 can be prevented, and the reduction in the joining strength can be suppressed by ensuring a sufficient joining depth.

[0074] In addition, the order of performing friction stir welding can be set appropriately, but in this embodiment, the friction stir welding is performed in the order of the fourth moving path L4, the first moving path L1, the third moving path L3, the second moving path L2 and the fifth moving path L5. In this way, by performing friction stir welding on the fourth moving path L4 before performing friction stir welding on the first moving path L1 (the fourth overlapping portion U), the closure member 3 can be temporarily joined (temporarily fixed) to the sleeve body 2.

[0075] In addition, as long as the insertion depth of the rotating tool F is appropriately set within the range in which the joined members can be joined, in the joining process of the present embodiment, in the third moving path L3, the height position of the front end F2a of the stirring pin F2 is set at the same height position as the first step bottom surface 12C, 12D, 12E, in the fourth moving path L4, the height position of the front end F2a of the stirring pin F2 is set at the same height position as the second step bottom surface 12A, 12B, in the fifth moving path L5, the height position of the front end F2a of the stirring pin F2 is set at the same height position as the third step bottom surface 12F, 12G, 12H, and in the second moving path L2, the height position of the front end F2a of the stirring pin F2 is set lower than the front surface (first bottom surface) 15a of the cross frame portion 15. Thus, the rolling up of the oxide film in each butt overlap portion can be prevented, and the decrease in joining strength can be suppressed by ensuring a sufficient joining depth.

[0076] In addition, the depth of the rotating tool F only needs to be appropriately set within a range in which the joined members can be joined, but when entering the first moving path L1 from the fourth moving path L4 of the present embodiment and when entering the fifth moving path L5 from the second moving path L2, the insertion depth of the rotating tool F is reduced while the rotating tool F is moved. When the insertion depth of the rotating tool F is changed, there is no problem even if it is changed sharply when it is deepened, but when it is reduced, the generation of front defects can be suppressed by reducing the depth while the rotating tool F is moved.

[0077] Furthermore, in the joining process of the present embodiment, in the third moving path L3, the fourth moving path L4, and the fifth moving path L5, the sleeve body (first joined member) 2 and the closure (second joined member) 3 are frictionally stirred and joined in a state where the rotation axis C of the rotating tool F is located slightly closer to the closure (second joined member) 3 side than each docking portion. That is, friction stirring is performed in a state where the rotating tool F is slightly in contact with the sleeve body 2, so that the mixing of materials from the sleeve body (first joined member) 2 to the closure (second joined member) 3 can be reduced as much as possible. As a result, in each docking portion, the material on the closure (second joined member) side is mainly frictionally stirred, so that the decrease in the joining strength can be suppressed.

[0078] In addition, it is sufficient to appropriately select the material of the joined member, but in the present embodiment, the sleeve body (first joined member) 2 is formed of a first aluminum alloy, and the closure member (second joined member) 3 is formed of a second aluminum alloy, and the first aluminum alloy is a material type having a higher hardness than the second aluminum alloy. Assuming that friction stir welding is performed in a state where the rotation axis C of the rotating tool F overlaps with each docking portion, since the material impedance received from each joined member is different, the material is not uniformly stirred, which may cause poor joining. However, according to the present embodiment, the rotation axis C of the rotating tool F is shifted toward the side of the closure member 3 relative to each docking portion, and the second aluminum alloy that is easy to stir can be involved in a large amount of friction stirring, thereby facilitating uniform stirring and preventing poor joining from occurring.

[0079] In addition, the rotating tool may be in any form, but in this embodiment, the rotating tool F including the shoulder portion F1 is used, and the friction stir welding is performed in a state where the shoulder portion F1 is in contact with the member to be joined. Thus, the plastic flow material softened during the friction stir welding can be pressed in, which can prevent the occurrence of defects.

[0080] [1-4. Others] In the above embodiment, the friction stir welding is performed in the order of the fourth moving path L4, the first moving path L1, the third moving path L3, the second moving path L2 and the fifth moving path L5 in the joining process. In the joining process, at least a part of the plasticized area formed in the first moving path L1 is subjected to friction stirring in the second moving path L2 and plastic fluidized again. For example, after friction stirring in the first moving path L1, the rotating tool F is separated from the joined member, and then the rotating tool F is inserted into the joined member again, and friction stirring is performed in the second moving path L2.

[0081] In the above-mentioned embodiment, the case where there is a first moving path L1 for performing friction stir welding on the fourth overlapping portion U for the first time and a second moving path L2 for performing friction stir welding on the fourth overlapping portion U for the second time in the joining process is exemplified and explained. The structure or combination of the parts of the joined members in the first moving path L1 and the second moving path L2 that are joined are not limited, for example, it may be an overlapping part formed by overlapping the joined members, it may be a butt joint part formed by butt jointing the joined members, or it may be a butt joint overlapping part formed by overlapping and butt jointing.

[0082] In addition, for example, the step side surface 13 of the cover body 2 may be inclined outward. In addition, the plate thickness of the sealing member 3 may be larger than the height dimension of the step side surface 13. This can prevent the thickness of the joint portion from being reduced.

[0083] [2. Second Embodiment] Next, a friction stir welding method according to a second embodiment of the present invention will be described. In this embodiment, the shape of the sleeve body and the welding process are different from those of the first embodiment described above.

[0084] [2-1. Members to be joined and joined body] like Fig. 20 As shown, the liquid cooling jacket 101 of the present embodiment is composed of a jacket body 102 and a closure member 103. The jacket body (first joined member) 102 includes a bottom 110, a peripheral wall portion 111, and a support portion 118. The bottom 110 is a rectangular plate-shaped portion. The peripheral wall portion 111 is a portion that stands up in a frame shape from the peripheral edge of the bottom 110. A recessed portion 116 as a hollow portion is formed inside the bottom 110 and the peripheral wall portion 111, and an opening portion 117 that opens upward is formed.

[0085] The support portion 118 is plate-shaped and extends vertically from one inner side surface of the peripheral wall portion 111. The support portion 118 is not connected to the other inner side surfaces of the peripheral wall portion 111. A step portion 114 is formed over the entire circumference at the inner periphery of the peripheral edge portion 111. The step portion 114 is formed by a step bottom surface 112 and a step side surface 113 rising from the step bottom surface 112. The step bottom surface 112 is coplanar with the front surface (first bottom surface) 118a of the support portion 118.

[0086] The closing member (second joining member) 103 is a rectangular plate-shaped member. The closing member 103 has substantially the same shape as the outer edge of the step portion 114. The closing member 103 includes a front surface 103a, a back surface 103b, and side surfaces 103c.

[0087] [2-2. Manufacturing method] Next, a method for producing a joined body (friction stir welding method) according to the present embodiment will be described. In the friction stir welding method according to the present embodiment, a preparation step, a placement step, and a joining step are performed.

[0088] <Preparation process> The preparation step is a step of preparing the cover body 102 and the closure member 103. The cover body 102 and the closure member 103 are not particularly limited in the manufacturing method, but the cover body 102 is molded by, for example, casting, and the closure member 103 is molded by, for example, extrusion.

[0089] <Placing process> like Fig.21 As shown in FIG. 1 , the placing step is a step of placing the sealing member 103 on the sleeve body 102 to form the butting portions and the overlapping portions. In this embodiment, the butting overlapping portion J11 and the overlapping portion U11 are formed. Fig. 22 As shown, the docking portion J11A is formed by docking the side surface 103c of the closure member 103 with the step side surface 113. The docking portion J11A is in a rectangular frame shape when viewed from above. In addition, the overlapping portion J11B is formed by overlapping the step bottom surface 112 with the back surface 103b of the closure member 103. The docking overlap portion J11 is formed by the docking portion J11A and the overlapping portion J11B. The end surface 111a of the peripheral wall portion 111 is coplanar with the front surface 103a of the closure member 103.

[0090] like Fig.23 As shown, the overlapped portion U11 is a portion formed by the overlapped front surface (first surface) 118a of the support portion 118 and the back surface 103b of the closing member 103. The overlapped portion U11 is rectangular in a plan view.

[0091] <Joining process> like Fig.24 As shown, the joining process is a process of friction stir welding the sleeve body 102 and the closure 103 using a rotating tool F. In the joining process, the rotating tool F is rotated to the right and friction stir welding is performed. In the joining process, the rotating tool F is moved along the docking portion J11A and the overlapping portion U11, and friction stir welding is continuously performed without disengaging the rotating tool F in the middle. In the joining process, after the rotating tool F is inserted into the starting position SP11, it is moved along the overlapping portion U11, and after reaching the front end of the support portion 118, it is turned back and moved again along the overlapping portion U11. After reaching the vicinity of the intermediate position S11, the rotating tool F is moved clockwise along the docking portion J11A and rotated around the closure 3. After passing the intermediate position S11, the rotating tool F is disengaged at the end position EP11.

[0092] More specifically, first, the starting position SP11 for inserting the rotary tool F is set at the end surface 111a of the peripheral wall portion 111. The starting position SP11 may also be set on the front surface 103a of the closure 103. After the rotary tool F is inserted to the starting position SP11, it is gradually pushed deeper while being moved toward the overlap portion U11.

[0093] <Overlapping portion U11: First time: First moving path L11> like Fig.25 As shown, in the first overlap portion U11, while the lower end face F1a of the shoulder portion F1 is brought into contact with the front face 103a of the closure 103, the insertion depth D11 is set so that the front end F2a of the stirring pin F2 does not reach the overlap portion U11. Although the front end F2a of the stirring pin F2 does not reach the support portion 118, the plasticized region W reaches the front face 118a, and therefore, the overlap portion U11 can be friction stir welded. Furthermore, even in the case where the plasticized region W does not reach the overlap portion U11, when the closure 3 and the sleeve body 2 are engaged with each other by forming a concave and convex shape by the action of the rotating tool F, the oxide film between the closure 3 and the sleeve body 2 is destroyed, causing the base materials of the two to be partially mixed, thereby enabling crimping.

[0094] like Fig.25 As shown in FIG. 1 , if the moving path of the rotating tool F when performing the friction stir welding of the overlapping portion U11 for the first time is set as the first moving path L11, the first moving path L11 is set at the approximate center of the width direction of the overlapping portion U11. After the rotating tool F reaches the front end side of the overlapping portion U11, it turns back and enters the friction stir welding of the overlapping portion U11 for the second time.

[0095] <Overlapping portion U11: Second time: Second moving path L12> like Fig.26 As shown, in the second overlapped portion U11, the lower end face F1a of the shoulder portion F1 is slightly pressed into the front face 103a of the closure 103, and the insertion depth D12 is set so that the front end F2a of the stirring pin F2 reaches the support portion 118 (overlapped portion U11). When entering the second moving path L12 from the first moving path L11, the height position of the rotary tool F is gradually lowered (while becoming deeper) and turned back.

[0096] like Fig.26As shown, if the moving path of the rotating tool F when the overlapped portion U11 is frictionally stirred for the second time is set as the second moving path L12, the second moving path L12 is slightly shifted to the left and right direction (here, to the right direction) relative to the moving direction of the rotating tool F when the position of the rotation axis C in the first moving path L11 is used as a reference. As a result, the first plasticized area W (Wa) and the second plasticized area W (Wb) are slightly offset and formed. In the overlapped portion U11, it is sufficient to appropriately set the displacement amount P11 of the first moving path L11 (first time) and the second moving path L12 (second time), but preferably 0.1<P11 (mm), more preferably 0.2<P11 (mm), further preferably 0.3<P11 (mm), and preferably P11<1.2 (mm), more preferably P11<1.0 (mm), and further preferably P11<0.8 (mm).

[0097] Furthermore, when the insertion depth of the rotating tool F in the second moving path L12 (second time) is set to D12 and the insertion depth of the rotating tool F in the first moving path L1 (first time) is set to D11, preferably D12<D11×1.25, more preferably D12<D11×1.20, and further preferably D12<D11×1.15. The insertion depth refers to the distance from the front face of the joined component (here, the front face 103a of the closure 103) to the front end F2a of the stirring pin F2. Fig.24 As shown, after the rotary tool F reaches the vicinity of the intermediate position S11, the friction stir welding of the butted overlap portion J11 is started.

[0098] <Butt-jointed overlapping portion J11: third moving path L13> like Fig. 27 As shown, after reaching the butt-jointing overlap portion J11, the lower end face F1a of the shoulder portion F1 is slightly pressed into the end face 111a of the peripheral wall portion 111 and the front face 103a of the closure 103, while being inserted to an insertion depth D13 set in such a way that the front end F2a of the stirring pin F2 is at the same height position as the step bottom surface 112. While maintaining the insertion depth D13, the butt-jointing portion J11A and the overlap portion J11B are friction-stir-joined by moving the rotating tool F clockwise along the butt-jointing portion J11A. When entering the butt-jointing overlap portion J11 from the overlap portion U11, it is preferred to perform friction-stir-joining while moving the rotating tool F and gradually raising the height position of the rotating tool F (while becoming shallower).

[0099] The rotation axis C of the rotating tool F may overlap with the butt joint J11A, but in this embodiment, the friction stir welding is performed while the rotation axis C is shifted to the inner side (the side of the sealing member 103) of the butt joint J11A. Fig. 27 As shown, if the moving path of the rotating tool F when performing friction stir welding on the butt-jointed overlapping portion J11 is set as the third moving path L13, the third moving path L13 is set along the butt-jointed portion J11A and is slightly shifted to the inside of the butt-jointed portion J11A. The displacement amount P12 from the butt-jointed portion J11A to the third moving path L13 is preferably 0.1<P12(mm), more preferably 0.2<P12(mm), and preferably P12<0.5(mm), more preferably P12<0.4(mm). After the rotating tool F is rotated along the butt-jointed overlapping portion J11 for one circle and passes through the middle position S11, the rotating tool F is gradually pushed up while being moved toward the end position EP11. After reaching the end position EP11, the rotating tool F is detached at the peripheral wall portion 111.

[0100] The friction stir welding method of the present embodiment described above can also achieve substantially the same effects as those of the first embodiment. The support portion 118 is included, and the support portion 118 and the sealing member 103 are friction stir welded, so that the strength of the liquid cooling jacket 101 can be improved.

[0101] [3. Third embodiment] Next, a friction stir welding method according to a third embodiment of the present invention will be described. In this embodiment, the shape of the sleeve body and the welding process are different from those of the first embodiment described above.

[0102] [3-1. Members to be joined and joined body] like Fig.28 As shown, the liquid cooling jacket 201 of the present embodiment is composed of a jacket body 202 and closure members 203, 203. The jacket body (first joined member) 202 includes a bottom 210 and a peripheral wall portion 211. The bottom 210 is a rectangular plate-shaped portion. The peripheral wall portion 211 is a portion rising from the peripheral edge of the bottom 210. Concave portions 216, 216 as hollow portions are formed inside the peripheral wall portion 211, and opening portions 217, 217 opening upward are respectively formed. The concave portions 216, 216 are formed so that the corners of each other are adjacent.

[0103] A step portion 214 is formed over the entire circumference of the outer peripheral edge of the recess 216. The step portion 214 is formed by a step bottom surface 212 and a step side surface 213 rising from the step bottom surface 212. The dimensions of each part of the step portions 214 and 214 are the same.

[0104] The closing member (second joined member) 203 is a rectangular plate-shaped member and has substantially the same shape as the outer edge of the step portion 214. The closing member 203 includes a front surface 203a, a back surface 203b, and side surfaces 203c.

[0105] [3-2. Manufacturing method] Next, a method for manufacturing a joined body (friction stir welding method) according to the present embodiment will be described. In the friction stir welding method according to the present embodiment, a preparation step, a placement step, and a joining step are performed.

[0106] <Preparation process> The preparation step is a step of preparing the cover body 202 and the sealing member 203. The cover body 202 and the sealing member 203 are not particularly limited in the manufacturing method, but the cover body 202 is molded by, for example, casting, and the sealing member 203 is molded by, for example, extrusion.

[0107] <Placing process> like Fig.29 As shown in FIG. 1 , the placing step is a step of placing the sealing member 203 on the sleeve body 202 to form each butting portion. In this embodiment, butting overlap portions J21 and J22 are formed. Fig.30 As shown, the butt-joint overlap portion J21 is composed of a butt-joint portion J21A and an overlap portion J21B. The butt-joint portion J21A is the portion where the step side surface 213 butts with the side surface 203c of the closure member 3. The overlap portion J21B is the portion where the step bottom surface 212 overlaps with the back surface 203b of the closure member 203. The butt-joint overlap portion J21 is rectangular when viewed from above. The butt-joint overlap portion J22 is the same as the butt-joint overlap portion J21, and therefore, a detailed description thereof is omitted. The corners of the butt-joint overlap portions J21 and J22 touch at one point (middle position S21).

[0108] <Joining process> like Fig.30 As shown, the joining process is a process of friction stir welding the sleeve body 202 and the closure 203 using a rotating tool F. In the joining process, the rotating tool F is rotated to the right and friction stir welding is performed. In the joining process, the rotating tool F is moved along the butt-jointing overlap J21 on one side, and the butt-jointing overlap J21 and J22 are continuously friction stir welded without disengaging the rotating tool F in the middle. In the joining process, after the rotating tool F is inserted into the starting position SP21, it is moved along the butt-jointing overlap J21A, and after passing through the relay position S21, it penetrates into the butt-jointing overlap J22. After the rotating tool F is moved along the butt-jointing overlap J22A and passes through the intermediate position S21 again, the portion in the butt-jointing overlap J21 that has not been friction stir welded is friction stir welded. After the butt-jointing overlap J21 is completely friction stir welded, the rotating tool F is disengaged at the end position EP21.

[0109] More specifically, first, the starting position SP21 for inserting the rotary tool F is set at the end surface 211a of the peripheral wall portion 211. The starting position SP21 may also be set at the front surface 203a of the closure member 203. After the rotary tool F is inserted to the starting position SP21, it is pressed gradually deeper while moving toward the butting overlap portion J21.

[0110] <Butt overlap J21> like Fig.30 As shown, after the rotary tool F reaches the butt-jointed overlapping portion J21, the lower end surface F1a of the shoulder portion F1 is slightly pressed into the end surface 211a of the peripheral wall portion 211 and the front surface 203a of the sealing member 203, and the rotary tool F is inserted to an insertion depth D21 set so that the front end F2a of the stirring pin F2 is at the same height position as the step bottom surface 212. While maintaining the insertion depth D21, the rotary tool F is moved clockwise along the butt-jointed overlapping portion J21 to friction stir join the butt-jointed portion J21A and the overlapped portion J21B.

[0111] The rotation axis C of the rotating tool F may overlap with the butt joint J21A, but in this embodiment, the friction stir welding is performed while the rotation axis C is shifted to the inner side (closed member 203 side) of the butt joint J21A. Fig.30 As shown in FIG. 1 , if the moving path of the rotating tool F when performing friction stir welding on the butt overlap portion J21 is set as the moving path L21, the moving path L21 is set along the butt overlap portion J21A and is slightly shifted to the inside of the butt overlap portion J21A. The displacement amount P21 from the butt overlap portion J21A to the moving path L21 is preferably 0.1<P21(mm), more preferably 0.2<P21(mm), preferably P21<0.5(mm), and more preferably P21<0.4(mm).

[0112] <Middle position S21: First time> After the rotary tool F reaches the vicinity of the intermediate position S21, the height position of the rotary tool F does not change, and the rotary tool F passes through the intermediate position S21 while maintaining the insertion depth D21, and friction stir welding of the butted overlap portion J22 is performed.

[0113] <Butt overlap J22> like Fig.29 As shown, in the butt-jointed overlapping portion J22, the rotating tool F is moved clockwise to perform friction stir welding of the sleeve body 202 and the closing member 203. In the butt-jointed overlapping portion J22, friction stir welding is performed in the same manner as in the butt-jointed overlapping portion J21.

[0114] <Middle position S21: Second time> like Fig.29 As shown, after the rotary tool F approaches the middle position S21 again, the rotary tool F is gradually pressed in (while becoming deeper) and the rotary tool F continues to move along the butt overlap portion J22. Fig.31 As shown, when passing through the intermediate position S21, the insertion amount of the rotating tool F is set to an insertion depth D22 deeper than that of the first friction stir welding. In this embodiment, the insertion depth D22 is set so that the plasticized area W (Wb) formed during the second pass is formed at a deeper position than the first plasticized area W (Wa).

[0115] <Butt overlap J21> After passing the intermediate position S21, friction stir welding is performed on the portion (equivalent to three sides) in the butt-joint overlap portion J21 that has not been friction stir welded. That is, the rotating tool F is moved counterclockwise along the butt-joint portion J21A to perform friction stir welding of the sleeve body 202 and the sealing member 203. After friction stir welding is performed on the entire butt-joint overlap portion J21, the rotating tool F is gradually pushed up while being moved toward the end position EP21. After reaching the end position EP21, the rotating tool F is separated from the peripheral wall portion 211.

[0116] Even when the overlapping portions J21 and J22 intersect at one place in a manner that is approximately ∞ (a mark close to infinity) when viewed from above as in the present embodiment, the same effect as in the first embodiment can be achieved. When the rotating tool F passes through the intersecting portion (the intermediate position S21 in the present embodiment) for the second time, it is preferred that the rotating tool F gradually deepens from the front of the intermediate position S21, and after passing through, the rotating tool F gradually moves upward. In other words, the occurrence of defects can be prevented by avoiding a sharp movement of the rotating tool F in the height direction.

[0117] In addition, in the present embodiment, the rotation direction of the rotating tool F is set to be constant, but for example, the rotation directions of the rotating tool F can be made opposite to each other in the butt overlap portion J21 and the butt overlap portion J22 in such a way that one side of the sleeve body 202 is always the flow side (or one side of the closure member 203 is always the flow side). In addition, in this embodiment, the starting position may be set at the middle position S21, and friction stir welding may be performed on the butt-jointed overlapping portion J21 in a clockwise manner from the middle position S21, and friction stir welding may be performed on the butt-jointed overlapping portion J22 in a counterclockwise manner after passing the middle position S21. In this way, the sleeve body 202 side may be always set as the flow side (or the sealing member 203 side may be always set as the flow side). In other words, the travel directions of the rotating tool F may be opposite to each other in the butt-jointed overlapping portion J21 and the butt-jointed overlapping portion J22.

[0118] [4. First Modification Example] Next, a first variation of the above-mentioned embodiment will be described. In the friction stir welding method of this variation, Fig.32 As shown, the present invention is different from the above-mentioned embodiment in that a rotating tool K is used.

[0119] The rotating tool K includes a base K1 and a stirring pin F2. The base K1 is a portion connected to the output shaft of the coupling device (not shown), and is columnar or frustoconical. The stirring pin K2 hangs down from the center of the lower end surface K1a of the base K1. The stirring pin K2 is in the shape of a frustum of a cone with the lower end surface K1a of the base K1 as the base end and the diameter decreasing toward the front end side. The front end K2a of the stirring pin K2 is flat. A spiral groove is formed on the outer peripheral surface of the stirring pin K2 throughout the entire height direction. The spiral groove may be either right-handed or left-handed, but in the present embodiment, it is left-handed (counterclockwise when viewed from above).

[0120] The friction stir welding method of this modification includes a preparation step, a placement step, and a welding step. In the preparation step, the thickness of the sealing material 303 is set larger than the height dimension of the second step side surface 13A. The placement step is substantially the same as that of the above-mentioned embodiment.

[0121] In the bonding process of this modification, Fig.32 As shown, the rotating tool K is moved in such a manner that the rotating tool K is rotated to the right while the rotating axis C is made to coincide with the fourth moving path L4 and to be parallel to the second docking portion J2A. It is sufficient to set the insertion depth of the stirring pin F2 appropriately, but in this modified example, the insertion depth D4 is set so that the front end K2a is at the same height position as the second step bottom surface 12A. In the joining process, only the stirring pin K2 is brought into contact with the joined components (here, the sleeve body 2 and the closure 303), and friction stir joining is performed with the base end side of the stirring pin K2 exposed.

[0122] Even the rotary tool K of this modified example can achieve substantially the same effect as the aforementioned embodiment. In addition, in the joining process, only the stirring pin K2 is in contact with the joined member, and friction stir joining is performed in a state where the base K1 is not in contact with the joined member, thereby reducing the load acting on the joining device.

[0123] [5. Second Modification Example] Next, a second variation of the above-mentioned embodiment will be described. In the manufacturing method of the joint body of this variation, as Fig.33 As shown, the present invention is different from the above-mentioned embodiment in that a rotating tool G is used.

[0124] The rotary tool G is made of tool steel, for example, and mainly consists of a base G1 and stirring pins (base end pin G2 and front end pin G3). The base G1 is columnar or frustum-shaped and is connected to the output shaft of the joining device.

[0125] The base end pin G2 is continuous with the base G1 and tapers toward the front end. The base end pin G2 is in the shape of a truncated cone. It is sufficient to set the taper angle A of the base end pin G2 appropriately, for example, to 135 to 160 degrees. If the taper angle A is 135 to 160 degrees, the roughness of the joining surface after friction stirring can be reduced.

[0126] The taper angle A is larger than the taper angle B of the front end side pin G3 described later. Fig.34 As shown in FIG. 1 , a stepped pin step portion G21 is formed on the outer peripheral surface of the base end side pin G2 over the entire height direction. The pin step portion G21 is formed in a spiral shape in a clockwise or counterclockwise manner. In other words, the pin step portion G21 is spiral in a plan view and is stepped in a side view. In this modified example, the pin step portion G21 is set to be counterclockwise from the base end side to the front end side.

[0127] like Fig.34 As shown, the pin step portion G21 is composed of a step bottom surface G21a and a step side surface G21b. The distance X1 (horizontal distance) between each vertex G21c, G21c of adjacent pin step portions G21 is appropriately set according to the step angle M1 described later and the height Y1 of the step side surface G21b.

[0128] The height Y1 of the step side surface F21b can be appropriately set, for example, to 0.1 to 0.4 mm. If the height Y1 is less than 0.1 mm, the roughness of the joint front surface becomes larger. On the other hand, if the height Y1 is greater than 0.4 mm, there is a tendency for the joint surface roughness to become larger, and the number of effective step portions (the number of pin step portions G21 in contact with the metal member to be joined) also decreases.

[0129] It is sufficient to appropriately set the step angle M1 formed by the step bottom surface G21a and the step side surface G21b, but it is set to 85 to 120°, for example. In the present embodiment, the step bottom surface G21a is parallel to the horizontal plane (here, the plane perpendicular to the rotation axis C). The step bottom surface G21a can also be inclined from the rotation axis C toward the peripheral direction within a range of -5 to 15° relative to the horizontal plane (negative below the horizontal plane and positive above the horizontal plane). The distance X1, the height Y1 of the step side surface G21b, the step angle M1 and the angle of the step bottom surface G21a relative to the horizontal plane are appropriately set so that the plastic flow material will not be retained and attached to the inside of the pin step portion G21 during friction stirring, but will be discharged to the outside, and the plastic flow material can be pressed by the step bottom surface G21a to reduce the roughness of the joining surface.

[0130] like Fig.33 As shown, the front end side pin G3 is formed continuously with the base end side pin G2. The front end side pin G3 is in the shape of a truncated cone. The front end G3a of the front end side pin G3 is flat. The taper angle B of the front end side pin G3 is smaller than the taper angle A of the base end side pin G2. Fig.34 As shown in FIG. 1 , a spiral groove G31 is engraved on the outer peripheral surface of the front end side pin G3. The spiral groove G31 may be either clockwise or counterclockwise, but in the present embodiment, the spiral groove G31 is engraved counterclockwise.

[0131] The spiral groove G31 is composed of a spiral bottom surface G31a and a spiral side surface G31b. The distance (horizontal distance) between the vertices G31c and G31c of adjacent spiral grooves G31 is set to length X2. The height of the spiral side surface G31b is set to height Y2. The spiral angle M2 formed by the spiral bottom surface G31a and the spiral side surface G31b is formed to, for example, 45 to 90 degrees. The spiral groove G31 increases frictional heat by contacting with the joined member, and includes the function of guiding the plastic flow material toward the front end side. It is sufficient to appropriately set the spiral angle M2, length X2 and height Y2.

[0132] In the friction stir welding method of this modification, a preparation step, a placement step, and a welding step are performed. The preparation step and the placement step are the same as those of the first embodiment described above.

[0133] In the joining process, Fig.33 As shown in the figure, the rotary tool G is moved in such a manner that the rotation axis C coincides with the fourth movement path L4 and is parallel to the second butting portion J2A while the rotary tool G is rotated rightward (positive rotation). In the joining process, the insertion depth D4 is set so that the tip of the tip pin G3 is at the same height position as the second step bottom surface 12A while the outer peripheral surface of the base end side pin G2 is in contact with the front surface 3j of the sealing member 3 and the end surface 11a of the peripheral wall portion 11.

[0134] Even the rotary tool G of this modified example can achieve substantially the same effects as those of the aforementioned embodiment. In addition, during the joining process, the plastic flow material can be pressed by the outer peripheral surface of the base end side pin G2, so the step groove formed on the joining surface can be reduced, and the raised portion formed near the step groove can be eliminated or reduced. In addition, since the stepped pin step portion G21 is shallow and has a large outlet, it is easy to press the plastic flow material using the step bottom surface G21a while discharging the plastic flow material to the outside of the pin step portion G21. Therefore, even if the plastic flow material is pressed by the base end side pin G2, the plastic flow material is not easy to adhere to the outer peripheral surface of the base end side pin G2. As a result, the roughness of the joining surface can be reduced, and the joining quality can be ideally stabilized.

[0135] In addition, the rotary tool G of the present embodiment is a structure including the base end pin G2 and the front end pin G3 having a smaller taper angle than the taper angle A of the base end pin G2. Thus, it is easy to insert the rotary tool G into the sleeve body 2 and the sealing member 3. In addition, since the taper angle B of the front end pin G3 is small, the rotary tool G can be easily inserted into a deeper position of the second docking portion J2A. Example

[0136] Next, in order to confirm the effect of the present invention, a test 1 was conducted. In the test 1, friction stir welding was performed in the same manner as in the first embodiment described above. Figure 2 In Test 1, stirring and joining were performed in the order of the second butt-jointing overlapping portion J2 (fourth moving path L4), the fourth overlapping portion U (first moving path L1), the first butt-jointing overlapping portion J1 (third moving path L3), the fourth overlapping portion U (second moving path L2) and the third butt-jointing overlapping portion J3 (fifth moving path L5).

[0137] In the embodiment, the outer diameter of the shoulder F1 of the rotating tool F is set to 11.5 mm, and the length of the stirring pin F2 is set to 3.05 mm. The taper angle of the stirring pin F2 is set to 26.4°. In addition, the spiral groove of the stirring pin F2 is set to rotate counterclockwise, and the rotating tool F is rotated clockwise to perform friction stir welding.

[0138] In the second butt overlap J2 (fourth moving path L4) of the embodiment, the insertion depth (the distance from the end face 11a of the peripheral wall portion 11 to the front end F2a of the stirring pin F2) is set to 3.4 mm. The lower end face F1a of the shoulder portion F1 is slightly pressed into the joined member while the front end F2a of the stirring pin F2 is set to the same height position as the second step bottom face 12A.

[0139] In the fourth overlap section U (first time: first moving path L1) of the embodiment, the insertion depth is set to 3.2 mm. The lower end face F1a of the shoulder portion F1 is slightly pressed into the joined member, and the front end F2a of the stirring pin F2 is set to be located above the front face 15a of the cross frame portion 15.

[0140] In the first butt overlap portion J1 (third moving path L3) of the embodiment, the insertion depth is set to 3.4 mm. The lower end face F1a of the shoulder portion F1 is slightly pressed into the joined member, and the front end F2a of the stirring pin F2 is set to the same height position as the first step bottom face 12E.

[0141] In the fourth overlap portion U (second time: second moving path L2) of the embodiment, the insertion depth is set to 3.7 mm. The lower end face F1a of the shoulder portion F1 is slightly pressed into the joined member while the front end F2a of the stirring pin F2 is positioned below the front face 15a of the cross frame portion 15.

[0142] In the third butt overlap portion J3 (fifth moving path L5) of the embodiment, the insertion depth is set to 3.4 mm. The lower end face F1a of the shoulder portion F1 is slightly pressed into the joined member, and the front end F2a of the stirring pin F2 is set to the same height position as the third step bottom face 12G.

[0143] In the comparative example, the height positions of the rotating tool F in the first and second times of the fourth overlapping portion U were set to the same height position. Other conditions were the same as those in the example.

[0144] According to the aforementioned embodiment, during the friction stir welding of the fourth overlapped portion U for the second time, the rotating tool F is inserted deeper than the first time, so that the thickness reduction during the second friction stir welding can be compensated. That is, even when the moving path of the rotating tool F is repeated, the generation of defects on the front side of the joined member can be suppressed.

[0145] On the other hand, in the comparative example, the height positions of the rotation tool F in the first and second times were set to the same height, so the amount of material that plastically flows during the second friction stir welding is reduced, resulting in front defects. (Explanation of symbols)

[0146] 1 liquid cooling jacket (joint); 2 sets of main bodies (first joined components); 3. Closing member (second joined member); 10 bottom; 11 peripheral wall; 15a front side (first bottom side); D1 insertion depth; D2 insertion depth; F Rotary tool; F1 shaft shoulder; F2 stirring pin; G Rotary tool; G2 base end side pin; G3 front end side pin; G21 pin layer difference part; J1 first butting overlap portion; J2 second butting overlap portion; J3 third butting overlap portion; K Rotary tool; K1 base; K2 stirring pin; L1 first moving path; L2 second moving path; L3 third moving path; L4 fourth moving path; L5 fifth movement path; U fourth overlap; W plasticization zone.

Claims

1. A friction stir welding method, comprising: performing friction stir welding on the members to be welded using a rotating tool; It is characterized in that The method comprises a joining step in which the rotating tool is moved along a moving path set on the joined member to join the joined member. The moving path is set to have: In the first movement path, the rotation tool is moved to frictionally stir the joined member to form a first movement path of a plasticized region; as well as In the second moving path, the rotating tool is moved to frictionally stir the joined member while inserting the rotating tool into a part of the plasticized area formed in the first moving path from the same side as the first moving path, and the joined member is plastically fluidized again. The insertion depth of the rotation tool when the rotation tool in the second movement path is plastically fluidized again is deeper than the insertion depth of the rotation tool when the plasticized area is formed in the first movement path.

2. The friction stir welding method according to claim 1, wherein: The position of the rotation axis of the rotation tool in the second movement path is displaced in the left-right direction relative to the travel direction of the rotation tool when the position of the rotation axis in the first movement path is used as a reference.

3. The friction stir welding method according to claim 1, wherein: When the insertion depth of the rotation tool in the second movement path is set to D2 and the insertion depth of the rotation tool in the first movement path is set to D1, D1×1.05<D2<D1×1.25 is satisfied.

4. The friction stir welding method according to claim 1, wherein: After the rotary tool passes through the first moving path, the rotary tool passes through the second moving path in such a manner as to become the same direction as the traveling direction of the rotary tool in the first moving path.

5. The friction stir welding method according to claim 1, wherein: After the rotary tool passes through the first moving path, the rotary tool passes through the second moving path in such a manner as to become a direction opposite to the traveling direction of the rotary tool in the first moving path.

6. The friction stir welding method according to claim 1, wherein: After the rotary tool passes through the first moving path, the rotary tool passes through the second moving path in a manner intersecting with the traveling direction of the rotary tool in the first moving path.

7. The friction stir welding method according to claim 1, wherein: In the bonding process, The overlapped portion formed by overlapping the joined members is joined, and the position of the front end of the rotation tool in the second movement path is made lower than the overlapped portion.

8. The friction stir welding method according to claim 1, wherein: The joined member includes a first joined member and a second joined member, the first joined member has an opening, and the second joined member closes the opening. The first joined member comprises: bottom; a peripheral wall portion, the peripheral wall portion rising from the bottom portion and including the opening portion; a first step portion having a first step bottom surface and a first step side surface rising from the first step bottom surface and provided at an inner peripheral edge of an end surface of the peripheral wall portion; and a first bottom surface, the first bottom surface is continuous with the first step difference bottom surface and is at substantially the same height position, The method further includes a placing step, in which the second joined member is placed on the first step bottom surface and the first bottom surface so that the first bottom surface overlaps with the back surface of the second joined member to form an overlapping portion, and the first step side surface is butted with the side surface of the second joined member to form a first butting portion. In the bonding step, there are: In the overlapped portion, the first movement path is formed by frictionally stirring at least the second joined member by the movement of the rotating tool to form a plasticized region; a third movement path for frictionally stirring the first joined member and the second joined member by movement of the rotation tool in the first butting portion; as well as In the overlapped portion, the second moving path is configured to frictionally stir and plastically fluidize the first and second joined members by moving the rotating tool, while the rotating tool is inserted into a part of the plasticized area formed in the first moving path from the same side as the first moving path. The first and second members to be joined are joined by moving the rotary tool in the order of the first moving path, the third moving path, and the second moving path.

9. The friction stir welding method according to claim 8, wherein: In the joining step, the rotating tool is in contact with only the second joined member when joining the first movement path.

10. The friction stir welding method according to claim 8, wherein: In the bonding process, In the third moving path, the front end of the rotating tool is located at the same height as the bottom surface of the first step difference. In the second moving path, the front end of the rotating tool is located lower than the first bottom surface.

11. The friction stir welding method according to claim 8, wherein: The first joined member comprises: a second step portion, the second step portion having a second step bottom surface that is continuous with the first step bottom surface and located at substantially the same height position, and a second step side surface that rises from the second step bottom surface; and a third step portion, the third step portion having a third step bottom surface which is continuous with the first step bottom surface and is located at substantially the same height position, and a third step side surface which rises from the third step bottom surface, In the placing step, In the placing step, the second joined member is placed on the first step bottom surface, the second step bottom surface, the third step bottom surface and the first bottom surface, the second step side surface is butted against the side surface of the second joined member to form a second butted portion, and the third step side surface is butted against the side surface of the second joined member to form a third butted portion, In the bonding step, there are: In the second butting portion, a fourth movement path for frictionally stirring the first joined member and the second joined member by movement of the rotation tool; as well as In the third butting portion, a fifth movement path for frictionally stirring the first joined member and the second joined member by movement of the rotation tool, The first and second engaged members are engaged by moving the rotary tool in the order of the fourth moving path, the first moving path, the third moving path, the second moving path, and the fifth moving path.

12. The friction stir welding method according to claim 11, wherein: In the bonding process, In the third moving path, the front end of the rotating tool is located at the same height as the bottom surface of the first step difference. In the fourth moving path, the front end of the rotating tool is located at the same height as the bottom surface of the second step difference. In the fifth moving path, the front end of the rotating tool is located at the same height as the bottom surface of the third step difference. In the second moving path, the front end of the rotating tool is located lower than the first bottom surface.

13. The friction stir welding method according to claim 11, wherein: When entering the first movement path from the fourth movement path, the insertion depth of the rotation tool is reduced while the rotation tool is moved.

14. The friction stir welding method according to claim 8, wherein: The thickness of the second joined member is made larger than the height dimension of the first step side surface.

15. The friction stir welding method according to claim 8, wherein: In the third movement path, the first and second members to be joined are friction stir welded in a state where the rotation axis of the rotation tool is located slightly closer to the second member to be joined than the first abutting portion.

16. The friction stir welding method according to claim 15, wherein: The first joined member is formed of a first aluminum alloy, and the second joined member is formed of a second aluminum alloy. The first aluminum alloy is a material type having a higher hardness than that of the second aluminum alloy.

17. The friction stir welding method according to claim 1, wherein: The rotary tool comprises a shaft shoulder portion and a stirring pin hanging down from the center of the lower end surface of the shaft shoulder portion. In the joining step, friction stir welding is performed in a state where the lower end surface of the shoulder portion is in contact with the front surface of the member to be joined.

18. The friction stir welding method according to claim 1, wherein: The rotary tool comprises a base and a stirring pin hanging down from the center of the lower end surface of the base. In the joining step, friction stir welding is performed in a state where only the stirring pin is in contact with the member to be joined while the base portion and the member to be joined are separated.

19. The friction stir welding method according to claim 1, wherein: The rotary tool comprises a base and a stirring pin arranged on the base. The stirring pin includes a base end side pin continuous with the base and a front end side pin continuous with the base end side pin. The taper angle of the base end side pin is larger than the taper angle of the front end side pin, and a stepped pin step portion is formed on the outer peripheral surface of the base end side pin. In the joining step, friction stir welding is performed in a state where the outer peripheral surface of the base end side pin is in contact with the front surface of the joined member.

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