Friction stir welding apparatus and friction stir welding method

Abstract

To provide a friction agitation joint device which can suppress the occurrence of galvanic corrosion during a joint process without providing another corrosion treatment process, and to provide a friction agitation joint method.SOLUTION: This device comprises an anvil 10 which supports a laminate PP, a probe 20 arranged so as to advance / retreat and rotate with respect to the laminate PP, and a shoulder member 30 which clamps the laminate PP with the anvil 10 while being arranged by opposing the anvil 10, where the probe 20 comprises: a joint probe 21 which joints a joint hole P4 with a plate-like member P softened by a friction heat generated on slide contact with the plate-like member P while forming this hole and forms a padding part P5, projecting in a bank-like form, around the joint hole P4, and a back-filling probe 22 for back-filling the padding part P5 softened by the friction heat generated on slide contact with the padding part P5 to the joint hole P4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a friction stir welding apparatus and a friction stir welding method for joining stacked plate-like members using friction stirring. [Background technology]

[0002] In recent years, there has been a strong demand to reduce the negative environmental impact of product manufacturing processes on air quality (SDG 11.6) and to improve energy efficiency (SDG 7.3). In this context, methods for joining multiple components are being reconsidered. For example, welding methods such as arc welding are widely used as a method for joining multiple metal plates together. However, compared to these joining methods, a friction stir welding method as proposed in Patent Document 1 has attracted attention because it can suppress gas generation during the joining process and reduce power consumption. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-013804 Summary of the Invention [Problem to be solved by the invention]

[0004] When metals made of different materials are joined using friction stirring, adjacent portions of the materials with a large potential difference are exposed on the surface at the joined portion. Therefore, if the joint comes into contact with water due to condensation or other reasons, electrolytic corrosion will occur. To prevent this, corrosion-resistant treatment (chemical conversion coating, application of a waterproof sealant, etc.) is required, which creates the problem of making the process complicated.

[0005] The present invention has been made in consideration of the above-mentioned points, and aims to provide a friction stir welding apparatus and a friction stir welding method that can suppress the occurrence of electrolytic corrosion during the joining process without requiring an additional process of applying a waterproof sealant to adjacent parts of the materials. [Means for solving the problem]

[0006] In order to achieve the above object, the friction stir welding apparatus of the present invention comprises an anvil that supports a stack of stacked plate-like members, a probe that is arranged opposite the anvil, is capable of advancing and retreating relative to the stack, and is rotatable about a rotation axis along the advancing and retreating direction, and a shoulder member that has a cylindrical shape through which the probe can be inserted and that clamps the stack together with the anvil, wherein the probe advances toward the plate-like members, forming a joining hole in the plate-like members that have been softened by frictional heat generated at the joining surface that slides against the plate-like members, and joining the plate-like members, and forming a built-up portion that protrudes from the plate surface in a bank-like shape around the joining hole and along the inner surface of the shoulder member, and a backfilling probe that advances toward the plate-like members, and refills the softened built-up portion into the joining hole by frictional heat generated at the backfilling surface that slides against the built-up portion, and the joining probe and the backfilling probe are arranged interchangeably. [Effects of the Invention]

[0007] According to the present invention, friction stir welding can be performed that can suppress the occurrence of electrolytic corrosion during the joining process without the need for an additional step of applying a waterproof sealant to adjacent parts of the materials. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing the configuration of a friction stir welding apparatus according to an embodiment of the present invention. [Figure 2] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a laminate is arranged in a friction stir welding process. [Figure 3]FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a joining probe advances and comes into sliding contact with a laminate in a friction stir joining process. [Figure 4] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a weld hole is formed in a laminated body and a build-up portion is formed in the laminated body during a friction stir welding process. [Figure 5] FIG. 10 is an enlarged cross-sectional view of a main portion showing a state in which plate-shaped members are welded by resistance welding in a friction stir welding process. [Figure 6] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which the welding probe is retracted in the friction stir welding process. [Figure 7] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a joining probe is replaced with a backfilling probe stack in a friction stir joining process. [Figure 8] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a backfilling probe advances and comes into sliding contact with a buildup portion in a friction stir welding process. [Figure 9] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which the joining hole is backfilled in the friction stir joining process. [Figure 10] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which the backfilling probe has retracted in the friction stir welding process and the welding process has been completed. [Figure 11] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a backfilling probe of a first modified example advances and comes into sliding contact with a buildup portion in a friction stir welding process. [Figure 12] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a joining hole is backfilled by a first modified example in a friction stir joining process. [Figure 13] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a backfilling probe of a second modified example in a friction stir welding process has advanced and is in sliding contact with a buildup portion. [Figure 14] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which the joining holes are backfilled by a second modified example of the friction stir joining process. [Figure 15] FIG. 10 is a perspective view showing a backfilling probe of a third modified example. [Figure 16]FIG. 10 is a plan view showing a backfilling surface in a backfilling probe of a third modified example. [Figure 17] FIG. 17 is a cross-sectional view taken along the line AA in FIG. [Figure 18] FIG. 10 is an enlarged cross-sectional view of a main part showing a state in which a joining hole is backfilled by a first modified example in a friction stir joining process. DETAILED DESCRIPTION OF THE INVENTION

[0009] A friction stir welding apparatus S according to one embodiment of the present invention will be described in detail with reference to FIGS. In the description, the same elements are given the same reference numerals and redundant description will be omitted. The friction stir welding apparatus S of this embodiment is for welding plate-like members P stacked in the plate thickness direction (see FIG. 1). The stacked plate-like members P are referred to as a laminate PP. In the friction stir welding apparatus S of this embodiment, the laminate PP is arranged so that its plate surfaces face in the up-down direction.

[0010] The laminate PP is composed of three laminated metal plate-shaped members P (see FIG. 1). In the laminate PP, the topmost plate-like member P (upper member P1) is made of an aluminum alloy. In the laminate PP, the plate-shaped member P (middle member P2) located in the middle and the plate-shaped member P (lower member P3) located at the bottom are made of the same iron alloy material. That is, the upper member P1 is made of a material having a lower melting point than the middle member P2 and the lower member P3.

[0011] The friction stir welding apparatus S includes an anvil 10, a probe 20, a shoulder member 30, a drive mechanism 40, a resistance welding unit 50, and a control unit 60. The anvil 10 is disposed so as to be movable forward and backward relative to the probe 20 (laminate PP) along a rotation axis 20a of the probe 20, and is moved by a drive mechanism 40. The direction along the rotation axis 20a is referred to as the advancing / retreating direction. The anvil 10 supports the laminate PP from below while advancing toward the probe 20 . The anvil 10 has a receiving portion 11 and a hemispherical portion 12 . The receiving portion 11 and the hemispherical portion 12 are formed from separate members.

[0012] The receiving portion 11 has a cylindrical shape and is arranged to be movable along the rotation axis 20a. The receiving portion 11 has an insulating material 13 disposed on the upper end surface that contacts the laminate PP. The hemispherical portion 12 is made of a cylindrical member having an upwardly convex hemispherical shape at its upper end, and is disposed inside the cylinder of the receiving portion 11 . The hemispherical portion 12 is arranged to be movable together with the receiving portion 11 along the rotation axis 20a. The hemispherical portion 12 is made of a conductive material. The anvil 10 has a receiving portion 11 that supports the laminate PP, and a tip of a hemispherical portion 12 that abuts against the laminate PP.

[0013] The probe 20 performs bonding and backfilling on the laminate PP. The probe 20 is arranged so as to be rotatable around a rotation axis 20a and so as to be movable forward and backward along the rotation axis 20a relative to the anvil 10 (laminate PP). The probe 20 rotates and moves using a driving mechanism 40 as a driving source. The probe 20 is made of a material such as ceramic or cemented carbide.

[0014] That is, a material that is harder and has a higher melting point than the material of the laminated PP is selected for the probe 20 . The probe 20 is composed of a joint probe 21 and a first backfilling probe 22 (backfilling probe). The probe 20 is configured to be detachable from the friction stir welding apparatus S, and the welding probe 21 and the first backfilling probe 22 are interchangeable.

[0015] The joining probe 21 joins the three plate-like members P that make up the laminate PP. The junction probe 21 has a generally cylindrical shape, and its tip has a tapered shape. The bonding probe 21 advances toward the laminate PP from above to below in FIGS. 1 to 10 while rotating, and the bonding surface 21a formed at the tip of the bonding probe 21 comes into sliding contact with the laminate PP. Due to the frictional heat generated between the tip of the bonding probe 21 and the laminate PP by the sliding contact, the laminate PP softens in the order of the upper member P1, the middle member P2, and the lower member P3.

[0016] Then, as the bonding probe 21 advances further, the tip of the bonding probe 21 pushes aside the components of the softened laminate PP, forming a bonding hole P4 and bonding the components together. Furthermore, the pushed-aside member forms a padded portion P5 that protrudes from the plate surface in a bank-like shape inside the inner circumferential surface of the shoulder member 30 around the joining hole P4.

[0017] The first backfilling probe 22 backfills the buildup portion P5 into the joining hole P4. The first backfilling probe 22 has an approximately cylindrical shape, and at its tip is provided a first backfilling surface 22a (backfilling surface) consisting of a circular flat surface that is perpendicular to the rotation axis 20a and has a diameter larger than the outer diameter of the buildup portion P5 (the inner diameter of the shoulder member 30). A first backfilling protrusion 22b is formed at the center of the first backfilling surface 22a (on the rotation axis 20a).

[0018] The first backfilling projection 22b has a generally conical shape and projects toward the laminate PP. Furthermore, the protrusion dimension of the first backfilling protrusion 22b from the first backfilling surface 22a is set to be smaller than the plate thickness dimension of the upper member P1, and the diameter of its base portion is set to be smaller than the hole diameter of the joining hole P4. That is, the shape of the first backfilling projection 22b is set so that the layer of aluminum alloy in the joining hole P4 after backfilling has dimensions sufficient to suppress the occurrence of electrolytic corrosion.

[0019] The shoulder member 30 has a cylindrical shape with the rotation axis 20a as its central axis. The probe 20 rotates and moves back and forth within the cylindrical shoulder member 30 . The shoulder member 30 is disposed so as to be movable forward and backward relative to the anvil 10 (laminate PP) along the rotation axis 20a. The shoulder member 30 moves forward and backward using a shoulder drive mechanism 44 as a drive source. The shoulder member 30 is made of a conductive material.

[0020] The drive mechanism 40 includes a rotation drive mechanism 41, a forward / backward drive mechanism 42, an anvil drive mechanism 43, and a shoulder drive mechanism 44. The rotation drive mechanism 41 is a drive source for rotating the probe 20 . The advance / retract drive mechanism 42 is a drive source for moving the probe 20 forward and backward. The anvil drive mechanism 43 is a drive source for moving the anvil 10 back and forth. The shoulder drive mechanism 44 is a drive source for moving the anvil 10 back and forth.

[0021] In the resistance welding 50, the hemispherical portion 12 of the anvil 10 and the shoulder member 30 are used as electrodes, and a current for the laminate PP is passed through the electrodes to weld together the members that make up the laminate PP. The control unit 60 controls the drive mechanism 40 and the resistance welding mechanism 50 .

[0022] Next, the operation (welding procedure) of the friction stir welding apparatus S will be described (see FIG. 2-10). First, a step is performed in which the anvil 10 supports the laminate PP (see FIG. 2). Before this step is performed, the bonding probe 21 is attached to the main body of the device (see FIG. 2). In this step, first, the laminate PP is placed on the anvil 10 . Here, the laminate PP is placed so that the joint is positioned on the hemispherical portion 12. Then, the shoulder member 30 is advanced, and the shoulder member 30 and the anvil 10 sandwich and fix the laminate PP.

[0023] In the above description, the laminate PP is moved to match the position of the friction stir welding apparatus S, but the present invention is not limited to this. For example, the procedure may be such that the stack PP remains in its original position, and the position and orientation of the friction stir welding apparatus S are moved and changed in accordance with the stack PP.

[0024] Next, the joining surface 21a of the joining probe 21 is pressed against the laminate PP, and the laminate PP is softened by frictional heat caused by sliding contact, joining the plate-like members P together and forming a build-up portion P5 (see FIGS. 3 to 6). In this step, the control unit 60 operates the driving mechanism 40 to rotate the bonding probe 21 and move it toward the laminate PP (see FIG. 3). Then, the rotating joining surface 21a is pressed against the laminated body PP, and the frictional heat generated by the sliding contact softens each plate-like member P in turn.

[0025] Furthermore, while rotating, the bonding probe 21 is advanced toward the laminate PP, and the bonding probe 21 pushes aside the softened member, forming a bonding hole P4 (see FIG. 4). Then, the pushed-aside members form padding portions P5 around the joining holes P4, and the plate-like members P are joined together. Furthermore, when the advancement dimension of the joining probe 21 reaches a set value, the control unit 60 operates the resistance welding 50 to weld the middle member P2 and the lower member P3 together (see FIG. 5). After welding, the control unit 60 stops the resistance welding 50, and moves the joining probe 21 backward while rotating it, thereby separating the joining probe 21 and the anvil 10 from the stack PP (see FIG. 6). In this state, the wall of the bonding hole P4 remains exposed as an adjacent portion of the material with a large potential difference.

[0026] Next, a step of replacing the bonding probe 21 with the first backfilling probe 22 is performed (see FIG. 7). In this step, the welding probe 21 is removed from the main body (not shown) of the friction stir welding apparatus S, and the first backfilling probe 22 is attached instead, thereby replacing the probe 20. The shoulder member 30 may be moved to a position where it does not interfere with the first backfilling probe 22.

[0027] Next, the first backfilling surface 22a of the first backfilling probe 22 is pressed against the buildup portion P5, the buildup portion P5 is softened by the frictional heat generated by the sliding contact, and the softened buildup portion P5 is backfilled into the joining hole P4 by the first backfilling surface 22a (see Figures 8 to 10). In this step, the first backfilling probe 22 is rotated and advanced toward the build-up portion P5 (layered body PP) (see FIG. 8). The rotating first backfilling surface 22a is pressed against the build-up portion P5, and the build-up portion P5 is softened by frictional heat generated by sliding contact. The first backfilling surface 22a is further advanced to backfill the softened portion of the build-up portion P5 into the joining hole P4 (see FIG. 9). Then, the joining hole P4 is backfilled, thereby covering and concealing the exposed adjacent material portion of the hole wall.

[0028] When the advancement dimension of the first backfilling probe 22 reaches the set value, the control unit 60 rotates and retracts the joining probe 21, separating the first backfilling probe 22 and the anvil 10 from the laminate PP (see Figure 6). This completes the joining process at one joining location, and the joining process at the next joining location is then carried out.

[0029] Next, the effects of this embodiment will be described. By using the friction stir welding apparatus S of this embodiment, it is possible to backfill the welding holes P4 that occur during welding during the welding process. Furthermore, since the adjacent portions of the material having a large potential difference can be covered and hidden without being exposed to the surface, the occurrence of electrolytic corrosion on the surface of the material can be prevented. This eliminates the need for a new process of applying a waterproof sealant to the joining surfaces to prevent electrolytic corrosion. Furthermore, by backfilling the joining holes P4, the fracture cross section increases, and therefore the joining strength between the lower member P3 and the middle member P2 can be improved.

[0030] In the friction stir welding apparatus S of this embodiment, the first backfilling probe 22 is provided with a first backfilling projection 22b at the center of the first backfilling surface 22a. When the padding portion P5 is backfilled into the joining hole P4, the joining hole P4 is gradually filled from the outer periphery side of the hole. However, since there is no friction between the softened member and the first backfilling surface 22a, the softened member cools and hardens while moving toward the center of the hole, which may cause insufficient filling. Therefore, by providing the first backfilling projections 22b, the friction surface near the center is increased. This allows the first backfilling protrusion 22b to slide against the material that hardens as it moves from the outer periphery of the hole toward the center, re-softening the hardening material and more reliably backfilling the area near the center.

[0031] In the friction stir welding apparatus S of this embodiment, the welding probe 21 and the first backfilling probe 22 are replaced by attaching and detaching them to the apparatus main body, but the present invention is not limited to this configuration. For example, it is possible to arrange the joining probe 21 and the first backfilling probe 22 adjacent to each other in the device body, and to move the probe 20 laterally, rotate, or otherwise during joining and backfilling. That is, it is possible to configure the joining probe 21 and the first backfilling probe 22 so that they can be replaced while they are still attached to the device body, and the same effects can be obtained.

[0032] Furthermore, when multiple locations are set for joining the laminate PP, it is possible to use a work procedure in which all joining locations are joined using the joining probe 21, and then the probe 20 is replaced with the first backfilling probe 22, and all joining holes P4 are backfilled. This reduces the time required to replace the probe, thereby shortening the work time required for joining and backfilling.

[0033] Furthermore, it is also possible to configure a single friction stir welding apparatus S as a unit (a joining unit) of the welding probe 21 and the anvil 10 and a unit (a backfilling unit) of the first backfilling probe 22 and the anvil 10 separately. By arranging these units adjacent to each other and replacing the units, the same effect can be obtained by replacing the probe 20. Furthermore, in this configuration, backfilling can be performed by the backfilling unit, and at the same time, joining of another portion can be performed by the joining unit. Therefore, this configuration is more suitable when multiple locations need to be joined, as it can reduce the work time.

[0034] Furthermore, in the friction stir welding apparatus S of this embodiment, the stack PP is stacked one on top of the other, and the anvil 10 supports the stack PP from below while the probe 20 joins and backfills the stack PP from above, but this is not limited to this configuration. For example, it is possible to configure the laminate PP so that it is stacked horizontally, with the anvil 10 supporting the laminate PP from the right side, and the probe 20 joining and backfilling the laminate PP from the left side. In other words, joining and backfilling can be performed without being limited to the direction in which the plate-like members are stacked.

[0035] Next, a first modified example of the backfilling probe will be described in detail with reference to FIGS. In the description, the same elements as those in the above-described embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted. In the second backfilling probe 23 of this modification, the shape of the second backfilling surface 23a is different from that of the first backfilling surface 22a of the above-described embodiment.

[0036] The second backfilling surface 23a of the second backfilling probe 23 of this modified example has a circular shape centered on the rotation axis 20a and formed so that its outer periphery is positioned outside the outer periphery of the buildup portion P5. The second backfilling surface 23a has a concave shape with a curved surface recessed so that the central portion thereof is farthest from the plate surface of the laminate PP. That is, the outer circumferential edge of the second backfilling surface 23a is provided at a position farther from the rotation axis 20a than the inner periphery of the shoulder member 30. In addition, the second backfilling surface 23a has a concave shape that is recessed rearward in the advancing direction.

[0037] By backfilling the joining hole P4 using the second backfilling probe 23 of this modified example, the softened member is pressed into the second backfilling surface 23a from the outer periphery side toward the center side. This prevents the softened material from flowing out of the second backfilling surface 23a, and makes it possible to more reliably backfill the joining hole P4.

[0038] Next, a second modified example of the backfilling probe will be described in detail with reference to FIGS. In the description, the same elements as those in the above-described embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted. The third backfilling probe 24 of this modification has a third backfilling surface 24a whose shape is different from that of the first backfilling surface 22a of the above-described embodiment.

[0039] The third backfilling surface 24a of the third backfilling probe 24 of this modified example has a shape that combines the first backfilling protrusion 22b of the first backfilling probe 22 of the embodiment and the second backfilling surface 23a of the second backfilling probe 23 of the first modified example. That is, a third backfilling projection 24b having a substantially conical shape is provided at the center of the concave shape. With this configuration, the softened material is moved from the outer periphery to the center in the concave-shaped portion, and the third backfilling protrusion 24b slides against the material that has cooled and hardened while moving toward the center, thereby re-softening it. This allows the central portion of the joining hole P4 to be backfilled more reliably.

[0040] Next, a third modified example of the backfilling probe will be described in detail with reference to FIGS. In the description, the same elements as those in the above-described embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted. The fourth backfilling probe 25 of this modification has a fourth backfilling surface 25a whose shape is different from that of the first backfilling surface 22a of the above-described embodiment.

[0041] The fourth backfilling surface 25a of the fourth backfilling probe 25 of this modified example has a circular shape centered on the rotation axis 20a and formed so that its outer peripheral edge is positioned outside the outer peripheral edge of the buildup portion P5. Furthermore, the fourth backfilling surface 25a is formed with a spiral groove (spiral groove 25b) that continues from the outer periphery to the center (see FIG. 16). Furthermore, a fourth backfilling protrusion 25c similar to the first backfilling protrusion 22b of the embodiment is provided in the center of the fourth backfilling surface 25a.

[0042] The end of the spiral groove on the center side is connected to the fourth backfilling projection 25c. Therefore, by rotating the fourth backfilling probe 25 counterclockwise in FIG. 16, the softened material is gathered toward the fourth backfilling projection 25c. Then, the fourth backfilling projections 25c come into sliding contact with the material that has cooled and hardened while moving toward the center of the spiral groove 25b, and can re-soften it.

[0043] By backfilling the joining hole P4 using the fourth backfilling probe 25 of this modified example, the softened material moves within the spiral groove 25b and is pressed from the outer periphery to the center of the fourth backfilling surface 25a. This prevents the softened material from flowing out of the fourth backfilling surface 25a, and makes it possible to more reliably backfill the joining hole P4. [Explanation of symbols]

[0044] S Friction Stir Welding Equipment P Plate-shaped member PP laminate P4 joint hole P5 Meat filling section 10 Anvil 20 probes 20a Rotating shaft 21 Bonded Probe 21a Joint surface 22 Backfill probe (first backfill probe) 22a Backfill surface (first backfill surface) 22b Backfill protrusion (first backfill protrusion) 23 Backfill probe (second backfill probe) 23a Backfill surface (second backfill surface) 24 Backfill probe (third backfill probe) 24a Backfill surface (third backfill surface) 24b Backfill protrusion (third backfill protrusion) 25 Backfill probe (4th backfill probe) 25a Backfill surface (fourth backfill surface) 25b spiral groove 25c Backfill protrusion (fourth backfill protrusion) 30 Shoulder member

Claims

1. an anvil that supports a stack of plate-like members; a probe disposed opposite the anvil, capable of advancing and retreating relative to the laminate, and rotatable about a rotation axis along the advancing and retreating direction; a shoulder member having a cylindrical shape through which the probe can be inserted and which holds the laminate together with the anvil; Equipped with The probe is a joining probe that advances toward the plate-like member, forms a joining hole in the plate-like member that has been softened by frictional heat generated by sliding contact between the joining surface of the joining probe and the plate-like member, and joins the plate-like member, and forms a built-up portion that protrudes in a bank-like shape from the plate surface around the joining hole and along the inner peripheral surface of the shoulder member; a backfilling probe that advances toward the plate-like member and backfills the buildup portion, which has been softened by frictional heat generated by the backfilling surface sliding in contact with the buildup portion, into the joining hole; Equipped with The bonding probe and the backfilling probe are arranged interchangeably. Friction stir welding apparatus characterized by:

2. The friction stir welding apparatus according to claim 1, The backfill probe comprises: The device is arranged to be rotatable around a rotation axis along the forward / backward direction, The backfill surface is having a circular shape centered on the rotation axis, A backfilling projection is provided at the center thereof, which projects toward the laminate. Friction stir welding apparatus characterized by:

3. The friction stir welding apparatus according to claim 1, The backfill probe comprises: The device is arranged to be rotatable around a rotation axis along the forward / backward direction, The backfill surface is a circular shape having a center on the rotation axis and an outer circumferential edge of the circular shape positioned outside the outer circumferential edge of the padding portion; The central portion has a concave shape formed by a curved surface that is recessed so as to be farthest from the plate surface of the laminate. Friction stir welding apparatus characterized by:

4. The friction stir welding apparatus according to claim 1, The backfill probe comprises: The device is arranged to be rotatable around a rotation axis along the forward / backward direction, The backfill surface is a circular shape having a center on the rotation axis and an outer circumferential edge of the circular shape positioned outside the outer circumferential edge of the padding portion; The rotating shaft is provided with a spiral groove extending from its outer periphery to the rotating shaft. Friction stir welding apparatus characterized by:

5. an anvil supporting the laminate; a step of pressing a joining surface of the joining probe against the laminated body, softening the laminated body by frictional heat caused by sliding contact, and joining the plate-like members together while forming a joining hole and a build-up portion; replacing the bonded probe with a backfilled probe; a step of pressing a backfilling surface of the backfilling probe against the buildup portion, softening the buildup portion by frictional heat caused by sliding contact, and backfilling the softened buildup portion into the joining hole with the backfilling surface; A friction stir welding method comprising:

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