Friction stir welding tool

Abstract

To provide a friction stir welding tool capable of further improving the welding strength of workpieces while suppressing the expansion of a welding width and the occurrence of a welding defect.SOLUTION: The friction stir welding tool includes a shank, a first spiral part integrally formed with the shank and having a first spiral surface spirally extending around an axial center extending coaxially with the rotary member so as to approach the axial center as separating from the shank in an axial direction, a second spiral part integrally formed with the first spiral part and having a second spiral surface spirally extending around the axial center in a direction opposite to the first spiral surface so as to separate from the axial center as separating from the first spiral part in the axial direction on a side opposite to the shank side, and a heat receiving part integrally extending from the second spiral part to a side opposite to the first spiral part side and receiving heat from the second spiral part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a friction stir welding tool for joining workpieces together. [Background technology]

[0002] Conventionally, a friction stir welding tool equipped with a stir probe has been known (see, for example, Patent Document 1). In this friction stir welding tool, a spiral pressure-receiving surface inclined with respect to the rotation axis of the stir probe is provided on the side of the stir probe. The pressure-receiving surface includes a pressure-receiving region perpendicular to the rotation tangent direction in a cross section perpendicular to the rotation axis. When such a friction stir welding tool is used to join workpieces, the stir probe is rotated in a rotation direction in which the normal direction to the pressure-receiving surface is positive. This causes the pressure-receiving surface to induce plastic flow of the material in the rotation direction, reducing the proportion of plastic flow of the material in the extension direction of the rotation axis, thereby making it possible to suppress the generation of burrs. Furthermore, the friction stir welding tool described in Patent Document 1 can omit a so-called shoulder that is pressed against the workpieces, making it possible to suppress an increase in the weld width even if the stir region becomes deep.

[0003] Also, a known friction stir welding device includes a cylindrical outer holder, a cylindrical inner holder disposed inside the outer holder, a slide shaft inserted into the inner holder, and a bobbin tool attached to the tip of the slide shaft as a rotary tool for friction stir welding (see, for example, Patent Document 2). The outer holder is fixed to a chuck of the friction stir welding device and is rotated by the friction stir welding device around an axis extending in the vertical direction. The inner holder has an elongated hole penetrating the outer periphery in the radial direction and is fixed to the outer holder so as to rotate integrally with the outer holder. The slide shaft has a protrusion protruding outward from the side surface, and the protrusion engages with the elongated hole of the inner holder. This allows the inner holder and the slide shaft to rotate integrally, and the slide shaft can move up and down relative to the inner holder within the range of the elongated hole. The bobbin tool is connected to the slide shaft and rotates forward and backward around the axis extending in the vertical direction in accordance with the rotation of the slide shaft. The bobbin tool includes a cylindrical first shoulder, a cylindrical second shoulder spaced below the first shoulder, and a pin connecting the first and second shoulders. The pin passes through the second shoulder, and a nut is threaded onto the pin at the lower end of the second shoulder. An upper spiral groove is formed on the outer circumferential surface of the pin, extending from the lower end of the first shoulder to a midpoint in the pin's height direction, and a lower spiral groove extending from the midpoint to the upper end of the second shoulder, extending in the opposite direction to the upper spiral groove.

[0004] When joining a pair of workpieces using such a friction stir welding device, the end faces of the workpieces are butted together, and the pin of the rotating bobbin tool is moved along the butted portion. This allows the materials around the pin to be friction-stirred, thereby joining the workpieces. Furthermore, by using a bobbin tool including first and second shoulders, it is possible to omit a backing member placed on the back side of the pair of workpieces, thereby reducing the complexity of the joining process. Furthermore, in the above-mentioned friction stir welding device, since the slide shaft is movable within the internal holder, even if the workpieces are deformed by the frictional heat of friction stirring, the bobbin tool can be moved up and down to follow the positional misalignment of the end faces, thereby reducing the occurrence of welding defects due to misalignment of the joining position. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-185597 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-208654 Summary of the Invention [Problem to be solved by the invention]

[0006] The friction stir welding tool described in Patent Document 1 can suppress the increase in the welding width, but because it can only join the workpieces from one side, it is difficult to further improve the welding strength. In contrast, the bobbin tool described in Patent Document 2 can join the workpieces from both the front and back sides, further improving the welding strength. However, with the bobbin tool described in Patent Document 2, the pin expands due to frictional heat generated by friction stirring, which may cause welding defects due to fluctuations in the distance between the first and second shoulders.

[0007] Therefore, a main object of the present disclosure is to provide a friction stir welding tool that can further improve the joining strength between materials to be joined while suppressing the increase in joining width and the occurrence of joining defects. [Means for solving the problem]

[0008] The friction stir welding tool disclosed herein is a friction stir welding tool for joining materials to be welded, and includes: a shank coaxially connected to a rotating member; a first helical portion formed integrally with the shank and having a first helical surface that extends spirally around an axis extending coaxially with the rotating member, approaching the axis as it moves away from the shank in the axial direction; a second helical portion formed integrally with the first helical portion and having a second helical surface that extends spirally in the opposite direction to the first helical surface around the axis as it moves away axially from the first helical portion toward the opposite side to the shank side; and a heat receiving portion that extends integrally from the second helical portion toward the opposite side to the first helical portion side and receives heat from the second helical portion.

[0009] The friction stir welding tool disclosed herein rotates around its axis during welding of workpieces, and moves in one direction through a pair of workpieces that are butted or overlapping each other, with the boundary between the first and second spiral portions. This friction stirs the surrounding material with the rotating first and second spiral portions, forming a plasticized region behind the direction of travel of the first and second spiral portions. Furthermore, the first and second spiral surfaces are formed to approach the axis and extend in opposite directions toward the boundary between the first and second spiral portions, respectively, thereby generating plastic flow in the direction of rotation of the friction stir welding tool and reducing the rate of plastic flow in the direction of extension of the axis. This enables the workpieces to be firmly welded from both the front and back sides while suppressing the expansion of the weld width and the generation of burrs during friction stir welding. Furthermore, heat generated in the first and second spiral portions by friction stirring the material is transferred from the second spiral portion to the heat receiving portion. This suppresses expansion around the boundary between the first and second helical portions due to frictional heat, effectively suppressing the occurrence of welding defects due to variations in the distance between the first and second helical surfaces. As a result, the friction stir welding tool disclosed herein can further improve the welding strength between the workpieces while suppressing the expansion of the welding width and the occurrence of welding defects. In addition, by integrating the shank, first helical portion, second helical portion, and heat receiving portion, the cost of the friction stir welding tool can be reduced by eliminating moving parts and reducing the number of parts. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a friction stir welding tool of the present disclosure. [Figure 2] FIG. 2 is an enlarged view showing a main part of the friction stir welding tool of the present disclosure. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] 1 is an explanatory diagram showing an example of a usage mode of a friction stir welding tool according to the present disclosure. FIG. [Figure 5] FIG. 10 is an explanatory diagram showing another example of a usage mode of the friction stir welding tool of the present disclosure. [Figure 6] 10 is a chart showing temperatures measured immediately after friction stir welding of a shank, a non-spiral portion, and a heat-receiving portion of the friction stir welding tool of the present disclosure. [Figure 7] FIG. 10 is an enlarged view showing a main portion of another friction stir welding tool of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, embodiments of the present disclosure will be described with reference to the drawings.

[0012] FIG. 1 is a perspective view showing a friction stir welding tool 1 according to the present disclosure, and FIG. 2 is an enlarged view showing a main portion of the friction stir welding tool 1. The friction stir welding tool 1 shown in these drawings is attached to a rotating member such as a spindle of a machine tool (not shown) and is rotated by the spindle to join a pair of workpieces that are butted against each other or overlap each other by friction stir welding. As shown in FIGS. 1 and 2, the friction stir welding tool 1 includes a shank 2, a first helical portion 3, a non-helical portion 4, a second helical portion 5, and a heat-receiving portion 6, which are integrally formed. That is, the shank 2, the first helical portion 3, the non-helical portion 4, the second helical portion 5, and the heat-receiving portion 6 are formed by cutting a base material made of tool steel such as SKD61.

[0013] The shank 2 is a portion coaxially connected to a rotating member such as a spindle of a machine tool. The first helical portion 3 is integral with the tip end portion 20 (the lower end portion in FIG. 1 ) of the shank 2. The first helical portion 3 is formed so as to decrease in diameter (taper) as it moves axially away from the end face 20s of the tip end portion 20 of the shank 2, and has a first helical surface 30. The first helical surface 30 extends helically (e.g., clockwise) around an axis a that extends coaxially with the rotating member (spindle), approaching the axis a in the radial direction as it moves axially away from the end face 20s of the tip end portion 20 of the shank 2. In this embodiment, the inclination angle θ1 of the first helical surface 30 with respect to a plane perpendicular to the axis a is determined to satisfy 0<θ1≦45°. However, the inclination angle θ may also be determined to satisfy 45°<θ1<90°.

[0014] The non-helical portion 4 extends integrally from the end of the first helical portion 3 opposite the shank 2 side (the lower end in FIG. 2 ) to the opposite side of the shank 2 side, i.e., downward in FIGS. 1 and 2 , and is formed in a cylindrical shape in this embodiment. The axial length (height) of the non-helical portion 4 is set to be smaller than the thickness of one workpiece to be joined that is butted against each other, or the total thickness of a pair of workpieces that are overlapped on each other. However, the non-helical portion 4 does not necessarily have to be formed in a cylindrical shape and may include a chamfered portion. In addition, a helical groove (thread groove) may be formed on the outer circumferential surface of the cylindrical non-helical portion 4.

[0015] The second helical portion 5 extends integrally from an end of the non-helical portion 4 opposite the first helical portion 3 side (the lower end in FIG. 2 ) toward the opposite side of the first helical portion 3 side, i.e., downward in FIGS. 1 and 2 . In other words, the non-helical portion 4 forms the boundary between the first and second helical portions 3, 5. The second helical portion 5 is formed so that its diameter increases as it moves axially away from the non-helical portion 4 (first helical portion 3) toward the opposite side of the shank 2 side, and has a second helical surface 50. The second helical surface 50 extends spirally in the opposite direction (e.g., left-handed) to the first helical surface 30 around an axis a that extends coaxially with the rotating member (main shaft) so as to move radially away from the axis a as it moves axially away from the non-helical portion 4 (first helical portion 3) toward the opposite side of the shank 2 side. In this embodiment, the inclination angle θ2 of the second helical surface 50 with respect to a plane perpendicular to the axis a is determined so that its absolute value is equal to the inclination angle θ1 of the first helical surface 30 and so that it satisfies -45°≦θ2<0. However, the inclination angle θ2 may also be determined so that it satisfies -90°<θ2<45°. Furthermore, as can be seen in FIG. 2 , the end 30e of the first helical surface 30 on the non-helical portion 4 side and the end 50e of the second helical surface 50 on the non-helical portion 4 side are positioned with a 180° offset.

[0016] Furthermore, in the friction stir welding tool 1, the first helical surface 30 and the second helical surface 50 have the same helical width w and helical pitch p. However, the helical width w and helical pitch p of the first and second helical surfaces 30, 50 do not necessarily have to be constant, and may be set to vary in the extending direction of the first and second helical surfaces 30, 50, as long as they are the same between the first and second helical surfaces 30, 50 in the range from the end 30e to the end on the opposite side from the non-helical portion 4 side (the end face 20s side) and in the range from the end 50e to the end on the opposite side from the non-helical portion 4 side (the heat receiving portion 6 side).

[0017] The heat receiving portion 6 extends integrally from the second helical portion 5 to the side opposite to the non-helical portion 4 (first helical portion 3), i.e., downward in FIGS. 1 and 2, and receives heat from the non-helical portion 4 via the second helical portion 5. In this embodiment, the heat receiving portion 6 is formed in a cylindrical shape. However, the heat receiving portion 6 does not necessarily have to be formed in a cylindrical shape and can be formed in any shape. Furthermore, the heat receiving portion 6 has a volume that is at least larger than the volume of the second helical portion 5. The volume of the heat receiving portion 6 may be as large as possible within a range that does not interfere with processing using the friction stir welding tool 1. Furthermore, in this embodiment, the surface roughness of the outer peripheral surface and end face (the lower surface in FIG. 2, etc.) of the heat receiving portion 6 is larger than the surface roughness of the first and second helical surfaces 30, 50 and the non-helical portion 4.

[0018] As shown in Fig. 4, when a pair of workpieces (e.g., metal materials) 100a, 100b butted together are joined using a friction stir welding tool 1, the workpieces 100a, 100b are positioned with respect to the friction stir welding tool 1 so that their butted surfaces face the axis a and the centers of the workpieces 100a, 100b in the thickness direction and the center of the non-helical portion 4 in the axial direction are included in the same plane. Also, as shown in Fig. 5, when a pair of workpieces (metal materials) 200a, 200b superimposed on each other are joined using the friction stir welding tool 1, the workpieces 200a, 200b are positioned with respect to the friction stir welding tool 1 so that their to-be-welded portions face the axis a and the butted surfaces of the workpieces 200a, 200b and the center of the non-helical portion 4 in the axial direction are included in the same plane. When the workpieces 100a, 100b or 200a, 200b to be welded are positioned relative to the friction stir welding tool 1, the friction stir welding tool 1 is rotated around the axis a by a machine tool, and the non-helical portion 4 is moved so as to penetrate a pair of workpieces 100a, 100b or 200a, 200b that are abutted against each other or overlap each other and proceed in one direction (for example, toward the back of the paper in Figures 4 and 5).

[0019] As a result, the rotating non-helical portion 4 and the portions of the first and second helical portions 3 and 5 close to the non-helical portion 4 frictionally stir the surrounding material, and a plasticized region is formed behind the direction of travel of the non-helical portion 4. Furthermore, the first and second helical surfaces 30 and 50 are formed so that they approach the axis a and extend in opposite directions as they approach the non-helical portion 4, causing plastic flow of the material in the direction of rotation of the friction stir welding tool 1 and reducing the rate of plastic flow of the material in the direction of extension of the axis a. Therefore, it is possible to firmly join the workpieces 100a, 100b or 200a, 200b from both the front and back sides while suppressing the expansion of the weld width and the occurrence of burrs due to friction stir welding.

[0020] Furthermore, heat generated in the non-helical portion 4 and the adjacent first and second helical portions 3 and 5 due to frictional stirring of the material is mainly transferred to the heat-receiving portion 6 via the second helical portion 5. This suppresses expansion of the non-helical portion 4 due to frictional heat, effectively suppressing the occurrence of welding defects due to variations in the axial distance between the first helical surface 30 and the second helical surface 50. Figure 6 shows temperatures measured immediately after friction stir welding of the shank 2, non-helical portion 4, and heat-receiving portion 6 of the friction stir welding tool 1. As shown in the figure, immediately after friction stir welding, the temperature of the heat-receiving portion 6 is higher than the temperatures of the non-helical portion 4 and the shank 2. It can be seen from these measurement results that frictional heat generated in the non-helical portion 4 is transferred to the heat-receiving portion 6 via the second helical portion 5, thereby effectively suppressing thermal expansion of the non-helical portion 4. As a result, the friction stir welding tool 1 makes it possible to further improve the welding strength between the workpieces 100a, 100b or 200a, 200b while suppressing an increase in the welding width and the occurrence of welding defects. In addition, by integrating the shank 2, first helical portion 3, non-helical portion 4, second helical portion 5, and heat receiving portion 6, it is possible to reduce the cost of the friction stir welding tool 1 by eliminating the need for a movable portion for moving the pair of upper and lower shoulders toward and away from each other and by reducing the number of parts.

[0021] The friction stir welding tool 1 also includes a non-helical portion 4 extending integrally from the end of the first helical portion 3 opposite the shank 2, and a second helical portion 5 extending integrally from the end of the non-helical portion 4 opposite the first helical portion 3. Forming the non-helical portion 4, which does not include the first and second helical surfaces 30, 50, between the first and second helical portions 3, 5 in this manner prevents excessive material agitation near the center in the thickness direction of the pair of butted workpieces 100a, 100b or near the intended welding portions of the pair of overlapping workpieces 200a, 200b, thereby preventing defects caused by excessive agitation. Additionally, adjusting the axial length of the non-helical portion 4 (cylindrical portion) depending on the welding target can optimize the amount of material agitation around the non-helical portion 4.

[0022] Furthermore, in the friction stir welding tool 1, the volume of the heat receiving portion 6 is set to be at least larger than the volume of the second helical portion 5. This makes it possible to transfer heat from the non-helical portion 4 to the heat receiving portion 6 without accumulating it in the second helical portion 5, thereby effectively suppressing a temperature rise in the non-helical portion 4 during friction stir welding.

[0023] Furthermore, in the friction stir welding tool 1, the end 30e of the first helical surface 30 on the non-helical portion 4 side and the end 50e of the second helical surface 50 on the non-helical portion 4 side are positioned with a 180° offset. This allows the first and second helical surfaces 30, 50 to press both of the pair of workpieces 100a, 100b or 200a, 200b that are abutted against or overlapped with each other in the direction of movement of the non-helical portion 4, thereby effectively preventing the friction stir welding tool 1 moving in one direction from wobbling due to a reaction force from the pair of workpieces 100a, 100b or 200a, 200b. As a result, it is possible to suppress the generation of frictional heat associated with wobbling of the friction stir welding tool 1 and effectively suppress the temperature rise of the non-helical portion 4 during friction stir welding.

[0024] Furthermore, in the friction stir welding tool 1, the surface roughness of the outer circumferential surface and end surface of the heat receiving portion 6 is greater than the surface roughness of the first and second helical surfaces 30, 50 and the non-helical portion 4. This simplifies the surface treatment of the heat receiving portion 6 that is not directly involved in friction stir welding, i.e., processing by the non-helical portion 4, etc., and makes it possible to further reduce the cost of the friction stir welding tool 1. However, the surface roughness of the heat receiving portion 6 may be approximately the same as the surface roughness of the first and second helical surfaces 30, 50 and the non-helical portion 4.

[0025] 7 is an enlarged view showing a main part of another friction stir welding tool 1B of the present disclosure. Note that, among the components of the friction stir welding tool 1B, the same elements as those of the above-described friction stir welding tool 1 are denoted by the same reference numerals, and redundant explanations will be omitted.

[0026] 7, the friction stir welding tool 1B includes an integrally formed shank 2, first helical portion 3, second helical portion 5, and heat-receiving portion 6, and corresponds to the friction stir welding tool 1 described above without the non-helical portion 4. That is, in the friction stir welding tool 1B, the second helical portion 5 extends integrally from the end of the first helical portion 3 opposite the shank 2 side to the opposite side from the shank 2 side. Also in the friction stir welding tool 1B, the end 30e of the first helical surface 30 on the non-helical portion 4 side and the end 50e of the second helical surface 50 on the non-helical portion 4 side are positioned with a 180° offset.

[0027] When a pair of workpieces butted together are joined using the friction stir welding tool 1B, the pair of workpieces are positioned relative to the friction stir welding tool 1B so that their butted surfaces face the axis a and so that the centers in the thickness direction of the pair of workpieces and the boundary (boundary surface) between the first and second spiral portions 3, 5 are included in the same plane. When a pair of workpieces overlapped on top of each other are joined using the friction stir welding tool 1B, the pair of workpieces are positioned relative to the friction stir welding tool 1B so that their to-be-welded portions face the axis a and so that the butted surfaces of the pair of workpieces and the boundary between the first and second spiral portions 3, 5 are included in the same plane. Once a pair of workpieces are positioned relative to the friction stir welding tool 1B, the friction stir welding tool 1B is rotated around the axis a by a machine tool, and the boundary between the first and second spiral portions 3, 5 is moved in one direction so that they are abutted against each other or pass through the pair of workpieces that are overlapped on top of each other.

[0028] As a result, the surrounding material is friction-stirred by the portion near the boundary between the rotating first and second spiral portions 3, 5, and a plasticized region is formed behind the direction of travel of the first and second spiral portions 3, 5. Furthermore, the first and second spiral surfaces 30, 50 are formed so that they approach the axis a and extend in opposite directions toward the boundary between the first and second spiral portions 3, 5, respectively, causing plastic flow of the material in the direction of rotation of the friction stir welding tool 1B and reducing the rate of plastic flow of the material in the direction of extension of the axis a. Therefore, the friction stir welding tool 1B also makes it possible to firmly join the workpieces from both the front and back sides while suppressing the expansion of the weld width and the occurrence of burrs due to friction stir welding.

[0029] Furthermore, heat generated in the first and second helical portions 3 and 5 by frictional stirring of the materials is mainly transferred from the second helical portion 5 to the heat-receiving portion 6. This suppresses expansion around the boundary between the first and second helical portions 3 and 5 due to frictional heat, effectively suppressing the occurrence of welding defects due to variations in the axial distance between the first helical surface 30 and the second helical surface 50. As a result, the friction stir welding tool 1B can further improve the welding strength between the workpieces while suppressing the increase in welding width and the occurrence of welding defects. Furthermore, by integrating the shank 2, the first helical portion 3, the second helical portion 5, and the heat-receiving portion 6, the cost of the friction stir welding tool 1B can be reduced by eliminating the need for a moving part for moving the upper and lower shoulders toward and away from each other and reducing the number of parts. Furthermore, by extending the second helical portion 5 directly from the first helical portion 3 without providing a non-helical portion 4, the material-stirring force in the area adjacent to the boundary between the first and second helical portions 3 and 5 can be further improved. In addition, in the friction stir welding tool 1B, the helical pitch p on the boundary side of the first and second helical portions 3, 5 of the first helical surface 30 may be larger than that on the shank 2 side, and the helical pitch p on the boundary side of the first and second helical portions 3, 5 of the second helical surface 50 may be larger than that on the heat receiving portion 6 side.

[0030] As described above, the friction stir welding tool 1, 1B of the present disclosure includes an integrally formed shank 2, a first helical portion 3, a second helical portion 5, and a heat receiving portion 6. The shank 2 is coaxially connected to a rotating member such as a spindle of a machine tool. The first helical portion 3 is formed integrally with the shank 2 and has a first helical surface 30 that extends helically around an axis a that extends coaxially with the rotating member, approaching the axis a as it moves away from the shank 2 in the axial direction. The second helical portion 5 is formed integrally with the first helical portion 3 and has a second helical surface 50 that extends helically in the opposite direction to the first helical surface 30 around the axis a as it moves away from the first helical portion 3 toward the side opposite the shank 2 side. The heat receiving portion 6 extends integrally from the second helical portion 5 toward the side opposite the first helical portion 3 and receives heat from the second helical portion 5. The above-described friction stir welding tools 1, 1B can further improve the welding strength between the workpieces 100a, 100b or 200a, 200b while suppressing the increase in welding width and the occurrence of welding defects. In addition, by integrating the shank 2, first helical portion 3, second helical portion 5, and heat receiving portion 6, the cost of the friction stir welding tool 1 can be reduced by eliminating moving parts and reducing the number of parts.

[0031] It should be noted that the invention of the present disclosure is not limited to the above-described embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above-described embodiment is merely one specific form of the invention described in the Summary of the Invention section, and does not limit the elements of the invention described in the Summary of the Invention section. [Industrial Applicability]

[0032] The invention of the present disclosure can be used in the friction stir welding tool manufacturing industry and the like. [Explanation of symbols]

[0033] 1,1B Friction stirring joint tool, 2 Shrink, 3 First spiral part, 30 First spiral surface, 30e,50e End, 4 Non-spiral part, 5 Second spiral part, 50 Second spiral surface, 6 Heated part, 100a,100b,200a,200b Joined material.

Claims

1. In a friction stir welding tool for joining materials to be joined, a shank coaxially connected to the rotating member; a first helical portion formed integrally with the shank and having a first helical surface that extends helically around an axis that extends coaxially with the rotating member so as to approach the axis as it moves away from the shank in the axial direction; a second helical portion formed integrally with the first helical portion, the second helical portion having a second helical surface extending in a spiral manner in a direction opposite to the first helical surface so as to move away from the axis as the second helical surface moves away from the axis in the axial direction away from the first helical portion toward the opposite side to the shank side around the axis; a heat receiving portion that extends integrally from the second spiral portion toward a side opposite to the first spiral portion and receives heat from the second spiral portion; A friction stir welding tool comprising:

2. The friction stir welding tool according to claim 1, a non-helical portion extending integrally from an end of the first helical portion opposite to the shank side, The friction stir welding tool, wherein the second spiral portion extends integrally from an end of the non-spiral portion opposite to the first spiral portion side.

3. The friction stir welding tool according to claim 1 or 2, A friction stir welding tool, wherein the volume of the heat receiving portion is at least larger than the volume of the second spiral portion.

4. The friction stir welding tool according to claim 1 or 2, A friction stir welding tool, wherein an end of the first spiral surface on the side of the second spiral portion and an end of the second spiral surface on the side of the first spiral portion are arranged to be offset by 180°.

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