Friction stir spot welding tool and method of use

Abstract

Provided is a friction stir spot welding tool which prevents leakage of an oil agent from the base of the tool even when an axial center of the tool is inclined from a vertical direction. A tool 1 includes a pin 11, and a shoulder 12 into which the pin 11 is inserted. The pin 11 is inserted into a hollow part 12B of the shoulder 12 in a state in which a pin tip portion 111 is inserted into a shoulder tip portion 121 and a pin base portion 112 is inserted into a shoulder base portion 122. Due to this configuration, a gap C is formed between an outer peripheral surface of the pin 11 and an inner peripheral surface of the shoulder 12. A base-side surface roughness, which is a value expressing, by an arithmetic average roughness Ra, the surface roughness of at least one of the outer peripheral surface 112a of the pin base portion 112 and the inner peripheral surface 122a of the shoulder base portion 122, is set to a range greater than 0.04 and less than 5.9.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to a friction stir spot welding tool with a pin and a shoulder, and a method of use thereof. [Background technology]

[0002] Friction stir welding is a well-known technique for joining two or more overlapping components, such as metal components and fiber-reinforced thermoplastic resin components. For friction stir welding, a friction stir spot welding tool equipped with a pin and a shoulder having a hollow portion for accommodating the pin is sometimes used. For example, in a shoulder-first process, the shoulder is rotated and extended to press-fit the overlapping portion of the components, while the pin is retracted to accommodate any overflow material.

[0003] Because part of the tool is rotated while being pressed into the workpieces, some of the material that separates from the workpieces may adhere and become caught inside the tool when the tool is pressed in. As the number of welding points increases, the amount of material that separates from the workpieces that are being joined also increases, eventually adhering to the surface of the pin and hindering the operation of the tool.

[0004] In the tool described in Patent Document 1, an oil is filled in the gap formed between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder. The filled oil prevents adhesion of debris separated from the workpieces to be joined that has entered the gap between the pin and shoulder of the tool. In addition, the oil's lubrication between the pin and shoulder reduces the load on the tool during friction stir welding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-53657 Summary of the Invention [Problem to be solved by the invention]

[0006] When using the above-mentioned tool for friction stir spot welding, if the two workpieces to be joined are stacked vertically, that is, when they are stacked vertically, the tip of the tool can be pointed directly downward during the joining process. However, if the two workpieces are stacked at an angle to the vertical, the tool's axis must be tilted from the vertical and the tip of the tool must be pointed toward the workpieces. For example, the tool's axis may be tilted horizontally, or the tool's tip may be tilted so that it points diagonally upward or directly upward. In this case, there is a risk of the oil leaking from the base of the tool.

[0007] An object of the present disclosure is to provide a friction stir spot welding tool that prevents leakage of oil from the base of the tool even when the axis of the tool is tilted from the vertical direction. [Means for solving the problem]

[0008] A friction stir spot welding tool according to one aspect of the present disclosure comprises a pin and a shoulder having a hollow portion into which the pin is inserted, the shoulder having a cylindrical shoulder tip portion and a cylindrical shoulder root portion connected to a root side end of the shoulder tip portion, the hollow portion being formed by the shoulder tip portion and the shoulder root portion, the pin having a cylindrical pin tip portion inserted into the shoulder tip portion and a cylindrical pin root portion connected to the root side end of the pin tip portion and inserted into the shoulder root portion, a gap being formed between an outer peripheral surface of the pin and an inner peripheral surface of the shoulder, and a root side roughness, which is a value obtained by expressing the surface roughness of at least one of the outer peripheral surface of the pin root portion and the inner peripheral surface of the shoulder root portion in terms of arithmetic mean roughness Ra, is 1.8 It is set to a range greater than or equal to 5.9 and less than 5.9.

[0009] A friction stir spot welding tool according to another aspect of the present disclosure includes a pin and a shoulder having a hollow portion through which the pin is inserted, the shoulder having a cylindrical shoulder tip portion and a cylindrical shoulder root portion continuous with a root-side end portion of the shoulder tip portion, the hollow portion being formed by the shoulder tip portion and the shoulder root portion, and the pin having a cylindrical pin tip portion inserted into the shoulder tip portion and a cylindrical pin root portion connected to the root-side end portion of the pin tip portion and inserted into the shoulder root portion. a base portion, and a gap is formed between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder, and when the surface roughness of at least one of the outer peripheral surface of the pin base portion and the inner peripheral surface of the shoulder base portion expressed in arithmetic mean roughness Ra is defined as a base side roughness, and the surface roughness of at least one of the outer peripheral surface of the pin tip portion and the inner peripheral surface of the shoulder tip portion expressed in arithmetic mean roughness Ra is defined as a tip side roughness, a surface roughness ratio, which is a value obtained by dividing the root side roughness by the tip side roughness, is set in a range greater than 1 and not greater than 118. At least one of the outer peripheral surface of the pin root portion and the inner peripheral surface of the shoulder root portion is formed of a bare surface obtained by sintering a cemented carbide alloy so that the root side roughness is in the range of greater than 1.8 and less than 5.9. .

[0010] A method of using a friction stir spot welding tool according to yet another aspect of the present disclosure is the above-described method of using a friction stir spot welding tool, in which an oil is filled in the gap between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder, the axis of the tool is tilted from the vertical direction while the tip of the tool is directed toward objects to be friction stir spot welded, and the objects are friction stir spot welded. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a friction stir spot welding tool that prevents leakage of oil from the base of the tool even when the axis of the tool is tilted from the vertical direction. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cutaway cross-sectional view showing a configuration of a friction stir spot welding tool according to an embodiment of the present disclosure. FIG. [Figure 2] FIG. 2 is an exploded view of the friction stir spot welding tool of FIG. [Figure 3] FIG. 2 is a schematic diagram of a friction stir spot welding apparatus equipped with the friction stir spot welding tool of FIG. 1, in which the tool is filled with an oil agent. [Figure 4] FIG. 2 is an explanatory diagram showing an example in which the surface roughness of the inner peripheral surface is changed by changing the finishing process on the inner peripheral surface of the shoulder base portion in FIG. 1, and is a diagram schematically showing the roughness state of the inner peripheral surface in each of the cases of (I) as sintered, (II) fine processing, (III) medium processing, and (IV) rough processing. [Figure 5] FIG. 2 is a cross-sectional explanatory view showing a state in which the entire pin of the tool in FIG. 1 is inserted into the inside of the shoulder, and shows a case in which the clearance distance, which is the axial length of the root gap portion, is 42 mm. [Figure 6] 1 is pulled X mm toward the base, part of the pin base protrudes outside the shoulder, and the axial length of the base gap portion becomes 42-X mm. [Figure 7] This is a diagram showing the state in which the entire pin of the tool in Figure 1 is inserted into the hollow portion of the shoulder, and is an explanatory cross-sectional view showing the volume ratios of the tip gap portion, the base gap portion, and the intermediate gap portion to the volume of the entire gap. [Figure 8] This figure shows whether or not oil leaks from the base of the tool when the clearance distance and the rate of oil dripping into the gap in the tool are changed at room temperature and 70°C, in order to determine whether or not oil leaks from the base of the tool by turning the tool upside down with the inner circumferential surface of the shoulder base in the as-sintered state shown in Figure 1. [Figure 9] This figure shows whether or not oil leaks from the base of the tool when the clearance distance and the rate of oil dripping into the gap between the tool are changed at room temperature and 70°C, in order to determine whether or not oil leaks from the base of the tool by turning the tool upside down with the inner circumferential surface of the shoulder base in Figure 1 roughly machined. [Figure 10] This graph shows the change in the contact angle of an oil droplet immediately after and 3 seconds after a drop of oil was applied to the sample surface in the following cases: (I) as-sintered, (II) finely machined, (III) medium-machined, and (IV) roughly machined, in order to verify the difference in oil wettability for different surface roughnesses. [Figure 11]FIG. 1 is an explanatory diagram showing the contact angle and wetting spreading area of ​​an oil droplet on a sample surface, showing the state of the oil droplet in the cases of (I) as-sintered, (II) fine-machined, and (III) medium-machined. [Figure 12] FIG. 4 is an explanatory diagram showing the contact angle of an oil droplet on a sample surface and the wetted spreading area, and shows the state of the oil droplet in the case of (IV) rough processing. [Figure 13] FIG. 10 is a diagram showing the change in wetting and spreading of an oil droplet on a sample surface, showing the state of the oil agent 3 seconds and 50 seconds after dropping. [Figure 14] This is a graph showing the change in the wetted and spread area from 3 seconds to 50 seconds after oil was dropped onto the sample surface in the cases of (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) coarse-machined. [Figure 15] This is a bar graph showing the wetting and spreading speed from 3 seconds to 50 seconds after oil was dropped onto the sample surface in the cases of (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) coarse-machined. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] The present disclosure provides a detailed description of embodiments thereof, based on the accompanying drawings. The friction stir spot welding tool according to the present disclosure can be used to manufacture various joined structures formed by spot-joining two or more overlapping structural members, such as metal or resin plates, frames, exterior materials, or columnar members. The joined structures thus manufactured are components of structures such as aircraft, railcars, and automobiles.

[0014] (Tool 1 configuration) 1 and 2, a tool 1 for friction stir spot welding includes a pin 11 and a shoulder 12 having a hollow portion 12B through which the pin 11 is inserted. Note that the drawings relating to the tool 1 in the following Figures 1 to 7 are schematic diagrams and do not limit the actual shape of the tool.

[0015] 2, the pin 11 is a cylindrical body whose diameter gradually tapers toward the bottom end 11T. The pin 11 has a cylindrical pin tip portion 111, a cylindrical pin base portion 112, and a tapered pin middle portion 113. The pin base portion 112 is connected to the base end of the pin tip portion 111 via the tapered pin middle portion 113.

[0016] The pin tip portion 111 is the portion of the pin 11 with the smallest outer diameter that forms the tip portion, and its tip surface is the lower end portion 11T of the pin 11. The pin root portion 112 is located at the axial root portion of the pin 11 and is a cylindrical portion with a larger diameter than the pin tip portion 111. The pin intermediate portion 113 is a tapered portion that connects the upper end of the pin tip portion 111 and the lower end of the pin root portion 112. The pin intermediate portion 113 has a lower end having the same outer diameter as the upper end of the pin tip portion 111 and an upper end having the same outer diameter as the lower end of the pin root portion 112. The pin intermediate portion 113 has a tapered outer shape in which the outer diameter increases from the lower end to the upper end. Note that if the regions corresponding to the pin tip portion 111 and the pin root portion 112 have the same or similar outer diameters, the tapered pin intermediate portion 113 may be omitted.

[0017] 2, shoulder 12 is a cylindrical body whose inner diameter gradually decreases toward bottom end 12T. Shoulder 12 has shoulder tip 121, which has the smallest inner diameter, shoulder base 122, which has the largest inner diameter, and shoulder intermediate 123, which has a tapered inner surface 123a. Shoulder base 122 is connected to the base end of shoulder tip 121 via shoulder intermediate 123.

[0018] The shoulder tip portion 121 is the portion of the shoulder 12 that has the smallest inner diameter and forms the tip portion, and its tip surface is the lower end portion 12T of the shoulder 12. The lower end portion 12T is a ring-shaped portion. The shoulder root portion 122 is located at the axial root portion of the shoulder 12 and is a cylindrical portion with an inner diameter larger than the inner diameter of the shoulder tip portion 121. The shoulder intermediate portion 123 has a tapered inner surface 123a that connects the upper end of the shoulder tip portion 121 and the lower end of the shoulder root portion 122. The tapered inner surface 123a has a lower end that has the same inner diameter as the shoulder tip portion 121, an upper end that has the same inner diameter as the shoulder root portion 122, and an intermediate portion whose inner diameter increases from the lower end to the upper end.

[0019] The shoulder 12 is made up of the shoulder tip 121, shoulder intermediate 123, and shoulder base 122, which form a hollow portion 12B. The hollow portion 12B is open to the outside of the shoulder 12 through a tip opening 12A formed at the lower end of the shoulder tip 121 and a base opening 12C formed at the upper end of the shoulder base 122. In the tool 1 that is actually used, a gripping portion that is connected to the shoulder drive portion 23 shown in Fig. 3 is provided at the upper end of the shoulder base 122, but the gripping portion is omitted in Figs. 1 to 3.

[0020] The pin 11 is inserted into the hollow portion 12B with the pin tip portion 111 inserted into the shoulder tip portion 121 and the pin root portion 112 inserted into the shoulder root portion 122. As a result, a gap C is formed between the outer circumferential surface of the pin 11 and the inner circumferential surface of the shoulder 12, into which the oil agent A shown in FIG.

[0021] The gap C has a tip gap portion C1 on the tip side of the tool 1, a root gap portion C2 on the root side of the tool 1, and an intermediate gap portion C3. The tip gap portion C1 is a cylindrical space sandwiched between the outer peripheral surface 111a of the pin tip portion 111 and the inner peripheral surface 121a of the shoulder tip portion 121. The root gap portion C2 is a cylindrical space sandwiched between the outer peripheral surface 112a of the pin root portion 112 and the inner peripheral surface 122a of the shoulder root portion 122. The intermediate gap portion C3 is a cylindrical space surrounded by the outer peripheral surface 111a of the pin tip portion 111 and the outer peripheral surface 113a of the pin intermediate portion 113, and the inner peripheral surface 122a of the shoulder root portion 122 and the tapered inner surface 123a of the shoulder intermediate portion 123.

[0022] The width of the above-mentioned gap C is a width that can be filled with the oil agent A, and is set to a width that allows the pin 11 to move relative to the shoulder 12 inside the hollow portion 12B, specifically, a linear reciprocating movement and a rotational movement in the axial direction. The widths w1, w2, and w3 of the tip gap portion C1, the root gap portion C2, and the intermediate gap portion C3 that constitute the gap C are set in consideration of the following points.

[0023] The width w1 of the tip gap portion C1 is set very narrow in order to prevent a part separated from the joining material from adhering inside the tip gap portion C1 of the tool 1 during friction stir spot joining. From such a viewpoint, the width w1 is set in a narrow range of about 0.01 to 0.1 mm. The width w2 of the root gap portion C2 is set wider than the width w1 of the tip gap portion C1 because the risk of adhesion of the separated material from the joining material inside the root gap portion C2 is low. From such a viewpoint, the width w2 is set in a wide range of about 0.1 to 3.5 mm. The width w3 of the intermediate gap portion C3 is set to a width sufficiently wider than the width w2 of the root gap portion C2 in order to hold a sufficient amount of the oil agent A inside the tool 1 during friction stir spot joining. Therefore, the widths w1, w2, and w3 of the root gap portion C2 and the intermediate gap portion C3 are set in the relationship of w1 < w2 < w3.

[0024] When friction stir spot welding is performed on metal materials as the joining materials, the oil A filled into the gap C can be a liquid or grease-like oil that is effective in preventing the adhesion of metal powder that separates from the metal materials during the joining process. For example, lubricating base oils, mineral oils, or synthetic oils whose main components are petroleum hydrocarbons, etc., can be used as the oil. Furthermore, mineral oils or synthetic oils to which molybdenum, graphite, solid paraffin, or metal powder has been added as a solid lubricant can also be used as the oil.

[0025] The viscosity of oil A filled in gap C is 1 to 101 mm under a temperature condition of 40°C. 2 / sec range, preferably 1-21 mm 2 Viscosities in the range of 1 / sec are preferred.

[0026] (Configuration of friction stir spot welding device M) Fig. 3 is a schematic diagram of a friction stir spot welding apparatus M equipped with the friction stir spot welding tool 1 configured as described above, with the tool 1 filled with oil agent A. The friction stir spot welding apparatus M includes the friction stir spot welding tool 1 configured as described above, a tool drive unit 2 that drives the tool 1 to rotate and raise and lower, and a controller CT that controls the operation of each part of the friction stir spot welding apparatus M, i.e., the control unit of the tool 1. Note that although Fig. 3 shows directional indications of "up" and "down," this is for ease of explanation and is not intended to limit the actual direction in which the tool 1 is used.

[0027] The tool 1 is supported by various tool fixing parts. The tool fixing part is, for example, the tip of an articulated robot. A backup 15 is arranged facing the lower end surface of the tool 1. At least two members to be joined are arranged between the tool 1 and the backup 15. FIG. 3 shows an example in which an overlapping part 30, in which a part of a first member 31 made of a flat plate and a part of a second member 32 also made of a flat plate are overlapped in the vertical direction, is arranged between the tool 1 and the backup 15.

[0028] The tool 1 in Fig. 3 is disposed so that the axis of the tool 1 extends in the vertical direction. The pin 11 is rotatable about the axis as a rotation axis R, and is also movable up and down along the rotation axis R. When the tool 1 is in use, the rotation axis R is aligned with the spot joining position W at the overlapping portion 30.

[0029] The axis of the shoulder 12 is coaxial with the axis of the pin 11, i.e., the rotation axis R. The shoulder 12 is rotatable around the rotation axis R and is also movable up and down along the rotation axis R. An oil agent A is filled in a gap C between the outer peripheral surface of the pin 11 and the inner peripheral surface of the shoulder 12, specifically in a tip gap portion C1, a base gap portion C2, and a middle gap portion C3 that make up the gap C. The oil agent A increases the lubricity between the pin 11 and the shoulder 12 and suppresses the adhesion of adhered matter in the gap C.

[0030] When filling the gap C with oil agent A, the pin 11 in Figure 1 is raised to a position where the pin middle part 113 is outside the shoulder base part 122, and oil agent A is then filled into the gap C using an oil supply device.

[0031] When friction stir spot welding is performed, the pin 11 and shoulder 12 of the tool 1 move independently in the axial direction. That is, the shoulder 12 and the pin 11 inserted into the shoulder 12 can both rotate around the rotation axis R, while moving relatively in the direction of the rotation axis R. Specifically, the pin 11 and shoulder 12 can not only move up and down simultaneously along the rotation axis R, but also independently move, with one moving down and the other moving up.

[0032] The tool 1 in Figure 3 further includes a clamp 13 that covers the outer periphery of the shoulder 12. The clamp 13 is a cylindrical member with a hollow portion into which the shoulder 12 is inserted. The axis of the clamp 13 is also coaxial with the rotation axis R. The clamp 13 does not rotate around its axis, but moves up and down, that is, moves forward and backward, along the rotation axis R. The clamp 13 serves to surround the outer periphery of the pin 11 or shoulder 12 when they perform friction stir welding. The enclosure by the clamp 13 prevents the friction stir material from scattering, and enables the friction stir spot welded portion to be finished smoothly.

[0033] The backup 15 has a flat surface that abuts against the underside of the overlapping portion 30 to be joined. The backup 15 is a backing member that supports the overlapping portion 30 when the pin 11 or the shoulder 12 is press-fitted into the overlapping portion 30. The clamp 13 presses the overlapping portion 30 against the backup 15 by receiving a biasing force from a pressure mechanism such as a spring.

[0034] The tool driving unit 2 includes a rotation driving unit 21, a pin driving unit 22, a shoulder driving unit 23, a clamp driving unit 24, and a swivel driving unit 25. The rotation driving unit 21 includes a motor, a drive gear, etc., and drives the pin 11 and the shoulder 12 to rotate about the rotation axis R. The pin driving unit 22 is a mechanism that moves the pin 11 back and forth along the rotation axis R. The pin driving unit 22 drives the pin 11 so as to press the pin 11 into the overlapping portion 30 and retract it from the overlapping portion 30. The shoulder driving unit 23 is a mechanism that moves the shoulder 12 back and forth along the rotation axis R, and presses the shoulder 12 into and retracts the overlapping portion 30. The clamp driving unit 24 is a mechanism that moves the clamp 13 back and forth along the rotation axis R. The clamp driving unit 24 moves the clamp 13 in the vertical direction toward the overlapping portion 30 , and presses the overlapping portion 30 against the backup 15 .

[0035] The swivel drive unit 25 is a mechanism that swivels and moves the tool 1 in a direction that is inclined vertically. The point joining position W at the overlapping portion 30 of the first member 31 and the second member 32 to be joined may face a direction that is inclined vertically depending on the shape of the product being manufactured, such as an aircraft. For example, the point joining position W may face a horizontal direction or a direction that is inclined upward from the horizontal direction. Even in such cases, the swivel drive unit 25 can swivel and move the tool 1 in a direction that is inclined vertically, so that the tip of the tool 1 can be directed toward the overlapping portion 30.

[0036] The controller CT is comprised of a microcomputer or the like, and controls the operation of the tool driving unit 2 and other mechanisms by executing a predetermined control program. Specifically, the controller CT controls the rotation driving unit 21 to cause the pin 11 and shoulder 12 to perform the required rotational motion. The controller CT also controls the pin driving unit 22, shoulder driving unit 23, clamp driving unit 24, and swivel driving unit 25 to cause the pin 11, shoulder 12, and clamp 13 to perform the required forward / backward movement and swivel motion.

[0037] (Friction welding using friction stir spot welding device M) The friction joining methods using the friction stir spot joining apparatus M are roughly classified into a pin-first process in which the pin 11 of the tool 1 is first pressed into the overlapping portion of the joining members, and a shoulder-first process in which the shoulder 12 is first pressed into the overlapping portion of the joining members.

[0038] For example, in the shoulder-first process, first, as a preheating step of the overlapping portion 30, the controller CT rotates the pin 11 and the shoulder 12 around the axis at a predetermined rotation speed while the lower end of the tool 1 is in contact with the surface of the first member 31. Next, in a press-fitting step of the shoulder 12, the controller CT lowers the shoulder 12 to press it into the overlapping portion 30, while retracting the pin 11 upward. This action stirs the material in the press-fit region of the shoulder 12. Furthermore, the overflowing material that overflows from the overlapping portion 30 due to the press-fitting is released into the space inside the tip of the shoulder 12, which is created by the retraction of the pin 11. Thus, in this embodiment, the pin 11 is moved upward relative to the shoulder 12 during friction stir welding. Thereafter, in a backfilling step of the overflowing material, the controller CT raises and retracts the shoulder 12, while lowering the pin 11. As the pin 11 descends, the overflow material that escaped into the space inside the tip of the shoulder 12 is refilled into the press-fit area of ​​the shoulder 12. Then, in a leveling process, the pin 11 and shoulder 12 are rotated with their lower end surfaces returned to the same height as the surface of the first member 31, smoothing the spot-joined portion. This makes it possible to join the first member 31 and the second member 32 at the spot-joined portion.

[0039] (Preventing leakage of oil A from the base of tool 1) When the tool 1 is applied to the above-mentioned friction stir spot welding apparatus M to perform friction welding, if the spot welding position W of the overlapping portion 30 is facing in a direction that is inclined vertically, the swivel drive unit 25 swivels the tool 1 in a direction that is inclined vertically, so that the tip of the tool 1 is used facing the overlapping portion 30.

[0040] In the tool 1 of this embodiment, to prevent leakage of the oil agent A from the base of the tool 1 even when the axis of the tool 1, i.e., the rotation axis R shown in the figure, is tilted from the vertical direction, the surface roughness of at least one of the outer peripheral surface 112a of the pin base portion 112 and the inner peripheral surface 122a of the shoulder base portion 122 is set within a range that can prevent leakage of the oil agent A. Specifically, the base side roughness, which is the surface roughness of at least one of the outer peripheral surface 112a of the pin base portion 112 and the inner peripheral surface 122a of the shoulder base portion 122 expressed as an arithmetic mean roughness Ra, is set within a range greater than 0.04 and less than 5.9. In this embodiment, the base side roughness is set within the above range by adjusting the surface roughness of the inner peripheral surface 122a of the shoulder base portion 122 shown in FIG. 4. By setting the root side surface roughness within the above range in this way, when the tool 1 is used for joining work with the oil agent A filled in the gap C between the pin 11 and shoulder 12, it is possible to prevent leakage of the oil agent A from the root of the tool 1 even when the axis of the tool 1, i.e., the rotation axis R in Figure 3, is tilted from the vertical direction. Note that even if the outer peripheral surface 112a of the pin root portion 112 has the above root side surface roughness, it is possible to prevent leakage of the oil agent A from the root of the tool 1.

[0041] For example, if tool 1 is rotated with its tip pointing diagonally upward or nearly directly upward, the base of tool 1 will be below the tip. Even in this case, by setting the base side surface roughness within the above range, oil agent A will be retained inside the base gap portion C2 of gap C, preventing oil agent A from leaking from the base of tool 1.

[0042] In the tool 1 of this embodiment, it is preferable that the pin 11 is movable in the axial direction relative to the shoulder 12 by controlling the pin drive unit 22 by the controller CT so that the axial length of the root gap portion C2 formed by the outer peripheral surface 112a of the pin root portion 112 and the inner peripheral surface 122a of the shoulder root portion 122 in the gap C is in a range of 27 mm or more. With the above configuration, it is possible to reliably prevent leakage of the oil agent A from the root of the tool 1.

[0043] In the tool 1 of this embodiment, the inner circumferential surface 122a of the shoulder base portion 122 is preferably formed of a bare surface made of sintered cemented carbide so that the base side roughness is in the range of greater than 0.04 and less than 5.9. By forming the inner circumferential surface 122a of the shoulder base portion 122 from a bare surface made of sintered cemented carbide, the inner circumferential surface 122a has predetermined dimensions and a predetermined base side roughness. Therefore, leakage can be prevented without performing finishing to achieve the predetermined base side roughness.

[0044] In a method of using the tool 1 of this embodiment, first, as shown in FIG. 3 , oil A is filled into the gap C between the outer peripheral surface of the pin 11 and the inner peripheral surface of the shoulder 12. Next, if the overlapping portion 30, which is the object to be friction stir spot welded, overlaps in a direction inclined from the vertical, the pivot drive unit 25 pivots the axis of the tool 1 to tilt it from the vertical, and the tip of the tool 1 is directed toward the overlapping portion 30, which is the object to be friction stir spot welded. Then, friction stir spot welding of the overlapping portion 30 is performed. In this way, even when friction stir spot welding is performed with the tip of the tool 1 directed in a direction inclined from the vertical, the tool 1 of this embodiment has the above-described base side surface roughness, so it is possible to prevent oil A from leaking from the base of the tool 1.

[0045] In the method of using the tool 1 of this embodiment, it is preferable to fill the gap C with oil agent A in a volume that is 70% or less of the volume of the gap C in the entire tool 1. By filling the gap C with oil agent A in the above volume range, it is possible to reliably prevent leakage of oil agent A from the base of the tool 1.

[0046] (Explanation of the demonstration experiment to prevent leakage of oil agent A) Next, the tool 1 that makes it possible to prevent leakage of the oil agent A described above and the method of using it will be described with reference to Figs. 4 to 9, based on a demonstration experiment of preventing leakage of the oil agent A.

[0047] FIG. 4 is an explanatory diagram showing an example in which the surface roughness of the inner peripheral surface 122a of the shoulder base portion 122 in FIG. 1 is changed by changing the finishing processing of the inner peripheral surface 122a, and shows the roughness state of the inner peripheral surface in the cases of (I) as sintered, (II) fine processing, (III) medium processing, and (IV) rough processing.

[0048] In the as-sintered state shown in Figure 4(I), the inner circumferential surface 122a of the shoulder base portion 122 is formed from the bare surface of sintered cemented carbide, and has a low surface roughness. As a result, the surface roughness of the inner circumferential surface 122a is approximately 1.8 in terms of arithmetic mean roughness Ra. The inner diameter of the inner circumferential surface 122a is approximately the designed dimension. In other words, the inner circumferential surface 122a can be formed in a near-net shape.

[0049] The inner peripheral surface 122a of the shoulder base portion 122 in the cases of (II) fine machining, (III) medium machining, and (IV) rough machining in Figure 4 is a surface in which the surface roughness is gradually increased in the order of (II) to (IV) by electrical discharge machining of the inner peripheral surface 122a formed from the bare surface of the sintered cemented carbide alloy in the as-sintered case in Figure 4 (I). In Figures 4 (II) to (IV), the surface roughness of the inner peripheral surface 122a is approximately 3.1 in the case of (II) fine machining, approximately 4.8 in the case of (III) medium machining, and approximately 5.9 in the case of (IV) rough machining, in terms of arithmetic mean roughness Ra.

[0050] 4, for (I) as-sintered, (II) fine-machined, and (III) medium-machined, the surface roughness of the inner peripheral surface 122a is approximately 1.8 in arithmetic mean roughness Ra, approximately 3.1 in (II) fine-machined, and approximately 4.8 in (III) medium-machined. Since the arithmetic mean roughness Ra is within the range of greater than 0.04 and less than 5.9, it is believed that no leakage will occur from the base of the tool 1. On the other hand, for (IV) roughly machined: approximately 5.9, it is beyond the above range, and it is believed that leakage of the oil agent A from the base of the tool 1 cannot be prevented.

[0051] Therefore, using Figures 8 and 9, we verify that leakage of oil agent A from the base of tool 1 can be suppressed in the states of Figure 4 (I) as-sintered, (II) fine processing, (III) medium processing, and (IV) rough processing, but that it is difficult to suppress leakage of oil agent A from the base of tool 1 in the state of (IV) rough processing.

[0052] As shown in Figures 8 and 9, when oil agent A was filled into gap C of tool 1 at dripping oil amounts (%) of 35% and 70%, the clearance distance (mm) of tool 1 was changed from 27 to 42 mm, and the tool 1 was turned upside down with the base of tool 1 facing downwards and maintained for 30 minutes to verify whether oil agent A leaked from the base of tool 1. This verification was carried out at room temperature and at a room temperature of 70°C.

[0053] Figure 8 shows whether or not oil agent A leaks from the base when the clearance distance, which is the axial length of the base gap portion C2, and the ratio of the amount of oil dripped into the gap C of the tool 1 are changed under temperature conditions of room temperature and 70°C, in order to determine whether or not oil agent A leaks from the base by turning the tool 1 upside down, with the inner surface 122a of the shoulder base portion 122 in Figure 1 in the as-sintered state shown in Figure 4(I).

[0054] Figure 9 is a diagram showing whether or not oil agent A leaks from the base of the tool when the clearance distance and the rate of oil dripping into the gap in the tool are changed under temperature conditions of room temperature and 70°C, in order to determine whether or not oil agent A leaks from the base by turning the tool 1 upside down, with the inner surface 122a of the shoulder base portion 122 in Figure 1 in the rough-machined state shown in Figure 4(IV).

[0055] Here, region G1 in Figures 8 and 9 is the range in which no leakage of oil agent A occurred at room temperature, and includes the range of region G2, which is the range in which no leakage of oil agent A occurred at a temperature condition of 70°C. Region N1 in Figures 8 and 9 is the range in which leakage of oil agent A occurred at room temperature, and region N2 indicates the range in which oil agent A could not be filled into gap C of tool 1.

[0056] The clearance distance shown in FIGS. 8 and 9 varies within a range of 27 to 42 mm depending on the amount of withdrawal of the pin 11, as shown in FIGS. 5 and 6. FIG. 5 is a cross-sectional view illustrating the state in which the entire pin 11 of the tool 1 in FIG. 1 is inserted into the hollow portion 12B of the shoulder 12, and illustrates a case in which the clearance distance, which is the axial length of the root gap portion C2, is 42 mm. FIG. 6 is a cross-sectional view illustrating a case in which the pin 11 in FIG. 1 is withdrawn by X mm toward the root side, i.e., to the left in FIG. 6, so that part of the pin root portion 112 protrudes outside the shoulder 12, resulting in a clearance distance, which is the axial length of the root gap portion C2, of 42-X mm. If the withdrawal amount X mm of the pin 11 in FIG. 6 is changed within a range of 0 to 15 mm, the clearance distance varies within a range of 27 to 42 mm, as shown in FIGS. 8 and 9.

[0057] The amount of dripped oil (%) shown in Figures 8 and 9 will be explained in detail using Figure 7. Figure 7 is a cross-sectional view showing the state in which the entire pin 11 of the tool 1 in Figure 1 is inserted into the hollow portion 12B of the shoulder 12, and is an explanatory cross-sectional view showing the volumetric ratios of the tip gap portion C1, the root gap portion C2, and the middle gap portion C3 to the entire volume of the gap C. As shown in Figure 7, the volumetric ratio of the tip gap portion C1 is 1.0%, the volumetric ratio of the root gap portion C2 is 62.4%, and the volumetric ratio of the middle gap portion C3 is 36.6%. In this case, the sum of the volumetric ratio of the tip portion of the gap C, the volumetric ratio of the tip gap portion C1, and the volumetric ratio of the middle gap portion C3 is 37.6%. When 35% of the oil agent A is dripped relative to the entire volume of the gap C, i.e., when the dripped oil amount (%) is 35%, the volumetric ratio is approximately the same as the volumetric ratio of the middle gap portion C3, 36.6%. Furthermore, when oil A is dropped to 70% of the total volume of the gap C, that is, when the amount of dropped oil (%) is 70%, this amount exceeds the sum of the volume percentages of the tip gap C1 and the middle gap C3 (37.6%), and it can be seen that this amount of oil A fills not only the tip gap C1 and the middle gap C3 but also part of the base gap C2. The above 35% and 70% are the values ​​shown on the vertical axis of the graphs in Figures 8 and 9.

[0058] 8, when the inner peripheral surface 122a of the shoulder base portion 122 is in the as-sintered state shown in FIG. 4(I), when the amount of dripped oil is 35%, it falls within the range of region G1 where no leakage of oil agent occurs when the clearance distance is in the range of 27 to 42 mm at room temperature, and it falls within the range of region G2 where no leakage of oil agent occurs when the clearance distance is in the range of 35 to 42 mm at 70° C. Furthermore, when the amount of dripped oil is 70%, it falls within the range of region G1 where no leakage of oil agent occurs when the clearance distance is in the range of 32 to 42 mm at room temperature, and it falls within the range of region G2 where no leakage of oil agent A occurs when the clearance distance is in the range of 37 to 42 mm at 70° C.

[0059] Furthermore, it was experimentally confirmed that no leakage of oil agent A occurred in the finely machined state of Figure 4(II) and the medium-machined state of Figure 4(III) when the amount of dripped oil was 35%, the clearance distance was 27 mm, and the temperature was room temperature. Furthermore, it was experimentally confirmed that no leakage of oil agent A occurred when the amount of dripped oil was 35%, the clearance distance was 37 mm, and the temperature was 70°C. Therefore, it is estimated that the same judgment results as those in Figure 8, which were verified in the as-sintered state of Figure 4(I), will be obtained in the finely machined state of Figure 4(II) and the medium-machined state of Figure 4(III).

[0060] Next, referring to Figure 9, when the inner circumferential surface 122a of the shoulder base portion 122 is in the rough-machined state of Figure 4(IV), it can be seen that when the amount of dripped oil is 35%, it is included in the range of region N1 where leakage of oil occurs at room temperature when the clearance distance is 27 mm. It can also be seen that leakage occurs at 70°C when the clearance distance is 37 mm, as it falls outside the range of region G2 where leakage of oil A does not occur. When the amount of dripped oil is 70%, it can be seen that leakage occurs at 70°C when the clearance distance is 39 mm, as it falls outside the range of region G2 where leakage of oil A does not occur. Comparing the judgment results of Figures 8 and 9, it can be seen that in the rough-machined state of Figure 4(IV), both regions G1 and G2 where leakage of oil A does not occur are narrow, as shown in Figure 9.

[0061] The above results show that in order to prevent leakage from the base of the tool 1, it is sufficient to set the surface roughness of at least one of the outer peripheral surface 112a of the pin base portion 112 and the inner peripheral surface 122a of the shoulder base portion 122 within a range that can prevent leakage of the oil agent A. Specifically, it is understood that the surface roughness should be set within the range of greater than 0.04 and less than 5.9 in terms of the arithmetic mean roughness Ra mentioned above.

[0062] Furthermore, from the judgment results in Figure 8, it can be seen that in addition to setting the above-mentioned base side roughness, if the tool 1 is able to move axially relative to the shoulder 12 within a range in which the clearance distance, i.e., the axial length of the base gap portion C2, is 27 mm or more, leakage of oil agent A from the base of the tool 1 can be reliably prevented.

[0063] Furthermore, when tool 1 is used at an operating temperature of 70°C or higher, if oil agent A is filled into gap C within a range in which the clearance distance, i.e., the axial length of root gap portion C2, is 37 mm or more, it is understood that leakage of oil agent A from the root of tool 1 can be reliably prevented even when the operating temperature is high.

[0064] (Relationship between contact angle and surface roughness) Figure 10 is a graph showing the change in the contact angle of an oil droplet immediately after and 3 seconds after oil agent A was dropped onto the surface of sample S in Figures 11 and 12 in the cases of (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) coarse-machined, corresponding to Figures 4(I) to (IV), in order to verify the difference in the wettability of the oil agent at different surface roughnesses.

[0065] 11 and 12 are explanatory diagrams showing the contact angle and wetting spreading area of ​​an oil droplet on the surface of sample S. Fig. 11 shows the state of the oil droplet in the cases of (I) as-sintered, (II) fine processing, and (III) medium processing. Fig. 12 shows the state of the oil droplet in the case of (IV) rough processing.

[0066] Looking at the graph in Figure 10, in the cases of (I) as-sintered, (II) fine-machined, and (III) medium-machined, the surface roughness is in the range of average surface roughness Ra greater than 0.04 and less than 5.9, and the difference in the contact angle of the oil droplet immediately after dripping oil agent A and 3 seconds later is smaller than in the case of (IV) coarse-machined, indicating an improved leakage prevention effect.

[0067] Moreover, in the cases of (II) fine processing and (III) medium processing, the contact angle of the oil droplet was larger both immediately after dropping and 3 seconds later compared to the case of (IV) rough processing, indicating a significant improvement in the leakage prevention effect.

[0068] The contact angle in the (IV) rough machining case, which caused leakage of oil A from the base of tool 1, was significantly lower than the contact angle in the (III) medium machining case. The reason for this is thought to be as follows. In the (I) as-sintered, (II) fine-machined, and (III) medium-machined cases shown in Figure 11, the contact angle α of the oil droplet A on the surface of sample S is large, so the increase from the droplet area S1' immediately after application to the wetted and spread area S1 after 3 seconds is small. The large contact angle α is thought to contribute to preventing leakage of oil A. On the other hand, in the (IV) rough machining case shown in Figure 12, the surface of sample S is highly uneven, and the contact angle β is smaller than the contact angle α in Figure 11. Therefore, oil A easily spreads between two adjacent convex portions, and the increase from the droplet area S2' immediately after application to the wetted and spread area S2 after 3 seconds is large. Therefore, it is thought that leakage prevention cannot be achieved.

[0069] (Wetting and spreading speed) In addition to the setting of the root side surface roughness, at least one of the outer peripheral surface 112a of the pin root portion 112 and the inner peripheral surface 122a of the shoulder root portion 122 is set to have an oil wetting and spreading speed of 5.65 mm for 3 to 20 seconds. 2 With the above-described configuration, it is possible to reliably prevent leakage of the oil agent A from the base of the tool 1.

[0070] The wetting and spreading speed described above will be further examined with reference to Figures 13 to 15. Figure 13 shows the change in wetting and spreading of oil agent A on the surface of sample S in the case of rough processing (IV), which corresponds to Figure 4 (IV). Looking at Figure 13, it can be seen that the wetting and spreading area of ​​oil agent A 50 seconds after dropping increases rapidly compared to the wetting and spreading area of ​​oil agent A 3 seconds after dropping.

[0071] Figure 14 is a graph showing the change in the wetted and spread area from 3 seconds to 50 seconds after oil agent A was dropped onto the surface of sample S in the cases of (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) roughly machined, which correspond to Figures 4(I) to (IV). Figure 14 shows that the rate of change in the wetted and spread area is small in the cases of (I) as-sintered, (II) fine-machined, and (III) medium-machined, but the rate of change is greater in the case of (IV) roughly machined than in the cases of (I) to (III). In other words, the slopes of the lines in (I) to (III) are gentle, while the slope of the line in (IV) is steeper than the lines in (I) to (III).

[0072] From the graph in Fig. 14, the wetting and spreading speeds for (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) rough-machined can be expressed as in Fig. 15. Fig. 15 is a bar graph showing the wetting and spreading speeds from 3 seconds to 50 seconds after oil was dropped onto the surface of sample S for (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) rough-machined, which correspond to (I) to (IV) in Fig. 4.

[0073] Looking at the graph in Figure 15, in the cases of (I) as-sintered, (II) fine-machined, and (III) medium-machined, the wetting and spreading speed from 3 seconds to 50 seconds after oil agent A was dropped was 4 to 4.5 mm. 2 / sec, whereas (IV) roughing has a spreading rate of 5.65 mm 2 / sec, which is significantly larger than the other cases (I) to (III). Looking at the results in Figure 15, the wetting and spreading speed of the oil from 3 to 20 seconds is 5.65 mm 2It can be seen that leakage of oil agent A from the base of tool 1 can be reliably prevented by providing a surface with a viscosity of less than 1 / second.

[0074] (Other parameters of surface roughness) In addition to the arithmetic mean roughness Ra, other parameters that represent surface roughness include the maximum peak height Rp and the maximum valley height Rv. Optimizing the maximum peak height Rp and the maximum valley height Rv can be considered to reliably prevent leakage of the oil A from the base of the tool 1.

[0075] Specifically, the surface roughness of at least one of the outer peripheral surface 112a of the pin base portion 112 and the inner peripheral surface 122a of the shoulder base portion 122 is preferably set to be equal to or greater than 6.9 and less than 29.2 at the maximum peak height Rp in addition to the above-mentioned arithmetic mean roughness Ra. By adopting the above-mentioned configuration, it is possible to reliably prevent leakage of the oil agent A from the base of the tool 1.

[0076] Furthermore, it is preferable that the surface roughness of at least one of the outer peripheral surface 112a of the pin base portion 112 and the inner peripheral surface 122a of the shoulder base portion 122 is set to be equal to or greater than 5.4 and less than 22.5 at the maximum valley height Rv in addition to the above-mentioned arithmetic mean roughness Ra. By adopting the above-mentioned configuration, it is possible to reliably prevent leakage of the oil agent A from the base of the tool 1.

[0077] [Second embodiment] In the above-described first embodiment, in order to prevent leakage of oil agent A from the base of tool 1, the surface roughness of at least one of the outer peripheral surface 112a of pin base portion 112 and the inner peripheral surface 122a of shoulder base portion 122, i.e., the surface roughness on the base side of tool 1, is focused on, and the surface roughness is set in the range of greater than 0.04 and less than 5.9 in terms of arithmetic mean roughness Ra.

[0078] In the second embodiment, attention is paid to both the surface roughness on the base side and the surface roughness on the tip side of the tool 1, and the ratio of the surface roughness on the base side to the surface roughness on the tip side of the tool 1 is optimized to prevent leakage of oil agent A from the base of the tool 1.

[0079] That is, when the surface roughness of at least one of the outer peripheral surface 112a of the pin root portion 112 and the inner peripheral surface 122a of the shoulder root portion 122, expressed in arithmetic mean roughness Ra, is defined as the root side roughness, and the surface roughness of at least one of the outer peripheral surface 111a of the pin tip portion 111 and the inner peripheral surface 121a of the shoulder tip portion 121, expressed in arithmetic mean roughness Ra, is defined as the tip side roughness, the surface roughness ratio, which is the value obtained by dividing the root side roughness by the tip side roughness, is set in the range greater than 1 and not greater than 118. By setting the root side roughness and the tip side roughness within the above ranges, when the tool 1 is used for joining work with the oil agent A filled in the gap C between the pin 11 and the shoulder 12, the oil agent A does not leak from the root of the tool 1 even when the axis of the tool 1 is tilted from the vertical direction.

[0080] Here, the root side roughness is set, for example, in the same manner as in the first embodiment described above, in a range of greater than 0.04 and less than 5.9 in terms of arithmetic mean roughness Ra to prevent leakage of the oil agent A from the root of the tool 1. The tip side roughness is set smaller than the root side roughness to suppress adhesion of material separated from the joining material inside the tip gap portion C1. Specifically, the tip side roughness is set in a range of greater than 0.04 and less than 1.8 in terms of arithmetic mean roughness Ra. Therefore, by setting the surface roughness ratio, which is the value obtained by dividing the root side roughness by the tip side roughness in terms of arithmetic mean roughness Ra, in a range of greater than 1 and less than 118, as described above, leakage of the oil agent A from the root of the tool 1 can be prevented.

[0081] The width w2 of the base gap portion C2 is set in a wide range of, for example, about 0.1 to 3.5 mm, as in the first embodiment. The width w1 of the tip gap portion C1 is set in a narrow range of about 0.01 to 0.1 mm, as in the first embodiment, to suppress adhesion of material separated from the bonding material. Therefore, the ratio of the width w2 of the base gap portion C2 to the width w1 of the tip gap portion C1, i.e., w2 / w1, is set in a range of 1 to 350, preferably 3 to 150, and more preferably 5 to 50.

[0082] The other configurations and usage methods of the tool 1 of the second embodiment are common to the tool 1 and usage method of the first embodiment, and therefore description thereof will be omitted.

[0083] Summary of this disclosure A friction stir spot welding tool according to a first aspect of the present disclosure comprises a pin and a shoulder having a hollow portion through which the pin is inserted, the shoulder having a cylindrical shoulder tip and a cylindrical shoulder root connected to the root end of the shoulder tip, the hollow portion being formed by the shoulder tip and the shoulder root, the pin having a cylindrical pin tip inserted into the shoulder tip and a cylindrical pin root connected to the root end of the pin tip and inserted into the shoulder root, a gap being formed between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder, and the root side roughness, which is a value expressed as the arithmetic mean roughness Ra of at least one of the outer peripheral surface of the pin root and the inner peripheral surface of the shoulder root, is set to a range greater than 0.04 and less than 5.9.

[0084] According to the first aspect, by setting the base side roughness within the above range, when the tool is used for joining operations with the gap between the pin and shoulder filled with oil, it is possible to prevent oil from leaking from the base of the tool even when the axis of the tool is tilted from the vertical direction.

[0085] A friction stir spot welding tool according to a second aspect of the present disclosure comprises a pin and a shoulder having a hollow portion through which the pin is inserted, the shoulder having a cylindrical shoulder tip portion and a cylindrical shoulder root portion continuous with a root side end portion of the shoulder tip portion, the hollow portion being formed by the shoulder tip portion and the shoulder root portion, the pin having a cylindrical pin tip portion inserted into the shoulder tip portion and a cylindrical pin root portion connected to a root side end portion of the pin tip portion and inserted into the shoulder root portion a base portion, and a gap is formed between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder, and when the surface roughness of at least one of the outer peripheral surface of the pin base portion and the inner peripheral surface of the shoulder base portion, expressed in arithmetic mean roughness Ra, is defined as a base side roughness, and the surface roughness of at least one of the outer peripheral surface of the pin tip portion and the inner peripheral surface of the shoulder tip portion, expressed in arithmetic mean roughness Ra, is defined as a tip side roughness, the surface roughness ratio, which is the value obtained by dividing the root side roughness by the tip side roughness, is set to be in the range of greater than 1 and not more than 118.

[0086] According to the second aspect, by setting the base side surface roughness and the tip side surface roughness within the above ranges, when the tool is used for joining operations with oil filled in the gap between the pin and the shoulder, the oil does not leak from the base of the tool even when the axis of the tool is tilted from the vertical direction.

[0087] A friction stir spot welding tool according to a third aspect of the present disclosure is the friction stir spot welding tool according to the first and second aspects, wherein the root side surface roughness is such that the wetting and spreading speed of the oil in 3 to 20 seconds is 5.65 mm 2 The value should be less than / sec.

[0088] According to the third aspect, it is possible to reliably prevent leakage of oil from the base of the tool.

[0089] A friction stir spot welding tool according to a fourth aspect of the present disclosure is a friction stir spot welding tool according to the first to third aspects, wherein the root side roughness is a value that is equal to or greater than 6.9 and less than 29.2 at the maximum peak height Rp.

[0090] According to the fourth aspect, it is possible to reliably prevent leakage of oil from the base of the tool.

[0091] A friction stir spot welding tool according to a fifth aspect of the present disclosure is a friction stir spot welding tool according to the first to fourth aspects, wherein the root side roughness is a value that is 5.4 or more and less than 22.5 at the maximum valley height Rv.

[0092] According to the fifth aspect, it is possible to reliably prevent leakage of oil from the base of the tool.

[0093] A friction stir spot welding tool according to a sixth aspect of the present disclosure is a friction stir spot welding tool according to the first to fifth aspects, wherein the pin is capable of moving axially relative to the shoulder within a range in which the axial length of the root gap portion formed by the outer peripheral surface of the pin root portion in the gap and the inner peripheral surface of the shoulder root portion is 27 mm or more.

[0094] According to the sixth aspect, it is possible to reliably prevent leakage of oil from the base of the tool.

[0095] A friction stir spot welding tool according to a seventh aspect of the present disclosure is a friction stir spot welding tool according to any one of the first to sixth aspects, wherein at least one of the outer peripheral surface of the pin base portion and the inner peripheral surface of the shoulder base portion is formed of a bare surface made of sintered cemented carbide so that the base side roughness is in the range of greater than 0.04 and less than 5.9.

[0096] According to the seventh aspect, at least one of the outer peripheral surface of the pin base and the inner peripheral surface of the shoulder base is formed of a bare surface obtained by sintering cemented carbide so that the base side roughness is in the range of greater than 0.04 and less than 5.9, thereby achieving the predetermined dimensions and the predetermined base side roughness. Therefore, leakage can be prevented without performing finishing to achieve the predetermined base side roughness.

[0097] A method of using a friction stir spot welding tool according to an eighth aspect of the present disclosure is a method of using a friction stir spot welding tool according to any one of the first to seventh aspects, in which an oil agent is filled in the gap between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder, the axis of the tool is tilted from the vertical direction while the tip of the tool is directed toward objects to be friction stir spot welded, and the objects are friction stir spot welded.

[0098] According to the eighth aspect, when friction stir spot welding is performed using the tools according to the first to seventh aspects, an oil agent is filled in the gap between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder, and the tool is tilted from the vertical while the tip of the tool is directed toward the objects to be joined, thereby performing friction stir spot welding of the objects to be joined. In this way, even when friction stir spot welding is performed with the tip of the tool directed in a direction tilted from the vertical, it is possible to prevent oil agent from leaking from the base of the tool because the tool of the present disclosure has the above-mentioned root side surface roughness.

[0099] A method of using a friction stir spot welding tool according to a ninth aspect of the present disclosure is the method of using a friction stir spot welding tool according to the eighth aspect, in which the oil is filled into the gap at a volume that is 70% or less of the volume of the gap in the entire tool.

[0100] According to the ninth aspect, by filling the gap with oil in the above-mentioned volume range, it is possible to reliably prevent oil from leaking from the base of the tool. [Explanation of symbols]

[0101] 1. Tools 11-pin 12 Shoulder 12B Hollow part 111 Pin tip 112 Pin base 112a Outer surface 121 Shoulder tip 122 Shoulder base 122a Inner surface A oil solution C Gap C1 Tip gap C2 Base gap

Claims

1. Pin, a shoulder having a hollow portion through which the pin is inserted; Equipped with the shoulder has a cylindrical shoulder tip portion and a cylindrical shoulder root portion connected to a root-side end of the shoulder tip portion, and the hollow portion is formed by the shoulder tip portion and the shoulder root portion; the pin has a cylindrical pin tip portion that is inserted into the shoulder tip portion, and a cylindrical pin root portion that is connected to a root side end of the pin tip portion and is inserted into the shoulder root portion, A gap is formed between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder, a root side roughness, which is a value of the surface roughness of at least one of the outer peripheral surface of the pin root portion and the inner peripheral surface of the shoulder root portion expressed in arithmetic mean roughness Ra, is set in a range of greater than 1.8 and less than 5.9; Friction stir spot welding tool.

2. Pin, a shoulder having a hollow portion through which the pin is inserted; Equipped with the shoulder has a cylindrical shoulder tip portion and a cylindrical shoulder root portion that is continuous with a root-side end of the shoulder tip portion, and the hollow portion is formed by the shoulder tip portion and the shoulder root portion; the pin has a cylindrical pin tip portion that is inserted into the shoulder tip portion, and a cylindrical pin root portion that is connected to a root side end of the pin tip portion and is inserted into the shoulder root portion, A gap is formed between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder, a surface roughness ratio, which is a value obtained by dividing the root side surface roughness by the tip side surface roughness, is set in the range of greater than 1 and not greater than 118, when the value obtained by expressing the surface roughness of at least one of the outer peripheral surface of the pin root portion and the inner peripheral surface of the shoulder root portion in arithmetic mean roughness Ra is defined as a root side surface roughness, and the value obtained by expressing the surface roughness of at least one of the outer peripheral surface of the pin tip portion and the inner peripheral surface of the shoulder tip portion in arithmetic mean roughness Ra is defined as a tip side surface roughness, At least one of the outer peripheral surface of the pin root portion and the inner peripheral surface of the shoulder root portion is formed of a bare surface obtained by sintering a cemented carbide alloy so that the root side roughness is in the range of greater than 1.8 and smaller than 5.

9. Friction stir spot welding tool.

3. The friction stir spot welding tool according to claim 1 or 2, The root side roughness is such that the wetting and spreading speed of the oil agent in 3 to 20 seconds is 5.65 mm ２ A friction stir spot welding tool having a value of less than 1 / second.

4. The friction stir spot welding tool according to claim 1 or 2, A friction stir spot welding tool, wherein the root side surface roughness is a value that is 6.9 or more and less than 29.2 at the maximum peak height Rp.

5. The friction stir spot welding tool according to claim 1 or 2, A friction stir spot welding tool, wherein the root side surface roughness is a value that is 5.4 or more and less than 22.5 at a maximum valley height Rv.

6. The friction stir spot welding tool according to claim 1 or 2, A friction stir spot welding tool, wherein the pin is movable axially relative to the shoulder within a range in which the axial length of the root gap portion formed by the outer peripheral surface of the pin root portion in the gap and the inner peripheral surface of the shoulder root portion is 27 mm or more.

7. The friction stir spot welding tool according to claim 1, A friction stir spot welding tool, wherein at least one of the outer peripheral surface of the pin base portion and the inner peripheral surface of the shoulder base portion is formed of a bare surface made of sintered cemented carbide so that the base side roughness is in the range of greater than 1.8 and less than 5.

9.

8. 3. The method for using the friction stir spot welding tool according to claim 1 or 2, Filling a gap between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder with an oil agent; tilting the axis of the tool from the vertical direction while directing the tip of the tool toward the objects to be joined that are to be friction stir spot joined; Friction stir spot welding of the objects to be joined is performed. How to use tools for friction stir spot welding.

9. The method for using the friction stir spot welding tool according to claim 8, A method for using a friction stir spot welding tool, comprising filling the gap with the oil in an amount of 70% or less of the volume of the gap in the entire tool.

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