Friction stir spot welding tool and method for using same

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

Friction stir spot welding tool and method of use

[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.

[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.

[0005] Japanese Patent Application Laid-Open No. 2021-53657

[0006] When performing friction stir spot welding using the above-mentioned tool, if two workpieces to be joined are stacked vertically, that is, if they are stacked vertically, the tip of the tool can be pointed directly downward. 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.

[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 through which the pin is inserted, the shoulder having a cylindrical shoulder tip portion and a cylindrical shoulder root portion connected to a root 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 end of the pin tip 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 expressed as an arithmetic mean roughness Ra 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, is set in a range of greater than 0.04 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 a root-side end portion of the pin tip portion and inserted into the shoulder root portion. a 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 root portion and the inner peripheral surface of the shoulder root portion, expressed in arithmetic mean roughness Ra, is defined as a root 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 the range of greater than 1 and not more than 118.

[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.

[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.

[0012] 1 is a cutaway cross-sectional view showing the configuration of a friction stir spot welding tool according to an embodiment of the present disclosure. It is an exploded view of the friction stir spot welding tool of FIG. 1. It is a schematic view of a friction stir spot welding device including the friction stir spot welding tool of FIG. 1 and filled with an oil agent. It is an explanatory view showing an example in which the surface roughness of the inner peripheral surface is changed by changing the finish processing of the inner peripheral surface of the shoulder root portion of FIG. 1, and is a view schematically showing the roughness state of the inner peripheral surface in each case of (I) as sintered, (II) fine processing, (III) medium processing, and (IV) rough processing. It is a cross-sectional explanatory view showing a state in which the entire pin of the tool of FIG. 1 is inserted inside the shoulder, and showing a clearance distance, which is the axial length of the root gap portion, of 42 mm. It is an explanatory cross-sectional view showing a case in which the pin of FIG. 1 is pulled X mm toward the root side, so that a part of the pin root portion protrudes outside the shoulder, and the axial length of the root gap portion is 42-X mm. 1 is a diagram showing the state in which the entire pin of the tool in FIG. 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, the root gap, and the intermediate gap to the total volume of the gap. This diagram shows whether or not oil leaks from the root of the tool when the clearance distance and the ratio of oil dripped into the tool gap are changed at room temperature and at 70°C, in order to determine whether or not oil leaks from the root of the tool by turning upside down the tool in which the inner peripheral surface of the shoulder root of FIG. 1 is sintered. This diagram shows whether or not oil leaks from the root of the tool when the clearance distance and the ratio of oil dripped into the tool gap are changed at room temperature and at 70°C, in order to determine whether or not oil leaks from the root of the tool by turning upside down the tool in which the inner peripheral surface of the shoulder root of FIG. 1 is roughly machined. This graph shows the change in the contact angle of an oil droplet immediately after and 3 seconds after dripping oil on the sample surface in the cases of (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) rough-machined, in order to verify the difference in oil wettability for different surface roughnesses. 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 processing, and (III) medium processing. Fig. 2 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 case of (IV) coarse processing.

[0023] Figure 1 shows the change in wetting and spreading of an oil droplet on a sample surface, illustrating the state of the oil agent 3 seconds and 50 seconds after dropping. Figure 2 is a graph showing the change in the wetting and spreading area from 3 to 50 seconds after dropping the oil agent on the sample surface in the cases of (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) roughly machined. Figure 3 is a bar graph showing the wetting and spreading speed from 3 to 50 seconds after dropping the oil agent on the sample surface in the cases of (I) as-sintered, (II) fine-machined, (III) medium-machined, and (IV) roughly machined.

[0013] [First Embodiment] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The friction stir spot welding tool according to the present disclosure can be used to manufacture various joined bodies formed by spot-joining two or more structural materials, such as metal or resin plates, frames, exterior materials, or columnar materials, one on top of the other. The joined bodies thus manufactured are components of structures such as aircraft, railway vehicles, and automobiles.

[0014] 1 and 2, the 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 connecting 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 whose 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, the shoulder 12 is a cylindrical body whose inner diameter gradually decreases toward the lower end 12T. The shoulder 12 has a shoulder tip portion 121 with the smallest inner diameter, a shoulder base portion 122 with the largest inner diameter, and a shoulder intermediate portion 123 with a tapered inner surface 123a. The shoulder base portion 122 is connected to the base end of the shoulder tip portion 121 via the shoulder intermediate portion 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 portion 123, and shoulder root 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 root opening 12C formed at the upper end of the shoulder root 122. In the tool 1 that is actually used, a gripping portion that is connected to the shoulder drive portion 23 shown in Figure 3 is provided at the upper end of the shoulder root 122, but the gripping portion is omitted from Figures 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 Figure 3 can be filled.

[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, the outer peripheral surface 113a of the pin intermediate portion 113, 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 gap C is set to a width that allows the oil agent A to be filled and that allows the pin 11 to move relative to the shoulder 12 inside the hollow portion 12B, specifically, to move linearly back and forth in the axial direction and to move rotationally. The widths w1, w2, and w3 of the tip gap portion C1, base gap portion C2, and middle gap portion C3 that make up the gap C are set taking the following points into consideration.

[0023] The width w1 of the tip gap C1 is set very narrow to prevent adhesion of a portion of the joining material separated from the tip gap C1 of the tool 1 during friction stir spot welding. From this perspective, the width w1 is set in a narrow range of approximately 0.01 to 0.1 mm. The width w2 of the root gap C2 is set wider than the width w1 of the tip gap C1 because there is a low risk of adhesion of a portion of the joining material separated from the tip gap C1 to the root gap C2. From this perspective, the width w2 is set in a wide range of approximately 0.1 to 3.5 mm. The width w3 of the middle gap C3 is set sufficiently wider than the width w2 of the root gap C2 to retain a sufficient amount of oil agent A inside the tool 1 during friction stir spot welding. Therefore, the widths w1, w2, and w3 of the root gap C2 and the middle gap C3 are set to satisfy the relationship w1 < w2 < w3.

[0024] When friction stir spot welding is performed on metal materials as the joining materials, a liquid or grease-like oil can be used as the oil A filled into the gap C. This oil has the effect of preventing adhesion of metal powder that separates from the metal materials during the joining process. For example, a lubricating base oil, a mineral oil or synthetic oil containing petroleum hydrocarbons as its main component, or the like can be used as the oil. Furthermore, a mineral oil or synthetic oil containing molybdenum, graphite, solid paraffin, or metal powder as a solid lubricant can also be used as the oil.

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

[0026] (Configuration of friction stir spot welding apparatus M) Figure 3 is a schematic diagram of a friction stir spot welding apparatus M including 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 elevate, and a controller CT that controls the operation of each part of the friction stir spot welding apparatus M, i.e., a control unit for the tool 1. Note that although Figure 3 includes 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. Figure 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 overlap each other in the vertical direction, is arranged between the tool 1 and the backup 15.

[0028] 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 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 extends outside the shoulder base part 122, and oil agent A is then filled into the gap C using an oil supply device.

[0031] When performing friction stir spot welding, 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 and move 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 the 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 inclined toward the vertical direction. 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 inclined toward the vertical direction depending on the shape of the product, such as an aircraft, being manufactured. For example, the point joining position W may face a horizontal direction or a direction 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 inclined toward the vertical direction, 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 required rotational movements. 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 required forward / backward movement and swivel movements.

[0037] (Friction welding using friction stir spot welding apparatus M) Methods of friction welding using the friction stir spot welding 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 is lowered, 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] (Regarding prevention of leakage of oil A from the base of tool 1) When 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 and moves tool 1 in a direction that is inclined vertically, so that the tip of tool 1 is used toward the overlapping portion 30.

[0040] In the tool 1 of this embodiment, in order to prevent leakage of the oil 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 A. Specifically, the base side roughness, which is the value of 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 in arithmetic mean roughness Ra, is set within a range that is 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 the 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, when tool 1 is rotated with the tip of tool 1 directed diagonally upward or nearly directly upward, the base of tool 1 is located below the tip. Even in this case, by setting the base side surface roughness within the above range, oil agent A is retained inside 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 A from the root of the tool 1.

[0043] In the tool 1 of this embodiment, the inner peripheral surface 122a of the shoulder base portion 122 is preferably 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. By forming the inner peripheral surface 122a of the shoulder base portion 122 from a bare surface obtained by sintering cemented carbide, the inner peripheral 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 axis of the tool 1 is rotated by the swivel drive unit 25 to tilt the tool 1 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 leakage of oil A 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 Demonstration Experiment for Preventing Leakage of Oil Agent A) Next, the tool 1 that enables the prevention of leakage of oil agent A described above and the method of using it will be explained with reference to Figures 4 to 9 in a demonstration experiment for preventing leakage of oil agent A.

[0047] FIG. 4 is an explanatory diagram showing an example in which the surface roughness of the inner peripheral surface 122 a of the shoulder base portion 122 in FIG. 1 is changed by changing the finishing process of the inner peripheral surface 122 a, 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 peripheral 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 peripheral surface 122a is approximately 1.8 in terms of arithmetic mean roughness Ra. The inner diameter of the inner peripheral surface 122a is approximately the same as the designed dimension. In other words, the inner peripheral 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 is a surface in which the surface roughness is gradually increased in the order of (II) to (IV) by applying electric discharge machining to the inner peripheral surface 122a formed from the bare surface of the sintered cemented carbide in the case of (I) as sintered. 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) finely machined, and (III) medium machined, the surface roughness of the inner peripheral surface 122a is, in arithmetic mean roughness Ra, approximately 1.8 for (I) as sintered, approximately 3.1 for (II) finely machined, and approximately 4.8 for (III) medium machined, and 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 oil agent A from the base of the tool 1 cannot be prevented.

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

[0052] 8 and 9, when oil agent A was filled into gap C of tool 1 at dripping oil amounts (%) of 35% and 70%, the tool 1 was turned upside down and held with the base of tool 1 facing downwards for 30 minutes with the clearance distance (mm) of tool 1 changed from 27 to 42 mm, and the presence or absence of leakage of oil agent A from the base of tool 1 was verified. This verification was carried out at room temperature and at a room temperature of 70°C.

[0053] Figure 8 shows whether or not oil 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 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 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 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] 8 and 9 is the range in which no leakage of oil agent A occurred at room temperature, and includes the range in region G2, which is the range in which no leakage of oil agent A occurred at a temperature 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 is the range in which oil agent A could not be filled into gap C of tool 1.

[0056] The clearance distances shown in Figures 8 and 9 vary within a range of 27 to 42 mm depending on the amount of withdrawal of the pin 11, as shown in Figures 5 and 6 . Figure 5 is a cross-sectional explanatory diagram showing the pin 11 of the tool 1 of Figure 1 in its entirety inserted into the hollow portion 12B of the shoulder 12, where the clearance distance, which is the axial length of the root gap portion C2, is 42 mm. Figure 6 is a cross-sectional explanatory diagram showing the pin 11 of Figure 1 in its state when it is pulled X mm toward the root side, i.e., to the left in Figure 6 , so that part of the pin root portion 112 protrudes outside the shoulder 12, and the clearance distance, which is the axial length of the root gap portion C2, is 42-X mm. If the withdrawal amount X mm of the pin 11 in Figure 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 Figures 8 and 9 .

[0057] The dripped oil amounts (%) 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 pin 11 of the tool 1 in Figure 1 is entirely inserted into the hollow portion 12B of the shoulder 12, and is an explanatory cross-sectional view showing the volumetric proportions of the tip gap C1, the root gap C2, and the intermediate gap C3 relative to the total volume of the gap C. As shown in Figure 7, the volumetric proportion of the tip gap C1 is 1.0%, the volumetric proportion of the root gap C2 is 62.4%, and the volumetric proportion of the intermediate gap C3 is 36.6%. In this case, the sum of the volumetric proportion of the tip portion of the gap C, the volumetric proportion of the tip gap C1, and the volumetric proportion of the intermediate gap C3 is 37.6%. When 35% of the oil agent A is dripped relative to the total volume of the gap C, i.e., when the dripped oil amount (%) is 35%, the volumetric proportion of the intermediate gap C3 is approximately the same as 36.6%. Furthermore, when 70% of the oil A is dropped relative to 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 axes 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 in the clearance distance 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 in the clearance distance 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 in the clearance distance 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 in the clearance distance range of 37 to 42 mm at 70° C.

[0059] Furthermore, it has been experimentally confirmed that no leakage of oil agent A occurred when the amount of dripped oil was 35%, the clearance distance was 27 mm, and the temperature was room temperature, in the finely machined state of Figure 4(II) and the medium-machined state of Figure 4(III). Furthermore, it has been 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 presumed 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, it can be seen that when the inner circumferential surface 122a of the shoulder base portion 122 is in the rough-machined state of Figure 4(IV), with an oil drip amount of 35%, it is included in the range of region N1 where leakage of oil agent 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 agent A does not occur. It can also be seen that when the oil drip amount is 70%, it falls outside the range of region G2 where leakage of oil agent A does not occur at 70°C when the clearance distance is 39 mm, as it falls outside the range of region G2 where leakage of oil agent 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 agent 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 surface 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 wettability of oil agents with 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-machined, and (III) medium-machined. Fig. 12 shows the state of the oil droplet in the case of (IV) coarse-machined.

[0066] Looking at the graph in Figure 10, it can be seen that 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 contact angle of the oil droplet immediately after dripping oil agent A and 3 seconds later is smaller than in the case of (IV) rough-machined, thereby improving the leakage prevention effect.

[0067] Furthermore, in the cases of (II) fine processing and (III) medium processing, the contact angle of the oil droplet is larger both immediately after dropping and 3 seconds later compared to the case of (IV) rough processing, which shows that the leakage prevention effect is significantly improved.

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

[0069] (Regarding Wetting and Spreading Speed) In addition to the setting of the root side surface roughness described above, 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 a wetting and spreading speed of the oil agent 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). Looking at Figure 14, it can be seen 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 polygonal lines for (I) to (III) are gentle, while the slope of the polygonal line for (IV) is steeper than the polygonal lines for (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] As can be seen from the graph in Figure 15, in the cases of (I) as-sintered, (II) fine processing, and (III) medium processing, 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) rough processing has a wetting spreading speed of 5.65 mm ２ 15, the wetting and spreading speed of the oil agent from 3 to 20 seconds was 5.65 mm / sec, which is significantly higher than the other cases (I) to (III). ２ It can be seen that leakage of the oil agent A from the base of the tool 1 can be reliably prevented by providing a surface having a viscosity of less than 1 / second.

[0074] (Regarding Other Parameters of Surface Roughness) In addition to the above-mentioned arithmetic mean roughness Ra, other parameters that represent surface roughness include the maximum peak height Rp and the maximum valley height Rv. It is conceivable that by optimizing the maximum peak height Rp and the maximum valley height Rv, leakage of the oil A from the base of the tool 1 can be reliably prevented.

[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 arithmetic mean roughness Ra described above. By adopting the above configuration, it is possible to reliably prevent leakage of the oil A from the base of the tool 1.

[0076] Furthermore, 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 5.4 or more 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 A from the base of the tool 1.

[0077] [Second embodiment] In the first embodiment described above, in order to prevent leakage of oil A from the base of the tool 1, 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, i.e., the surface roughness on the base side of the tool 1, is focused on, and the surface roughness is set in a range of greater than 0.04 and less than 5.9 in 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 greater than 0.04 and less than 5.9 in 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 described above in order 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 greater than 0.04 and less than 1.8 in 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 arithmetic mean roughness Ra, in a range 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 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 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 joining material. Therefore, the ratio of the width w2 of the base gap C2 to the width w1 of the tip gap 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 the Disclosure A friction stir spot welding tool according to a first aspect of the disclosure includes 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 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 end of the pin tip 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 arithmetic mean roughness Ra, is set in a range of 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 into 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, a surface roughness ratio, which is a value obtained by dividing the base side roughness by the tip side roughness, is set 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 work 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 for 3 to 20 seconds is 5.65 mm ２ The value is 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 6.9 or more 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 any one of 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 any one of 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 a 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 work 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 the same as the method of using a friction stir spot welding tool according to 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 an eighth aspect, when friction stir spot welding is performed using the tool according to any one of 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 tip of the tool is directed toward the objects to be joined while tilting the tool from the vertical direction, 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 direction, 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.

[0101] REFERENCE SIGNS LIST 1 tool 11 pin 12 shoulder 12B hollow portion 111 pin tip portion 112 pin root portion 112a outer peripheral surface 121 shoulder tip portion 122 shoulder root portion 122a inner peripheral surface A oil C gap C1 tip gap portion C2 root gap portion

Claims

1. A friction stir spot welding tool, comprising a pin and a shoulder having a hollow portion into which the pin is inserted. The shoulder has a cylindrical shoulder tip portion and a cylindrical shoulder base portion connected to an end on the base side of the shoulder tip portion. The hollow portion is formed by the shoulder tip portion and the shoulder base portion. The pin has a cylindrical pin tip portion inserted into the shoulder tip portion and a cylindrical pin base portion connected to an end on the base side of the pin tip portion and inserted into the shoulder base portion. A gap is formed between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder. The root side surface roughness, which is a value representing at least one of the outer peripheral surface of the pin base portion and the inner peripheral surface of the shoulder base portion in terms of the arithmetic mean roughness Ra, is set in a range greater than 0.04 and less than 5.

9.

2. A friction stir spot welding tool, comprising a pin and a shoulder having a hollow portion into which the pin is inserted. The shoulder has a cylindrical shoulder tip portion and a cylindrical shoulder base portion continuous with an end on the base side of the shoulder tip portion. The hollow portion is formed by the shoulder tip portion and the shoulder base portion. The pin has a cylindrical pin tip portion inserted into the shoulder tip portion and a cylindrical pin base portion connected to an end on the base side of the pin tip portion and inserted into the shoulder base portion. A gap is formed between the outer peripheral surface of the pin and the inner peripheral surface of the shoulder. When the value representing at least one of the outer peripheral surface of the pin base portion and the inner peripheral surface of the shoulder base portion in terms of the arithmetic mean roughness Ra is defined as the root side surface roughness, and the value representing at least one of the outer peripheral surface of the pin tip portion and the inner peripheral surface of the shoulder tip portion in terms of the arithmetic mean roughness Ra is defined as the tip side surface roughness, the surface roughness ratio, which is the value obtained by dividing the root side surface roughness by the tip side surface roughness, is set in a range greater than 1 and less than or equal to 118.

3. The friction stir spot welding tool according to claim 1 or 2, wherein the root side surface roughness is a value such that the wetting spread rate of an oil agent for 3 to 20 seconds is less than 5.65 mm ２ / second.

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

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

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

7. The friction stir spot welding tool according to claim 1 or 2, wherein at least one of the outer peripheral surface of the root portion of the pin and the inner peripheral surface of the root portion of the shoulder is formed of a base material obtained by sintering cemented carbide so that the root side surface roughness is in a range greater than 0.04 and less than 5.9, the friction stir spot welding tool.

8. In the method of using the friction stir spot welding tool according to claim 1 or 2, 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 tip of the tool is directed toward a joining target for performing friction stir spot welding while inclining the axis of the tool from the vertical direction, and friction stir spot welding of the joining target is performed, the method of using the friction stir spot welding tool.

9. The method of using the friction stir spot welding tool according to claim 8, wherein the oil agent is filled in the gap in a volume of 70% or less of the volume of the gap in the whole tool, the method of using the friction stir spot welding tool.

Images