TOOL MEMBER FOR FRICTION STIR WELDING, FRICTION STIR WELDING APPARATUS, AND FRICTION STIR WELDING METHOD

Abstract

A friction stir welding tool member including a shoulder portion and a probe portion has a helical recessed / protruding portion having peak portions and valley portions on a side circumferential surface of the probe portion. Furthermore, in a cross section through an axis of rotation of the probe portion of the friction stir welding tool member, a difference ratio of the area of parts of the valley portions that are adjacent to one another along an axis parallel to the axis of rotation, among the valley portions, lies in a range of 5% or more to 30% or less. Further, it is preferable that a difference between pitches of parts of the peak portions that are adjacent to one another along the axis parallel to the axis of rotation of the probe portion, among the peak portions, lies in a range of 0.01 mm or more to 0.2 mm or less. Further, it is preferable that a difference between depths of the parts of the peak portions that are adjacent to one another along the axis parallel to the axis of rotation of the probe portion, among the valley portions, lies in a range of 0.01 mm or more to 0.1 mm or less.

Description

[Technical field]

[0001] The embodiments described below relate to a friction stir welding tool member, a friction stir welding apparatus, and a friction stir welding method. [Background technology]

[0002] Friction stir welding (FSW) is a joining method in which a joining tool called a probe is pressed against a component while rotating at high speed, and frictional heat is used to integrate multiple components. The frictional heat softens the component (base material), and the rotational force of the probe causes plastic flow around the joint, integrating multiple components (base material and mating material). For this reason, friction stir welding can be considered a type of solid-state welding.

[0003] Friction stir welding is a solid-state welding method, so the amount of heat input to the joint is small, and the heat-affected zone is less likely to form, and the degree of softening and distortion of the joint objects is small. In addition, since no brazing filler metal is used, costs can be reduced. The welding tool members used in friction stir welding are required to have both wear resistance to withstand high-speed rotation and heat resistance to withstand frictional heat.

[0004] International Publication No. 2016 / 047376 (Patent Document 1) discloses a joining tool member using a silicon nitride sintered body. Patent Document 1 uses a silicon nitride sintered body with enhanced Vickers hardness, etc. This improves the durability of the joining tool member. However, it has not been possible to further improve the durability.

[0005] Japanese Patent Application Laid-Open No. 2003-25077 (Patent Document 2) discloses a joining tool member having a screw groove structure on the probe portion. In Patent Document 2, the spiral groove is shaped as a JIS M6 metric coarse thread (pitch 1 mm) from the rotor side of the probe portion up to the second turn, and as a JIS M6 metric fine thread (pitch 0.75 mm) from the third turn onwards up to the tip side of the probe portion. Patent Document 2 improves joint efficiency by having a screw groove structure with a changed pitch. However, it cannot be said that the durability of the joining tool member itself is necessarily sufficient. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2016 / 047376 [Patent Document 2] JP 2003-25077 A Summary of the Invention [Problem to be solved by the invention]

[0007] When the thread groove structure of Patent Document 2 is provided on the joining tool member made of the silicon nitride sintered body of Patent Document 1, a certain degree of improvement in durability is seen, but no further effect is obtained. When the cause was investigated, it was found to be due to the shape of the thread groove. In Patent Document 2, the thread is a regular thread up to the second turn, and a fine thread from the third turn onwards. Although the shape of the thread changes when switching between regular threads and fine threads, the shape of the thread is constant in other places. It was found that if the shape of the thread is constant, the improvement of the mixing force is not sufficient.

[0008] Furthermore, with conventional metal-based tools, wear begins at the tip of the threads with the number of welding operations, and when the tool reaches the end of its life and is replaced, the threads are almost completely gone. In other words, the threads become smaller due to wear during use, and the stirring force gradually decreases, which also affects the appearance and quality of the joint after welding. [Means for solving the problem]

[0009] A friction stir welding tool member having a shoulder portion and a probe portion according to an embodiment has a spiral concave-convex portion having peaks and valleys on a circumferential side surface of the probe portion, and in a cross section passing through a rotation axis of the probe portion, the difference rate of areas between adjacent valley portions along an axis parallel to the rotation axis is within a range of 5% to 30%. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing an example of an outer shape of a friction stir welding tool member according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of a probe portion of a friction stir welding tool member according to an embodiment. [Diagram 3] 1A to 1C are views showing an example of a friction stir welding method according to an embodiment. [Figure 4] FIG. 4 is a view showing another example of the outer shape of the friction stir welding tool member according to the embodiment. Embodiment

[0011] A friction stir welding tool member having a shoulder portion and a probe portion according to an embodiment has a spiral concave-convex portion having peaks and valleys on a circumferential side surface of the probe portion. In the friction stir welding tool member, in a cross section passing through the rotation axis of the probe portion, the difference in area between adjacent valley portions along an axis parallel to the rotation axis is within a range of 5% to 30%. In addition, in a cross section passing through the rotation axis of the probe portion, it is preferable that the difference in area between adjacent peak portions along an axis parallel to the rotation axis is within a range of 5% to 30%.

[0012] 1(A) and (B) are diagrams showing an example of the external shape of a friction stir welding tool member according to an embodiment. Reference numeral 1 denotes a friction stir welding tool member, reference numeral 2 denotes a probe portion, reference numeral 3 denotes a shoulder portion, reference numeral 4 denotes an uneven portion, reference numeral 5 denotes a rotating shaft, reference numeral 6 denotes a tip surface, reference numeral 7 denotes a crest portion, reference numeral 8 denotes a valley portion, and reference numeral 9 denotes a base portion. The friction stir welding tool member 1 broadly comprises a probe portion 2 and a shoulder portion 3. The probe portion 2 comprises an uneven portion 4 on its side peripheral surface, and a tip surface 6 of the tip portion. Furthermore, the uneven portion 4 is composed of the crest portion 7 and the valley portion 8. On the other hand, the shoulder portion 3 comprises a base portion 9.

[0013] FIG. 1(A) shows a side view of a friction stir welding tool member 1, and FIG. 1(B) shows a top view of the friction stir welding tool member 1. A friction stir welding tool member may simply be called a welding tool member or a tool member. The welding tool member 1 has a probe portion 2 at its tip. The probe portion 2 and the shoulder portion 3 may be of an integral type or a separate type. The integral type means that the probe portion 2 and the shoulder portion 3 are made of a single member and cannot be detached. An example of such a member is a ceramic sintered body. The separate type means that the probe portion 2 and the shoulder portion 3 can be separated, that is, they can be detached. The following description will be given taking as an example a welding tool member 1 in which the probe portion 2 and the shoulder portion 3 are integral. However, the welding tool member may be of a separate type.

[0014] First, the welding tool member 1 has a spiral concave-convex portion 4 having peaks 7 and valleys 8 on the circumferential side surface of the probe portion 2. The convex portions of the concave-convex portion 4 are the peaks 7, and the concave portions are the valleys 8. The joining tool member 1 is also characterized in that in a cross section C passing through the rotation axis of the joining tool member 1, i.e., the rotation axis 5 of the probe portion 2, the difference rate of area between adjacent valley portions along an axis parallel to the rotation axis 5 is within a range of 5% to 30%. For example, the difference in area can be measured with a three-dimensional shape measuring device. The rotation axis 5 indicates the axis about which the joining tool member 1 rotates at high speed. The rotation axis 5 is an axis passing through the center of the joining tool member 1, i.e., the probe portion 2.

[0015] The shape of the uneven portion 4 can be measured by a three-dimensional shape measuring machine. FIG. 2 shows an example of the probe portion 2. FIG. 2 shows a cross-sectional view of the probe portion 2 at cross-section C for convenience. In FIG. 2, reference numeral 71 denotes a first peak, reference numeral 72 denotes a second peak, and reference numeral 73 denotes a third peak. The peaks 71 to 73 each indicate a peak portion of the helical peak 7 that appears in cross-section C. Reference numeral 81 denotes a first valley, reference numeral 82 denotes a second valley, reference numeral 83 denotes a third valley, and reference numeral 84 denotes a fourth valley. The valleys 81 to 84 each indicate a valley portion of the helical valley 8 that appears in cross-section C.

[0016] Also, A1, A2, and A3 are the apexes of the peaks. Specifically, A1 is the apex of the first peak 71. A2 is the apex of the second peak 72. A3 is the apex of the third peak 73. Also, B1, B2, B3, and B4 are the apexes of the valleys. Specifically, B1 is the apex of the first valley 81. B2 is the apex of the second valley 82. B3 is the apex of the third valley 83. B4 is the apex of the fourth valley 84. Also, P1 and P2 are the pitches of the adjacent peaks. Specifically, P1 is the pitch between the first peak 71 and the second peak 72. Also, P2 is the pitch between the second peak 72 and the third peak 73. Also, Q2 and Q3 are the depths of the adjacent valleys. Specifically, Q2 is the depth of the second valley 82, and Q3 is the depth of the third valley 83.

[0017] First, a method for calculating the area of ​​the valley portion in cross section C will be described. A method for calculating the area of ​​the second valley portion 82 will be described as an example. A1 is the apex of the first peak portion 71, and A2 is the apex of the second peak portion 72. Also, B2 is the apex of the second valley portion 82. Here, the apex of the valley portion is the deepest part of the valley portion. A straight line is drawn from the apex A1 to the apex A2. The straight line from the apex A1 to the apex A2 is set as the upper side (base side), and the space formed by the cavity when the straight line is moved to the apex B2 is set as the area of ​​the second valley portion 82. Similarly, the straight line from the apex A2 to the apex A3 is set as the upper side (base side), and the space formed by the cavity when the straight line is moved to the apex B3 is set as the area of ​​the third valley portion 83.

[0018] The difference rate (%) of the areas of the adjacent valleys 82, 83 along the parallel axis of the rotation shaft 5 is calculated by the following formula (1). The difference rate (%) of the areas of adjacent valleys 82, 83 along the parallel axis of the rotation shaft 5 = | (area of ​​valley 82 - area of ​​valley 83) / area of ​​valley 82 | × 100 ... (1) That is, in general, the difference rate (%) of the area of ​​adjacent valley portions can be calculated from the following formula (2): where m is an integer of 1 or more. Difference in area between adjacent valleys (%) = | (area of ​​the mth valley portion - area of ​​the m+1th valley portion) / area of ​​the mth valley portion | × 100 ... (2) It should be noted that the mth valley portion and the (m+1)th valley portion are adjacent valley portions.

[0019] It is preferable that the difference rate between the areas of adjacent valley portions calculated by the above formula (2) is within a range of 5% to 30%. The difference rate between the areas of adjacent valley portions being within a range of 5% to 30% means that the relationship of the following formula (3) is satisfied. 5% ≦|(area of ​​m-th valley part-area of ​​m+1-th valley part) / area of ​​m-th valley part|×100 ≦30% …(3) Furthermore, when a plurality of valley portions are present, the difference in area between adjacent peak portions is within the range of 5% to 30%.

[0020] A method for calculating the area of ​​the peak portion in cross section C will be described. The method for calculating the area of ​​the second peak portion 72 will be described as an example. B2 is the apex of the second valley portion 82. B3 is the apex of the third valley portion 83. Here, the apex of the valley portion is the deepest part of the valley portion. A straight line is drawn from the apex B2 to the apex B3. The line from the apex B2 to the apex B3 is set as the base, and the space formed by the entity when the line is moved to the apex A2 is set as the area of ​​the second peak portion 72. Similarly, the line from the apex B1 to the apex B2 is set as the base, and the space formed by the entity when the line is moved to the apex A1 is set as the area of ​​the first peak portion 71. Similarly, the line from the apex B3 to the apex B4 is set as the base, and the space formed by the entity when the line is moved to the apex A3 is set as the area of ​​the third peak portion 73. In this way, the area of ​​the range with the line connecting the apexes of the valley portions as the base is calculated. Therefore, a location W1 before the formation of the first valley 81 that forms the uneven portion 4 and a location W2 after the formation of the last valley 84 are not counted as peaks.

[0021] In addition, the drawings obtained by the 3D shape measuring machine shall be enlarged by 40 times or more. The areas of the valleys and peaks may be obtained by image analysis using the enlarged drawings. A laser microscope may be used instead of the 3D shape measuring machine.

[0022] The difference rate (%) of the areas of the ridges 72, 73 adjacent to each other along the parallel axis of the rotation shaft 5 is calculated by the following formula (4). The difference rate (%) of the areas of adjacent peaks 72, 73 along the parallel axis of the rotation shaft 5 = | (area of ​​ridge 72 - area of ​​ridge 73) / area of ​​ridge 72 | × 100 ... (4) That is, in general, the difference rate (%) of the areas of adjacent peak portions can be calculated from the following formula (5): where n is an integer of 1 or more. The difference rate (%) between the areas of adjacent peaks along the parallel axis of the rotation shaft 5 = | (area of ​​the nth peak part - area of ​​the nth + 1st peak part) / area of ​​the nth peak part | × 100 ... (5) It should be noted that the n-th peak portion and the (n+1)-th peak portion are adjacent peak portions.

[0023] It is preferable that the difference rate between the areas of adjacent peak portions calculated by the above formula (5) is within the range of 5% to 30%. The difference rate between the areas of adjacent peak portions being within the range of 5% to 30% means that the relationship of the following formula (6) is satisfied. 5% ≦|(area of ​​nth peak part - area of ​​nth + 1th peak part) / area of ​​nth peak part|×100 ≦30% …(6) Furthermore, when there are multiple peaks, the difference in area between adjacent peaks is within the range of 5% to 30%.

[0024] As described above, the area between adjacent valley portions or peak portions in the spiral concave-convex portion 4 is To By providing the difference, the mixing force of the joining tool member 1 can be improved. When the difference rate between the areas of adjacent valley portions or peak portions is less than 5%, To If the difference in area between adjacent valley portions or peak portions exceeds 30%, the durability of the probe portion 2 decreases. For this reason, the difference in area between adjacent peak portions 7 is preferably within a range of 5% to 30%, more preferably 10% to 25%.

[0025] The area of ​​adjacent valley portions of the spiral valley portion 8 To The difference indicates that the height, width, shape of the inclined surface, etc. of the adjacent valley portions are different. Similarly, the area of ​​the adjacent peak portions of the spiral peak portion 7 To The difference indicates that at least one of the height, width, shape of the inclined surface, etc. of the adjacent peaks is different. The tip of the peak may be flat or may be a curved surface with the center of rotation as the peak. In order to improve the mixing force of the joining tool member 1, it is preferable that the tip be a curved surface with the center of rotation as the peak.

[0026] In the joining tool member of Patent Document 2, when joining coarse threads or fine threads, the area To There was no difference. The joining tool member rotates at high speed along an axis parallel to the rotation axis. In the joining tool member 1 of this embodiment, the area of ​​adjacent peak portions To Due to the difference, it is possible to cause unsteady plastic flow. Friction stir welding is a joining method in which a high-speed rotating joining tool member is pressed against the workpieces to integrate the workpieces by utilizing frictional heat. The workpieces are softened by frictional heat, and the rotational force of the probe portion causes plastic flow around the joint, thereby integrating the workpieces. Unsteady plastic flow can be generated by making the shapes of adjacent peaks different. Unsteady plastic flow means that plastic flow is caused while varying the strength of the stress generated by the rotation of the probe portion 2. Unsteady plastic flow can increase the stirring force. In addition, the temperature rise of the joint portion of the workpieces can be accelerated. This can accelerate the softening of the workpieces. Therefore, the load on the joining tool member 1 can be reduced.

[0027] Furthermore, it is preferable that the valley portion 8 of the spiral uneven portion 4 is formed continuously by a single series (as shown in FIG. 1), or is formed intermittently by multiple series that correspond to less than one revolution of the probe portion 2.

[0028] FIG. 4 illustrates a spiral uneven portion 4A having intermittently formed grooves. In the figure, reference numeral 1A denotes a joining tool member, reference numeral 2A denotes a probe portion, reference numeral 3 denotes a shoulder portion, reference numeral 4A denotes an uneven portion, reference numeral 5 denotes a rotating shaft, reference numeral 6 denotes a tip surface, reference numeral 7A denotes a crest portion, reference numeral 8A denotes a valley portion, and reference numeral 9 denotes a base portion. The joining tool member 1A generally comprises a probe portion 2A and a shoulder portion 3. The probe portion 2A comprises an uneven portion 4A on the side peripheral surface and a tip surface 6 of the tip portion. Furthermore, the uneven portion 4A is composed of a crest portion 7A and a valley portion 8A. On the other hand, the shoulder portion 3 comprises a base portion 9. Reference numerals 851 to 856 denote the first to sixth valley portions of the multiple consecutive valley portions 8A. FIG. 4 is a schematic diagram of the probe portion 2A as viewed from the side. In FIG. 4, the same members as those in FIG. 1(A) are denoted by the same reference numerals and the description thereof will be omitted.

[0029] The multiple continuous valley portion 8A is composed of multiple valley portions 851 to 856. "Composed of multiple valley portions 851 to 856" refers to a shape that is divided into multiple valley portions when going around the side circumferential surface of the probe portion 2A. For example, in the line of sight of FIG. 4, a curved line for half the circumference is divided into three by a first valley portion 851 to a third valley portion 853. With such a distribution of valley portions where the length of the portion without valley portions is short, substantially the same effect can be obtained even if the valley portions are not continuous.

[0030] In addition, when the length of each of the multiple valleys 8A is less than one revolution of the probe portion 2A, the valleys may be continuous or divided into multiple units as a unit of less than one revolution. A continuous valley that is less than one revolution leads to an improvement in the mixing force of the joining tool member 1A. Furthermore, multiple valleys lead to an improvement in the strength of the probe portion 2A.

[0031] The length of the valley portion 8A may be a combination of more than one revolution and less than one revolution. For example, the valley portion 8A near the base of the probe portion 2A may be less than one revolution, and the rest may be more than one revolution. This method can improve both the strength of the probe portion 2A and the mixing force of the joining tool member 1A.

[0032] 4, the fourth valley 854 and the sixth valley 856 are continuous, but if there is a valley on the back side when going around the probe portion 2A, the valley will be divided into multiple valleys. Therefore, the multiple valleys 851 to 856 of the valley portion 8A only need to exist on the same curve when going around the probe portion 2A.

[0033] Furthermore, when the gap is formed by the multiple valleys 851 to 856, it is preferable that a fourth valley 854 is present immediately below (adjacent to) the gap between the first valley 851 and the second valley 852 and the gap between the second valley 852 and the third valley 853. As shown in Fig. 4, the presence of the fourth valley 854 immediately below the gap can prevent a decrease in the stirring force of the joining tool member 1A.

[0034] For example, if the valleys that make up half the circumference of the probe portion 2A are arranged vertically (along the axis parallel to the rotation shaft 5), the number of locations where no valleys are formed increases, which may reduce the mixing force of the joining tool member 1A. For this reason, it is preferable that the gap on the curve where the multiple valleys 8A are formed, for example, the gap between the first valley 851 and the second valley 852, is 2 mm or less, and more preferably 0.5 mm or less. For example, this shows that the gap on the curve where the multiple valleys 8A are formed is 2 mm or less.

[0035] In addition, in a cross section passing through the rotation axis 5 of the joining tool member 1, 1A, the pitch between adjacent peaks along an axis parallel to the rotation axis 5 is preferably within a range of 0.01 mm to 0.2 mm. The pitch between adjacent peaks refers to the distance between the apexes of the peaks on the cross section C. The apex of a peak refers to the highest position in one peak (for example, peaks 71 to 73 shown in FIG. 2). In FIG. 2, the apex of the first peak 71 is A1, the apex of the second peak 72 is A2, and the apex of the third peak 73 is A3. The pitch between the first peak 71 and the second peak 72 is P1. The pitch between the second peak 72 and the third peak 73 is P2. The pitch is determined by drawing a vertical line from each apex and measuring the distance between the vertical lines.

[0036] The pitch between adjacent peaks along the parallel axis of the rotation shaft 5 can be calculated from the following formula (7). The difference in pitch between adjacent peaks along the parallel axis of the rotation shaft 5 =|P1-P2| …(7)

[0037] The difference in pitch between adjacent peak portions along the parallel axis of the rotating shaft 5 being within the range of 0.01 mm or more and 0.2 mm or less indicates that the following formula (8) is satisfied. 0.01mm≦|P1-P2|≦0.2mm …(8) Either pitch P1 or pitch P2 may be larger. This means that either of the adjacent pitches may be larger. In addition, if there are multiple pitches, it is preferable that the difference in pitch between adjacent peaks is within the range of 0.01 mm to 0.2 mm.

[0038] When the pitch difference is within the range of 0.01 mm or more and 0.2 mm or less, the stirring force of the joining tool member 1, 1A can be increased. By providing a pitch difference, it is possible to easily generate unsteady plastic flow. When the pitch difference is less than 0.01 mm, the gap may become too uniform, making it difficult to generate unsteady plastic flow. Furthermore, when the pitch difference is large and exceeds 0.2 mm, the stirring force of the joining tool member 1, 1A may decrease. For this reason, it is preferable that the pitch difference between adjacent peaks is within the range of 0.01 mm or more and 0.2 mm or less, and furthermore, 0.01 mm or more and 0.1 mm or less.

[0039] In addition, in a cross section passing through the rotation axis 5 of the joining tool member 1, the difference in depth between adjacent valley portions along an axis parallel to the rotation axis 5 is preferably within a range of 0.01 mm to 0.1 mm. More preferably, it is 0.01 mm to 0.05 mm. The valley portion 8 is formed between the peak portions 7. Explaining with reference to FIG. 2, the valley portion between the first peak portion 71 and the second peak portion 72 becomes the second valley portion 82. The valley portion between the second peak portion 72 and the third peak portion 73 becomes the third valley portion 83. The joining tool member 1A is similar to the joining tool member 1.

[0040] A method for determining the depth of a valley will be described with reference to Figure 2, using second valley 82 as an example. Draw a straight line connecting vertex A1 of first peak 71 and vertex A2 of second peak 72. Draw a perpendicular line from vertex B2 of second valley 82 to rotation axis 5. Find the point of contact between the perpendicular line from vertex B2 and the straight line connecting vertex A1 and vertex A2. The distance from vertex B2 to the point of contact is defined as the depth Q2 of second valley 82.

[0041] Similarly, the depth Q3 of the third valley 83 is to be found. A straight line is drawn connecting the apex A2 of the second peak 72 and the apex A3 of the third peak 73. A point of contact is found from the apex B3 of the third valley 83 to the line connecting the apex A2 and the apex A3. The distance from the apex B3 to the point of contact is defined as the depth Q3 of the third valley 83.

[0042] The difference in depth between adjacent valley portions along the parallel axis of the rotation shaft 5 can be calculated by the following formula (9). The difference in depth between adjacent valley portions along the parallel axis of the rotation shaft 5 =|Q1-Q2| …(9) The difference in depth between adjacent valley portions being within the range of 0.01 mm or more and 0.1 mm or less indicates that the following formula (10) is satisfied. 0.01mm≦|Q1-Q2|≦0.1mm …(10) Either of the depths Q1 and Q2 may be larger. This means that either of the adjacent valleys may be deeper. In addition, if there are multiple valleys along the parallel axis of the rotating shaft 5, it is preferable that the difference in depth between the adjacent valleys is within a range of 0.01 mm to 0.1 mm.

[0043] By providing a difference in depth between adjacent valley portions, it is possible to generate unsteady plastic flow. If the difference in depth between adjacent valley portions is less than 0.01 mm, there is a possibility that the stress generating unsteady plastic flow will be insufficient. If the difference in depth between adjacent valley portions exceeds 0.1 mm, stress will be concentrated in the higher peak portion, which may reduce durability. A more preferable range is 0.01 mm to 0.05 mm. below It is.

[0044] Moreover, the shoulder portion 3 connected to the probe portions 2 and 2A preferably has an inclined surface that is inclined from the base portion 9 toward the outer edge of the shoulder portion 3. Moreover, the inclination of the inclined surface is preferably within a range of 3° to 20°, and more preferably within a range of 5° to 15°. Moreover, the inclination of the inclined surface is the angle between the horizontal line from the base portion 9 and a straight line drawn from the base portion 9 to the apex of the shoulder portion 3. The inclination of the inclined surface being positive indicates that the apex of the shoulder portion 3 is higher than the base portion 9. Moreover, the apex of the shoulder portion 3 refers to the highest point in the shoulder portion 3. The inclined surface is preferably a concave surface, which means that the shoulder portion is curved in an arc shape when viewed in cross section.

[0045] Moreover, it is preferable that the outer diameter of the probe portions 2, 2A relative to the outer diameter of the shoulder portion 3 satisfies the following formula (11). 0.2 x outer diameter of shoulder part ≦ outer diameter of probe part ≦0.7 × outer diameter of shoulder part …(11)

[0046] The joining tool member 1 according to the embodiment has a spiral concave-convex portion 4 in the probe portion 2. As described above, the mixing force is improved by providing a difference in area between adjacent ridges. By setting the outer diameter of the probe portion 2 within a range of 0.2 to 0.7 times the outer diameter of the shoulder portion, the mixing force of the shoulder portion 3 can be added to the mixing force of the probe portion 2. The joining tool member 1A is similar to the joining tool member 1.

[0047] Furthermore, it is preferable that the root portion 9 of the probe portion 2 of the joining tool member 1 has a curved shape with a radius of curvature of 0.1 mm or more. By having the root portion 9 have a curved shape, the stress applied to the probe portion 2 can be alleviated. In other words, it is preferable that the uneven portion 4 is not formed up to the root portion 9. For this reason, it is preferable that the radius of curvature of the root portion 9 is 0.1 mm or more, and further 0.2 mm or more. The same applies to the joining tool member 1A as to the joining tool member 1.

[0048] In addition, the outer edge of the shoulder portion 3 of the joining tool member 1, 1A preferably has a radius of curvature of 0.3 mm or more, more preferably 0.5 mm or more. By providing the outer edge of the shoulder portion 3 with a predetermined radius of curvature, the durability of the shoulder portion 3 can be improved.

[0049] It is also preferable that the tips of the peaks 7 of the uneven portion 4 of the joining tool member 1 are rounded. This can improve the durability of the peaks 7. If the tips of the peaks 7 are sharp, the durability of the peaks 7 may decrease. To round the tips of the peaks 7, it is effective to use a method of polishing them with sandpaper or the like. The same applies to the joining tool member 1A as to the joining tool member 1.

[0050] The radius of curvature is measured by placing the joining tool member 1 with the probe portion 2 facing up and using a three-dimensional shape measuring machine, and the image obtained is used. The measurement conditions for the three-dimensional shape measuring machine are as described above. The radius of curvature of the root portion 9 is measured when the root portion 9 is viewed from the outside. The radius of curvature of the outer edge of the shoulder portion 3 is measured when the outer edge is viewed from the inside. The tip of the peak portion 7 is observed using a 40x magnification photograph. The same is true for the joining tool member 1A.

[0051] Furthermore, it is preferable that the tip surface 6 of the probe portion 2 of the joining tool member 1 has a curved shape. It is also preferable that the surface roughness Ra of the tip surface 6 of the probe portion 2 is within the range of 0.2 μm to 15 μm. The tip surface 6 of the probe portion 2 is the part that is pressed against the workpieces. By making the tip surface 6 a curved shape as shown in FIG. 1, it becomes easier for it to penetrate into the workpieces. A curved surface is a shape that has an arc-shaped cross section. The same applies to the joining tool member 1A as to the joining tool member 1.

[0052] In addition, the surface roughness Ra of the tip surface 6 of the joining tool member 1, 1A is within the range of 0.2 μm to 15 μm, so that the tool can easily penetrate into the workpiece. For this reason, the tip surface 6 is curved, and the surface roughness Ra is preferably within the range of 0.2 μm to 15 μm. If the surface roughness Ra is less than 0.2 μm, the surface may be too flat and the stirring force may be insufficient. Slip occurs on the workpiece and the tool may spin freely. For this reason, the temperature of the workpiece does not rise, and the load on the tool increases, which may lead to a shortened lifespan. In addition, if the surface roughness Ra is greater than 15 μm, the stirring force is improved, but the strength of the tip surface 6 may be insufficient. In addition, the surface roughness Ra of the shoulder portion 3 is also preferably within the range of 0.2 μm to 15 μm. The surface roughness Ra is determined in accordance with JIS-B-0601 (2001). The surface roughness is measured using a stylus surface roughness meter or a non-contact surface roughness meter using a laser microscope.

[0053] The outer diameter and length of the probe portion 2 and shoulder portion 3 of the joining tool member 1 may be changed according to the material and thickness of the workpieces. The length of the probe portion 2 is preferably longer than the thickness of one workpiece. The length of the probe portion 2 is preferably approximately equal to the thickness of the workpieces to be joined, and is preferably shortened by about 0.2 mm so as not to come into contact with the backing material. The same applies to the joining tool member 1A as to the joining tool member 1.

[0054] Moreover, it is preferable that the ratio between the outer diameter of the probe portion 2 and the outer diameter of the shoulder portion 3 of the joining tool member 1 satisfies the following formula (12). 0.1≦Outer diameter of probe portion 2 / Outer diameter of shoulder portion 3≦0.6 … (12) If the ratio of the outer diameter of the probe portion 2 to the outer diameter of the shoulder portion 3 is less than 0.1, the stirring force may be insufficient due to the small size of the probe portion 2. If the ratio exceeds 0.6, the effect of providing the shoulder portion 3 may decrease. The same applies to the joining tool member 1A as to the joining tool member 1.

[0055] Moreover, it is preferable that the depth of the valley portion 8 of the welding tool member 1 satisfies the following formula (13). 0.02≦depth of valley 8 / outer diameter of probe portion 2≦0.2 … (13) If the depth of valley portion 8 / the outer diameter of probe portion 2 is less than 0.02, the effect of providing concave-convex portion 4 may be insufficient. If the depth of valley portion 8 / the outer diameter of probe portion 2 exceeds 0.2, the grooves are deep and the strength of probe portion 2 may decrease. The same applies to joining tool member 1A as to joining tool member 1.

[0056] As described later, in spot joining, a plurality of plate-shaped workpieces are overlapped and joined. It is preferable that the length of the probe portion 2 of the joining tool member 1 is shorter than the thickness of the overlapped workpieces. It is also preferable that the length of the probe portion 2 is shorter than the thickness of the overlapped workpieces by about 0.2 mm. This makes it possible to suppress contact with the backing material. Moreover, "about 0.2 mm" means 0.2 mm±0.1 mm. The same applies to the joining tool member 1A as to the joining tool member 1.

[0057] The length of the probe portion 2 of the joining tool member 1 refers to the length of the probe portion 2 protruding from a horizontal line drawn from the highest point of the shoulder portion 3. The probe portion 2 is placed facing upwards and a horizontal line is drawn from the highest point of the shoulder portion 3. By making the length of the probe portion 2 shorter than the thickness of the overlapping materials to be joined, the probe portion 2 will not penetrate to the back side of the materials to be joined. This makes it possible to prevent the probe portion 2 from coming into contact with the backing material. The same applies to the joining tool member 1A as to the joining tool member 1.

[0058] The material constituting the joining tool members 1 and 1A is preferably a material having high strength and heat resistance. Examples of the material constituting the joining tool member 1 include silicon nitride sintered body, cubic boron nitride sintered body (PCBN), iridium alloy, WC cemented carbide, etc. Among these, it is preferable to use silicon nitride sintered body, which has the best wear resistance. Silicon nitride sintered body can have a Vickers hardness HV of 1400 or more. The spiral concave and convex parts 4, 4A are formed by cutting using a diamond grinding wheel. NC machine tools are used for cutting. Silicon nitride sintered body is a hard material. Because it is a hard material, only a small amount can be cut at a time. In other words, cutting can be done little by little. This makes it possible to control the area ratio of the peak parts 7, 7A. The Vickers hardness is measured at HV20 (test force 196.1N) according to JIS-R-1610 (2003). JIS-R-1610 corresponds to ISO14705.

[0059] In addition, silicon nitride sintered body has a fracture toughness value of 5.5 MPa m 1 / 2 It is possible to increase the fracture toughness to above 100%. This improves the durability of the joining tool members 1 and 1A. The fracture toughness value was calculated using the IF method in accordance with JIS-R-1607 (2015) and the Niihara formula. JIS-R-1607 corresponds to ISO15732.

[0060] The joining tool member 1, 1A having the spiral concave-convex portion 4, 4A as described above can improve the stirring force. In addition, since unsteady plastic flow can be generated, the temperature rise of the joining portion of the materials to be joined can be accelerated. Therefore, the time required for one joining can be shortened. As a result, the durability of the joining tool member 1, 1A can be improved. In addition, by making the joining tool members 1, 1A from sintered silicon nitride, it is possible to further improve the wear resistance. In other words, by making the joining tool members 1, 1A from sintered silicon nitride having the predetermined uneven portions 4, 4A, it is possible to improve both the mixing force and the durability.

[0061] Next, a friction stir welding apparatus and a friction stir welding method using the friction stir welding tool member according to the embodiment will be described. An example of a friction stir welding method is shown in Fig. 3. In the figure, 1 (1A) is a joining tool member, and 10 is a workpiece. Fig. 3 illustrates an example in which two workpieces 10 are stacked, but the friction stir welding method according to the embodiment is not limited to this. Three or more workpieces 10 may be stacked. Also, parts of the workpieces 10 may be stacked, and the overlapped parts may be friction stir welded. Also, the workpieces 10 may be butted together, and the butted parts may be friction stir welded.

[0062] The friction stir welding apparatus includes a welding tool member 1 (or a welding tool member 1A) according to the embodiment. The welding tool member 1 is pressed against the workpieces 10 while rotating at high speed. The probe portion 2 is pressed against the workpieces 10. Plastic flow occurs in the workpieces 10, and the workpieces 10 penetrate into the shoulder portion 3. The workpieces 10 are not limited to being plate-shaped. In addition, the friction stir welding method can be performed using any material. cormorant In this case, a backing member (not shown) may be used. The backing member is a member used as a base plate for the workpieces 10. It is preferable to use a backing member with low thermal conductivity. This is because it reduces heat loss and allows the generated heat to be effectively transferred to the workpiece. For this reason, it is preferable for the thermal conductivity of the backing material to be 30 W / m K or less.

[0063] There are two types of friction stir welding: spot welding and line welding. Spot welding is a method in which a joining tool member 1 is pressed against the workpieces 10 and the joining is performed by pushing the joining tool member 1 in. Line welding is a method in which a joining tool member 1 is pressed against the workpieces 10 and the joining tool member 1 is moved while being pushed in. Spot welding leaves dot-like weld marks, while line welding leaves line-like weld marks.

[0064] Furthermore, when performing the friction stir welding method, the joining tool member 1 may be tilted and pressed against the workpieces 10. The tilt angle of the joining tool member 1 is called the advance angle. A forward angle in a direction perpendicular to the workpieces 10 is defined as an advance angle of 0°. An advance angle tilted by 5° from the perpendicular direction is an advance angle of 5°. The advance angle is determined by the tilt of the rotation axis 5. A positive advance angle is defined as an advance angle in which the probe portion 2 is tilted in a protruding direction relative to the moving direction of the joining tool member 1. In the case of spot joining, the advance angle is preferably 0°, and in the case of line joining, the advance angle is preferably within the range of 1° to 20°.

[0065] The thickness of the workpieces 10 is preferably 0.1 mm or more. The thickness of the workpieces 10 is more preferably 0.5 mm or more and 20 mm or less. The thickness of the workpieces 10 is the thickness of a single sheet.

[0066] Various materials can be used as the material to be joined 10. The material to be joined 10 is preferably one or more selected from iron, iron alloys, aluminum, aluminum alloys, magnesium, magnesium alloys, copper, copper alloys, and fiber-reinforced composite resins such as carbon fiber reinforced plastics (CFRP). When joining two or more materials to be joined 10, the materials may be made of the same material or different materials. For example, aluminum alloy plates may be joined together, or an aluminum alloy plate and a magnesium alloy plate may be joined. Iron alloys include various alloys such as carbon steel, tool steel, chromium-molybdenum steel, stainless steel, manganese steel, and cast iron.

[0067] These alloys have a Vickers hardness Hv of 140 or more. The Vickers hardness Hv of aluminum is about 25. The Vickers hardness Hv of magnesium alloy is about 60. The Vickers hardness Hv of copper alloy is about 30. By forming the joining tool member 1 from silicon nitride sintered body, it can be applied to soft aluminum to hard iron. In particular, the joining tool member 1 is preferably a joining material 10 selected from aluminum, aluminum alloy, magnesium, magnesium alloy, copper, and copper alloy. The joining tool member 1 according to the embodiment is provided with an uneven portion 4 to improve the stirring force. Aluminum, aluminum alloy, magnesium, magnesium alloy, copper, copper alloy, and fiber reinforced composite resin have a Vickers hardness Hv of 80 or less. The lower the hardness of the joining material 10, the easier it is to stir. In other words, it can be said that it is suitable for joining materials having a Vickers hardness Hv of 80 or less. Furthermore, when using a workpiece having a Vickers hardness Hv of 140 or more, it is preferable that the material is thin. A thin material allows friction stir welding at a joining temperature in the range of 300°C to 600°C. When the uneven portion 4 is provided, durability decreases compared to when no uneven portion 4 is provided. By setting the joining temperature in the range of 300 to 600°C, excellent durability is exhibited even when joining workpieces having a Vickers hardness Hv of 140 or more.

[0068] It is also preferable that the rotation speed of the joining tool member 1 is 200 rpm or more, and the plunge load of the joining tool member 1 is 1 kN or more. 300 It is preferable to set the rotation speed at or above mm / min. The rotation speed of the joining tool member 1 is preferably within the range of 200 rpm to 5000 rpm. If the rotation speed is less than 200 rpm, the heating and stirring power may be insufficient. If the rotation speed exceeds 5000 rpm, the stirring power becomes too strong, and the unevenness of the joining marks on the workpieces 10 to be joined increases. If the unevenness of the joining marks increases, the appearance of the joint deteriorates. For this reason, it is preferable that the rotation speed of the joining tool member 1 is within the range of 200 rpm to 5000 rpm, and furthermore, 1000 rpm to 4000 rpm.

[0069] Furthermore, if the indentation load is less than 1 kN, the indentation force may be insufficient, resulting in a decrease in the mixing force. A decrease in the mixing force will result in a longer joining time and a decrease in manufacturing efficiency. Although there is no particular limit to the upper limit of the indentation load, it is preferable that it is 20 kN or less. If the indentation load exceeds 20 kN, the life of the joining tool member 1 may be reduced. For this reason, the indentation load is preferably within a range of 1 kN to 20 kN, and more preferably 2 kN to 15 kN.

[0070] The rotation speed and the plunge load of the joining tool member 1 can be applied to both point joining and line joining. In addition, when performing line joining, the moving speed is preferably in the range of 300 mm / min to 1500 mm / min. If the moving speed is less than 300 mm / min, the speed is too slow and mass productivity decreases. The joining temperature also rises more than necessary. On the other hand, if the moving speed is faster than 1500 mm / min, the temperature does not rise in some places and the stirring force decreases, so that the load on the tool increases and there is a concern about the impact on the lifespan. In addition, the joining strength between the materials to be joined decreases. For this reason, the moving speed is preferably 300 to 1500 mm / min, and more preferably 400 to 1000 mm / min.

[0071] In addition, the friction stir welding method according to the embodiment is preferably spot welding. As described above, the friction stir welding according to the embodiment can be applied to either spot welding or line welding. On the other hand, the welding tool member 1 according to the embodiment is provided with a spiral uneven portion 4 on the probe portion 2. This allows for unsteady plastic flow to occur. Spot welding is often performed at a forward angle of 0°. The forward angle of 0° is a direction perpendicular to the workpiece 10. When the probe portion 2 is pressed against the workpiece 10 at a forward angle of 0°, it becomes easier to penetrate deeper due to the drill effect of the spiral uneven portion 4. Therefore, the plastic flow of the joint can be accelerated. With point welding, it is easier to obtain the drill effect of the spiral uneven portion 4. Also, the higher the rotation speed, the more the drill effect can be obtained. For this reason, point welding is preferable.

[0072] The above-described friction stir welding method can achieve both high stirring power and durability of the joining tool members 1, 1A. Furthermore, when the joining tool members 1, 1A made of sintered silicon nitride are used to spot join workpieces having a Vickers hardness Hv of 80 or less, the wear amount of the tool member 1 can be reduced to almost zero even after 5,000 spot joining.

[0073] Next, a manufacturing method of the joining tool member 1 (or the joining tool member 1A) according to the embodiment will be described. As long as the joining tool member 1 according to the embodiment has the above-mentioned configuration, the manufacturing method is not particularly limited, but the method for obtaining a good yield is as follows. The manufacturing method hereinafter will be exemplified by one using a silicon nitride sintered body.

[0074] First, a silicon nitride sintered body is prepared. The silicon nitride sintered body preferably has a Vickers hardness HV20 of 1400 or more. The silicon nitride sintered body also has a fracture toughness value of 5.5 MPa m 1 / 2 It is preferable that the above is the case. Next, the silicon nitride sintered body is subjected to a cutting process. NC machine tool processing is suitable for the cutting process. An NC machine tool is a device that combines a general-purpose lathe and a numerical control device. An NC machine tool enables automatic processing using a processing program. By programming the size of the area of ​​the peaks, the pitch, the depth of the valleys, etc., the desired unevenness 4, 4A can be obtained. In addition, when processing with an NC machine tool, if one grinding wheel is used, it is easy to process the unevenness 4, 4A. In addition, if the silicon nitride sintered body is made cylindrical, it is easy to process the unevenness 4, 4A. In addition, if the method is to form the unevenness 4, 4A on a cylindrical silicon nitride sintered body, the shape control of the unevenness 4, 4A can be linked to the shape control of the peaks. It is also preferable to perform polishing to control the surface roughness of the tip surface and shoulder portion of the probe portion, and polishing using a diamond grindstone is suitable for controlling the surface roughness.

[0075] (Example) (Examples 1 to 11, Comparative Examples 1 to 3) A friction stir welding tool member was fabricated from silicon nitride sintered body. The friction stir welding tool member was made of a probe part and a shoulder part integrated together. The silicon nitride sintered body used had a Vickers hardness of HV20 and fracture toughness values ​​shown in Table 1.

[0076] [Table 1] TIFF0007651713000001.tif25170

[0077] A spiral uneven portion was formed on the probe portion of the silicon nitride sintered body by using an NC machine tool. The inclination angle of the inclined surface inclined from the base portion 9 of the probe portion 2 toward the outer edge of the shoulder portion was set to 15°. Next, the tip surface 6 of the probe portion 2 and the shoulder portion 3 were polished to adjust the surface roughness Ra. The surface roughness Ra of the shoulder portion was set to a range of 0.2 μm to 15 μm. The shapes of the obtained friction stir welding tool members are as shown in Tables 2 and 3. The shape of the uneven portion was measured using a three-dimensional shape measuring machine from a direction perpendicular to the rotation axis. The measurement method was as described above.

[0078] In Comparative Example 1, no unevenness was formed. In Comparative Example 2, the difference in area between adjacent peaks along the parallel axis of the rotating shaft 5 was 1% or less. In Comparative Example 3, there were some locations where the difference in area between adjacent peaks along the parallel axis of the rotating shaft 5 was 40%.

[0079] Moreover, in Examples 1 to 11 and Comparative Examples 2 to 3, the following condition was satisfied: 0.02≦depth of valley part / outer diameter of probe part≦0.2. In Examples 1, 3 to 11 and Comparative Examples 2 to 3, the tip of the peak part was rounded (curved). In Examples 1 to 6, Example 11 and Comparative Examples 2 to 3, a series of valley parts was provided in the spiral-shaped uneven part. In Examples 7 to 8, a series of valley parts (corresponding to valley part 8A in FIG. 4) with gaps was provided in the uneven part. In Example 7, the gap formed on the curved line of half a circumference was set to 0.1 mm. In Example 7, three valley parts were provided on the curved line of one circumference. In Example 8, the gap formed on the curved line of half a circumference was set to 0.2 mm. In Example 8, two valley parts were provided on the curved line of one circumference. In Example 9, one valley part of less than one circumference (90% of one circumference) was provided. In Example 10, a single valley portion is provided in the vicinity of the base of the probe portion, the valley portion being less than one revolution (90% of one revolution). In Example 10, the gap formed on the curve for the valley portions other than the vicinity of the base of the probe portion 2 is set to 0.1 mm. In Examples 7 to 10, a valley portion exists immediately below the formed gap.

[0080] [Table 2] TIFF0007651713000002.tif105114

[0081] [Table 3] TIFF0007651713000003.tif109170

[0082] As can be seen from the table, in the friction stir welding tool members according to the examples, the difference rate in area between adjacent peak portions along the parallel axis of the rotation shaft was within the range of 5% to 30%.

[0083] Next, the friction stir welding tool members according to the examples and the comparative examples were placed in a friction stir welding apparatus, and a friction stir welding method was performed using the friction stir welding apparatus. Aluminum plates were prepared as the materials to be joined. Two aluminum plates were stacked and spot joined. The durability of the friction stir welding tool components was evaluated by spot joining. The spot joining was performed at a forward angle of 0° (the tool component was pushed perpendicularly into the materials to be joined). The spot joining was performed using a backing material made of sintered silicon nitride. The aluminum plates were 1 mm thick. The aluminum plates used had a Vickers hardness Hv of 25.

[0084] In the durability test, spot joining was repeated and the wear of the tool member was measured after 50,000 hits. The wear was measured with a vernier caliper as the change in diameter of the uneven part before and after joining. The change (%) was calculated by [(diameter before joining - diameter after joining) / diameter before joining] x 100.

[0085] The amount of wear was also measured every 1000 hits. The end of the life was determined when 90% of the depth of the valleys in the uneven parts had worn away and disappeared. The spot joining conditions and evaluation results are shown in Table 4.

[0086] [Table 4] TIFF0007651713000004.tif79114

[0087] As can be seen from Table 4, the friction stir welding tool material according to the embodiment had a wear amount of the uneven portion of almost 0%. In addition, when the tip of the probe part was flat as in Example 2, it took a long time to penetrate into the workpiece. Therefore, the temperature rose sharply in the initial stage when the probe part penetrated into the workpiece, but there was no problem as the penetration progressed. If the temperature rise when the probe part penetrates is large, the appearance of the welding mark may become dirty. The welding mark is sometimes called a nugget part. In addition, in the case of Example 6, in which the radius of curvature of the base part is small, chipping was confirmed in the probe part after 50,000 strokes. Examples 1, 3 to 5 had excellent wear resistance, and no defects or poor appearance of the nugget part were confirmed.

[0088] In addition, even when the spiral uneven portion was formed with a plurality of valley portions as in Examples 7 to 10, the characteristics were good. However, the amount of wear increased slightly because gaps were formed in the valley portions. This shows that the spiral uneven portion has a series of valley portions. In Example 11, the amount of wear increased when the peak portions were out of the preferred range.

[0089] In all of the comparative examples, the amount of wear in the uneven portion was large. In addition, in the case of the comparative example 1 in which the uneven portion was not provided, a cavity was formed in the nugget portion, and a poor appearance was observed. In the comparative example 2, a void-like defect was observed in a part of the nugget portion. In the comparative example 3, a void-like defect was observed in the nugget portion. In the comparative example 3, chipping occurred in the shoulder portion.

[0090] Although some embodiments of the present invention have been illustrated above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. In addition, the above-mentioned embodiments can be implemented in combination with each other.

Claims

1. A friction stir welding tool member having a shoulder portion and a probe portion, The friction stir welding tool member is made of a silicon nitride sintered body, a spiral concave-convex portion having peaks and valleys on a side circumferential surface of the probe portion, and in a cross section passing through the rotation axis of the probe portion, a difference in area between each valley portion formed along an axis parallel to the rotation axis and an adjacent valley portion is within a range of 5% to 30%, a difference in depth between each of the valley portions formed along an axis parallel to the rotation shaft and the adjacent valley portion is within a range of 0.01 mm or more and 0.1 mm or less; A friction stir welding tool member comprising:

2. The valley portion of the spiral concave-convex portion is continuously formed by a series, or is intermittently formed by a plurality of series of less than one revolution of the probe portion.

2. The friction stir welding tool member according to claim 1.

3. In a cross section passing through the rotation axis, a difference rate of area between each peak portion formed along an axis parallel to the rotation axis among the peak portions and an adjacent peak portion is within a range of 5% to 30%.

2. The friction stir welding tool member according to claim 1.

4. a difference in pitch between each of the peaks formed along an axis parallel to the rotation shaft and an adjacent peak is within a range of 0.01 mm or more and 0.2 mm or less; 2. The friction stir welding tool member according to claim 1.

5. a difference in pitch between each of the peaks formed along an axis parallel to the rotation shaft and an adjacent peak is within a range of 0.01 mm or more and 0.1 mm or less; 2. The friction stir welding tool member according to claim 1.

6. The tip surface of the probe portion has a curved shape with a peak at the center of rotation, The surface roughness Ra of the tip surface of the probe portion is in the range of 0.2 μm to 15 μm.

2. The friction stir welding tool member according to claim 1.

7. The base of the probe portion has a curved shape with a curvature radius of 0.1 mm or more.

2. The friction stir welding tool member according to claim 1.

8. The friction stir welding tool member according to claim 1 is provided. The friction stir welding apparatus is characterized by the above.

9. A friction stir welding method, comprising friction stir welding workpieces using the friction stir welding apparatus according to claim 8.

10. The workpieces are spot-joined; The friction stir welding method according to claim 9 .

11. The material to be joined is one or more selected from iron, iron alloys, aluminum, aluminum alloys, copper, copper alloys, and fiber-reinforced composite resins; The friction stir welding method according to claim 9 .

12. In a cross section passing through the rotation axis, a difference rate of area between each peak portion formed along an axis parallel to the rotation axis among the peak portions and an adjacent peak portion is within a range of 5% to 30%.

3. The friction stir welding tool member according to claim 2.

13. a difference in pitch between each of the peaks formed along an axis parallel to the rotation shaft and an adjacent peak is within a range of 0.01 mm or more and 0.2 mm or less; The friction stir welding tool member according to claim 12.

14. a difference in depth between each of the valley portions formed along an axis parallel to the rotation shaft and the adjacent valley portion is within a range of 0.01 mm or more and 0.1 mm or less; The friction stir welding tool member according to claim 13.

15. The friction stir welding tool member is made of a silicon nitride sintered body. The friction stir welding tool member according to claim 14.

16. The tip surface of the probe portion has a curved shape with a peak at the center of rotation, The surface roughness Ra of the tip surface of the probe portion is in the range of 0.2 μm to 15 μm. The friction stir welding tool member according to claim 15.

17. The friction stir welding tool member according to claim 16, The friction stir welding apparatus is characterized by the above.

18. A friction stir welding method, comprising friction stir welding workpieces using the friction stir welding apparatus according to claim 17.

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