Rotary tool for friction stir welding and friction stir welding method using the same

Abstract

To provide a rotary tool for friction stir welding that can achieve sufficient joint strength without generating protrusions during joining, while adequately suppressing the curling phenomenon at the joining interface. [Solution] A rotary tool 1 having a shoulder portion 11 that constitutes the tip side of the rotary tool, the shoulder portion 11 having a pin portion 110 projecting outward from its tip side, and an arc-shaped surface 111 arranged on the outer circumference of the pin portion, the arc-shaped surface having a shape that is inclined downward while forming an arc in the direction from the rotation axis side to the outer circumference side in a cross view, and having a helical groove 3, the helical direction of the helical groove of the arc-shaped surface being in the direction that causes the material to flow from the inner circumference side to the outer circumference side of the rotary tool in a bottom view with respect to the rotation direction of the rotary tool, the pin portion having a helical groove 1101 on its outer circumference surface, the helical direction of the helical groove of the pin portion being in the direction that causes the material to flow toward the tip side of the rotary tool with respect to the rotation direction of the rotary tool.

Description

Technical Field

[0004] , , , , , , , , , , ,

[0005]

[0001] The present invention relates to a rotary tool for friction stir welding and a friction stir welding method using the same.

Background Art

[0002] Conventionally, in fields such as automobiles, railway vehicles, and aircraft, from the viewpoint of improving productivity, a so-called friction stir spot welding (FSSW) method has been proposed as a method for joining two members. The friction stir welding method is a method in which a first member and a second member are overlapped between a rotary tool and a receiving member, the rotary tool is rotated, and pressure is applied from the first member side to generate frictional heat, and the first member and the second member are plastically flowed (or melted and solidified) with each other by this frictional heat to join the first member and the second member.

[0003] In such a friction stir welding method, for example, as shown in FIG. 21, a rotary tool 500 provided with a pin portion 510 on the tip side is used. In the rotary tool 500, specifically, in a cross-sectional view, an inclined surface 511 is provided which is disposed on the outer periphery of the pin portion 510 and has an inclination angle θ of 90 degrees or less with respect to the tip direction m' of the rotation axis. However, when friction stir welding is performed using such a rotary tool 500, as shown in FIG. 22, a curling phenomenon Z occurs in which the joining interface between the first member 517 and the second member 518 rises up to the vicinity of the base (root) of the pin portion 510 without disappearing. Therefore, the joining strength between the first member and the second member was not sufficient.

[0004] Therefore, for example, in Patent Document 1, a technique is disclosed in which a recess is provided on the pressure receiving surface of the receiving member to sink the interface between the first member and the second member.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] However, in the technology described in Patent Document 1, a protrusion is provided on the lower surface of the second member (the contact surface with the receiving member) with a shape corresponding to the shape of the recess of the receiving member. Therefore, this technology has the problem that it cannot be applied to structures that require a flat surface as the lower surface of the second member.

[0007] The present invention aims to provide a rotary tool for friction stir welding that can sufficiently suppress the curling phenomenon at the joining interface without generating protrusions during joining, and can obtain sufficient joining strength.

[0008] More specifically, the present invention aims to provide a rotary tool for friction stir welding that, when friction stir welding a first member positioned above a second member positioned below a second member, can sufficiently suppress the curling phenomenon at the joint interface without generating a protrusion on the lower surface of the second member, thereby obtaining sufficient joint strength. [Means for solving the problem]

[0009] The present invention A rotary tool for friction stir welding, The rotating tool has a shoulder portion that forms the tip side, The shoulder portion is provided with a pin portion projecting outward at its tip and an arc-shaped surface arranged on the outer circumference of the pin portion. The aforementioned arc-shaped surface, in cross-sectional view, is a surface that forms an arc and slopes downward in the direction from the axis of rotation side to the outer circumference side, and has a helical groove. The spiral direction of the helical grooves in the arc-shaped surface is such that, when viewed from the bottom, the material flows from the inner circumference to the outer circumference of the rotating tool, relative to the rotational direction of the rotating tool. The aforementioned pin portion has a helical groove on its outer surface, The spiral direction of the helical groove in the pin portion is such that, relative to the rotational direction of the rotary tool, the material flows toward the tip of the rotary tool. (Rotary tool for friction stir welding) Regarding.

[0010] The present invention also, A friction stir welding method comprising performing friction stir welding using the above-described rotary tool for friction stir welding and a receiving member positioned opposite the rotary tool. Regarding. [Effects of the Invention]

[0011] The rotary tool of the present invention allows for the joining of a first member and a second member with greater joint strength using a simple drive mechanism. Specifically, during joining, the lifting of the first member can be suppressed without requiring any other members, such as a pressing member and an outer ring member, or a drive device to drive those other members, on the upper side relative to the first member. At this time, circulating plastic flow can be sufficiently induced near the pin portion inside the first and second members. As a result, the first member and the second member can be joined with sufficient joint strength. According to the rotary tool of the present invention, since no other component and a drive device for that component are required, a portion of the pressure applied to the first component by the shoulder portion is not absorbed as pressure by a spring or the like. Therefore, joining can be performed with a sufficiently efficient pressurizing action. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic perspective view showing the vicinity of the pin portion in an example (first embodiment) of the rotary tool of the present invention is shown. [Figure 2] Figure 1 shows a schematic bottom view of the rotation tool. [Figure 3] Figure 1 shows a schematic front view of the vicinity of the pin portion in the rotary tool. [Figure 4]It is a schematic cross-sectional view for explaining the dimensions in the vicinity of the pin portion in the rotary tool of FIG. 1, and is a schematic cross-sectional view in a cross-section passing through the rotation axis of the rotary tool. [Figure 5] It is a schematic cross-sectional view showing another example of the cross-sectional view shape of the arc-shaped surface (first inclined surface) in the rotary tool. [Figure 6] It is a schematic cross-sectional view showing another example of the cross-sectional view shape of the arc-shaped surface (first inclined surface) in the rotary tool. [Figure 7] It is a schematic cross-sectional view showing another example of the bottom view shape of the spiral groove provided in the arc-shaped surface (first inclined surface) in the rotary tool. [Figure 8] It is a schematic cross-sectional view showing another example of the bottom view shape of the spiral groove provided in the arc-shaped surface (first inclined surface) in the rotary tool. [Figure 9] A schematic perspective view showing the vicinity of the pin portion in another example (second embodiment) of the rotary tool of the present invention is shown. [Figure 10] A schematic bottom view of the rotary tool shown in FIG. 9 is shown. [Figure 11] A schematic front view of the vicinity of the pin portion in the rotary tool shown in FIG. 9 is shown. [Figure 12] It is a schematic cross-sectional view for explaining the dimensions in the vicinity of the pin portion in the rotary tool of FIG. 9, and is a schematic cross-sectional view in a cross-section passing through the rotation axis of the rotary tool. [Figure 13] It is a schematic bottom view showing another example of the cross-sectional view shape of the tapered surface (second inclined surface) in the rotary tool. [Figure 14] It is a schematic bottom view showing another example of the cross-sectional view shape of the tapered surface (second inclined surface) in the rotary tool. [Figure 15] It is a schematic bottom view showing another example of the cross-sectional view shape of the tapered surface (second inclined surface) in the rotary tool. [Figure 16] A schematic bottom view of another example (third embodiment) of the rotary tool of the present invention is shown. [Figure 17] It is a schematic cross-sectional view for explaining the dimensions in the vicinity of the pin portion in the rotary tool of FIG. 16, and is a schematic cross-sectional view in a cross-section passing through the rotation axis of the rotary tool. [Figure 18] This is a schematic cross-sectional view illustrating the joining mechanism using the rotary tool of the present invention, and is a schematic cross-sectional view showing the state at the time of joining. [Figure 19] This graph shows the results for the examples and comparative examples. [Figure 20] This shows a cross-sectional photograph of the vicinity of the joint in one of the joints obtained in Example 1. [Figure 21] A schematic cross-sectional view of the vicinity of the pin portion in a conventional rotary tool is shown. [Figure 22] This is a schematic cross-sectional view illustrating a joining mechanism using a conventional rotary tool, and shows the state during joining. [Modes for carrying out the invention]

[0013] The rotary tool for friction stir welding (hereinafter sometimes simply referred to as the "rotary tool") and the friction stir welding method using the rotary tool of the present invention will be described in detail with reference to the drawings. It should be noted that the various elements shown in the drawings are only schematically represented for the purpose of understanding the present invention, and that dimensional ratios and appearances may differ from those of the actual objects. Furthermore, the term "vertical direction" used directly or indirectly in this specification corresponds to the vertical direction in the drawings. Unless otherwise specified, common symbols in these drawings indicate the same member, part, dimension, or area.

[0014] In this specification, "section view" refers to the form of an object when viewed from a direction substantially perpendicular to the rotation axis (or central axis) M of the rotary tool, and includes cross-sectional views. In particular, a "section view" may also refer to the form obtained when the object is cut by a plane parallel to the rotation axis M of the rotary tool and passing through the rotation axis M. "Plan view" refers to the form of an object when viewed from above (upper) or below (lower) along the rotation axis (or central axis) M of the rotary tool in the arrangement state at the time of joining, and includes plan views (top view and bottom view). In particular, "bottom view" refers to the form of an object when viewed from below (lower) along the rotation axis (or central axis) M of the rotary tool in the arrangement state at the time of joining, and includes bottom views. "Front view" refers to the form of an object when viewed along a direction perpendicular (horizontal) to the rotation axis (or central axis) M of the rotary tool in the arrangement state at the time of joining, and includes front views. "Perspective view" refers to the form of an object when viewed from diagonally above, and includes perspective views. In various drawings, the axis of rotation (or central axis) M may be visualized and shown.

[0015] [Rotate Tool] The rotary tool of the present invention is a rotary tool used in a friction stir welding method. A friction stir welding method involves overlapping a first member and a second member, rotating a rotary tool while pressing it against the first member to generate frictional heat, and using this frictional heat to cause plastic flow (or melting and solidifying) of the first and second members at their interfaces, thereby joining the first and second members. "Plastic flow" refers to the irreversible flow that occurs in a material (or substance) subjected to stress (or pressure) exceeding a certain limit. In a friction stir welding method, joining may be achieved in a spot or linear manner in a plan view, and is usually achieved in a spot manner. When joining is achieved in a spot manner, the friction stir welding method may be called a friction stir spot welding method. The materials constituting the first and second members are not particularly limited and may be, for example, any metallic material or any polymeric material. Among these, the following metals and alloys, particularly those used in the automotive field, are preferably used as constituent materials for the first and second members: aluminum; Aluminum alloys used in the 5000 series, 6000 series, etc. Steel; Magnesium and its alloys; Titanium and its alloys.

[0016] In the present invention, the metal constituting each of the first and second members is preferably aluminum or an aluminum alloy, and more preferably an aluminum alloy, from the viewpoint of more sufficiently suppressing the winding phenomenon at the joint interface between the first and second members (hereinafter sometimes simply referred to as the "winding phenomenon").

[0017] The rotary tool is a component that applies a pressing force to the first component and generates heat through friction with the first component due to its own rotation. More specifically, the rotary tool 1 has a shoulder portion 11 that constitutes the tip side of the rotary tool 1, as shown in Figures 1 to 4. The tip side of the rotary tool 1 means the side that directly contacts the first component when the rotary tool applies a pressing force to the first component. Figure 1 is a schematic perspective view showing the vicinity of the pin portion in an example of a rotary tool (particularly its tip side) according to the first embodiment of the present invention. Figure 2 is a schematic bottom view of the rotary tool shown in Figure 1. Figure 3 is a schematic front view of the vicinity of the pin portion in the rotary tool (particularly its tip side) shown in Figure 1. Figure 4 is a schematic cross-sectional view for explaining the dimensions of the vicinity of the pin portion in the rotary tool (particularly its tip side) of Figure 1, and is a schematic cross-sectional view in a cross section passing through the rotation axis of the rotary tool.

[0018] As shown in Figures 1 to 4, the shoulder portion 11 is provided with a pin portion 110 projecting outward (or towards the tip direction m) on the rotation axis M line at its tip end. The shoulder portion 11 is also provided with an arc-shaped surface 111 located on the outer circumference of the pin portion 110 in a cross-sectional view at the tip end of the rotary tool, as shown in Figures 1 to 4. The arc-shaped surface 111 is a surface that forms an arc in the direction from the rotation axis side toward the outer circumference in a cross-sectional view, and has a shape that is inclined downward in the direction from the rotation axis M side toward the outer circumference. More specifically, as shown in Figure 4, the arc-shaped surface 111 has a concave curved shape (or curved shape) that sinks in the direction opposite to the tip direction m of the rotation axis M in a cross-sectional view, and has a shape that is inclined downward in the direction from the rotation axis M side toward the outer circumference. The downward-sloping shape means that, in the arrangement state at the time of joining (when the tip of the rotating tool is positioned downward in the vertical direction), in the direction from the rotation axis M side toward the outer circumference, the starting point y1 and ending point y2 of the line segment representing the arc-shaped surface are positioned such that the ending point y2 is positioned lower than the starting point y1. The starting point y1 is the point located at the boundary between the pin portion and the arc-shaped surface in a cross-sectional view. In a cross-sectional view, in the direction from the pin portion (or its side surface) toward the arc-shaped surface on the surface of the rotating tool, at the starting point y1, the diameter corresponding to the pin portion diameter D1 begins to become larger than D1. The ending point y2 is the lowest end of the arc-shaped surface in the arrangement state at the time of joining (when the tip of the rotating tool is positioned downward in the vertical direction), and may also be the lowest end in the vertical direction. Because the arc-shaped surface 111 has this kind of inclination, it may be called the "first inclined surface". The arc-shaped surface 111 may, in cross-sectional view, have a concave curved shape that is recessed in the direction opposite to the tip direction m compared to the straight line passing through the starting point y1 and ending point y2 described above.

[0019] The effects of this invention are thought to be based on the following mechanism of action. The shoulder portion 11 has such an arc-shaped surface 111, which allows plastic flow along the arc-shaped surface 111 to occur during joining. Specifically, in the first member 7 and the second member 8, a plastic flow F1 (see Figure 18 described later) flowing in the radial direction of the rotating tool 1 (specifically, in the direction from the rotation axis M side toward the outer circumference) can be generated along the arc-shaped surface 111. As a result, the plastic flow F1 is significantly guided downwards. On the other hand, the helical groove 1101 of the pin portion 110 allows plastic flow F2 (see Figure 18 described later) to occur along the side surface of the pin portion. As a result, a plastic flow F3 (see Figure 18 described later) flowing upwards occurs between the plastic flow F1 and plastic flow F2 flowing downwards. As a result, more sufficient stirring (plastic flow) occurs near the base (root) of the pin portion in the first member 7 and the second member 8, the interface between the first member and the second member disappears, and the winding phenomenon caused by the rise of the joint interface is sufficiently suppressed. Therefore, the joint strength between the first member and the second member is more significantly improved.

[0020] If the arc-shaped surface 111 does not have an arc shape in cross-sectional view (for example, if it has a straight shape), and / or does not have a shape that is inclined downward in the direction from the rotation axis M side toward the outer circumference (for example, if the overall inclination angle α1 described later is greater than 90 degrees), sufficient stirring will not occur near the base (root) of the pin portion. As a result, the interface between the first member and the second member will rise without disappearing, causing a winding phenomenon, and thus reducing the joint strength. Even if the arc-shaped surface has a shape that is inclined downward in the direction from the rotation axis M side to the outer circumference side in a cross-sectional view (i.e., even if the overall inclination angle α1 of the arc-shaped surface 111 described later is 90 degrees or less), if the arc-shaped surface does not have a helical groove, and if the helical direction of the helical groove is in the opposite direction to the direction in which the material (e.g., the constituent material of the first member) flows from the inner circumference side to the outer circumference side of the rotating tool with respect to the rotation direction N of the rotating tool, then plastic flow F1 along the arc-shaped surface will not occur effectively, and sufficient stirring will not occur, resulting in a curling phenomenon at the joint interface and a decrease in joint strength.

[0021] Regarding the cross-sectional shape of the arc-shaped surface 111, the arc-shaped surface 111 has a concave curved shape (or curved shape) that sinks in in the direction opposite to the tip direction m. The arc-shaped surface 111 may have, for example, a curvature reduction shape as shown in Figure 4, an elliptical arc shape as shown in Figure 5, a circular arc shape as shown in Figure 6, or a composite shape thereof. From the viewpoint of more sufficient suppression of the winding phenomenon, the arc-shaped surface 111 has a curvature reduction shape in cross-sectional view. Curvature is an index that indicates the degree of bending, and the reciprocal of curvature indicates the radius of curvature. The radius of curvature is the radius of the circle when the curve is locally considered as an "arc of a circle". Figure 5 is a schematic cross-sectional view showing another example of the cross-sectional shape of the arc-shaped surface (first inclined surface) in the rotation tool. Figure 6 is a schematic cross-sectional view showing another example of the cross-sectional shape of the arc-shaped surface (first inclined surface) in the rotation tool.

[0022] For example, the arc-shaped surface 111 having a curvature reduction shape as shown in Figure 4 is a surface that, in cross-sectional view, has a shape in which the curvature decreases as it moves away from the axis of rotation M with respect to the starting point y1. For example, the arc-shaped surface 111A having an elliptical arc shape as shown in Figure 5 is a surface that, in cross-sectional view, has a shape in which the curvature decreases as it moves away from the axis of rotation M with respect to the starting point y1, but increases as it moves further away. For example, the arc-shaped surface 111B having a true circular arc shape as shown in Figure 6 is a surface that, in cross-sectional view, has a shape in which the curvature remains approximately constant (especially constant) even when moving away from the axis of rotation M with respect to the starting point y1.

[0023] The arc-shaped surface 111 is typically gradually inclined in cross-sectional view. "Gradually" means that when the arc-shaped surface is represented in cross-sectional view, the line indicating the inclined surface changes smoothly from the starting point y1 to the ending point y2 of the arc-shaped surface without forming any steps.

[0024] Regarding the overall inclination of the arc-shaped surface 111, as shown in Figure 4, the arc-shaped surface 111 has an overall inclination angle α1 of 90 degrees or less with respect to the tip direction m of the rotation axis M. Therefore, in a cross-sectional view, the arc-shaped surface 111 has a shape that is inclined downward in the direction from the rotation axis side toward the outer circumference. If the overall inclination angle α1 exceeds 90 degrees, the plastic flow F1 along the surface is not effectively guided downward, and sufficient stirring does not occur, resulting in a curling phenomenon at the joint interface and a decrease in joint strength.

[0025] The overall inclination angle α1 of the arc-shaped surface 111 (see Figure 4) is preferably 85 degrees or less, more preferably 80 degrees or less, from the viewpoint of more sufficiently suppressing the winding phenomenon. The lower limit of the overall inclination angle α1 of the arc-shaped surface is not particularly limited as long as the winding phenomenon is suppressed, and the overall inclination angle α1 may normally be 60 degrees or more, and particularly 70 degrees or more.

[0026] The overall inclination angle α1, as shown in Figure 4, is the inclination angle of the entire arc-shaped surface in a cross-sectional view. More specifically, it is the angle of the line segment passing through the starting point y1 and ending point (lowest end) y2 of the arc-shaped surface 111 described above, with respect to the direction m of the tip of the rotation axis.

[0027] Regarding the inclination of the tangent at the outermost part in a cross-sectional view of the arc-shaped surface 111, it is preferable that the arc-shaped surface 111 has an outermost tangent angle α2 of 0 degrees or more and less than 90 degrees, as shown in Figure 4. The outermost tangent angle α2 is the inclination of the tangent at the outermost part of the arc-shaped surface (especially the endpoint y2) in a cross-sectional view, and more specifically, as shown in Figure 4, it is represented by the angle between the tangent and the tip direction m of the rotation axis M. A smaller outermost tangent angle α2 is preferable because it allows the plastic flow F1 to be effectively guided downwards, resulting in more sufficient stirring. From the viewpoint of more sufficient suppression of the winding phenomenon, the outermost tangent angle α2 of the arc-shaped surface 111 is preferably 0 degrees or more and 70 degrees or less, preferably 0 degrees or more and 50 degrees or less, more preferably 0 degrees or more and 30 degrees or less, and even more preferably 10 degrees or more and 30 degrees or less. An outermost tangent angle α2 of 0 degrees means that the tangent at the outermost part (especially the endpoint y2) is parallel to the rotation axis M. The outermost tangent angle α2 may, for example, be greater than 0 degrees.

[0028] The arc-shaped surface 111 is provided with one or more helical grooves 3. A helical groove 3 is a groove having a helical shape. A helical shape is a shape that, when viewed from below, is oriented such that the distance from the rotation axis M (center) decreases or increases in the rotation direction N. The helical shape of each of the one or more helical grooves 3 on the arc-shaped surface 111 is a helical shape in which the distance from the rotation axis M (center) decreases in the rotation direction N, as shown in Figures 2, 7, and 8 when viewed from below. Therefore, the helical direction of each helical groove 3 on the arc-shaped surface 111 is such that, with respect to the rotation direction N of the rotary tool 1, the material (for example, the constituent material of the first member) flows from the inner circumference to the outer circumference of the rotary tool. In more detail, the helical shape of each helical groove 3 on the arc-shaped surface is such that, with respect to the rotation direction N of the rotary tool 1, the inner circumference end is positioned upstream of the outer circumference end, as shown in Figures 2, 7, and 8 when viewed from below. If the arc-shaped surface does not have helical grooves, or if the arc-shaped surface does have helical grooves, but the helical direction of each groove on the arc-shaped surface is such that the material (e.g., the constituent material of the first member) flows from the outer circumference to the inner circumference of the rotating tool, the plastic flow F1 along the arc-shaped surface is not effectively guided downwards, and sufficient stirring does not occur, resulting in a curling phenomenon at the joint interface and a decrease in joint strength. Even if the arc-shaped surface has a helical groove, and the helical direction of the helical groove is such that the material (e.g., the constituent material of the first member) flows from the inner circumference to the outer circumference of the rotating tool with respect to the rotation direction N of the rotating tool 1, if the arc-shaped surface does not have a shape that is inclined downward in the direction from the rotation axis M to the outer circumference in a cross-sectional view (i.e., the overall inclination angle α1 of the arc-shaped surface 111 is greater than 90 degrees), then plastic flow F1 along the arc-shaped surface will not occur effectively, and sufficient stirring will not occur, resulting in a curling phenomenon at the joint interface and a decrease in joint strength. Figure 7 is a schematic cross-sectional view showing another example of the bottom view shape of the helical groove on the arc-shaped surface (first inclined surface) of the rotating tool. Figure 8 is a schematic cross-sectional view showing another example of the bottom view shape of the helical groove on the arc-shaped surface (first inclined surface) of the rotating tool. Figures 7 and 8 are diagrams illustrating the bottom view shape of the helical groove, and therefore the helical groove is simplified and shown as a simple "line."

[0029] Among the spiral shapes of the spiral grooves on the arc-shaped surface, the spiral shape of spiral groove 3A shown in Figure 7, in particular, has a spiral shape in which the curvature increases steplessly as you approach the center of the spiral when viewed from below. Steplessly increasing curvature means that, when viewed from below, the curvature of the curve defining the spiral groove increases gradually (or continuously). More specifically, when the position on the curve is plotted on the x-axis and the curvature of a specific length of the curve including that position is plotted on the y-axis, the plot changes gradually (or continuously).

[0030] Each of the helical grooves on the arc-shaped surface may have a curved shape (or a curved shape) when viewed from the bottom, as shown in Figures 2 and 7, or it may have a straight shape, as shown in Figure 8. From the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferable that each of the helical grooves on the arc-shaped surface has a curved shape (or a curved shape) when viewed from the bottom, as shown in Figures 2 and 7.

[0031] When each of the helical grooves 3 of the arc-shaped surface 111 has a curved shape (or curved shape), each of the helical grooves 3 may have a curved shape (or curved shape) in which the curvature increases steplessly as it approaches the center of the spiral, as shown in Figure 7, or it may have a constant curvature, as shown in Figure 2. When each of the helical grooves of the arc-shaped surface has a curved shape (or curved shape), it is preferable that each of the helical grooves 3 has a constant curvature, as shown in Figure 2, from the viewpoint of more sufficient suppression of the winding phenomenon.

[0032] When each of the helical grooves 3 of the arc-shaped surface 111 has a curved shape (or curved shape), each of the helical grooves 3 may be curved convexly in the direction of rotation N, as shown in Figure 7, or convexly in the direction opposite to the direction of rotation N, as shown in Figure 2. When each of the helical grooves 3 of the arc-shaped surface 111 has a curved shape (or curved shape), it is preferable that each of the helical grooves 3 be curved convexly in the direction opposite to the direction of rotation N, as shown in Figure 2, from the viewpoint of more sufficiently suppressing the winding phenomenon.

[0033] When the arc-shaped surface 111 is provided with two or more helical grooves 3, these two or more helical grooves 3 are usually arranged at equal intervals from each other in the circumferential direction when viewed from the bottom.

[0034] The cross-sectional shape of the helical groove 3 on the arc-shaped surface 111 is not particularly limited, and the helical groove 3 may have various shapes such as a semicircular shape or a V-shape, as shown in the helical groove 3 of Figure 4.

[0035] From the viewpoint of more sufficiently suppressing the curling phenomenon at the joint interface and further improving the joint strength based on suppressing the lifting of the first member (creation of a gap between the first member and the second member), the rotary tool 1 preferably has a tapered portion 12 that constitutes the outer circumference of the shoulder portion 11, as shown in detail in Figures 9 to 12. In this case, the shoulder portion 11 constitutes the axial side of the rotary tool 1. The axial side of the rotary tool 1 means the side that includes the rotation axis (or central axis) M of the rotary tool 1, assuming that the rotary tool is composed of multiple rotating bodies. Figure 9 shows a schematic perspective view showing the vicinity of the pin portion in another example (second embodiment) of the rotary tool of the present invention. Figure 10 shows a schematic bottom view of the rotary tool shown in Figure 9. Figure 11 shows a schematic front view of the vicinity of the pin portion in the rotary tool shown in Figure 9. Figure 12 is a schematic cross-sectional view for explaining the dimensions of the vicinity of the pin portion in the rotary tool of Figure 9, and is a schematic cross-sectional view in a cross section passing through the rotation axis of the rotary tool. Note that the rotary tool 1A shown in Figures 9 to 12 is the same as the rotary tool 1 shown in Figures 1 to 4, except that it has a tapered portion 12.

[0036] The tapered portion 12 has a tapered surface 121 in cross-sectional view at the tip side of the rotary tool. The tapered surface 121 has an inclination angle β with respect to the tip direction m of the rotation axis M in cross-sectional view. For this reason, the tapered surface 121 may be referred to as the "second inclined surface". Because the tapered surface 121 has an inclination angle β, it can continue to hold down the first member during joining. As shown in Figure 12, the tapered surface 121 has an inclination angle β of more than 90 degrees with respect to the tip direction m of the rotation axis M. The inclination angle β of the tapered surface (see Figure 12) is preferably 95 degrees or more, more preferably 100 degrees or more, and even more preferably 105 degrees or more, from the viewpoint of more sufficient suppression of the winding phenomenon. The upper limit of the inclination angle β of the tapered surface is not particularly limited as long as the lifting of the first member is suppressed, and the inclination angle β is usually 130 degrees or less, and particularly 120 degrees or less.

[0037] Due to the presence of a tapered surface, especially in pressure-controlled systems, the surface pressure is lower at the correct insertion position, making it difficult to insert beyond the target position. Furthermore, the insertion position remains stable even with variations in bonding time. As a result, this also contributes to stable bonding quality.

[0038] The inclination angle β is the angle with respect to the rotation axis tip direction m of the line segment passing through the lowest point y2 (for example, the endpoint or lowest point y2 of the arc-shaped surface) and the highest point y3 of the tapered surface 121 in a cross-sectional view, as shown in Figure 12. Note that the lowest point y2 and the highest point y3 are the lowest and highest points in the arrangement state at the time of joining (when the tip side of the rotating tool is positioned lower in the vertical direction), and may also be the lowest and highest points in the vertical direction.

[0039] The tapered surface 121 may be gradually or stepwise in cross-sectional view, and it is preferable that it be gradually inclined from the viewpoint of more sufficiently suppressing the winding phenomenon. "Gradual" means that when the inclined surface is represented in cross-sectional view, the line representing the inclined surface changes smoothly from the lowest end to the highest end of the inclined surface without forming a single step. "Stepwise" means that when the inclined surface is represented in cross-sectional view, the line representing the inclined surface changes while having one or more steps from the lowest end to the highest end of the inclined surface. A "step" is a tier that provides a difference in height, and one "step," when assumed to be a staircase, has a part corresponding to at least two treads and one riser between them.

[0040] For example, the tapered surface 121 shown in Figure 12, the tapered surface 121A shown in Figure 13, and the tapered surface 121B shown in Figure 14 are gradually inclined in cross-sectional view. For example, the tapered surface 121C shown in Figure 15 is inclined in stages when viewed in cross-section.

[0041] The tapered surface 121 may also have a linear shape, a curved shape, or a combination thereof in cross-sectional view. A linear shape is a shape in which, when the inclined surface is represented in cross-sectional view, the lines representing the inclined surface are represented only by straight lines. A curved shape is a shape in which, when the inclined surface is represented in cross-sectional view, the lines representing the inclined surface are represented only by curves. A combination shape is a shape in which, when the inclined surface is represented in cross-sectional view, the lines representing the inclined surface are represented by both straight lines and curves.

[0042] For example, the tapered surface 121A shown in Figure 13, the tapered surface 121B shown in Figure 14, and the tapered surface 121C shown in Figure 15 have a linear shape in cross-sectional view. For example, the tapered surface 121 shown in Figure 12 has a curved shape in cross-sectional view.

[0043] If the tapered surface 121 has a curved shape, the curved shape may be a concave curved shape that sinks in the direction opposite to the direction m of the rotation axis tip, as shown in Figure 12 when viewed in cross-section, or it may be a convex curved shape that rises in the direction m of the rotation axis tip. From the viewpoint of more sufficiently suppressing the winding phenomenon, the concave curved shape is preferred.

[0044] The tapered surface 121 may or may not have a helical groove 4. From the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferable that the tapered surface 121 has a helical groove 4, as shown in Figures 16 and 17. Figure 16 shows a schematic bottom view of another example (third embodiment) of the rotary tool of the present invention. Figure 17 is a schematic cross-sectional view for illustrating the dimensions near the pin portion of the rotary tool of Figure 16, and is a schematic cross-sectional view in a cross section passing through the rotation axis of the rotary tool. Note that the rotary tool 1B shown in Figures 16 to 17 is the same as the rotary tool 1A shown in Figures 9 to 12, except that the tapered portion 12 (particularly its tapered surface 121) has a helical groove 4.

[0045] If the tapered surface 121 is provided with helical grooves 4, the tapered surface 121 may have one or more helical grooves 4. A helical groove 4 is a groove having a helical shape. The helical shape of each of the one or more helical grooves 4 on the tapered surface 121 is not particularly limited, but from the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferable that, in a bottom view, as shown in Figure 16, the helical shape is such that the distance from the rotation axis M (center) increases in the rotation direction N. For this reason, it is preferable that the helical direction of each helical groove 4 on the tapered surface 121 is such that, with respect to the rotation direction N of the rotary tool 1, the material (for example, the constituent material of the first member) flows from the outer circumference to the inner circumference of the rotary tool. More specifically, it is preferable that, in a bottom view, as shown in Figure 16, the helical shape of each helical groove 4 on the tapered surface is such that, with respect to the rotation direction N of the rotary tool 1, the outer circumference end is positioned upstream of the inner circumference end. When the helical direction of each helical groove on the tapered surface is such that the material (e.g., the constituent material of the first member) flows from the outer circumference to the inner circumference of the rotating tool, relative to the rotational direction N of the rotating tool 1, plastic flow along the arc-shaped surface is more effectively guided downwards, resulting in more sufficient stirring, and thus the curling phenomenon at the joint interface is further suppressed.

[0046] Each of the helical grooves 4 of the tapered surface 121 may have a curved shape (or a curved shape) or a straight shape when viewed from the bottom, as shown in Figure 16. From the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferable that each of the helical grooves of the tapered surface 121 has a curved shape (or a curved shape) when viewed from the bottom, as shown in Figure 16.

[0047] If each of the helical grooves 4 of the tapered surface 121 has a curved shape (or curved shape) when viewed from the bottom, each of the helical grooves 4 may have a curved shape (or curved shape) in which the curvature increases steplessly as it approaches the center of the spiral, similar to the helical groove 3, or it may have a constant curvature regardless of the distance from the center of the spiral (axis of rotation), as shown in Figure 16. If each of the helical grooves of the tapered surface 121 has a curved shape (or curved shape) when viewed from the bottom, it is preferable that each of the helical grooves 4 has a constant curvature, as shown in Figure 16, from the viewpoint of more sufficient suppression of the winding phenomenon.

[0048] If each of the helical grooves of the tapered surface 121 has a curved shape (or curved shape) when viewed from the bottom, each of the helical grooves 4 may be curved convexly in the direction of rotation N, or convexly in the direction opposite to the direction of rotation N, as shown in Figure 16. If each of the helical grooves 4 of the tapered surface 121 has a curved shape (or curved shape) when viewed from the bottom, it is preferable that each of the helical grooves 4 be curved convexly in the direction opposite to the direction of rotation N, as shown in Figure 16, from the viewpoint of more sufficiently suppressing the winding phenomenon.

[0049] When the tapered surface 121 is provided with two or more helical grooves 4, these two or more helical grooves 4 are usually arranged at equal intervals from each other in the circumferential direction when viewed from the bottom.

[0050] The cross-sectional shape of the helical grooves 4 on the tapered surface 121 is not particularly limited, and each of the helical grooves 4 may have various shapes, such as a semicircular shape or a V-shape, as shown in Figure 17.

[0051] When the tapered surface 121 has helical grooves 4, it is preferable that the helical grooves 4 of the tapered surface 121 are discontinuous with the helical grooves 3 of the arc-shaped surface 111 when viewed from below, from the viewpoint of more sufficiently suppressing the winding phenomenon. More specifically, it is preferable that each of the helical grooves 4 of the tapered surface 121 is discontinuous with any of the helical grooves 3 of the arc-shaped surface 111 when viewed from below. "Discontinuous" means that they do not overlap (or do not come into contact) when viewed from below.

[0052] The tapered portion 12 is usually integrated with the shoulder portion 11. The integration of the tapered portion with the shoulder portion means that the tapered portion is connected to the shoulder portion, and when the shoulder portion is driven, the tapered portion is also driven in accordance with the movement of the shoulder portion. Therefore, a separate drive device for the tapered portion is unnecessary; the drive device for the shoulder portion drives the tapered portion as well. The tapered portion may be configured as a separate component from the shoulder portion and connected to it, or it may be an inseparable component from the shoulder portion, forming a single structure with the shoulder portion.

[0053] The pin portion 110 positions the rotating tool when it first contacts and presses against the first member while rotating. The pin portion usually has a cylindrical shape overall. In cross-sectional view, the pin portion may have an arc shape at its tip side (particularly the tip side in the direction m of the rotation axis M), as shown in Figures 1 to 4, 9 to 12, and 16 to 17, or it may have a linear shape (or a planar shape). From the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferable that the pin portion has an arc shape at its tip side (particularly the tip side in the direction m of the rotation axis M) in cross-sectional view.

[0054] The pin portion 110 typically has a helical groove 1101 on its outer surface (especially the side surface), as shown in Figures 4, 12, and 17. The helical groove 1101 of the pin portion is a groove having a three-dimensional helical shape, and may also be a screw thread. The helical direction of the helical groove 1101 in the pin portion is the direction in which the material (especially the constituent materials of the first and second members) flows toward the tip of the rotary tool, relative to the rotational direction of the rotary tool. In other words, the rotary tool is used by rotating it in the opposite direction to the screwing direction of the helical groove 1101 of the pin portion 110. Specifically, the helical direction of the helical groove 1101 of the pin portion 110 is the direction in which the screw loosens when the rotary tool rotates, assuming the pin portion with the helical groove is a screw (i.e., the opposite direction to the screwing direction). If the helical direction of the helical groove in the pin portion is opposite to the direction in which the material (especially the constituent materials of the first and second members) flows toward the tip of the rotating tool, the plastic flow F2 along the arc-shaped surface is not effectively guided downwards, and sufficient stirring does not occur. As a result, a curling phenomenon occurs at the joint interface, and the joint strength decreases.

[0055] The cross-sectional shape of the helical groove of the pin portion 110 is not particularly limited and may have various shapes, such as a semicircular shape or a V-shape as the helical groove 1101 in Figures 4, 12, and 17.

[0056] The pin portion 110 is integrated with the shoulder portion 11. The integration of the pin portion with the shoulder portion means that the pin portion is connected to the shoulder portion, and when the shoulder portion is driven, the pin portion is also driven in accordance with the movement of the shoulder portion. Therefore, a separate drive device for the pin portion is unnecessary; the drive device for the shoulder portion drives the pin portion as well. The pin portion may be configured as a separate component from the shoulder portion and connected to it, or it may be an inseparable component from the shoulder portion, forming a single structure with the shoulder portion.

[0057] The constituent materials and dimensions of the rotary tool (especially its various components (e.g., shoulder, tapered, and pin portions)) may be appropriately set according to the types of constituent materials of the first and second members that the rotary tool presses against. For example, if the first and second members are made of metal (especially aluminum or aluminum alloy), the rotary tool (especially its constituent materials) is made of tool steel (e.g., SKD61). Also, for example, if the first member is made of steel, the rotary tool (especially its constituent materials) is made of silicon nitride or PCBN (cubic boron nitride sintered body), etc. In these cases, the preferred dimensions of the various constituent materials are as follows.

[0058] The diameter D1 of the shoulder portion 11 (see Figures 4, 12, and 17) is usually 5 to 20 mm, and is preferably 8 to 15 mm, more preferably 8 to 12 mm (especially 10 mm), from the viewpoint of more sufficient suppression of the winding phenomenon. The diameter D2 of the pin portion 110 (see Figures 4, 12, and 17) is usually smaller than the diameter D1 of the shoulder portion 11. From the viewpoint of more sufficiently suppressing the winding phenomenon, the diameter D2 of the pin portion 11 is preferably 0.2 × D1 (mm) or more and 0.8 × D1 (mm) or less, more preferably 0.4 × D1 (mm) or more and 0.6 × D1 (mm) or less (especially 0.5 × D1 (mm)) relative to the diameter D1 of the shoulder portion 11. The protruding height H of the pin portion 110 (see Figures 4, 12, and 17) is usually 0.1 × D1 (mm) or more and 0.8 × D1 (mm) or less with respect to the diameter D1 of the shoulder portion 11. From the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferably 0.1 × D1 (mm) or more and 0.5 × D1 (mm) or less, more preferably 0.2 × D1 (mm) or more and 0.4 × D1 (mm) or less, and even more preferably 0.3 × D1 (mm) or more and 0.4 × D1 (mm) or less (especially 0.38 × D1 (mm)).

[0059] The width D3 of the arc-shaped surface (see Figures 4, 12, and 17) is not particularly limited as long as the above-mentioned D1 and D2 are ensured. The width D3 of the arc-shaped surface (see Figures 4, 12, and 17) is usually 0.1 × D1 (mm) or more and 0.6 × D1 (mm) or less with respect to the diameter D1 of the shoulder portion 11, and from the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferably 0.1 × D1 (mm) or more and 0.4 × D1 (mm) or less, more preferably 0.2 × D1 (mm) or more and 0.3 × D1 (mm) or less (especially 0.25 × D1 (mm)). The width D3 of the arc-shaped surface is the width in the diametrical direction of the rotating tool in a cross-sectional view. The inclination height E1 of the arc-shaped surface (see Figures 4, 12, and 17) is usually between 0.01 × D1 (mm) and 0.20 × D1 (mm) with respect to the diameter D1 of the shoulder portion 11. From the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferably between 0.04 × D1 (mm) and 0.16 × D1 (mm), more preferably between 0.06 × D1 (mm) and 0.12 × D1 (mm) (particularly 0.09 × D1 (mm)). The inclination height E1 of the arc-shaped surface is the height in a cross-sectional view in the arrangement state at the time of joining.

[0060] The width D4 of the tapered surface (see Figures 12 and 17) is usually 0.1 × D1 (mm) or more and 0.6 × D1 (mm) or less with respect to the diameter D1 of the shoulder portion 11. From the viewpoint of more sufficient suppression of the winding phenomenon and improvement of joint strength based on suppression of the lifting of the first member (creation of a gap between the first member and the second member), it is preferably 0.1 × D1 (mm) or more and 0.5 × D1 (mm) or less, more preferably 0.2 × D1 (mm) or more and 0.4 × D1 (mm) or less (especially 0.3 × D1 (mm)). The width D4 of the tapered surface is the width in the diametrical direction of the rotary tool in a cross-sectional view. The tapered surface inclination depth E2 (see Figures 4, 12, and 17) is usually 0.01 × D1 (mm) or more and 0.20 × D1 (mm) or less with respect to the diameter D1 of the shoulder portion 11. From the viewpoint of more sufficient suppression of the winding phenomenon and improvement of joint strength based on suppression of the lifting of the first member (creation of a gap between the first member and the second member), it is preferably 0.05 × D1 (mm) or more and 0.15 × D1 (mm) or less, more preferably 0.08 × D1 (mm) or more and 0.15 × D1 (mm) or less (especially 0.11 × D1 (mm)). The tapered surface inclination depth E2 is the depth in a cross-sectional view in the arrangement state at the time of joining.

[0061] The helical groove 3 on the arc-shaped surface and the helical groove 4 on the tapered surface may each independently have the following groove depth and groove width: The groove depth is typically 0.1 to 1.0 mm, preferably 0.3 to 0.7 mm, and more preferably 0.7 mm, from the viewpoint of more sufficient suppression of the winding phenomenon; The groove width is typically 0.1 to 1.0 mm, and more preferably 0.3 to 0.7 mm, and more preferably 0.7 mm, from the viewpoint of more sufficient suppression of the winding phenomenon. The groove depth and groove width of the helical grooves on the arc-shaped surface and the tapered surface may be the groove depth and groove width in a cross-sectional view perpendicular to the helical direction (or tangential direction to the helical groove) of the helical groove when viewed from the bottom.

[0062] The helical groove 1101 that the pin portion 110 may have may have the following groove depth and groove width: The groove depth is typically 0.1 to 1.0 mm, preferably 0.1 to 0.5 mm, and more preferably 0.2 to 0.4 mm, from the viewpoint of more sufficient suppression of the winding phenomenon; The groove width is typically 0.1 to 1.0 mm, preferably 0.3 to 0.7 mm, and more preferably 0.4 to 0.6 mm, from the viewpoint of more sufficient suppression of the winding phenomenon. The groove depth and groove width of the helical groove in the pin portion may be the groove depth and groove width in a cross-sectional view, respectively. The helical groove in the pin portion may be equivalent to an M5 fine-thread screw.

[0063] When the pin portion 110 has an arc shape at the tip, the tip diameter is usually R3-20mm, and from the viewpoint of insertion stability and tool wear resistance, it is preferably R4-10mm, more preferably R5mm. The tip diameter at the pin portion may also be the tip diameter in a cross-sectional view.

[0064] [Friction Stir Welding Method] The friction stir welding method of the present invention uses the rotating tool of the present invention described above, and a receiving member positioned opposite the rotating tool. Specifically, as shown in Figure 18, for example, the first member 7 and the second member 8 are overlapped between the rotating tool 1 and the receiving member 2, and pressure is applied to the second member 8 by pressing from the first member 7 side by the rotating tool 1, while frictional heat is applied to the first member 7 and the second member 8 by the rotation of the rotating tool 1. As a result, as described above, a plastic flow F1 (see Figure 18 described later) flowing in the first member 7 and the second member 8 in the radial direction of the rotating tool 1 (specifically, in the direction from the rotation axis M side toward the outer circumference) can be generated along the arc-shaped surface 111. Therefore, the plastic flow F1 is significantly guided to a lower direction. On the other hand, the helical groove 1101 of the pin portion 110 can generate a plastic flow F2 (see Figure 18 described later) along the side surface of the pin portion. Therefore, a plastic flow F3 (see Figure 18 below) flows upward between the plastic flow F1 and plastic flow F2 flowing downward. As a result, more sufficient stirring (plastic flow) occurs near the base (root) of the pin portion in the first member 7 and the second member 8, the interface between the first member and the second member disappears, and the winding phenomenon due to the rise of the joining interface is sufficiently suppressed. Therefore, the joining strength between the first member and the second member is more sufficiently improved. Figure 18 is a schematic cross-sectional view for explaining the joining mechanism using the rotary tool of the present invention, and is a schematic cross-sectional view showing the state at the time of joining. In Figure 18, the rotary tool 1 is shown, but instead of the rotary tool 1, the rotary tool 1A or 1B may be shown.

[0065] As shown in Figure 18, the receiving member 2 is positioned below the rotating tool 1 and may have a cylindrical shape with the same diameter as or a larger diameter than the rotating tool 1. In this case, the receiving member 2 is usually positioned coaxially with the rotating tool 1. The receiving member 2 is a member that directly supports the second member 8, with its upper surface 20 in contact with the lower surface of the second member 8, and may be driven to move upward by a drive source (not shown), or it may be fixed without being driven. The upper surface of the receiving member 2 may usually have a planar shape (especially a flat shape). Therefore, when friction stir welding is performed between the first member and the second member, the curling phenomenon at the joint interface can be sufficiently suppressed without generating a protrusion on the lower surface of the second member, and sufficient joint strength can be obtained.

[0066] The constituent material of the receiving member 2 may be appropriately set according to the types of constituent materials of the first and second members, similar to the rotary tool 1. For example, if the first and second members are made of metal (especially aluminum or aluminum alloy), the receiving member may be made of tool steel (e.g., SKD61). Also, for example, if the second member is made of steel, the receiving member may be made of silicon nitride or PCBN (cubic boron nitride sintered body), etc.

[0067] In the present invention, the rotary tool 1 is typically driven by a drive device (not shown). Not only the rotary tool 1, but also the receiving member 2 may be driven by the drive device. The drive device controls the driving of the rotary tool (particularly pressing and / or rotational driving, preferably pressing and rotational driving) and, optionally, also controls the driving of the receiving member (particularly vertical driving for vertical movement).

[0068] The drive unit may employ a pressure control method that controls the pressure applied to the first member of the rotating tool, the pressurizing time, and the rotational speed, as will be described in detail later, or it may employ a position control method that controls the coordinate position of the rotating tool, the holding time at a specific position, and the rotational speed.

[0069] In Figure 18, the first member 7 and the second member 8 each have a substantially flat shape as an overall form, but are not limited to this. The first member and the second member may have any shape as long as at least the overlapping portion has a substantially flat shape. In the overlapping portions of the first member and the second member, both sides are usually composed of flat surfaces.

[0070] The thickness T1 of the first member 7 (see Figure 18) is usually 0.01 × D1 (mm) or more and 1.0 × D1 (mm) or less with respect to the diameter D1 of the shoulder portion 11, and from the viewpoint of more sufficient suppression of the curling phenomenon, it is preferably 0.05 × D1 (mm) or more and 0.5 × D1 (mm) or less, more preferably 0.1 × D1 (mm) or more and 0.3 × D1 (mm) or less (particularly 0.2 × D1 (mm)). The thickness T1 may be, for example, 1 mm or more, and from the viewpoint of more sufficient suppression of the curling phenomenon, it may be preferably 1.2 mm or more (particularly 1.2 to 10 mm), more preferably 1.5 to 5 mm, and even more preferably 1.5 to 3 mm (particularly 2 mm). The thickness T1 of the first member may be the thickness of the substantially flat plate-shaped portion of the first member that overlaps with the second member (thickness before joining).

[0071] The thickness T2 of the second member 8 (see Figure 18) is usually 0.01 × D1 (mm) or more and 2.0 × D1 (mm) or less with respect to the diameter D1 of the shoulder portion 11. From the viewpoint of more sufficient suppression of the curling phenomenon, it is preferably 0.05 × D1 (mm) or more and 1.5 × D1 (mm) or less, more preferably 0.1 × D1 (mm) or more and 1.0 × D1 (mm) or less, and even more preferably 0.1 × D1 (mm) or more and 0.5 × D1 (mm) or less (especially 0.2 × D1 (mm)). The thickness T2 is, for example, 1 mm or more, and from the viewpoint of more sufficient suppression of the curling phenomenon, it may be preferably 1.2 mm or more (especially 1.2 to 20 mm), more preferably 1.5 to 10 mm, and even more preferably 1.5 to 5 mm (especially 2 mm). The thickness T2 of the second member may be the thickness of the substantially flat plate-shaped portion of the second member that overlaps with the first member (thickness before joining).

[0072] The friction stir welding method according to the present invention includes at least the following steps: The first step is to overlap the first member 7 and the second member 8 between the rotating tool 1 and the receiving member 2; and The second step involves rotating the rotary tool 1 while pressing it against the first member 7 to generate frictional heat, and using this frictional heat to cause the first member 7 and the second member 8 to plastically flow (or melt and solidify) at their interface, thereby joining the first member 7 and the second member 8.

[0073] In the first step, the first member 7 and the second member 8 are overlapped at the desired joint.

[0074] In the second step, the drive of the rotary tool is controlled so that the first member 7 and the second member 8 undergo plastic flow (or melting) with each other at their interface near the rotary tool. In the second step, as described above, a pressure control method is employed to control the pressure applied by the rotary tool to the first member, the pressurizing time, and the rotational speed, or a position control method is employed to control the coordinate position of the rotary tool, the holding time at a specific position, and the rotational speed. Hereinafter, the second step employing the pressure control method will be described as the first embodiment, and the second step employing the position control method will be described as the second embodiment.

[0075] <First Embodiment: Pressure Control Method> In the second step of this embodiment, it is preferable to perform at least a pressing and stirring step C2 in which the rotating tool 1 is inserted to a depth in which the arc-shaped surface 111 (especially its entire surface) comes into contact with the constituent material of the first member.

[0076] In the second step of this embodiment, it is preferable to perform a preheating step C1 before the pressing and stirring step, in which the tip of the rotating tool 1 is in contact with the surface of the first member 7 and the rotating tool 1 is rotated, but it is not necessarily required.

[0077] After the aforementioned intrusion and stirring step, it is preferable to perform a stirring maintenance step C3 in which the rotating tool 1 continues to rotate at the position in which it was inserted during the intrusion and stirring step, but this step is not necessarily required.

[0078] The following describes these steps in this embodiment in detail.

[0079] (Preheating process C1) The preheating step C1 is a step in which the rotating tool 1 is rotated while the tip of the rotating tool 1 (or "pin portion 110") is in contact with the first member 7 by bringing the rotating tool 1 and the receiving member 2 close to each other. In the preheating step C1, the rotating tool 1 is rotated at a predetermined rotational speed with a first pressing force for a first pressing time.

[0080] Specifically, in the preheating step C1, frictional heat is generated on the surface of the first member 7 by the pressure of the rotating tool 1. This frictional heat is transmitted to the interior of the first member 7, preheating the area of ​​the pressing region of the first member 7 (the area pressed by the rotating tool 1) and the area near the pressing region. This makes it easier to press the rotating tool 1 into the first member in the subsequent pressing and stirring step C2.

[0081] The first pressing force and first pressing time in the preheating process C1 are set from the viewpoint of more sufficient suppression of the winding phenomenon, ease of pressing the rotary tool 1, ease of plastic flow of the second member 8, and productivity, and their values ​​change depending on, for example, the rotation speed of the rotary tool 1, the thickness and material type of the first member 7 and the second member 8. For example, when using the first member 7 and the second member 8 which have a thickness of 1.5 mm or more and 3 mm or less and are made of aluminum alloy, the first pressing force in the preheating process C1 is preferably 1 N or more and less than 1300 N. The first pressing time is preferably 0.1 seconds or more and 2.0 seconds or less. The rotation speed of the rotary tool is preferably 2000 rpm or more and 4000 rpm or less.

[0082] The amount of heat input in this process is determined by the magnitude of the first pressurizing force, the length of the first pressurizing time, and the rotational speed of the rotary tool.

[0083] (Pressing and stirring process C2) In the pressing and stirring process C2, the rotating tool 1 is pressed into the first member 7 and the second member 8 by bringing the rotating tool 1 and the receiving member 2 closer together, as shown in Figure 18. If the pressing and stirring process C2 is performed after the preheating process C1, the rotating tool 1 and the receiving member 2 are brought even closer together to press the rotating tool 1 into the first member 7 and the second member 8, as shown in Figure 18. In this process, more specifically, the rotating tool 1 is inserted to a predetermined depth. The predetermined depth is "the depth to which the arc-shaped surface (especially its entire surface) comes into contact with the constituent material of the first member." More specifically, in the process of this step, the constituent material of the first member that has been removed by the pin portion is filled between the first member and the arc-shaped surface. Therefore, when the inclination height of the arc-shaped surface is E1 (mm) (see Figures 4, 12, and 17), it is not necessarily required to push the rotary tool in until the amount K (see Figure 18) of the arc-shaped surface being pushed into the first member is 1.0 × E1 (mm) or more. Accordingly, in this process, the rotary tool is pushed in to a depth at least to "the depth to which the arc-shaped surface (especially its entire surface) is in contact with the constituent material of the first member." In this process, for example, the rotary tool is pushed in until the amount of push-in K is 0 mm or more and less than 0.1 × E1 (mm). In this process, stirring (flow) is initiated, and plastic flow F1 to F3 occurs. This process causes sufficient stirring inside the first and second members, and sufficiently suppresses the curling up of the joining interface. In this process, the rotary tool 1 (especially the tip of its pin portion 110) usually penetrates to a depth that reaches the interface between the first member 7 and the second member 8. It is preferable that the rotary tool 1 (especially the tip of the pin portion) penetrates to a depth that reaches the interface between the first member 7 and the second member 8, but not to the bottom surface of the second member 8, as shown in Figure 18. If the rotary tool has a tapered portion and a part of the tapered surface of the tapered portion is pressed into the first member, the lifting of the first member is sufficiently suppressed.

[0084] In the indentation and stirring process C2, the rotary tool 1 is typically rotated at a predetermined rotational speed (second rotational speed) for a second pressurizing time, with a second pressurizing pressure that is greater than the first pressurizing pressure. The second pressurizing time is appropriately set according to the constituent materials and thicknesses of the first and second members, and may be shorter or longer than the first pressurizing time.

[0085] In the pressing and stirring process C2, the second pressing force becomes greater than the first pressing force in the preheating process C1, causing the rotating tool 1 to be pressed into the first member 7 and the second member 8. Specifically, the rotating tool 1 enters the interior of the first member 7, and its arc-shaped surface (especially its entire surface) comes into contact with the constituent material of the first member.

[0086] The second pressing force and second pressing time in the indentation and stirring process C2 usually vary depending on the rotation speed of the rotary tool 1, the thickness and material type of the first member 7 and the second member 8, etc. For example, when using the first member 7 and the second member 8 which have a thickness of 1.5 mm or more and 3 mm or less and are made of aluminum alloy, the second pressing force in the indentation and stirring process C2 is preferably 1300 N or more and less than 8000 N. The second pressing time is preferably 0.5 seconds or more and 10.0 seconds or less. The second rotation speed of the rotary tool is preferably 2000 rpm or more and 4000 rpm or less.

[0087] The amount of heat input in this process is determined by the magnitude of the second pressing force, the length of the second pressing time, and the magnitude of the second rotation speed of the rotating tool.

[0088] (Stirring maintenance process C3) The stirring maintenance step C3 is a step in which the rotation of the rotating tool 1 is stopped from approaching the receiving member 2, thereby continuing the rotation of the rotating tool 1 at the position where it has entered to the depth described above (this is called the "reference position"). The third pressure, third pressurization time, and third rotational speed in the stirring maintenance step C3 are not particularly limited as long as the plastic flow F1 to F3 inside the first and second members is maintained. For example, in the stirring maintenance step C3, the rotating tool 1 is rotated at a third rotational speed smaller than the second rotational speed for a third pressure equal to the second pressure, for a third pressurization time equal to or shorter than the second pressurization time. The third pressure does not need to be changed from the second pressure.

[0089] In this process, it is not necessarily required to strictly stop the mutual proximity between the rotating tool 1 and the receiving member 2. More specifically, the rotating tool 1 may be gradually pushed further beyond the "reference position" in this process, as long as stirring (or plastic flow) inside the first and second members is maintained. In this process, more specifically, the rotating tool may be pushed in until the amount K (see Figure 18) of the arc-shaped surface being pushed into the first member is 0.1 × E1 (mm) or more, when the inclination height of the arc-shaped surface is E1 (mm) (see Figures 4, 12, and 17). Therefore, in this process, the state in which the "arc-shaped surface (especially its entire surface) is in contact with the constituent material of the first member" is maintained in the rotating tool, and as a result, stirring is also maintained. In this process, the amount K being pushed in is preferably 0.2 × E1 (mm) or more, more preferably 0.3 × E1 (mm) or more, and even more preferably 0.4 × E1 (mm) or more, from the viewpoint of more sufficiently suppressing the winding phenomenon. The upper limit of the indentation amount K in this process is not particularly limited, and the indentation amount K is usually 5.0 × E1 (mm) or less. From the viewpoint of more sufficiently suppressing the winding phenomenon, it is preferably 3.0 × E1 (mm) or less, more preferably 2.0 × E1 (mm) or less, even more preferably 1.5 × E1 (mm) or less, very preferably 1.0 × E1 (mm) or less, and very preferably 0.8 × E1 (mm) or less.

[0090] In the stirring maintenance step C3, the rotation speed is reduced compared to the intrusion stirring step C2, so the rotating tool 1 is maintained almost at the reference position. As the rotation of the rotating tool 1 continues at this reference position, a large amount of frictional heat is generated. Therefore, the stirring by plastic flow described above is further promoted.

[0091] The third pressure and third pressurization time in the stirring maintenance process C3 are usually set from the viewpoint of more sufficient suppression of the winding phenomenon and productivity, and their values ​​vary depending on, for example, the rotation speed of the rotary tool 1, the thickness and material type of the first member 7 and the second member 8. For example, when using the first member 7 and the second member 8 which have a thickness of 1.5 mm or more and 3 mm or less and are made of aluminum alloy, the third pressure in the stirring maintenance process C3 is preferably 1300 N or more and less than 8000 N. The third pressurization time is preferably 0.5 seconds or more and 10.0 seconds or less. The rotation speed of the rotary tool is preferably 100 rpm or more and 2000 rpm or less.

[0092] The amount of heat input in this process is determined by the magnitude of the third pressing force, the length of the third pressing time, and the rotational speed of the rotary tool.

[0093] In this embodiment, after the stirring maintenance step C3, the pressing member 16 is usually separated from the joint and allowed to cool naturally. It may also be forcibly cooled from the outside.

[0094] <Second Embodiment: Position Control Method> In the second step of this embodiment, it is preferable to perform at least a pressing and stirring step C2 in which the rotating tool 1 is inserted to a depth in which the entire arc-shaped surface is pressed into the first member.

[0095] In the second step of this embodiment, a preheating step C1 may be performed before the pressing and stirring step, in which the rotating tool 1 is rotated with only the tip of the rotating tool 1 in contact with the surface of the metal member 11. However, since a position control method is employed, this step is not required.

[0096] After the aforementioned intrusion and stirring step, it is preferable to perform a stirring maintenance step C3 in which the rotating tool 1 continues to rotate at the position in which it was inserted during the intrusion and stirring step, but this step is not necessarily required.

[0097] The following describes these steps in this embodiment in detail.

[0098] (Pressing and stirring process C2) The indentation and stirring process C2 of this embodiment is the same as the indentation and stirring process C2 of the first embodiment, except that a position control method is employed. Specifically, in the indentation and stirring process C2 of this embodiment, as shown in Figure 18, the rotary tool 1 is rotated at a predetermined rotational speed and inserted to a predetermined depth. The predetermined depth is the same depth as in the indentation and stirring process C2 of the pressure control method, and more specifically, it is the depth to which the arc-shaped surface 111 (especially its entire surface) comes into contact with the constituent material of the first member, and more specifically, it is the depth to which the amount K of indentation of the arc-shaped surface into the first member falls within the aforementioned range. As a result, similar to the indentation and stirring process C2 of the pressure control method, sufficient plastic flow stirring occurs inside the first and second members, and the reduction of winding up at the joint interface is sufficiently suppressed.

[0099] In this embodiment as well, the rotary tool 1 is pressed in such a way that the rotary tool 1 does not penetrate the first member 7 and the second member 8. If the rotary tool 1 penetrates the first member 7 and the second member 8, the joint will be in a perforated state with a hole through which the rotary tool 1 passed, resulting in a faulty joint.

[0100] When the rotary tool 1 has entered to a predetermined depth, the pushing movement of the rotary tool 1 is stopped.

[0101] The rotational speed of the rotary tool is preferably between 2000 rpm and 4000 rpm.

[0102] The amount of heat input in this process is determined by the entry time of the rotary tool and the rotation speed of the rotary tool, and the entry time of the rotary tool is determined by the entry amount and entry speed of the rotary tool.

[0103] In this process, the entry speed of the rotary tool is not particularly limited, but is preferably, for example, 10 to 100 mm / min, and especially 20 to 50 mm / min.

[0104] (Stirring maintenance process C3) The stirring maintenance step C3 in this embodiment is the same as the stirring maintenance step C3 in the first embodiment, except that no pressure is applied to the first member 7 and the second member 8 because a position control method is employed. Without applying pressure to the first member 7 and the second member 8 by the rotating tool 1, the rotational movement of the rotating tool 1 is continued at the position in which the rotating tool 1 was inserted in the pushing stirring step C2. This generates a large amount of frictional heat. Therefore, the stirring by plastic flow described above is further promoted.

[0105] In the stirring maintenance step C3, the rotating tool 1 is held in the predetermined position for a predetermined time while being rotated at a predetermined speed.

[0106] The holding time in the stirring maintenance step C3 is usually set from the viewpoint of more sufficient suppression of the winding phenomenon and productivity, and its value changes depending on, for example, the rotation speed of the rotary tool 1, the thickness and material type of the first member 7 and the second member 8. For example, when using the first member 7 and the second member 8 which have a thickness of 1.5 mm or more and 3 mm or less and are made of aluminum alloy, the holding time in the stirring maintenance step C3 is preferably 0 seconds or more and less than 10.0 seconds. The rotation speed of the rotary tool is preferably 2000 rpm or more and 4000 rpm or less. A holding time of 0 seconds means that the stirring maintenance step C3 may not be performed in this embodiment. This is because the amount of heat input can be adjusted by the entry time of the rotary tool in the push-in stirring step C2 described above. In particular, when the entry amount, entry speed and rotation speed of the rotary tool in the push-in stirring step C2 described above are within the above range, the holding time in this stirring maintenance step C3 is usually 0 seconds or more and less than 5.0 seconds.

[0107] The amount of heat input in this process is determined by the length of the holding time and the rotation speed of the rotating tool. In particular, the longer the holding time within the above range, the more the stirring by plastic flow is promoted.

[0108] In this embodiment as well, after the stirring maintenance step C3, the pressing member 16 is usually separated from the joint and left to cool. It may also be forcibly cooled from the outside.

[0109] The present invention encompasses the following preferred embodiments. <1> A rotary tool for friction stir welding, The rotating tool has a shoulder portion that forms the tip side, The shoulder portion is provided with a pin portion projecting outward at its tip and an arc-shaped surface arranged on the outer circumference of the pin portion. The aforementioned arc-shaped surface, in cross-sectional view, is a surface that forms an arc and slopes downward in the direction from the axis of rotation side to the outer circumference side, and has a helical groove. The spiral direction of the helical grooves in the arc-shaped surface is such that, when viewed from the bottom, the material flows from the inner circumference to the outer circumference of the rotating tool, relative to the rotational direction of the rotating tool. The aforementioned pin portion has a helical groove on its outer surface, A rotary tool for friction stir welding, wherein the spiral direction of the helical groove in the pin portion is such that the material flows toward the tip of the rotary tool, relative to the rotational direction of the rotary tool. <2> The aforementioned arc-shaped surface is a surface having a concave curved shape that is recessed in the direction opposite to the tip direction m of the rotation axis when viewed in cross-section. <1> A rotary tool for friction stir welding as described above. <3> The arc-shaped surface has one or more helical grooves, and each of the one or more helical grooves has a helical shape in which the distance from the rotation axis of the rotary tool decreases in the rotational direction when viewed from the bottom. <1> or <2> A rotary tool for friction stir welding as described above. <4> The aforementioned arc-shaped surface has an overall inclination angle α1 of 90 degrees or less with respect to the tip direction m of the rotation axis in cross-sectional view. <1> ~ <3> A rotary tool for friction stir welding as described in any of the following. <5> The overall inclination angle α1 is between 60 degrees and 85 degrees. <4> A rotary tool for friction stir welding as described above. <6> The aforementioned arc-shaped surface, in cross-sectional view, has an outermost tangent angle α2 that is between 0 and 70 degrees with respect to the direction m of the tip of the axis of rotation. <1> ~ <5> A rotary tool for friction stir welding as described in any of the following. <7> The rotating tool further has a tapered portion that forms the outer circumference of the shoulder portion, The tapered portion has a tapered surface on its tip side that has an inclination angle β of more than 90 degrees with respect to the tip direction m of the rotation axis in a cross-sectional view. <1> ~ <6> A rotary tool for friction stir welding as described in any of the following. <8> The aforementioned inclination angle β is between 95 degrees and 130 degrees. <7> A rotary tool for friction stir welding as described above. <9> The tapered surface has a helical groove. <7> or <8> A rotary tool for friction stir welding as described above. <10> The helical direction of the helical grooves in the tapered surface is such that, when viewed from the bottom, the material flows from the outer circumference to the inner circumference of the rotating tool, relative to the rotational direction of the rotating tool. <9> A rotary tool for friction stir welding as described above. <11> The helical grooves in the tapered surface have a curved shape with a constant curvature when viewed from the bottom. <9> or <10> A rotary tool for friction stir welding as described above. <12> The helical grooves of the tapered surface are discontinuous with the helical grooves of the arc-shaped surface when viewed from the bottom. <9> ~ <11> A rotary tool for friction stir welding as described in any of the following. <13> The tapered surface has a straight or curved shape in cross-sectional view. <7> ~ <12> A rotary tool for friction stir welding as described in any of the following. <14> The tapered surface, in cross-sectional view, has a concave curved shape that sinks in in the direction opposite to the direction m of the rotation axis tip. <7> ~ <13> A rotary tool for friction stir welding as described in any of the following. <15> The aforementioned friction stir welding is a method for joining a first member and a second member. The first member and the second member are metal members. <1> ~ <14> A rotary tool for friction stir welding as described in any of the following. <16> <1> ~ <15> A friction stir welding method comprising performing friction stir welding using a rotary tool for friction stir welding described in any of the above, and a receiving member positioned opposite the rotary tool. <17> A first step of overlapping the first member and the second member between the rotating tool and the receiving member; and The second step involves rotating the rotary tool while pressing it against the first member to generate frictional heat, and using this frictional heat to cause the first member and the second member to undergo plastic flow at their interface, thereby joining the first member and the second member. including, <16> The friction stir welding method described above. <18> In the second step described above, a pressure control method is adopted. The rotating tool controls the pressure applied to the first member, the pressurizing time, and the rotation speed. <17> A method for joining metal components as described in [the relevant document]. <19> In the second step described above, a position control method is adopted. The coordinate position of the rotating tool, the holding time at a specific position, and the rotation speed are controlled. <17> or <18> A method for joining metal components as described in [the relevant document]. <20> The second step described above is: The process includes a pressing and stirring step in which the rotating tool is pushed in from the first member side until it penetrates to a depth in which the entire surface of the arc-shaped surface comes into contact with the constituent material of the first member, <17> ~ <19> A friction stir welding method as described in any of the following. <21> In the aforementioned pressing and stirring step, when the inclination height of the arc-shaped surface is E1 (mm), the rotating tool is pressed from the first member side until the amount K of the arc-shaped surface pressed into the first member is 0 mm or more and less than 0.1 × E1 (mm). <20> The friction stir welding method described above. [Examples]

[0110] (Example 1) [First member and second member] Flat plate-shaped members made of 6000 series aluminum alloy (100 mm long x 30 mm wide x 2.0 mm thick (=T1=T2)) were used as the first and second members.

[0111] [Rotating tool] (A rotating tool having a shoulder section with an arc-shaped surface (first inclined surface) and a tapered section with a tapered surface (second inclined surface), and having spiral grooves on both the arc-shaped and tapered surfaces.) The rotary tool 1B (made of tool steel) shown in Figures 16-17 was used. Its dimensions and shape are as follows: Shoulder section; diameter D1 = 10 mm Pin section; height H = 3.8 mm (= 0.38 × D1) Pin section; diameter D2 = 5.0 mm (= 0.50 × D1) Pin section; spiral groove; cross-sectional shape = V-shape Pin section; spiral groove; depth = 0.27 mm, width = 0.5 mm Pin section; spiral groove; spiral direction = the direction in which the material flows toward the tip of the rotary tool relative to the rotation direction of the rotary tool (the spiral groove corresponds to a counterclockwise screw groove). Pin section; tip diameter = R5mm; 1st inclined plane; overall inclination angle α1=77° 1st inclined plane; outermost tangent angle α2=22° 1st slope; width D3=2.5mm (=0.25×D1) First inclined surface; spiral groove; cross-sectional shape = semicircular First inclined surface; spiral groove; depth = 0.35 mm, width = 0.7 mm First inclined surface; spiral groove; spiral direction = in a bottom view, the direction in which the material flows from the inner circumference to the outer circumference of the rotating tool, relative to the rotation direction of the rotating tool. First inclined surface; inclination height E1 = 0.9 mm (= 0.09 × D1) 2nd slope; slope angle β=110° 2nd slope; width D4=3.0mm (=0.30×D1) Second inclined surface; spiral groove; cross-sectional shape = semicircular Second inclined surface; spiral groove; depth = 0.35 mm, width = 0.7 mm 2nd slope; slope depth E2=1.1mm (=0.11×D1) Second inclined surface; spiral groove; spiral direction = in a bottom view, the direction in which the material flows from the outer circumference to the inner circumference of the rotating tool, relative to the rotation direction of the rotating tool.

[0112] [Support member] The receiving member 2 (made of tool steel) shown in Figure 18 was used. Its shape is as follows. Planar shape

[0113] [Joining the first and second members] (Pressure control method) First, the first member 7 and the second member 8 were placed on top of each other. Next, as shown in Figure 18, the rotary tool 1 was pressed into the first member 7 and the second member 8 with a pressing force of 5.88 kN, a rotation speed of 3000 rpm, and a joining time of 1.0 second (pressing and stirring process). As a result, the amount K into which the arc-shaped surface 111 was pressed into the first member 7 became 0 mm. Next, with a pressing force of 5.88 kN, a rotation speed of 1000 rpm, and a total bonding time as shown in Figure 19, the mutual proximity between the rotating tool 1 and the receiving member 2 was stopped, and the rotation of the rotating tool 1 was continued at the position where it had been pushed in to the aforementioned amount (this is called the "reference position") (stirring and maintenance process). As a result, the rotating tool 1 was pushed in further, and the amount of push-in K became 0.4 × E1 with respect to the inclination height E1 of the arc-shaped surface (see Figure 17). The total bonding time is the sum of the bonding time in the pushing and stirring process and the bonding time in the stirring and maintenance process. Subsequently, the mixture was allowed to cool, and a joint was obtained. As a result, the amount K (see Figure 18) of the arc-shaped surface 111 being pressed into the first member 7 was 0.4 × E1 relative to the inclination height E1 (see Figure 17) of the arc-shaped surface. We manufactured these bonded structures seven times by varying the bonding time.

[0114] Figure 20 shows a cross-sectional photograph of one of the obtained joints. As shown in Figure 20, the joint interface between the first member and the second member disappeared near the base (root) of the pin portion (area S shown by the dashed line in Figure 20), and the winding phenomenon due to the rise of the joint interface was sufficiently suppressed. Figure 20 shows a cross-sectional photograph of the vicinity of the joint in one of the joints obtained in Example 1.

[0115] For the seven resulting joints, the joint strength between the first and second members was measured. For details, the joint strength between the first and second members was measured using the Autograph "AGX-100kNVD" manufactured by Shimadzu Corporation and is shown in Figure 19.

[0116] (Comparative Example 1) The first member and the second member were joined in the same manner as in Example 1, except that the rotary tool was changed to the following rotary tool and the joining time was changed. The amount K of the first inclined surface being pressed into the first member was 0.4 × E1 with respect to the inclination height E1 of the first inclined surface.

[0117] [Rotating tool] (A rotating tool that does not have a tapered section and does not have an arc-shaped surface or spiral groove on the shoulder section) A rotary tool 500 (made of tool steel) shown in Figure 21 was used. Specifically, a rotary tool with the same cross-sectional shape and dimensions as shown in Figure 4 was used, except that the first inclined surface 111 of the shoulder portion was a straight surface rather than an arc-shaped surface in cross-sectional view, and the first inclined surface 111 did not have a helical groove. The following dimensions are indicated by the reference numerals in Figure 4. Shoulder section; diameter D1 = 10.0 mm Pin section; height H=3.3mm Pin section; diameter D2 = 5.0 mm Pin section; spiral groove; cross-sectional shape = V-shape Pin section; spiral groove; depth = 0.27 mm, width = 0.5 mm Pin section; spiral groove; spiral direction = the direction in which the material flows toward the tip of the rotating tool relative to the rotation direction of the rotating tool. Pin section; tip diameter = R5mm; 1st inclined plane; overall inclination angle α1=77° 1st slope; width D3=5.0mm First inclined surface; inclination height E1 = 0.5 mm

[0118] During joining, as shown in Figure 22, the joining interface between the first member 517 and the second member 518 did not disappear, but instead rose to the vicinity of the base (root) of the pin portion 510 due to a winding phenomenon Z. We manufactured these bonded bodies nine times by varying the bonding time. For the nine resulting joints, the joint strength between the first and second members was measured. For details, the joint strength between the first and second members was measured using the Autograph "AGX-100kNVD" manufactured by Shimadzu Corporation and is shown in Figure 19.

[0119] (Comparative Example 2) The first and second members were joined in the same manner as in Example 1, except that the rotary tool was changed to the following rotary tool. The amount K of the first inclined surface being pressed into the first member was 0.4 × E1 with respect to the inclination height E1 of the first inclined surface.

[0120] [Rotating tool] (A rotating tool that does not have a tapered section and does not have an arc-shaped surface on the shoulder section, but has a helical groove.) A rotation tool with the same cross-sectional shape and dimensions as shown in Figure 4 was used, except that the first inclined surface 111 of the shoulder portion is a straight surface rather than an arc-shaped surface in cross-sectional view. The following dimensions are indicated by the reference numerals in Figure 4. Shoulder section; diameter D1 = 10 mm Pin section; height H=3.3mm Pin section; diameter D2 = 5.0 mm Pin section; spiral groove; cross-sectional shape = V-shape Pin section; spiral groove; depth = 0.27 mm, width = 0.5 mm Pin section; spiral groove; spiral direction = the direction in which the material flows toward the tip of the rotating tool relative to the rotation direction of the rotating tool. Pin section; tip diameter = R5mm; 1st inclined plane; overall inclination angle α1=77° 1st slope; width D3=5.5mm First inclined surface; spiral groove; cross-sectional shape = semicircular First inclined surface; spiral groove; depth = 0.35 mm, width = 0.7 mm First inclined surface; inclination height E1 = 0.88 mm First inclined surface; spiral groove; spiral direction = in a bottom view, the direction in which the material flows from the inner circumference to the outer circumference of the rotating tool, relative to the rotation direction of the rotating tool.

[0121] When the joint strength between the first and second members was measured using the Autograph "AGX-100kNVD" manufactured by Shimadzu Corporation, it was clear that the measured value was significantly lower than the measured value in Example 1, similar to the measured value in Comparative Example 1. It is thought that during joining, a winding phenomenon occurs in which the joint interface between the first and second members does not completely disappear, and rises to the vicinity of the base (root) of the pin portion.

[0122] (Comparative Example 3) The first and second members were joined in the same manner as in Example 1, except that the rotation tool was changed to the following rotation tool.

[0123] [Rotation Tool] (A rotation tool that does not have a tapered section and has an arc-shaped surface on the shoulder section, but the arc-shaped surface is not inclined downwards.) A rotation tool was used that had the same cross-sectional shape and dimensions as shown in Figure 4, except that the arc-shaped surface of the first inclined surface 111 of the shoulder portion formed an arc in the direction from the rotation axis side to the outer circumference side in a cross-sectional view, but did not have a shape that was inclined downwards. The following dimensions are indicated by the reference numerals in Figure 4. Shoulder section; diameter D1 = 10 mm Pin section; height H = 3.8 mm (= 0.38 × D1) Pin section; diameter D2 = 5.0 mm (= 0.50 × D1) Pin section; spiral groove; cross-sectional shape = V-shape Pin section; spiral groove; depth = 0.27 mm, width = 0.5 mm Pin section; spiral groove; spiral direction = the direction in which the material flows toward the tip of the rotating tool relative to the rotation direction of the rotating tool. Pin section; tip diameter = R5mm; 1st inclined plane; overall inclination angle α1=100° 1st inclined plane; outermost tangent angle α2=22° 1st slope; width D3=2.5mm (=0.25×D1) First inclined surface; spiral groove; cross-sectional shape = semicircular First inclined surface; spiral groove; depth = 0.35 mm, width = 0.7 mm First inclined surface; spiral groove; spiral direction = in a bottom view, the direction in which the material flows from the inner circumference to the outer circumference of the rotating tool, relative to the rotation direction of the rotating tool. First inclined surface; inclination height E1 = 0 mm 2nd slope; slope angle β=110° 2nd slope; width D4=3.0mm (=0.30×D1) Second inclined surface; spiral groove; cross-sectional shape = semicircular Second inclined surface; depth = 0.35 mm, width = 0.7 mm 2nd slope; slope depth E2=1.1mm (=0.11×D1) Second inclined surface; spiral groove; spiral direction = in a bottom view, the direction in which the material flows from the outer circumference to the inner circumference of the rotating tool, relative to the rotation direction of the rotating tool.

[0124] When the joint strength between the first and second members was measured using the Autograph "AGX-100kNVD" manufactured by Shimadzu Corporation, it was clear that the measured value was significantly lower than the measured value in Example 1, similar to the measured value in Comparative Example 1. It is thought that during joining, a winding phenomenon occurs in which the joint interface between the first and second members does not completely disappear, and rises to the vicinity of the base (root) of the pin portion. [Industrial applicability]

[0125] The rotary tool and joining method according to the present invention are useful for joining (especially joining metal members) in fields such as automobiles, railway vehicles, aircraft, and home appliances. [Explanation of symbols]

[0126] 1:1A:1B: Rotation Tool 3: Helical grooves on the arc-shaped surface 4: Helical grooves on tapered surfaces 11: Shoulder section 12: Tapered section 110: Pin part 111: Arc-shaped surface (first inclined surface) 121:121A:121B:121C:Tapered surface (second inclined surface) M: Rotation axis (center axis) m: Tip direction N: Rotational direction

Claims

1. A rotary tool for friction stir welding, The rotating tool has a shoulder portion that forms the tip side, The shoulder portion is provided with a pin portion projecting outward at its tip and an arc-shaped surface arranged on the outer circumference of the pin portion. The aforementioned arc-shaped surface, in cross-sectional view, is a surface that forms an arc and slopes downward in the direction from the axis of rotation side to the outer circumference side, and has a helical groove. The spiral direction of the helical grooves in the arc-shaped surface is such that, when viewed from the bottom, the material flows from the inner circumference to the outer circumference of the rotating tool, relative to the rotational direction of the rotating tool. The aforementioned pin portion has a helical groove on its outer surface, A rotary tool for friction stir welding, wherein the spiral direction of the helical groove in the pin portion is such that the material flows toward the tip of the rotary tool, relative to the rotational direction of the rotary tool.

2. The rotary tool for friction stir welding according to claim 1, wherein the arc-shaped surface is a concave curved surface that is recessed in the direction opposite to the tip direction m of the rotation axis when viewed in cross-section.

3. The rotary tool for friction stir welding according to claim 1, wherein the arc-shaped surface has one or more helical grooves, and each of the one or more helical grooves has a helical shape in which the distance from the rotation axis of the rotary tool decreases in the rotation direction when viewed from the bottom.

4. The rotary tool for friction stir welding according to claim 1, wherein the arc-shaped surface has an overall inclination angle α1 of 90 degrees or less with respect to the tip direction m of the rotation axis in a cross-sectional view.

5. The rotary tool for friction stir welding according to claim 4, wherein the overall inclination angle α1 is 60 degrees or more and 85 degrees or less.

6. The rotary tool for friction stir welding according to claim 1, wherein the arc-shaped surface has an outermost tangent angle α2 in a cross-sectional view that is 0 degrees or more and 70 degrees or less with respect to the tip direction m of the rotation axis.

7. The rotating tool further has a tapered portion that forms the outer circumference of the shoulder portion, The rotary tool for friction stir welding according to claim 1, wherein the tapered portion has a tapered surface on its tip side having an inclination angle β of more than 90 degrees with respect to the tip direction m of the rotation axis in a cross-sectional view.

8. The rotary tool for friction stir welding according to claim 7, wherein the inclination angle β is 95 degrees or more and 130 degrees or less.

9. The rotary tool for friction stir welding according to claim 7, wherein the tapered surface has a helical groove.

10. The rotary tool for friction stir welding according to claim 9, wherein the spiral direction of the helical grooves in the tapered surface is, in a view from the bottom, a direction that causes the material to flow from the outer circumference to the inner circumference of the rotary tool with respect to the rotational direction of the rotary tool.

11. The rotary tool for friction stir welding according to claim 9, wherein the helical grooves of the tapered surface have a curved shape with a constant curvature when viewed from the bottom.

12. The rotary tool for friction stir welding according to claim 9, wherein the helical grooves of the tapered surface are discontinuous with the helical grooves of the arc-shaped surface when viewed from the bottom.

13. The rotary tool for friction stir welding according to claim 7, wherein the tapered surface has a straight or curved shape in cross-sectional view.

14. The rotary tool for friction stir welding according to claim 7, wherein the tapered surface has a concave curved shape that sinks in the direction opposite to the direction m of the tip of the rotation axis in a cross-sectional view.

15. The aforementioned friction stir welding is a method for joining a first member and a second member. The rotary tool for friction stir welding according to claim 1, wherein the first member and the second member are metal members.

16. A friction stir welding method comprising performing friction stir welding using a rotary tool for friction stir welding according to any one of claims 1 to 15, and a receiving member positioned opposite the rotary tool.

17. A first step of overlapping the first member and the second member between the rotating tool and the receiving member; and The second step involves rotating the rotary tool while pressing it against the first member to generate frictional heat, and using this frictional heat to cause the first member and the second member to undergo plastic flow at their interface, thereby joining the first member and the second member. The friction stir welding method according to claim 16, including the following:

18. In the second step described above, a pressure control method is adopted. The method for joining metal members according to claim 17, further comprising controlling the pressure applied to the first member by the rotary tool, the pressurizing time, and the rotational speed.

19. In the second step described above, a position control method is adopted. The method for joining metal members according to claim 17, comprising controlling the coordinate position of the rotating tool, the holding time at a specific position, and the number of rotations.

20. The second step described above is: A friction stir welding method according to any one of claims 17 to 19, comprising a push-and-stir step of pushing the rotating tool from the first member side to a depth in which the entire surface of the arc-shaped surface comes into contact with the constituent material of the first member.

21. The friction stir joining method according to claim 20, wherein in the pressing and stirring step, when the inclination height of the arc-shaped surface is E1 (mm), the rotating tool is pushed from the first member side until the amount K of the arc-shaped surface pressed into the first member is 0 mm or more and less than 0.1 × E1 (mm).

Images