JP2002001548A - Friction stir jointing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction stir jointing method in which a thick-walled first joint member and a thin-walled second joint member are butted against each other so that both surfaces are connected to the flush with each other, joints this abutted part of both joint members, can obtain a butt joint having excellent strength reliability, minimize producing cost, and lighten weight in the obtained butt joint. SOLUTION: With a jointing tool 20 which has a large diameter of rotor 21 and a small diameter of probe 22 projectingly provided on a rotational axis Q of a side face 21a of the large diameter of rotor, a rotating probe 22 is inserted in an abutted part 3 of both joint members 1 and 2 from the surface side. Furthermore, the side face 21a of the rotor is brought into contact with the surface of the joint member. Then, the probe 22 is relatively shifted along the abutted part 3 in a state where the rotational axis Q of the rotor is inclined on the first joint member 1 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction stir welding method for butt joining metal materials such as aluminum materials (including their alloy materials, the same applies hereinafter), and more specifically, for example, automobiles, railway vehicles and ships. The present invention relates to a friction stir welding method used when manufacturing a body panel of a vehicle or the like, or used when manufacturing a suspension arm or an engine mount of an automobile.

[0002]

2. Description of the Related Art Friction stir welding is included in the category of solid-phase welding and is not limited by the type of metal material used as a joining member.
It has advantages such as little deformation due to thermal distortion at the time of joining, and has recently been used as a joining means for various structures.

[0003] A joining method of the friction stir welding will be described with reference to FIG. In the figure, (101) and (102) are two flat metal joining members, and both joining members (101) (1)
02), one of the joining members (101) is
It is thicker than 02). Here, for convenience of explanation, in these two joining members (101) and (102), the thick one (101) is replaced with the first joining member and the thin one (1).
02) is referred to as a second joining member. The two joining members (101) and (102) have their end faces in the width direction abutting on each other in such a manner that the front surfaces are flush with each other, and the back surface applied to the back surfaces of the two joining members (101) and (102). Guess (10
This state is maintained by 5).

[0004] In the figure, reference numeral (120) denotes a welding tool for friction stir welding. The joining tool (120) includes a large-diameter cylindrical rotor (121) and an end face (121a) of the rotor (121).
And a small-diameter pin-shaped probe (122) integrally protruding on the rotation axis (Q ′). The end face (121a) of the rotor (121) is a flat face.

Using this joining tool (120), a rotor (12
While rotating the probe (122) by rotating 1), the probe (122) is inserted into the butting portion (103) from the surface side of both joining members (101) and (102), and the rotor (121) is rotated. End surface (121a) of both joining members (101) (10
Press against the surface of 2). Then the probe (1
22) along the butting part (103) with both joining members (101) (10
Move relative to 2).

[0006] The frictional heat generated by the rotation of the probe (122) and the frictional heat generated by the sliding between the end face (121a) of the rotor (121) and the surface of the joining member cause the probe (122) to be in contact with the probe (122). Both joining members (101) near the contact part
(102) is softened and the meat in the softened portion is probe (12
While being stirred by the rotational force of 2), the probe (1
With the movement of 22), the softened meat plastically flows in such a manner that it receives the advancing pressure of the probe (122) and wraps backward in the traveling direction of the probe (122) so as to fill the passage groove of the probe (122). After that, it loses frictional heat rapidly and is cooled and solidified. This phenomenon is sequentially repeated with the movement of the probe (122), and finally the two joining members (101) (102)
Are joined and integrated at the butt portion (103), whereby a desired butt joint (A3) is obtained. (W ') indicates a joint of the butt joint (A3). Also, P ′ indicates the normal line of the surface at the probe insertion position of both joining members (101) and (102).

FIG. 6 shows a first joining member (111) made of a solid metal having a circular cross section and a second joining member (112) made of a hollow metal material having a circular cross section. The case where the end surfaces are butted and the butted portion (113) is joined by friction stir welding is shown.

In the two joining members (111) and (112), the first
The outer diameter of the joining member (111) and the outer diameter of the second joining member (112) are set to be the same. Then, the end faces in the length direction of the two joining members (111) and (112) are abutted with each other such that the surfaces (that is, the outer peripheral surfaces) are continuous with each other. In this state, in the hollow portion (112a) of the second joining member (112), a fitting projection (111a) integrally projecting from the center of the end face of the first joining member (111) fits exactly. Or they are tightly fitted.

The desired butt joint (A4) can be obtained by butt-joining the two joining members (111) and (112) by the same joining procedure as described above. That is, while rotating the probe (122) of the joining tool (120), the probe (122) is inserted into the butting portion (113) from the surface side of both joining members (111) and (112), and the rotor (121) is rotated. ) Is pressed against the surface (121a). Then, in this state, the probe (122) is moved along the butting portion (113) to make one rotation around the two joining members (111) and (112). Alternatively, the probe (12
The position of (2) is fixed, and the joining members (111) (11)
2) Make one rotation around its axis. By doing so, the butting portion (113) is friction stir welded over its entire length, and the two joining members (111) and (112) are joined and integrated.
Thus, a desired butt joint (A4) is obtained.

By the way, when performing friction stir welding,
At the time of joining, it is desirable that the end face (121a) of the rotor (121) is pressed against the surfaces of both joining members, so that the softened portion can be pressed by the end face (121a) of the rotor (121), A good joint (W ′) can be formed.

[0011]

However, when the end face (121a) of the rotor (121) is pressed against the surfaces of the two joining members in order to press the softened portion, FIGS.
As shown in (b), the softened part is the end face (1) of the rotor (121).
21a), the joint (W ') is dented because it loses frictional heat and is cooled and solidified in this state. As a result, each joint member (10
The wall thickness near the joint (W ′) of (1, 111) (102, 112) is reduced. In such a case, the butt joints (A3, A3)
4) When the butt joint (A3, A4) is subjected to a load such as a tensile load or a bending load,
The butt joints (A3, A4) break or bend at this portion. That is, the second joining member (102, 1
Various strengths such as tensile strength and bending strength of the butt joints (A3, A4) decrease with the decrease in the thickness of 12).
In addition, in the figure, the concave portion (107) of the joint portion (W ') is exaggerated for convenience of explanation.

On the other hand, in order to prevent a decrease in the strength of the butt joints (A3, A4) due to the depression of the joint (W '),
As shown in FIGS. 7 (a) and 8 (a), each joining member (101, 111) (102, 112)
It is proposed to increase the wall thickness of the abutted ends of the two. In FIG. 7 (a), ridges (101b) and (102b) are provided along the side edges on the surface at the ends in the width direction of the joining members (101) and (102). On the other hand, in FIG.
A protruding ridge (112b) is provided along the periphery at the surface (outer peripheral surface) at the longitudinal end of the joining member (112), and the first joining member (111) is provided with the ridge (112b). Is formed to be thicker by the thickness.

The two joining members (101, 111) (10
2 and 112), the butted portions (103) and (113) are friction stir welded, so that the welded portion (W ′) is recessed as shown in FIGS. 7 (b) and 8 (b). Even in the case where the butt joints (A3, A4) are in a state where the thickness of the butt joints (A3, A4) is no longer the minimum thickness of the butt joints (A3, A4), the thickness of the butt joints (A3, A4) is no longer the minimum. The strength can be prevented from lowering.

However, according to the proposed method, there is a problem that the weight increases by the amount of the ridges (101b, 102b, 112b) and the thickness of the thick portion (thick portion 111b). Furthermore, since the protruding ridges (101b, 102b, 112b) must be formed, it takes time and effort to manufacture the device, which increases the manufacturing cost, and also matches the ridges (101b, 102b, 112b). There was also the drawback that the design of the joints (A3, A4) had to be changed.

The present invention has been made in view of such a technical background, and an object of the present invention is to form a thick first joining member and a thin second joining member in such a manner that their surfaces are continuous with each other. This is a friction stir welding method of butt-joining the two joining members while butt-joining, whereby a butt-joint having excellent strength reliability can be obtained, and butt-joining without changing the design of the shape of the butt-joint. It is another object of the present invention to provide a friction stir welding method that can reduce the manufacturing cost as much as possible and can reduce the weight of the obtained butt joint.

[0016]

In order to achieve the above object, the present invention provides a joining tool having a large-diameter rotor and a small-diameter probe provided on the rotation axis at the end face of the rotor. The first joining member having a large thickness and the second joining member having a small thickness are butted in such a manner that their surfaces are flush with each other, and the joining tool of the two joining members or the vicinity thereof is joined to the joining tool from the surface side. While inserting the rotating probe, the end face of the rotor is brought into contact with the surface of the joining member,
In this state, the probe is relatively moved along the butt portion, and the two members are butt-joined by friction stir welding. In this state, the rotation axis of the rotor is inclined toward the first member. The butt joint is performed.

According to this, the rotation axis of the rotor is inclined toward the first joining member, so that the meat in the softened portion receives the pressure from the end face of the rotor and moves toward the second joining member. In this state, the meat in the softened portion loses frictional heat and is cooled and solidified in this state. As a result, the amount of decrease in the thickness of the second joint member is reduced, and thus a decrease in the strength of the butt joint due to the decrease in the thickness of the second joint member can be prevented.

Further, the strength of the butt joint can be prevented from being reduced only by tilting the rotation axis of the rotor toward the first joining member, so that the butt joining can be performed with high work efficiency. As a result, manufacturing costs are reduced. Further, since it is not necessary to provide the ridge, it is possible to reduce the weight, and it is not necessary to change the design of the shape of the butt joint.

In the present invention, if the inclination angle of the rotation axis of the rotor to the first joint member side with respect to the normal of the surface at the probe insertion position of both joint members is θ, the inclination angle θ is 0 ° <θ. It is desirable to incline the rotation axis of the rotor under the condition of ≦ 10 °. By doing this,
A decrease in the strength of the butt joint can be reliably prevented, and the following problems can be prevented. That is, when the inclination angle θ exceeds 10 °, the meat in the softened portion is too lean toward the second joining member, and the portion of the joining portion on the side of the second joining member rises, and as a result, the joining portion The problem that the surface state of the surface is deteriorated is likely to occur. Therefore, it is desirable to set the inclination angle θ to 10 ° or less. By doing so, such a problem can be prevented.
In particular, it is desirable to incline the rotation axis of the rotor under the condition that the inclination angle θ satisfies 2 ° ≦ θ ≦ 6 °, so that the strength of the butt joint can be more reliably prevented from lowering. become.

[0020]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of the present invention, and FIGS. 3 and 4 show a second embodiment of the present invention. First, the first embodiment will be described, and then the second embodiment will be described.

The first embodiment shown in FIG. 1 and FIG.
The case where two flat aluminum joining members are butt-joined is shown. In FIG. 1, (1) is a thick first joining member, and (2) is a thin second joining member.
Each of the joining members (1) and (2) has an end face in the width direction as an abutting face. The two joining members (1) and (2) are arranged such that their front surfaces are flush with each other, the end faces in the width direction abut each other, and are applied to the back surfaces of the two joining members (1) and (2). It is held in this state by the backing (5).

Reference numeral (20) denotes a welding tool for friction stir welding, which is integrally formed with a large-diameter cylindrical rotor (21) and a rotation axis (Q) of an end face (21a) of the rotor (21). And a small-diameter pin-shaped probe (22) protruding therefrom. The rotor (21) and the probe (22) are both made of a heat-resistant material that is harder than the two joining members (1) and (2) and that can withstand frictional heat generated during joining. In addition, a convex portion (not shown) for stirring the meat in the softened portion is provided on the outer peripheral surface of the probe (22). The end face (21a) of the rotor (21) is connected to both joining members (1) at the time of joining.
It is a portion to be pressed against the surface of (2) and is in a plane orthogonal to the rotation axis (Q). In this embodiment, the end face (21a) of the rotor (21) is a flat face. In the present invention, the flat surface (21a) of the rotor (21)
Although not shown, the central portion may have a concave shape.

Using the joining tool (20), the butting portion (3) of the two joining members (1) and (2) is joined as follows. That is, the probe (22) is rotated by rotating the rotor (21) of the welding tool (20) about its rotation axis (Q). By tilting the rotor (21), the rotation axis (Q) of the rotor (21) is tilted toward the first joining member (1), and in this state, the rotating probe (22) is joined to both ends. Butting part (3) of members (1) and (2)
And the end faces (21a) of the rotor (21) are inserted into the two joining members (1) and (2).
The surface of (2) is pressed in a direction perpendicular to the surface or in a direction along the rotation axis (Q) of the rotor. At this time, as shown in FIGS. 1 and 2 (a), the normal line of the surface of both joining members (1) and (2) at the position where the probe (22) is inserted (that is, the probe insertion position) is changed. P, and the rotation axis (Q) of the rotor (21) with respect to the normal P
Is the angle of inclination of the first member toward the first joining member (1), the inclination angle θ is 0 ° <θ ≦ 10 ° (particularly preferably 2 ° ≦ θ).
It is desirable that the rotation axis (Q) of the rotor (21) be inclined toward the first joining member (1) under the condition of ≦ 6 °). In the present invention, the probe (22) is inserted into the butting portion (3) from the longitudinal end surfaces of the two joining members (1) and (2), thereby connecting the probe (22) to the two joining members (1).
It may be inserted from the front side of (2), or after the probe (22) is inserted into the butting portion (3), the rotation axis (Q) of the rotor (21) is connected to the first joining member (1). You may lean to the side.

Then, in this state, the probe (22) is moved along the butting portion (3) over the entire length of the butting portion (3). According to the present invention, the position of the probe (22) of the joining tool (20) is fixed, and the joining members (1) are moved so that the butting portion (3) passes through the probe (22) sequentially.
It goes without saying that (2) may be moved.

The frictional heat generated with the rotation of the probe (22) and the joining member (1) of the end face (21a) of the rotor (21)
Due to the frictional heat generated due to the sliding of the butting portion (3) with the surface in (2), the two joining members (1) and (2) are softened in the vicinity of the contact portion with the probe, and the softening portion in the softened portion The meat is stirred by receiving the rotational force of the probe (22), and the meat in the softened portion is moved to the end face (21a) of the rotor (21).
Receiving the pressure from the second joint member (2). In this state, the probe (2) is filled so that the meat in the softened portion fills the passage groove of the probe (22) as the probe (22) moves.
After plastically flowing in a manner of wrapping backward in the traveling direction of 2), the frictional heat is rapidly lost and solidified by cooling. This phenomenon is sequentially repeated as the probe (22) moves,
Finally, the two joining members (1) and (2) are joined and integrated at the butt portion (3), so that the desired butt joint (A1)
Is obtained. (W) shows the joint of the butt joint (A1). 2 (b), (7) shows a concave portion formed on the surface of the joint (W) of the butt joint (A1).

The butt joint (A1) obtained as described above is obtained by cooling and solidifying the meat in the softened portion at the time of joining while being leaned toward the second joining member (2). As shown, the thickness of the second joint member (2) near the joint (W) is hardly reduced. Therefore, this butt joint (A1) is prevented from various strength reductions such as a reduction in tensile strength, and has excellent strength reliability.

In addition, this friction stir welding method can prevent a decrease in the strength of the butt joint (A1) only by tilting the rotation axis (Q) of the rotor (21) of the welding tool (20). Therefore, there is an advantage that the joining can be performed with high work efficiency, the manufacturing cost can be reduced, and there is no need to change the design of the shape of the butt joint (A1).

Here, the tensile strength of the butt joint (A1) obtained in the first embodiment will be considered. Generally, in the butt joint (A1), the tensile strength F depends on the thickness of the second joining member (2) of the thick first joining member (1) and the thin second joining member (2), It can be calculated by the following equation (i).

F = (T−t) × L × σ _B × α (i) In the equation (i), T is the thickness of the second joining member (2), t is the recess (7) ), Depth at the side of the second joining member (2), σ _B : tensile strength per unit sectional area of the second joining member (2), L: full length of the butt portion (3), α: strength by joining heat It is a decrease coefficient.

From the equation (i), it can be seen that the smaller the t, the higher the tensile strength F of the butt joint (A1). In other words, to obtain a butt joint (A1) with high tensile strength,
What is necessary is just to make t small. For example, when the thickness T of the second joining member (2) is 4 mm, t is 0.5 mm according to the conventional method, but according to the present invention, t is 0 mm.
Can be That is, according to this friction stir welding method, the tensile strength F of the butt joint (A1) can be increased by about 14% with respect to the tensile strength of the butt joint obtained by the conventional method.

Next, a second embodiment shown in FIGS. 3 and 4 will be described. In these figures, (11) is a thick first joining member made of a solid aluminum material having a circular cross section, and (12) is a thin second joining member made of a hollow aluminum material having a circular cross section. The outer diameter of the first joint member (11) and the outer diameter of the second joint member (12) are set to the same size. Then, both joining members (11) and (12) are arranged such that the surfaces (that is, the outer peripheral surfaces) are flush with each other, and end faces in the length direction are abutted with each other. In this state, as shown in FIG. 4 (a), in the hollow portion (12a) of the second joint member (12), the central portion of the end face of the first joint member (11) is integrally protruded. The fitting projections (11a) are fitted tightly or tightly, whereby the two joining members (11) and (12) are held in this state.

The butting portion (13) of the two joining members (11) and (12) is joined by the same joining operation as in the first embodiment. That is, the rotation axis (Q) of the rotor (21) is tilted toward the first bonding member (11) by tilting the rotor (21) using the bonding tool (20) shown in the first embodiment. In this state, the rotating probe (22) is inserted into the butting portion (13) of both the joining members (11) and (12) from the front side of the two joining members (11) and (12), and the rotor ( The end face (21a) of 21) is pressed against the surfaces of both joining members (11) and (12). At this time, the inclination angle θ of the rotation axis (Q) of the rotor (21) to the first joint member (1) with respect to the normal line P of the surface at the probe insertion position of the joint members (11) and (12) is 0. ° <θ ≦ 10 ° (particularly preferably 2 ° ≦ θ ≦
It is desirable to incline the rotation axis (Q) of the rotor (21) toward the first joining member (11) so that the angle becomes 6 °).

Then, in this state, the probe (22) is moved along the butting portion (13), and the two joining members (11) (1) are moved.
Make a full turn around 2). In the present invention, the position of the probe (22) of the joining tool (20) is fixed, and the joining members (11) and (12) are moved so that the butting portion (13) passes through the probe (22) sequentially. One rotation may be made around the axis.

By doing so, the phenomenon described in the first embodiment is sequentially repeated with the movement of the probe (22), and finally the two joining members (11) and (12) are brought into contact with the butted portion (13). And a desired butt joint (A2) is obtained.

As shown in FIG. 4B, the butt joint (A2) obtained in this manner has almost no decrease in wall thickness in the vicinity of the joint (W) of the second joint member (12). Various strength reductions such as strength reduction are prevented,
Has excellent strength reliability. Therefore, the butt joint (A2) can be suitably used, for example, as a member for a suspension arm of an automobile or a member for an engine mound.

Although the embodiment of the present invention has been described above, the present invention is not limited to the first and second embodiments.

For example, in the first and second embodiments,
In any case, the state where the rotation axis (Q) of the rotor (21) is inclined toward the first joining member (1, 11) is realized by inclining the rotor (21). With the posture of the tool (20) fixed, both joining members (1, 11)
Such a state may be realized by inclining (2, 12) in the abutted state.

[0039]

Next, specific embodiments of the present invention will be described.

The first and second flat aluminum joining members (1) and (2) described below are prepared, and both joining members (1) and (2) are prepared according to the joining method described in the first embodiment.
Were butt-joined. <First joining member>-Material: A6061-T5-Thickness: 8 mm-Length: 100 mm <Second joining member>-Material: A6061-T5-Thickness: 4 mm-Length: 100 mm Also, joining conditions and joining The dimensions of the tool are as follows. <Joining conditions and dimensions of welding tool> Rotation speed of rotor: 1000 rpm Outer diameter of rotor end: 10 mm Probe dimensions: diameter 4 mm × length 3.3 mm Inclination angle θ: described in Table 1 .

The butt joint (A1) obtained as described above was evaluated by measuring the tensile strength. Table 1 shows the results. As an evaluation of the tensile strength, a butt joint having a tensile strength higher than that of a butt joint (comparative example 1) in which the butt joint was performed under the condition of the inclination angle θ = 0 ° by 5% or more was used. The symbol "O" indicates that the butt joint was increased by 10% or more.

[0042]

[Table 1]

As can be seen from Table 1, the inclination angle θ is 0 ° <
Under the condition that θ ≦ 10 ° (especially preferably 2 ° ≦ θ ≦ 6 °), if the butt joint is performed with the rotation axis of the rotor inclined to the first joint member side, the tensile strength of the butt joint is increased. Can be higher than the tensile strength of the butt joint obtained by the conventional method (Comparative Example 1). Examples 1 to 3
By examining the surface condition of the joints of these butt joints, it was confirmed that the surface condition of each of these butt joints was good.

[0044]

As described above, according to the present invention, the flesh in the softened portion softened by frictional heat is reduced by setting the rotation axis of the rotor of the welding tool to be inclined toward the first welding member. Since the meat in the softened portion loses frictional heat and is cooled and solidified in this state,
The thickness reduction of the joining member can be reduced,
It is possible to prevent a decrease in the strength of the butt joint due to a decrease in the thickness of the joining member. Therefore, various strengths such as tensile strength of the butt joint can be made higher than those obtained by the conventional method, and the strength reliability of the butt joint can be improved.

Moreover, the strength of the butt joint can be prevented from being reduced only by setting the rotation axis of the rotor to be inclined.
Butt joining can be performed with high work efficiency, and the manufacturing cost can be reduced. In addition, since it is not necessary to provide a ridge on each joining member, it is possible to reduce the weight of the obtained butt joint, and it is not necessary to change the design of the shape of the butt joint.

If the angle of inclination of the rotation axis of the rotor with respect to the surface normal at the probe insertion position of both joint members toward the first joint member is θ, the inclination angle θ is 0 ° <θ ≦ 1.
When the rotation axis of the rotor is inclined under the condition of 0 °, a decrease in the strength of the butt joint can be reliably prevented, and a joint having a good surface condition can be formed. The effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention in a state in which both joining members are in the middle of butt joining.

2A is a cross-sectional view taken along line II-II in FIG. 1, and FIG. 2B is a cross-sectional view corresponding to FIG.

FIG. 3 is a perspective view showing a second embodiment of the present invention in a state where both joining members are being joined.

4A is a cross-sectional view taken along the line IV-IV in FIG. 3, and FIG. 4B is a cross-sectional view corresponding to FIG.

FIG. 5 is a view showing a first embodiment of the conventional friction stir welding method, in which (a) is a perspective view of a state in which both joining members are in the process of butt joining, and (b) is a cross-sectional view in a state after the joining. .

FIGS. 6A and 6B are views showing a second embodiment of the conventional friction stir welding method, wherein FIG. 6A is a perspective view of a state in which both welding members are in the middle of butt welding, and FIG. 6B is a sectional view of the state after welding. .

FIG. 7 is a view showing a third embodiment of the conventional friction stir welding method, in which (a) is a perspective view of a state in which both joining members are in the process of butt joining, and (b) is a cross-sectional view in a state after joining. .

FIG. 8 is a view showing a fourth embodiment of the conventional friction stir welding method, in which (a) is a cross-sectional view of a state before joining of both joining members,
(B) is a cross-sectional view of the state after joining.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st joining member 2 ... 2nd joining member 3 ... Butt part 7 ... Recess 20 ... Joining tool 21 ... Rotor 21a ... Rotor end surface 22 ... Probe W ... Joining part

Claims (2)

[Claims] 1. A joining tool (20) comprising a large-diameter rotor (21) and a small-diameter probe (22) provided on a rotation axis (Q) of an end face (21a) of the rotor. Using the thick first
Joint member (1, 11) and thin second joint member (2, 12)
Are joined in such a manner that the surfaces are flush with each other, and a probe (22) rotating the joining tool is inserted from the front surface side into or near the joining portions (3, 13) of the two joining members. At the same time, the end face (21a) of the rotor is brought into contact with the surface of the joining member, and in this state, the probe (22)
Is a friction stir welding method in which the two joining members (1, 11) and (2, 12) are butt-joined by relatively moving each other along the butt portions (3, 13). The friction stir welding method, wherein the butt welding is performed in a state where Q) is inclined toward the first joining member (1, 11). 2. The first joint member (1, 1) of the rotation axis (Q) of the rotor (21) with respect to the normal line (P) of the surface at the probe insertion position of the two joint members (1, 11) (2, 12). 11) The friction stir welding method according to claim 1, wherein the rotational axis (Q) of the rotor is inclined under the condition that the inclination angle θ is 0 ° <θ ≦ 10 °, where θ is the inclination angle toward the side.