JP2018083217A - Friction stir welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction stir welding method capable of preventing metal shortage at a welding part of an inner corner.SOLUTION: There is provided a friction stir welding method which comprises welding the first and second metallic components 10, 20 using a rotary tool F equipped with a stirring pin F2. The method includes: a butting process of butting the first and second metallic components 10, 20 in which a surface height changes while forming an inner corner formed by the end face of the first component 10 and the surface of the second component 20 to form a height-changing butting part J1; a disposing process of disposing an auxiliary component 30 along the inner corner formed by the first and second components 10, 20; and a welding process of performing a friction stir welding along the inner corner in such a state as inserting the stirring pin F2 of the rotating rotary tool F in the inner corner to contact the stirring pin F2 only with the first and second components 10, 20 and the auxiliary component 30.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a friction stir welding method.

  In the prior art described in Patent Document 1, metal members are butted in an L shape in cross-sectional view, and a rotary tool is relatively moved along an inner corner to perform friction stir welding.

JP-A-2015-120203

  In the prior art, since only the stirring pin of the rotary tool is inserted into the inner corner, the plastic fluidized metal overflows to the outside, and the joining portion (plasticization region) may become insufficient.

  Then, this invention makes it a subject to provide the friction stir welding method which can prevent the metal shortage in the junction part of an inner corner.

  In order to solve the above-mentioned problem, the present invention is a friction stir welding method for joining a first metal member and a second metal member using a main welding rotary tool provided with a stirring pin, the first metal member And the second metal member whose surface height changes, but the inner surface formed by the end surface of the first metal member and the surface of the second metal member is formed, and the butt where the height changes A butting step for forming a portion, an arranging step for arranging an auxiliary member along the inner corner, and inserting the stirring pin of the rotating tool for main joining rotating at the inner corner, so that only the stirring pin is And a main joining step of performing friction stir welding along the inner corner in a state where the first metal member, the second metal member, and the auxiliary member are brought into contact with each other.

  According to the friction stir welding method, in addition to the first metal member and the second metal member, the auxiliary member is also friction stir welded in a state of being in contact with the stirrer pin. Moreover, it can join suitably also in the inner corner where the height of a butt | matching part changes.

  Moreover, it is preferable to include the removal process which removes the said auxiliary member in which the burr | flash was formed from said 1st metal member and said 2nd metal member.

  According to this friction stir welding method, burrs can be removed together with the auxiliary members.

  In the main joining step, it is preferable to set the joining conditions so that burrs generated by friction stirring are formed on the auxiliary member.

  According to this friction stir welding method, the burrs can be collected on the auxiliary member, so that the burrs can be more easily removed.

  In the arranging step, the auxiliary member is brought into surface contact with the surface of the second metal member, and the auxiliary member is arranged so that the surface of the auxiliary member is lower than the surface of the first metal member. It is preferable. Further, in the arranging step, the auxiliary member is arranged such that the auxiliary member is brought into surface contact with the end surface of the first metal member and the end surface of the auxiliary member is positioned higher than the surface of the first metal member. It is preferable.

  According to this friction stir welding method, the auxiliary member can be easily removed.

  Prior to the main joining step, only the stirring pin of the temporary joining rotary tool is inserted into the inner corner, and at least one of the first metal member and the second metal member and the auxiliary member are spotted. It is preferable to include a temporary joining step in which friction stir welding is performed.

  According to the friction stir welding method, the amount of heat input can be reduced, so that the thermal strain of the first metal member and the second metal member can be reduced and the temporary joining process can be performed in a short time. .

  Moreover, it is preferable that the said temporary rotating tool for temporary joining and the said rotational tool for main joining are the same rotating tools.

  According to such a friction stir welding method, it is not necessary to change the rotating tool for each process, so that the joining cycle can be shortened.

  According to the friction stir welding method according to the present invention, it is possible to prevent metal shortage at the joint portion at the inner corner.

It is a perspective view which shows the preparatory process of the friction stir welding method which concerns on 1st embodiment of this invention. It is a perspective view which shows the butt | matching process of the friction stir welding method which concerns on 1st embodiment. It is a perspective view which shows the arrangement | positioning process of the friction stir welding method which concerns on 1st embodiment. It is a perspective view which shows the temporary joining process of the friction stir welding method which concerns on 1st embodiment. It is sectional drawing which shows the temporary joining process of the friction stir welding method which concerns on 1st embodiment. It is a perspective view which shows the main joining process of the friction stir welding method which concerns on 1st embodiment. It is sectional drawing which shows the main joining process of the friction stir welding method which concerns on 1st embodiment. It is sectional drawing which shows the removal process of the friction stir welding method which concerns on 1st embodiment. It is a perspective view which shows the butt | matching process of the friction stir welding method which concerns on 2nd embodiment of this invention. It is a perspective view which shows the arrangement | positioning process of the friction stir welding method which concerns on 2nd embodiment. It is sectional drawing which shows the arrangement | positioning process of the friction stir welding method which concerns on 2nd embodiment. It is a perspective view which shows the temporary joining process of the friction stir welding method which concerns on 2nd embodiment. It is sectional drawing which shows the temporary joining process of the friction stir welding method which concerns on 2nd embodiment. It is sectional drawing which shows the main joining process of the friction stir welding method which concerns on 2nd embodiment. It is sectional drawing which shows the removal process of the friction stir welding method which concerns on 2nd embodiment.

[First embodiment]
The friction stir welding method according to the first embodiment of the present invention will be described in detail with reference to the drawings. In the first embodiment, two metal members (a first metal member and a second metal member) having different thicknesses are joined. Both the first metal member and the second metal member have convex portions on the surface, and the height of the surface changes. In the friction stir welding method according to the present embodiment, a preparation process, a butting process, an arrangement process, a temporary bonding process, a main bonding process, and a removing process are performed. In the following description, “front surface” means a surface opposite to the “back surface”.

  As shown in FIG. 1, the preparation process is a process of preparing the first metal member 10 and the second metal member 20 having different thicknesses. The first metal member 10 and the second metal member 20 are aluminum alloy plate-like members. The material of the 1st metal member 10 and the 2nd metal member 20 is suitably selected from the metals which can be friction-stirred, such as aluminum, aluminum alloy, copper, copper alloy, titanium, titanium alloy, magnesium, magnesium alloy, for example.

  The 1st metal member 10 is comprised by the main-body part 11 which exhibits a rectangular parallelepiped, and the convex part 12 which is formed on the main-body part 11 and exhibits cross-sectional trapezoid shape. The convex portion 12 is disposed at the center of the main body portion 11. The surface 12 a of the convex portion 12 is located above the surfaces 11 a and 11 b of the main body portion 11. The first inclined surface 12b of the convex part 12 is a part corresponding to the trapezoidal hypotenuse part, and connects the surface 11a of the main body part 11 and the surface 12a of the convex part 12. The second inclined surface 12c of the convex portion 12 is a portion corresponding to a trapezoidal hypotenuse and connects the surface 11b of the main body portion 11 and the surface 12a of the convex portion 12.

  The 2nd metal member 20 is comprised by the main-body part 21 which exhibits a rectangular parallelepiped, and the convex part 22 which is formed on the main-body part 21 and exhibits cross-sectional trapezoid shape. The convex portion 22 is disposed at the center of the main body portion 21. The thickness of the main body portion 21 of the second metal member 20 is thinner than the thickness of the main body portion 11 of the first metal member 10. The shape of the convex portion 22 is equivalent to that of the convex portion 12. The surface 22 a of the convex portion 22 is located above the surfaces 21 a and 21 b of the main body portion 21. The first inclined surface 22 b of the convex portion 22 is a portion corresponding to a trapezoidal hypotenuse and connects the surface 21 a of the main body portion 21 and the surface 22 a of the convex portion 22. Further, the second inclined surface 22 c of the convex portion 22 is a portion corresponding to a trapezoidal hypotenuse and connects the surface 21 b of the main body portion 21 and the surface 22 a of the convex portion 22.

  The butting process is a process in which the first metal member 10 and the second metal member 20 are butted together. In the butting step, as shown in FIGS. 1 and 2, the end surface 10 a of the first metal member 10 and the end surface 20 a of the second metal member 20 are butted. At this time, since the back surface (lower surface) 10c of the first metal member 10 and the back surface (lower surface) 20c of the second metal member 20 are flush with each other, each surface (upper surface) 11a of the main body portion 11 of the first metal member 10 is used. , 11b are located above the respective surfaces (upper surfaces) 21a, 21b of the main body portion 21 of the second metal member 20. Moreover, each surface (upper surface) 12a, 12b, 12c of the convex part 12 of the first metal member 10 is respectively higher than each surface (upper surface) 22a, 22b, 22c of the corresponding convex part 22 of the second metal member 20. positioned. The side surface 10d of the first metal member 10 and the side surface 20d of the second metal member 20 are flush with each other.

  The end faces 10a and 20a are brought into surface contact with each other by the butting process to form a butt portion J1. The butting portion J1 is formed such that its height position changes. At the end of the butted portion J1 (the upper end in the thickness direction of the second metal member 20), the end surface 10a of the first metal member 10 and the surfaces 21a, 22b, 22a, 22c, and 21b of the second metal member 20 An inner corner is formed. As for the inner corner, if the height (elevation) of the starting point (insertion position) of the friction stirrer is the reference height, there are sections having different reference heights and heights from the starting point to the end point. In the present embodiment, the inner corner includes a first flat portion Ca, a first inclined portion Cb, a second flat portion Cc, a second inclined portion Cd, and a third flat portion Ce.

  Moreover, tab material T, T is arrange | positioned at a butt | matching process. The tab material T has the same thickness as the main body 21 of the second metal member 20. In the butting process, the tab materials T and T are arranged at both ends of the inner corner in the extending direction. The surface Ta of the tab material T is flush with the surfaces 21 a and 21 b of the second metal member 2. The back surface Tb of the tab material T is flush with the back surface 10 c of the first metal member 1 and the back surface 20 c of the second metal member 2.

  An arrangement | positioning process is a process of arrange | positioning the auxiliary member 30 in an inner corner. As shown in FIG. 2, the auxiliary member 30 is a metal material and has a plate shape. The auxiliary member 30 is preferably made of the same material as the first metal member 10 and the second metal member 20. The auxiliary member 30 has a shape in surface contact with the surface of the second metal member 20. The thickness of the auxiliary member 30 is set to such an extent that a metal shortage does not occur in the joined portion (plasticization region) after the main joining step is finished.

  In the placement step, the side surface 30c of the auxiliary member 30 is abutted against the end surface 10a of the first metal member 10, and the back surface 30b of the auxiliary member 30 is brought into surface contact with the surface of the second metal member 20 as shown in FIG. The surface 30 a of the auxiliary member 30 is at a position lower than the surface of the first metal member 10.

  As shown in FIG. 4, the temporary joining step is a step of temporarily joining the inner corner using a rotary tool F (temporary joining rotary tool). The rotary tool F is made of, for example, tool steel. The rotary tool F includes a connecting portion F1 and a stirring pin F2. The connecting part F1 is a part connected to the rotating shaft of the friction stirrer. The connecting part F1 has a cylindrical shape.

  The stirring pin F2 extends from the connecting portion F1 and is coaxial with the connecting portion F1. The stirring pin F2 is tapered as it is separated from the connecting portion F1. A spiral groove is formed on the outer peripheral surface of the stirring pin F2. In the first embodiment, in order to rotate the rotary tool F to the right, the spiral groove is formed counterclockwise as it goes from the proximal end to the distal end.

  In addition, when rotating the rotation tool F counterclockwise, it is preferable to form the spiral groove clockwise as it goes from the proximal end to the distal end. By setting the spiral groove in this way, the metal plastically fluidized during friction stirring is guided to the tip side of the stirring pin F2 by the spiral groove. Thereby, the quantity of the metal which overflows outside the to-be-joined metal member (the 1st metal member 10, the 2nd metal member 20, and the auxiliary member 30) can be decreased.

  In the temporary joining step, as shown in FIG. 5, only the stirring pin F2 of the rotating tool F rotated to the right is brought into contact with the inner corner of the end portion of the abutting portion J1 to perform spot tacking. In the temporary joining process, only the stirring pin F2 is shallowly pushed into the butt portion J1 with a predetermined interval. At this time, the rotary tool F is inclined so that the stirring pin F2 does not interfere with the upper part of the end surface 10a of the first metal member 10. The rotary tool F is inclined so that the connecting portion F1 is on the second metal member 20 side. A point-like plasticized region W1 is formed in the trace of pushing of the stirring pin F2.

  The rotary tool F is preferably attached to an arm robot (not shown) provided with a rotation drive means such as a spindle unit at the tip. Thereby, since the rotation center axis | shaft of the rotation tool F can be tilted, the spot temporary attachment of an inner corner can be performed easily.

  In the temporary joining step, spot tacking is also performed on the abutting portion between the first metal member 10 and the tab material T and the abutting portion between the second metal member 20 and the tab material T. The metal member 10 and the second metal member 20 are temporarily joined.

  As shown in FIG. 6, the main joining step is a step of performing friction stir welding on the inner corner of the abutting portion J <b> 1 using the rotary tool F (the main welding rotary tool). In the main joining step, after the rotation tool F rotated to the right is inserted into the start position Sp set on one of the tab members T, the rotation tool F is relatively moved along the inner corner of the abutting portion J1. In the main joining step, the auxiliary member 30 is set to be positioned on the right side in the traveling direction of the rotary tool F. In the main joining step, friction stir welding is performed with only the stirring pin F2 in contact with the first metal member 10, the second metal member 20, and the auxiliary member 30, and the proximal end side of the stirring pin F2 is exposed.

  On the tab material T, the rotation tool F is moved in a state where the rotation center axis of the rotation tool F is orthogonal to the surface Ta of the tab material T. When the rotary tool F moves to the vicinity of the inner corner, the rotary tool F is inclined to the second metal member 20 side (the metal member side having a low surface). As shown in FIG. 7, in this embodiment, the rotation center axis of the rotary tool F is inclined by about 45 to 60 ° with respect to the surface 22a of the second metal member 20, and the tip of the stirring pin F2 is The first metal member 10 and the second metal member 20 are not too far apart from the abutting surface (the contact surface between the end surface 10a of the first metal member 10 and the end surface 20a of the second metal member 20).

  When the rotary tool F moves away from the inner corner and moves onto the other tab member T, the rotation center axis of the rotary tool F is returned to a state orthogonal to the surface Ta of the tab member T. When the rotation tool F reaches the end position set for the other tab material T, the rotation tool F is detached from the tab material T. Through the above steps, a plasticized region W2 is formed in the movement locus of the rotary tool F.

  In the main joining process according to the first embodiment, the first metal member 10, the second metal member 20, and the auxiliary metal plate are only connected to the stirring pin F2 while the insertion depth of the stirring pin F2 with respect to the inner corner of the abutting portion J1 is kept substantially constant. Friction stirring is performed in a state where the member 30 is in contact. Further, when the end surface 10a of the first metal member 10 is viewed from the front, the rotary tool F is relatively moved so that the rotation center axis of the rotary tool F and the vertical direction are parallel to each other.

  In the main joining step according to the first embodiment, friction stirring is performed by moving the rotary tool F up and down with respect to a gantry (not shown) to which the first metal member 10 and the second metal member 20 are fixed. Thereby, the depth of the plasticization area | region W2 can be made substantially equivalent. The “insertion depth” of the stirring pin F2 means a distance from the surface of the second metal member 20 on the rotation center axis of the rotating tool F to the tip of the stirring pin F2.

  In the main joining process according to the first embodiment, the rotary tool F is moved up and down with respect to the gantry (not shown), but the height position of the rotary tool F is fixed and the gantry is moved up and down. Friction stirring may be performed.

  As shown in FIGS. 6 and 7, in the main joining step, the rotation direction and the traveling direction of the rotating tool F are set so that the auxiliary member 30 is positioned on the right side in the traveling direction while rotating the rotating tool F to the right. For example, when the rotational speed of the rotary tool F is low, the shearing side (advancing side: the rotating tool of the rotating tool is compared with the flow side (retreating side: the side where the moving speed of the rotating tool is subtracted from the tangential speed on the outer periphery of the rotating tool)). Since the temperature of the plastic fluidized material is likely to increase on the side where the moving speed of the rotary tool is added to the tangential speed on the outer periphery, there is a tendency that more burrs V are generated on the shear side outside the plasticized region W2. On the other hand, for example, when the rotational speed of the rotary tool F is fast, the temperature of the plastic fluidized material increases on the shear side, but a larger amount of burrs V are generated on the flow side outside the plasticized region W2 because the rotational speed is faster. There is a tendency.

  In this embodiment, since the rotation speed of the rotary tool F is set high, as shown in FIG. 7, there is a tendency that many burrs V are generated on the flow side outside the plasticized region W2. That is, the burrs V can be collected on the auxiliary member 30. Further, by setting the rotation speed of the rotary tool F faster, the moving speed (feed speed) of the rotary tool F can be increased. Thereby, a joining cycle can be shortened.

  Which side of the rotating tool F travels in the direction of travel of the rotating tool F during the friction stirring process depends on the joining conditions. The joining conditions include the rotational speed, rotational direction, moving speed (feeding speed) of the rotary tool F, the inclination angle (taper angle) of the stirring pin F2, the first metal member 10, the second metal member 20, and the auxiliary member 30. It is determined by each element such as the material and the thickness of the auxiliary member 30 and the combination of these elements. It is preferable to set the side where the burrs V are generated or the side where many burrs V are generated to be the auxiliary member 30 side according to the joining conditions, since the removal step described later can be easily performed.

  The removing step is a step of removing the auxiliary member 30 from the first metal member 10 and the second metal member 20 as shown in FIG. In the removing step, the auxiliary member 30 is bent in a direction away from the second metal member 20 and cut away. In the removal process, a cutting device or the like may be used, but in this embodiment, the removal process is performed manually.

  According to the friction stir welding method according to the first embodiment described above, in addition to the first metal member 10 and the second metal member 20, the auxiliary member 30 is also friction stir welded while being in contact with the stirring pin F2. It is possible to prevent metal shortage at the joint (plasticized region W2). In addition, since the shape of the auxiliary member 30 is formed in accordance with the shape of the surface of the second metal member 20, it is possible to suitably join the inner corner where the height of the butt portion J1 changes.

  Further, according to the present embodiment, the auxiliary member 30 in which the burrs V are gathered can be removed from the first metal member 10 and the second metal member 20. According to this, the burr V can be easily removed together with the auxiliary member 30.

  Moreover, since the temporary joining process is performed by spot tacking as in this embodiment, the amount of heat input can be reduced. Thereby, the thermal distortion of the 1st metal member 10 and the 2nd metal member 20 can be made small. Moreover, according to this embodiment, a temporary joining process can be performed in a short time. Further, the same rotary tool F is used in the temporary joining process and the main joining process. Thereby, since it is not necessary to replace | exchange a rotating tool at each process, work efficiency can be improved.

  Also in the main joining process, the load acting on the friction stirrer is reduced by performing the friction stir welding with only the stirring pin F2 in contact with the first metal member 10, the second metal member 20, and the auxiliary member 30. In this state, the deep position of the butt J1 can be joined. Furthermore, since only the stirring pin F2 is inserted in both the temporary joining step and the main joining step, the heat input can be further reduced and the thermal strain can be reduced.

  Moreover, in this joining process, since the friction stir is performed while the insertion depth of the stirring pin F2 with respect to the inner corner of the butt portion J1 whose height changes is kept substantially constant, the joining strength of the joint is kept almost constant. be able to.

  While the first embodiment of the present invention has been described above, design changes can be made as appropriate without departing from the spirit of the present invention. For example, different rotary tools may be used in the temporary bonding process and the main bonding process. Moreover, in this embodiment, when the end surface 10a of the 1st metal member 10 was seen from the front about this joining process, the friction stir welding was performed so that the rotation center axis | shaft of the rotation tool F and a perpendicular direction might become parallel. . In the main joining step, when the end surface 10a of the first metal member 10 is viewed from the front, the main axis of rotation of the rotary tool F, the first inclined surface 22b, and the second inclined surface 22c are made perpendicular to each other. You may adjust so that the depth of the plasticization area | region W2 of a process may become fixed. In the temporary joining step, welding may be performed instead of friction stirring. Although the kind of welding is not ask | required, it can carry out by laser welding, TIG welding, or MIG welding, for example. In the temporary joining step, the first metal member 10, the second metal member 20, and the auxiliary member 30 are spot-temporarily attached, but only the first metal member 10 and the auxiliary member 30 may be temporarily attached.

[Second Embodiment]
Next, the friction stir welding method according to the second embodiment of the present invention will be described. In the friction stir welding method according to the second embodiment, a preparation process, a butting process, an arrangement process, a temporary bonding process, a main bonding process, and a removing process are performed. In the friction stir welding method according to the second embodiment, the auxiliary member disposition method is different from that of the first embodiment. In the second embodiment, the description will focus on the parts that are different from the first embodiment. As shown in FIG. 9, the preparation process and the matching process are common to the first embodiment.

  The arrangement process is a process of arranging the auxiliary member 40. The auxiliary member 40 is a plate-like member made of the same material as the first metal member 10 and the second metal member 20. A notch 41 is formed in the lower part of the auxiliary member 40. The notch 41 has a shape that makes contact with the convex portion 22 of the second metal member 20 without a gap. In the placement step, the auxiliary member 40 is placed upright along the inner corners of the first metal member 10 and the second metal member 20, as shown in FIGS. 10A and 10B.

  In the arranging step, as shown in FIG. 10B, the one end surface 40 d of the auxiliary member 40 and the surface of the second metal member 20 are brought into surface contact with the surface 40 a of the auxiliary member 40 and the end surface 10 a of the first metal member 10. Make contact. The other end surface 40 c of the auxiliary member 40 is positioned above the surface of the first metal member 10.

  As shown in FIG. 11, the temporary joining step is a step of temporarily joining the inner corner using a rotary tool F (temporary joining rotary tool). In the temporary joining step, spot tacking is performed by bringing only the stirring pin F2 of the rotating tool F rotated counterclockwise into contact with the inner corner of the end portion of the butting portion J1. In the temporary joining process, only the stirring pin F2 is shallowly pushed into the butt portion J1 with a predetermined interval. As shown in FIG. 12, the rotary tool F is inclined so that the connecting portion F1 is on the second metal member 20 side. A plasticized region W1 is formed at the trace of pushing of the stirring pin F2.

  As shown in FIG. 13, the main joining step is a step of performing friction stir welding on the inner corner of the abutting portion J <b> 1 using the rotary tool F (the main welding rotary tool). In the main joining step of the present embodiment, the auxiliary member 40 is positioned on the left side in the traveling direction, and the rotating tool F is rotated counterclockwise. Accordingly, the right side in the traveling direction of the rotary tool F is the shear side, and the left side is the flow side. In the present embodiment, since the rotary tool F is rotated at a high speed, the burrs V generated by friction stirring are collected in the auxiliary member 40.

  The removing step is a step of removing the auxiliary member 40 from the first metal member 10 and the second metal member 20 as shown in FIG. In the removing step, the auxiliary member 40 is bent in a direction away from the first metal member 10 and cut away. In the removal process, a cutting device or the like may be used, but in this embodiment, the removal process is performed manually.

  The effect substantially equivalent to 1st embodiment can be acquired also by the friction stir welding method which concerns on 2nd embodiment demonstrated above. In the arrangement process of this embodiment, since the other end surface 40c of the auxiliary member 40 is positioned above the surface of the first metal member 10, the auxiliary member 40 can be easily bent. Thereby, a removal process can be performed easily. In the temporary joining step, the first metal member 10, the second metal member 20, and the auxiliary member 40 are spot-temporarily attached, but only the second metal member 20 and the auxiliary member 40 may be temporarily attached.

  Although the embodiments of the present invention have been described above, design changes can be made as appropriate without departing from the spirit of the present invention. For example, the first metal member and the second metal member may have different shapes. Further, the first metal member and the second metal member may be abutted by shifting the same shape member. Moreover, you may perform preliminary joining by friction stirring or welding with respect to the butt | matching part J1 of the 1st metal member 10 and the 2nd metal member 20 before a temporary joining process. The preliminary joining may be performed by joining the butt portion J1 as a whole or by spot temporary joining. Thereby, the opening of the 1st metal member 10 and the 2nd metal member 20 can be prevented in the case of an arrangement process and a temporary joining process.

10 1st metal member 20 2nd metal member F Rotating tool (Rotating tool for temporary joining, Rotating tool for main joining)
F2 Stirring pin J1 Butting part T Tab material W1 Plasticization area W2 Plasticization area

Claims (7)

A friction stir welding method for joining a first metal member and a second metal member using a main welding rotary tool provided with a stirring pin,
The first metal member and the second metal member whose surface height changes are abutted to form an inner corner formed by the end surface of the first metal member and the surface of the second metal member. A butting process for forming a butting portion of varying length,
An arranging step of arranging an auxiliary member along the inner corner;
The inner corner is inserted in a state where only the stirring pin is brought into contact with the first metal member, the second metal member, and the auxiliary member by inserting the stirring pin of the rotating tool for main joining rotating at the inner corner. And a main joining step of performing friction stir welding along the friction stir welding method.   The friction stir welding method according to claim 1, further comprising a removing step of removing the auxiliary member on which the burr is formed from the first metal member and the second metal member.   3. The friction stir welding method according to claim 2, wherein in the main joining step, joining conditions are set so that burrs generated by friction stirring are formed on the auxiliary member.   In the arranging step, the auxiliary member is brought into surface contact with the surface of the second metal member, and the auxiliary member is arranged so that the surface of the auxiliary member is lower than the surface of the first metal member. The friction stir welding method according to claim 2 or claim 3, wherein   In the arranging step, the auxiliary member is placed in contact with the end surface of the first metal member, and the auxiliary member is arranged such that the end surface of the auxiliary member is higher than the surface of the first metal member. The friction stir welding method according to claim 2 or claim 3, wherein Before the main joining step, only the stirring pin of the temporary joining rotary tool is inserted into the inner corner,
6. The method according to claim 1, further comprising a temporary joining step in which at least one of the first metal member and the second metal member and the auxiliary member are friction stir welded with a spot. The friction stir welding method according to 1.   The friction stir welding method according to claim 6, wherein the temporary welding rotary tool and the main welding rotary tool are the same rotary tool.

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