JP2015223609A - Frictional agitation joint method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a metal shortage of an inner corner, when frictionally agitating-joining a butting part from the inner corner of mutual metal members.SOLUTION: A frictional agitation joint method for joining two metal members 1 and 2 by using a joining rotary tool F having an agitation pin F2, includes a butting process of forming a front view T-shaped joining object metal member by forming a butting part J1 by butting an end surface 2c of the other metal member 2 against a side surface 1a of one metal member 1, a padding process of covering the inner corner with weld metal U1 by applying padding to at least one inner corner of the joining object metall member and a joining process of executing frictional agitation of the butting part J1 in a state of contacting only the agitation pin F2 with the weld metal U1 and the joining object metal member by inserting the rotated agitation pin F2 into the inner corner.

Description

  The present invention relates to a friction stir welding method for joining metal members together by friction stirring.

  Friction stir welding (FSW = Friction Stir Welding) is known as a method for joining metal members. Friction stir welding is a method in which the metal members are fixed together by rotating the rotary tool along the abutting portion between the metal members and plastically flowing the metal at the abutting portion by frictional heat between the rotating tool and the metal member. Phase joining is performed.

  For example, Patent Document 1 discloses a technique for performing friction stir welding of a butted portion by inserting only a stirring pin of a rotary tool into inner corners of metal members vertically butted. The conventional rotary tool of the friction stir welding method does not include a shoulder portion, and only the stirring pin of the rotary tool is inserted into the inner corner, so that the friction stir can be performed up to a deep position of the butt portion.

JP 2013-049072 A

  However, in the conventional friction stir welding method, the plastic fluidized metal is not pressed by the shoulder portion, so that the plastic fluidized metal tends to overflow to the outside of the inner corner. As a result, there is a problem that the inner corner becomes lack of metal.

  Then, this invention makes it a subject to provide the friction stir welding method which can eliminate the metal shortage of an inner corner, when abutting part is friction stir welded from the inner corner of metal members.

  In order to solve the above-mentioned problem, the present invention is a friction stir welding method for joining two metal members using a rotary tool equipped with a stirring pin, and the end surface of the other metal member on the side surface of one metal member. A butting step for forming a T-shaped joined metal member in front view by forming a butted portion, and overlay welding is applied to at least one inner corner of the joined metal member to form the inner Overlay welding process for covering corners, and joining in which friction stir of the butt portion is performed with a rotating stirring pin inserted into the inner corner and only the stirring pin in contact with the weld metal and the metal member to be joined And a process.

  According to this friction stir welding method, the metal shortage in the inner corner can be solved by performing friction stir after performing the overlay welding on the inner corner formed by abutting the metal members in advance.

  Further, in the build-up welding step, build-up welding is performed on two inner corners of the bonded metal member to cover each inner corner with a weld metal, and in the bonding step, two inner corners of the bonded metal member are covered. A first joining step in which friction stirring is performed on one side and a second joining step in which friction stirring is performed on the other. In the second joining step, the stirring pin is placed in the plasticized region formed in the first joining step. Friction stirring is preferably performed while entering.

  According to this friction stir welding method, the joining strength between the metal members can be increased in the overlay welding process, so that the joining process can be performed stably. Further, by performing frictional stirring on the two inner corners, the air tightness and water tightness of the joint can be enhanced, and the joint strength can be enhanced. Furthermore, the airtightness and watertightness can be further improved by performing the other joining step in a state where the stirring pin is inserted into one plasticized region.

  Further, the present invention is a friction stir welding method for joining two metal members using a rotary tool equipped with a stirring pin, and abutting portions are formed by abutting the end face of the other metal member on the side surface of one metal member. A joining step of forming a T-shaped joined metal member in front view by forming, and an auxiliary member that covers the inner corner with the auxiliary member by arranging an auxiliary member at at least one inner corner of the joined metal member And a joining step of inserting the rotated stirring pin into the inner corner and performing frictional stirring of the butted portion in a state where only the stirring pin is in contact with the auxiliary member and the metal member to be joined. It is characterized by that.

  According to this friction stir welding method, the shortage of metal in the inner corner can be solved by performing friction stirring after the auxiliary member is previously placed in the inner corner formed by abutting the metal members.

  Further, in the auxiliary member arranging step, the auxiliary members are respectively arranged at two inner corners of the metal member to be joined and each inner corner is covered with the auxiliary member, and in the joining step, two of the metal members to be joined are covered. A first joining step for performing friction stirring on one of the inner corners and a second joining step for performing friction stirring on the other are performed, and in the second joining step, the plasticizing region formed in the first joining step It is preferable to perform frictional stirring while inserting the stirring pin.

  According to this friction stir welding method, by performing friction stirring on the two inner corners, the air tightness and water tightness of the joint can be increased, and the joint strength can be increased. Moreover, airtightness and watertightness can be further improved by performing the other joining process in the state which put the stirring pin in one plasticization area | region.

  Further, after the abutting step, it includes a tab material arranging step of abutting a tab material having two tool insertion surfaces against the front surface of the metal member to be joined, and in the tab material arranging step, an exposed surface of one of the auxiliary members Preferably, the one tool insertion surface of the tab member is flush with the exposed surface of the other auxiliary member and the other tool insertion surface of the tab member is flush.

  According to this friction stir welding method, the insertion position of the rotary tool in the joining process can be set to the tab material. Moreover, friction stirring can be performed smoothly by making the exposed surface of each auxiliary member and the two tool insertion surfaces of the tab material flush with each other. Moreover, since the insertion position of two joining processes can be set to one tab material, work efficiency can be improved.

  According to the friction stir welding method according to the present invention, when the butt portion is friction stir welded from the inner corners of the metal members, the metal shortage in the inner corners can be solved.

It is the side view which showed the rotation tool for joining of this embodiment. (A) is sectional drawing which shows the butt | matching process and overlay welding process which concern on 1st embodiment, (b) is sectional drawing which shows a 1st joining process. It is sectional drawing which shows the 2nd joining process which concerns on 1st embodiment. (A) is sectional drawing which shows the matching process and auxiliary member arrangement | positioning process which concern on 2nd embodiment. It is a perspective view which shows the tab material arrangement | positioning process which concerns on 2nd embodiment. It is a perspective view which shows the 1st joining process which concerns on 2nd embodiment. It is sectional drawing which shows the 1st joining process which concerns on 2nd embodiment. It is sectional drawing which shows the 2nd joining process which concerns on 2nd embodiment.

[First embodiment]
Embodiments of the present invention will be described in detail with reference to the drawings. First, the joining rotary tool used in this embodiment will be described.

  As shown in FIG. 1, the joining rotary tool F is composed of a connecting portion F1 and a stirring pin F2. The joining rotary tool F corresponds to a “rotary tool” in the claims. The joining rotary tool F is made of, for example, tool steel. The connecting part F1 is a part connected to a rotating shaft (not shown) of the friction stirrer. The connecting portion F1 has a cylindrical shape, and is formed with screw holes B and B to which bolts are fastened.

  The stirring pin F2 hangs down 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 F3 is formed on the outer peripheral surface of the stirring pin F2. In the present embodiment, the spiral groove F3 is formed in a counterclockwise direction from the proximal end toward the distal end in order to rotate the joining rotary tool F to the right. In other words, the spiral groove F3 is formed counterclockwise as viewed from above when the spiral groove F3 is traced from the base end to the tip.

  In addition, when rotating the rotation tool F for joining counterclockwise, it is preferable to form the spiral groove F3 clockwise as it goes to the front-end | tip from a base end. In other words, the spiral groove F3 in this case is formed clockwise when viewed from above when the spiral groove F3 is traced from the proximal end to the distal end. By setting the spiral groove F3 in this way, the plastic fluidized metal at the time of frictional stirring is guided to the tip side of the stirring pin F2 by the spiral groove F3. Thereby, the quantity of the metal which overflows to the exterior of a to-be-joined metal member (metal members 1 and 2) can be decreased.

  When performing friction stir welding using the welding rotary tool F, only the rotated stirring pin F2 is inserted into the metal member to be bonded, and the metal member to be bonded and the connecting portion F1 are moved apart from each other. In other words, the friction stir welding is performed with the base end portion of the stirring pin F2 exposed.

  Although a specific illustration is omitted, when performing the joining process described later, for example, the joining rotary tool F is attached to a robot arm having a rotation driving means such as a spindle unit at the tip, and friction stirring can be performed. . According to such a friction stirrer, the insertion position and the insertion angle of the joining rotary tool F can be easily changed.

  Next, the friction stir welding method according to the first embodiment of the present invention will be described. In the friction stir welding method according to the present embodiment, a butt process, an overlay welding process, and a joining process are performed.

  As shown in FIG. 2, in this embodiment, the butt | matching part J1 formed by abutting the metal members 1 and 2 is joined by friction stirring. The metal members 1 and 2 are made of metal and have a rectangular parallelepiped (plate shape). The metal members 1 and 2 are formed of the same material. The material of the metal members 1 and 2 is not particularly limited as long as it is a metal capable of friction stir, but may be appropriately selected from, for example, aluminum, aluminum alloy, copper, copper alloy, titanium, titanium alloy, magnesium, magnesium alloy, and the like. .

  The butting process is a process in which the metal members 1 and 2 are butted together to form the butting portion J1. As shown in FIG. 2A, in the butting step, a butting portion J1 is formed by butting the end surface 2c of the metal member 2 at the center of the side surface 1a of the metal member 1. By the butting process, a metal member to be joined including the metal members 1 and 2 is formed. The bonded metal member has a T-shape when viewed from the front. A first inner corner S1 and a second inner corner S2 are formed on both sides of the metal member 2. The first inner corner S <b> 1 is a corner formed by the side surface 1 a of the metal member 1 and the side surface 2 a of the metal member 2. The second inner corner S <b> 2 is a corner formed by the side surface 1 a of the metal member 1 and the side surface 2 b of the metal member 2.

  The build-up welding process is a process of performing build-up welding on the butt joint J1. As shown in FIG. 2A, in the build-up welding process, build-up welding such as TIG welding or MIG welding is performed over the extending direction of the first inner corner S1 and the second inner corner S2. By performing overlay welding, the first inner corner S1 and the second inner corner S2 are respectively covered with the weld metals U1 and U2. As for the build-up amount of weld metal U1, U2, after performing a joining process, a ditch | groove is not formed in the surface of plasticization area | region W1, W2 (joining part), or weld metal U1, U2 does not protrude from the said surface. It is preferable to set the degree.

  A joining process is a process of performing frictional stirring with respect to the butt | matching part J1 using the rotating tool F for joining. As shown in FIGS. 2B and 3, in the present embodiment, the joining process includes a first joining process in which friction stirring is performed on the first inner corner S <b> 1, and a second process in which friction stirring is performed on the second inner corner S <b> 2. A two-joining process is performed.

  In the first joining step, the joining rotary tool F rotated to the right is inserted into the first inner corner S1, and friction stir is performed so as to trace the weld metal U1. As shown in FIG. 2B, in the first joining step, friction stirring is performed in a state where only the stirring pin F2 is in contact with the metal members 1, 2 and the weld metal U1. That is, friction stirring is performed with the proximal end side of the stirring pin F2 exposed. A plasticized region W1 is formed in the movement locus of the welding rotary tool F. The insertion angle of the stirring pin F2 may be set as appropriate, but in this embodiment, the rotation center axis of the bonding rotary tool F is inclined by 45 ° with respect to the vertical plane.

  In the second joining step, the joining rotary tool F rotated to the right is inserted into the second inner corner S2, and friction stirring is performed so as to trace the weld metal U2 (see FIG. 2A). As shown in FIG. 3, in the second joining step, friction stirring is performed in a state where only the stirring pin F2 is in contact with the metal members 1, 2 and the weld metal U2. That is, friction stirring is performed with the proximal end side of the stirring pin F2 exposed. A plasticized region W2 is formed on the movement locus of the welding rotary tool F. The insertion angle of the stirring pin F2 may be set as appropriate, but in this embodiment, the rotation center axis of the bonding rotary tool F is inclined by 45 ° with respect to the vertical plane.

  In the second joining step, it is preferable to insert the stirring pin F2 so that at least the plasticizing region W2 comes into contact with the plasticizing region W1, but in this embodiment, the tip of the stirring pin F2 enters the plasticizing region W1. Is set.

  According to the friction stir welding method described above, overlay welding is performed in advance on the first inner corner S1 and the second inner corner S2, and friction stir is performed on the butt joint J1 from above the weld metals U1 and U2. The metal shortage at the first inner corner S1 and the second inner corner S2 can be solved.

  Moreover, in this embodiment, since build-up welding is performed to two inner corners (1st inner corner S1 and 2nd inner corner S2), the joint strength of a to-be-joined metal member can be improved. Thereby, a joining process can be performed stably.

  Further, in the present embodiment, by performing frictional stirring on the two inner corners (first inner corner S1 and second inner corner S2), the air tightness and water tightness of the joint portion can be increased, and the joint strength is increased. be able to. In addition, there is a possibility that a joining defect may occur in the plasticized region W1 formed in the first joining step, but by performing frictional stirring by inserting the stirring pin F2 into the plasticized region W1 as in the present embodiment, The junction defect can be repaired. Thereby, watertightness and airtightness can be improved more.

  In the build-up welding process, build-up welding is performed on both the first inner corner S1 and the second inner corner S2 in the present embodiment, but it may be performed at least in any one. Further, in this case, the friction stir may be performed on the inner corner where the overlay welding is performed.

[Second Embodiment]
Next, the friction stir welding method according to the second embodiment of the present invention will be described. The friction stir welding method according to the present embodiment is different from the first embodiment in that the first auxiliary member 10 and the second auxiliary member 11 are disposed at the first inner corner S1 and the second inner corner S2, respectively. The friction stir welding method according to the second embodiment will be described with a focus on differences from the first embodiment.

  In the friction stir welding method according to the present embodiment, a butt process, an auxiliary member arranging process, a tab material arranging process, and a joining process are performed. As shown in FIG. 4, the matching process is performed in the same manner as in the first embodiment.

  The auxiliary member arranging step is a step of arranging the first auxiliary member 10 and the second auxiliary member 11 at the abutting portion J1. The first auxiliary member 10 and the second auxiliary member 11 are made of metal and are triangular prisms. The first auxiliary member 10 and the second auxiliary member 11 are formed in the same shape. Although the 1st auxiliary member 10 and the 2nd auxiliary member 11 should just be a metal which can be friction-stirred, it is preferable to be formed with the material equivalent to the metal members 1 and 2 like this embodiment.

  The 1st auxiliary member 10 and the 2nd auxiliary member 11 exhibit a cross-sectional right angled isosceles triangle. The length of the 1st auxiliary member 10 and the 2nd auxiliary member 11 is equivalent to the length of the butt | matching part J1. As shown in FIG. 4, in the auxiliary member arranging step, the bottom surface 10 a of the first auxiliary member 10 is brought into surface contact with the side surface 1 a of the metal member 1, and the rising surface 10 b of the first auxiliary member 10 is brought into contact with the side surface 2 a of the metal member 2. Make surface contact. Thereby, the first inner corner S <b> 1 is covered with the first auxiliary member 10.

  Further, in the auxiliary member arranging step, the bottom surface 11 a of the second auxiliary member 11 is brought into surface contact with the side surface 1 a of the metal member 1, and the rising surface 11 b of the second auxiliary member 11 is brought into surface contact with the side surface 2 b of the metal member 2. As a result, the second inner corner S <b> 2 is covered with the second auxiliary member 11.

  The size of the first auxiliary member 10 and the second auxiliary member 11 is such that, after performing the joining process, concave grooves are formed on the surfaces of the plasticized regions W1, W2 (joining portions), or each auxiliary member is provided on the surface. It is preferable to set it to such an extent that it does not remain.

  A tab material arrangement | positioning process is a process of arrange | positioning the tab material T in the front of a to-be-joined metal member. As shown in FIG. 5, the tab member T is formed of a metal equivalent to the metal members 1 and 2 and has a triangular prism shape. The cross section of the tab material T is a right-angled isosceles triangle. The tab material T includes a bottom surface T1 and inclined surfaces T2 and T3.

  In the tab material arranging step, the bottom surface T1 of the tab material T and the side surface 1b of the metal member 1 are flush with each other, and the end surface of the tab material T is placed in front of the metal member to be joined (the front surface 1d of the metal member 1 and the metal member 2). Are brought into surface contact with the front surface 2d). And the tab material T and a to-be-joined metal member are temporarily joined by welding. By the tab material arranging step, the inclined surface (tool insertion surface) T2 of the tab material T and the inclined surface (exposed surface) 10c of the first auxiliary member 10 are flush with each other. Further, the inclined surface (tool insertion surface) T3 of the tab member T and the inclined surface (exposed surface) 11c of the second auxiliary member 11 are flush with each other.

  A joining process is a process of performing frictional stirring with respect to the butt | matching part J1 using the rotating tool F for joining. As shown in FIG.6 and FIG.7, in this real form, the 1st joining process which performs friction stirring to 1st inner corner S1, and the 2nd joining process which performs friction stirring to 2nd inner corner S2 are performed.

  In the first joining step, first, the joining rotation tool F rotated to the right is inserted into the start position SP set on the inclined surface T2 of the tab member T. In this real view form, it inserts so that the rotation center axis | shaft of the rotation tool F for joining may become perpendicular | vertical with respect to the inclined surface T2. And the rotation tool F for joining is relatively moved toward the to-be-joined metal member direction.

  When the rotating tool F for joining reaches the first auxiliary member 10, friction agitation is performed on the butted portion J1 while tracing the inclined surface 10c as it is. That is, the rotating tool F for bonding is relatively moved in the depth direction from the front side of the metal member to be bonded (the front surface 1d of the metal member 1 and the front surface 2d of the metal member 2). As shown in FIG. 7, in the first joining step, friction stirring is performed in a state where only the stirring pin F <b> 2 is in contact with the metal members 1, 2 and the first auxiliary member 10. That is, friction stirring is performed with the proximal end side of the stirring pin F2 exposed. A plasticized region W1 is formed in the movement locus of the welding rotary tool F. The insertion angle of the stirring pin F2 may be set as appropriate, but in this embodiment, the rotation center axis of the bonding rotary tool F is inclined by 45 ° with respect to the vertical plane. That is, the friction stirring is performed in a state where the rotation center axis of the bonding rotary tool F is set to be perpendicular to the inclined surface 10c.

  In the second joining step, first, the joining rotary tool F rotated to the right is inserted into the start position set on the inclined surface T3 of the tab material T. In this real view form, it inserts so that the rotation center axis | shaft of the rotation tool F for joining may become perpendicular | vertical with respect to the inclined surface T3. And the rotation tool F for joining is relatively moved toward the to-be-joined metal member direction.

  When the rotating tool F for joining reaches the second auxiliary member 11, friction stir is performed on the butt portion J1 while tracing the inclined surface 11c as it is. As shown in FIG. 8, in the second joining step, friction stirring is performed in a state where only the stirring pin F <b> 2 is in contact with the metal members 1, 2 and the second auxiliary member 11. That is, friction stirring is performed with the proximal end side of the stirring pin F2 exposed. A plasticized region W2 is formed on the movement locus of the welding rotary tool F. The insertion angle of the stirring pin F2 may be set as appropriate, but in this embodiment, the rotation center axis of the bonding rotary tool F is inclined by 45 ° with respect to the vertical plane. That is, the friction stir is performed in a state where the rotation center axis of the bonding rotary tool F is set perpendicular to the inclined surface 11c.

  In the second joining step, it is preferable to insert the stirring pin F2 so that at least the plasticizing region W2 comes into contact with the plasticizing region W1, but in this embodiment, the tip of the stirring pin F2 enters the plasticizing region W1. Is set. When the joining process is completed, the tab material T is cut out from the metal member to be joined.

  According to the friction stir welding method described above, the first auxiliary member 10 and the second auxiliary member 11 are arranged in advance in the first inner corner S1 and the second inner corner S2, respectively, and the first auxiliary member 10 and the second auxiliary member 11 are arranged. By performing frictional stirring on the butt portion J1 from above the member 11, the metal shortage at the first inner corner S1 and the second inner corner S2 can be solved.

  Further, in the present embodiment, by performing frictional stirring on the two inner corners (first inner corner S1 and second inner corner S2), the air tightness and water tightness of the joint portion can be increased, and the joint strength is increased. be able to. In addition, there is a possibility that a joining defect may occur in the plasticized region W1 formed in the first joining step, but by performing frictional stirring by inserting the stirring pin F2 into the plasticized region W1 as in the present embodiment, The junction defect can be repaired. Thereby, watertightness and airtightness can be improved more.

  In addition, by arranging the tab material T, the start position (insertion position) of the joining rotary tool F in the joining process can be set to the tab material T. Moreover, since the start position (insertion position) of a 1st joining process and a 2nd joining process can be set to one tab material T, work efficiency can be improved. Further, the inclined surface (tool insertion surface) T2 of the tab material T and the inclined surface (exposed surface) 10c of the first auxiliary member 10 are set to be flush with each other, and the inclined surface (tool insertion surface) T3 of the tab material T is set. And the inclined surface (exposed surface) 11c of the second auxiliary member 11 are set to be flush with each other, the joining process can be performed smoothly.

  In the present embodiment, since the first auxiliary member 10 and the second auxiliary member 11 are triangular prisms, the surfaces into which the stirring pin F2 is inserted, that is, the exposed surfaces exposed at the inner corners are inclined surfaces 10c and 11c. However, it is not limited to this. Of the first auxiliary member and the second auxiliary member, the surface (exposed surface) into which the stirring pin F2 is inserted may be a curved surface. In this case, it is preferable to change the shape of the tool insertion surface of the tab material T so as to be flush with the curved surface. Thereby, a joining process can be performed smoothly.

  Moreover, you may perform a joining process using the tab material T also in 1st embodiment. Also in this case, it is preferable to set the tool insertion surfaces of the tab material T and the exposed surfaces of the weld metals U1 and U2 to be substantially flush with each other.

DESCRIPTION OF SYMBOLS 1 Metal member 1a Side surface 2 Metal member 2a Side surface 2b Side surface 2c End surface 10 1st auxiliary member (auxiliary member)
11 Second auxiliary member (auxiliary member)
F Joining rotation tool (Rotation tool)
F2 stirring pin J1 butt section S1 first inner corner (inner corner)
S2 Second inner corner (inner corner)
T Tab material U1 Weld metal U2 Weld metal W1 Plasticization region W2 Plasticization region

Claims (5)

A friction stir welding method for joining two metal members using a rotary tool equipped with a stirring pin,
A butting step of forming a T-shaped joined metal member in front view by abutting the end face of the other metal member to the side surface of one metal member to form a butting portion;
Overlay welding step of performing overlay welding on at least one inner corner of the bonded metal member and covering the inner corner with a weld metal;
A joining step of inserting a rotated stirring pin into the inner corner and performing frictional stirring of the butt portion in a state where only the stirring pin is in contact with the weld metal and the metal member to be joined. Friction stir welding method. In the overlay welding process, overlay welding is performed on the two inner corners of the metal member to be joined, and each inner corner is covered with a weld metal,
In the joining step, a first joining step in which friction stirring is performed on one of the two inner corners of the metal member to be joined and a second joining step in which friction stirring is performed on the other are performed.
2. The friction stir welding method according to claim 1, wherein in the second joining step, friction stir is performed while the stirring pin is inserted into the plasticized region formed in the first joining step. A friction stir welding method for joining two metal members using a rotary tool equipped with a stirring pin,
A butting step of forming a T-shaped joined metal member in front view by abutting the end face of the other metal member to the side surface of one metal member to form a butting portion;
An auxiliary member disposing step of disposing an auxiliary member on at least one inner corner of the metal member to be joined and covering the inner corner with the auxiliary member;
A joining step of inserting a rotated stirring pin into the inner corner and performing frictional stirring of the abutting portion in a state where only the stirring pin is in contact with the auxiliary member and the metal member to be joined. Friction stir welding method. In the auxiliary member arranging step, the auxiliary members are respectively arranged at two inner corners of the metal member to be joined and each inner corner is covered with the auxiliary member,
In the joining step, a first joining step in which friction stirring is performed on one of the two inner corners of the metal member to be joined and a second joining step in which friction stirring is performed on the other are performed.
4. The friction stir welding method according to claim 3, wherein in the second joining step, friction stir is performed while the stirring pin is inserted into the plasticized region formed in the first joining step. 5. After the abutting step, including a tab material arrangement step of contacting a tab material having two tool insertion surfaces with the front surface of the metal member to be joined,
In the tab material arranging step,
While making the exposed surface of one of the auxiliary members flush with one of the tool insertion surfaces of the tab material,
The friction stir welding method according to claim 4, wherein the exposed surface of the other auxiliary member and the other tool insertion surface of the tab member are flush with each other.

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