JP5553732B2 - Metal joint - Google Patents

Description

  The present invention relates to a joined body of metal materials obtained by superposing a plurality of metal materials and joining them by ultrasonic waves.

  In recent years, the use of aluminum or aluminum alloy materials for automobile structures has been promoted from the viewpoint of reducing the weight of automobiles. For the formation of a structure, fusion welding such as spot welding of members and members, or continuous line joining by MIG welding, laser welding, or the like is generally employed.

  On the other hand, the joining method by welding generates thermal strain due to welding heat, so friction stir wire joining (FSW) is widely used as a method for avoiding this thermal strain (Patent Document 1). Further, friction stir spot joining has been proposed as a spot joining method (Patent Document 2).

Japanese Patent No. 2712838 JP 2004-337891 A

  However, the friction stir wire joining described in Patent Document 1 described above causes the plastic flow of the materials to be joined by moving the tool along the welding line while the tool is rotated, and stir welding. Yes. Such a joining method is extremely effective in suppressing thermal strain, but it is necessary to dispose a discard plate for the tool to enter and exit the weld line at the joining start site and the joining end site. There is. Further, in this prior art, it is necessary to remove the discarded plate after the joining is completed.

  On the other hand, in the friction stir spot welding described in Patent Document 2, such a discarding plate is unnecessary. However, in the friction stir spot welding described in Patent Document 2, the tool is immersed in the material to be joined in a rotation stopped state, and after this immersion, the tool is rotated to friction stir the material to be joined. For this reason, in this prior art, it is necessary to push the tool deeply into the material to be joined, and there is a problem that the strength of the joint is lowered, and it is particularly difficult to join thin materials.

  The present invention has been made in view of such problems, and provides a joined body of a metal material that can be joined even if the thickness of the joined material is reduced and the joined body has a high joining strength. For the purpose.

The joined body of metal material according to the first invention of the present application,
In the joined body of metal materials in which the materials to be joined made of a plurality of metals or alloys are stacked and joined to each other,
The joints for joining the joined materials to be joined together are a first recess and a second recess by pressing the lap joint with a pressing member on the front and back surfaces of the lap joint of the joined materials, respectively. Is formed,
Each of the materials to be joined is agitated by plastic flow at a position aligned with the first and second recesses, and the joining interface disappears.

The joined body of metal material according to the second invention of the present application,
In the joined body of metal materials in which the materials to be joined made of a plurality of metals or alloys are stacked and joined to each other,
In the joining portion for joining the stacked materials to be joined to each other, the lap joint of the materials to be joined is pushed in one direction in the thickness direction, and a protruding portion protruding in the one direction is formed in the lap joint. Has been
Each of the materials to be joined is agitated by plastic flow at a position aligned with a third recess formed on the opposite surface of the protruding portion, and the joining interface disappears.

In the joined body of these metal materials, for example,
The pre-joined material is a plate material of aluminum or aluminum alloy. Moreover, the said to-be-joined material is a board | plate material whose thickness is 1 mm or less.

  According to the first and second inventions of the present application, as a joined body of metal materials obtained by superimposing a plurality of metal materials, the joint portion is joined in a state where the joint interface disappears due to plastic flow of the metal material, so that high strength The joined body can be obtained.

  In particular, in the joined body of the second invention of the present application, since the lap joint is pushed in one direction in the thickness direction and the third recess is formed in the entire lap joint, the joint strength of the joined body can be further increased. .

It is a schematic diagram which shows the ultrasonic vibration provision apparatus used for the manufacturing method of the conjugate | zygote which concerns on embodiment of this invention. It is a schematic diagram which shows the relationship between the stress distribution and displacement distribution in this invention. (A) thru | or (c) is a schematic diagram which shows the process of the mechanical clinch joining which provided the ultrasonic vibration of embodiment of this invention. It is a schematic diagram which shows the junction part of 1st Embodiment (1st Example) of this invention. It is a schematic diagram which shows the shape of the junction part of 2nd Embodiment (2nd Example) of this invention. Similarly, it is a figure which expands and shows a part of FIG. It is a schematic diagram which shows the metal structure at the time of carrying out mechanical clinch joining, without providing an ultrasonic vibration. (A) thru | or (c) is a schematic diagram which shows the flow state of the metal structure | tissue at the time of giving a ultrasonic vibration and clinching joining. It is a figure which shows the inclined surface of the inner edge part of die | dye.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. First, the manufacturing method of the joined body of 1st Embodiment of this invention is demonstrated. FIG. 1 is a schematic diagram showing an ultrasonic vibration applying device used in the method of manufacturing the joined body, and a waveform diagram showing an ultrasonic vibration mode. FIGS. 3A, 3B, and 3C are diagrams showing a process of mechanical clinching of the materials to be joined. As shown in FIG. 3, a lap joint 1 of materials to be joined 1 a and 1 b such as A1050 aluminum alloy material is placed on a die 12, and a stripper 11 is further disposed on the lap joint 1. The die 12 is formed with a forming hole 14 into which the counter punch 4 is inserted at the center thereof, with the axial direction thereof being vertical, and the stripper 11 has a punch hole 13 into which the punch 2 is inserted at the center. It is formed with its axial direction vertical. The lap joint 1 is pushed into the molding hole 14 by the punch 2 to mold the shape of the lap joint 1 after joining.

  In this case, as shown in FIG. 9, the inner surface of the die 12 that defines the molding hole 14 provided in the die 12 can be inclined so that the upper portion thereof spreads upward. This inclination is, for example, 7 ° in the longitudinal section of the die 12 as shown in FIG. Thus, if the upper part of the inner surface defining the forming hole 14 of the die 12 is inclined, the punch 2 can be easily pulled out from the lap joint 1 after joining, which is preferable from the viewpoint of productivity.

  Although FIG. 1 shows an ultrasonic vibration applying device, the die 12 and the stripper 11 shown in FIG. 3 are not shown in FIG. 1 for simplicity of illustration. A counter punch 4 is disposed on the lower surface of the lower material to be bonded 1a, and a punch 2 is disposed on the upper surface of the upper material to be bonded 1b. The counter punch 4 is connected to the horn 5, and the punch 2 is connected to the horn 3. The upper horn 3 is connected to an ultrasonic transducer 6. These horns 3 and 5 expand the ultrasonic vibration applied by the ultrasonic vibrator 6 and transmit it to the punch 2 and the counter punch 4, respectively.

  Such a horn is fastened to a punch in a normal ultrasonic vibration device, and the horn and the punch are fixed to each other. However, in the present embodiment, the punch 2 and the counter punch 4 and the horns 3 and 5 are not fastened. This is because by applying ultrasonic vibration, not only the punch but also a fastening member such as a bolt that fastens the punch may be subjected to a large load, and the fastening member may be damaged in a short period of time after the start of joining. It is. This problem can be solved by leaving the punch 2 and the counter punch 4 free without being fastened to the horns 3 and 5, respectively. In this case, the punch 2 and the counter punch 4 may be detached from the horns 3 and 5, but the punch 2 and the counter punch 4 are attached to the horns 3 and 5 with appropriate jigs, respectively. 5, after the punch 2 and the counter punch 4 contact the lap joint 1, the jig is removed, and the punch 2, the counter punch 4 and the horns 3, 5 are replaced by the horns 3, 5. 2 and the counter punch 4 are supported, but the horns 3, 5 and the punch 2 and the counter punch 4 are not fastened, that is, the above-described free state may be set. In addition, after the mechanical clinching, when the punch 2 is restrained by the lap joint 1 to be joined, the punch 2 is fixed to the horn 3 by the jig and the horn 3 is pulled up, whereby the punch 2 Can be detached from the lap joint 1. Note that the horn 3 and the ultrasonic vibrator 6 are fixed to each other by screws or the like.

  A molding hole 14 is formed in the center portion of the die 12, and an operation portion (tip portion) of the counter punch 4 is inserted into the hole 14. A punch hole 13 is formed in the central portion of the stripper 11, and an operation portion (tip portion) of the punch 2 is inserted into the hole 13. The operation portion of the counter punch 4 and the operation portion of the punch 2 sandwich the lap joint 1 to apply ultrasonic vibration to the lap joint 1 and lower the punch 2 as shown in FIG. Clinch the lap joint 1. In the present embodiment, a counter punch 4 is installed. Therefore, as shown in FIGS. 3A to 3C, when the punch 2 descends and presses the lap joint 1 downward, the counter punch 4 exerts a clamping force on the lap joint 1 with the punch 2. While applying, it moves downward together with the punch 4 and the lap joint 1. Thus, although the joint part of the lap joint 1 moves in the axial direction by pushing the punch 2, the movement stops at a predetermined position, and the counter punch 4 is made of the same material as the die bottom part in the conventional mechanical clinch. It acts as an anvil that crushes the lap joint 1.

  The ultrasonic vibration generated from the ultrasonic vibrator 6 is magnified by the horn 3 and transmitted to the punch 2. The ultrasonic vibration is transmitted from the counter punch 4 to the horn 5 on the counter punch side, and the entire vibration system maintains a resonance state.

  During the processing of the lap joint 1 by mechanical clinching, in order to maintain a steady resonance state, for example, transmission control is controlled by a PLL (phase synchronization circuit) type low amplitude frequency automatic tracking method. The die 12 and the stripper 11 sandwich the lap joint 1.

  Next, a method for producing a joined body according to an embodiment of the present invention using the above-described apparatus will be described. On the die 12, the lap joint 1 of the materials to be joined 1a, 1b such as A1050 aluminum alloy material is placed, and the stripper 11 is lowered onto the periphery of the lap joint 1. The lap joint 1 is sandwiched between the stripper 11 and the die 12. Then, the counter punch 4 and the punch 3 are inserted into the holes of the die 12 and the stripper 11, and the lap joint 1 is sandwiched between the counter punch 4 and the punch 2. At this time, the counter punch 4 and the punch 2 are fixed to the horns 5 and 3, respectively, by appropriate jigs when inserted into the holes. 3 and 5 and the punch 2 and the counter punch 4 are connected to each other so that vibration is transmitted in the vertical direction in a state where they are not mechanically fastened.

  Next, after sandwiching the lap joint 1 between the punch 2 and the counter punch 4 as described above, the punch 2 and the counter punch 4 are pressed against the lap joint 1 with a pressure of, for example, 75 MPa or more. Thereby, the working parts at the tips of the punch 2 and the counter punch 4 are caused to bite into the materials 1a and 1b of the lap joint 1 by, for example, a depth of 40 to 70% of the entire thickness of the lap joint 1. . In addition, in order to bite into the surface of the to-be-joined material 1a, 1b only 40 to 70% of the thickness of the whole lap joint 1, the required stress changes with kinds of to-be-joined material 1a, 1b. Therefore, depending on the type, at 75 MPa, the punch 2 and the counter punch 4 may not be able to bite into the lap joint 1 by 40 to 70% of the total thickness. Or, even if it is less than 75 MPa, the above bite-in condition may be satisfied. However, in the case of a general aluminum alloy, the above biting condition can be satisfied by applying a pressure of 75 MPa or more.

  In this way, when ultrasonic vibration is applied to the lap joint 1 in a state where the punch 2 and the counter punch 4 do not bite into the lap joint 1 as described later, the ultrasonic vibration from the punch 2 and the counter punch 4 is applied to the lap joint 1. Not effectively transmitted, resonance vibration is less likely to occur in the lap joint 1.

  The biting amount may be 40 to 70% of the total thickness of the lap joint 1 as described above, but more preferably, the biting amount is about 60%.

  Moreover, as mentioned above, it is preferable that the pressure with respect to the lap joint 1 of the punch 2 and the counter punch 4 is 75 MPa or more. This is because, in addition to the purpose of securing the amount of biting of the punch 2 and the counter punch 4 into the lap joint 1, if the load of the punch 2 and the counter punch 4 is too low, the lap joint made of the punch 2 and the material to be joined is used. 1 and the counter punch 4 are not integrated as a resonator, and a large load is applied to the connecting portion between the punch 2 and the horn 3, which is not suitable for mass production. Therefore, in order to maintain the resonance state and not apply a load to the apparatus, it is preferable to pressurize the lap joint 1 with a pressure of 75 MPa or more by the punch 2 and the counter punch 4 before applying the ultrasonic vibration. In addition, even if a large stress of 120 MPa or more is applied as the applied pressure, the above-described effect is not improved so much, so the applied pressure is preferably less than 120 MPa.

  In this manner, the lap joint 1 is sandwiched between the punch 2 and the counter punch 4, and further, the lap joint 1 is loosely sandwiched between the die 12 and the stripper 11, and the ultrasonic vibrator 6 is used to sandwich the lap joint 1 between the punch 2 and the counter punch 4. Ultrasonic vibration is applied in the axial direction. At this time, the working portions at the tips of the punch 2 and the counter punch 4 are biting into the lap joint 1 and the peripheral portion of the lap joint 1 is sandwiched between the die 12 and the stripper 11. 12 and the inner portion of the portion sandwiched between the stripper 11 are vibrated in the vertical direction (in the axial direction of the punch 2), so that the axial direction of the punch 2 is independent of the shape of the materials to be joined 1a and 1b. A vibration state is obtained.

  Further, by loosely sandwiching the lap joint 1 between the die 2 and the stripper 4, the material can be supplied to the joint portion of the lap joint 1 being pushed in while correcting the warp and the bending of the material.

  In applying the ultrasonic vibration, it is preferable to resonate so that the stress distribution is maximized at the position where the members 1a and 1b are in contact with each other, that is, at the portion to be bonded. As shown in FIG. 1, the positions of the punch 2 and the counter punch 4 and the boundary between the horn 3 and the punch 2 and the boundary between the horn 5 and the counter punch 4 are antinodes of the vibration shown in FIG. Is applied to the horn 3 from the ultrasonic transducer 6. If the positions of the boundary between the horn 3 and the punch 2 and the boundary between the horn 5 and the counter punch 4 are antinodes of vibration, the displacement is maximum at the position, and the center position between the antinodes, that is, the covered position. The positions of the joining members 1a and 1b are nodes, and the displacement distribution is 0 and the stress distribution is maximum at the positions of the nodes. As described above, when the ultrasonic vibration generated from the ultrasonic vibrator 6 is such that the position of the boundary between the horn 3 and the punch 2 and the position of the boundary between the horn 5 and the counter punch 4 become antinodes, Ultrasonic vibration that maximizes the stress distribution is obtained at the position of the surface between the workpiece 2 and the counter punch 4 where the members to be joined 1a and 1b contact.

  The ultrasonic vibration oscillated from the ultrasonic vibrator 6 is magnified by the horn 3 and transmitted to the punch 2, transmitted from the punch 2 to the counter punch 4, and further transmitted from the counter punch 4 to the horn 5. The ultrasonic vibration expanded by the horns 3 and 4 is transmitted to the punch 2 and the counter punch 4 and applied to the joint as a resonance wave that maximizes the stress distribution at the joint of the members 1a and 1b. The At this time, the displacement distribution has an opposite phase to the stress distribution. In such a vibration mode, when the lap joint 1 of the materials to be joined 1a and 1b made of aluminum or an aluminum alloy is vibrated, clockwise and counterclockwise vortices alternately in the thickness direction of the metal plate of the lap joint 1 And the metal material is agitated. Thereby, even if oil remains on the surfaces of the materials to be joined 1a and 1b, a joined body having a strong joining strength can be obtained.

  The joined body thus obtained has a metal structure as shown in FIG. FIG. 4 is a trace of this metallographic photograph. The magnification of this tissue photograph is 50 times.

  FIG. 4 is a metallographic photograph showing a cross-section in the thickness direction of the joint portion of the lap joint (its trace view), but the portion to which the pressure in the clamping direction is applied by the punch 2 and the counter punch 4 is flat, The periphery of the flat portion rises when the punch 2 and the counter punch 4 bite into the front and back surfaces of the lap joint 1, and the raised portions 22 and 23 are formed around the portion where the punch 2 and the counter punch 4 bite. Therefore, the first concave portion 20 on the lap joint surface side and the second concave portion 21 on the lap joint rear surface side are formed in the portion sandwiched by the punch 2 and the counter punch 4. And in these 1st and 2nd recessed parts 20 and 21, the joining interface of the to-be-joined materials 1a and 1b lose | disappears, and it has an integral metal structure. This is because the punch 2 and the counter punch 4 are pressed on the front surface and the back surface of the lap joint 1, respectively, and the punch 2 and the counter punch 4 bite, and in this state, the lap joint 1 is applied with ultrasonic vibration. The plastic flow of the metal structure occurs in the portion that receives the sandwiching pressure of the materials to be joined 1a and 1b, whereby the joining interface disappears and the structure is integrated. Thereby, a junction part with high joining force is obtained.

  Next, a second embodiment of the present invention will be described. In the present embodiment, as described above, the ultrasonic vibration is applied to the lap joint 1 and then the ultrasonic vibration is applied to the fixed die 12 and the stripper 11 as shown in FIG. The punch 2 and the counter punch 4 are lowered and the lap joint 1 is pushed by the punch 2.

  As described above, as shown in FIG. 3A, with the ultrasonic vibration applied to the lap joint 1, the punch 2 is lowered as shown in FIG. When the joint portion of the lap joint 1 is pushed downward, the lowering of the punch 2 and the counter punch 4 is stopped at a predetermined position as shown in FIG. At this time, the material to be bonded 1a and the material to be bonded 1b of the lap joint 1 are crushed at the tip of the working portion of the punch 2, and a portion extending in the lateral direction is formed at the bottom of the pressed portion. The lap joint 1 is joined by mechanical clinching at the pushed-in portion.

  In the present embodiment, even if oil is attached to the surfaces of the materials to be bonded 1a and 1b, the bonded surfaces of the materials to be bonded 1a and 1b are subjected to ultrasonic vibration having a waveform that becomes a node, and the maximum stress is applied to the bonding surfaces. As a result, a clockwise and counterclockwise vortex is generated in the thickness direction of the lap joint 1 at this joint, and the material is agitated, so that the oil on the surfaces of the materials to be joined 1a and 1b is vaporized and disappears. Even if it does not disappear, the fastened materials are fastened to each other by stirring. For this reason, the junction part excellent in joining strength is obtained.

  FIG. 5 is a schematic view showing a cross section of the joined body subjected to the mechanical clinch, and FIG. 6 is a partially enlarged view thereof. As shown in FIG. 5, when the lap joint 1 is pushed in by the punch 2, the lap joint 1 protrudes as a whole in the direction of the back surface of the lap joint, and a third recess 24 is formed in the entire lap joint. In the joint portion at the bottom of the third recess 24, plastic flow of the metal structure occurs, and the joining interface disappears. Further, the corner portion of the third recess portion is a corner portion of the upper material to be joined 1b. However, as a result of entering into the corner of the lower material to be joined 1a in the lateral direction, the parts are locked to each other. For this reason, the materials to be joined are more firmly joined by the effect of the plastic flow of the metal structure due to the ultrasonic vibration and the mechanical clinch.

Hereinafter, the effect of the Example of this invention is demonstrated compared with the comparative example which remove | deviates from the scope of the present invention. As a first example, after degreasing two aluminum alloy plates (A1050 aluminum alloy, thickness: 0.5 mm, width: 25 mm, length: 75 mm), the kinematic viscosity is 1.2 mm ² · s ⁻¹ Rolling oil was applied and combined in a cross to join the center. For the joining, the ultrasonic vibration applying device shown in FIG. 1 was used, and D4427PC (resonance frequency 27 kHz, maximum input 700 W) manufactured by Nippon Specialty Ceramics was used for the ultrasonic vibrator 6.

  The end face of the horn vibrated with an amplitude of 9 μm. The punch 2, the materials to be bonded 1a and 1b, and the counter punch 4 all vibrate as a single resonator, and a computer simulation by a finite element method is performed so that the maximum stress can be obtained on the overlapping surface of the materials to be bonded 1a and 1b. Then, the shape of the punch 2 or the like was designed and the dimensions were determined.

  The punch 2, counter punch 4, stripper 11, and die 12 were all made of SKD11 steel having a Rockwell hardness HRC of 58-61.

  Next, after pressing the punch to a position where the bottom plate thickness of the joint portion was 0.20 mm, ultrasonic vibration was applied to join the materials to be joined. Thereafter, the obtained cruciform joint was subjected to a tensile peel strength test to measure the peel strength. The results of this peel strength test are shown in Table 1 below. In Table 1, Examples 1 to 7 are bonded by applying ultrasonic vibration so that the vibration stress is maximized at the bonded portion, and satisfy the requirements of claim 1 of the present invention. On the other hand, Comparative Examples 1 to 7 were joined without applying ultrasonic vibration, and Comparative Example 8 was applied with ultrasonic vibration so that the phase of vibration was 180 ° different from Examples 1 to 7. . Moreover, the thickness of a bottom part is the thickness of the part pressed by the punch 2 in a lap joint.

  As shown in Table 1, each of Examples 1 to 7 of the present invention had a high peel strength of 8.2 MPa or more and an excellent bonding strength. On the other hand, in the case of Comparative Examples 1 to 7 in which the lap joint was pushed by punching without applying ultrasonic vibration, the bonding strength was low. Further, in Comparative Example 8 to which ultrasonic vibration was applied, since the vibration phase was different from that of the present invention, the bonding strength remained at a low value.

  Subsequently, the joined body was cut to prepare a sample. After embedding the sample in a resin, the cross section was polished, and the cross section was etched with Keller's solution to observe the metal structure. A photograph of this metal structure is shown in FIG. As described above, the interface between the two aluminum alloy plates continues on the outside of the punch indented portion (first and second recesses), but the interface between the two aluminum alloy plates in the indented portion of the punch. It was observed that the metal structure was integrated at this joint.

  Next, a second embodiment of the present invention will be described. Using an aluminum alloy plate of the same type as in the first embodiment and applying ultrasonic waves under the same conditions, the punch 2 and the counter punch 4 are moved downward to perform mechanical clinch joining (caulking joining). went. As a result, as shown in FIG. 4 and FIG. 6, it was observed that the interface disappeared and the materials to be joined 1 a and 1 b were integrated at the joint. On the other hand, in the case where ultrasonic vibration was not applied, even if mechanical clinch joining was performed, the disappearance of the interface at the joint did not occur. As a result, when the interface of the bonded portion disappears as shown in FIGS. 4 and 6, the bonded portion is one of the bonded bodies when the interface is not lost without applying ultrasonic vibration. It had a peel load (cross tension) of 6 times. The plate thickness at the bottom of FIG. 6 is 0.28 mm.

  FIG. 7 is a schematic view showing a metal structure when seven sheets of A1050 aluminum alloy having a thickness of 0.15 mm are overlapped and caulked and joined under the same conditions as in the second embodiment. In FIG. 7, since no ultrasonic vibration is applied, plastic flow at the joining interface does not occur. On the other hand, FIGS. 8A to 8C are schematic views showing a metal structure when seven similar aluminum alloy plates are overlapped and caulked and joined while applying ultrasonic vibration according to the present invention. . The observation location is a portion indicated by a two-dot chain line in FIG. In FIG. 8, the ultrasonic energy is changed into three levels at three levels within 700 W at the maximum by the input of the ultrasonic transducer, and the ultrasonic energy is changed from FIG. 8 (a) to FIG. 8 (c). It is high. In FIG. 8A, the flow direction changes so that the central material flows preferentially and winds. In FIG. 8C, the material is being stirred.

  As shown in FIGS. 8A to 8C, as the applied amount of ultrasonic energy increases in this order, the plastic flow of vortices clockwise and counterclockwise in the plate thickness direction is promoted, and the material Since it was stirred, the bonding interface disappeared and a good bonded body was obtained.

1: Lap joint 1a, 1b: Material to be joined 2: Punch 3, 5: Horn 4: Counter punch 6: Ultrasonic vibrator 11: Stripper 12: Die 14: Hole for molding

Claims (4)

In the joined body of metal materials in which the materials to be joined made of a plurality of metals or alloys are stacked and joined to each other,
The joints for joining the joined materials to be joined together are a first recess and a second recess by pressing the lap joint with a pressing member on the front and back surfaces of the lap joint of the joined materials, respectively. Is formed,
The metal-material joined body, wherein each of the materials to be joined is agitated by plastic flow at a position aligned with the first and second recesses, and a joining interface disappears. In the joined body of metal materials in which the materials to be joined made of a plurality of metals or alloys are stacked and joined to each other,
In the joining portion for joining the stacked materials to be joined to each other, the lap joint of the materials to be joined is pushed in one direction in the thickness direction, and a protruding portion protruding in the one direction is formed in the lap joint. Has been
Joining of metal materials characterized in that each of the materials to be joined is agitated by plastic flow at a position aligned with a third recess formed on the surface on the opposite side of the protruding portion, and the joining interface disappears. body. The metal material joined body according to claim 1, wherein the material to be joined is a plate material of aluminum or an aluminum alloy. 4. The joined body of metal materials according to claim 1, wherein the material to be joined is a plate material having a thickness of 1 mm or less. 5.

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