JP2005254323A - Ultrasonic welding tip and welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding tip by which a high joining strength can be stably obtained in ultrasonic welding between an aluminum-based material and a steel material, and also to provide the welding method. <P>SOLUTION: As the ultrasonic welding tip for performing welding by applying ultrasonic vibration to a stacked body of the aluminum-based material and the steel material, a tip in a form of R type electrode is used having a curved face that forms a projected shape curved in the direction orthogonal to the vibrating direction. As a result, a stable joining strength can be obtained in the ultrasonic welding between the aluminum-based material and the steel material. Thus, welding of different kinds of metal between the aluminum or aluminum-based material and the steel material can be performed at a low cost without using special consumables like filler metal or welding flux. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultrasonic bonding tip and bonding method between dissimilar metals of aluminum or an aluminum alloy material (hereinafter collectively referred to as an aluminum-based material) and a steel material.

  Aluminum-based materials are lightweight and excellent in aesthetics, and are used as materials for weight reduction of transport aircraft and the like. In particular, a hybrid structure in which an aluminum-based material is combined with a steel material excellent in strength and formability has attracted attention.

  However, when joining an aluminum-based material and a steel material, it is difficult to apply various welding techniques conventionally used in joining steel materials as they are. For example, when resistance spot welding is applied, a normal nugget is not formed at the joint interface because there is a large difference in thermal conductivity and electrical conductivity between an aluminum-based material and a steel material. Further, a brittle intermetallic compound is formed at the bonding interface, and the bonded portion between the aluminum-based material and the steel material is easily peeled off at the interface, so that sufficient bonding quality cannot be obtained.

  A method of joining these dissimilar metals by ultrasonic bonding instead of the resistance spot welding has been proposed. In ultrasonic bonding, a stress generated by pressurization in a direction perpendicular to the bonding interface and a repetitive stress due to high vibration acceleration in a parallel direction are applied to generate frictional heat at the bonding interface. As a result, the atoms of the material to be welded are diffused and joined. For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-202643), a flux is applied to a portion to be joined of a steel material, followed by hot dip galvanizing, and the portion to be joined of an aluminum-based material is brought into contact with the galvanized film. And applying ultrasonic vibration to melt and bond the galvanized film. Patent Document 1 describes that a sufficient rust prevention treatment can be applied to the joint between the steel material and the aluminum-based material without impairing the joint strength.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 10-71465) discloses a technique of ultrasonically bonding an aluminum material and a steel material in which a solder layer is formed at a portion to be joined.

  However, these techniques have the following problems. In Patent Document 1, an aluminum-based material and a steel material are joined using a galvanized film as an adhesive layer. For this reason, the process of giving galvanization to the steel material surface is needed. The same applies to Patent Document 2, and an extra step of forming a solder layer is required.

  On the other hand, Non-Patent Document 1 (Light Metal Welding Vol. 37 (1999) No. 10) discloses a technique for solid-phase bonding without melting metal using ultrasonic vibration. The possibility of joining between dissimilar metals without the use of brazing material or flux has been suggested.

  FIG. 1 is a cross-sectional view showing a conventional ultrasonic bonding apparatus. FIG. 4 is a view showing the shape of a chip used in a conventional ultrasonic bonding apparatus. As shown in FIG. 1, in this ultrasonic bonding apparatus, an aluminum-based material 2 and a steel material 1 are stacked and this laminated body 3 is fixed to an anvil 5. Then, vertical pressure P and horizontal ultrasonic vibration (S) are applied to the bonding interface of the laminate 3 by the chip 4. As shown in FIG. 4, the surface 6 of the conventional chip 4c is subjected to anti-slip processing called knurling so that the material is firmly held and vibration is transmitted to the interface between the aluminum-based material 2 and the steel material 1. Has been.

Japanese Patent Application Laid-Open No. 2000-202643

JP-A-10-71465

Light metal welding Vol. 37 (1999) No. 10

  However, there is a problem with the above-described prior art. Non-Patent Document 1 does not describe a specific example in which ultrasonic bonding is applied to bonding between different kinds of metals. Moreover, generally the optimal joining conditions and tool shape in ultrasonic joining are not known. With conventional tool shapes and joining conditions, it is difficult to ensure sufficient joining strength.

  This invention is made | formed in view of this problem, Comprising: The chip | tip used for ultrasonic bonding of the aluminum-type material and steel material which can obtain high joint strength stably, and the ultrasonic bonding method using the same are provided. For the purpose.

  The chip for ultrasonic bonding of an aluminum-based material and a steel material according to the present invention is an ultrasonic bonding device chip for performing ultrasonic bonding by applying ultrasonic waves to superposed bonded materials. The contact surface is not knurled.

  In this case, it is desirable that the tip of the tip has a convex curved surface that is curved in a cross section orthogonal to the vibration direction.

  The ultrasonic bonding method according to the present invention is characterized in that, for example, an aluminum material or an aluminum alloy material and a steel material are bonded using the ultrasonic bonding chip.

  According to the present invention, stable bonding strength can be obtained in ultrasonic bonding between an aluminum-based material and a steel material. Therefore, joining of dissimilar metals of aluminum or an aluminum-based material and a steel-based material can be performed at low cost without using a special consumable such as a brazing material or a welding flux.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an ultrasonic bonding apparatus according to this embodiment. 2 and 3 are views showing the shape of a chip used in the ultrasonic bonding apparatus according to the present invention. As shown in FIG. 1, in the ultrasonic bonding apparatus according to the present embodiment, a laminate 3 in which an aluminum-based material 2 and a steel material 1 are stacked is fixed to an anvil 5 that is installed in a horizontal posture. . Further, the laminate 3 is sandwiched between the tip 4 directly connected to a horn (not shown) that performs ultrasonic vibration (S) in the horizontal direction and the anvil 5. As shown in FIG. 2, the tip 4a used in the present invention is not subjected to anti-slip knurling. Furthermore, as shown in FIG. 3, it is desirable that the tip 4b used in the present invention has a convex shape that curves with a predetermined radius of curvature in a cross section orthogonal to the ultrasonic vibration direction during ultrasonic bonding. .

  Next, the operation and joining method of the ultrasonic joining tip between the aluminum-based material and the steel material according to this embodiment configured as described above will be described. As shown in FIG. 1, the aluminum-based material 2 and the steel material 1 are stacked, and the laminate 3 is fixed to the anvil 5 fixed in a horizontal posture. The aluminum-based material 2 is held by the chip 4 by being sandwiched between the chips 4 and applying a pressure P perpendicular to the bonding surface to the laminated body 3 via the chips 4. In this state, the chip 4 is subjected to ultrasonic vibration (S) in the horizontal direction, and the aluminum-based material 2 is ultrasonically vibrated with high vibration acceleration together with the chip 4. As a result, heat is generated by frictional force between the aluminum-based material 2 that vibrates ultrasonically and the fixed steel material 1. At this time, movement of atoms is promoted at the bonding interface, and diffusion of Fe atoms into the aluminum-based material 2 occurs. Thereby, the aluminum-based material 2 and the steel material 1 are solid-phase bonded at the bonding interface between the steel material 1 and the aluminum-based material 2.

  In the initial stage of bonding, in order to start solid phase diffusion, it is necessary to mechanically remove the surface oxide film between the materials and make the new metal surfaces face each other. For this reason, the chip needs to hold the aluminum-based material 2 firmly and transmit ultrasonic vibration to the aluminum-based material efficiently.

  In addition, after diffusion bonding has progressed to some extent, it is necessary to prevent sliding from occurring at the bonding interface between the aluminum-based material 2 and the steel material 1 while continuing solid-phase diffusion of the bonded portion. Therefore, it is necessary to generate friction overheating due to sliding at the interface between the tip 4 and the aluminum-based material 2.

  In the present embodiment, an optimum chip shape for holding and releasing the aluminum-based material 2 during the joining process is used as described above. As shown in FIG. 2, considering the clamp release from the middle of the process, it is necessary that the surface of the chip 4 is not knurled to prevent slipping. Moreover, in order to improve the retainability of the aluminum-based material 2 that has been lowered due to the elimination of the knurling process, it is preferable that the tip of the chip has a convex curved surface. Thereby, the load per unit area applied to the aluminum-based material 2 from the chip 4 can be increased. At this time, if the tip shape is conical, the frictional resistance is too small in shape, so that ultrasonic vibration cannot be efficiently transmitted to the material to be joined. Therefore, it is desirable that the chip 4 has an R shape as shown in FIG. 3 which is convex only in the direction orthogonal to the ultrasonic vibration direction during ultrasonic vibration. By adopting such a shape, the friction resistance between the tip 4 and the aluminum-based material 2 in the vibration direction is increased to hold the aluminum-based material 2, and when diffusion bonding proceeds to some extent, there is no knurling, so the aluminum-based material 2 Freed from holding.

  Note that the radius of curvature of the tip of the tip 4 is preferably 30 to 150 mm. If the radius of curvature is less than 30 mm, the contact area between the two materials at the interface is too narrow and limited, resulting in insufficient bond breaking load. In addition, the applied pressure becomes excessive, the aluminum-based material is thinned, and the joint breaking load is insufficient. Further, even after diffusion bonding has progressed to some extent, the holding is not released, and sliding occurs at the bonding interface, resulting in a decrease in bonding breaking load. If it exceeds 150 mm, the contact area becomes excessive and the applied pressure becomes excessive. As a result, the frictional resistance becomes too small, and the ultrasonic vibration is not efficiently transmitted to the material to be joined, so that the joint breaking load is reduced.

  In addition, the anvil 5 holding the steel material 1 needs to always hold the steel material 1, and it is desirable that there is a knurling process.

  As in the present embodiment, the tip shape of the ultrasonic bonding tip 4 is made appropriate, so that bonding can be performed stably.

  In addition, in this embodiment, although the example which piles up the aluminum-type material 2 on the steel material 1 was shown, this invention is not limited to this, You may pile up the steel material 1 on the aluminum-type material 2. The ultrasonic bonding method itself may be a conventionally known method and is not particularly limited.

  Next, the results of tests conducted to show the effects of the present invention will be described. As an aluminum-based material, AA6022 alloy (AA: US standard, Al-1.2 mass% Si-0.6 mass% Mg-0.5 mass% Cu-0.1 mass% Fe-0.05 mass% Mn) A plate material having a thickness of 1 mm was used, and an SPCE steel plate (described in JIS G 3141) having a thickness of 0.8 mm was used as the steel material. As shown in FIG. 1, an aluminum alloy material (aluminum-based material 2) is disposed on the chip side, and a steel plate (steel material 1) is disposed on the anvil side. The applied pressure is 500 N, the vibration frequency is 20 kHz, the amplitude is 20 μm, and the joining time is 0.23 seconds. Bonding was performed. About what was able to join, the U-shaped joint tensile test was done and the breaking load was calculated | required. The results are shown in Table 1.

  In Examples 1 to 7, since the knurling process is not performed on the surface in contact with the material to be bonded, a high bonding strength of 230 N or more was obtained. However, in Comparative Examples 8 and 9, the knurling process was performed. The strength was as low as 200 N or less. Further, in Examples 3 to 6, the tip shape was provided with an appropriate curved surface having a curvature radius of 30 to 150 mm, so that the bonding strength was higher than that of the flat Example 1.

It is sectional drawing which shows the ultrasonic bonding apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the chip | tip shape which concerns on embodiment of this invention. It is a schematic diagram which shows the chip | tip shape which concerns on embodiment of this invention. It is a schematic diagram which shows the conventional chip shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Aluminum type material 2; Steel material 3; Laminated body 4, 4a, 4b, 4c; Chip 5; Anvil 6; Surface P; Pressure S: Ultrasonic vibration

Claims (5)

An ultrasonic bonding device chip for performing ultrasonic bonding by applying ultrasonic vibrations to superposed bonded materials, the ultrasonic waves characterized in that the surface in contact with the bonded materials is not knurled. Joining tip. The tip for ultrasonic bonding according to claim 1, wherein the tip of the tip has a curved surface having a convex shape curved in a cross section orthogonal to the ultrasonic vibration direction. The tip for ultrasonic bonding according to claim 2, wherein a curvature radius of a curved surface of a tip portion of the tip is 30 mm to 150 mm. An ultrasonic bonding method using the chip according to any one of claims 1 to 3. The ultrasonic joining method according to claim 4, wherein an aluminum material or an aluminum alloy material and a steel material are joined.

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