JPH0639563A - Ceramic and metal joint - Google Patents

Abstract

PURPOSE:To provide a sound joined body of a large ceramics body and a metal body by executing the joining by using the brazing filler metal through a buffer metallic layer constituted by a plurality of metallic balls arranged on the plane. CONSTITUTION:A ceramics 1 and a metal 5 are joined by a brazing filler metal 2 and a brazing filler metal 4 through a buffer metallic layer 3 constituted by a plurality of metallic balls arranged on the plane. This constitution reduces the internal residual stresses of the ceramics to be generated in the cooling process of the joining, and a sound joined body can be manufactured. No restrictions on the material, the size and the thickness are applied to either the ceramics or the metal, and a joined body can be manufactured without using any special intermediate layer except the buffer metal which is constituted by arranging a plurality of metallic balls on the plane between the ceramics and the metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic-metal bonded body in which ceramics and metal are bonded via an intermediate layer or a buffer metal layer.

[0002]

2. Description of the Related Art Ceramics have excellent heat resistance, abrasion resistance, and corrosion resistance as compared with metals, but also have drawbacks such as low toughness and difficult workability. For this reason, ceramics are rarely used alone, and ceramics are used only in the parts that require the required properties such as heat resistance, wear resistance, and corrosion resistance, and the parts that require toughness and workability are metal. In most cases, it is used in the form of a ceramic-metal bonded body. The ceramic-metal bonded body is generally manufactured by a brazing method from the viewpoint of workability, reliability, and cost. However, in the ceramic-metal direct bonding by the brazing method, since cooling is performed after the bonding in a high temperature furnace, a large residual stress is generated inside the ceramic due to the difference in thermal expansion coefficient between the ceramic and the metal in the cooling process, In many cases, it is difficult to manufacture a sound bonded body because cracks occur near the bonded interface where the internal residual stress of ceramics becomes highest.

Ceramics are roughly classified into alumina type, zirconia type, silicon carbide type, and silicon nitride / sialon type, but they are used as structural members which are required to have heat resistance, abrasion resistance and corrosion resistance. From the viewpoint of high temperature strength and fracture toughness, aluminum type and silicon nitride / sialon type are used. In particular, the silicon nitride-sialon type has much better characteristics than the alumina type, but its thermal expansion coefficient is 8 × 1.
In contrast to 0 ^-6 / ° C, 3 to 4 for silicon nitride / sialon
Since it is ^{x10 -6} / ° C, which is less than half that of alumina, it is even more difficult to manufacture a sound bonded body.

As a method for relaxing the internal residual stress of ceramics in the ceramics-metal bonded body,
(1) A method of interposing a soft metal as an intermediate layer between the ceramics and the metal, (2) A method of interposing a plurality of layers of the soft metal and the hard metal as an intermediate layer between the ceramics and the metal,
(3) Proposal of a method in which an intermediate layer is partially interposed between ceramics and metal to reduce the bonding area, and (4) a method in which a slit or the like is provided in the intermediate layer or metal to absorb deformation in the cooling process. Has been done. These are technologies that have been partially put into practical use, and although they have the effect of reducing the internal residual stress of ceramics, it is difficult to significantly reduce the internal residual stress. Therefore, small ceramics
It is possible to manufacture a metal bonded body, but it is difficult to manufacture a large bonded body. Especially, in the silicon nitride-sialon system having a low coefficient of thermal expansion, the size of the ceramic is L20 mm × W.
A bonded body of about 20 mm is considered to be the limit of production as a practical level. As a method for significantly reducing the internal residual stress of ceramics, in Japanese Patent Laid-Open No. 62-148124, a metal 5 and a ceramic 1 are joined and integrated via an intermediate layer as shown in FIGS. Ceramics-Ceramic-Metal Joining Member-Ceramics with Metal Intermediate Layers 6a, 6b Intermediate or Metal Intermediate Layers 7, 8, 9-
We propose a metal joining member.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Japanese Patent No. 8124 attempts to significantly reduce the residual stress inside the ceramics, but has the following problems, and produces a large ceramics, in particular, a silicon nitride / sialon-based ceramic and a sound metal bonded body. Is difficult to do.

First, the above invention proposes to interpose an intermediate layer between the ceramics and the buffer metal layer, and also in the embodiment, a copper plate having a thickness of 1 mm is used as an intermediate layer for joining alumina and a steel sheet. . Copper plates are widely used as an intermediate layer because of their high plastic deformability, but copper has a high coefficient of thermal expansion of 16 × 10 ⁻⁶ / ° C. and is not a perfect plastic body. The present inventors perform a logical analysis of internal residual stress of ceramics with a direct bonding model of sialon and copper,
It was clarified that when the ceramics were made larger, high residual stress was generated inside the ceramics even if the copper plate was made thinner. From this result, it can be said that the intermediate layer between the ceramics and the buffer metal layer, which are the constituent elements of the invention, is conversely harmful for producing a sound bonded body.

Next, the above invention proposes a buffer metal layer composed of a stretchable metal member having a mesh shape, a comb shape, a bundled wire shape, or the like as the buffer metal layer. A perforated plate is used. The inventors of the present invention conducted a bonding experiment through a buffer metal layer of sialon and stainless steel, and showed a shape such as a comb tooth shape, a bundled wire shape, or the like in which a line contact is made at a bonding surface, and a mesh shape is partially cut like a perforated plate. It was confirmed that the effect of reducing the internal residual stress of ceramics is small in the shape of surface contact with.

[0008]

The present invention has been made for the purpose of producing a sound joined body of a large-sized ceramic, particularly a silicon nitride-sialon-based ceramic, and a metal, which is difficult to achieve by the conventional improved techniques. The ceramic-metal bonded body is characterized in that the ceramic and the metal are bonded by a brazing material through a buffer metal layer formed by arranging a plurality of metal balls on a plane.

[0009]

The structure of the ceramic-metal bonded body according to the present invention is shown in FIG. The ceramics 1 and the metal 5 are joined by a brazing material 2 and a brazing material 4 via a buffer metal layer 3 formed by arranging a plurality of metal balls on a plane. The intermediate layer between the ceramic and the buffer metal layer is not used because it is harmful from the viewpoint of relaxing the internal residual stress of the ceramic as described above. In ceramics-metal brazing, in order to improve brazing properties, it is common to pre-metallize the surface of ceramics with an active metal. In the present invention, however, an active metal brazing material is used for the brazing material 2. Bonding is possible without metallizing ceramics, and metallizing ceramics is not always necessary.

It is well known that the residual stress inside the ceramic can be reduced by reducing the ceramic-metal joint area. However, in the method of line contact or local surface contact, a high residual stress is locally generated. With the silicon nitride-sialon system, it is difficult to manufacture a healthy large ceramic-metal bonded body. In the present invention, using a buffer metal layer configured by arranging a plurality of metal spheres in point contact with the bonding surface of the ceramics and the metal,
When the brazing filler metal reaches the melting temperature during brazing, the brazing filler metal is concentrated in the point contact area due to the capillary phenomenon, and when cooled to below the melting temperature, it solidifies in a very narrow range of the contact point, so the joint area is even. It can be reduced and high residual stress is not generated locally inside the ceramic unlike the method of line contact or local surface contact, and the deformation in the cooling process is mostly absorbed by the displacement of each metal ball. Therefore, the residual stress inside the ceramic is significantly reduced.

Although it is extremely difficult to control the bonding strength of the ceramic-metal bonded body by the conventional method,
According to the present invention, by changing the size of the metal sphere,
The bonding strength per unit area can be easily changed. According to the bonding method of the present invention, the optimum bonding strength for producing a sound ceramic-metal bonded body is theoretically or experimentally determined according to the size of the ceramic, and the metal having the optimum bonding strength is obtained. Select the sphere size.

As a result of a shear test, a joined body produced by brazing Sialonan and stainless steel in a vacuum furnace through a buffer metal layer made of copper balls was found to be 8 kg / mm when a copper ball having a diameter of 1 mm was used. ^{2. When} a copper ball having a diameter of 3 mm was used, the shear strength was 3 kg / mm ² . By increasing the size of the metal balls, the shear strength is reduced, but it is possible to manufacture a larger and sound ceramic-metal bonded body, and the bonding strength of the entire bonding surface is smaller ceramic-
Since it can be made much larger than a metal bonded body, there is no problem in practical use. Furthermore, by increasing the size of ceramics, the manufacturing cost per unit area can be greatly reduced, and as a wear-resistant member that collides with lumps and particles, the ability to absorb impact energy is improved and the impact resistance is greatly improved. The merits such as improvement are extremely large.

[0013]

[Embodiment] In FIG. 2, ceramics 1 is L200 × W200 × T200 mm in which the bonding surface is metallized with active metal.
Sialon, metal 5 is 1200 × w200 × t6mm stainless steel (SUS410), buffer metal layer 3 has a diameter of 3
mm copper balls are arranged on a flat surface without any gap. Silver brazing foils were inserted above and below the buffer metal layer and brazed in vacuum under brazing conditions of 800 ° C. × 40 minutes to produce a joined body.
In order to quantitatively evaluate the effect of reducing the internal residual stress of the ceramic of this joined body, the residual stress of the end face of the ceramic was measured by X-ray diffraction at 5 points in the thickness direction × 3 points in the width direction, and The magnitude of stress is + 10-10kgf /
It was confirmed that the residual stress was within the range of mm ² and that the residual stress was hardly generated in the ceramic when the bonding was cooled.

In the above-mentioned embodiment, sialon having the lowest thermal expansion coefficient among structural ceramics and 9 to 15 × 10 ^{-6 are used.}
/ C is a stainless steel joint with a high coefficient of thermal expansion,
It is much easier to manufacture a joined body with ceramics such as alumina having a thermal expansion coefficient larger than that of Sialon, as compared with the present embodiment.

[0015]

According to the present invention, it is possible to significantly reduce the internal residual stress of ceramics that occurs during the cooling process at the time of joining, and to manufacture a sound joined body. Also, neither ceramics nor metals are restricted by material, size and thickness,
In addition, the joined body can be manufactured without using a special intermediate layer other than the buffer metal formed by arranging a plurality of metal balls on the plane between the ceramic and the metal.

[Brief description of drawings]

FIG. 1 is a side view of the structure of a joined body according to the present invention.

2A and 2B show a structure of a ceramics-metal bonded body of an example, FIG. 2A being a plan view and FIG. 2B being a side view.

FIG. 3 is a structure diagram of a conventional example, in which a cushioning metal for comb teeth is used.

FIG. 4 is a structure diagram of a conventional example, in which a bundle-shaped buffer metal is used.

FIG. 5 is a structure diagram of a conventional example, in which a mesh-shaped buffer metal is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramics 2,4 Brazing material 3 Buffer metal layer 5 Metal 6a, b Metal intermediate layer 7,8,9 Buffer metal layer

Claims (1)

[Claims] 1. A bonded body of ceramics and metal, wherein ceramics and metal are bonded by a brazing material through a buffer metal layer formed by arranging a plurality of metal balls on a plane.