JPH0223501B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a novel ceramic-metal composite, and particularly to a composite optimal for preventing ceramics from breaking due to thermal stress.

[Background of the invention]

At the location where ceramics and metal are bonded, the physical properties of the two, especially the coefficient of thermal expansion, are significantly different, so thermal stress is generated during the bonding process or under usage conditions that are subjected to thermal loads, resulting in destruction of the ceramic, peeling of the bonded part, etc. occurs. This tendency becomes particularly noticeable as the object to be joined becomes larger. Therefore, it has been extremely difficult to produce ceramics and metals, especially for large structures.

Conventionally, as a method for preventing thermal stress fracture of ceramics, they are bonded via a thermal stress buffering material such as Mo, W, Kovar, or Furni steel, which has a coefficient of thermal expansion approximately intermediate between ceramics and metal. There are also examples in which composites of metal fibers and metal matrices or inorganic fibers and metal matrices are bonded as thermal stress buffering materials. For example, JP-A-58-176182
In Japanese Patent Application No. 58-37598 (Japanese Unexamined Patent Publication No. 59-162185), a composite of C fiber and Cu matrix is bonded as a thermal stress buffer material.

However, there is a limit to the size of the bonded body of ceramics and metal bonded in the conventional direction, and under conditions of high thermal load, the ceramic or the bonded part may break, limiting the conditions of use. .

[Purpose of the invention]

The object of the present invention is to provide a ceramic-metal composite which is most suitable for avoiding the conventional drawbacks and, in particular, for preventing thermal stress fracture of ceramics.

[Summary of the invention]

In order to avoid the drawbacks of the prior art, the inventors have considered joining ceramics and metal bodies through a composite body having an intermediate coefficient of thermal expansion. That is, the present invention provides a joined body of ceramics and metal that are joined by a brazing filler metal through a thermal stress relieving material, in which the coefficient of thermal expansion of the thermal stress relieving material is such that the side in contact with the metal has a thermal expansion coefficient of the metal. The coefficient of thermal expansion changes continuously or stepwise in the thickness direction between the joints so that the side in contact with the ceramic has a value that approximates the coefficient of thermal expansion of the ceramic,
The thermal stress relieving material is a ceramic-metal composite characterized by being made of a composite of inorganic fibers and a metal matrix.

That is, in joining ceramics and metal,
As the intermediate member, it is necessary to use a metal or a composite material whose coefficient of thermal expansion is intermediate between that of ceramics and a metal body and whose modulus of elasticity is small, so as to provide a thermal stress relieving effect. It has been confirmed through experiments that it is effective to use a structure in which two or more layers of composites of inorganic fibers and metal matrix are stacked together in order to impart a thermal stress relaxation effect to the intermediate member itself.

On the other hand, among the composites of inorganic fibers and metals, the composite of carbon fiber and Cu matrix has the greatest thermal stress relaxation effect, and the composite made of two or more layers with different coefficients of thermal expansion is the most effective. It was confirmed through experiments that the thermal stress relaxation effect is large.

As a composite of carbon fiber and Cu, the volume percentage of carbon fiber is 30 to 40% in the first layer, 40 to 50% in the second layer,
It is desirable that the third layer should be 50-60%.
The coefficient of thermal expansion of this composite varies between 4 and 12×10 ^-6 /°C. In addition, the elastic modulus is 5 to 13×10 ³ Kg/
It was confirmed that as a result of reducing the thermal stress of the bonded body by using the deformability ^of the composite, a good bonded body could be obtained.

The zygote of the present invention is the first vacuum vessel of a nuclear fusion device.
Suitable for walls and insulating walls for MHD power generation.

[Embodiments of the invention]

Comparative example First, as ceramics, a 10 mm thick, 30 mm square
When joining SuS304 stainless steel plates with a thickness of 5 mm and a square of 30 mm using a SiC sintered body containing 2% by weight of BeO, Cu-C between the two joining members is
A fiber composite construct was used.

Example 1 When the two-layer structure of the composite structure is used as an intermediate member, the volume percentage of C fiber in the first layer is 30 to 40%, and 2
A composite with a layer thickness of 40 to 50% was used. That is, Cu-40%Mn is placed between the SiC sintered body and the composite structure.
Also, there is Cu-40% between the composite structure and the SuS304 steel plate.
A good bonded body with low thermal stress was obtained by pressurizing and heating in an Ar atmosphere at 870° C. and 5 to 10 kg/cm ² with a Mn foil interposed.

Example 2 Similarly, when a SiC sintered body with a thickness of 10 mm and a square of 40 mm and containing 2% by weight of BeO is used as the ceramic, and a 40 mm square SuS304 stainless steel plate is used as the metal, the Cu - Bonded using a C fiber composite structure. As shown in Fig. 1, first the composite structure 5 and the SiC sintered body 7 are joined, and then the composite structure 3 has a SuS304 stainless steel plate 1 on its side.
were brazed with brazing material 2. The SiC sintered body has a thermal conductivity of 0.6 cal/cm・sec, °C, and a specific resistance of 10 ¹³ Ω・cm.
It contains 0.1 to 3.5% by weight of BeO. Cu―
The thermal expansion coefficient of the C fiber composite is 10-12×10 ^-6 /℃ for a 30-40% C fiber member, and 6-7× for a 40-50% member.
10 ^-6 /°C, and 50 to 60% members have a value of 4 to 6 × 10 ^-6 /°C. The Cu--C fiber composite structure 5, the side and
A Cu-40% Mn foil 6 with a thickness of 50 μm was interposed between the SiC sintered body 7 and the foil 6 was bonded by heating under pressure in an Ar atmosphere at 870° C. and a pressure of 5 to 10 kg/cm ² . next
A 100 μm thick silver solder foil 2 is interposed between the SuS304 stainless steel plate 1 and the composite structure 3.
By heating and bonding in an Ar atmosphere at 700-710° C. and 5-10 Kg/cm ^{2 ,} a good bonded body with low thermal stress was obtained. As shown in Figure 3, the composite structure and
Since the thermal expansion coefficients of the SiC sintered bodies were almost the same, the thermal stress of the joined body could be reduced, and as a result, a good joined body was obtained.

Example 3 As shown in Fig. 2, a 30 mm square copper plate was used as the metal, and the aforementioned Cu-C fiber composite structure was used as the intermediate member.
A Cu-40% Mn foil 13 is interposed between the Mo metalized Si ₃ N ₄ sintered body 14 and the composite structure 12, and a Cu-40% Mn foil 9 is also interposed between the copper plate 8 and the composite structure 10. By pressurizing and heating in an Ar atmosphere at 870° C. and 5 to 10 kg/cm ² to bond, thermal stress could be reduced and a good bonded body was obtained.

〔Effect of the invention〕

According to the present invention, when bonding ceramics and metal, it is possible to reduce thermal stress during the bonding process and under usage conditions under thermal load, and it is possible to prevent cracks from occurring in the ceramics, resulting in ceramics with good thermal conductivity. This has the effect that a healthy bonded body between the metal and the metal can be easily obtained.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views of the composite of the present invention, and Figure 3 shows the composite during heating and cooling during bonding.
FIG. 3 is a diagram showing changes in thermal expansion of a SiC sintered body. 1...SuS304 stainless steel plate, 2...silver solder foil,
3...Cu-30~40% C fiber composite, 4...Cu-40~
50% C fiber composite, 5... Cu-50-60% C fiber composite, 6... Cu-40% Mn foil, 7... SiC sintered body, 8
...Copper plate, 9...Cu-40%Mn foil, 10...Cu-30~
40% C fiber composite, 11...Cu-40-50% C fiber composite, 12...Cu-50-60% C fiber composite, 1
3...Cu-40%Mn foil, 14... _Si3N4 , Mo _metallized sintered body.

Claims (1)

[Claims] 1. In a joined body of ceramics and metal that are joined by a brazing filler metal through a thermal stress relaxation material, the coefficient of thermal expansion of the thermal stress relaxation material is close to the coefficient of thermal expansion of the metal on the side in contact with the metal. The thermal stress relieving material changes continuously or stepwise in the thickness direction between the joints so that the side in contact with the ceramic has a coefficient of thermal expansion that approximates the coefficient of thermal expansion of the ceramic, and the thermal stress relaxation material is made of inorganic fibers and A composite of ceramics and metal characterized by being composed of a composite with a metal matrix.