JPH0761869A - Method for joining material different in coefficient of thermal expansion - Google Patents

Abstract

PURPOSE:To obtain a healthy joined body reduced in residual stress and free from breakage by keeping a material different in coefficient of thermal expansion to a definite temperature halfway during cooling from a joining temperature to a ambient temperature in heating and joining the material through an intermediate layer. CONSTITUTION:In a method heating and joining a material different in coefficient of thermal expansion, the temperature of the material is kept to a definite temperature halfway during cooling from joining temperature to ambient temperature. In this joining method, in the case of the intermediate layer consisting of Cu or Cu alloy when the keeping temperature is >=600 deg.C, the heating effect is not produced, because the difference of temperature cooled to ambient temperature become larger even if stress is released by the keeping temperature and as a result, residual stress becomes also larger and when the keeping temperature is <600 deg.C, the effect is not produced, because Cu or Cu alloy is not softened and as a result, the stress is not released. Similarly, in the case of an intermediate layer consisting of Al or Al alloy, when the keeping temperature is >=500 deg.C, the effect is not produced because the difference of temperature cooled to ambient temperature becomes larger, though the stress is released by the keeping temperature and as a result, the residual stress becomes also larger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating and joining materials having different coefficients of thermal expansion. More specifically, it is difficult to form a part having a complicated shape with poor workability, The present invention relates to a joining method in which high strength is required, for example, when joining metal and ceramics.

[0002]

2. Description of the Related Art Conventionally, when joining materials having different thermal expansion coefficients, a stress relaxation material is arranged between the materials to be joined in order to obtain a sound joined body (Japanese Patent Laid-Open No. 61-21527).
No. 2), or controlling the shape of the bonded body (Japanese Patent Laid-Open No.
-77369) or, after joining, the joined body is processed (see Japanese Patent Publication No. 3-71391) to relieve the residual stress.

[0003]

As described above, when materials having different thermal expansion coefficients are heated and bonded together, residual stress is often relaxed in order to obtain a sound bonded body.
Among them, the heat bonding method using a stress relaxation material as the intermediate layer is effective because residual stress can be easily relaxed.

However, when the difference in the coefficient of thermal expansion between the materials to be joined is large or the area to be joined is large, even if a stress relaxation material is used, the residual stress cannot be sufficiently relaxed, and ceramics or the like cannot be relaxed. There is a problem that cracks occur and a healthy joined body cannot be obtained. In order to solve this problem, the present inventors have conducted extensive research.

The present invention relates to such a problem,
It is an object of the present invention to reduce residual stress and obtain a sound joined body without cracks when joining materials with different thermal expansion coefficients by heating.

[0006]

The above object can be achieved by the method for joining materials having different coefficients of thermal expansion described in the claims. The gist of the joining method according to the present invention is to maintain the temperature at a constant temperature during the cooling step from the joining temperature to room temperature in the case of heat joining using the intermediate layer.

[0007]

According to the present invention, in the method of heat-bonding materials having different thermal expansion coefficients through the intermediate layer, there is no defect such as cracking by holding at a constant temperature in the cooling stage from the bonding temperature to room temperature. It is possible to obtain a healthy joined body. The material to be joined may be ceramics such as Al ₂ O ₃ and SiC, or metals such as steel and titanium.

If the intermediate layer is held at a constant temperature in the cooling step from the bonding temperature to room temperature, the stress generated during the cooling process up to the holding temperature is released and becomes zero because the intermediate layer is softened. Therefore, the residual stress actually generated when cooled to room temperature is only the residual stress generated in the cooling process from the holding temperature to room temperature. Therefore, the residual stress at room temperature can be reduced and cracking and interfacial peeling can be prevented as compared with the case of not holding during cooling.

When the intermediate layer is made of Cu or Cu alloy and the holding temperature is higher than 600 ° C., even if the stress is released at the holding temperature, the temperature difference up to room temperature becomes large thereafter and the residual stress also becomes large. There is no. The holding temperature is 2
If the temperature is lower than 00 ° C., the Cu or Cu alloy does not soften, so that the stress is not released and the effect is not recognized. Similarly, in the case where the intermediate layer is aluminum (hereinafter referred to as Al) or Al alloy, if the holding temperature is higher than 500 ° C, even if the stress is released at the holding temperature, the temperature difference up to room temperature increases thereafter. Therefore, the residual stress also becomes large and there is no effect.

If the holding temperature is lower than 150 ° C., A
1 or Al alloy does not soften, so stress is not released,
No effect is observed. Therefore, the holding temperature is C for the intermediate layer.
In the case of u or Cu alloy, 200 ° C to 600 ° C,
If the intermediate layer is Al or Al alloy, 150 ° C or higher 5
A temperature of 00 ° C or lower is suitable.

From the above viewpoint, it is more effective to keep the temperature as low as possible in order to reduce the residual stress generated at room temperature. Further, the softening of the intermediate layer does not occur instantly, and in order to sufficiently soften the intermediate layer, it is more effective to hold it for at least 1 minute during cooling.

Next, examples of the present invention will be described in comparison with comparative examples.

Example 1 In joining the cemented carbide 11 and the steel (S45C) 15, as shown in FIG. 1, between the cemented carbide 11 and the steel 15, an Ag-Cu-Ti alloy brazing material is sequentially placed from the steel 15 side. Material 14, oxygen-free copper 13, Ag-Cu-Ti alloy brazing material 12
Are laminated and arranged, and the brazing filler metals are melted by heating to bond the cemented carbide 11 and the steel 15. The alloy brazing filler metals 12 and 14 used had a composition of 72% by weight Ag-27% by weight Cu-1% by weight Ti and were heat-bonded in a vacuum furnace at a bonding temperature of 870 ° C. The residual stress in the vicinity of the interface on the cemented carbide 11 side of the obtained joined body was measured. Table 1 shows the values of the residual stress and the results of the appearance.

[0013]

[Table 1]

As is clear from Table 1, 2 during cooling
When held at a temperature of 00 ° C or higher and 600 ° C or lower, the residual stress when cooled to room temperature is greatly reduced compared to when the temperature is not held during cooling and when the temperature is held below 200 ° C or higher than 600 ° C. Moreover, the occurrence of cracks is prevented, which proves that it is effective for obtaining a sound joined body.

[0015]

[Embodiment 2] In joining pure titanium 21 and high-purity alumina 27, as shown in FIG.
7 and Ag-Cu-Ti in order from the alumina 27 side.
Alloy brazing material 26, oxygen-free copper 25, Ag—Cu alloy brazing material 24, Kovar 23, and Ag—Cu alloy brazing material 2
The two brazing materials are melted by heating and the titanium base material 21 and the alumina 27 are bonded to each other.

The alloy brazing material 26 between the alumina 27 and the oxygen-free copper 25 contains 72 wt% Ag-27 wt% C.
u-1 wt% Ti alloy brazing material, oxygen-free copper 25 and Kov
A 72 wt% Ag-28 wt% Cu alloy brazing material was used between the ar23 and the Kovar23 and the titanium 21 at a joining temperature of 850 ° C. to perform heat joining in a vacuum furnace. With respect to the joined test piece, the joint interface between the oxygen-free copper 25 and the alumina 27 was inspected by visual observation and ultrasonic flaw detection (UT). Table 2 shows the test results of the bonded body.

[0017]

[Table 2]

As shown in the examples, 200 ° C. during cooling.
It can be seen that when the temperature is kept at 600 ° C. or lower, the residual stress when cooled to room temperature is reduced, and the appearance and the result of ultrasonic flaw detection are good.

On the other hand, as shown in Comparative Examples, when the temperature is not maintained during cooling and when the temperature is maintained below 200 ° C. or higher than 600 ° C., the bonding interface between copper and alumina peels off or cracks in alumina. Since the residual stress was not sufficiently reduced, such as the occurrence of cracks, it was clarified that they were not joined properly.

[0020]

[Embodiment 3] In the joining of SUS304 and silicon nitride 33 indicated by numeral numeral 31, as shown in FIG.
A brazing sheet 32 having a core material of Al is disposed between 431 and silicon nitride 33, and the brazing material on brazing sheet 32 is melted by heating to bond SUS30431 and silicon nitride 33. Heat bonding was performed in a vacuum furnace at a bonding temperature of 600 ° C. Table 3 shows the test results of the joined body.

[0021]

[Table 3]

As shown in the examples, 150 ° C. during cooling.
It can be seen that when the temperature is kept at 500 ° C. or lower, the residual stress when cooled to room temperature is reduced and good bonding is performed. On the other hand, as shown in the comparative example, when the temperature is not maintained during cooling and when the temperature is less than 150 ° C or 500 ° C.
When the temperature is maintained at a higher temperature, the residual interface stress is not sufficiently reduced, such as the peeling of the bonding interface between Al and silicon nitride, or the cracking of silicon nitride. Became.

[0023]

As described in detail above, according to the present invention,
It is possible to reduce the residual stress when joining materials having different thermal expansion coefficients, and it is possible to provide a sound joined body without cracks or interfacial peeling.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a joining method according to an example and a comparative example of the present invention.

FIG. 2 is a schematic diagram showing a joining method according to an example and a comparative example of the present invention.

FIG. 3 is a schematic diagram showing a joining method according to an example and a comparative example of the present invention.

[Explanation of symbols]

 11 Cemented Carbide 12,14 Al-Cu-Ti Alloy Brazing Material 13 Oxygen Free Copper 15 Steel 21 Titanium 22,24 Ag-Cu Alloy Brazing Material 23 Kovar 25 Oxygen Free Copper 26 Ag-Cu-Ti Alloy Brazing Material 27 Alumina 31 SUS304 32 Brazing sheet 33 Silicon nitride

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takato Mizoguchi 1-5-5 Takatsukadai, Nishi-ku, Kobe City Kobe Steel Research Institute, Kobe Steel Research Institute

Claims (3)

[Claims] 1. A method of heat-bonding materials having different thermal expansion coefficients via an intermediate layer, wherein the materials are held at a constant temperature during cooling from the bonding temperature to room temperature, and materials having different thermal expansion coefficients. How to join. 2. The method for joining materials having different thermal expansion coefficients according to claim 1, wherein the intermediate layer is Cu or a Cu alloy, and the holding temperature is 200 ° C. or higher and 600 ° C. or lower. 3. The method for joining materials according to claim 1, wherein the intermediate layer is aluminum or an aluminum alloy and the holding temperature is 150 ° C. or higher and 500 ° C. or lower.