JPS63201071A - Method of joining ceramic to metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a ceramic-metal bonded body using a brazing agent.

[Conventional technology]

Structural ceramics, represented by silicon nitride and silicon carbide, have greater high-temperature strength, wear resistance, and corrosion resistance than metal materials, and are being considered for application to mechanical parts. In such cases, there is often a need for a method for producing a strong bonded body of ceramic and metal, and various bonding methods are being researched. Among these methods, brazing is particularly promising, but there are several problems such as residual stress due to the difference in coefficient of thermal expansion between the two, and deterioration of bonding strength due to brittle intermetallic compounds generated at the bonding interface. However, a method for joining ceramics and metals with high strength and little variation in strength has not yet been developed.

[Problem that the invention seeks to solve]

In general, ceramics have poor wettability to brazing agents, so methods have been developed for brazing using active metals, but ceramics and metals have different chemical reactivity to brazing agents, and ceramics and brazing agents do not have a strong bond. The temperature range in which this occurs is different from the temperature range in which the metal and brazing agent form a strong bond. For this reason, it is difficult to produce a strong joined body of ceramic and metal, and especially when joining large parts, there has been a problem that the two parts will peel off during cooling due to stress caused by the difference in their coefficients of expansion.

For example, a method of joining ceramics using aluminum as an active metal solder is known. It was impossible to manufacture a joined body.

□ The present invention uses a brazing agent to produce a high-strength bonded body of ceramics and metal.

[Means for solving problems]

As a result of intensive research aimed at solving the above-mentioned problems, the inventors discovered a bonding method that provides a strong bonding surface for both ceramic and solder joints and metal and solder joints, and completed the present invention.

That is, the present invention provides a method for bonding ceramics and metal using a brazing agent, which includes: (1) heating to a temperature higher than the melting point of the brazing agent to melt the brazing agent and fusing the ceramic and the brazing agent; This is a method consisting of a second joining step of joining the brazing agent and the metal at a temperature lower than this temperature.

[Effect]

Ceramics to which the present invention is applied are oxide ceramics such as alumina and zirconia, or non-oxide ceramics such as silicon nitride and silicon carbide. These sintered bodies may or may not contain a sintering aid. The material may be manufactured by any method such as pressureless sintering or hot pressing.

On the other hand, metalwork refers to general structural metal materials such as mild steel, stainless steel, and aluminum alloy.

The brazing agent may be any brazing agent that can firmly bond ceramics and metals together, such as pure An, A!
; L alloy, Ag-Cu-Ti, etc. are preferred.

In the first bonding step, a brazing agent is placed on the surfaces of the ceramics to be bonded and heated to a temperature higher than the melting point of the brazing agent. In order to obtain a stronger bond, the following procedure may be used. After producing several bonded bodies at various temperatures, a strength test is conducted to determine the bending strength of the bonded bodies. Performing the first bonding at a bonding temperature at which this value takes the maximum value (hereinafter referred to as maximum strength),
However, the first bonding is not limited to one temperature at which the maximum strength is obtained, and there is no practical problem in bonding at a temperature at which 90% or more of the maximum strength is obtained.

If the brazing agent does not spread over the entire surface to be joined, this surface may be coated with metal to improve wettability.
The metal for coating the above-mentioned ceramics may be any so-called metal, but from the viewpoint of wettability and bonding strength, Ti, M
o, Ni, Cr, C.

Examples of coating methods include vacuum evaporation, CV
D, ion blasting, etc. may be used.The thickness of the coating layer may be 1000 Å or more, but from the viewpoint of wettability, strength, and workability, it is practical for about 2000 people5.

The thickness of the brazing agent layer formed by the above first step is several mm.
It is. This brazing agent layer is shaped into a shape suitable for the second bonding process.
After processing to the surface roughness and thickness, a second bonding is performed.

The second type of bonding is brazing when the bonding temperature is higher than the melting point of the brazing agent, and solid phase diffusion bonding when the bonding temperature is lower than the melting point of the brazing agent.

Furthermore, by applying surface treatment such as plating to the surfaces of the base metals to be joined, it is possible to suppress the formation of brittle intermetallic compounds and obtain a stronger joined body.

To obtain a strong bond, do the following. After several metals are bonded at various temperatures, a strength test is conducted to determine the bending strength of the bonded bodies. If the second bonding is performed at the bonding temperature at which this value is at its maximum, a strong bonded body can be obtained. However, the second bonding is not limited to one temperature at which the maximum strength is obtained, and there is no practical problem in bonding at a temperature at which 90% or more of the maximum strength is obtained.

Hereinafter, the present invention will be specifically explained based on Examples. The aluminum sheets used in the Examples and Comparative Examples described below are all pure aluminum with a melting point of 660°C.

Example 1 A preliminary test was conducted in which silicon nitrides and stainless steels (SUS304) were joined together using an aluminum sheet as a brazing agent. An aluminum sheet is sandwiched between the samples and 1O-
A bonded body was obtained by heating at various temperatures for 3 minutes in a vacuum of 5 Torr. The size of each sample is 1010X
It was 10x20.

The joint strength of the joined body is determined by setting the upper span to 10 mm and the lower span to 3.
Evaluation was performed by a 4-point bending test at 0 mm. The relationship between the bonding temperature and the bonding strength of the bonded body of silicon nitride was as shown in FIG. 1, and the maximum strength was 49 kg/mrn'. 8 again
A strength of 90% or more of the maximum strength was obtained in the temperature range of 50 to 1100°C.

On the other hand, stainless steels (SUS304) were joined together using an aluminum sheet in the same manner as in the case of silicon nitrides.

The relationship between bonding temperature and bonding strength was shown by curve ◯ in Figure 1, and its maximum strength was 38 kg/mm'. Also 540~
A strength of 90% or more of the maximum strength was obtained in a temperature range of 620°C.

Next, silicon nitride and stainless steel (SUS) according to the present invention are
304) was joined. As shown in FIG. 2, a silicon nitride sintered body 1 having a size of 1010×10×20 and a stainless steel (SUS304) 2 having the same size were joined using an aluminum sheet as a brazing agent 3.

First, an aluminum sheet with a thickness of 1.0 mm was placed on the surface of silicon nitride 1, and heated in a vacuum of 1 O-5 Torr for 3 minutes.
Heating to 950°C to fuse aluminum to silicon nitride,
A first bond was made.

Next, after polishing the fused aluminum to a thickness of 0.8 mm, a bonding stainless steel was placed on it and the 1O-
Heat to 570°C for 3 minutes in a vacuum of 5 Torr, and
The welding was performed.

When this joint was subjected to a 4-point bending test, the average weight was 22 kg.
It showed a high bonding strength value of /mm'.

Comparative Example 1 An aluminum sheet was sandwiched between silicon nitride and stainless steel of the same type and size as in Example 1, and the temperature was 550°C, where maximum strength was obtained between metals, 950°C, where maximum strength was obtained between ceramics, and intermediate temperatures. 3 at 700℃
A bonded body of silicon nitride and stainless steel was obtained by heat treatment for a minute. The average 4-point bending strength of each is 10 kg/m m'' when joined at 550°C, 4 kg/mrn' when joined at 950°C, and 11 kg when joined at 700°C.
/mtn', and in both cases, only one heat treatment for bonding was required, but only a bonded body with lower bonding strength than in Example 1 was obtained.

Example 2 In the same manner as in Example 1, a thickness of 1
．． Place a 0 mm aluminum sheet at 10-5T.
o r rrr) The first bonding was performed by heating at 900° C. for 3 minutes in a vacuum to fuse aluminum to alumina.

Next, after polishing this fused aluminum to a thickness of 0.3 mm, a mild steel plate for joining was placed on the 1O-5
A second bonding was performed by heating at 550° C. for 3 minutes in a vacuum of Torr.

When this joint was subjected to a 4-point bending test, the average weight was 20 kg/
The bonding strength of mrn' was obtained. As in Example 1, a high-strength alumina/mild steel plate joined body can be manufactured according to the present invention.

In addition, in the second welding, approximately 1
．． When Ni plating was applied to a thickness of 0 gm, the average strength in a 4-point bending test was improved to 26 kg/mm'.

Comparative Example 2 10-5T Or r (7) 700°C for 3 minutes in vacuum 1
An alumina/mild steel plate joint was produced by heat treatment twice. However, the average 4-point bending strength of this joint is 8 kg/m
The value was as low as rn'.

Example 3 A stainless steel (SUS 304
) were joined using an aluminum sheet with a thickness of 1 mm under the same conditions as in Example 1, and a strong joined body was obtained.

Comparative Example 3 A silicon nitride sintered body of the same size as in Example 3 and stainless steel (SUS 304) were joined by a diffusion bonding method using a 1 mm thick aluminum lamb sheet.

The specific joining method is as follows.

An aluminum sheet was placed on the surface of the silicon nitride sintered body to be joined, and a pressure of 2 kg/mrn' was applied for 60 minutes at a temperature of 620°C (aluminum sheet melting point 660°C) in a vacuum of 10-'Torr to bond silicon nitride and aluminum. After joining the aluminum, stainless steel (SUS
304) and heat-treated in a vacuum of 10-5 Torr at a temperature of 570° C. for 3 minutes without any load, but they peeled off during cooling and no bonded body was obtained.

〔Effect of the invention〕

By using the method of the present invention, it is possible to produce a bonded body having strong bonding strength at both the bonding surface between the ceramic and the brazing agent and the bonding surface between the brazing agent and the metal.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between bonding temperature and bonding strength when ceramics and metals are bonded together using a brazing agent, and FIG. 2 is a side view of a bonded body for bending strength testing. 1... Ceramics 2... Metals 3... Brazing agent

Claims (1)

[Claims] 1. In a method of joining ceramics and metal using a brazing agent, the first joining step involves heating to a temperature higher than the melting point of the brazing agent to melt the brazing agent and fusing the ceramics and the brazing agent, and this temperature. A method for joining ceramics and metal, comprising a second joining step of heating and joining the brazing agent and metal at a temperature below 1.