JPH0497962A - Method for joining carbon material to carbon material - Google Patents

Abstract

PURPOSE:To maintain uniform joining strength between carbon materials over a wide temp. range and to prevent the exfoliation of the joined surfaces by interposing a metallic silicon sheet between the carbon materials and holding them in a flow of gaseous nitrogen under special conditions. CONSTITUTION:A metallic silicon sheet is interposed between carbon materials, 50-500kg/cm<2> load is placed and they are heated to 1,400-1,900 deg.C at 100-250 deg.C/min rate in a flow of gaseous nitrogen under ordinary pressure and are held for 2-15 min.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of joining carbon materials.

Prior art and its problems At present, carbon abrasives have properties such as heat resistance, heat insulation, conductivity, corrosion resistance,
Because of its excellent lubricity, it is widely used in almost all industrial fields such as steel, communications, transportation, marine, and medical fields. Carbon materials are also expected to be used as next-generation materials because they can be used in extreme environments such as nuclear reactors, outer space, and extremely high temperatures.

In order for such carbon materials to be used even more in the industrial field in the future, techniques for processing carbon materials into products with complex shapes, large products, etc. are required.

However, processing into complex shapes usually involves removal processing such as cutting, resulting in poor work efficiency and high costs, and processing into large products requires large-scale manufacturing equipment, which increases equipment costs. There are some problems such as it takes a lot of time. One way to increase the size is to process carbon materials into a certain shape and assemble the resulting parts, but this requires extremely high precision machining when manufacturing the parts, which is time-consuming and economical. In response to these problems, research is currently being conducted into techniques for bonding carbon materials together as a means to relatively easily process carbon materials into complex shapes or large products.

For example, a method of joining by heating and carbonizing using coal tar pitch with a relatively high carbonization rate, an organic polymer material, etc. as a joining material, a method of joining by brazing using a metal or alloy as a joining material, etc. is being considered. However, when coal tar pitch, an organic polymer material, or the like is used as a bonding material, the bonded portion becomes porous due to volatile components volatilized during carbonization during bonding, resulting in a low bonding strength. Further, when a metal-based bonding material is used, the bonded portion expands at high temperatures, so there is a drawback that a constant bonding strength cannot be obtained.

Means for Solving the Problems In view of the problems of the prior art as described above, the inventors have
As a result of research, it has been found that the above problems can be solved or alleviated by using metal silicon as a bonding material for bonding carbon materials together.

The present invention provides the following method for joining carbon materials together.

"A thin plate of metal silicon is sandwiched between two carbon materials, heated to 1400 to 1900°C in a nitrogen stream, and held for 2 to 15 minutes under a load of 50 to 500 g/cm2. A method for bonding carbon materials and carbon materials, characterized by the following." Carbon materials used in the present invention include natural graphite, artificial graphite, and amorphous carbon before graphitization, which are commonly used in industry. Bonding may be performed not only between materials of the same type but also between materials of different types.

Metallic silicon has a relatively high melting point, good wettability with carbon materials at high temperatures, and a coefficient of thermal expansion extremely close to that of carbon, so it can exhibit a constant bonding strength over a wide temperature range from room temperature to high temperature. can. Such metal silicon is used as a thin plate of 0.2 to 1011I11.

In the method of the present invention, a thin metal silicon plate is sandwiched between two carbon materials, and then a load of 50 to 500 g/cJ is applied. The magnitude of the load may be appropriately selected depending on the type and thickness of the carbon material, but if it is smaller than 50 g/cd, sufficient bonding strength cannot be obtained;
/cd, there is a risk of damaging the carbon material.

Next, under the above-mentioned load, the air in the apparatus is replaced with nitrogen, and the temperature is raised to usually 100 to 1400 to 1900 degrees Celsius in a nitrogen atmosphere or nitrogen stream at normal pressure, and then heated for 2 to 15 minutes.
After holding for a minute, allow to cool to room temperature.

In this process, by using nitrogen gas, a thin film of nitride formed on the surface of metal silicon greatly suppresses the outflow and diffusion of molten silicon into the pores of the carbon material. of silicon flows into the pores,
The majority may be present between the carbon materials near the joint. On the other hand, if another inert gas such as argon is used as the atmospheric gas, molten silicon flows out and diffuses through the pores of the carbon material, making it impossible to obtain a good bonding state.

The joining temperature varies depending on the size of the carbon materials to be joined and the pressure within the reactor, but is usually 1400 to 1900°C, preferably 1500 to 1700°C. 1400
If the temperature is lower than 1900°C, the transition or melting of the metal silicon to the carbon material will not occur, so no bonding will occur, and if the temperature exceeds 1900°C, the fluidity of the molten metal silicon will become too high.
Because it flows out and diffuses through the pores of the carbon material,
The bonding area decreases and the bonding strength decreases.

The holding time for the heat treatment varies depending on the bonding temperature, but is usually 2 to 15 minutes, preferably 3 to 10 minutes. If it is shorter than 2 minutes, the metal silicon will not melt sufficiently, resulting in insufficient bonding, and if it exceeds 15 minutes, the molten metal silicon will flow out and diffuse, reducing the bonding area and reducing the bonding strength. become weak.

Effects of the Invention According to the present invention, carbon materials can be easily joined without requiring special equipment.

The bonded body obtained by the method of the present invention has a constant bonding strength over a wide temperature range, and the bonded surfaces do not easily peel off.

Therefore, by the method of the present invention, carbon materials can be easily processed into complex-shaped products, large-sized products, and the like.

Example The present invention will be specifically explained below with reference to Examples.

Example 1 Two pieces of high-density isotropic graphite material IG-11 (manufactured by Toyo Tanso)
A thin plate (10 mm) of metal silicon (manufactured by Mitsuwa Kagaku, 99.5%) was placed between the cylindrical blocks (10 mm φ x 30 m 112 mm).
mmφxO, 5+u+Q) and add 80g (1
A weight of 0.02 g/cd) was placed on the tube and placed in a high frequency induction furnace. 1500°C at a rate of 150°C/min in a nitrogen stream inside the furnace.
The temperature was raised to .degree. C., maintained at that temperature for 8 minutes, and then allowed to cool to room temperature.

A three-point bending test was conducted on the obtained bonded carbon material at room temperature and 1350°C. The bending strength of the obtained bonded carbon material was 198 kg/cd at room temperature.

It was 173 kg/c at 1350°C.

Example 2 Example 1 except that the bonding temperature was held at 1600°C for 8 minutes.
Carbon materials were bonded in the same manner as above.

The bending strength of the obtained bonded carbon material was measured in the same manner as in Example 1, and it was found to be 357 kg/cd at room temperature, 1
It was 325 kg/cl at 350°C.

Example 3 Example 1 except that the bonding temperature was held at 1700°C for 8 minutes.
Carbon materials were bonded in the same manner as above.

When the bending strength of the obtained bonded carbon material was measured in the same manner as in Example 1, it was found to be 151 kg/co? at room temperature. ,
It was 149 kg/cd at 1350°C.

Test Example 1 A bonded carbon material was obtained in the same manner as in Example 2, except that bonding was performed in a vacuum or argon atmosphere instead of a nitrogen atmosphere.

When a cross section of bonded carbon materials bonded in vacuum or in an argon atmosphere was observed using a scanning electron microscope, metallic silicon was not observed at or near the bond, but was observed within the pores of the carbon material quite far away from the bond. It was done.

On the other hand, when the cross section of the bonded carbon material obtained in Example 2 was similarly observed using a scanning electron microscope, metallic silicon was observed in the bonded portion and its vicinity, indicating a good bonded state.

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Claims (1)

[Claims] (1) A thin plate of metal silicon is sandwiched between carbon materials, heated to 1400 to 1900°C in a nitrogen stream, and heated for 2 to 15 minutes under a load of 50 to 500 g/cm^2. A method for bonding carbon materials together, characterized by holding the carbon materials together for a minute.