JPH04125107A - Binderless molding method for carbon product - Google Patents

Abstract

PURPOSE:To mold carbon powder including no volatile component into the desired shape without using a bonding material by feeding the carbon powder including no volatile content into a mold and retaining the same in a high-frequency induction oven or a graphite electric resistance oven for a given time under the given atmosphere, load and temperature. CONSTITUTION:Carbon powder prepared by coking coal or petroleum pitch, removing completely the volatile content to a substantial extent and pulverized carbon powder is fed into a proper molding tool and is set in a high-frequency induction oven. Then, a reaction device is vacuumized or turned into inactive gas atmosphere. 100-5000kg/cm<2> load is applied from above the molding tool. After that, the temperature in the device is raised up to 1700-3000 deg.C. Also the retaining time for heat treatment is different for different sintering temperature, and usually is in the range of 1-100 minutes. A carbon product can be molded easily and at low cost by using an easily available raw material without requiring a special device.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a binderless molding method for carbon products.
Specifically, the present invention relates to a method of forming carbonaceous powder containing no volatile components into a carbon product in a desired shape without using a binder.

Conventional technology and its problems At present, carbon products such as graphite products have excellent heat resistance, heat insulation, conductivity, corrosion resistance, and lubricity, so they are used in most industries such as steel, communications, transportation, marine, medical, etc. It is widely used in all industrial fields.

In addition, carbon products have recently been particularly expected as next-generation materials because they can be used in extreme environments such as around nuclear reactors with strong particle beams, outer space, and ultra-high temperature fields of 3000° C. or higher.

In order for carbon products to be used even more as structural materials in the industrial field in the future, it is necessary to obtain high-density products with high mechanical strength. Generally, carbon products are manufactured by adding petroleum-based or coal-based pitch (binder) to coke powder (aggregate), kneading, shaping, and carbonizing or graphitizing. For this reason, the obtained carbon product becomes porous due to the volatile components volatilized from the pitch by thermal decomposition or the like during carbonization and the pores of the coke powder, resulting in a decrease in strength.

Currently, in order to manufacture high-density carbon products with greater mechanical strength, we are developing a method that uses mesophase microbeads, which are spherical ultrafine powders, as the main raw material. A method of high-temperature, high-pressure molding by mixing a very small amount of binder is being considered. However, the former method is costly and time-consuming and does not produce a product with improved properties, while the latter method requires less binder because the surface area increases when the coke is turned into ultra-fine powder. Therefore, a high-density product cannot be obtained.

As a result of research in view of the above-mentioned problems, the present inventor has discovered that using conventional carbonaceous powder without using any binder,
We have found a way to obtain the desired carbon product.

That is, an object of the present invention is to provide the following method for molding an anisotropic carbon product.

[Carbonaceous powder containing no volatile components is placed in a mold and placed in a high frequency induction furnace or a graphite electric resistance furnace,
100-5000 under vacuum or inert gas atmosphere
A binderless molding method for an anisotropic carbon product characterized by raising the temperature to 1700 to 3500°C under a load of kg/cJ and holding it for 1 to 100 minutes. ” The carbonaceous powder containing no volatile components used in the present invention is prepared by heating coal-based or petroleum-based pitch at 600 to 1800°C.
Preferably, it is coked at 1200° C. or higher to substantially completely remove volatile components and is pulverized to a particle size of about 10 μm or less.

The obtained carbonaceous powder is placed in a suitable mold, and this is set in a high frequency induction furnace. Next, a non-oxidizing atmosphere is created in the reactor. i.e. 0,5 x 10-'
~0.9 X 100-2) c/crI, preferably 0
．． A vacuum of 5 x 10-3 to 0.8 x 10-2) cg/cj or an inert gas atmosphere of nitrogen or argon at normal pressure.

A load of 100 to 5000 kg/cd, preferably 50 C1 to 3000 kg/c+# is applied from above the mold.

If it is less than 100 kg/cJ, sintering will not be performed sufficiently, and if it exceeds 5000 kg/cJ, a mold with good performance will be required, which will increase the cost, which is not preferable.

Thereafter, the temperature inside the device is increased to 1700 to 3500 C, preferably 2000 to 3 C, at a rate of about 2 to 10 C/min.
Raise the temperature to 000℃. If the temperature is lower than 1000°C, the carbonaceous powder will not be sintered due to insufficient crystallization, and if it exceeds 3500°C, the carbonaceous powder will sublimate.

The holding time of the heat treatment varies depending on the sintering temperature, but is usually 1 to 100 minutes, preferably 5 to 30 minutes. If it is shorter than 1 minute, the carbonaceous powder will not be sufficiently crystallized and will not be sintered, and even if it exceeds 100 minutes, no further effect will be obtained.

The above-mentioned anisotropic carbon products of the present invention have different strengths in parallel and perpendicular directions to the pressurizing direction, such as where high strength is required in one force direction and where heat needs to be diffused in one direction. It is extremely effective when used for.

The present invention also provides the following binderless molding method for isotropic carbon products.

``A pre-shaped compact formed from carbonaceous powder that does not contain volatile components is placed in a hot isostatic pressing apparatus (HIP), heated to 1,700 to 3,500°C using an inert gas as a medium, and the pressure inside the apparatus is reduced. Pressurize to 500 to 10,000 kg/c-,
A binderless molding method for an isotropic carbon product characterized by holding the product for ~100 minutes. A pre-shaped compact is produced from the carbonaceous powder containing no volatile components according to the method for forming an anisotropic carbon product described above. In the process of manufacturing a pre-biased compact, uniform isotropy may not be provided due to the next hot isostatic pressing process, so a load of 300 kg/cd or more and a temperature of 1700°C are required.
It is preferable not to exceed this.

The obtained pre-biased compact was placed in a hot isostatic pressing machine (HIP).
and create an argon gas atmosphere inside the device. 30
The temperature is raised to 0° C., and at this temperature, the atmosphere is further replaced with pure argon, and the pressure is increased using argon gas as a medium. After that, at 2-b degrees, 1700-3500°C, preferably 2000-3
The temperature is raised to 000℃. If it is lower than 1700°C, sufficient mechanical strength cannot be obtained, and if it exceeds 3500°C, sublimation of the graphite mold and the carbonaceous raw material becomes intense.

As the temperature increases, the argon gas expands and the pressure within the device increases. Pressure 500~10000)cg/
cTi, preferably 1000 to 3000), is kept constant in the range of cg/cd. If the pressure is less than 500 kg/cj, the crystallization of graphite will be insufficient, the resulting product will have a low bulk density, and sufficient mechanical strength will not be obtained.
If it exceeds /cj, it is economically unfavorable since it becomes necessary to improve the performance of the device.

Hold at constant temperature and pressure for 1-100 minutes. 1
If it is shorter than 100 minutes, sufficient mechanical strength cannot be obtained, and even if it exceeds 100 minutes, no further effect can be obtained.

The above-mentioned isotropic carbon product of the present invention has substantially the same physical properties in all directions, and is used for nuclear reactor cores, ultra-high pressure and high circumferential speed sliding materials, and the like.

Effects of the Invention According to the present invention, carbon products can be easily molded at low cost using readily available raw materials without requiring any special equipment.

Further, according to the method of the present invention, since no binder is used, the obtained carbon product has high density and high mechanical strength.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited thereto.

Example 1 Put 500 g of petroleum-based medium pitch into a quartz crucible, place it in an autoclave, reduce the pressure inside the autoclave to about 0.1 kg/crI with a vacuum pump, and then introduce nitrogen gas to reduce the pressure to 50 kg/cI#. Pressure increased. Thereafter, the temperature was raised to 80° C. at a rate of about 00° C./hour, and the temperature was maintained for 1 hour to carbonize. At this time, the final pressure is 350
It was about kg/c. The temperature of the obtained carbonized material was raised to 1250° C. at a rate of about 20° C./hour in a nitrogen gas stream, and the temperature was maintained for 5 hours to completely remove volatile components.

The thus obtained carbide was pulverized by a pulverizer to a particle size of 10 μm or less to obtain a carbonaceous powder containing no volatile components.

Molding mold made of isotropic high-density graphite material (base area = 40+
amX I C) + m), 10 g of the obtained carbonaceous powder
I put it in. This mold was placed in a high frequency induction furnace, and a load of 3000 kg/cm2 was applied from the top of the mold.

After reducing the pressure inside the furnace to 0.5 kg/c- with a vacuum pump, nitrogen gas was introduced to bring the pressure to normal pressure. Thereafter, the temperature was raised to 2000° C. at a rate of 150° C./min, maintained at that temperature for 10 minutes, and then allowed to cool to room temperature.

The physical and mechanical properties of the obtained carbon products, including bulk density, electrical resistance, bending strength, compressive strength, Young's modulus, and coefficient of expansion, were measured. electrical resistance, bending strength, compressive strength,
Young's modulus and expansion coefficient were measured in parallel and perpendicular directions to the pressing direction during molding. The measurement results are shown in Table 1 below. For comparison, commercially available carbon product 1 (trade name "IG-11"), which is an isotropic high-density graphite product, was used.
manufactured by Toyo Tanso Co., Ltd.) and commercially available carbon product 2 (trade name “I 5”)
D-88'', manufactured by Toyo Tanso Co., Ltd.), the same measurements as above were carried out and are also listed in Table 1.

% Table Example 2 Using 10 g of the same carbonaceous powder as in Example 1, it was placed in a similar mold, placed in a high frequency induction furnace, and weighed 4000 kg.
A load of /cJ was applied. The inside of the furnace is vacuum pumped to 0. 3k
The pressure was reduced to g/cJ. Then, 2
The temperature was raised to 600°C, held for 10 minutes, and then allowed to cool to room temperature.

The obtained carbon product was subjected to the same test as in Example 1, and the results are shown in Table 2. In addition, similar to Table 1, results for commercially available carbon products are also listed.

Table 1 Example 3 Using 10 g of the same carbonaceous powder as in Example 1, it was placed in a similar mold, placed in a high frequency induction furnace, and 300) cg
A load of /cd was applied. After replacing the air in the furnace with argon gas, the temperature was raised to 1700°C at a rate of 150°C/min, held for 10 minutes, and allowed to cool to room temperature to produce a pre-shaped compact.

The pre-shaped compact obtained above was heated using a hot isostatic pressing machine (HI).
The air inside the apparatus was replaced with argon gas, and the temperature was raised to 300°C. Furthermore, the argon gas inside the device was pulled with a vacuum pump, and pure argon gas (99,
99%). Repeat this operation twice to remove oxygen attached to the inner wall of the device or contained in the sample.
Water vapor was completely removed. Temperature inside the device is 300℃
While maintaining the temperature, pure argon gas was further introduced to raise the internal pressure to 800 kg/cJ. After that, 10
The temperature inside the apparatus was raised to 2200°C at a rate of °C/min. At this time, adjust the pressure inside the device to 2000 kg/c.
I kept it male. After maintaining this state for 30 minutes, it was allowed to cool to room temperature.

The obtained isotropic carbon product was subjected to the same tests as in Example 1, and the results are shown in Table 3 below.

Also, similar to the above embodiment, Measurement results of commercially available carbon products The results are also listed in Table 3.

Suburb table

Claims (1)

[Claims] 1. Carbonaceous powder containing no volatile components is placed in a mold, and the powder is heated to 100 to 500% in a high frequency induction furnace or a graphite electric resistance furnace under vacuum or an inert gas atmosphere.
1700~3500℃ under a load of 0kg/cm^2
1. A binderless molding method for an anisotropic carbon product, the method comprising raising the temperature to 100°C and holding it for 1 to 100 minutes. 2. A pre-shaped compact formed from carbonaceous powder containing no volatile components is placed in a hot isostatic pressing apparatus (HIP), and the temperature is raised to 1700 to 3500°C using an inert gas as a medium, and the pressure inside the apparatus is increased to 500°C. A binderless molding method for isotropic carbon products, characterized by pressurizing to ~10,000 kg/cm^2 and holding for 1 to 100 minutes.