JP2002265210A - Refractory raw material, refractory raw material composition, refractory and production process of graphite particle usable for them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refractory which is excellent in thermal shock resistance, oxidation resistance and corrosion resistance and has a low carbon content, and also to provide graphite particles used as a raw material for the refractory. SOLUTION: The production process of this refractory comprises preparing a refractory raw material composition comprising refractory aggregate and a refractory raw material that consists of graphite particles having a <=500 nm average particle size, or another refractory raw material that consists of graphite particles produced by graphitizing carbon black, and forming the prepared refractory raw material composition into a refractory formed body, wherein, by adding at least one element selected from metals, boron and silicon, to the graphite particles, corrosion resistance and oxidation resistance of the resulting refractory are further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refractory raw material comprising graphite particles and a refractory raw material composition containing the same. The present invention also relates to a refractory obtained by molding the refractory raw material composition, particularly to a refractory excellent in corrosion resistance, oxidation resistance and thermal shock resistance and suitable as a lining for a smelting vessel.
Further, the present invention relates to a method for producing graphite particles usable as the refractory raw material.

[0002]

2. Description of the Related Art Refractories containing carbon have excellent durability because carbon has a property of being hardly wetted by a molten material such as slag. Therefore, in recent years, it has been widely used as a refractory lining for various molten metal containers. For example, when magnesia is used as the refractory aggregate, excellent durability is exhibited as the refractory lining of the molten metal container due to the properties of the carbon and the corrosion resistance to the molten material of magnesia.

[0003] However, as the use of carbon-containing refractories has expanded, the elution of carbon in refractories into molten steel, so-called carbon pickup, has become a problem. In particular, in recent years, the demand for higher quality steel has become even more severe, and the demand for refractories having a lower carbon content has been increasing. On the other hand, it is desired to use a refractory having low thermal conductivity from the viewpoint of environmental protection such as suppression of heat dissipation from a container and energy saving. From this point, a refractory having a low carbon content is required. I have.

Heretofore, scaly graphite, pitch, coke, mesocarbon and the like have been mainly used as carbonaceous raw materials used for carbon-containing refractories. If the amount of these carbonaceous materials used is simply reduced in order to obtain a refractory having a low carbon content, there has been a problem that the thermal shock resistance is reduced. To solve this problem, Japanese Patent Application Laid-Open No. Hei 5-30177
No. 2 proposes a refractory using expanded graphite as a carbonaceous raw material. In this example, a refractory raw material composition comprising 95 parts by weight of sintered magnesia, 5 parts by weight of expanded graphite and 3 parts by weight of a phenol resin was kneaded, press-molded, and then heat-treated at 300 ° C. for 10 hours. Magnesia-carbon brick is described, and it is described that spalling resistance is improved as compared with the case where an equivalent amount of flake graphite is used.

[0005] Japanese Patent Application Laid-Open No. H11-322405 discloses that in a raw material mixture containing a refractory raw material and a carbonaceous raw material containing carbon, the carbonaceous material is mixed with the hot residue of 100% by weight of the raw material mixture. Fixed carbon content of raw material is 0.2-5% by weight
A low carbonaceous carbon-containing refractory, characterized in that carbon black is used for at least a part of the carbonaceous raw material (claim 5). In this publication, carbon black has a very small particle diameter, so the degree of dispersion in the refractory structure is significantly increased, and the aggregate particle surface can be coated with fine carbon particles, and at high temperatures Also describes that over-sintering can be suppressed by blocking contact between aggregate particles for a long period of time. In the examples, a raw material mixture obtained by mixing 2.5 parts by weight of a phenol resin, 1 part by weight of a pitch, and 1 part by weight of carbon black (thermal) with a refractory aggregate composed of 50 parts by weight of magnesia and 50 parts by weight of alumina. The product is molded, 120-400
Refractories obtained by baking at ℃ are described,
It is shown to have excellent spalling resistance and oxidation damage resistance.

[0006] Japanese Patent Application Laid-Open No. 2000-86334 discloses that a compound comprising a refractory aggregate and a metal has a specific surface area of 24 m ^2.
/ G or less of carbon black of 0.1 to 10% by weight, and an organic binder is further added, kneaded, molded, and then subjected to a heat treatment at a temperature of 150 to 1000 ° C. to form a brick for a sliding nozzle device. Has been described. By blending a specific carbon black with a large particle diameter and a spherical shape, the filling properties are improved, the brick structure is densified and the porosity is reduced, and the carbon black itself used has oxidation resistance In addition to being excellent,
A refractory excellent in oxidation resistance can be obtained.
In the examples, a mixture of 97 parts by weight of alumina, 3 parts by weight of aluminum, 3 parts by weight of phenol resin, 3 parts by weight of silicon resin and 3 parts by weight of carbon black was molded and heated at a temperature of 500 ° C. or less. The refractory is described as having excellent oxidation resistance.

On the other hand, Japanese Patent Application Laid-Open No. 2000-273351 discloses a method for producing graphitized carbon black in which a mixture containing carbon black and a graphitization promoting substance is heat-treated at 2000 to 2500 ° C. By heating with an element such as boron, silicon, aluminum and iron or a graphitization promoting substance composed of a compound thereof, the conventional 28
The temperature required for graphitizing carbon black, which was about 00 ° C., can be reduced to about 2000 to 2500 ° C.

[0008]

Problems to be Solved by the Invention
As described in Japanese Unexamined Patent Publication No. 2, the use of expanded graphite as a carbonaceous raw material, compared to the case where the same amount of scale-like graphite is used even in a low carbonaceous refractory having an amount of use of about 5% by weight. Good thermal shock resistance is obtained. However, since expanded graphite is a very bulky raw material, even if it is used in an amount of about 5% by weight, the refillability of the refractory decreases, and the corrosion resistance to the molten material is poor. In addition, oxidization and disappearance of the carbonaceous raw material during use of the refractory was also a major problem.

JP-A-11-322405 and JP-A-2000-86334 disclose examples of using carbon black as a carbonaceous raw material. In any of the publications, the use of carbon black is said to improve spalling resistance, but the corrosion resistance and oxidation resistance were not yet sufficient.

Further, in order to densify the structure and improve the oxidation resistance, a method of adding a simple powder of aluminum, silicon, magnesium or the like, or a powder of a compound other than oxides such as boron carbide or silicon carbide is known. It was mainly employed.
However, such techniques require the use of large amounts of these additives in order to achieve a sufficient effect, which often has a negative effect on other properties, and has to be compromised to some extent. I didn't get it.

Japanese Patent Application Laid-Open No. 2000-273351 discloses that
A method of heat-treating a graphitization-promoting substance such as carbon black and boron to graphitize is described. The use of the method is for a catalyst for a phosphoric acid type fuel cell, and the graphitized carbon black is used as a refractory material. No mention is made as to whether it is useful as a raw material for the product or no suggestion is made.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a carbon-containing refractory which is excellent in corrosion resistance, oxidation resistance and thermal shock resistance and has a low carbon content. Such a carbon-containing refractory having a low carbon content is useful because the carbon pickup into the molten steel is small and the heat dissipation from the container is small. The object of the present invention is
Another object of the present invention is to provide a refractory raw material and a refractory raw material composition for obtaining such a refractory. Still another object of the present invention is to provide a method for producing graphite particles that can be used for them.

[0013]

The refractory is composed of particles of various sizes ranging from coarse particles of about 5 mm to fine powder of 1 μm or less, and is an aggregate of fine powder called a matrix that fills the gaps of relatively large particles. Greatly affects the durability. There are many pores and voids in the matrix part, which is the strength of refractory, permeability of melt such as slag,
It has an effect on the mitigation of thermal shock.

The particle size of the refractory matrix is generally 44
μm or less.
Attention was paid to the fact that the behavior of ultrafine particles of not more than 1 μm, more specifically 1 μm or less, that is, nanometer order has a great effect. In most cases, in carbon-containing refractories, a carbonaceous raw material is used for the matrix portion. However, studies were made to control the performance of the entire refractory by controlling the carbonaceous raw material on a nanometer order.

The present inventors have studied the following points when controlling the carbonaceous raw material on the order of nanometers. The first is control of the pore structure. Reduction of the amount of pores leads to improvement of corrosion resistance, and control and subdivision of pore shape (specific surface area) can contribute to optimization of dynamic elastic modulus and improvement of thermal shock resistance. As described above, the thermal shock resistance is first assured by controlling the pore structure, and then the corrosion resistance and the oxidation resistance are also improved.

Carbon black is known as a carbonaceous raw material which is fine powder of the order of nanometers, and the pore structure can be controlled to some extent by controlling its particle size. However, when carbon black is used as a matrix material, the corrosion resistance and oxidation resistance are not always sufficient, and a method of improving the corrosion resistance and oxidation resistance of carbon black itself while keeping the particle size unchanged has been earnestly studied.

That is, according to the present invention, the average particle diameter is 500 n.
It is a refractory raw material comprising graphite particles of m or less.
Since graphite has a more developed crystal structure than carbon black, graphite is a material having a high oxidation initiation temperature, excellent oxidation resistance, excellent corrosion resistance, and high thermal conductivity.
By using fine graphite particles on the order of nanometers, pores can be divided and the structure can be controlled, and the corrosion resistance and oxidation resistance of the particles themselves are improved. As a result, thermal shock resistance, corrosion resistance and oxidation resistance A refractory excellent in quality can be obtained.

Further, the present invention is a refractory raw material comprising graphite particles obtained by graphitizing carbon black. Carbon black is a carbonaceous fine particle having a particle size on the order of nanometers which is easily available at present.
This is because it is easy to obtain various brands according to the purpose, such as the particle size, association state, and surface state.

In the above graphite particles, it is preferable that the graphite particles contain at least one element selected from metals, boron and silicon. By including such elements other than carbon in graphite particles, so-called `` composite graphite particles '', the oxidation start temperature of the graphite particles themselves further increases,
This is because the oxidation resistance and the corrosion resistance are improved, and the oxidation resistance and the corrosion resistance of the refractory obtained using the composite graphite particles as a raw material are improved.

The graphite particles containing at least one element selected from metals, boron and silicon are:
It is preferably obtained by heating carbon black and at least one element selected from the group consisting of metals, boron and silicon, or a compound containing the element. Carbon black, metal, boron More preferably, it is obtained by heating at least one element selected from the group consisting of silicon and silicon.

The present invention is also a refractory raw material composition comprising a refractory aggregate and the graphite particles. At this time,
100 parts by weight of refractory aggregate and the graphite particles 0.1
A refractory raw material composition comprising from 10 to 10 parts by weight is suitable.
Considering the useful use of the refractory having a low carbon content, a refractory raw material composition in which the refractory aggregate is composed of magnesia is preferable. Further, the present invention is a refractory obtained by molding the refractory raw material composition.

The present invention further provides a carbon black,
Heating an alcoholate of at least one element selected from metals, boron and silicon, wherein at least one selected from metals, boron and silicon is heated.
This is a method for producing graphite particles containing more than one element. This is because if it is a single element, it is easy to ignite and if it is a dangerous element, it can be handled easily by using alcoholate, and the risk of dust explosion and the like is reduced. At this time, it is needless to say that the graphite particles manufactured by the present manufacturing method solve the problems of the present invention when used as a refractory raw material as described above, but the present manufacturing method is applicable to other uses. A useful method is also available.

Further, the present invention is characterized in that carbon black, an oxide of at least one element selected from metals, boron and silicon, and a metal for reducing the oxide are heated. This is a method for producing graphite particles containing at least one element selected from boron and silicon. With such a combination, the elements constituting the oxide can be easily reduced and contained in the graphite.

Further, in the present invention, graphite particles obtained by heating carbon black and a simple substance of at least one element selected from metals, boron and silicon or a compound containing the element are further subjected to an oxidation treatment. And a method for producing graphite particles. By doing so, further oxidation resistance can be obtained.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has an average particle diameter of 500 nm.
It is a refractory raw material comprising the following graphite particles. Here, it is important that the average particle diameter is 500 nm or less, and by using graphite particles having such an extremely fine particle size, the pore structure in the refractory matrix can be made fine. It is. The average particle size of any of scale graphite or expanded graphite which has been conventionally used as a refractory raw material is much larger than 1 μm, and could not express a fine pore structure in a matrix. Such a pore structure is realized by using fine graphite particles.

The average particle size is preferably 200 nm or less, more preferably 100 nm or less. The average particle size is usually 5 nm or more, preferably 10 nm or more. If the average particle size exceeds 500 nm, the pore structure cannot be made fine, and if it is less than 5 nm, handling becomes difficult. Here, the average particle size refers to the number average particle size of primary particles of graphite particles. Therefore, for example, in the case of a particle having a structure in which a plurality of primary particles are associated, it is calculated that a plurality of primary particles constituting the particle are included. Such a particle size can be measured by observation with an electron microscope.

The method for producing graphite particles is not particularly limited, and graphite having a larger particle size may be pulverized mechanically or electrically so as to have the above-mentioned particle size. However, since it is not easy to pulverize into extremely fine particles of 500 nm or less, a method of graphitizing carbonaceous particles originally having a particle size of 500 nm or less is preferable.

The present invention is also a refractory raw material comprising graphite particles obtained by graphitizing carbon black. Carbon black is a carbonaceous fine particle having a particle size on the order of nanometers which is easily available at present.
It is easy to obtain various brands according to the purpose, such as particle size, association state, surface state, and the like. The use of carbon black itself as a refractory raw material was already known as described in the section of the prior art, but it was insufficient in corrosion resistance and oxidation resistance. By graphitizing the material, a crystal structure is developed, and a material having a high oxidation initiation temperature, excellent oxidation resistance, excellent corrosion resistance, and high thermal conductivity can be obtained.

The carbon black used as a raw material is not particularly limited. Carbon black composed of primary particles having a diameter of 500 nm or less is preferably used. Specifically, any of furnace black, channel black, acetylene black, thermal black, lamp black, Ketjen black and the like can be used.

Preferred are First Extruding Furnace Black (FEF) and Super Ablation Furnace Black (SA).
F) and high ablation furnace black (HAF), fine thermal black (FT),
Medium Thermal Black (MT), Semi Reinforcing Furnace Black (SRF), General Purpose Furnace Black (GPF)
And various carbon blacks. At this time,
A plurality of types of carbon black may be blended and used as a raw material.

The method of graphitizing (graphitizing) carbon black is not particularly limited, but it can be graphitized by heating at a high temperature in an inert atmosphere. Usually, carbon black can be graphitized by heating at a temperature of 2000 ° C. or higher.

By graphitization, peaks derived from the crystal structure are observed in X-ray diffraction measurement. Then, as the graphitization progresses, the interstitial distance decreases. The 002 diffraction line of graphite shifts to the wide-angle side with the progress of graphitization, and the diffraction angle 2θ of this diffraction line corresponds to the interstitial distance (average plane distance). In the present invention, it is preferable to use graphite having an interstitial distance d of 3.47 ° or less. When the interstitial distance exceeds 3.47 °, the graphitization is insufficient, and the thermal shock resistance, oxidation resistance, and corrosion resistance may be insufficient.

In the above graphite particles, it is preferable that the graphite particles contain at least one element selected from metals, boron and silicon. By including such elements other than carbon in graphite particles, so-called `` composite graphite particles '', the oxidation start temperature of the graphite particles themselves further increases,
This is because the oxidation resistance and the corrosion resistance are improved, and the oxidation resistance and the corrosion resistance of the refractory obtained using the composite graphite particles as a raw material are improved.

Here, specific examples of at least one element selected from metals, boron and silicon contained in the graphite particles include magnesium, aluminum, calcium, titanium, chromium, cobalt, nickel, yttrium, zirconium, Niobium, tantalum,
Examples include molybdenum, tungsten, boron, and silicon. Among them, preferred for improving the oxidation resistance and corrosion resistance of refractories, boron, titanium,
Mention may be made of silicon, zirconium and nickel, with boron and titanium being most preferred.

The manner in which each element is present in the graphite particles is not particularly limited, and may be contained inside the particles or in a form that covers the surface of the particles. Each element can be contained as its oxide, nitride, boride or carbide, but is preferably contained as a compound such as oxide, nitride, boride or carbide. More preferably, it is contained as an oxide or a carbide. More preferably, it is contained as a carbide or oxide. B ₄ C and Ti as carbides
C is exemplified, and the oxide is exemplified by Al ₂ O ₃ .

The carbides are contained in the graphite particles in such a manner as to bond to the carbon atoms constituting the graphite as appropriate. However, if the total amount is such a carbide, the performance as graphite is not exhibited, which is not preferable. Therefore, it is necessary to have a graphite crystal structure. The state of such graphite particles can be analyzed by X-ray diffraction. For example, a peak corresponding to a crystal of a compound such as TiC or B ₄ C is observed in addition to a peak corresponding to a graphite crystal.

The method for incorporating at least one element selected from the group consisting of metal, boron and silicon into the graphite particles is not particularly limited, but includes carbon black and at least one element selected from the group consisting of metal, boron and silicon. It is preferably obtained by heating a simple substance of the element or a compound containing the element. The heating causes the above elements to be contained in the graphite structure at the same time as the graphitization proceeds.

At this time, it is more preferable that the carbon black is obtained by heating carbon black and a simple substance of at least one element selected from metals, boron and silicon. This is because, by heating the element alone, the reaction can be advanced by utilizing the heat generated during the generation of carbides by combustion synthesis. Specifically, it is preferable to heat together with aluminum, calcium, titanium, zirconium, boron and silicon. This is because synthesis can be performed by a self-combustion synthesis method using this reaction heat. Since the own reaction heat can be used, the temperature in the furnace can be lowered as compared with the case where carbon black alone is graphitized. Maintaining a furnace temperature exceeding 2000 ° C is problematic in terms of equipment and cost, so this is important.

For example, the reaction formula of combustion synthesis of boron and carbon and the reaction formula of combustion synthesis of titanium and carbon are as follows. 4B + xC → B ₄ C + (x−1) C Ti + xC → TiC + (x−1) C These reactions are all exothermic, and self-combustion synthesis is possible.

As a method for incorporating at least one element selected from metals, boron and silicon into graphite particles, carbon black and an alcoholate of at least one element selected from metals, boron and silicon are heated. This is also preferable because heat generated by combustion synthesis can be used. If it is a simple element that is easy to ignite and is a dangerous element, it can be handled easily by using alcoholate,
This is because the danger of dust explosion and the like is reduced.

The alcoholate herein is obtained by replacing the hydrogen of the hydroxyl group of an alcohol with at least one element selected from metals, boron and silicon.
R) _n . Here, M is 1-4.
Valent, preferably divalent to tetravalent elements are used, and preferred elements include magnesium, aluminum, titanium, zirconium, boron and silicon. n corresponds to the valence of the element M and is an integer of 1 to 4, preferably 2 to 4. R is not particularly limited as long as it is an organic group, but is preferably an alkyl group having 1 to 10 carbon atoms, and a methyl group,
Examples include an ethyl group, a propyl group, an isopropyl group, and an n-butyl group. One of these alcoholates may be used alone, or a plurality of alcoholates may be used in combination. Alternatively, an alcoholate may be used in combination with a simple element or an oxide.

As a method for incorporating at least one element selected from metals, boron and silicon into graphite particles, carbon black, an oxide of at least one element selected from metals, boron and silicon are used. It is also preferable to heat a metal that reduces the oxide, because heat generated by combustion synthesis can be used. With such a combination, the metal can reduce the oxide, and the element constituting the oxide can be contained in the graphite. For example, when carbon black, aluminum, and boron oxide are heated, first, boron oxide is reduced by aluminum to form boron alone, which reacts with carbon black to obtain boron carbide. The chemical formula is as follows. 4Al + 2B ₂ O ₃ + xC →
2Al ₂ O ₃ + B ₄ C + (x−1) C The chemical formula when carbon black, aluminum and titanium oxide are reacted is as follows. 4Al + 3TiO ₂ +
xC → 2Al ₂ O ₃ + 3TiC + (x−3) C These reactions are also exothermic reactions, combustion synthesis is possible, and graphitization is possible even if the temperature in the furnace is not so high.

Further, the graphite particles obtained by heating the carbon black and at least one element selected from the group consisting of metal, boron and silicon or a compound containing the element may be further oxidized. It is suitable. By performing the oxidation treatment, an oxide film can be formed mainly on the surface of the graphite particles, so that the oxidation resistance is further improved.

The method of oxidation is not particularly limited, and examples include a method of treating with an oxidizable high-temperature gas. Specifically, a so-called hot gas method in which a hot gas obtained by burning air and fuel reacts with graphite particles for a certain period of time can be used. At this time, if the contact time with the gas is too long, the entire graphite is oxidized, so it is necessary to set conditions so that only a part can be oxidized.

It goes without saying that the graphite particles produced by the above-described production method can solve the problems of the present invention when used as a refractory raw material as described above. This is a useful method that can be used for

Other components are blended with the graphite particles obtained as described above to obtain the refractory raw material composition of the present invention. Specifically, it is a refractory raw material composition comprising a refractory aggregate and the above graphite particles.

The refractory aggregate mixed with the graphite particles of the present invention is not particularly limited, and various types can be used based on the use as a refractory and the required performance. Refractory oxides such as magnesia, calcia, alumina, spinel, and zirconia; carbides such as silicon carbide and boron carbide; borides such as calcium boride and chromium boride; and nitrides can be used as refractory aggregates. Among them, magnesia, alumina and spinel are preferred in view of the usefulness of being low carbonaceous,
Magnesia is best. Magnesia includes electrofused or sintered magnesia clinker. These refractory aggregates are blended after adjusting the particle size.

At this time, a refractory raw material composition comprising 100 parts by weight of refractory aggregate and 0.1 to 10 parts by weight of the graphite particles is preferable. When the amount of the graphite particles is less than 0.1 part by weight, the effect of the addition of the graphite particles is hardly recognized in many cases. Preferably, 0.
5 parts by weight or more. On the other hand, if the blending amount of the graphite particles exceeds 10 parts by weight, the carbon pickup becomes severe, heat dissipation from the container becomes remarkable, and the corrosion resistance decreases. It is preferably at most 5% by weight.

Further, as the binder used in the refractory raw material composition of the present invention, a usual organic binder or inorganic binder can be used. As the binder having high fire resistance, use of an organic binder such as phenol resin or pitch is preferable, and phenol resin is more preferable in view of wettability of the refractory raw material and high residual carbon. The content of the organic binder is not particularly limited, but is suitably about 1 to 5 parts by weight based on 100 parts by weight of the refractory aggregate.

Although the refractory raw material composition of the present invention uses graphite particles as the carbonaceous raw material, the graphite particles and other carbonaceous raw materials may be used in combination.
For example, in the case where non-graphitized carbon black is blended, the cost may be lower than that of graphitized carbon black. Therefore, it may be preferable to use a mixture of both in view of the balance between cost and performance. Further, for the same reason, it may be used by mixing with other graphite components such as scaly graphite and expanded graphite, or may be used by mixing with pitch or coke.

The refractory raw material composition of the present invention may contain components other than those described above as long as the gist of the present invention is not impaired. For example, metal powders such as aluminum and magnesium, alloy powders, silicon powders, and the like may be contained. When kneading, an appropriate amount of water or a solvent may be added.

The refractory raw material composition thus obtained is kneaded, molded and, if necessary, heated to obtain the refractory of the present invention. Here, when heating, baking may be performed at a high temperature, but in the case of, for example, magnesia brick, baking is usually only performed at a temperature of 400 degrees or less.

The so-called amorphous refractories, when in the amorphous state, are included in the refractory raw material composition of the present invention. Further, when the shape of the amorphous refractory becomes constant, it is included in the molded refractory of the present invention. For example, even a shape sprayed on a furnace wall is included in the molded refractory of the present invention because it has a certain shape.

The refractory thus obtained is excellent in corrosion resistance, oxidation resistance and thermal shock resistance, and is therefore extremely useful as a furnace material for obtaining high-quality metallurgical products.

[0055]

The present invention will be described below with reference to examples. In the examples, various analysis methods and evaluation methods were performed according to the following methods.

(1) Observation Method of Average Particle Size A sample was photographed at a magnification of 100,000 times using a transmission electron microscope. The number average value of the diameter was obtained from the obtained photograph. At this time, when the particles of the sample were associated with each other, they were considered as separate particles, and were obtained as the average primary particle diameter.

(2) Method for calculating the distance between graphite lattices The target graphite powder was measured using a powder X-ray diffractometer. The measurement wavelength λ is 1.5418 ° which is the wavelength of the Kα ray of copper. Among the crystal peaks obtained by the X-ray diffraction measurement, a large peak having a value of 2θ around 26 ° is a peak corresponding to the 002 plane of graphite.
From this, the interstitial distance d (Å) of graphite was calculated by the following equation. d = λ / 2 sin θ

(3) Apparent Porosity and Bulk Specific Gravity after Heating at 1400 ° C. A sample cut to 50 × 50 × 50 mm was buried in coke in an electric furnace, and heated at 1400 ° C. in a carbon monoxide atmosphere at 5 ° C.
Heated for hours. After the treated sample was allowed to cool to room temperature, the apparent porosity and bulk specific gravity were measured according to JIS R2205.

(4) A sample having a dynamic elastic modulus of 110 × 40 × 40 mm was buried in coke in an electric furnace, and was heated at 1000 ° C. or 140 ° C. in a carbon monoxide atmosphere.
Heat treatment was performed at 0 ° C. for 5 hours. After allowing the treated sample to cool to room temperature, the ultrasonic propagation time was measured using an Ultrasonoscope, and the dynamic elastic modulus E was determined based on the following equation. E = (L / t) ² · ρ where L is the ultrasonic wave propagation distance (the length of the sample) (mm),
t is the ultrasonic propagation time (μsec), and ρ is the bulk specific gravity of the sample.

(5) Oxidation resistance test A 40 × 40 × 40 mm sample was placed in an electric furnace (atmosphere) for 14 hours.
After being kept at 00 ° C. for 10 hours, it was cut, and the thickness of the decarburized layer on the three cut surfaces except the lower side was measured, and the average value was calculated.

(6) Corrosion resistance test A 110 × 60 × 40 mm sample was attached to a rotary erosion tester, and the basicity (Ca) was maintained at 1700 to 1750 ° C.
A test in which the step of holding for 1 hour in a slag of (O / SiO ₂ ) = 1 was repeated five times was performed, and the erosion dimension was measured on the cut surface after the test.

[Synthesis Example 1] Production of Graphite Particle A "Niteron # 10 Kai" manufactured by Shin Nikka Carbon Co., Ltd. was used as a carbon black raw material. The carbon black is a type of carbon black called First Extruding Furnace Black (FEF) and has an average primary particle diameter of 41 nm. This was converted into a carbon furnace (FVS-200 / Fuji Denpa Kogyo KK).
200/200, FRET-50) in an argon gas atmosphere at 2100 ° C. for 3 hours to graphitize. When the obtained particles were subjected to X-ray diffraction measurement, a peak derived from the graphite structure was observed, and it was found that graphite particles were generated. The interstitial distance calculated from the diffraction line corresponding to the 002 plane spacing of graphite was 3.40 °. The average primary particle size of the particles was 38 nm.

[Synthesis Example 2] Synthesis of Graphite Particle B Synthesis was performed in the same manner as in Synthesis Example 1 except that carbon black as a raw material was changed. As the carbon black, "HTC # 20" manufactured by Shin Nikka Carbon Co., Ltd. was used. The carbon black is a type of fine thermal black (FT) having an average primary particle size of 82%.
nm. When the obtained particles were subjected to X-ray diffraction measurement, a peak derived from the graphite structure was observed, and it was found that graphite particles were generated. The interstitial distance calculated from the diffraction line corresponding to the 002 plane spacing of graphite was 3.42 °. The average primary particle size of the particles was 70 nm.

[Synthesis Example 3] Synthesis of Graphite Particle C Carbon black “Niteron # 10 Kai” and boron powder were mixed so that the molar ratio of carbon element to boron element was 10: 4, and the mixture was mixed with a silica crucible. The graphite sheet was placed on the top of the crucible, and electrodes were connected to both ends of the graphite sheet.
The electrodes were energized to cause the graphite sheet to generate heat, ignite the mixture, and obtain graphite particles C by a self-combustion synthesis method utilizing heat of reaction when carbides were generated.
When the obtained particles were subjected to X-ray diffraction measurement, a peak derived from the graphite structure was observed, and it was found that graphite particles were generated. Graphite 0
The interstitial distance calculated from the diffraction line corresponding to the 02 plane interval was 3.38 °. Also, a peak at 2θ = 37.8 ° derived from the B ₄ C 021 diffraction line was observed. An X-ray diffraction chart is shown in FIG. The average primary particle size of the particles was 40 nm.

[Synthesis Example 4] Synthesis of Graphite Particle D Same as Synthesis Example 3 except that carbon black “HTC # 20” and titanium powder were mixed so that the molar ratio of carbon element and titanium element was 10: 1. And graphite particles D
I got When X-ray diffraction measurement of the obtained particles was performed,
A peak derived from the graphite structure was observed, and it was found that graphite particles were generated. The interstitial distance calculated from the diffraction line corresponding to the 002 plane spacing of graphite was 3.44 °. In addition, 200 of TiC
A peak at 2θ = 41.5 ° derived from the diffraction line was also observed. The average primary particle size of the particles was 71 nm.

[Synthesis Example 5] Synthesis of Graphite Particle E Carbon black “HTC # 20”, aluminum powder and titanium oxide powder were mixed so that the molar ratio of carbon, aluminum and titanium was 10: 4: 3. Except for mixing, graphite particles E were obtained in the same manner as in Synthesis Example 3. When the obtained particles were subjected to X-ray diffraction measurement, a peak derived from the graphite structure was observed, and it was found that graphite particles were generated. The interstitial distance calculated from the diffraction line corresponding to the 002 plane spacing of graphite was 3.42 °. Also, 113 of Al ₂ O ₃
2θ = 43.4 ° peak derived from diffraction lines, and Ti
A peak at 2θ = 41.5 ° derived from 200 diffraction lines of C was also observed. The average primary particle diameter of the particles was 70 nm.

[Synthesis Example 6] Synthesis of Graphite Particles F Synthesis Example 3 was the same as Synthesis Example 3 except that carbon black “HTC # 20” and trimethoxyborane were mixed so that the molar ratio of carbon element to boron element was 10: 1. Similarly, graphite particles F were obtained. When the obtained particles were subjected to X-ray diffraction measurement, a peak derived from the graphite structure was observed, and it was found that graphite particles were generated.
The interstitial distance calculated from the diffraction line corresponding to the 002 plane spacing of graphite was 3.41 °. In addition, B ₄ C
A peak at 2θ = 37.8 ° derived from the 021 diffraction line was also observed. The average primary particle size of the particles was 72 nm.

[Synthesis Example 7] Synthesis of Graphite Particles G The graphite particles C obtained in Synthesis Example 3 were put in a stainless steel tube, and a mixture of propane and oxygen mixed at a volume ratio of 1: 8 was burned. The resulting hot gas was introduced. The temperature of the hot gas was 1000 ° C. and the residence time was 5 seconds.
Thereafter, water was sprayed to cool to 250 ° C., and then the graphite particles G generated by the bag filter were collected. The interstitial distance calculated from the diffraction line corresponding to the 002 plane spacing of graphite was 3.40 °. In addition, B ₂ O ₃
A peak at 2θ = 32.1 ° derived from the 102 diffraction line was also observed. The average primary particle size of the particles was 42 nm.

The raw materials, formed compounds and average particle diameters of the graphite particles A to G obtained in Synthesis Examples 1 to 7 are collectively described in Table 1.

[0070]

[Table 1]

Example 1 100 parts by weight of electrofused magnesia having a particle size of 98% purity, 2 parts by weight of the graphite particles A obtained in Synthesis Example 1, and a phenol resin (a hardener was added to a novolak type phenol resin) 3 parts by weight were mixed, kneaded with a kneader, molded by a friction press, and baked at 250 ° C. for 8 hours.
As a result, the apparent porosity after the heat treatment at 1400 ° C. was 9.2.
% And bulk specific gravity was 3.10. The kinetic elastic modulus after heat treatment at 1000 ° C. was 10.8 GPa,
The dynamic elastic modulus after heat treatment at 400 ° C. is 12.4 GPa.
Met. The thickness of the decarburized layer was 7.8 mm, and the erosion size was 11.0 mm.

Examples 2 to 11, Comparative Examples 1 to 7 Refractories were prepared and evaluated in the same manner as in Example 1 except that the raw materials to be added were changed as described in Tables 2 and 3. The results are summarized in Tables 2 and 3.

[0073]

[Table 2]

[0074]

[Table 3]

When the graphitized carbon black shown in Examples 1 and 2 was used, the kinetic elastic modulus was lower than that in the case where 5 parts by weight of the flaky graphite and the expanded graphite shown in Comparative Examples 4 and 6 were blended. Excellent thermal shock resistance is obtained with a small carbon content and a small decarburized layer thickness and small erosion dimension.
It shows excellent oxidation resistance and corrosion resistance. As shown in Comparative Example 5, the same level of thermal shock resistance as when 20 parts by weight of flaky graphite was blended can be achieved by adding only 2 parts by weight.

In addition, these examples have smaller decarburized layer thicknesses and smaller erosion dimensions than the non-graphitized carbon blacks shown in Comparative Examples 1 and 2 and excellent acid resistance. It shows chemical resistance and corrosion resistance. From these facts, the advantage of using extremely fine particles of the order of nanometers and the advantage of using graphitized particles are apparent.

Further, in Examples 3, 4, 9 and 10,
In the example using graphite particles containing boron, titanium or aluminum, the thickness of the decarburized layer and the erosion dimension are further reduced as compared with the examples of Examples 1 and 2, which are graphite particles not containing those elements. Yes,
It can be seen that the oxidation resistance and corrosion resistance are further improved.

Further, when the graphite particles containing the boron element shown in Example 11 and subjected to the oxidation treatment were used, the graphite particles before the oxidation treatment were used. Oxidation resistance and corrosion resistance are improved.

[0079]

By using the graphite particles of the present invention as a refractory raw material, it is possible to obtain a refractory excellent in thermal shock resistance, oxidation resistance and corrosion resistance while reducing the carbon content.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction chart of graphite particles C.

Continued on the front page F term (reference) 4G030 AA07 AA35 AA36 AA46 AA49 AA60 BA23 BA28 BA32 BA33 GA01 GA11 GA14 4G046 EA05 EA06 EB02 EC02 EC05

Claims (12)

[Claims] 1. A refractory raw material comprising graphite particles having an average particle size of 500 nm or less. 2. A refractory raw material comprising graphite particles obtained by graphitizing carbon black. 3. The refractory raw material according to claim 1, wherein the graphite particles contain at least one element selected from metals, boron and silicon. 4. The refractory raw material according to claim 3, which is obtained by heating carbon black and a simple substance of at least one element selected from metals, boron and silicon or a compound containing said element. 5. The refractory raw material according to claim 3, obtained by heating carbon black and a simple substance of at least one element selected from metals, boron and silicon. 6. A refractory raw material composition comprising a refractory aggregate and the refractory raw material according to claim 1. 7. A refractory aggregate having a weight of 100 parts by weight.
A refractory raw material composition comprising 0.1 to 10 parts by weight of the refractory raw material described in any one of the above. 8. A refractory aggregate comprising magnesia.
Or the refractory raw material composition according to 7. 9. A refractory obtained by molding the refractory raw material composition according to claim 6. Description: 10. A method comprising heating carbon black and an alcoholate of at least one element selected from metals, boron and silicon, wherein at least one element selected from metals, boron and silicon is heated. A method for producing graphite particles. 11. A method of heating a metal, boron and silicon comprising heating carbon black, an oxide of at least one element selected from metals, boron and silicon, and a metal that reduces the oxide. A method for producing graphite particles containing at least one element selected from the group consisting of: 12. A graphite, wherein graphite particles obtained by heating carbon black and a simple substance of at least one element selected from metals, boron and silicon or a compound containing the element are further oxidized. Method for producing particles.