JPH05194044A - Composition for castable refractory containing graphite and its preparation - Google Patents

Abstract

PURPOSE:To produce the subject composition for refractories, containing graphite, having a high bulk specific gravity and excellent in corrosion and oxidation resistance by subjecting graphite powder and fine particle powder such as a metallic oxide in a specific proportion to impact treatment and blending a specific amount of the resultant graphitic powder containing the fine particle powder fixed thereon with refractory compound powder. CONSTITUTION:Mixed powder of 70-97wt.% draphite powder with 3-30wt.% powder of hydrophilic particles having an average particle diameter of <=40% that of graphite powder particles is fed from a hopper 12 into an impact treating device. A metal and a metallic oxide, 6 carbide, nitride and boride are used as the hydrophilic particles. This device is capable of rotating a rotating plate 4 equipped with blades 5 in an impact chamber 7 of a easing 1 and subjecting the mixed powder to impact treatment in a high-speed air stream. Thereby, the hydrophilic particles are fixed on the surfaces of the graphite particles. Refractory compound powder is then added and mixed with the resultant graphitic powder and the amount of the blended graphitic powder in the mixture is regulated to 2-40% expressed in terms of the amount of carbon. As a result, the objective composition for castable refractories, containing the graphite and good in characteristics such as oxidation and corrosion resistance is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon-containing amorphous refractory composition used for the lining of containers used in the processes of pig iron and steel making and the repair thereof, and a method for preparing the same.

[0002]

BACKGROUND OF THE INVENTION Graphite-containing refractories including graphite powder have desirable properties such as heat resistance and thermal shock resistance, and
It is widely used in the fields of pig iron and steel making because it is hard to get wet with molten pig iron, molten steel, molten slag, etc. and has excellent corrosion resistance. However, the conventional graphite-containing standard shaped refractory that has been preformed and baked or fired requires a lot of work and energy during its manufacture and construction, so that it is superior in performance, but as a whole. It requires a lot of expense and work time. On the other hand, as a general tendency in the refractory field, labor saving is a necessary condition for the survival of corporate activities, and the present situation is that the proportion of irregular refractory materials used is increasing.

The amorphous refractory is constructed by adding a dispersion medium such as water to a premixed powder composition at the site, and spraying, pouring by vibrating, and solidifying. It is constructed by. Although it is possible to use an organic solvent having good wettability for the graphite particles as the dispersion medium, it is the most preferable method to use water as the dispersion medium from the viewpoints of working environment and cost.

In the case of a graphite-containing amorphous refractory, since graphite powder lacks hydrophilicity (similar to dispersibility in water), water is used as a dispersion medium like many other amorphous refractories. Even if it is used, a molded product having a large bulk specific gravity cannot be obtained. Therefore, the obtained graphite-containing amorphous refractory is significantly inferior in oxidation resistance, corrosion resistance, strength and the like to the standard refractory, and the fact that a durable refractory cannot be obtained is an obstacle to its practical application. There is.

On the surface of the graphite particles, only a few hydrophilic functional groups such as --OH and --COOH exist, and the surface has a non-hydrophilic hexagonal network structure of carbon atoms. And the small absolute value of the zeta (ζ) potential at the interface when water is used as the dispersion medium explains that the graphite particles have low hydrophilicity. Strong acid treatment method, CVD method, sol-gel method, polymer coating method, etc. are being investigated as a means for avoiding the problem that the graphite particles have low hydrophilicity, that is, low dispersibility in water. However, neither method has yielded satisfactory results.

In the strong acid treatment method, the graphite powder can be immersed in concentrated sulfuric acid, concentrated nitric acid, hydrofluoric acid, etc. and reacted with these acids at room temperature to 100 ° C. to make the surface of the graphite particles hydrophilic. The graphite particles expand due to the acid component penetrating into the graphite crystal layer to form an intercalation compound, and the acid component remaining inside the graphite particles after the treatment is added to the water as a dispersion medium. Even if it is used as a raw material powder of an irregular shaped refractory, it cannot be obtained as a molded product having a large bulk specific gravity due to the fact that it is melted into and the pH value is changed and the dispersed state is obstructed or made unstable.

In the CVD method, for example, gas components such as SiO and B2 O3 are brought into contact with the surface of graphite particles at 1000 ° C. or higher to form a thin film such as SiC and B4 C on the surface. As a result, the surface of the graphite particle is oxidized, the surface of the graphite particle becomes rough with many pores, and the oxidation resistance of the graphite particle decreases. Although the halide CVD method is also known, as a method for treating a raw material powder of a refractory which cannot be said to have a large added value, because the raw material gas is expensive or exhaust gas treatment is required. Not suitable.

In the sol-gel method, for example, silicon alkoxide, aluminum alkoxide, etc. are hydrolyzed in an aqueous alcohol solution in the presence of an acid catalyst, and the obtained sol solution is impregnated with graphite powder and dried to gel to form graphite particles. Although SiO2 or Al2O3 is adhered to the surface, the wettability between the graphite particles and the sol solution is poor, and pores are formed between the graphite particles and the coating layer, and many parts not covered with the coating layer remain. A molded article having a large bulk specific gravity cannot be obtained even if it is used for an irregular shaped refractory material because, for example, a sufficient dispersibility with respect to is not obtained.

Further, in the polymer coating method disclosed in Japanese Patent Publication No. 2-33666, graphite powder is impregnated with a solution of phenol resin, furan resin, silicone resin or the like to coat the surface of the graphite particles with an organic resin. Although it can be formed, it has the same poor wettability as in the sol-gel method and has the problem that the resin is thermally decomposed to become porous at the time of use, and thus a molded article of a graphite-containing amorphous refractory having good durability cannot be obtained.

As a conventional attempt to solve the problem that the graphite powder lacks hydrophilicity in the graphite-containing amorphous refractory, there is a description in Japanese Patent Publication No. 1-46473, for example.
That is, a graphite powder obtained by mixing a graphite powder with a thermosetting resin or a thermoplastic resin and pressing the pellet or crushing the pressed solidified product (hereinafter, the modified graphite powder is referred to as a graphite powder). .) Is used to improve the dispersibility in water.

However, the hydrophilicity of the graphite particles can be improved to some extent by any treatment method,
Most of the organic resin coated on the surface of the graphite particles or incorporated in the graphite particles is thermally decomposed during use and is released as a gas to increase the porosity of the refractory,
This impairs the oxidation resistance and corrosion resistance, which are important properties in this type of refractory.

Further, the above-mentioned proposal also describes that particles of aluminum or silicon are coated with an organic resin at the same time as the graphite particles, but the surface of aluminum or silicon is also coated with an organic resin, which is not always hydrophilic. The hydrophilicity of the organic resin, which does not have good properties, regulates the hydrophilicity of these powders.

As a recent technique, Japanese Patent Publication No. 3-2009 proposes a method for modifying the surface of solid particles. That is,
0.01 on the surface of powder in the range of 0.1 to 100 μm
A method using mechanical impact force has been proposed as a preferable method for fixing the powder in the range of 10 μm to 10 μm, and a method of impact treatment in a high-speed airflow is disclosed as a specific means therefor. However, there is no suggestion in the specification as to whether or not graphite particles containing a large amount of scaly particles can be surface-modified by this treatment method, which shows the unique property of cleaving into scaly particles.

[0014]

DISCLOSURE OF THE INVENTION The present inventors have realized a graphite powder having excellent hydrophilicity, which is free from the drawbacks of the conventional surface-treated graphite powder. It is intended to provide a graphite-containing composition for an amorphous refractory, which is used as an amorphous refractory and has a large bulk specific gravity when applied to obtain a molded article excellent in corrosion resistance and oxidation resistance.

[0015]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and a graphite-containing amorphous refractory composition of the present invention is mainly composed of a graphite powder and a refractory compound powder. In the composition, the graphite powder has a surface of the graphite particles of the graphite powder, a metal oxide, a metal carbide, a metal nitride, a metal boride having a smaller average particle size than the graphite particles and having hydrophilicity, and One or more kinds of small particles selected from metals are fixed, and the composition is characterized in that the graphite powder is contained in an amount of 2 to 40% by weight in terms of carbon amount.

In the present invention, the powder and the average particle diameter of the powder refer to the particle diameter at a location where the cumulative volume measured by a laser diffraction type particle size distribution analyzer is ½. Further, the small particles fixed to the surface of the graphite particles are those in which the small particles are strongly adhered to or bonded to the graphite particles without using an adhesive or the like for mediating the bonding. After that, even if it is mixed with the refractory compound powder or mixed with the dispersion medium at the time of construction, the small particles are in a state of being difficult to peel off. Further, the weight% is based on the weight of the refractory material excluding the weight of the dispersion medium and the thermally decomposable organic additive.

When the amount of carbon in the graphite-containing composition for amorphous refractory is less than 2% by weight, the molded article of the refractory thus constructed is hard to be wetted by slag, and the preferable characteristic of good thermal shock resistance is not exhibited. However, if the carbon content is more than 40% by weight, the porosity of the fireproof molded product that has been applied is increased, and the oxidation resistance and corrosion resistance are reduced, such being undesirable.

The refractory compound powder used in the graphite-containing amorphous refractory composition of the present invention is at least one selected from metal oxides, metal carbides, metal nitrides and metal borides. Specific examples thereof include magnesia, chromia, dolomite, spinel, alumina, zirconia, zircon, silica stone, wax stone, chamotte and gravel shale as the metal oxide, silicon carbide as the metal carbide, and metal nitride as the metal nitride. Is silicon nitride, and metal borides include zirconium boride and titanium boride, both of which are heat resistant and have corrosion resistance under the conditions used, and the graphite-containing amorphous refractory material of the present invention It is preferably used as a refractory compound powder for a composition. Further, as the refractory compound powder, in order to increase the bulk specific gravity of the refractory molded body and ensure the corrosion resistance, usually coarse and dense particles (referred to as aggregate)
Is used.

In a preferred embodiment of the graphite-containing amorphous refractory composition of the present invention, the composition contains the graphite powder in an amount of 4 to 25% by weight in terms of carbon amount. The amount of carbon in the refractory is 4 to 2
By adjusting the content to 5% by weight, thermal shock resistance, oxidation resistance,
It is possible to obtain a graphite-containing amorphous refractory material having a better balance of properties such as corrosion resistance and better durability.

In another preferred embodiment of the graphite-containing amorphous refractory composition of the present invention, the average particle size of the hydrophilic small particles is 40% or less of the average particle size of the graphite particles. By setting the average particle size of the small particles to 40% or less, and more preferably 20% or less of the average particle size of the graphite particles, the surface energy of the small particles becomes larger and the adhesion of the graphite particles to the surface increases, The surface of the graphite particles can be more completely covered with a relatively small amount of small particles.

Specific examples of hydrophilic small particles include silica, mullite, alumina, and
Magnesia, spinel, chromia, zirconia, titania, boron oxide, zircon, alumina cement and clay, metal carbides of boron carbide and silicon carbide, metal nitrides of silicon nitride and boron nitride, and metal borides of boron. Zirconium bromide and titanium boride are selected as metals, and aluminum, silicon, titanium, magnesium and alloys thereof are selected according to the application of the refractory.

The reason why the surface of the particles of these compounds is hydrophilic is that even when the surface of these particles is not an oxide, it is in an oxidized state and has a polarity, and is This is because it gets wet easily.

In another preferred embodiment of the graphite-containing amorphous refractory composition of the present invention, the hydrophilic small particles are one or more selected from alumina, silica, silicon carbide, silicon and aluminum. Alumina, silica, and silicon carbide are relatively easily available and have heat resistance, and small particles of silicon, aluminium, and silicon carbide impart hydrophilicity to graphite particles, and at the same time, have a preferable function of preventing oxidation of graphite. Demonstrate.

As the small particles, when the amorphous refractory is used as, for example, a spray kneading clay, a pouring kneading clay, a solidifying kneading clay, etc., zeta to water (including conditions such as pH) as a dispersion medium is used. A combination that has a large absolute value of electric potential, shows good dispersibility, and can reduce the amount of water, and also heat resistance, thermal shock resistance, thermal conductivity, electrical conductivity, and oxidation prevention of graphite particles depending on the end product application. It is advisable to select small particles that impart characteristics such as function.

From the viewpoint that some desirable characteristics other than hydrophilicity are imparted to the graphite particles, the powder of silicon carbide is the most preferable as the small particles having hydrophilicity. Alumina and silica are powders that are easily available as small particles having hydrophilicity and also have heat resistance, and can be preferably used as small particles for the graphite-containing amorphous refractory composition of the present invention.

Hydrophilic small particles that impart an antioxidant function to graphite particles include silicon, aluminum and silicon carbide, and silicon is used as the hydrophilic small particles that are oxidized to reduce the air permeability of the sintered body. Silica and silicate are examples of hydrophilic small particles having a property that silicon carbide melts at a high temperature to form a glass phase to cover the surface of a refractory and improve the oxidation resistance.

In another preferred embodiment of the graphite-containing amorphous refractory composition of the present invention, the refractory compound powder is magnesia or alumina. Refractory compound powders that are often used as refractory compound powders in conventional graphite-containing refractory materials in the processes of pig iron and steelmaking are readily available and have excellent heat resistance, and are suitable for molten steel, hot metal and slag. Magnesia and alumina, which have excellent corrosion resistance. Magnesia and alumina, in particular, a powder obtained by electromelting these, when used as a refractory compound powder of the graphite-containing amorphous shaped refractory composition of the present invention, has excellent durability in the applications of pig iron and steelmaking. This is particularly preferable because a refractory molded body can be obtained.

Examples of the graphite powder that can be used in the graphite-containing amorphous refractory composition of the present invention include flaky natural graphite, soil natural graphite, artificial graphite such as electrode scrap, pitch coke and carbon black heat-treated at high temperature. , Or a mixture of these. Of these, flaky natural graphite is a preferable graphite powder that is excellent in terms of oxidation resistance and corrosion resistance.

The average particle size of the graphite powder is 0.1 μm.
It is possible to use coarse particles having a size of 1 to 1 mm or more, but it is preferable to use particles having an average particle size of 1 μm to 1 mm.

When the average particle size of the graphite powder is 1 μm or more, preferable characteristics such as corrosion resistance and oxidation resistance inherent to graphite are exhibited, and when the average particle size is 1 mm or less, impact of small particles having hydrophilicity is exerted. It is easy to adhere to the surface of the graphite particles by the treatment, and a stable coating of the hydrophilic small particles is easily formed on the surface of the graphite particles.

The method for preparing a graphite-containing amorphous refractory composition of the present invention comprises 70 to 97% by weight of graphite powder and a hydrophilic metal having an average particle size of 40% or less of the graphite particles of the graphite powder. Powder 3 to 30 consisting of particles of one or more kinds selected from oxides, metal carbides, metal nitrides, metal borides and metals
By subjecting the mixed powder with the weight% to impact treatment in a high-speed air stream to form a graphite powder in which small hydrophilic particles are fixed to the surface of the graphite particle, and the refractory compound powder is added to this graphite powder. It is characterized in that the blending amount of the graphite powder in this mixture is converted into the amount of carbon to be 2 to 40% by weight.

The preferable mixing ratio of the hydrophilic small particles fixed to the surface of the graphite particles of the graphite powder depends on the ratio of the average particle size of the small particle powder to the average particle size of the graphite powder, but the graphite It is an amount necessary and sufficient to almost completely cover the surface of the particle. For example, in order to obtain hydrophilicity that imparts dispersibility to water on the surface of graphite particles, if ultrafine powder having an average particle size of 10 μm or less is mixed as small particles, a small amount of small particle powder of 3% by weight or more is used. Thereby, effective hydrophilicity can be imparted to the surface of the graphite particles.

However, since the small particles are not a constituent component of a refractory having a main feature of corrosion resistance in many cases, the mixing ratio thereof is usually 30% by weight or less, preferably 20% by weight in the total amount with the graphite powder. % Or less.

When the average particle size of the small particles is larger than or equal to the average particle size of the graphite particles, the number of hydrophilic small particles adhered to the surface of the graphite particles decreases, and the adhesion of the small particles is reduced. In addition to the decrease in strength, when it is subsequently applied as an amorphous refractory, the porosity is large and only poor performance as a refractory is obtained, which is not preferable.

The hydrophilicity of the graphite powder is obtained by mixing a powder of small particles having an average particle size smaller than the graphite particles of the graphite powder and having hydrophilicity and a mixed powder of the graphite powder with a conventionally known dry type machine. It can be obtained by throwing it into a mechanical crushing device, but in particular, the impact processing device described in Japanese Patent Publication No. 3-2009 is used to apply a shock in a high-speed airflow or to perform a process of colliding both particles. Can be achieved efficiently and simply. Further, if a mixed powder in which hydrophilic small particles are weakly adhered to the surface of the graphite particles in advance is put into the impact treatment device, the small particles are more efficiently fixed to the surface of the graphite particles.

When the small particles cannot be attached to the surface of the graphite particles due to static electricity, water (a small amount of a surfactant or a binder may be added) is sprayed on the surface of the graphite particles to form a graphite powder. Another method is to wet the surface and then mix.

In the combination with most of the hydrophilic small particles, the hardness of the graphite particles is smaller than that of the small particles, so that the small particles that have been subjected to the impact treatment are partly embedded in the surface of the graphite particles. The particles are firmly fixed to the graphite particles, and the hydrophilicity due to the small particles can be easily added to the graphite particles having a small hydrophilicity.

A specific example of processing using the shock processing device will be described below. First, a predetermined ratio of graphite powder and powder of hydrophilic small particles are put into a mixer equipped with a stirring blade and mixed, and preferably the small particles adhere around the graphite particles due to static electricity or the like and are evenly distributed. To be a mixed powder dispersed in. Next, this mixed powder is put into an apparatus for impact treatment in a high-speed air stream, and mechanical effects such as impact force, compression force, frictional force, and shearing force are repeatedly applied to the particles of the mixed powder. During this period, the small particles are fixed to the surface of the graphite particles while adjusting the impact strength so that the graphite particles are not crushed.

By this impact treatment, the graphite particles are rounded and approach a spherical or elliptical shape, and at the same time, small hydrophilic particles are stuck in the surface of the graphite particles and are fixed.
The graphite particles are covered with the small particles. The shape of the graphite particles of the graphite powder is not a large aspect ratio (meaning the ratio of major axis / minor axis) such as scales and needles, but a small aspect ratio such as dice or spheres. In some cases, the graphite particles are less likely to be crushed and the small particles are easily fixed.

Therefore, it is preferable to subject the graphite powder to mechanical shock treatment in advance to reduce the aspect ratio, or to select the graphite powder having a small aspect ratio.
However, the method of performing impact treatment in a high-speed airflow simultaneously promotes the action of reducing the aspect ratio of the graphite powder particles, and even if there are cracks or irregularities on the surface of the graphite particles, small particles are present in this part. By being stuck and fixed, the density of the particles is increased, and a molded product of an amorphous refractory having a large bulk specific gravity can be obtained.

That is, the thus-hydrophilized graphite powder has a good filling property and can reduce the porosity even when the construction is carried out without using water as a dispersion medium, and the amorphous refractory having a large bulk specific gravity. Can be obtained.

The graphite powder having the hydrophilic small particles adhered to the surface of the particles as described above has a large absolute value of the zeta potential at the interface when mixed with water as a dispersion medium, and thus is dispersed in water. It has good porosity and can be mixed with other refractory compound powder and a relatively small amount of water to obtain a kneaded material with good fluidity or a kneaded material with a good filling property, and the porosity when applied is It is possible to obtain an effect that it becomes a molded product of an amorphous refractory having a small size, a large bulk density, and excellent oxidation resistance and corrosion resistance.

The graphite-containing amorphous refractory composition containing the graphite powder having good dispersibility in water thus obtained is applied as an amorphous refractory to obtain a conventional graphite-containing amorphous Even if the bulk specific gravity is larger than that of the graphite-containing regular refractory, and the bulk specific gravity is slightly smaller than that of the graphite-containing irregular refractory, the irregular refractory is treated like a regular refractory. This is advantageous because it has no joint joints that are easily eroded, and a graphite-containing amorphous refractory that is comparable to the graphite-containing regular refractory in overall characteristics such as oxidation resistance and corrosion resistance can be obtained.

When two or more kinds of small particles are fixed to the surface of the graphite particles of the graphite powder at the same time or in an overlapping manner, each small particle can have a different function other than hydrophilicity. Further, when different small particles are fixed to the surface of the graphite particles in a stacked manner, a hydrophilic graphite powder can be obtained by making the small particles to be fixed finally hydrophilic.

The graphite-containing amorphous refractory composition of the present invention contains lactic acid, phosphate, silicate, borate, lactate, clay, alumina cement, siligasol, etc. as a binder.
In the range of 1 to 5% by weight, and as the dispersant, phosphates, silicates, sulfonates and other surfactants can be contained in the range of 0.01 to 1% by weight.

In this way, a dispersant and water were added to a composition prepared by adding and mixing a graphite powder composed of graphite particles having hydrophilic small particles adhered to the surface thereof, a refractory compound powder and a binder. By mixing or kneading, it is possible to obtain a graphite-containing amorphous refractory material such as a casting material, a ramming material, a stamp material, and a spraying material, in which a small amount of water is added, that is, the bulk density of the molded product is large.

A molded article of graphite-containing amorphous refractory obtained by applying the composition of the present invention on-site requires less manpower for application when used as a lining material for containers used for pig iron and steelmaking. It has superior oxidation resistance and corrosion resistance compared to the conventional graphite-containing amorphous refractory, and because it does not have joints with poor corrosion resistance like the regular refractory, it is overall superior to the graphite-containing regular refractory. It becomes an amorphous refractory material containing graphite with excellent cost performance ratio.

[0048]

EXAMPLES Hereinafter, the graphite-containing amorphous refractory composition of the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. In the following example, an impact treatment device (model name: NHS-3) manufactured by Nara Machinery Co., Ltd. was used as a device for impact treatment of a mixed powder of graphite powder and hydrophilic small particle powder in a high-speed air stream.

The main part of this device has the construction shown in cross-section in FIGS. 1 and 2, FIG. 1 being a front cross-sectional view and FIG. 2 being a side cross-sectional view thereof. 1 and 2,
1 is a casing, 2 is a front wall, 3 is a rear wall, 4 is a rotating plate, 5 is a blade, 6 is a rotating shaft, 7 is an impact chamber, 8 is an impact wall, 9 is a powder outlet valve, 10 is a powder circulation. A circuit tube, 11 is a raw material powder introduction valve, and 12 is a hopper.

In this apparatus, the mixed powder of graphite powder and small particle powder placed in the hopper 12 is introduced into the impact chamber 7 having a ring-shaped space by opening the raw material inlet valve 11. In the impact chamber 7, there are a rotary plate 4 fixed to a rotary shaft 6 driven by an electric motor (not shown) and a blade 5 fixed to the rotary plate 4, so that the rotary chamber rotates at high speed.

Rotational energy of the blade 5 is generated by the impact chamber 7
Inside the shock chamber 7
The air flow carries the powder and circulates in the direction of the arrow in the closed flow path of the powder circulation circuit tube 10 attached to the.

The graphite particles and the hydrophilic small particles of the mixed powder collide with each other in the powder particles, and in addition, the graphite particles and the hydrophilic small particles are circulated by receiving the impact force of the blade 5 rotating at a high speed, so that the compression force and the friction are reduced. Repeatedly receives mechanical action such as force and shearing force.

As a result, the graphite particles of the graphite powder gradually have their corners approaching a spherical or ellipsoidal particle shape with a small aspect ratio, and at the same time, small hydrophilic particles are fixed on the surface of the graphite particles. And, by being coated, the graphite particles are rendered hydrophilic.

At this time, the rotation speed of the blade 5 is adjusted to a speed at which the graphite particles of the graphite powder are not crushed. After impact treatment for a predetermined time, the graphite powder made of graphite particles whose surfaces are coated with hydrophilic small particles is
Is opened and taken out.

Test Example As a graphite powder, carbon content is 98% by weight and particle size is 150 μm.
m is used, and flaky natural graphite powder having an average particle size of about 51 μm and artificial graphite powder having a carbon content of 99% by weight and a particle size of 150 μm or less and an average particle size of about 32 μm are used. As a powder consisting of particles, the absolute value of the zeta potential is remarkably larger than that of graphite powder, and alumina (average particle size of about 0.6 μm) and silica (average particle size of 0.
2 μm), silicon carbide (average particle size of about 5.4 μm), and aluminum (average particle size of about 12 μm) are used alone or in combination, and graphite is used under the combinations and conditions shown in Table 1, Table 2 and Table 3. Hydrophilic treatment of the powder was performed to obtain hydrophilic graphite powder.

That is, the mixed powders of the respective combinations were put into the above-described high-speed air current impact treatment device to perform impact treatment. The temperature of the powder during this impact treatment is at most 1
The temperature is about 50 ° C., and the graphite particles and small particles are not chemically changed. The peripheral speed of the rotary plate 4 in the high-speed air current impact treatment device can be adjusted in the range of 10 to 150 m / sec, but in the case of the graphite particles of the graphite powder used in the test, crushing does not occur much. As described above, it was found that it is appropriate to perform the impact treatment at the peripheral speed of 100 m / sec or less.
During this time, there is no problem even if the small particles are crushed to some extent.

In the impact treatment, the adhesion of the small hydrophilic particles to the graphite particles is better when a strong impact force is applied so that the graphite particles are crushed to some extent. In the following test, the rotation speed of the rotary shaft 6 was adjusted so that the peripheral speed was 60 m / sec so that the crushing of the graphite particles did not occur remarkably and the small particles were effectively fixed. About 1 kg of the mixed powder was charged at one time to carry out impact treatment.

The average particle size of the powder is measured by a laser diffraction type particle size distribution measuring device (Model 799, manufactured by Microtrac).
The particle size distribution is measured according to 7), and the particle size at a location where the integrated volume is ½ is obtained. The impact treatment time can be changed within the range of 1 to 20 minutes,
As a condition for obtaining a sufficient treatment effect even for a short time, it was set to 3 minutes.

Table 1 shows the types of hydrophilic small particles combined to obtain the hydrophilic graphite powder and the results of measuring the zeta potential of the impact-treated graphite powder.
The results are summarized in Tables 2 and 3. Examples 18, 19, 2
0 and 23 are comparative examples.

Using the thus obtained hydrophilic graphite powder, a graphite-containing composition for amorphous refractory containing a combination of electro-melted magnesia powder and electro-melted alumina powder as the refractory compound powder. I prepared it. These compositions were evaluated by the following methods, and the results are summarized in Tables 4, 5 and 6.

A. Zeta potential 10 parts by weight of 0.01 molar KCl aqueous solution was added to 1 part by weight of impact-treated graphite powder or other graphite powder and mixed to prepare a slurry. After degassing this slurry for 30 minutes under reduced pressure, add 0.01N KOH aqueous solution to adjust the pH.
Was adjusted to 11, and the zeta potential was measured at 25 ° C. by the colloidal vibration potential method. It is said that the larger the absolute value of this zeta potential, the better the dispersibility in water.

B. Fluidity of kneaded material Magnesia-based (Examples 1 to 20) Graphite powder having hydrophilic particles fixed on the surface by impact treatment and graphite powder of Comparative Example or 6 of graphite powder
~ 22 parts by weight, maximum particle size 20 mm, minimum particle size 40μ
86 parts by weight of electro-fused magnesia powder, 4 parts by weight of alumina fine powder (average particle size of about 0.6 μm), 4 parts by weight of silica fine powder (average particle size of about 0.2 μm), metallic silicon powder (particle size) 149 μm or less), 3 parts by weight of lactic acid as a binder, 1.5 parts by weight of lactic acid as a binder, 0.1 parts by weight of sodium β-naphthalenesulfonate as a surfactant, and 8 to 12 parts by weight of distilled water. The mixture was put into a mixer and mixed for 1 minute to obtain a kneaded material having thixotropy.

Alumina-based (Examples 21 to 23) Similarly, to 6 parts by weight of graphite powder, 72 parts by weight of fused alumina powder having a maximum particle size of 5 mm and a minimum particle size of 40 μm as a refractory compound powder, Alumina fine powder (average particle size of about 2.
3 parts by weight, silica fine powder (average particle size 0.2 μ)
m) and 4 parts by weight of silicon carbide powder having a particle size of 74 μm or less.
Parts by weight, 3 parts by weight of metallic silicon powder having a particle size of 149 μm or less, 5 parts by weight of alumina cement as a binder, 0.1 parts by weight of sodium tripolyphosphate as a dispersant, and 6.3 to 8.3 parts by weight of distilled water. Parts were weighed and put into a universal mixer and mixed for 1 minute to obtain a thixotropic kneaded clay.

These kneaded clays had an inner diameter of 100 mm and a height of 50 m.
The mold of m is filled, and the kneaded clay with the mold removed is subjected to a vibration of 3G strength in the vertical direction for 10 seconds to soften and deform the kneaded clay, and the maximum spread length of the kneaded clay is measured to flow. It was used as an index of sex. However, of these kneaded clays, which have insufficient fluidity for pouring, a large amount of distilled water is added, so this point needs to be taken into consideration when comparing the fluidity.

C. Bulk specific gravity 50 mm x 50 mm x the same kneaded material from which the fluidity was measured
Each of the test pieces was subjected to vibration casting into a mold having an inner dimension of 50 mm, molded, left to stand at room temperature for one day to cure, and then removed from the mold, and then dried at 110 ° C. for 24 hours. It was measured and the bulk specific gravity was calculated.

[0066]

[Table 1]

[0067]

[Table 2]

[0068]

[Table 3]

[0069]

[Table 4]

[0070]

[Table 5]

[0071]

[Table 6]

D. Oxidation resistance Magnesia-based refractories (Examples 1 to 20, 24) Each test piece of 50 mm × 50 mm × 50 mm whose bulk specific gravity was investigated was heated and held in air at 1500 ° C. for 2 hours,
After cooling, it was cut at the central portion and the depth of the decarburized layer in the cross section was measured and used as an index of its oxidation resistance. Further, as another comparative example, the same test was carried out on a magnesia graphitic unfired fixed-size brick having a bulk specific gravity of 2.9 containing 15% by weight of flake graphite (Example 24), and the depth of the decarburized layer was 4.6 mm. Met.

Alumina-based refractory materials (Examples 21 to 23, 25) Each test piece whose bulk specific gravity was examined in the same manner was heated and held in air at 1450 ° C. for 5 hours, and after cooling, cut at the central portion to obtain a cross section. The depth of the decarburized layer was measured and used as an index of its oxidation resistance. Further, as another comparative example, the same test was performed on an alumina graphite non-fired shaped brick (Example 25) having a bulk specific gravity of 2.9 containing 10% by weight of flake graphite and 5% by weight of silicon carbide. Had a depth of 6.7 mm.

E. Corrosion resistance Magnesia-based refractories (Examples 1 to 20 and 24) 50 mm x 160 m with a trapezoidal cross section by casting
A test piece of graphite-containing amorphous refractory having a size of m × 45 to 95 mm was prepared, and as a comparative example, the above-mentioned magnesia graphitic unfired shaped brick (Example 24) cut into the same size was combined to obtain 6 pieces.
Combining pieces, forming a pillar with a hexagonal hole (inner diameter of about 7.8 cm) in the center, and holding this prism in a sideways state,
While rotating at a predetermined temperature while rotating at rpm, a slag and a carbon steel piece were continuously added inside the hexagonal hole to perform a rotary erosion test comparing the corrosion resistance of refractories.

That is, a combination of test pieces in a columnar shape was fixed in a rotary erosion test furnace, and a carbon steel piece and a slag were combined in a central hole of the test piece at a weight ratio of 1: 1 and then an erosion agent was added. Put 6kg, while keeping the furnace temperature at 1650 ° C,
A rotary erosion test was carried out for 5 hours while adding 0.3 kg of additional erosion agent every 30 minutes and extracting the same amount of erosion agent. Each test piece taken out after cooling was cut in the longitudinal direction at the central portion, and the erosion rate was obtained from the erosion amount of the deepest eroded portion, which was used as an index of corrosion resistance.

The erosion rate of the magnesia graphitic unfired shaped brick (Example 24) in this test was 5.8 mm / hour. The chemical composition of the slag used in this test was 40% by weight, CaO 40%, CaF2 20%, SiO2 1%.
0% and Al2 O3 30%.

Alumina-based refractory (Examples 21 to 23, 25) Alumina-graphite amorphous refractory was prepared by casting a 40 mm × 120 mm × 50-83 mm test piece having a trapezoidal cross section, and As a comparative example, a test piece (Example 25) of the same shape is prepared by cutting an alumina graphite non-firing shaped refractory, and a total of eight test pieces are combined to form an octagonal hole (inner diameter about 8.7 cm). In the crucible of the induction furnace, fix it with a mortar at the position to be the surface of the molten metal, and put a total of about 50 kg of erosion agent combining pig iron and slag in a ratio of 1: 1 in this crucible and conduct induction heating at 1500 ° C for 5 hours. After melt-holding and cooling, the test pieces were taken out, each test piece was cut in the longitudinal direction, and the erosion rate was examined from the maximum erosion depth.

The erosion rate of the alumina-graphite unfired shaped refractory material (Example 25) in this test was 3.4 mm / hour. The chemical composition of the slag used in this test was% by weight: CaO 50%, CaF2 25%, SiO2 1
0% and 15% FeO.

From the above test results, the graphite powder in which the hydrophilic small particles are adhered to the surface of the graphite particles can be obtained even when one kind of hydrophilic small particles is adhered to the surface of the graphite particles. Even when two or more kinds of small particles having hydrophilicity are fixed on the surface of the graphite particles, the zeta potential of the graphite particles is higher than that of the graphite powder which is not surface-treated or is surface-treated by the conventional technique. It was revealed that the absolute value was large and the dispersibility in water was excellent.

As is clear from the test results of Example 20, S
Graphite powder coated with iC by CVD in SiO gas has a large absolute value of zeta potential and excellent dispersibility, but has a large porosity when used as a refractory material and is inferior in performance such as corrosion resistance. I found out. This is because the surface of the graphite particles is in a rough state with many pores, so that the bulk specific gravity is small.

The amorphous refractory obtained by using the hydrophilic graphite powder according to the amorphous refractory composition of the present invention is
When water is used as the dispersion medium, even if the amount of added water is small, the flowability of the kneaded clay is good, and the shaped refractory molded product obtained by molding this kneaded clay has a large bulk specific gravity, corrosion resistance and oxidation resistance. Will be excellent.

Further, comparing the graphite-containing regular refractory material, which is widely used in the field of ironmaking and steelmaking and has a well-established performance, with the graphite-containing amorphous refractory material according to the present invention, corrosion resistance and oxidation resistance Although there is not much difference in the above, the irregular-shaped refractory is advantageous because there are no joints with poor corrosion resistance. Thus,
It is possible to obtain a graphite-containing amorphous refractory having an excellent cost performance ratio at least by the effect of significantly reducing the labor and energy consumption required in the manufacturing process and construction.

[0083]

The graphite powder used in the carbon-containing amorphous refractory composition of the present invention has a large absolute value of zeta potential in water, and a graphite powder not surface-treated,
Compared with the graphite powder surface-treated by other methods, it shows excellent dispersibility when water, which is easy to use as a dispersion medium, is used.

Therefore, even if an organic solvent, which causes a problem of working environment, is not used as a dispersion medium, the excellent dispersibility in water is utilized, the bulk specific gravity is large, the corrosion resistance is excellent, and the oxidation resistance is also excellent. A graphite-containing amorphous refractory can be provided.

Further, by selecting the material of the hydrophilic small particles to be fixed to the surface of the graphite particles, or by fixing the two or more kinds of hydrophilic small particles to the graphite particles, graphite having desirable characteristics other than hydrophilicity is also provided. It is possible to obtain a fine powder, and thereby a graphite-containing amorphous refractory having excellent oxidation resistance can be provided.

By subjecting the mixed powder of the graphite powder and the powder of small particles having hydrophilicity to the impact treatment, the graphite powder excellent in dispersibility in water can be simply and efficiently obtained. Even if the particle shape of the powder is scale-like or needle-like with a large aspect ratio, processing to reduce the aspect ratio to make it more spherical or ellipsoidal, and processing to fix small hydrophilic particles to the surface of graphite particles Since this is simultaneously performed, when used as a graphite-containing amorphous refractory material, a molded article having a good filling property and a large bulk specific gravity can be obtained.

Thus, conventionally, water cannot be used as a dispersion medium to obtain a molded product of a refractory having a large bulk specific gravity, and its oxidation resistance and corrosion resistance are insufficient, so that it has not been often used in the fields of pig-making and steel-making. The graphite-containing amorphous refractory, by using the graphite-containing amorphous refractory composition of the present invention, it is possible to obtain a molded article of an amorphous refractory having a large bulk specific gravity, oxidation resistance and corrosion resistance Greatly improved. Therefore, the effect of labor saving and energy saving, which is a characteristic feature of the amorphous refractory, can be utilized also in the graphite-containing refractory, and its industrial utility value is great.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an example of an apparatus used for hydrophilizing graphite particles of a graphite powder used for a carbon-containing amorphous refractory composition of the present invention.

FIG. 2 is a side sectional view of FIG.

[Explanation of symbols]

 1: Casing 2: Front wall 3: Rear wall 4: Rotating plate 5: Blade 6: Rotating shaft 7: Impact chamber 8: Impact wall 9: Powder outlet valve 10: Powder circulation circuit pipe 11: Raw material powder introduction valve 12: Hopper

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[Procedure amendment]

[Submission date] October 23, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

In the CVD method, for example, a gas component such as SiO or B ₂ O ₃ is brought into contact with the surface of graphite particles at 1000 ° C. or higher to form a thin film such as SiC or B ₄ C on the surface. There is a problem that the surface of the graphite particle is oxidized by the reaction at this time, the surface of the graphite particle becomes rough with many pores, and the oxidation resistance of the graphite particle is lowered. Although the halide CVD method is also known, as a method for treating a raw material powder of a refractory which cannot be said to have a large added value, because the raw material gas is expensive or exhaust gas treatment is required. Not suitable.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

In the sol-gel method, for example, silicon alkoxide, aluminum alkoxide, etc. are hydrolyzed in an alcohol aqueous solution in the presence of an acid catalyst, and the obtained sol solution is impregnated into graphite powder and dried to gel to form graphite particles. Although SiO ₂ or Al ₂ O ₃ is attached to the surface, the wettability between the graphite particles and the sol solution is poor, and there are many areas where pores are formed between the graphite particles and the coating layer, or where the coating layer is not covered. A molded article having a large bulk specific gravity cannot be obtained even if it is used for an irregular shaped refractory because it remains and does not have sufficient dispersibility in water.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0076

[Correction method] Change

[Correction content]

The erosion rate of the magnesia graphitic unfired shaped brick (Example 24) in this test was 5.8 mm / hour. The chemical composition of the slag used in this test is 40% by weight, CaO 40%, CaF ₂ 20%, SiO ₂ 1
0% and Al ₂ O ₃ 30%.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0078

[Correction method] Change

[Correction content]

The erosion rate of the non-fired alumina graphite shaped refractory material (Example 25) in this test was 3.4 mm / hour. The chemical composition of the slag used in this test was% by weight, CaO 50%, CaF ₂ 25%, SiO ₂ 1
0% and 15% FeO.

Claims (6)

[Claims] 1. A composition mainly composed of a graphite powder and a refractory compound powder, wherein the graphite powder has a smaller average particle size than the graphite particles and is hydrophilic on the surface of the graphite particles. The small particles of at least one selected from the group consisting of metal oxides, metal carbides, metal nitrides, metal borides, and metals having are fixed, and the graphite powder in the composition is converted into the amount of carbon. 2-40% by weight of the graphite-containing amorphous refractory composition. 2. The graphite-containing amorphous refractory composition according to claim 1, wherein the composition contains graphite powder in an amount of 4 to 25% by weight in terms of carbon amount. 3. The graphite-containing amorphous refractory composition according to claim 1, wherein the hydrophilic small particles have an average particle size of 40% or less of the average particle size of the graphite particles. 4. The graphite-containing amorphous refractory composition according to claim 1, wherein the hydrophilic small particles are at least one selected from alumina, silica, silicon carbide, silicon and aluminum. object. 5. The graphite-containing amorphous refractory composition according to any one of claims 1 to 4, wherein the refractory compound powder is magnesia or alumina. 6. A metal oxide, a metal carbide, a metal nitride, a metal boride and a metal having a hydrophilicity of 70 to 97% by weight of graphite powder and an average particle diameter of 40% or less of the graphite particles of the graphite powder. Powder 3 to 30 consisting of one or more kinds of particles selected from
By subjecting the mixed powder with the weight% of the powder to impact treatment in a high-speed air stream to form a graphite powder in which small hydrophilic particles are fixed to the surface of the graphite particle, and the refractory compound powder is added to this graphite powder. A method for preparing a graphite-containing composition for an amorphous refractory, which comprises mixing 2 to 40% by weight of the graphite powder in terms of the amount of carbon in the mixture.