JPH09241012A - Oxidation resistant graphite and graphite-containing monolithic refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure superior corrosion resistance by incorporating a specified amt. of oxidation resistant graphite obtd. by coating the surface of graphite powder of a prescribed average particle diameter with glass powder and further incorporating refractory aggregate, fine powder, additives and auxiliaries. SOLUTION: Graphite powder of 10-500μm average particle diameter is coated with glass powder whose particle diameter is <=1/5 of that of the graphite powder by mechanical sticking with a mechanochemical modifying device or graphite powder is coated with a mixture of glass powder with a binder such as phenolic resin added by about 5-50wt.% of the amt. of the glass powder and the average particle diameter of the coated powder is regulated to <=50μm. The resultant oxidation resistant graphite is blended with refractory aggregate of magnesia, spinel, alumina, etc., in the form of coarse, medium or fine particles or fine powder, additives such as pitch powder and auxiliaries such as a dispersant and a softening agent in a specified ratio to prepare a blend contg. 3-20wt.% of the oxidation resistant graphite. This blend is molded and fired to obtain the objective graphite-contg. monolithic refractories.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to oxidation resistant graphite and an amorphous refractory material containing the same, and particularly proposes a graphite-containing amorphous refractory material for a metallurgical furnace excellent in slag resistance and its raw material.

[0002]

2. Description of the Related Art Refractory materials containing carbon materials such as graphite have the inherent properties of carbon, that is, they are difficult to wet with slag, have excellent thermal stability, have high thermal conductivity, and have a coefficient of thermal expansion. It has been widely used as a refractory material for metallurgy since it has a small value.
For example, magnesia-carbon bricks are used for converter linings, and alumina-carbon bricks are used as refractory materials for speeded cars and continuous casting nozzles.

On the other hand, in recent years, refractory materials have been indefinite in shape for the purpose of labor saving in furnace construction work. For example, alumina / magnesia system for steelmaking pots or alumina / silicon carbide system for blast furnace gutters. Unshaped refractories such as are used. In reality, the performance requirements for such amorphous refractories are becoming more and more severe, and in order to further improve durability, it is considered that carbon materials (graphite) will be applied to amorphous refractories. There is.

However, there are restrictions on the use of antioxidants in using graphite for amorphous refractories. That is, the inclusion of graphite in the regular refractory, there is little problem because metal powder such as aluminum powder can be used as an antioxidant of graphite, in the irregular refractory,
Since water is used at the time of kneading, when metal powder is used, hydrogen is generated under the alkaline condition caused by cement or the like and converted into a hydroxide, which does not function as an antioxidant. Therefore, although boron carbide and the like are used as an antioxidant, there is a problem that the effect is small and it is necessary to add a large amount, and the refractory price becomes high.

On the other hand, conventionally, there is a proposal to enhance the antioxidant effect by coating the surface of graphite with boron carbide. For example, Japanese Patent Application Laid-Open No. 4-16545 reports an oxidation-resistant graphite granule obtained by coating graphite powder with boron carbide powder with a pitch or a carbonizing thermoplastic resin. However, this technique has a problem that the amount of the binder is inevitably increased because the graphite powder surface is coated with a material in which boron carbide is dispersed in pitch or a resin liquid. That is, in the graphite-containing amorphous refractory using water, a large amount of pores are generated due to the two actions associated with the decomposition of the binder and the removal of water.
Therefore, there is a problem that the porosity is significantly increased, and thus a tissue body having high strength cannot be obtained.

Further, Japanese Patent Publication No. 63-397 discloses an amorphous refractory material in which coarse graphite particles are coated with earth-like graphite. According to the disclosure, a phenol resin used as a binder for graphite coating is disclosed. , Molasses, waste pulp, sodium silicate, potassium silicate, aluminum phosphate, silica sol, alumina sol, etc. are described to be effective in preventing or delaying the oxidation of graphite. However, organic substances such as phenolic resin have a problem that many pores are generated when they are baked, and sodium silicate (water glass) dissolves in the water added when it is used as an irregular refractory material and has oxidation resistance. There is a problem that the effect as a coating is lost.

Further, Japanese Patent Laid-Open No. 5-194044 reports a method of fixing a metal carbide on the surface of graphite by using a mechanochemical reformer without using a binder.
However, in this method, it is necessary to use a metal carbide having an extremely small particle size in order to obtain a good fixed state, but such a metal carbide is generally difficult to obtain,
There is a risk of ignition and explosion, and it is very expensive. Furthermore, since graphite has a not so strong adhesion force as that of general metal carbides, there is a problem that the oxidation resistance of such treated graphite cannot be expected so much.

[0008]

As described above, the conventional amorphous refractories, particularly graphite-containing amorphous refractories, have a high porosity and a low porosity because they contain a large amount of binder when the lack of oxidation resistance is compensated for. There are problems that only strong products can be obtained and that they are expensive. From this, recently
There has been an urgent need to develop a technique for imparting oxidation resistance to graphite for amorphous refractories at low cost.

Therefore, a first object of the present invention is to propose a graphite excellent in surface treatment and oxidation resistance, which does not have the above-mentioned problems that the conventional techniques have. A second object of the present invention is to inexpensively provide a carbon-containing amorphous refractory having excellent corrosion resistance, abrasion resistance (strength) and oxidation resistance.

[0010]

SUMMARY OF THE INVENTION The present invention proposes a graphite having an improved oxidation resistance by subjecting graphite, which is originally weak against oxidation, to a simple oxidation resistance treatment, and to provide such oxidation resistance. By blending so that the content of graphite is 3 to 20 wt%, preferably 5 to 15 wt%,
It is intended to obtain a carbon-containing amorphous refractory having excellent spalling resistance, corrosion resistance, abrasion resistance (strength) and oxidation resistance.

The present invention proposes, as an oxidation-resistant graphite that meets these requirements, an oxidation-resistant graphite having the following constitution and an amorphous refractory material using the same. Oxidation-resistant graphite characterized in that the surface of graphite powder is coated with glass powder. Oxidation-resistant graphite made by adhering glass powder having a size of 1/5 or less of the raw graphite through a binder on the surface of graphite powder having an average particle size of 10 to 500 μm. Acid resistance that is obtained by press-bonding glass powder with a size of 1/5 or less of the raw graphite on the surface of graphite powder with an average particle size of 10 to 500 μm by applying mechanical force by a mechanochemical reformer without using a binder. Chemical graphite. In each of the above inventions, the glass powder is made of one or more selected from borate glass, borosilicate glass, silicate glass, phosphate glass and soda glass, and is mixed in an amount of 3 to 15 wt% with respect to graphite. To do. Further, in the present invention, as the binder, one kind or two or more kinds selected from phenol resin, pitch, fatty acid such as stearic acid, and silicone resin is used. Further, the present invention contains 3 to 20% of the refractory graphite according to any one of the above 1 to 4, and further contains refractory aggregate, fine powder, necessary additives and auxiliary agents. It is an irregular refractory material.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The method of oxidation resistance treatment on the surface of graphite according to the present invention is carried out by arranging a raw graphite (powder) having an average particle diameter of 10 to 500 μm around /Five
Those coated with glass powder having the following sizes, for example, glass powder coated with a small amount of binder, or a machine such as impact force and grinding force with a mechanochemical reformer without using any binder. It is characterized by press-fitting and fixing by applying force (pressurizing coating so that glass powder is embedded in the graphite surface). Therefore, even in the latter case, the graphite powder of the present invention is a composite particle in which the glass powder is firmly adhered to the surface of the raw material graphite powder by pressure bonding by applying a binder or impact force or grinding force. In addition, the fixed powder is not peeled off even when kneading with water, and therefore a high oxidation resistance effect can be obtained with a small amount of glass powder. In particular, in the latter case, since the binder can be eliminated, there are few pores generated during firing, and a more dense and high-strength composite structure can be obtained.

As described above, in the graphite powder of the present invention, the glass powder is fixed around the graphite particles, so that the glass component on the outer surface is melted during use, especially in a high temperature range, and the molten glass is melted. Effectively coats around the graphite powder. Moreover, since effective coating can be performed with a small amount of glass, high antioxidant property can be imparted.

In the present invention, the raw material graphite is at least one of phosphorus (flake) graphite, artificial graphite and earth-like graphite having an average particle size of 10 to 500 μm, preferably 20 to 300 μm. The above is used. The reason for limiting the particle size is that the particle size is easily available, and if it is larger than this, the effect of corrosion resistance decreases, and if it is small, the oxidation resistance deteriorates even if treated.

In the present invention, the glass powder adhered to the surface of the graphite powder is one or more selected from borate glass, borosilicate glass, silicate glass, phosphate glass, silica glass and soda glass. An average particle size of 1/5 or less, preferably 1/10 to 1/100 of the graphite powder is used. This is because if the average particle diameter is out of this range, the coating (fixation) becomes ineffective and the oxidation resistance effect deteriorates.

The amount of this glass powder is preferably in the range of 3 to 15 wt% with respect to graphite. The reason for this is that the antioxidant effect is saturated even if added in excess of 15 wt%, which is economically disadvantageous. On the other hand, if it is less than 3 wt%, the antioxidant effect is insufficient.

The binder used in the present invention is preferably one or more selected from phenol resins, pitch, fatty acids such as stearic acid, and silicone resins. The properties of these binders may be liquid or powder. The amount of this binder used is 5 to 50 wt.
The amount corresponds to%. The reason for this is that if the amount exceeds 50 wt%, the porosity becomes large, the strength of the refractory becomes insufficient, and the corrosion resistance is poor. On the other hand, if it is less than 5% by weight, the fixation becomes insufficient. It is preferably 10 to 30 wt%.

Next, in the present invention, a method for forming an oxidation resistant film of glass powder on the surface of graphite powder will be described. In the present invention, the glass powder is kneaded with the above binder to form a composite powder, or the glass powder is strongly bonded to the surface of the graphite powder by a strong mechanical force due to the addition of impact force or grinding force by a mechanochemical reformer. Press in and stick. As the device used for the latter reforming treatment, a mechanochemical reforming device such as an Ong mill (made by Hosokawa Micron), a hybridization system (made by Nara Machinery), Hiex (made by Nisshin Flour Milling), a vibrating ball mill, or a Henschel mixer is used. High speed mixers are well suited. In these devices, particles are given a mechanical impact force and a grinding force, so the particles themselves become hot,
Binders such as granular phenolic resin and pitch are melted and become a liquid binder to cover the surface of the graphite powder with the glass powder.

In order to coat the surface of the graphite powder with the glass powder by using the above mechanochemical reforming apparatus, the graphite powder, the glass powder and the binder are mixed and supplied into the above-mentioned reforming apparatus. In the case of a liquid binder, operations such as spraying the binder later can be performed. When a liquid binder is used, the medium evaporates and the binding effect is further enhanced. Above all, it is desirable to heat from the outside in a Henschel mixer or the like.

For the oxidation-resistant graphite obtained by the above treatment method, the production conditions such as the treatment capacity (impact force, grinding force) of the reformer are selected so that the average particle size is 50 μm or less. When the particle size is 50 μm or more, it is desirable to further pulverize and adjust. The reason is that if the particle size of graphite exceeds 50 μm, the corrosion resistance decreases.

Next, the amorphous refractory material according to the present invention containing the above oxidation resistant graphite will be described. First, as the aggregate constituting the skeletal component of the amorphous refractory, one kind or two or more kinds selected from basic, neutral and acidic ones are used. For example, magnesia, spinel, alumina, zirconia, zircon, silica, silica, wax, shale shale, silicon carbide, chamotte and the like. It is desirable to use coarse particles, medium particles, fine particles, and fine powder, which are separately adjusted so as to obtain a densely packed structure.

The content of the oxidation resistant graphite to be blended with the above-mentioned aggregate in this amorphous refractory material is in the range of 3 to 20 wt%. It is difficult to obtain the high thermal conductivity and slag permeation prevention effect of graphite when the content is less than 3 wt%, while
This is because if it exceeds 20 wt%, the filling property is obstructed, the refractory becomes porous, and the thermal shock resistance deteriorates.

In the present invention, in addition to the above oxidation resistant graphite, other tar sources such as ordinary tar pitch powder, phenol resin powder, and carbon black powder may be used in combination.

In the present invention, in addition to the above-mentioned aggregate, fine powder, and other necessary additives, a dispersant (surfactant), a hardening agent, a hardening retarder, etc. are used as auxiliary materials. For example, as the dispersant, inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, acidic sodium hexametaphosphate, sodium borate, sodium carbonate, sodium citrate, tartrate, polyacrylate, naphthalene sulfone One or more selected from organic salts such as acid condensate salts can be used. As the curing agent, general alumina cement used for refractories can be used, and as the curing retarder, oxalic acid, citric acid, polyacrylic acid, etc. can be used.

Further, as the amorphous refractory material according to the present invention, in addition to the above-mentioned compounds, known sintering aids, fibers, metal powders, etc. can be used as long as the essential characteristics of the present invention are not impaired. A strengthening component or a binder may be added.

[0026]

【Example】

Example 1 It was confirmed by an experiment that the oxidation resistance is improved by fixing the glass powder on the surface of the graphite powder. The oxidation resistance is 5 parts by weight of graphite powder and 93 parts by weight of fine alumina powder,
10% water is added to the mixture of 2 parts by weight of alumina cement, compression molded and pelletized (diameter 20 x height 10 mm)
Was prepared, heated to 900 ℃ in air and held for 1 hour, the weight loss after cooling the furnace was measured, and the oxidation resistance was evaluated by the ratio to the graphite powder amount before heating (oxidation weight loss%). (The same applies to other examples below). Figure 1 shows that scaly graphite (average particle size 100 μm) and borosilicate glass powder (average particle size)
15 μm) in a hybridization system without using a binder (A) and artificial graphite (average particle size 50 μm) with borosilicate glass powder (average particle size 5,15 μm) and phenol resin as binder. As a result, the relationship between the amount of glass powder and the amount of oxidization loss when fixed by a Henschel mixer (B and C) is shown. If the glass powder is not adhered, there is no oxidation resistance at all, but by adhering 5 wt% or more of the glass powder, the oxidation loss is 15 wt% or less, and the oxidation resistance is remarkably improved. However, it was found that the effect of oxidation resistance is low when the particle size of the glass powder is 15 μm, that is, when it exceeds 1/5 of the particle size of graphite.

Example 2 Various graphite powders were fixed with 5 wt% of glass powder, and the average particle size and oxidation loss of the graphite powder after the treatment were examined. The results are summarized in Table 1. It can be seen that the oxidation-resistant graphites A, B, and C that have been treated according to the present invention, that is, obtained by fixing glass powder to graphite powder by various methods, have improved oxidation resistance as compared with untreated graphite. .

[0028]

[Table 1]

Example 3 This example is an example in which the inventive example and the comparative example were applied to a cast amorphous refractory for blast furnace tappipe, and the results are shown in Table 2. The oxidation resistant graphites A, B, and C in Table 2 are shown in Table 1 respectively.
It corresponds to those described as A, B, and C in the remarks column and is within the scope of the present invention. Comparative Example 1 is a conventional cast-in-place refractory material for blast furnace tappipe, and Comparative Example 2 is a case where untreated graphite is used. Compared to Comparative Example 2, the example has excellent oxidation resistance, and the Comparative Examples 1 and 2 also have excellent corrosion resistance.

[0030]

[Table 2]

[0031]

As described above, according to the present invention,
Oxidation resistance of graphite can be significantly improved by coating with glass powder, and the porosity of the amorphous refractory using this graphite can be suppressed to provide high strength and high corrosion resistance. Is obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of glass powder and the weight loss due to oxidation.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Takashi Haraoka, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Technical Research Institute, Kawasaki Steel Co., Ltd. (72) Keiichiro Isomura, 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki (72) Inventor Masato Kumagai, 1st Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture In-house Research Laboratory, Kawasaki (72) Inventor, Kyunobu Toritani 1576, Toho, Ako, Hyogo Prefecture No. 2 in Kawasaki Furnace Co., Ltd. (72) Inventor Katsumi Shirono, Nakaho, Ako-shi, Hyogo Prefecture 1576 East Off-Kawasaki Furnace Co., Ltd. (72) Inventor Junichiro Mori Nakahiro, Ako-shi, Hyogo 2 Kawasaki Furnace Material Co., Ltd.

Claims (6)

[Claims] 1. Oxidation resistant graphite characterized in that the surface of graphite powder is coated with glass powder. 2. The oxidation resistant graphite according to claim 1, wherein glass powder having a size of 1/5 or less of the raw graphite is adhered to the surface of graphite powder having an average particle diameter of 10 to 500 μm through a binder. . 3. A surface of graphite powder having an average particle size of 10 to 500 μm is coated with a glass powder having a size of 1/5 or less of that of raw graphite by applying mechanical force by a mechanochemical reformer without using a binder. Oxidation resistant graphite formed by pressure bonding. 4. The glass powder comprises one or more selected from borate glass, borosilicate glass, silicate glass, phosphate glass and soda glass, and is mixed in an amount of 3 to 15 wt% with respect to graphite. The oxidation resistant graphite according to claim 1, 2, or 3. 5. The binder according to claim 1, wherein the binder is composed of one or more selected from a phenol resin, pitch, a fatty acid such as stearic acid, and a silicone resin. Oxidation resistant graphite. 6. A refractory aggregate, a fine powder, necessary additives and auxiliaries, which contain 3 to 20% of the oxidation resistant graphite according to any one of claims 1, 2, 3, 4 and 5. A graphite-containing amorphous refractory characterized by containing.