JPH08143373A - Surface-treated graphite for castable refractory and castable refractory - Google Patents

Abstract

PURPOSE: To easily and inexpensively obtain hydrophilic pseudo-granular surface- treated graphite suitable for use as powdery starting material for castable refractories. CONSTITUTION: Fine particles of carbon having imparted hydrophilic property are fixed in a dispersed state on the surfaces of hydrophobic mother particles of graphite to obtain the objective pseudo-granular surface-treated graphite and the objective castable refractories for casting contg. 3-40wt.% of the surface- treated graphite are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated graphite for amorphous refractory which is excellent in hydrophilicity, corrosion resistance and strength, and an amorphous refractory containing this graphite.

[0002]

2. Description of the Related Art In recent years, amorphous refractories containing carbon raw materials such as graphite have a problem in terms of the characteristic of carbon, that is, oxidation resistance, but show high thermal conductivity, and have a high melting point for molten metal and slag. It exhibits high corrosion resistance because it is difficult to wet and react with, and has excellent durability because it has a small thermal expansion, and is therefore widely used as various refractory materials for metallurgy. By the way, the use environment of such amorphous refractory materials is becoming more and more severe in recent years. Against this background, in order to further improve the above-mentioned characteristics, the carbon content is further increased. Is being considered. However, carbon materials such as graphite are generally poor in dispersibility in water because they show hydrophobicity, and therefore, when added in large amounts in cast amorphous refractories, they cause agglomeration, resulting in a dense and homogeneous structure. There was a drawback that it was hard to become. In this sense, it has been conventionally difficult to add a large amount of carbon material to the amorphous refractory.

On the other hand, conventionally, in order to overcome the drawbacks of such carbon materials, especially graphite, attempts have been made to surface-treat such graphite. For example, a method of coating a surface of graphite with a surfactant (Japanese Patent Laid-Open No. 4-12064).
However, in the case of this method, in the coexistence with metal oxides, etc., the surfactant is redissolved in water, so that it is not possible to find a significant advantage in the fluidity of the product. It was In addition, a method in which fine particles of a metal oxide or a metal refractory are adhered to the surface of graphite to make it hydrophilic (Japanese Patent Laid-Open No. 5-194044).
(See Japanese Patent Publication). However, for this method, it is necessary to make the metal compound adhered to the graphite surface into ultrafine particles, but it is extremely difficult to produce such metal fine particles,
It also had the problem of becoming expensive. Furthermore, an example of blending silicon carbide and hydrophilically treated carbon (carbon is surface-treated with sodium linoleate, etc.) in its skeleton component in a cast refractory for casting (see Japanese Patent Laid-Open No. 5-330930) is also proposed. However, since this technique is a method of completely covering the surface of carbon graphite with a thin film of sodium linoleate, there is a problem that the dispersion is incomplete because sodium linoleate is redissolved.

[0004]

As described above, the conventional techniques, particularly the conventional surface-treated graphite for amorphous refractory, are difficult to manufacture and expensive, and the undissolved problem that the dispersibility is insufficient remains unsolved. It remains, and it was necessary to solve these problems. Therefore, an object of the present invention is to propose a surface-treated graphite that does not have the above-mentioned problems that the prior art has, that is, graphite particles that are originally hydrophobic, have a hydrophilic property suitable as a raw material powder for amorphous refractories. The purpose is to establish a technique for changing to the pseudo-granular surface-treated graphite, and to propose a surface-treated graphite that can be easily and inexpensively obtained and an amorphous refractory material using this graphite.

[0005]

According to the present invention, the surface of graphite which is originally hydrophobic is modified to be hydrophilic graphite by hydrophilizing the surface of the graphite, and at the same time, the surface-treated graphite is
The content of -40% by weight is intended to obtain a carbon-containing amorphous refractory having excellent thermal shock resistance and slag resistance. The present invention as a surface-treated graphite that can meet such demands is: (1) An amorphous refractory material in which pseudo-granular particles are formed by fixing carbonaceous particles having hydrophilicity in a dispersed state on the surface of graphite mother particles that are hydrophobic. We propose a surface-treated graphite. (2) However, it is preferable that the hydrophilic carbon particles have an average particle size of 1/100 to 1/10 of the average particle size of the graphite mother particles. (3) The hydrophilic carbon child particles are preferably at least one selected from hydrophilic carbon black, earth-like graphite, and earth-like hydrophilic graphite. (4) Further, the amorphous refractory according to the present invention containing graphite in the skeleton component, as the graphite, hydrophilic carbon particles are fixed so as to surround the surface of the graphite mother particles. 3-40 wt% of surface-treated graphite for standard refractories in the composition
It is characterized by being manufactured by containing it. (5) The above-mentioned amorphous refractory is a composition in which skeleton components, such as aggregate, fine powder, carbon material and auxiliary agents such as dispersant, curing agent, curing retarder, are appropriately mixed. The frame amount is preferably 5 to 20 wt%.

[0006]

According to the present invention, the fine carbon powder (child particles) having a smaller average particle size than the mother particles and having hydrophilicity is fixed to the surface of the graphite powder (matrix particle) which is a prime number in a dispersed state. Then, it is a surface-treated graphite in the form of pseudo particles. The graphite powder as the mother particles has an average particle diameter of 4 to 150 μm, preferably 5 to 150 μm.
The carbon particles having a size of 100 μm and fixed to the surface thereof are 1/100 to 1/10 of the size of the mother particles. If the ratio of both is less than 1/100, the exposed surface of the hydrophobic mother particle surface is relatively large and the ratio of the hydrophilic carbon particles is small, which is insufficient for imparting hydrophilicity, and the purpose of modification is I can't achieve it. On the other hand, if it is larger than 1/10, it is difficult to form pseudo particles, and the surface of the mother particle is exposed too much, resulting in insufficient modification.

[0007] It is preferable that the graphite mother particles used in the present invention include general natural flake-like graphite, earthy graphite, artificial graphite and the like which exhibit hydrophobicity. On the other hand, as the hydrophilic carbon particles, it is preferable to use hydrophilic carbon black, earth-like graphite itself, or earth-like graphite to which hydrophilicity is further added, or hydrophilic artificial graphite. For example, as the hydrophilic carbon black, used is carbon black of 0.01 to 0.1 μm which is rendered hydrophilic by vapor-phase oxidation with air or oxygen or wet oxidation with sulfuric acid, potassium permanganate, or the like. Further, hydrophilic earth graphite or the like is also made hydrophilic by oxidation or fluorination.

The surface-treated graphite according to the present invention is so-called graphite powder which is mechanochemically modified to impart hydrophilicity. As a method of imparting hydrophilicity by this mechanochemical modification, the following method is effective. First, the graphite mother particles and the hydrophilic carbon black are mixed at a predetermined blending ratio, and the mixture is subjected to impact treatment in a high-speed air stream to uniformly disperse the hydrophilic carbon black on the surface of the graphite mother particles. At the same time, the pseudo particles are formed by adhering with each other, and at the same time, they are mechanically and firmly joined by being joined by being embedded while applying an impact force, a grinding force, and a shearing force. The equipment used for this modification treatment is a mixer that can apply strong impact force, grinding force, and shearing force to particles, such as Ongmill (manufactured by Hosokawa Micron), hybridization system (manufactured by Nara Kikai), and Hiex. (Nissin Flour Milling), Henschel mixer (Mitsui Miike Machinery), etc. are advantageously used.

In the modification treatment, in order to obtain a preferable surface-treated graphite, it is important to adjust the compounding ratio of the graphite mother particles and the hydrophilic carbon particles in addition to the above-mentioned control of the particle diameter. . That is, the mixing ratio of these two is
It is preferably in the range of 99.9: 0.1 to 50:50, particularly preferably 99: 1 to 80:20. The reason for this is that when the amount of child particles outside this range increases, the number of child particles that do not adhere to the surface of the mother particles increases, and the characteristics as surface-treated graphite for amorphous refractory deteriorate, and in addition, in terms of cost. Is also a disadvantage. On the other hand, if the amount of the child particles is less than the ratio within the above range, the exposed area of the surface of the mother particles becomes large and the purpose of modification cannot be achieved.

Next, the amorphous refractory material according to the present invention containing the above-mentioned surface-treated graphite will be described. First, the aggregates that make up the skeletal component of this refractory are basic, neutral,
One or more selected from acidic ones are used. For example, magnesia, spinel, alumina, zirconia, zircon, silica, silica, pyrophyllite, silicon carbide,
Such as chamotte. It is preferable to use coarse particles, medium particles, fine particles, and fine powder, which are separately adjusted so as to obtain a densely packed structure.

The amount of the above-mentioned hydrophilic surface-treated graphite mixed with the above-mentioned aggregate in this amorphous refractory is 3-4.
The range is 0 wt%. This is because if the content is less than 3 wt%, it is difficult to obtain the slag penetration preventing effect, and if it exceeds 40 wt%, the filling property is impaired, the refractory becomes porous, and the thermal shock resistance deteriorates.

In the present invention, as other carbon source, in addition to the above surface-treated graphite, usual tar pitch powder, phenol resin powder and the like can be added.

In the present invention, in addition to the above-mentioned skeleton component, a dispersant (surfactant), a curing agent, a curing retarder or the like can be used as an auxiliary agent. For example, as the dispersant, sodium tripolyphosphate, sodium hexametaphosphate, ultrapolyphosphate sodium, acidic sodium hexametaphosphate, sodium borate, inorganic salts such as sodium carbonate, sodium citrate, tartrate, sodium polyacrylate, sulfonic acid One or more of soda and the like can be used. As the curing agent, general alumina cement used for refractories can be used, and as the curing retardant, 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 compound, known sintering aids, fibers, metal powders, etc. may be used as long as the essential characteristics of the present invention are not impaired. A strengthening component of, or a binder may be added.

[0015]

【Example】

Example 1 As shown in Table 1, the surface-treated graphite used in this example had hydrophobic phosphorus-like graphite, earth-like graphite, and artificial graphite having an average particle diameter of 1 to 150 μm as the mother particles. As hydrophilic carbon particles attached to the surface, the average particle size is 0.01 ~
Tokai Carbon hydrophilic hydrophilic carbon black having a size of 0.1 μm was blended in an amount of 1 to 10% to form a pseudo-particle shape as shown in FIG. 2 (a). As a surface modification device for adjusting the surface-treated graphite, a Hosokawa Micron Ong Mill and a high-speed gas impactor (NHS) were used.
FIG. 1 shows the hydrophilicity of the surface-treated graphite evaluated by the amount of graphite in a floating state that does not contribute to the formation of pseudo particles. That is, in this evaluation test, the surface-treated graphite was placed in pure water, and the amount of graphite powder floating on the surface after 5 minutes was shown as a weight percentage of the amount of added graphite. As shown in the figure, in the surface-treated graphite according to the present invention, when the modification treatment time exceeds 10 minutes, the amount of graphite floating in water is remarkably reduced, and the wettability with water is significantly improved. I understand. Further, as can be seen by comparing with the graphites shown as Comparative Examples 3 to 4 in Table 1, the untreated graphite of Comparative Example 2, the graphite of Comparative Example 3 having no child particles, and the Comparative Example coated with alumina fine powder. The graphite of No. 4 had an amount of floating graphite of 70 to 9
It was as large as 5%, and it was confirmed that the hydrophilicity was poor.

Example 2 In this Example 2, the characteristics of an amorphous refractory for casting for a blast furnace trough which was mixed with the surface-treated graphite used in Example 1 were tested. Table 1 shows the results. The surface-treated graphites A to E in Table 1 are compatible with the present invention, and Comparative Example 1
Is a conventional castable alumina-SiC-C system, Comparative Example 2
Is a phosphorous graphite that has not been surface-treated, Comparative Example 3 is an artificial graphite having no child particles, and Comparative Example 4 is an example using graphite in which 5% of alumina (5μ) child particles are fixed. As is clear from this table, in Examples 1 to 5, not only is the compactness (apparent porosity) significantly improved over the untreated graphite product of Comparative Example 2, but also thermal shock resistance (bending Strength, and the corrosion resistance is obviously improved over the conventional alumina-SiC-C type castable (Comparative Example 1). On the other hand, in Comparative Examples 2 to 4, it is apparent that the apparent porosity is large and the hydrophilicity is poor, and the bending strength is small and the corrosion resistance is poor, as seen in the amount of floating graphite. is there. In addition, the castable refractory of the present invention can be used not only as the castable refractory for the blast furnace gutter described above but also as a cast refractory for the hot metal ladle, the mixed pig iron car and the molten steel ladle slag line.

[0017]

[Table 1]

[0018]

As described above, according to the present invention, surface-treated graphite having excellent hydrophilicity can be obtained easily and inexpensively, and at the same time, it is dense and excellent in thermal shock resistance and corrosion resistance. A standard refractory material can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing hydrophilic properties of surface-treated graphite according to the present invention.

FIG. 2 is a sectional view schematically showing a heat-treated graphite according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location C04B 41/87 R (72) Inventor Keiichiro Isomura 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Steel Research Laboratory Co., Ltd. (72) Inventor Masato Kumagai, 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Steel Research Laboratory, Ltd. (72) Inventor, Kyunobu Toritani, 1576, Nakaho, Higashi, Ako City, Hyogo Prefecture 2 Inside Kawasaki Furnace Co., Ltd. (72) Inventor Junichiro Mori 1576, Higashioki, Aki, Ako City, Hyogo Prefecture 2 At 2576 Kawasaki Furnace Co., Ltd. (72) Inventor, Katsufumi Sino, Ako City, Hyogo 2 Kawasaki Furnace Co., Ltd. at 1576 Oki

Claims (4)

[Claims] 1. Surface-treated graphite for amorphous refractory, wherein hydrophilic carbon particles are fixed in a dispersed state on the surface of graphite mother particles. 2. The hydrophilic carbon child particles having an average particle size of 1/100 to 1/10 of the average particle size of the graphite mother particles are used. Graphite described. 3. The hydrophilic carbon child particle is any one or more selected from hydrophilic carbon black, earth-like graphite and hydrophilic earth-like graphite, and is characterized by the above-mentioned. Graphite. 4. An amorphous refractory having graphite as a skeleton component, wherein the graphite is an amorphous refractory in which hydrophilic carbon child particles are fixed in a dispersed state on the surface of graphite mother particles. A refractory having an irregular shape, characterized by containing 3 to 40 wt% of surface-treated graphite.