JP3210242B2 - Graphite-containing amorphous refractories - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly durable amorphous refractory containing graphite, particularly scaly graphite.

[0002]

2. Description of the Related Art In recent years, amorphous refractories containing a carbon material such as graphite have a high thermal conductivity, although there is a problem in the characteristics of carbon, that is, oxidation resistance, and have a high degree of thermal conductivity. It is widely used as various refractory materials for metallurgy because it exhibits high corrosion resistance because it is hardly wetted and hardly reacts with water, and has low thermal expansion and excellent durability. By the way, the use environment of such amorphous refractories is in fact becoming more and more severe in recent years, and under such circumstances, the carbon content is further increased in order to further improve the above-mentioned properties. That is being considered. However, general graphite is poor in dispersibility in water due to its hydrophobicity, and therefore, when added in large amounts in cast amorphous refractories, it causes agglomeration, resulting in a dense and homogeneous structure. There was a disadvantage that it was difficult. In this sense, it has been conventionally difficult to add a large amount of graphite to amorphous refractories.

[0003] On the other hand, in order to overcome the drawbacks of such carbon materials, particularly graphite, attempts have been made to surface-treat such graphite and the like. For example, there is a method of coating a surface of graphite with a surfactant (see JP-A-4-12064). In this method, the surfactant is re-eluted into water in the presence of a metal oxide or the like. for,
No significant advantage in the fluidity of the product could be found. There is also a method in which fine particles such as metal oxides and metal carbides are fixed to the graphite surface to make them hydrophilic (see JP-A-5-194044). However, in this method, it is necessary to make the metal compound adhered to the graphite surface into ultrafine particles, but there has been a problem that production of such metal fine particles is extremely difficult and expensive.

[0004]

As described above, the prior art, particularly the conventional surface-treated graphite using scaly graphite, has some degree of improvement in hydrophobicity, but its shape is originally scaly. However, there is a problem that it is difficult to form a densely packed structure as an amorphous refractory for casting, and it was necessary to solve this problem. Therefore, an object of the present invention is to propose scaly graphite that does not have the above-mentioned problems of the prior art, and in particular, has basic characteristics as graphite; characteristics that are excellent in spalling resistance, corrosion resistance, and abrasion resistance. An object of the present invention is to obtain a graphite-containing amorphous refractory which can be used effectively to obtain a more dense construction without hindering the refractory.

[0005]

SUMMARY OF THE INVENTION The present invention focuses on scaly graphite among various types of graphite which originally exhibit hydrophobicity, and mainly controls the shape of this scaly graphite, particularly by controlling the average particle size and average aspect ratio. At the same time as obtaining hydrophilic, preferably spheroidized, scale-like graphite, the proportion thereof in the refractory is 3 to 20% by weight, and the refractory raw material is 80 to 9%.
By blending it in an amount of 7 wt%, it is possible to obtain a graphite-containing amorphous refractory which is convenient for obtaining the above-mentioned properties, especially a dense construction body, and has excellent durability. The scale-like graphite has an average particle size of 10 to 100 μm and an average aspect ratio of 0.5 to 2.0, preferably 0.8.
The shape is controlled to a nearly spherical granular material in the range of ~ 1.2.

In the present invention, the above average aspect ratio is defined as follows. Normally, the aspect ratio of flake graphite refers to the ratio of the diameter to the thickness of the flakes. In this regard, in the present invention, as described below,
As external force is applied to the scales, the scales are shredded at the same time, and the strips are pressed together in the thickness direction, or the scales are bent and pressed to reduce the diameter, increase the thickness and granulate, There is a possibility that the diameter and the thickness cannot be distinguished. Therefore, in the present invention, the aspect ratio is defined as follows. That is, the ratio is the ratio of the average diameter in the horizontal direction to the average thickness in the vertical direction when a force is applied only to the gravitational direction to the graphite piece and then left. According to such a display, as for the normal scale-like graphite, the scale can be almost aligned in the thickness direction of the scale, so that the conventional aspect ratio, which is the ratio of the diameter and the thickness of the graphite piece, must be followed. become. In other words, it can be said that the directionality decreases as the particles become granular.

[0007] In actual measurement, graphite is put into a cylindrical container, and after tapping several times, resin is filled, and after solidification,
Cut in the horizontal and vertical directions, measure the average length of the graphite flakes in the vertical cut plane and the average diameter of the graphite flakes in the horizontal cut plane, and determine the ratio by the aspect ratio of the graphite flakes. Ratio. Then, the aspect ratio is measured for a sufficiently large number of graphite pieces, and the average value is defined as the average aspect ratio. This value can be easily determined by using image analysis.

[0008]

The present invention focuses on scaly graphite among graphite, and adjusts the particle size so that the average particle size becomes 10 to 100 μm, and the shape of the graphite is almost spherical. That is, it is an amorphous refractory containing scaly graphite in the form of granules having an average aspect ratio of about 0.5 to 2.0.

[0009] Scaly graphite has the largest degree of graphitization among graphite raw materials, and is excellent in thermal conductivity and oxidation resistance. Therefore, in general carbon-containing fixed refractories, this scaly graphite is widely used. However, this scaly graphite originally has a low affinity for water and its shape is scaly, so when it is used as an amorphous refractory, it forms a structure with many gaps, and a dense construction body is obtained. Therefore, it has been considered difficult to add a large amount. On the other hand, in the present invention, the hydrophilicity is solved by directly controlling the particle size and shape of the scaly graphite itself without using a coating of a hydrophilic material. That is, the present invention
The hydrophilicity was imparted by setting the average particle size of the scale graphite used to 10 to 100 μm and the average aspect ratio to 0.5 to 2.0.

The particle size adjustment and shape control of the scale-like graphite are performed, for example, by applying an external force to the scale-like graphite with a pulverizer such as a hybridization system, a supermicron mill, an ang mill or the like, as described later, to simultaneously shrink the scale into pieces. This is performed by compressing the strips in the thickness direction or by bending the scales and pressing to reduce the diameter and gradually increase the thickness to granulate.

The reason why the hydrophilicity is improved by adjusting the particle size of the scale-like graphite to a size of 10 to 100 μm is as follows.
Although it has not been completely elucidated, it is considered that the surface properties (porosity, etc.) of graphite change when the particle size is adjusted by a pulverizer.

Here, the reason why the lower limit of the average particle size of the shape-controlling flaky graphite is set to 10 μm is that if the average particle size is smaller than 10 μm, the specific surface area of the graphite particles increases and the oxidation resistance decreases. On the other hand, when the average particle size exceeds 100 μm, the fluidity decreases when mixed with refractory raw materials,
When poured, a dense construction body cannot be obtained because a structure having many gaps is easily formed.

In the present invention, in order to obtain a dense castable construction, the scale-like graphite has a shape close to granular. As a result, when such graphite is contained in the castable, a castable refractory excellent in particle dispersibility, dense and excellent in durability can be obtained.

Another reason for controlling the shape of the scale-like graphite to have a particle shape close to a sphere is that if the scale-like graphite is flat like a general scale-like graphite, the flowability of the castable refractory decreases and the scale becomes denser. This is because the effect of the present invention cannot be exhibited because a construction body cannot be obtained.

In the present invention, the degree of granularity of the spheroidized scale-like graphite is about 0.5 to 2.0 in average aspect ratio. This is because if the aspect ratio of the scale graphite is out of this range, a structure having many gaps is easily formed, and a dense construction body cannot be obtained.

FIG. 1 shows 10% by weight of graphite obtained by controlling the shape of scaly graphite to a desired average aspect ratio using a hybridization system (manufactured by Nara Machinery), and 86% by weight of alumina particles.
8 wt% of water was added to a mixture of the mixture and 4 wt% of alumina cement, and the mixture was kneaded, and the mixture was cast to a size of 20 mm in outer diameter × 10 mm in height to form a test specimen. FIG. 4 shows the relationship between the aspect ratio of graphite and the porosity of a refractory after firing at 1400 ° C. FIG. As shown in this figure, when the average aspect ratio is 0.5 to 2.0, the porosity is
It becomes 24% or less, and it is observed that graphite is sufficiently dispersed in water, that is, a state in which hydrophilicity is imparted. Above all,
20% porosity when average aspect ratio is 0.8-1.2
The results are as follows, and it can be seen that they are preferable.

In the present invention, it is inevitable to reduce the amount of added water and to increase the density by using various surface treatments, such as a method of coating an inorganic or organic hydrophilic substance, on the scaly graphite.

In the present invention, for controlling the particle size and the shape of the flake graphite, for example, a supermicron mill (manufactured by Hosokawa Micron), an ACM pulverizer
(Hosokawa Micron), Ongmill (Hosokawa Micron), hybridization system (Nara Machinery), HIEX (Nisshin Flour Milling), Henschel mixer (Mitsui Miike Machinery), vibrating ball mill, and the like. In addition, scale-like graphite produced in a state falling within the scope of the present invention can be used as it is.

Next, the amorphous refractory according to the present invention containing the above-mentioned scaly graphite will be described. First, as the refractory raw material constituting the skeleton component of the refractory, one or more selected from basic, neutral, and acidic materials are used. For example, magnesia, spinel, alumina, zirconia,
Examples include zircon, silica, silica, silica, limestone, silicon carbide, and chamotte. The particle size of these refractory raw materials is coarse, medium, fine,
It is preferable to use those which are separately adjusted for fine powder.

The amount of the granulated scale graphite mixed with the refractory raw material in the amorphous refractory is 3
-20% by weight. If the blending amount is less than 3 wt%, it is difficult to obtain the high thermal conductivity and slag permeation preventing effect of graphite, while if it exceeds 20 wt%, not only the amount of mixing water increases but also the refractory becomes porous and dense. This is because a construction body cannot be obtained and the thermal shock resistance deteriorates.

In the present invention, in addition to the above-mentioned refractory raw materials and scaly graphite, which are skeletal components,
Dispersants (surfactants), curing agents, curing retarders and the like can be used. For example, as a dispersant, inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, sodium polypolyphosphate, sodium acid hexametaphosphate, sodium borate, sodium carbonate, sodium citrate, tartrate, sodium polyacrylate, sulfonic acid One or more selected from organic salts such as soda can be used. Further, as a hardening agent, general alumina cement used for refractories can be used, and as a hardening retarder, oxalic acid, citric acid, polyacrylic acid, or the like can be used.

The amorphous refractories according to the present invention include, in addition to the above-mentioned compounds, known sintering aids, fibers, metal powders and the like, as long as the essential characteristics of the present invention are not impaired. May be added, or a binder or the like may be added.

[0023]

【Example】

Example 1 This example is an example in which the present invention example and a comparative example are applied to a cast amorphous refractory for a blast furnace tapping gutter, and the results are shown in Table 1. Each of the scale-like graphites A, B, C, and D in Table 1 conforms to the present invention, and E and F are examples that do not conform to the present invention. That is, A, C and E are those obtained by treating scale-like graphite having an average particle size of 300 μm using a hybridization system (manufactured by Nara Kikai).
D and F were obtained by treating scale-like graphite having an average particle size of 300 μm using a supermicron mill (manufactured by Hosokawa Micron).

As shown in Table 1, Comparative Example 1 is a conventional cast refractory for blast furnace tapping gutters containing no scale graphite at all, and Comparative Examples 2 and 3 use scale graphite which is not compatible with the present invention. However, Comparative Examples 4 and 5 are examples in which the amount of scaly graphite added is out of the range of the present invention. As is clear from Table 1, the porosity of each of the examples of the present invention is slightly increased and the strength is slightly decreased as compared with the conventional product of Comparative Example 1, but the values are practically sufficient. Corrosion resistance is improved by the effect of the addition of spheroidal scale graphite. On the other hand, Comparative Example 2
In Nos. To 4, the conditions of the present invention are not satisfied, the porosity is significantly increased, and the corrosion resistance and strength are poor. Further, in Comparative Example 5, although the porosity and the strength were little deteriorated, the corrosion resistance was not improved, and the effect of adding scaly graphite was not obtained.

[0025]

[Table 1]

The amorphous refractory according to the present invention is not limited to the above embodiments, and various applications and modifications can be made within the scope of the present invention.
It can be applied not only to blast furnace cast refractories but also to cast refractories for hot metal pots, mixed iron wheels, and hot metal slag lines.

[0027]

As described above, according to the present invention, by using scale-like graphite whose particle size and shape are controlled, it is effective to obtain a dense construction body, and further, the general characteristics of blending graphite, That is, it is possible to obtain an amorphous refractory which is excellent not only in durability but also in properties such as thermal shock resistance, corrosion resistance, abrasion resistance and oxidation resistance.

[Brief description of the drawings]

FIG. 1 shows an average aspect ratio of scaly graphite and 1400 ° C.
FIG. 3 is a diagram showing a relationship with a porosity after firing.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Haraoka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (72) Masato Takagi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Inside the Technical Research Institute Co., Ltd. (72) Katsufumi Kino, Inventor 1576, Nakahiro, Higashi-oki, Ako City, Hyogo Prefecture 2 Kawasaki Reactor Co., Ltd. (72) Inventor Junichiro Mori, 1,576 Higashi-oki, Ako City, Hyogo Prefecture 2 Inside Kawasaki Furnace Materials Co., Ltd. (72) Inventor Yasunobu Toritani 1576, east offshore of Nakahirohiro, Ako City, Hyogo Prefecture 2 Inside Kawasaki Furnace Materials Co., Ltd. (72) Inventor Seijiro Tanaka, east offshore Nakahirohiro, Ako City, Hyogo Prefecture Reference No. 1576 2 Kawasaki Reactor Co., Ltd. (56) References JP-A-1-111780 (JP, A) JP-A-2-204317 (JP, A) JP-A-8-301609 (JP, A) (58 ) Key The field (Int.Cl. ^7, DB name) C04B 35/66 C01B 31/04 B22D 41/02

Claims (1)

(57) [Claims] 1. A spheroidal graphite having an average particle diameter in the range of 10 to 100 μm and an average aspect ratio in the range of 0.5 to 2.0 is contained in an amount of 3 to 20 wt %, and a refractory raw material is contained in an amount of 80 to 97 wt %. An amorphous refractory containing graphite.