JP7709124B2 - Graphite-containing refractories - Google Patents

Description

The present invention relates to a graphite-containing refractory material in which carbon fiber bundles are arranged inside the refractory body.

The equipment used in the iron-making and steel-making processes in steelworks (refining vessels, transport vessels, etc.) is lined with refractories to withstand long-term use at high temperatures. In general, magnesia-carbonaceous refractories are used for the lining of converters used in the refining process, while alumina-silicon carbide-carbonaceous refractories are used for the lining of torpedoes and blast furnace ladles used in the molten iron pretreatment process.
The refractories used for lining these refining vessels and transport vessels are used under extremely harsh conditions, including mechanical shock from the charges, abrasion from stirring of molten steel and molten slag, slag erosion from molten slag, and sudden temperature changes during operation. For this reason, in order to ensure stable operation, it is necessary to use refractories with high durability that can withstand such harsh conditions.

In particular, the tuyere bricks that make up the tuyere of the converter have room temperature gas (oxygen, cooling hydrocarbon gas, etc.) flowing inside, and the inner surface near the inside of the furnace is cooled by the room temperature gas, while the outer surface is exposed to high temperatures due to heat transfer from the molten steel in the furnace, so the thermal gradient inside the tuyere bricks is extremely large, and each time one charge of blowing is completed, the temperature drops due to the discharge of the molten steel, and large thermal fluctuations are repeated. The tuyere bricks installed in converters are used as frequently as 2,500 to 4,000 charges, and are used under extremely harsh conditions where a situation in which a large thermal gradient as described above occurs and large thermal fluctuations are repeated for each charge, so they need to have high durability to withstand such conditions. In addition, converter refractory linings other than tuyere bricks (bricks that make up the inner wall of the converter) are also used under harsh conditions where large thermal fluctuations as described above are repeated, so they need to have high durability, although not as high as tuyere bricks.

As a technology for improving the durability of refractories, Patent Document 1 describes how carbon fibers 100 mm or longer in length are bundled with adhesive and placed inside the refractory in a sticky bundle state, significantly increasing the fracture energy.

Republished Publication No. 2018-155118

However, as a result of the inventors' investigations, it was found that with the technology of charging (arranging) carbon fiber bundles inside a refractory material as in Patent Document 1, depending on the properties of the adhesive used, the full effect of charging (arranging) carbon fiber bundles inside the refractory material cannot be obtained. Patent Document 1 does not disclose the conditions for the adhesive to maximize the effect of charging such carbon fiber bundles.

The object of the present invention is therefore to solve the problems of the prior art as described above, and to provide a graphite-containing refractory that can suppress the growth of cracks caused by thermal stress and provide high durability even when used under conditions where temperature increases and decreases are repeated over long periods of time, such as the refractory lining of a converter, and that can provide high durability even when used under conditions where the internal temperature gradient is particularly large, such as the tuyere bricks of a converter.

As a result of extensive research into solving the above problems, the inventors have found that in a graphite-containing refractory in which carbon fiber bundles are arranged inside the refractory, by using an organic substance and/or inorganic fine particles having a predetermined residual carbon ratio as an adhesive component that binds and integrates the carbon fibers and adheres or adheres the carbon fiber bundles to the refractory raw material, and by optimizing the fiber diameter and number of the carbon fibers that make up the carbon fiber bundles, as well as the density and occupied area ratio of the carbon fibers in the cross section of the refractory, it is possible to obtain high durability even in the extremely severe usage environment described above.

The present invention has been made based on these findings, and has the following gist.
[1] A graphite-containing refractory having a carbon fiber bundle (B) disposed inside a refractory body (A),
The carbon fiber bundles (B) contain an adhesive component (c) therein and are bonded or adhered to the refractory body (A) via the adhesive component (c);
The graphite-containing refractory material is characterized in that the adhesive component (c) is composed of an organic substance and/or inorganic fine particles having a residual carbon ratio of 6 to 80 mass %.

[2] The graphite-containing refractory according to [1] above, wherein the adhesive component (c) is at least one selected from the group consisting of organic resins, organic substances derived from tar and/or pitch, organic substances derived from organic glue, and inorganic fine particles derived from inorganic sol.
[3] The graphite-containing refractory according to the above [1] or [2], characterized in that the carbon fiber bundles (B) have a width of 1 to 15 mm.
[4] The graphite-containing refractory according to any one of the above [1] to [3], wherein the carbon fiber bundle (B) is a bundle of carbon fibers having a length of 100 mm or more and a fiber diameter of 1 to 45 μm, and the number of carbon fibers per bundle is 1,000 to 300,000.

[5] The graphite-containing refractory according to any one of the above [1] to [4], characterized in that a plurality of carbon fiber bundles (B) are arranged in parallel inside the refractory body (A), and the interval between adjacent carbon fiber bundles (B) exceeds 3 mm.
[6] The graphite-containing refractory according to any one of the above [1] to [5], characterized in that the density of the carbon fibers constituting the carbon fiber bundles (B) in a cross section of the graphite-containing refractory parallel to a working surface of the graphite-containing refractory is 10 to 2000 fibers/ ^mm2 .
[7] The graphite-containing refractory according to any one of the above [1] to [6], characterized in that the area ratio of the carbon fibers constituting the carbon fiber bundles (B) in a cross section of the graphite-containing refractory parallel to a working surface of the graphite-containing refractory is 0.1 to 40%.

[8] The graphite-containing refractory according to any one of the above [1] to [7], wherein the refractory body (A) contains 1 to 80 mass% of a graphite raw material.
[9] The graphite-containing refractory according to any one of the above [1] to [8], wherein the refractory body (A) contains 20 to 99 mass% of a magnesia raw material.
[10] The graphite-containing refractory according to any one of the above [1] to [8], wherein the refractory body (A) contains 10 to 95 mass% of an alumina raw material.

[11] The graphite-containing refractory according to any one of the above [1] to [8] and [10], characterized in that the refractory body (A) contains 1 to 50 mass% of a silica raw material.
[12] The graphite-containing refractory according to the above [10] or [11], wherein the refractory body (A) contains 1 mass% or more of a silicon carbide raw material.
[13] The graphite-containing refractory according to any one of the above [1] to [12], characterized in that the refractory body (A) contains 10 to 90 mass% of refractory chips obtained by pulverizing used refractories.

The graphite-containing refractory of the present invention has high fracture energy, so even when used under conditions where the temperature is repeatedly raised and lowered over a long period of time, such as the refractory lining of a converter, the growth of cracks caused by thermal stress is suppressed, resulting in high durability. In particular, high durability is obtained even when used under conditions where the internal temperature gradient is very large, such as the tuyere bricks of a converter.

FIG. 1 is a schematic diagram showing one of the brick components constituting the tuyere brick in one embodiment in which the graphite-containing refractory of the present invention is applied to a tuyere brick, in which FIG. 1(A) is a perspective view, and FIG. 1(B) is a cross-sectional view taken along the dashed line in FIG. 1(A) (a cross-sectional view parallel to the refractory operating surface). FIG. 1 is a flow chart showing an example of a process for producing the graphite-containing refractory material of the present invention. FIG. 3 shows a test method for evaluating the corrosion resistance of a graphite-containing refractory material in the examples. FIG. 3(A) is an explanatory diagram showing the test furnace and a cylindrical sample in vertical section as the test is carried out. FIG. 3(B) is a plan view of the cylindrical sample shown in FIG. 3(A). FIG. 3(C) is a perspective view showing one of the test pieces constituting the cylindrical sample shown in FIGS. 3(A) and (B). FIG. 4 shows a method for measuring the bending strength of a graphite-containing refractory in an embodiment. FIG. 4(A) is an explanatory diagram showing a typical implementation state of a three-point bending strength test, and FIG. 4(B) is an explanatory diagram showing a typical end face of the test piece in FIG. 4(A). FIG. 1 is a diagram showing an example of fracture energy calculated from a load-displacement curve obtained in a three-point bending strength test in an embodiment.

The graphite-containing refractory of the present invention is a graphite-containing refractory having a carbon fiber bundle B disposed inside a refractory body A, the carbon fiber bundle B containing an adhesive component c therein and adhering or bonding to the refractory body A via the adhesive component c, the adhesive component c being composed of an organic material and/or inorganic fine particles having a residual carbon ratio of 6 to 80 mass%. This graphite-containing refractory is usually an unfired refractory manufactured without high-temperature firing (reducing firing). Here, the residual carbon ratio of the adhesive component c is measured based on the fixed carbon measurement method described in JIS K6910 (phenolic resin test method).
In the graphite-containing refractory of the present invention, the carbon fiber bundles B arranged inside the refractory body A are integrated into a bundle due to the inclusion of adhesive component c within the bundle, and the carbon fiber bundles B are integrated with the refractory by being adhered or bonded to the refractory body A via the adhesive component c. In addition, the adhesive component c is made of an organic substance and/or inorganic fine particles having a specific residual carbon ratio, so that a high fracture energy that can suppress the occurrence of cracks can be obtained.

The configuration and embedding conditions of the carbon fiber bundle B will be described below.
Fig. 1 is a schematic diagram showing one embodiment of the graphite-containing refractory of the present invention (a brick component constituting a tuyere brick), in which Fig. 1(a) is a perspective view and Fig. 1(b) is a cross-sectional view (a cross-sectional view parallel to the refractory working surface) taken along the dashed line in Fig. 1(a), where x is the working surface of the refractory (y is the counter-working surface). In the graphite-containing refractory of this embodiment, a plurality of carbon fiber bundles B are arranged (embedded) in parallel at predetermined intervals inside a refractory body A.
The carbon fiber bundles B are placed on the refractory raw material with an adhesive attached to their outer surfaces and with the adhesive also permeating into the bundles, and a graphite-containing refractory is obtained. Therefore, the carbon fiber bundles B contain the adhesive component c within the bundles (i.e., the adhesive component c is present in the gaps between the carbon fibers that make up the carbon fiber bundles B, thereby integrating the carbon fibers into a bundle), and the adhesive component c is interposed between the carbon fiber bundles B and the refractory main body A, and the carbon fiber bundles B are adhered or adhered to the refractory main body A via the adhesive component c.

The adhesive component c is composed of an organic material such as an organic resin having a predetermined carbon residue rate and/or inorganic fine particles such as alumina and silica.
When the refractory is used (when the actual machine is in operation), the temperature reaches a high level of 500°C or more (measured at 900°C in JIS K6910) even inside. At this time, even in an environment with almost no oxygen inside, such as a graphite-containing refractory, if the adhesive component is an organic substance, a part of the adhesive attached to the carbon fiber bundle will gasify by decomposition or evaporation and dissipate outside the refractory. The carbon residue rate is thought to be an index of the weight ratio of the adhesive that remains without gasification and dissipation, and varies depending on the type and quality of the adhesive. The inventors of the present invention were inspired by the idea that the carbon residue rate of the adhesive affects the fracture energy when a graphite-containing refractory using a carbon fiber bundle is exposed to high temperatures, which is an actual use environment, and conducted an investigation. As a result, they found that a high fracture energy can be obtained by using an adhesive (organic substance) with a carbon residue rate of 6 to 80 mass%. This is believed to be because the use of an adhesive (organic substance) with such a specific residual carbon ratio increases the adhesion between the refractory raw material (refractory body A) and the carbon fiber bundles B, making it easier to densify the refractory brick during molding. In addition, the amount of gas that escapes from the inside of the refractory when exposed to high temperatures can be suppressed, thereby suppressing the occurrence of cracks and increasing the fracture energy.
The present inventors have also found that high fracture energy can be obtained when the adhesive component is inorganic fine particles such as alumina, silica, etc. This is believed to be because, even when inorganic fine particles (particularly inorganic fine particles derived from an inorganic sol) are used, the adhesion between the refractory raw material (refractory body A) and the carbon fiber bundles B is increased, making it easier to densify the refractory brick during molding, and in addition, when exposed to high temperatures during use, the inorganic fine particles are sintered, suppressing the occurrence of cracks and increasing the fracture energy.

When the adhesive component c is an organic substance, if the residual carbon ratio is less than 6% by mass, the amount of gas escaping from the inside of the refractory at high temperatures increases, and many defects such as pores are generated, so that the fracture energy does not increase. On the other hand, if the residual carbon ratio exceeds 80% by mass, almost no gas escapes from the inside of the refractory at high temperatures, and the refractory becomes too dense and brittle, so that the fracture energy does not increase. From the above viewpoints, the residual carbon ratio of the organic substance is preferably 20 to 80% by mass, and more preferably 40 to 80% by mass.
The adhesive component c is present (permeates) in the carbon fiber bundles (gaps between the carbon fibers) to integrate the carbon fiber bundles B as a bundle, and also covers the outer surface of the carbon fiber bundles B to adhere or bond the carbon fiber bundles B to the refractory body A, so it is desirable that the adhesive used be in a liquid state. In addition, the adhesive component c needs to remain without decomposition or evaporation even at high temperatures, but since combustion by oxygen hardly occurs when used for graphite-containing refractories, it is possible to use a resin that is highly combustible in the presence of oxygen. From these conditions, the adhesive component c is suitable to be one or more selected from organic resins (organic resins derived from organic resin solutions), organic substances derived from tar and/or pitch, organic substances derived from organic pastes, and inorganic fine particles derived from inorganic sols (i.e., any of these or a mixture of these).

Therefore, examples of adhesives (tackifiers) that are attached to carbon fiber bundles during production include organic resins (solutions), pitch, tar, organic pastes, inorganic sols, etc. Specific examples include phenolic resins, epoxy resins, melamine resins, urea resins, alkyd resins, unsaturated polyester resins, polyurethane resins, thermosetting polyimide resins (resin solutions consisting of one or more of these organic resins), pitch, tar, starch paste, alumina sol, silica sol, zirconia sol, chromia sol, titania sol, magnesia sol, calcia sol, yttria sol, etc., and one or more selected from these can be used.
In addition, these adhesives can be thinned with a solvent to adjust the viscosity during production, but it is desirable to limit the use of solvents (e.g., water) that gasify even in the absence of oxygen at high temperatures of 500°C or higher to an amount equal to or less than the weight of the adhesive components.
In addition, by using two or more types of adhesives, a higher bending strength and breaking energy can be obtained than when using one type of adhesive. The reason for this is that the adhesion between the refractory raw material and the carbon fiber is further increased. Therefore, in order to obtain a higher bending strength and breaking energy, it is preferable that the adhesive component c is composed of two or more types of adhesives (composed of adhesive components derived from two or more types of adhesives).

The arrangement of the carbon fiber bundles B inside the refractory body A is arbitrary and is not particularly limited, but since the tensile stress that causes cracks during operation occurs in the longitudinal direction of the refractory, it is preferable to arrange (embed) the carbon fiber bundles B linearly along one direction, and particularly preferable to arrange (embed) the carbon fiber bundles B along a direction perpendicular to the operating surface x of the refractory. In addition, when a plurality of carbon fiber bundles B are arranged, it is preferable to arrange (embed) them in parallel at a predetermined interval.
The carbon fiber bundles B embedded inside the refractory body A may or may not have their ends exposed on the surface of the refractory body A. In the latter case, on the working surface x side of the refractory, it is preferable that the distance between the end of the carbon fiber fabric B and the working surface x is as small as possible, but on the counter working surface y side, the distance between the end of the carbon fiber bundles B and the counter working surface y may be relatively large. This is because the carbon fiber bundles B do not need to be embedded in the part on the counter working surface y side of the refractory that is expected to remain even after use is finished.

The carbon fiber bundles B preferably have a width w (width per bundle) of 1 to 15 mm. Here, the width of the carbon fiber bundles B refers to the length of the long side or major axis in the cross section of the carbon fiber bundle in the width direction (however, if the cross section in the width direction is a square or circle, the length of one side or diameter). By making the width w of the carbon fiber bundles B 1 mm or more, the number of carbon fiber bundles B can be reduced when the same number of carbon fibers are used, and it becomes easier to arrange the carbon fiber bundles B evenly inside the refractory body A. On the other hand, by making the width w of the carbon fiber bundles B 15 mm or less, it is possible to reduce interference between the carbon fiber bundles B and the coarse grain material (generally with a grain size of 5 to 20 mm) among the raw materials used for the refractory body A, and to reduce the melting damage of the carbon fiber bundles B themselves as a trigger for melting damage of the refractory.

The carbon fiber bundle B is a bundle of carbon fibers having a length L of 100 mm or more and a fiber diameter of 1 to 45 μm, and preferably contains 1,000 to 300,000 carbon fibers per bundle.
When the length L of the carbon fiber (the length of the carbon fiber bundle B) is less than 100 mm, the binding force between the refractory body A is small, so that the effect of the carbon fiber bundle B in suppressing the crack growth is small. In addition, when the fiber diameter of the carbon fiber is less than 1 μm or the number of carbon fibers per bundle is less than 1000, the carbon fiber bundle B is too thin, so that the effect of suppressing the local crack growth is reduced, and the increase in fracture energy is small. On the other hand, when the fiber diameter of the carbon fiber is more than 45 μm or the number of carbon fibers per bundle is more than 300,000, the carbon fiber bundle B is too thick, so that the compatibility between the refractory raw material (refractory body A) and the carbon fiber bundle B is poor, and defects due to the elasticity of the carbon fiber bundle, called springback, are likely to occur during molding.

A plurality of carbon fiber bundles B are arranged in parallel inside the refractory body A, and the interval d between adjacent carbon fiber bundles B (the distance between carbon fiber bundles B) is preferably more than 3 mm. By arranging the adjacent carbon fiber bundles B so that the interval d between them is more than 3 mm, the entanglement of the refractory raw material (refractory body A) with the carbon fiber bundles B can be improved, and peeling caused by the carbon fiber bundles during molding, called lamination, can be made less likely to occur. Note that there is no particular upper limit to this interval d, but in view of the relationship with the density of carbon fibers described below, the upper limit is generally about 100 mm.
In the cross section of the refractory parallel to the working surface x of the graphite-containing refractory, the density of the carbon fibers constituting the carbon fiber bundle B is preferably 10 to 2000 fibers/mm ² , which ensures a contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B, increasing adhesion, and increasing the fracture energy, while suppressing the occurrence of defects due to elastic deformation of the carbon fiber bundle B. When the density of the carbon fibers is less than 10 fibers/mm ² , the contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B is too narrow, so the adhesion between the refractory raw material and the carbon fiber bundle B is not increased, and the increase in fracture energy is small. On the other hand, when the density of the carbon fibers is more than 20,000 fibers/mm ² , the contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B is too wide, so defects due to the elasticity of the carbon fiber bundle, called springback, are likely to occur during molding.

In the cross section of the graphite-containing refractory parallel to the working surface x, the area ratio of the carbon fibers constituting the carbon fiber bundle B is preferably 0.1 to 40%, which ensures a sufficient contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B, improving adhesion and increasing the fracture energy, while suppressing the occurrence of defects due to the elasticity of the carbon fiber bundle B. If the area ratio of the carbon fibers is less than 0.1%, the contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B is too narrow, so the adhesion between the refractory raw material and the carbon fiber bundle B is not increased, and the increase in fracture energy is small. On the other hand, if the area ratio of the carbon fibers is more than 40%, the contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B is too wide, so defects due to the elasticity of the carbon fiber bundle B, known as springback, are likely to occur during molding.

Next, the composition of the refractory body A will be described.
The refractory body A preferably contains 1 to 80 mass % of graphite raw material. By making the content of the graphite raw material 1 mass % or more, the crack resistance of the graphite-containing refractory can be ensured and the oxidative loss of carbon fibers inside the refractory can be suppressed. On the other hand, by making the content of the graphite raw material 80 mass % or less, the oxidative loss of the graphite raw material on the surface of the refractory can be suppressed. As the graphite (carbon raw material), scaly graphite or the like is generally used.

In general, the lining (including the tuyere) of the converter used in the refining process is made of magnesia-carbon refractory (graphite-containing refractory with magnesia raw material as aggregate), which is a refractory mainly composed of magnesia and carbon. When the refractory body A is a magnesia-carbon refractory, it is preferable that the refractory body A contains 20 to 99 mass% of magnesia raw material, which suppresses cracking due to thermal spalling and provides a refractory with corrosion resistance that can withstand the erosion of converter slag containing a large amount of FeO. It is preferable to use a high-purity magnesia raw material with a magnesia concentration of 90 mass% or more as the magnesia raw material.

In addition, generally, alumina-silicon carbide-carbon refractories (graphite-containing refractories with aggregates of alumina raw materials and silicon carbide raw materials) which are refractories mainly composed of alumina, silicon carbide, and carbon, and alumina-silicon carbide-silica-carbon refractories (graphite-containing refractories with aggregates of alumina raw materials, silicon carbide raw materials, and silica raw materials) which are refractories mainly composed of alumina, silicon carbide, silica, and carbon are used for the lining of torpedoes and blast furnace ladles used in the hot metal pretreatment process. When the refractory body A is an alumina-silicon carbide-carbon refractory or an alumina-silicon carbide-silica-carbon refractory, it is preferable that the alumina raw material is contained in an amount of 10 to 95 mass%, which provides high corrosion resistance against hot metal pretreatment slag and further suppresses the occurrence of cracks due to thermal spalling. It is preferable to use a high-purity alumina raw material with an alumina concentration of 70 mass% or more as the alumina raw material.

Furthermore, when the refractory body A is an alumina-silicon carbide-carbonaceous refractory or an alumina-silicon carbide-silica-carbonaceous refractory, it is preferable that the refractory body A contains 1 mass% or more of silicon carbide raw material. By containing 1 mass% or more of silicon carbide raw material, oxidation of graphite in the air atmosphere can be suppressed, so that high crack resistance can be maintained. In addition, it is preferable to use a high-purity silicon carbide raw material with a silicon carbide concentration of 80 mass% or more as the silicon carbide raw material.
When the refractory body A is an alumina, silicon carbide, silica or carbonaceous refractory, it preferably contains 1 to 50 mass % of silica raw material, which makes it possible to achieve both high crack resistance and high resistance to melting damage.

The magnesia-carbon refractories used for lining converters are used under very severe conditions, such as mechanical impacts from the charges, abrasion from stirring of molten steel and molten slag, slag erosion from molten slag, and sudden temperature changes during converter operation. For this reason, it is preferable to use magnesia-carbon refractories that are highly durable and can withstand the severe conditions in order to ensure stable operation. Similarly, alumina-silicon carbide-carbon refractories and alumina-silicon carbide-silica-carbon refractories used for lining molten pig iron pretreatment vessels such as torpedoes and blast furnace ladles are also used under very severe conditions, so it is preferable to use refractories that can withstand these conditions. According to the present invention, the fracture energy of graphite-containing refractories used under these very severe conditions is significantly improved compared to conventional graphite-containing refractories, and high durability is obtained.

In addition, when the refractory body A is a silica-silicon carbide-carbonaceous refractory, which is a refractory whose main components are silica, silicon carbide, and carbon, it is preferable that the refractory contains 1% by mass or more of silicon carbide raw material and 1 to 50% by mass of silica raw material, which allows both high cracking resistance and high resistance to melting damage to be achieved. By containing 1% by mass or more of silicon carbide raw material, oxidation of graphite in the air atmosphere can be suppressed, so high cracking resistance can be maintained. Note that it is preferable to use a high-purity silicon carbide raw material with a silicon carbide concentration of 80% by mass or more as the silicon carbide raw material.

Here, as the alumina raw material, for example, one or more of alumina shale, white alumina, brown alumina, etc. are used. As the silicon carbide raw material, for example, one or more of green silicon carbide, black silicon carbide, etc. are used. As the silica raw material, for example, one or more of rosewood, mullite, etc. are used.
The graphite-containing refractory may further contain (mix) a metal powder raw material for the purpose of suppressing the amount of heat radiation from the steelmaking vessel while increasing durability. Examples of the metal powder raw material include metal Si, metal Al, metal Al-Si, Al ₄ SiC ₄ , and B ₄ C, and one or more of these may be contained. The content of the metal powder raw material is not particularly specified, but is usually preferably about 1 to 5 mass %. If the content (mixture amount) of the metal powder raw material is less than 1 mass %, the effect of improving durability by mixing the metal powder raw material is not sufficiently obtained, while if it exceeds 5 mass %, the strength becomes too high, so that cracks are likely to occur when used in an actual machine, making the bricks more likely to break, and the number of times of use in the actual machine may be reduced.

The refractory body A can contain about 10 to 90 mass % of refractory chips obtained by crushing used refractories as an aggregate raw material. In particular, when the refractory body A is an alumina/silicon carbide/carbonaceous refractory (including alumina/silicon carbide/silica/carbonaceous refractories further containing a silica raw material; the same applies below), the refractory chips obtained by crushing used alumina/silicon carbide/carbonaceous refractories (including alumina/silicon carbide/silica/carbonaceous refractories further containing a silica raw material; the same applies below) can be suitably used as the aggregate raw material.
When the refractory waste is contained in this manner, the remainder of the refractory raw material is unused raw material (virgin raw material).

In the refractory body A made of alumina, silicon carbide, and carbonaceous refractories, when the content of refractory scrap obtained by crushing used alumina, silicon carbide, and carbonaceous refractories is 10 to 90 mass%, the cracking resistance and corrosion resistance are the same as those of a graphite-containing refractory using only virgin raw materials. The reason for this is that although the purity of the refractory scrap raw material is lower than that of the virgin raw material, by using the refractory scrap raw material and the virgin raw material in combination, a significant decrease in corrosion resistance of the Al ₂ O ₃ component in the refractory scrap raw material can be suppressed. However, when the content of the refractory scrap is more than 90 mass%, the content of the virgin raw material is too small, so that a significant decrease in corrosion resistance of the Al ₂ O ₃ component in the refractory scrap raw material cannot be suppressed. In addition, when the content of the refractory scrap is less than 10 mass%, the reuse rate of the refractory scrap is too low, so the cost of processing the refractory scrap as industrial waste increases significantly.

Next, the method for producing the graphite-containing refractory material of the present invention will be described.
2 shows an example of a manufacturing process for the graphite-containing refractory of the present invention. In this manufacturing process, an appropriate amount of binder is added to the refractory raw material and kneaded, and the kneaded mixture is filled into a mold together with carbon fiber bundles in which a specific adhesive has been permeated (impregnated) into the inside of the bundle and attached to the outer surface, and press-molded to obtain a molded refractory product. As the binder, for example, phenol resin (base agent) + hexamine (hardener), carbon bond, ceramic bond, etc. are used.
As a method for filling a mold with the kneaded refractory raw material mixture together with carbon fiber bundles (carbon fiber bundles having an adhesive permeated (impregnated) into the interior of the bundles and also attached to the outer surface; the same applies below), there is, for example, a method in which a certain amount of the kneaded material is charged into the mold, a plurality of carbon fiber bundles are arranged (charged) in parallel, and a certain amount of the kneaded material is further charged into the mold. Therefore, to produce a graphite-containing refractory in which a plurality of carbon fiber bundles B are embedded inside a refractory body A as shown in Figure 1 by this method, a step of charging a certain amount of the kneaded material into the mold, and then arranging a plurality of carbon fiber bundles arranged in parallel on top of it, and a step of charging a certain amount of the kneaded material on top of it are repeatedly carried out.

To make the carbon fiber bundles penetrate (impregnate) and adhere with the adhesive (tackifier), for example, the carbon fiber bundles are immersed in the resin (resin solution) or inorganic sol that constitutes the adhesive, or the resin (resin solution) or inorganic sol that constitutes the adhesive is sprayed onto the carbon fiber bundles to make the adhesive penetrate and adhere to the carbon fiber bundles, and the carbon fiber bundles with the adhesive penetrated and adhered to them are loaded into a mold together with the kneaded material in the manner described above. Here, the adhesive that penetrates and adheres to the carbon fiber bundles may be in a state where it has a certain degree of hardening or solidification when the carbon fiber bundles are placed into the kneaded material, as long as it has enough adhesiveness to bond or adhere to the carbon fiber bundles and the refractory material (kneaded material) (so-called semi-dried state). As another method, the bundles may be impregnated with the adhesive in advance, and then the hardened or solidified carbon fiber bundles may be prepared, and the adhesive may be adhered to the outer surface of the carbon fiber bundles again when they are placed into the kneaded material.

Press molding can be performed using general die press molding, which compresses in one direction within a die, but CIP molding, which applies pressure evenly from all directions using a liquid, may also be used. For shapes where it is difficult to apply even pressure by unidirectional compression, such as shapes with different thicknesses depending on the part, it is preferable to use CIP molding, as this reduces bias in the degree of compression depending on the part.
The molding process may be performed by a molding method other than press molding. Examples of molding methods other than press molding include molding by pouring, one of which is a method of installing an inner frame at a construction site, which is a working surface of a pot or tundish, pouring an amorphous refractory (a refractory raw material) into the inner frame, drying (drying process) and solidifying, and then removing the inner frame. There is also a method of pouring an amorphous refractory (a refractory raw material) into a formwork of a refractory shape, rather than pouring it into the construction site, and transporting the refractory removed from the formwork after drying (drying process) and solidifying to the construction site, and although this method requires a lot of work to install the refractory at the construction site, it is desirable because it is easy to embed the carbon fiber bundle when pouring the amorphous refractory into the formwork and to control the temperature during solidification. In these casting molding methods, carbon fiber bundles are placed in the inner frame or mold described above, and then amorphous refractory (refractory raw material) is poured into the inner frame or mold, and then dried (drying process) and solidified.

The refractory molded article thus obtained is dried. This drying is usually carried out at about 200 to 230° C. for the purpose of drying (curing) the refractory molded article.
In addition, the refractory molded body obtained by the above-mentioned casting molding is dried and solidified by heating the refractory molded body held in an inner frame installed at the construction site or in a form installed in another location with a heating means such as a heating burner, after which the inner frame is removed and the mold is taken out.

As a result of the above, the graphite-containing refractory of the present invention is obtained, which is a graphite-containing refractory in which carbon fiber bundles B are arranged (embedded) inside a refractory body A, and the carbon fiber bundles B contain adhesive component c (adhesive component consisting of an organic substance and/or inorganic fine particles having a residual carbon ratio of 6 to 80 mass%) within the bundles, and are adhered or tightly attached to the refractory body A via the adhesive component c.
The graphite-containing refractory of the present invention can be used as a refractory for various facilities and containers, and is particularly suitable as a refractory lining for refining vessels and transport vessels used in steelworks, particularly as a refractory lining for converters, which are used in very severe environments, and is particularly suitable as a tuyere brick for forming the tuyere.

In order to study the blending of magnesia-carbonaceous refractories (graphite-containing refractories with magnesia raw materials as aggregate) used in converters, refractory molded products were produced using magnesia raw materials as aggregate with the raw material blend shown in Table 1, i.e., graphite-containing refractories without embedded carbon fiber bundles. When kneading and molding the refractory raw materials, 3 mass% of phenolic resin and 0.3 mass% of hexamine were blended as binders on an outer basis relative to the refractory raw materials. The melting resistance and cracking resistance of the graphite-containing refractories produced were evaluated using the following methods. The results are also shown in Table 1.

The corrosion resistance was evaluated based on the amount of corrosion measured by the lining method using a high-frequency induction furnace as shown in Fig. 3 (Test Method). In the test using the lining method, the test temperature was 1650°C, the temperature was held for 4 hours, and synthetic slag having the composition shown in Table 2 was added every hour. After cooling, the amount of corrosion on the working surface was measured. From the amount of corrosion, a corrosion index was calculated with the amount of corrosion of Blend Example 1-4 in Table 1 taken as 100. Fig. 3(A) is an explanatory diagram showing the test implementation state in a vertical cross section of the test furnace and the cylindrical sample, Fig. 3(B) is a plan view of the cylindrical sample shown in Fig. 3(A), and Fig. 3(C) is a perspective view showing one of the test pieces constituting the cylindrical sample shown in Figs. 3(A) and (B).
For crack resistance, the dynamic modulus of elasticity _E0 in the longitudinal direction of a 40 x 40 x 200 mm sample was measured according to the ultrasonic pulse method specified in JIS R1605, and then a cycle of heating at 1500°C for 10 minutes, water cooling for 5 minutes, and air cooling for 10 minutes was repeated three times. After these three cycles were completed, the dynamic modulus of elasticity _E3 was measured again by the above method, and the rate of change in the dynamic modulus of elasticity _E3 / _E0 before and after the test was used as an index for evaluation.

As shown in Example 1-2 to Example 1-8 in Table 1, when the graphite content was 1 to 80 mass% and the magnesia raw material content was 20 to 99 mass%, the corrosion resistance and cracking resistance were almost constant. However, as shown in Example 1-1, when the graphite content was less than 1 mass%, the corrosion resistance was significantly reduced. Also, as shown in Example 1-9, when the magnesia raw material content was less than 20 mass%, the corrosion resistance was significantly reduced. From these results, it can be seen that in order to ensure the cracking resistance of graphite-containing refractories, the graphite content must be 1 mass% or more, and further, in order to achieve both corrosion resistance and cracking resistance in the compounding of magnesia and carbonaceous raw materials, it is preferable to set the graphite content to 1 to 80 mass% and the magnesia raw material content to 20 to 99 mass%.

The graphite-containing refractories of the invention and comparative examples, in which carbon fiber bundles B were arranged (embedded) inside the refractory body A, were manufactured according to the procedure shown in Figure 2. In the manufactured graphite-containing refractories, as shown in Figure 1, multiple carbon fiber bundles B are embedded in parallel at equal intervals along the longitudinal direction of the refractory body A, and the carbon fiber bundles B contain adhesive component c within the bundles and are adhered or bonded to the refractory body A via the adhesive component c. When kneading and molding the refractory raw materials, 3 mass% of phenolic resin and 0.3 mass% of hexamine were blended as binders on the outer side of the refractory raw materials. The manufactured graphite-containing refractories were evaluated for bending strength, fracture energy, melting resistance, and cracking resistance by the following methods.

The bending strength was measured in accordance with the three-point bending test method described in JIS R2213 using a test piece (test piece size: 40 mm x 40 mm x 160 mm) in which a plurality of carbon fiber bundles B were embedded in parallel at equal intervals inside a refractory body A along its longitudinal direction, with a center distance of 100 mm and a load application speed of 0.5 mm/min, as shown in Fig. 4 (Test Method). Fig. 4(A) is an explanatory diagram showing a schematic diagram of the implementation of the three-point bending strength test, and Fig. 4(B) is an explanatory diagram showing a schematic diagram of the end face of the test piece in Fig. 4(A).
As shown in FIG. 5, the breaking energy was determined by taking the position at which the first peak value was shown in the load-displacement curve obtained in the three-point bending strength test as the reference position and calculating the area within a range of 1 mm of displacement from the reference position.
The cracking resistance and erosion resistance were evaluated by the above-mentioned methods, and the test piece used for evaluating the cracking resistance was one in which a plurality of carbon fiber bundles were embedded in parallel at equal intervals inside the refractory body along its longitudinal direction, and the test piece used for evaluating the erosion resistance was one in which a plurality of carbon fiber bundles were embedded in parallel at equal intervals perpendicular to the surface (working surface x of the refractory) in contact with slag or molten steel.

Tables 3 to 9 show the configurations and properties (flexural strength, fracture energy, melting resistance, and cracking resistance) of the graphite-containing refractories of the invention examples and comparative examples (graphite-containing refractories in which the carbon fiber woven bundles B are embedded inside the refractory body A).
First, the examples in Table 3 examine the effect of adhesive component c, which is contained within the carbon fiber bundles B and which bonds or adheres the carbon fiber bundles B to the refractory body A, on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory.
In this example, carbon fiber bundles with a fiber diameter of 7 μm, a length of 200 mm, 75,000 carbon fibers per bundle, and a width of 8 mm were embedded in parallel at intervals of 10 mm inside a magnesia-carbonaceous refractory (refractory body) using adhesives such as phenolic resin (solution) and inorganic sol with different residual carbon ratios, and the adhesives were permeated and attached to the inside and outside of the bundle to give adhesiveness. In this case, the carbon fiber bundles were immersed in the adhesive (solution) in advance, and the carbon fiber bundles with the adhesive permeated and attached to the inside and outside of the bundle were embedded in the refractory body. When two types of adhesives were used in combination, they were mixed and used. In one comparative example, multiple carbon fiber bundles without adhesive were embedded in the refractory body in the same manner.

As shown in Examples 1-1 to 1-10, when carbon fiber bundles that have been made sticky using a specific adhesive that satisfies the conditions of the present invention are embedded, high bending strength and breaking energy are obtained. Furthermore, as shown in Examples 1-11 to 1-15, when carbon fiber bundles that have been made sticky using two types of adhesives are embedded, higher bending strength and breaking energy are obtained compared to when one type of adhesive is used.
On the other hand, as shown in Comparative Example 1-1, when an adhesive (organic resin) with a residual carbon rate of less than 6 mass% is used, a large amount of gas escapes from the inside of the refractory material under high temperatures, and many defects such as pores are generated inside, so that high bending strength, fracture energy, and crack resistance cannot be obtained.

In addition, as shown in Comparative Example 1-2, when an adhesive (organic resin) having a residual carbon rate of more than 80 mass% is used, almost no gas escapes from inside the refractory at high temperatures, and the refractory becomes too dense, so that high bending strength, fracture energy, and crack resistance cannot be obtained.
Furthermore, as shown in Comparative Example 1-3, when no adhesive is used and no adhesiveness is imparted to the carbon fiber bundles, the adhesion between the refractory raw material and the carbon fiber bundles is not improved, and therefore high bending strength, fracture energy, and crack resistance are not obtained.
From the above, it can be seen that by making the adhesive component c contained in the carbon fiber bundles B embedded inside the refractory body A and which bonds or adheres the carbon fiber bundles B to the refractory body A an organic substance and/or inorganic fine particles having a residual carbon ratio of 6 to 80 mass%, a graphite-containing refractory material having high bending strength, fracture energy, and cracking resistance can be obtained.

The examples in Table 4 examine the effects of the width w, length L, fiber diameter, number of carbon fibers per bundle, density of carbon fibers in a cross section of the refractory parallel to the operating surface of the refractory (embedding density), and area ratio of carbon fibers on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory.
In this embodiment, the fiber diameter of the carbon fibers constituting the carbon fiber bundle B is 0.5 to 50 μm, and the number of carbon fibers (number) per bundle of the carbon fiber bundle B is 900 to 350,000, so that the density of the carbon fibers and the occupied area ratio in the cross section of the refractory parallel to the refractory operating surface are different. A plurality of carbon fiber bundles B are embedded in parallel at intervals of 10 mm inside the magnesia-carbonaceous refractory (refractory body A). At that time, the carbon fiber bundles were immersed in a phenolic resin (resin solution) with a residual carbon rate of 40 mass% as an adhesive in advance, and the carbon fiber bundles with the phenolic resin (resin solution) permeating and adhering to the inside and outside of the bundles were embedded in the refractory body A. The maximum particle size of the aggregate (magnesia) constituting the refractory body A is 8 to 5 mm.

As shown in Examples 1-4 and 2-1 to 2-5, when the fiber diameter of the carbon fibers constituting the carbon fiber bundle B is 1 to 45 μm and the number of carbon fibers (number of fibers) per bundle of the carbon fiber bundle B is 1,000 to 300,000, the density of the carbon fibers in the cross section of the refractory parallel to the operating surface of the refractory is 10 to 2,000 fibers/mm ² , and the area ratio of the carbon fibers is 0.1 to 40%, and high bending strength, fracture energy, and crack resistance are obtained.

On the other hand, as shown in Example 2-0, when the fiber diameter of the carbon fibers constituting the carbon fiber bundle B was less than 1 μm and the number of carbon fibers (number of fibers) per bundle of the carbon fiber bundle B was less than 1,000, the presence density (embedding density) of the carbon fibers in the refractory cross section parallel to the refractory operating surface was less than 10 fibers/ ^mm2 , and the occupied area ratio of the carbon fibers was less than 0.1%, and the fracture energy was reduced compared to Example 2-1.
In addition, as shown in Example 2-6, when the fiber diameter of the carbon fibers constituting the carbon fiber bundle B exceeds 45 μm and the number of carbon fibers (number) per bundle of the carbon fiber bundle B exceeds 300,000, the density of the carbon fibers in the cross section of the refractory parallel to the refractory working surface exceeds 2,000 fibers/ ^mm2 , and the area ratio of the carbon fibers exceeds 40%, and the bending strength and fracture energy are lowered compared to Example 2-5. The reason for this is that the carbon fiber bundle is too thick, so that the entanglement between the carbon fiber bundle and the refractory raw material is poor, and springback is likely to occur during molding.

From the above, it is found that the conditions for disposing the carbon fiber bundle B inside the refractory body A are preferably such that the fiber diameter of the carbon fibers constituting the carbon fiber bundle B is 1 to 45 μm, the number of carbon fibers (number) per bundle of the carbon fiber bundle B is 1,000 to 300,000, the density of the carbon fibers in the refractory cross section parallel to the refractory operating surface is 10 to 2,000 fibers/mm ² , and the area ratio of the carbon fibers is 0.1 to 40%, thereby increasing the contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B and improving adhesion, thereby stably obtaining particularly high bending strength, fracture energy, and crack resistance.

The examples in Table 5 were obtained by investigating the effect of the spacing d between the carbon fiber bundles B embedded inside the refractory body A (the distance between the carbon fiber bundles B) on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory.
In this embodiment, the fiber diameter of the carbon fiber constituting the carbon fiber bundle B is 7 μm, the number of carbon fibers (number) per bundle of the carbon fiber bundle B is 75,000, and a plurality of carbon fiber bundles B are embedded in parallel inside the magnesia-carbonaceous refractory (refractory body) with mutual intervals of 3 mm, 5 mm, 10 mm, 20 mm, and 30 mm. At that time, the carbon fiber bundle was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40 mass% as an adhesive in advance, and the carbon fiber bundle with the phenolic resin (resin solution) permeating and adhering to the inside and outside of the bundle was embedded in the refractory body. The maximum particle size of the aggregate (magnesia) constituting the refractory body A is 8-5 mm.

As shown in Examples 1-4 and 3-2 to 3-4, when the interval d between adjacent carbon fiber bundles B (the distance between the carbon fiber bundles) exceeds 3 mm, the refractory raw material (refractory body A) and the carbon fiber bundles B are well entangled, and high fracture energy is obtained.
On the other hand, as shown in Example 3-1, when the distance d between adjacent carbon fiber bundles B is set to 3 mm or less, the entanglement between the refractory raw material (refractory body A) and the carbon fiber bundles B is poor, and the fracture energy and crack resistance are reduced.
From the above, it can be seen that for multiple carbon fiber bundles B arranged in parallel, if the spacing between adjacent carbon fiber bundles B (the distance between carbon fiber bundles B) is more than 3 mm, the refractory raw material (refractory body A) and the carbon fiber bundles B are well entangled and the fracture energy can be maintained high.

A similar study was also carried out on graphite-containing refractories made of alumina raw material, silicon carbide raw material, and silica raw material as aggregates, which are used to line the inside of hot metal pretreatment vessels.
The examples in Table 6 examine the effects of the composition of alumina, silica, silicon carbide, and carbonaceous refractories (graphite-containing refractories using alumina raw materials, silicon carbide raw materials, and silica raw materials as aggregates) used for the lining of a molten iron pretreatment vessel on the bending strength, fracture energy, crack resistance, and corrosion resistance of the graphite-containing refractories.
In this embodiment, the fiber diameter of the carbon fiber constituting the carbon fiber bundle B is 7 μm, the number of carbon fibers (number) per bundle of the carbon fiber bundle B is 75,000, and a plurality of carbon fiber bundles B are embedded in parallel at intervals of 10 mm inside the alumina-silica-silicon carbide-carbonaceous refractory (refractory body A). At this time, the carbon fiber bundle is immersed in a phenolic resin (resin solution) with a residual carbon rate of 40 mass% as an adhesive in advance, and the carbon fiber bundle with the phenolic resin (resin solution) permeating and adhering to the inside and outside of the bundle is embedded in the refractory body. The maximum particle size of the aggregate (alumina raw material, silicon carbide raw material, silica raw material) constituting the refractory body A is 8-5 mm.

As shown in Examples 4-2 to 4-8, when the content of the alumina raw material is 10 to 95 mass%, the content of the silica raw material is 1 to 50 mass%, the content of the silicon carbide raw material is 1 mass% or more, and the graphite content is 1 to 80 mass%, high bending strength, fracture energy, crack resistance, and melting resistance are obtained.
In contrast, as shown in Example 4-1, when the content of the alumina raw material is less than 10 mass%, the content of the silica raw material is less than 1 mass%, the content of the silicon carbide raw material is less than 1 mass%, and the graphite content is more than 80 mass%, the fracture energy/crack resistance and the corrosion resistance are all decreased.
Furthermore, as shown in Example 4-9, when the content of the alumina raw material exceeds 95 mass%, the content of the silica raw material is less than 1 mass%, the content of the silicon carbide raw material is less than 1 mass%, and the content of graphite is less than 1 mass%, the generation of cracks due to thermal spalling cannot be suppressed, and the fracture energy and crack resistance are reduced.
From the above, it can be seen that in an alumina-silica-silicon carbide-carbonaceous refractory, if the alumina raw material content is 10 to 95 mass%, the silica raw material content is 1 to 50 mass%, the silicon carbide raw material content is 1 mass% or more, and the graphite content is 1 to 80 mass%, then it is possible to achieve both high resistance to corrosion and high fracture energy/crack resistance.

The examples in Table 7 are alumina-silica-silicon carbide-carbonaceous refractories (graphite-containing refractories using alumina raw materials, silicon carbide raw materials, and silica raw materials as aggregates) used for lining the inside of a molten iron pretreatment vessel, and for graphite-containing refractories using refractory scrap obtained by crushing used alumina-silica-silicon carbide-carbonaceous refractories as part of the aggregate raw materials, the effects of the refractory scrap content on the bending strength, fracture energy/crack resistance, and corrosion resistance of the graphite-containing refractories were investigated.
In this embodiment, the amount of refractory waste in the alumina-silica-silicon carbide-carbonaceous refractory was changed, the fiber diameter of the carbon fiber constituting the carbon fiber bundle B was 7 μm, and the number of carbon fibers (number) per bundle of the carbon fiber bundle B was 75,000. A plurality of carbon fiber bundles B were embedded in parallel at intervals of 10 mm inside the alumina-silica-silicon carbide-carbonaceous refractory (refractory body A). At that time, the carbon fiber bundle was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40 mass% as an adhesive in advance, and the carbon fiber bundle with the phenolic resin (resin solution) permeating and adhering to the inside and outside of the bundle was embedded in the refractory body. The maximum particle size of the aggregate (alumina raw material, silicon carbide raw material, silica raw material) constituting the refractory body A was 8-5 mm.

As shown in Examples 5-1 to 5-3, when the content of refractory scrap was set to 10 to 90 mass%, the fracture energy, crack resistance, and corrosion resistance were comparable to those of the graphite-containing refractory using only virgin raw materials shown in Table 6.
On the other hand, as shown in Example 5-4, when the content of refractory scrap exceeded 90 mass %, the fracture energy, crack resistance, and melting resistance decreased.
From the above, it can be seen that with respect to a graphite-containing refractory material using refractory shavings obtained by crushing used alumina, silicon carbide, and carbonaceous refractory shavings as an aggregate raw material, if the refractory shavings content is 10 to 90 mass %, the fracture energy can be maintained high and further the graphite-containing refractory material using only virgin raw materials has the same level of cracking resistance and corrosion resistance as a graphite-containing refractory material using only virgin raw materials.

The examples in Table 8 are for alumina-silicon carbide-carbonaceous refractories (graphite-containing refractories using alumina raw materials and silicon carbide raw materials as aggregates), and the effects of the composition of the graphite-containing refractories on the bending strength, fracture energy, crack resistance, and corrosion resistance were investigated.
In this embodiment, the fiber diameter of the carbon fiber constituting the carbon fiber bundle B is 7 μm, the number of carbon fibers (number) per bundle of the carbon fiber bundle B is 75,000, and a plurality of carbon fiber bundles B are embedded in parallel at intervals of 10 mm inside the alumina, silicon carbide, and carbonaceous refractory (refractory body A). At this time, the carbon fiber bundles are immersed in a phenolic resin (resin solution) with a residual carbon rate of 40 mass% as an adhesive in advance, and the carbon fiber bundles with the phenolic resin (resin solution) permeating and adhering to the inside and outside of the bundle are embedded in the refractory body. The maximum particle size of the aggregate (alumina raw material, silicon carbide raw material) constituting the refractory body A is 8-5 mm.

As shown in Examples 6-2 to 6-4, when the content of the alumina raw material is 10 to 95 mass% and the content of graphite is 1 to 80 mass%, high bending strength, fracture energy, crack resistance, and melting resistance are obtained.
On the other hand, as shown in Example 6-1, when the content of the alumina raw material is less than 10 mass% and the content of graphite is more than 80 mass%, the fracture energy, crack resistance, and corrosion resistance are decreased. Also, as shown in Example 6-5, when the content of the alumina raw material is more than 95 mass% and the content of graphite is less than 1 mass%, the fracture energy and crack resistance are decreased.
From the above, it can be seen that in an alumina-silicon carbide-carbonaceous refractory, if the alumina raw material content is 10 to 95 mass % and the graphite content is 1 to 80 mass %, high fracture energy, crack resistance, and melting resistance can be obtained.

The examples in Table 9 are for silica, silicon carbide, and carbonaceous refractories (graphite-containing refractories using silica raw material and silicon carbide raw material as aggregates), and are intended to examine the effects of the composition of the graphite-containing refractories on the bending strength, fracture energy, crack resistance, and corrosion resistance.
In this embodiment, the fiber diameter of the carbon fiber constituting the carbon fiber bundle B is 7 μm, the number of carbon fibers (number) per bundle of the carbon fiber bundle B is 75,000, and a plurality of carbon fiber bundles B are embedded in parallel at intervals of 10 mm inside the silica-silicon carbide-carbonaceous refractory (refractory body A). At this time, the carbon fiber bundles are immersed in advance in a phenolic resin (resin solution) with a residual carbon rate of 40 mass% as an adhesive, and the carbon fiber bundles with the phenolic resin (resin solution) permeating and adhering to the inside and outside of the bundles are embedded in the refractory body. The maximum particle size of the aggregate (silica raw material, silicon carbide raw material) constituting the refractory body A is 8-5 mm.

As shown in Examples 7-2 to 7-4, when the content of the silica raw material is 1 to 50 mass% and the content of graphite is 1 to 80 mass%, high bending strength, fracture energy, crack resistance, and melting resistance are obtained.
On the other hand, as shown in Example 7-1, when the content of the silica raw material is less than 1 mass% and the content of graphite is more than 80 mass%, the fracture energy and crack resistance are reduced. Also, as shown in Comparative Example 7-5, when the content of the silica raw material is more than 50 mass%, the generation of cracks due to thermal spalling cannot be suppressed, and the fracture energy and crack resistance are reduced.
From the above, it can be seen that in silica/silicon carbide/carbonaceous refractories, if the content of silica raw material is 1 to 50 mass % and the content of graphite is 1 to 80 mass %, high bending strength, fracture energy, crack resistance, and melting resistance can be obtained.

A Refractory body B Carbon fiber bundle c Adhesive component x Working surface y Non-working surface

Claims (13)

A graphite-containing refractory having a refractory body (A) and a carbon fiber bundle (B) (excluding carbon fiber bundles as a part of a carbon fiber fabric),
The carbon fiber bundles (B) contain an adhesive component (c) therein and are bonded or adhered to the refractory body (A) via the adhesive component (c);
The graphite-containing refractory material is characterized in that the adhesive component (c) is composed of an organic substance having a residual carbon ratio of 6 to 80 mass %, or an organic substance having a residual carbon ratio of 6 to 80 mass % and inorganic fine particles . 2. The graphite -containing refractory material according to claim 1, characterized in that the organic substance which is the adhesive component (c) is one or more selected from organic resins, organic substances derived from tar and/or pitch, and organic substances derived from organic glue, and the inorganic fine particles are inorganic fine particles derived from an inorganic sol . The graphite-containing refractory material according to claim 1 or 2, characterized in that the carbon fiber bundle (B) has a width of 1 to 15 mm. The graphite-containing refractory material according to any one of claims 1 to 3, characterized in that the carbon fiber bundle (B) is a bundle of carbon fibers having a length of 100 mm or more and a fiber diameter of 1 to 45 μm, and the number of carbon fibers per bundle is 1,000 to 300,000. The graphite-containing refractory according to any one of claims 1 to 4, characterized in that a plurality of carbon fiber bundles (B) are arranged in parallel inside the refractory body (A) and the interval between adjacent carbon fiber bundles (B) is more than 3 mm. The graphite-containing refractory according to any one of claims 1 to 5, characterized in that the density of the carbon fibers constituting the carbon fiber bundles (B) in a cross section of the graphite-containing refractory parallel to the working surface of the graphite-containing refractory is 10 to 2000 fibers/ ^mm2 . The graphite-containing refractory according to any one of claims 1 to 6, characterized in that the area ratio of the carbon fibers constituting the carbon fiber bundles (B) in the cross section of the graphite-containing refractory parallel to the working surface of the graphite-containing refractory is 0.1 to 40%. The graphite-containing refractory according to any one of claims 1 to 7, characterized in that the refractory body (A) contains 1 to 80 mass% of graphite raw material. The graphite-containing refractory according to any one of claims 1 to 8, characterized in that the refractory body (A) contains 20 to 99 mass% of magnesia raw material. The graphite-containing refractory according to any one of claims 1 to 8, characterized in that the refractory body (A) contains 10 to 95 mass% of alumina raw material. The graphite-containing refractory according to any one of claims 1 to 8 and 10, characterized in that the refractory body (A) contains 1 to 50 mass% of silica raw material. The graphite-containing refractory according to claim 10 or 11, characterized in that the refractory body (A) contains 1 mass% or more of silicon carbide raw material. The graphite-containing refractory according to any one of claims 1 to 12, characterized in that the refractory body (A) contains 10 to 90 mass% refractory chips obtained by crushing used refractories.