Graphite-containing refractory

Abstract

To provide a graphite-containing refractory that can obtain high durability by suppressing progress of crack generated by thermal stress, even when used under the condition where temperature rising and temperature lowering are repeated over a long term like a lining refractory of a converter, and, in particular, when used under the condition where a temperature gradient of the inside is very large like tuyere brick of the converter, high durability can be obtained.SOLUTION: A graphite-containing refractory in which a carbon fiber bundle B is arranged inside a refractory body A, and the carbon fiber bundle B contains an adhesive component c within the bundle and is adhered or attached to the refractory body A via an adhesive component c, the adhesive component c is made of an organic substance and / or inorganic fine particles having a residual carbon content of 6 to 80 mass%. Preferably, the density of the carbon fibers composing the carbon fiber bundle B in a cross section of the refractory parallel to the working surface of the refractory is 10 to 2000 fibers / mm2, and an occupied area ratio of the carbon fibers is also 0.1 to 40%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a graphite-containing refractory in which a carbon fiber bundle is disposed inside a refractory body.

Background Art

[0002] Equipment (refining vessels, transfer vessels, etc.) used in the pig iron making process and the steel making process in a steelworks is lined with refractory so as to withstand long-term use at high temperatures. Generally, magnesia-carbon refractories are used for the lining of converters used in the refining process, and alumina-silicon carbide-carbon refractories are used for the lining of torpedoes and blast furnace ladles used in the hot metal pretreatment process. The refractories used for the lining in these refining vessels and transfer vessels are used under extremely harsh conditions where mechanical shock due to the charged material, wear due to stirring of molten steel and molten slag, slag erosion due to molten slag, and rapid temperature changes during operation occur. Therefore, in order to perform stable operation, it is necessary to use a highly durable refractory that can withstand such harsh conditions.

[0003] In particular, the tuyere bricks that make up the tuyere part of a converter have normal temperature gas (such as oxygen and cooling hydrocarbon gas) flowing inside. In the part close to the furnace interior, the inner surface is cooled by the normal temperature gas, and the outer surface is exposed to high temperatures due to heat transfer from the molten steel in the furnace. Therefore, the thermal gradient inside the tuyere bricks is extremely large. Moreover, every time the blowing for one charge of the converter ends, a temperature drop occurs due to the discharge of the molten steel, and large thermal fluctuations are repeated. The tuyere bricks installed in the converter reach a usage frequency of about 2,500 to 4,000 charges, and are used under extremely harsh conditions where the above-mentioned large thermal gradient occurs and large thermal fluctuations are repeated every charge. Therefore, high durability that can withstand use under such conditions is required. In addition, the refractory lining inside the converter other than the tuyere bricks (the bricks that make up the inner wall of the converter) is also used under harsh conditions where the large thermal fluctuations described above are repeated. Although not as severe as the tuyere bricks, high durability is required.

[0004] As a technique for enhancing the durability of refractory materials, Patent Document 1 describes that carbon fibers with a length of 100 mm or more are bundled with an adhesive and placed inside the refractory material in a bundled state with adhesiveness imparted, resulting in a significant increase in fracture energy.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, as a result of investigations by the present inventors, in the technique of loading carbon fiber bundles inside a refractory material as in Patent Document 1, depending on the properties of the adhesive used, the effect of loading (placing) the carbon fiber bundles inside the refractory material cannot be sufficiently obtained. Patent Document 1 does not disclose the conditions of the adhesive for maximizing the loading effect of such carbon fiber bundles.

[0007] Therefore, an object of the present invention is to solve the problems of the prior art as described above, and even when used under conditions where heating and cooling are repeated over a long period, such as the inner lining refractory of a converter, the progress of cracks generated by thermal stress is suppressed and high durability is obtained. In particular, to provide a graphite-containing refractory material that can obtain high durability even when used under conditions where the internal temperature gradient is very large, such as the tuyere bricks of a converter.

Means for Solving the Problems

[0008] As a result of repeated studies to solve the above problems, the inventors have found that in a graphite-containing refractory in which a carbon fiber bundle is disposed inside the refractory, an organic substance or / and inorganic fine particles having a predetermined residual carbon rate are used as an adhesive component for bundling and integrating carbon fibers and adhering or closely adhering the carbon fiber bundle to the refractory raw material. Preferably, by optimizing the fiber diameter and the number of carbon fibers constituting the carbon fiber bundle, and further the density of carbon fibers and the occupied area ratio in the refractory cross section, high durability can be obtained even in an extremely harsh use environment as described above.

[0009] The present invention has been made based on such findings, and the gist thereof is as follows. [1] A graphite-containing refractory in which a carbon fiber bundle (B) is disposed inside a refractory body (A), The carbon fiber bundle (B) contains an adhesive component (c) in the bundle and is adhered or closely adhered to the refractory body (A) via the adhesive component (c), The adhesive component (c) is a graphite-containing refractory characterized by being composed of an organic substance or / and inorganic fine particles having a residual carbon rate of 6 to 80% by mass.

[0010] [2] In the graphite-containing refractory according to [1] above, the adhesive component (c) is at least one selected from organic resins, organic substances derived from tar or / and pitch, organic substances derived from organic pastes, and inorganic fine particles derived from inorganic sols. A graphite-containing refractory characterized by the above. [3] The graphite-containing refractory according to [1] or [2] above, wherein the width of the carbon fiber bundle (B) is 1 to 15 mm. [4] In any of the graphite-containing refractories according to [1] to [3] above, 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 1000 to 300000. A graphite-containing refractory characterized by the above.

[0011] [5] In the graphite-containing refractory according to any one of [1] to [4] above, a plurality of carbon fiber bundles (B) are arranged in parallel inside the refractory body (A), and the distance between adjacent carbon fiber bundles (B) is more than 3 mm. The graphite-containing refractory is characterized by this. [6] In the graphite-containing refractory according to any one of [1] to [5] above, the density of the carbon fibers constituting the carbon fiber bundle (B) in the refractory cross section parallel to the operating surface of the graphite-containing refractory is 10 to 2000 fibers / mm 2 The graphite-containing refractory is characterized by this. [7] In the graphite-containing refractory according to any one of [1] to [6] above, the occupied area ratio of the carbon fibers constituting the carbon fiber bundle (B) in the refractory cross section parallel to the operating surface of the graphite-containing refractory is 0.1 to 40%. The graphite-containing refractory is characterized by this.

[0012] [8] In the graphite-containing refractory according to any one of [1] to [7] above, the refractory body (A) contains 1 to 80% by mass of graphite raw material. The graphite-containing refractory is characterized by this. [9] In the graphite-containing refractory according to any one of [1] to [8] above, the refractory body (A) contains 20 to 99% by mass of magnesia raw material. The graphite-containing refractory is characterized by this.

[10] In the graphite-containing refractory according to any one of [1] to [8] above, the refractory body (A) contains 10 to 95% by mass of alumina raw material. The graphite-containing refractory is characterized by this.

[0013]

[11] In the graphite-containing refractory according to any one of [1] to [8],

[10] above, the refractory body (A) contains 1 to 50% by mass of silica raw material. The graphite-containing refractory is characterized by this.

[12] In the graphite-containing refractory according to

[10] or

[11] above, the refractory body (A) contains 1% by mass or more of silicon carbide raw material. The graphite-containing refractory is characterized by this.

[13] In the graphite-containing refractory according to any one of [1] to

[12] above, the refractory body (A) contains 10 to 90% by mass of refractory debris obtained by pulverizing used refractories. The graphite-containing refractory is characterized by this.

Advantages of the Invention

[0014] Since the graphite-containing refractory of the present invention has high fracture energy, even when used under conditions where heating and cooling are repeated over a long period, such as the inner lining refractory of a converter, the progress of cracks generated by thermal stress is suppressed, resulting in high durability. In particular, high durability can be obtained even when used under conditions where the internal temperature gradient is very large, such as the tuyere bricks of a converter.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0016] The graphite-containing refractory of the present invention is a graphite-containing refractory in which a carbon fiber bundle B is disposed inside a refractory body A. The carbon fiber bundle B contains an adhesive component c in the bundle, and is adhered or closely attached to the refractory body A via the adhesive component c. The adhesive component c is characterized by being composed of an organic substance or / and inorganic fine particles having a residual carbon rate of 6 to 80% by mass. This graphite-containing refractory is usually an un-fired refractory manufactured without high-temperature firing (reductive firing). Here, the residual carbon rate of the adhesive component c is measured based on the fixed carbon measurement method described in JIS K6910 (Phenolic Resin Test Method). In such a graphite-containing refractory of the present invention, the carbon fiber bundle B disposed inside the refractory body A is integrated as a bundle by containing the adhesive component c in the bundle, and the carbon fiber bundle B is integrated with the refractory by adhering or closely attaching to the refractory body A via the adhesive component c. In addition, since the adhesive component c is composed of an organic substance or / and inorganic fine particles having a specific residual carbon rate, high fracture energy capable of suppressing the occurrence of cracks can be obtained.

[0017] Hereinafter, the configuration and embedding conditions of the carbon fiber bundle B will be described. FIG. 1 schematically shows an embodiment of the graphite-containing refractory of the present invention (a brick constituent member constituting a tuyere brick). FIG. 1(a) is a perspective view, and FIG. 1(b) is a cross-sectional view along the dashed-dotted line in FIG. 1(a) (a cross-sectional view parallel to the refractory operating surface), where x is the operating surface of the refractory (y is the non-operating surface). In the graphite-containing refractory of this embodiment, a plurality of carbon fiber bundles B are arranged (embedded) in parallel at a predetermined interval inside the refractory body A. The carbon fiber bundle B is disposed in the refractory raw material in a state where an adhesive is attached to the outer surface and the adhesive also penetrates into the bundle, and a graphite-containing refractory is obtained. Therefore, the carbon fiber bundle B contains the adhesive component c in the bundle (that is, the adhesive component c exists in the gaps between the carbon fibers constituting the carbon fiber bundle B, whereby the carbon fibers are integrated into a bundle state), and the adhesive component c is interposed between the carbon fiber bundle B and the refractory body A, and is adhered or closely attached to the refractory body A via the adhesive component c.

[0018] The adhesive component c is composed of an organic substance such as an organic resin having a predetermined char residue rate or / and inorganic fine particles such as alumina and silica. During the use of the refractory (during actual operation), the temperature inside reaches 500 °C or higher (measured at 900 °C in JIS K6910). At this time, even in an environment where there is almost no oxygen inside, like in a graphite-containing refractory, when the adhesive component is an organic substance, a part of the adhesive adhering to the carbon fiber bundle gasifies by decomposition or evaporation and escapes outside the refractory. The char residue rate is considered to be an index of the ratio of the weight remaining without gasifying and escaping in the adhesive, and it varies depending on the type and quality of the adhesive. As a result of investigating based on the idea that the char residue rate of the adhesive affects the fracture energy when a graphite-containing refractory using carbon fiber bundles is exposed to the high temperature of the actual use environment, it was found that when using an adhesive (organic substance) with a char residue rate of 6 to 80 mass%, high fracture energy can be obtained. This is because when using an adhesive (organic substance) with such a specific char residue rate, the adhesion between the refractory raw material (refractory body A) and the carbon fiber bundle B increases, so in addition to the refractory bricks being easily densified during molding, when exposed to high temperatures, the amount of gas escaping from inside the refractory can be suppressed, the generation of cracks can be suppressed, and the fracture energy increases. In addition, the inventors have also found that high fracture energy can be obtained even when the adhesive component is inorganic fine particles such as alumina and silica. This is because when using inorganic fine particles (especially inorganic fine particles derived from inorganic sols), the adhesion between the refractory raw material (refractory body A) and the carbon fiber bundle B increases, so in addition to the refractory bricks being easily densified during molding, when exposed to high temperatures during use, the inorganic fine particles sinter, which can suppress the generation of cracks and increase the fracture energy.

[0019] When the adhesive component c is an organic substance, if its char residue rate is less than 6% by mass, the amount of gas escaping from inside the refractory at high temperatures increases, and many defects such as pores are generated, so the fracture energy does not increase. On the other hand, if the char residue rate is more than 80% by mass, the amount of gas escaping from inside the refractory at high temperatures is almost zero, and the refractory becomes too dense and brittle, so the fracture energy does not increase. Also, from the above viewpoints, the char residue rate of the organic substance is preferably 20 - 80% by mass, and more preferably 40 - 80% by mass. Since the adhesive component c exists (penetrates) in the bundles of carbon fibers (the gaps between carbon fibers) to integrate the carbon fiber bundles B as bundles, and covers the outer surface of the carbon fiber bundles B to adhere or closely attach the carbon fiber bundles B to the refractory body A, it is desirable that the adhesive used is in a liquid state. Also, the adhesive component c needs to remain without decomposing or evaporating even at high temperatures. However, when used in a graphite-containing refractory, combustion by oxygen hardly occurs, so it is possible to use a resin rich in combustibility in the presence of oxygen. From these conditions, the adhesive component c is preferably one or more selected from organic resins (organic resins derived from organic resin solutions), organic substances derived from tar or / and pitch, organic substances derived from organic pastes, and inorganic fine particles derived from inorganic sols (that is, any of these or a mixture of these).

[0020] Therefore, examples of the adhesive (adhesiveness-imparting agent) attached to the carbon fiber bundles during production include organic resins (solutions), pitch, tar, organic pastes, inorganic sols, etc. Specifically, phenol resins, epoxy resins, melamine resins, urea resins, alkyd resins, unsaturated polyester resins, polyurethane resins, thermosetting polyimide resins (resin solutions composed 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. can be mentioned, and one or more selected from these can be used. Also, in order to adjust the viscosity of these adhesives during manufacturing, they can be thinned with a solvent. However, it is desirable to limit the use of a solvent (such as water) that gasifies even without oxygen at a high temperature of 500°C or higher to an amount equal to or less than the weight of the adhesive component. Also, by using two or more types of adhesives, higher flexural strength and fracture energy can be obtained than when using a single type of adhesive. This is because the adhesion between the refractory raw material and the carbon fiber is further enhanced. Therefore, in order to obtain higher flexural strength and fracture 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).

[0021] The arrangement form of the carbon fiber bundles B inside the refractory body A is arbitrary and there are no special restrictions. However, during operation, since the tensile stress that causes cracks occurs in the longitudinal direction of the refractory, it is preferably arranged (embedded) linearly along one direction. In particular, it is preferably arranged (embedded) along the direction perpendicular to the operating surface x of the refractory. Also, when arranging a plurality of carbon fiber bundles B, it is preferably arranged (embedded) in parallel at a predetermined interval. Note that the ends of the carbon fiber bundles B embedded inside the refractory body A may or may not be exposed on the surface of the refractory body A. Also, in the latter case, on the operating surface x side of the refractory, it is preferable that the distance between the end of the carbon fiber fabric B and the operating surface x is as small as possible. However, on the non-operating surface y side, the distance between the end of the carbon fiber bundle B and the non-operating surface y may be somewhat large. This is because it is not necessary to embed the carbon fiber bundles B in the portion on the non-operating surface y side of the refractory that is assumed to remain even at the end of use.

[0022] The carbon fiber bundle B preferably has a width w (width per bundle) of 1 to 15 mm. Here, the width of the carbon fiber bundle B refers to the length of the long side or major axis in the cross-section in the width direction of the carbon fiber bundle (however, when the cross-section in the width direction is a quadrilateral or circular, it refers to the length of one side or the diameter). When the width w of the carbon fiber bundle B is 1 mm or more, the number of carbon fiber bundles B can be reduced when using the same number of carbon fibers, and it becomes easier to arrange the carbon fiber bundles B evenly inside the refractory body A. On the other hand, when the width w of the carbon fiber bundle B is 15 mm or less, interference between the coarse-grained material (generally, those with a particle size of 5 to 20 mm) among the raw materials used for the refractory body A and the carbon fiber bundle B can be reduced, and the melting loss of the carbon fiber bundle B itself triggering the melting loss of the refractory can be mitigated.

[0023] The carbon fiber bundle B is formed by bundling carbon fibers with a length L of 100 mm or more and a fiber diameter of 1 to 45 μm, and preferably has 1000 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 restraining force between the carbon fiber bundle B and the refractory body A becomes small, so the effect of the carbon fiber bundle B suppressing the propagation of cracks becomes small. Also, 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 the effect of suppressing the propagation of local cracks decreases, and the increase in fracture energy becomes small. On the other hand, when the fiber diameter of the carbon fiber exceeds 45 μm or the number of carbon fibers per bundle exceeds 300,000, the carbon fiber bundle B is too thick, so 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.

[0024] A plurality of carbon fiber bundles B are arranged in parallel inside the refractory body A, and it is preferable that the distance d (the distance between adjacent carbon fiber bundles B) between adjacent carbon fiber bundles B is more than 3 mm. By arranging the adjacent carbon fiber bundles B so that the distance d therebetween is more than 3 mm, the entanglement between the refractory raw material (refractory body A) and the carbon fiber bundles B can be improved, and also, delamination caused by the carbon fiber bundles called lamination during molding can be hardly caused. Although there is no particular upper limit for this distance d, generally, about 100 mm is the upper limit in view of the relationship with the existence density of the carbon fibers described below. The existence density of the carbon fibers constituting the carbon fiber bundle B in the refractory cross-section parallel to the working surface x of the graphite-containing refractory is 10 to 2000 fibers / mm 2 which is preferable. Thereby, the contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B is ensured, the adhesiveness is enhanced, the fracture energy can be increased, and the generation of defects due to the elastic deformation of the carbon fiber bundle B can also be suppressed. When the existence 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 adhesiveness between the refractory raw material and the carbon fiber bundle B does not increase, and the increase in fracture energy is small. On the other hand, when the existence density of the carbon fibers exceeds 20000 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.

[0025] In a refractory cross-section parallel to the working surface x of the graphite-containing refractory, the occupancy area ratio of the carbon fibers constituting the carbon fiber bundle B is preferably 0.1 to 40%. Thereby, the contact area between the refractory raw material (refractory main body A) and the carbon fiber bundle B is ensured, the adhesion is enhanced, the fracture energy can be increased, and the generation of defects due to the elasticity of the carbon fiber bundle B can also be suppressed. When the occupancy area ratio of the carbon fibers is less than 0.1%, the contact area between the refractory raw material (refractory main 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 does not increase, and the increase in fracture energy is small. On the other hand, when the occupancy area ratio of the carbon fibers exceeds 40%, the contact area between the refractory raw material (refractory main body A) and the carbon fiber bundle B is too wide, so defects due to the elasticity of the carbon fiber bundle B called springback are likely to occur during molding.

[0026] Next, the composition of the refractory main body A will be described. The refractory main body A preferably contains 1 to 80% by mass of a graphite raw material. By setting the content of the graphite raw material to 1% by mass or more, the crack resistance of the graphite-containing refractory can be ensured, and the oxidation and disappearance of the carbon fibers inside the refractory can be suppressed. On the other hand, by setting the content of the graphite raw material to 80% by mass or less, the oxidation and disappearance of the graphite raw material on the refractory surface can be suppressed. As the graphite (carbon raw material), generally flake graphite etc. are used.

[0027] Generally, for the lining (including the tuyere part) of a converter used in the refining process, a magnesia-carbon refractory (a graphite-containing refractory with a magnesia raw material as the aggregate), which is a refractory mainly composed of magnesia and carbon, is used. When the refractory main body A is a magnesia-carbon refractory, the refractory main body A preferably contains 20 to 99% by mass of a magnesia raw material. Thereby, cracks due to thermal spalling can be suppressed, and a refractory having corrosion resistance that can withstand the erosion of converter slag containing a large amount of FeO can be obtained. Note that as the magnesia raw material, it is preferable to use a high-purity magnesia raw material with a magnesia concentration of 90% by mass or more.

[0028] In general, for the toppings used in the hot metal pretreatment process and the linings of blast furnace ladles, refractory materials mainly composed of alumina, silicon carbide, and carbon, such as alumina-silicon carbide-carbon refractory materials (graphite-containing refractory materials with alumina raw materials and silicon carbide raw materials as aggregates), and refractory materials mainly composed of alumina, silicon carbide, silica, and carbon, such as alumina-silicon carbide-silica-carbon refractory materials (graphite-containing refractory materials with alumina raw materials, silicon carbide raw materials, and silica raw materials as aggregates), are used. When the refractory body A is an alumina-silicon carbide-carbon refractory material or an alumina-silicon carbide-silica-carbon refractory material, it is preferably contained 10 to 95% by mass of alumina raw materials, whereby high corrosion resistance against hot metal pretreatment slag can be obtained, and the generation of cracks due to thermal spalling can be further suppressed. As the alumina raw material, it is preferable to use a high-purity alumina raw material having an alumina concentration of 70% by mass or more.

[0029] Furthermore, when the refractory body A is an alumina-silicon carbide-carbon refractory material or an alumina-silicon carbide-silica-carbon refractory material, it is preferably contained 1% by mass or more of silicon carbide raw materials. By containing 1% by mass or more of silicon carbide raw materials, the oxidation of graphite in an air atmosphere can be suppressed, so that high crack resistance can be maintained. As the silicon carbide raw material, it is preferable to use a high-purity silicon carbide raw material having a silicon carbide concentration of 80% by mass or more. In addition, when the refractory body A is an alumina-silicon carbide-silica-carbon refractory material, it is preferably contained 1 to 50% by mass of silica raw materials, whereby both high crack resistance and high corrosion resistance can be achieved.

[0030] The magnesia-carbon refractory used for the lining of a converter is used under extremely harsh conditions, such as mechanical shock by the charged material, wear due to stirring of molten steel and molten slag, slag erosion by molten slag, and rapid temperature changes during converter operation. Therefore, in order to perform stable operation, it is preferable to use a magnesia-carbon refractory with high durability that can withstand harsh conditions. Similarly, since alumina-silicon carbide-carbon refractories and alumina-silicon carbide-silica-carbon refractories used for the lining of hot metal pretreatment vessels such as torpedo cars and blast furnace ladles are also used under extremely harsh conditions, it is preferable to use refractories that can withstand these conditions. According to the present invention, since the fracture energy of the graphite-containing refractory used under these extremely harsh conditions is significantly improved compared to conventional graphite-containing refractories, high durability can be obtained.

[0031] Further, in the case of a silica-silicon carbide-carbon refractory in which the refractory body A is a refractory mainly composed of silica, silicon carbide, and carbon, it is preferable to contain 1% by mass or more of a silicon carbide raw material and 1 to 50% by mass of a silica raw material, whereby high crack resistance and high corrosion resistance can be achieved simultaneously. By containing 1% by mass or more of the silicon carbide raw material, oxidation of graphite in an air atmosphere can be suppressed, so that high crack resistance can be maintained. In addition, as the silicon carbide raw material, it is preferable to use a high-purity silicon carbide raw material having a silicon carbide concentration of 80% by mass or more.

[0032] Here, as the alumina raw material, for example, one or more of bauxite shale, white alumina, brown alumina, etc. are used. Further, as the silicon carbide raw material, for example, one or more of green silicon carbide, black silicon carbide, etc. are used. Further, as the silica raw material, for example, one or more of wollastonite, mullite, etc. are used. The graphite-containing refractory can further contain (compound) a metal powder raw material for the purpose of increasing durability while suppressing the heat dissipation amount from the iron-making vessel. Examples of the metal powder raw material include metallic Si, metallic Al, metallic Al-Si, Al4SiC4, B4C, etc., and one or more of these can be contained. The content of the metal powder raw material is not particularly specified, but usually, about 1 to 5% by mass is preferable. If the content (compounding amount) of the metal powder raw material is less than 1% by mass, the effect of improving durability by compounding the metal powder raw material cannot be sufficiently obtained. On the other hand, if it exceeds 5% by mass, the strength becomes too high, so cracks are likely to occur when used in an actual machine, the bricks are likely to break, and the number of times of use in an actual machine may decrease.

[0033] The refractory body A can contain about 10 to 90% by mass of refractory scraps obtained by pulverizing used refractories as an aggregate raw material. In particular, when the refractory body A is an alumina-silicon carbide-carbon refractory (including the case of an alumina-silicon carbide-silica-carbon refractory containing a silica raw material. The same applies hereinafter), the refractory scraps obtained by pulverizing the used alumina-silicon carbide-carbon refractory (including the case of an alumina-silicon carbide-silica-carbon refractory containing a silica raw material. The same applies hereinafter) can be suitably used as an aggregate raw material. When containing refractory scraps in this way, the remainder of the refractory raw material is an unused raw material (virgin raw material).

[0034] In a refractory body A made of alumina-silicon carbide-carbon refractory, when the content of refractory debris obtained by pulverizing used alumina-silicon carbide-carbon refractory is 10 to 90 mass%, the same crack resistance and corrosion resistance as those of a graphite-containing refractory using only virgin raw materials can be obtained. The reason is that although the refractory debris raw material has a lower purity compared to the virgin raw material, by using the refractory debris raw material and the virgin raw material together, it is possible to suppress a significant decrease in the corrosion resistance of the Al2O3 component in the refractory debris raw material. However, when the content of refractory debris exceeds 90 mass%, since the content of virgin raw material is too small, a significant decrease in the corrosion resistance of the Al2O3 component in the refractory debris raw material cannot be suppressed. Also, when the content of refractory debris is less than 10 mass%, since the recycling rate of refractory debris is too low, the treatment cost of refractory debris as industrial waste increases significantly.

[0035] Next, the method for manufacturing the graphite-containing refractory of the present invention will be described. Figure 2 shows an example of the manufacturing process of 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 material is filled into a mold together with a carbon fiber bundle in which a predetermined adhesive has penetrated (impregnated) into the inside of the bundle and adhered to the outer surface, and press molding is performed to obtain a refractory molded product. As the binder, for example, phenol resin (main agent) + hexamine (hardening agent), carbon bond, ceramic bond, etc. are used. As a method of filling the kneaded material of the refractory raw material into a mold together with a carbon fiber bundle (a carbon fiber bundle in which an adhesive has penetrated (impregnated) into the inside of the bundle and adhered to the outer surface; the same applies hereinafter), for example, after charging a certain amount of the kneaded material into the mold, a plurality of carbon fiber bundles are arranged (charged) in parallel, and then a certain amount of the kneaded material is charged into the mold. Therefore, in order to manufacture a graphite-containing refractory in which a plurality of carbon fiber bundles B are embedded inside the refractory body A as shown in Figure 1 by this method, after charging a certain amount of the kneaded material into the mold, the step of arranging a plurality of carbon fiber bundles arranged in parallel thereon and the step of charging a certain amount of the kneaded material thereon are repeated.

[0036] In addition, in order to infiltrate (impregnate) and adhere an adhesive (tackifier) to a carbon fiber bundle, for example, the carbon fiber bundle is immersed in a 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 bundle, so that the adhesive infiltrates and adheres to the carbon fiber bundle. The carbon fiber bundle with the adhesive infiltrated and adhered is charged into a mold together with the kneaded material in the above-mentioned manner. Here, the adhesive infiltrated and adhered to the carbon fiber bundle may be in a state where it has a certain degree of hardening or solidification when the carbon fiber bundle is placed in the kneaded material, as long as it has adhesiveness that allows the carbon fiber bundle and the refractory (kneaded material) to adhere or closely contact (so-called semi-dry state). As another method, a carbon fiber bundle impregnated with an adhesive in advance and then hardened or solidified may be prepared, and when it is placed in the kneaded material, the adhesive may be adhered to the outer surface of the carbon fiber bundle again.

[0037] For press molding, general die press molding that compresses in one direction in a mold can be performed, or CIP molding that applies pressure evenly from all directions using a liquid may be performed. For a shape with different thicknesses depending on the part, such as a shape where it is difficult to apply uniform pressure by one-way compression, it is desirable to use CIP molding because the deviation in the degree of compression depending on the part is reduced. In addition, the shaping process may be performed by a shaping method other than press shaping. Examples of shaping methods other than press shaping include, for example, casting. In one such method, an inner frame is installed at the construction site, which is the working surface such as a pot or tundish. An amorphous refractory (refractory raw material) is poured into this inner frame, dried (drying process) and solidified, and then the inner frame is removed. Also, instead of pouring into the construction site, an amorphous refractory (refractory raw material) is poured into a refractory-shaped mold, dried (drying process) and solidified, and then the refractory removed from the mold is transported to the construction site for construction. Although this method is laborious for refractory construction at the construction site, it is desirable because it is easy to embed carbon fiber bundles when pouring the amorphous refractory into the mold and to control the temperature during solidification. In these casting-based shaping methods, after arranging the carbon fiber bundles in the above-described inner frame or mold, an amorphous refractory (refractory raw material) is poured into the inner frame or mold, and dried (drying process) and solidified.

[0038] The refractory molded product obtained as described above is dried. This drying is usually carried out at about 200 to 230 °C for the purpose of drying (curing) the refractory molded product. Also, for the refractory formed body obtained by casting as described above, the refractory formed body held in the inner frame installed at the construction site or the mold installed at other locations is heated by heating means such as a heating burner to be dried and solidified. Thereafter, the inner frame is removed or the mold is taken out.

[0039] As described above, a graphite-containing refractory in which carbon fiber bundles B are arranged (embedded) inside the refractory body A, wherein the carbon fiber bundles B contain an adhesive component c (an adhesive component composed of an organic substance or / and inorganic fine particles having a residual carbon rate of 6 to 80% by mass) in the bundle, and are adhered or closely attached to the refractory body A via the adhesive component c, is obtained. 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 lining refractory for refining containers and transport containers used in steelworks. In particular, it is suitable as a lining refractory for converters, which are in a very harsh use environment, and is particularly suitable as a tuyere brick that constitutes the tuyere part.

Examples

[0040] Regarding the magnesia-carbon refractory used in a converter (a graphite-containing refractory with magnesia raw material as the aggregate), in order to study the formulation of the magnesia-carbon raw material, refractory molded products with magnesia raw material as the aggregate were produced with the raw material formulations shown in Table 1, that is, graphite-containing refractories without embedded carbon fiber bundles. When kneading and molding the refractory raw materials, as a binder, 3% by mass of phenolic resin and 0.3% by mass of hexamine were added externally to the refractory raw materials. Regarding the produced graphite-containing refractories, the corrosion resistance and crack resistance were evaluated by the following methods respectively. The results are also shown in Table 1.

[0041] Regarding the corrosion resistance, as shown in Fig. 3 (test method), the corrosion loss was measured by the internal partition method using a high-frequency induction furnace, and the evaluation was based on the corrosion loss. In the test by the internal partition method, the test temperature was 1650 °C, the temperature holding time was 4 hours, and synthetic slag with the composition shown in Table 2 was charged every hour. After cooling, the corrosion loss of the working surface was measured. Then, from the corrosion loss, a corrosion index was obtained with the corrosion loss of Formulation Examples 1-4 in Table 1 as 100. Fig. 3(A) is an explanatory diagram schematically showing the test implementation status in a state where the test furnace and the cylindrical sample are longitudinally sectioned, 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 Fig. 3(A) and (B). Regarding the crack resistance, after measuring the dynamic elastic modulus E0 in the longitudinal direction of a 40×40×200 mm sample according to the ultrasonic pulse method shown in JIS R1605, a process with heating at 1500 °C for 10 minutes, water cooling for 5 minutes, and air cooling for 10 minutes as one cycle was repeated 3 times. After the end of these 3 cycles, the dynamic elastic modulus E3 was measured again by the above method, and the change rate E3 / E0 of the dynamic elastic modulus before and after the test was used as an index for evaluation.

[0042] As shown in Blending Examples 1-2 to 1-8 in Table 1, when the graphite content was 1 to 80% by mass and the content of the magnesia raw material was 20 to 99% by mass, the erosion resistance and crack resistance were almost constant. However, as shown in Blending Example 1-1, when the graphite content was less than 1% by mass, the crack resistance was significantly reduced. Also, as shown in Blending Example 1-9, when the content of the magnesia raw material was less than 20% by mass, the erosion resistance was significantly reduced. From these facts, it is necessary that the graphite content be 1% by mass or more in order to ensure the crack resistance of the graphite-containing refractory. Further, in the blending of magnesia-carbon raw materials, in order to achieve both erosion resistance and crack resistance, it is found that it is preferable that the graphite content be 1 to 80% by mass and the content of the magnesia raw material be 20 to 99% by mass.

[0043] Graphite-containing refractories of the invention examples 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 FIG. 2. In the manufactured graphite-containing refractory, as shown in FIG. 1, a plurality of carbon fiber bundles B were embedded in parallel at equal intervals along the longitudinal direction of the refractory body A. The carbon fiber bundles B contain an adhesive component c in the bundle and are adhered or closely attached to the refractory body A via the adhesive component c. When kneading and molding the refractory raw material, 3% by mass of phenol resin and 0.3% by mass of hexamine were blended as an external coating with respect to the refractory raw material as a binder. Regarding the manufactured graphite-containing refractory, the flexural strength, fracture energy, erosion resistance, and crack resistance were evaluated by the following methods, respectively.

[0044] Regarding the flexural strength, as shown in FIG. 4 (test method), using a test piece (test piece size: 40 mm × 40 mm × 160 mm) in which a plurality of carbon fiber bundles B were embedded in parallel at equal intervals along the longitudinal direction inside the refractory body A, with a center distance of 100 mm and a load application acceleration of 0.5 mm / min, the measurement was carried out in accordance with the three-point bending test method described in JIS R2213. Note that FIG. 4(a) is an explanatory diagram schematically showing the implementation status of the three-point bending strength test, and FIG. 4(b) is an explanatory diagram schematically showing the end face of the test piece of FIG. 4(a). Regarding the breaking energy, as shown in Fig. 5, based on the position showing the first peak value in the load-displacement curve obtained from the three-point bending strength test, the area within a displacement range of 1 mm from the reference position was used. Also, for crack resistance and erosion resistance, evaluation was carried out by the method described above. As the test piece for evaluating crack resistance, a test piece in which a plurality of carbon fiber bundles were embedded in parallel at equal intervals along the longitudinal direction inside the refractory body was used. As the test piece for evaluating erosion resistance, a test piece in which a plurality of carbon fiber bundles were embedded in parallel at equal intervals perpendicular to the surface (operating surface x of the refractory) in contact with slag or molten steel was used.

[0045] Tables 3 to 9 show the compositions and properties (bending strength, breaking energy, erosion resistance, crack resistance) of the graphite-containing refractories (graphite-containing refractories with carbon fiber woven bundles B embedded inside the refractory body A) of the inventive examples and comparative examples. First, the example in Table 3 examined the influence of the adhesive component c contained within the carbon fiber bundle B and for adhering or closely attaching the carbon fiber bundle B to the refractory body A on the bending strength, breaking 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, and adhesives such as phenolic resins (solutions) and inorganic sols with different residual carbon rates were used. A plurality of carbon fiber bundles with adhesives infiltrated and adhered inside and outside the bundles to impart adhesiveness were embedded in parallel at 10-mm intervals inside a magnesia-carbon refractory (refractory body). At that time, the carbon fiber bundles were immersed in the adhesive (solution) in advance, and the carbon fiber bundles with the adhesive infiltrated and adhered inside and outside the bundles were embedded in the refractory body. When using two types of adhesives in combination, they were mixed and used. Also, in one of the comparative examples, a plurality of carbon fiber bundles without adhesives adhered were similarly embedded in the refractory body.

[0046] As shown in Invention Examples 1-1 to 1-10, when a carbon fiber bundle imparted with adhesiveness using a specific adhesive that satisfies the conditions of the present invention is embedded, high bending strength and fracture energy are obtained. Furthermore, as shown in Invention Examples 1-11 to 1-15, when a carbon fiber bundle imparted with adhesiveness using two types of adhesives is embedded, higher bending strength and fracture energy are obtained compared to the case where 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% by mass is used, a large amount of gas escapes from inside the refractory at high temperatures, and many defects such as pores are generated inside. Therefore, high bending strength, fracture energy, and crack resistance cannot be obtained.

[0047] Also, as shown in Comparative Example 1-2, when an adhesive (organic resin) with a residual carbon rate of more than 80% by mass is used, almost no gas escapes from inside the refractory at high temperatures, and the refractory becomes too dense. Therefore, 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 bundle at all, the adhesion between the refractory raw material and the carbon fiber bundle is not improved. Therefore, high bending strength, fracture energy, and crack resistance cannot be obtained. From the above, it can be seen that by using an adhesive component c contained in the carbon fiber bundle B embedded inside the refractory body A and bonding or closely adhering the carbon fiber bundle B to the refractory body A, which is an organic substance and / or inorganic fine particles with a residual carbon rate of 6 to 80% by mass, a graphite-containing refractory having high bending strength, fracture energy, and crack resistance can be obtained.

[0048] The examples in Table 4 examined the effects of the width w, the length L of the carbon fibers constituting the carbon fiber bundle B, the fiber diameter, the number of carbon fibers per bundle, the existence density (embedding density) of the carbon fibers in the cross-section of the refractory parallel to the operating surface of the refractory, and also the occupation area ratio of the carbon fibers on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory for the carbon fiber bundle B embedded inside the refractory body A. In this example, the fiber diameter of the carbon fibers constituting the carbon fiber bundle B is set to 0.5 to 50 μm, and the number of carbon fibers per bundle of the carbon fiber bundle B is set to 900 to 350,000, so that the density of the carbon fibers and the occupied area ratio in the refractory cross-section parallel to the refractory working surface are different. A plurality of carbon fiber bundles B are embedded in parallel at 10 mm intervals inside a magnesia-carbon refractory (refractory body A). At that time, the carbon fiber bundle was previously immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass as an adhesive, and the carbon fiber bundle with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundle was embedded in the refractory body A. The maximum particle size of the aggregate (magnesia) constituting the refractory body A is 8 - 5 mm.

[0049] As shown in Invention Examples 1-4 and Invention Examples 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 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 working surface is 10 to 2,000 fibers / mm 2 and similarly, the occupied area ratio of the carbon fibers is 0.1 to 40%, and high flexural strength, fracture energy, and crack resistance are obtained.

[0050] On the other hand, as shown in Invention Example 2-0, when the fiber diameter of the carbon fibers constituting the carbon fiber bundle B is less than 1 μm and the number of carbon fibers per bundle of the carbon fiber bundle B is less than 1,000, the density of the carbon fibers (embedding density) in the refractory cross-section parallel to the refractory working surface is less than 10 fibers / mm 2 and similarly, the occupied area ratio of the carbon fibers is less than 0.1%, and the fracture energy is reduced compared to Invention Example 2-1. Also, as shown in Invention 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 per bundle of the carbon fiber bundle B exceeds 300,000, the density of the carbon fibers in the refractory cross-section parallel to the refractory working surface is 2,000 fibers / mm 2The same also applies to when the occupied area ratio of carbon fibers exceeds 40%, and the flexural strength and fracture energy decreased compared to Invention Examples 2-5. The reason for this is that since the carbon fiber bundles were too thick, the entanglement between the carbon fiber bundles and the refractory raw materials was poor, and springback was likely to occur during molding.

[0051] From the above, as the conditions for arranging the carbon fiber bundle B inside the refractory body A, the fiber diameter of the carbon fibers constituting the carbon fiber bundle B is 1 to 45 μm, the number of carbon fibers (pieces) per bundle of the carbon fiber bundle B is 1000 to 300000 pieces, and the density of the presence of carbon fibers in the refractory cross-section parallel to the refractory operating surface is 10 to 2000 pieces / mm 2 It is also preferable that the occupied area ratio of carbon fibers is 0.1 to 40%. As a result, the contact area between the refractory raw material (refractory body A) and the carbon fiber bundle B increases and the adhesion also increases. It can be seen that particularly high flexural strength, fracture energy, and crack resistance can be stably obtained.

[0052] The examples in Table 5 investigated the influence of the interval d (the distance between the carbon fiber bundles B) between the carbon fiber bundles B embedded inside the refractory body A on the flexural strength, fracture energy, and crack resistance of the graphite-containing refractory. In this example, the fiber diameter of the carbon fibers constituting the carbon fiber bundle B was 7 μm, the number of carbon fibers (pieces) per bundle of the carbon fiber bundle B was 75000 pieces, and a plurality of carbon fiber bundles B were embedded in parallel inside a magnesia-carbon refractory (refractory body) with an interval of 3 mm, 5 mm, 10 mm, 20 mm, and 30 mm between them. At that time, the carbon fiber bundles were immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass, which is an adhesive, and the carbon fiber bundles with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundles were embedded in the refractory body. The maximum particle size of the aggregate (magnesia) constituting the refractory body A is 8 - 5 mm.

[0053] As shown in Invention Examples 1-4 and Invention Examples 3-2 to 3-4, when the interval d (the distance between adjacent carbon fiber bundles) between adjacent carbon fiber bundles B exceeds 3 mm, the entanglement between the refractory raw material (refractory body A) and the carbon fiber bundle B is good, and high fracture energy is obtained. On the one hand, as shown in Invention Example 3-1, when the distance d between adjacent carbon fiber bundles B is 3 mm or less, the entanglement between the refractory raw material (refractory main body A) and the carbon fiber bundle B is poor, and the fracture energy and crack resistance decrease. From the above, it can be seen that for a plurality of carbon fiber bundles B arranged in parallel, if the distance between adjacent carbon fiber bundles B (the mutual distance between carbon fiber bundles B) is more than 3 mm, the entanglement between the refractory raw material (refractory main body A) and the carbon fiber bundle B is good and the fracture energy can be maintained high.

[0054] The same examination was also carried out on the graphite-containing refractory using alumina raw material, silicon carbide raw material, and silica raw material as aggregates for the inner lining of the hot metal pretreatment vessel. The examples in Table 6 examined the influence of the composition on the flexural strength, fracture energy, crack resistance, and corrosion resistance of the alumina-silica-silicon carbide-carbonaceous refractory (graphite-containing refractory using alumina raw material, silicon carbide raw material, and silica raw material as aggregates) used for the inner lining of the hot metal pretreatment vessel. In this example, the fiber diameter of the carbon fibers constituting the carbon fiber bundle B was 7 μm, the number of carbon fibers per bundle of the carbon fiber bundle B was 75,000, and a plurality of carbon fiber bundles B were buried in parallel at 10 mm intervals inside the alumina-silica-silicon carbide-carbonaceous refractory (refractory main body A). At that time, the carbon fiber bundle was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass as an adhesive in advance, and the carbon fiber bundle with the phenolic resin (resin solution) infiltrated and adhered to the inside and outside of the bundle was buried in the refractory main body. The maximum particle size of the aggregates (alumina raw material, silicon carbide raw material, silica raw material) constituting the refractory main body A is 8 - 5 mm.

[0055] As shown in Invention Examples 4-2 to 4-8, when the content of the alumina raw material is 10 - 95% by mass, the content of the silica raw material is 1 - 50% by mass, the content of the silicon carbide raw material is 1% by mass or more, and the graphite content is 1 - 80% by mass, high flexural strength, fracture energy, crack resistance, and corrosion resistance are obtained. On the other hand, as shown in Invention Example 4-1, when the content of the alumina raw material is less than 10% by mass, the content of the silica raw material is less than 1% by mass, the content of the silicon carbide raw material is less than 1% by mass, and the graphite content is more than 80% by mass, both the fracture energy and crack resistance and corrosion resistance decrease. Also, as shown in Invention Example 4-9, when the content of the alumina raw material is more than 95% by mass, the content of the silica raw material is less than 1% by mass, the content of the silicon carbide raw material is less than 1% by mass, and the graphite content is less than 1% by mass, the generation of cracks due to thermal spalling cannot be suppressed, and the fracture energy and crack resistance decrease. From the above, in alumina-silica-silicon carbide-carbon refractory materials, if the content of the alumina raw material is 10 to 95% by mass, the content of the silica raw material is 1 to 50% by mass, the content of the silicon carbide raw material is 1% by mass or more, and the graphite content is 1 to 80% by mass, it can be seen that high corrosion resistance and high fracture energy and crack resistance can be achieved simultaneously.

[0056] The examples in Table 7 are alumina-silica-silicon carbide-carbon refractory materials (graphite-containing refractories with alumina raw materials, silicon carbide raw materials, and silica raw materials as aggregates) used for the lining of a hot metal pretreatment vessel. Regarding graphite-containing refractories using refractory debris obtained by pulverizing used alumina-silica-silicon carbide-carbon refractory materials as part of the aggregate raw materials, the influence of the refractory debris content on the bending strength, fracture energy and crack resistance, and corrosion resistance of the graphite-containing refractories was investigated. In this example, the blending amount of refractory debris in the alumina-silica-silicon carbide-carbon refractory material was changed. The fiber diameter of the carbon fibers constituting the carbon fiber bundle B was 7 μm, and the number of carbon fibers per bundle of the carbon fiber bundle B (number) was 75,000. A plurality of carbon fiber bundles B were buried in parallel at 10 mm intervals inside the alumina-silica-silicon carbide-carbon refractory material (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% by mass, which is an adhesive, and the carbon fiber bundle with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundle was buried in the refractory body. The maximum particle size of the aggregates (alumina raw material, silicon carbide raw material, silica raw material) constituting the refractory body A is 8 - 5 mm.

[0057] As shown in Invention Examples 5-1 to 5-3, when the content of refractory waste is 10 to 90% by mass, the fracture energy, crack resistance, and corrosion resistance equivalent to those of the graphite-containing refractory using only the virgin raw materials shown in Table 6 are obtained. On the other hand, as shown in Invention Example 5-4, when the content of refractory waste exceeds 90% by mass, the fracture energy, crack resistance, and corrosion resistance decreased. From the above, regarding the graphite-containing refractory using refractory waste obtained by pulverizing used alumina-silicon carbide-carbonaceous refractory waste as the aggregate raw material, if the content of refractory waste is 10 to 90% by mass, the fracture energy can be maintained high, and furthermore, it can be seen that it has the same crack resistance and corrosion resistance as the graphite-containing refractory using only virgin raw materials.

[0058] The examples in Table 8 examined the influence of the composition of alumina-silicon carbide-carbonaceous refractory (graphite-containing refractory using alumina raw material and silicon carbide raw material as aggregates) on the flexural strength, fracture energy, crack resistance, and corrosion resistance of the graphite-containing refractory. In this example, the fiber diameter of the carbon fibers constituting the carbon fiber bundle B was 7 μm, and the number of carbon fibers per bundle of the carbon fiber bundle B was 75,000. A plurality of carbon fiber bundles B were embedded in parallel at 10 mm intervals inside an alumina-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% by mass, which is an adhesive, and the carbon fiber bundle with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundle was embedded in the refractory body. The maximum particle size of the aggregates (alumina raw material, silicon carbide raw material) constituting the refractory body A is 8 - 5 mm.

[0059] As shown in Invention Examples 6-2 to 6-4, when the content of the alumina raw material is 10 to 95% by mass and the content of graphite is 1 to 80% by mass, high flexural strength, fracture energy, crack resistance, and corrosion resistance are obtained. On the one hand, as shown in Invention Example 6-1, when the content of the alumina raw material is less than 10% by mass and the graphite content exceeds 80% by mass, the fracture energy, crack resistance, and corrosion resistance are reduced. Also, as shown in Invention Example 6-5, when the content of the alumina raw material exceeds 95% by mass and the graphite content is less than 1% by mass, the fracture energy and crack resistance are reduced. From the above, it can be seen that in alumina-silicon carbide-carbon refractories, when the content of the alumina raw material is 10 to 95% by mass and the graphite content is 1 to 80% by mass, high fracture energy, crack resistance, and corrosion resistance can be obtained.

[0060] The examples in Table 9 examined the influence of the composition of silica-silicon carbide-carbon refractories (graphite-containing refractories with silica raw materials and silicon carbide raw materials as aggregates) on the flexural strength, fracture energy, crack resistance, and corrosion resistance of the graphite-containing refractories. In this example, the fiber diameter of the carbon fibers constituting the carbon fiber bundle B was 7 μm, and the number of carbon fibers per bundle of the carbon fiber bundle B was 75,000. A plurality of carbon fiber bundles B were buried in parallel at 10 mm intervals inside a silica-silicon carbide-carbon 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% by mass, which is an adhesive, and the carbon fiber bundles with the phenolic resin (resin solution) penetrating and adhering inside and outside the bundles were buried in the refractory body. The maximum particle size of the aggregates (silica raw materials, silicon carbide raw materials) constituting the refractory body A is 8 - 5 mm.

[0061] As shown in Invention Examples 7-2 to 7-4, when the content of the silica raw material is 1 to 50% by mass and the graphite content is 1 to 80% by mass, high flexural strength, fracture energy, crack resistance, and corrosion resistance are obtained. On the one hand, as shown in Invention Example 7-1, when the content of the silica raw material is less than 1% by mass and the graphite content exceeds 80% by 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 exceeds 50% by 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 understood that in silica-silicon carbide-carbon refractories, when the content of the silica raw material is 1 to 50% by mass and the graphite content is 1 to 80% by mass, high flexural strength, fracture energy, crack resistance, and corrosion resistance can be obtained.

[0062]

Table 1

[0063]

Table 2

[0064]

Table 3-1

[0065]

Table 3-2

[0066]

Table 4

[0067]

Table 5

[0068]

Table 6

[0069]

Table 7

[0070]

Table 8

[0071]

Table 9

Explanation of Symbols

[0072] A Refractory Body B Carbon Fiber Bundle c Adhesive Component x Operating Surface y Non-operating Surface

Claims

1. A graphite-containing refractory in which carbon fiber bundles (B) (excluding carbon fiber bundles as part of a carbon fiber fabric) are arranged inside a refractory body (A), the carbon fiber bundles (B) contain an adhesive component (c) within the bundles and are adhered or closely attached to the refractory body (A) via the adhesive component (c), and the adhesive component (c) is an organic substance having a residual carbon ratio of 6 to 80% by mass, or a graphite-containing refractory characterized by being composed of an organic substance having a residual carbon ratio of 6 to 80% by mass and inorganic fine particles.

2. The organic substance that is the adhesive component (c) is one or more selected from organic resins, organic substances derived from tar or / and pitch, and organic substances derived from organic pastes, and the inorganic fine particles are inorganic fine particles derived from an inorganic sol. The graphite-containing refractory according to Claim 1, characterized in that.

3. The graphite-containing refractory according to Claim 1 or 2, characterized in that the width of the carbon fiber bundles (B) is 1 to 15 mm.

4. The carbon fiber bundles (B) are formed by bundling 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 1000 to 300000. The graphite-containing refractory according to any one of Claims 1 to 3, characterized in that.

5. A plurality of carbon fiber bundles (B) are arranged in parallel inside the refractory body (A), and the distance between adjacent carbon fiber bundles (B) is more than 3 mm. The graphite-containing refractory according to any one of Claims 1 to 4, characterized in that.

6. In a refractory cross-section parallel to the working surface of the graphite-containing refractory, the density of carbon fibers constituting the carbon fiber bundle (B) is 10 to 2,000 fibers / mm ２ The graphite-containing refractory according to any one of claims 1 to 5, characterized in that it is as described above.

7. The graphite-containing refractory according to any one of Claims 1 to 6, characterized in that the occupation area ratio of the carbon fibers constituting the carbon fiber bundles (B) in a refractory cross section parallel to the operating surface of the graphite-containing refractory is 0.1 to 40%.

8. The refractory body (A) contains 1 to 80% by mass of a graphite raw material. The graphite-containing refractory according to any one of Claims 1 to 7, characterized in that.

9. The refractory body (A) contains 20 to 99% by mass of a magnesia raw material. The graphite-containing refractory according to any one of Claims 1 to 8, characterized in that.

10. The refractory body (A) contains 10 to 95% by mass of an alumina raw material. The graphite-containing refractory according to any one of Claims 1 to 8, characterized in that.

11. The refractory body (A) contains 1 to 50% by mass of a silica raw material. The graphite-containing refractory according to any one of Claims 1 to 8, 10, characterized in that.

12. The refractory body (A) is a graphite-containing refractory according to claim 10 or 11, characterized by containing 1% by mass or more of a silicon carbide raw material. **Claim 13** The refractory body (A) is a graphite-containing refractory according to any one of claims 1 to 12, characterized by containing 10 to 90% by mass of refractory debris obtained by pulverizing used refractories.

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