Graphite-containing refractory

Abstract

To provide graphite-containing refractory having high durability by suppressing crack development caused by thermal stress, even when used in a condition of repeated heating up and cooling down over a long time, like the refractory liner of a converter, and having high durability, even when used in a condition of very large inner temperature gradient, particularly like tuyere bricks of the converter.SOLUTION: There is provided graphite-containing refractory in which carbon fiber fabric B is embedded along one direction, inside a refractory body A containing 1-80 mass% of graphite. The carbon fiber fabric B has mass of 40-1300 g per 1 m2, preferably, existing density of the carbon fiber forming the carbon fiber fabric B, in the refractory cross section parallel to a refractory work face, is 10-2000 pieces / mm2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a graphite-containing refractory having carbon fibers embedded therein.

Background Art

[0002] Facilities (such as refining vessels and transfer vessels) used in the pig iron making process and the steel making process in a steelworks are lined with refractories 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 and the like 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 impact by the charged material, wear due to stirring of molten steel and molten slag, slag erosion by molten slag, and rapid temperature changes during operation occur. Therefore, in order to perform stable operation, it is necessary to use refractories with high durability that can withstand such harsh conditions.

[0003] In particular, the tuyere bricks that make up the tuyere part of the 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 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 for each charge. Therefore, high durability that can withstand use under such conditions is required. Also, the refractory lining inside the converter other than the tuyere bricks (the bricks that make up the inner wall of the converter) is used under harsh conditions where the above-mentioned large thermal fluctuations are repeated. Although not as severe as the tuyere bricks, high durability is required.

[0004] As a technique for enhancing the durability of refractories, Patent Document 1 describes disposing a rod-shaped or net-shaped solidified body obtained by subjecting a high-strength fiber bundle impregnated with a synthetic resin, pitch, or the like to a curing treatment such as heat treatment inside the refractory. Since the solidified body of the high-strength fiber bundle is disposed inside the refractory without losing its shape, it is said that the mechanical strength and spalling resistance of the refractory can be enhanced. Further, Patent Document 2 describes adhering a unidirectional bundle or fabric made of fibers having a higher tensile strength than the refractory to a part or the whole of the surface of the refractory with a heat-resistant adhesive. By this technique, the refractory can be maintained at a high strength for a longer time than before, the tensile strength of the refractory can be improved, the occurrence of cracks and breakage can be suppressed, and the life and reliability of the refractory can be enhanced. Specifically, for nozzles through which molten steel flows inside, such as long nozzles, immersion nozzles, and sliding nozzles used in the continuous casting process of steel, a bundle or fabric of fibers is adhered with a phenolic resin in a direction to restrain the outer surface thereof, and an antioxidant base layer or antioxidant layer is disposed on the surface thereof. In these nozzles, when molten steel flows inside, the thermal expansion toward the outer surface side is restrained by the bundle or fabric of fibers, causing a compressive stress in the refractory constituting the nozzle and suppressing the occurrence of cracks and breakage.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, as a result of investigations by the inventors, it has been found that even when carbon fibers are disposed in a refractory in the forms shown in Patent Documents 1 and 2, the strength is insufficient for use as a refractory for a converter or the like exposed to severe conditions. In addition, since the technique described in Patent Document 1 involves disposing a rod-shaped or net-shaped solidified body obtained by solidifying a high-strength fiber bundle with resin, pitch, etc. inside a refractory, when the weight per unit area of the carbon fiber bundle is large, when molding or constructing the refractory raw material by compression molding or pouring, the solidified body becomes a resistance and uniform compression or inflow of the refractory raw material is hindered. As a result, there is a problem that the strength and fracture energy of the refractory decrease, and the durability of the refractory decreases.

[0007] In addition, in the continuous casting process in which the nozzle described in Patent Document 2 is used, since molten steel for a plurality of charges blown in a converter is continuously cast, the cycle of temperature change of the nozzle used is longer than that of the inner lining refractory of the converter. Also, since the outer surface of the nozzle receives radiation from the molten steel stored in the downstream container located below, the temperature difference from the molten steel flowing through the nozzle is not so large. On the other hand, the inner lining refractory of the converter (the bricks constituting the inner wall of the converter), particularly the tuyere bricks constituting the tuyere part, are used under extremely harsh conditions as described above. According to the study by the present inventors, it has been found that the technique described in Patent Document 2 cannot sufficiently enhance the durability of such refractories.

[0008] 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 like the inner lining refractory of a converter, the progress of cracks generated by thermal stress is suppressed and high durability is obtained. Also, to provide a graphite-containing refractory that can obtain high durability even when used under conditions where the internal temperature gradient is extremely large, particularly like the tuyere bricks of a converter.

Means for Solving the Problems

[0009] As a result of repeated studies to solve the above problems, the inventors of the present invention have found that by embedding a specific carbon fiber fabric in a predetermined form inside a refractory, preferably optimizing the fiber diameter and number of carbon fibers constituting the carbon fiber fabric, and further optimizing the density of carbon fibers present in the cross-section of the refractory, high durability can be obtained even in an extremely harsh use environment as described above. The present invention has been made based on such findings, and the gist thereof is as follows.

[0010] [1] A graphite-containing refractory in which a carbon fiber fabric (B) is embedded inside a refractory body (A) having a graphite content of 1 to 80% by mass, The carbon fiber fabric (B) is characterized in that the mass per 1 m 2 is 40 to 1300 g. [2] In the graphite-containing refractory of [1] above, the carbon fiber fabric (B) is a fabric in which carbon fiber bundles (b) are woven in two or more directions at intervals exceeding the maximum particle size of the aggregate constituting the refractory body (A), The carbon fiber bundle (b) is a bundle of carbon fibers having a fiber diameter of 1 to 45 μm, and the number of carbon fibers per bundle is 1000 to 300000, The density of carbon fibers constituting the carbon fiber fabric (B) in a cross-section of the refractory parallel to the operating surface of the refractory is 10 to 2000 fibers / mm 2 is characterized by being.

[0011] [3] In the graphite-containing refractory of [1] or [2] above, the carbon fiber fabric (B) is embedded inside the refractory body (A) along a direction perpendicular to the operating surface of the refractory. [4] In any of the graphite-containing refractories of [1] to [3] above, the carbon fiber fabric (B) is characterized in that the interval between carbon fiber bundles (b) woven in the same direction exceeds 3 mm. [5] In any of the graphite-containing refractories of [1] to [4] above, the carbon fiber fabric (B) is composed of one or two or more laminated fabrics. [6] In any of the graphite-containing refractories of [1] to [5] above, a carbon fiber fabric (B) is embedded in one layer or two or more layers with intervals inside the refractory body (A), and the graphite-containing refractory is characterized by this.

[0012] [7] In the graphite-containing refractory of [6] above, the interval between two or more carbon fiber fabrics (B) embedded inside the refractory body (A) is 10 mm or more, and the graphite-containing refractory is characterized by this. [8] In any of the graphite-containing refractories of [1] to [7] above, the carbon fiber fabric (B) is in close contact with the refractory body (A) via an adhesive component, and the adhesive component is one or more selected from organic resins, inorganic fine particles derived from inorganic sols, organic substances derived from tar or / and pitch, and organic substances derived from organic pastes, and the graphite-containing refractory is characterized by this.

[0013] [9] In any of the graphite-containing refractories of [1] to [8] above, the refractory body (A) contains 20 to 99% by mass of a magnesia raw material with a magnesia concentration of 90% by mass or more, and the graphite-containing refractory is characterized by this.

[10] In any of the graphite-containing refractories of [1] to [8] above, the refractory body (A) contains 10 to 95% by mass of an alumina raw material with an alumina concentration of 70% by mass or more, and the graphite-containing refractory is characterized by this.

[11] In any of the graphite-containing refractories of [1] to [8],

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

[12] In the graphite-containing refractory of

[10] or

[11] above, the refractory body (A) contains 1% by mass or more of a silicon carbide raw material with a silicon carbide concentration of 80% by mass or more, and the graphite-containing refractory is characterized by this.

[13] In any of the graphite-containing refractories of [1] to

[12] above, the refractory body (A) contains 10 to 90% by mass of refractory debris obtained by pulverizing used refractories, and the graphite-containing refractory is characterized by this. [Effects 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 extremely large, such as the tuyere bricks of a converter.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5-1

Figure 5-2

Figure 6

Embodiments for Carrying Out the Invention

[0016] The graphite-containing refractory of the present invention is a graphite-containing refractory in which a carbon fiber fabric B is embedded inside a refractory body A having a graphite content of 1 to 80% by mass. The carbon fiber fabric B is 1 m 2 The mass per unit area is characterized by being 40 to 1300 g. By embedding such a carbon fiber fabric B inside the refractory body A, the carbon fiber fabric B is integrated with the refractory, so that the carbon fiber fabric B does not slip inside the refractory body A. Therefore, the fracture energy of the entire refractory is significantly increased, and the crack propagation suppression effect is also improved.

[0017] FIG. 1 schematically shows an embodiment of the graphite-containing refractory of the present invention. FIG. 1(a) is a side view, and FIG. 1(b) is a cross-sectional view taken along line II in FIG. 1(a) (a cross-sectional view parallel to the refractory operating surface), where x is the refractory operating surface (y is the non-operating surface). In the graphite-containing refractory of this embodiment, three layers of carbon fiber fabrics B are embedded inside the refractory body A at intervals. Further, FIG. 2 is a plan view schematically showing an embodiment of the carbon fiber fabric B embedded inside the refractory body A. The carbon fiber fabric B of this embodiment is formed by weaving carbon fiber bundles b in two directions (two orthogonal directions).

[0018] Hereinafter, the configuration and embedding conditions of the carbon fiber fabric B will be described. The carbon fiber fabric B is formed by weaving carbon fiber bundles b in two or more directions, and the number of orientations is arbitrary. Note that when the orientation direction of the carbon fiber bundle b is one direction, a carbon fiber fabric cannot be formed, and thus a graphite-containing refractory in which the carbon fiber fabric is embedded cannot be obtained. The carbon fiber fabric B is 1 m 2 The mass per unit area is 40 to 1300 g. Here, the mass per unit area means, as will be described later, the total mass of a plurality of laminated fabrics when the carbon fiber fabric B is composed of a plurality of laminated fabrics. The 1 m 2 The mass per unit area is the total mass of the plurality of laminated fabrics. The 1 m 2When the mass per unit area is less than 40 g, the carbon fiber fabric is too thin, so the effect of suppressing crack propagation does not improve and the fracture energy does not increase. On the other hand, when the mass per unit area of carbon fiber fabric B exceeds 1300 g, the carbon fiber fabric is too thick, so when the refractory is compression-molded, a rebound after compression called springback occurs, or the transmission of the compression force becomes non-uniform, resulting in internal defects in the refractory or non-uniform properties, etc., and the durability decreases. Also, even when the refractory is molded by pouring instead of compression molding, uniform inflow is hindered, or voids contained or associated with the carbon fiber fabric remain, resulting in a decrease in durability. 2 When the mass per unit area exceeds 1300 g, the carbon fiber fabric is too thick, so when the refractory is compression-molded, a rebound after compression called springback occurs, or the transmission of the compression force becomes non-uniform, resulting in internal defects in the refractory or non-uniform properties, etc., and the durability decreases. Also, even when the refractory is molded by pouring instead of compression molding, uniform inflow is hindered, or voids contained or associated with the carbon fiber fabric remain, resulting in a decrease in durability.

[0019] The arrangement form of the carbon fiber fabric B inside the refractory body A is arbitrary and there is no special restriction. 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. Note that the end of the carbon fiber fabric 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, the distance between the end of the carbon fiber fabric B and the operating surface x is preferably as small as possible. However, on the non-operating surface y side, the distance between the end of the carbon fiber fabric B and the non-operating surface y may be relatively large. This is because there is no need to embed the carbon fiber fabric 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.

[0020] Among the carbon fiber bundles b that make up the carbon fiber fabric B, the interval between the carbon fiber bundles b woven in the same direction is preferably larger than the maximum particle size of the aggregate (coarse particles called aggregate among the refractory raw materials) that makes up the refractory body A. That is, the carbon fiber bundles b in the same direction are preferably woven at an interval exceeding the maximum particle size of the aggregate that makes up the refractory body A. Thereby, the aggregate (coarse particles) can enter between the stitches of the carbon fiber fabric b, and the progress of cracks generated along the surface of the aggregate (coarse particles) can be suppressed.

[0021] The carbon fiber bundles b that make up the carbon fiber fabric B are formed by bundling carbon fibers with a fiber diameter of 1 to 45 μm, and preferably the number of carbon fibers per bundle is 1000 to 300000. If the fiber diameter of the carbon fibers that make up the carbon fiber fabric B (carbon fiber bundles b) is 1 μm or more and the number of carbon fibers per bundle of the carbon fiber bundles b is 1000 or more, a higher crack propagation suppression effect can be obtained. On the other hand, if the fiber diameter of the carbon fibers that make up the carbon fiber fabric B (carbon fiber bundles b) is 45 μm or less and the number of carbon fibers per bundle of the carbon fiber bundles b is 300000 or less, non-uniformity during molding can be suppressed and durability can be improved. Also, if the fiber diameter of the carbon fibers that make up the carbon fiber bundles b is less than 1 μm and the number of carbon fibers per bundle of the carbon fiber bundles b is less than 1000, the mass per 1 m of the carbon fiber fabric B 2 tends to be less than 40 g. On the other hand, if the fiber diameter of the carbon fibers that make up the carbon fiber bundles b is more than 45 μm and the number of carbon fibers per bundle of the carbon fiber bundles b is more than 300000, the mass per 1 m of the carbon fiber fabric B 2 tends to be more than 1300 g.

[0022] Also, the carbon fiber fabric B is preferably embedded inside the refractory body A such that the density (embedded density) of the carbon fibers that make up the carbon fiber fabric B in the refractory cross-section parallel to the refractory working surface x is 10 to 2000 fibers / mm 2 . As a result, the contact area between the refractory raw material and the carbon fiber bundles b that make up the carbon fiber fabric B increases, and the adhesion between the refractory raw material and the carbon fiber fabric B also increases, so the fracture energy increases significantly. Here, the density (embedded density) of the carbon fibers is the total number of carbon fibers (pieces) that make up the carbon fiber bundles b excluding the carbon fiber bundles b parallel to the refractory working surface among the carbon fiber bundles b that make up the carbon fiber fabric B, divided by the area (mm 2 ) of the refractory cross-section parallel to the refractory working surface. The density (embedded density) of the carbon fibers is 10 fibers / mm 2If it is less than that, since the contact area between the refractory raw material and the carbon fiber bundle b is too small, the adhesion between the refractory raw material and the carbon fiber fabric B does not increase either, and a significant increase in fracture energy cannot be expected. Also, when the density of the carbon fibers (embedded density) is more than 2000 fibers / mm 2 If it is more than 2 , since the contact area between the refractory raw material and the carbon fiber bundle b is too large, the carbon fiber bundle b is likely to cause springback during molding, which may hinder the molding.

[0023] The carbon fiber fabric B preferably has a distance of more than 3 mm between the carbon fiber bundles b woven in the same direction. Thereby, not only the coarse particles but also the fine particles as described above are well entangled with the carbon fiber fabric B, and the bending strength and the fracture energy can be made higher. Here, the distance between the carbon fiber bundles b is the distances L1 and L2 between the centers of the carbon fiber bundles b shown in FIG. 2. When the distance varies depending on the direction, it is desirable that the shorter distance is more than 3 mm. The carbon fiber fabric B is composed of one or two or more laminated fabrics, and the number of fabrics in the case of using two or more laminated fabrics of the carbon fiber fabric B is arbitrary. Also, the carbon fiber fabric B can be embedded in one layer or two or more layers with an interval inside the refractory body A, and the number of layers in the case of embedding two or more layers is arbitrary. By increasing the number of fabrics per layer of the carbon fiber fabric B or increasing the number of layers of the carbon fiber fabric B, the effect of suppressing the progress of cracks in the refractory is further improved. Also, when two or more layers of the carbon fiber fabric B are embedded inside the refractory body A, if the distance between the layers of the carbon fiber fabric B is too narrow, the carbon fiber bundles b constituting the carbon fiber fabric B cause springback during molding, and cracks are likely to occur in the molded body. Therefore, in order to suppress the springback of the carbon fiber bundles b, the distance between the layers of the carbon fiber fabric B is preferably 10 mm or more.

[0024] The carbon fiber fabric B is preferably adhered to the refractory body A via an adhesive (adhesion - imparting agent) component. By doing so, the adhesion between the refractory raw material A and the carbon fiber fabric B is enhanced, the refractory is easily densified during forming, and the fracture energy is significantly improved. Examples of the adhesive component (solid component) interposed between the carbon fiber fabric B and the refractory body A include organic resins, inorganic fine particles derived from inorganic sols, organic substances derived from tar or / and pitch, and organic substances derived from organic pastes. One or more of these can be selected therefrom. Therefore, examples of the adhesive (adhesion - imparting agent) to be adhered to the carbon fiber fabric during manufacturing include organic resins (solutions), inorganic sols, pitch, tar, organic pastes, etc. Specifically, phenolic resins, epoxy resins, melamine resins, urea resins, alkyd resins, unsaturated polyester resins, polyurethane resins, thermosetting polyimide resins, alumina sols, silica sols, zirconia sols, chromia sols, titania sols, magnesia sols, calcia sols, yttria sols, pitch, tar, starch paste, etc. can be mentioned, and one or more selected from these can be used.

[0025] Next, the composition of the refractory body A will be described. The graphite content of the refractory body A is 1 - 80 mass%. If the graphite content is less than 1 mass%, the generation of cracks due to thermal stress cannot be suppressed, and the crack resistance is significantly reduced. On the other hand, if the graphite content exceeds 80 mass%, depending on the material of the refractory body A, properties such as corrosion resistance, crack resistance, and fracture energy may be adversely affected. Generally, flake graphite etc. is used as the graphite (carbon raw material). Generally, magnesia-carbon refractories (graphite-containing refractories with magnesia raw materials as aggregates), which are refractories mainly composed of magnesia and carbon, are used for the lining (including the tuyere part) of converters used in the refining process. When the refractory body A is a magnesia-carbon refractory, the refractory body A preferably contains 20 to 99% by mass of a high-purity magnesia raw material with a magnesia concentration of 90% by mass or more. Thereby, cracking due to thermal spalling can be suppressed, and a refractory that can withstand the erosion of converter slag can be obtained. If the content of the magnesia raw material exceeds 99% by mass, cracking cannot be suppressed and the crack resistance is significantly reduced. On the other hand, if the content of the magnesia raw material is less than 20% by mass, it cannot withstand the erosion of converter slag, and the corrosion resistance is significantly reduced.

[0026] Also, generally, for the lining of torpedo ladles and blast furnace pots used in the hot metal pretreatment process, alumina-silicon carbide-carbon refractories (graphite-containing refractories with alumina raw materials and silicon carbide raw materials as aggregates), which are refractories mainly composed of alumina, silicon carbide, and carbon, and alumina-silicon carbide-silica-carbon refractories (graphite-containing refractories with alumina raw materials, silicon carbide raw materials, and silica raw materials as aggregates), which are refractories mainly composed of alumina, silicon carbide, silica, and carbon, etc. are used. When the refractory body A is an alumina-silicon carbide-carbon refractory or an alumina-silicon carbide-silica-carbon refractory, it preferably contains 10 to 95% by mass of a high-purity alumina raw material with an alumina concentration of 70% by mass or more. Thereby, it can withstand the erosion of hot metal pretreatment slag, and cracking due to thermal spalling can also be suppressed. If the content of the alumina raw material is less than 10% by mass, it cannot withstand the erosion of hot metal pretreatment slag, the slag penetrates into the matrix part of the refractory body A (brick), and the corrosion resistance decreases. On the other hand, if the content of the alumina raw material exceeds 95% by mass, the generation of cracks due to thermal spalling cannot be suppressed, and the crack resistance decreases.

[0027] Furthermore, when the refractory body A is an alumina-silicon carbide-carbon refractory or an alumina-silicon carbide-silica-carbon refractory, it is preferable to contain 1% by mass or more of a high-purity silicon carbide raw material having a silicon carbide concentration of 80% by mass or more. 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. When the content of the silicon carbide raw material is less than 1% by mass, oxidation of graphite in an air atmosphere cannot be suppressed, resulting in a decrease in crack resistance. Also, when the refractory body A is an alumina-silicon carbide-silica-carbon refractory, it is preferable to contain 1 to 50% by mass of a silica raw material, whereby both high crack resistance and high corrosion resistance can be achieved. When the content of the silica raw material is less than 1% by mass, the amount of expansion is small and no fine cracks are generated, so the thermal shock fracture resistance does not increase and the crack resistance is likely to decrease. On the other hand, when the content of the silica raw material exceeds 50% by mass, the corrosion resistance is significantly deteriorated.

[0028] The magnesia-carbon refractory used for the lining of a converter is used under very severe 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 severe conditions. Similarly, since the alumina-silicon carbide-carbon refractory and the alumina-silicon carbide-silica-carbon refractory used for the lining of hot metal pretreatment vessels such as torpedo cars and blast furnace ladles are also used under very severe conditions, it is preferable to use a refractory that can withstand these conditions. According to the present invention, since the fracture energy of the graphite-containing refractory used under these very severe conditions is significantly improved compared with that of the conventional graphite-containing refractory, high durability can be obtained.

[0029] In addition, 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 high-purity silicon carbide raw material having a silicon carbide concentration of 80% by mass or more and 1 to 50% by mass of a silica raw material. This makes it possible to achieve both high crack resistance and high corrosion resistance. By containing 1% by mass or more of the silicon carbide raw material, oxidation of graphite in an air atmosphere can be suppressed, so high crack resistance can be maintained. If the content of the silicon carbide raw material is less than 1% by mass, oxidation of graphite in an air atmosphere cannot be suppressed, so the crack resistance decreases. Also, if the content of the silica raw material is less than 1% by mass, the amount of expansion is small and fine cracks are not generated, so the thermal shock fracture resistance does not increase and the crack resistance tends to decrease. On the other hand, if the content of the silica raw material exceeds 50% by mass, the corrosion resistance deteriorates significantly.

[0030] Here, as the alumina raw material, for example, one or more of bauxite shale, white alumina, brown alumina, etc. are used. Also, as the silicon carbide raw material, for example, one or more of green silicon carbide, black silicon carbide, etc. are used. Also, 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 container. Examples of the metal powder raw material include metal Si, metal Al, metal 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 and the bricks are likely to break, and the number of times of use in an actual machine may decrease.

[0031] The refractory body A can contain about 10 to 90% by mass of refractory debris 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 as well; the same applies hereinafter), refractory debris obtained by pulverizing used alumina-silicon carbide-carbon refractories (including the case of an alumina-silicon carbide-silica-carbon refractory containing a silica raw material as well; the same applies hereinafter) can be suitably used as the aggregate raw material. When containing refractory debris in this way, the remainder of the refractory raw material is unused raw material (virgin raw material).

[0032] In the refractory body A made of an alumina-silicon carbide-carbon refractory, when the content of refractory debris obtained by pulverizing used alumina-silicon carbide-carbon refractories is 10 to 90% by mass, crack resistance and corrosion resistance similar to those of a graphite-containing refractory using only virgin raw materials can be obtained. The reason is that although the purity of the refractory debris raw material is lower than that of the virgin raw material, by using the refractory debris raw material and the virgin raw material together, a significant decrease in the corrosion resistance of the Al2O3 component in the refractory debris raw material can be suppressed. On the other hand, when the content of refractory debris exceeds 90% by mass, since the content of the 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% by mass, since the recycling rate of refractory debris is too low, the treatment cost of refractory debris as industrial waste increases significantly. The graphite-containing refractory of the present invention includes, in addition to the so-called refractory bricks manufactured through press molding, refractories that are molded by pouring at the construction site, which is the operating surface such as pots and tundishes, and then dried and solidified as they are, as will be described later.

[0033] Next, the manufacturing method of the graphite-containing refractory of the present invention will be described. Figure 3 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 fabric and press-molded 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 mold with the kneaded material of the refractory raw material together with the carbon fiber fabric, for example, there is a method in which a certain amount of the kneaded material is charged into the mold, then the carbon fiber fabric is charged, and further 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 layers of carbon fiber fabric as shown in FIG. 1 are embedded by this method, after charging a certain amount of the kneaded material into the mold, the charging of the carbon fiber fabric and the subsequent charging of a certain amount of the kneaded material are repeated. When an adhesive (adhesiveness-imparting agent) is attached to the carbon fiber fabric, for example, the carbon fiber fabric is immersed in a resin (resin solution) or sol that constitutes the adhesive, or the resin (resin solution) or sol that constitutes the adhesive is sprayed onto the carbon fiber fabric, so that the adhesive is attached to the carbon fiber fabric, and the carbon fiber fabric with the adhesive attached is filled into the mold together with the kneaded material in the above-described manner.

[0034] For the press molding, general mold press molding that compresses in one direction in the mold can be performed, but CIP molding that applies pressure evenly from all directions using a liquid may also be performed. For a shape in which it is difficult to apply uniform pressure by one-way compression, such as a shape with different thicknesses depending on the part, it is desirable to use CIP molding because the deviation in the degree of compression due to the part is reduced. In addition, the shaping process may be carried out by a shaping method other than press shaping. Examples of shaping methods other than press shaping include, for example, casting. One such method is to install an inner frame at the construction site, which is the working surface such as a pot or tundish, pour the amorphous refractory (refractory raw material) into this inner frame, and after drying (drying process) and solidifying, remove the inner frame. Also, instead of pouring it into the construction site, there is a method of pouring the amorphous refractory (refractory raw material) into a refractory-shaped mold, drying (drying process) and solidifying it, and then transporting the refractory removed from the mold 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 the carbon fiber fabric when pouring the amorphous refractory into the mold and to control the temperature during solidification. In these casting shaping methods, after arranging the carbon fiber fabric B in the above-mentioned inner frame or mold, pour the amorphous refractory (refractory raw material) into the inner frame or mold, and dry (drying process) and solidify it.

[0035] 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. Further, after drying (curing), reduction firing (coking treatment) may be performed to obtain product bricks (fired bricks). Regarding the refractory formed body obtained by casting as described above, the refractory formed body held by 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.

[0036] Thus, the graphite-containing refractory of the present invention in which the carbon fiber fabric is embedded inside the refractory body is obtained. The graphite-containing refractory of the present invention can be used as a refractory for various equipment and containers, and is particularly suitable as a lining refractory for refining containers and transport containers used in steelworks. In particular, it is particularly suitable as a lining refractory for a converter, which has a very severe use environment, and among them, it is particularly suitable as a tuyere brick that constitutes the tuyere part.

Example

[0037] A graphite-containing refractory with a carbon fiber fabric embedded inside the refractory body was manufactured by the procedure shown in Fig. 3. 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 manufactured graphite-containing refractory, the flexural strength, fracture energy, corrosion resistance, and crack resistance were evaluated by the following methods, respectively. Regarding the flexural strength, as shown in Fig. 4 (test method), using a test piece (test piece size: 40 mm × 80 mm × 160 mm) with a single layer or multiple layers of carbon fiber fabric embedded inside the refractory body along its longitudinal direction, with a center-to-center distance of 100 mm and a load application acceleration of 0.5 mm / min, it was measured in accordance with the three-point bending test method described in JIS R2213.

[0038] Regarding the fracture energy, as shown in Fig. 5-1 and Fig. 5-2, in the load-displacement curve obtained from the three-point bending strength test, based on the position showing the first peak value, it was evaluated by the area in the range of 1 mm displacement from the reference position. Fig. 5-1 shows an example of the fracture energy obtained from the load-displacement curve of the present invention example, and Fig. 5-2 shows an example of the fracture energy obtained from the load-displacement curve of a comparative example in which no carbon fiber fabric is embedded inside, respectively. Regarding the corrosion resistance, as shown in Fig. 6 (test method), the amount of corrosion was measured by the inner-lining partition method using a high-frequency induction furnace and evaluated based on the amount of corrosion. In the test by the inner-lining 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 amount of corrosion on the working surface was measured. Then, from the amount of corrosion, a corrosion index was obtained with the amount of corrosion of Invention Blending Examples 1-3 in Table 1 taken as 100. As the test piece, as shown in Fig. 6(C), a test piece with a carbon fiber fabric embedded perpendicular to the surface (refractory working surface) in contact with slag and molten steel was used. Fig. 6(A) is an explanatory diagram schematically showing the test implementation situation in a state where the test furnace and the cylindrical sample are longitudinally sectioned, Fig. 6(B) is a plan view of the cylindrical sample shown in Fig. 6(A), and Fig. 6(C) is a perspective view showing one of the test pieces constituting the cylindrical sample shown in Fig. 6(A) and (B).

[0039] Regarding the crack resistance, after measuring the longitudinal dynamic elastic modulus E0 of a 40×80×200 mm sample according to the ultrasonic pulse method shown in JIS R1605, a process of heating at 1500 °C for 10 minutes, water cooling for 5 minutes, and air cooling for 10 minutes was repeated three times as one cycle. After three 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. As the test piece, a refractory body with a carbon fiber fabric embedded along the longitudinal direction as shown in Fig. 1 was used.

[0040] Refractory products using magnesia raw materials as aggregates with the raw material formulations shown in Table 1, that is, graphite-containing refractories without embedded carbon fiber fabrics, were fabricated, and their corrosion resistance and crack resistance were evaluated. The results are shown together in Table 1. As shown in Invention Formulation Examples 1-1 to 1-7 in Table 1, when the graphite content is 1 to 80 mass%, the corrosion resistance and crack resistance are good. However, as shown in Comparative Formulation Example 1-1, when the graphite content is less than 1 mass%, the crack resistance is significantly reduced. Also, as shown in Comparative Formulation Example 1-2, when the graphite content exceeds 80 mass%, the corrosion resistance is significantly reduced. Also, as shown in Invention Formulation Examples 1-1 to 1-7, in the formulation of magnesia-carbonaceous raw materials, if the content of magnesia raw materials (magnesia concentration of 100 mass% in the case of Table 1) is 20 to 99 mass%, the corrosion resistance and crack resistance are good. From the above, in order to achieve both corrosion resistance and crack resistance of graphite-containing refractories, the graphite content needs to be 1 to 80 mass%, and in the case of magnesia-carbonaceous raw materials, it can be seen that it is appropriate to set the content of magnesia raw materials to 20 to 99 mass%.

[0041] Tables 3 to 11 show the compositions and properties (bending strength, fracture energy, corrosion resistance, crack resistance) of the graphite-containing refractories (graphite-containing refractories with carbon fiber fabrics embedded inside the refractory body) of the invention examples and comparative examples. First, in the examples of Table 3, regarding the carbon fiber fabric embedded inside the refractory body, the fiber diameter of the carbon fibers constituting the carbon fiber bundle, the number of carbon fibers per bundle of the carbon fiber bundle (number), the mass per 1 m 2 of the carbon fiber fabric, and the presence density (embedding density) of the carbon fibers in the refractory cross-section parallel to the refractory working surface were investigated for their effects on the flexural strength, fracture energy, and crack resistance of the graphite-containing refractory.

[0042] In this example, by setting the fiber diameter of the carbon fibers constituting the carbon fiber bundle to 0.5 to 50 μm and the number of carbon fibers per bundle of the carbon fiber bundle (number) to 900 to 350,000, carbon fiber fabrics with different masses per 1 m 2 were prepared, and these were embedded inside a magnesia-carbon refractory (refractory body) so that the presence density of the carbon fibers in the refractory cross-section parallel to the refractory working surface was different. As the magnesia-carbon refractory, one having the composition of Invention Formulation Examples 1 - 3 in Table 1 was used. The number of embedded layers of the carbon fiber fabric was 1 layer, and it was composed of a single fabric. Also, the carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric with this phenolic resin (resin solution) attached was embedded in the refractory body. The maximum particle size of the aggregate (magnesia) constituting the refractory body is less than 5 mm. As shown in Invention Examples 2 - 1 to Invention Examples 2 - 7, when the fiber diameter of the carbon fibers constituting the carbon fiber bundle is 1 to 45 μm and the number of carbon fibers per bundle of the carbon fiber bundle (number) is 1000 to 300,000, the mass per 1 m 2 of the carbon fiber fabric is 40 to 1300 g, and the presence density of the carbon fibers in the refractory cross-section parallel to the refractory working surface is 10 to 2000 fibers / mm 2 resulting in high flexural strength, fracture energy, and crack resistance.

[0043] On the other hand, as shown in Comparative Example 2 - 1, when the fiber diameter of the carbon fibers constituting the carbon fiber bundle is less than 1 μm and the number of carbon fibers per bundle of the carbon fiber bundle (number) is less than 1000, the mass per 1 m 2 of the carbon fiber fabric is less than 40 g, and the presence density (embedding density) of the carbon fibers in the refractory cross-section parallel to the refractory working surface is 10 fibers / mm2 It becomes less than, and since the carbon fiber fabric is too thin, high bending strength, fracture energy, and crack resistance cannot be obtained. Also, as shown in Comparative Example 2-2, when the fiber diameter of the carbon fibers constituting the carbon fiber bundle exceeds 45 μm and the number of carbon fibers (number) per bundle of the carbon fiber bundle exceeds 300,000, 1 m of the carbon fiber fabric 2 The mass per is more than 1300 g, and the density of carbon fibers in the refractory cross-section parallel to the operating surface of the refractory exceeds 2000 fibers / mm 2 exceeds, and when molding the refractory raw material (magnesia-carbon raw material) with the carbon fiber fabric embedded, cracks occurred on the side surface of the molded body and the carbon fiber fabric protruded, making molding difficult. As this factor, since the carbon fiber bundles constituting the carbon fiber fabric were too thick, the carbon fiber fabric became thick, the entanglement between the carbon fiber fabric and the refractory raw material was poor, and springback was likely to occur during molding. Furthermore, as shown in Comparative Example 2-3, since the carbon fiber fabric could not be formed only by orienting the carbon fiber bundles in one direction, it was impossible to manufacture a graphite-containing refractory with the carbon fiber fabric embedded.

[0044] From the above, the mass per 1 m of the carbon fiber fabric embedded in the refractory body 2 is set to 40 to 1300 g, and the density of carbon fibers in the refractory cross-section parallel to the operating surface of the refractory is set to 10 to 2000 fibers / mm 2 It can be seen that by doing so, a graphite-containing refractory that can be molded and has high bending strength, fracture energy, and crack resistance can be obtained. Also, in order to make the mass per 1 m of the carbon fiber fabric 2 40 to 1300 g, it can be seen that it is preferable to set the fiber diameter of the carbon fibers constituting the carbon fiber bundle to 1 to 45 μm and the number of carbon fibers (number) per bundle of the carbon fiber bundle to 1000 to 300,000.

[0045] The examples in Table 4 examined the influence of the interval between the carbon fiber bundles constituting the carbon fiber fabric (the interval between the carbon fiber bundles woven in the same direction) on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory. In this example, a carbon fiber bundle with a fiber diameter of 7 μm and 75,000 carbon fibers per bundle was woven at intervals of 3 mm, 5 mm, 10 mm, 20 mm, and 30 mm, respectively, in a 1 m 2 carbon fiber fabric with a mass of 110 - 1120 g per square meter was prepared. This was embedded inside a magnesia-carbon refractory (refractory body) so that the density of carbon fibers in the refractory cross-section parallel to the working surface of the refractory was 200 - 2000 fibers / mm 2 Two. A magnesia-carbon refractory having the composition of Invention Formulation Examples 1 - 3 in Table 1 was used. The number of embedded layers of the carbon fiber fabric was one layer, which was composed of a single fabric. The carbon fiber fabric was previously immersed in a phenolic resin (resin solution) as an adhesive, and the carbon fiber fabric adhered with this phenolic resin (resin solution) was embedded in the refractory body. The maximum particle size of the aggregate (magnesia) constituting the refractory body is less than 5 mm.

[0046] As shown in Invention Examples 2 - 4 and Invention Examples 3 - 2 to 3 - 4, when the interval (weaving interval) between the carbon fiber bundles constituting the carbon fiber fabric is more than 3 mm, the entanglement between the carbon fiber fabric and the refractory raw material (magnesia-carbon raw material) is good, and high bending strength, fracture energy, and crack resistance are obtained. On the other hand, as shown in Invention Example 3 - 1, when the interval (weaving interval) between the carbon fiber bundles constituting the carbon fiber fabric is 3 mm or less, the entanglement between the carbon fiber fabric and the refractory raw material is poor, and the bending strength, fracture energy, and crack resistance are lower than those of Invention Examples 3 - 2 to 3 - 4. From the above, it was found that if the interval (weaving interval) between the carbon fiber bundles constituting the carbon fiber fabric is more than 3 mm, the entanglement between the carbon fiber fabric and the refractory raw material is good, and a graphite-containing refractory having high bending strength, fracture energy, and crack resistance can be obtained.

[0047] The examples in Table 5 investigated the effect of pre-treating the carbon fiber fabric with an adhesive on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory. In this example, a carbon fiber fabric with a fiber diameter of 7 μm for carbon fibers and 75,000 carbon fibers per bundle was woven at intervals of 10 mm, and the mass per 1 m 2 was 335 g. This carbon fiber fabric was immersed in various adhesives (solutions), and the carbon fiber fabric with the adhesive (solution) attached was embedded inside a magnesia-carbon refractory (refractory body) so that the density of carbon fibers in the refractory cross-section parallel to the operating surface of the refractory was 610 fibers / mm 2 . In some inventive examples, the carbon fiber fabric was embedded inside the magnesia-carbon refractory (refractory body) at the same density as above without attaching an adhesive (solution). As the magnesia-carbon refractory, those having the compositions of Inventive Formulation Examples 1-3 in Table 1 were used. The number of embedded layers of the carbon fiber fabric was one layer, and it was composed of a single fabric. The maximum particle size of the aggregate (magnesia) constituting the refractory body was less than 5 mm.

[0048] As shown in Inventive Examples 2-4 and Inventive Examples 4-1 to 4-10, when a carbon fiber fabric with an adhesive attached was embedded, the adhesion between carbon fibers and the adhesion between the carbon fiber fabric and the refractory raw material were improved. Therefore, the bending strength, fracture energy, and crack resistance were higher compared to the case where no adhesive was attached to the carbon fiber fabric as shown in Inventive Example 4-11. Also, as shown in Inventive Examples 4-6 to 4-10, when a carbon fiber fabric with two types of adhesives attached was embedded, the adhesion was further improved, and particularly high bending strength, fracture energy, and crack resistance were obtained. From the above, it was found that when a carbon fiber fabric with an adhesive such as a phenolic resin attached was embedded in a refractory body, a graphite-containing refractory having high bending strength, fracture energy, and crack resistance could be obtained.

[0049] The examples in Table 6 examined the effects of the number of fabric sheets per layer of the carbon fiber fabric and the number of embedded layers of the carbon fiber fabric on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory. In this example, a carbon fiber fabric with a fiber diameter of 7 μm and 75,000 carbon fibers per bundle was woven at intervals of 10 mm, and the mass per 1 m 2 was 335 - 1050 g. This fabric was used, and it was embedded inside a magnesia - carbon refractory (refractory body) such that the density of carbon fibers in the refractory cross - section parallel to the working surface of the refractory was 610 - 1900 fibers / mm 2 by changing the number of fabric layers per layer of the carbon fiber fabric and the number of embedded layers of the carbon fiber fabric. The magnesia - carbon refractory used had the composition of Invention Formulation Examples 1 - 3 in Table 1. The carbon fiber fabric was previously immersed in a phenolic resin (resin solution) as an adhesive, and the carbon fiber fabric with the attached phenolic resin (resin solution) was embedded in the refractory body. The maximum particle size of the aggregate (magnesia) constituting the refractory body was less than 5 mm.

[0050] As shown in Invention Examples 2 - 4 and Invention Examples 5 - 1 to 5 - 4, regardless of the number of fabric layers per layer of the carbon fiber fabric and the number of embedded layers of the carbon fiber fabric, high flexural strength, fracture energy, and crack resistance are obtained. However, the higher the number of fabric layers per layer of the carbon fiber fabric and the number of embedded layers of the carbon fiber fabric, the slightly higher the flexural strength, fracture energy, and crack resistance. From the above, it was found that if the number of fabric layers per layer of the carbon fiber fabric is 1 or more and the carbon fiber fabric is embedded in 1 or more layers, a graphite - containing refractory with high flexural strength, fracture energy, and crack resistance can be obtained.

[0051] The examples in Table 7 investigated the influence of the interval (embedding interval) between layers of the carbon fiber fabric on the moldability of the graphite - containing refractory when two or more layers of carbon fiber fabric were embedded inside the refractory body at intervals. In this example, a carbon fiber bundle with a fiber diameter of 7 μm and 75,000 carbon fibers per bundle was woven at intervals of 10 mm, and the mass per 1 m 2Carbon fiber fabrics with a mass of 44-513g per layer were used, and three or five layers of this carbon fiber fabric were embedded inside the magnesia-carbonaceous refractory (the refractory body) at intervals of 8mm, 10mm, 20mm, and 30mm, and the press-molded bodies were examined for the occurrence of cracks. The magnesia-carbonaceous refractories used had the compositions of invention blend examples 1-3 in Table 1. Each layer of the carbon fiber fabric was composed of one or three sheets of fabric, and the density of carbon fibers in the cross section of the refractory parallel to the working surface of the refractory was 71-925 fibers / mm. 2 The carbon fiber fabric was immersed in phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric with the phenolic resin (resin solution) attached was embedded in the refractory body. The maximum particle size of the aggregate (magnesia) that constitutes the refractory body is less than 5 mm.

[0052] As shown in Examples 2-4, 5-3, 5-4, 6-2, 6-3, and 6-5 to 6-8, when the embedding spacing between multiple layers of carbon fiber fabric was 10 mm or more, the spacing between the carbon fiber fabric in the press molding direction was not too narrow, so that the carbon fiber bundles that make up the carbon fiber fabric did not spring back during molding and no cracks occurred in the molded body. On the other hand, as shown in Examples 6-1 and 6-4, when the embedding spacing between multiple layers of carbon fiber fabric was less than 10 mm, the spacing between the carbon fiber fabric layers in the press molding direction was too narrow, causing the carbon fiber bundles to spring back during molding, resulting in cracks in the molded body. From the above, it was found that when multiple layers of carbon fiber fabric are embedded at intervals, in order to form a refractory material without generating cracks, it is preferable to set the embedding interval between the layers of carbon fiber fabric to 10 mm or more.

[0053] 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 8 examined the effects of the composition of alumina-silica-silicon carbide-carbon refractory (graphite-containing refractory with alumina raw material, silicon carbide raw material, and silica raw material as aggregates) used for the lining of the hot metal pretreatment vessel on the bending strength, fracture energy, crack resistance, and corrosion resistance of the graphite-containing refractory. In this example, a carbon fiber fabric with a fiber diameter of 7 μm and 75,000 carbon fibers per bundle was woven at 10 mm intervals, and the mass per 1 m 2 was 335 g. This was used and embedded inside an alumina-silica-silicon carbide-carbon refractory (refractory body) so that the density of carbon fibers in the refractory cross-section parallel to the refractory operating surface was 610 fibers / mm 2 . The number of embedded layers of the carbon fiber fabric was 1 layer, and it was composed of a single fabric. The carbon fiber fabric was previously immersed in a phenolic resin (resin solution) as an adhesive, and the carbon fiber fabric with this phenolic resin (resin solution) attached was embedded 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 was less than 5 mm.

[0054] As shown in Invention Examples 7-1 to 7-7, when the content of the alumina raw material was 10 to 95% by mass, the content of the silica raw material was 1 to 50% by mass, and the graphite content was 1 to 80% by mass, high bending strength, fracture energy, crack resistance, and corrosion resistance were obtained. On the other hand, as shown in Comparative Example 7-1, when the content of the alumina raw material was less than 10% by mass, the content of the silica raw material was less than 1% by mass, and the graphite content was more than 80% by mass, both the fracture energy and the corrosion resistance were significantly reduced. Also, as shown in Comparative Example 7-2, when the content of the alumina raw material was more than 95% by mass, the content of the silica raw material was less than 1% by mass, and the graphite content was less than 1% by mass, the generation of cracks due to thermal spalling could not be suppressed, and the fracture energy and crack resistance were significantly reduced. From the above, it can be seen that in alumina-silica-silicon carbide-carbon refractory materials, when the content of alumina raw material is 10-95% by mass, the content of silica raw material is 1-50% by mass, and the graphite content is 1-80% by mass, it is possible to achieve both high corrosion resistance and high fracture energy and crack resistance.

[0055] Examples in Table 9 are alumina-silica-silicon carbide-carbon refractory materials (graphite-containing refractory materials with alumina raw material, silicon carbide raw material, and silica raw material as aggregates) used for the lining of a hot metal pretreatment vessel. Regarding graphite-containing refractory materials 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 flexural strength, fracture energy and crack resistance, and corrosion resistance of the graphite-containing refractory materials was investigated. In this example, a carbon fiber fabric with a fiber diameter of 7 μm and 75,000 carbon fibers per bundle was woven at intervals of 10 mm, and the mass per 1 m 2 was 335 g. This was used and embedded inside an alumina-silica-silicon carbide-carbon refractory material (refractory body) so that the density of carbon fibers in the refractory cross-section parallel to the refractory operating surface was 610 fibers / mm 2 . The number of embedded layers of the carbon fiber fabric was 1 layer, and it was composed of a single fabric. The carbon fiber fabric was previously immersed in a phenolic resin (resin solution) as an adhesive, and the carbon fiber fabric with this phenolic resin (resin solution) attached was embedded in the refractory body. The maximum particle size of the aggregates (alumina raw material, silicon carbide raw material, silica raw material, refractory debris obtained by pulverizing used alumina-silica-silicon carbide-carbon refractory materials) constituting the refractory body was less than 5 mm.

[0056] As shown in Invention Examples 8-1 to 8-3, when the content of refractory debris is 10-90% by mass, the content of silica raw material is 1% by mass or more, and the graphite content is 1-80% by mass, fracture energy, crack resistance, and corrosion resistance comparable to those of the graphite-containing refractory materials using only virgin raw materials shown in Table 8 are obtained. In contrast, as shown in Comparative Example 8-1, when the refractory waste content exceeds 90% by mass, the content of the silica raw material is less than 1% by mass, and the graphite content is less than 1% by mass, the fracture energy, crack resistance, and corrosion resistance are significantly reduced. From the above, for the graphite-containing refractory using refractory waste obtained by pulverizing used alumina-silica-silicon carbide-carbonaceous refractory as part of the aggregate raw material in alumina-silica-silicon carbide-carbonaceous refractory, if the content of the refractory waste is 10 to 90% by mass, the content of the silica raw material is 1% by mass or more, and the graphite content is 1 to 80% by mass, it can be seen that the fracture energy and crack resistance can be maintained at a high level, and furthermore, it has the same corrosion resistance as the graphite-containing refractory using only virgin raw materials.

[0057] The examples in Table 10 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, a carbon fiber fabric with a fiber diameter of 7 μm and 75,000 carbon fibers per bundle and a mass of 335 g per 1 m was used, and it was woven in at intervals of 10 mm. 2 The carbon fiber fabric was used, and the density of the carbon fibers in the cross-section of the refractory parallel to the operating surface of the refractory was 610 fibers / mm. 2 It was embedded inside the alumina-silicon carbide-carbonaceous refractory (refractory body). The number of embedded layers of the carbon fiber fabric was one layer, and it was composed of one piece of fabric. The carbon fiber fabric was previously immersed in a phenolic resin (resin solution) as an adhesive, and the carbon fiber fabric with the phenolic resin (resin solution) attached was embedded in the refractory body. The maximum particle size of the aggregates (alumina raw material, silicon carbide raw material) constituting the refractory body is less than 5 mm.

[0058] As shown in Invention Examples 9-1 to 9-3, 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 flexural strength, fracture energy, crack resistance, and corrosion resistance are obtained. In contrast, as shown in Comparative Example 9-1, when the content of the alumina raw material is less than 10% by mass and the graphite content is more than 80% by mass, the fracture energy and erosion resistance are significantly reduced. Also, as shown in Comparative Example 9-2, when the content of the alumina raw material is more than 95% by mass and the graphite content is less than 1% by mass, the fracture energy and crack resistance are significantly 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 erosion resistance can be obtained.

[0059] The examples in Table 11 examined the effect 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 and crack resistance, and erosion resistance of the graphite-containing refractories. In this example, a carbon fiber fabric with a fiber diameter of 7 μm and 75,000 carbon fibers per bundle (number) was woven at intervals of 10 mm, and the mass per 1 m 2 was 335 g. This was used and embedded inside a silica-silicon carbide-carbon refractory (refractory body) so that the density of carbon fibers in the cross-section of the refractory parallel to the operating surface of the refractory was 610 fibers / mm 2 The number of embedded layers of the carbon fiber fabric was 1 layer, and it was composed of a single fabric. The carbon fiber fabric was previously immersed in a phenolic resin (resin solution) as an adhesive, and the carbon fiber fabric with this phenolic resin (resin solution) attached was embedded in the refractory body. The maximum particle size of the aggregates (silica raw materials, silicon carbide raw materials) constituting the refractory body is less than 5 mm.

[0060] As shown in Invention Example 10-1 and Invention Example 10-2, 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 and crack resistance, and erosion resistance are obtained. In contrast, as shown in Comparative Example 10-1, when the content of the silica raw material is less than 1% by mass and the graphite content is more than 80% by mass, the fracture energy and crack resistance decrease. Also, as shown in Comparative Example 10-2, when the graphite content is more than 80% by mass, the fracture energy and crack resistance also decrease. From the above, it can be seen that in silica - silicon carbide - carbon refractories, when the content of the silica raw material is 1 - 50% by mass and the graphite content is 1 - 80% by mass, high flexural strength, fracture energy, crack resistance, and corrosion resistance can be obtained.

[0061]

Table 1

[0062]

Table 2

[0063]

Table 3

[0064]

Table 4

[0065]

Table 5

[0066]

Table 6

[0067]

Table 7

[0068]

Table 8

[0069]

Table 9

[0070]

Table 10

[0071]

Table 11

Explanation of Symbols

[0072] A Refractory Body B Carbon Fiber Fabric b Carbon Fiber Bundle x Refractory Operating Surface y Reverse Operating Surface

Claims

1. A graphite-containing refractory in which a carbon fiber fabric (B) is embedded inside a refractory body (A) having a graphite content of 1 to 80% by mass, The carbon fiber fabric (B) has a mass per 1 m ２ of 40 to 1300 g, wherein the carbon fiber fabric (B) is in close contact with the refractory body (A) via an adhesion-imparting agent component, and the adhesion-imparting agent component is one or more selected from organic resins, inorganic fine particles derived from inorganic sols, organic substances derived from tar or / and pitch, and organic substances derived from organic pastes. The graphite-containing refractory is characterized by this.

2. The carbon fiber fabric (B) is a fabric in which carbon fiber bundles (b) are woven in two or more directions at intervals exceeding the maximum particle size of the aggregate constituting the refractory body (A), and the carbon fiber bundles (b) are bundles of carbon fibers having a fiber diameter of 1 to 45 μm, and the number of carbon fibers per bundle is 1000 to 300000. The density of carbon fibers constituting the carbon fiber fabric (B) in the refractory cross-section parallel to the working surface of the refractory is 10 to 2000 fibers / mm ２ The graphite-containing refractory according to claim 1, characterized in that it is as described above.

3. The graphite-containing refractory according to claim 1, wherein the carbon fiber fabric (B) is embedded inside the refractory body (A) along a direction perpendicular to the refractory operating surface.

4. The graphite-containing refractory according to any one of claims 1 to 3, wherein the carbon fiber fabric (B) has an interval of more than 3 mm between carbon fiber bundles (b) woven in the same direction.

5. The graphite-containing refractory according to any one of claims 1 to 3, wherein the carbon fiber fabric (B) is composed of one sheet or two or more laminated sheets of fabric.

6. The graphite-containing refractory according to any one of claims 1 to 3, wherein one layer or two or more layers of the carbon fiber fabric (B) are embedded inside the refractory body (A) with an interval therebetween.

7. The graphite-containing refractory according to claim 6, wherein the interval between two or more layers of the carbon fiber fabric (B) embedded inside the refractory body (A) is 10 mm or more.

8. The graphite-containing refractory according to any one of claims 1 to 3, wherein the refractory body (A) contains 20 to 99% by mass of a magnesia raw material having a magnesia concentration of 90% by mass or more.

9. The graphite-containing refractory according to claim 1, wherein the refractory body (A) contains 10 to 95% by mass of an alumina raw material having an alumina concentration of 70% by mass or more.

10. The graphite-containing refractory according to claim 1, wherein the refractory body (A) contains 1 to 50% by mass of a silica raw material.

11. The graphite-containing refractory according to claim 9 or 10, wherein the refractory body (A) contains 1% by mass or more of a silicon carbide raw material having a silicon carbide concentration of 80% by mass or more.

12. The graphite-containing refractory according to any one of claims 1 to 3, wherein the refractory body (A) contains 10 to 90% by mass of refractory debris obtained by pulverizing used refractories.

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