Method for producing refractory containing graphite

Abstract

To provide a manufacturing method capable of stably manufacturing a graphite-containing refractory that can obtain high durability, 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 manufacturing method of a graphite-containing refractory comprises steps of: attaching an adhesive c containing an organic substance or / and inorganic fine particles with a residual carbon percentage of 6 to 80 mass% to a carbon fiber bundle B; and burying a carbon fiber bundle B to which the adhesive c is attached in this preparation step inside the a refractory raw material, and molding a refractory raw material A where the carbon fiber bundle B is buried to obtain a refractory molding x. Preferably, in the forming step, inside of the refractory raw material A, such that the density of carbon fibers constituting the carbon fiber bundle B in the refractory cross section parallel to an operating surface of the graphite-containing refractory is 10 to 2000 fibers / mm2, similarly, the carbon fiber bundle B is buried so that the occupied area ratio of the carbon fibers is 0.1 to 40%.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Facilities (refining vessels, transport vessels, etc.) 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 are used for the lining of torpedoes and blast furnace pots used in the hot metal pretreatment process. The refractories used for lining these refining vessels and transport vessels are used under extremely harsh conditions where 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 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, and the inner surface is cooled by the normal temperature gas in the part close to the furnace, 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, and 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 and large thermal fluctuations are repeated every charge. Therefore, high durability that can withstand use under such conditions is required. In addition, the converter lining refractories (bricks that make up the converter inner wall) other than the tuyere bricks are also 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 refractory materials, Patent Document 1 describes that by bundling carbon fibers with a length of 100 mm or more using an adhesive and arranging them inside the refractory material in a bundled state with adhesiveness imparted, the fracture energy was significantly increased.

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 incorporating carbon fiber bundles inside a refractory material as in Patent Document 1, depending on the properties of the adhesive used, the effect of incorporating (arranging) the carbon fiber bundles inside the refractory material may not be sufficiently obtained. Patent Document 1 does not disclose the conditions of the adhesive for maximizing the incorporation 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 temperature increase and decrease are repeated over a long period, such as in the inner lining refractory of a converter, the progress of cracks generated by thermal stress is suppressed and high durability is obtained. Also, in particular, even when used under conditions where the internal temperature gradient is very large, such as in the tuyere bricks of a converter, a manufacturing method that can stably manufacture a graphite-containing refractory material with high durability is provided.

Means for Solving the Problems

[0008] As a result of repeated studies to solve the above problems, the present inventors have found that when manufacturing a graphite-containing refractory in which a carbon fiber bundle is embedded inside the refractory, in order to adhere or closely attach the carbon fiber bundle to the refractory raw material, an adhesive having a predetermined residual carbon rate or / and an adhesive containing inorganic fine particles is used as an adhesive to be attached to the carbon fiber bundle. Preferably, by optimizing the fiber diameter and number of carbon fibers constituting the carbon fiber bundle, and further, the existence density and occupation area ratio of carbon fibers in the refractory cross-section, it is possible to stably manufacture a graphite-containing refractory having high durability even in an extremely harsh use environment as described above.

[0009] The present invention has been made based on such findings and has the following gist. [1] A method for manufacturing a graphite-containing refractory in which a carbon fiber bundle (B) is disposed inside a refractory raw material (A) containing graphite, A preparation step of attaching an adhesive (c) containing an organic substance or / and inorganic fine particles having a residual carbon rate of 6 to 80% by mass to the carbon fiber bundle (B), A molding step of embedding the carbon fiber bundle (B) to which the adhesive (c) has been attached in the refractory raw material (A) in the preparation step, and molding the refractory raw material (A) in which the carbon fiber bundle (B) is embedded to obtain a refractory molded body (x). A method for manufacturing a graphite-containing refractory, characterized by comprising: [2] The method for manufacturing a graphite-containing refractory according to [1] above, wherein in the molding step, a binder is added to the refractory raw material (A) and kneaded, and after embedding the carbon fiber bundle (B) in the kneaded material, it is molded.

[0010] [3] The method for manufacturing a graphite-containing refractory according to [1] or [2] above, further comprising a drying step of drying the refractory molded body (x) obtained in the molding step. [4] The method for manufacturing a graphite-containing refractory according to [3] above, further comprising a firing step of reducing and firing the refractory molded body (x) that has undergone the drying step. [5] In the manufacturing method according to any one of [1] to [4] above, the adhesive (c) is composed of one or more selected from an organic resin solution, an inorganic sol, tar, pitch, and an organic paste. A method for manufacturing a graphite-containing refractory characterized by this. [6] In the manufacturing method according to any one of [1] to [5] above, the width of the carbon fiber bundle (B) is 1 to 15 mm. A method for manufacturing a graphite-containing refractory characterized by this.

[0011] [7] In the manufacturing method according to any one of [1] to [6] above, the carbon fiber bundle (B) is a bundle of carbon fibers with 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 method for manufacturing a graphite-containing refractory characterized by this. [8] In the molding step of the manufacturing method according to any one of [1] to [7] above, a plurality of carbon fiber bundles (B) are embedded in parallel inside the refractory raw material (A) so that the distance between adjacent carbon fiber bundles (B) exceeds 3 mm. A method for manufacturing a graphite-containing refractory characterized by this. [9] In the molding step of the manufacturing method according to any one of [1] to [8] above, inside the refractory raw material (A), in the refractory cross-section parallel to the working surface of the graphite-containing refractory, the density of the carbon fibers constituting the carbon fiber bundle (B) is 10 to 2000 fibers / mm 2 A method for manufacturing a graphite-containing refractory characterized by embedding the carbon fiber bundle (B) so as to be.

[0012]

[10] In the molding step of the manufacturing method according to any one of [1] to [9] above, inside the refractory raw material (A), in the refractory cross-section parallel to the working surface of the graphite-containing refractory, the occupied area ratio of the carbon fibers constituting the carbon fiber bundle (B) is 0.1 to 40%. A method for manufacturing a graphite-containing refractory characterized by embedding the carbon fiber bundle (B) so as to be.

[11] In the manufacturing method according to any one of [1] to

[10] above, the refractory raw material (A) contains 1 to 80% by mass of a graphite raw material. A method for manufacturing a graphite-containing refractory characterized by this.

[12] In the manufacturing method according to any one of [1] to

[11] above, the refractory raw material (A) contains 20 to 99% by mass of magnesia raw material, and is a method for manufacturing a graphite-containing refractory.

[0013]

[13] In the manufacturing method according to any one of [1] to

[11] above, the refractory raw material (A) contains 10 to 95% by mass of alumina raw material, and is a method for manufacturing a graphite-containing refractory.

[14] In the manufacturing method according to any one of [1] to

[11] ,

[13] above, the refractory raw material (A) contains 1 to 50% by mass of silica raw material, and is a method for manufacturing a graphite-containing refractory.

[15] In the manufacturing method according to any one of

[13] or

[14] above, the refractory raw material (A) contains 1% by mass or more of silicon carbide raw material, and is a method for manufacturing a graphite-containing refractory.

[16] In the manufacturing method according to any one of [1] to

[15] above, the refractory raw material (A) contains 10 to 90% by mass of refractory scraps obtained by pulverizing used refractories, and is a method for manufacturing a graphite-containing refractory.

Advantages of the Invention

[0014] According to the present invention, since it has high fracture energy, 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, so high durability is obtained. In particular, a graphite-containing refractory with high durability can be stably manufactured 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

Mode for Carrying Out the Invention

[0016] The manufacturing method of the present invention is a method for manufacturing a graphite-containing refractory in which a carbon fiber bundle B is embedded inside a refractory raw material A containing graphite, and includes a preparation step (i) of attaching an adhesive c containing an organic substance or / and inorganic fine particles having a residual carbon rate of 6 to 80% by mass to the carbon fiber bundle B, and a molding step (ii) of embedding the carbon fiber bundle B to which the adhesive c has been attached in the refractory raw material A in step (i) and molding the refractory raw material A in which the carbon fiber bundle B is embedded to obtain a refractory molded body x. Here, the residual carbon rate of the adhesive c is measured based on the fixed carbon measurement method described in JIS K6910 (Phenolic Resin Test Method).

[0017] The graphite-containing refractory produced by such a method of the present invention is such that the carbon fiber bundle B disposed (embedded) inside the refractory raw material A is adhered or closely attached to the refractory raw material A via the adhesive c, so that the carbon fiber bundle B is integrated with the refractory. In addition, since the adhesive c contains an organic substance and / or inorganic fine particles having a specific residual carbon rate, high fracture energy capable of suppressing the generation of cracks can be obtained. Further, in the preparation step (i), not only is the adhesive c attached to the outer surface of the carbon fiber bundle B, but also the adhesive c is infiltrated (impregnated) into the bundle, so that the carbon fiber bundle B is integrated as a bundle by the adhesive c, and thus higher fracture energy can be obtained.

[0018] Figure 1 shows an example of the manufacturing process in the manufacturing method of the present invention. Further, Figure 2 schematically shows an example of a graphite-containing refractory produced by the method of the present invention (one of the brick constituent members constituting the tuyere brick), Figure 2(a) is a perspective view, and Figure 2(b) is a cross-sectional view along the dashed-dotted line in Figure 2(a) (a cross-sectional view parallel to the operating surface of the refractory), s1 is the operating surface of the refractory (the surface in contact with molten steel or slag), and s2 is the non-operating surface. In this graphite-containing refractory, a plurality of carbon fiber bundles B are arranged (embedded) in parallel at a predetermined interval inside the refractory main body (the part composed of the refractory raw material A; the same applies hereinafter). In the preparation step (i), an adhesive c containing an organic substance and / or inorganic fine particles having a residual carbon rate of 6 to 80% by mass (that is, an adhesive c having an organic substance and / or inorganic fine particles having a residual carbon rate of 6 to 80% by mass as an active ingredient) is attached to the carbon fiber bundle B. At this time, in order to adhere and integrate the carbon fiber bundle B and the refractory raw material A, the adhesive c is attached so as to cover the outer surface of the carbon fiber bundle B. More preferably, in order to integrate the carbon fiber bundle B as a bundle, the adhesive c is infiltrated (impregnated) into the bundle of carbon fibers (the gaps between the carbon fibers).

[0019] The refractory material reaches a high temperature of 500 °C or higher (measured at 900 °C in JIS K6910) inside during its use or pre-firing. At this time, even in an environment where there is almost no oxygen inside, such as in a graphite-containing refractory material, when the active ingredient of the adhesive c is an organic substance such as an organic resin, a part of the adhesive c attached to the carbon fiber bundle B is gasified by decomposition or evaporation and dissipated outside the refractory material. The residual carbon rate is considered to be an index of the ratio of the weight that remains without being gasified and dissipated among the adhesives, and it varies depending on the type and quality of the adhesive. As a result of investigating based on the idea that the residual carbon rate of the adhesive affects the fracture energy when a graphite-containing refractory material using a carbon fiber bundle is exposed to a high temperature in the actual use environment, it has been found that when an adhesive c (organic substance) with a residual carbon rate of 6 to 80 mass% is used, a graphite-containing refractory material with high fracture energy can be obtained. This is because when an adhesive c (organic substance) with such a specific residual carbon rate is used, the adhesion between the refractory raw material A (refractory body) and the carbon fiber bundle B is enhanced, so that the refractory brick is easily densified during molding. In addition, when exposed to a high temperature during use or pre-sintering, the amount of gas escaping from inside the refractory can be suppressed, so that the occurrence of cracks can be suppressed and the fracture energy increases. In addition, the present inventors have also found that high fracture energy can be obtained even when the active ingredient of the adhesive c is inorganic fine particles such as alumina or silica. This is because even when inorganic fine particles (especially inorganic fine particles derived from inorganic sols) are used, the adhesion between the refractory raw material (refractory body A) and the carbon fiber bundle B is enhanced, so that the refractory brick is easily densified during molding. In addition, when exposed to a high temperature during use or pre-sintering, the inorganic fine particles are sintered, which can suppress the occurrence of cracks and increase the fracture energy.

[0020] When the active ingredient of the adhesive c is an organic substance, if the residual carbon 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 residual carbon 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 residual carbon rate of the organic substance is preferably 20 to 80% by mass, and more preferably 40 to 80% by mass. Since the adhesive c covers the outer surface of the carbon fiber bundle B and adheres or closely adheres the carbon fiber bundle B to the refractory body A, and more preferably exists (penetrates) into the carbon fiber bundle (the gap between carbon fibers) to integrate the carbon fiber bundle B as a bundle, it is desirable that the adhesive c used in the preparation step (i) is in a liquid state. Also, the adhesive c needs to remain without decomposition or evaporation 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, as the adhesive c to be attached to the carbon fiber bundle B in the preparation step (i), one or more selected from organic resin solutions, tar, pitch, organic paste, and inorganic sol (that is, any of these or a mixture thereof) are suitable.

[0021] Specific examples of the adhesive c (tackifier) include phenolic resin, epoxy resin, melamine resin, urea resin, alkyd resin, unsaturated polyester resin, polyurethane resin, thermosetting polyimide resin (a resin solution 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. One or more selected from these can be used. Also, in order to adjust the viscosity of these adhesives c, they can be thinned with a solvent. However, at high temperatures of 500 °C or higher, it is desirable to suppress the use of a solvent that gasifies even without oxygen (for example, water) to an amount equal to or less than the weight of the adhesive component. Also, by using two or more types of adhesives c, higher bending strength and fracture energy can be obtained compared to the case of using one type of adhesive c. This is because the adhesion between the refractory raw material and the carbon fiber is further enhanced. Therefore, in order to obtain higher bending strength and fracture energy, it is preferable that the adhesive c is composed of two or more types of adhesives.

[0022] In the preparation step (i), when the adhesive c is adhered so as to cover the outer surface of the carbon fiber bundle B and the adhesive c is infiltrated (impregnated) into the inside of the carbon fiber bundle (the gaps between the carbon fibers), for example, the carbon fiber bundle B is immersed in a resin (resin solution) or an inorganic sol that is the adhesive c, or a resin (resin solution) or an inorganic sol that is the adhesive c is sprayed onto the carbon fiber bundle B. As another method, after previously impregnating the inside of the bundle with the adhesive c and then curing or solidifying the carbon fiber bundle B, in the preparation step (i), the adhesive c may be adhered again so as to cover the outer surface of the carbon fiber bundle B.

[0023] In the molding step (ii), the carbon fiber woven bundle B (preferably the carbon fiber bundle B in which the adhesive c has penetrated (impregnated) into the inside of the bundle and adhered to the outer surface) to which the adhesive c has been adhered in the preparation step (i) is embedded in the refractory raw material A while the adhesive c has adhesiveness, and the refractory raw material A in which this carbon fiber woven bundle B is embedded is molded to obtain a refractory molded body x (a molded product of the refractory raw material). When molding is performed by press molding as shown in FIG. 1, usually, an appropriate amount of binder is added to the refractory raw material A and kneaded, the carbon fiber bundle B is embedded in the kneaded material, and then press molding is performed. As the binder, for example, phenol resin (main agent) + hexamine (hardening agent), carbon bond, ceramic bond, etc. are used. The refractory raw material A is a mixture containing graphite (carbon raw material) and aggregate raw material, etc., and its specific composition will be described in detail later.

[0024] Here, the adhesive c attached to the carbon fiber bundle B only needs to have adhesiveness such that the carbon fiber bundle B and the refractory raw material A (the kneaded material) can adhere or closely contact each other even when the hardening or solidification has progressed to a certain extent when the carbon fiber bundle B is embedded in the kneaded material (a so-called half-dried state). The carbon fiber bundle B embedded in the refractory raw material A adheres or closely contacts the refractory raw material A through the adhesive c. Further, when the carbon fiber bundle B is embedded in the refractory raw material A with the adhesive c attached to the outer surface and the adhesive c also penetrating into the bundle, the carbon fiber bundle B contains the adhesive c in the bundle (that is, the adhesive 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 c is interposed between the carbon fiber bundle B and the refractory raw material A, and the carbon fiber bundle B is adhered or closely contacted to the refractory raw material A through the adhesive c.

[0025] Press molding is performed by filling a mold with the kneaded material of the refractory raw material A and the carbon fiber bundle B. As a method of filling the mold with the kneaded material of the refractory raw material A together with the carbon fiber bundle B (the carbon fiber bundle B to which the adhesive c is attached; the same applies hereinafter), for example, there is a method in which a certain amount of the kneaded material is charged into the mold, and then a plurality of carbon fiber bundles B 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 raw material A as shown in FIG. 2 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 B arranged in parallel thereon and the step of charging a certain amount of the kneaded material thereon are repeatedly performed.

[0026] Press molding can be performed by general mold press molding that compresses in one direction in the mold, 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 compression in one direction, 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 forming step (ii) may be performed by a forming method other than press forming. Examples of forming methods other than press forming 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 ladle or tundish, pour the unshaped refractory (refractory raw material A) into this inner frame, and after drying (drying step) and solidifying, remove the inner frame. Another method is to pour the unshaped refractory (refractory raw material A) into a refractory-shaped mold, dry (drying step) and solidify it, and then transport 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 bundle B when pouring the unshaped refractory into the mold and to control the temperature during solidification. In these casting forming methods, after arranging the carbon fiber bundle B in the above-mentioned inner frame or mold, the unshaped refractory (refractory raw material A) is poured into the inner frame or mold, and dried (drying step) and solidified. Therefore, the graphite-containing refractory produced according to the present invention includes, in addition to the so-called refractory bricks produced through press forming, refractory materials that are formed by casting at the construction site, which is the working surface such as a ladle or tundish, and are directly dried and solidified as described above.

[0027] Hereinafter, the configuration of the carbon fiber bundle B embedded in the refractory raw material A and the embedding conditions of the carbon fiber bundle B in the forming step (ii) will be described. The arrangement form of the carbon fiber bundle B embedded in the refractory raw material A is arbitrary and there is no special limitation. However, during operation, since the tensile stress that causes crack generation 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 s1 of the refractory. When arranging a plurality of carbon fiber bundles B, it is preferably arranged (embedded) in parallel at a predetermined interval.

[0028] Incidentally, the carbon fiber bundle B embedded inside the refractory compact x may or may not have its end exposed on the surface of the refractory compact x. Also, in the case of the latter, on the operating surface s1 side of the refractory compact x, it is preferable that the distance between the end of the carbon fiber fabric B and the operating surface s1 is as small as possible. However, on the non-operating surface s2 side, the distance between the end of the carbon fiber bundle B and the non-operating surface s2 may be somewhat large. This is because it is not necessary to embed the carbon fiber bundle B in the portion on the non-operating surface s2 side of the refractory that is assumed to remain even at the end of use.

[0029] 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, in the case where 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 raw material A. On the other hand, when the width w of the carbon fiber bundle B is 15 mm or less, it is possible to reduce the 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 raw material A and the carbon fiber bundle B, and to reduce the possibility that the melting loss of the carbon fiber bundle B itself triggers the melting loss of the refractory.

[0030] 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 300000 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 refractory raw material A becomes small, so the effect of the carbon fiber bundle B suppressing the crack propagation 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 A (refractory body) 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.

[0031] In the molding step (ii), it is preferable to embed a plurality of carbon fiber bundles B in parallel inside the refractory raw material A so that the distance d (the mutual distance between the carbon fiber bundles B) between adjacent carbon fiber bundles B exceeds 3 mm. By arranging the adjacent carbon fiber bundles B so that the distance d exceeds 3 mm, the entanglement between the refractory raw material (refractory body A) and the carbon fiber bundle B can be improved, and peeling caused by the carbon fiber bundle called lamination during molding can be made difficult to occur. 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 fiber described below. Also, inside the refractory raw material A, in the refractory cross-section parallel to the working surface s1 of the graphite-containing refractory, the existence density of the carbon fibers constituting the carbon fiber bundle B is 10 to 2000 fibers / mm 2 It is preferable to embed the carbon fiber bundle B so that it becomes like this. Thereby, the contact area between the refractory raw material A (refractory body) and the carbon fiber bundle B is ensured, the adhesion is increased, the fracture energy can be increased, and the occurrence of defects due to the elastic deformation of the carbon fiber bundle B can also be suppressed. When the existence density of the carbon fiber is less than 10 fibers / mm 2 the contact area between the refractory raw material A (refractory body) and the carbon fiber bundle B is too narrow, so the adhesion between the refractory raw material A 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 fiber is 20,000 fibers / mm 2In the case of the super type, since the contact area between the refractory raw material A (refractory body) and the carbon fiber bundle B is too large, defects due to the elasticity of the carbon fiber bundle B called springback are likely to occur during molding.

[0032] Also, it is preferable to embed the carbon fiber bundle B inside the refractory raw material A so that the occupation area ratio of the carbon fibers constituting the carbon fiber bundle B in the refractory cross-section parallel to the operating surface s1 of the graphite-containing refractory is 0.1 to 40%. Thereby, the contact area between the refractory raw material A (refractory body) and the carbon fiber bundle B is ensured, the adhesion is enhanced, the fracture energy can be increased, and the occurrence of defects due to the elasticity of the carbon fiber bundle B can also be suppressed. When the occupation area ratio of the carbon fibers is less than 0.1%, since the contact area between the refractory raw material A (refractory body) and the carbon fiber bundle B is too small, the adhesion between the refractory raw material A and the carbon fiber bundle B does not increase, and the increase in fracture energy is small. On the other hand, when the occupation area ratio of the carbon fibers exceeds 40%, since the contact area between the refractory raw material A (refractory body) and the carbon fiber bundle B is too large, defects due to the elasticity of the carbon fiber bundle B called springback are likely to occur during molding.

[0033] The refractory formed body x obtained in the forming step (ii) may be used as a product as it is, but is usually dried in the drying step (iii). This drying step (iii) is usually carried out at about 200 to 230 °C for the purpose of drying (curing) the refractory formed body x. Further, after drying (curing), it may be subjected to reduction firing (coking treatment) in the firing step (iv) to obtain a product brick (fired brick). Also, for the refractory formed body x obtained by casting molding as described above, the refractory formed body x held by the inner frame installed at the construction site or the mold installed at other places is heated by heating means such as a heating burner to be dried and solidified. Thereafter, the inner frame is removed or taken out from the mold.

[0034] As described above, a carbon fiber bundle B is embedded inside a refractory raw material A (refractory body), and this carbon fiber bundle B is adhered or closely attached to the refractory raw material A (refractory body) via an adhesive c (preferably, the adhesive c further penetrates into the bundle of the carbon fiber bundle B, so that the adhesive c exists inside the bundle of the carbon fiber bundle B, and the carbon fiber bundle B is integrated as a bundle by the adhesive c), thereby obtaining a graphite-containing refractory. The graphite-containing refractory produced by the method 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 a steelworks. In particular, it is suitable as a lining refractory for a converter in a very severe use environment, and is particularly suitable as a tuyere brick constituting the tuyere part among them.

[0035] Next, the composition of the refractory raw material A will be described. The refractory raw material 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 or the like is used.

[0036] Generally, for the lining (including the tuyere part) of a converter used in a refining process, a magnesia-carbon refractory (a graphite-containing refractory with a magnesia raw material as an aggregate), which is a refractory mainly composed of magnesia and carbon, is used. When the refractory body is a magnesia-carbon refractory, the refractory raw material A preferably contains 20 to 99% by mass of a magnesia raw material, whereby cracking 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 having a magnesia concentration of 90% by mass or more.

[0037] Also, generally, for the top lid and the inner lining of the blast furnace ladle used in the hot metal pretreatment process, 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 is an alumina-silicon carbide-carbon refractory material or an alumina-silicon carbide-silica-carbon refractory material, the refractory raw material A preferably contains 10 to 95% by mass of alumina raw materials. Thereby, high corrosion resistance against the 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 with an alumina concentration of 70% by mass or more.

[0038] Furthermore, when the refractory body is an alumina-silicon carbide-carbon refractory material or an alumina-silicon carbide-silica-carbon refractory material, the refractory raw material A preferably contains 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 the 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 with a silicon carbide concentration of 80% by mass or more. Also, when the refractory body is an alumina-silicon carbide-silica-carbon refractory material, the refractory raw material A preferably contains 1 to 50% by mass of silica raw materials, whereby both high crack resistance and high corrosion resistance can be achieved.

[0039] Magnesia-carbon refractories used for the lining of converters are used under extremely harsh conditions, such as mechanical impact by charged materials, abrasion 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 carry out stable operation, it is preferable to use magnesia-carbon refractories with high durability that can withstand harsh conditions. Similarly, 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. Therefore, it is preferable to use refractories that can withstand these conditions. According to the present invention, since the fracture energy of the graphite-containing refractories used under these extremely harsh conditions is significantly improved compared to conventional graphite-containing refractories, high durability can be obtained.

[0040] Further, in the case of a silica-silicon carbide-carbon refractory in which the refractory body is a refractory mainly composed of silica, silicon carbide, and carbon, the refractory raw material A preferably contains 1% by mass or more of a silicon carbide raw material and 1 to 50% by mass of a silica raw material. Thereby, 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.

[0041] Here, as the alumina raw material, for example, one or more of bauxite shale, white alumina, brown alumina, etc. are used. As the silicon carbide raw material, for example, one or more of green silicon carbide, black silicon carbide, etc. are used. As the silica raw material, for example, one or more of wollastonite, mullite, etc. are used. For refractory raw material A, in order to suppress the heat dissipation from the iron-making container and increase durability, a metal powder raw material can be further contained (blended). 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 mass% is preferred. If the content (blending amount) of the metal powder raw material is less than 1 mass%, the effect of improving durability by blending the metal powder raw material cannot be sufficiently obtained. On the other hand, if it exceeds 5 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 uses in an actual machine may decrease.

[0042] Refractory raw material A can contain about 10 to 90 mass% of refractory scraps obtained by pulverizing used refractories as aggregate raw materials. In particular, when the refractory body 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 the aggregate raw material. When refractory raw material A contains refractory scraps in this way, the remainder of the refractory raw material is an unused raw material (virgin raw material).

[0043] When the graphite-containing refractory is an alumina-silicon carbide-carbonaceous refractory, when the content of refractory debris obtained by pulverizing the used alumina-silicon carbide-carbonaceous refractory in refractory raw material A is 10 to 90% by mass, the same degree of crack resistance and corrosion resistance as that of the 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. However, when the content of the 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 the refractory debris is less than 10% by mass, since the recycling rate of the refractory debris is too low, the treatment cost of the refractory debris as industrial waste increases significantly.

Example

[0044] Regarding the magnesia-carbonaceous refractory (graphite-containing refractory using magnesia raw material as aggregate) used in the converter, in order to study the blending of the magnesia-carbonaceous raw material, a refractory molded product using magnesia raw material as aggregate with the raw material blending as shown in Table 1, that is, a graphite-containing refractory without embedding carbon fiber bundles was produced. When kneading and molding the refractory raw material, as a binder, 3% by mass of phenolic resin and 0.3% by mass of hexamine were blended externally to the refractory raw material. Regarding the produced graphite-containing refractory, the corrosion resistance and crack resistance were evaluated by the following methods respectively. The results are shown together in Table 1.

[0045] Regarding the erosion resistance, as shown in Fig. 3 (test method), the erosion amount was measured by the internal lining splitting method using a high-frequency induction furnace, and the evaluation was based on the erosion amount. In the test by the internal lining splitting method, the test temperature was 1650 °C, the temperature holding time was 4 hours, and the synthetic slag with the composition shown in Table 2 was charged every hour. After cooling, the erosion amount of the working surface was measured. Then, from the erosion amount, the erosion index was obtained with the erosion amounts of Blending Examples 1-4 in Table 1 being 100. Note that 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 Figs. 3(A) and (B). Regarding the crack resistance, after measuring the longitudinal dynamic elastic modulus E0 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 evaluation was made using the change rate E3 / E0 of the dynamic elastic modulus before and after the test as an index.

[0046] As shown in Blending Examples 1-2 to 1-8 in Table 1, when the graphite content was 1 to 80 mass% and the magnesia raw material content was 20 to 99 mass%, the erosion resistance and crack resistance were almost constant. However, as shown in Blending Example 1-1, when the graphite content was less than 1 mass%, the crack resistance was significantly reduced. Also, as shown in Blending Example 1-9, when the magnesia raw material content was less than 20 mass%, the erosion resistance was significantly reduced. From these facts, it can be seen that in order to ensure the crack resistance of graphite-containing refractories, the graphite content needs to be 1 mass% or more. Also, in the blending of magnesia-carbon raw materials, in order to achieve both erosion resistance and crack resistance, it is preferable that the graphite content is 1 to 80 mass% and the magnesia raw material content is 20 to 99 mass%.

[0047] The graphite-containing refractories of the inventive examples and comparative examples in which carbon fiber bundles B were arranged (embedded) inside the refractory raw material A (refractory body) were manufactured according to the procedure shown in Fig. 1. In the manufactured graphite-containing refractories, as shown in Fig. 2, a plurality of carbon fiber bundles B were embedded in parallel and at equal intervals along the longitudinal direction of the refractory body. The carbon fiber bundles B contain an adhesive component (adhesive c) within the bundle and are adhered or closely attached to the refractory body via the adhesive component (adhesive c). When kneading and molding the refractory raw material, as a binder, 3% by mass of phenolic resin and 0.3% by mass of hexamine were compounded as an external application to the refractory raw material. For the manufactured graphite-containing refractories, the flexural strength, fracture energy, corrosion resistance, and crack resistance were evaluated by the following methods, respectively.

[0048] Regarding the flexural strength, as shown in Fig. 4 (test method), 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 and at equal intervals along the longitudinal direction inside the refractory raw material A (refractory body) was used. The center-to-center distance was 100 mm, and the load application acceleration was 0.5 mm / min. The measurement was carried out in accordance with the three-point bending test method described in JIS R2213. Fig. 4(a) is an explanatory diagram schematically showing the implementation status of the three-point bending strength test, and Fig. 4(i) is an explanatory diagram schematically showing the end face of the test piece in Fig. 4(a). Regarding the fracture energy, as shown in Fig. 5, based on the position showing the first peak value in the load-displacement curve obtained in the three-point bending strength test, the area within a displacement range of 1 mm from the reference position was taken. Also, regarding the crack resistance and corrosion resistance, they were evaluated by the methods described above. As the test piece for evaluating the crack resistance, a test piece in which a plurality of carbon fiber bundles B were embedded in parallel and at equal intervals along the longitudinal direction inside the refractory raw material A (refractory body) was used. As the test piece for evaluating the corrosion resistance, a test piece in which a plurality of carbon fiber bundles B were embedded in parallel and at equal intervals perpendicular to the surface (operating surface s1 of the refractory) in contact with slag or molten steel was used.

[0049] Tables 3 to 9 show the composition and properties (bending strength, fracture energy, corrosion resistance, crack resistance) of the graphite-containing refractories (graphite-containing refractories with carbon fiber woven bundles B embedded inside refractory body A) of the inventive examples and comparative examples. First, the example in Table 3 examined the influence of the adhesive c, which is contained within the carbon fiber bundle B and adheres or closely adheres the carbon fiber bundle B to the refractory raw material A, on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory. In this example, carbon fiber bundles with a fiber diameter of 7 μm, a length of 200 mm, 75,000 carbon fibers per bundle, and a width of 8 mm, and adhesives such as phenolic resins (solutions) and inorganic sols with different residual carbon rates were used. The adhesive c was infiltrated and adhered inside and outside the bundles to impart adhesiveness, and multiple carbon fiber bundles B were embedded in parallel at 10 mm intervals inside a magnesia-carbon refractory (refractory raw material A). At that time, the carbon fiber bundles B were immersed in the adhesive (solution) in advance, and the carbon fiber bundles B with the adhesive infiltrated and adhered inside and outside the bundles were embedded in the refractory raw material A. When using two types of adhesives in combination, they were mixed and used. Also, in one of the comparative examples, multiple carbon fiber bundles without the adhesive were similarly embedded in the refractory body.

[0050] As shown in Inventive Examples 1-1 to 1-10, when carbon fiber bundles B with adhesiveness imparted using a specific adhesive c that satisfies the conditions of the present invention were embedded in the refractory raw material A, high bending strength and fracture energy were obtained. Furthermore, as shown in Inventive Examples 1-11 to 1-15, when carbon fiber bundles B with adhesiveness imparted using two types of adhesives were embedded, higher bending strength and fracture energy were obtained compared to the case of using one type of adhesive. 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 was used, a large amount of gas escaped from inside the refractory at high temperatures, and many defects such as pores were generated inside, so high bending strength, fracture energy, and crack resistance could not be obtained.

[0051] Also, as shown in Comparative Examples 1-2, when an adhesive (organic resin) with a residual carbon rate exceeding 80% by mass is used, there is almost no gas escaping from inside the refractory at high temperatures, and the refractory becomes too dense, so high flexural 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, so high flexural strength, fracture energy, and crack resistance cannot be obtained. From the above, it can be seen that by using an adhesive c containing an organic substance and / or inorganic fine particles with a residual carbon rate of 6 to 80% by mass as an active ingredient, a graphite-containing refractory having high flexural strength, fracture energy, and crack resistance can be obtained.

[0052] 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 presence density (embedding density) of the carbon fibers in the refractory cross-section parallel to the refractory operating surface, and the occupancy area ratio of the carbon fibers on the flexural strength, fracture energy, and crack resistance of the graphite-containing refractory for the carbon fiber bundle B embedded inside the refractory raw material A. In this example, by setting the fiber diameter of the carbon fibers constituting the carbon fiber bundle B to 0.5 to 50 μm and the number of carbon fibers per bundle of the carbon fiber bundle B to 900 to 350,000, a plurality of carbon fiber bundles B were embedded in parallel at 10 mm intervals inside a magnesia-carbon refractory (refractory raw material A) so that the presence density and occupancy area ratio of the carbon fibers in the refractory cross-section parallel to the refractory operating surface were different. At that time, the carbon fiber bundle B was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass, which is the adhesive c, and the carbon fiber bundle B with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundle was embedded in the refractory raw material A. The maximum particle size of the aggregate (magnesia) constituting the refractory raw material A is 8 - 5 mm.

[0053] 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 (number) per bundle of the carbon fiber bundle B is 1,000 to 300,000, the presence 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.

[0054] 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 (number) per bundle of the carbon fiber bundle B is less than 1,000, the presence density (embedding density) of the carbon fibers 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 is more than 45 μm and the number of carbon fibers (number) per bundle of the carbon fiber bundle B is more than 300,000, the presence density of the carbon fibers in the refractory cross-section parallel to the refractory working surface is more than 2,000 fibers / mm 2 , and similarly, the occupied area ratio of the carbon fibers is more than 40%, and the flexural strength and fracture energy are reduced compared to Invention Example 2-5. The reason for this is that since the carbon fiber bundle is too thick, the entanglement between the carbon fiber bundle and the refractory raw material is poor, and springback is likely to occur during molding.

[0055] From the above, as the conditions for arranging the carbon fiber bundle B inside the refractory raw material A, the fiber diameter of the carbon fibers constituting the carbon fiber bundle B is 1 to 45 μm, the number of carbon fibers (number) per bundle of the carbon fiber bundle B is 1,000 to 300,000, and the presence 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 preferably 0.1 to 40%. As a result, the contact area between the refractory raw material A (refractory body) and the carbon fiber bundle B increases and the adhesion also increases, and it can be seen that particularly high flexural strength, fracture energy, and crack resistance can be stably obtained.

[0056] The examples in Table 5 examined the influence of the distance d (the mutual distance between carbon fiber bundles B) between carbon fiber bundles B embedded inside the refractory raw material 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, 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 inside a magnesia-carbon refractory (refractory raw material A) with intervals of 3 mm, 5 mm, 10 mm, 20 mm, and 30 mm between them. At that time, the carbon fiber bundle B was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass, which is the adhesive c, and the carbon fiber bundle B with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundle was embedded in the refractory raw material A. The maximum particle size of the aggregate (magnesia) constituting the refractory raw material A is 8 - 5 mm.

[0057] As shown in Invention Examples 1 - 4 and Invention Examples 3 - 2 to 3 - 4, when the distance d (the mutual distance between carbon fiber bundles) between adjacent carbon fiber bundles B is more than 3 mm, the entanglement between the refractory raw material A (refractory body) and the carbon fiber bundle B is good, and high fracture energy is obtained. On the other 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 A (refractory body) 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 (the mutual distance between carbon fiber bundles B) between adjacent carbon fiber bundles B is more than 3 mm, the entanglement between the refractory raw material A (refractory body) and the carbon fiber bundle B is good and the fracture energy can be maintained at a high level.

[0058] Similar examinations were also conducted on graphite-containing refractories using alumina raw materials, silicon carbide raw materials, and silica raw materials as aggregates for the inner lining of the hot metal pretreatment vessel. The examples in Table 6 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, 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-silica-silicon carbide-carbon refractory (refractory raw material A). At that time, the carbon fiber bundle B was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass, which is the adhesive c, and the carbon fiber bundle B with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundle was embedded in the refractory raw material A. The maximum particle size of the aggregates (alumina raw material, silicon carbide raw material, silica raw material) constituting the refractory raw material A is 8 - 5 mm.

[0059] As shown in Invention Examples 4-2 to 4-8, when the content of the alumina raw material was 10 - 95% by mass, the content of the silica raw material was 1 - 50% by mass, the content of the silicon carbide raw material was 1% by mass or more, and the graphite content was 1 - 80% by mass, high bending strength, fracture energy, crack resistance, and corrosion resistance were obtained. On the other hand, as shown in Invention Example 4-1, 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, the content of the silicon carbide raw material was less than 1% by mass, and the graphite content was more than 80% by mass, both the fracture energy, crack resistance, and corrosion resistance decreased. Also, as shown in Invention Example 4-9, 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, the content of the silicon carbide 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 decreased. From the above, it can be understood that in alumina-silica-silicon carbide-carbon refractory, when the content of alumina raw material is 10 to 95% by mass, the content of silica raw material is 1 to 50% by mass, the content of silicon carbide raw material is 1% by mass or more, and the graphite content is 1 to 80% by mass, it is possible to achieve both high corrosion resistance and high fracture energy and crack resistance.

[0060] Examples in Table 7 are 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 a hot metal pretreatment vessel. Regarding the graphite-containing refractory using refractory debris obtained by pulverizing used alumina-silica-silicon carbide-carbon refractory as part of the aggregate raw material, the influence of the refractory debris content on the bending strength, fracture energy and crack resistance, and corrosion resistance of the graphite-containing refractory was investigated. In this example, the blending amount of refractory debris in the alumina-silica-silicon carbide-carbon refractory 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 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 (refractory raw material A). At that time, the carbon fiber bundle B was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass, which is an adhesive c, and the carbon fiber bundle B with the phenolic resin (resin solution) penetrating and adhering inside and outside the bundle was buried in the refractory raw material A. The maximum particle size of the aggregates (alumina raw material, silicon carbide raw material, silica raw material) constituting the refractory raw material A is 8 - 5 mm.

[0061] As shown in Invention Examples 5-1 to 5-3, when the content of refractory debris is 10 to 90% by mass, fracture energy, crack resistance, and corrosion resistance comparable to those of the graphite-containing refractory using only 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 debris exceeds 90% by mass, fracture energy, crack resistance, and corrosion resistance decrease. From the above, regarding the graphite-containing refractory using refractory debris obtained by pulverizing used alumina-silicon carbide-carbonaceous refractory debris as the aggregate raw material, if the content of the refractory debris is 10 to 90% by mass, the fracture energy can be maintained at a high level, 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.

[0062] The examples in Table 8 examined the influence of the composition of alumina-silicon carbide-carbonaceous refractory (graphite-containing refractory with 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, 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 embedded in parallel at 10 mm intervals inside the alumina-silicon carbide-carbonaceous refractory (refractory raw material A). At that time, the carbon fiber bundle B was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass as the adhesive c in advance, and the carbon fiber bundle B with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundle was embedded in the refractory raw material A. The maximum particle size of the aggregates (alumina raw material, silicon carbide raw material) constituting the refractory raw material A is 8 - 5 mm.

[0063] 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 other hand, as shown in Invention Example 6-1, when the content of the alumina raw material is less than 10% by mass and the content of graphite is more than 80% by mass, the fracture energy, crack resistance, and corrosion resistance decrease. Also, as shown in Invention Example 6-5, when the content of the alumina raw material is more than 95% by mass and the content of graphite is less than 1% by mass, the fracture energy and crack resistance decrease. From the above, it can be seen that in the alumina-silicon carbide-carbonaceous refractory, 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 fracture energy, crack resistance, and corrosion resistance can be obtained.

[0064] The examples in Table 9 examined the effects of the composition of silica - silicon carbide - carbonaceous refractories (graphite - containing refractories using 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 (number of strands) was 75,000. A plurality of carbon fiber bundles B were buried in parallel at 10 - mm intervals inside a silica - silicon carbide - carbonaceous refractory (refractory raw material A). At that time, the carbon fiber bundle B was immersed in a phenolic resin (resin solution) with a residual carbon rate of 40% by mass, which is the adhesive c, and the carbon fiber bundle B with the phenolic resin (resin solution) penetrating and adhering to the inside and outside of the bundle was buried in the refractory raw material A. The maximum particle size of the aggregates (silica raw materials, silicon carbide raw materials) constituting the refractory raw material A is 8 - 5 mm.

[0065] As shown in Invention Examples 7 - 2 to 7 - 4, when the content of the silica raw material is 1 - 50% by mass and the content of graphite 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 7 - 1, when the content of the silica raw material is less than 1% by mass and the content of graphite is more than 80% by mass, the fracture energy and crack resistance decrease. Also, as shown in Comparative Example 7 - 5, when the content of the silica raw material is more than 50% by mass, the generation of cracks due to thermal spalling cannot be suppressed, and the fracture energy and crack resistance decrease. From the above, it can be understood that in silica - silicon carbide - carbonaceous refractories, when the content of the silica raw material is 1 - 50% by mass and the content of graphite is 1 - 80% by mass, high flexural strength, fracture energy, crack resistance, and corrosion resistance can be obtained.

[0066]

Table 1

[0067]

Table 2

[0068]

Table 3-1

[0069]

Table 3-2

[0070]

Table 4

[0071]

Table 5

[0072]

Table 6

[0073]

Table 7

[0074]

Table 8

[0075]

Table 9

Explanation of Symbols

[0076] A Refractory Raw Material B Carbon Fiber Bundle c Adhesive s1 Operating Surface s2 Reverse Operating Surface x Refractory Formed Body

Claims

1. A method for manufacturing a graphite-containing refractory in which a carbon fiber bundle (B) (excluding a carbon fiber bundle as part of a carbon fiber fabric) is disposed inside a refractory raw material (A) containing graphite, a preparation step of attaching an organic substance having a residual carbon rate of 6 to 80% by mass or an adhesive (c) containing an organic substance having a residual carbon rate of 6 to 80% by mass and inorganic fine particles to the carbon fiber bundle (B); a forming step of embedding the carbon fiber bundle (B) to which the adhesive (c) has been attached in the refractory raw material (A) and forming the refractory raw material (A) in which the carbon fiber bundle (B) is embedded to obtain a refractory formed body (x), characterized in that it has a forming step. A method for manufacturing a graphite-containing refractory.

2. In the forming step, a binder is added to the refractory raw material (A) and kneaded, and after embedding the carbon fiber bundle (B) in the kneaded product, it is formed. The method for manufacturing a graphite-containing refractory according to claim 1, characterized in that

3. Furthermore, it has a drying step of drying the refractory formed body (x) obtained in the forming step, and is characterized by the method for manufacturing a graphite-containing refractory according to claim 1 or 2.

4. Furthermore, it has a firing step of reducing and firing the refractory formed body (x) that has undergone the drying step, and is characterized by the method for manufacturing a graphite-containing refractory according to claim 3.

5. The organic substance contained in the adhesive (c) is composed of one or more selected from an organic resin solution, tar, pitch, and organic paste, and the inorganic fine particles are composed of an inorganic sol. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 4, characterized in that

6. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 5, characterized in that the width of the carbon fiber bundle (B) is 1 to 15 mm.

7. 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. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 6, characterized in that

8. In the forming step, a plurality of carbon fiber bundles (B) are embedded in parallel inside the refractory raw material (A) so that the interval between adjacent carbon fiber bundles (B) exceeds 3 mm. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 7, characterized in that

9. In the forming process, the presence density of carbon fibers constituting the carbon fiber bundle (B) in the refractory cross-section parallel to the working surface of the graphite-containing refractory is 10 to 2000 fibers / mm within the refractory raw material (A). ２ A method for manufacturing a graphite-containing refractory according to any one of claims 1 to 8, characterized in that the carbon fiber bundle (B) is embedded so as to have the above density.

10. In the forming process, the carbon fiber bundles (B) are embedded inside the refractory raw material (A) such that the occupied area ratio of the carbon fibers constituting the carbon fiber bundles (B) in the refractory cross-section parallel to the operating surface of the graphite-containing refractory is 0.1 to 40%, and the method for manufacturing a graphite-containing refractory according to any one of claims 1 to 9.

11. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 10, characterized in that the refractory raw material (A) contains 1 to 80% by mass of a graphite raw material.

12. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 11, characterized in that the refractory raw material (A) contains 20 to 99% by mass of a magnesia raw material.

13. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 11, characterized in that the refractory raw material (A) contains 10 to 95% by mass of an alumina raw material.

14. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 11, 13, characterized in that the refractory raw material (A) contains 1 to 50% by mass of a silica raw material.

15. The method for manufacturing a graphite-containing refractory according to claim 13 or 14, characterized in that the refractory raw material (A) contains 1% by mass or more of a silicon carbide raw material.

16. The method for manufacturing a graphite-containing refractory according to any one of claims 1 to 15, characterized in that the refractory raw material (A) contains 10 to 90% by mass of refractory debris obtained by pulverizing used refractories.

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