JP7704066B2 - Graphite-containing refractories - Google Patents

Description

The present invention relates to a graphite-containing refractory material with carbon fibers embedded inside.

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

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

As a technology for improving the durability of refractories, Patent Document 1 describes a method of impregnating high-strength fiber bundles with synthetic resin or pitch, and then subjecting the resultant bundle to a hardening treatment such as heat treatment to obtain a rod-shaped or mesh-shaped solidified body, which is then placed inside the refractory. Since the solidified high-strength fiber bundle is placed inside the refractory without losing its shape, it is said that the mechanical strength and spalling resistance of the refractory can be improved.
Patent Document 2 also describes a technique in which a unidirectional bundle or woven fabric made of fibers having a higher tensile strength than the refractory is bonded to a part or the entire surface of a refractory with a heat-resistant adhesive, and claims that this technique can maintain the refractory at a high strength for a long time compared to conventional techniques, improve the tensile strength of the refractory, suppress cracking and destruction, and improve the life and reliability of the refractory. Specifically, it describes a technique in which a bundle or woven fabric of fibers is bonded to a nozzle through which molten steel flows, such as a long nozzle, a submerged nozzle, or a sliding nozzle used in a continuous casting process of steel, in a direction that restrains the outer surface of the nozzle, and an oxidation prevention base layer or oxidation prevention layer is disposed on the surface. In these nozzles, the bundle or woven fabric restrains the thermal expansion toward the outer surface when molten steel flows through the nozzle, and compressive stress is generated in the refractory constituting the nozzle, thereby suppressing the occurrence of cracks and destruction.

JP 2005-320196 A JP 2007-106618 A

However, as a result of investigations conducted by the present inventors, it was found that even if carbon fibers are arranged in a refractory material in the manners shown in Patent Documents 1 and 2, the strength of the refractory material is insufficient for use in a converter or the like that is exposed to severe conditions.
In addition, the technology described in Patent Document 1 involves placing a rod-shaped or mesh-shaped solidified body made by solidifying high-strength fiber bundles with resin, pitch, or the like within a refractory material. Therefore, if the weight per unit area of the carbon fiber bundles is large, when the refractory raw material is molded or constructed by compression molding or pouring, the solidified body acts as resistance, preventing uniform compression and flow of the refractory raw material, resulting in a decrease in the strength and breaking energy of the refractory material and a decrease in its durability.

In addition, in the continuous casting process in which the nozzle described in Patent Document 2 is used, multiple charges of molten steel blown in a converter are continuously cast, so the temperature change cycle of the nozzle used is longer than that of the converter's refractory lining, and since the outer surface of the nozzle is exposed to radiation from the molten steel stored in a downstream vessel located below, the temperature difference with the molten steel flowing inside the nozzle is not that large. In contrast, the converter's refractory lining (bricks that make up the inner wall of the converter), especially the tuyere bricks that make up the tuyere section, are used under extremely harsh conditions as described above, and the inventors have found that the technology described in Patent Document 2 cannot sufficiently improve the durability of such refractories.

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

As a result of extensive investigations aimed at solving the above problems, the inventors have found that high durability can be obtained even in the above-mentioned extremely severe usage environments by embedding a specific carbon fiber fabric in a predetermined form inside the refractory material, and preferably by optimizing the fiber diameter and number of the carbon fibers constituting the carbon fiber fabric, and further the density of the carbon fibers in the cross section of the refractory material.
The present invention has been made based on these findings, and has the following gist.

[1] A graphite-containing refractory having a refractory body (A) having a graphite content of 1 to 80 mass% and a carbon fiber fabric (B) embedded therein,
A graphite-containing refractory material, characterized in that the carbon fiber fabric (B) has a mass of 40 to 1,300 g per ^m2 .
[2] In the graphite-containing refractory of [1] above, the carbon fiber fabric (B) is a fabric in which the carbon fiber bundles (b) are woven in two or more directions at intervals greater than 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 1,000 to 300,000;
A graphite-containing refractory, characterized in that 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/ ^mm2 .

[3] The graphite-containing refractory according to the above [1] or [2], characterized in that a carbon fiber fabric (B) is embedded inside the refractory body (A) along a direction perpendicular to a working surface of the refractory.
[4] The graphite-containing refractory according to any one of the above [1] to [3], wherein the carbon fiber fabric (B) has a spacing of more than 3 mm between the carbon fiber bundles (b) woven in the same direction.
[5] The graphite-containing refractory according to any one of the above [1] to [4], characterized in that 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 the above [1] to [5], characterized in that one layer of carbon fiber fabric (B) is embedded inside the refractory body (A) or two or more layers of carbon fiber fabric (B) are embedded at intervals therebetween.

[7] The graphite-containing refractory according to the above [6], characterized in that the two or more layers of carbon fiber fabric (B) embedded inside the refractory body (A) have an interval of 10 mm or more between them.
[8] The graphite-containing refractory according to any one of the above [1] to [7], characterized in that the carbon fiber fabric (B) is adhered to the refractory body (A) via an adhesive component, and the adhesive component is one or more selected from the group consisting of organic resins, inorganic fine particles derived from inorganic sols, organic substances derived from tar and/or pitch, and organic substances derived from organic glue.

[9] The graphite-containing refractory according to any one of the above [1] to [8], characterized in that the refractory body (A) contains 20 to 99 mass% of a magnesia raw material having a magnesia concentration of 90 mass% or more.
[10] The graphite-containing refractory according to any one of the above [1] to [8], wherein the refractory body (A) contains 10 to 95 mass% of an alumina raw material having an alumina concentration of 70 mass% or more.
[11] The graphite-containing refractory according to any one of the above [1] to [8] and [10], characterized in that the refractory body (A) contains 1 to 50 mass% of a silica raw material.
[12] The graphite-containing refractory according to the above [10] or [11], wherein the refractory body (A) contains 1 mass% or more of a silicon carbide raw material having a silicon carbide concentration of 80 mass% or more.
[13] The graphite-containing refractory according to any one of the above [1] to [12], characterized in that the refractory body (A) contains 10 to 90 mass% of refractory chips obtained by pulverizing used refractories.

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

FIG. 1 is a schematic diagram showing one of the brick components constituting the tuyere brick in one embodiment in which the graphite-containing refractory of the present invention is applied to a tuyere brick, in which FIG. 1(A) is a 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). FIG. 1 is a plan view showing an embodiment of a carbon fiber fabric embedded in a refractory body in a graphite-containing refractory of the present invention. FIG. 1 is a flow chart showing an example of a process for producing the graphite-containing refractory material of the present invention. FIG. 4 shows a method for measuring the bending strength of a graphite-containing refractory in an embodiment. FIG. 4(A) is an explanatory diagram showing a typical implementation state of a three-point bending strength test, and FIG. 4(B) is an explanatory diagram showing a typical end face of the test piece in FIG. 4(A). FIG. 1 is a diagram showing an example of fracture energy (fracture energy of an example of the present invention) calculated from a load-displacement curve obtained in a three-point bending strength test in an embodiment. FIG. 1 is a diagram showing another example of fracture energy (fracture energy of a comparative example) calculated from a load-displacement curve obtained in a three-point bending strength test in the examples. FIG. 6 shows a test method for evaluating the corrosion resistance of a graphite-containing refractory material in the examples. FIG. 6(A) is an explanatory diagram showing the test furnace and a cylindrical sample in vertical section as the test is carried out. FIG. 6(B) is a plan view of the cylindrical sample shown in FIG. 6(A). FIG. 6(C) is a perspective view showing one of the test pieces constituting the cylindrical sample shown in FIGS. 6(A) and (B).

The graphite-containing refractory of the present invention is a graphite-containing refractory having a carbon fiber fabric B embedded inside a refractory body A having a graphite content of 1 to 80% by mass, the carbon fiber fabric B having a mass of 40 to 1,300 g per ^m2 . By embedding such carbon fiber fabric B inside the refractory body A, the carbon fiber fabric B is integrated with the refractory and does not slip inside the refractory body A, so that the fracture energy of the entire refractory is significantly increased and the crack propagation suppression effect is also improved.

Fig. 1 shows a schematic diagram of one embodiment of the graphite-containing refractory of the present invention, in which 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 working surface), where x is the refractory working surface (y is the opposite working surface). In the graphite-containing refractory of this embodiment, three layers of carbon fiber fabric B are embedded at intervals inside a refractory body A.
FIG. 2 is a plan view 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 oriented in two directions (two perpendicular directions).

The configuration and embedding conditions of the carbon fiber fabric B will be described below.
The carbon fiber fabric B is made by weaving the carbon fiber bundles b oriented in two or more directions, and the number of orientations is optional. Note that if the carbon fiber bundles b are oriented in one direction, a carbon fiber fabric cannot be formed, and therefore a graphite-containing refractory material having an embedded carbon fiber fabric cannot be obtained.
The mass of the carbon fiber fabric B is 40 to 1300 g per ^m2 . Here, the mass per ^m2 refers to the total mass of the laminated multiple sheets of fabric when the carbon fiber fabric B is composed of multiple laminated sheets as described below. If the mass of the carbon fiber fabric B per ^m2 is less than 40 g, the carbon fiber fabric is too thin, so the crack growth suppression effect is not improved and the fracture energy does not increase. On the other hand, if the mass of the carbon fiber fabric B per ^m2 exceeds 1300 g, the carbon fiber fabric is too thick, so that when the refractory is compression molded, a rebound called springback occurs after compression, or the transmission of the compression force becomes uneven, causing internal defects in the refractory or causing defects such as uneven properties, thereby reducing durability. In addition, even when the refractory is molded by pouring rather than compression molding, uniform inflow is hindered or voids contained in or associated with the carbon fiber fabric remain, reducing durability.

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

The intervals between the carbon fiber bundles b woven in the same direction that constitute the carbon fiber fabric B are preferably larger than the maximum particle size of the aggregate (coarse particles called aggregate among the refractory raw materials) that constitutes the refractory body A. In other words, the carbon fiber bundles b woven in the same direction are preferably woven at intervals that are greater than the maximum particle size of the aggregate that constitutes the refractory body A. This allows the aggregate (coarse particles) to enter between the stitches of the carbon fiber fabric b, and the progression of cracks that occur along the surface of the aggregate (coarse particles) can be suppressed.

The carbon fiber bundle b constituting the carbon fiber fabric 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 preferably 1,000 to 300,000. If the fiber diameter of the carbon fibers constituting the carbon fiber fabric B (carbon fiber bundle b) is 1 μm or more and the number of carbon fibers per bundle of the carbon fiber bundle b is 1,000 or more, a higher crack propagation suppression effect can be obtained. On the other hand, if the fiber diameter of the carbon fibers constituting the carbon fiber fabric B (carbon fiber bundle b) is 45 μm or less and the number of carbon fibers per bundle of the carbon fiber bundle b is 300,000 or less, non-uniformity during molding is suppressed and durability is improved.
Furthermore, when the fiber diameter of the carbon fibers constituting the carbon fiber bundle b is less than 1 μm and the number of carbon fibers per bundle of carbon fiber bundle b is less than 1,000, the mass per ^m2 of the carbon fiber fabric B is likely to be less than 40 g. On the other hand, 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 per bundle of carbon fiber bundle b is more than 300,000, the mass per ^m2 of the carbon fiber fabric B is likely to be more than 1,300 g.

In addition, the carbon fiber fabric B is preferably embedded inside the refractory body A so that the density of carbon fibers constituting the carbon fiber fabric B in the cross section of the refractory parallel to the refractory operating surface x (embedding density) is 10 to 2000 fibers/ ^mm2 . This increases the contact area between the refractory raw material and the carbon fiber bundles b constituting the carbon fiber fabric B, and also increases the adhesion between the refractory raw material and the carbon fiber fabric B, resulting in a significant increase in fracture energy. Here, the density of carbon fibers (embedding density) is the value obtained by dividing the total number of carbon fibers (fibers) constituting the carbon fiber bundles b of the carbon fiber fabric B, excluding the carbon fiber bundles b parallel to the refractory operating surface, by the area ( ^mm2 ) of the cross section of the refractory parallel to the refractory operating surface.
If the density of carbon fibers (embedding density) is less than 10 fibers/ ^mm2 , the contact area between the refractory raw material and the carbon fiber bundle b is too small, so that the adhesion between the refractory raw material and the carbon fiber fabric B is not increased, and a significant increase in the fracture energy cannot be expected. If the density of carbon fibers (embedding density) is more than 2000 fibers/ ^mm2 , the contact area between the refractory raw material and the carbon fiber bundle b is too large, so that the carbon fiber bundle b is likely to spring back during molding, which may cause problems in molding.

In the carbon fiber fabric B, the interval between the carbon fiber bundles b woven in the same direction is preferably more than 3 mm. This allows the carbon fiber fabric B to be well entangled with not only the coarse particles but also the fine particles as described above, thereby increasing the bending strength and breaking energy. Here, the interval between the carbon fiber bundles b refers to the distances _L1 and _L2 between the centers of the carbon fiber bundles b shown in Figure 2, and when the intervals differ depending on the direction, it is desirable that the shorter interval exceeds 3 mm.
The carbon fiber fabric B is composed of one layer or two or more laminated layers of fabric, and when the carbon fiber fabric B is composed of two or more laminated layers of fabric, the number of fabrics is optional. The carbon fiber fabric B can be embedded in the refractory body A in one layer or in two or more layers spaced apart from each other, and when two or more layers are embedded, the number of layers is optional. By increasing the number of fabrics per layer of the carbon fiber fabric B or by 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.
Furthermore, when two or more layers of carbon fiber fabric B are embedded inside the refractory body A, if the spacing between the layers of carbon fiber fabric B is too narrow, the carbon fiber bundles b constituting the carbon fiber fabric B will spring back during molding, making the molded body more susceptible to cracks. Therefore, in order to suppress the spring back of the carbon fiber bundles b, it is preferable that the spacing between the layers of carbon fiber fabric B be 10 mm or more.

The carbon fiber fabric B is preferably adhered to the refractory body A via an adhesive (tackifier) component, which increases the adhesion between the refractory raw material A and the carbon fiber fabric B, making it easier to densify the refractory during molding and significantly improving the breaking energy. 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 and/or pitch, and organic substances derived from organic glues, and the adhesive component may be one or more selected from these.
Therefore, examples of adhesives (tackifiers) that are applied to carbon fiber fabrics during production include organic resins (solutions), inorganic sols, pitch, tar, organic glues, etc. Specific examples include 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 glue, etc., and one or more selected from these can be used.

Next, the composition of the refractory body A will be described.
The graphite content of the refractory body A is 1 to 80% by mass, and if the graphite content is less than 1% by mass, the occurrence of cracks due to thermal stress cannot be suppressed, and crack resistance is significantly reduced. On the other hand, if the graphite content exceeds 80% by mass, properties such as resistance to melting, crack resistance, and fracture energy may be adversely affected depending on the material of the refractory body A. As the graphite (carbon raw material), flake graphite or the like is generally used.
In general, the lining (including the tuyere) of the converter used in the refining process is made of magnesia-carbonaceous refractories (graphite-containing refractories with magnesia raw materials as aggregates), which are refractories mainly composed of magnesia and carbon. When the refractory body A is a magnesia-carbonaceous refractory, the refractory body A preferably contains 20 to 99 mass% of high-purity magnesia raw materials with a magnesia concentration of 90 mass% or more, which makes it possible to suppress cracking due to thermal spalling and to make the refractory resistant to erosion by converter slag. If the content of the magnesia raw materials exceeds 99 mass%, cracking cannot be suppressed and cracking resistance is significantly reduced. On the other hand, if the content of the magnesia raw materials is less than 20 mass%, the refractory cannot withstand erosion by converter slag and corrosion resistance is significantly reduced.

In addition, generally, alumina-silicon carbide-carbon refractories (graphite-containing refractories with aggregates of alumina raw materials and silicon carbide raw materials) which are refractories mainly composed of alumina, silicon carbide, and carbon, and alumina-silicon carbide-silica-carbon refractories (graphite-containing refractories with aggregates of alumina raw materials, silicon carbide raw materials, and silica raw materials) which are refractories mainly composed of alumina, silicon carbide, silica, and carbon are used for the lining of torpedoes and blast furnace ladles used in the hot metal pretreatment process. When the refractory body A is an alumina-silicon carbide-carbon refractory or an alumina-silicon carbide-silica-carbon refractory, it is preferable that it contains 10 to 95 mass% of high-purity alumina raw material with an alumina concentration of 70 mass% or more, which can withstand the erosion of the hot metal pretreatment slag and suppress cracking due to thermal spalling. If the alumina raw material content is less than 10% by mass, the material cannot withstand the erosion of the molten iron pretreatment slag, and the slag penetrates into the matrix of the refractory body A (brick), reducing its resistance to corrosion. On the other hand, if the alumina raw material content exceeds 95% by mass, the generation of cracks due to thermal spalling cannot be suppressed, reducing its resistance to cracking.

Furthermore, when the refractory body A is an alumina-silicon carbide-carbonaceous refractory or an alumina-silicon carbide-silica-carbonaceous refractory, it is preferable that the refractory body A contains 1 mass% or more of high-purity silicon carbide raw material with a silicon carbide concentration of 80 mass% or more. By containing 1 mass% or more of silicon carbide raw material, oxidation of graphite in the air atmosphere can be suppressed, so high cracking resistance can be maintained. If the content of silicon carbide raw material is less than 1 mass%, oxidation of graphite in the air atmosphere cannot be suppressed, so cracking resistance decreases.
Furthermore, when the refractory body A is an alumina, silicon carbide, silica, or carbonaceous refractory, it is preferable that the silica raw material content is 1 to 50 mass%, which allows both high crack resistance and high resistance to erosion. If the content of the silica raw material is less than 1 mass%, the amount of expansion is small and microcracks are not generated, so the thermal shock fracture resistance is not increased and the crack resistance is likely to decrease. On the other hand, if the content of the silica raw material exceeds 50 mass%, the resistance to erosion is significantly deteriorated.

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

In addition, when the refractory body A is a silica-silicon carbide-carbonaceous refractory, which is a refractory mainly composed of silica, silicon carbide, and carbon, it is preferable to contain 1% by mass or more of high-purity silicon carbide raw material with a silicon carbide concentration of 80% by mass or more and 1 to 50% by mass of silica raw material, which allows both high crack resistance and high resistance to erosion. By containing 1% by mass or more of silicon carbide raw material, oxidation of graphite in the air atmosphere can be suppressed, so high crack resistance can be maintained. If the content of silicon carbide raw material is less than 1% by mass, oxidation of graphite in the air atmosphere cannot be suppressed, and crack resistance decreases. Also, if the content of 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 is not increased and crack resistance is easily reduced. On the other hand, if the content of silica raw material exceeds 50% by mass, resistance to erosion is significantly deteriorated.

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

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

In the refractory body A made of alumina, silicon carbide, and carbonaceous refractories, when the content of refractory scrap obtained by crushing used alumina, silicon carbide, and carbonaceous refractories is 10 to 90 mass%, the cracking resistance and corrosion resistance are the same as those of a graphite-containing refractory using only virgin raw materials. The reason for this is that although the refractory scrap raw material has a lower purity than the virgin raw material, by using the refractory scrap raw material and the virgin raw material in combination, a significant decrease in corrosion resistance of the Al ₂ O ₃ component in the refractory scrap raw material can be suppressed. On the other hand, when the content of the refractory scrap is more than 90 mass%, the content of the virgin raw material is too small, so that a significant decrease in corrosion resistance of the Al ₂ O ₃ component in the refractory scrap raw material cannot be suppressed. In addition, when the content of the refractory scrap is less than 10 mass%, the reuse rate of the refractory scrap is too low, so the cost of processing the refractory scrap as industrial waste increases significantly.
The graphite-containing refractory of the present invention includes not only so-called refractory bricks produced through press molding, but also refractories which are molded by pouring into a construction site, which is a working surface such as a ladle or a tundish, and then dried and solidified as is, as described below.

Next, the method for producing the graphite-containing refractory material of the present invention will be described.
3 shows an example of a manufacturing process for the graphite-containing refractory of the present invention. In this manufacturing process, an appropriate amount of binder is added to the refractory raw material and kneaded, and the kneaded mixture is filled into a mold together with carbon fiber fabric and press-molded to obtain a molded refractory product. Examples of binders that can be used include phenol resin (base material) + hexamine (hardener), carbon bond, and ceramic bond.
As a method for filling a mold with a kneaded refractory raw material together with carbon fiber fabric, for example, there is a method in which a certain amount of the kneaded material is charged into a mold, the carbon fiber fabric is charged, and then a certain amount of the kneaded material is charged into the mold. Therefore, to produce a graphite-containing refractory having multiple layers of carbon fiber fabric embedded therein as shown in Fig. 1 by this method, a certain amount of the kneaded material is charged into a mold, and then the carbon fiber fabric and a certain amount of the kneaded material are repeatedly charged.
Furthermore, when an adhesive (tackifier) is applied to a carbon fiber fabric, the adhesive is applied to the carbon fiber fabric by, for example, immersing the carbon fiber fabric in a resin (resin solution) or sol that constitutes the adhesive, or by spraying the resin (resin solution) or sol that constitutes the adhesive onto the carbon fiber fabric, and the carbon fiber fabric with the adhesive still attached is loaded into a mold together with the kneaded material in the manner described above.

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

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. After drying (curing), the refractory molded product may be subjected to further reduction firing (caulking treatment) to produce a product brick (fired brick).
In addition, the refractory molded body obtained by the above-mentioned casting molding is dried and solidified by heating the refractory molded body held in an inner frame installed at the construction site or in a form installed in another location with a heating means such as a heating burner, after which the inner frame is removed and the mold is taken out.

In this manner, the graphite-containing refractory of the present invention having the carbon fiber fabric embedded inside the refractory body is obtained.
The graphite-containing refractory of the present invention can be used as a refractory for various facilities and containers, and is particularly suitable as a refractory lining for refining vessels and transport vessels used in steelworks, particularly as a refractory lining for converters, which are used in very severe environments, and is particularly suitable as a tuyere brick for forming the tuyere.

A graphite-containing refractory having carbon fiber fabric embedded inside the refractory body was manufactured by the procedure shown in Fig. 3. When the refractory raw materials were kneaded and molded, 3 mass% of phenol resin and 0.3 mass% of hexamine were blended as binders on an outer basis with respect to the refractory raw materials.
The produced graphite-containing refractories were evaluated for bending strength, fracture energy, resistance to melting damage, and resistance to cracking by the following methods.
The bending strength was measured in accordance with the three-point bending test method described in JIS R2213 using test specimens (test specimen size: 40 mm×80 mm×160 mm) in which a single layer or multiple layers of woven carbon fiber fabric were embedded inside a refractory body along its longitudinal direction, with a center-to-center distance of 100 mm and a load application rate of 0.5 mm/min, as shown in FIG. 4 (Test Method).

As shown in Figures 5-1 and 5-2, the fracture energy was evaluated based on the area within a range of 1 mm displacement from the reference position, which was the position showing the first peak value in the load-displacement curve obtained in the three-point bending strength test. Figure 5-1 shows an example of fracture energy obtained from the load-displacement curve of an example of the present invention, and Figure 5-2 shows an example of fracture energy obtained from the load-displacement curve of a comparative example in which no carbon fiber fabric is embedded.
The corrosion resistance was evaluated based on the amount of corrosion measured by the lining method using a high-frequency induction furnace as shown in FIG. 6 (Test Method). In the test using the lining method, the test temperature was 1650°C, the temperature was held for 4 hours, and synthetic slag having the composition shown in Table 2 was charged every hour. After cooling, the amount of corrosion on the working surface was measured. From the amount of corrosion, the corrosion index was calculated by taking the amount of corrosion of the invention blending example 1-3 in Table 1 as 100. As shown in FIG. 6(C), the test specimen had a carbon fiber fabric embedded perpendicularly on the surface (working surface of the refractory) that contacts the slag and molten steel. FIG. 6(A) is an explanatory diagram showing the test furnace and the cylindrical sample in a vertical cross section, 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 specimens constituting the cylindrical sample shown in FIG. 6(A) and (B).

For crack resistance, the dynamic modulus of elasticity _E0 in the longitudinal direction of a 40x80x200 mm sample was measured according to the ultrasonic pulse method specified in JIS R1605, and then a cycle of heating at 1500°C for 10 minutes, water cooling for 5 minutes, and air cooling for 10 minutes was repeated three times, after which the dynamic modulus of elasticity _E3 was measured again by the above method, and the rate of change in the dynamic modulus of elasticity _E3 / _E0 before and after the test was used as an index for evaluation. The test specimen used had a carbon fiber fabric embedded along the longitudinal direction of the refractory body as shown in Figure 1.

Refractory molded products were produced using magnesia raw material as aggregate with the raw material composition shown in Table 1, i.e., graphite-containing refractories without embedded carbon fiber fabric, and their melting resistance and cracking resistance were evaluated. The results are also shown in Table 1.
As shown in Inventive Blend Example 1-1 to Inventive Blend Example 1-7 in Table 1, when the graphite content is 1 to 80 mass%, the corrosion resistance and cracking resistance are good, but as shown in Comparative Blend Example 1-1, when the graphite content is less than 1 mass%, the cracking resistance is significantly reduced. Also, as shown in Comparative Blend Example 1-2, when the graphite content is more than 80 mass%, the corrosion resistance is significantly reduced.
Furthermore, as shown in Invention Blend Example 1-1 to Invention Blend Example 1-7, in the blending of magnesia/carbonaceous raw materials, if the content of the magnesia raw material (magnesia concentration 100% by mass in the case of Table 1) is 20 to 99% by mass, the corrosion resistance and cracking resistance are good. From the above, in order to achieve both corrosion resistance and cracking resistance of a graphite-containing refractory material, the graphite content needs to be 1 to 80% by mass, and in the case of magnesia/carbonaceous raw materials, it is also found that the content of the magnesia raw material should be 20 to 99% by mass.

Tables 3 to 11 show the configurations and properties (flexural strength, fracture energy, melting resistance, and cracking resistance) of the graphite-containing refractories (graphite-containing refractories having carbon fiber fabric embedded inside the refractory body) of the invention examples and comparative examples.
First, the examples in Table 3 are for carbon fiber fabrics embedded inside the refractory body, and the effects of the fiber diameter of the carbon fibers constituting the carbon fiber bundles, the number of carbon fibers (strands) per carbon fiber bundle, the mass per ^m2 of the carbon fiber fabric, and the density of the carbon fibers (embedding density) in a cross section of the refractory parallel to the operating surface of the refractory on the bending strength, fracture energy, and crack resistance of the graphite-containing refractory were examined.

In this embodiment, carbon fiber fabrics with different masses ^per m2 were prepared 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 (number) per bundle to 900 to 350,000, and were embedded inside the magnesia-carbonaceous refractory (refractory body) so that the density of the carbon fibers in the refractory cross section parallel to the refractory operating surface was different. The magnesia-carbonaceous refractory had the composition of the invention blend example 1-3 in Table 1. The number of embedded layers of the carbon fiber fabric was one layer, which was composed of one piece of fabric. In addition, the carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric to which the phenolic resin (resin solution) was attached was embedded in the refractory body. The maximum particle size of the aggregate (magnesia) constituting the refractory body was less than 5 mm.
As shown in Examples 2-1 to 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 (number) per carbon fiber bundle is 1,000 to 300,000, the mass per ^m2 of the carbon fiber fabric is 40 to 1,300 g, the density of the carbon fibers in the refractory cross section parallel to the refractory operating surface is 10 to 2,000 fibers/ ^mm2 , and high bending strength, fracture energy, and crack resistance are obtained.

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 (number of fibers) per carbon fiber bundle is less than 1,000, the mass per ^m2 of the carbon fiber fabric is less than 40 g, the density of the carbon fibers (embedding density) in the refractory cross section parallel to the refractory operating surface is less than 10 fibers/ ^mm2 , and the carbon fiber fabric is too thin, so that high bending strength, fracture energy, and crack resistance cannot be obtained.
In addition, as shown in Comparative Example 2-2, when the fiber diameter of the carbon fiber 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, the mass per ^m2 of the carbon fiber fabric exceeds 1,300 g, and the density of the carbon fibers in the cross section of the refractory parallel to the refractory operating surface exceeds 2,000 fibers/ ^mm2 . When the refractory raw material (magnesia-carbonaceous raw material) is molded with the carbon fiber fabric embedded, cracks occur on the side of the molded body, causing the carbon fiber fabric to protrude, making molding difficult. This is because the carbon fiber bundles constituting the carbon fiber fabric are too thick, the carbon fiber fabric is poorly entangled with the refractory raw material, and springback is likely to occur during molding. Furthermore, as shown in Comparative Example 2-3, it is not possible to form a carbon fiber fabric by simply orienting the carbon fiber bundles in one direction, so it is impossible to manufacture a graphite-containing refractory with the carbon fiber fabric embedded therein.

From the above, it is understood that a graphite-containing refractory that is moldable and has high bending strength, fracture energy, and crack resistance can be obtained by setting the mass per 1 ^m2 of the carbon fiber fabric embedded in the refractory body to 40 to 1300 g and the density of the carbon fibers in the refractory cross section parallel to the refractory operating surface to 10 to 2000 fibers/ ^mm2 . It is also understood that in order to set the mass per 1 ^m2 of the carbon fiber fabric to 40 to 1300 g, it is preferable that the fiber diameter of the carbon fibers constituting the carbon fiber bundle is 1 to 45 μm and the number of carbon fibers (number) per bundle of the carbon fiber bundle is 1000 to 300,000.

The examples in Table 4 examine the effect of the spacing between carbon fiber bundles constituting a carbon fiber fabric (the spacing between carbon fiber bundles woven in the same direction) on the bending strength, fracture energy, and crack resistance of a graphite-containing refractory material.
In this embodiment, carbon fiber bundles with a fiber diameter of 7 μm and a number of carbon fibers (number) per bundle of 75,000 were woven at intervals of 3 mm, 5 mm, 10 mm, 20 mm, and 30 mm to prepare a carbon fiber fabric with a mass of 110 to 1120 g per ^m2 . The carbon fiber fabric was embedded inside a magnesia-carbonaceous refractory (refractory body) so that the density of the carbon fibers in the refractory cross section parallel to the refractory operating surface was 200 to 2000 fibers/ ^mm2 . The magnesia-carbonaceous refractory had the composition of the invention blend example 1-3 in Table 1. The number of embedded layers of the carbon fiber fabric was one, and it was composed of one sheet of fabric. The carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric with the phenolic resin (resin solution) attached thereto 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 Examples 2-4 and 3-2 to 3-4, when the interval (weaving interval) between the carbon fiber bundles constituting the carbon fiber fabric exceeds 3 mm, the carbon fiber fabric and the refractory raw material (magnesia/carbonaceous raw material) are well entangled, and high bending strength, fracture energy, and crack resistance are obtained.
On the other hand, as shown in 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 Examples 3-2 to 3-4.
From the above, it was found that if the spacing (weaving spacing) between the carbon fiber bundles constituting the carbon fiber fabric is more than 3 mm, the carbon fiber fabric and the refractory raw material are well entangled, and a graphite-containing refractory having high bending strength, fracture energy, and cracking resistance can be obtained.

The examples in Table 5 were conducted to examine the effect of pre-treating a carbon fiber fabric with an adhesive on the bending strength, fracture energy and crack resistance of a graphite-containing refractory material.
In this example, a carbon fiber fabric having a mass of 335 g ^{per m2} was used, in which carbon fiber bundles with a fiber diameter of 7 μm and a number of carbon fibers (number) of 75,000 per bundle were woven at intervals of 10 mm. This carbon fiber fabric was immersed in various adhesives (solutions), and the carbon fiber fabric with the adhesives (solutions) attached was embedded inside a magnesia-carbonaceous refractory (refractory body) so that the density of the carbon fibers in the refractory cross section parallel to the refractory operating surface was 610 fibers/ ^mm2 . In some of the invention examples, the carbon fiber fabric was embedded inside a magnesia-carbonaceous refractory (refractory body) at the same density as above without attaching an adhesive (solution). The magnesia-carbonaceous refractory had the composition of the invention blending example 1-3 in Table 1. The number of embedded layers of the carbon fiber fabric was one, and it was composed of one piece of fabric. The maximum particle size of the aggregate (magnesia) constituting the refractory body is less than 5 mm.

As shown in Examples 2-4 and 4-1 to 4-10, when carbon fiber fabric with an adhesive attached is embedded, the adhesion between the carbon fibers and between the carbon fiber fabric and the refractory raw material is improved, and therefore the bending strength, fracture energy, and crack resistance are higher than when no adhesive is attached to the carbon fiber fabric as shown in Example 4-11. Also, as shown in Examples 4-6 to 4-10, when carbon fiber fabric with two types of adhesive attached is embedded, the adhesion is further improved, and therefore particularly high bending strength, fracture energy, and crack resistance are obtained.
From the above, it was found that by adhering a carbon fiber fabric with an adhesive such as phenolic resin and then embedding it in a refractory body, a graphite-containing refractory with high bending strength, fracture energy, and crack resistance can be obtained.

The examples in Table 6 were obtained by investigating the influence of the number of woven fabrics per layer of carbon fiber fabric and the number of embedded layers of carbon fiber fabric on the bending strength, fracture energy and crack resistance of graphite-containing refractories.
In this embodiment, a carbon fiber fabric having a mass of 335 to 1050 g ^{per m2} was used, in which carbon fiber bundles with a fiber diameter of 7 μm and a number of carbon fibers (number) per bundle of 75,000 were woven at intervals of 10 mm, and this was embedded inside a magnesia-carbonaceous refractory (refractory body) so that the density of carbon fibers present in the refractory cross section parallel to the refractory operating surface was 610 to 1900 fibers/ ^mm2 , and the number of fabrics per layer and the number of embedded layers of carbon fiber fabric were changed. The magnesia-carbonaceous refractory had the composition of the invention blend example 1-3 in Table 1. The carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric with the phenolic resin (resin solution) attached thereto was embedded in the refractory body. The maximum particle size of the aggregate (magnesia) constituting the refractory body was less than 5 mm.

As shown in Examples 2-4 and 5-1 to 5-4, high bending strength, fracture energy, and crack resistance were obtained regardless of the number of fabrics per carbon fiber fabric layer or the number of embedded layers of carbon fiber fabric. However, the bending strength, fracture energy, and crack resistance were slightly higher when the number of fabrics per carbon fiber fabric layer or the number of embedded layers of carbon fiber fabric was larger.
From the above, it was found that by making the number of sheets of fabric per layer of carbon fiber fabric one or more and embedding one or more layers of carbon fiber fabric, a graphite-containing refractory material having high bending strength, fracture energy, and crack resistance can be obtained.

The examples in Table 7 were obtained by investigating the effect of the spacing between layers of carbon fiber fabric (embedding spacing) on the moldability of the graphite-containing refractory when two or more layers of carbon fiber fabric were embedded at intervals inside the refractory body.
In this example, a carbon fiber fabric was used in which carbon fiber bundles with a fiber diameter of 7 μm and a number of carbon fibers (number) of 75,000 per bundle were woven at intervals of 10 mm, and the mass per ^m2 was 44 to 513 g. The carbon fiber fabric was embedded in the magnesia-carbonaceous refractory (refractory body) in three or five layers at intervals of 8 mm, 10 mm, 20 mm, and 30 mm, respectively, and the press-molded molded body was examined for cracks. The magnesia-carbonaceous refractory had the composition of the invention blend example 1-3 in Table 1. Each layer of the carbon fiber fabric was composed of one or three pieces of fabric, and the density of carbon fibers in the refractory cross section parallel to the refractory operating surface was ⁷¹ to 925 fibers/mm2. The carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric with the phenolic resin (resin solution) attached thereto 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 Examples 2-4, 5-3, 5-4, 6-2, 6-3, and 6-5 to 6-8, when the embedding interval between multiple layers of carbon fiber fabric was 10 mm or more, the interval between the carbon fiber fabric layers in the press molding direction was not too narrow, so that the carbon fiber bundles constituting the carbon fiber fabric did not spring back during molding, and no cracks were generated in the molded body.
On the other hand, as shown in Examples 6-1 and 6-4, when the embedding interval between the layers of the carbon fiber fabric was less than 10 mm, the interval between the carbon fiber fabric layers in the press molding direction was too narrow, so that the carbon fiber bundles caused 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.

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 examine the effects of the composition of alumina, silica, silicon carbide, and carbonaceous refractories (graphite-containing refractories using alumina raw materials, silicon carbide raw materials, and silica raw materials as aggregates) used for the lining of a molten iron pretreatment vessel on the bending strength, fracture energy, crack resistance, and corrosion resistance of the graphite-containing refractories.
In this embodiment, a carbon fiber fabric having a mass of 335 g ^{per m2} was used, in which carbon fiber bundles with a fiber diameter of 7 μm and a number of carbon fibers (number) of 75,000 per bundle were woven at intervals of 10 mm, and this was embedded inside an alumina-silica-silicon carbide-carbonaceous refractory (refractory body) so that the density of carbon fibers present in the refractory cross section parallel to the refractory operating surface was 610 fibers/ ^mm2 . The number of embedded layers of the carbon fiber fabric was one layer, which was composed of one piece of fabric. The carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric to which the phenolic resin (resin solution) was 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.

As shown in Examples 7-1 to 7-7, when the content of the alumina raw material is 10 to 95 mass%, the content of the silica raw material is 1 to 50 mass%, and the content of graphite is 1 to 80 mass%, high bending strength, fracture energy, crack resistance, and melting resistance are obtained.
In contrast, as shown in Comparative Example 7-1, when the content of the alumina raw material is less than 10 mass%, the content of the silica raw material is less than 1 mass%, and the graphite content is more than 80 mass%, both the fracture energy and the corrosion resistance are significantly reduced.
In addition, as shown in Comparative Example 7-2, when the content of the alumina raw material is more than 95% by mass, the content of the silica raw material is less than 1% by mass, and the content of graphite is less than 1% by mass, the occurrence of cracks due to thermal spalling cannot be suppressed, and the fracture energy and crack resistance are significantly reduced.
From the above, it can be seen that in an alumina-silica-silicon carbide-carbonaceous refractory, if the content of the alumina raw material is 10 to 95 mass %, the content of the silica raw material is 1 to 50 mass %, and the graphite content is 1 to 80 mass %, then it is possible to achieve both high resistance to corrosion and high fracture energy/crack resistance.

The examples in Table 9 are alumina-silica-silicon carbide-carbonaceous refractories (graphite-containing refractories using alumina raw materials, silicon carbide raw materials, and silica raw materials as aggregates) used for lining the inside of a molten iron pretreatment vessel, and for graphite-containing refractories using refractory scrap obtained by crushing used alumina-silica-silicon carbide-carbonaceous refractories as part of the aggregate raw materials, the effects of the refractory scrap content on the bending strength, fracture energy/crack resistance, and corrosion resistance of the graphite-containing refractories were investigated.
In this embodiment, a carbon fiber fabric having a mass of 335 g ^{per m2} was used, in which carbon fiber bundles with a fiber diameter of 7 μm and a number of carbon fibers (number) of 75,000 per bundle were woven at intervals of 10 mm, and this was embedded inside an alumina-silica-silicon carbide-carbonaceous refractory (refractory body) so that the density of carbon fibers present in the refractory cross section parallel to the refractory operating surface was 610 fibers/ ^mm2 . The number of embedded layers of the carbon fiber fabric was one layer, which was composed of one piece of fabric. The carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric to which the phenolic resin (resin solution) was attached was embedded in the refractory body. The maximum particle size of the aggregate (alumina raw material, silicon carbide raw material, silica raw material, and refractory chips obtained by crushing used alumina-silica-silicon carbide-carbonaceous refractory) constituting the refractory body was less than 5 mm.

As shown in Examples 8-1 to 8-3, when the content of refractory scrap is 10 to 90 mass%, the content of silica raw material is 1 mass% or more, and the content of graphite is 1 to 80 mass%, the fracture energy, crack resistance, and corrosion resistance are comparable to those of the graphite-containing refractory material using only virgin raw materials shown in Table 8.
In contrast, as shown in Comparative Example 8-1, when the refractory scrap content is more than 90% by mass, the silica raw material content 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, it can be seen that in alumina-silica-silicon carbide-carbonaceous refractories, graphite-containing refractories using refractory scrap obtained by crushing used alumina-silica-silicon carbide-carbonaceous refractories as part of the aggregate raw material can maintain high fracture energy and crack resistance and further have the same level of melting wear resistance as graphite-containing refractories using only virgin raw materials if the refractory scrap content is 10 to 90 mass %, the silica raw material content is 1 mass % or more, and the graphite content is 1 to 80 mass %.

The examples in Table 10 are for alumina-silicon carbide-carbonaceous refractories (graphite-containing refractories using alumina raw materials and silicon carbide raw materials as aggregates), and are intended to examine the effects of the composition of the graphite-containing refractories on the bending strength, fracture energy, crack resistance, and corrosion resistance.
In this embodiment, a carbon fiber fabric having a mass of 335 g ^{per m2} was used, in which carbon fiber bundles with a fiber diameter of 7 μm and a number of carbon fibers (number) of 75,000 per bundle were woven at intervals of 10 mm, and this was embedded inside an alumina-silicon carbide-carbonaceous refractory (refractory body) so that the density of carbon fibers present in the refractory cross section parallel to the refractory operating surface was 610 fibers/ ^mm2 . The number of embedded layers of the carbon fiber fabric was one layer, which was composed of one piece of fabric. The carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric to which the phenolic resin (resin solution) was attached was embedded in the refractory body. The maximum particle size of the aggregate (alumina raw material, silicon carbide raw material) constituting the refractory body was less than 5 mm.

As shown in Examples 9-1 to 9-3, when the content of the alumina raw material is 10 to 95 mass% and the content of graphite is 1 to 80 mass%, high bending strength, fracture energy, crack resistance, and corrosion resistance are obtained.
In contrast, as shown in Comparative Example 9-1, when the alumina raw material content is less than 10 mass% and the graphite content is more than 80 mass%, the fracture energy and corrosion resistance are significantly decreased. Also, as shown in Comparative Example 9-2, when the alumina raw material content is more than 95 mass% and the graphite content is less than 1 mass%, the fracture energy and crack resistance are significantly decreased.
From the above, it can be seen that in an alumina-silicon carbide-carbonaceous refractory, if the alumina raw material content is 10 to 95 mass % and the graphite content is 1 to 80 mass %, high fracture energy, crack resistance, and melting resistance can be obtained.

The examples in Table 11 are for silica, silicon carbide, and carbonaceous refractories (graphite-containing refractories using silica raw material and silicon carbide raw material as aggregates) and are intended to examine the effects of the composition of the graphite-containing refractories on the bending strength, fracture energy, crack resistance, and corrosion resistance.
In this embodiment, a carbon fiber fabric having a mass of 335 g ^{per m2} was used, in which carbon fiber bundles with a fiber diameter of 7 μm and a number of carbon fibers (number) of 75,000 per bundle were woven at intervals of 10 mm, and this was embedded inside a silica-silicon carbide-carbonaceous refractory (refractory body) so that the density of carbon fibers present in the refractory cross section parallel to the refractory operating surface was 610 fibers/ ^mm2 . The number of embedded layers of the carbon fiber fabric was one layer, which was composed of one piece of fabric. The carbon fiber fabric was immersed in a phenolic resin (resin solution) as an adhesive in advance, and the carbon fiber fabric to which the phenolic resin (resin solution) was attached was embedded in the refractory body. The maximum particle size of the aggregate (silica raw material, silicon carbide raw material) constituting the refractory body was less than 5 mm.

As shown in Examples 10-1 and 10-2, when the content of the silica raw material is 1 to 50 mass% and the content of graphite is 1 to 80 mass%, high bending strength, fracture energy, crack resistance, and melting resistance are obtained.
In contrast, as shown in Comparative Example 10-1, when the content of silica raw material is less than 1 mass% and the content of graphite is more than 80 mass%, the fracture energy and crack resistance are decreased. Also, as shown in Comparative Example 10-2, when the content of graphite is more than 80 mass%, the fracture energy and crack resistance are decreased.
From the above, it can be seen that in silica/silicon carbide/carbonaceous refractories, when the content of silica raw material is 1 to 50 mass % and the content of graphite is 1 to 80 mass %, high bending strength, fracture energy, crack resistance, and melting resistance can be obtained.

A Refractory body
B Carbon fiber fabric
b Carbon fiber bundle
x Refractory working surface
y Counter moving surface

Claims (12)

A graphite-containing refractory having a refractory body (A) having a graphite content of 1 to 80 mass% and a carbon fiber fabric (B) embedded therein,
The carbon fiber fabric (B) has a mass of 40 to 1,300 g per ^m2 ,
A graphite-containing refractory material, characterized in that the carbon fiber fabric (B) is adhered to the refractory body (A) via a tackifier component, and the tackifier component is at least one selected from the group consisting of organic resins, inorganic fine particles derived from inorganic sols, organic substances derived from tar and/or pitch, and organic substances derived from organic glues. The carbon fiber fabric (B) is a fabric in which carbon fiber bundles (b) are woven in two or more directions at intervals greater than 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 1,000 to 300,000;
The graphite-containing refractory according to claim 1, characterized in that the carbon fibers constituting the carbon fiber fabric (B) have a density of 10 to 2000 fibers/ ^mm2 in a cross section of the refractory parallel to a refractory operating surface. The graphite-containing refractory according to claim 1, characterized in that a carbon fiber fabric (B) is embedded inside the refractory body (A) along a direction perpendicular to the refractory operating surface. The graphite-containing refractory material according to any one of claims 1 to 3, characterized in that the carbon fiber fabric (B) has a spacing of more than 3 mm between the carbon fiber bundles (b) woven in the same direction. The graphite-containing refractory material according to any one of claims 1 to 3, characterized in that the carbon fiber fabric (B) is composed of one sheet or two or more laminated sheets of fabric. The graphite-containing refractory according to any one of claims 1 to 3, characterized in that one layer or two or more layers of carbon fiber fabric (B) are embedded at intervals inside the refractory body (A). The graphite-containing refractory according to claim 6, characterized in that the spacing between the two or more layers of carbon fiber fabric (B) embedded inside the refractory body (A) is 10 mm or more. The graphite-containing refractory according to any one of claims 1 to 3, characterized in that the refractory body (A) contains 20 to 99 mass% of magnesia raw material having a magnesia concentration of 90 mass% or more. The graphite-containing refractory according to claim 1, characterized in that the refractory body (A) contains 10 to 95 mass% of an alumina raw material having an alumina concentration of 70 mass% or more. The graphite-containing refractory according to claim 1, characterized in that the refractory body (A) contains 1 to 50 mass% of silica raw material. The graphite-containing refractory according to claim 9 or 10, characterized in that the refractory body (A) contains 1 mass % or more of silicon carbide raw material having a silicon carbide concentration of 80 mass % or more. The graphite-containing refractory according to any one of claims 1 to 3, characterized in that the refractory body (A) contains 10 to 90 mass% refractory chips obtained by crushing used refractories.

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