Refractory bricks and method for producing the same

Abstract

To provide a dense refractory brick made of alumina, silica, silicon carbide and carbon, the refractory brick having excellent durability not inferior to that of refractory bricks made of virgin raw materials only, even when a large amount of refractory waste with relatively small particle size is blended.SOLUTION: A refractory brick contains 17 mass% or more and 90 mass% or less, preferably more than 60 mass% and 90 mass% or less, of refractory waste x with a grain size of 8 mm or less in a total refractory material, and further contains 3 mass% or more of refractory waste with a grain size of more than 2.36 mm out of the refractory waste x in the total refractory material, wherein a content ratio (by mass) of refractory waste with a grain size of more than 2.36 mm to refractory waste with a grain size of 2.36 mm or less and more than 1 mm out of the refractory waste x, is 1:1 to 1:20, or the refractory brick contains more than 1 mass% of refractory waste with a grain size of more than 2.8 mm out of the refractory waste x in the total refractory raw material, wherein a content ratio (by mass) of refractory waste with a grain size of more than 2.8 mm to refractory waste with a grain size of 2.8 mm or less and more than 1 mm out of the refractory waste x in the total refractory raw material is 1:6 to 1:69.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to refractory bricks using used refractories (refractory waste) as part of the raw materials and a method for manufacturing the same.

Background Art

[0002] In steelworks, refractories are used in various facilities for treating melts (hot metal, molten steel, molten slag) and in transport containers for melts in the ironmaking process and the steelmaking process. These refractories are required to have the functions of being stable even when in contact with high-temperature melts and having little temperature drop during transportation. However, it is inevitable that they deteriorate over time during continued use. These refractories gradually become damaged due to long-term use at high temperatures. When it is determined that stable operation is impossible, they are disassembled and become refractory waste. This refractory waste has limited uses and is mostly treated as industrial waste. In recent years, however, it has been required to suppress the generation amount of refractory waste, and it is desired to reuse refractory waste as a refractory raw material.

[0003] Regarding bricks that reuse used refractories as part of the raw materials, for example, Patent Document 1 states that recycled bricks containing 10 to 60% by mass of a pulverized product obtained by pulverizing used alumina-silica (fireclay)-silicon carbide-carbon refractories to a particle size of 3 mm or less as it is as part of the raw materials have spalling resistance equivalent to or higher than that of bricks using only virgin raw materials, which are unused refractory raw materials. However, it is described that when the pulverized product of used refractories is blended in an amount exceeding 60% by mass, the spalling resistance decreases. Also, Patent Document 2 describes that for refractory bricks using refractory waste obtained by pulverizing used alumina-silica-silicon carbide-carbon refractories as part of the raw materials, by optimizing the particle size distribution of the refractory waste, the particle size distribution of the virgin raw materials, the component amounts of the refractory waste and the virgin raw materials, they have durability equivalent to that of refractories using only virgin raw materials.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2010-155764 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2018-62459 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] However, according to the findings of Patent Document 1, when the refractory waste is blended in an amount exceeding 60% by mass, the spalling resistance and corrosion resistance decrease, and the refractory waste cannot be blended in an amount exceeding 60% by mass. In addition, for the refractory bricks of Patent Document 2, it is necessary to blend a large amount of relatively large refractory waste with a particle size exceeding 2.8 mm, and a large amount of refractory waste with a particle size of 2.8 mm or less, which is generated in a large amount among the refractory waste, cannot be blended. Further, unless the particle size distribution and component amount of all the refractory raw materials, including the refractory waste and virgin raw materials, are optimized, the refractory bricks cannot be densified unless a sufficient molding pressure is applied.

[0006] Therefore, an object of the present invention is to solve the problems of the prior art as described above, and to provide a dense refractory brick made of alumina-silica-silicon carbide-carbonaceous material, which contains a large amount of refractory waste and has excellent durability equivalent to that of a refractory brick using only virgin raw materials, that is, spalling resistance (cracking resistance) and corrosion resistance (erosion resistance), even when a large amount of refractory waste with a relatively small particle size (particle size of 2.8 mm or less or particle size of 2.36 mm or less) is blended. Another object of the present invention is to provide a manufacturing method capable of stably manufacturing such refractory bricks. [Means for Solving the Problems]

[0007] The features of the present invention for solving the above problems are as follows. [1] In an alumina-silica-silicon carbide-carbonaceous refractory brick, Refractory debris (x) with a particle size of 8 mm or less, which is a pulverized material of used alumina-silica-silicon carbide-carbon refractory, is contained in the total refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded.) at 17% by mass or more and 90% by mass or less. Refractory debris with a particle size exceeding 2.36 mm among the refractory debris (x) is contained in the total refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded.) at 3% by mass or more. A refractory brick characterized in that the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.36 mm and refractory debris with a particle size of more than 1 mm and 2.36 mm or less among the refractory debris (x) is 1:1 to 1:20. [2] In the refractory brick of [1] above, the refractory debris with a particle size of 2.36 mm or less among the refractory debris (x) is contained in the total refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded.) at 42% by mass or more.

[0008] [3] In an alumina-silica-silicon carbide-carbon refractory brick, Refractory debris (x) with a particle size of 8 mm or less, which is a pulverized material of used alumina-silica-silicon carbide-carbon refractory, is contained in the total refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded.) at 17% by mass or more and 90% by mass or less. Refractory debris with a particle size exceeding 2.8 mm among the refractory debris (x) is contained in the total refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded.) at 1% by mass or more. A refractory brick characterized in that the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.8 mm and refractory debris with a particle size of more than 1 mm and 2.8 mm or less among the refractory debris (x) is 1:6 to 1:69.

[0009] [4] In the refractory brick of [3] above, the refractory debris with a particle size of 2.8 mm or less among the refractory debris (x) is contained in the total refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded.) at 42% by mass or more. [5] In any of the refractory bricks [1] to [4] above, the refractory debris (x) is contained in an amount of more than 60% by mass and 90% by mass or less in all refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded). A refractory brick characterized by this. [6] In any of the refractory bricks [1] to [5] above, the proportion of refractory raw materials with a particle size of 1 mm or less among the unused refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded) is 10% by mass or more and 40% by mass or less. A refractory brick characterized by this.

[0010] [7] In any of the refractory bricks [1] to [6] above, the alumina content in all refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded) is 50% by mass or more and 70% by mass or less, and the silica content is 10% by mass or more and 30% by mass or less. A refractory brick characterized by this. [8] In any of the refractory bricks [1] to [7] above, the alumina content in the refractory raw materials with a particle size of 1 mm or less (however, when the unused refractory raw materials contain metallic Si, this is excluded) is 10% by mass or more and 30% by mass or less. A refractory brick characterized by this. [9] In any of the refractory bricks [1] to [8] above, the free carbon content in all refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded) is 12% by mass or less. A refractory brick characterized by this.

[0011]

[10] In any of the refractory bricks [1] to [9] above, the unused silica raw materials are contained in an amount of 2% by mass or more and 30% by mass or less in all refractory raw materials (however, when the unused refractory raw materials contain metallic Si, this is excluded). A refractory brick characterized by this.

[11] In any of the refractory bricks [1] to

[10] above, the silica raw material consists of wollastonite or mullite, and the content ratio (mass ratio) of the silica raw material with a particle size of more than 1 mm and 2.8 mm or less to the silica raw material with a particle size of 1 mm or less is 2:1 to 2:4. A refractory brick characterized by this.

[12] In any of the refractory bricks [1] to

[11] above, the unused alumina raw material is contained in an amount of 6% by mass or more and 45% by mass or less in all refractory raw materials (provided that when the unused refractory raw material contains metallic Si, this is excluded). A refractory brick characterized by this.

[13] In any of the refractory bricks [1] to

[12] above, the unused silicon carbide raw material is contained in an amount of 2% by mass or more and 8% by mass or less in all refractory raw materials (provided that when the unused refractory raw material contains metallic Si, this is excluded). A refractory brick characterized by this.

[0012]

[14] In a method for manufacturing an alumina-silica-silicon carbide-carbonaceous refractory brick, Refractory debris with a particle size of 8 mm or less obtained by pulverizing used alumina-silica-silicon carbide-carbonaceous refractory materials, where the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.36 mm and refractory debris with a particle size of more than 1 mm and 2.36 mm or less is 1:1 to 1:20 (refractory debris (x)), and the proportion of refractory debris (x) in all refractory raw materials (provided that when the unused refractory raw material contains metallic Si, this is excluded) is 17% by mass or more and 90% by mass or less, and the proportion of refractory debris with a particle size exceeding 2.36 mm among the refractory debris (x) in all refractory raw materials (provided that when the unused refractory raw material contains metallic Si, this is excluded) is 3% by mass or more. A method for manufacturing a refractory brick, characterized by blending with the unused refractory raw material.

[15] In the manufacturing method of

[14] above, a method for manufacturing a refractory brick, characterized by blending the refractory debris (x) with the unused refractory raw material such that the proportion of refractory debris with a particle size of 2.36 mm or less among the refractory debris (x) in all refractory raw materials (provided that when the unused refractory raw material contains metallic Si, this is excluded) is 42% by mass or more.

[0013]

[16] In a method for manufacturing an alumina-silica-silicon carbide-carbonaceous refractory brick, Refractory debris with a particle size of 8 mm or less obtained by crushing used alumina-silica-silicon carbide-carbon refractory materials, wherein the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.8 mm to refractory debris with a particle size of more than 1 mm and 2.8 mm or less is 1:6 to 1:69. The refractory debris (x) is blended into all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) such that the proportion of refractory debris (x) is 17% by mass or more and 90% by mass or less, and the proportion of refractory debris with a particle size exceeding 2.8 mm in the refractory debris (x) among all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 1% by mass or more. A method for manufacturing refractory bricks is characterized by this.

[0014]

[17] In the manufacturing method of

[16] above, the refractory debris (x) is blended into the unused refractory raw materials such that the proportion of refractory debris with a particle size of 2.8 mm or less in the refractory debris (x) among all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 42% by mass or more. A method for manufacturing refractory bricks is characterized by this.

[18] In any of the manufacturing methods of

[14] to

[17] above, the refractory debris (x) is blended into the unused refractory raw materials such that the proportion of refractory debris (x) among all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is more than 60% by mass and 90% by mass or less. A method for manufacturing refractory bricks is characterized by this.

[19] In any of the manufacturing methods of

[14] to

[18] above, the proportion of refractory raw materials with a particle size of 1 mm or less among the unused refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 10% by mass or more and 40% by mass or less. A method for manufacturing refractory bricks is characterized by this.

[0015]

[20] In any of the manufacturing methods of

[14] to

[19] above, the refractory debris (x) is blended into the unused refractory raw materials such that the alumina content in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 50% by mass or more and 70% by mass or less, and the silica content is 10% by mass or more and 30% by mass or less. A method for manufacturing refractory bricks is characterized by this.

[21] In any of the manufacturing methods

[14] to

[20] above, refractory waste (x) is blended with unused refractory raw materials so that the alumina content in the refractory raw materials with a particle size of 1 mm or less (however, excluding those containing metallic Si as unused refractory raw materials) is 10% by mass or more and 30% by mass or less. A method for manufacturing refractory bricks, characterized by this.

[22] In any of the manufacturing methods

[14] to

[21] above, refractory waste (x) is blended with unused refractory raw materials so that the free carbon content in all refractory raw materials (however, excluding those containing metallic Si as unused refractory raw materials) is 12% by mass or less. A method for manufacturing refractory bricks, characterized by this.

[0016]

[23] In any of the manufacturing methods

[14] to

[22] above, the unused silica raw material is blended so that the proportion in all refractory raw materials (however, excluding those containing metallic Si as unused refractory raw materials) is 2% by mass or more and 30% by mass or less. A method for manufacturing refractory bricks, characterized by this.

[24] In any of the manufacturing methods

[14] to

[23] above, the silica raw material consists of wollastonite or mullite, and the content ratio (mass ratio) of the silica raw material with a particle size of more than 1 mm and 2.8 mm or less to the silica raw material with a particle size of 1 mm or less is 2:1 to 2:4. A method for manufacturing refractory bricks, characterized by this.

[25] In any of the manufacturing methods

[14] to

[24] above, the unused alumina raw material is blended so that the proportion in all refractory raw materials (however, excluding those containing metallic Si as unused refractory raw materials) is 6% by mass or more and 45% by mass or less. A method for manufacturing refractory bricks, characterized by this.

[26] In any of the manufacturing methods

[14] to

[25] above, the unused silicon carbide raw material is blended so that the proportion in all refractory raw materials (however, excluding those containing metallic Si as unused refractory raw materials) is 2% by mass or more and 8% by mass or less. A method for manufacturing refractory bricks, characterized by this.

Advantages of the Invention

[0017] The refractory brick of the present invention contains a considerable amount of used refractories of alumina, silica, silicon carbide, and carbonaceous materials, and also contains a considerable amount of used refractories with relatively small particle sizes. Nevertheless, it has excellent durability equivalent to that of refractory bricks made only from virgin raw materials, that is, excellent spalling resistance (cracking resistance) and corrosion resistance (erosion resistance). The blast furnace ladle used for hot metal pretreatment has a structure with an open top without a lid. Since the hot metal charging and discharging are repeated, the temperature change during operation is large. Therefore, refractory bricks of alumina, silica, silicon carbide, and carbonaceous materials are used because they are less likely to embrittle due to repeated heating and cooling over a long period. In steelworks, a large amount of used refractories are generated from such blast furnace ladles. According to the present invention, refractory bricks with a high blending ratio of used refractories can be produced, which has a great effect on reducing the raw material cost of refractories.

Brief Description of the Drawings

[0018]

Figure 1

Modes for Carrying Out the Invention

[0019] As described below, the present inventors have developed a refractory brick and its manufacturing method that have excellent durability (cracking resistance, erosion resistance) equivalent to that of refractory bricks made only from unused refractory raw materials, even when containing a relatively large amount of used refractories of alumina, silica, silicon carbide, and carbonaceous materials and a relatively large amount of used refractories with relatively small particle sizes. The refractory brick of the present invention is a brick made of refractories of alumina, silica, silicon carbide, and carbonaceous materials, that is, refractories mainly composed of alumina, silica, silicon carbide, and carbon. In order to recycle used refractories, it is a refractory brick containing a pulverized product of used refractories of alumina, silica, silicon carbide, and carbonaceous materials (hereinafter sometimes referred to as "recycled raw materials") at a predetermined ratio as a refractory raw material.

[0020] The remainder of the refractory raw materials is unused new refractory raw materials (hereinafter referred to as "virgin raw materials"). Usually, as virgin raw materials, it contains oxide-based raw materials (such as alumina raw materials, silica raw materials), carbon raw materials, silicon carbide, metallic Si, etc. Here, examples of the oxide-based raw materials include bentonite shale, brown alumina, white alumina, wax stone, mullite, etc., and one or more of these can be blended. Examples of the carbon raw materials include flaky graphite, etc., and one or more of these can be blended. In the present application, those with an alumina content exceeding 50% by mass and a silica content of 15% by mass or less, such as bentonite shale, brown alumina, white alumina, etc., are referred to as alumina raw materials, and those with a silica content exceeding 15% by mass, such as wax stone, mullite, etc., are referred to as silica raw materials.

[0021] In the present invention, the recycled raw material is refractory debris (hereinafter referred to as "refractory debris (x)") with a particle size of 8 mm or less, which is a pulverized product of used alumina-silica-silicon carbide-carbonaceous refractories. By using refractory debris (x) of such a particle size, the pores in the brick structure can be reduced during molding, and the required packing density can be obtained. If refractory debris (x) with a particle size exceeding 8 mm is included, the packing density of the molded body cannot be increased, and the proportion of pores in the brick structure increases, so there is a risk that it will be difficult to mold. Also, for virgin raw materials, similar to refractory debris, a particle size of 8 mm or less is preferable.

[0022] Here, the material with a particle size of 8 mm or less (such as refractory scraps) means the material passing through a sieve with a mesh size of 8 mm (nominal size), and the material with a particle size exceeding 8 mm (such as refractory scraps) means the material remaining on the sieve. Also, in the following description, the material with a particle size of 2.8 mm or less (such as refractory scraps) means the material passing through a sieve with a mesh size of 2.8 mm (nominal size), and the material with a particle size exceeding 2.8 mm (such as refractory scraps) means the material remaining on the sieve. Also, the material with a particle size of 2.36 mm or less (such as refractory scraps) means the material passing through a sieve with a mesh size of 2.36 mm (nominal size), and the material with a particle size exceeding 2.36 mm (such as refractory scraps) means the material remaining on the sieve. Also, the material with a particle size of 1 mm or less (such as refractory scraps) means the material passing through a sieve with a mesh size of 1 mm (nominal size), and the material with a particle size exceeding 1 mm (such as refractory scraps) means the material remaining on the sieve. Also, the material with a particle size of 4.7 mm or less means the material passing through a sieve with a mesh size of 4.7 mm (nominal size), and the material with a particle size of 5.15 mm or less (such as refractory scraps) means the material passing through a sieve with a mesh size of 5.15 mm (nominal size).

[0023] In the refractory brick of the present invention, in all refractory raw materials (excluding metal Si when it is contained as a virgin raw material), the content of refractory scraps (x) is 17% by mass or more and 90% by mass or less, preferably more than 60% by mass and 90% by mass or less, and the balance is virgin raw material. By blending refractory scraps (x) at such a ratio, it is possible to achieve both high spalling resistance (cracking resistance) and corrosion resistance (erosion resistance), and it is also possible to reduce the thermal conductivity (especially when the content of refractory scraps (x) exceeds 60% by mass). The reason is that although the recycled raw material has a lower purity compared to the virgin raw material, by using the recycled raw material and the virgin raw material together, it is possible to suppress a significant decrease in the corrosion resistance of the alumina component in the recycled raw material. Furthermore, by using the recycled raw material and the virgin raw material together, the bulk density and the thermal conductivity are decreased compared to bricks made entirely of virgin raw materials (hereinafter referred to as "virgin bricks").

[0024] In the present invention, the particle size distribution of refractory debris (x) (the ratio of refractory debris of a predetermined particle size, the blending ratio of refractory debris divided by particle size), the ratio of virgin raw materials of a predetermined particle size, the alumina and silica contents of the refractory raw materials, etc. are optimized under the conditions described below, whereby refractory bricks with excellent durability and low thermal conductivity can be obtained. The numerical values of the content and content ratio (mass ratio) of refractory debris, the content of virgin raw materials, and the component content of refractory raw materials (amount of free carbon, contents of alumina and silica, etc.) defined in the present invention are numerical values with decimal places rounded off.

[0025] Also, the refractory brick of the first invention of the present application contains refractory debris (x) with a particle size exceeding 2.36 mm (coarse refractory debris) at 3 mass% or more, preferably 5 mass% or more in all refractory raw materials (however, when containing metallic Si as a virgin raw material, this is excluded). By setting the ratio of refractory debris with a particle size exceeding 2.36 mm in all refractory raw materials to 3 mass% or more, preferably 5 mass% or more in this way, a decrease in crack resistance and corrosion resistance can be suppressed. Note that even if the ratio of refractory debris with a particle size exceeding 2.36 mm is somewhat large, as long as other conditions are satisfied and it is within the range that can be molded, the upper limit of the ratio of refractory debris with a particle size exceeding 2.36 mm is not particularly defined. Furthermore, the content ratio (mass ratio) of refractory debris (x) with a particle size exceeding 2.36 mm (coarse refractory debris) and refractory debris with a particle size of 1 mm or more and less than 2.36 mm (medium refractory debris) is set to 1:1 to 1:20. By setting the content ratio of coarse refractory debris and medium refractory debris within the above range, the densification of the brick does not proceed too much, so the dynamic elastic modulus does not increase significantly, and slag penetration into the pore portions in the brick structure is suppressed, and crack resistance and corrosion resistance can be improved.

[0026] Further, it is preferable that the proportion of refractory debris (x) having a particle size of 2.36 mm or less (medium-grained and fine-grained refractory debris) in all refractory raw materials (excluding metal Si when it is contained as virgin raw material) is 42% by mass or more. This is because, by setting the proportion of medium-grained and fine-grained refractory debris in all refractory raw materials to 42% by mass or more, high crack resistance and corrosion resistance can be ensured while the formability is improved, making it easier for bricks to become dense and enabling mass production. Note that even if the proportion of refractory debris with a particle size of 2.36 mm or less is somewhat large, as long as other conditions are satisfied and it can be formed, the upper limit of the proportion of refractory debris with a particle size of 2.36 mm or less is not particularly specified.

[0027] First, the refractory brick of the second invention of the present application contains refractory debris (x) having a particle size exceeding 2.8 mm (coarse-grained refractory debris) in an amount of 1% by mass or more, preferably 5% by mass or more, in all refractory raw materials (excluding metal Si when it is contained as virgin raw material). By setting the proportion of refractory debris with a particle size exceeding 2.8 mm in all refractory raw materials to 1% by mass or more, preferably 5% by mass or more in this way, a decrease in crack resistance and corrosion resistance can be suppressed. Note that even if the proportion of refractory debris with a particle size exceeding 2.8 mm is somewhat large, as long as other conditions are satisfied and it can be formed, the upper limit of the proportion of refractory debris with a particle size exceeding 2.8 mm is not particularly specified. Furthermore, the content ratio (mass ratio) of refractory debris (x) having a particle size exceeding 2.8 mm (coarse-grained refractory debris) to refractory debris having a particle size of more than 1 mm and 2.8 mm or less (medium-grained refractory debris) is set to 1:6 to 1:69. By setting the content ratio of coarse-grained refractory debris to medium-grained refractory debris within the above range, the densification of the brick does not proceed too much, so the dynamic elastic modulus does not increase significantly, and slag penetration into the pore portion in the brick structure is suppressed, improving crack resistance and corrosion resistance.

[0028] Also, it is preferable that the proportion of refractory debris (x) with a particle size of 2.8 mm or less (medium and fine refractory debris) in all refractory raw materials (excluding metal Si when it is contained as a virgin raw material) is 42% by mass or more. This is because by setting the proportion of medium and fine refractory debris in all refractory raw materials to 42% by mass or more, high crack resistance and corrosion resistance can be ensured, and the formability is improved, making it easier for bricks to be densified and enabling mass production. Note that even if the proportion of refractory debris with a particle size of 2.8 mm or less is somewhat large, as long as other conditions are satisfied and it can be formed, the upper limit of the proportion of refractory debris with a particle size of 2.8 mm or less is not particularly specified.

[0029] Hereinafter, the optimum conditions common to the first and second inventions of the present application will be described. The refractory brick of the present invention contains virgin raw materials (excluding metal Si when it is contained as a virgin raw material) in an amount of 10% by mass or more and 83% by mass or less, preferably 10% by mass or more and less than 40% by mass in all refractory raw materials (excluding metal Si when it is contained as a virgin raw material). Among these virgin raw materials, it is preferable that the proportion of virgin raw materials with a particle size of 1 mm or less is 10% by mass or more and 40% by mass or less. Thereby, the corrosion resistance can be further enhanced, and a high residual expansion rate can also be maintained. The reason is that if the proportion of virgin raw materials with a particle size of 1 mm or less is within the above range, virgin raw materials with a particle size of 1 mm or less are added to the matrix in the brick structure, so slag penetration into the matrix can be further suppressed, and the densification of the brick does not proceed too much, thus a high residual expansion rate can be maintained.

[0030] The alumina content in all refractory raw materials (excluding metal Si when it is contained as virgin raw material) is preferably 50% by mass or more and 70% by mass or less, and the silica content is preferably 10% by mass or more and 30% by mass or less. Thereby, crack resistance and corrosion resistance can be maintained at a high level. The reason is as follows. Alumina is a high melting point substance of 2000 °C or higher and has a corrosion resistance effect against slags in a relatively wide composition range. When the alumina content is 50% by mass or more, the corrosion resistance effect appears remarkably. However, when the alumina content exceeds 70% by mass, the silica content is less than 30% by mass, so the crack resistance decreases. Also, when silica undergoes a phase transition reaction at high temperature, it generates fine cracks due to expansion, and these fine cracks lower the elastic modulus, thereby increasing the thermal shock fracture resistance proportional to the strength / elastic modulus ratio. When the silica content is 10% by mass or more, the thermal shock fracture resistance increases, but when it is less than 10% by mass, the expansion amount is small and no fine cracks are generated, so the thermal shock fracture resistance does not increase and the crack resistance decreases. However, when the silica content exceeds 30% by mass, a low melting point substance is easily generated at high temperature and the amount of liquid phase generated also increases, so the corrosion resistance decreases.

[0031] Also, the alumina content in refractory raw materials with a particle size of 1 mm or less (excluding metal Si when it is contained as virgin raw material) is preferably 10% by mass or more and 30% by mass or less. Thereby, corrosion resistance and crack resistance can be maintained at a high level. The reasons include that slag penetration into the matrix, which greatly affects the quality of brick corrosion resistance, can be suppressed. Also, the free carbon content in all refractory raw materials (excluding metal Si when it is contained as virgin raw material) is preferably 12% by mass or less. That is, by adding virgin carbon raw material so that the free carbon content in all refractory raw materials becomes 12% by mass or less, the thermal conductivity of the brick can be made almost constant at about 10 - 12 W / mK, and low thermal conductivity can be achieved.

[0032] To investigate the relationship between the free carbon content and the thermal conductivity of alumina-silica-silicon carbide-carbon refractory bricks, bricks made of refractory raw materials (virgin raw materials) as shown in Table 1 with five levels of flake graphite content of 1 wt%, 6 wt%, 9 wt%, 12 wt%, and 15 wt% were manufactured by the process shown in Figure 1. For these refractory bricks, the thermal conductivity was measured by the laser flash method. As shown in Table 1, the thermal conductivity decreased with the decrease in the free carbon content, but was almost constant at about 10 - 12 W / mK when the free carbon content was 12 wt% or less. From this result, it can be seen that reducing the free carbon content to 12 wt% or less can lower the thermal conductivity of alumina-silica-silicon carbide-carbon refractory bricks.

[0033]

Table 1

[0034] It is preferable that at least a part of the virgin raw materials contains 2 wt% or more and 30 wt% or less of silica raw materials in all the refractory raw materials (however, when the refractory raw materials not used contain metallic Si, this is excluded). By setting the content of the virgin silica raw materials in all the refractory raw materials to 2 wt% or more and 30 wt% or less, high crack resistance and high corrosion resistance can be achieved simultaneously. When the content of the virgin silica raw materials in all the refractory raw materials is less than 2 wt%, the expansion amount during the phase transition of quartz (SiO2) contained in the raw materials at high temperatures is small and no fine cracks are generated, so the elastic modulus does not decrease. As a result, the thermal shock fracture resistance does not increase and the crack resistance is likely to decrease. Also, when the content of the virgin silica raw materials in all the refractory raw materials exceeds 30 wt%, a high-temperature melt containing a large amount of slag components is likely to penetrate, so the corrosion resistance is likely to decrease.

[0035] As the virgin silica raw material, wollastonite or mullite is preferable. In that case, for the silica raw material (wollastonite or mullite), the content ratio (mass ratio) of the silica raw material with a particle size of more than 1 mm and 2.8 mm or less and the silica raw material with a particle size of 1 mm or less is preferably 2:1 to 2:4. Thereby, particularly, the crack resistance and the corrosion resistance can be improved. The reason is that within the above particle size range, the grain boundary area into which the slag penetrates can be reduced, and since the aggregate with a particle size of 1 mm or less exists in the matrix in the brick structure, the penetration of the slag into the matrix can be suppressed. In addition, since the densification of the brick does not proceed too much and creep deformation is applied, not only can the joint opening between the bricks be suppressed, but also a significant increase in the dynamic elastic modulus can be suppressed, and the occurrence and peeling of cracks can be suppressed by improving the crack resistance.

[0036] As at least a part of the virgin raw material, it is preferable to contain 6% by mass or more and 45% by mass or less of the alumina raw material in all the refractory raw materials (however, when containing metallic Si as the unused refractory raw material, this is excluded). By setting the content of the virgin alumina raw material in all the refractory raw materials to 6% by mass or more and 45% by mass or less, the erosion of the slag can be suppressed and the corrosion resistance can be maintained at a high level. If the content of the virgin alumina raw material in all the refractory raw materials is less than 6% by mass, the erosion of the slag cannot be suppressed and the corrosion resistance is likely to decrease. The reason is that alumina is a high melting point substance and shows an excellent corrosion resistance effect against slags in a relatively wide composition range at 2000 °C or higher. However, when the content of the alumina raw material is less than 6% by mass, the amount of alumina in the raw material decreases, and the corrosion resistance effect decreases. On the other hand, if the content of the virgin alumina raw material in all the refractory raw materials exceeds 45% by mass, the impurity components in the alumina raw material increase, and the melt is likely to penetrate, so the corrosion resistance is likely to decrease.

[0037] As at least a part of the virgin raw materials, it is preferable that the silicon carbide raw material is contained in the total refractory raw materials (excluding, however, when metallic Si is contained as an unused refractory raw material) in an amount of 2% by mass or more and 8% by mass or less. By setting the content of the virgin silicon carbide raw material in the total refractory raw materials to 2% by mass or more and 8% by mass or less, the effect of preventing oxidation of carbon and high corrosion resistance can be maintained. If the content of the virgin silicon carbide raw material in the total refractory raw materials is less than 2% by mass, the effect of preventing oxidation of carbon is small, and oxidation of carbon progresses, so the crack resistance tends to decrease. On the other hand, if the content of the virgin silicon carbide raw material in the total refractory raw materials exceeds 8% by mass, the oxidation reaction of SiC progresses and changes to SiO2, so the corrosion resistance tends to decrease.

[0038] In the used refractory that becomes a recycled raw material in the present invention, impurities such as slag may be contained. If the amount of impurities mixed in increases, the quality of the refractory brick may deteriorate. Therefore, it is preferable that the amount of impurities such as slag contained in the used refractory is 3.5 mass% or less. In the refractory brick of the present invention, particularly when the content of the refractory debris (x) is more than 60% by mass and 90% by mass or less in the total refractory raw materials (excluding, however, when metallic Si is contained as a virgin raw material), it is preferable to blend the refractory raw materials so as to satisfy all of the above conditions. As a result, a refractory debris recycled brick having particularly excellent crack resistance and corrosion resistance, being dense and having a low thermal conductivity can be obtained.

[0039] Next, the manufacturing method of the refractory brick of the present invention will be described. When manufacturing the refractory bricks of the present invention, first, after crushing the recovered alumina-silica-silicon carbide-carbonaceous used refractory materials and then classifying them, refractory debris with a particle size of 8 mm or less that becomes a recycled raw material is obtained. The content ratio (mass ratio) of refractory debris with a particle size exceeding 2.36 mm and refractory debris with a particle size exceeding 1 mm and less than or equal to 2.36 mm is 1:1 to 1:20, or the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.8 mm and refractory debris with a particle size exceeding 1 mm and less than or equal to 2.8 mm is 1:6 to 1:69, and refractory debris (x) is prepared. As a specific preparation method, the recovered alumina-silica-silicon carbide-carbonaceous used refractory materials are crushed to a particle size of, for example, 8 mm or less by a crusher, and then sieved. The refractory debris is separated into three particle size categories: refractory debris with a particle size exceeding 2.36 mm (8 mm or less), refractory debris with a particle size exceeding 1 mm and less than or equal to 2.36 mm, and refractory debris with a particle size of 1 mm or less, or the refractory debris is separated into three particle size categories: refractory debris with a particle size exceeding 2.8 mm (8 mm or less), refractory debris with a particle size exceeding 1 mm and less than or equal to 2.8 mm, and refractory debris with a particle size of 1 mm or less. Then, by mixing (blending) these three particle size categories of refractory debris at a predetermined ratio, refractory debris (x) that satisfies the above conditions is prepared.

[0040] This prepared refractory debris (x) is blended into virgin raw materials so that the ratio of refractory debris (x) in all refractory raw materials (excluding metal Si when it is contained as a virgin raw material) is 17% by mass or more and 90% by mass or less, and the ratio of refractory debris with a particle size exceeding 2.36 mm in refractory debris (x) in all refractory raw materials (excluding metal Si when it is contained as a virgin raw material) is 3% by mass or more, or the ratio of refractory debris with a particle size exceeding 2.8 mm in refractory debris (x) in all refractory raw materials (excluding metal Si when it is contained as a virgin raw material) is 1% by mass or more, to be used as a refractory raw material for forming into bricks.

[0041] Also, preferably, the raw material blending is carried out under one or more of the following conditions (i) to (x). (i) Incorporate refractory debris (x) into virgin raw materials such that the proportion of refractory debris with a particle size of 2.36 mm or less or refractory debris with a particle size of 2.8 mm or less among all refractory raw materials (excluding metal Si when it is contained as virgin raw material) is 42% by mass or more. (ii) Incorporate refractory debris (x) into virgin raw materials such that the proportion of refractory debris (x) among all refractory raw materials (excluding metal Si when it is contained as virgin raw material) exceeds 60% by mass and is 90% by mass or less. (iii) Set the proportion of virgin raw materials with a particle size of 1 mm or less among virgin raw materials (excluding metal Si when it is contained) to be 10% by mass or more and 40% by mass or less.

[0042] (iv) Incorporate refractory debris (x) into virgin raw materials such that the alumina content in all refractory raw materials (excluding metal Si when it is contained as virgin raw material) is 50% by mass or more and 70% by mass or less, and the silica content is 10% by mass or more and 30% by mass or less. (v) Incorporate refractory debris (x) into virgin raw materials such that the alumina content in refractory raw materials with a particle size of 1 mm or less (excluding metal Si when it is contained as virgin raw material) is 10% by mass or more and 30% by mass or less. (vi) Incorporate refractory debris (x) into virgin raw materials such that the free carbon content in all refractory raw materials (excluding metal Si when it is contained as virgin raw material) is 12% by mass or less.

[0043] (vii) Incorporate unused silica raw materials such that the proportion in all refractory raw materials (excluding metal Si when it is contained as unused refractory raw material) is 2% by mass or more and 30% by mass or less. (viii) The silica raw material consists of wollastonite or mullite, and the content ratio (mass ratio) of the silica raw material with a particle size exceeding 1 mm and less than 2.8 mm to the silica raw material with a particle size of 1 mm or less is 2:1 to 2:4. (ix) The unused alumina raw material is blended so that the proportion in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 6% by mass or more and 45% by mass or less. (x) The unused silicon carbide raw material is blended so that the proportion in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 2% by mass or more and 8% by mass or less. The reasons for the limitations such as the particle size, blending amount, blending ratio (mass ratio), free carbon amount of the refractory scraps, particle size of the virgin raw materials, and the contents of alumina and silica as described above are as previously stated.

[0044] A binder is added to the refractory raw materials prepared as above and kneaded, and then formed (press-molded) into the shape of bricks. After that, it is usually subjected to curing (drying) to obtain product bricks (unfired bricks). Also, after curing (drying), it may be further subjected to reduction firing (coking treatment) to obtain product bricks (fired bricks). As the binder, for example, phenol resin (main agent) + hexamine (hardening agent), carbon bond, ceramic bond, etc. are used. The addition amount of the binder is, for example, in the case of phenol resin (main agent) + hexamine (hardening agent), usually, the external application to the refractory raw materials is about 3% by mass of phenol resin and 0.3% by mass of hexamine. The molding pressure when molding (press-molding) the refractory raw materials is preferably 150 MPa or more in order to obtain dense bricks.

[0045] Usually, curing (drying) is carried out at 200 - 230 °C for about 18 - 48 hours, and when reduction firing (coking treatment) is carried out, it is carried out at 1400 - 1500 °C for about 3 - 5 hours. The refractory bricks of the present invention can be used as refractories for various equipment and containers, and among them, they are particularly suitable as the inner lining refractories for the refining equipment of steelworks and the transport containers for molten materials (hot metal, slag), and especially suitable as the refractories for blast furnace ladles used in hot metal pretreatment.

Examples

[0046] In the following description, among the refractory scraps used as recycled raw materials, refractory scraps with a particle size exceeding 2.8 mm (up to 5.15 mm) are referred to as "+2.8 mm refractory scraps", refractory scraps with a particle size of 2.8 mm or less and exceeding 1 mm are referred to as "2.8 - 1 mm refractory scraps", refractory scraps with a particle size exceeding 2.36 mm (up to 5.15 mm) are referred to as "+2.36 mm refractory scraps", refractory scraps with a particle size of 2.36 mm or less and exceeding 1 mm are referred to as "2.36 - 1 mm refractory scraps", and refractory scraps with a particle size of 1 mm or less are referred to as "-1 mm refractory scraps". Also, virgin raw materials with a particle size of 1 mm or less are referred to as "-1 mm virgin raw materials", and refractory raw materials with a particle size of 1 mm or less are referred to as "-1 mm refractory raw materials".

[0047] The recovered alumina-silica-silicon carbide-carbonaceous used refractory bricks were pulverized with a pulverizer to a particle size of 5.15 mm or less, then sieved, and separated into three particle size categories: coarse-grained (+2.8 mm or +2.36 mm) refractory scraps, medium-grained (2.8 - 1 mm or 2.36 - 1 mm) refractory scraps, and fine-grained (-1 mm) refractory scraps. As virgin raw materials, -1 mm bentonite shale, which is an oxide-based refractory raw material, as well as 2.8 - 1 mm or 2.36 - 1 mm wollastonite, SiC (micropowder), flaky graphite (micropowder), and metallic Si (micropowder) were used. Refractory bricks were manufactured using the manufacturing process shown in Fig. 1 by mixing the above refractory scraps and virgin raw materials in the ratios shown in Tables 2 to 9 and Tables 11 to 14. When kneading and molding the refractory raw materials, as a binder, 3% by mass of phenol resin and 0.3% by mass of hexamine were externally added to the refractory raw materials.

[0048] Here, the examples in Table 2 examined the content (mixing amount) of refractory chips of +2.36 mm and the content ratio (mixing ratio) of refractory chips of +2.36 mm and refractory chips of 2.36 - 1 mm. The examples in Table 3 examined the content (mixing amount) of refractory chips of +2.8 mm and the content ratio (mixing ratio) of refractory chips of +2.8 mm and refractory chips of 2.8 - 1 mm. The examples in Table 4 examined the content (mixing amount) of refractory chips of -2.36 mm. The examples in Table 5 examined the content (mixing amount) of refractory chips. The examples in Table 6 examined the content (mixing amount) of virgin raw material of -1 mm. The examples in Table 7 examined the alumina content and silica content in the refractory raw material. The examples in Table 8 examined the alumina content in the refractory raw material of -1 mm. The examples in Table 9 examined the molding pressure when molding (press molding) the refractory raw material. Also, the examples in Table 11 examined the content of virgin silica raw material (feldspar) in the refractory raw material. The examples in Table 12 examined the influence of the particle size range of the virgin silica raw material (feldspar). The examples in Table 13 examined the content of virgin alumina raw material in the refractory raw material. The examples in Table 14 examined the content of virgin silicon carbide raw material in the refractory raw material. For the convenience of explanation, Invention Examples 2 - 3 described in Table 3 are also described in Tables 5, 7, and 9.

[0049] Regarding the manufactured refractory bricks, the bulk density, apparent porosity, thermal conductivity, flexural strength, dynamic elastic modulus, residual expansion rate, and free carbon content were measured, and the crack resistance and corrosion resistance were evaluated. These measurement methods and evaluation methods are as follows. The bulk density and apparent porosity were measured by the methods shown in JIS R2205. The thermal conductivity was measured by the laser flash method. The flexural strength was measured by the method shown in JIS R2213. The dynamic elastic modulus was measured in accordance with the sound velocity measurement method. Also, the free carbon content was measured by the chemical analysis method shown in JIS R2011. Regarding the residual expansion rate, a thermal expansion test was carried out using a cylindrical sample by the method shown in JIS R2207. The difference ΔL = L1 - L0 between the dimension L0 before the test and the dimension L1 after the test was calculated, and the residual expansion rate E i was obtained. Residual expansion rate E i (%) = ΔL / L0 × 100 The alumina content and silica content of the refractory raw material were determined by component analysis in accordance with the "Chemical Analysis Method for Refractories Containing Carbon and Silicon Carbide" described in JIS R2011.

[0050] Regarding crack resistance, in accordance with the ultrasonic pulse method shown in JIS R1605, after measuring the dynamic elastic modulus E0 in the longitudinal direction of a 30×30×100 mm sample, spalling with one cycle of heating at 1500°C for 10 minutes, water cooling for 5 minutes, and air cooling for 10 minutes was repeated 3 cycles. After the spalling was completed, the dynamic elastic modulus E3 was measured again, and the change rate E3 / E0 of the dynamic elastic modulus before and after the test was used as an index for evaluation. Regarding corrosion resistance, it was evaluated by the internal lining splitting method using a high-frequency induction furnace. The test temperature was 1500°C, and the synthetic slag shown in Table 10 was charged 4 times every hour. After the test, the amount of corrosion was measured, and the corrosion index was determined with the amount of corrosion of Reference Example A in Table 1 as 100. The measured values of the above bulk density, apparent porosity, thermal conductivity, flexural strength, dynamic elastic modulus, residual expansion rate, and free carbon content, as well as the evaluation results of crack resistance and corrosion resistance, are shown in Tables 2 to 9, Tables 11 to 14 together with the raw material formulation and brick structure.

[0051] As shown in Table 2, when considering the content of refractory chips of +2.36 mm and the content ratio of refractory chips of +2.36 mm and 2.36 - 1 mm, as shown in Invention Examples 1-1 to 1-7, refractory bricks containing 3 mass% or more of refractory chips of +2.36 mm and with the content ratio of refractory chips of +2.36 mm and 2.36 - 1 mm in the range of 1:1 to 1:20 had bulk density, apparent porosity, residual expansion rate, crack resistance, and corrosion resistance comparable to those of virgin bricks. In contrast, as shown in Comparative Examples 1-1 to 1-3, when the content of refractory chips of +2.36 mm was less than 3 mass% or the content ratio of refractory chips of +2.36 mm and 2.36 - 1 mm was outside the range of 1:1 to 1:20, the crack resistance or corrosion resistance was significantly reduced. From these results, it was found that the content of refractory chips of +2.36 mm should be 3% by mass or more, and the content ratio of refractory chips of +2.36 and refractory chips of 2.36 - 1 mm should be within the range of 1:1 to 1:20.

[0052] As shown in Table 3, when the content of refractory chips of +2.8 mm and the content ratio of refractory chips of +2.8 mm and refractory chips of 2.8 - 1 mm were examined, as shown in Invention Examples 2-1 to 2-5, the refractory bricks containing 1% by mass or more of refractory chips of +2.8 mm and having the content ratio of refractory chips of +2.8 mm and refractory chips of 2.8 - 1 mm within the range of 1:6 to 1:69 had a bulk density, apparent porosity, residual expansion rate, crack resistance, and corrosion resistance comparable to those of virgin bricks. On the other hand, as shown in Comparative Examples 2-1 to 2-3, when the content of refractory chips of +2.8 mm was less than 1% by mass or the content ratio of refractory chips of +2.8 mm and refractory chips of 2.8 - 1 mm was outside the range of 1:6 to 1:69, the crack resistance or corrosion resistance was significantly reduced. From these results, it was found that the content of refractory chips of +2.8 mm should be 1% by mass or more, and the content ratio of refractory chips of +2.8 mm and refractory chips of 2.8 - 1 mm should be within the range of 1:6 to 1:69.

[0053] As shown in Table 4-1, when the content of refractory chips with a particle size of 2.36 mm or less was examined, as shown in Invention Example 3-1, when the content of refractory chips with a particle size of 2.36 mm or less was less than 42% by mass, the crack resistance was comparable to that when the content of refractory chips with a particle size of 2.36 mm or less was 42% by mass or more, but the corrosion resistance was slightly inferior. However, the amount of deterioration is such that it does not have a significant impact on the actual use. Also, as shown in Table 4-2, when the content of refractory chips with a particle size of 2.8 mm or less was examined, as shown in Invention Example 3-5, when the content of refractory chips with a particle size of 2.8 mm or less was less than 42% by mass, the crack resistance was comparable to that when the content of refractory chips with a particle size of 2.8 mm or less was 42% by mass or more, but the corrosion resistance was slightly inferior. However, the amount of deterioration is such that it does not have a significant impact on the actual use. As shown in Table 5, when the content of refractory waste was examined, as shown in Invention Examples 2-3 and Invention Examples 4-2 to 4-4, when the content of refractory waste was more than 60% by mass and 90% by mass or less, corrosion resistance comparable to that of virgin bricks was obtained. On the other hand, as shown in Invention Example 4-1, when the content of refractory waste was less than 60% by mass, the bulk density was high and the thermal conductivity was considerably high. Also, as shown in Comparative Example 4-1, when the content of refractory waste was more than 90% by mass, the corrosion resistance decreased significantly.

[0054] As shown in Table 6, when the content of virgin raw material of -1 mm (excluding metallic Si; the same shall apply hereinafter) was examined, as shown in Invention Examples 5-2 to 5-5, when the content of virgin raw material of -1 mm was 10% by mass or more and 40% by mass or less, the bulk density, apparent porosity, residual expansion rate, crack resistance, and corrosion resistance were comparable to those of virgin bricks. On the other hand, as shown in Invention Example 5-1, when the content of virgin raw material of -1 mm was less than 10% by mass, the crack resistance was comparable, but the corrosion resistance was slightly inferior compared to the case where the content of virgin raw material of -1 mm was 10% by mass or more and 40% by mass or less. However, the amount of deterioration was such that it did not have a significant impact on the actual use. Also, as shown in Invention Example 5-6, when the content of virgin raw material of -1 mm was more than 40% by mass, the corrosion resistance was comparable, but the crack resistance was slightly inferior compared to the case where the content of virgin raw material of -1 mm was 10% by mass or more and 40% by mass or less. However, the amount of deterioration was such that it did not have a significant impact on the actual use.

[0055] As shown in Table 7, when examining the alumina content and silica content in all refractory raw materials combining recycled raw materials (refractory waste) and virgin raw materials, as shown in Invention Examples 2-3 and Invention Examples 6-2 and 6-3, when the alumina content is 50% by mass or more and 70% by mass or less, and the silica content is 10% by mass or more and 30% by mass or less, crack resistance and corrosion resistance comparable to those of virgin bricks were obtained. On the other hand, as shown in Invention Example 6-1, when the alumina content is less than 50% by mass and the silica content exceeds 30% by mass, the corrosion resistance was slightly inferior compared to the case where the alumina content is 50% by mass to 70% by mass and the silica content is 10% by mass or more and 30% by mass or less. However, the amount of deterioration is such that it does not have a significant impact on actual machine use. Also, as shown in Invention Example 6-4, when the alumina content exceeds 70% by mass and the silica content is less than 10% by mass, the crack resistance was slightly inferior compared to the case where the alumina content is 50% by mass to 70% by mass and the silica content is 10% by mass or more and 30% by mass or less. However, the amount of deterioration is such that it does not have a significant impact on actual machine use.

[0056] As shown in Table 8, when examining the alumina content in refractory raw materials of -1 mm, as shown in Invention Examples 7-2 and 7-3, when the alumina content is 10% by mass or more and 30% by mass or less, corrosion resistance and crack resistance comparable to those of virgin bricks were obtained. On the other hand, as shown in Invention Example 7-1, when the alumina content is less than 10% by mass, the corrosion resistance was slightly inferior compared to the case where the alumina content is 10% by mass or more and 30% by mass or less. However, the amount of deterioration is such that it does not have a significant impact on actual machine use. Also, as shown in Invention Example 7-3, when the alumina content exceeds 30% by mass, the crack resistance was slightly inferior compared to the case where the alumina content is 10% by mass or more and 30% by mass or less. However, the amount of deterioration is such that it does not have a significant impact on actual machine use. As shown in Table 9, when the raw materials of the formulation of Invention Example 2-3 are molded by apparatuses with different molding pressures, it can be seen that in order to obtain particularly dense refractory bricks, it is preferable to set the molding pressure at 150 MPa or more.

[0057] As shown in Table 11, when the content of virgin silica raw material (feldspar) in all refractory raw materials was examined, as shown in Invention Examples 9-2 to 9-5, high crack resistance and high corrosion resistance could be achieved when the content of virgin silica raw material (feldspar) in all refractory raw materials was 2% by mass or more and 30% by mass or less. On the other hand, as shown in Invention Example 9-1, when the content of silica raw material (feldspar) was less than 2% by mass, corrosion resistance could be maintained, but the crack resistance was slightly inferior. Also, as shown in Invention Example 9-6, when the content of silica raw material (feldspar) exceeded 30% by mass, crack resistance could be maintained, but corrosion resistance was slightly inferior. However, the amount of their deterioration is such that it does not have a significant impact on the actual machine use.

[0058] As shown in Table 12, when the influence of the particle size range of virgin silica raw material (feldspar) was examined, as shown in Invention Examples 10-3 to 10-6, high crack resistance and high corrosion resistance could be achieved when the content ratio (mass ratio) of 2.8-1 mm silica raw material (feldspar) and -1 mm silica raw material (feldspar) was in the range of 2:1 to 2:4. On the other hand, when the content ratio (mass ratio) of 2.8-1 mm silica raw material (feldspar) and -1 mm silica raw material (feldspar) was outside the range of 2:1 to 2:4, slight deterioration of corrosion resistance due to slag penetration into the matrix or slight deterioration of crack resistance due to the brick becoming too dense occurred. However, the amount of its deterioration is such that it does not have a significant impact on the actual machine use.

[0059] As shown in Table 13, when the content of virgin alumina raw material in all refractory raw materials was examined, as shown in Invention Examples 11-2 to 11-5, high corrosion resistance could be maintained when the content of virgin alumina raw material in all refractory raw materials was 6% by mass or more and 45% by mass or less. On the one hand, as shown in Invention Example 11-1, when the content of virgin alumina raw material in all refractory raw materials was less than 6% by mass, crack resistance could be maintained, but corrosion resistance was slightly inferior. On the other hand, as shown in Invention Example 11-6, when the content of virgin alumina raw material in all refractory raw materials exceeded 45% by mass, corrosion resistance could be maintained, but crack resistance was slightly inferior. However, the amount of their deterioration is such that it does not have a significant impact on the actual machine use.

[0060] As shown in Table 14, when the content of virgin silicon carbide raw material in all refractory raw materials was examined, as shown in Invention Examples 12-2 to 12-5, when the content of virgin silicon carbide raw material in all refractory raw materials was 2% by mass or more and 8% by mass or less, the effect of preventing carbon oxidation was exhibited, and high crack resistance and high corrosion resistance could be achieved simultaneously. On the other hand, as shown in Invention Example 12-1, when the content of virgin silicon carbide raw material in all refractory raw materials was less than 2% by mass, the effect of preventing carbon oxidation decreased, so the crack resistance slightly decreased. On the other hand, as shown in Invention Example 12-6, when the content of virgin silicon carbide raw material in all refractory raw materials exceeded 8% by mass, the oxidation reaction of the silicon carbide raw material proceeded too much, so the corrosion resistance slightly decreased. However, the amount of their deterioration is of such a degree that it does not have a great influence on the use in actual machines.

[0061] From the above results, in alumina-silica-silicon carbide-carbon refractory bricks that reuse refractory scraps as part of the raw materials, in order to have crack resistance and corrosion resistance comparable to virgin bricks and have an alumina-silica-silicon carbide-carbon refractory brick with low thermal conductivity, refractory scraps (x) with a particle size of 8 mm or less, which are pulverized products of used alumina-silica-silicon carbide-carbon refractory materials, should be contained in all refractory raw materials (however, excluding this when containing metallic Si as a virgin raw material) at 17% by mass or more and 90% by mass or less. Furthermore, refractory scraps with a particle size exceeding 2.36 mm among the refractory scraps (x) should be contained in all refractory raw materials (however, excluding this when containing metallic Si as a virgin raw material) at 3% by mass or more, and the content ratio (mass ratio) of refractory scraps with a particle size exceeding 2.36 mm and refractory scraps with a particle size of more than 1 mm and less than 2.36 mm among the refractory scraps (x) should be 1:1 to 1:20. Or, refractory scraps with a particle size exceeding 2.8 mm among the refractory scraps (x) should be contained in all refractory raw materials (however, excluding this when containing metallic Si as a virgin raw material) at 1% by mass or more, and the content ratio (mass ratio) of refractory scraps with a particle size exceeding 2.8 mm and refractory scraps with a particle size of more than 1 mm and less than 2.8 mm among the refractory scraps (x) should be 1:6 to 1:69. It can be seen that this is necessary.

[0062] Moreover, more preferable conditions for the refractory bricks are as follows: (i) the refractory debris (x) with a particle size of 2.8 mm or less accounts for 42% by mass or more in all refractory raw materials (excluding metal Si when it is contained as virgin raw material); (ii) the refractory debris (x) accounts for more than 60% by mass and 90% by mass or less in all refractory raw materials (excluding metal Si when it is contained as virgin raw material); (iii) the proportion of refractory raw materials with a particle size of 1 mm or less in virgin raw materials (excluding metal Si when it is contained as virgin raw material) is 10% by mass or more and 40% by mass or less; (iv) the alumina content in all refractory raw materials (excluding metal Si when it is contained as virgin raw material) is 50% by mass or more and 70% by mass or less, and the silica content is 10% by mass or more and 30% by mass or less; (v) the alumina content in refractory raw materials with a particle size of 1 mm or less (excluding metal Si when it is contained as virgin raw material) is 10% by mass or more and 30% by mass or less; (vi) the free carbon content in all refractory raw materials (excluding metal Si when it is contained as virgin raw material) is 12% by mass or less; (vii) the unused silica raw material accounts for 2% by mass or more and 30% by mass or less in all refractory raw materials (excluding metal Si when it is contained as unused refractory raw material); (viii) the silica raw material consists of wollastonite or mullite, and the content ratio (mass ratio) of the silica raw material with a particle size of more than 1 mm and less than 2.8 mm to the silica raw material with a particle size of 1 mm or less is 2:1 to 2:4; (ix) the unused alumina raw material accounts for 6% by mass or more and 45% by mass or less in all refractory raw materials (excluding metal Si when it is contained as unused refractory raw material); (x) the unused silicon carbide raw material accounts for 2% by mass or more and 8% by mass or less in all refractory raw materials (excluding metal Si when it is contained as unused refractory raw material). By satisfying these conditions, it can be understood that particularly excellent performance can be obtained.

[0063]

Table 2

[0064]

Table 3

[0065]

Table 4-1

[0066]

Table 4-2

[0067]

Table 5

[0068]

Table 6

[0069]

Table 7

[0070]

Table 8

[0071]

Table 9

[0072]

Table 10

[0073]

Table 11

[0074]

Table 12

[0075]

Table 13

[0076]

Table 14

Claims

1. In an alumina-silica-silicon carbide-carbonaceous refractory brick used as an inner refractory of a refining facility or a molten material transfer container in a steelworks, refractory debris (x) with a particle size of 8 mm or less, which is a pulverized material of used alumina-silica-silicon carbide-carbonaceous refractory, is contained in 17% by mass or more and 90% by mass or less of all refractory raw materials (however, when the unused refractory raw material contains metallic Si, this is excluded), refractory debris with a particle size exceeding 2.36 mm among the refractory debris (x) is contained in 3% by mass or more of all refractory raw materials (however, when the unused refractory raw material contains metallic Si, this is excluded), a refractory brick, characterized in that the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.36 mm and refractory debris with a particle size of more than 1 mm and 2.36 mm or less among the refractory debris (x) is 1:1 to 1:

20.

2. The refractory brick according to Claim 1, characterized in that refractory debris with a particle size of 2.36 mm or less among the refractory debris (x) is contained in 42% by mass or more of all refractory raw materials (however, when the unused refractory raw material contains metallic Si, this is excluded).

3. In an alumina-silica-silicon carbide-carbonaceous refractory brick used as an inner refractory of a refining facility or a molten material transfer container in a steelworks, refractory debris (x) with a particle size of 8 mm or less, which is a pulverized material of used alumina-silica-silicon carbide-carbonaceous refractory, is contained in 17% by mass or more and 90% by mass or less of all refractory raw materials (however, when the unused refractory raw material contains metallic Si, this is excluded), refractory debris with a particle size exceeding 2.8 mm among the refractory debris (x) is contained in 1% by mass or more of all refractory raw materials (however, when the unused refractory raw material contains metallic Si, this is excluded), a refractory brick, characterized in that the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.8 mm and refractory debris with a particle size of more than 1 mm and 2.8 mm or less among the refractory debris (x) is 1:6 to 1:

69.

4. The refractory brick according to Claim 3, characterized in that refractory debris with a particle size of 2.8 mm or less among the refractory debris (x) is contained in 42% by mass or more of all refractory raw materials (however, when the unused refractory raw material contains metallic Si, this is excluded).

5. The refractory brick according to any one of claims 1 to 4, characterized in that it contains refractory debris (x) in an amount exceeding 60% by mass and not exceeding 90% by mass in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material).

6. The refractory brick according to any one of claims 1 to 4, characterized in that the proportion of refractory raw materials having a particle size of 1 mm or less among the unused refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 10% by mass or more and 40% by mass or less.

7. The refractory brick according to any one of claims 1 to 4, characterized in that the alumina content in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 50% by mass or more and 70% by mass or less, and the silica content is 10% by mass or more and 30% by mass or less.

8. The refractory brick according to any one of claims 1 to 4, characterized in that the alumina content in refractory raw materials having a particle size of 1 mm or less (excluding metal Si if it is contained as an unused refractory raw material) is 10% by mass or more and 30% by mass or less.

9. The refractory brick according to any one of claims 1 to 4, characterized in that the free carbon content in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material) is 12% by mass or less.

10. The refractory brick according to any one of claims 1 to 4, characterized in that it contains 2% by mass or more and 30% by mass or less of unused silica raw materials in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material).

11. The refractory brick according to any one of claims 1 to 4, characterized in that the silica raw material consists of wollastonite or mullite, and the content ratio (mass ratio) of the silica raw material having a particle size exceeding 1 mm and not exceeding 2.8 mm to the silica raw material having a particle size of 1 mm or less is 2:1 to 2:

4.

12. The refractory brick according to any one of claims 1 to 4, characterized in that it contains 6% by mass or more and 45% by mass or less of unused alumina raw materials in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material).

13. The refractory brick according to any one of claims 1 to 4, characterized in that it contains 2% by mass or more and 8% by mass or less of unused silicon carbide raw materials in all refractory raw materials (excluding metal Si if it is contained as an unused refractory raw material). In a method for manufacturing alumina-silica-silicon carbide-carbonaceous refractory bricks used as an inner refractory of a refining facility or a molten material transfer container in a steelworks, refractory debris with a particle size of 8 mm or less obtained by pulverizing used alumina-silica-silicon carbide-carbonaceous refractories, where the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.36 mm to refractory debris with a particle size of more than 1 mm and 2.36 mm or less is 1:1 to 1:20, and the proportion of refractory debris (x) in all refractory raw materials (excluding metallic Si if it is contained as an unused refractory raw material) is 17% by mass or more and 90% by mass or less, and the proportion of refractory debris with a particle size exceeding 2.36 mm in refractory debris (x) in all refractory raw materials (excluding metallic Si if it is contained as an unused refractory raw material) is 3% by mass or more, the method for manufacturing refractory bricks characterized by blending with unused refractory raw materials.

15. The method for manufacturing refractory bricks according to claim 14, characterized by blending refractory debris (x) with unused refractory raw materials so that the proportion of refractory debris with a particle size of 2.36 mm or less in refractory debris (x) in all refractory raw materials (excluding metallic Si if it is contained as an unused refractory raw material) is 42% by mass or more. In a method for manufacturing alumina-silica-silicon carbide-carbonaceous refractory bricks used as an inner refractory of a refining facility or a molten material transfer container in a steelworks, refractory debris with a particle size of 8 mm or less obtained by pulverizing used alumina-silica-silicon carbide-carbonaceous refractories, where the content ratio (mass ratio) of refractory debris with a particle size exceeding 2.8 mm to refractory debris with a particle size of more than 1 mm and 2.8 mm or less is 1:6 to 1:69, and the proportion of refractory debris (x) in all refractory raw materials (excluding metallic Si if it is contained as an unused refractory raw material) is 17% by mass or more and 90% by mass or less, and the proportion of refractory debris with a particle size exceeding 2.8 mm in refractory debris (x) in all refractory raw materials (excluding metallic Si if it is contained as an unused refractory raw material) is 1% by mass or more, the method for manufacturing refractory bricks characterized by blending with unused refractory raw materials.

17. The method for manufacturing a refractory brick according to claim 16, wherein refractory debris (x) is blended with unused refractory raw materials such that the proportion of refractory debris having a particle size of 2.8 mm or less among the refractory debris (x) is 42% by mass or more in all the refractory raw materials (provided that when the unused refractory raw materials contain metallic Si, this is excluded).

18. The method for manufacturing a refractory brick according to any one of claims 14 to 17, wherein refractory debris (x) is blended with unused refractory raw materials such that the proportion of the refractory debris (x) in all the refractory raw materials (provided that when the unused refractory raw materials contain metallic Si, this is excluded) is more than 60% by mass and 90% by mass or less.

19. The method for manufacturing a refractory brick according to any one of claims 14 to 17, wherein the proportion of refractory raw materials having a particle size of 1 mm or less among the unused refractory raw materials (provided that when the unused refractory raw materials contain metallic Si, this is excluded) is 10% by mass or more and 40% by mass or less.

20. The method for manufacturing a refractory brick according to any one of claims 14 to 17, wherein refractory debris (x) is blended with unused refractory raw materials such that the alumina content in all the refractory raw materials (provided that when the unused refractory raw materials contain metallic Si, this is excluded) is 50% by mass or more and 70% by mass or less, and the silica content is 10% by mass or more and 30% by mass or less.

21. The method for manufacturing a refractory brick according to any one of claims 14 to 17, wherein refractory debris (x) is blended with unused refractory raw materials such that the alumina content in the refractory raw materials having a particle size of 1 mm or less (provided that when the unused refractory raw materials contain metallic Si, this is excluded) is 10% by mass or more and 30% by mass or less.

22. The method for manufacturing a refractory brick according to any one of claims 14 to 17, wherein refractory debris (x) is blended with unused refractory raw materials such that the free carbon content in all the refractory raw materials (provided that when the unused refractory raw materials contain metallic Si, this is excluded) is 12% by mass or less.

23. The method for manufacturing a refractory brick according to any one of claims 14 to 17, wherein unused silica raw materials are blended such that the proportion in all the refractory raw materials (provided that when the unused refractory raw materials contain metallic Si, this is excluded) is 2% by mass or more and 30% by mass or less.

24. The silica raw material consists of wollastonite or mullite, and the content ratio (mass ratio) of the silica raw material with a particle size of more than 1 mm and 2.8 mm or less and the silica raw material with a particle size of 1 mm or less is 2:1 to 2:

4. The method for manufacturing a refractory brick according to any one of claims 14 to 17, characterized in that.

25. The method for manufacturing a refractory brick according to any one of claims 14 to 17, characterized in that the unused alumina raw material is blended so that the ratio in all refractory raw materials (however, when containing metallic Si as an unused refractory raw material, this is excluded) is 6% by mass or more and 45% by mass or less.

26. The method for manufacturing a refractory brick according to any one of claims 14 to 17, characterized in that the unused silicon carbide raw material is blended so that the ratio in all refractory raw materials (however, when containing metallic Si as an unused refractory raw material, this is excluded) is 2% by mass or more and 8% by mass or less.

Images