Irregular refractory
Technical field
[0001]
　The present invention relates to an amorphous refractory material containing a silicon carbide raw material.
Background technology
[0002]
　Silicon carbide is characterized by a low coefficient of thermal expansion and a low reactivity with slag, and has been used as a raw material for amorphous refractories in many cases (see Patent Documents 1 and 2, for example).
Advanced technical literature
Patent literature
[0003]
Patent Document 1: Japanese Patent No. 3502437
Patent Document 2: Japanese Patent Laid-Open No. 2002-220290
Summary of the invention
Problems to be Solved by the Invention
[0004]
　However, since the characteristic of high thermal conductivity of the silicon carbide raw material increases the thermal conductivity of the amorphous refractory, it cannot be used in a region where a certain level of heat insulation performance is required. In addition, the amorphous refractory containing a silicon carbide raw material as an aggregate having a grain size of 1 mm or more has a thermal conductivity of the irregular refractory when the interface between the aggregate and the matrix composed of the raw material having a grain size of less than 1 mm is used. The thermal conductivity of the amorphous refractory may become excessive due to a slight difference in the manufacturing conditions and heat treatment conditions, probably because it has a large effect on the heat resistance, and there was a problem in securing stable heat insulation.
[0005]
　The problem to be solved by the present invention is to secure a stable heat insulating property in an amorphous refractory material containing a silicon carbide raw material.
Means for solving the problems
[0006]
　In order to solve this problem, the inventors of the present invention have made extensive studies by paying attention to the relationship between a matrix composed of a raw material having a grain diameter of less than 1 mm and a silicon carbide raw material having a grain diameter of 1 mm or more. We came up with the idea of ​​standard refractories.
[0007]
　That is, according to one aspect of the present invention, the following amorphous refractory material is provided.
　In proportion to 100% by mass of the refractory raw material, 20% by mass or more and 50% by mass or less of the silicon carbide raw material having a particle size of 1 mm or more, 2% by mass or more and 15% by mass or less of the alumina fine powder having a particle size of 1 μm or more and 10 μm or less, and a particle size of 1 μm 1% by mass or more and 8% by mass or less of silica ultrafine powder, and
　the content of the alumina cement is 15% by mass or less (including 0) and the particle size is 1 mm. An amorphous refractory having a silicon carbide raw material content of less than 5% by mass or less (including 0).
The invention's effect
[0008]
　The amorphous refractory material of the present invention contains a specific amount of alumina fine powder and silica ultrafine powder in a matrix, and a silicon carbide raw material having a particle diameter of 1 mm or more as an aggregate. Here, FIG. 1 is a diagram showing expansion coefficients of a silicon carbide raw material having a particle diameter of 1 mm or more according to the present invention and a matrix (a refractory made of a raw material having a particle diameter of less than 1 mm in the refractory raw material) according to the present invention. is there. A predetermined amount of water was added, kneaded, cast into a mold having a predetermined shape, cured and dried, and the expansion coefficient was measured according to JIS R 2207-1. As shown in FIG. 1, at a high temperature, the silicon carbide raw material having a grain size of 1 mm or more is in an expanded state, and the matrix shrinks during the sintering process, so that minute cracks or voids are generated in the matrix. Therefore, the thermal conductivity of the amorphous refractory can be reduced and stable even though the composition contains 20% by mass or more and 50% by mass or less of the silicon carbide raw material having a high thermal conductivity and a particle size of 1 mm or more. It is possible to secure the heat insulating property. Further, since the content of the silicon carbide raw material having a particle diameter of less than 1 mm forming the matrix is ​​limited, the thermal conductivity of the matrix itself can be lowered, and from this point as well, stable heat insulation can be ensured. it can. Furthermore, since the content of the alumina cement is suppressed to 15% by mass or less, it is possible to prevent the corrosion resistance from being lowered due to the formation of a low melt.
Brief description of the drawings
[0009]
FIG. 1 is an explanatory view showing the thermal expansion behavior of a silicon carbide raw material having a particle diameter of 1 mm or more and a matrix in the amorphous refractory material of the present invention.
[FIG. 2] An example of a microstructure photograph of an amorphous refractory material of the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0010]
　The amorphous refractory material of the present invention comprises, as a refractory raw material, a silicon carbide raw material having a particle diameter of 1 mm or more (hereinafter referred to as “silicon carbide coarse particles”) and an alumina fine powder having a particle diameter of 1 μm to 10 μm (hereinafter simply referred to as “alumina fine powder”). ) And a silica ultrafine powder having a particle size of less than 1 μm (hereinafter, simply referred to as “silica ultrafine powder”).
[0011]
　The content of the silicon carbide coarse particles is 20% by mass or more and 50% by mass or less as a proportion of 100% by mass of the refractory raw material. When the content of the silicon carbide coarse particles is less than 20% by mass, the low expansion property, which is an advantage of the silicon carbide coarse particles, is not sufficiently exhibited, and the thermal shock resistance is deteriorated. On the other hand, when the content of the silicon carbide coarse particles exceeds 50% by mass, high thermal conductivity cannot be avoided, and as a result, the heat insulating property deteriorates. The preferable content of the silicon carbide coarse particles is 30% by mass or more and 50% by mass or less in proportion to 100% by mass of the refractory raw material.
[0012]
　Alumina fine powder is one of the matrix constituent materials. The content of the alumina fine powder is 2% by mass or more and 15% by mass or less as a proportion of 100% by mass of the refractory raw material. If the content of the alumina fine powder is less than 2% by mass, the amount of sintering shrinkage of the matrix decreases, and as a result, the effect of forming fine cracks or voids (hereinafter, the effect of forming fine cracks or voids in the matrix is ​​referred to as "fine crack effect". "), And the effect of suppressing thermal conductivity cannot be sufficiently obtained. That is, the thermal conductivity is increased, and as a result, the heat insulating property is reduced. On the other hand, when the content of the alumina fine powder exceeds 15% by mass, the matrix is ​​excessively sintered and becomes excessively dense, and as a result, the thermal shock resistance is deteriorated.
[0013]
　Ultrafine silica powder is also one of the matrix constituent materials. The content of the ultrafine silica powder is 1% by mass or more and 8% by mass or less based on 100% by mass of the refractory raw material. If the content of the silica ultrafine powder is less than 1% by mass, the amount of sintering shrinkage of the matrix decreases, resulting in a decrease in the effect of microcracking, and the effect of suppressing thermal conductivity cannot be sufficiently obtained. That is, the thermal conductivity is increased, and as a result, the heat insulating property is reduced. On the other hand, when the content of the ultrafine silica powder exceeds 8% by mass, the matrix is ​​excessively sintered and becomes excessively dense, resulting in a decrease in thermal shock resistance. In addition, the low melt formation also reduces corrosion resistance. A preferable content of the ultrafine silica powder is 2% by mass or more and 5% by mass or less in a ratio of 100% by mass of the refractory raw material.
[0014]
　The amorphous refractory material of the present invention can contain, as a refractory raw material, a silicon carbide raw material having a particle size of less than 1 mm (hereinafter referred to as "silicon carbide fine particles"). However, the content of the silicon carbide fine particles is 5% by mass or less (including 0) in proportion to 100% by mass of the refractory raw material. If the content of the silicon carbide fine particles exceeds 5% by mass, the matrix has high thermal conductivity, and even if the microcracking effect is obtained, the thermal conductivity of the amorphous refractory increases. The content of the silicon carbide fine particles is preferably 2.5% by mass or less (including 0) in a ratio of 100% by mass of the refractory raw material.
[0015]
　The amorphous refractory material of the present invention, like many refractory materials, contains a binder. In the amorphous refractory material of the present invention, the binder is included in the refractory raw material. As the binder, alumina cement, hydraulic transition alumina, Portland cement, magnesia cement, silicate, phosphate, etc., which are commonly used as a binder of amorphous refractory can be used. .. In addition, a part or all of the binder may form a cohesive bonding portion by combining magnesia fine powder having a particle size of 75 μm or less and silica ultrafine powder. When alumina cement is used as the binder, the content of alumina cement is 15% by mass or less (including 0) in proportion to 100% by mass of the refractory raw material. When the content of alumina cement exceeds 15% by mass, sintering proceeds excessively and becomes excessively dense, resulting in a decrease in thermal shock resistance. Also, the corrosion resistance is reduced due to the formation of low melt. The content of the alumina cement is preferably 5% by mass or less (including 0) in a ratio of 100% by mass of the refractory raw material.
[0016]
　The amorphous refractory of the present invention may include a carbon raw material as a refractory raw material, but since the carbon raw material has low oxidation resistance, the content of the carbon raw material is 1% by mass or less in a proportion of 100% by mass of the refractory raw material. It is preferably (including 0).
[0017]
　The refractory raw material that can be used in the amorphous refractory material of the present invention has been described above, but the balance can be at least one of an alumina raw material, a spinel raw material, a mullite raw material, and an andalusite raw material.
[0018]
　The amorphous refractory material of the present invention can contain various additives generally used for the amorphous refractory material such as a dispersant and a curing modifier, in addition to the refractory raw material. The amorphous refractory of the present invention may also contain large coarse particles (particle size of about 10 to 30 mm) that are generally used for irregular refractory. In addition, in the irregular refractory material of the present invention, large coarse particles are not included in the refractory raw material. That is, in the amorphous refractory material of the present invention, the coarse particles are added to 100% by mass of the refractory raw material by external coating. Further, the amorphous refractory may be added with auxiliary materials such as metal powder, metal fiber, and organic fiber, but in the irregular refractory of the present invention, these auxiliary materials are not included in the refractory raw material. The external additive is added to 100% by mass of the refractory raw material.
[0019]
　In the amorphous refractory material of the present invention, it is preferable that the refractory material composed of a raw material having a particle diameter of less than 1 mm in the refractory material, that is, the expansion coefficient of the matrix is ​​not more than 0.2% at 1000 ° C. By lowering the expansion coefficient of the matrix at 1000 ° C. in this way, a sufficient microcracking effect can be obtained.
[0020]
　INDUSTRIAL APPLICABILITY The amorphous refractory material of the present invention described above is suitably applied to a lance, impeller or tundish cover as an application in which heat insulation is important.
Example
[0021]
　Table 1 shows the raw material composition and the evaluation results of the examples of the present invention. In addition, Table 2 shows the raw material composition and the evaluation result of the comparative example. The evaluation items and evaluation methods in Examples and Comparative Examples are as follows.
[0022]
A
　predetermined amount of water and resin are added to the raw material having a particle size of less than 1 mm in the refractory raw material of each example, kneaded, and cast into a mold Then, a 20 × 20 × 80 mm shaped cured body was produced. Then, the cured product dried by heat treatment at 110 ° C. for 24 hours was used as a test piece. The measurement atmosphere was air, and the temperature was from room temperature to 1500 ° C. The measuring method was based on JIS R 2207-1. In Tables 1 and 2, when the coefficient of thermal expansion at 1000 ° C. is 0.2% or less, it is indicated by ◯ (good), and when it exceeds 0.2%, it is indicated by × (defective).
[0023]
A
　predetermined amount of water was added to each example, the mixture was kneaded, and the mixture was cast into a mold to prepare a cured product having a shape of 114 × 65 × 230 mm. Then, the cured product was cured, dried by heat treatment at 110 ° C. for 24 hours, and then baked by heat treatment at 1400 ° C. for 5 hours, which was used as a test piece. The measurement was performed by the hot wire method according to JIS R 2616. The measurement temperature was room temperature and 1200 ° C. at two points.
[0024]
A
　predetermined amount of water was added to each example, and the mixture was kneaded and cast into a mold having a predetermined shape to produce a hardened body having a predetermined shape. Then, after curing the cured body, it was dried by heat treatment at 110 ° C. for 24 hours and used as a test piece. The test piece was subjected to a slag rotary erosion test for 3 hours at 1550 ° C. using a converter slag, and the amount of erosion loss and the amount of infiltration were measured. In Tables 1 and 2, ◎ (excellent) when the erosion infiltration amount (total of erosion amount and infiltration amount) is 5 mm or less, ○ (good) when 5 mm or more and 7 mm or less, and 7 mm or more and 11 mm or less The case was described as Δ (OK), and the case of larger than 11 mm was described as × (poor). The amount of erosion infiltration is an index of corrosion resistance, and the smaller the amount of infiltration erosion, the higher the corrosion resistance.
[0025]
A
　predetermined amount of water was added to each example, the mixture was kneaded, and the mixture was cast into a mold to prepare a 230 × 114 × 65 mm-shaped cured body. Then, after curing the cured body, it was dried by heat treatment at 110 ° C. for 24 hours, and then baked by heat treatment at 1000 ° C. for 3 hours, which was used as a test piece. Using this test piece, heating and cooling were repeated to observe the occurrence of cracks. Specifically, the operation of raising the 230 × 65 mm surface to 1600 ° C. for 5 minutes with a gas burner, holding it for 10 minutes, and then allowing it to cool for 10 minutes was repeated twice to observe the occurrence of cracks. In Tables 1 and 2, the case where the cracks were slight was indicated by ◯ (good), the case where the slightly large cracks were generated was indicated by Δ (acceptable), and the case where the large cracks were generated was indicated by × (defective).
[0026]
The
　following criteria were used to evaluate the result in three grades: ◯ (good), Δ (acceptable), and × (bad).
　Good (good): A refractory made of a raw material of less than 1 mm has an expansion coefficient of 1000 at 1000 ° C., a thermal conductivity of 6.5 or less at room temperature and 1200 ° C., a corrosion resistance of ◎ or ○, and a thermal shock resistance. In the case of ○.
　△ (Fair): When the comprehensive evaluation is other than the above ○, and the following requirements are satisfied.
　A refractory made of a raw material of less than 1 mm has a coefficient of expansion at 1000 ° C., a thermal conductivity of 9 or less at room temperature or 1200 ° C., corrosion resistance of ⊚, ○ or Δ, and thermal shock resistance of ○ or Δ.
　X (Poor): When any one of the evaluation items corresponds to the following.
　A refractory made of a raw material of less than 1 mm has an expansion coefficient of 1000 at 1000 ° C, a thermal conductivity of more than 9 at room temperature and 1200 ° C, a corrosion resistance of ×, and a thermal shock resistance of ×.
[0027]
[Table 1]

[0028]
[Table 2]

[0029]
　As shown in Table 1, Examples 1 to 14 within the scope of the present invention have a low thermal conductivity (high thermal insulation) of 7.9 or less at room temperature and 1200 ° C. The overall evaluation was also good. As illustrated in the micrograph of Example 1 in FIG. 2, in the amorphous refractory material of the present invention (Examples 1 to 14), fine cracks are formed in the matrix, and voids are also formed. there were. It is considered that the existence of these fine cracks or voids lowers the thermal conductivity and improves the heat insulating property. In addition, Example 7 is an example not using alumina cement. In this Example 7, the magnesia fine powder and the silica ultrafine powder act as a binder.
[0030]
　Comparative Example 1 is an example in which the amount of coarse silicon carbide particles is small. The low expansion characteristics, which are the advantages of coarse particles of silicon carbide, were not fully exhibited, and the thermal shock resistance was reduced.
[0031]
　Comparative Example 2 is an example in which the content of coarse particles of silicon carbide is large. Since the content of coarse particles of silicon carbide, which is a high thermal conductivity material, is large, high thermal conductivity cannot be avoided, and the thermal conductivity at room temperature and 1200 ° C. becomes high. The higher the thermal conductivity, the lower the heat insulating property.
[0032]
　Comparative Example 3 is an example in which the content of silicon carbide fine particles is large. The matrix has high thermal conductivity and high thermal conductivity at room temperature.
[0033]
　Comparative Example 4 is an example in which the content of alumina fine powder is small. The amount of sintering shrinkage of the matrix decreased, and the expansion coefficient at 1000 ° C. of the refractory material composed of the raw material of less than 1 mm increased. As a result, the effect of fine cracks was not sufficiently obtained, and the effect of suppressing thermal conductivity was not sufficiently obtained. That is, the thermal conductivity at room temperature and 1200 ° C. increased.
[0034]
　Comparative Example 5 is an example in which the content of alumina fine powder is large. Sintering proceeded too much and became too dense, resulting in poor thermal shock resistance.
[0035]
　Comparative Example 6 is an example in which the content of silica ultrafine powder is small. The amount of sintering shrinkage of the matrix decreased, and the expansion coefficient at 1000 ° C. of the refractory made of the raw material of less than 1 mm increased. As a result, the effect of fine cracks was not sufficiently obtained, and the effect of suppressing thermal conductivity was not sufficiently obtained. That is, the thermal conductivity at room temperature and 1200 ° C. increased.
[0036]
　Comparative Example 7 is an example in which the content of ultrafine silica powder is high. The sintering of the matrix proceeded too much and became too dense, resulting in a decrease in thermal shock resistance. In addition, the low melt formation also reduced the corrosion resistance.
[0037]
　Comparative Example 8 is an example in which the content of alumina cement is large. Sintering proceeded too much and became too dense, resulting in a decrease in thermal shock resistance. In addition, the low melt formation also reduced the corrosion resistance.
The scope of the claims
[Request 1]
　In proportion to 100% by mass of the refractory raw material, 20% by mass or more and 50% by mass or less of the silicon carbide raw material having a particle size of 1 mm or more, 2% by mass or more and 15% by mass or less of the alumina fine powder having a particle size of 1 μm or more and 10 μm or less, and a particle size of 1 μm 1% by mass or more and 8% by mass or less of silica ultrafine powder, and
　the content of the alumina cement is 15% by mass or less (including 0) and the particle size is 1 mm. An amorphous refractory having a silicon carbide raw material content of less than 5% by mass or less (including 0).
[Request 2]
　The content of the silicon carbide raw material having a particle size of 1 mm or more in the proportion of 100 mass% of the refractory raw material is 30 mass% or more and 50 mass% or less, and the content of the silica ultrafine powder is 2 mass% or more and 5 mass% or less, The content of the alumina cement is 5 mass% or less (including 0), and the content of the silicon carbide raw material having a particle size of less than 1 mm is 2.5 mass% or less (including 0). Unshaped refractories.
[Request 3]
　The amorphous refractory material according to claim 1 or 2, wherein the remainder of the refractory raw material is at least one of an alumina raw material, a spinel raw material, a mullite raw material, and an andalusitic raw material.
[Request 4]
　The amorphous refractory material according to any one of claims 1 to 3, wherein the content of the carbon raw material is 1 mass% or less (including 0) in a proportion of 100 mass% of the refractory raw material.
[Request 5]
　The amorphous refractory material according to any one of claims 1 to 4, wherein the refractory material composed of a raw material having a particle size of less than 1 mm in the refractory material has an expansion amount of 0.2% or less at 1000 ° C.
[Request 6]
　The amorphous refractory according to any one of claims 1 to 5, which is applied to a lance, an impeller, or a tundish cover.