JP2013234092A - Cast refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cast refractory in which working hours for furnace wall repair can be reduced and the time for temperature elevation after completion of the repair can be shortened.SOLUTION: A cast refractory includes an aggregate raw material comprised of an amorphous silica raw material of which the mass ratio of an SiOcomponent is 99% or more, and one or two or more kinds of quartz, tridymite, and cristobalite, and an additive containing fumed silica, colloidal silica and alumina cement. The mass ratio of the amorphous silica raw material in the aggregate raw material is 40 to 65 mass%, and the mass ratio of the one or two or more kinds of quartz, tridymite and cristobalite is 35 to 60 mass%.

Description

  The present invention relates to a cast refractory applicable to a coke oven or the like.

  In order to produce coke, a coke oven for high-temperature carbonization of coal is widely used. As is well known, a coke oven has a structure in which carbonization chambers (dry distillation chambers) having furnace walls made of refractory are arranged in parallel, and combustion chambers are arranged between the carbonization chambers. . The total length of the carbonization chamber in the direction along the combustion chamber is larger than the interval between the combustion chambers on both sides, and the combustion chamber is provided over the entire length of the carbonization chamber. Coal charged into the carbonization chamber from the charging port provided in each carbonization chamber is dry-distilled by heat generated in the combustion chamber. Furnace lids are provided at both ends in the longitudinal direction of the carbonization chamber, and the coke generated in the carbonization chamber is placed outside one furnace lid from one side to the other side with both the furnace lids open. An extruder for extruding is arranged.

  In the coke oven, coal is repeatedly carbonized and discharged over an operation period exceeding 20 to 30 years, so that the refractory forming the furnace wall of the carbonization chamber is worn out or squeezed out. In particular, a refractory in the vicinity of the furnace lid that is opened and closed when the coke is carried out has a severe temperature history of temperature rise and fall and is easily damaged. Such wear and protrusion increase the frictional resistance between the coke and the wall surface in the coke extrusion operation and reduce the work efficiency. Further, when the damage becomes severe, clogging occurs in the extrusion operation. Therefore, the damaged furnace wall is repaired by transshipment of the refractory constituting the furnace wall.

  As described above, the furnace wall of the carbonization chamber separates adjacent carbonization chambers, and the inside thereof constitutes a combustion chamber. Conventionally, the furnace wall has been repaired as follows. First, two adjacent carbonization chambers are emptied, and a work space is configured by installing a heat insulating wall inside each carbonization chamber. Next, the temperature of the work space is lowered to a temperature at which work can be performed. Thereafter, the furnace wall body to be transshipped is dismantled, and the furnace wall body is restored by manually stacking bricks one by one in the dismantling trace.

  In such a repair method in which bricks are stacked one by one, the size of the space portion is measured after the brick to be repaired is dismantled. Then, based on the measurement result, the dimensions after completion of the temperature rise are calculated in consideration of the three-dimensional position of the non-repaired portion of the combustion chamber wall brick and the expansion of the brick used, and based on the calculation result. The thickness of the joints of the bricks of the repairing part and the position of the fitting part between the bricks are adjusted. Thereby, it can form as a smooth continuous wall surface between the non-repair part and repair part of a furnace wall, and can reduce frictional resistance of a coke and a wall surface in coke extrusion operation | work.

  However, in the repair method as described above, bricks are stacked one by one in a narrow furnace, so that a long time is required for the work, and the production of coke is greatly reduced. In addition, the repair work space cannot be completely lowered to the outside air temperature even if the temperature is lowered. Therefore, the worker will work for a long time in a harsh working environment, which is a heavy load on the worker. Various techniques have been proposed to solve such problems (for example, Patent Documents 1 to 5).

  For example, Patent Document 1 divides a wall to be repaired into a plurality of laminated portions, combines a large number of silica bricks for a coke oven to form a refractory aggregate, and reduces the construction work by constructing it. The technology is disclosed.

  Patent Document 2 describes a technique for reducing the furnace construction time and shortening the construction work time by creating a cordierite brick that is precast-molded into an L-shape and is made of cordierite brick. Is disclosed.

  Patent Document 3 discloses a technique that enables a reduction in furnace construction work and a rapid temperature increase after completion of repair by performing a construction in which a fused siliceous castable is poured into a mold on site. Patent Documents 4 and 5 also disclose castables using fused silica.

Japanese Patent Laid-Open No. 2001-19968 JP 2003-193059 A Special table 2011-503254 gazette U.S. Pat. No. 4,560,025 JP 56-78476 A

  However, since the silica brick used in Patent Document 1 has a large coefficient of thermal expansion in the vicinity of 500 ° C., there is a drawback that it is cracked when the heating rate is increased. In order to suppress such cracking and destruction of bricks at the time of temperature increase, it is necessary to increase the temperature over time after completion of the repair, and the repair work period becomes long. In addition, since the refractory aggregate is a combination of a large number of bricks, there is also a problem that it takes time to complete the desired shape. Furthermore, since it is necessary to prepare a large number of bricks, there is a problem that the manufacturing process becomes long and the manufacturing cost increases.

  The technique disclosed in Patent Document 2 also has the same problem as Patent Document 1. In addition, when cordierite is used in a high temperature range for a long period of time, deformation, cracks, and the like occur due to structural changes caused by changes in constituent phases. Therefore, there exists a problem that durability is inferior.

  On the other hand, the fused siliceous castable used in Patent Document 3 has a smaller thermal expansion than that of silica brick, and is more advantageous than Patent Documents 1 and 2 in terms of thermal shock resistance (heat resistant spalling property) at the time of temperature rise. It is. However, in a service temperature range of 1250 to 1400 ° C., unrepaired silica bricks thermally expand a certain amount, whereas a portion repaired by a fused siliceous castable hardly undergoes thermal expansion. That is, an imbalance occurs in the thermal expansion in the repaired part and the unrepaired part. It is not preferable that such a situation occurs in a coke oven as a building structure. Further, the fused siliceous castable also has a drawback that it is slightly deformed when exposed to a high temperature for a long time under a load. Therefore, when it is used for a repair portion of a coke oven where a long-term load is applied at a high temperature due to thermal stress or its own weight, there is a problem that deformation of the repair portion becomes large and the above-mentioned unbalance is increased. Naturally, the techniques disclosed in Patent Documents 4 and 5 also have the same problems as in Patent Document 3.

  On the other hand, there is an example in which chamotte brick is used for the furnace wall of the carbonization chamber. However, chamotte bricks also lack stability against high temperature use. That is, when the usage period exceeds one year, there is a problem that warp deformation occurs in the brick, and problems such as clogging occur in the coke extrusion operation.

  The present invention has been proposed in view of the above-described conventional circumstances, and provides a cast refractory that can shorten the work time for furnace wall repair and can shorten the temperature raising time after completion of repair. With the goal.

  The inventors of the present application have earnestly studied refractory raw materials that can be used stably for a long period of time without causing deformation or cracking even if the temperature is raised in a short time after completion of repair, and have reached the present invention. .

That is, the cast refractory according to the present invention includes an amorphous siliceous material having a SiO ₂ component mass ratio of 99% or more, and an aggregate material composed of one or more of quartz, tridymite, and cristobalite. And additives including fumed silica, colloidal silica and alumina cement. The mass ratio of the amorphous siliceous raw material in the aggregate raw material is 40 to 65 mass%, and the mass ratio of one or more of quartz, tridymite, and cristobalite is 35 to 60 mass%.

  This cast refractory has a small coefficient of thermal expansion from room temperature to high temperature, has an appropriate coefficient of thermal expansion, is dense and has high strength, and can realize a molded refractory having excellent heat-resistant spalling properties.

  In addition, the addition amount of fumed silica can be 8-17 mass% on the outside with respect to 100 mass% of the said aggregate raw material. Moreover, the addition amount of colloidal silica can be made into 5-15 mass% on the exterior with respect to 100 mass% of said aggregate raw materials. Furthermore, the addition amount of alumina cement can be set to 1.0 to 5.0 mass% as an outer shell with respect to 100 mass% of the aggregate raw material.

  According to the present invention, it is possible to realize a molded refractory having a small coefficient of thermal expansion from a room temperature to a high temperature, an appropriate coefficient of thermal expansion, a dense and high strength, and an excellent heat-resistant spalling property. As a result, even when used for repairing the furnace wall of a coke oven, deformation and cracking do not occur even if the temperature is raised in a short time after the repair is completed. That is, rapid temperature increase is possible, and the temperature increase time after completion of repair can be shortened. In addition, since the difference in thermal expansion between the unrepaired portion and the repaired portion is small and deformation is not easily caused by a long-time load at a high temperature, the coke oven can be stably used for a long time after completion. Moreover, since it is an aspect of the cast refractory, it is also possible to manufacture a large block having an arbitrary shape. By using this large block, the working time of the worker in a narrow furnace and in a high temperature atmosphere can be shortened. Combined with the above, it is possible to shorten the construction period and thus reduce the manufacturing cost.

The cast refractory according to the present invention includes an amorphous siliceous material having a mass ratio of SiO ₂ component of 99% or more, an aggregate material composed of one or more of quartz, tridymite, and cristobalite, fumed And additives including silica, colloidal silica and alumina cement.

The amorphous siliceous raw material only needs to have a mass ratio of SiO ₂ component of 99% or more. For example, amorphous silica sold as fused silica, fused silica, or quartz glass can be used. Such an amorphous siliceous raw material has a thermal expansion coefficient of 0.05% or less from room temperature to 1000 ° C. and is extremely small. By using such low-expansion aggregate, the heat of the molded refractory can be obtained even when the molded refractory composed of the main cast refractory is used as the refractory constituting the carbonization chamber wall of the coke oven. Expansion can be suppressed and heat spalling property can be improved.

  In addition, one or more of quartz, tridymite, and cristobalite (hereinafter referred to as crystalline siliceous raw material) in the aggregate raw material can be used in any combination. It is preferable to mainly use tridymite which is excellent in mechanical stability. By using such a crystalline siliceous raw material, it is possible to provide an appropriate thermal expansion coefficient and creep resistance as a refractory for repair, and at the same time, it is possible to maintain heat-resistant spalling properties.

  The mass ratio of the amorphous siliceous material in the aggregate material is preferably 40 to 65% by mass (40% by mass or more and 65% by mass or less), and more preferably 46 to 62% by mass (46% by mass or more). And 62% by mass or less). A mass ratio of less than 40% by mass is not preferable because a sufficient expansion suppressing effect cannot be obtained. On the other hand, if the mass ratio exceeds 65 mass%, the coefficient of thermal expansion becomes too small, and deformation under high temperature load becomes too large, which is not preferable. Although it does not specifically limit, the particle size (particle size) of an amorphous siliceous raw material can be 0.01-10 mm (0.01 mm or more and 10 mm or less).

  The mass ratio of the crystalline siliceous material in the aggregate material is preferably 35 to 60% by mass (35% to 60% by mass), more preferably 38 to 54% by mass (38% by mass). And 54% by mass or less). If the mass ratio is less than 35 mass%, the coefficient of thermal expansion becomes too small as described above, and deformation under high temperature load becomes too large, which is not preferable. On the other hand, when the mass ratio is more than 60 mass%, the ratio of the amorphous siliceous raw material in the aggregate raw material is relatively lowered and the coefficient of thermal expansion is increased, which is not preferable. In addition, in a composition containing a large amount of quartz as a crystalline siliceous raw material, the quartz phase transitions to tridymite or cristobalite when used as a furnace wall for a long time. In this case, cracking is likely to occur due to expansion, and the heat spalling property is lowered. In this respect, the content of quartz is preferably 20% by mass or less, and more preferably 10% by mass or less. Moreover, although it does not specifically limit, the particle size (particle size) of a crystalline siliceous raw material can be 0.01-10 mm (0.01 mm or more and 10 mm or less).

On the other hand, fumed silica, which is an additive, is amorphous silica containing a SiO ₂ component, and the addition increases fluidity and enables low moisture construction. Therefore, a dense molded body can be obtained. And as a result of being able to obtain a dense molded body, the curing strength of the molded refractory is improved, and it is possible to prevent the occurrence of cracking and corner chipping during de-framework and handling. Although fumed silica is also an amorphous siliceous material, it is distinguished from the amorphous siliceous material of the aggregate material in that the mass ratio of the SiO ₂ component is not 99% or more.

  The amount of fumed silica added to 100% by mass of the above-mentioned aggregate raw material is preferably 8 to 17% by mass (8% by mass or more and 17% by mass or less), more preferably 10 to 15% by outer coating. % (10 mass% or more and 15 mass% or less). If the amount of fumed silica added is less than 8% by mass, it is not preferable because the fluidity is lowered and low-moisture construction is impossible, so that a dense molded body cannot be obtained. On the other hand, if the amount added exceeds 17% by mass, the fumed silica has a high sinterability, so that rapid sintering shrinkage occurs at high temperatures and cracks are likely to occur.

Colloidal silica as an additive is a colloid composed of SiO ₂ or a hydrate thereof, and the chemical composition after heating is SiO ₂ . By adding colloidal silica, the hot strength in the intermediate temperature range of 600 to 800 ° C. can be improved, and as a result, the heat resistant spalling property can be improved. The concentration of the colloidal silica is preferably 5 to 50% by mass (5% by mass or more and 50% by mass or less) of the silica component, and more preferably 10 to 40% by mass (10% by mass or more and 40% by mass or less). It is.

  The amount of colloidal silica added to 100% by mass of the above-mentioned aggregate raw material is preferably 5 to 15% by mass (5 to 15% by mass), more preferably 8 to 12% by mass. (8 mass% or more and 12 mass% or less). If the amount of colloidal silica added is less than 5% by mass, the effect of improving the hot strength in the intermediate temperature range cannot be obtained, and the heat-resistant spalling property is lowered, which is not preferable. Moreover, since it becomes easy to isolate | separate a castable when the addition amount exceeds 15 mass% of outer shells, it is not preferable.

  Moreover, the alumina cement which is an additive functions as a hardening | curing agent of colloidal silica. Addition of alumina cement improves the curing strength of the molded refractory, and can prevent cracking and corner chipping during frame removal and handling. As the alumina cement, any commercially available alumina cement can be used. For example, fondue cement (fourth type alumina cement standardized in former JIS R 2511-1995), No. 1 cement (third type alumina cement standardized in old JIS R 2511-1995), high alumina Cement (the second type alumina cement standardized in the former JIS R 2511-1995) can be used. In particular, it is preferable to use No. 1 cement from the viewpoint of improving the strength after curing. In addition, in the above-mentioned Patent Documents 4 and 5, examples using Portland cement are disclosed, but when using colloidal silica as a binder like a main cast refractory, when Portland cement is used, agglomeration occurs immediately. It happens and construction becomes impossible.

The addition amount of the alumina cement with respect to the above-mentioned aggregate raw material 100% by mass is preferably 1.0 to 5.0% by mass (1.0% by mass or more and 5.0% by mass or less), more preferably, It is 1.5-2.5 mass% (1.5 mass% or more and 2.5 mass% or less) by outer coating. If the amount of alumina cement added is less than 1.0% by mass, it is not preferable because sufficient curing strength cannot be obtained. On the other hand, when the amount added exceeds 5.0% by mass, the amount of Al ₂ O _{3 in the} refractory increases, and the creep characteristics of the molded refractory deteriorate, which is not preferable.

  In addition to the above, organic dispersants, inorganic dispersants, and the like can be added for the purpose of promoting peptization and reducing water in the casting material within a range that does not impair the effects of the present invention.

  By blending the raw materials as described above, the cast refractory according to the present invention can be obtained. In the production of the cast refractory, a general production apparatus can be used. As a mixer after mixing raw materials, for example, an omni mixer, a V-type mixer, or the like can be used.

  According to the cast refractory, a refractory having a small change in thermal expansion coefficient from room temperature to high temperature and having an appropriate thermal expansion coefficient, being dense and high in strength, and having excellent heat spalling properties should be realized. Can do. As a result, when used for repairing the furnace wall of a coke oven, rapid temperature increase is possible after completion of repair, and the temperature increase time after completion of repair can be shortened. In addition, since the difference in thermal expansion between the unrepaired portion and the repaired portion is small and deformation is not easily caused by a long-time load at a high temperature, the coke oven can be stably used for a long time after completion. Furthermore, since it is an aspect of the cast refractory, it is also possible to manufacture a large block having an arbitrary shape. By using this large block, the working time of the worker in a narrow furnace and in a high temperature atmosphere can be shortened. Combined with the above, the repair period can be shortened and the manufacturing cost can be reduced.

  In addition, when applying a main casting refractory for repair of a coke oven, the construction method is not specifically limited. For example, a cast refractory may be used to produce a molded refractory, and may be constructed by stacking the molded refractories. Pouring may be performed using a formwork.

  Moreover, when obtaining a molded refractory, it can follow the following procedures, for example. First, the above-described raw materials are kneaded using a known kneading mixer such as a universal mixer, mortar mixer, flat mixer, vortex mixer, or twin screw kneader. The cast refractory according to the present invention produced by kneading is poured into a mold having a desired shape. In that case, you may add a vibration by methods, such as a rod-like vibrator, a formwork vibration, and table vibration. After the predetermined time has elapsed and the cast refractory is cured, the molded refractory is removed from the mold and dried. In this drying, a known drying method such as electrothermal drying, hot air drying, hot air drying, radiation heating drying, or burner drying can be used.

  Examples and comparative examples are presented below to illustrate the cast refractory of the present invention.

Cast refractories were prepared at the blending ratios shown in Tables 1 and 2, and the properties were evaluated as cast refractories for coke oven repair. The amorphous siliceous raw material used in each cast refractory is fused silica having a mass ratio of SiO ₂ component of 99.5% or more. In addition, the particle diameter of a fused silica is 0.4-3 mm (0.4 mm or more and 3 mm or less). In addition, the crystalline siliceous raw materials used in each cast refractory are silica brick scrap and silica raw materials. Silica brick scrap contains 85% by mass of tridymite and 3% by mass of cristobalite. In addition, the quartz raw material is mainly composed of quartz. In addition, the particle diameter of a silica brick waste and a silica raw material is 1 mm or less. In addition, No. 1 cement is used as the alumina cement.

  For molded refractories with each cast refractory, the bending strength after curing, the bending strength after drying, the heat spalling property, the thermal expansion coefficient, and the creep characteristics are evaluated. The evaluation results for each item are shown in Tables 1 and 2 It was described in. Hereinafter, each test item will be briefly described.

  Each test sample is formed by the following procedure. First, each cast refractory material was kneaded for 3 minutes with a universal mixer. The kneaded material (cast-in refractory) was poured into molds having various shapes, which will be described later, placed on a vibration table and cast while applying vibration. After casting, the cast surface was covered with a wet cloth, each mold was placed in a plastic bag, and curing was performed in a curing room at 40 ° C. for 24 hours. After curing, the mold was taken out from the plastic bag, the cloth covered on the casting surface was removed, the frame was removed, and then dried with a hot air dryer at 110 ° C. for 24 hours.

  Regarding the bending strength after curing and the bending strength after drying, the bending strength of the post-curing test sample and the post-drying test sample having a shape of 40 mm × 40 mm × 160 mm was evaluated at room temperature by a three-point bending test. When the strength after curing is low, the molded refractory is cracked or chipped at the time of deframement, or it is destroyed. In addition, when the bending strength after drying is low, the molded refractory is cracked or chipped or destroyed during construction. Therefore, both items need to have sufficient strength to withstand practical use. In the table, “◎” indicates that the strength is extremely high, and “◯” indicates that the strength has no practical problem. “Δ” indicates that the strength is slightly weak and the margin is low, and “×” indicates that the strength is extremely low and there is a problem in practical use.

  The heat spalling resistance was evaluated based on the state of cracks on the surface of the test sample taken out by heating the test sample after drying having a shape of 65 mm × 115 mm × 230 mm in an electric furnace maintained at 500 ° C. for 20 minutes. If the heat spalling property is low, it will crack or break when the temperature rises after it is applied to the coke oven. That is, in order to prevent the accumulated coke oven wall from collapsing, the heat spalling resistance needs to be sufficiently high. The symbol in the table indicates that “◎” indicates that there is no crack, “○” indicates that a practically acceptable microcrack has occurred, and “×” indicates that a thick crack that is not acceptable in practice has occurred. It is shown that.

  The coefficient of thermal expansion was evaluated based on the coefficient of thermal expansion at 1200 ° C. in an air atmosphere in which a post-drying test sample having a shape of 20 mm × 15 mm × 85 mm was obtained using a thermal expansion measuring device (based on JIS R 2207-1). When the coefficient of thermal expansion is high, cracks occur in the molded refractory when the temperature is raised. In order to suppress the occurrence of cracks, the heating rate must be reduced, the heating time becomes longer, and the construction work period becomes longer. That is, in order to shorten the temperature raising time, it is preferable that the coefficient of thermal expansion is small. On the other hand, if the coefficient of thermal expansion is too small, the difference in thermal expansion from the unrepaired brick becomes too large, which is not preferable. For this reason, it is desirable to have an appropriate coefficient of thermal expansion. The symbol in the table indicates that “◎” indicates that the coefficient of thermal expansion is within an appropriate range that does not cause an imbalance with the unrepaired part, and “○ large” indicates that the coefficient of thermal expansion is slightly large, but acceptable. “O small” indicates that the coefficient of thermal expansion is slightly small but within the allowable range. “X large” indicates that the coefficient of thermal expansion is too large and deviates from the allowable range, and “× small” indicates that the coefficient of thermal expansion is too small and deviates from the allowable range.

  Creep characteristics were evaluated by the amount of creep deformation when a test sample after drying having a shape of 40 mm in diameter and 40 mm in height was heated under a load of 0.4 MPa. In addition, the heating conditions are heating to 1450 ° C. at 5 ° C./min and holding at 1450 ° C. for 25 hours. The amount of creep deformation is obtained from the amount of deformation after 25 hours starting from the time when the temperature reaches 1450 ° C. When the amount of creep deformation is large, the refractory is deformed by the thermal stress generated by heating and the weight of the wall, and the side wall collapses or protrudes. That is, in order to suppress the protrusion of the side wall, the amount of creep deformation needs to be small. In the table, “◯” indicates that the amount of creep deformation is within the allowable range, and “X” indicates that the amount of creep deformation is outside the allowable range.

  As can be understood from Tables 1 and 2, in Examples 1 to 13, each of each of the bending strength after curing, bending strength after drying, thermal spalling property, thermal expansion coefficient, and creep characteristics are compared with Comparative Examples 1 to 10. It can be said that the characteristics are excellent overall.

  Here, the formulations shown in Tables 1 and 2 will be briefly described.

  In Table 1, Examples 1-5 have changed the compounding ratio of a fused silica and a silica brick brick. In Examples 6 and 7, a silica material containing quartz as a main component is used instead of a part of the silica brick waste in the combination of Examples 1 and 5. In Examples 8 and 9, the blending ratio of fumed silica is changed. In Examples 10 and 11, the blending ratio of colloidal silica is changed. In Examples 12 and 13, the mixing ratio of the alumina cement is changed.

  In Table 2, the comparative examples 1 and 2 are changing the compounding ratio of a fused silica and a silica stone brick in the mixing | blending of Examples 1-5. In Comparative Examples 3 and 4, the blending ratio of fumed silica in the blends of Examples 8 and 9 is changed. Comparative Example 5 uses water instead of colloidal silica in the formulations of Examples 10 and 11. In Comparative Examples 6 and 7, the blending ratio of colloidal silica is changed in the blending of Examples 10 and 11. In Comparative Examples 8 and 9, the blending ratio of the alumina cement is changed in the blending of Examples 12 and 13. Comparative Example 10 uses Portland cement instead of alumina cement in the formulations of Examples 12 and 13. In Comparative Example 10, agglomeration started immediately after kneading, so it could not be poured into the mold and a test sample could not be prepared. Therefore, in the evaluation results of Table 2, the symbol “−” indicating that the evaluation could not be performed is described.

  As can be understood from Tables 1 and 2, in Examples 1 to 5, good characteristics were obtained, whereas Comparative Example 1 in which the blended amount of silica brick was increased while the blended amount of fused silica was decreased. Shows a result that the heat-resistant spalling property is deteriorated and the coefficient of thermal expansion is large. That is, in Comparative Example 1, a sufficient expansion suppressing effect is not obtained. Moreover, in Comparative Example 2 in which the blending amount of fused silica was increased and the blending amount of silica brick was reduced, the coefficient of thermal expansion was too small, and the creep characteristics were also deteriorated.

  In Examples 8 and 9, good characteristics were obtained, whereas in Comparative Example 3 in which the amount of fumed silica was reduced, the bending strength after curing and the bending strength after drying were slightly reduced. Yes. That is, in Comparative Example 3, the flowability of the cast refractory is lowered, and a dense molded refractory is not obtained. Moreover, in the comparative example 4 which increased the compounding quantity of the fumed silica, it resulted in the heat resistant spalling characteristic and the creep characteristic getting worse because of rapid sintering resulting from the fumed silica.

  Moreover, in Examples 10 and 11, good characteristics were obtained, whereas in Comparative Example 6 in which the amount of colloidal silica was reduced, the heat spalling property was deteriorated. That is, in Comparative Example 6, a sufficient heat spalling improvement effect due to the addition of colloidal silica is not obtained. Moreover, in the comparative example 5 which added water instead of colloidal silica, the bending strength after curing and the bending strength after drying were also reduced. On the other hand, in Comparative Example 7 in which the amount of colloidal silica was increased, the castable was easily separated, and as a result, the bending strength after curing and the bending strength after drying were slightly lowered.

Further, in Examples 12 and 13, good characteristics were obtained, whereas in Comparative Example 8 in which the amount of alumina cement was reduced, the bending strength after curing and the bending strength after drying decreased, and the heat resistance As a result, the spalling performance deteriorated. In Comparative Example 9 in which the amount of alumina cement was increased, the amount of Al ₂ O ₃ in the refractory increased, resulting in an increase in the creep characteristics to an unacceptable level.

  As described above, according to each embodiment of the present invention, a cast refractory having comprehensively excellent characteristics can be obtained.

  The present invention can reduce the furnace wall repair work time and the temperature rise time after completion of repair, and is useful as a cast refractory.

Claims (4)

An amorphous siliceous raw material having a mass ratio of SiO ₂ component of 99% or more is 40 to 65 mass%,
35 to 60% by mass of one or more of quartz, tridymite and cristobalite,
An aggregate material consisting of
An additive comprising fumed silica, colloidal silica and alumina cement;
Cast refractory containing.   2. The cast refractory according to claim 1, wherein the amount of the fumed silica added is 8 to 17% by mass on the basis of 100% by mass of the aggregate raw material.   The cast refractory according to claim 1 or 2, wherein an addition amount of the colloidal silica is 5 to 15% by mass on the basis of 100% by mass of the aggregate raw material.   The cast refractory according to any one of claims 1 to 3, wherein an addition amount of the alumina cement is 1.0 to 5.0 mass% as an outer shell with respect to 100 mass% of the aggregate raw material.