Pouring material

Abstract

Provided is a castable material that can reduce the work load during construction and eliminate the drying process. 【Solution means】Based on 100% by mass of a refractory raw material composition containing 0.2 to 12% by mass of silica fume and 0.1 to 2% by mass of reactive alumina, with the balance being other refractory raw materials, one or more selected from CA, CA2, and C12A7 in calcium aluminate are in total 0.05 to 1% by mass, and aluminum lactate is added at an addition rate of 0. to 1.2% by mass, a castable material.

Description

Technical Field

[0001] The present invention relates to a pourable material used, for example, in blast furnace troughs, molten iron pretreatment equipment (KR) impellers, ladle covers, tundish covers, heating furnace skid pipes, various kilns, incinerators, fluidized bed furnaces, industrial waste kiln treatment furnaces, circulating fluidized bed (CFB) boiler furnaces, cement manufacturing equipment furnaces, gasification melting furnaces, stoker furnaces, and the like.

Background Art

[0002] The pourable material is a general term for refractory castables that can be poured and constructed, and is also called a castable refractory. As such a pourable material, those using cement (alumina cement, Portland cement, magnesia cement, etc.) as a binder are widely used. However, when cement is used as a binder, a hydration reaction occurs at room temperature and the matrix of the poured construction body becomes dense, making dehydration difficult, and there is a risk of explosion when the temperature of the construction body rises. Therefore, a drying process is required after the pouring construction, which incurs costs and requires a long operation stop time.

[0003] On the other hand, a pourable material using silica sol, that is, colloidal silica, as a binder is also known. For example, Patent Document 1 discloses a pourable material for a firing furnace that does not require a drying process after pouring construction, can suppress physical impact from furnace contents, and can suppress alkali attack by using colloidal silica as a binder.

[0004] In the construction of the pouring material, water is usually used as the kneading liquid used during kneading. Also, water meters and water tanks are installed in many kneading mixers. Here, the colloidal silica used in the pouring material has a role not only as a binder but also as a kneading liquid. Therefore, when carrying out construction using colloidal silica as the kneading liquid, if the water meter and water tank installed in the kneading mixer are used, meticulous cleaning is required after construction, which requires a lot of time and labor. On the other hand, if the water meter and water tank installed in the kneading mixer are not used, the tank containing colloidal silica has to be transported to the construction site such as a steelworks, and then, after measuring the required amount with a beaker with a handle or the like, the colloidal silica is added to the kneading mixer containing the refractory raw material. Thus, when using colloidal silica in the pouring material, there is a problem that the work load increases compared to the case of using water.

[0005] On the other hand, Non-Patent Document 1 discloses a no-cement castable that forms a microsilica gel bond. The microsilica gel bond can be obtained by using water as the kneading liquid with refractory raw materials such as silica fume. Here, what is disclosed in Non-Patent Document 1 is a no-cement castable, but even if it is called "no-cement", it does not mean that it does not contain cement at all. That is, in ASTM C401-91, there are four classifications: general castable, low-cement castable, ultra-low-cement castable, and no-cement castable, depending on the content rate of the CaO component. Among them, the no-cement castable has a CaO component content rate of 0.2 mass% or less. In this regard, the no-cement castable disclosed in Non-Patent Document 1 contains 0.5 mass% of 70%CAC (calcium aluminate cement of 70 mass% Al2O3·30 mass% CaO), and the CaO component content rate is approximately 0.5×0.3 = 0.15 mass%, belonging to the classification of no-cement castable. Thus, the no-cement castable disclosed in Non-Patent Document 1 contains a CaO component, and Ca in the solution 2+(And / or other polyvalent cations) elute to cause a gelling action on the surface of negatively charged microsilica (silica fume). The microsilica gel bond is a state in which the linked microsilica particles form a three-dimensional network due to this gelling action. The cast-in-place material that utilizes the formation of the microsilica gel bond can be constructed using only water as the liquid without using a special liquid such as colloidal silica, and the work load during construction is reduced.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] As described above, the cast-in-place material that utilizes the formation of the microsilica gel bond can reduce the work load during construction. However, it has not reached the characteristic of not requiring a drying process like the cast-in-place material using colloidal silica. Therefore, the problem to be solved by the present invention is to provide a castable material that can reduce the working load during construction and eliminate the drying process.

Means for Solving the Problem

[0009] As a result of repeated tests and research to obtain the property of eliminating the drying process in a castable material utilizing the formation of a microsilica gel bond, the present inventors have found that the addition of aluminum lactate is effective. That is, for a refractory raw material composition containing silica fume and A refractory raw material that undergoes a rehydration reaction and hardens when water is added reactive alumina at respective content rates within a specific range, one or more selected from CA, CA2, and C12A7 among calcium aluminate is added at an addition rate within a specific range, and aluminum lactate is added at an addition rate within a specific range. During construction, aluminum lactate gels due to the kneading water, and then, during the process leading to drying, numerous fine cracks are generated in the constructed body due to volume shrinkage, which serves as escape routes for water vapor, thereby greatly increasing the dehydration rate. As a result, the inventors have found that the property of eliminating the drying process can be obtained.

[0010] That is, according to one aspect of the present invention, the following castable material is provided. A castable material obtained by adding 0.2 to 12% by mass of silica fume, A refractory raw material that undergoes a rehydration reaction and hardens when water is added 0.1 to 2% by mass of reactive alumina, and, based on 100% by mass of a refractory raw material composition in which the balance consists of other refractory raw materials, a total of 0.05 to 1% by mass of one or more selected from CA, CA2, and C12A7 among calcium aluminate and 0.1 to 1.2% by mass of aluminum lactate at an addition rate.

Effect of the Invention

[0011] According to the unshaped castable material of the present invention, the working load during construction can be reduced, and drying can be eliminated.

Mode for Carrying Out the Invention

[0012] The castable material of the present invention contains 0.2 to 12% by mass of silica fume, A refractory raw material that undergoes a rehydration reaction and hardens when water is added 0.1 to 2% by mass of reactive alumina, and based on 100% by mass of a refractory raw material composition in which the balance is composed of other refractory raw materials, a total of 0.05 to 1% by mass of one or more selected from CA, CA2, and C12A7 among calcium aluminates, and aluminum lactate is added at an addition rate of 0.1 to 1.2% by mass. In the following description, The reactive alumina, which is a refractory raw material that undergoes a rehydration reaction and hardens when water is added, is simply referred to as "reactive alumina", one or more calcium aluminates selected from CA, CA2, and C12A7 among calcium aluminates is referred to as "specific calcium aluminate". In the present invention, silica fume and reactive alumina in the refractory raw material composition, and specific calcium aluminate added to the refractory raw material composition mainly serve as a micro silica gel bond forming material for forming a micro silica gel bond. That is, as described above, the present invention, for the purpose of forming a micro silica gel bond, adds specific calcium aluminate at a specific addition rate to a refractory raw material composition containing silica fume and reactive alumina at respective specific content rates, and adds aluminum lactate at a specific addition rate, thereby imparting the characteristic of eliminating the drying process. This will be specifically described below.

[0013] [[ID=ID=10]]The content rate of silica fume is 0.2 to 12% by mass. If the content rate of silica fume is less than 0.2% by mass, the micro silica gel bond is not sufficiently formed, and the strength after curing (hereinafter referred to as "curing strength") is insufficient. On the other hand, if the content rate of silica fume exceeds 12% by mass, the matrix of the cast construction body becomes excessively dense and dehydration becomes difficult, and there is a risk of explosion when the temperature of the construction body rises. That is, the explosion resistance decreases and the characteristic of eliminating the drying process cannot be obtained. The content rate of silica fume is preferably 0.5 to 12% by mass. As the silica fume, those generally used for castable materials can be used.

[0014] The content rate of reactive alumina is 0.1 to 2% by mass. When the content rate of reactive alumina is less than 0.1% by mass, the microsilica gel bond is not sufficiently formed and the curing strength is insufficient. On the other hand, when the content rate of reactive alumina exceeds 2% by mass, the matrix of the cast body becomes excessively dense and the air permeability decreases, and as a result, the property of making the drying process unnecessary cannot be obtained. The content rate of reactive alumina is preferably 0.5 to 1.5% by mass. Here, reactive alumina refers to a refractory raw material that undergoes a rehydration reaction and hardens when water is added, and typically includes ρ-alumina. Note that reactive alumina is an ultrafine powder with an average particle diameter (D50) of less than about 10 μm, but it is clearly distinguished from alumina ultrafine powders such as activated alumina generally used as refractory raw materials from the perspective of reactivity with water. Also, generally, reactive alumina is amorphous and can be distinguished from ordinary alumina ultrafine powders such as activated alumina from the perspective of crystal structure.

[0015] Thus, in the present invention, the refractory raw material composition contains silica fume and reactive alumina as a part of the microsilica gel binder-forming material, and the remainder consists of other refractory raw materials. Note that other refractory raw materials refer to refractory raw materials other than silica fume and reactive alumina. As other refractory raw materials, refractory raw materials generally used in castable materials such as alumina raw materials, magnesia raw materials, spinel raw materials, silica raw materials, carbon raw materials, alumina-silica raw materials, and silicon carbide raw materials can be used. Also, the particle size distribution of other refractory raw materials can be made the same as that of refractory raw materials generally used in castable materials.

[0016] The addition rate of the specific calcium aluminate is 0.05 to 1% by mass. When the addition rate of the specific calcium aluminate is less than 0.05% by mass, the microsilica gel bond is not sufficiently formed, and the curing strength is insufficient. On the other hand, when the addition rate of the specific calcium aluminate exceeds 1% by mass, the hydration reaction occurs at room temperature and the matrix of the cast-in-place construction body becomes dense, making dehydration difficult, and there is a risk of explosion when the temperature of the construction body rises. That is, the explosion resistance decreases and the property of eliminating the drying process cannot be obtained. The addition rate of the specific calcium aluminate is preferably 0.1 to 0.6% by mass. Here, as described above, the specific calcium aluminate is one or more calcium aluminates selected from CA (CaO·Al2O3), CA2 (CaO·2Al2O3), and C12A7 (12CaO·7Al2O3), and is widely known as a main hydraulic mineral constituting alumina cement, which is a typical binder for cast-in-place materials. Therefore, in the present invention, the specific calcium aluminate can be added as alumina cement. In this case, the addition rate of the specific calcium aluminate can be calculated based on the addition rate of the alumina cement and the content of the specific calcium aluminate in the alumina cement. On the other hand, the specific calcium aluminate can also be added alone as a mineral or in combination with alumina cement.

[0017] The addition rate of aluminum lactate is 0.1 to 1.2% by mass based on 100% by mass of the refractory raw material formulation. When the addition rate of aluminum lactate is less than 0.1% by mass, the number of fine cracks generated is small, so the effect of improving the explosion resistance cannot be sufficiently obtained, and the property of eliminating the drying process cannot be obtained. On the other hand, when the content of aluminum lactate exceeds 1.2% by mass, excessive fine cracks occur and the porosity increases, resulting in a decrease in corrosion resistance. The addition rate of aluminum lactate is preferably 0.3 to 0.8% by mass. Here, aluminum lactate refers to additives such as basic aluminum lactate, modified basic aluminum lactate, and basic aluminum lactate-hydroxyacetic acid, which are commonly used in amorphous refractories.

[0018] In the present invention, various additives such as an anti-explosion agent and a dispersant can be appropriately added to the refractory raw material composition in addition to specific calcium aluminate (alumina cement) and aluminum lactate. Specific examples of the anti-explosion agent are organic fibers, organic foaming agents, metallic aluminum, etc. Specific examples of the organic fibers are polymer organic fibers such as vinylon (including polyvinyl alcohol), rayon, polyester, nylon, polypropylene, polyethylene. The dispersant imparts fluidity during the construction of the refractory. Specific examples include inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, acidic sodium hexametaphosphate, sodium borate, sodium carbonate, polymetaphosphates, and organic salts such as sodium citrate, sodium tartrate, sodium polyacrylate, sodium sulfonate, polycarboxylates, β-naphthalenesulfonates, naphthalenesulfonic acid. These additives are added based on 100% by mass of the refractory raw material composition, similar to specific calcium aluminate (alumina cement) and aluminum lactate. The addition rate may be equivalent to that of a general casting material.

[0019] Moreover, in the casting material of the present invention, in addition to the above refractory raw material composition, specific calcium aluminate (alumina cement), aluminum lactate, and various additives, large coarse grains with a particle size of 8 mm or more can also be used. These large coarse grains serve to prevent the progression of cracks generated in the matrix of the cast construction body.

[0020] In the present invention, the particle size of the refractory raw material refers to the size of the sieve mesh when the refractory raw material is sieved and separated. For example, a refractory raw material with a particle size of less than 8 mm is a refractory raw material that passes through a sieve with a mesh size of 8 mm, and a refractory raw material with a particle size of 8 mm or more is a refractory raw material that does not pass through a sieve with a mesh size of 8 mm.

Examples

[0021] Tables 1 to 4 show the raw material formulations and evaluation results of the examples and comparative examples of the present invention. Here, in each example shown in Tables 1 to 3, the specific calcium aluminate was added as alumina cement. And the addition rate of the specific calcium aluminate shown in Tables 1 to 3 was calculated based on the addition rate of the alumina cement and the content rate of the specific calcium aluminate in this alumina cement as described above. On the other hand, in each example shown in Table 4, the specific calcium aluminate was added alone as a mineral. The evaluation items and evaluation methods for the pouring materials of each example shown in Tables 1 to 4 are as follows.

[0022] <Curing strength (flexural strength after curing)> Approximately 5% by mass of construction water was added to the pouring material of each example and kneaded. Using the test piece obtained by pouring the kneaded material into a mold, curing at 20 °C for 24 h, and then demolding, the flexural strength was measured according to JIS R 2553. The curing strength was evaluated in three grades: ○ (excellent) when it was 0.5 MPa or more, △ (good) when it was 0.2 MPa or more and less than 0.5 MPa, and × (poor) when it was less than 0.2 MPa. ○ (excellent) or △ (good) was regarded as passing. If the evaluation of this curing strength passed, the construction body could be stably demolded without collapse or the like during actual construction.

[0023] <Apparent porosity> Approximately 5% by mass of construction water was added to the pouring material of each example and kneaded. Using the test piece obtained by pouring the kneaded material into a mold, curing at 20 °C for 24 h, demolding, and then drying at 110 °C for 24 h, the apparent porosity was measured according to JIS R 2205. The apparent porosity was evaluated in three grades: ○ (excellent) when it was less than 15%, △ (good) when it was 15% or more and less than 20%, and × (poor) when it was 20% or more. ○ (excellent) or △ (good) was regarded as passing. If the evaluation of this apparent porosity passed, a construction body with a dense structure and excellent corrosion resistance could be obtained.

[0024] <Air permeability> Approximately 5% by mass of construction water was added to the pouring material for each example and kneaded. The kneaded material was poured into a mold, cured at 20 °C for 24 h, demolded, and further dried at 110 °C for 24 h. The air permeability was measured in accordance with JIS R 2115 using the obtained test pieces. The air permeability was evaluated in three grades: ○ (excellent) if it was 1.0×10 -14 m 2 or more, △ (good) if it was 1.0×10 -16 m 2 or more and less than 1.0×10 -14 , and × (poor) if it was less than 1.0×10 -16 m 2 . ○ (excellent) or △ (good) was regarded as passing.

[0025] <Explosion resistance> Approximately 5% by mass of construction water was added to the pouring material for each example and kneaded. The kneaded material was poured into a cylindrical mold with a diameter of 100 mm and a height of 100 mm, cured at 20 °C for 24 h, and demolded. Two cylindrical test pieces obtained were each put into an electric furnace at a temperature of 900 °C, heated, held for 30 minutes, and then taken out. The explosion resistance was evaluated by examining the presence or absence of explosion and the presence or absence of crack generation for each test piece. The explosion resistance was evaluated in three grades: ○ (excellent) if there was no crack or only minor cracks, △ (good) if partial fracture occurred on the surface layer, and × (poor) if damage of 50% or more such as fracture occurred. ○ (excellent) or △ (good) was regarded as passing. If both the evaluation of this explosion resistance and the evaluation of the above air permeability passed, the drying process after the pouring construction could be made unnecessary.

[0026] <Comprehensive evaluation> For the comprehensive evaluation, if all the evaluation results were 〇, it was rated as ◎ (excellent); if at least one of the evaluation results was △ and there was no × evaluation result, it was rated as 〇 (good); if at least one of the evaluation results was ×, it was rated as × (poor). ◎ (excellent) or 〇 (good) was regarded as passing.

[0027]

Table 1

[0028]

Table 2

[0029]

Table 3

[0030]

Table 4

[0031] Each example shown in Tables 1 to 2 is an example using an alumina raw material as another refractory raw material. Among these, the castable materials of Examples 1 to 12, which are examples of the present invention, passed all evaluations of curing strength, apparent porosity, air permeability, and spalling resistance, and also passed the comprehensive evaluation. Specifically, Examples 1 to 4 are examples in which the content rate of silica fume was changed. All of them are within the scope of the present invention and passed all evaluations. On the other hand, Comparative Example 1 is an example that does not contain silica fume, and sufficient curing strength could not be obtained. On the other hand, Comparative Example 2 is an example in which the content rate of silica fume exceeds the upper limit value of the present invention, and the spalling resistance decreased. Examples 5 to 6, 3, 7 to 8 are examples in which the content rate of reactive alumina was changed. All of them are within the scope of the present invention and passed all evaluations. On the other hand, Comparative Example 3 is an example that does not contain reactive alumina, and sufficient curing strength could not be obtained. On the other hand, Comparative Example 4 is an example in which the content rate of reactive alumina exceeds the upper limit value of the present invention, and the air permeability decreased. Examples 9 to 10, 3, 11 to 12 are examples in which the addition rate of specific calcium aluminate was changed. All of them are within the scope of the present invention and passed all evaluations. On the other hand, Comparative Example 5 is an example that does not add specific calcium aluminate (alumina cement), and sufficient curing strength could not be obtained. On the other hand, Comparative Example 6 is an example in which the addition rate of specific calcium aluminate exceeds the upper limit value of the present invention, and the air permeability and spalling resistance decreased. Examples 13 - 14, 3, 15 - 16 are examples where the addition rate of aluminum lactate was changed. All are within the scope of the present invention, and all evaluations passed. In contrast, Comparative Example 7 is an example where no aluminum lactate was added, and the air permeability and burst resistance decreased. On the other hand, Comparative Example 8 is an example where the addition rate of aluminum lactate exceeded the upper limit value of the present invention, the apparent porosity increased, and sufficient curing strength could not be obtained.

[0032] Each example shown in Table 3 is an example where the raw material composition of other refractory raw materials was changed. All are within the scope of the present invention, and all evaluations passed. Each example shown in Table 4 is an example where specific calcium aluminate was added as a single mineral. All are within the scope of the present invention, and all evaluations passed.

[0033] Among the above Examples 1 - 29, in Examples 2, 3, 4, 6, 7, 10, 11, 14, 15, 17 - 25 where the respective content rates of silica fume and reactive alumina, and the respective addition rates of specific calcium aluminate and aluminum lactate are all within the preferable ranges, the comprehensive evaluation is ◎ (excellent), and particularly excellent characteristics are obtained.

Claims

1. The castable material is prepared by adding 0.2 to 12% by mass of silica fume, 0.1 to 2% by mass of reactive alumina which is a refractory raw material that undergoes a rehydration reaction and hardens when water is added, and the balance being other refractory raw materials. Based on 100% by mass of the refractory raw material blend, a total of 0.05 to 1% by mass of one or more selected from CA, CA2, and C12A7 among calcium aluminate and 0.1 to 1.2% by mass of aluminum lactate are added at an addition rate.

2. In the proportion of the refractory raw material blend by 100% by mass, the content of silica fume is 0.5 to 12% by mass, and the content of reactive alumina which is a refractory raw material that undergoes a rehydration reaction and hardens when water is added is 0.2 to 1.5% by mass. The castable material according to Claim 1, wherein in the addition ratio with respect to 100% by mass of the refractory raw material blend, the total addition rate of one or more selected from CA, CA2, and C12A7 among calcium aluminate is 0.1 to 0.6% by mass, and the addition rate of aluminum lactate is 0.3 to 0.8% by mass.

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