Method for producing chromia-containing castable refractory and chromia-containing castable refractory

Abstract

The present invention provides a chromia-containing castable refractory having excellent explosion resistance, spalling resistance, and corrosion resistance as well as good workability, and a simple and efficient method for producing the same. [Solution] A method for producing a chromia-containing castable refractory material, characterized in that a refractory raw material mainly composed of alumina and / or mullite and a chromia raw material are kneaded using silica sol, so that the content of the chromia raw material is 30 to 90 mass%, the content of the chromia raw material (fine-particle chromia raw material) having a particle size of 0.09 mm or less is 20 to 30 mass%, and the SiO2 solid content concentration of the silica sol is 30 to 40 mass%.

Description

[Technical field]

[0001] The present invention relates to a castable refractory that can be used as a lining refractory material for a waste treatment furnace, etc. [Background technology]

[0002] Refractories containing chromia (Cr2O3) have excellent corrosion resistance against CaO-SiO2-based slag, and are therefore widely used as refractory materials for steel, non-ferrous metals, cement burning, etc. In particular, chromia-based castables tend to be used in waste treatment furnaces that melt ash, sludge, garbage, etc., because they are subject to erosion by slag.

[0003] However, dense castable refractories containing a relatively large amount of chromia have the problem that, while they have excellent corrosion resistance, they are inferior in spalling resistance and explosion resistance. In response to this, for example, Patent Document 1 (JP Patent Publication No. 293570 / 1994) proposes an alumina-chromia castable refractory that is characterized by being composed of 30-85% by weight of alumina raw material or a mixture of alumina raw material and zircon raw material with particle size adjustment, 7-50% by weight of chromia coarse powder with a particle size of 1 mm-1 μm, 3-20% by weight of refractory fine powder with a particle size of 45 μm or less, 0.5-10% by weight of alumina cement with a particle size of 100-1 μm, and an appropriate amount of dispersant, and has a total SiO2 content of 6% by weight or less.

[0004] In the alumina-chromia castable refractory described in the above Patent Document 1, it is said that by using rough chromia particles with a particle size of 1 mm to 1 μm, it is possible to obtain an alumina-chromia castable refractory that effectively improves corrosion resistance even when the amount of chromia added is kept relatively low, and that does not deteriorate in thermal shock resistance or workability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-293570 Summary of the Invention [Problem to be solved by the invention]

[0006] Although the alumina-chromia castable refractory described in Patent Document 1 has improved corrosion resistance without impairing thermal shock resistance or workability, there has been an increasing demand in recent years for energy saving and extended furnace operating times, and there is a strong demand for better explosion resistance and spalling resistance.

[0007] In addition, while castables containing chromia have excellent corrosion resistance, they also have high viscosity, and so workability must be ensured for use in actual furnaces. Specifically, they must have a high vibration flow value, which is an index of workability.

[0008] In view of the problems in the prior art as described above, an object of the present invention is to provide a chromia-containing castable refractory having excellent explosion resistance, spalling resistance, and corrosion resistance as well as good workability, and a simple and efficient method for producing the same. [Means for solving the problem]

[0009] In order to achieve the above object, the present inventors have conducted extensive research into the composition and mixing method of chromia-containing castable refractories. As a result, they have discovered that when mixing raw materials using silica sol, the corrosion resistance, spalling resistance and workability of chromia-containing castable refractories can be improved by adding an appropriate amount of fine chromia raw material having a particle size of 0.09 mm or less, and have arrived at the present invention.

[0010] That is, the present invention provides: A refractory raw material mainly composed of alumina and / or mullite and a chromia raw material are kneaded with a silica sol; The content of the chromia raw material is 30 to 90 mass %, The content of the chromia raw material (fine chromia raw material) having a particle size of 0.09 mm or less is 20 to 30 mass %, The SiO2 solid content concentration of the silica sol is 30 to 40 mass%. The present invention provides a method for producing a chromia-containing castable refractory material, comprising the steps of:

[0011] In the manufacturing method of the chromia-containing castable refractory of the present invention, 30 to 90 mass% of chromia (Cr2O3) is contained, thereby imparting excellent corrosion resistance to the chromia-containing castable refractory. Here, within the range of 30 to 90 mass%, the chromia content can be increased if corrosion resistance is important, and reduced if workability (vibration flow value) is desired. If the chromia content is less than 30 mass%, sufficient corrosion resistance cannot be achieved, and if the chromia content exceeds 90 mass%, heat spalling resistance and explosion resistance decrease.

[0012] In addition, in the method for producing a chromia-containing castable refractory of the present invention, by kneading each raw material of the castable refractory with a silica sol having a SiO2 solid content of 30 to 40 mass%, fine continuous mesh-like pores can be formed in the structure obtained after drying. The formation of the pores extremely effectively improves the explosion resistance and spalling resistance of the chromia-containing castable refractory. These effects can be achieved by making the SiO2 solid content of the silica sol 30 mass% or more, and by making it 40 mass% or less, the decrease in the flowability of the castable can be suppressed.

[0013] In addition, the addition of silica sol having a SiO2 solid content of 30 to 40 mass% results in the formation of continuous network pores, which shortens the drying time of the chromia-containing castable refractory material and reduces the amount of energy consumption required for the drying.

[0014] In addition, in the manufacturing method of the chromia-containing castable refractory of the present invention, by adding 20 to 30 mass% of chromia raw material having a particle size of 0.09 mm or less (fine chromia raw material), the fluidity of the chromia-containing castable refractory can be improved and practical workability can be imparted. In addition, by adding the fine chromia raw material, the corrosion resistance of the chromia-containing castable refractory, which is reduced by adding silica sol, can be improved. If the amount of the fine chromia raw material added is less than 20 mass%, these effects cannot be fully exhibited, and if the amount of the fine chromia raw material added exceeds 30 mass%, aggregation proceeds and the viscosity of the chromia-containing castable refractory increases, making it impossible to use in practical construction.

[0015] In addition, in the manufacturing method of the chromia-containing castable refractory material of the present invention, when the content of the fine chromia raw material is 20 mass% or more and 25 mass% or less, it is preferable that the SiO2 solid concentration of the silica sol is more than 35 mass% and 40 mass% or less, and when the content of the fine chromia raw material is more than 25 mass% and 30 mass% or less, the SiO2 solid concentration of the silica sol is 30 mass% or more and 35 mass% or less.

[0016] The use of silica sol improves the explosion resistance and spalling resistance of the chromia-containing castable refractory. On the other hand, the addition of silica sol reduces the workability (fluidity) of the chromia-containing castable refractory and impairs the corrosion resistance due to the lowering of the melting point of the chromia-containing castable refractory. On the other hand, the addition of fine chromia improves the fluidity and corrosion resistance of the chromia-containing castable refractory. Based on this relationship, the inventors have conducted extensive research into the SiO2 solid content concentration of the silica sol and the amount of fine chromia to be added to the chromia-containing castable refractory. As a result, it has become clear that when the content of the fine chromia raw material is from 20% by mass to 25% by mass, the SiO2 solid content concentration of the silica sol is more than 35% by mass and not more than 40% by mass, and when the content of the fine chromia raw material is more than 25% by mass and not more than 30% by mass, the SiO2 solid content concentration of the silica sol is more than 30% by mass and not more than 35% by mass, thereby making it possible to maintain the fluidity and corrosion resistance of the chromia-containing castable refractory while achieving high levels of good explosion resistance and spalling resistance.

[0017] Further, in the method for producing the chromia-containing castable refractory of the present invention, it is preferable to adjust the vibration flow value by the SiO2 solid content concentration of the silica sol. The vibration flow value (workability) of the chromia-containing castable refractory is also affected by the SiO2 solid content concentration of the silica sol, and the vibration flow value can be adjusted by the SiO2 solid content concentration of the silica sol. Here, the vibration flow value of the chromia-containing castable refractory is preferably 200 mm or more, more preferably 215 mm or more, and most preferably 230 mm or more. Here, the amount of silica sol added may be appropriately adjusted according to the composition of the chromia-containing castable refractory, etc., but it is preferable to set it to 7.0 to 8.5 mass% of the total. By adding 7.0 mass% or more of silica sol, sufficient fluidity can be imparted to the chromia-containing castable refractory, and good workability can be ensured. On the other hand, by setting the amount of silica sol added to 8.5 mass% or less, it is possible to suppress the lack of strength caused by the separation of fine powder and coarse particles.

[0018] The present invention also provides a method for producing a semiconductor device comprising the steps of: The present invention comprises a refractory raw material mainly composed of alumina and / or mullite and a chromia raw material, The content of the chromia raw material is 30 to 90 mass %, The content of the chromia raw material (fine chromia raw material) having a particle size of 0.09 mm or less is 20 to 30 mass %, It is kneaded with silica sol having a SiO2 solid content of 30 to 40 mass %, Also provided is a chromia-containing castable refractory, characterized in that

[0019] In the chromia-containing castable refractory of the present invention, excellent corrosion resistance is imparted to the chromia-containing castable refractory by containing 30 to 90 mass% of chromia (Cr2O3). Here, within the range of 30 to 90 mass%, if corrosion resistance is important, the chromia content can be increased, and if workability (vibration flow value) is to be improved, the content can be reduced. If the chromia content is less than 30 mass%, sufficient corrosion resistance cannot be achieved, and if the chromia content exceeds 90 mass%, heat spalling resistance and explosion resistance decrease.

[0020] In addition, the chromia-containing castable refractory of the present invention contains 20 to 30 mass% of chromia raw material having a particle size of 0.09 mm or less (fine chromia raw material), which improves the fluidity of the chromia-containing castable refractory and provides practical workability. In addition, the addition of the fine chromia raw material improves the corrosion resistance that was reduced by the inclusion of silica sol. If the content of the fine chromia raw material is less than 20 mass%, these effects cannot be fully exhibited, and if the content of the fine chromia raw material exceeds 30 mass%, aggregation proceeds, the viscosity of the chromia-containing castable refractory increases, and it cannot be used in actual construction.

[0021] In addition, in the chromia-containing castable refractory of the present invention, each raw material of the castable refractory is kneaded with a silica sol having a SiO2 solid content of 30 to 40 mass %, and as a result, the explosion resistance and spalling resistance of the chromia-containing castable refractory are improved.

[0022] In the chromia-containing castable refractory of the present invention, it is preferable that the content of the fine chromia raw material is 20 mass% or more and 25 mass% or less, and that the SiO2 solid content is kneaded with the silica sol having a content of more than 35 mass% and 40 mass% or less.

[0023] In addition, in the chromia-containing castable refractory of the present invention, it is preferable that the content of the fine chromia raw material is more than 25 mass% and 30 mass% or less, and that the SiO2 solid content is kneaded with the silica sol having 30 mass% or more and 35 mass% or less.

[0024] When the content of the fine chromia raw material is 20% by mass or more and 25% by mass or less, the SiO2 solid concentration of the silica sol is set to more than 35% by mass and 40% by mass or less, and when the content of the fine chromia raw material is more than 25% by mass and 30% by mass or less, the SiO2 solid concentration of the silica sol is set to be more than 30% by mass and 35% by mass or less, thereby making it possible to achieve high levels of good explosion resistance and spalling resistance while maintaining the fluidity and corrosion resistance of the chromia-containing castable refractory material.

[0025] Furthermore, in the chromia-containing castable refractory of the present invention, it is preferable that after drying at 110° C. for 24 hours, a network structure in which pores having a diameter of 10 to 100 nm are continuous is formed within the structure.

[0026] In the chromia-containing castable refractory of the present invention, the raw materials of the castable refractory are kneaded with a silica sol having a SiO2 solid content of 30 to 40 mass%, so that fine continuous mesh-like pores are formed in the structure obtained after drying. By making the diameter of the pores 10 to 100 nm, the explosion resistance and spalling resistance of the chromia-containing castable refractory are improved very effectively. These effects can be achieved by making the SiO2 solid content of the silica sol 30 mass% or more, and by making it 40 mass% or less, the decrease in strength due to the formation of excessive pores can be suppressed.

[0027] The chromia-containing castable refractory of the present invention has workability suitable for application to an actual furnace, and the vibration flow value is preferably 200 mm or more, more preferably 215 mm or more, and most preferably 230 mm or more. Effect of the Invention

[0028] According to the present invention, it is possible to provide a chromia-containing castable refractory having excellent explosion resistance, spalling resistance and corrosion resistance as well as good workability, and a simple and efficient method for producing the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Representative embodiments of the chromia-containing castable refractory material and the method for producing the same of the present invention will be described in detail below, but the present invention is not limited to these.

[0030] 1. Chromia-containing castable refractories The chromia-containing castable refractory of the present invention is a refractory raw material mainly composed of alumina and / or mullite and a chromia raw material kneaded with silica sol. The main components, each additive component, and the characteristics of the castable refractory are described in detail below.

[0031] (1) Main component (fire-resistant aggregate) The main components are alumina and / or mullite, and either one or both may be used. The content of the main components is not particularly limited as long as it does not impair the effects of the present invention, and may be appropriately adjusted depending on the properties required for the castable refractory material, but is preferably 10 to 70 mass%.

[0032] (1-1) Alumina As the main component of the chromia-containing castable refractory of the present invention, an alumina raw material whose particle size has been appropriately adjusted can be used. The type of the alumina raw material is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known alumina raw materials can be used.

[0033] As the alumina raw material, for example, high-alumina raw materials such as fused alumina, fused mullite, sintered alumina, synthetic mullite, bauxite, sillimanite, and alumina shale can be used.

[0034] (1-2) Mullite In addition, as the main component of the chromia-containing castable refractory of the present invention, a mullite raw material whose particle size has been appropriately adjusted can be used. The type of mullite raw material is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known mullite raw materials can be used.

[0035] The mullite raw material may be, for example, electrofused mullite or sintered mullite. The particle size of the mullite raw material is not particularly limited as long as it does not impair the effects of the present invention, but by making it into a fine powder of 200 μm or less, sintering is promoted and thermal expansion is suppressed, thereby enhancing the effect of improving thermal shock resistance.

[0036] (2) Essential additives (2-1) Chromia (Cr2O3): 30~90% by mass By containing 30-90% by mass of chromia, the castable refractory can be given excellent corrosion resistance against CaO-SiO2-based slag. By making the chromia content 30% by mass or more, the effect can be clearly expressed, and by making the chromia content 90% by mass or less, even when kneading with silica sol, a good mixed state can be easily obtained. Here, the corrosion resistance improves with an increase in the chromia content, and when the chromia content is low, the alumina content increases, and the heat spalling resistance improves. Therefore, the amount of chromia added may be adjusted in the range of 30-90% by mass, taking into consideration the balance between the corrosion resistance and the heat spalling resistance required for the place where the castable refractory is used and the furnace.

[0037] In addition, the chromia-containing castable refractory of the present invention is characterized in that the content of the chromia raw material (fine chromia raw material) having a particle size of 0.09 mm or less is 20 to 30 mass %. By containing 20 to 30 mass % of the chromia raw material (fine chromia raw material) having a particle size of 0.09 mm or less, the fluidity of the chromia-containing castable refractory is improved, and practical workability can be imparted. In addition, the addition of the fine chromia raw material improves the corrosion resistance that is reduced by the inclusion of silica sol. If the content of the fine chromia raw material is less than 20 mass %, these effects cannot be fully exhibited, and if the fine chromia raw material is contained in excess of 30 mass %, aggregation proceeds, the viscosity of the chromia-containing castable refractory increases, and it cannot be used in practical construction.

[0038] As the raw material of chromia, it is preferable to use at least one of chromium oxide, electrofused chromia, calcined chromia, electrofused raw material containing chromia, calcined raw material containing chromia, and chromium ore. By using these raw materials, a desired amount of chromia can be added to the castable refractory simply and efficiently.

[0039] (2-2) SiO2 solids In the chromia-containing castable refractory of the present invention, a silica sol having a SiO2 solid content of 30-40% by mass is used to knead each raw material, so that the finally obtained chromia-containing castable refractory contains a small amount of SiO2 solid content due to the silica sol. The content of the SiO2 solid content depends on the SiO2 solid content concentration of the silica sol and the amount of silica sol added, but is preferably 2-5% by mass. If the SiO2 solid content concentration of the silica sol is 40% by mass and the amount of silica sol added is 7% by mass, the content of the SiO2 solid content in the castable refractory is about 2.8% by mass.

[0040] The SiO2 solid content contained in the castable refractory depends on the SiO2 solid content concentration and the amount used of the silica sol used for kneading, but by kneading each raw material of the castable refractory with a silica sol having an SiO2 solid content of 30 to 40 mass%, fine continuous mesh-like pores are formed in the structure obtained after drying.

[0041] Therefore, by observing the network-like pores having such characteristics in the castable refractory containing chromia, it can be considered that each raw material of the castable refractory is kneaded with a silica sol having a SiO2 solid content of 30 to 40 mass %. The method for confirming the pores is not particularly limited, and the pores may be observed using an optical microscope, a scanning electron microscope, or the like.

[0042] In addition, when the content of the fine chromia raw material is 20% by mass or more and 25% by mass or less, the SiO2 solid content concentration of the silica sol is preferably more than 35% by mass and less than 40% by mass, and when the content of the fine chromia raw material is more than 25% by mass and less than 30% by mass, the SiO2 solid content concentration of the silica sol is preferably more than 30% by mass and less than 35% by mass. When the content of the fine chromia raw material is 20% by mass or more and 25% by mass or less, the SiO2 solid content concentration of the silica sol is more than 35% by mass and less than 40% by mass, and when the content of the fine chromia raw material is more than 25% by mass and less than 30% by mass, the SiO2 solid content concentration of the silica sol is more than 30% by mass and less than 35% by mass, thereby maintaining the fluidity and corrosion resistance of the chromia-containing castable refractory material while achieving good explosion resistance and spalling resistance at a high level.

[0043] (3) Optional Added Ingredients (3-1) Cement raw materials Alumina cement can be added as a binder to the chromia-containing castable refractory of the present invention. Alumina cement generally available on the market can be used as the alumina cement, and the amount added is preferably 1 to 5 mass%. If the cement content is less than 1 mass%, the effect of improving the strength of the chromia-containing castable refractory is poor, and if it is 5 mass% or more, the excess CaO component causes a decrease in corrosion resistance. It is more preferable that the upper limit of the cement content is 2 mass% or less. By setting the cement content to 2 mass% or less, the heat resistance and corrosion resistance of the chromia-containing castable refractory can be improved.

[0044] (3-2) Zirconia (ZrO2) fine powder Adding ZrO2 to a chromia-containing castable refractory can improve the thermal shock resistance of the chromia-containing castable refractory. For the ZrO2 fine powder, it is preferable to use a zirconia raw material with a particle size of 1 mm or less, and the content is preferably 1 to 10 mass%.

[0045] (3-3) Fire-resistant ultrafine powder Ultrafine powder raw materials such as silica flour and clay may be added to the chromia-containing castable refractory. By using ultrafine powder raw materials with a particle size of 10 μm or less, the fluidity is improved and a dense construction can be obtained. The content of the refractory ultrafine powder is not particularly limited as long as it does not impair the effects of the present invention, and may be appropriately adjusted according to the fluidity required for the chromia-containing castable refractory.

[0046] (4) Characteristics of Chromia-Containing Castable Refractories The chromia-containing castable refractory of the present invention contains 30-90% by mass of chromia, and the chromia-containing castable refractory is endowed with excellent corrosion resistance. Here, within the range of 30-90% by mass, if corrosion resistance is important, the chromia content can be increased, and if workability (vibration flow value) is to be improved, the content can be reduced. If the chromia content is less than 30% by mass, sufficient corrosion resistance cannot be achieved, and if the chromia content is more than 90% by mass, heat spalling resistance and explosion resistance decrease.

[0047] In addition, by containing 20-30% by mass of chromia raw material having a particle size of 0.09 mm or less (fine chromia raw material), the fluidity of the chromia-containing castable refractory is improved, and practical workability can be imparted. In addition, the addition of the fine chromia raw material improves the corrosion resistance that was reduced by the inclusion of silica sol. If the content of the fine chromia raw material is less than 20% by mass, these effects cannot be fully exerted, and if the content of the fine chromia raw material exceeds 30% by mass, aggregation proceeds, the viscosity of the chromia-containing castable refractory increases, and it cannot be used in actual construction.

[0048] In addition, since the raw materials of the castable refractory are kneaded with a silica sol having a SiO2 solid content of 30 to 40 mass%, fine continuous mesh-like pores are formed in the structure of the chromia-containing castable refractory obtained after drying. The formation of the pores extremely effectively improves the explosion resistance of the chromia-containing castable refractory, and also improves its spalling resistance.

[0049] For example, in the chromia-containing castable refractory of the present invention, after drying at 110°C for 24 hours, a network structure is formed in which pores having a diameter of 10 to 100 nm are continuous within the structure. Since the diameter of the pores constituting the continuous network structure is 10 nm or more, the effect of improving the explosion resistance and spalling resistance of the chromia-containing castable refractory is fully exhibited. Meanwhile, since the diameter of the pores is 100 nm or less, the decrease in strength of the chromia-containing castable refractory is suppressed.

[0050] In addition, the formation of continuous network pores due to the silica sol having a SiO2 solid content of 30 to 40 mass % shortens the drying time of the chromia-containing castable refractory material, and reduces the amount of energy consumption required for the drying.

[0051] In addition, since the chromia-containing castable refractory of the present invention is kneaded with a silica sol having a SiO2 solid content of 30 to 40 mass%, the SiO2 solid content dispersed in the chromia-containing castable refractory traps alkali and alkaline earth elements that generate hexavalent chromium from Cr2O3, and as a result, the generation of hexavalent chromium is extremely effectively suppressed.

[0052] For example, a castable refractory material after a rotational erosion test at a test temperature of 1500°C for a test time of 10 hours is crushed and sieved to a particle size of 4 mm or less to be used as an evaluation sample, 20 g of the evaluation sample is immersed in 200 ml of distilled water, and stirred every hour. After 24 hours, 25 ml of evaluation solution is taken from the solution, which is then separated by a centrifuge and the supernatant is subjected to ICP measurement. In this case, the amount of hexavalent chromium eluted is preferably 5 mg / l or less.

[0053] Furthermore, the chromia-containing castable refractory of the present invention has workability that allows it to be applied to an actual furnace. More specifically, the vibration flow value is preferably 200 mm or more, more preferably 215 mm or more, and most preferably 230 mm or more. The vibration flow value is an index showing the fluidity of the chromia-containing castable refractory, and a large value means good fluidity.

[0054] Here, in the present invention, the value obtained by the following measurement is defined as the vibration flow value. A flow cone specified in JIS R 5201:92 is placed on a vibration table with the tip of the cone facing up, and the chromia-containing castable refractory is filled into the flow cone while being appropriately vibrated. Next, the cone is slowly removed so as not to destroy the shape of the filled chromia-containing castable refractory, and the refractory is left stationary for 30 seconds, after which vibration at 60 Hz is applied for 5 seconds. After the vibration is completed, the maximum diameter of the bottom surface of the chromia-containing castable refractory that has collapsed and spread and the diameter of the part perpendicular to the maximum diameter are measured, and the average value of the two measurements is defined as the vibration flow value (mm).

[0055] 2. Manufacturing method of chromia-containing castable refractories The method for producing a chromia-containing castable refractory material of the present invention is characterized by kneading a refractory raw material mainly composed of alumina and / or mullite with a chromia raw material using a silica sol, so that the content of the chromia raw material is 30 to 90 mass%, the content of the chromia raw material having a particle size of 0.09 mm or less (fine-grained chromia raw material) is 20 to 30 mass%, and the SiO2 solid content of the silica sol is 30 to 40 mass%.

[0056] The details of the refractory raw material mainly composed of alumina and / or mullite, the chromia raw material, the silica sol and any additive components used in the manufacturing method of the chromia-containing castable refractory of the present invention are as described above in "1. Chromia-containing castable refractory." Below, the characteristics of the manufacturing method will be described.

[0057] In the method for producing a chromia-containing castable refractory of the present invention, each raw material of the castable refractory is kneaded with a silica sol having a SiO2 solid content of 30 to 40 mass%, so that fine continuous mesh-like pores can be formed in the structure obtained after drying. The formation of the pores extremely effectively improves the explosion resistance and spalling resistance of the chromia-containing castable refractory. These effects can be achieved by making the SiO2 solid content of the silica sol 30 mass% or more, and by making it 40 mass% or less, the decrease in the flowability of the castable can be suppressed.

[0058] In addition, the addition of silica sol having a SiO2 solid content of 30 to 40 mass% results in the formation of continuous network pores, which shortens the drying time of the chromia-containing castable refractory material and reduces the energy consumption required for drying. The amount of silica sol added is not particularly limited as long as it does not impair the effects of the present invention, and may be appropriately adjusted depending on the composition of the chromia-containing castable refractory material, the desired drying time, the vibration flow value, etc.

[0059] In addition, by adding 20-30% by mass of chromia raw material having a particle size of 0.09 mm or less (fine chromia raw material), the fluidity of the chromia-containing castable refractory can be improved, and practical workability can be imparted. In addition, by adding the fine chromia raw material, the corrosion resistance of the chromia-containing castable refractory, which is reduced by adding silica sol, can be improved. If the amount of the fine chromia raw material added is less than 20% by mass, these effects cannot be fully exerted, and if the amount of the fine chromia raw material added exceeds 30% by mass, aggregation proceeds, the viscosity of the chromia-containing castable refractory increases, and it cannot be used in actual construction.

[0060] Furthermore, when the content of the fine chromia raw material is 20% by mass or more and 25% by mass or less, the SiO2 solid content concentration of the silica sol is preferably more than 35% by mass and 40% by mass or less, and when the content of the fine chromia raw material is more than 25% by mass and 30% by mass or less, the SiO2 solid content concentration of the silica sol is preferably 30% by mass or more and 35% by mass or less.

[0061] The use of silica sol improves the explosion resistance and spalling resistance of the chromia-containing castable refractory. On the other hand, the addition of silica sol reduces the workability (fluidity) of the chromia-containing castable refractory and impairs the corrosion resistance due to the lowering of the melting point of the chromia-containing castable refractory. On the other hand, the addition of fine chromia improves the fluidity and corrosion resistance of the chromia-containing castable refractory. Based on this relationship, the inventors have conducted extensive research into the SiO2 solid content concentration of the silica sol and the amount of fine chromia added to the chromia-containing castable refractory. As a result, when the content of the fine chromia raw material is from 20% by mass to 25% by mass, the SiO2 solid content concentration of the silica sol is more than 35% by mass and not more than 40% by mass, and when the content of the fine chromia raw material is more than 25% by mass and not more than 30% by mass, the SiO2 solid content concentration of the silica sol is more than 30% by mass and not more than 35% by mass, thereby making it possible to maintain the fluidity and corrosion resistance of the chromia-containing castable refractory while achieving high levels of good explosion resistance and spalling resistance.

[0062] Furthermore, the vibration flow value of the chromia-containing castable refractory is adjusted by the SiO2 solid content concentration of the silica sol or the amount of silica sol added, and the vibration flow value is preferably 200 mm or more, more preferably 215 mm or more, and most preferably 230 mm or more. By imparting a high vibration flow value to the chromia-containing castable refractory, on-site construction can be carried out smoothly.

[0063] Representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design modifications are possible, all of which are included in the technical scope of the present invention. EXAMPLES

[0064] Example Raw materials were prepared in the proportions shown in Table 1 as Examples 1 to 10, and silica sol was added to the mixture to make up 7 mass % of the total. The mixture was mixed in a Dalton mixer for 3 minutes and then cast into a 40 mm x 40 mm x 160 mm metal frame. The mixture was left to naturally cure for 24 hours, removed from the frame, and dried in an electric furnace at 110°C for 24 hours to obtain a castable refractory material according to the present invention.

[0065] Table 1 also shows the characteristics of the raw materials, such as the chromia (Cr2O3) content (mass%), the content (mass%) of chromia raw material with a particle size of 0.09 mm or less (fine chromia raw material), and the silica sol concentration (mass%).

[0066] [Table 1]

[0067] [evaluation] Each of the obtained chromia-containing castable refractories was evaluated for vibration flow value, explosion resistance, spalling resistance and corrosion resistance.

[0068] (1) Vibration flow value A flow cone as specified in JIS R 5201:92 was placed on a vibration table with the tip of the cone facing upward, and the chromia-containing castable refractory was filled into the flow cone while vibrating appropriately. Next, the cone was slowly removed so as not to destroy the shape of the filled chromia-containing castable refractory, and the cone was left stationary for 30 seconds, after which vibration at 60 Hz was applied for 5 seconds. After the vibration was completed, the maximum diameter of the bottom surface of the chromia-containing castable refractory that had collapsed and spread and the diameter of the part perpendicular to the maximum diameter were measured at two points, and the average value of the two points was taken as the vibration flow value (mm). The vibration flow value obtained and the evaluation results are shown in Table 1, with a ◯ for a vibration flow value of 200 mm or more and an × for a vibration flow value of less than 200 mm.

[0069] (2) Explosion resistance The chromia-containing castable refractory material kneaded with the addition of silica sol was poured into a paper cup and left to cure naturally for 24 hours. After curing, the sample was removed from the paper cup and placed in an electric furnace kept at a given temperature, heated for 15 minutes, and the presence or absence of explosion was confirmed. If no explosion was observed even at 1300°C, it was recorded as "no explosion." The results obtained (the temperature at which explosion was observed, if any) are shown in Table 1.

[0070] (3) Heat spalling resistance Heat spalling resistance was evaluated by the water cooling method based on JIS R2657. The temperature condition was 1500℃, and heating and cooling were performed a maximum of 10 times. If more than half of the area of ​​the heated surface (114 x 65 mm) of the test piece peeled off, it was marked as ×, if spalling was observed within 10 times but more than half of the heated surface did not peel off, it was marked as △, and if spalling did not occur until the end, it was marked as ◯. The results are shown in Table 1.

[0071] (4) Corrosion resistance The corrosion resistance was evaluated by a rotating drum corrosion test. The test method is as follows. The test piece was lined inside the drum, and the test was performed at 1500°C using an oxygen-propane burner. Molten slag (basicity of slag: CaO / SiO2 = 1.19) was added as the corrosion agent. After holding for 8 hours while replacing the slag every hour, the temperature was naturally lowered, and the temperature was raised again the next day and the same operation was performed. After performing the operation for a total of 5 days (heating for 8 hours x 5 days), the sample was cut in a direction perpendicular to the operating surface, and the amount of wear was measured at 8 points to obtain the average amount of wear. The average amount of wear was expressed as an index with the amount of wear in Example 1 set to 100. The obtained results are shown in Table 1. The smaller the index, the better the corrosion resistance.

[0072] Comparative Example Chromia-containing castable refractories were obtained in the same manner as in the Examples, except that the raw materials were adjusted in the proportions shown in Table 1 as Comparative Examples 1 to 8. The vibration flow value, explosion resistance, spalling resistance, and corrosion resistance of each chromia-containing castable refractory were evaluated in the same manner as in the Examples. The obtained results are shown in Table 1.

[0073] From the results in Table 1, it can be seen that the vibration flow values ​​of the chromia-containing castable refractories of the present invention are all 200 mm or more, and have good fluidity.In contrast, in Comparative Example 1, which does not contain a chromia raw material having a particle size of 0.09 mm or less (fine chromia raw material), Comparative Example 2, in which the amount of fine chromia raw material added is less than 20 mass%, Comparative Example 3, in which the amount of fine chromia raw material added is more than 30 mass%, and Comparative Example 5, in which the silica sol concentration is more than 40 mass%, the vibration flow value is less than 200 mm, and sufficient fluidity is not obtained.

[0074] In addition, from the results of Table 1, all of the chromia-containing castable refractories of the present invention show good explosion resistance. In Examples 1 to 3 and 7, explosion was not observed even at 1300°C, and in the other Examples, explosion was not observed up to 1300°C. In contrast, in Comparative Example 4, in which the silica sol concentration was less than 30 mass%, fine continuous mesh-like pores were not sufficiently formed, and explosion occurred at 1200°C. In Comparative Example 7, in which the chromia content was too high, explosion occurred at 1200°C, and in Comparative Example 8, which was kneaded using water (silica sol concentration of 0 mass%), explosion occurred at 1000°C, and sufficient explosion resistance was not obtained.

[0075] In addition, the results in Table 1 show that all of the chromia-containing castable refractories of the present invention exhibit good heat spalling resistance. In contrast, Comparative Example 4, in which the silica sol concentration is less than 30 mass%, was evaluated as △ in heat spalling resistance, and Comparative Example 7, in which the chromia content is too high, and Comparative Example 8, which was kneaded using water (silica sol concentration is 0 mass%), were evaluated as × in heat spalling resistance.

[0076] Furthermore, from the results of Table 1, the corrosion resistance of the chromia-containing castable refractory of the present invention is better in all cases than that of Example 1. In contrast, Comparative Example 1, which does not contain a fine chromia raw material, Comparative Example 2, which contains too little fine chromia raw material, and Comparative Example 6, which contains less than 30 mass% chromia, show a larger amount of corrosion and a decrease in corrosion resistance compared to Example 1. It is also found that Comparative Example 4, which contains a silica sol concentration of less than 30 mass%, and Comparative Example 5, which contains a silica sol concentration of more than 40 mass%, show a decrease in corrosion resistance compared to Example 1.

[0077] Furthermore, when comparing the evaluation test results between the Examples, it can be seen that Examples 1 to 7, in which the content of the fine chromia raw material is 20 to 25 mass%, and Examples 1 to 3 and 7, in which the silica sol concentration is 35 to 40 mass%, exhibit particularly good explosion resistance.

[0078] In order to confirm the effect of suppressing the generation of hexavalent chromium by the SiO2 solid content, the amount of hexavalent chromium eluted from the chromia-containing castable refractories obtained in Example 5 and Comparative Example 8 was measured. Specifically, the castable refractories after the rotary erosion test at a test temperature of 1500°C and a test time of 10 hours were crushed and sieved to a particle size of 4 mm or less to be used as evaluation samples, 20 g of the evaluation sample was immersed in 200 ml of distilled water, and 25 ml of evaluation solution was collected from the solution after 24 hours while stirring every hour. The evaluation solution was separated by a centrifuge, and the supernatant was subjected to ICP measurement. As a result, the amount of hexavalent chromium eluted from the chromia-containing castable refractory of Example 5 was 2.91 mg / l, and the amount of hexavalent chromium eluted from the chromia-containing castable refractory of Comparative Example 8 was 9.73 mg / l.

[0079] In Example 5, in which silica sol was added, the amount of hexavalent chromium eluted was suppressed to 5 mg / L or less, even though the sample contained 40 mass% chromia. On the other hand, the chromia content of Comparative Example 8 was 30 mass%, which is lower than that of Example 5, but the amount of hexavalent chromium eluted was a large value of 9.73 mg / L.

[0080] From the above results, it is found that in order to obtain a chromia-containing castable refractory having excellent explosion resistance, spalling resistance, and corrosion resistance as well as good workability, it is extremely important that the content of the chromia raw material is 30 to 90 mass%, the content of the chromia raw material having a particle size of 0.09 mm or less (fine-grain chromia raw material) is 20 to 30 mass%, and the SiO2 solid concentration of the silica sol is 30 to 40 mass%.

Claims

1. A refractory raw material mainly composed of alumina and / or mullite and a chromia raw material are kneaded with a silica sol; The content of the chromia raw material is 30 to 90 mass %, The content of the chromia raw material (fine chromia raw material) having a particle size of 0.09 mm or less is 20 to 28 mass %, The SiO of the silica sol ２ The solid content concentration is 30 to 40% by mass. A method for producing a chromia-containing castable refractory material, comprising the steps of:

2. When the content of the fine chromia raw material is 20% by mass or more and 25% by mass or less, the SiO ２ The solid content concentration is more than 35% by mass and not more than 40% by mass, When the content of the fine chromia raw material is more than 25% by mass and not more than 30% by mass, the SiO ２ The solid content concentration is 30% by mass or more and 35% by mass or less; 2. A method for producing the chromia-containing castable refractory material according to claim 1 ,

3. The SiO of the silica sol ２ Adjusting the vibration flow value according to the solid content concentration; 3. A method for producing a chromia-containing castable refractory material according to claim 1 or 2, characterized in that

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