Electrocast refractory, method of manufacturing electrocast refractory, and glass melting furnace

Abstract

This invention provides an electroformed refractory, a method for manufacturing the same, and a glass melting furnace using the electroformed refractory. The chemical composition of the electroformed refractory, based on oxides, is set to 100% by mass, containing 85.0% by mass or more of ZrO2, 8.0 to 12.0% by mass of SiO2, 0.10% by mass or more but less than 0.80% by mass of Al2O3, 0.01 to 1.0% by mass of P2O5, a total of 0.10 to 0.20% by mass of Na2O and / or K2O, and 0.05 to 2.0% by mass of B2O3, and the total amount of Fe2O3 and TiO2 is less than 0.55% by mass.

Description

Technical Field

[0001] This disclosure relates to electroformed refractories, methods for manufacturing electroformed refractories, and glass melting furnaces. Background Technology

[0002] Previously, high-zirconia electroformed refractories containing a large amount of ZrO2 in their chemical composition were known. Because high-zirconia electroformed refractories exhibit high corrosion resistance and low contamination to molten glass, they are commonly used in parts of glass melting furnaces that come into contact with molten glass. Such high-zirconia electroformed refractories contain a large number of zirconia grains and a small amount of matrix glass between these grains. For example, Patent Documents 1-9 disclose high-zirconia refractories containing ZrO2 and various other components in specific proportions.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 6-287059

[0006] Patent Document 2: Japanese Patent Application Publication No. 8-277162

[0007] Patent Document 3: Japanese Patent Application Publication No. 2009-155150

[0008] Patent Document 4: Japanese Patent Application Publication No. 2010-260782

[0009] Patent Document 5: Japanese Patent Publication No. 2012-518588

[0010] Patent Document 6: Japanese Patent Application Publication No. 2019-048761

[0011] Patent Document 7: Chinese Patent Application Publication No. 101443290

[0012] Patent Document 8: Chinese Patent Application Publication No. 104583154

[0013] Patent Document 9: Chinese Patent Application Publication No. 113454045 Summary of the Invention

[0014] From the viewpoint of suppressing current flow to the refractories in a glass melting furnace where glass is electro-melted, for example, electroformed refractories preferably have high resistivity at the operating temperature.

[0015] Furthermore, ZrO2 undergoes phase transformation expansion due to the phase transition from monoclinic to tetragonal crystals at around 1150℃ during heating and around 850℃ during cooling, resulting in significant volume changes with both heating and cooling. The matrix glass filling the interstices of ZrO2 helps to mitigate the stress caused by the volume changes of ZrO2. However, large volume changes during heating and cooling can lead to cracking in the refractory; therefore, it is desirable to reduce the expansion rate after temperature cycling, i.e., the residual volume expansion rate.

[0016] Furthermore, for example, when using a glass melting furnace, at the contact point between the refractory and the molten glass, the matrix glass in the refractory may sometimes seep into the molten glass (also known as "glass seepage"). If glass seepage occurs, it can cause defects in the resulting glass products.

[0017] In view of the above, this disclosure relates to providing an electroformed refractory with high resistivity, low residual volume expansion rate, and the ability to suppress glass exudation, a method for manufacturing the same, and a glass melting furnace using the aforementioned electroformed refractory.

[0018] The means to solve the above problems include the following methods.

[0019] <1> An electroformed refractory, as a chemical composition based on oxides, wherein the total amount of oxides is set to 100% by mass, contains: more than 85.0% by mass of ZrO2, 8.0 to 12.0% by mass of SiO2, more than 0.10% by mass and less than 0.80% by mass of Al2O3, 0.01 to 1.0% by mass of P2O5, a total of 0.10 to 0.20% by mass of Na2O and / or K2O, and 0.05 to 2.0% by mass of B2O3, and the total amount of Fe2O3 and TiO2 is less than 0.55% by mass.

[0020] <2> according to <1> The electroformed refractory, as a chemical composition, is based on oxides, with the total amount of oxides set at 100% by mass, containing: 0.10-0.70% by mass of Al2O3, 0.01-0.5% by mass of P2O5, and 0.10-1.5% by mass of B2O3.

[0021] <3> according to <1> or <2> The electroformed refractory, as a chemical composition, is based on oxides, with the total oxides set at 100% by mass, containing: 0.10-0.60% by mass of Al2O3, 0.01-0.3% by mass of P2O5, and 0.50-1.3% by mass of B2O3.

[0022] <4> according to <1> ~ <3> The electroformed refractory according to any one of the following methods contains a total of 0.11 to 0.20% by mass of Na₂O and / or K₂O.

[0023] <5> according to <1> ~ <4> The electroformed refractory according to any one of the following methods, wherein, as a chemical composition, the total amount of oxides is set to 100% by mass, and the total amount of Fe2O3 and TiO2 is less than 0.30% by mass.

[0024] <6> according to <1> ~ <5> The electroformed refractory according to any one of the following methods, wherein the value obtained by dividing the total mass of Na2O and K2O by the mass of SiO2 is 0.01 or more.

[0025] <7> according to <1> ~ <6> The electroformed refractory according to any one of the following methods, wherein the total mass of B2O3 and P2O5 divided by the mass of Al2O3 has a value of 1.0 or more.

[0026] <8> according to <1> ~ <7> The electroformed refractory according to any one of the following methods, wherein the resistivity at 1600°C is 300Ω. cm or more.

[0027] <9> according to <1> ~ <8> The electroformed refractory according to any one of the following methods, wherein the resistivity at 1600°C is 400Ω. cm or more.

[0028] <10> according to <1> ~ <9> The electroformed refractory in any one of the following embodiments, wherein after subjecting the electroformed refractory to a thermal cycling test consisting of 40 cycles of the following repeated cycles, the residual volume expansion rate, calculated by the following formula, is less than 10%, wherein the cycles involve heating from 800°C to 1250°C at a rate of 450°C / h and then cooling from 1250°C to 800°C at a rate of 450°C / h.

[0029] Residual volume expansion rate (%) = {(volume after thermal cycling test / volume before thermal cycling test) -1}×100.

[0030] <11> A glass melting furnace, comprising <1> ~ <10> The electroformed refractory as described in any one of the following.

[0031] <12> A method for manufacturing electroformed refractory involves heating and melting the following refractory raw materials, then cooling them in a mold. The refractory raw materials, relative to the total mass of oxides, contain: 85.0% by mass or more ZrO2, 8.0 to 12.0% by mass SiO2, 0.10% by mass or more but less than 0.80% by mass Al2O3, 0.01 to 1.0% by mass P2O5, a total of 0.10 to 0.20% by mass Na2O and / or K2O, 0.05% to 2.0% by mass B2O3, and the total mass of Fe2O3 and TiO2 is less than 0.55% by mass.

[0032] According to this disclosure, an electroformed refractory with high resistivity, low residual volume expansion rate, and ability to suppress glass exudation can be provided, as well as a method for manufacturing the same and a glass melting furnace using the aforementioned electroformed refractory. Detailed Implementation

[0033] The embodiments for carrying out this disclosure will now be described in detail. However, the embodiments of this disclosure are not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps, etc.) are not essential unless specifically stated otherwise. The same applies to numerical values ​​and their ranges, which do not limit the embodiments of this disclosure.

[0034] In this disclosure, the numerical range represented by “~” includes the values ​​recorded before and after “~” as the minimum and maximum values, respectively.

[0035] In this disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the composition, unless otherwise specified, the content or percentage of each component refers to the total content or percentage of the multiple substances present in the composition.

[0036] In this disclosure, a combination of two or more preferred methods is a more preferred method.

[0037] <Electroformed Refractory>

[0038] The electroformed refractory disclosed herein (hereinafter also simply referred to as "refractory"), as a chemical composition based on oxides, with the total amount of oxides set at 100% by mass, contains: more than 85.0% by mass of ZrO2, 8.0 to 12.0% by mass of SiO2, more than 0.10% by mass and less than 0.80% by mass of Al2O3, 0.01 to 1.0% by mass of P2O5, a total of 0.10 to 0.20% by mass of Na2O and / or K2O, 0.05 to 2.0% by mass of B2O3, and the total amount of Fe2O3 and TiO2 is less than 0.55% by mass.

[0039] The inventors have discovered that refractory materials having the above-described composition have high resistivity, low residual volume expansion, and can suppress glass exudation. The reason for this may not be clear, but it is speculated to be as follows.

[0040] In the refractory disclosed herein, Al2O3 is suppressed to less than 0.80% by mass. It is believed that by suppressing the amount of Al2O3 within the above range, the resistivity of ZrO2 and the matrix glass can be increased.

[0041] In addition, P2O5 and B2O3, which form glass phases similarly to SiO2, can improve resistivity or suppress its decrease by adjusting the viscosity of the matrix glass, thus preventing cracks during manufacturing.

[0042] Furthermore, in the refractories of this disclosure, the combined amount of Na₂O and K₂O is suppressed to below 0.20% by mass. Na₂O and K₂O are present in the matrix glass, and by keeping their combined amount below 0.20% by mass, the decrease in resistivity can be suppressed. On the other hand, Na₂O and / or K₂O facilitates the melting of the raw materials. In addition, the presence of Na₂O and / or K₂O in the matrix glass helps to reduce the viscosity of the matrix glass. In the refractories of this disclosure, by containing a total of 0.10% by mass or more of Na₂O and / or K₂O, good resistivity can be ensured, while mitigating poor melting of the refractories, and the expansion during the zirconium phase transformation in slow cooling can be absorbed. Therefore, dense bricks can be obtained, thereby suppressing residual volume expansion and glass exudation.

[0043] Moreover, SiO2 becomes the main component of the matrix glass, which helps to absorb the stress caused by the volume change of ZrO2 and suppress the residual volume expansion rate.

[0044] Furthermore, in the refractory disclosed herein, B2O3 is suppressed to below 2.0% by mass, which also helps to suppress the residual volume expansion rate.

[0045] Fe2O3 and TiO2 can be contained as impurities, but in the refractory disclosed herein, the effects of these components can be effectively utilized by suppressing their amounts.

[0046] As described above, by maintaining the proportions of ZrO2, SiO2, Al2O3, P2O5, Na2O and / or K2O, B2O3, and Fe2O3 and TiO2 within specific ranges, refractory materials with high resistivity, low residual volume expansion, and suppressed glass exudation can be obtained. For example, regarding Na2O and / or K2O, it is preferable to suppress their content to improve resistivity. However, if the content of Na2O and / or K2O is low, the density of the refractory structure decreases, making it difficult to suppress residual volume expansion and glass exudation. Thus, maintaining or increasing resistivity and suppressing residual volume expansion and glass exudation easily become a trade-off, making it difficult to achieve both simultaneously. In the refractory materials of this disclosure, it is believed that the effects of the above-mentioned components in specific proportions complement each other, enabling the achievement of these properties.

[0047] It should be noted that the implementation of this disclosure is not limited by the above-described presumption mechanism.

[0048] In this disclosure, the content or amount of the refractory components expressed as % by mass, unless otherwise specified, is, as a chemical composition, expressed on an oxide basis, as the content or amount when the total amount of oxides in the refractory is set to 100% by mass.

[0049] The chemical composition of refractory materials is determined quantitatively using wavelength dispersive X-ray fluorescence analysis. For B2O3, the quantitative analysis is performed using high-frequency inductively coupled plasma atomic emission spectrometry (ICP-AES). For Na2O and K2O, the quantitative analysis is performed using atomic absorption spectrometry (AES). The ZrO2 content is obtained by subtracting the mass of components other than ZrO2 from the mass of the refractory material.

[0050] The refractory contains 85.0% by mass or more of ZrO2. ZrO2 improves the corrosion resistance of the refractory to molten glass. From the viewpoint of further improving the corrosion resistance of the refractory to molten glass, the ZrO2 content is preferably 85.5% by mass or more, more preferably 86.0% by mass or more. From the viewpoint of suppressing cracks caused by volume changes of ZrO2, the ZrO2 content is preferably 91.5% by mass or less, more preferably 91.0% by mass or less, and even more preferably 90.0% by mass or less. From the above viewpoints, the ZrO2 content is preferably 85.0 to 91.5% by mass, more preferably 85.5 to 91.0% by mass, and even more preferably 86.0 to 90.0% by mass.

[0051] It should be noted that in refractories using zirconia sources, trace amounts (typically less than 2% by mass) of HfO2 are inevitably mixed in with ZrO2. Since HfO2 and ZrO2 function similarly, it is customary to denote the sum of HfO2 and ZrO2 as ZrO2. In this disclosure, for clarity, ZrO2 mixed with HfO2 (i.e., a mixture of ZrO2 and HfO2) is referred to only by the terms "ZrO2" or "zirconia." That is, unless otherwise specified, the terms "ZrO2" or "zirconia" refer to a mixture of ZrO2 and the mixed HfO2. For example, a refractories "containing 85.0% by mass or more of ZrO2" means that the total amount of ZrO2 and the mixed HfO2 is 85.0% by mass or more.

[0052] The refractory contains 8.0 to 12.0% by mass of SiO2. SiO2 is a component that forms the matrix glass. By containing 8.0% or more by mass of SiO2 in the refractory, the volume change of ZrO2 can be suppressed, and it also helps to improve the resistivity. From the viewpoint of further suppressing volume change and further improving resistivity, and from the viewpoint of taking into account the above advantages, the content of SiO2 is preferably 8.5% by mass or more, more preferably 9.0% by mass or more, more preferably 9.5% by mass or more, and more preferably 10.0% by mass or more. From the viewpoint of suppressing the adhesion of the matrix glass to suppress crack formation, the content of SiO2 is preferably less than 12.0% by mass, more preferably 11.5% by mass or less, and more preferably 11.0% by mass or less. From the above viewpoints, the content of SiO2 is preferably 8.5 to 11.5% by mass, more preferably 9.0 to 11.0% by mass, and more preferably 10.0 to 11.0% by mass.

[0053] The refractory contains 0.10% by mass and less than 0.80% by mass of Al₂O₃. It is believed that by including 0.10% by mass or more of Al₂O₃ in the refractory, the viscosity of the matrix glass can be suppressed, thereby inhibiting crack formation. Furthermore, if a portion of the matrix glass reacts with zircon crystals, zircon will be formed, thus reducing the amount of matrix glass and sometimes hindering its function. It is believed that including Al₂O₃ in the refractory can also suppress zircon formation. Based on the above viewpoints, the Al₂O₃ content can be 0.20% by mass or more, 0.30% by mass or more, 0.40% by mass or more, or 0.45% by mass or more.

[0054] On the other hand, the inventors have discovered that by suppressing the Al2O3 content in the refractory to less than 0.80% by mass, the resistivity of the refractory increases. Furthermore, by suppressing the Al2O3 content in the refractory, it is possible to suppress the formation of aluminosilicate crystals such as mullite during the manufacture or use of the refractory, thus preventing cracking. From the above perspective, the Al2O3 content is preferably 0.70% by mass or less, more preferably 0.60% by mass or less.

[0055] Based on the above viewpoints, the Al2O3 content is preferably 0.10–0.70% by mass, and more preferably 0.10–0.60% by mass.

[0056] The refractory contains 0.01 to 1.0% by mass of P2O5. P2O5 helps to improve resistivity. From the viewpoint of further improving resistivity, the content of P2O5 can be 0.03% by mass or more, 0.07% by mass or more, or 0.1% by mass or more. From the viewpoint of suppressing zircon formation, suppressing residual expansion, and suppressing chip-off of partial loss of the refractory surface during heating, the content of P2O5 is preferably 0.5% by mass or less, more preferably 0.3% by mass or less. From the above viewpoints, the content of P2O5 is preferably 0.01 to 0.5% by mass, more preferably 0.01 to 0.3% by mass.

[0057] The refractory contains a total of 0.10 to 0.20% by mass of Na₂O and / or K₂O. The presence of Na₂O and K₂O in the matrix glass, with a total content of 0.20% by mass or less, suppresses the decrease in resistivity. Furthermore, from the viewpoint of ensuring a desired resistivity while simultaneously suppressing zircon formation and improving meltability, resulting in increased density of the refractory structure, thereby suppressing residual volume expansion, cracking, and glass exudation, the total content of Na₂O and / or K₂O is 0.10% by mass or more, can exceed 0.10% by mass, can be 0.11% by mass or more, can be 0.12% by mass or more, or can be 0.13% by mass or more. From the viewpoint of improving resistivity, the total content of Na₂O and / or K₂O is 0.20% by mass or less, preferably 0.19% by mass or less, can be 0.18% by mass or less, can be 0.17% by mass or less, can be 0.16% by mass or less, or can be 0.15% by mass or less. Based on the above viewpoints, the total amount of Na2O and / or K2O is preferably more than 0.10% by mass and less than 0.20% by mass, more preferably 0.11 to 0.20% by mass, and particularly preferably 0.11 to 0.15% by mass.

[0058] Na₂O and K₂O may be present in only one or both. The total content of Na₂O and K₂O is 0.10 to 0.20% by mass, and each is independently 0.10 to 0.20% by mass, preferably more than 0.10% by mass and less than 0.18% by mass, more preferably 0.11 to 0.15% by mass.

[0059] Furthermore, it is preferable to use a higher proportion of K2O in Na2O and K2O. This is because, due to the difference in ionic radii, Na2O has greater ionic conductivity, and higher ionic conductivity tends to reduce resistance. Therefore, when it is desired to further increase resistance, it is preferable to use a higher proportion of K2O.

[0060] The refractory contains 0.05% to 2.0% by mass of B2O3. The presence of 0.05% or more by mass of B2O3 in the refractory has the effect of suppressing crack formation during manufacturing. Furthermore, by coexisting B2O3 and P2O5, the viscosity of the matrix glass can be reduced, thus suppressing crack formation. On the other hand, as the content of B2O3 increases, the resistivity is less likely to decrease compared to alkali metal oxides such as Na2O or K2O. From the above viewpoint, the content of B2O3 is preferably 0.10% by mass or more, more preferably 0.50% by mass or more, and even more preferably 0.60% by mass or more. From the viewpoint of suppressing residual volume expansion, the content of B2O3 is preferably 1.5% by mass or less, more preferably 1.0% by mass or less. From the above viewpoint, the content of B2O3 is preferably 0.10% to 2.0% by mass, more preferably 0.50% to 1.0% by mass.

[0061] The combined amount of Fe2O3 and TiO2 in the refractory is less than 0.55% by mass. Fe2O3 and TiO2 are impurities that may be introduced from the raw materials and reduce resistivity, therefore a lower amount is preferred. Furthermore, from the viewpoint of suppressing delamination caused by the expansion of reaction products of iron and phosphorus at high temperatures, a lower amount of Fe2O3 is preferable. Additionally, from the viewpoint of suppressing residual volume expansion, a lower amount of TiO2 is also preferable. From the above perspectives, the combined amount of Fe2O3 and TiO2 is preferably 0.40% by mass or less, more preferably 0.30% by mass or less.

[0062] Fe2O3 and TiO2 may be present in only one of them, or both of them, or neither of them may be present. The amount of either one is 0.55% by mass or less, preferably 0.40% by mass or less, and more preferably 0.30% by mass or less.

[0063] From the viewpoint of improving the density of the refractory structure, suppressing residual volume expansion, suppressing cracking, and suppressing glass exudation, the value obtained by dividing the total mass of Na₂O and K₂O by the mass of SiO₂ in the refractory is preferably 0.01 or more (or 0.010 or more), more preferably 0.011 or more. From the viewpoint of improving resistivity, the above value is preferably 0.020 or less, more preferably 0.017 or less, more preferably 0.015 or less, and even more preferably 0.013 or less. From the above viewpoints, the above value is preferably 0.010 to 0.020, more preferably 0.010 to 0.013.

[0064] In refractory materials, the value obtained by dividing the total mass of B2O3 and P2O5 by the mass of Al2O3 is preferably 1.0 or more (or 1.00 or more), more preferably 1.3 or more (or 1.30 or more), and can be 1.4 or more (or 1.40 or more), or 1.5 or more (or 1.50 or more). Reducing the amount of Al2O3 and adding P2O5 both contribute to increasing resistivity, while B2O3 helps to suppress cracking. To obtain refractory materials with high resistivity and free from cracking during manufacturing, this parameter is preferably within the above range. It is believed that if the above value is 1.0 or more, the resistivity will increase, in particular. From the viewpoint of residual expansion rate, the upper limit of the above value is preferably 3.0 or less (or 3.00 or less), more preferably 2.5 or less (or 2.50 or less), and even more preferably 2.0 or less (or 2.00 or less). From the above perspective, the value is preferably 1.0 to 3.0 (or 1.00 to 3.00), more preferably 1.3 to 3.0 (or 1.30 to 3.00), even more preferably 1.4 to 2.5 (or 1.40 to 2.50), and particularly preferably 1.5 to 2.0 (or 1.50 to 2.00).

[0065] Refractory materials may contain, independently, any components other than those mentioned above (i.e., ZrO2, SiO2, Al2O3, P2O5, Na2O, K2O, B2O3, Fe2O3, TiO2), or they may not contain any of these components. Examples of components derived from raw materials other than those mentioned above include CaO, MgO, SrO, BaO, CuO, Y2O3, and ZnO.

[0066] In the refractory, the total amount of components other than those mentioned above (i.e., ZrO2, SiO2, Al2O3, P2O5, Na2O, K2O, B2O3) is preferably 0.7% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.4% by mass or less, particularly preferably 0.2% by mass or less, extremely preferably 0.1% by mass or less, even more preferably less than 0.1% by mass, and even more preferably 0.05% by mass or less.

[0067] For example, CuO is sometimes included as an impurity in refractory raw materials. From the viewpoint of suppressing the coloration of molten glass and suppressing the reduction in durability when coexisting with P2O5 and / or B2O3, the amount of CuO is preferably low. The amount of CuO is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.01% by mass or less.

[0068] In addition, MgO and CaO are sometimes included as impurities in refractory raw materials. From the viewpoint of suppressing the decrease in resistivity, the amount of MgO and CaO is preferably low, preferably 0.1% by mass or less each, and more preferably 0.05% by mass or less.

[0069] Similarly, Y2O3 is sometimes included as an impurity in refractory raw materials. From the viewpoint of suppressing the decrease in resistivity, the amount of Y2O3 is preferably low, preferably 0.3% by mass or less, and more preferably 0.2% by mass or less.

[0070] In the refractory disclosed herein, even without the intentional addition of components such as V2O5, CrO3, Nb2O5, MoO3, Ta2O5, WO3, and SnO2 as described in Patent Documents 7 and 8, high resistivity, low residual volume expansion rate, and suppression of glass exudation can be achieved. For example, when the total amount of oxides is set to 100% by mass, the total mass of V2O5, CrO3, Nb2O5, MoO3, Ta2O5, WO3, and SnO2, based on oxides, can be less than 0.01% by mass or less than 0.005% by mass.

[0071] The preferred chemical composition of the refractory is based on oxides, with the total amount of oxides set at 100% by mass, containing 0.10 to 0.70% by mass of Al2O3, 0.01 to 0.5% by mass of P2O5, and 0.10 to 1.5% by mass of B2O3.

[0072] The refractory is more preferably chemically composed of, based on oxides, the total amount of oxides is set at 100% by mass, containing 0.10 to 0.60% by mass of Al2O3, 0.01 to 0.3% by mass of P2O5, and 0.50 to 1.3% by mass of B2O3.

[0073] The preferred chemical composition of the refractory is based on oxides, with the total amount of oxides set at 100% by mass, containing more than 85.0% by mass of ZrO2, 8.0 to 12.0% by mass of SiO2, 0.10 to 0.65% by mass of Al2O3, 0.01 to 0.15% by mass of P2O5, and 0.50 to 1.0% by mass of B2O3, and the total amount of Fe2O3 and TiO2 is less than 0.30% by mass.

[0074] [Methods for manufacturing refractory materials]

[0075] Refractory materials can be manufactured by heating and melting refractory raw materials and then cooling them in a mold.

[0076] In one embodiment of this disclosure, the method for manufacturing a refractory includes the steps of heating and melting a refractory raw material, and then cooling it in a mold. The refractory raw material, relative to the total mass of oxides, contains at least 85.0% by mass of ZrO2, 8.0 to 12.0% by mass of SiO2, at least 0.10% by mass and less than 0.80% by mass of Al2O3, 0.01 to 1.0% by mass of P2O5, a total of 0.10% to 0.20% by mass of Na2O and / or K2O, and 0.05% to 2.0% by mass of B2O3, and the total mass of Fe2O3 and TiO2 is less than 0.55% by mass. Details of the components contained in the refractory raw material are as described above.

[0077] Specifically, refractory materials are manufactured, for example, by mixing powdered raw materials according to the above-mentioned proportions, melting them in an electric arc furnace, pressing the molten material into a graphite mold, and then cooling it. Refractory materials manufactured in this way through melt casting have a dense ZrO2 crystal structure and large crystal size, thus exhibiting excellent corrosion resistance. Heating during melting is achieved, for example, by bringing a graphite electrode into contact with the raw material powder and applying an electric current to the electrode.

[0078] [Properties of Refractory Materials]

[0079] The resistivity of the refractory material at 1600℃ is preferably 300Ω. cm or more, preferably 350Ω cm or larger, further preferably 400Ω cm or larger, with 450Ω being particularly preferred. Above cm. There is no particular upper limit to resistivity; for example, it can be 1000Ω. cm.

[0080] Resistivity was measured using a three-terminal electrode structure with a protective electrode under AC voltage at a frequency of 120 Hz.

[0081] In the refractory, the residual volume expansion rate, as determined below, is preferably 10% or less, more preferably 8% or less, even more preferably 6% or less, and particularly preferably 4% or less.

[0082] Thermal cycling tests were conducted on the above-mentioned refractory materials: the temperature was increased from 800°C to 1250°C at a rate of 450°C / h, and then decreased from 1250°C to 800°C at a rate of 450°C / h, and this cycle was repeated 40 times. It should be noted that the heating from room temperature (approximately 25°C) to 800°C and the cooling from 800°C to room temperature (approximately 25°C) were carried out at a rate of approximately 160°C / h. The residual volumetric expansion rate was obtained using the following formula.

[0083] Residual volume expansion rate (%) = {(Volume after thermal cycling test / Volume before thermal cycling test) - 1} × 100

[0084] From the viewpoint of density and corrosion resistance to molten glass, the preferred bulk density of the refractory is 4.7 g / cm³. 3 The above, more preferably 4.8 g / cm³ 3 The above is further optimized to 4.9 g / cm³. 3 above.

[0085] The volumetric specific gravity was determined by the Archimedes method.

[0086] The porosity of the refractory is preferably 1.5% or less. Lower porosity improves the corrosion resistance to molten glass. More preferably, the porosity is 0.1% to 1%. Porosity is determined by the Archimedes method.

[0087] The preferred mass of the refractory is 200 kg or more. When manufacturing large refractory materials, it is also preferable to suppress the residual volume expansion rate of the refractory material to inhibit crack formation. More preferably, the mass of the refractory material is 400–1500 kg.

[0088] [Uses of Refractory Materials]

[0089] Refractory materials are suitable for use, for example, in glass melting furnaces. Glass melting furnaces are used in the manufacture of glass products such as sheet glass. The refractory material is suitable for use in parts of the glass melting furnace that come into contact with molten glass. Due to the high resistivity of the refractory material disclosed herein, it is particularly suitable for use, for example, in and around the electrode locations of glass melting furnaces.

[0090] Therefore, in one embodiment of this disclosure, the glass melting furnace includes the refractory of this disclosure described above. It is particularly preferred to use the refractory of this disclosure in the parts of the glass melting furnace that come into contact with the molten glass, such as the electrode placement areas and their surroundings.

[0091] Example

[0092] Next, embodiments will be described in detail, but the embodiments of this disclosure are not limited to these embodiments. It should be noted that Examples 1-5, 10-12, and 15 are comparative examples, and Examples 6-9, 13, and 14 are embodiments.

[0093] <Manufacturing of Refractory Materials>

[0094] As raw materials, desilicationized zirconium oxide, alumina, zircon sand, silica, sodium carbonate, potassium carbonate, boron phosphate, and boron oxide are mixed to obtain refractory raw materials. The refractory raw materials are heated by an electric arc method, in which a graphite electrode is lifted from the molten surface, until it melts. The molten refractory raw materials are poured into a graphite mold pre-embedded in a slow-cooling material, namely Bayer alumina or silica sand, for casting, and then cooled to a temperature near room temperature (approximately 25°C). In Examples 1-7 and 10-15, the molds produce cuboid refractory bodies with dimensions of 130 mm × 160 mm × 300 mm, and in Examples 8 and 9, they produce cuboid refractory bodies with dimensions of 125 mm × 575 mm × 950 mm. After casting and cooling, the ingot and graphite mold are removed from the slow-cooling material, and the graphite mold and ingot are separated to obtain the refractory.

[0095] The composition of the refractory materials of Examples 1-15, obtained by adjusting the raw material composition, is shown in Tables 1 and 2. The chemical composition was determined quantitatively by wavelength dispersive X-ray fluorescence analysis, with B₂O₃ determined by high-frequency inductively coupled plasma atomic emission spectrometry, and Na₂O and K₂O determined by atomic absorption spectrometry. The ZrO₂ content was obtained by subtracting the mass of components other than ZrO₂ from the mass of the refractory material.

[0096] <Evaluation>

[0097] [Residual volume expansion rate]

[0098] Cylindrical specimens with a diameter of 35 mm × 40 mm were cut from the manufactured refractory. The refractory was subjected to a thermal cycling test in an electric furnace: heating from 800 °C to 1250 °C at a rate of 450 °C / h, then cooling from 1250 °C to 800 °C at a rate of 450 °C / h, and repeating this cycle 40 times. It should be noted that the heating from room temperature (approximately 25 °C) to 800 °C and the cooling from 800 °C to room temperature (approximately 25 °C) were carried out at a rate of approximately 160 °C / h. The residual volume expansion rate was calculated using the following formula.

[0099] Residual volume expansion rate (%) = {(Volume after thermal cycling test / Volume before thermal cycling test) - 1} × 100

[0100] [Glass seepage]

[0101] Cylindrical samples with a diameter of 30 mm and a height of 30 mm were cut using a diamond core drill. These samples were then calcined in an electric furnace at 1500℃ for 16 hours, followed by natural cooling within the furnace. Visual inspection was conducted to check for glass exudation before and after calcination.

[0102] [Resistivity]

[0103] A circular plate-shaped specimen with a diameter of 20 mm and a thickness of 3 mm was cut from the refractory material. A platinum slurry was sintered on one side of the specimen to obtain the main electrode and the protective electrode; sintering the remaining side yielded only the counter electrode. A platinum electrode for measuring the resistivity of the specimen was placed inside an electric furnace capable of reaching a maximum temperature of 1650 °C, and the specimen was then placed inside the furnace. While heating at a rate of 5 °C / min, an AC voltage of 120 Hz was applied using an insulation resistance measuring device, and the volume resistivity was continuously measured. The volume resistivity was calculated from the obtained volume resistivity and expressed as resistivity (Ω). cm).

[0104] In Tables 1 and 2, the composition indicates the proportion (mass%) of each component when the total amount of oxides is set to 100% by mass, based on the chemical composition of oxides. A "-" in the composition indicates that the corresponding component was not detected, and a "-" in the evaluation indicates that the corresponding evaluation was not performed or could not be determined. "Na2O+K2O" represents the total proportion (mass%) of Na2O and K2O; "Fe2O3+TiO2" represents the total proportion (mass%) of Fe2O3 and TiO2; "(Na2O+K2O)SiO2" represents the value obtained by dividing the total mass of Na2O and K2O by the mass of SiO2; and "(B2O3+P2O5) / Al2O3" represents the value obtained by dividing the total mass of B2O3 and P2O5 by the mass of Al2O3. The numbers in parentheses in the tables are rounded to one decimal place.

[0105]

[0106]

[0107] In any example, the total of oxides is set to 100% by mass, and the total mass of oxides of V2O5, CrO3, Nb2O5, MoO3, Ta2O5, WO3, and SnO2 is less than 0.01% by mass.

[0108] In the refractory of Example 1, which has a low total ratio of Na2O to K2O, the residual volume expansion rate is high.

[0109] Similarly, in the refractory of Example 2, which had a low total ratio of Na2O to K2O, the residual volume expansion rate was high, and glass exudation was observed after calcination.

[0110] In the refractory of Example 3, which had a low total ratio of Na2O to K2O, glass exudation was observed after calcination.

[0111] In the refractory of Example 4, which had a low total ratio of Na2O to K2O, glass exudation was observed after calcination.

[0112] One reason for these results is believed to be the low alkali ratio and insufficient compactness of the refractory structure. It should be noted that in Examples 2–4 where glass seepage was observed, resistivity was not evaluated because it would lead to equipment malfunction.

[0113] In Example 5, the refractory with a high Al2O3 content, the resistivity is low.

[0114] In Example 10, the proportion of P2O5 was low, and the combined proportion of Na2O and K2O was high, resulting in a high residual volume expansion rate and low resistivity.

[0115] In Example 11, the proportion of B2O3 was high, the residual volume expansion rate was high, and glass exudation was observed.

[0116] In Example 12, the combined ratio of Na2O and K2O is high, resulting in low resistivity.

[0117] In Example 15, the proportion of SiO2 was low, and the combined proportion of Na2O and K2O was also low, resulting in significant volume expansion, making it impossible to determine the residual volume expansion rate. Furthermore, glass exudation was observed, along with high resistivity.

[0118] In the refractory materials of Examples 6-9, 13, and 14, high resistivity and low residual volume expansion were observed, and no glass exudation was observed. Among them, the refractory material of Example 9, with a high proportion of P2O5, exhibited particularly high resistivity.

[0119] The results above show that the refractory material disclosed herein has high resistivity, low residual volume expansion rate, and suppressed glass exudation.

[0120] (Postscript)

[0121] This disclosure includes the following methods.

[0122] <1> An electroformed refractory, as a chemical composition based on oxides, wherein the total amount of oxides is set to 100% by mass, contains more than 85.0% by mass of ZrO2, 8.0 to 12.0% by mass of SiO2, more than 0.10% by mass and less than 0.80% by mass of Al2O3, 0.01 to 1.0% by mass of P2O5, a total of 0.10 to 1.0% by mass of Na2O and / or K2O, and 0.05 to 3.0% by mass of B2O3, and the total amount of Fe2O3 and TiO2 is less than 0.55% by mass.

[0123] <2> according to <1> The electroformed refractory, as a chemical composition, is based on oxides, with the total oxides set at 100% by mass, containing 0.10-0.70% by mass of Al2O3, 0.01-0.5% by mass of P2O5, a total of 0.10-0.50% by mass of Na2O and / or K2O, and 0.10%-2.0% by mass of B2O3.

[0124] <3> according to <1> or <2> The electroformed refractory, as a chemical composition, is based on oxides, with the total oxides set at 100% by mass, containing 0.10-0.60% by mass of Al2O3, 0.01-0.3% by mass of P2O5, a total of 0.10-0.30% by mass of Na2O and / or K2O, and 0.50-1.0% by mass of B2O3.

[0125] <4> according to <1> ~ <3> The electroformed refractory according to any one of the following methods, wherein, as a chemical composition, the total amount of oxides is set to 100% by mass, and the total amount of Fe2O3 and TiO2 is less than 0.30% by mass.

[0126] <5> according to <1> ~ <4> The electroformed refractory according to any one of the following methods, wherein the value obtained by dividing the total mass of Na2O and K2O by the mass of SiO2 is 0.01 or more.

[0127] <6> according to <1> ~ <5> The electroformed refractory according to any one of the following methods, wherein the total mass of B2O3 and P2O5 divided by the mass of Al2O3 is 1.3 or more.

[0128] <7> according to <1> ~ <6> The electroformed refractory according to any one of the following methods, wherein the resistivity at 1600°C is 350Ω. cm or more.

[0129] <8> according to <1> ~ <7> The electroformed refractory according to any one of the following methods, wherein the resistivity at 1600°C is 400Ω. cm or more.

[0130] <9> according to <1> ~ <8> The electroformed refractory in any one of the following embodiments is subjected to a thermal cycling test: the temperature is increased from 800°C to 1250°C at a rate of 450°C / h, and then decreased from 1250°C to 800°C at a rate of 450°C / h, and this cycle is repeated 40 times, and the residual volume expansion rate is less than 10% as determined by the following formula.

[0131] Residual volume expansion rate (%) = {(Volume after thermal cycling test / Volume before thermal cycling test) - 1} × 100

[0132] <10> A glass melting furnace, comprising <1> ~ <9> The electroformed refractory as described in any one of the following.

[0133] <11> A method for manufacturing electroformed refractory involves heating and melting refractory raw materials, then cooling them in a mold. The refractory raw materials, relative to the total mass of oxides, contain 85.0% by mass or more ZrO2, 8.0 to 12.0% by mass SiO2, 0.10% by mass or more but less than 0.80% by mass Al2O3, 0.01 to 1.0% by mass P2O5, a total of 0.10% to 1.0% by mass Na2O and / or K2O, 0.05% to 3.0% by mass B2O3, and the total mass of Fe2O3 and TiO2 is less than 0.55% by mass.

[0134] The disclosure of Japanese Patent Application No. 2024-006270, filed on January 18, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical specifications described in this specification are incorporated herein by reference to the same extent that each document, patent application, and technical specification is specifically and separately described and incorporated herein by reference.

Claims

1. An electroformed refractory, wherein, based on oxides, the total amount of oxides is set to 100% by mass, and it contains 85.0% by mass or more of ZrO2, 8.0 to 12.0% by mass of SiO2, 0.10% by mass or more but less than 0.80% by mass of Al2O3, 0.01 to 1.0% by mass of P2O5, a total of 0.10 to 0.20% by mass of Na2O and / or K2O, and 0.05 to 2.0% by mass of B2O3, and the total amount of Fe2O3 and TiO2 is less than 0.55% by mass.

2. The electrocast refractory of claim 1, wherein, As a chemical composition, based on oxides, the total amount of oxides is set at 100% by mass, containing 0.10 to 0.70% by mass of Al2O3, 0.01 to 0.5% by mass of P2O5, and 0.10 to 1.5% by mass of B2O3.

3. The electroformed refractory according to claim 1, wherein, As a chemical composition, based on oxides, the total amount of oxides is set at 100% by mass, containing 0.10 to 0.60% by mass of Al2O3, 0.01 to 0.3% by mass of P2O5, and 0.50 to 1.3% by mass of B2O3.

4. The electrocast refractory of claim 1, wherein, It contains a total of 0.11 to 0.20% by mass of Na₂O and / or K₂O.

5. The electrocast refractory of claim 1, wherein, As a chemical composition, based on oxides, the total amount of oxides is set at 100% by mass, and the total amount of Fe2O3 and TiO2 is less than 0.30% by mass.

6. The electrocast refractory of claim 1, wherein, The value obtained by dividing the total mass of Na2O and K2O by the mass of SiO2 is greater than 0.

01.

7. The electrocast refractory of claim 1, wherein, The total mass of B2O3 and P2O5 divided by the mass of Al2O3 yields a value greater than 1.

0.

8. The electrocast refractory of claim 1, wherein, Its resistivity at 1600℃ is 300Ω. cm or more.

9. The electrocast refractory of claim 1, wherein, Its resistivity at 1600℃ is 400Ω. cm or more.

10. The electrocast refractory of claim 1, wherein, The electroformed refractory was subjected to the following thermal cycling test: the temperature was increased from 800℃ to 1250℃ at a rate of 450℃ / h, and then decreased from 1250℃ to 800℃ at a rate of 450℃ / h. This cycle was repeated 40 times. The residual volume expansion rate, calculated by the following formula, was found to be less than 10%. Residual volume expansion rate (%) = {(volume after thermal cycling test / volume before thermal cycling test) - 1} × 100.

11. A glass melting furnace comprising the electroformed refractory as described in any one of claims 1 to 10.

12. A method for manufacturing an electroformed refractory, wherein a refractory raw material is heated and melted, and then cooled in a mold, wherein the refractory raw material, relative to the total mass of oxides, contains more than 85.0% by mass of ZrO2, 8.0 to 12.0% by mass of SiO2, more than 0.10% by mass and less than 0.80% by mass of Al2O3, 0.01 to 1.0% by mass of P2O5, a total of 0.10% to 0.20% by mass of Na2O and / or K2O, and 0.05% to 2.0% by mass of B2O3, and the total mass of Fe2O3 and TiO2 is less than 0.55% by mass.

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