TW201402519A - High zirconia fused cast refractory - Google Patents

Abstract

Provided is a high zirconia fused cast refractory that is highly durable and is not prone to cracking during refractory manufacturing, when heating increases, when temperature varies during use, or when heating decreases during an operational pause. The high zirconia fused cast refractory is characterized by containing, as a chemical composition, 87 to 96 mass% of ZrO2, 2.5 to 9.0 mass% of SiO2, more than 1.5 mass% but not more than 2.5 mass% of Al2O3, 0.15 to 0.6 mass% of Na2O, 0.3 to 1.3 mass% of K2O, and approximately 0 to 0.3 mass% of Li2O.

Description

High zirconia electroformed refractory

The present invention relates to a high zirconia electroformed refractory, and more particularly to a high zirconia electroforming refractory which has excellent durability and reusability when applied to a glass melting furnace and is also excellent in productivity. .

A high zirconia electroformed refractory containing 80% by mass or more of ZrO ₂ as a chemical component has been used as a refractory for a glass melting furnace since the prior art. Since the high zirconia electroformed refractory has high corrosion resistance and low contamination with respect to molten glass, it is often used in a glass melting furnace which requires high quality in a substrate glass for flat panel display or the like. Contact part.

The fine structure of the high zirconia electroformed refractory is composed of a small amount of pores, a large amount of zirconia (ZrO ₂ ) crystal grains, and a small amount of matrix glass filled between the particles. The matrix glass is mainly composed of SiO ₂ , and the other oxide is composed of an oxide such as Al ₂ O ₃ , Na ₂ O, B ₂ O ₃ or P ₂ O ₅ .

The high zirconia electroformed refractory is subjected to temperature changes due to the cooling process during its manufacture, the heat rise in the glass melting furnace, the heat drop when the operation is suspended, and the operation of the operation or the refractory itself. Thermal stress and phase transition stress are generated inside the refractory by the temperature change, and the phase transition stress is caused by a reversible phase transition of the zirconia crystal with a large volume change in a temperature region around 1000 ° C. produce. When the refractory contains a matrix glass having suitable thermomechanical properties and amounts, the refractory becomes soft and relieves stress with respect to the stress, so that cracks do not occur in the refractory. again In the present specification, the electroformed refractory is also referred to as a refractory.

On the other hand, when the thermomechanical properties of the matrix glass are not appropriate or the amount of the matrix glass is insufficient, cracks are generated when the high zirconia electroformed refractory is produced or when the heat is applied to the glass melting furnace. When the refractory is applied to the molten glass contact portion, if cracks are present, part of the refractory is severely corroded by the molten glass, so that the durability of the refractory is largely lowered.

The high zirconia electroformed refractory has a case where zirconium crystals (ZrO ₂ -SiO ₂ ) are formed inside. The zirconium crystal system ZrO ₂ in the interior of the refractory is formed by reacting with SiO ₂ in the matrix glass, so that the formation of the zirconium crystal causes a decrease in the matrix glass in the refractory. The refractory is embrittled by the formation of zirconium crystals and the reduction of the amount of the matrix glass of the thermal stress and the phase transformation stress, and cracks are likely to occur even if the temperature is slightly changed.

Further, a high zirconia electroformed refractory which is difficult to form zirconium crystals in a refractory monomer may also have a zirconium crystal formed by reaction with molten glass. The reason for this is that either or both of the chemical components that inhibit the formation of zirconium crystals in the refractory are eluted into the molten glass, and the chemical components that promote the formation of zirconium crystals are transferred from the molten glass. Infiltration into the refractory. The tendency to form zirconium crystals by reaction with molten glass is apparently produced when a low alkali glass or an alkali-free glass such as a liquid crystal substrate glass is in contact with the refractory.

Therefore, a high zirconia electroformed refractory which is easy to use a refractory monomer and generates zirconium crystal by a thermal history, and a zirconium crystal which is difficult to form in a refractory monomer can be easily reacted with molten glass. When a high zirconia electroformed refractory which forms a zirconium crystal is used as a refractory of a glass melting furnace, there is a case where even if there is no crack at the time of manufacture and no crack occurs when the heat rises, it is also in operation. Zirconium crystals are formed inside the refractory material, and cracks are easily generated by temperature fluctuations during operation, so that the durability of the refractory material is greatly reduced.

Generally, the durability of the refractory is a factor in determining the life of the glass melting furnace. because Thus, the occurrence of cracks in the refractory material shortens the life of the glass melting furnace, which is a cause of an increase in glass manufacturing cost.

Further, the high zirconia electroformed refractory system which does not form zirconium crystals in the state in which the glass melting furnace is in operation does not cause cracking, or even if it occurs, cracks are less than those of the refractory material which forms zirconium crystals. When the heat of the glass melting furnace is suspended due to production adjustment or the like, the occurrence of new cracks and the propagation of existing cracks are small, so that it is relatively easy to reuse.

On the other hand, the high zirconia electroformed refractory which forms zirconium crystal is caused by the occurrence of new cracks and the propagation of existing cracks when the heat is lowered, and the cracks are similarly formed when the heat rises again. Produced and spread, so it is difficult to reuse. Even if it is temporarily used repeatedly, high durability cannot be obtained, and the life of the glass melting furnace is shortened. In other words, the high zirconia electroformed refractory which is easily formed by the reaction with the monomer or the molten glass to form zirconium crystals is not suitable for repeated use after the operation is suspended, even if it is continuously used in the state in which the glass melting furnace is in operation.

Since the prior art, cracking prevention means for the production of high zirconia electroformed refractories, heat rise, and operation have been studied.

Patent Document 1 discloses a high zirconia electroformed refractory having a chemical composition of ZrO ₂ of 85 to 97% by mass, SiO ₂ of 2 to 10% by mass, and Al ₂ O _{3 of at} most 3 as a chemical composition of the refractory. The mass% and P ₂ O ₅ are 0.1 to 3% by mass, and substantially do not contain a rare earth oxide, and it is possible to suppress cracking during production. However, there is a disadvantage in that P ₂ O ₅ which promotes the formation of zirconium crystals is formed, and even if it is a refractory monomer, zirconium crystals are easily formed.

Patent Document 2 discloses a high zirconia electroformed refractory having a chemical composition of ZrO ₂ of 90 to 98% by mass and Al ₂ O ₃ of 1% by mass or less, and containing no Li ₂ O. Na ₂ O, CuO, CaO, MgO, containing 0.5 to 1.5% by mass of B ₂ O ₃ , or B ₂ O ₃ of 0.5 to 1.5%, and selected from K ₂ O, SrO, BaO, Rb ₂ O, Cs _{One of 2} O is 1.5% or less, or a total of two or more kinds is 1.5% or less, and cracking at the time of production is suppressed, and a component having a large cation radius is used, and the electric resistance is also high. However, there is a disadvantage that B ₂ O _{3 which} promotes the formation of zirconium crystals has a high content, and even if it is a refractory monomer, zirconium crystals are easily formed.

Patent Document 3 discloses a refractory material containing, as a chemical composition of a refractory, 90 to 95% by mass of ZrO ₂ , 3.5 to 7% by mass of SiO ₂ , and 1.2 to 3% by mass of Al ₂ O ₃ . The total amount contains 0.1 to 0.35 mass% of Na ₂ O and/or K ₂ O, and substantially does not include any of P ₂ O ₅ , B ₂ O ₃ and CuO, and suppresses improvement of heat cycle resistance and zirconium. The formation of crystals. However, even in the case of the refractory according to the invention, the effect of suppressing the formation of zirconium crystal under the contact condition of the molten glass is insufficient. Further, there is a problem that cracks are likely to occur when a refractory is produced, in particular, when a large refractory such as an ingot having a mass of 300 kg or more is produced.

Patent Document 4 discloses a refractory material having a chemical composition of ZrO ₂ of 89 to 96% by mass, SiO ₂ of 3.5 to 7% by mass, Al ₂ O ₃ of 0.2 to 1.5% by mass, and Na ₂ O+K. ₂ O is 0.05 to 1.0% by mass, B ₂ O _{3 is} less than 1.2% by mass, P ₂ O _{5 is} less than 0.5% by mass, and B ₂ O ₃ + P ₂ O ₅ is 0.01% by mass or more and less than 1.7% by mass. CuO is less than 0.3% by mass, Fe ₂ O ₃ +TiO ₂ is 0.3% by mass or less, BaO is 0.01 to 0.5% by mass, and SnO ₂ is 0.3% by mass or less. According to this patent document, it is considered that cracking caused by cracking and thermal cycle in the production of a refractory material does not occur, and Na ₂ O, K ₂ O, and BaO are further added, so that P ₂ O ₅ and BaO have a zirconium-promoting effect. The characteristics of the generated undesirable phenomenon disappear. However, the effect of the invention for suppressing the formation of zirconium crystal under molten glass contact conditions is still insufficient. As the reason include: an embodiment of the invention contains a relatively high content of B to promote the generation of crystals of the zirconium ₂ O ₃ and P ₂ O _5, and further, the relative high content containing B ₂ O ₃ and In the case of P ₂ O ₅ , the content of K ₂ O and Al ₂ O ₃ is insufficient.

According to Patent Document 5, as a chemical composition of the refractory, ZrO ₂ is 87 to 94% by mass, SiO ₂ is 3.0 to 8.0% by mass, Al ₂ O ₃ is 1.2 to 3.0% by mass, and Na ₂ O is 0.35. The mass% or more is 1.0% by mass or less, the B ₂ O ₃ is 0.02% by mass or more and less than 0.05% by mass, substantially does not contain P ₂ O ₅ or CuO, and the mass ratio of Al ₂ O ₃ to Na ₂ O is 2.5 to 5.0, inhibiting the formation of zirconium crystals in the refractory monomer. However, the refractory according to the present invention optimizes the content ratio of Na ₂ O to Al ₂ O ₃ to suppress the formation of zirconium crystals, and thus is produced under contact with molten glass containing only Na ₂ O at a low content. The preferred dissolution of Na ₂ O. There is a disadvantage that the ratio of Na ₂ O to Al ₂ O ₃ is rapidly deviated from the initial value of the unused state due to the elution, and the composition of the refractory is detached from the favorable composition for suppressing the formation of zirconium crystal in a short time. The effect of suppressing the formation of zirconium crystals obtained by the refractory monomer disappears in advance.

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. SHO 56-129675

[Patent Document 2] Japanese Patent Laid-Open Publication No. SHO 63-285173

[Patent Document 3] Japanese Patent Laid-Open No. Hei 6-72766

[Patent Document 4] Japanese Patent Laid-Open No. 9-2870

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2007-176736

In order to solve the above problems, an object of the present invention is to provide a high zirconia electroformed refractory which is subjected to any of the conditions of producing a refractory, a rise in heat, a temperature change during use, and a heat drop at the time of suspension of operation. It is difficult to produce cracks and has high durability.

The present inventors have repeatedly conducted intensive studies, and as a result, have found a high zirconia electroformed refractory which adjusts the composition of the matrix glass, in particular, the content of K ₂ O and Al ₂ O ₃ is set to an appropriate range. Even in the case of the refractory monomer, it is difficult to form zirconium crystal under the contact condition of the molten glass, and the residual volume expansion is small even under the temperature cycle condition, and the occurrence of cracks in the production of the refractory can be efficiently suppressed.

That is, the high zirconia electroformed refractory of the present invention is characterized in that it contains, as a chemical composition, ZrO ₂ of 87 to 96% by mass, SiO ₂ of 2.5 to 9.0% by mass, and Al ₂ O ₃ of 1.5 mass. % or more, 2.5% by mass or less, Na ₂ O is 0.15 to 0.6% by mass, K ₂ O is 0.3 to 1.3% by mass, and the amount of Li ₂ O in other portions is 0 to 0.3% by mass.

According to the high zirconia electroformed refractory of the present invention, a refractory can be obtained which does not have the problem of cracking when the refractory is produced, and is excellent in productivity, and even if the refractory monomer is in contact with the molten glass, it is difficult. Zirconium crystals are formed, and it is difficult to produce cracks when the refractory is produced, when the heat rises, when it is used, and when the heat is lowered, and it is durable and reusable.

Further, the high zirconia electroformed refractory of the present invention is less likely to be cracked under the contact of molten glass and is durable, so that if it is applied to the molten glass contact portion of the glass melting furnace, a longer furnace life can be obtained. It can reduce the amount of refractory erosion and reduce the pollution of molten glass. Further, when the heat is lowered when the operation of the glass melting furnace is stopped by the production adjustment or the like, and the heat is raised again, cracking is less likely to occur, so that the refractory having less corrosion and having a short life can be easily reused. Further, the high zirconia electroformed refractory of the present invention does not have a problem of cracking which affects the yield at the time of production. Therefore, it is excellent in productivity of a refractory, and as a result, it is advantageous in terms of manufacturing cost.

The high zirconia electroformed refractory of the present invention is composed of five chemical components of ZrO ₂ , SiO ₂ , Al ₂ O ₃ , Na ₂ O and K ₂ O described above as main components. Hereinafter, the action of each of the chemical components in the refractory will be described. Further, in the present specification, the contents of the five components are represented by internal components. In addition, the component which is not described above is represented by an external component when the total of the five components is 100% by mass.

In the present specification, the internal component is a component ratio of each of 100% by mass in the case where the total amount of the above five components in the high zirconia electroformed refractory is 100% by mass. For example, the inclusion of 90% by mass of ZrO ₂ as an internal component means that the total amount of the above five components is 100% by mass, and 90% by mass of ZrO ₂ is contained in 100% by mass.

On the other hand, when the total amount of the above five components in the high zirconia electroformed refractory is 100% by mass, the component other than the five components is based on the above 100% by mass. The ratio. For example, the content of the external portion is 0.01% by mass of B ₂ O ₃ , and the total amount of the above five components is 100% by mass, and 0.01% by mass of B ₂ O ₃ is additionally contained.

The zirconia raw material and the zirconium raw material for producing the high zirconia electroformed refractory inevitably contain 1 to 3% by mass of HfO ₂ , and the HfO ₂ system remains in the refractory without loss of evaporation or the like during production. Therefore, the conventional high zirconia electroformed refractory contained in the present invention contains 1 to 3% by mass of HfO ₂ . HfO ₂ lines are usually high zirconia electrocast refractory exhibit the ZrO same as the effect of _2, so practices based accordance ZrO ₂ + HfO the value ₂ and abbreviated as ZrO _2, in the present invention, also in accordance with ZrO ₂ + The value of HfO ₂ is referred to as ZrO ₂ .

The high zirconia electroformed refractory of the present invention is a high zirconia electroformed refractory composed of a large amount of zirconia crystals, a small amount of matrix glass and a small amount of pores. The ZrO ₂ system, which is an internal component, has a strong resistance to erosion by molten glass and is contained as a main component of the refractory. This ZrO ₂ exists almost as a zirconia crystal having excellent corrosion resistance to molten glass, and is present only in a very small amount in the matrix glass.

That is, the ZrO ₂ content governs the zirconia crystal content in the high zirconia electroformed refractory of the present invention, which in turn affects the corrosion resistance of the refractory to molten glass. In order to obtain high corrosion resistance to molten glass, ZrO ₂ must be 87% by mass or more, preferably 88% by mass or more. On the other hand, when ZrO _{2 is} more than 96% by mass, the amount of the matrix glass which acts to relax the stress is relatively reduced, and cracks are likely to occur due to temperature changes during production, heat rise, use, and heat drop. Therefore, the ZrO _{2 in} the high zirconia electroformed refractory of the present invention is 87 to 96% by mass.

SiO _{2 which} is an internal component component forms a main component of the matrix glass. In order to secure the amount of the matrix glass which functions to relax the stress, 2.5% by mass or more of SiO _{2 is required} . On the other hand, if a large amount of SiO ₂ is contained in the refractory, ZrO ₂ is inevitably contained in a large amount, and the corrosion resistance is impaired. Therefore, the SiO _{2 in} the high zirconia electroforming refractory of the present invention is from 2.5 to 9.0% by mass, preferably from 3.0 to 8.5% by mass.

Al ₂ O ₃ , which is an internal component, lowers the viscosity of the matrix glass and suppresses the formation of zirconium crystal to some extent. That is, under the condition of low alkali glass and alkali-free glass which are favorable for the formation of zirconium crystal, the majority of the glass is relatively high in Al ₂ O ₃ , and the difference in concentration gradient between the refractory and the molten glass is small. The dissolution of Al ₂ O ₃ from the refractory is slower. Therefore, the effect of suppressing the formation of zirconium crystals caused by Al ₂ O ₃ can be enjoyed for a long time. Further, when Al ₂ O ₃ is contained in an appropriate amount, the solubility in the production of the refractory is improved, and the effect of reducing the time and power required for the production of the refractory can be obtained. Further, the flow of the liquid at the time of casting is improved, and the molten metal is surrounded by the respective corners of the mold, so that the defects caused by the molten metal not reaching the corner portion of the mold can be suppressed. Further, the liquid flow is preferable, whereby the production of the refractory material, for example, when a relatively thin mold having a thickness of 100 mm or less is used, becomes easy. That is, when Al ₂ O _{3 is} contained in an appropriate amount, the productivity of the cast refractory can be improved.

When the Al ₂ O _{3 is} less than 1.6% by mass, particularly 1.5% by mass or less, the effect of suppressing the formation of zirconium crystals cannot be obtained. Moreover, the solubility in the case of producing a refractory material is unsatisfactory, and the effect of reducing the time required for the production of the refractory and the electric power cannot be obtained. Further, the liquid flow during casting is insufficient, and when the refractory is used in the case of using a relatively thin mold, the defects caused by the molten metal not reaching the corner portion of the mold are increased. When Al ₂ O ₃ exceeds 2.5% by mass, an aluminosilicate crystal such as mullite is formed at the time of production or during use, which causes a decrease in the amount of the matrix glass, and is likely to be used during production and heat rise. The temperature changes when the heat is lowered and cracks occur. Therefore, the Al ₂ O ₃ in the high zirconia electroforming refractory of the present invention is more than 1.5% by mass and 2.5% by mass or less, preferably 1.6 to 2.5% by mass, and more preferably 1.8 to 2.3% by mass.

The Na ₂ O system, which is an internal component, can effectively suppress the occurrence of cracks in the production of the electroformed refractory. Further, Na ₂ O is a component having an effect of suppressing the formation of zirconium crystals in the thermal history of the refractory monomer. However, the effect of suppressing the formation of zirconium crystal by Na ₂ O is inferior to that of K ₂ O and Cs ₂ O, and similarly to Al ₂ O ₃ and K ₂ O, Na ₂ O is also a component which lowers the viscosity of the matrix glass. The viscosity-reducing effect is particularly remarkable, and the elution of Al ₂ O ₃ , K ₂ O, and Cs ₂ O as a component effective for suppressing the formation of zirconium crystals to the molten glass is accelerated under the contact condition of the molten glass, and the promotion of B _{2 is} promoted. Since the infiltration of the component of the zirconium crystal such as O _{3 is} accelerated from the molten glass, it cannot be contained in a large amount.

According to the above, Na ₂ O content is preferably low, the present invention high zirconia electrocast refractory of Na ₂ O content of 0.15 to 0.6% by mass, preferably 0.17 to 0.58% by mass, and further preferably 0.20 to 0.55 mass%.

K ₂ O, which is an internal component, is also a component which lowers the viscosity of the matrix glass and suppresses the formation of zirconium crystals. Similarly to Al ₂ O ₃ and Na ₂ O, K ₂ O has an effect of lowering the viscosity of the matrix glass. When K ₂ O is contained in the refractory, the following effects can be obtained: suppression of use during production, heat rise, and use The crack of the refractory caused by the temperature change at the time of the heat drop. Further, since the cation radius of K is large, the elution is slow even when it comes into contact with the molten glass, and the effect of suppressing the formation of zirconium crystal is exhibited for a long period of time.

When K ₂ O is insufficient, an aluminosilicate crystal such as mullite is formed during heating at the time of production and use, which causes a decrease in the amount of the matrix glass, which is liable to cause a decrease in the amount of the substrate during the production, heat rise, use, and heat. When the temperature changes, cracks occur. On the other hand, when K ₂ O is 1.3% by mass or more, particularly more than 1.3% by mass, potassium-containing aluminosilicate crystals such as leucite are formed by heating at the time of production or use, resulting in a matrix glass. When the amount is lowered, cracks are likely to occur due to temperature changes during production, during heat rise, during use, and when heat is lowered. Even if only a small amount of K ₂ O is used, the effect of suppressing the formation of zirconium crystals in the refractory monomer can be obtained, but under the conditions of molten glass contact, especially in contact with low alkali glass and alkali-free glass, 0.3 mass is required. More than % K ₂ O to suppress the formation of zirconium crystals. Therefore, the K ₂ O in the high zirconia electroformed refractory of the present invention is 0.3 to 1.3% by mass, preferably 0.4 to 1.2% by mass, and more preferably 0.5 to 1.1% by mass.

Here, on the refractory content of Na ₂ O and K ₂ O, the preferred relationship is prepared for a specific ₂ O ratio of K ₂ O (K ₂ O / Na ₂ O) for the phase Na. Specifically, the value of K ₂ O/Na ₂ O is preferably from 0.5 to 8, more preferably from 0.8 to 7, further preferably from 1.1 to 6.

When the amount of the Na ₂ O is too large, the effect of suppressing the formation of zirconium crystals upon contact with the molten glass cannot be sufficiently obtained as in the case of heat rise, use, and heat fall. On the other hand, K ₂ O can stably suppress the formation of zirconium crystals even under the contact conditions of the molten glass as described above. However, the inventors of the present invention have found that it is easy to cause cracks when manufacturing an electroformed refractory under the condition that K ₂ O and Al ₂ O ₃ are contained in a large amount and Na ₂ O is not contained.

Therefore, in the present invention, it has been newly found that even in the case of producing a refractory, it is necessary to sufficiently and well-balance the crack in the case where the heat of the melting furnace rises, when it is used, and when the heat is lowered. The refractory that produces the effect.

Further, the content of Na ₂ O and K ₂ O (Na ₂ O+K ₂ O) is preferably 0.5 to 1.6% by mass, more preferably 0.55 to 1.4% by mass, still more preferably 0.6 to 1.2% by mass. When the total amount of Na ₂ O and K ₂ O (Na ₂ O+K ₂ O) is insufficient, it is easy to cause cracks when the refractory is produced, and it is difficult to suppress the formation of zirconium crystals in the refractory monomer, and further, manufacture The solubility in the case of the refractory material is unsatisfactory, and the effect of reducing the time and power necessary for the dissolution of the refractory material cannot be obtained. Further, the liquid flow during casting is insufficient, and when the refractory is used in the case of using a relatively thin mold, the defects caused by the molten metal not reaching the corner portion of the mold are increased. On the other hand, if the total amount of Na ₂ O and K ₂ O (Na ₂ O+K ₂ O) is excessive, cracking tends to occur during the production of the refractory.

Further, the amount of the other portion may contain 0 to 0.3% by mass of Li ₂ O. Although Li ₂ O does not participate in suppressing the formation of zirconium crystals, it has an effect of promoting the melting of other raw materials, thereby improving the productivity in producing a refractory. On the other hand, when the content of Li ₂ O exceeds 0.3% by mass, cracks may occur in the refractory during the production of the refractory. The content of Li ₂ O is preferably 0.15% by mass or less, more preferably 0.1% by mass or less, and further preferably substantially not contained in addition to unavoidable impurities. In the case of containing Li ₂ O, it is preferably 0.03% by mass or more, and more preferably 0.05% by mass or more.

B ₂ O ₃ , which is an external component, promotes the formation of zirconium crystals. When B ₂ O ₃ is contained in a large amount, the refractory generates zirconium crystal only in the heat history, and even in a small amount, there is a case where zirconium crystals in the molten glass contact condition are promoted. Therefore, B ₂ O _{3 is} preferably a low content in terms of suppressing the formation of zirconium crystals. In the present invention in which Al ₂ O ₃ , Na ₂ O, K ₂ O, and Cs ₂ O contribute greatly to suppressing the formation of zirconium crystals, the amount of B ₂ O ₃ in other portions is allowed to be 0.25 mass% or less. Preferably, it is 0.15 mass% or less. More preferably, B ₂ O ₃ is 0.08% by mass or less.

On the other hand, B ₂ O ₃ also has a low level even as a crack generated when the effect of suppressing the refractory material, and therefore in the range of non-refractory to suppress the formation of undesirable phenomena of crystals of zirconium and comprising B ₂ O _3, The implementation of precise composition control maintains high refractory productivity.

The P ₂ O _{5 which} is an external component is a component which promotes the formation of zirconium crystal in the same manner as B ₂ O ₃ . When P ₂ O ₅ is contained in a large amount, the refractory generates zirconium crystal only in the thermal history, and even in a small amount, there is a case where zirconium crystal in the molten glass contact condition is promoted. Therefore, in suppressing the formation of zirconium crystals, P ₂ O _{5 is} preferably at a low level which is acceptable.

On the other hand, P ₂ O ₅ has an effect of suppressing generation of cracks in the production of a refractory material even at a low content, and further, a component which is inevitably mixed depending on the type of the zirconia raw material and the zirconium raw material. If P ₂ O ₅ is not allowed to be contained, it is necessary to use expensive purified raw materials and relatively expensive zirconium raw materials and zirconia raw materials, but in Al ₂ O ₃ , Na ₂ O, K ₂ O and Cs ₂ In the present invention in which the production of the zirconium crystal is suppressed to a large extent, the amount of P ₂ O ₅ in the other portion is 0.25 mass% or less, preferably 0.15 mass% or less. P ₂ O _{5 is more} preferably 0.08% by mass or less. Therefore, the selection range of the zirconium raw material and the zirconia raw material is not narrow, and a relatively inexpensive raw material cost can be achieved. Further, in the same manner as in the case of B ₂ O ₃ , if P ₂ O ₅ is contained in the range of the refractory which suppresses the formation of zirconium crystals, and precise composition control is carried out, the refractory can be kept high. Productive.

Further, as described above, B ₂ O ₃ and P ₂ O ₅ together promote the formation of zirconium crystals, and in order to sufficiently ensure the action of suppressing the formation of zirconium crystals in the refractory, the present invention is The total amount of B ₂ O ₃ and P ₂ O _{5 in} the middle portion is preferably 0.4% by mass or less, and more preferably 0.3% by mass or less, and particularly preferably 0.1% by mass or less. In consideration of suppression of formation of zirconium crystals, it is preferably 0.05% by mass or less, and more preferably contains substantially no impurities other than unavoidable impurities.

Further, in the present invention, in addition to the components described above, Cs ₂ O may be contained as an external component. Cs ₂ O also inhibits the formation of zirconium crystals, and even at low levels, it can exhibit its effects. Further, since the cation radius of Cs is extremely large, even if it is in contact with the molten glass, the elution from the refractory is extremely slow, and in particular, the effect of suppressing the formation of zirconium crystal is exhibited for a long period of time. On the other hand, although the reason is not clear, excessive Cs ₂ O tends to crack at the time of production. Therefore, the content of Cs ₂ O in the other portion is 0.05 to 3.8% by mass, and more preferably 0.05 to 0.05. 3.5% by mass, more preferably 0.05 to 2.5% by mass or less, even more preferably 0.05 to 0.7% by mass.

Fe ₂ O ₃ and TiO ₂ contained as impurities in the raw material mainly cause coloring and foaming of the molten glass, and if it is a high content, it is not preferable. When the total amount of these Fe ₂ O ₃ and TiO ₂ is 0.3% by mass or less, there is no problem of coloring, and it is preferably not more than 0.2% by mass.

Similarly, Y ₂ O ₃ and CaO are contained as impurities in the raw material, and the like tends to increase the residual volume expansion ratio in the heat cycle test, and the total amount of the other Y ₂ O ₃ and CaO is When it is 0.3% by mass or less, there is no problem, and it is preferably not more than 0.2% by mass.

Further, the BaO system as an external component has an alkaline earth metal oxide component which lowers the viscosity of the matrix glass. BaO is not an essential component, and the low concentration does not deteriorate the properties of the refractory. Therefore, there is no problem in the case where the refractory is contained at a low concentration. On the other hand, when BaO is contained in a high concentration in the refractory, the viscosity of the matrix glass is drastically lowered, and there is a tendency to promote cracking of the refractory during production. Therefore, in the case of containing BaO, it is preferably 0 to 1% by mass in terms of the amount of the other portion.

Example

Hereinafter, the high zirconia refractory of the present invention will be specifically described by way of examples, but the present invention is not limited by the examples.

In order to obtain a refractory by an electrofusion casting method, a raw material such as alumina, zircon sand, alumina, potassium carbonate, cesium carbonate, B ₂ O ₃ , P ₂ O ₅ is prepared by dissolving zirconium as a raw material of zirconia. The raw materials were mixed, and the mixed raw materials were placed in a three-phase arc electric furnace having an output of three graphite electrodes of 1500 kVA, and completely melted by electric heating.

500 to 600 kg of the molten metal was poured into a graphite mold previously filled in quartz sand as a slow cooling material, and left to cool to a temperature near room temperature. The mold made of the graphite was produced in such a manner that a raw material of a refractory product containing no shrinkage cavities having a thickness of 250 mm × a width of 310 mm × a height of 820 mm was obtained. Specifically, the mold is designed and manufactured in such a manner that an ingot having the same volume as the part of the raw material of the refractory product is provided above the part for the raw material of the refractory product.

After casting and cooling, the ingot and the graphite mold are extracted from the slow cooling material, and the graphite mold and the ingot are separated to produce a high zirconia electroformed refractory.

The raw material composition was adjusted to obtain a high zirconia electroformed refractory having the chemical compositions shown in Tables 1 to 5. Here, Examples (Examples 1 to 15 and Examples 23 to 25) are shown in Table 1, Table 2, and Table 4, and Comparative Examples (Examples 16 to 22, Examples 26 to 28) are shown in Table 3. table 5. Further, regarding the chemical composition of the refractory, ZrO ₂ , SiO ₂ , and Al ₂ O ₃ are quantitatively determined by wavelength-dispersive fluorescent X-ray analysis, and other components are coupled by high-frequency inductively coupled plasma. Quantitative analysis values determined by bulk emission spectroscopy. However, the quantification of each component is not limited to the analysis method, and may be carried out by other quantitative analysis methods.

[Cracks at the time of manufacture]

The crack in the appearance of the ingot was evaluated in the following manner.

First, a raw material of a refractory product having a thickness of 250 mm, a width of 310 mm, and a height of 820 mm was produced by cutting the riser portion from the ingot of the high-zirconia electroformed refractory. Then, the length of the crack which can be visually confirmed in the raw material is measured by a vernier caliper.

When the maximum length of the crack in the raw material of the refractory product is 100 mm or more, it is necessary to produce an ingot which is very large in size relative to the necessary refractory product, and to perform high-load grinding and cutting, and thus the refractory Manufacturing costs are very high and unrealistic. If the crack length in the raw material of the refractory product is short, the ingot having a slightly larger size than the refractory product which is required for the refractory product can be lightly ground on the surface, so that the refractory can be easily produced. Therefore, the crack length in the raw material of the refractory product is preferably less than 100 mm, more preferably 70 mm or less, further preferably 50 mm or less, and most preferably less than 30 mm.

[Residual volume expansion ratio in thermal cycle test]

A sample of 40 mm × 40 mm × 40 mm was cut from the manufactured electroformed refractory, and heating and cooling were performed 40 times between 800 ° C and 1250 ° C in an electric furnace. At this time, the heating from room temperature to 800 ° C is performed at 160 ° C per hour, and then, after reaching 800 ° C, the heating is performed at 450 ° C per hour at 450 ° C, and immediately after reaching 1250 ° C at 450 ° C per hour. The cooling was performed at 800 ° C, and the above was set as one thermal cycle, and the thermal cycle of 800 ° C and 1250 ° C as the primary thermal cycle was repeated 40 times. After the final thermal cycle, it was cooled from 800 ° C to room temperature at 160 ° C per hour. The size of the sample was measured before and after the test, and the residual volume expansion ratio was determined from the dimensional change.

In this thermal cycle test, a high zirconia electroformed refractory usually exhibits a residual volume expansion and sometimes cracks. The residual volume expansion is obtained by a test using a refractory monomer for thermal cycling in a relatively low temperature region, and is separated from the molten glass when the refractory is applied to a glass melting furnace to be displayed as a relatively low temperature near the outer surface of the furnace. Crack resistance. The residual volume expansion ratio by the test is preferably less than 3% by volume, and more preferably less than 2% by volume.

[Zirconium crystal formation rate in thermal cycle test]

Further, there is also a refractory in which zirconium crystals are formed by the heat cycle test. Regarding the electroformed refractory subjected to the above thermal cycle test, the rate of formation of zirconium crystals was determined by a powder X-ray diffraction method. In other words, the powder obtained by pulverizing the sample after the test is subjected to X-ray diffraction measurement, and the peak area ratio of the zirconium crystal and the zirconia crystal is determined based on the diffraction pattern, and the amount of zirconium crystals/(zirconium crystal amount + oxidation) The mass % is determined by the ratio of the amount of zirconium crystals. This was set as the zirconium crystal formation rate in the heat cycle test. The zirconium crystal formation rate is preferably 4% by mass or less, and more preferably 2% by mass or less.

[Zirconium crystal formation rate in immersion test]

The zirconium crystal formation rate under the contact conditions with the molten glass was determined by the following immersion test. That is, a sample of 15 mm × 25 mm × 30 mm was cut from the obtained electroformed refractory, and inserted into a 200 cc white gold crucible together with 250 g of alkali-free cullet, and heated in an electric furnace at a specific temperature and for a specific time. After cooling, the sample is extracted and the sample is pulverized, and the pulverized sample powder is subjected to X-ray diffraction measurement, and the peak area ratio of the zirconium crystal and the zirconia crystal is determined according to the diffraction pattern thereof, and the amount of zirconium crystal is/ The ratio of the amount of zirconium crystals to the amount of zirconia crystals was determined by mass ratio, and this was set as the zirconium crystal formation rate in the immersion test.

The glass-based chemical composition used in this test is an alkali-free glass as shown below: SiO ₂ is 60% by mass, B ₂ O ₃ is 8% by mass, Al ₂ O ₃ is 17% by mass, MgO is 3% by mass, and CaO is 4% by mass and SrO were 8% by mass.

Further, the test conditions in the immersion test are as follows.

As the immersion test 1, the test was carried out at 1250 ° C for 20 days. At this time, the heating system from room temperature to 1250 ° C is set to 300 ° C per hour, after reaching 1250 ° C, the temperature is maintained for 20 days, and thereafter, it is cooled to 700 ° C at 500 ° C per hour, and further from 700 ° C to room temperature. Cooling at 60 ° C per hour is performed. In this test, the zirconium crystal formation rate is preferably 4 mass. % or less, more preferably 2% by mass or less.

As the immersion test 2, the test was carried out at 1450 ° C for 4 days. At this time, the heating system from room temperature to 1450 ° C is set to 300 ° C per hour, after reaching 1450 ° C, the temperature is maintained for 4 days, and thereafter, it is cooled to 700 ° C at 500 ° C per hour, and further from 700 ° C to room temperature. Cooling at 60 ° C per hour is performed. In this test, the zirconium crystal formation rate is preferably 4% by mass or less, and more preferably 2% by mass or less.

The results of the above tests are shown together in Tables 1 to 5.

According to Table 1, Table 2, and Table 4, it is clear that the crack of the high zirconia electroformed refractory of the present invention is not sufficiently 30 mm at the time of production, or is 70 mm or less even if cracks are present. Therefore, the high zirconia electroformed refractory of the present invention can be easily produced with high productivity.

The electroformed refractories of Examples 1 to 15 and Examples 23 to 25 of the examples were all less than 3 vol% in the residual volume expansion rate in the heat cycle test. Further, although not shown in the table, in all the examples in the test, cracks were not generated in the sample. It can be seen that the high zirconia electroformed refractory refractory monomer of the present invention has higher crack resistance with respect to temperature change.

The electroformed refractory of Examples 1, 3, 7-14, 23, and 25 did not detect zirconium crystals in the sample after the autothermal cycle test. According to this measurement method, when the value of the zirconium crystal formation rate is 0.5% by mass or more, the zirconium crystal can be detected, and therefore, the electroformed refractories of Examples 1, 3, 7 to 14, 23, and 25 are considered to be in the thermal cycle test. There is virtually no reaction to form zirconium crystals. Further, Examples 2, 4 to 6, 15, and 24 are components which suppress the formation of zirconium crystals, that is, Al ₂ O ₃ , K ₂ O, and Cs ₂ O, and components which promote the formation of zirconium crystals, that is, B ₂ O ₃ and P. _When the content of ₂ O ₅ is equalized, a composition in which only a small amount of zirconium crystal is formed is formed. Therefore, although a small amount of zirconium crystal is formed, the crystal formation ratio is 1.2% by mass or less, which is a range in which crack generation can be sufficiently suppressed. That is, the high zirconia electroformed refractory of the present invention can suppress the formation of zirconium crystals in the refractory monomer.

Zirconium crystal formation rate in the impregnation test 1 of the electroformed refractories of Examples 1 to 15, 23 to 25 It is 1.8% by mass or less. Further, in the immersion test 2 of the electroformed refractories of Examples 1 to 15 and 23 to 25, the zirconium crystal formation rate was also 2.0% by mass or less.

In both of the immersion test 1 and the test 2, the zirconium crystal formation rate of the refractories of Examples 1 to 15 and 23 to 25 is extremely low, and is 2.0% by mass or less, and it can be said that the high zirconia electroformed refractory of the present invention is even Zirconium crystals are also difficult to form under glass contact conditions.

That is, the high zirconia electroformed refractory of the present invention is a refractory having high durability, and the crack at the time of manufacture is not problematic, and the residual volume expansion ratio caused by thermal cycle in the refractory monomer is also When it is low, it is difficult to form zirconium crystals, and even under the contact condition of molten glass, the formation of zirconium crystals can be suppressed, and the productivity, temperature change at the time of use, and reusability are also excellent.

In Tables 3 and 5, a high zirconia electroformed refractory which does not conform to the present invention is shown as a comparative example.

In the refractories of Examples 16, 18 to 22, and Example 26, the crack at the time of production was 100 mm or more. Therefore, the refractories have no problem in terms of crack resistance with respect to temperature change in the refractory monomer, formation of zirconium crystals in the refractory monomer, and formation of zirconium crystal under glass contact conditions. There are problems with productivity. Regarding Examples 17, 27, and 28 in which the crack at the time of manufacture was less than 30 mm, there was a problem that zirconium crystals in the refractory monomer and zirconium crystals in the glass contact condition were easily generated as described below.

The residual volume expansion ratio in the heat cycle test of the refractories of Examples 21 and 22 was 3% by volume or more. That is, the crack resistance of the refractory monomer of the refractory with respect to temperature change is insufficient.

In the refractory materials of Examples 16, 17, 22, and 28, zirconium crystals of 4% by mass or more were detected based on the samples after the heat cycle test. That is, the refractories tend to form zirconium crystals in the refractory monomer.

The zirconium crystal formation rates in the immersion test 1 and the immersion test 2 of the refractories of Examples 16, 17, 22, 27, and 28 were all 5 mass% or more. That is, the refractory is easy to contact with the glass contact strip Zirconium crystals are formed under the pieces.

According to the above results, the high zirconia electroformed refractory of the present invention is excellent in productivity, and it is difficult to generate cracks when heat rises, and it is difficult to form zirconium crystals even when subjected to heat history in the refractory monomer, and even if it is melted. It is also difficult to form zirconium crystals by glass contact. Therefore, it is a high-zirconia electroformed refractory which is difficult to generate cracks even when the temperature is changed during use and the heat is lowered during operation, and has high durability and excellent reusability, and is particularly suitable. In the melting furnace of low alkali glass and alkali-free glass.

[Industrial availability]

The high zirconia electroformed refractory of the invention has excellent productivity, high durability and good reusability, prolongs the life of the glass melting furnace, reduces glass defects, stops the operation of the glass melting furnace and re-transports Turning becomes easy, so it is particularly suitable as a refractory for a glass melting furnace.

In addition, the entire contents of the specification, the scope of the patent application, and the abstract of the Japanese Patent Application No. 2012-087309, filed on Apr.

Claims (5)

A high zirconia electroformed refractory characterized by containing, as a chemical composition, ZrO ₂ of 87 to 96% by mass, SiO ₂ of 2.5 to 9.0% by mass, and Al ₂ O _{3 of} more than 1.5% by mass and more It is 2.5% by mass or less, Na ₂ O is 0.15 to 0.6% by mass, K ₂ O is 0.3 to 1.3% by mass, and the amount of Li ₂ O in other portions is 0 to 0.3% by mass. A high zirconia electroformed refractory characterized by having a chemical composition of: 87 to 96% by mass of ZrO ₂ , 2.5 to 9.0% by mass of SiO ₂ , and more than 1.5% by mass of Al ₂ O _{3 .} 2.5 mass% or less, Na ₂ O is 0.15 to 0.6 mass%, and K ₂ O is 0.3 to 1.3 mass%. A high zirconia electroformed refractory according to claim 1 or 2, which contains B ₂ O ₃ and P ₂ O ₅ , and the total amount of the other parts (B ₂ O ₃ + P ₂ O ₅ ) is The range of 0.4% by mass or less. The high zirconia electroformed refractory according to any one of claims 1 to 3, which further contains 0.05 to 3.8% by mass of Cs ₂ O in terms of the external portion. A high zirconia electroformed refractory according to any one of claims 1 to 4 for use in a glass melting furnace.