WO2016006531A1 - Fused-cast alumina-zirconia-silica refractory, glass melting furnace, and method for producing glass plate - Google Patents

Abstract

This invention provides a fused-cast alumina-zirconia-silica refractory that both suppresses the occurrence of stones in a glass and has high glass corrosion resistance. The fused-cast alumina-zirconia-silica refractory contains, as essential components, AI₂O₃, ZrO₂, SiO₂, and Na₂O, wherein, in mass percent on an oxide basis, Al₂O₃: 30-80%, ZrO₂: 15-50%, SiO₂: 2.0-10.5%, and Na₂O: 0.5-10% are contained. In this fused-cast alumina-zirconia-silica refractory, Al₂O₃/SiO₂≥6.5, Na₂O/SiO₂≥0.25, and the total amount of the essential components is 85% or more.

Description

Alumina / zirconia / silica fusion cast refractory, glass melting furnace, and method for producing glass plate

The present invention relates to an alumina / zirconia / silica fused cast refractory, a glass melting furnace, and a method for producing a glass plate, and particularly as a stone of badelite crystal in contact with molten glass in a temperature range of 1450 ° C. or lower. The present invention relates to an alumina / zirconia / silica fusion cast refractory capable of suppressing outflow, a glass melting furnace, and a method for producing a glass plate.

The molten cast refractory is usually obtained by pouring hot water in which a refractory raw material having a predetermined composition is completely melted in an electric furnace into a mold having a predetermined shape, and cooling and re-solidifying to normal temperature. The molten cast refractory obtained in this way is widely known as a highly erodible refractory that is completely different from the structure and manufacturing method of the fired and unfired bonded refractory.

Since the molten cast refractory obtained by the present invention is generally produced by casting a refractory raw material melted in an electric furnace into a desired shape, it will be described as a molten cast refractory hereinafter. However, the molten cast refractory in the present specification includes those that are solidified in the furnace after melting, and the molten cast refractory obtained by pulverizing the molten refractory is useful as an aggregate of the bonded refractory. .

As the alumina or zirconia molten cast refractories used in conventional glass melting furnaces, there are mainly fused cast refractories of high alumina, alumina / zirconia / silica, and high zirconia.

By the way, high-alumina melt-cast refractories have high erosion resistance against glass, do not cause defects such as bubbles and cords in glass, are stable against alkali vapor, and deform under load. There is nothing to do. However, since the content of alumina, which is lower in erosion resistance than zirconia, is larger, the erosion resistance is lower than in other molten cast refractories.

On the other hand, the alumina / zirconia / silica fused cast refractory contains a relatively large amount of zirconia as disclosed in, for example, Patent Document 1, and has a high erosion resistance against molten glass. Furthermore, a high zirconia molten cast refractory containing 90% or more of ZrO ₂ has also been proposed as described in Patent Document 2, and a molten cast refractory containing a large amount of zirconia is molten glass or scattered raw refractory. It has very high erosion resistance with respect to the batch, and is sufficiently satisfactory in terms of erosion resistance when used in a portion in direct contact with molten glass.

Among such molten cast refractories, refractories containing a relatively large amount of zirconia are preferably used for glass melting kilns because they are particularly excellent in erosion resistance. Typical refractory is a high zirconia fused cast refractories containing alumina-zirconia-silica fusion cast refractories containing ZrO ₂ 33% to 41% and a ZrO ₂ 80% to 95%.

Among them, high zirconia fused cast refractories with high zirconia content and high erosion resistance have high erosion resistance to glass and low probability of causing glass defects. It came to be used for. However, high zirconia melt cast refractories have a very high ZrO ₂ content, so such refractories are expensive and costly during production.

In contrast, alumina, zirconia, and siliceous molten cast refractories have been used most widely over decades because they have good erosion resistance and low manufacturing costs, and are mainly in contact with molten glass. It is also used for the zones to be used and for the superstructure of the glass melting furnace.

This alumina / zirconia / silica fused cast refractory generally consists of about 80-85% crystals and 15-20% matrix glass phase filling the crystal gaps. The crystal phase is composed of corundum crystals, which are trigonal crystals of alumina, and badelite crystals, which are monoclinic crystals of zirconia. The composition thereof is, for example, 45.8% to 52% of alumina / zirconia / silica fused cast refractories such as ZB1681, ZB1691, ZB1711 (above, trade name, manufactured by AGC Ceramics Co., Ltd.) currently available on the market. Al ₂ O ₃ , 33% to 41% ZrO ₂ , 12% to 13.5% SiO ₂ , and 1% to 1.9% Na ₂ O.

Here, the matrix glass is an amorphous glass phase having no specific crystal structure mainly composed of silica. As is well known, zirconia has a transformation transition due to monoclinic and tetragonal phase transitions at around 1150 ° C. when the temperature is raised and around 1000 ° C. when the temperature is lowered, and exhibits rapid contraction and expansion. . The matrix glass phase acts as a cushion between crystals, and absorbs stress due to transformation expansion due to the transition from tetragonal to monoclinic zirconia in the production of fused refractories of alumina, zirconia, and siliceous. Therefore, it plays an important role for producing an ingot without cracks.

However, since this matrix glass phase exists so as to surround the corundum crystal and the baderite crystal, the corundum crystal and the baderite crystal are not continuously connected, and therefore when used in a contact portion with the glass, There is a problem that the badelite crystals flow into the glass and cause stone defects. The reason for the specific outflow of badelite crystals than corundum crystals is that when contacted with glass, the corundum crystals dissolve faster than the badelite crystals, forming a fragile layer in which only the badelite crystals remain on the refractory surface. Because.

Since most of the beddelite particles in the remaining layer of this bedrite are present in the surface of the refractory in a suspended state in the glass, external forces such as changes in the convection of the molten glass and contact with bubbles in the molten glass are applied. It flows out into the glass as a stone.

In such an alumina / zirconia / silica fusion cast refractory, the above-mentioned badelite residual layer is formed, so that the outflow of stone from the alumina / zirconia / silica fusion cast refractory is suppressed. That is very difficult.

In recent years, particularly high-quality glass has been demanded, and the demand for suppression of defects has been increasing. Therefore, even in alumina / zirconia / silica fused cast refractories, the erosion resistance of refractories has been increased. There is a need for a refractory that can control the outflow of stone at the expense of a little.

Alumina / zirconia / silica fused cast refractories that suppress the occurrence of stone defects include alumina / zirconia / Al ₂ O ₃ / SiO ₂ ratio of 1 or less in Patent Document 3 containing 62% or more of ZrO _2. Siliceous fused cast refractories have been proposed. In the said refractory material, it is possible to suppress the cracking of the refractory material that occurs during production, and to reduce the wear rate and the amount of stone generated on the glass.

However, the alumina / zirconia / silica fused cast refractory of Patent Document 3 is expensive because of its high ZrO ₂ content, and it is difficult to use it widely as a general-purpose glass melting refractory.

In addition, in Patent Document 4, in the production of alumina / zirconia / silica fused cast refractories, by adding an oxidant such as tin oxide and sodium nitrate to the refractory raw material, the number of bubbles foamed upon contact with glass Low-alumina / zirconia / siliceous fusion cast refractories have been proposed. Although not described in the patent document, in the case of alumina / zirconia / silica fused cast refractories, it is easy to generate stones when bubbles come into contact with the remaining bedderite layer, so the generation of bubbles on the surface of the refractory is suppressed. There is a possibility that the amount of stone generated can be suppressed in the refractory to be tried.

However, in the alumina / zirconia / silica fusion cast refractory of Patent Document 4, the formation of the remaining bedderite layer is inevitable as before, and external forces such as changes in convection of glass and contact with bubbles in the molten glass are not avoided. It is thought that stone flows out into the glass by adding.

JP 62-065981 A Japanese Patent Laid-Open No. 3-028175 Japanese Patent Laid-Open No. 48-032408 Japanese Patent Laid-Open No. 10-072264

The present invention solves the problems of the prior art described above, suppresses the generation of stone in the glass, and also has high erosion resistance against the glass, and is suitable as a refractory for a glass manufacturing apparatus. An object of the present invention is to provide an alumina / zirconia / silica fused cast refractory and a glass melting furnace using the same.

As a result of intensive studies, the inventors of the present invention are alumina / zirconia / siliceous fusion cast refractories containing Al ₂ O ₃ , ZrO ₂ , SiO ₂ and Na ₂ O as essential components, and the content of the above essential components It was found that the above-mentioned problems could be solved by blending so as to be a predetermined amount, and the present invention was completed.

[1] Alumina / zirconia / siliceous fusion cast refractory containing Al ₂ O ₃ , ZrO ₂ , SiO ₂ and Na ₂ O as essential components, and having a mass percentage based on oxide, Al ₂ O ₃ : 30 % To 80%, ZrO ₂ : 15% to 50%, SiO ₂ : 2.0% to 10.5%, Na ₂ O: 0.5% to 10%, and Al ₂ O ₃ / SiO _{2 2} ≧ 6.5, Na ₂ O / SiO ₂ ≧ 0.25, and the total amount of the essential components is 85% or more, and is an alumina / zirconia / siliceous fused cast refractory.
[2] The alumina / zirconia / silica fusion cast refractory according to [1], wherein Al ₂ O ₃ / SiO ₂ ≦ 25.0.
[3] The alumina / zirconia / silica fusion cast refractory according to [1] or [2], wherein Na ₂ O / SiO ₂ ≦ 3.
[4] The alumina / zirconia / silica fusion cast refractory according to any one of [1] to [3], further comprising 0.8 to 5.0% of Y ₂ O ₃ .
[5] The alumina / zirconia / silica fused cast refractory according to any one of [1] to [4], further containing 0.1 to 3.0% of a total amount of K ₂ O and Li ₂ O.
[6] The alumina / zirconia / silica fusion cast refractory according to any one of [1] to [5], further containing CaO in an amount of 0.1% to 2.0%.
[7] The alumina / zirconia / silica fusion cast refractory according to any one of [1] to [6], wherein ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ) ≦ 0.39.
[8] The alumina / zirconia / siliceous molten cast refractory according to any one of [1] to [7], wherein 0.33 ≦ ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ).
[9] A glass melting furnace comprising the alumina / zirconia / siliceous fusion cast refractory according to any one of [1] to [8].
[10] The glass melting furnace according to [9], wherein the alumina / zirconia / silica fusion cast refractory is disposed in a region in contact with at least one of molten glass and gas released by melting the glass. .
[11] A method for producing a glass plate, comprising: heating a glass raw material in the glass melting furnace according to [9] or [10] to obtain molten glass, and forming the molten glass into a plate shape.

According to the alumina / zirconia / silica fusion cast refractory of the present invention, the occurrence of stones in the glass at the time of melting the glass is suppressed, and the glass has a high erosion resistance. An alumina / zirconia / siliceous fusion cast refractory suitable as a product can be provided.

In addition, according to the glass melting furnace of the present invention, since the generation of stones in the molten glass is suppressed and the glass has high erosion resistance, the glass can be stably melted, and the quality is improved. Good glass products can be manufactured with good yield.

Further, according to the method for producing glass of the present invention, the generation of stones in the molten glass is suppressed, the glass can be stably melted, and a glass having a good quality can be produced with a high yield.

Hereinafter, an embodiment of the present invention will be described in detail.
As described above, the alumina / zirconia / silica fusion cast refractory according to one embodiment of the present invention contains Al ₂ O ₃ , ZrO ₂ , SiO ₂ and Na ₂ O as essential components, and the content of these essential components Is characterized in that it is blended so as to have a predetermined amount. In the present specification, the molten cast refractory may be referred to as a refractory or an ingot.

When the molten soda lime glass comes into contact with the conventional alumina / zirconia / silica fused cast refractory, as described above, a vaderite residual layer in which the corundum crystals are dissolved is formed on the surface of the refractory, and this residual caderite is the stone. It becomes the source of

In addition, when molten soda-lime glass comes into contact with alumina, zirconia, or siliceous molten cast refractory, it depends on the environment of use. For example, the refractory used on the wall of the glass melting furnace in a low temperature range of about 1300 ° C. In, a nepheline layer is formed on the back side of the remaining beddelite layer. Further, in a static environmental field where the convection velocity of the glass is very low in a low temperature range of about 1300 ° C., for example, a nepheline layer may be formed on the surface side of the remaining badelite layer. Non-Patent Document 1 does not specify whether it is crystalline or glassy, but it is described that a nepheline layer is formed on the surface of the alumina / zirconia / silica fused cast refractory after use.

A nepheline crystal is a tridymite-based silica derivative compound having a stoichiometric composition of NaAlSiO ₄ , and is known to undergo a crystal transition to a cristobalite-based carnegiaite crystal in a high-temperature field exceeding 1254 ° C. Further, as described in Non-Patent Document 2, nepheline crystals maintain their crystal structures in a wide range of compositions, and the crystal transition temperature and melting point to carnegite crystals change. The crystal transition temperature and melting point are greatly affected by the composition.

Here, in this specification, the term “nepheline layer” means a nepheline crystal represented by a stoichiometric composition of NaAlSiO ₄ , a carnegiaite crystal that is a high-temperature form of nepheline, and a composition range in which the crystal structure is maintained. It includes all crystals and glass containing these crystals by melting (hereinafter also referred to as nepheline glass). The carnegite crystal is a crystal that is generated when the nepheline crystal undergoes a crystal transition in a high temperature field.

Note that the melting point of nepheline crystal or carnegite crystal varies greatly with the composition as described above. For example, as the content of SiO ₂ increases, the melting point of nepheline crystal or carnegite crystal decreases. For example, the nepheline crystal composition of Na ₂ Al ₂ Si ₃ O ₁₀ starts to partially melt at around 1120 ° C. and around 1330 ° C. Then it melts completely. Further, the melting point is further lowered by including impurities such as CaO, K ₂ O, Fe ₂ O ₃ in this crystal composition.

The term “nepheline-like glass” means a glass rich in Na ₂ O and Al ₂ O ₃ , and is not limited to a glass represented by the composition of NaAlSiO ₄ , for example, K ₂ O, CaO, MgO, etc. The impurities may be included. This nepheline glass is known to have a very high viscosity as compared with ordinary soda lime glass.

When the soda lime glass comes into contact with the alumina / zirconia / silica fused cast refractory, the above-mentioned nepheline layer is composed of Na ₂ O contained in the soda lime glass and Al ₂ O ₃ eluted from the refractory in the vicinity of the surface of the refractory. However, the present inventors have studied to use this nepheline layer positively to suppress stones.

That is, the nepheline layer is actively generated to the vicinity of the surface layer of the refractory during use of the refractory, and the condition where the residual beddelite is protected by the nepheline layer and the stone is prevented from falling off is completed. did.

If nepheline or carnegiaite crystals can be generated near the surface of the refractory during use of the refractory, the outflow of badelite as a stone is physically suppressed. At this time, as described above, the melting point of the nepheline crystal or the carnegite crystal varies greatly with the composition, so depending on the composition formed near the surface of the refractory and the operating temperature of the refractory, it is not always possible to use the It may not exist, and may exist as a molten highly viscous nepheline glass. However, even when a highly viscous nepheline glass is produced, the viscosity of the glass is so high that it is possible to suppress the fall of the stone.

That is, the alumina / zirconia / silica fusion cast refractory according to an embodiment of the present invention is a vitreous layer of a nepheline layer made of glass or a highly viscous glass, and actively uses the refractory in the vicinity of the surface layer of the refractory. And the remaining beddelite layer is protected by this nepheline layer, so that the stone can be prevented from falling off.

Hereinafter, each composition of the alumina / zirconia / siliceous fusion cast refractory according to an embodiment of the present invention will be described in detail.
Al ₂ O ₃ is an essential component in one embodiment of the present invention. Alumina constitutes a corundum crystal, and this corundum crystal has high erosion resistance and does not exhibit abnormal expansion and contraction due to temperature change. In addition to these characteristics, alumina is a component having an action of forming a nepheline layer near the surface of the refractory when the refractory comes into contact with the molten glass. Since this nepheline layer acts as a protective layer that suppresses the falling off of the stone, it is possible to suppress the amount of generated stone.

The Al ₂ O ₃ content is 30 to 80%. When the content of Al ₂ O ₃ is 80% or less, the content of ZrO ₂ becomes relatively low without being relatively low, and the erosion resistance is good. Moreover, it is difficult to produce mullite and it is easy to obtain an ingot without cracks. When the content of Al ₂ O ₃ is 30% or more, the content of ZrO ₂ is relatively high without becoming too high, and in this case as well, it becomes easy to obtain an ingot without cracks. The Al ₂ O ₃ content is preferably 40 to 75%, more preferably 50% to 70%, and even more preferably 55% to 65%. Unless otherwise indicated, all percentages in the present specification are mass percentages based on oxides.

ZrO ₂ is a component that constitutes a badelite crystal and enhances the erosion resistance of the refractory to the molten glass, and is an essential component in one embodiment of the present invention.

The ZrO ₂ content is 15 to 50%. ZrO ₂ is preferably contained in a large amount from the viewpoint of improving the erosion resistance. When the content is 15% or more, the erosion resistance is good. When the content of ZrO ₂ is 50% or less, in the range of the amount of matrix glass described later, expansion and contraction due to the phase transition of zirconia are alleviated, and an ingot without cracks is obtained. Moreover, when the content of ZrO ₂ with respect to the alumina content increases, primary zirconia tends to be generated, and the amount of stone generated tends to increase. The ZrO ₂ content is preferably 22 to 45%, more preferably 26% to 41%, and even more preferably 30% to 37%.

Here, eutectic zirconia is a small zirconia crystal that precipitates at the eutectic point at the end of cooling during the production of alumina, zirconia, and siliceous refractories by the melting method. On the other hand, primary zirconia is a large zirconia crystal that precipitates in the early stage of cooling. The distinction between the two can be easily distinguished by the size of the crystal by observing with a microscope. Moreover, when observed with a microscope, eutectic zirconia crystals are observed as a collection of fine crystals in corundum grains, and adjacent crystals are oriented in the same direction, but primary zirconia crystals are present. In the case of crystals, there is almost no directivity between adjacent crystals. In addition, eutectic zirconia crystals are formed in corundum with a series of fine zirconia crystals, whereas primary crystal zirconia has almost no connection between crystal grains. Furthermore, in terms of the crystal grain size, the crystal grain size of the eutectic zirconia crystal is about 1/5 or less of the maximum crystal grain size of the zirconia crystal.

SiO ₂ is a main component that forms the skeleton of the matrix glass, and is an essential component in one embodiment of the present invention. Its content is 2.0 to 10.5%. If it is 2.0% or more, the absolute amount of the matrix glass increases, and an ingot without cracks is easily obtained, and the obtained ingot exhibits a good structure. Further, if it is 10.5% or less, the content of Al ₂ O ₃ and ZrO ₂ which are relatively crystalline components is increased, the erosion resistance is improved, and the thickness of the residual bedderite is decreased. Reduces stone production. The content of SiO ₂ is preferably 3.5 to 8.5%, more preferably 4.5% to 7.5%, and even more preferably 5.0% to 7.0%.

Na ₂ O exhibits the action of controlling the viscosity of the matrix glass and the action of nephelinizing the matrix glass in the production of the alumina / zirconia / silica fused cast refractory, and is an essential component in one embodiment of the present invention as in the case of alumina. It is.

In the present invention, the content of Na ₂ O is 0.5 to 10%. By including Na ₂ O in a range that satisfies the above content, a nepheline layer can be formed near the surface of the refractory when the refractory comes into contact with the molten glass. Since this nepheline layer acts as a protective layer that suppresses the falling off of the stone, it is possible to suppress the amount of generated stone.

When the content of Na ₂ O is 10% or less, the content of corundum crystals and zirconia crystals is relatively increased, so that the erosion resistance is improved. Moreover, when it is 0.5% or more, the melting point of the nepheline layer formed in the vicinity of the refractory surface when immersed in glass is increased, and the effect as a protective layer for suppressing the fall of the stone is increased. Moreover, the production | generation of a mullite is suppressed and an ingot without a crack is easy to be obtained. The content of Na ₂ O is preferably 0.9 to 5%, more preferably 1.6% to 4.0%, and even more preferably 1.9% to 3.5%.

Y ₂ O ₃ is not an essential component, but Y ₂ O ₃ has the effect of stabilizing part or all of ZrO ₂ into cubic crystals. Therefore, when using a refractory, zirconia is generated when the temperature is increased. The shrinkage and expansion due to the phase transition can be alleviated. For this reason, at the time of refractory use, it becomes possible to suppress the opening of the joint between refractories, and it becomes possible to improve erosion resistance and to suppress the amount of stone formation.

When Y ₂ O ₃ ≧ 0.8%, the effect of relaxation of expansion and shrinkage due to the phase transition of the zirconia is increased, and when Y ₂ O ₃ ≦ 5%, the content of Y ₂ O ₃ is small, so that the cost is low. It is easy to use widely as a typical glass melting refractory. The content of Y ₂ O ₃ is preferably 0.8 to 5.0%. The content of Y ₂ O ₃ is preferably 1.0 to 4.0%, more preferably 1.3 to 3.0%, further preferably 1.5 to 2.7%, and 1.7 to 2%. .4% is particularly preferred.

Y ₂ O ₃ may be used in combination with a component containing at least one member of the group consisting of CeO ₂ , MgO, Sc ₂ O ₃ and V ₂ O ₅ , or may be replaced by a combination of these components alone or in combination. May be.

K ₂ O and Li ₂ O are not essential components, but are components that have an effect of adjusting the viscosity of the matrix glass and the high-temperature viscosity of the nepheline layer. These K ₂ O and Li ₂ O are preferably contained in a total content of 0.1% to 3.0%. K ₂ O and Li ₂ O in the total amount the production of low-viscosity matrix glass and 3.0% or less can be suppressed.

CaO is not an essential component, but is a component that exhibits an effect of adjusting the viscosity of the matrix glass and the high temperature viscosity of the nepheline layer. This CaO is preferably contained in the range of 0.1% to 2.0%. When the total amount of CaO is 2.0% or less, the formation of low-viscosity matrix glass is suppressed. Further, the zirconia crystals are not dissolved, and the erosion resistance of the product is improved.

In the alumina / zirconia / silica fusion cast refractory according to an embodiment of the present invention, the total amount of essential components of Al ₂ O ₃ + ZrO ₂ + SiO ₂ + Na ₂ O contained in the refractory is 85% or more. To do. This is because if the refractory contains too many other components, the content of Al ₂ O ₃ and ZrO ₂ decreases, the erosion resistance to the glass decreases, and the amount of stone generated increases. It is because it will do. In order to improve the erosion resistance, the total amount of Al ₂ O ₃ + ZrO ₂ + SiO ₂ + Na ₂ O is preferably 90% or more, more preferably 95% or more, further preferably 98% or more, and 99% The above is particularly preferable.

Further, in the alumina-zirconia-silica fusion cast refractory according to an embodiment of the present invention, the content of _Al 2 _{O 3} and Na ₂ O with respect to _{SiO 2 Al 2 O 3 / SiO} 2 ≧ 6.5, Na ₂ O / SiO ₂ ≧ 0.25.

As described above, the content of Al ₂ O ₃ , ZrO ₂ , SiO ₂ , and Na ₂ O in the refractory is set within a predetermined range, and further, the relationship between the amounts of these components is set as a predetermined relationship. Thus, an alumina / zirconia / silica fused cast refractory material that suppresses the generation of stones and has high erosion resistance to glass can be obtained.

In _{SiO 2, Al 2 O 3,} Na 2 O is an essential component, the content of _Al 2 _{O 3} and Na ₂ O with respect to _{SiO 2, Al 2 O 3 /} SiO 2 ≧ 6.5 respectively, _Na 2 O / The reason for limiting to the range of SiO ₂ ≧ 0.25 will be described in more detail.

The nepheline crystal is a compound having a stoichiometric composition of NaAlSiO ₄ . When refractory comes into contact with soda lime glass, nepheline crystals and carnegite crystals are actively produced in the vicinity of the surface of the refractory. It is necessary to positively supply Al ₂ O ₃ not contained in the refractory from the inside. That is, as the Al ₂ O ₃ content in the refractory is increased, a nepheline layer is more likely to be generated near the surface layer of the refractory.

Whether or not a nepheline layer can be generated near the surface of the refractory and the amount of generated stones can be suppressed depends on the amount of zirconia contained in the refractory, the ZrO ₂ / (ZrO ₂ + Al ₂ O ₃ ) ratio, and Na ₂ O / SiO. Also affected by ₂ ratios. However, the inclusion of Al ₂ O ₃ in the range of Al ₂ O ₃ / SiO ₂ ≧ 6.5 has a particularly large influence. Under such conditions, a protective layer made of a nepheline layer is placed near the refractory surface layer. It can be formed effectively, and the generation amount of stone can be suppressed.

In view of the above, the content of _Al 2 _{O 3} with respect to SiO ₂ in the alumina-zirconia-silica fusion cast refractories is _{Al 2 O 3 / SiO 2 ≧} 6.5. The content ratio is preferably Al ₂ O ₃ / SiO ₂ ≧ 8.0, more preferably Al ₂ O ₃ / SiO ₂ ≧ 9.0, and further preferably Al ₂ O ₃ / SiO ₂ ≧ 10.0.

In addition, the nepheline crystal has a melting point of 1526 ° C. ± 2 ° C. in the case of the stoichiometric composition as described above, but the composition of nepheline generated in the vicinity of the surface of the refractory by contact with glass is the stoichiometric composition. a low compositional a content of Na 2 _O than, the melting point is greatly reduced in such nepheline crystals. When a conventional alumina / zirconia / silica fusion cast refractory is used, it starts to partially melt at approximately 1100 ° C. to 1400 ° C., depending on the use environment. When the melting point of nepheline is low, the heat resistance of the refractory is lowered, and the protective effect of the nepheline layer is reduced.

Therefore, by generating a nepheline layer having a high Na ₂ O content in the vicinity of the refractory surface layer, it becomes possible to suppress the generation amount of stones to a higher temperature range. The nepheline layer is generated by supplying Na ₂ O from molten soda lime glass, but the Na ₂ O content in the refractory is increased as in the present invention, and Na ₂ O is also added from the refractory side. Is supplied, the melting point of the nepheline layer formed near the surface of the refractory is improved (increased).

The melting point of the nepheline layer to be generated is affected by the amount of zirconia, the ratio of ZrO ₂ / (ZrO ₂ + Al ₂ O ₃ ), the ratio of Al ₂ O ₃ / SiO _{2, and the} like. However, the inclusion of Na ₂ O in the range of Na ₂ O / SiO ₂ ≧ 0.25 has a particularly great influence. When such conditions are used, a protective layer composed of a nepheline layer can be formed into a refractory to a higher temperature range. It can be formed in the vicinity of the surface layer, and the generation amount of stone can be suppressed. In the production of refractory, nepheline is partially generated in the matrix glass having a high Na ₂ O concentration in the range of 0.25 ≦ Na ₂ O / SiO ₂ <0.40, and 0.40 In the range of ≦ Na ₂ O / SiO ₂ , the matrix glass becomes substantially all nepheline.

In view of the above, the content of Na ₂ O with respect to SiO ₂ in the alumina-zirconia-silica fusion cast refractories are _{Na 2 O / SiO 2 ≧ 0.25} . Na ₂ O / SiO ₂ ≧ 0.29 is preferable, Na ₂ O / SiO ₂ ≧ 0.35 is more preferable, and Na ₂ O / SiO ₂ ≧ 0.40 is still more preferable. With such a blending amount, it is possible to obtain an alumina / zirconia / silica fused cast refractory that suppresses the generation of stones in the glass and also has high erosion resistance against the glass.

In the alumina-zirconia-silica fusion cast refractory according to an embodiment of the present invention, nepheline quality content of Na 2 _O with respect to content and SiO ₂ to Al ₂ O ₃ with respect to SiO ₂ is higher up hotter zone A protective layer consisting of layers can be formed near the surface of the refractory and it is possible to reduce the amount of stones generated, but on the other hand, the cause is not clear, but cracks in the ingot tend to occur easily It is in.

Therefore, the content ratio of Al ₂ O ₃ with respect to SiO ₂ in the alumina / zirconia / silica fusion cast refractory according to one embodiment of the present invention is preferably Al ₂ O ₃ / SiO ₂ ≦ 25. Al ₂ O ₃ / SiO ₂ ≦ 20 is more preferable, Al ₂ O ₃ / SiO ₂ ≦ 15 is more preferable, and Al ₂ O ₃ / SiO ₂ ≦ 12 is particularly preferable.

Further, the content of Na ₂ O with respect to SiO ₂ in the alumina-zirconia-silica fusion cast refractories is preferably _{Na 2 O / SiO 2 ≦ 3} . Na ₂ O / SiO ₂ ≦ 2 is more preferable, Na ₂ O / SiO ₂ ≦ 1 is more preferable, and Na ₂ O / SiO ₂ ≦ 0.5 is particularly preferable.

The alumina / zirconia / siliceous fusion cast refractory according to an embodiment of the present invention may include hafnium oxide HfO ₂ naturally present in a zirconia source. The content of the refractory of the present invention is 5% or less, and generally 2% or less. Conventionally, the term “ZrO ₂ ” means zirconia and trace amounts of hafnium oxide contained therein.

The other components are not particularly limited as long as they do not impair the characteristics of the alumina / zirconia / silica fusion cast refractory according to one embodiment of the present invention, and the alumina / zirconia / silica fusion The well-known component used for a cast refractory is mentioned. Examples of other components include oxides such as SnO ₂ , ZnO, CuO, MnO ₂ , Cr ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₅ , As ₂ O ₅ , and Yb ₂ O ₃ . When these components are contained, the total amount is preferably 10% or less, preferably 3% or less, and more preferably 1% or less.

In addition, the amount of stone generated is affected by the Al ₂ O ₃ / SiO ₂ ratio, Na ₂ O / SiO ₂ ratio, ZrO ₂ content, etc. In order to further reduce the amount of stone generated, zirconia and The ratio of zirconia to alumina is preferably ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ) ≦ 0.39. This is because primary crystal zirconia is not continuous with crystal particles, and primary crystal zirconia is more likely to fall out as stone than eutectic zirconia. This is because the amount of primary zirconia produced can be reduced. Further, it is preferable that _{0.33 ≦ ZrO 2 / (Al 2} O 3 + ZrO 2). This is because when ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ) is 0.33 or more, the production amount of primary crystals of alumina does not increase, and eutectic zirconia is segregated around primary crystal alumina. This is because the eutectic zirconia is easily entangled in the remaining bedderite layer, and it is difficult to fall off as a stone. 0.35 ≦ ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ) is more preferable.

Alumina-zirconia-silica melt cast refractory according to an embodiment of the present invention is a component present in the starting material used or produced during the manufacture of the product, i.e. halogens such as fluorine, chlorine, Magnesium, boron, titanium, and iron may be contained as impurities, but these impurities are preferable because they reduce the erosion resistance.

Here, the term “impurity” means an unavoidable composition that is inevitably incorporated in the starting material or due to the reaction of these compositions. In particular, iron or titanium oxides are harmful and their content must be limited to the traces incorporated into the starting material as impurities. In particular, the mass of Fe ₂ O ₃ + TiO ₂ is preferably 1% or less, and more preferably less than 0.5%.

When the alumina / zirconia / silica fusion cast refractory according to an embodiment of the present invention is configured to contain such a predetermined amount of components, for example, when immersed in soda lime glass at 1300 ° C. In addition, a protective layer composed of a nepheline layer can be formed in the vicinity of the surface layer of the refractory, and the amount of stone generated can be suppressed.

Here, the amount of stone generated is determined by directly observing the amount of stone falling from the surface of the refractory by observing the cross section of the refractory with an optical microscope (Nikon Corporation, ECLIPSE LV100) after performing an erosion test. Can be evaluated. In this specification, the amount of generated stone is evaluated by a sample in which a predetermined shear rate is given after immersion in glass at 1300 ° C. for 20 days (480 hours). This result is compared with the result of the same test in the alumina / zirconia / silica fusion cast refractory (AGC Ceramics Co., Ltd., trade name: ZB-1691) that is widely used in glass manufacturing equipment. % Or less refractory is preferred. The generation amount of stone is more preferably 80% or less, further preferably 70% or less, and particularly preferably 60% or less.

The shape, size, and mass of the alumina / zirconia / silica fusion cast refractory according to an embodiment of the present invention are not limited. For example, it may be in the form of a slab having a thickness of 100 mm or less. Preferably, the block or slab forms part of a glass melting furnace or constitutes a wall or hearth. At this time, if the block or slab is disposed in a region in contact with the molten glass or in contact with the gas released from the molten glass, the effect of suppressing the generation of stone as described above is preferable. .

The alumina / zirconia / silica fusion cast refractory according to an embodiment of the present invention is, for example, alumina / zirconia widely used in a glass manufacturing apparatus when the amount of generated stone is tested as described above.・ Compared to siliceous molten cast refractory (manufactured by AGC Ceramics, trade name: ZB-1691), the amount of generated stone is 90% or less, and the erosion rate for glass is 115% or less (the relative erosion amount is 115). (Synonymous with the following). Here, the erosion resistance is determined by, for example, immersing the glass at 1300 ° C. for 480 hours in the same manner as the measurement of the amount of generated stone, and measuring the maximum erosion depth in the flux line. This result is evaluated by comparing with the result of the same test in an alumina / zirconia / silica fusion cast refractory (manufactured by AGC Ceramics, trade name: ZB-1691). That is, erosion resistance is preferably a refractory having a relative erosion amount with ZB-1691 of 115 or less, more preferably 105 or less, and even more preferably 95 or less.

The protective layer made of a nepheline layer is difficult to form near the surface of the refractory in an environment where the convection speed of the glass is very high. Therefore, depending on the environment of use, it is difficult to generate a protective layer consisting of a nepheline layer near the refractory surface layer in the flux line where strong convection called Marangonin convection occurs, which improves erosion resistance. The contribution is limited. Therefore, the erosion resistance of the flux line is basically strongly influenced by the zirconia content.

In a region other than the flux line, the use of the alumina / zirconia / silica fusion cast refractory of the present invention makes it possible to sufficiently generate a protective layer composed of a nepheline layer up to the vicinity of the refractory surface layer. Therefore, the amount of generated stones can be effectively reduced.

The alumina / zirconia / silica fusion cast refractory according to an embodiment of the present invention is obtained by mixing homogeneously powder raw materials so as to have the above-mentioned blending ratio, melting the mixture in an arc electric furnace, and converting the molten raw material into graphite. It is manufactured by pouring into a mold and cooling. This refractory is expensive because it takes a large amount of energy when melted, but the structure of the ZrO ₂ crystal is dense and the size of the crystal is large. Therefore, the refractory has better corrosion resistance stability than the sintered refractory. In addition, the heating at the time of melting is performed by bringing a graphite electrode and raw material powder into contact with each other and energizing the electrode. The thus obtained alumina / zirconia / silica fusion cast refractory according to one embodiment of the present invention exhibits excellent erosion resistance against molten glass, and is used when producing glass products such as plate glass. It is suitable for furnace materials for glass melting kilns.

A glass melting furnace according to an embodiment of the present invention comprises the above-described alumina / zirconia / silica melting cast refractory according to an embodiment of the present invention. If it is a glass melting furnace equipped with the above-described alumina / zirconia / siliceous molten cast refractory according to one embodiment of the present invention, the generation of stones in the molten glass is suppressed, and the glass has a high erosion resistance. Therefore, the glass can be stably melted, and a glass product with good quality can be manufactured with a high yield. The above-described alumina / zirconia / siliceous fusion cast refractory according to one embodiment of the present invention is preferably used in a place where it comes into contact with glass.

A glass melting kiln according to an embodiment of the present invention is the above-described alumina / zirconia / silica molten cast refractory according to an embodiment of the present invention. You may arrange | position in the area | region which contacts one side. If it is a glass melting kiln using the alumina, zirconia, siliceous molten cast refractory according to one embodiment of the present invention, it suppresses the generation of stones in the molten glass and has high erosion resistance to glass. Therefore, glass can be stably melted even if it is disposed in the region in contact with the molten glass, and a glass product with good quality can be manufactured with a high yield. In a glass melting furnace, a gas containing Na or K is generated from molten glass or glass melting. When the refractory is a glass melting kiln made of quartz brick, the refractory is lowered in melting point and easily deformed by these gases. If it is a glass melting kiln using an alumina / zirconia / siliceous fusion cast refractory according to an embodiment of the present invention, it contains high heat-resistant ZrO ₂ and has an Al ₂ O ₃ / SiO ₂ ratio of Since it is difficult to be deformed due to a small number of matrix glass portions that are high and easily melted, even if it is disposed in a region that is in contact with gas released by melting glass, it can have high heat resistance.

Next, the manufacturing method of the glass plate which concerns on one Embodiment of this invention is demonstrated.
The manufacturing method of the glass plate which concerns on one Embodiment of this invention heats a glass raw material in the glass melting furnace which concerns on one Embodiment of this invention mentioned above, obtains molten glass, and shape | molds the said molten glass in plate shape. Is.

In the method for producing a glass plate according to an embodiment of the present invention, first, the raw material prepared so as to have the composition of the obtained glass plate is charged into the glass melting furnace according to the embodiment of the present invention, preferably Heat to about 1400-1650 ° C. to obtain molten glass.
Etc. may be used SO ₃ and SnO ₂ as a fining agent to the raw material. Bubbles can be removed from the glass by using a fining agent. Further, a defoaming method using reduced pressure may be applied.
Next, in the glass plate manufacturing method according to an embodiment of the present invention, the molten glass is formed into a plate shape by a fusion method, a float method, a press molding method, or the like. For example, in the float process, molten glass is flowed over molten metal and formed into a plate shape.
In the manufacturing method of the glass plate which concerns on one Embodiment of this invention, it is preferable to cool slowly the glass plate shape | molded in plate shape. The gradually cooled glass plate is cut into a desired shape.

According to the manufacturing method of the glass plate which concerns on one Embodiment of this invention, in order to obtain a molten glass by heating a glass raw material in the glass melting furnace which concerns on one embodiment of this invention mentioned above, Generation | occurrence | production is suppressed, glass can be fuse | melted stably and a glass with favorable quality can be manufactured with a sufficient yield.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not construed as being limited to these descriptions. In particular, the refractory of the present invention is not limited to a specific shape or dimension, and is not limited to application to a glass melting furnace.

(Example 1 to Example 42)
ZrO ₂ raw materials such as desiliconized zirconia and zircon sand, Al ₂ O ₃ raw materials such as Bayer alumina, SiO ₂ raw materials such as silica sand, Na ₂ O, Y ₂ O ₃ , Li ₂ O, K ₂ O, CaO, MgO, A batch mixture in which raw materials such as Cr ₂ O ₃ , P ₂ O ₅ , and B ₂ O ₅ were adjusted to a predetermined amount was charged into a 500 KVA single-phase arc electric furnace and completely melted at a melting temperature of around 1900 ° C. did.

The hot water obtained by melting is poured into a mold made of sand surrounded by a heat insulating material made of siliceous hollow spheres or Bayer alumina around an inner volume of 130 mm x 160 mm x 350 mm, and cast to room temperature. Chilled. In the same way as the conventional method, melting is a so-called long arc method in which the electrode is lifted from the molten metal surface. For example, oxygen is blown in the middle of melting to keep the melt in an oxidized state as much as possible. I got a thing.

Tables 1 to 5 show the chemical analysis values (unit: mass%) and various properties of the obtained molten cast refractories. Examples 1-27 are examples, and examples 28-42 are comparative examples. Examples 28 and 29 are alumina, zirconia, and siliceous fused cast refractories widely used in glass production apparatuses (manufactured by AGC Ceramics, trade names: ZB1691 and ZB1711).

Regarding the chemical composition in the molten cast refractory, ZrO ₂ , SiO ₂ , and Al ₂ O ₃ are quantitative analysis values determined by a wavelength dispersive X-ray fluorescence analyzer (manufactured by Rigaku Corporation, apparatus name: ZSX Primus II). The other components are quantitative analysis values determined by a high-frequency inductively coupled plasma emission spectrometer (manufactured by Seiko Instruments Inc., apparatus name: SPS 1100). However, the quantification of each component is not limited to this analysis method, and can be carried out by other quantitative analysis methods.

The obtained molten cast refractories all had (A) corundum crystal, (B) badelite crystal, and (C) matrix glass and / or nepheline crystal as a basic structure. The type and presence of the crystal is determined by cutting the molten cast refractory after manufacture and cutting the cut surface with SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Detector, manufactured by Hitachi High-Technologies Corporation, product name: S-3000H ), And the crystal structure was analyzed by XRD (X-ray Diffraction, manufactured by Rigaku Corporation, trade name: RINT-TTRIII).

The presence or absence of cracks on the appearance of the manufactured molten cast refractory was evaluated as follows. First, visually inspect the presence or absence of cracks. For refractories with cracks, grind the surface of the refractory to a depth of 10 mm on each surface, cut the resulting refractory from the center, and observe the cut surface. The crack length was evaluated. When the crack length in the refractory after grinding becomes 10 mm or less, the crack at the time of manufacture is “small”, and when the crack length exceeds 10 mm and is 50 mm or less, the crack at the time of manufacture is “medium”. When the crack length exceeded 50 mm, the crack at the time of manufacture was classified as “large”.

If there is no crack at the time of production, there will be no problem in the production of refractories. Moreover, if the crack at the time of manufacture is below the inside, manufacture of a refractory is easy since it is only necessary to manufacture an ingot slightly larger than the required refractory size and to perform light grinding on the surface. On the other hand, if the crack at the time of manufacture is large, it is necessary to manufacture a very large refractory (ingot) with respect to the required refractory dimensions, and then severe grinding or cutting is required. The cost of manufacturing is very unrealistic.

In addition, the stone formation characteristics of the manufactured molten cast refractories were evaluated as follows. A test piece of 15 mm × 25 mm × 50 mm (length × width × length) was cut out from the refractory and immersed in soda lime glass (Asahi Glass Co., Ltd., trade name: Clear FL) at 1300 ° C. for 480 hours in an air atmosphere. Thereafter, the test piece was drawn upward at a shear rate of 0.8 / s, held for 5 minutes, and then cooled at a rate of 300 ° C./Hr. After cooling, the test piece covered with glass was cut in half from the center, the cross-section was observed with an optical microscope, and the number of stones that fell from the refractory surface layer to the glass side was counted.

Also, the erosion resistance was evaluated as follows. A 15 mm x 25 mm x 50 mm (length x width x length) test piece was cut from the refractory and immersed in soda lime glass (Asahi Glass Co., Ltd., trade name: Clear-FL) at 1300 ° C in air for 480 hours. Thereafter, the amount of erosion was measured to examine the erosion resistance.

Stone formation amount and erosion resistance are known alumina / zirconia / silica fusion cast refractories widely used in glass manufacturing equipment in the temperature range of 1300 ° C. (trade name: ZB-1691, manufactured by AGC Ceramics) In comparison with Example 28, the stone generation amount of this ZB-1691 (Example 28) or the maximum erosion depth of the erosion part after the erosion test was taken as 100, and the relative stone generation amount and erosion amount were shown.

It is preferable that the amount of generated stone is small, but if the amount of generated relative to ZB-1691 is 90 or less, the stone generation characteristics are sufficiently improved than before, which is satisfactory.

It is preferable that the amount of erosion is small, but in recent years, for example, by placing another alumina, zirconia, siliceous fused cast refractory outside the alumina, zirconia, siliceous fused cast refractory used in the kiln, Since it is possible to extend the life of the melting furnace, the erosion resistance is not necessarily high. Therefore, practically, the erosion resistance is satisfactory when the relative erosion amount with ZB-1691 is 115 or less.

Examples 28 and 29 are alumina / zirconia / siliceous fused cast refractories having a known composition, and are refractories having a small composition of Al ₂ O ₃ / SiO ₂ and Na ₂ O / SiO ₂ . Although the erosion resistance to the glass is almost the same as in Examples 1 to 27, the amount of stones generated is large due to the lack of the formation component of the nepheline layer.

Example 30 is an alumina / zirconia / silica fused cast refractory with a reduced Na ₂ O / SiO ₂ composition, and the erosion resistance to glass is almost the same as in Examples 1 to 27, but a nepheline layer is formed. Due to the lack of ingredients, the amount of stone generated is large.

Example 31 is alumina-zirconia-silica fusion cast refractory composition with a reduced content of ZrO _2, very corrosion resistance against glass to ZrO ₂ content is small as compared with Examples 1-27 Low.

Example 32 is alumina-zirconia-silica fusion cast refractory compositions that many ZrO ₂ content is high in corrosion resistance to glass, is very large cracks during production for ZrO ₂ content is high .

Examples 33 and 34 are alumina / zirconia / silica fusion cast refractories with a reduced SiO ₂ content, and although the amount of stones generated is small, cracks during production are very large due to the low SiO ₂ content. .

Example 35 is an alumina / zirconia / silica fusion cast refractory having a composition with an increased SiO ₂ content. Since the SiO ₂ content is large, the erosion resistance is low and the amount of generated stones is large.

Example 36 is an alumina / zirconia / siliceous fusion cast refractory with a reduced Na ₂ O content, has low erosion resistance, a large amount of stones, and very large cracks during production.

Example 37 is an alumina / zirconia / siliceous fusion cast refractory having a composition with an increased Na ₂ O content. Since the amount of generated stone is large and the content of Na ₂ O is large, the erosion resistance is very high. Low.

Example 38 is an alumina / zirconia / siliceous fused cast refractory having a composition with a _high Al ₂ O ₃ content. Although the amount of stones generated is small, cracks during production are very large.

Examples 39 and 40 are alumina / zirconia / silica fused cast refractories with a reduced Al ₂ O ₃ content, which have high erosion resistance but a large amount of stones generated, resulting in very high cracks during production. Big.

Examples 41 and 42 are alumina / zirconia / silica fused cast refractories having a composition with an essential component content of less than 85%, because the contents of Al ₂ O ₃ and ZrO _{2 in} the refractories are small. , Low erosion resistance to glass and a large amount of stones.

On the other hand, Examples 1 to 27, which are examples of the present invention, are alumina / zirconia / silica fused cast refractories containing a predetermined amount of components. Compared with Examples 28 to 42, the amount of generated stones and corrosion resistance And the manufacturing characteristics are good results. More specifically, compared to conventional alumina / zirconia / silica fused cast refractories, the amount of stone produced is small, and the erosion resistance is at a level that is practically satisfactory, and there are no cracks during production. Even if there is, it is less than medium.

Example 2, Example 5, Example 6, Examples 8-12, Example 14, Example 16, Examples 18-24, and Examples 25-27 are relatively large in Al ₂ O ₃ / SiO ₂ and Na ₂ O / SiO _2. Alumina / zirconia / siliceous fusion cast refractory having the composition described above, and the amount of stone produced is small. In addition, it has good corrosion resistance, and cracks during production are also moderate or less. In particular, Example 5, Example 14, Example 14 and Example 19 have a particularly small amount of stone because ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ) is in a more preferable range.

Examples 1 and 17 are alumina / zirconia / silica fused cast refractories having a composition in which Al ₂ O ₃ / SiO ₂ is relatively small within the scope of the present invention, and the effect of suppressing generation of stone is maintained. It has good corrosion resistance and few manufacturing cracks.

Example 3 is an alumina / zirconia / silica fused cast refractory having a composition in which Na ₂ O / SiO ₂ is relatively small within the scope of the present invention, the effect of suppressing the occurrence of stones is maintained, and the corrosion resistance is high. Good and few manufacturing cracks.

Examples 4 and 15 are large Al ₂ O ₃ / SiO ₂ and Na ₂ O / SiO ₂ alumina / zirconia / silica fusion cast refractories, with large ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ). However, the effect of suppressing the generation of stones is maintained, the corrosion resistance is good, and there are few manufacturing cracks.

Example 7 is an alumina / zirconia / silica fused cast refractory having a composition in which Al ₂ O ₃ / SiO ₂ and Na ₂ O / SiO ₂ are relatively small within the scope of the present invention, and suppresses the occurrence of stones. Is maintained, corrosion resistance is good, and there are few manufacturing cracks.

Example 13 is an alumina / zirconia / siliceous fusion cast refractory having a composition in which Al ₂ O ₃ / SiO ₂ is relatively small within the scope of the present invention. Is good and there are few manufacturing cracks.

In the melting kiln comprising the alumina / zirconia / siliceous molten cast refractory of Examples 1 to 27, the generation of stones in the molten glass is suppressed. In addition, since the glass has high erosion resistance, the glass can be stably melted, and a glass product with good quality can be manufactured with high yield.

Since the alumina / zirconia / siliceous fusion cast refractory of the present invention suppresses the occurrence of stones in the glass, and also has high erosion resistance against the glass, it can be easily manufactured with high productivity. Suitable as a refractory for a glass melting furnace.

Claims (11)

1. Alumina / zirconia / siliceous fusion cast refractory containing Al ₂ O ₃ , ZrO ₂ , SiO ₂ and Na ₂ O as essential components, wherein Al ₂ O ₃ : 30% to 80% in mass percentage based on oxide ,
   ZrO ₂ : 15% to 50%,
   SiO ₂ : 2.0% to 10.5%,
   Na ₂ O: 0.5% to 10%,
   And Al ₂ O ₃ / SiO ₂ ≧ 6.5,
   Na ₂ O / SiO ₂ ≧ 0.25,
   And
   Alumina / zirconia / silica fused cast refractory, wherein the total amount of the essential components is 85% or more.
2. The alumina / zirconia / siliceous fused cast refractory according to claim 1, wherein Al ₂ O ₃ / SiO ₂ ≦ 25.0.
3. 3. The alumina / zirconia / silica fused cast refractory according to claim 1 or 2, wherein Na ₂ O / SiO ₂ ≦ 3.
4. 4. The alumina / zirconia / siliceous fusion cast refractory according to claim 1, further comprising 0.8 to 5.0% of Y ₂ O ₃ .
5. The alumina / zirconia / silica fused cast refractory according to any one of claims 1 to 4, further comprising a total amount of K ₂ O and Li ₂ O of 0.1 to 3.0%.
6. 6. The alumina / zirconia / silica fusion cast refractory according to claim 1, further comprising CaO in an amount of 0.1% to 2.0%.
7. The alumina / zirconia / siliceous molten cast refractory according to claim 1, wherein ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ) ≦ 0.39.
8. The alumina / zirconia / siliceous molten cast refractory according to claim 1, wherein 0.33 ≦ ZrO ₂ / (Al ₂ O ₃ + ZrO ₂ ).
9. A glass melting furnace comprising the alumina / zirconia / siliceous fusion cast refractory according to any one of claims 1 to 8.
10. 10. The glass melting furnace according to claim 9, wherein the alumina / zirconia / silica molten cast refractory is disposed in a region in contact with at least one of molten glass and a gas released by melting the glass.
11. A glass raw material is heated in the glass melting furnace according to claim 9 or 10 to obtain a molten glass,
    A method for producing a glass plate, comprising molding the molten glass into a plate shape.