JP7099898B2 - High zirconia electroformed refractory and its manufacturing method - Google Patents

Description

The present invention relates to a high zirconia electric casting refractory and a method for producing the same, and more particularly to a high zirconia electric casting refractory suitable for use in a glass melting furnace which is a glass manufacturing kiln and a method for producing the same.

A high zirconia electroformed refractory containing 80% by mass or more of ZrO ₂ as a chemical component has been conventionally used as a refractory for a glass melting furnace. High zirconia electrocast refractories have high corrosion resistance and low contamination resistance to molten glass, and are often used in parts that come into contact with molten glass in glass melting furnaces. Such high zirconia electroformed refractories are composed of a large amount of zirconia crystal grains and a small amount of matrix glass that fills the spaces between the grains.

By the way, in recent years, there has been an increasing demand for further increasing the melting temperature of glass, and even a highly zirconia electroformed refractory may not be sufficiently satisfactory in corrosion resistance. Therefore, in a glass melting furnace, a refractory material having higher corrosion resistance is required.

In a refractory using zirconia crystals, in order to improve the corrosion resistance to high-temperature molten glass, it is generally sufficient to increase the content of ZrO ₂ in the refractory. Various studies have been conducted. As such a high zirconia electric casting refractory, specifically, a high zirconia electric casting refractory in which the content of ZrO ₂ is increased to 90% by mass or more and further to 95% by mass or more is used. It is known (see, for example, Patent Documents 1 to 4).

In the high zirconia electrocast refractory containing 95% by mass or more of ZrO ₂ , the matrix glass has a maximum of 5% by mass, which is a small proportion of the total refractory. However, the physical characteristics of the matrix glass greatly contribute to the reduction of the characteristics of the refractory, for example, the residual volume expansion (hereinafter, abbreviated as the residual expansion) and the prevention of cracks during manufacturing. Therefore, in high zirconia electroformed refractories, it is important to adjust the optimum glass composition of the matrix glass, especially the content of trace components.

Further, a high zirconia electrocast refractory having a zirconia content of 96% by mass or more is liable to crack in the refractory, and it is difficult to manufacture the refractory in a size that can be used as a furnace material for a glass kiln. Usually, a high zirconia electroformed refractory is manufactured by melting the raw material of the refractory at a high temperature of 2500 ° C. or higher and cooling it in a mold. The higher the zirconia content in the refractory, the higher the melting temperature of the raw material, and the more likely it is that cracks will occur when a large refractory is manufactured.

In recent years, high zirconia electroformed refractories with improved corrosion resistance to a very high level as described above are known, and cracks occur during the production of large refractories and when used as a furnace material for glass kilns. It is expected to provide refractory materials that do not.

On the other hand, the present inventors have, as chemical components, 96.5 to 98.5% by mass of ZrO ₂ , 0.8 to 2.7% by mass of SiO ₂ , Na ₂ O and based on oxides. The total amount of K ₂ O is 0.04 to 0.35% by mass, B ₂ O ₃ is 0.02 to 0.18% by mass, and the contents of Na ₂ O, K ₂ O and B ₂ O ₃ are A high zirconia electrocast refractory that satisfies a predetermined relationship may contain Al ₂ O ₃ and has extremely high corrosion resistance to molten glass, and can suppress the generation of cracks during its manufacture. It has been found that the above-mentioned problem that cracks do not occur during use in a material can be solved (see Patent Document 5).

Japanese Unexamined Patent Publication No. 3-28175 Special Publication No. 59-12619 Special Table 2009-527454 Special Publication No. 55-3319 Japanese Unexamined Patent Publication No. 2014-129199

Under such circumstances, there is a demand for a high zirconia electroformed refractory that has excellent manufacturing cost and enables stable use even during use by further reducing residual expansion and suppressing cracks during manufacturing.

INDUSTRIAL APPLICABILITY The present invention provides a high zirconia electroformed refractory and a method for producing the same, in which the occurrence of cracks during manufacturing and the occurrence of cracks during use as a furnace material are further reduced while maintaining extremely high corrosion resistance to molten glass. With the goal.

As a result of diligent studies, the present inventors have made the ZrO ₂ content 96.7% by mass or more by optimizing the refractory composition, and in the refractory having high corrosion resistance to molten glass, the refractory is said. We have found a high zirconia refractory refractory that can suppress the occurrence of cracks during manufacturing even if the refractory is large and has a small residual expansion of the refractory.

That is, the high zirconia electrocasting refractory material of the present invention contains 96.7 to 98.5% by mass of ZrO ₂ , 0.8 to 2.7% by mass of SiO ₂ , and Al as chemical components based on oxides. ₂ O ₃ is contained in an amount of 0.1 to 0.4% by mass, Na ₂ O is contained in an amount of 0 to 0.2% by mass, K ₂ O is contained in an amount of 0.21 to 1% by mass, and B ₂ O ₃ is substantially contained. However, the content of the Na ₂ O and the K ₂ O is the following formula (1).

0.15% by mass ≤ C _K2O / 2 + C _{Na2O ≤0.6} % by mass ... (1)

(In the formula, C K2O is the content of _{K2O, CNa2O is the content of Na2O , and both} of these contents are expressed by mass% in the refractory). And.

According to the high zirconia electrocast refractory of the present invention and the method for producing the same, since the content of ZrO ₂ is high, it exhibits high corrosion resistance to molten glass and the content of components other than the ZrO ₂ component is optimized. Therefore, when a large-sized high zirconia electrocast refractory is manufactured, the occurrence of cracks can be suppressed and the residual expansion of the refractory can be reduced.

It is a graph which showed the relationship between ( _CK2O / 2 + C _Na2O ) and residual expansion about the high zirconia electroformed refractory of an Example and a comparative example. It is a graph which showed the relationship between ( _CK2O / 2 + C _Na2O ) and the total crack length about the high zirconia electroformed refractory of an Example and a comparative example. It is a graph which showed the relationship between [( _CK2O / 2 + C _Na2O ) / C _SiO2 ] and the residual expansion with respect to the electroformed refractory of an Example and a comparative example. It is a graph which showed the relationship between [( _CK2O / 2 + C _Na2O ) / C _SiO2 ] and the total crack length about the electroformed refractory of an Example and a comparative example. It is a graph which showed the relationship between _CK2O / C _Na2O and residual expansion about electroformed refractories of an Example and a comparative example. It is a graph which showed the relationship between _CK2O / C _Na2O and the total crack length about the electroformed refractory of an Example and a comparative example.

The high zirconia electric casting refractory of the present invention is a high zirconia electric casting refractory containing a predetermined component in a predetermined compounding ratio as described above, and has a large amount of zirconia crystals, a small amount of matrix glass, and a small amount. It is composed of pores. The role played by each chemical component contained in the refractory material in the refractory material will be described below with reference to the embodiments.

In the high zirconia electroformed refractory of the present embodiment, ZrO ₂ is a component that enhances the corrosion resistance of the refractory to the molten glass, and is an essential component.

The content of this ZrO ₂ is 96.7 to 98.5% by mass in the high zirconia electroformed refractory. By containing 96.7% by mass or more of ZrO ₂ , the refractory has excellent corrosion resistance to molten glass as compared with the conventional high zirconia electroformed refractory. On the other hand, if the content exceeds 98.5% by mass, the content of the matrix glass and other components becomes too small, cracks are likely to occur during manufacturing, and it becomes difficult to increase the size of the refractory.

The content of ZrO ₂ is preferably 96.9 to 98.2% by mass, more preferably 97.2 to 98% by mass, from the viewpoint of ensuring the content of the matrix glass while maintaining high durability against the molten glass. preferable.

The zirconia raw material and the zircon raw material used for producing a high zirconia electroformed refractory inevitably contain 1 to 3% by mass of HfO ₂ . Since HfO ₂ remains in the refractory with almost no loss such as evaporation during production, the ordinary high zirconia electroformed refractory also contains HfO ₂ derived from the raw material. Since HfO ₂ plays the same role as ZrO ₂ in high zirconia electroformed refractories in general, it is customary to simply refer to the value of ZrO ₂ + HfO ₂ as ZrO ₂ . Also in this specification, the value of ZrO ₂ + HfO ₂ is referred to as ZrO ₂ .

In the high zirconia electroformed refractory of the present embodiment, SiO ₂ is a component forming matrix glass and is an essential component.

The content of SiO ₂ is 0.8 to 2.7% by mass in the high zirconia electroformed refractory. By containing 0.8% by mass or more of SiO ₂ , the thermal stress due to the temperature change during manufacturing can be relaxed and cracks can be prevented. On the other hand, if it exceeds 2.7% by mass, the ratio of SiO ₂ in the matrix glass becomes high, the viscosity of the matrix glass becomes high, and there is a possibility that cracks may occur during the production of the refractory. The SiO ₂ content is preferably 1 to 2.4% by mass, more preferably 1.2 to 2.1% by mass.

In the high zirconia electrocast refractory of the present embodiment, Al ₂ O ₃ is a component that lowers the viscosity of the matrix glass and at the same time is a component that suppresses the formation of zircon in the refractory and is an essential component. .. Zircon is produced by the reaction of a part of the matrix glass with zirconia crystals. When zircon is produced, the amount of matrix glass in the refractory material decreases, and the function of the matrix glass may not be fully exhibited. In addition, the decrease in matrix glass increases the residual expansion of the refractory and can cause cracks to occur during use as the furnace material of the glass kiln.

The content of this Al ₂ O ₃ is 0.1 to 0.4% by mass in the high zirconia electroformed refractory. In the present embodiment, since the amount of matrix glass is smaller than that of zirconia crystals, Al ₂ O ₃ can be effective at a content of 0.1% by mass or more. On the other hand, if it is contained in an amount of 0.4% by mass or more, aluminosilicate-based crystals such as mullite may be generated during the production or use of the refractory, and the refractory may be cracked. The content of Al ₂ O ₃ is preferably 0.2 to 0.3% by mass.

In the high zirconia electroformed refractory of the present embodiment, Na ₂ O and K ₂ O are components that can suppress the generation of cracks during the production of the refractory. In the present embodiment, Na ₂ O is an optional component, and the content thereof is preferably 0 to 0.2% by mass, more preferably 0 to 0.15% by mass in the high zirconia electrocast refractory. It is more preferably 0 to 0.12% by mass.

On the other hand, in the present embodiment, _K2O is an essential component, and the content thereof is preferably 0.21 to 1% by mass, preferably 0.21 to 0.9% by mass in the high zirconia electrocast refractory. Is more preferable, and 0.3 to 0.75% by mass is further preferable. By using _K2O as an essential component, the viscosity of the matrix glass at the time of manufacturing can be lowered and cracks can be prevented. In addition, it is possible to prevent the formation of zircon in the matrix glass when it is used as a furnace material for a glass kiln and prevent cracks.

Then, these Na ₂ O and K ₂ O have the content of Na ₂ O and K ₂ O in the high zirconia electroformed refractory according to the following formula (1).

0.15% by mass ≤ C _K2O / 2 + C _{Na2O ≤0.6} % by mass ... (1)

(In the formula, C K2O is the content of _{K2O, CNa2O is the content of Na2O , and both} of these contents are expressed by mass% in the refractory). Will be done.

When this ( _CK2O / 2 + C _Na2O ) is 0.15% by mass or more, the formation of zircon in the refractory is suppressed, which contributes to the suppression of crack generation during the production of the refractory. The higher this value, the lower the viscosity of the matrix glass, but if the amount of alkaline component is too large, it becomes difficult to vitrify. Therefore, ( _CK2O / 2 + C _Na2O ) is 0.6% by mass or less in order to adjust the content of other components in the matrix glass.

This ( _CK2O / 2 + C _Na2O ) is preferably 0.15 to 0.55% by mass, more preferably 0.2 to 0.45% by mass. In this value, the content of K ₂ O is divided by 2, because the balance between the crack and the action of Na ₂ O on the influence on the residual expansion is taken into consideration.

Further, in Na ₂ O, K ₂ O and SiO ₂ , the content of Na ₂ O, K ₂ O and SiO ₂ in the highly zirconia electroformed refractory has the following formula (2).

0.09 ≤ (C _K2O / 2 + C _Na2O ) / C _SiO2 ≤ 0.4 ... (2)

(In the formula, C _{Na 2O} is the content of Na ₂ O, C K ₂ O is the content of K 2 O, and C _{SiO 2} is the content of SiO 2, and these contents are all expressed by mass% in the fireproof material. ) Satisfying the relationship.

When this [(C _K2O / 2 + C _Na2O ) / C _SiO2 ] is 0.09 or more, the formation of zircon in the refractory is suppressed, which contributes to the suppression of crack generation during the production of the refractory. The higher this value, the lower the viscosity of the matrix glass, but if the amount of alkaline component is too large, it becomes difficult to vitrify. Therefore, [( _CK2O / 2 + C _Na2O ) / C _SiO2 ] is 0.4 or less in order to adjust the content of other components in the matrix glass.

This [(C _K2O / 2 + C _Na2O ) / C _SiO2 ] is preferably 0.09 to 0.3, more preferably 0.12 to 0.27.

Further, in Na ₂ O, K ₂ O and SiO ₂ , the content of Na ₂ O, K ₂ O and SiO ₂ in the highly zirconia electroformed refractory has the following formula (3).

0.11 ≤ (C _{K2O /1.5+CNa2O} ) _/CSiO2≤0.5 ... (3)

(In the formula, C _{Na 2O} is the content of Na ₂ O, C K ₂ O is the content of K 2 O, and C _{SiO 2} is the content of SiO 2, and these contents are all expressed by mass% in the fireproof material. ) Satisfying the relationship.

When this [(C _{K2O /1.5+CNa2O)/CSiO2} ] is _set to 0.11 or more, the formation of zircon in the refractory is suppressed, which contributes to the suppression of crack generation during the production of the refractory. The higher this value, the lower the viscosity of the matrix glass, but if the amount of alkaline component is too large, it becomes difficult to vitrify.
Therefore, [( _{CK2O /1.5+CNa2O)/CSiO2} ] is 0.5 or less in _order to adjust the content of other components in the matrix glass.

This [(C _{K2O /1.5+CNa2O} ) / _CSiO2 ] is preferably 0.11 to 0.4, more preferably 0.14 to 0.35. This formula (3) differs from the formula (1) only in that _CK2O is divided by 1.5, but _K2O has a molar mass of about 1.5 times that of _Na2O . Therefore, the effect evaluated based on their content can be evaluated more accurately when the mass is used as a reference. The tendency is almost the same in the equation (1) and the equation (3).

Further, Na ₂ O and K ₂ O have the content of Na ₂ O and K ₂ O in the high zirconia electroformed refractory according to the following formula (4).

2 ≤ C _K2O / C _Na2O ... (4)

(In the formula, C K2O is the content of _{K2O, CNa2O is} , and _both of these contents are expressed by mass% in the refractory).

When the ratio of the Na ₂ O to K ₂ O content (C _K2O / C _Na2O ) is 2 or more, the generation of cracks in the refractory and the increase in residual expansion can be effectively suppressed. This ratio (C _K2O / C _Na2O ) is preferably 2 to 11, more preferably 3.5 to 8. Specifically, it is preferable in that the residual volume expansion coefficient of the produced high zirconia electroformed refractory can be 20% or less, and the generation of cracks when used as a furnace material for a glass kiln can be effectively suppressed. .. In the present specification, the residual volume expansion rate is the volume derived from the amount of dimensional change before and after the thermal cycle test in which the sample is reciprocated 40 times between 800 ° C and 1250 ° C. The amount of change. That is, the residual volume expansion coefficient can be calculated by the following formula.
Residual volume expansion rate (%) = (volume after thermal cycle test / volume before thermal cycle test) -1) x 100

In the high zirconia electroformed refractory of the present embodiment, B ₂ O ₃ is substantially not contained. Here, "substantially not contained" means that the component is not intentionally contained, and that mixing by unavoidable impurities is allowed. It can be said that B ₂ O ₃ is substantially not contained if it is 0.01% by mass or less.

As described above, this B ₂ O ₃ is known to have an effect of suppressing the generation of cracks during the production of high zirconia electroformed refractories, and in this field, it is usually contained in consideration of productivity. It is an ingredient. However, in the present embodiment containing _K2O as an essential component, it was found that co-evaporation may occur due to the coexistence thereof. That is, it was found that when K ₂ O and B ₂ O ₃ coexist, the effect of suppressing crack generation tends to be reduced as compared with the blending amount thereof. Therefore, in this embodiment, B ₂ O ₃ is substantially not contained.

In the high zirconia electrocast refractory of the present embodiment, P ₂ O ₅ is a component that adjusts the viscosity of the matrix glass and suppresses cracks during the production of the refractory, and is not an essential component.

From the above viewpoint, the content of P ₂ O ₅ is preferably 0.03 to 0.15% by mass in the high zirconia electroformed refractory. In this case, the effect can be exhibited if it is contained in a small amount. The P ₂ O ₅ content is preferably 0.03 to 0.12% by mass, more preferably 0.03 to 0.06% by mass.

On the other hand, if P ₂ O ₅ is contained, the production of zircon may be promoted, and from the viewpoint of suppressing chip-off and residual expansion, it is preferable that the content of P ₂ O ₅ is low. The content thereof is more preferably 0.04% by mass or less, and particularly preferably not substantially contained in the high zirconia electroformed refractory. Even in P ₂ O ₅ , if it is 0.01% by mass or less, it can be said that it is substantially not contained.

In the high zirconia electrocast refractory of the present embodiment, when CuO colors molten glass or is contained at the same time as P ₂ O ₅ and B ₂ O ₃ , it forms a low melting point glass and is chemically durable. It is a component that may have reduced sex or may be affected. Therefore, in the present invention, it is preferable that CuO is not substantially contained.

Further, Fe ₂ O ₃ and TiO ₂ may be contained as impurities in the raw material. These components are components that cause coloring and foaming of the molten glass, and a high content is not preferable. If the total content of Fe ₂ O ₃ and TiO ₂ is 0.3% by mass or less, there is no problem of coloring, and preferably 0.2% by mass or less.

Similarly, the raw material may contain MgO and CaO as impurities. These tend to increase the residual expansion in the thermal cycle test, and if the contents of MgO and CaO are 0.05% by mass or less, there is no problem, and preferably 0.03% by mass or less.

Similarly, depending on the raw material, Y ₂ O ₃ may be contained as an impurity. _The inclusion of _Y2O3 in the refractory tends to harden the matrix glass and increase residual expansion in thermal cycle tests. If the content of Y ₂ O ₃ is 0.3% by mass or less, there is no problem, and preferably 0.2% by mass or less.

The bulk specific gravity of the high zirconia electroformed refractory is preferably 5.4 g / cm ³ or more. The highly zirconia electroformed refractory of the present invention has higher corrosion resistance to molten glass, and the more dense it is, the more preferable it is. Therefore, the bulk specific density is more preferably 5.45 to 5.55 g / cm ³ .

The porosity of the high zirconia electroformed refractory is preferably 1.5% or less. The highly zirconia electroformed refractory of the present invention is preferably more resistant to corrosion against molten glass. Since the porosity affects the corrosion resistance characteristics, it is preferable that the porosity is low. Therefore, the porosity is more preferably 0.1 to 1%.

The mass of the high zirconia electroformed refractory is preferably 200 kg or more. The high zirconia electroformed refractory of the present invention can suppress the occurrence of cracks in the refractory even when manufacturing such a large electroformed refractory, and the yield of large products can be dramatically improved as compared with the conventional case. Can be improved. This mass is more preferably 400 to 1500 kg.

Hereinafter, the high zirconia refractory of the present invention will be specifically described with reference to Examples (Examples 1 to 8) and Comparative Examples (Examples 9 to 14), but the present invention is to be interpreted in any limitation by these. It's not something.

In order to obtain a refractory by the electric fusion casting method, raw materials such as alumina, zircon sand, silica, sodium carbonate, potassium carbonate _{, and B2 O 3 are} mixed with desiliconized zirconia, which is a zirconia raw material, to make a mixed raw material, and this mixture is used. The raw material was charged into a three-phase arc electric furnace having an output of 1500 kVA equipped with three graphite electrodes, and completely melted by energization heating.

600 kg of this molten metal was poured into a graphite mold previously embedded in silica sand, which is a slow-cooling material, cast, and allowed to cool until the temperature was close to room temperature. This graphite mold was manufactured so as to obtain a refractory product material having a thickness of 200 mm, a width of 400 mm, and a height of 900 mm and containing no shrinkage cavities. Specifically, the mold was designed and manufactured so as to form an ingot having a hot water part having the same volume as the part for the material of the refractory product above the part for the material of the refractory product.

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

The raw material composition was adjusted to obtain a highly zirconia electroformed refractory having the chemical composition shown in Table 1. Here, Examples are Examples 1 to 8, and Comparative Examples are Examples 9 to 14. In addition, Table 2 shows the relationship between the relational expression and the physical properties of each Example and Comparative Example. The chemical composition in the refractory material is basically a quantitative analysis value determined by the wavelength dispersion type fluorescent X-ray analysis method, but B ₂ O ₃ and P ₂ O ₅ which require accuracy are high frequency induction. It is a quantitative analysis value determined by the coupled plasma emission spectroscopic analysis method. However, the quantification of each component is not limited to this analysis method, and other quantitative analysis methods may be used.

〔crack〕
The cracks on the appearance of the ingot were evaluated as follows.
The pressed water portion was excised from the ingot of the highly zirconia electroformed refractory to produce an electroformed refractory having a thickness of 200 mm × a width of 400 mm × a height of 900 mm (mass: about 400 kg). All the lengths of cracks visible to the naked eye on the surface of this electroformed refractory were measured, and the total lengths were evaluated according to the following criteria.
Excellent: The total crack length is 150 mm or less.
Good: The total crack length is more than 150 mm and 300 mm or less.
Possible: The total crack length is more than 300 mm and 600 mm or less.
Impossible: The total crack length is over 600 mm.

[Residual expansion]
A sample having a thickness of 50 mm, a width of 50 mm, and a height of 50 mm was cut out from the manufactured electroformed refractory, and heating and cooling were carried out in an electric furnace by reciprocating between 800 ° C. and 1250 ° C. 40 times. At this time, heating between room temperature and 800 ° C. is performed at 160 ° C. per hour, from which heating to 1250 ° C. is performed immediately after reaching 800 ° C. and cooling to 800 ° C. immediately after reaching 1250 ° C. Was performed at 450 ° C. per hour to obtain one heat cycle. Then, in the same operation as above, a thermal cycle reciprocating between 800 ° C. and 1250 ° C. was repeated 40 times. After the final heat cycle, the mixture was cooled from 800 ° C. to room temperature at a rate of 160 ° C. per hour. The size of the sample was measured before and after this test, and the residual volume expansion coefficient was determined from the change in the size. The residual volume expansion coefficient obtained at this time was evaluated according to the following criteria.

Excellent: The residual volume expansion coefficient is 10% or less.
Good: The residual volume expansion coefficient is more than 10% and 20% or less.
Possible: The residual volume expansion coefficient is more than 20% and 30% or less.
Impossible: The residual volume expansion rate is more than 30%.

〔Comprehensive judgment〕
According to the evaluation result of the crack and the residual expansion coefficient, the judgment was made according to the following criteria.
Excellent: Both cracks and residual volume expansion rate are excellent.
Good: One of the cracks and the residual volume expansion coefficient is good, and the other is not acceptable or unacceptable.
Possible: One of the crack and the residual volume expansion coefficient is acceptable, and the other is not impossible.
Impossible: Either crack or residual volume expansion rate is impossibility.

The above test results are also shown in Tables 1 and 2. Further, with respect to the numerical values of the relational expressions of the above equations (1), (2) and (4), the relationship between the residual volume expansion coefficient and the total length of cracks is shown in FIGS. 1A to 3B.

As is clear from Tables 1 and 2, the high zirconia electroformed refractories having excellent corrosion resistance in Examples 1 to 8 can improve the production efficiency because the total length of cracks generated in the produced ingot is short. It is also possible to manufacture large cast refractory materials. Further, this high zirconia electroformed refractory has a small residual volume expansion coefficient and high crack resistance to temperature changes during use, so that it can be a long-life cast refractory.

Further, Tables 1 and 2 show high zirconia electroformed refractories not applicable to the present invention as comparative examples.

Since the refractories of Examples 9 to 14 have a relatively low content of Na ₂ O and K ₂ O, the total length of cracks is very long, the residual expansion coefficient is high, and cracks are likely to occur during manufacturing. The crack resistance to temperature changes during use is low. Therefore, these refractories may cause problems in productivity or service life.

From the above results, the high zirconia electrocast refractory of the present invention has a very high zirconia content, is excellent in productivity, has a low residual expansion rate, and is manufactured or used. Is a stable refractory with suppressed cracking.

The highly zirconia refractory refractory of the present invention has high corrosion resistance, is less likely to cause cracks during manufacturing and use, and is not likely to contaminate the molten glass even when applied to a glass melting furnace. It is suitable as a refractory material for glass melting furnaces.

Claims (7)

As for the chemical composition, based on oxides, ZrO ₂ is 96.7 to 98.5% by mass, SiO ₂ is 0.8 to 2.7% by mass, and Al ₂ O ₃ is 0.1 to 0.4% by mass. It contains 0 to 0.2% by mass of Na ₂ O, 0.21 to 1% by mass of K ₂ O, and substantially no B ₂ O ₃ .
The content of the Na ₂ O and the K ₂ O is the following formula (1).
0.175 % by mass ≤ C _K2O / 2 + C _{Na2O ≤0.6} % by mass ... (1)
(In the formula, C K2O is the content of _{K2O, CNa2O is the content of Na2O , and both} of these contents are expressed by mass% in the refractory). High zirconia electric casting refractory. The content of the Na ₂ O, the K ₂ O and the SiO ₂ is the following formula (2).
0.09 ≤ (C _K2O / 2 + C _Na2O ) / C _SiO2 ≤ 0.4 ... (2)
(In the formula, C _K2O is the content of K2O, _{CNa2O is the content of Na2O, and CSiO2 is the content of SiO2 , and these} contents _are all expressed in% by mass in the refractory. ). The high zirconia electrocast refractory according to claim 1. The high zirconia electroformed refractory according to claim 1 or 2, wherein the ratio of _CK2O to C _Na2O (C _K2O / C _Na2O ) is 2 or more. The high zirconia electroformed refractory according to any one of claims 1 to 3, wherein the bulk specific density is 5.4 or more. The highly zirconia electroformed refractory according to any one of claims 1 to 4, wherein the porosity is 1.5% or less. The highly zirconia electroformed refractory according to any one of claims 1 to 5, wherein the mass is 200 kg or more. The high zirconia electric casting refractory according to any one of claims 1 to 6, wherein the refractory raw material is melted at a high temperature and cooled in a mold to produce the high zirconia electric casting refractory. Manufacturing method of goods.

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