High-zirconia electro-fused cast refractory material

Abstract

The purpose of the present invention is to provide a high-zirconia electro-fused cast refractory material which is prevented from the opening of a joint at a contacting part between refractory materials, is also prevented from the generation of zircon crystals, does not undergo the extreme increase in a residual volume expansion ratio even when zircon crystals are generated, and has high corrosion resistance against a glass. The present invention relates to a high-zirconia electro-fused cast refractory material, in which, with respect to chemical components, the total content of ZrO2 and HfO2 is more than 80% by mass and 92% by mass or less, the content of Al2O3 is 0.2-3.0% by mass, the content of SiO2 is 1.5-10% by mass, the content of Na2O is 0.05-2.0% by mass, the content of K2O is 1.0% by mass or less, the content of B2O3 is 0-1.5% by mass, the content of Y2O3 is more than 4.0% by mass and 9.0% by mass or less, the total content of MgO and CaO is 0.02-0.4% by mass, the content of CaO is 0.01% by mass or more, the total content of Fe2O3 and TiO2 is 0.5% by mass or less, and the content of P2O5 is 0.04% by mass or less.

Description

High zirconia electrofusion cast refractories

[0001] The present invention relates to a high-zirconia electrofusion cast refractory suitable for use in glass melting furnaces.

[0002] Electrically fused cast refractories (hereinafter sometimes simply referred to as "refractories") have conventionally been widely used as refractories for glass melting furnaces.

[0003] Electrically melted cast refractories are produced by melting raw materials, which are a mixture of major components such as alumina, silica, and zirconia and minor components such as soda and boric acid in predetermined amounts, in an electric arc furnace, casting the molten material into a refractory mold, and cooling it together with the mold in an annealing material to solidify it into the shape of the mold.These refractories are dense and have excellent corrosion resistance against molten glass.

[0004] Since electrically fused cast refractories are produced through a process of casting a molten material into a mold, the manufacturing method is different from that of sintered refractories, which are produced by sintering and bonding crystal particles. In addition, the technical development means and methods, and solutions and methods for sintered refractories cannot be used for electrically fused cast refractories, and vice versa.

[0005] One such electrically melted cast refractory material is generally ZrO ２ A high-zirconia electrically fused cast refractory containing 85 mass % or more of the above is used.

[0006] High zirconia electrofusion cast refractories have low solubility in glass and a high melting point. ２ is the main component, and ZrO ２ Due to its high content and dense structure, it has excellent corrosion resistance against all types of molten glass.

[0007] Furthermore, high-zirconia electrically fused cast refractories have the property of not forming a reaction layer at the interface with molten glass, making them an excellent option in that they are less likely to produce defects such as stones or cords in the molten glass.

[0008] Therefore, high zirconia electrically fused cast refractories are particularly suitable for producing high quality glass.

[0009] The mineral structure of high zirconia electrofusion cast refractories is mostly monoclinic ZrO ２ The crystals are dominated by a small amount of glass phase. ２ It is constructed by filling the grain boundaries of the crystals.

[0010] This small amount of glass phase is very different from the composition of glasses used in the glass industry and is very SiO ２ Rich glass with high ZrO content ２ Therefore, the technical development means and methods, solutions and methods of the glass industry cannot be applied to electrically melted and cast refractories, and vice versa.

[0011] The glass phase of high zirconia electrofusion cast refractories is generally Al ２ O ３ , SiO ２ , Na ２ O, B ２ O ３ , P ２ O ５ It is composed of oxides such as:

[0012] ZrO, which accounts for the majority of high-zirconia electrofusion cast refractories, ２ The crystal undergoes a reversible crystal phase transformation between monoclinic and tetragonal, accompanied by a rapid volume change, from about 1000° C. (when cooling) to about 1150° C. (when heating).

[0013] This ZrO ２ The stress generated by the volume change accompanying the transformation of the crystal is expressed as ZrO ２ The glass phase filling the grain boundaries relaxes the glass, resulting in crack-free ZrO during manufacturing and heating. ２ High zirconia electrofused cast refractories with a content of 93 to 94 mass% have become available for production and are now on sale.

[0014] However, this ZrO ２ The reversible crystal phase transformation between monoclinic and tetragonal crystals, accompanied by a rapid volume change of the crystals at temperatures from about 1000°C (when cooling) to about 1150°C (when heating), has a significant impact on glass melting furnaces when high-zirconia electric melting cast refractories are used in the glass industry.

[0015] That is, the high zirconia electrically fused cast refractory expands when heated, but ZrO ２ In the crystal phase transformation temperature range, the crystal changes from monoclinic to tetragonal, and this is accompanied by a sudden volume contraction. As the temperature rises further, the refractory material expands, but in the operating temperature range of a glass melting furnace, this expansion is due to the ZrO ２ The maximum expansion of the monoclinic phase in the crystal phase transformation temperature range was not exceeded.

[0016] Therefore, in a typical high-zirconia electrically fused cast refractory, a temperature distribution occurs between the inner furnace surface that contacts the molten glass and reaches the maximum temperature (generally 1300°C to 1700°C) in an operating glass melting furnace, and the outer surface that contacts the atmosphere (or insulating material) outside the glass melting furnace, and the maximum expansion occurs between these two surfaces.

[0017] That is, when the temperature rises, ZrO ２ This means that at the inside of the furnace in contact with the molten glass, the refractory has a smaller than maximum expansion rate, as the crystals shrink due to the transformation of the crystalline phase from monoclinic to tetragonal.

[0018] If the refractory material has an expansion coefficient smaller than the maximum expansion rate in the part of the furnace interior that comes into contact with the molten glass, in a glass melting furnace that uses a combination of refractories, the areas where the refractories come into contact with each other, called "joints," will open up slightly.

[0019] If the joints, which are the contact points between the refractories, are open, the flow rate of the glass changes near the joints, accelerating the erosion of the refractory from the glass.

[0020] Furthermore, the high zirconia electrically fused cast refractories can be heated by themselves or by adding ZrO ２ When the refractory is subjected to a thermal cycle across a temperature range where a reversible crystal phase transformation between monoclinic and tetragonal occurs, accompanied by a rapid volume change, from 1000°C (when cooling) to 1150°C (when heating), silica (SiO ２ ) and zirconia (ZrO ２ ) crystals react to form zircon (ZrO ２ SiO ２) crystals may form.

[0021] When heated or subjected to thermal cycling, zircon crystals turn into ZrO ２ Since zircon crystals are formed at the interface between the crystals and the glass phase filling the grain boundaries, or at the glass phase, the formation of zircon crystals leads to a relative decrease in the glass phase. Furthermore, as the decrease in the glass phase progresses due to the growth and increase of zircon crystals, ZrO ２ The glass phase becomes less able to absorb the sudden volume change of the crystals at temperatures between 1000°C and 1150°C, which reduces the strength of the refractory and makes it more susceptible to cracking.

[0022] At this time, selective corrosion occurs from the cracked portion, and as the corrosion progresses, crystals constituting the high-zirconia electrically fused cast refractory may become mixed into the molten glass, which may lead to a deterioration in the quality of the glass.

[0023] Therefore, in order to operate a glass melting furnace stably for a long period of time and maintain stable glass quality, it is extremely important to suppress the formation of zircon crystals in high-zirconia electrically fused cast refractories.

[0024] In this way, refractories that suppress the opening of joints at the contact points between refractories, known as "joints," have traditionally been used as refractories. ２ O ３ The addition of

[0025] Furthermore, high-zirconia electrically fused cast refractories that suppress the formation of zircon crystals have been studied.

[0026] In Patent Document 1, the ZrO content is 89 mol % or less. ２ ≦99, 1≦Y ２ O ３ A fused cast zirconia heat-resistant mechanical material has been proposed, which is characterized by being made of a single crystal and / or polycrystalline body having a composition of ≦11.

[0027] The refractory material in Reference 1 is SiO ２ Although it does not contain SiO and does not form zircon crystals, ２ Since it does not contain ZrO ２This material cannot absorb the sudden volume change that occurs when the crystals transform from monoclinic to tetragonal, making it difficult to mass-produce refractories industrially.

[0028] Patent Document 2 proposes a fused zirconia refractory material characterized by containing 1 to 30 wt % of calcium oxide and 0.05 to 2 wt % of yttrium oxide or a rare earth mineral containing yttrium oxide as a stabilizer.

[0029] In the refractory material of Reference 2, SiO ２ Although it does not contain SiO and does not form zircon crystals, ２ Since it does not contain ZrO ２ This material cannot absorb the sudden volume change that occurs when the crystals transform from monoclinic to tetragonal, making it difficult to mass-produce refractories industrially.

[0030] In Patent Document 3, more than 85% zirconia (ZrO ２ Refractory products comprising, by weight percent on an oxide basis: ZrO ２ >92%, SiO ２ : 2-8%, Na ２ O: 0.12-1%, Al ２ O ３ : 0.2 to 2%, 0.5%≦Y ２ O ３ + CaO≦2.6%, but Y ２ O ３ : 0.3 to 2% or CaO: 0.5 to 1.93% has been proposed.

[0031] The refractory material of Reference 3 was difficult to manufacture on a production level due to cracks that occurred during production. As will be explained below, this is due to the ２ O ３ This is thought to be due to the relatively low content.

[0032] In Patent Document 4, the weight percentage based on the oxides is expressed as ZrO, with the total being 100%. ２ : 100% residual, Hf ２ O: <5%, SiO ２ :2%~10%, 0.9<Y ２ O ３ + CeO ２+CaO+MgO≦4.0%, B ２ O ３ : ≦4.5%, B ２ O ３ : ≧0.09 × (Y ２ O ３ +1 / 3 (CeO ２ +CaO+MgO))×SiO ２ , Al ２ O ３ :0.3%~2.0%, Na ２ O+K ２ O: ≦0.5%, P ２ O ５ :<0.05%, Fe ２ O ３ + TiO ２ : <0.55%, other species: <1.0%, except Y ２ O ３ The content is 0.5% or more or CeO ２ Fused and cast refractories have been proposed which have a CaO+MgO content of 2% or more.

[0033] The refractory of Document 4 contains large amounts of CaO and MgO, which significantly promote the formation of zircon crystals. The increase in residual volume expansion after heating caused by the formation of zircon crystals may cause cracks to occur in the refractory, resulting in a decrease in the strength of the refractory structure.

[0034] In Patent Document 5, ZrO is used as a weight percentage based on oxides and relative to a total of 100%. ２ : Remainder to 100%, Hf ２ O: <5%, SiO ２ : 2% to 10%, Y ２ O ３ :0.4~2.0%, CaO:4.0%~8.0%, B ２ O ３ +Na ２ O+K ２ O: 0.4-3.0%, Al ２ O ３ :0.3%~2.0%, P ２ O ５ :<0.05%, Fe ２ O ３ + TiO ２Fused cast refractories containing <0.55% of Cr, <1.5% of other species have been proposed.

[0035] In Reference 5, it is reported that the sintered material contains a large amount of CaO, which significantly promotes the formation of zircon crystals, and that the formation of zircon crystals and anorthite crystals (CaAl ２ Si ２ O ８ The increase in residual volume expansion after heating due to the formation of SiO 2 may cause cracks to form in the refractory, resulting in a decrease in the strength of the refractory structure.

[0036] In Patent Document 6, the weight percentage based on the oxides is expressed as ZrO, with the total being 100%. ２ : 100% balance, SiO ２ :2%~10%, 0.9<Y ２ O ３ + CeO ２ +CaO+MgO≦4.0%, B ２ O ３ : ≦4.5%, B ２ O ３ : ≧0.09 × (Y ２ O ３ +1 / 3 (CeO ２ +CaO+MgO))×SiO ２ , Al ２ O ３ : 0.3% to 2.0%, and Y ２ O ３ : ≧0.8%, and the following requirement: HfO ２ : <5%, CeO ２ :<0.7%, MgO:<0.7%, CaO:<0.7%, Na ２ O+K ２ O: ≦0.5%, P ２ O ５ :<0.05%, Fe ２ O ３ + TiO ２ : <0.55%, and ZrO ２ , HfO ２ , SiO ２ , Y ２ O ３ , CeO ２ , CaO, MgO, B ２ O ３ , Al ２ O ３, Na ２ O.K. ２ O, P ２ O ５ , Fe ２ O ３ , and TiO ２ A fused and cast refractory material is proposed which meets the above requirements: <0.2% of each of the species other than Cr.

[0037] The refractory material of Reference 6 cracks during production, making it difficult to mass-produce the refractory material industrially. As will be explained below, this is because ２ O ３ This is thought to be because the content is 4% or less.

[0038] In Patent Document 7, ZrO ２ 85 to 95% by weight of Al ２ O ３ 0.4 to 2.5% by weight of SiO ２ 3.5 to 10% by weight of Na ２ O and K ２ The total of O is 0.05 to 1% by weight, B ２ O ３ is more than 0.04% by weight and not more than 1% by weight, P ２ O ５ 0.02% by weight or less, MgO 0.05% by weight or less, CaO 0.01 to 0.2% by weight, when SrO and BaO are contained alone, SrO is 0.3 to 3% by weight, or BaO is more than 0.5% by weight and 3% by weight or less, when both are contained, SrO is 0.3% by weight or more and the total of SrO and BaO is 0.3 to 3% by weight, SnO ２ 0.01 to 0.7 wt %, Fe ２ O ３ and TiO ２ A high-zirconia electrically fused cast refractory material has been proposed in which the total of these elements is 0.3% by weight or less.

[0039] The refractory material in Reference 7 is Y ２ O ３ Because the content was extremely low, the opening of the joints could not be suppressed, and the corrosion resistance of the joints was insufficient.

[0040] In Patent Document 8, ZrO is used as a mass percentage based on oxides and relative to 100% of the total of oxides. ２ +HfO２ : The remainder up to 100%, except for Hf ２ O≦5%, SiO ２ :1.5% to 7.5%, Al ２ O ３ :1.0%~3.0%, CaO+SrO:1.2~3.0%, Y ２ O ３ :1.5-3.0%, Na ２ O+K ２ O:<0.15%, B ２ O ３ : <1.0%, P ２ O ５ :<0.15%, Fe ２ O ３ + TiO ２ :<0.55%, ZrO ２ , HfO ２ , SiO ２ , Al ２ O ３ , Na ２ O.K. ２ O, B ２ O ３ , CaO, SrO, Y ２ O ３ , P ２ O ５ , Fe ２ O ３ , and TiO ２ A fused cast refractory product containing <1.5% of oxide species other than Cr has been proposed.

[0041] The refractory material of Reference 8 was difficult to manufacture on a production level, as cracks sometimes occurred. As explained below, this is ２ O ３ This is thought to be because the content is 4% or less.

[0042] JP-A-59-131585 Publication JP-A-4-42813 Special Publication No. 2005-526683 Publication Special Publication No. 2013-514254 Special Publication Table 2015-506898 publication JP 2015-212223 publication JP 2015-40144 publication Special table publication 2018-509363 publication

[0043] Generally, Y ２ O ３ When the high zirconia electrofusion cast refractory contains Y, ２O ３ Most of the ２ It dissolves in the crystals and is partly contained in the glass phase of the refractory material. ２ O ３ ZrO ２ Due to solid solution in the crystal, some of the ZrO is tetragonal ２ ZrO ２ The crystal properties change, i.e. ZrO ２ The temperature at which the crystal undergoes a reversible crystal phase transformation between monoclinic and tetragonal crystals, accompanied by a rapid volume change from 1000°C (when cooling) to 1150°C (when heating), and therefore the maximum expansion temperature, is shifted to a lower temperature.

[0044] On the other hand, as described above, in a refractory during operation, a temperature distribution occurs between the furnace inner surface that comes into contact with molten glass in a glass melting furnace and the outer surface that comes into contact with the atmosphere (or heat insulating material) outside the glass melting furnace, and a typical high-zirconia electrically fused cast refractory has a maximum expansion between these two surfaces. ２ When the crystal transformation temperature shifts to the lower temperature side, the maximum expansion of the refractory material moves toward the surface that is in contact with the atmosphere (or heat insulating material) outside the glass melting furnace, and ZrO ２ As the crystals transform into tetragonal crystals and then expand, the expansion of the part of the furnace interior that comes into contact with the molten glass in the glass melting furnace is the same as or slightly smaller than the maximum expansion of the refractories, and the joints, which are the contact points between the refractories, are closed or the opening of the joints is suppressed.

[0045] However, ZrO ２ When the transformation temperature of the crystalline phase shifts to the lower temperature side, the viscosity of the glass phase is high at the lower temperature side, and at an even lower temperature side, the glass phase solidifies. ２ The glass phase cannot relax the stress generated by the volume change accompanying the transformation of the crystals, which makes cracks more likely to occur, and there is a risk that industrial mass production of refractories will be difficult.

[0046] Also, ZrO ２ When the degree of shift of the transformation temperature of the crystalline phase to the lower side increases, ZrO ２ The stress generated by the volume change accompanying the transformation of the crystals cannot be further alleviated, and the occurrence of cracks may be accelerated.

[0047] Therefore, Y ２ O ３ By increasing the content of ZrO ２ It has been considered difficult to increase the degree of shift of the crystalline phase transformation temperature to the lower side, thereby producing a high-zirconia electrofusion cast refractory having good quality.

[0048] Also, ZrO ２ When a refractory material with a crystal phase transformation temperature shifted to the lower side is used in a glass melting furnace, if zircon crystals are generated during operation, the glass phase will be relatively reduced in amount. In addition, the viscosity of the glass phase is high at low temperatures, and the glass phase solidifies at even lower temperatures. Therefore, when a thermal cycle occurs due to changes in operating temperature during glass melting furnace operation, the ZrO content will be higher than that of a general high-zirconia electrically fused cast refractory material. ２ This may make it difficult for the crystal to absorb sudden volume changes, and may also make cracks more likely to occur.

[0049] Therefore, Y ２ O ３ High zirconia electrofusion cast refractories with a relatively increased content have been considered unsuitable for use in parts of glass melting furnaces where thermal cycles occur due to changes in operating temperature.

[0050] Also, Y ２ O ３ When the content is increased, the relative amount of ZrO ２ The content decreases. ２ The content of ZrO has a significant effect on the corrosion resistance of the refractory from the glass. ２ Since it is proportional to the content, it is relatively ZrO ２ Refractories with low content were considered to have insufficient corrosion resistance.

[0051] Therefore, Y ２ O ３ It has been thought that high zirconia electrofusion cast refractories with increased content may have insufficient corrosion resistance in glass melting furnaces.

[0052] In this context, an object of the present invention is to provide an improved high-zirconia electrically fused cast refractory, and in particular to provide a high-zirconia electrically fused cast refractory that is easy to mass-produce industrially, that suppresses the opening of joints at the contact points between refractories called "joints," that suppress the formation of zircon crystals, that does not result in an extremely large coefficient of residual volume expansion even if some zircon crystals are formed, that does not cause cracks in the refractory when subjected to heating or thermal cycles, and that has high corrosion resistance from glass.

[0053] The present invention provides a high-zirconia electrofusion cast refractory material as follows: <Aspect 1> Chemical components: ZrO ２ and HfO ２ the total of which is more than 80 mass% and not more than 92 mass%, ２ O ３ 0.2 to 3.0 mass% of SiO ２ 1.5 to 10 mass% of Na ２ O is 0.05 to 2.0 mass %, K ２ O is 1.0 mass% or less, B ２ O ３ 0 to 1.5 mass% of Y ２ O ３ is more than 4.0 mass% and not more than 9.0 mass%, the sum of MgO and CaO is 0.02 to 0.4 mass%, CaO is 0.01 mass% or more, Fe ２ O ３ and TiO ２ The total of these is 0.5% by mass or less, ２ O ５ A high zirconia electrically fused cast refractory material having a content of 0.04 mass % or less of ZrO as a chemical component. ２ and HfO ２ the total of which is more than 80 mass% and not more than 92 mass%, ２ O ３ 0.4 to 2.5 mass% of SiO ２ 1.5 to 7.0 mass% of Na ２ O is 0.3 to 1.8 mass %, K ２ O is 1.0 mass% or less, B ２ O ３ 0 to 1.0 mass % of Y ２ O３ is more than 4.0 mass% and 7.5 mass% or less, the sum of MgO and CaO is 0.02 to 0.4 mass%, CaO is 0.01 mass% or more, Fe ２ O ３ and TiO ２ The total of these is 0.5% by mass or less, ２ O ５ The high zirconia electrically fused cast refractory according to Aspect 1, wherein the content of Y is 0.04 mass% or less. ２ O ３ The high zirconia electrically fused cast refractory according to aspect 1 or 2, wherein the mass content of Y is 4.5 to 7.5 mass%. ２ O ３ The high zirconia electrically fused cast refractory according to aspect 3, wherein the mass content of SiO is more than 4.5 mass% and not more than 6.0 mass%. ２ The high zirconia electrically fused cast refractory according to any one of Aspects 1 to 4, wherein the mass content of Al is 4.0 to 6.5 mass%. ２ O ３ The high zirconia electrically fused cast refractory according to any one of Aspects 1 to 5, wherein the mass content of Na is 0.5 to 1.2 mass%. ２ The high-zirconia electrically fused cast refractory according to any one of Aspects 1 to 6, wherein the mass content of O is 0.5 to 1.2 mass%. <Aspect 8> B ２ O ３ The high-zirconia electrically fused cast refractory according to any one of Aspects 1 to 7, wherein the mass content of ZrO is 0.01 to 0.6 mass%. <Aspect 9> The high-zirconia electrically fused cast refractory according to any one of Aspects 1 to 8, wherein the temperature at which the expansion coefficient of the refractory is maximized is between 1300°C and 1500°C during a temperature rise from 200°C to 1500°C. <Aspect 10> The high-zirconia electrically fused cast refractory according to any one of Aspects 1 to 8, wherein the temperature at which the expansion coefficient of the refractory is maximized is between 1300°C and 1500°C during a cooling process from 1500°C. ２ The high-zirconia electrically fused cast refractory according to any one of Aspects 1 to 9, wherein the crystals shrink without transforming from tetragonal to monoclinic. Aspect 11: The high-zirconia electrically fused cast refractory according to any one of Aspects 1 to 10, which is for use in a glass melting furnace.

[0054] According to the present invention, an improved high-zirconia electrically fused cast refractory can be provided. In particular, when the high-zirconia electrically fused cast refractory of the present invention, which can be easily mass-produced industrially, is used in a glass melting furnace, the opening of joints at the contact points between refractories is suppressed, and the formation of zircon crystals is suppressed. Even if zircon crystals are formed, the coefficient of permanent volume expansion does not become extremely large, and cracks do not occur in the refractory. As a result, a refractory with high corrosion resistance against glass can be provided. Therefore, long-term operation becomes possible, which is extremely beneficial industrially.

[0055] FIG. 1 shows a graph of the zirconia 93% by mass (Y ２ O ３ 2 is a graph showing the thermal expansion coefficient measurement results for a high-zirconia electrofusion cast refractory having a zirconia content of 0.24% by mass and for Examples 2 and 8. ２ O ３ Fig. 3 is a diagram of the apparatus used to evaluate corrosion resistance. Fig. 4 is a photograph of the appearance of the sample after the corrosion resistance evaluation. Fig. 5A is a diagram of the thermal expansion coefficient measurement of the high-zirconia electrofusion cast refractory with a zirconia content of 0.24% by mass (Y 0.24%) and Comparative Example 16. Fig. 5B is a diagram of the apparatus used to evaluate corrosion resistance. Fig. 5C is a photograph of the appearance of the sample after the corrosion resistance evaluation. Fig. 5D is a diagram of the high-zirconia electrofusion cast refractory with a zirconia content of 0.24% by mass (Y 0.24%) and Comparative Example 16. ２ O ３ 5A is a photograph of the internal structure of the high-zirconia electrically fused cast refractory having a zirconia content of 0.24% by mass. Fig. 5B is a photograph of the internal structure of the high-zirconia electrically fused cast refractory according to Example 1 after evaluation of corrosion resistance.

[0056] As a result of extensive research, the present inventors have found that ZrO ２ and HfO ２ In the refractory material having a total content of more than 80% by mass and not more than 92% by mass, ２ O ３ , SiO ２ , Na ２ O.K. ２ O, B ２ O ３ , MgO, CaO, P ２ O ５ , Fe ２ O ３ , and TiO ２ The content of each component of Y is set to a specific range, and further, ２ O ３It has been found that the problem of the present invention can be solved by setting the content to more than 4 mass % and not more than 9 mass %. Specifically, with such a composition, ZrO ２ The crystal phase can be changed to tetragonal, not only partially, but entirely or almost entirely, resulting in ZrO ２ They found that this method can almost completely eliminate the reversible crystal phase transformation between monoclinic and tetragonal crystals, and also eliminate abrupt volume changes. Furthermore, they found that if the temperature at which the expansion rate of the refractory reaches its maximum is between 1300°C and 1500°C during the temperature rise process from 200°C to 1500°C, the maximum expansion area, which conventionally exists between the outer side surface and the inner side surface of a high-zirconia electrically fused cast refractory, can be moved to the inner side of the furnace, which is in contact with molten glass, and therefore joints at the contact points between the refractories can be completely or substantially completely suppressed.

[0057] That is, Y ２ O ３ By making the content more than 4 mass% and not more than 9 mass%, ZrO ２ The reversible crystal phase transformation between monoclinic and tetragonal crystals is eliminated or almost eliminated, resulting in ZrO ２ Even if the transformation temperature of the crystalline phase shifts to the lower temperature side, ZrO ２ Since the stress generated by the volume change accompanying the transformation of the crystals is small or almost nonexistent, the occurrence of cracks during the manufacture of the refractory can be suppressed, making industrial mass production easier, and the opening of joints when the refractory is used in a glass melting furnace can be suppressed, improving corrosion resistance against glass. ２ The crystals shrink without transforming from tetragonal to monoclinic. Therefore, even if zircon crystals are generated when subjected to heating or thermal cycles during glass melting furnace operation, ZrO ２ The inventors have found that it is possible to provide a high-zirconia electrofusion cast refractory that does not develop cracks because the reversible crystal phase transformation between monoclinic and tetragonal crystals is eliminated or almost eliminated.

[0058] In addition, Y ２ O ３ When the content is increased, the relative amount of ZrO ２ The concentration decreases, but Y２ O ３ ZrO ２ By solid solution in Y ２ O ３ is ZrO ２ It plays a role almost equivalent to that of conventional ZrO ２ It has corrosion resistance equivalent to that of a high zirconia electrofusion cast refractory having a content of 93 to 94 mass %, or the Y partially contained in the glass phase during heating and holding is ２ O ３ Crystallized nodules or ZrO ２ Y solid solution in ２ O ３ High concentrations of Y were formed by dissolving into the glass phase. ２ O ３ Through the nodules, ZrO ２ It was found that the particles easily form a three-dimensional network, improving corrosion resistance (see Figure 5B).

[0059] <<Contained Components>> Each component of the refractory material according to the present invention will be explained below. "Substantially not contained" means that the content is less than 0.01 mass %.

[0060] <ZrO ２ > ZrO contained in high zirconia electrically fused cast refractories ２ The content of ZrO can be determined relatively depending on the contents of other components. ２ If the content is too high, the contents of other components will be relatively low.

[0061] Also, ZrO, which is used as a raw material for high zirconia electrofusion cast refractories, ２ The raw material, zircon raw material, inevitably contains 1 to 2 mass % HfO ２ Contains HfO ２ Since ZrO does not volatilize during production, it is also included in high zirconia electrofusion cast refractories. ２ It is a stable oxide similar to ZrO ２ Since it has the same effect as ZrO ２ +HfO ２ The content is ZrO ２ It can also be treated as a content.

[0062] Therefore, the ZrO ２ and HfO ２ The total content of is more than 80% by mass and not more than 92% by mass, preferably 81 to 92% by mass, 82 to 92% by mass, 83 to 92% by mass, 84 to 92% by mass, 85 to 92% by mass, or 86 to 92% by mass, and more preferably 86 to 91% by mass, 86 to 90% by mass, or 86 to 89% by mass.

[0063] <SiO ２ > SiO ２ is the main component of the glass phase in the refractory material of the present invention.

[0064] SiO ２ The content is 1.5 to 10% by mass, more preferably 1.5 to 9.0% by mass, 1.5 to 8.0% by mass, or 1.5 to 7.0% by mass, and even more preferably 2.0 to 7.0% by mass, 3.0 to 7.0% by mass, 4.0 to 7.0% by mass, 4.0 to 6.5% by mass, or 4.0 to 6.0% by mass.

[0065] Y ２ O ３ ZrO ２ Even if the solid solution in the crystal causes almost no shrinkage during the transformation from the monoclinic to the tetragonal crystal phase, the shrinkage rate is small, but ZrO ２ Contraction may occur during the crystal phase transformation from monoclinic to tetragonal. ２ When the content is less than 1.5 mass %, the amount of glass phase formed decreases, and ZrO ２ The stress generated by the volume change that accompanies the transformation of the crystal cannot be suppressed, and cracks are likely to occur. ２ When the content exceeds 10 mass%, ZrO ２ The content decreases, which may result in a decrease in corrosion resistance.

[0066] <Al ２ O ３ > Al ２ O ３ In the present invention, even if the raw material is not directly added, it does not have much effect on industrial mass production. ２ O ３However, if the content exceeds 2.5 mass %, corundum or mullite crystals are likely to precipitate in the glass phase during manufacturing or heating. ２ O ３ ZrO ２ Since the transformation from monoclinic to tetragonal crystal phases is eliminated or almost eliminated by solid solution in the crystals, even if these products that cause cracks to occur during the production of high-zirconia electrofusion cast refractories are present, they do not have much impact on industrial mass production.

[0067] In the present invention, Al ２ O ３ The content of Al is 0.2 to 3.0 mass %. ２ O ３ is ZrO ２ Raw materials and SiO ２ Since it exists as an impurity in the raw materials, it is usually contained at 0.2 mass% or more even if it is not newly added. Furthermore, if it exceeds 3.0 mass%, ZrO ２ This may lead to a decrease in the content, resulting in a decrease in corrosion resistance.

[0068] Therefore, Al ２ O ３ The content is 0.2 to 3.0% by mass, more preferably 0.3 to 3.0% by mass, 0.3 to 2.50% by mass, 0.4 to 3.0% by mass, or 0.4 to 2.5% by mass, and even more preferably 0.4 to 2.0% by mass, 0.4 to 1.5% by mass, 0.5 to 1.5% by mass, or 0.5 to 1.2% by mass.

[0069] <Na ２ O>Na ２ O functions as a modifying oxide in the glass phase. It is an essential component for reducing the viscosity of the glass phase, reducing the occurrence of cracks during the production of high-zirconia electrofusion cast refractories, and facilitating industrial mass production. ２ O has the effect of significantly suppressing the formation of zircon crystals in the glass phase of the refractory material. However, if the content exceeds 2.0 mass %, the softening point of the glass phase decreases significantly, which may make the refractory material more susceptible to deformation and reduce corrosion resistance.

[0070] Therefore, Na ２ The O content is 0.05 to 2.0% by mass, more preferably 0.2 to 2.0% by mass, 0.2 to 1.8% by mass, 0.3 to 1.8% by mass, or 0.4 to 1.8% by mass, and even more preferably 0.5 to 1.7% by mass, 0.6 to 1.7% by mass, 0.7 to 1.7% by mass, or 0.5 to 1.4% by mass, 0.5 to 1.2% by mass, or 0.5 to 1.0% by mass.

[0071] <K ２ O>K ２ O is 1.0% by mass or less, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and it is particularly preferable that it is substantially free of O. "Substantially free of O" means that it is less than 0.01% by mass. ２ The lower limit of the O content is not particularly limited, but may be 0.001 mass % or 0.0001 mass %.

[0072] <B ２ O ３ > B ２ O ３ In the present invention, even if it is not contained, it does not have a significant effect on industrial mass production. ２ O ３ Even a low content of ZrO has the effect of suppressing cracks during manufacturing, which may facilitate industrial mass production. On the other hand, if the content exceeds 1.5 mass%, the relative amount of ZrO ２ The content decreases, which may result in a decrease in the corrosion resistance of the high-zirconia electrofusion cast refractory, and an excessively high content may facilitate the formation of zircon crystals.

[0073] Therefore, B ２ O ３ The content is 0 to 1.5% by mass, more preferably 0 to 1.2% by mass, 0 to 1.0% by mass, and even more preferably 0.01 to 0.8% by mass, 0.01 to 0.6% by mass, 0.01% by mass or more but less than 0.58% by mass, 0.01 to 0.5% by mass, 0.01 to 0.4% by mass, or 0.01 to 0.2% by mass.

[0074] <Y ２ O ３ > Y ２ O ３is the most important component in the present invention. ２ O ３ By making the content more than 4 mass% and not more than 9 mass%, ZrO ２ By changing the crystalline phase to tetragonal, not only partially, but entirely or almost entirely, ZrO ２ Since the reversible crystal phase transformation between monoclinic and tetragonal crystals is almost eliminated, ZrO ２ The sudden volume change that occurs when the crystal transforms between monoclinic and tetragonal crystals is almost eliminated, which has the effect of suppressing cracks during manufacturing and is thought to facilitate industrial mass production. ２ O ３ If the content is too high, cubic ZrO ２ This stabilizes the material and can cause cracks during manufacturing. ２ O ３ If the content is too low, the ZrO phase will be monoclinic rather than tetragonal. ２ The ratio of ZrO ２ The sudden volume change during the transformation of the crystal between monoclinic and tetragonal crystals becomes large, which can cause cracks to occur during manufacturing.

[0075] Therefore, Y ２ O ３ The content of is more than 4.0% by mass and not more than 9.0% by mass, more preferably more than 4.0% by mass and not more than 8.5% by mass, more than 4.0% by mass and not more than 8.0% by mass, or more than 4.0% by mass and not more than 7.5% by mass, and even more preferably 4.5 to 7.5% by mass, 4.5 to 7.0% by mass, 4.5 to 6.5% by mass, 4.5 to 6.0% by mass, more than 4.5% by mass and not more than 6.0% by mass, or 5.0 to 6.0% by mass.

[0076] <MgO> MgO is ZrO ２ Since it exists as an impurity in the raw materials, care must be taken when selecting raw materials. Furthermore, a high content of zircon may facilitate the formation of zircon crystals. In the present invention, it is not newly added, but the content is preferably 0.1 mass% or less, and it is more preferable that it is substantially not contained.

[0077] <CaO> When a certain amount of CaO is contained, it reduces the viscosity of the molten metal of the high-zirconia electrically fused cast refractory and can form a stable glass phase. If CaO is not substantially contained, a very unstable glass phase is formed, which causes cracks to occur during production. In other words, the occurrence of cracks makes mass production impossible. Therefore, it is essential that CaO is contained.

[0078] CaO is also ZrO ２ Raw materials and ZrO ２ Since ZrO exists as an impurity in the zircon raw material, which is the source of the refractory, if the content in the refractory is to be less than 0.01%, a high-purity reagent must be used as the raw material, which is very expensive and therefore unsuitable for mass production. Therefore, the content is 0.01 mass% or more, and preferably 0.02 mass% or more. However, if the content exceeds a certain amount, care must be taken because it promotes the formation of zircon crystals. ZrO ２ Since the reversible crystal phase transformation between monoclinic and tetragonal crystals is almost eliminated, it can be said that even if zircon crystals are generated, cracks will not occur in the refractory. In the present invention, although the shrinkage rate is small, ZrO ２ Since the refractories include those that undergo shrinkage during the crystal phase transformation from monoclinic to tetragonal, it is necessary to suppress the formation of zircon crystals.

[0079] Therefore, the CaO content is preferably 0.02 to 0.3% by mass, more preferably 0.02 to 0.2% by mass or 0.02 to 0.1% by mass, and particularly preferably 0.03 to 0.2% by mass or 0.03 to 0.1% by mass. The total content of MgO and CaO is 0.02 to 0.4% by mass, and preferably 0.02 to 0.35% by mass.

[0080] <Fe ２ O ３ and TiO ２ > Fe ２ O ３ and TiO ２ is ZrO ２ These oxides are impurities in the raw materials and zircon raw materials. These oxides cause coloration and foaming in the molten glass, so their content must be limited. ２ O ３and TiO ２ The total content of is 0.5 mass% or less, preferably 0.3 mass% or less, and more preferably 0.2 mass% or less. ２ O ３ and TiO ２ The total content may be 0.01 mass % or more.

[0081] <P ２ O ５ > P ２ O ５ is one of the components that make up glass, and has the effect of producing low-melting glass and adjusting the viscosity of the molten metal when producing high-zirconia electrically fused cast refractories. ２ O ５ When the refractory material contains P, the formation of zircon crystals is significantly promoted. ２ O ５ It is preferable that the material does not substantially contain P. ２ O ５ The content is preferably 0.04 mass % or less, more preferably 0.02 mass % or less.

[0082] <<Expansion Coefficient (Thermal Expansion Coefficient) of Refractory>> The expansion coefficient of a refractory can be evaluated, for example, by the expansion coefficient during a temperature rise process at every 100° C. in a temperature range of 200° C. to 1500° C. Alternatively, the expansion coefficient of a refractory can be evaluated, for example, by the expansion coefficient during a temperature fall process at every 300° C. in a temperature range of 1500° C. to 300° C.

[0083] If the temperature at which the expansion rate of the refractory reaches its maximum during the temperature rise from 200°C to 1500°C is in the range of 1300°C to 1500°C, the maximum expansion portion, which in the conventional technology existed between the outer surface and the inner surface of the furnace of the high-zirconia electrically fused cast refractory, can be made to exist on the inner surface of the furnace that comes into contact with the molten glass, and therefore joint opening can be completely or substantially completely suppressed at the contact portion between the refractories. Therefore, during the temperature rise from 200°C to 1500°C, it is preferable that the temperature at which the expansion rate of the refractory reaches its maximum be in the range of 1300°C to 1500°C.

[0084] Regarding the expansion rate of the refractory during the cooling process, ZrO ２It is preferable that the crystals shrink without transforming into monoclinic crystals. ２ When the crystals transform from tetragonal to monoclinic, a sudden volume expansion occurs. If zircon crystals are generated, the relative decrease in the glass phase makes it difficult for the glass phase to absorb this sudden volume expansion, which reduces the strength of the refractory and causes cracks. Therefore, in the temperature drop process from 1500°C to 300°C, it is preferable that the temperature at which the expansion rate of the refractory is maximum is between 1200°C and 1500°C. In this case, the temperature at which the tetragonal to monoclinic ZrO ２ It is believed that crystal transformation does not occur or is suppressed.

[0085] According to a preferred embodiment of the refractory material of the present invention, during the cooling process from 1500°C (temperature decreasing process), ZrO ２ The crystals shrink without transforming from tetragonal to monoclinic. This can be confirmed by the fact that when the expansion coefficient of the refractory material is measured every 300°C during the cooling process (temperature drop process) from 1500°C, there is no increase in the expansion coefficient corresponding to the transformation from tetragonal to monoclinic.

[0086] The expansion coefficient (linear expansion coefficient) of the refractory material during the temperature increase and decrease processes can be measured using a thermomechanical analyzer (for example, TMA4000SA manufactured by NETZSCH) on a sample extracted from the refractory material using a diamond drill in accordance with JIS R 2207-3.

[0087] High zirconia electrofused cast refractories according to preferred embodiments of the present invention will be described below, although the present invention is not limited to these embodiments.

[0088] Examples 1 to 14, Comparative Examples 15 to 24 Refractories according to Examples 1 to 14 and Comparative Examples 15 to 24 were produced, and their physical properties were evaluated.

[0089] <Production of refractories> ZrO obtained by desiliconizing zircon sand ２ The raw material is SiO ２ , Al ２ O ３ , Na ２ O, B ２ O ３ , Y ２ O３ The oxide raw materials, such as nitrate raw materials, were blended in a predetermined ratio in terms of oxide, and after mixing, they were melted in an electric arc furnace. After melting for a predetermined time, the mixture was cast into a mold, and the mold was immersed in a cooling medium to be cooled slowly to room temperature.

[0090] The mold used was made of graphite and had a product part measuring 100 mm x 300 mm x 300 mm, with a riser part having internal dimensions of 140 mm x 235 mm x 350 mm integrally connected to the top of the product part.

[0091] After slow cooling, the mold and casting were removed from the quartz sand slow cooling material, and then the mold and casting were separated. The product portion of the casting was separated from the riser portion to obtain the desired high-zirconia electrofusion cast refractory.

[0092] <Evaluation> The produced refractories of Examples 1 to 14 and Comparative Examples 15 to 24 were evaluated for physical properties and the like as follows. The compositions and properties of the high zirconia electrically fused cast refractories of Examples 1 to 14 are shown in Table 1, and the expansion coefficients during the temperature increase and decrease processes are shown in Table 2. The compositions and properties of the high zirconia electrically fused cast refractories of Comparative Examples 15 to 24 are shown in Table 3, and the expansion coefficients during the temperature increase and decrease processes are shown in Table 4. The amounts of each component in Tables 1 and 3 are in mass%.

[0093] <Component Analysis> Each component was analyzed by wavelength dispersive X-ray fluorescence spectrometry. ２ O ３ The content was analyzed by high frequency inductively coupled plasma atomic emission spectrometry, but the present invention is not limited to these analytical methods and can be carried out using other analytical methods.

[0094] <Cracks> For cracks during manufacturing, the state of the product after it was removed from the annealing material was first observed. Then, the product was cut in half to observe the internal state and evaluated according to the following criteria: +++: Refractory with no cracks on the block surface or inside, or with no cracks on the block surface and internal cracks less than 50 mm long ++: Refractory with no cracks on the block surface but with internal cracks 50 mm or longer long +: Refractory with cracks on the block surface spanning two sides and internal cracks 50 mm or longer long -: Refractory with cracks on the block surface spanning three or more sides, or refractory that was broken by cracks when it was removed from the annealing material

[0095] <Bulk density and porosity> The bulk density and porosity were determined by extracting a 23 mm diameter drill core from a portion of the 300 mm x 300 mm surface 50 mm from the bottom surface of the mold contact portion and 50 mm from the side surface of the mold contact portion, and calculating the bulk density and apparent porosity of a sample 90 mm long and 5 mm inside from the casting surface using the Archimedes method.

[0096] The bulk density of the refractory material is preferably 5.10 g / cm ３ ~5.70g / cm ３ The porosity of the refractory material is preferably 5.00% or less, or 3.00% or less (the lower limit of the porosity is not particularly limited, but may be 0.80%).

[0097] <Expansion Coefficient (Thermal Expansion Coefficient)> The expansion coefficient (linear expansion coefficient) of the refractory was measured in accordance with JIS R 2207-3. Samples for evaluating the expansion coefficient of the refractory were prepared by cutting a 5 mm diameter drill core from a 300 mm x 300 mm surface, 20 mm from the bottom surface of the mold contact area and 130 mm from the side surface of the mold contact area, and cutting 40 mm from each casting surface to prepare samples with a central length of 20 mm. The expansion coefficient of the samples extracted from the refractory was measured using a thermomechanical analyzer. The results for Examples 1 to 14 and Comparative Examples 15 to 24 are shown in Tables 2 and 4, respectively. Also, FIG. 1 shows the expansion coefficient of a refractory containing 93% by mass of zirconia (Y ２ O ３ The results of measuring the thermal expansion coefficient of the high zirconia electrofusion cast refractory material with a zirconia content of 0.24% by mass and Examples 2 and 8 are shown in FIG.２ O ３ 1 shows the results of measuring the thermal expansion coefficient of a high-zirconia electrically fused cast refractory having a zirconia content of 0.24% by mass and Comparative Example 16.

[0098] <Corrosion Resistance> A 22 mm diameter drill core was cut out from a position 50 mm from the bottom surface and side surface of the mold contact portion of a 300 mm x 300 mm surface, and each was cut 5 mm from the casting surface, and a 90 mm long central portion was used as a sample for evaluating corrosion resistance.

[0099] Figure 3 shows a diagram of the apparatus used to evaluate corrosion resistance. The corrosion resistance was evaluated using alkali-free glass as follows. The composition of the alkali-free glass used in this test was SiO ２ 62% by mass, Al ２ O ３ 16% by mass, B ２ O ３ 2% by mass, CaO 9% by mass, SrO 2% by mass, and BaO 9% by mass.

[0100] <Corrosion resistance test using alkali-free glass> Holes were drilled in the sample to be evaluated and in the alumina guide tube to which the sample was attached, and a refractory pin was inserted to attach the sample to the alumina guide tube. The refractory pin and the alumina guide tube were fixed using a heat-resistant adhesive. One end of the alumina guide tube was connected to the sample to be evaluated, and the other end was connected to the test device.

[0101] A high-zirconia electrocast refractory crucible (reference numeral 3 in FIG. 3 ) containing alkali-free glass (reference numeral 2 in FIG. 3 ) was heated to 1700°C, and then the test apparatus connected to the alumina guide tube was started, and the sample to be evaluated was rotated at 40 rpm. The sample (reference numeral 1 in FIG. 3 ) rotated at 40 rpm was brought into contact with alkali-free glass (reference numeral 2 in FIG. 3 ) whose temperature had been raised to 1700°C. The alkali-free glass and the sample to be evaluated were kept in contact with each other at 1700°C for 168 hours, after which the sample was pulled out of the refractory crucible, and the glass adhering to the sample to be evaluated was removed.

[0102] The amount of corrosion at the most corroded portion of the sample was measured using a vernier caliper. ２ Content 93% by mass (Y ２ O ３ 4 shows the appearances of a sample having a content of 0.24% by mass (reference numeral 4 in FIG. 4) and a sample according to Example 1 (reference numeral 5 in FIG. 4) after the corrosion resistance test.

[0103] For comparison, ZrO ２ Content 93% by mass (Y ２ O ３ The amount of erosion of the high zirconia electrically fused cast refractory with a content of 0.24% by mass was taken as the standard amount of erosion and evaluated according to the following criteria: ++: The amount of erosion was less than the standard amount +: The amount of erosion was the same as the standard amount -: The amount of erosion was more than the standard amount

[0104] ZrO ２ Content 93% by mass (Y ２ O ３ Photographs of the internal structures of the refractory having a Cr content of 0.24% by mass and the refractory according to Example 1 after the corrosion resistance evaluation were taken. The photographs are shown in Fig. 5A and Fig. 5B, respectively.

[0105] <Residual volume expansion coefficient after thermal cycle test> A 45 mm diameter drill core was cut out from a position 50 mm from the bottom surface of the mold contact portion of the 300 mm x 300 mm surface and the mold contact portion side, and 25 mm was cut from each casting surface, and the central 50 mm long section was used as an evaluation sample.

[0106] The sample was heated to 600°C at a heating rate of 3°C / min and held at that temperature for 1 hour. The sample was then heated to 1450°C at a heating rate of 3°C / min and held at 1450°C for 1 hour. After holding for 1 hour, the sample was cooled to 600°C at a cooling rate of 3°C / min and held at that temperature for 1 hour. This thermal cycle, consisting of holding at 600°C for 1 hour and at 1450°C for 1 hour, was repeated 20 times. After 20 thermal cycles, the residual volume expansion coefficient was calculated from the difference in volume of the evaluation sample obtained from the dimensions measured before and after heating.

[0107] The thus calculated residual volume expansion rate is preferably 2% or less, and more preferably 1% or less. If the residual volume expansion rate exceeds 5%, some of the sample will begin to powder, which is undesirable, and if it exceeds 10%, the sample will begin to powder overall, which is even more undesirable.

[0108] <Evaluation Results> Examples 1 to 14 are Y ２ O ３ The refractories have a ZrO content of more than 4 mass %. As can be seen from Table 2 (and FIG. 1), in the temperature increase process from 200°C to 1500°C, the temperature at which the expansion coefficient of the refractories reaches its maximum is in the range of 1300°C to 1500°C in all of Examples 1 to 14. In addition, in the temperature decrease process from 300°C to 1500°C, the temperature at which the expansion coefficient of the refractories reaches its maximum is in the range of 1200°C or higher in all of Examples 1 to 14. In all of Examples 1 to 14, ZrO ２ No sudden volume change was observed near the transformation temperature of the crystalline phase. ２ This indicates that the reversible crystal phase transformation between monoclinic and tetragonal crystals is eliminated or almost eliminated, and therefore the rapid volume change is alleviated or eliminated.

[0109] In Examples 7 and 8, the main component of the glass phase was SiO ２ Without intending to be limited by theory, it is believed that the ２ O ３ Due to the effect of ZrO ２ Since the reversible crystal phase transformation between monoclinic and tetragonal crystals is eliminated or almost eliminated, the crystal phase transformation accompanied by a sudden volume change is alleviated, and SiO ２ This shows that even a relatively low content provides good resistance to thermal cycling.

[0110] 5A is a photograph of the internal structure of a high-zirconia electrofusion cast refractory containing 93 mass % zirconia after corrosion resistance evaluation. ２ O ３ FIG. 5B is a photograph of the internal structure of the high-zirconia electrically fused cast refractory according to Example 1 after evaluation of corrosion resistance (Y ２ O ３As can be seen from these photographs, Y ２ O ３ In the refractory material having a content exceeding 4 mass%, Y contained in part in the glass phase ２ O ３ crystallized nodules, or ZrO ２ Y solid solution in ２ O ３ High concentration of Y ２ O ３ Through the nodules, ZrO ２ It is considered that the particles easily form a network. Therefore, even if the porosity is relatively high as in Examples 7, 8, and 11, ZrO ２ The corrosion resistance is equal to or higher than that of a high zirconia electrofused cast refractory material with a content of 93 mass %.

[0111] In Examples 5 and 11, the components that promote the formation of zircon crystals (CaO or B ２ O ３ ) but Y ２ O ３ If the content exceeds 4 mass%, even if zircon crystals are formed, ZrO ２ The transformation of the crystal phase, which is accompanied by a sudden change in volume from monoclinic to tetragonal, is alleviated, and this indicates that the residual expansion coefficient is 2% or less, and that resistance to thermal cycles is good.

[0112] As is clear from Table 1, after the high-zirconia electrically fused cast refractories of Examples 1 to 14 were removed from the annealed material, the cracks on their appearance were short or non-existent. Therefore, even if cracks were present, they could be partially removed, making industrial mass production possible, suppressing the opening of joints and the residual expansion coefficient against thermal cycles, and allowing them to be used as long-life refractories with high corrosion resistance from glass.

[0113] Table 3 shows refractories not corresponding to the present invention as comparative examples. All of the refractories according to comparative examples 15 to 24 exhibited poor quality in terms of the occurrence of cracks during production. In addition, some comparative examples also exhibited poor quality in terms of corrosion resistance and / or residual volume expansion coefficient after thermal cycling.

[0114] Among the comparative examples, Comparative Examples 15 to 17 are Y ２ O ３ The refractories have a relatively low content of Y. Comparative Example 15 is a composition corresponding to Patent Document 4 (JP-A No. 2013-514254). ２ O ３ As a result of containing ZrO ２ The transformation temperature from monoclinic to tetragonal crystals shifts to the lower temperature side, and the viscosity of the glass phase is high at the lower temperature side, so ZrO ２ It is thought that the refractory cracked when it was removed from the annealing material because it was unable to mitigate the sudden volume change.

[0115] In contrast, in Comparative Example 19, Y ２ O ３ In this comparative example, the refractory contains a relatively high amount of Y. ２ O ３ is ZrO ２ ZrO, which is solid-dissolved in the crystal and has a partly cubic crystal structure ２ This may have made the material more susceptible to cracking.

[0116] In the refractories according to Comparative Examples 18 and 20 to 24, Y ２ O ３ Although the content is in the range of more than 4.0 mass% to 9.0 mass%, SiO ２ , Al ２ O ３ , B ２ O ３ , Fe ２ O ３ , TiO ２ , MgO, CaO, K ２ O and P ２ O ５ It is believed that the occurrence of cracks and the like occurs because at least one of the components is too much or too little.

[0117] The refractories according to these comparative examples are difficult to mass-produce industrially and may be unsuitable for stable production.

[0118] From the above results, it can be seen that the high-zirconia electrically fused cast refractory of the present invention is highly effective as a refractory for glass melting furnaces, as it inhibits erosion from glass due to opening of joints, has high corrosion resistance, and exhibits good resistance to thermal cycles.

[0119] Furthermore, the high zirconia electrically fused cast refractory of the present invention is very useful for glass melting furnaces, but is not limited to glass melting furnaces.

[0120]

[0121]

[0122]

[0123]

[0124] 1 Sample for evaluating corrosion resistance 2 Molten glass 3 Crucible for high zirconia electrically fused cast refractory 4 High zirconia electrically fused cast refractory containing 93 mass % zirconia after corrosion resistance test 5 Refractory according to Example 1 after corrosion resistance test

Claims

1. As a chemical component, ZrO ２ and HfO ２ The total of more than 80% by mass and 92% by mass or less, Al ２ O ３ 0.2 to 3.0 mass% SiO ２ 1.5 to 10 mass% Na ２ O is 0.05 to 2.0 mass %, K ２ O is 1.0 mass% or less, B ２ O ３ 0 to 1.5 mass% Y ２ O ３ is more than 4.0 mass% and not more than 9.0 mass%, The total of MgO and CaO is 0.02 to 0.4 mass %, CaO is 0.01% by mass or more, Fe ２ O ３ and TiO ２ the total of which is 0.5% by mass or less, P ２ O ５ The content is 0.04% by mass or less, High zirconia electrofusion cast refractories.

2. As a chemical component, ZrO ２ and HfO ２ The total of more than 80% by mass and 92% by mass or less, Al ２ O ３ 0.4 to 2.5 mass% SiO ２ 1.5 to 7.0 mass% Na ２ O is 0.3 to 1.8 mass %, K ２ O is 1.0 mass% or less, B ２ O ３ 0 to 1.0 mass% Y ２ O ３ is more than 4.0 mass% and not more than 7.5 mass%, The total of MgO and CaO is 0.02 to 0.4 mass% CaO is 0.01% by mass or more, Fe ２ O ３ and TiO ２ the total of which is 0.5% by mass or less, P ２ O ５ The content is 0.04% by mass or less, 2. The high zirconia electrofused cast refractory according to claim 1.

3. Y ２ O ３ The high zirconia electrically fused cast refractory according to claim 1 or 2, wherein the mass content of

4. Y ２ O ３ The high zirconia electrically fused cast refractory according to claim 3, wherein the mass content of is more than 4.5 mass% and not more than 6.0 mass%.

5. SiO ２ The high zirconia electrically fused cast refractory according to claim 1 or 2, wherein the mass content of

6. Al ２ O ３ The high zirconia electrically fused cast refractory according to claim 1 or 2, wherein the mass content of

7. Na ２ 3. The high zirconia electrically fused cast refractory according to claim 1, wherein the mass content of O is 0.5 to 1.2 mass%.

8. B ２ O ３ The high zirconia electrically fused cast refractory according to claim 1 or 2, wherein the mass content of

9. 3. The high-zirconia electrically fused cast refractory according to claim 1, wherein the temperature at which the expansion coefficient of the refractory reaches its maximum is between 1300°C and 1500°C during the temperature rise process from 200°C to 1500°C.

10. During the cooling process from 1500°C, ZrO ２ 3. The high zirconia electrically fused cast refractory according to claim 1, wherein the crystals shrink without transforming from tetragonal to monoclinic.

11. 3. The high zirconia electrically fused cast refractory according to claim 1, which is for use in a glass melting furnace.