JPH1072264A - Production of alumina-zirconia-silica fused refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain alumina-zirconia-silica fused refractories less liable to the leaching of matrix glass and less liable to cause defects in molten glass by adding an oxidizing agent acting at high temp. and an oxidizing agent acting at low temp. to refractory material. SOLUTION: At the time of producing alumina-zirconia-silica fused refractories, an oxidizing agent acting at high temp. and an oxidizing agent acting at low temp. are added to refractory material. The oxidizing agent acting at high temp. is preferably one or more kinds of oxides selected from among cerium oxide, manganese oxide, tin oxide, antimony oxide and arsenic oxide and it is preferably added by 0.1-3.0wt.% of the amt. of the material in the case of one kind and by 0.3-5.0wt.% in the case of two or more kinds. The oxidizing agent acting at low temp. is preferably sodium nitrate and sodium sulfate and it is preferably added by 0.1-1.0wt.% of the amt. of the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alumina / zirconia / silica-based molten refractory mainly used for a contact portion with a molten glass or a superstructure portion of a glass melting furnace.

[0002]

2. Description of the Related Art A molten cast refractory is prepared by charging a mixed material of a refractory prepared to have a predetermined chemical composition into an arc electric furnace having graphite as an electrode, for example, and melting the molten metal. It is manufactured by pouring into a mold having required internal dimensions embedded in a heat insulating material, and cooling and solidifying to room temperature. The ingot obtained in this way is dense,
It has a developed crystal structure. For this reason, it is a refractory excellent in resistance to contamination of the molten glass with respect to the base material as compared with a normal bonded refractory.

[0003] The hot-melt refractory obtained according to the present invention is generally made by casting a refractory raw material melted in an electric furnace into a desired shape, and will be described below as an electroformed refractory. But solidified in the furnace after melting,
Alternatively, it is useful as an aggregate of a refractory by pulverization.

Among such electroformed refractories, refractories containing a relatively large amount of ZrO ₂ are preferably used in glass melting furnaces because of their particularly excellent corrosion resistance. Typical refractories include 33% by weight ZrO ₂ to 41%.
Is the weight percent of alumina-zirconia-silica electrocast refractories and high-zirconia electrocast refractory material to the ZrO ₂ and 80% by weight containing 95% by weight containing. Alumina, zirconia, and siliceous electroformed refractories are most widely used, but a phenomenon occurs in which a matrix glass phase surrounding a crystal phase of corundum and baddrite leaches at a high temperature. This phenomenon causes glass defects such as bubbles, streaks, and gravel on the molten glass. On the other hand, high-zirconia electroformed refractories have a low probability of causing the above glass defects, for example, because the amount of the matrix glass phase surrounding the baddleyite crystal phase is small. Became. But,
It is expensive due to the extremely high ZrO ₂ content.

[0005] One of the causes of the leaching phenomenon of the alumina-zirconia-silica electroformed refractory is a gas generated from the refractory (for example, Ceram. Eng. Sci. Proc.
10 pp. 338-347 1989). Furthermore, the mechanism of gas generation from refractories is various and complicated, for example,
This is a mechanism in which carbon mixed into the molten metal from the graphite electrode during melting is oxidized at a high temperature to generate carbon dioxide or carbon monoxide, which extrudes the softened matrix glass. Alternatively, it is a mechanism that, when mixed with carbon or the like, participates in an oxidation-reduction reaction at a high temperature to generate gas such as oxygen and cause leaching.

[0006] From the above, in order to reduce the exudation of the matrix glass, it is necessary to minimize the incorporation of gas-generating substances and to make the ingot as oxidized as possible. Conventionally, for this purpose, just before tapping,
Although oxygen is blown into the molten metal, leaching of the matrix glass cannot be sufficiently reduced only by this treatment.

Further, the following manufacturing method has been proposed.
The raw material is made into fine particles, the specific surface area is increased, the degree of oxidation is increased, and an oxidizing gas is adsorbed to the fine particles (Japanese Patent Publication No. Hei 5-
8143). An oxidizing agent having an oxidizing action at a low temperature is added to the raw material (Japanese Patent Publication No. 30793/1993). Fe and Ti in raw materials
The impurity content of the oxide of
8). Further, not only these but also other impurities (for example, C
that limit the content of r or Cu oxide) (Japanese Patent Publication 5-7)
350).

[0008] The former two methods of adsorbing an oxidizing gas and adding an oxidizing agent require that the oxidizing gas and the oxidizing agent be used at a temperature considerably lower than the melting temperature.
Since it is desorbed or decomposed, it does not exhibit an oxidizing action continuously and continuously during melting. The latter two methods of suppressing the content of impurities cannot reduce the incorporation of carbon and the like, and thus cannot sufficiently suppress the reduction of leaching. Furthermore, high purification of the raw material is not preferable because it is closely linked to an increase in price.

It has also been proposed to use iron, manganese, chromium, vanadium or the like as an oxidizing agent exhibiting an oxidizing action at a high temperature (JP-B-36-530). However, although this method is an effective method as such, it may not be possible to exert a sufficient effect by itself, for example, when the temperature such as the melting temperature at the time of charging the raw materials is lowered.

[0010]

As described above, many proposals have been made for the incorporation of carbon from a graphite electrode and the reduction of refractories associated therewith. However, an alumina-zirconia-silica electroformed refractory which has sufficiently solved the problem of leaching of the matrix glass has not yet been developed. Therefore, glass defects such as bubbles, streaks, and gravel have not been sufficiently reduced with respect to the molten glass.

The present invention has been made to solve these drawbacks, and provides an alumina-zirconia-silica electroformed refractory which has a small amount of matrix glass exudation and a low possibility of causing glass defects in molten glass. The purpose is to do.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and mainly comprises adding an oxidizing agent exhibiting an oxidizing effect even at a low temperature in combination with an oxidizing agent exhibiting an oxidizing effect at a high temperature. An object of the present invention is to provide an alumina / zirconia / silica electroformed refractory characterized in that the potential for leaching of matrix glass or the generation of glass defects is sufficiently reduced.

As the oxidizing agent used in the present invention, tin oxide, cerium oxide, manganese oxide, antimony oxide, and arsenic oxide are suitable as those exhibiting an oxidizing action at high temperatures. Also, as the oxidizing agent having an oxidizing action at a lower temperature, sodium nitrate and sodium sulfate are suitable. This is because when the temperature of the molten metal drops at the time of charging the raw materials,
It acts as an auxiliary to the oxidizing agent having an oxidizing action at the above-mentioned high temperature. Further, when the oxidizing agent having an oxidizing action at a high temperature is reduced, it is oxidized, and the oxidizing agent having an oxidizing action at a high temperature acts so as to exhibit the oxidizing ability more efficiently.

It is desirable that the oxidizing agent used in the present invention is mixed with the raw material in a solid state, and exhibits an oxidizing action in a molten state. Because at the time of injection, the oxidant in the liquid state
Even if mixed and melted with other raw materials, the molten metal may explode, and the melting operation is dangerous. Further, when the oxidizing agent itself decomposes and the oxidizing gas generated thereby exhibits an oxidizing effect, the effect is not sufficient.

Generally, the oxidizing agent often shows a large number of oxidation numbers, but the oxidizing agent used in the present invention is preferably an oxide having a higher oxidation number. However, it is also possible to use an oxidizing agent which does not have the highest oxidation number or is not in the form of an oxide. Further, the oxidizing agent used after melting,
It is desirable to be present in the matrix phase as much as possible. The reason for the bleeding phenomenon is that the matrix glass is mainly involved, and when present in the crystal phase, it selectively dissolves in the molten glass and is inferior in corrosion resistance.

In the present invention, when the oxide is carbon,
For example, they exhibit an oxidizing action as shown in the following Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, Chemical Formula 4, Chemical Formula 5, Chemical Formula 6, and Chemical Formula 7.

The oxidizing effect at high temperatures is

[0018]

Embedded image 2SnO ₂ + C = 2SnO + CO ₂

[0019]

## STR2 ## 4 CeO ₂ + C = ₂ CeO ₃ + CO ₂

[0020]

3MnO ₂ + C = Mn ₃ O ₄ + CO ₂

[0021]

Embedded image Sb ₂ O ₅ + C = Sb ₂ O ₃ + CO ₂

[0022]

Embedded image As ₂ O ₅ + C = As ₂ O ₃ + CO ₂

The oxidizing action at lower temperatures is

[0024]

Embedded image 4NaNO ₃ + 3C = 2Na ₂ O + 4NO + 3CO ₂

[0025]

Embedded image 2Na ₂ SO ₄ + C = 2Na ₂ O + 4SO ₂ + 3CO ₂

The above-mentioned oxidizing agents are usually limited to skeleton-forming ions (oxides) or skeleton-modifying ions (oxides) in a matrix glass, that is, sodium aluminosilicate, although the amount thereof is limited. sell.

Such an oxidizing agent exhibiting an oxidizing action at a high temperature requires 1 mol (Chem. 4 and 5) to 4 mol (Chem. 3) of oxidizing agent to oxidize 1 mol of carbon. When converted to weight, 19 (= 229/12) for 1 carbon
To 57 (= 172 × 4/12).

Normal alumina / zirconia / silica electroformed refractories are 100 to 300 ppm by weight.
Contains C carbon. Assuming that 300 ppm by weight of C is contained, stoichiometrically 0.75% by weight of SnO ₂ , 1.
7% by weight CeO ₂ , 0.63% by weight MnO ₂ , 0.81
An oxidizing agent of weight% Sb ₂ O ₅ and 0.57 weight% As ₂ O ₅ is required. The oxidizing agents and their oxidizing actions listed here are those in which each oxide is easily available and has the highest oxidation number.

The oxidizing agents that act at high temperatures, such as tin oxide, cerium oxide, manganese oxide, antimony oxide, and arsenic oxide, of the present invention can be used as SnO 2 materials for refractory raw materials.
₂ , CeO ₂ , MnO ₂ , Sb ₂ O ₅ , and As ₂ O ₅
In the form of a single 0.1% by weight or more and 3.0% by weight or less,
Alternatively, it is preferable to add 0.3 to 5.0% by weight in total of two or more kinds.

More preferably, a single component is used in an amount of 0.1% by weight or more and 1.5% by weight or less, or
It is to be added in an amount of not less than 5.0% by weight and not more than 5.0% by weight.

If the amount is less than these ranges, the oxidizing action is insufficient, and if the amount is too large, the matrix glass becomes too soft, and on the contrary, leaching is promoted. However, the range of the above-mentioned oxide addition amount is a case where the amount of the matrix glass phase is 18% by weight based on the whole refractory, and when the ratio is higher or lower than this, it is necessary to increase or decrease the oxide addition amount. Can be.

The oxidizing agent to be added may be mixed with other raw materials, but can be added to the molten metal collectively or separately by using only this.

NaNO ₃ and Na ₂ SO ₄ , particularly in the former, play an auxiliary role of the oxidizing agent acting at the above-mentioned high temperature.
Hereafter, it is particularly desirable to add it in the range of 0.5% by mass or less. The gas generated by decomposition of NaNO ₃ has an oxidizing effect, whereas Na ₂ SO ₄ has an oxidizing effect after melting. Therefore, it is conceivable to add all necessary Na ₂ O as Na ₂ SO ₄ ,
The generated S compound (especially SO ₂ ) easily dissolves in the glass, and in this case, causes oozing later.

Instead of NaNO ₃ and Na ₂ SO ₄ ,
Al (NO ₃ ) ₃ ,
Al ₂ (SO ₄ ) ₃ , Zr (NO ₃ ) ₂ , Zr (SO
₄ ) It is also conceivable to use ₂ , but these are usually marketed in the form containing coordinating water, so they must be used in such a form as to be dehydrated.

The above-mentioned oxidizing agent is in the form of an oxide or a sodium salt. However, when the matrix glass phase is not sodium silicate, a compound of another salt may be used within the above-mentioned range of oxidizing ability. . For example, K
MnO ₇ , Ca (NO ₃ ) ₂ , Na ₂ O ₂ , NaClO
It is.

[0036]

EXAMPLE A predetermined amount of Bayer alumina as an alumina source, zircon desilicated as a zirconia source, silica sand as a silica source, sodium carbonate, sodium nitrate or sodium sulfate as a sodium source, and an oxidizing agent were weighed and mixed. Tables 1 and 2 show the mixing ratio. this,
It was completely melted at about 1900 ° C. in a 500 kVA single-phase electric arc furnace using a graphite electrode. This melt is embedded in silica / alumina balls and has an inner dimension of 1360 mm.
Hot water was poured into a sand mold of 160 mm × 350 mm and allowed to cool to room temperature.

Examples 1 to 16 are examples of the present invention.
17 is a comparative example. Then, about the obtained ingot,
The exudation characteristics and foaming characteristics were examined, and the results are shown in Table 3. Seepage
Characteristics are 30mm to 100mm cross section from bottom
Not include the skin (at least 20 mm away from the side)
From the part), 30
mm cube sample, 1500 ° C and 1600 ° C
And by heating for 48 hours. Evaluation,
Calculate the weight loss by heating as a percentage of the weight before heating.
Depends on the method.

The foaming characteristics were determined by cutting a portion 40 mm × 40 mm from a portion not including the skin portion (a portion 15 mm or more away from the side surface) in a cross section of about 25 mm from the bottom surface.
A plate-shaped sample of mm × 5 mm was obtained, and an inner diameter of 30 mm was placed on the sample.
, And about 10 g of TV panel glass placed in the ring.
Performed by heating for 8 hours. In the evaluation, the number of bubbles existing in the glass after cooling was measured using an optical microscope, and the result was indicated by the number of cm ² .

From Table 3, it can be seen that those obtained according to the present invention show particularly excellent foaming properties (low foaming amount) or excellent leaching properties (low leaching amount). The excellent foamability of the product obtained in the present invention indicates that the oxidation is more advanced than in Comparative Example 1 of the conventional product. Generally, when the degree of oxidation increases, the amount of exudation decreases. However, in the product of the present invention, since the oxidizing agent to be added is introduced into the matrix glass, the viscosity of the matrix glass decreases. Therefore, although the foaming property decreases, the exudation property may decrease. In such a case, the use site may be specified in consideration of the characteristics of the brick.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

The oxidizing agent having an oxidizing effect at a high temperature and the alumina / zirconia-silica material obtained by adding an oxidizing agent having an oxidizing effect at a low temperature to the molten refractory of the present invention can be used for melting glass. It is a refractory suitable for glass melting furnaces, which exhibits excellent foam properties and / or excellent leaching properties. In particular, the improvement of foaming property is excellent, and it can be used not only for the non-contact portion with the molten glass such as for the upper structure, but also for the contact portion such as the roof tile, and the glass defect of the molten glass is greatly reduced. It is thought to decrease. When the product of the present invention, which is particularly excellent in foaming property, is used in a portion in contact with molten glass, it is considered that the foam defect, which is a main glass defect, is reduced. From the above, the industrial value of the present invention is enormous.

Claims (5)

[Claims] 1. An alumina / zirconia / silica-based silica refractory characterized in that an oxidizing agent that acts at a high temperature and an oxidizing agent that acts at a low temperature are added to a refractory raw material during the production of the alumina / zirconia / silica-based fused refractory. Manufacturing method of molten refractories. 2. An oxidizing agent which operates at a high temperature is cerium oxide,
2. The method according to claim 1, wherein one or more kinds selected from manganese oxide, tin oxide, antimony oxide, and arsenic oxide are used. 3. An oxidizing agent that acts at a high temperature is 0.1% or more and 3.0% or less by weight of the refractory raw material, and 0.3% or more and 5.0% by weight of two or more kinds. The production method according to claim 2, which is added below. 4. The method according to claim 1, wherein the oxidizing agent that acts at a low temperature is one or two selected from sodium nitrate and sodium sulfate. 5. An oxidizing agent which operates at a low temperature is added in an amount of 0.1% to 1.0% by weight based on the refractory raw material.
2, 3, or 4.