JPH0240017B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to electrocast refractories, particularly those used as furnace materials for glass melting furnaces. [Prior Art] As a furnace material for a glass melting furnace, an electrocast refractory whose main component is Cr ₂ O ₃ , which exhibits high corrosion resistance against molten glass, is used. As such electrocast refractories, for example, Monoflux K-3 and Monoflux E (trade names manufactured by Toshiba Monoflux Corporation) are known. These electroformed refractories are manufactured using cubic spinel, alumina-chromia solid solution, and glassy matrix as raw materials. When these compositions are expressed in mol%, they are as follows. In other words, Monoflux K-3 contains 16.3% MgO,
It consists of 62.2% Al ₂ O ₃ , 19.7% Cr ₂ O ₃ , 1.9% FeO and trace amounts of SiO ₂ , Na ₂ O, CaO and TiO ₂ . In addition, monoflux E has MgO24.8% and Al ₂ O ₃ 5.7%.
%, Cr ₂ O ₃ 64.8%, FeO 4.7% and trace amounts
Consists of SiO ₂ and Na ₂ O. [Problems to be Solved by the Invention] By the way, the required characteristics of the furnace material for a glass melting furnace vary depending on the properties of the glass and the usage conditions. However, conventional electroformed refractories have not been able to satisfy all of these characteristics. For example, Monoflux K-3 can withstand extremely long periods of use as a furnace material for soda-lime glass kilns. However, monoflux K-
No. 3 has insufficient corrosion resistance against borosilicate glass (hereinafter referred to as E glass), which is even more corrosive. For this reason, monoflux E, which has a higher Cr ₂ O ₃ content, is used as the furnace material for E glass kilns. Furthermore, in recent years, electric melting of glass has become widespread, and for this reason a requirement has been added that the electrical resistance of the furnace material must be at least higher than the electrical resistance of the molten glass. However, since Monoflux E has a low electrical resistance, it may not be able to meet the above requirements if the electrical resistance of the molten glass is high. Monoflux K is also used as a furnace material for glass melting furnaces used to vitrify nuclear fuel waste.
-3 is recognized as the best. However, during vitrification, the glass forming raw materials are charged as a slurry, so the furnace material of the glass melting kiln is repeatedly subjected to large thermal shocks. For this reason, even monoflux K-3 cannot be said to have sufficient spalling resistance, and there is a demand for electrocast refractories with further improved spalling resistance. The present invention was made to solve the above problems, and has high corrosion resistance against molten glass.
An object of the present invention is to provide an electroformed refractory that exhibits high electrical resistance and has good spalling resistance. [Means and effects for solving the problems] The electrocast refractory of the first invention of the present application contains MgO as a component represented by RO, and Al ₂ O ₃ and Cr ₂ O ₃ as components represented by R ₂ O ₃ . each containing MgO10
~40 mol%, _{R2O3 90-60} mol%,
It is characterized in that the molar ratio of Al ₂ O ₃ /R ₂ O ₃ is 0.2 to 0.7. In addition, the electrocast refractories of the second invention of the present application include MgO, MnO, PbO, and
At least one selected from CuO or BaO,
Contains _Al2O3 and _Cr2O3 as components _{represented by R2O3} , _RO10-40 mol%, _{R2O3 90-60}
MgO/RO molar ratio is 0.4 or more,
It is characterized in that the molar ratio of Al ₂ O ₃ /R ₂ O ₃ is 0.2 to 0.7. Such electroformed refractories of the first and second inventions of the present application have high corrosion resistance to molten glass, high electrical resistance, and good spalling resistance. In the first and second inventions of the present application, RO (only MgO in the first invention of the present application) 10 to 40 mol%,
R ₂ O ₃ was limited to 90 to 60 mol% because of the RO component and
If the content of the R ₂ O ₃ component is out of the above range, it becomes difficult to form a metastable monoclinic spinel solid solution, and no improvement in the mechanical strength of the electrocast refractory is observed, especially in terms of spalling resistance, etc. This is because it becomes difficult to improve. In the first and second inventions of the present application, Al ₂ O ₃ /
The reason why the molar ratio of R ₂ O ₃ is set to 0.2 to 0.7 is because high electrical resistance cannot be obtained if this molar ratio is less than 0.2.
On the other hand, if it exceeds 0.7, high corrosion resistance cannot be obtained. In the second invention of the present application, the reason why the MgO/RO molar ratio is set to 0.4 or more is because corrosion resistance and spalling resistance cannot be improved if this molar ratio is less than 0.4. In addition, in the first invention of the present application, since the RO component is only MgO, MgO/
The molar ratio of RO is 1.0, which satisfies the requirement of 0.4 or more. In addition, in the second invention of the present application, it is desirable that 25% or more of the component represented by RO be added in the form of a higher order oxide or nitrate. This is because higher-order oxides or nitrates suppress the ring element action caused by electrode carbon during melting, and prevent metal (metal Cr) in electrocast refractories.
This is because it has the effect of reducing the formation of bubbles in electrocast refractories caused by metals. [Examples] Examples of the present invention will be described below. Chromium oxide, alumina, and magnesia having the compositions shown in Table 1 (in weight percent), as well as commercially available (special grade) manganese oxide, lead oxide, copper oxide, and barium oxide were used as raw materials. In Table 1, the chromium oxide is 80-A manufactured by Nippon Denko, the alumina is A-21 manufactured by Sumitomo Aluminum Refining, and the magnesia is UBE-98 manufactured by Ube Chemical. First, these raw materials were weighed so as to have the blending ratios (mol %) shown in Table 2. In Table 2,
The molar ratio of MgO/RO and the molar ratio of Al ₂ O ₃ are also shown. Next, the raw material mixture was melted in a conventional manner using a 300 kVA single-phase L-type arc melting furnace, and cast into a mold made of a graphite plate. Furthermore, after slowly cooling the mold using alumina powder, 100mm x 300mm x 400mm
A cast ingot was obtained. For each of the obtained cast ingots, the corrosion rate, spalling resistance, and electrical resistance were measured as follows. Corrosion rate A sample with a diameter of 20 mm x 100 mm was taken from each cast ingot using a diamond drill core, and after immersing it in E-glass melted at 1300℃ for 720 hours, the depth of corrosion of the glass line was measured, and the corrosion depth was measured per 24 hours. The feeding rate (mm/day) was calculated by converting it into . Spalling resistance Five samples of 25 mm x 25 mm x 100 mm were cut out from each ingot, and each sample was heated to 1200°C at a heating rate of 40°C/min, held for 1 hour, and then removed from the furnace. This operation was repeated, with one cycle of rapid heating and cooling, in which the sample was taken out and allowed to cool for 15 minutes. Each time the sample was allowed to cool, the occurrence of cracks was examined, and the weight loss due to flaking was measured. And the weight loss is the initial weight
The number of cycles at which it reached 10% was determined, and the average value of the five samples was calculated and used as a value for evaluating spalling resistance. Electrical Resistance A sample with a diameter of 20 mm x 30 mm was cut from each cast ingot, and a platinum foil was attached as a current terminal and a platinum wire as a voltage terminal to this sample.
Measurements were made by applying Hz, 4V alternating current. The results of each of the above tests are also listed in Table 2. In addition, Reference Example 1 in Table 2 is Monoflux K-3,
Reference Example 2 is data for Monoflux E. Furthermore, in Comparative Example 3, many cracks occurred in the first cycle of the spalling resistance test, and no meaningful numerical value could be obtained for evaluating the spalling resistance. Furthermore, in Comparative Example 5, the molten material had a high viscosity and could not be cast, and therefore the corrosion rate measurement and spalling resistance test could not be conducted.

【table】

【table】

〔Effect of the invention〕

As detailed above, according to the present invention, the corrosion resistance against molten glass is high, the electrical resistance is high, and
Furthermore, it is possible to provide an electrocast refractory with good spalling resistance.

[Brief explanation of drawings]

Figure 1 is a ternary phase diagram of the MgO-Al ₂ O ₃ -Cr ₂ O ₃ electrocast refractories according to the present invention, and Figure 2 is the Al ₂ phase diagram of the electrocast refractories of Examples and Comparative Examples of the present invention. A characteristic diagram showing the relationship between the molar ratio of O ₃ /R ₂ O ₃ and the corrosion rate.
A characteristic diagram showing the relationship between the Al ₂ O ₃ /R ₂ O ₃ molar ratio and electrical resistance. Figure 4 shows the MgO/RO molar ratio and corrosion resistance of the electroformed refractories of Examples and Comparative Examples of the present invention. A characteristic diagram showing the relationship between speed and spalling resistance, Figure 5 shows the MnO/RO molar ratio of electroformed refractories in which MnO is added in the form of higher oxides in other embodiments of the present invention. FIG. 2 is a characteristic diagram showing the relationship with the amount of metal Cr produced in electrocast refractories.

Claims (1)

[Scope of Claims] 1 Contains MgO as a component represented by RO, Al ₂ O ₃ and Cr ₂ O ₃ as a component represented by R ₂ O ₃ , MgO 10 to 40 mol%, R ₂ O ₃ 90 to An electrocast refractory comprising 60 mol% of Al ₂ O ₃ /R ₂ O ₃ in a molar ratio of 0.2 to 0.7. 2 MgO and MnO as components represented by RO,
At least one selected from PbO, CuO or BaO, Al ₂ O ₃ and R ₂ O ₃ as a component
Contains _Cr2O3 , _RO10-40 mol%,
An electrocast refractory comprising 90 to 60 mol% of R ₂ O ₃ and having a MgO/RO molar ratio of 0.4 or more and an Al ₂ O ₃ /R ₂ O ₃ molar ratio of 0.2 to 0.7. 3. The electrocast refractory according to claim 2, wherein 25% or more of the component represented by RO is added in the form of a higher oxide or nitrate.