JPH05294764A - Carbon-containing refractory - Google Patents

Abstract

PURPOSE:To improve oxidation resistance by impregnation treating a refractory, obtained by kneading each of a specific quantity of an Al2O3-kind fire-proofing raw material, a SiC-kind fire-proofing raw material and graphite, molding and firing in a non-oxidizing atmosphere at a prescribed temp., with multiple alkoxide. CONSTITUTION:The Al2O3-kind fire-proofing raw material of 60-90 pts.wt. (hereafter pts.) having >=95% purity, the SiC-kind fire-proofing raw material of 5-20 pts. having >=90% purity and graphite of 5-20 pts. having >=90% purity where particle diameter of these raw materials is <=150mum are compounded. As the oxides having <=150mum particle diameter, 1.5-10 pts. sum total of a metallic powder high in fire resistance and a glass powder low in softening point are added and mixed into the powdery compound of 100 pts. Next, the mixture is kneaded, molded and is fired in the non-oxidizing atmosphere such as Ar at >=600 deg.C. After that, the multiple alkoxide having magnesium-aluminum spinel composition is impregnated into the fired material, is uniformly dispersed inside of the fired material and by heat treating, magnesium-aluminum spinel is formed and the carbon-containing refractory excellent in oxidation resistance and corrosion resistance is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a container for treating molten metal,
In particular, it relates to a refractory material containing carbon contained in a hot metal pretreatment furnace.

[0002]

2. Description of the Related Art As a refractory lining for a molten metal processing container, Al ₂ O ₃ -Si having excellent slag resistance and thermal shock resistance is used.
A C-carbon type refractory is applied to achieve high durability (for example, JP-A-58-64261 and JP-A-60-).
42273). Further, in order to improve the oxidation resistance of these refractories at high temperatures, various metals have been added or metals, glass and the like have been added in combination (JP-A-62-62).
132767, JP-A-63-117955). Further, in order to improve the oxidation resistance of a graphite roll used as a hearth roll for continuous annealing of electromagnetic steel sheets, alkoxide impregnation (Japanese Patent Laid-Open No. 03-211219) has been proposed.

[0003]

However, Al used as a refractory lining for molten metal processing containers.
₂ O ₃ -SiC-carbon refractory has a weak point in oxidation resistance at high temperatures. In order to improve this, various metals are added or metal, glass, etc. are added in combination, but since metal or glass is only added in the form of powder, it is unevenly distributed inside the refractory structure. However, there is a problem in terms of uniform distribution. The present invention is an improvement of a carbon-containing refractory that could not be obtained only by conventional metal addition or metal-glass combination addition, has a uniform structure, and is extremely excellent in oxidation resistance and corrosion resistance. To provide.

[0004]

According to the present invention, there are provided 65 to 90 parts by weight of an alumina refractory raw material, and 5 to 15 silicon carbide refractory raw materials.
Parts of graphite and 5 to 20 parts by weight of graphite are kneaded and molded, and then the refractory is fired at a temperature of 600 ° C. or higher in a non-oxidizing atmosphere and impregnated with a composite alkoxide of magnesium / aluminum spinel composition. It is characterized by

Further, the present invention relates to an alumina refractory raw material 6
5 to 90 parts by weight, 5 to 15 parts by weight of a silicon carbide refractory raw material, and 5 to 20 parts by weight of graphite, to 100 parts by weight of a refractory raw material, the total amount of metal powder and glass powder for the refractory raw material is 1.5 to The composition is characterized in that after 10 parts by weight of the compound added is kneaded and molded, a refractory material fired at a temperature of 600 ° C. or higher is impregnated with a composite alkoxide having a magnesium-aluminum spinel composition.

The composite alkoxide having a magnesium-aluminum spinel composition in the present invention is obtained by hydrolysis of a sol solution containing only magnesium element and an aluminum alkoxide solution obtained by hydrolysis of a magnesium alkoxide solution so as to have a magnesium-aluminum spinel composition. It is not a sol solution obtained by mixing with the obtained sol solution containing only aluminum element, but an alkoxide having a molecular formula of Mg [Al (OR) ₄ ] ₂ and directly converted into magnesium / aluminum spinel oxide by hydrolysis or heat treatment. Crystallize. In the molecular formula, O is oxygen and R is a hydrocarbon group.

The inventors of the present invention have paid attention to this characteristic and thought that impregnating a carbon-containing refractory material with an alkoxide has an effect of improving oxidation resistance and corrosion resistance, and arrived at the present invention.

The metal powder used in the present invention means Al, S
It means i, Ti, Al-Mg, etc., and it is desirable that the particle size is 150 μm or less and the generated metal oxide has a high fire resistance. Since these metal powders have a higher oxygen affinity than graphite in the high temperature range of 800 ° C. or higher, they are more easily oxidized to graphite and become metal oxides, and prevent oxidation of graphite. Further, by closing the pores that cannot be completely closed by the alkoxide impregnation due to the volume expansion at the time of forming the metal oxide, invasion of the oxidizing gas and slag into the refractory is suppressed, and the oxidation resistance and the corrosion resistance are improved.

The glass powder used in the present invention refers to water glass, borosilicate glass, phosphate glass, etc., and preferably has a particle size of 150 μm or less and a low softening point. These glass powders are softened and melted in a high temperature range of 800 ° C. or higher, and it becomes possible to coat carbon particles that cannot be completely coated by alkoxide impregnation and pores that cannot be completely closed by alkoxide impregnation. It becomes possible to close it and oxidation resistance is improved.
Further, the glass powder softens and melts in a high temperature range of 800 ° C. or higher, thereby relaxing the thermal stress generated in the refractory due to the temperature fluctuation, thereby improving the thermal shock resistance.

The content of alumina is 60 to 90 parts by weight because it is excellent in corrosion resistance and thermal shock resistance. This is because if the amount of alumina is less than 60 parts by weight, the corrosion resistance is poor, and if it exceeds 90 parts by weight, the thermal shock resistance is poor. As the alumina-based refractory raw material, an electromelted product, a sintered product or the like can be used, but a material having a purity of 95% or more, a bulk specific gravity and a large crystal grain size is desirable.

The content of silicon carbide is set to 5 to 20 parts by weight because it is excellent in corrosion resistance and oxidation resistance. This is because if the amount of silicon carbide is less than 5 parts by weight, the oxidation resistance is poor, and if it exceeds 20 parts by weight, the corrosion resistance is poor. Silicon carbide refractory raw material,
Uses α-SiC and has a purity of 90% or more and a crystal grain size of 1
It is preferably 50 μm or less.

The graphite content is set to 5 to 20 parts by weight because it is excellent in slag infiltration resistance and thermal shock resistance.
This is because if the amount of graphite is less than 5 parts by weight, the slag infiltration resistance and thermal shock resistance are poor, and if it exceeds 20 parts by weight, the oxidation resistance is poor. Graphite refers to natural or artificial graphite, mesophase carbon, coke, etc., and has a purity of 90% or more and a particle size of 50.
It is preferably 0 μm or less.

The total amount of the metal powder and the glass powder added is set to 1.5 to 10 parts by weight because they are excellent in oxidation resistance, corrosion resistance and thermal shock resistance. If the total amount of the metal powder and the glass powder added is less than 1.5 parts by weight, the oxidation resistance, the corrosion resistance and the thermal shock resistance are inferior, and if the total amount of the metal powder and the glass powder exceeds 10 parts by weight, the corrosion resistance, This is because it is inferior in thermal shock resistance.

The atmosphere for firing the carbon-containing refractory is preferably a non-oxidizing atmosphere such as Ar, N ₂ , CO or CO ₂ . The atmosphere is made non-oxidizing in order to prevent oxidation of graphite. This is because graphite is oxidized at a temperature of 600 ° C. or higher when the atmosphere is an oxidizing atmosphere.

The firing temperature is set to 600 ° C. or higher because pores are formed in the refractory so that the alkoxide can easily penetrate into the refractory. This is because if the firing temperature is lower than 600 ° C., the alkoxide does not penetrate into the refractory because there are few pores generated in the refractory.

To impregnate the carbon-containing refractory with the alkoxide, a method of immersing the carbon-containing refractory in an alkoxide solution in the air or under reduced pressure and / or pressure, or uniformly coating the carbon-containing refractory surface. The method etc. are used. The immersion time in the alkoxide solution may be appropriately selected depending on the size of the refractory material, for example, 40 × 40.
In the case of × 40 mm, the alkoxide sufficiently penetrates to the center in about 10 minutes.

[0017]

The composite alkoxide of the magnesium-aluminum spinel composition impregnated into the carbon-containing refractory fired at a temperature of 600 ° C. or higher in the non-oxidizing atmosphere has the oxidation resistance and the corrosion resistance by the reaction shown in the formula (1). Bring improvement.

[0018]

[Chemical formula 1] Al ₂ O ₃ -SiC-C + Mg [Al (OR) ₄ ] ₂ → Al ₂ O ₃ -SiC-C + MgAl ₂ O ₄ (1)

The complex alkoxide of magnesium-aluminum spinel composition is very wettable with the carbon material and easily penetrates into the refractory through the pores of the refractory. Since the complex alkoxide having a magnesium-aluminum spinel composition that has penetrated into the refractory is easily wet with carbon, it is uniformly distributed inside the refractory and heat-treated to generate magnesium-aluminum spinel. This magnesium-aluminum spinel is composed of very fine crystals and fills the pores inside the refractory and coats the surface of the carbon particles.

The magnesium-aluminum spinel filling the inside of the pores densifies the structure, thereby suppressing the penetration of oxidizing gas and slag into the refractory and improving the oxidation resistance and corrosion resistance. Further, since magnesium-aluminum spinel coats the surface of the carbon particles, the contact between the oxidizing gas and carbon is blocked, and the oxidation resistance is improved.

Further, the carbon-containing refractory material of the present invention improves the corrosion resistance, the oxidation resistance and the thermal shock resistance by the reaction of the formula (2) inside the refractory material of the added metal powder and glass powder. Here, the case where Al is used as the metal powder and borosilicate glass is used as the glass powder will be described as an example.

[0022]

Embedded image Al ₂ O ₃ -SiC-C + Al + B ₂ O ₃ -SiO ₂ + Mg [Al (OR) ₄ ] ₂ → Al ₂ O ₃ -SiC-C + Al ₂ O ₃ + B ₂ O _3- SiO ₂ -Al ₂ O ₃ -MgO + MgAl ₂ O ₄ (2)

The added metal Al and borosilicate glass react to react with Al ₂ O ₃ and B ₂ O ₃ --SiO ₂ --Al ₂ O ₃ --M.
Produces gO-based glass. By blocking the pores that cannot be completely blocked by the alkoxide impregnation due to the volume expansion at the time of Al ₂ O ₃ formation, the oxidation gas and the slag are prevented from entering the refractory and the oxidation resistance and the corrosion resistance are improved.
The produced B ₂ O ₃ —SiO ₂ —Al ₂ O ₃ —MgO type glass softens and melts in a high temperature range of 800 ° C. or higher, and it is possible to coat carbon particles that cannot be completely coated by alkoxide impregnation. In addition, it becomes possible to close the pores that cannot be completely closed by the alkoxide impregnation, and the oxidation resistance is improved. Also, 800 ℃
By softening and melting in the above-mentioned high temperature range, the thermal stress generated in the refractory due to the temperature fluctuation is relaxed, thereby improving the thermal shock resistance.

[0024]

EXAMPLES The present invention will be described below based on examples.

Example 1 Al of the present invention was used as a refractory lining for a molten metal processing container.
Table 1 shows examples of alkoxide impregnation of ₂ O ₃ —SiC—carbon refractory.

[0026]

[Table 1]

An appropriate amount of liquid phenolic binder was added to each raw material composition shown in Table 1, and kneading, vacuum friction molding, drying (90 ° C. × 24 hrs.), And curing treatment (250 ° C. × 10 hrs.) Were carried out. Al ₂ O ₃ -Si
C-C brick was obtained. This refractory was heat-treated under the conditions shown in Table 1 and then immersed in a composite alkoxide solution having a magnesium-aluminum spinel composition for 10 minutes in the air. Then, the refractory was taken out, kept at room temperature for about 24 hours, and dried at a temperature of 150 ° C. or lower for about 24 hours.

Here, the alumina-based refractory raw material uses fused alumina, and the silicon carbide-based refractory raw material uses α-SiC.
As the graphite, natural graphite having a purity of 99% was used. For Al ₂ O ₃ -SiC-C bricks subjected to alkoxide impregnation, the measurement of the apparent porosity, oxidation resistance test, carried out corrosion tests, the results were併載in Table 1 (Example). Further, Al ₂ O ₃ —SiC— which is not subjected to the alkoxide impregnation treatment of the present invention.
The results of the apparent porosity measurement, the oxidation resistance test, and the corrosion resistance test performed on the C bricks are also shown in Table 1 (Comparative Example).

Here, the oxidation resistance test is conducted in air at 1400.
It was performed by firing at a temperature of ° C for 3 hours. For the oxidation resistance index, the thickness of the decarburized layer after firing was measured and the unimpregnated brick was set to 100. The smaller the oxidation resistance index, the better the oxidation resistance.

The corrosion resistance test was carried out by a rotary erosion method at 1600 ° C. for 3 hours. Slag composition is CaO / SiO ₂
= 3.3, CaF ₂ = 10%, T.I. Fe = 18%. For the corrosion resistance index, the amount of erosion loss in the maximum erosion portion after the erosion test was measured, and the unimpregnated brick was shown as 100. The smaller the corrosion resistance index, the better the corrosion resistance.

A subjected to the alkoxide impregnation treatment of the present invention
As shown in Table 1, the 1 ₂ O ₃ —SiC—C brick showed excellent corrosion resistance as well as extremely excellent oxidation resistance. On the other hand, the comparative example is excellent in oxidation resistance but inferior in corrosion resistance,
Alternatively, it was not excellent in both properties of oxidation resistance and corrosion resistance.

Example 2

[0033]

[Table 2]

An appropriate amount of liquid phenolic binder was added to each of the raw material compositions shown in Table 2, kneading, vacuum friction molding, drying (90 ° C. × 24 hrs.), And curing treatment (250 ° C. × 10 hrs.) Were carried out. Al ₂ O ₃ -Si
C-C brick was obtained. This refractory was heat-treated under the conditions shown in Table 2 and then immersed in a composite alkoxide solution having a magnesium-aluminum spinel composition for 10 minutes in the air. Then, the refractory was taken out, kept at room temperature for about 24 hours, and dried at a temperature of 150 ° C. or lower for about 24 hours. Here, fused alumina was used as the alumina refractory raw material, α-SiC was used as the silicon carbide refractory raw material, and natural graphite having a purity of 99% was used as the graphite.

Al ₂ O ₃ − impregnated with alkoxide
With respect to the SiC-C brick, the apparent porosity was measured, the oxidation resistance test and the corrosion resistance test were performed under the same conditions as in Example 1, and the thermal shock resistance test was also performed. The results are also shown in Table 2.

In the thermal shock resistance test, the thermal shock resistance was evaluated by repeating immersion of hot metal at 1600 ° C. for 90 seconds, water cooling for 30 seconds, and then air cooling for 10 minutes. The thermal shock resistance was evaluated as follows: one with a crack in the refractory in one thermal shock test is bad, one with a crack in the refractory in two to four thermal shock tests is good, four thermal shocks The case where the refractory did not crack in the test was rated as excellent. As shown in Table 2, the Al ₂ O ₃ —SiC—C bricks subjected to the alkoxide impregnation treatment of the present invention exhibited extremely excellent oxidation resistance, corrosion resistance, and thermal shock resistance.

Comparative Example Al ₂ O ₃ -S not subjected to the alkoxide impregnation treatment of the present invention
Table 2 also shows the results of the apparent porosity measurement, the oxidation resistance test, the corrosion resistance test, and the thermal shock resistance test performed on the iC-C bricks.
Are also shown. As shown in Table 2, the comparative example is excellent in any one or two of oxidation resistance, corrosion resistance, and thermal shock resistance, but is not excellent in three characteristics of oxidation resistance, corrosion resistance, and thermal shock resistance. It was

[0038]

EFFECTS OF THE INVENTION According to the present invention, the oxidation resistance and the corrosion resistance are remarkably improved as compared with the conventional carbon-containing refractories containing only the addition of metal or the combination of metal and glass. It leads to reduction and is very effective.

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[Procedure amendment]

[Submission date] July 1, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

The metal powder used in the present invention means Al, S
It means i, Ti, Al-Mg, etc., and it is desirable that the particle size is 150 μm or less and the generated metal oxide has a high fire resistance. Since these metal powders have a higher oxygen affinity than graphite in a high temperature range of 800 ° C. or higher, they are more easily oxidized and become metal oxides than graphite, and prevent oxidation of graphite. Further, by closing the pores that cannot be completely closed by the alkoxide impregnation due to the volume expansion at the time of forming the metal oxide, invasion of the oxidizing gas and slag into the refractory is suppressed, and the oxidation resistance and the corrosion resistance are improved.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

The glass powder used in the present invention refers to water glass, borosilicate glass, phosphate glass, etc., and preferably has a particle size of 150 μm or less and a low softening point. These glass powders are softened and melted in a high temperature range of 800 ° C or higher, and it becomes possible to coat carbon particles that cannot be completely coated by alkoxide impregnation, and pores that cannot be completely closed by alkoxide impregnation. It becomes possible to close it and oxidation resistance is improved.
Further, the glass powder softens and melts in a high temperature range of 800 ° C. or higher, thereby relaxing the thermal stress generated in the refractory due to the temperature fluctuation, thereby improving the thermal shock resistance.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

[0033]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Nakao 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (2)

[Claims] 1. Alumina refractory raw material 60 to 90 parts by weight,
5-20 parts by weight of silicon carbide refractory raw material and 5-20 graphite
Carbon that is obtained by kneading and molding parts by weight of a refractory raw material and then impregnating a refractory that is fired at a temperature of 600 ° C. or higher in a non-oxidizing atmosphere with a composite alkoxide having a magnesium-aluminum spinel composition. Containing refractories. 2. Alumina refractory raw material 60 to 90 parts by weight,
1.5 to 10 parts by weight of metal powder and glass powder for refractory raw material were added to 100 parts by weight of refractory raw material composed of 5 to 20 parts by weight of silicon carbide refractory raw material and 5 to 20 parts by weight of graphite. A carbon-containing refractory material obtained by subjecting a refractory material that has been kneaded and molded in a non-oxidizing atmosphere to a temperature of 600 ° C. or higher and impregnated with a composite alkoxide having a magnesium-aluminum spinel composition, after kneading and molding the composition.