JPH07172909A - Carbon-containing refractory - Google Patents

Abstract

PURPOSE:To obtain a carbon-contg. refractory retaining its excellent resistance to spalling and corrosion and improved in oxidation resistance. CONSTITUTION:This carbon-contg. refractory is obtained by incorporating 0.5-10wt.% of aluminum borocarbide in a refractory material comprising 65-95wt.% of a refractory aggregate and 5-35wt.% of a carbonaceous material. Incorporation of the aluminum borocarbide causes its reaction with the oxygen in the atmosphere on the surface of the refractory during its use to produce alumina and boron oxides which melt at about 450 deg.C and cover the refractory surface, thus preventing the oxidation of the carbonaceous material from relatively low to higher temperatures. Furthermore, reaction between the alumina and the boron oxide raises the viscosity of the melt, the surface of the carbonaceous material is covered with this melt more firmly esp. at >=1300 deg.C, thus preventing the oxidation of the carbonaceous material; besides, the surface of the carbonaceous material is covered with a compound produced by reaction between an excess of the boron oxide and the various components of the refractory to effect prevention of the oxidative burn-off of the carbonaceous material, thus obtaining the objective carbon-contg. refractory retaining its resistance to corrosion and spalling and improved in oxidation resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon-containing refractory material, and more particularly to a carbon-containing refractory material having enhanced oxidation resistance without deteriorating corrosion resistance and spooling resistance.

[0002]

2. Description of the Related Art Carbonaceous raw materials have higher melting points and thermal conductivity than alumina and magnesia which are generally used as refractory aggregates, and have a low linear expansion coefficient. It has excellent ringability and has the property of preventing excessive sintering.

Since this property complements the shortcomings of other refractory aggregates, carbon-containing refractory materials have been conventionally obtained by adding carbonaceous raw materials in addition to other refractory aggregates.
This carbon-containing refractory material is widely used as a refractory material for metallurgy such as steelmaking and pig-making.

[0004]

However, a carbonaceous raw material such as graphite is extremely easily oxidized and disappears in an oxidizing atmosphere such as air, and along with this disappearance, its advantage is also lost. .

Conventionally, the following three methods have been proposed as methods for preventing the disappearance of the carbonaceous raw material by oxidation. The first method is to use a metal powder such as aluminum, silicon, or magnesium having a higher oxidation affinity than carbon or boron carbide (B ₄
C), silicon carbide (SiC) and other carbides are added (JP-A-54-163913, JP-A-59-59).
No. 107962, Japanese Patent Publication No. 60-59184,
Japanese Patent Publication No. 60-59191, Japanese Patent Publication No. 61-303, Japanese Patent Publication No. 61-882, etc.).

The second method is to add silicon hexaboride (SiB ₆ ) to form B ₂ O ₃ --SiO ₂ produced when a refractory material is used.
This is a method of forming a film on a carbonaceous raw material by a high-viscosity melt produced by the reaction of a glass-based glass phase and B ₂ O ₃ with a refractory aggregate (JP-A-60-176970).

The third method is to add a silicate, a borate or the like to form a glassy film on the surface of the carbonaceous raw material.

However, the above-mentioned first method has a low antioxidation effect, and the second method also has an insufficient viscosity of the carbonaceous raw material film and is damaged by melting or abrasion before the film is formed. However, it is not possible to obtain a sufficient effect.

Further, in the third method, the temperature range in which the antioxidant effect is effectively obtained is limited, and if the addition amount is increased in order to obtain sufficient oxidation resistance, the corrosion resistance and corrosion resistance of the refractory material can be improved. There is a problem that the sporting property is deteriorated.

[0010]

The present invention has been made in view of the above points, and in order to solve the above problems, refractory aggregates of 65 to 95% by weight and carbonaceous raw materials of 5 to 35% by weight. The present invention provides a refractory material containing carbon, characterized in that 0.5 to 10% by weight of aluminum borocarbide is added to the refractory material containing.

[0011]

In the present invention, by adding a predetermined amount of aluminum borocarbide to the refractory material containing the refractory aggregate and the carbonaceous raw material, the aluminum borocarbide reacts with oxygen in the atmosphere on the surface of the refractory during use, and alumina Also, boron oxide is produced, and this boron oxide melts at about 450 ° C. to coat the surface of the refractory material and prevent oxidation of the carbonaceous raw material even at a relatively low temperature.

Further, since the above-mentioned alumina and boron oxide react to make the melt highly viscous, the surface of the carbonaceous raw material is more strongly coated at a high temperature, particularly at 1300 ° C. or higher to prevent the oxidation, and the surplus is further increased. The compound produced by the reaction of the boron oxide with the components in the refractory covers the surface of the carbonaceous material to prevent the disappearance of the oxidation, thereby improving the durability.

The carbon-containing refractory material of the present invention is a refractory aggregate 65.
It is characterized in that 0.5 to 10% by weight of aluminum borocarbide is added to a refractory material containing ˜95% by weight and 5 to 35% by weight of carbonaceous raw material.

As the above-mentioned refractory aggregate, a usual refractory aggregate may be used. For example, magnesia, dolomite, spinel,
Examples thereof include oxides such as zircon, zirconia, alumina, silica, and mullite, carbides such as silicon carbide, and non-oxides such as nitrides such as silicon nitride.

The particle size of the refractory aggregate is not particularly limited, and for example, a commonly used particle of about 5 mm or less may be used. The content of the refractory aggregate is preferably about 65 to 95% by weight of the refractory material. The amount of refractory aggregate compounded is
If the amount of the refractory material is less than 65% by weight, the corrosion resistance is deteriorated, and if it exceeds 95% by weight, the effect of adding the carbonaceous raw material is lost, which is not preferable.

As the carbonaceous raw material, those usually used can be used. For example, natural graphite such as scaly graphite and earth-like graphite, artificial graphite, carbon black, and amorphous such as petroleum coke. Carbonaceous substances and the like can be used.

Of these, it is recommended to use scaly graphite which is the easiest to mix with the refractory aggregate and to mix with boroaluminum carbide. The particle size of the carbonaceous raw material is not particularly limited, and for example, a commonly used particle size of about 1 mm or less can be used.

The blending amount of the carbonaceous raw material varies depending on the purpose of use of the carbon-containing refractory material, but is preferably 5 to 35% by weight of the refractory material. If the blending amount of the carbonaceous raw material is less than 5% by weight of the refractory material, the effect of addition of the carbonaceous raw material is lost, and if it exceeds 35% by weight, the corrosion resistance is deteriorated, which is not preferable.

When aluminum borocarbide is added, it reacts with oxygen in the atmosphere on the surface of the refractory during use, and 4Al _x C
_y B _z + (3x + 3z + 2y) O ₂ → 2xAl ₂ O ₃ +
Alumina, boron oxide and CO are produced such as 2zB ₂ O ₃ + 4yCO.

By this reaction, the combustion of the carbonaceous raw material in the brick is suppressed, and the structure is densified due to the volume expansion at the time of oxide formation, and the gas diffusion is suppressed. Further, since boron oxide melts at about 450 ° C. and coats the surface of the refractory material, oxidation of the carbonaceous raw material can be prevented even at a relatively low temperature.

Further, the above-mentioned alumina reacts with boron oxide to make the melt highly viscous, and more strongly coats the surface of the carbonaceous raw material at high temperature, especially at 1300 ° C. or higher to prevent oxidation.

Further, a compound formed by the reaction of excess boron oxide with various components in the refractory covers the surface of the carbonaceous raw material to prevent the disappearance of oxidation.

Such an effect is obtained by adding the above-mentioned refractory material to metallic aluminum and metallic boron or boron carbide,
It is also recognized when boron nitride is added in combination, but in this case, the aluminum particles and the boron-based particles are present independently of each other in the refractory, and as a reaction form with oxygen,
First, the preferential oxidation of the aluminum particles occurs, and then the oxidation of the boron-based particles proceeds.

On the other hand, in the case of adding the aluminum borocarbide of the present invention, the reaction with oxygen proceeds simultaneously because it exists as a compound of aluminum and boron. As a result, direct oxidation of the carbonaceous raw material is suppressed, the reaction of the alumina-boron oxide system is promoted, the surface film effect is enhanced, and a high antioxidant effect can be obtained.

Therefore, the antioxidant effect can be obtained without reducing the corrosion resistance by reducing the addition amount.

The content of aluminum borocarbide is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the refractory material. Not preferable because the desired effect and less than 0.5 part by weight can not be obtained, exceeding 10 parts by weight B ₂ O
_It is not preferable because the amount of the ₃ type glass produced is too large and the corrosion resistance and the sponging resistance are deteriorated.

The particle size of the aluminum borocarbide is not particularly limited, and a generally used one having a particle size of about 60 mesh (0.25 mm) or less can be used, but it is 200 mesh (0 mesh for improving reactivity). It is preferable to use one having a diameter of about 0.07 mm or less.

The above aluminum borocarbide (Al _x C
_y B _z), the x: y: z = 5~45: 3~40: 2
Those of 0 to 90 are suitable from the above chemical reaction.

The method for producing the carbon-containing refractory of the present invention from these components is not particularly limited, and for example, a refractory material whose particle size and components are adjusted as described above and aluminum borocarbide are blended in the above blending ratio. The mixture is mixed with one or two or more binders such as tar, pitch, phenol resin and the like having a large amount of residual carbon, and the mixture is kneaded, followed by pressure molding.

Thereafter, a carbon-containing refractory as an unfired refractory can be obtained by drying or heat treatment at 25 to 200 ° C., and firing by firing in a reducing atmosphere at about 700 to 1500 ° C. A carbon-containing refractory as a refractory can be obtained.

[0031]

EXAMPLES As shown in Table 1 on the next page, the products of the present invention 1, 2,
3, 4 and Comparative Products 1, 2, and 3 were mixed with the components shown in the table, and after 3 parts by weight of a resole type phenol resin was added and kneaded,
It was pressure-molded at a pressure of 1000 Kgf / cm ^{2 into} a 40 mm × 40 mm × 40 mm cubic shape, and then heat-treated at 180 ° C. for 5 hours to obtain carbon-containing refractories as unfired refractories.

Using the obtained refractory material as a sample, oxidation resistance and oxidation wear resistance tests were conducted under the following conditions. The results are shown in Table 1.

In the oxidation resistance test, the above sample was placed in an electric furnace and heat-treated at 1300 ° C. for 10 hours in the atmosphere, and the weight loss rate (%) after the treatment was determined.

In the oxidative wear resistance test, each of the above samples was tested to have a diameter of 3
Put in a cylindrical container made of refractory of 00 mm and length of 300 mm, 1
Heat treatment was carried out at 1300 ° C. for 30 minutes while rotating at 5 rpm, and the weight reduction rate (%) after the treatment was determined.

As is clear from Table 1, the product 1 of the present invention,
Since the weight reduction ratios of Nos. 2, 3, and 4 in each test were smaller than those of Comparative products Nos. 1, 2, and 3, it was found that the amount of carbonaceous raw material lost by oxidation was small and the oxidation resistance was extremely excellent.

Further, according to each of the above-mentioned invention products having extremely excellent oxidation resistance, the preferable properties of the carbonaceous raw material are sufficiently exhibited, and the durability such as oxidation wear resistance, spalling resistance and the like is also improved. A remarkable improvement was recognized.

Table 1 Comparison table

[Table 1]

It is needless to say that the present invention is not limited to the above-mentioned embodiments, and various embodiments can be carried out without departing from the spirit of the present invention.

[0039]

As described above, according to the present invention, at the time of use, aluminum borocarbide reacts with oxygen in the atmosphere on the surface of the refractory to form alumina and boron oxide. As it melts and coats the refractory surface,
Oxidation of the carbonaceous raw material can be prevented even at a relatively low temperature.

Further, since the above-mentioned alumina and boron oxide react to make the melt highly viscous, the surface of the carbonaceous raw material is more strongly coated at a high temperature, especially at 1300 ° C. or higher to prevent the oxidation, and the surplus is further increased. The compound formed by the reaction between boron oxide and various components in the refractory covers the surface of the carbonaceous material and prevents the oxidation disappearance, so that the corrosion resistance and the sponging resistance are not deteriorated and the oxidation resistance is improved. It can be raised.

Claims (1)

[Claims] 1. A carbon-containing refractory material comprising 0.5 to 10% by weight of aluminum borocarbide added to a refractory material containing 65 to 95% by weight of a refractory aggregate and 5 to 35% by weight of a carbonaceous raw material. object.