JPH0543310A - Carbon-containing refractory - Google Patents

Abstract

PURPOSE:To provide carbon-containing refractory having excellent thermal shock resistance. CONSTITUTION:100wt.% mixture consisting of 1-20wt.% carbonaceous material, <=20wt.% silicon carbide material, <=10wt.% metallic material and the rest of alumina material is blended with 0.5-10wt.% pitch heat-treated at >=400 deg.C and <=0.05 mm particle size and a phenol resin as a binder.

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 having excellent thermal shock resistance.

[0002]

2. Description of the Related Art Conventionally, alumina-carbonaceous bricks, magnesia-carbonaceous bricks have been used as lining materials for molten pig iron and molten steel containers, and silicon carbide,
Many refractory materials containing various metals are used. These carbon-containing refractories have a property that they are hard to be wet with slag and have excellent thermal shock resistance, and when they are used as a lining material for containers for hot metal and molten steel, they show stable wear without peeling. However, while these carbon-containing refractories have excellent thermal shock resistance, they have high thermal conductivity and have the drawback of lowering the temperature of the hot metal and molten steel, and the fact that carbon dissolves in the molten steel and the quality of the steel deteriorates. is doing. In order to reduce the thermal conductivity, for example, amorphous carbon is used in JP-A-62-132767, or an attempt is made to use a small amount of graphite having a large specific surface area in JP-A-61-16866. , Has been given thermal shock resistance.

[0003]

However, in the method of adding amorphous carbon, the thermal conductivity of amorphous carbon is small,
Even if used in a large amount, the thermal conductivity of bricks is small, but if added in a large amount, the dissolution of carbon in the molten steel becomes a problem, and graphite with a large specific surface area is more likely to react with steel and a small amount is added. However, it was difficult to suppress the dissolution of carbon in the molten steel. As described above, the conventional technology has not been able to obtain a carbon-containing refractory material that simultaneously solves various problems such as thermal shock resistance, a decrease in hot metal temperature of molten pig iron, and dissolution of carbon in steel.

[0004]

Means for solving the above-mentioned problems of the prior art are 1 to 20% by weight of carbonaceous material,
20% by weight or less of silicon carbide material, 10% by weight of metal material
The following is a particle size of 0.05 mm obtained by heat-treating at 400 ° C. or higher with respect to 100% by weight of a mixture whose balance is an alumina-based material.
The carbon-containing refractory is characterized in that the following pitch of 0.5 to 10% by weight and a phenol resin are added as a binder.

The carbonaceous material used in the present invention is slag,
Natural graphite, artificial graphite, pitch coke, anthracite, carbon black, etc. can be used for the purpose of preventing penetration of molten pig iron and molten steel and imparting thermal shock resistance, and the addition amount is limited to 1 to 20% by weight. This is because if it is less than 20% by weight, the effect of carbon addition cannot be obtained and the thermal shock resistance is insufficient, and if it exceeds 20% by weight, the temperature of molten pig iron and molten steel is lowered and the components of molten steel are affected. The silicon carbide material is added to prevent oxidation of carbon, and the addition amount is limited to 20% by weight or less.
This is because if it exceeds 0% by weight, the corrosion resistance decreases. It is not necessary to add when used in an atmosphere where oxidation does not occur.

As the metallic material, for the purpose of preventing oxidation and developing strength, silicon, aluminum, magnesium, calcium, iron or the like can be used alone or as a mixture, or as an alloy. The amount added is limited to 10% by weight or less
This is because if it exceeds, the expansion when it becomes an oxide becomes large, cracks occur in the refractory, the strength decreases, and the oxidation is promoted through the cracks. If antioxidant and strength are unnecessary, they may not be added.

The reason for using an alumina-based material for the balance is that it has a high resistance to slag, hot metal and molten steel, has a small coefficient of hot expansion and is excellent in structural stability. As the aluminous material, fused alumina, sintered alumina, bauxite, shale shale, andalusite, kyanite and the like can be used.

The pitch used in the present invention is heat-treated at a temperature of 400 ° C. or higher, and as a result, the softening point is 300.
It has a high temperature of ℃ or more, has a small volatile content of 10 to 15% by weight, and has a high fixed carbon amount of 85% by weight. This pitch is added to impart thermal shock resistance, and the amount added is limited to 0.5% to 10% by weight.
This is because the effect obtained by the addition cannot be obtained below, and if it exceeds 10%, the corrosion resistance remarkably decreases. The reason for limiting the grain size of the pitch to 0.05 mm or less is that a grain size larger than 0.05 mm results in large voids after carbonization, resulting in reduced corrosion resistance.

[0009]

The present inventors have studied a method for improving the thermal shock resistance of a carbon-containing refractory, and as a result, the carbonized structure of a conventional resin bond has a large strength but is hard and brittle, so that a small amount of graphite cannot be used. Sufficient thermal shock resistance cannot be obtained with the combination,
The pitch has a liquid crystal (mesophase) in the structure during the heat treatment at 400 ° C. or higher, and coalescence between the liquid crystals progresses during the heating process to form a strong carbon bond, and the carbonized structure of this carbon bond forms a flow structure. It has been found that the flexible bond forms a soft bond advantageous in thermal shock resistance due to its flexible structure.

That is, compared with the elastic modulus of a brick made only by resin bonding, a grain size of 0.0 after heat treatment at 400 ° C. or higher
The elastic modulus of the brick formed by the combined use of the pitch of 5 mm or less and the resin is lowered, and thus the thermal shock resistance is improved. The carbon-containing refractory material of the present invention can be used as a non-fired form only by forming a bond by the effect of heat during use, or can be used after forming a bond by firing. It can also be used as an irregular refractory material.

[0011]

EXAMPLES Examples will be described below. After blending and kneading the respective blends of the present invention product, the comparative product and the conventional product at the blending ratios shown in Table 1, the mixture was press-molded into a parallel shape by a conventional method and dried at 250 ° C. for 24 hours to obtain a specimen. did. Thermal shock test is 40 × 40 × 114mm
The sample cut into pieces was immersed in molten steel at 1650 ° C. for 5 minutes, cooled at room temperature for 30 minutes, repeated 6 times and then cooled to room temperature, and the state of cracks was observed. In the erosion test, the above-mentioned test piece was subjected to a rotary erosion method at 1650 ° C. for 3 hours (erosion agent; slag 20%, steel 80%), and the erosion size after the test was measured. As is clear from the table, the product of the present invention has significantly improved thermal shock resistance as compared with the conventional product. Further, the product No. of the present invention. 2 and conventional product No. 1 and comparative product No. 1 and 3 were used by laminating 1/3 to the bottom of the molten steel pot, and comparing the mm / ch melt loss dimensions after use,
Conventional product No. 1 is 2.7 mm / ch, comparative product No. No. 1 was 2.5 mm / ch, whereas the product No. 1 of the present invention. 2 was 1.8 mm / ch, which was an improvement of about 30%. From the middle of use,
Conventional product No. 1 and comparative product No. In No. 1 of the present invention, peeling occurred from an early stage, whereas in the product No. 1 of the present invention. In No. 2, peeling was small and peeling occurred at a later time.

[0012]

[Table 1]

[0013]

As described above, in the product of the present invention, the added pitch has a liquid crystal (mesophase) in the structure during the heat treatment at a temperature of 400 ° C. or higher, and the coalescence between the liquid crystals progresses during the heating process, resulting in a strong structure. By forming a carbon bond, and the carbonized structure of this carbon bond shows a flow structure and a structure that is rich in flexibility, a soft bond that is advantageous for thermal shock resistance is formed, thereby improving the thermal shock resistance of bricks and at the same time. Alumina, magnesia, silicon carbide, and metal are used together to improve joint corrosion resistance, oxidation resistance, and strength characteristics to extend the service life, and its industrial value is great.

Front page continued (72) Inventor Tatsuo Matsumura 1-3-1 Niihama, Arai-cho, Takasago, Hyogo Prefecture Harima Maseramic Co., Ltd. (72) Masato Nakajima 1-3-1 Niihama, Arai-machi, Takasago, Hyogo Harima Maseramic Co., Ltd.

Claims (1)

[Claims] 1. A carbonaceous material of 1 to 20% by weight, a silicon carbide based material of 20% by weight or less, a metallic material of 10% by weight or less, and a balance of 100% by weight consisting of an alumina based material, and 400 ° C. or more. A carbon-containing refractory, characterized in that a phenol resin is added as a binder with 0.5 to 10% by weight of a pitch having a particle size of 0.05 mm or less heat-treated in step 1.