JPH0733513A - Magnesia-carbon brick and its production - Google Patents

Abstract

PURPOSE:To provide a magnesia.carbon brick capable of corresponding to severe using conditions required for magnesia.carbon bricks used as a lining material for melted metal containers such as converters or melting and reducing furnaces, having more excellent properties than those of conventional bricks on the hot strength, oxidation resistance, corrosion resistance and spalling resistance which are conditions to be fulfilled for the bricks, and having high durability. CONSTITUTION:The characteristic of this magnesia.carbon brick is that carbon powder mainly composed of carbon black and the magnesia raw material having a particle diameter of 0.2-1mm occupies 20-60wt.% of the whole amount of the magnesia raw material and furthermore A1 or an A2 alloy having a particle diameter of <=100mum is combinedly used depending on using conditions. The production conditions of the magnesia.carbon brick comprises adding a proper amount of an organic binder to the above-mentioned raw materials, mixing and molding the mixture, thermally treating the molded product at 150-300 deg.C or reducing and thermally treating the molded product at 800-1500 deg.C, and subsequently subjecting the treated product to the impregnation with tar.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnesia-carbonaceous brick suitably used as a lining material for a molten metal refining vessel such as a converter or a smelting reduction furnace, and a method for producing the same.

[0002]

Refractory materials used as lining materials for molten metal refining vessels are resistant to spalling, slag erosion,
It is necessary to have excellent wear resistance, and in order to satisfy this condition, refractory materials containing carbon-containing refractory aggregate as a main component have recently become mainstream.

As a lining material for a converter, magnesia-carbonaceous bricks are widely used. However, the refining temperature and the secondary combustion ratio have been increased due to the recent upgrading of steel, and a new smelting reduction method and scrap are used. The conditions for using bricks, such as the melting method, are extremely severe.

There are various possible causes of wear of magnesia-carbonaceous bricks under such conditions, and among these, deterioration of the brick structure due to oxidation of carbon is an important factor. Conventionally, it has been proposed to suppress the oxidation of carbon by the addition of metals, carbides, borides, etc. Regarding the respective addition formulations, for example, Al is disclosed in JP-B-60-16393, and JP-A-60-200857. The low melting point alloy is disclosed in the publication, and Si is disclosed in JP-A-59-232961.
And B ₄ C in combination, in JP-A-3-45553, the addition of CaB ₆ is further described, and in JP-A-60-176.
The 970 discloses the addition of SiB ₆ is disclosed.

[0005]

However, even with the addition of these compounding materials, the improvement of the oxidation resistance of the magnesia-carbonaceous bricks is still insufficient, and it is necessary to use a large amount of the bricks. In many cases, the characteristics are impaired.

For example, the addition of metals such as Al and Si is
Use in a strong oxidizing atmosphere requires quantitative use, and spoiling resistance and corrosion resistance are often impaired. Further, carbides or borides such as B ₄ C and SiC are apt to cause deterioration of corrosion resistance and deterioration of structure due to decomposition under heating conditions during use.

An object of the present invention is to provide a magnesia-carbonaceous brick capable of suppressing the deterioration of the structure of the refractory due to the oxidation of carbon without deteriorating the properties such as spalling resistance and corrosion resistance of the brick itself. is there.

[0008]

The magnesia-carbonaceous brick of the present invention is capable of improving the corrosion resistance by adjusting the particle size composition of the magnesia raw material and adopting uniform dispersion by finely sizing the added metal.

That is, the present invention is characterized in that carbon powder mainly containing graphite and a magnesia raw material having a particle diameter of 0.2 to 1 mm account for 20 to 60% by weight of the whole magnesia raw material. It is a quality brick.

Here, as the carbon powder mainly containing graphite, natural or artificial graphite, coke, carbon black, mesophase carbon and the like can be used, and those having as high a purity as possible are preferable. As the magnesia raw material, a material having a high bulk specific gravity with a purity as high as possible is preferable, and an electromelted product, a fired product and the like can be preferably used.

Depending on the use condition of the product brick, the particle size is 1
Al of 100 μm or less is used as a single metal or Mg, Si, C
Although it can be added and blended as an alloy with a or the like, it is preferable that the purity is as high as possible and the particle size is 100 μm or less. If the particle size is larger than 100 μm, oxidation resistance
The effect is insufficient in terms of tissue strength.

In this magnesia-carbonaceous brick, the carbon powder mainly containing graphite and the magnesia raw material having a particle diameter of 0.2 to 1 mm are 20 to 6 of the whole magnesia raw material.
The blended raw material adjusted to occupy 0% by weight, pitch,
Add an appropriate amount of organic binder such as tar, phenol resin, modified phenol resin, silicone resin, mix,
After molding, in the case of non-fired magnesia-carbonaceous brick, heat treatment is carried out at 150 to 300 ° C., or in the case of fired magnesia-carbonaceous brick 800-1500.
It can be manufactured by carrying out a reduction heat treatment at ℃ and then impregnating with tar.

[0013]

[Function] Conventionally, the top size of the particle size of the magnesia raw material used for the magnesia / carbonaceous brick is often about 5 mm in consideration of spalling resistance and strength, and its 5 m
The grain size is adjusted to m or less. Further, scaly graphite, which is the main carbon powder, is often used having a particle size of about 200 μm or less in terms of workability and supply ability.

On the other hand, the magnesia raw material has excellent heat resistance and is strong against molten metal and the like, but is easily damaged by oxide slag, especially iron oxide (FeO). Further, although scaly graphite is relatively strong against oxide slag, it is relatively liable to be damaged by molten metal.

The present invention aims to solve the drawbacks of magnesia-carbonaceous bricks by demonstrating the synergistic effect of the respective raw materials and eliminating their drawbacks. The magnesia raw material having a particle size of 2-1 mm is 20 to 6 of the whole magnesia raw material.
When occupying 0% by weight, a state is created in which the scaly graphite having a particle size of about 200 μm or less is protected inside the refractory structure, and the working surface of the brick is always occupied by a certain proportion of the magnesia raw material and the scaly graphite. It is considered that oxidation resistance and corrosion resistance are improved.

Further, a method of simply reducing the top size of the magnesia raw material was also examined, but it became clear that the spalling resistance was significantly reduced.

Further, when considering the combined use with a metal component,
Al or Al-based alloy contributes to improvement of oxidation resistance and hot strength of magnesia / carbonaceous brick by carbonization reaction and oxidation reaction of metal itself, but a magnesia raw material having a particle size of 0.2 to 1 mm is 20 to 6 of all magnesia raw materials
When the particle size of the metal used together is 100 μm or less, the characteristics are sufficiently exerted under the particle size constitution that occupies 0% by weight.

However, if it is larger than 100 μm, defects occur in the refractory structure and spalling resistance is impaired.

[0019]

EXAMPLES The effects of adjusting the grain size composition of the magnesia raw material and making the added metal finer in the magnesia-carbonaceous brick as the lining material for the converter will be described below as examples. However, the present invention is not limited to these examples.

Table 1 shows the raw material composition of unfired magnesia-carbonaceous brick and its characteristics.

[0021]

[Table 1] An appropriate amount of liquid phenolic binder is added to each of the raw material compositions shown in the table, and kneading, vacuum friction molding, drying (90 ° C. × 24 hr), curing treatment (250 ° C. × 250 ° C.)
6 hours) to obtain unfired magnesia-carbonaceous brick. Here, as the magnesia raw material, a sintered magnesia sizing product having a purity of 99% is used in combination, and the carbon powder has a purity of 98.
% Natural scaly graphite was used.

As a comparative example, an example is shown in which the particle size composition of the magnesia raw material and the particles of the added metal are outside the specified range. In comparison with this comparative example, the unfired magnesia / carbonaceous brick of the present invention has a hot strength / oxidation resistance /
It can be seen that both corrosion resistance and spalling resistance are excellent.

Table 2 shows the raw material composition of fired magnesia-carbonaceous brick and its characteristics.

[0024]

[Table 2] An appropriate amount of liquid phenolic binder is added to each of the raw material compositions shown in the table, kneading, vacuum friction molding, drying (90 ° C. × 2 hr), curing treatment (250 ° C. × 6)
hr), reduction heat treatment (1000 ° C. × 6 hr), and tar impregnation to obtain a fired magnesia-carbonaceous brick.

Here, the magnesia raw material is used in combination with a sintered magnesia sized product having a purity of 99%, and the carbon powder has a purity of 98%.
Of natural scaly graphite was used.

As a comparative example, as in the case of Table 1, an example is shown in which the particle size composition of the magnesia raw material and the particles of the added metal are outside the specified range. In comparison with this comparative example, it can be seen that the unfired magnesia / carbonaceous brick of the present invention is superior to the comparative example in hot strength, oxidation resistance, corrosion resistance, and spalling resistance.

The magnesia-carbonaceous bricks shown in the examples of Tables 1 and 2 have a comprehensive hot strength, oxidation resistance, corrosion resistance, and spalling resistance in both cases of non-firing and firing. Improved results have been obtained.

[0028]

According to the present invention, as one means for improving the durability of conventional magnesia / carbonaceous bricks, the hot strength / oxidation resistance is comprehensively adjusted by adjusting the grain size composition of the magnesia raw material and refining the added metal. The properties, corrosion resistance and spalling resistance could be improved almost at the same time.

Front page continuation (72) Inventor Koichiro Kataoka 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Steel Co., Ltd. (72) Inventor Takayoshi Sato Kimitsu, Chiba Prefecture Kimitsu New Japan Kimitsu Co., Ltd. Inside the Works (72) Noboru Okuyama No. 1 Kimitsu, Kimitsu-shi, Chiba Shin-Nippon Steel Co., Ltd. Inside Kimitsu Works Co., Ltd. Inside the ironworks

Claims (4)

[Claims] 1. A magnesia-carbonaceous brick containing carbon powder containing graphite as a main component in an amount of 0.2 to 1 m.
A magnesia carbonaceous brick characterized in that a magnesia raw material having a particle diameter of m accounts for 20 to 60% by weight of the whole magnesia raw material. 2. In a magnesia-carbonaceous brick containing carbon powder mainly containing graphite and Al or Al alloy powder, the magnesia raw material having a particle diameter of 0.2 to 1 mm is 20 to 20% of the whole magnesia raw material. 60% by weight, and the particle size of Al or Al alloy powder is 100 μm
Below is a magnesia carbon brick. 3. Carbon powder mainly containing graphite and 0.2 to
A magnesia raw material having a particle size of 1 mm is added to the compounding raw material adjusted so as to occupy 20 to 60% by weight of the entire magnesia raw material, an organic binder is added, and after mixing and molding, 150 ° C.
A method for manufacturing magnesia-carbonaceous bricks that is heat-treated at ~ 300 ℃. 4. A carbon powder mainly containing graphite and 0.2 to
A magnesia raw material having a particle size of 1 mm is added with an organic binder to a compounding raw material adjusted so as to occupy 20 to 60% by weight of the entire magnesia raw material, and after mixing and molding, 800 to
A method for producing magnesia-carbonaceous bricks in which tar is impregnated after reduction heat treatment at 1500 ° C.