JPH05170514A - Highly antioxidizing carbon-containing refractory compounded with magnesium boride - Google Patents

Abstract

PURPOSE:To provide a highly antioxidizing carbon-containing refractory having an additive and a blend composition effective in improving the oxidation and corrosion resistance and reinforcing the structure of a refractory in a relatively small amount. CONSTITUTION:A blend composed of 3-30wt.% carbon powder consisting essentially of graphite, 0.5-7wt.% one or two or more of Al, Mg, Ca and Si or an alloy thereof and the remainder composed of a refractory aggregate is compounded with 0.1-2wt.% magnesium boride powder such as MgB2, MgB4, MgB6 or MgB12. Thereby, the oxidation resistance and reinforcement of the structure can simultaneously be improved without impairing the spalling resistance at all by adding the oxidation resistance imparter in the relatively small amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter and a mixed pig car having a high secondary combustion ratio. Lining of molten metal container such as smelting reduction furnace,
The present invention relates to a carbon-containing refractory material suitably used for molten metal treatment equipment such as continuous casting equipment.

[0002]

2. Description of the Related Art Refractories applied to molten metal processing equipment generally have spalling resistance and slag erosion resistance. It is a condition that it has excellent wear resistance, and in order to satisfy this condition, a refractory material containing carbon as a main component and a refractory aggregate has recently become mainstream. For example, magnesia-carbon refractory is used as a lining material for steelmaking converters, and alumina is used as a smelter and smelting reduction furnace.
SiC / carbon, alumina / carbon refractory
Furthermore, alumina-carbon refractories are widely used in continuous casting equipment.

With the recent advancement of steel quality, converters,
For refining of refractory materials such as hot metal by increasing refining temperature, increasing secondary combustion ratio, new operating methods such as smelting reduction and scrap melting, and refining method for ladle and tundish. It is extremely harsh.

In the case of a refractory material containing carbon, under such conditions, deterioration of the properties due to deterioration of the structure of the refractory material due to oxidation of carbon is unavoidable.

As means for suppressing the oxidation of carbon, various metals such as Al, Mg, Ca and Si, SiC,
The fact that the addition of a carbide such as B ₄ C, and further a metal boride compound system is effective is disclosed in JP-B-61-303, JP-B-61-52100, and JP-A-60-1.
It is disclosed in Japanese Patent Laid-Open No. 95061 and Japanese Patent Laid-Open No. 64-14174.

[0006]

However, these additives are still insufficient for improving the oxidation resistance, and moreover, a large amount of them must be used. Therefore, the spalling resistance of the refractory itself must be improved. In many cases, properties such as corrosion resistance are impaired.
Specifically, addition of various metals such as Al and Si has a small effect of imparting oxidation resistance. Therefore, it is necessary to add a large amount in order to obtain strong oxidation, and spoiling spalling resistance and corrosion resistance. Become. Further, carbides such as B ₄ C and SiC are apt to cause deterioration of corrosion resistance and deterioration of structure due to their decomposition. Furthermore, the material using the metal boride compound-based additive is a sintered body that requires high temperature firing, and its use as an accessory to a molten metal refining facility is unsuitable in terms of characteristics.

The object of the present invention is to improve oxidation resistance and
An object of the present invention is to provide an additive effective for improving corrosion resistance and strengthening the structure of a refractory and a refractory containing carbon having a high oxidation resistance and having a composition.

[0008]

The refractory material containing high oxidation resistant carbon according to the present invention comprises carbon powder 3 to 3 containing graphite as a main component.
0% by weight and 0.5 to 7% by weight of one or more of Al, Mg, Ca and Si or alloys thereof.
The composition is characterized in that 0.1 to 2% by weight of magnesium boride powder is contained in the composition whose balance is made of refractory aggregate.

Magnesium boride includes MgB ₂ , MgB ₄ ,
There are compositions such as MgB ₆ and MgB ₁₂ , which can be used, but the most common one is MgB ₂ . This magnesium boride powder is highly pure, and preferably has a particle size of 100 μm or less from the viewpoint of reactivity and uniform dispersibility. When the addition amount is less than 0.1% by weight, its function is not sufficiently exhibited. If it is more than 2% by weight, the spalling resistance is significantly reduced.

Carbon powder which is mainly used in combination with graphite is natural or artificial graphite. Carbon black, mesophase carbon, etc. with as high a purity as possible are preferable, but if it is less than 3% by weight, the deterioration of spalling resistance and slag erosion resistance becomes noticeable, and if it is more than 30% by weight, the composition is filled. Sex is extremely reduced.

If the amount of the added metal such as Al is less than 0.5% by weight, the effect in terms of strength is insufficient, and if it is more than 7% by weight, the spall resistance is significantly deteriorated.

The aggregate used is preferably as high in purity and bulk specific gravity as possible, and an electromelted product, a calcined product or the like can be used.

The carbon-containing refractory of the present invention is prepared by adjusting a prescribed amount of the above-mentioned sized carbon powder, metal, refractory aggregate and magnesium boride powder to obtain pitch, tar. It is obtained by adding an appropriate amount of a binder such as phenol resin, modified phenol resin, silicone resin, and kneading, molding and heat treatment.

As the conditions of heat treatment, the unfired carbon-containing refractory material is obtained by treatment at 150 ° C. to 300 ° C., and the fired carbon-containing refractory material is obtained by reduction treatment at 500 ° C. to 1400 ° C.

[0015]

The magnesium boride in the carbon-containing refractory decomposes during use, and the boron component reacts with oxygen outside or inside the brick to form B ₂ O ₃ which contributes to oxidation resistance.
In particular, B ₂ O ₃ is 3MgO-when the refractory aggregate is MgO.
B ₂ O ₃ and 2MgO-B ₂ O _3, also to form a highly viscous product, such as in the case of _{Al 2 O 3 9Al 2 O 3} · 2B 2 O 3, coating the another material containing carbon, acid Improve the chemical conversion.

Furthermore, magnesium, which has a high oxygen affinity, forms MgO promptly, which contributes to the improvement of corrosion resistance and the strengthening of the structure. In addition, oxygen entering the refractory from the atmosphere is captured near the refractory surface, and Mg
It also has the function of forming O or a spinel layer to protect the refractory structure behind it.

Further, from the observation of the structure, it is recognized that it also has a sintering promoting function by heating, which further contributes to the structure strengthening.

These characteristics are recognized as a remarkable effect by adding a relatively small amount of magnesium boride, and are exhibited in combination with a metal such as Al and / or an alloy.

[0019]

EXAMPLES The effects of the magnesium boride powder will be described below based on examples.

However, the present invention is not limited to these examples.

Example 1 This is an example in which the present invention is applied to a magnesia carbonaceous refractory and is used as a lining material for a converter.

An appropriate amount of liquid phenolic binder was added to each of the raw material compositions shown in Table 1, kneading, vacuum friction molding, drying (90 ° C. × 24 hr), and curing treatment (2
50 ° C. × 10 hr) was applied to obtain a magnesia carbon brick.

In the raw material composition, the magnesia clinker was a combination of fused magnesia and sintered magnesia, and the carbon was natural graphite having a purity of 98%.

As shown in the comparative example of Table 1, when the addition amount of the magnesium boride powder is out of the specified range, the oxidation resistance, the corrosion resistance, the hot strength and the spalling resistance are higher than those of the examples. Inferior to either.

[0025]

[Table 1] Example 2 An example in which the present invention is applied to an alumina / SiC / carbon refractory and used as a lining material for a mixed pig car is shown.

An appropriate amount of liquid phenolic binder was added to each of the raw material compositions shown in Table 2 and kneading. Vacuum friction molding, drying (90 ° C x 24hr), curing treatment (2
50 ° C. × 10 hours) to obtain an alumina / SiC / carbon refractory material.

Here, as the alumina clinker, fused alumina was used, and as the carbon, natural graphite having a purity of 98% was used.

As shown in the comparative example in Table 2, when the addition amount of the magnesium boride powder is out of the specified range, the oxidation resistance, the corrosion resistance, the hot strength and the spalling resistance are higher than those of the examples. Inferior to either.

[0029]

[Table 2] Example 3 An example in which the present invention is applied to an alumina / carbon refractory and used as a dipping nozzle of a continuous casting facility will be described.

An appropriate amount of a liquid phenolic binder was used for each of the raw material compositions shown in Table 3 to prepare a molding compound, which was isostatically pressed and dried (90 ° C. × 24).
hr), reduction heat treatment (1000 ° C. × 10 hr),
An alumina / carbon soaking nozzle was obtained.

Here, as the aggregate clinker, fused alumina was used, and as the carbon, natural graphite having a purity of 98% was used.

As shown in the comparative example of Table 3, when the addition amount of the magnesium boride powder is out of the specified range, the oxidation resistance, corrosion resistance, hot strength and spalling resistance are higher than those of the examples. Inferior to either.

[0033]

[Table 3] As described above, the carbon-containing refractory materials shown in the examples of Tables 1 to 3 were comprehensively improved in oxidation resistance, corrosion resistance and hot strength.

[0034]

By adding a relatively small amount of the oxidation resistance-imparting agent to the carbon-containing refractory, it is possible to simultaneously improve the oxidation resistance and the microstructure strengthening without impairing the spalling resistance.

Claims (1)

[Claims] 1. A carbon powder 3 to 30 mainly composed of graphite.
%, Al, Mg, Ca, Si, one or more kinds, or alloys thereof in an amount of 0.5 to 7% by weight, and the balance being refractory aggregate, magnesium boride powder. A refractory material containing carbon of 0.1 to 2% by weight, which has high oxidation resistance.