JP2003183083A - Unfired brick and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an unfired SN (sliding nozzle) plate brick high in strength at a temperature of 1,000°C or lower, excellent in volume stability at a high temperature and in resistances to oxidation, wear, corrosion and thermal spalling. <P>SOLUTION: The method for producing this unfired SN plate brick comprises kneading an alumina fine powder which is a base material of the brick by replacing a part thereof with a powdery pitch in an amount of 0.5-5.0 wt.%, or further by replacing with an easily sinterable alumina fine powder having a mean particle size of 1 μm or less in the amount of 1-15 wt.% in addition to the above condition. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding nozzle plate (hereinafter referred to as "SN plate") brick mounted on a ladle, a tundish or the like in a steelmaking plant, and more particularly to a non-fired brick.

[0002]

2. Description of the Related Art An SN plate brick is one in which one of two plate refractories having holes is fixed and the other is slid to open and close the plate brick to flow out and stop the molten steel flow. Alumina-carbon is mainly used as the material of the SN plate brick. So S
N-plate bricks may be damaged by the flow of molten steel, cracking by rapid thermal shock, wear and wear on sliding surfaces, or surface roughness due to deterioration of the structure of bricks due to carbon oxidation, as well as by molten steel or slag. Subject to scientific erosion. Therefore, the properties that the SN plate brick must have include excellent wear resistance, heat resistant spall resistance, and corrosion resistance. In addition, SN plate bricks have been endowed with high balance of properties according to the usage conditions to extend their service life and extend their service life.

Recently, so-called firing is performed in addition to the firing SN plate that has been used conventionally for the purpose of further improving the heat-resistant spall property among various characteristics, rationalizing the manufacturing process of bricks, and reducing the manufacturing cost. Not fired S
N plates are also used.

[0004]

However, this unfired S
Since the N plate is not fired at a high temperature, the strength at 1000 ° C. or lower is low, and the residual expansion due to repeated heating at a high temperature of 1000 ° C. or higher is large, so that the tissue embrittlement easily occurs. Therefore, the carbon in bricks is oxidized due to the exfoliation of the structure during use, the oxygen in the high temperature atmosphere and the air in the molten steel, and the inflowing air from between the surfaces, and the surface roughness due to the weakening of the structure is significant, resulting in the firing SN plate. There was a problem that it was inferior in durability.

In order to increase the durability of the non-fired SN plate, it is considered that prevention of strength reduction in the intermediate temperature range of 1000 ° C. or less and suppression of residual expansion at high temperature, that is, improvement of volume stability is effective. To be Of course, for this problem, for example, an improved technique disclosed in Japanese Patent Laid-Open No. 57-11873 has been proposed. That is, in this technique, a superior drug having a melting point in the range of 300 to 800 ° C., or a low melting point compound as a component of a pigment is added, or colloidal silica, ethyl silicate, silicon resin sodium silicate, or lithium silicate is added. This aims to prevent strength deterioration in the intermediate temperature range of 1000 ° C or lower and to improve the volume stability at high temperature based on the densification of the brick structure.

Further, JP-A-6135765 and JP-A-7-2902
In No. 32, by adding a silicone-modified phenolic resin, an effect similar to that of the above-described technique is attempted.

These techniques are certainly aimed at 1000 ° C
It is effective in preventing strength reduction and improving high-temperature volume stability in the following intermediate temperature range. However, on the other hand, when the inner hole and sliding surface of the plate through which the steel passes in actual use are heated and a slight amount of oxygen is present, the above-mentioned additive promotes the formation of SiO ₂ . As a result, it is clear that the corrosion resistance of the plate itself is significantly deteriorated due to the following reasons. That is,
Al ₂ O _{3 in} newly formed SiO ₂ brick and FeO in steel
It is conceivable that a low melting point substance is generated by the reaction with, which leads to deterioration of corrosion resistance.

The present invention has been made in view of the above problems, and has high strength at 1000 ° C. or less, excellent volume stability at high temperature, and resistance to oxidation and abrasion in actual use. An object is to provide an unfired SN plate brick having excellent corrosion resistance and heat resistant spall resistance.

[0009]

The present invention employs the following means in order to achieve the above object.

The conventional non-fired brick is obtained by kneading a refractory aggregate and a refractory base material containing fine alumina powder, molding and drying. On the other hand, in the present invention, 0.5 to 5.0% by weight of powder pitch is kneaded in place of a part of the alumina fine powder. Alternatively, instead of a part of the alumina fine powder, 1 to 15% by weight of easily sinterable alumina fine powder having an average particle diameter of 1 μm or less is kneaded. As a result, the strength is prevented from lowering below 1000 ° C and the high-temperature volume stability is improved. Therefore, non-firing that is excellent in oxidation resistance, abrasion resistance, corrosion resistance, and heat spall resistance during actual use
SN plate brick is obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to examples.

In the case of calcined alumina-carbon SN plate, a thermosetting resin such as phenol resin is added, and the temperature is 800 ° C.
When baked at the above high temperature, carbon bonds are formed,
It becomes possible to develop strength below 00 ° C. Further, the volume stability at high temperature is also improved.

However, in the case of non-fired brick, the addition of a thermosetting resin such as the above-mentioned phenol resin cannot maintain the quality such as the strength of the fired brick, so that sufficient oxidation resistance, abrasion resistance and corrosion resistance can be maintained or improved. I can't expect. This is because the formation of the carbon bond does not proceed sufficiently in the temperature rising process when unfired brick is used,
The strength at temperatures below ℃ does not increase and the high-temperature volume stability is poor. Then, as a result, it is known that the oxidation resistance is lowered and the resistance to the heat spall resistance is weakened.

Therefore, in the present invention, in place of the alumina fine powder which is the base material of the alumina-carbonaceous SN plate, 0.5 to 5.0% by weight of powder pitch is added to achieve strength development at 1000 ° C. or less. Further, by adding 1 to 15% by weight of the easily sinterable alumina fine powder having an average particle diameter of 1 μm or less in place of the alumina fine powder, the effect of suppressing residual expansion due to repeated heating was confirmed. And it was found that the oxidation resistance, abrasion resistance, and corrosion resistance can be improved with this.

Here, the addition amount of the powder pitch is 0.5% by weight.
When the amount is less than the above range, sufficient strength is not exhibited, while when it exceeds 5.0% by weight, the filling property of the brick is deteriorated and cracking occurs during the drying.

The reason why the powder pitch contributes to the strength development at 1000 ° C. or less is that the powder pitch is usually 250 to 500.
It is considered that, at the temperature of 0 ° C., melting and softening promoted the close packing of the aggregate such as alumina, and in addition, it had a function of compensating for the strength decrease due to the decomposition and volatilization of the thermosetting resin added as the binder during the temperature rise.

Next, it is preferable to add the easily sinterable alumina fine powder having an average particle diameter of 1 μm or less in the range of 1 to 15% by weight. It is considered that when the non-firing plate is actually used, the temperature around the inner hole becomes high, and the fine alumina powder forming the matrix (matrix) is sintered with the aggregate such as alumina which comes into contact with the fine powder. . The strength of the connective structure is enhanced by the formation of the ceramic bond by the sintering, and the strength can be exhibited, and the effect of suppressing the residual expansion caused by repeated heating can be expected. From this, it is possible to quantitatively control the ceramic bond to be formed by adjusting the addition amount of the fine alumina powder, and it is possible not only to improve the durability but also to design the material in accordance with the characteristics to be provided. .

Here, if the amount of the fine alumina powder added is less than 1% by weight, the strength development becomes poor because the formation of ceramic bonds is small. On the contrary, if the addition amount exceeds 15% by weight, the ceramic bond is excessively formed and the brick structure has a high elastic modulus, so that the thermal shock resistance is lowered and cracks and cracks are likely to occur, which is not preferable.

The average particle diameter of the alumina fine powder is 1
The reason why the thickness is set to less than or equal to μm is to accelerate the sintering in a shorter time because it is limited to the sintering by heating during actual use.

The brick according to the present invention is prepared by kneading, molding and drying raw materials mixed in a predetermined ratio to form an SN plate brick having a shape suitable for the intended use. The purpose is to volatilize the solvent component in the added thermosetting resin and to cure the SN plate brick.

The results of the tests conducted on the unfired bricks for sliding nozzles of the present invention are shown below as examples.

[0022]

[Example] As a refractory aggregate, a mixture of 78% by weight of alumina and 15% by weight of alumina-zirconia, 2% by weight of carbon black, and 5% by weight of metallic aluminum powder was melted and softened at around 400 ° C. A predetermined amount of powder pitch was added by replacing a part of the alumina fine powder. Further, a predetermined amount of alumina fine powder having an average particle diameter of 0.7 μm is added by substituting with alumina fine powder, and 4% by weight of phenol resin is added as a binder to the mixture, and the mixture is kneaded, molded and dried to produce an SN plate. , Quality characteristics were investigated.

Table 1 shows the amount of powder pitch and the amount of easily sinterable alumina fine powder having an average particle diameter of 0.7 μm and the quality measurement results.

[0024]

[Table 1]

In producing the SN plate, a mixture of a predetermined refractory aggregate, carbon powder and aluminum metal was mixed in advance, and this was mixed with a binder and then kneaded. Mold this with a friction press and
It was dried at 0 ° C. As quality characteristics, strength, oxidation resistance / abrasion resistance, molten steel erosion resistance, and residual expansion / shrinkage ratio after heat treatment at 1500 ° C. for 3 hours were investigated.

The smaller the weight reduction rate, the better the oxidation resistance and wear resistance, and the smaller the erosion index, the better the corrosion resistance. Residual expansion / shrinkage rate is 1500 ℃ × 3h
It was determined from the test piece after the heat treatment. As is clear from these results, the unfired brick of the present invention is comprehensively superior in strength, oxidation / abrasion resistance, corrosion resistance, and residual expansion property to those of the comparative example produced at the same time. I understand.

[0027]

As described above, the present invention is 1000 ° C.
The following improvements in strength are seen, and the residual expansion coefficient is small,
It is possible to provide a non-fired SN plate brick having excellent volume stability, which is excellent in oxidation resistance, abrasion resistance, and corrosion resistance. Therefore, the sliding nozzle plate is inexpensive and can be expected to have a longer life and more stable operation than the conventional products.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Seijiro Tanaka             2 Kawasaki Furnace Materials at 1576, Higashi-oki, Nakahiro, Ako-shi             Within the corporation F-term (reference) 4E014 MA01 MA12                 4G033 AA02 AA07 AA14 AA24 AB10                       AB24 AB25 BA01

Claims (4)

[Claims] 1. A non-fired brick obtained by kneading a refractory aggregate and a refractory base material containing alumina fine powder, and molding and drying the same, in place of a part of the alumina fine powder, 0.5 to 5.0 weight. % Unburned brick characterized by kneading powder pitch of 100%. 2. In a non-fired brick obtained by kneading a refractory aggregate and a refractory base material containing fine alumina powder, and molding and drying, 0.5 to 5.0 parts by weight instead of a part of the fine alumina powder. % Of the powder pitch and 1 to 15% by weight of easily sinterable alumina fine powder having an average particle diameter of 1 μm or less are kneaded, and an unfired brick. 3. A method for producing an unfired brick, which comprises kneading a refractory aggregate and a refractory base material containing fine alumina powder, and molding and drying the mixture to replace 0.5 to 5.0 parts of the fine alumina powder. A method for producing an unfired brick, which comprises kneading a powder pitch in a weight percentage. 4. In a method for producing an unfired brick, which comprises kneading a refractory aggregate and a refractory base material containing fine alumina powder, and molding and drying the mixture, 0.5-5.0 instead of a part of the fine alumina powder. A method for producing an unfired brick, which comprises kneading 1% to 15% by weight of a powder pitch and 1 to 15% by weight of an easily sinterable alumina fine powder having an average particle diameter of 1 μm or less.