JPH09165270A - Alumina casting monolithic refractory and production of formed body using the refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material which can produce monolithic refractory capable of expressing properties similar to the conventional monolithic refractory when waste refractory materials is reused as aggregate in order to effectively utilize them and a method for producing the material. SOLUTION: Refractory waste is obtained by crushing alumina refractory which had been used in a kiln. Alumina casting monolithic refractory is produced by compounding <=30wt.% of the refractory waste whose particle diameter is larger than the maximum diameter of the aggregate constituting the refractory, <=15wt.% of fine powder consisting of alumina and magnesia of <=45μm in particle diameter and the remaining of alumina casting monolithic refractory. Magnesia content in the fine powder is >=28wt.% and <=40wt.%. In order to produce a formed body from the refractory, the refractory waste and the fine powder are mixed in advance to stick the fine powder on the surfaces of the refractory waste, and the treated refractory waste is mixed with other materials in construction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina cast amorphous refractory used for lining a kiln for producing steel and a method for producing a molded article thereof.

[0002]

2. Description of the Related Art Amorphous castable refractory made of alumina is composed of alumina, magnesia and cement components in such a particle size constitution that the packing density is highest.
At the time of use, it is used by adding water and kneading and pouring it into the required furnace wall shape. However, the used constructions, although the raw material particles are sintered or bonded with each other by the cement component, are easily pulverized at the time of dismantling, and therefore most of them were discarded.

As a technique for utilizing refractory waste, Japanese Unexamined Patent Publication (Kokai) No. Hei 6
-2119853 discloses a method for treating mag-carbon brick waste and a magnesia castable, which is a method of immersing mag-carbon brick waste in a silica sol solution, impregnating the silica inside the brick waste, and then adding the castable. Further, Japanese Patent Application Laid-Open No. 6-345548 discloses a method of manufacturing a casting material using a refractory waste material, a molded body thereof, and a method of manufacturing a molded body thereof. A method of adding to wood is disclosed.

[0004]

However, in both cases, there is not sufficient bonding between the refractory waste and the matrix, and when used at high temperature, a gap is created due to sintering shrinkage of the matrix, resulting in a decrease in strength. With respect to slag erosion, slag may infiltrate into the gap between the refractory waste and the matrix and the refractory waste may be liberated, resulting in large melt loss. Therefore, the present invention is intended to improve the bond strength between the refractory waste and the matrix and suppress the slag erosion into the gap to improve the durability of the cast amorphous refractory containing the refractory waste. .

[0005]

In the present invention, in order to solve the above-mentioned problems, among the refractory scraps obtained by crushing the alumina refractory used in the kiln, the particle size is the alumina refractory scrap. From 30% by weight or less of the maximum particle size of the aggregate constituting the refractory material, 15% by weight or less of fine powder composed of alumina and magnesia having a particle size of 45 μm or less, and the balance being an alumina cast amorphous refractory material The present invention provides an alumina cast amorphous refractory.

Particularly, the fine powder composed of alumina and magnesia having a particle size of 45 μm or less is advantageously a fine powder containing 28% by weight or more and 40% by weight or less of magnesia.

Further, according to the method for producing an alumina cast amorphous refractory molded article, refractory scraps having a particle size satisfying the above-mentioned conditions and fine powders are mixed in advance and the fine powders are adhered to the surface of the refractory scraps. It is characterized in that the refractory scraps to which the fine powder is adhered are mixed with the remaining cast-in amorphous refractory at the time of construction.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The used alumina refractory waste used in the present invention is a refractory containing 50% or more of alumina as a material, and it is necessary to remove the slag infiltration layer before crushing. The reason is that if a large amount of components other than alumina is contained, sufficient strength cannot be obtained. Further, the size of the refractory waste used in the present invention is not less than the maximum particle size of the aggregate constituting the used refractory. This is because the refractory waste that has become smaller than the maximum particle size of the aggregate due to crushing has a high possibility of becoming a particle size consisting of only the aggregate or particles containing a large amount of matrix components. Is not obtained.

The size of the refractory waste is more preferably 2.5 to 6 times the maximum particle size of the aggregate of the alumina cast amorphous refractory which constitutes the balance of the present invention. That is, the inventor mixed refractory scraps of various sizes and an alumina cast amorphous refractory that constitutes the balance in the present invention and constructed it, and the powder mixture was densely packed. It was found that the particle size of the refractory scraps, which reduces the porosity of the obtained irregular-shaped refractory construction product, is at least 2.5 times the maximum particle size of the aggregate that constitutes the cast amorphous refractory to be mixed. .

Further, when the fluidity at the time of construction and the distribution of refractory wastes in the construction body were investigated, it was found that when the particle size exceeded 6 times the maximum particle size of the aggregate constituting the cast amorphous refractory. It was found that the workability was poor and the above-mentioned mixing was non-uniform. Therefore, the more preferable size of the refractory waste used in the present invention is 2.5 to 6 times the maximum particle size of the aggregate that constitutes the cast amorphous refractory to be mixed.

The present invention is directed to refractory waste 3 having the above grain size.
0% by weight or less, 15% by weight or less of fine powder composed of alumina and magnesia having a particle size of 45 μm or less, and the balance consisting of an alumina cast amorphous refractory. The durability of the refractory waste itself has deteriorated due to the fact that it has undergone temperature history and that cracks have occurred due to the impact during crushing. An increase in the blending ratio of refractory scraps gradually deteriorates the characteristics of the irregular-shaped refractory work, but if the blending ratio is 30% by weight or less, it is possible to maintain the same durability as the conventional one.

By the way, one of the causes of the decrease in durability when the refractory waste is compounded is that the bonding strength with the matrix is insufficient and the strength is lowered, or the gap between the matrix and the refractory waste is caused. There was slag invading. To solve this problem, in the present invention, 15% by weight or less of fine powder of alumina and magnesia having a particle diameter of 45 μm or less is mixed. Thus, the addition of alumina and magnesia can produce spinels in use that expand and reduce the gap between the refractory debris and the matrix while simultaneously binding the matrix and the refractory debris.

As a result, the strength of the irregular-shaped refractory work body is improved, and the slag is prevented from entering the gap between the refractory waste and the matrix to improve the corrosion resistance. Also,
The fine powder made of alumina and magnesia to be blended has a particle size of 45 μm or less. This is because if the particle size exceeds 45 μm, a sufficient spinel forming reaction does not occur at the temperature during use. Further, the blending amount is 15% by weight or less. This is because if the amount exceeds 15% by weight, the amount of spinel produced becomes excessive, and expansion causes cracks in the irregular-shaped refractory construction product, resulting in reduced durability.

Further, the fine powder of alumina and magnesia used in the present invention contains magnesia in an amount of 28% by weight or more and 40% by weight or less. This is because by containing 28% by weight or more of magnesia, spinel having a theoretical composition is generated by reacting with alumina which is another component of fine powder, and excess magnesia reacts with refractory waste and forms a matrix. It is the one that tries to create a bond. However, if the magnesia exceeds 40% by weight, unreacted magnesia will remain, and the thermal expansion of this magnesia will cause cracks in the amorphous refractory construction product, resulting in reduced durability.

On the other hand, the amorphous refractory molding of the present invention comprises refractory scraps obtained by crushing an alumina refractory used in a kiln, and fine powder composed of alumina and magnesia.
Mix in advance and attach fine powder to the surface of refractory waste,
It is manufactured by mixing refractory scraps to which the fine powder is attached at the time of construction and other raw materials. Fine particles of alumina and magnesia generate spinel, fill the gap between the refractory waste and the matrix, and at the same time exhibit the effect of binding the two, the refractory waste and the fine powder are mixed in advance to obtain the refractory waste. It is effective to attach fine powder to the surface of. If the refractory waste, the fine powder, and the remaining castable amorphous refractory are mixed at the same time, the fine powder may disperse in the residual castable amorphous refractory that forms the matrix, and the above-mentioned effect can be obtained. Disappear.

[0016]

[Examples] Table 1 shows the characteristics of the examples and comparative examples of the alumina cast amorphous refractory and the molded article produced according to the present invention. That is, when a part without slag permeation was recovered from the alumina cast amorphous refractory used in the molten steel ladle, and the structure was investigated, the maximum particle size was 5 m.
m aggregate was used. Therefore, this amorphous refractory waste is crushed with a crusher to a size of 30 mm or less, and the particle size is 30 to 20.
mm, 20 to 10 mm, 10 to 5 mm, and less than 5 mm were classified into four stages and collected. As the fine powder of alumina and magnesia, those used as a refractory raw material and having a maximum particle size of 10, 45, and 75 μm were used.
Further, as the remaining cast alumina refractory, the same material as that used for the molten steel ladle was used. These raw materials were blended as shown in Table 1, and water was added in an external number of 7 wt% and kneaded to prepare a slag erosion test piece and a bending test piece for evaluation.

[0017]

[Table 1A] * 1 Mixing method: "Before" indicates that irregular refractory waste and fine powder are mixed in advance. "Same" indicates that the amorphous refractory waste, fine powder, and the remaining irregular refractory are mixed at the same time. * 2 Strength index: Relative value when the strength of Comparative Example 17 is set to 100 with respect to the result, after measuring the bending strength at room temperature after firing the molded body at 1400 ° C.

[0018]

[Table 1B] * 1 Mixing method: "Before" indicates that irregular refractory waste and fine powder are mixed in advance. "Same" indicates that the amorphous refractory waste, fine powder, and the remaining irregular refractory are mixed at the same time. * 2 Strength index: Relative value when the strength of Comparative Example 17 is set to 100 with respect to the result, after measuring the bending strength at room temperature after firing the molded body at 1400 ° C.

[0019]

[Table 1C] * 1 Mixing method: "Before" indicates that irregular refractory waste and fine powder are mixed in advance. "Same" indicates that the amorphous refractory waste, fine powder, and the remaining irregular refractory are mixed at the same time. * 2 Strength index: Relative value when the strength of Comparative Example 17 is set to 100 with respect to the result, after measuring the bending strength at room temperature after firing the molded body at 1400 ° C.

In the slag erosion test, C / S =
3.3, T. Using converter slag with Fe = 9%, 1700
A rotary erosion test was conducted at 4 ° C. for 4 hours. The slag erosion depth after the test is shown as a relative value when the erosion depth of the conventional amorphous refractory shown in Comparative Example 17 is 100. The smaller the value is, the more excellent the slag melting resistance is.

The bending strength is 65 × 114 × 230.
A test piece of mm was poured into the test piece, fired at 1400 ° C., and then tested at room temperature. The strength of the molded body after firing is Comparative Example 1
When the value of 7 was taken as 100, the relative value was obtained and used as the strength index, and this value was used for evaluation. The larger the value, the higher the strength and the better.

Examples 1, 2, 3, 4, and 5 have a maximum particle size of 10 μm, and are composed of 30% by weight of magnesia and 70% by weight of alumina, and sufficiently cover the particle surface of the amorphous refractory waste to be used. A sufficient amount of fine powder and the amorphous refractory scraps in the amounts shown in the table were mixed well in advance, and then the remaining castable amorphous refractory was further mixed to form an amorphous refractory. is there.

Compared with Comparative Example 17, the slag erosion resistance and the bending strength after firing showed almost the same characteristics. In addition, Example 1 has the same characteristics as Comparative Example 17, and it is considered that 20 to 10 mm is most preferable as the particle size of the irregular-shaped waste. In addition, Example 6 is a material in which the particle size of the fine powder is increased within the range of the present invention, but exhibits the same characteristics as Comparative Example 17. Furthermore, in Example 7, the magnesia amount of the fine powder was increased within the range of the present invention, but the corrosion resistance was slightly improved and the bending strength after firing was slightly lowered, but it could be used without problems.

In Comparative Example 8, the amorphous refractory waste was as small as less than 5 mm and the filling property was poor, so the slag erosion resistance was poor. In Comparative Example 9, the particle size of the irregular refractory waste was as large as 6 times or more the maximum aggregate particle size of the cast refractory, segregation was observed, and the strength was reduced. In Comparative Examples 10 and 11, since the amount of the amorphous refractory waste compounded exceeded 30% by weight, the influence of the properties of the amorphous refractory waste appeared, and both the corrosion resistance and the strength decreased. In Comparative Example 12, since the maximum particle size of the fine powder was larger than 45 μm, the spinelization reaction was not sufficiently performed and the strength was not obtained.

In Comparative Example 13, the amount of fine powder is 20% by weight.
And the strength decreased due to the influence of cracking due to expansion of the generated spinel. In Comparative Example 14, since the amount of magnesia in the fine powder exceeded 40% by weight, excess magnesia remained, and corrosion resistance was improved, but strength was reduced. In Comparative Example 15, since the amount of magnesia in the fine powder was less than 28% by weight, sufficient spinel was not formed and strength could not be obtained. Comparative Example 16 is a material obtained by simultaneously kneading amorphous refractory scraps, fine powder, and the remaining cast amorphous refractory, but the fine powder is not sufficiently distributed between the amorphous refractory scraps and the matrix, and the corrosion resistance and the strength are high. Both dropped.

[0026]

Industrial Applicability According to the present invention, refractory waste that has been conventionally disposed of can be effectively used. That is, with the composition of the present invention, fine powder consisting of alumina and magnesia is adhered to the surface of refractory scraps and kneaded to mix with the amorphous refractory, whereby the bond between the refractory scraps and the matrix is strengthened, and is conventionally used. It has become possible to manufacture an irregular shaped refractory molded body having properties equivalent to those of the conventional irregular shaped refractory molded body.

Claims (3)

[Claims] 1. A refractory scrap obtained by crushing an alumina refractory used in a kiln, the particle size of which is equal to or larger than the maximum particle size of the aggregate constituting the alumina refractory 30 weight %
An alumina cast amorphous refractory, characterized in that: 15% by weight or less of fine powder composed of alumina and magnesia having a particle size of 45 μm or less, and the balance being an alumina cast amorphous refractory. 2. A fine powder composed of alumina and magnesia having a particle diameter of 45 μm or less contains 28% by weight or more of magnesia,
The castable amorphous alumina refractory according to claim 1, which is a fine powder containing 40% by weight or less. 3. A method for producing an alumina cast amorphous refractory material according to claim 1 or 2, wherein the refractory waste is obtained by crushing the alumina refractory material used in a kiln. , A particle having a particle size equal to or larger than the maximum particle size of the aggregate constituting the alumina refractory and a fine powder made of alumina and magnesia are mixed in advance and the fine powder is adhered to the surface of the refractory waste. A method for manufacturing an alumina cast amorphous refractory body, characterized in that the refractory scrap to which the fine powder is attached at the time of construction is mixed with the rest of the alumina cast amorphous refractory.