JPH0643271B2 - Castable refractories for lining molten steel ladle - Google Patents

Description

TECHNICAL FIELD The present invention relates to a castable refractory for lining a molten steel ladle.

(Prior Art) The lining of molten steel ladle is shifting from conventional brick laying to laying with irregular refractory for the purpose of labor saving and mechanization. The amorphous refractory used here is, for example, in JP-A-60-60985, a spinel composed of at least 60 parts by weight of spinel clinker, 10 to 35 parts by weight of alumina clinker, and 3 to 10 parts by weight of alumina cement. -Alumina castable refractory, JP-A-60-60986 discloses that the weight ratio of magnesia clinker: alumina clinker is 7: 3 to 8:
A magnesia-alumina-spinel castable refractory having an aggregate of 60 to 80 parts by weight of a mixture of 2 and 20 to 40 parts by weight of spinel clinker has been proposed.

(Problems to be Solved by the Invention) The above-mentioned materials are superior in corrosion resistance to conventional non-standard refractory materials such as flake and flake-zircon. But,
It cannot be said to be sufficient in the recent trend toward severer furnace operation or reduction of the basic unit of refractory, and it is strongly desired to provide castable refractory having excellent durability.

(Means for Solving the Problem) The present inventors have made repeated developments in search of a more suitable material for lining a molten steel ladle while making the most of the corrosion resistance of the alumina-spinel castable refractory. As a result, when an appropriate amount of organic short fibers is added to a mixture in which alumina and MgO.A ₂ O ₃ based spinel (hereinafter referred to as spinel) are combined in a specific ratio, it is effective in improving hot strength and preventing peeling. As a result, the present invention has been completed.

That is, in the present invention, the weight ratio of alumina is 40 to 90%,
Compound containing 100% of O · A ₂ O ₃ based spinel and less than 50% and 2 to 25% of alumina cement as a main material
On the outside, 0.5 to 20 mm long organic short fibers are squeezed out to 0.0
A castable refractory for lining a molten steel ladle containing 1 to 0.5%.

Further, in the refractory material, the MgO.A ₂ O ₃ -based spinel has a particle size of 1 mm or less.

Next, the present invention will be described.

Alumina-spinel has a high coefficient of thermal expansion, but the inner lining of the molten steel ladle is bounded by the iron shell on the outer circumference and the upper holding metal fittings, so the expansion is absorbed by the refractory itself and the refractory structure weakens. . On the other hand, in the case of adding organic short fibers, it seems that when heated by use, short fibers are burned out to create fine voids, which absorb the expansion of the refractory and prevent weakening of the structure. Be done.

FIG. 1 shows the relationship between the amount of organic short fibers added and the maximum thermal expansion stress of castable refractories in alumina-spinel refractories. It can be seen that the maximum thermal expansion stress of castable refractories is reduced by adding organic short fibers. The compounding composition of the castable refractories used in this experiment was the same as that of Example 7 described later, and only the addition amount of the organic short fibers was changed.

This type of castable refractory uses alumina cement as a binder. Alumina cement is A ₂ O ₃
And CaO as the main components. C coming from this alumina cement
aO reacts with MgO from spinel and A ₂ O ₃ from alumina etc. at a high temperature during use to generate A ₂ O ₃
-MgO-CaO system low melt (melting point 1370 ° C) is produced.
This tendency becomes more remarkable as the particle size of the spinel is reduced. Conventional alumina-spinel castable refractories have a tendency to expand in the early stage of use, but with the passage of time, they contract due to the formation of low-melting material, causing crevices → ingots, causing peeling. .

On the other hand, the castable refractory of the present invention, the addition of the organic short fibers creates fine voids in the refractory structure, resulting in less contact between the components that cause the formation of the low melting point substance It is considered that the generation of swelling is reduced and peeling can be prevented.

FIG. 2 shows the high temperature expansion curves of the castable refractory having the same composition as that of Example 8 described later to which the organic short fibers were added and the castable refractory of Comparative Example 2 to which the organic short fibers were not added. It can be understood that the shrinkage of the organic short fiber added is smaller than that of the non-added organic fiber added.

Next, the compound used in the present invention will be described in detail. All the percentages shown below are weight ratios.

Alumina has roles such as corrosion resistance and volume stability. Examples thereof include artificial products such as sintered alumina and fused alumina, and natural products such as shale shale, bauxite, and sillimanite. In the present invention, one or more selected from these can be used. Above all, those having a small content of SiO _{2 which} causes the formation of a low melt are preferable. The particle size is not particularly different from the conventional one, and for example, the maximum particle size is set to 10 to 25 mm, and coarse particles,
It is appropriately adjusted to medium particles and fine particles.

The proportion of alumina is 40 to 90%, preferably 50 to 80
%. If it is less than 40%, the corrosion resistance and the slag penetration resistance are poor. On the other hand, if it exceeds 90%, the proportion of spinel decreases correspondingly, resulting in poor slag penetration resistance.

The spinel may be either an electromelted product or a sintered product, or may be a combination thereof. MgO · A ₂ that constitutes spinel
O ratio of each component of the ₃ MgO _· A 2 _{O 3} in a molar ratio of 0.7
The range of -1.3: 1.3-0.7 is preferable.

The particle size of the spinel is preferably 1 mm or less. Figure 3 shows
In an alumina-spinel castable refractory, it is a graph which showed the relationship between the particle size of spinel and the slag penetration of a castable refractory. The measuring method of slag permeability is
It was the same as the example described later. In this case, the mixing ratio of each raw material was 55% of sintered alumina, 30% of sintered spinel, 15% of alumina cement, and 0.1% of 5 mm long vinylon short fiber was externally applied. From the figure, it can be seen that the slag penetration resistance of castable refractories is further improved when the particle size of the spinel is 1 mm or less. The reason for this is that the fine spinel allows the matrix to be uniformly filled with no gaps, and the spinel dissolves all the components such as FeO and MnO in the slag as a solid solution to enhance the effect of preventing slag penetration.

When the particle size of the spinel in the alumina-spinel castable refractory is 1 mm or less, the above effects are obtained, but the shrinkage becomes more remarkable. However, in the present invention, the addition of the organic short fibers can prevent the shrinkage. Spinel ratio is 2
% Or more and less than 50%, more preferably 5 to 45%. If it is less than 2%, there is no effect in preventing slag penetration, and 50%
With the above, the expansion stress becomes too large.

Alumina cement may be similar to that conventionally used as a binder for refractories. The grain size is 1
Fine powder of 80 mesh or less. The ratio is 2 to 25%, preferably 5 to 20%. If it is less than 2%, there is no effect of imparting strength as a binder, and if it exceeds 25%, the corrosion resistance is lowered.

As the organic short fibers, materials such as polyester, polyamide, acrylic, cellulose, vinylon, polypropylene, nylon, polyvinyl and polyethylene can be used. The size should be 0.5 to 20 mm in length. If it is less than 0.5 mm, it has no effect as a fiber. If it exceeds 20 mm, the slag penetration resistance in castable refractories is poor. The amount of addition is 0.01 to 0.5% by external coating with respect to 100% of the mixture containing the refractory aggregate and the binder as the main materials. If it is less than 0.01%, there is no effect, and if it exceeds 0.5%, the corrosion resistance decreases.

In the present invention, in addition to the above-mentioned compounds and additives, other substances may be added within a range that inhibits the effects of the present invention. For example, magnesia may be added in an appropriate amount, but magnesia has a very large coefficient of thermal expansion, so that the proportion is preferably 5% or less. In addition, short metal fibers, metal powders, carbon powders, carbides, nitrides and the like may be added in appropriate amounts even in the lining of the molten steel ladle, depending on the use site.

(Example) Table 1 shows an example of the present invention and a comparative example thereof.

Each test was carried out by vibration-casting into a mold by adding an appropriate amount of water to the compound shown in the table and kneading the mixture, and then 110 ° C. × 24
After drying for an hour, the measurement was performed.

 Bending strength; conforms to JIS-R2553.

 Line change rate: According to JIS-R2554.

Rotational erosion; Steel slab: Molten steel ladle slag = 1: 1 was used as a solvent, and after 1650 ° C. × 4 hours, the melt loss dimension and the slag permeation dimension were measured.

Each of the castable refractories of the examples of the present invention has a small thermal expansion stress, a small shrinkage due to heating (measured by a linear change rate), and a high corrosion resistance of the alumina-spinel material. In addition, slag penetration resistance is further improved when spinel is blended in a particle size of 1 mm or less.

On the other hand, in Comparative Example 1, the strength (measured by bending strength) is low and the corrosion resistance is poor because the amount of alumina cement is small. Comparative Example 2 to which the organic short fibers are not added has a large thermal expansion stress and a large shrinkage. Comparative Example 3 has a large amount of alumina cement and thus has poor corrosion resistance. Comparative Example 4 has a large proportion of organic short fibers and has poor corrosion resistance. In Comparative Example 5, the spinel amount was too large and the slag penetration resistance was poor. Comparative Example 6 has poor slag penetration resistance because the organic short fibers are too long. In Comparative Example 7, the shrinkage is small because the particle size of the spinel is large, but the thermal expansion stress is large because the organic short fibers are not added.

As an actual machine test, some of the examples and comparative examples were
It was used as a lining of a 0t molten steel ladle and tested. In the examples of the present invention, the durability was not found in the conventional materials, and the excellent durability was obtained as shown in the results of Table 1.

(Effects of the Invention) As described above, the alumina-spinel castable refractory of the present invention is excellent in slag penetration resistance, and further, the structure becomes weak and low due to the thermal expansion stress observed when it is used as the lining of the ladle. This is a solution to the problem of shrinkage due to melt formation. As a result, the castable refractory of the present invention can fully exhibit the corrosion resistance of the alumina-spinel material, and the life of the castable refractory for lining a molten steel ladle is remarkably improved.

Therefore, the present invention, which can provide a castable refractory having an excellent service life, is extremely high in industrial value in view of the recent severer operation of the ladle ladle operation or the reduction of the basic unit of refractory.

[Brief description of drawings]

FIG. 1 shows the relationship between the amount of organic short fibers added and the maximum thermal expansion stress of castable refractories in alumina-spinel refractories. FIG. 2 shows the high temperature expansion curves of the castable refractory material of Example 8 to which the organic short fibers were added and the castable refractory material of Comparative Example 2 to which the organic short fibers were not added. FIG. 3 is a graph showing the relationship between the particle size of the spinel and the slag permeability of the castable refractory in the alumina-spinel castable refractory.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sumi Matsumoto 1-3-1 Niihama, Arai-cho, Takasago-shi, Hyogo Harima Ceramic Co., Ltd. (72) Inventor Toshihiro Isobe 1-3-1 Niihama, Arai-cho, Takasago-shi, Hyogo Harima Ceramics Co., Ltd. (56) Reference JP-A-59-128271 (JP, A) JP-A-61-10079 (JP, A) JP-A-59-190276 (JP, A)

Claims (2)

[Claims] 1. A weight ratio of 40 to 90% alumina and MgO.
A ₂ O ₃ -based spinel 2% or more and less than 50% and 100% of a mixture mainly composed of alumina cement 2 to 25%,
An organic short fiber with a length of 0.5 to 20 mm is applied outside 0.01 to
Castable refractory for lining molten steel ladle containing 0.5%. 2. The particle size of MgO.A ₂ O ₃ spinel is 1 mm.
The castable refractory for lining a molten steel ladle according to claim 1, which is as follows.