JPH10265275A - Monolithic refractory for executing slip casting and molten steel vessel lined by the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability by improving slaking resistance in an alumina- magnesia slip casting material. SOLUTION: A monolithic refractory for executing slip casting is obtained by adding 0.015-1.5 wt.% basic aluminum lactate, 0.01-1 wt.% PVA short fiber and an alumina cement by external ratio of 100 wt.% refractory aggregate containing 70-99 wt.% alumina and 1-30 wt.% magnesia and having <10 mm particle diameter so as to be 1-15 wt.% magnesia having <75 μm particle diameter in the ratio occupying the total refractory aggregate. A molten steel vessel is lined with the monolithic refractory for executing slip casting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory for casting and a molten steel container lined with the refractory.

[0002]

2. Description of the Related Art As an indefinite refractory for casting (hereinafter referred to as a "casting material") used for lining of a molten steel container such as a molten steel ladle, a tundish, a vacuum degassing furnace, etc.
Alumina-magnesia is proposed in JP-A-97526 or JP-A-8-2975.

[0003] This material has a corrosion resistance with alumina and magnesia, MgO · Al ₂ 0 ₃ spinel formed by reaction of alumina and magnesia (hereinafter, simply referred to as spinel) effect of preventing resistance to slag penetration of combined ,
Excellent durability is obtained.

[0004]

However, in recent years, the conditions of use of a molten steel container are such that the temperature of the molten steel is increased, the residence time is extended, the gas is blown and agitated, etc. But it is not enough. Therefore, there is a strong demand for a lining material that is more durable than conventional materials.

In an alumina-magnesia pouring material, by mixing magnesia in fine particles, spinel formation becomes remarkable due to improvement in reactivity with alumina, and slag penetration resistance becomes more effective. Further, magnesia itself has a large thermal expansion coefficient, but when magnesia is blended in fine particles, the thermal expansion as a casting material is reduced, which is also preferable in terms of spalling resistance.

However, magnesia is digested by reaction with construction water [MgO + H ₂ O → Mg (OH) ₂ ], and there is a problem that the construction of the cast material is weakened by the volume expansion accompanying the digestion. Magnesia improves slag penetration resistance and spalling resistance as described above by atomization, but on the other hand,
Atomization becomes easier to digest due to an increase in specific surface area, and as a result, sufficient durability cannot be obtained eventually.

An object of the present invention is to solve the above-mentioned problems in an alumina-magnesia cast material.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to a method for producing alumina 70-99.
Particle size 10mm containing wt%, magnesia 1-30wt%
To less than 100 wt% of the refractory aggregate, 0.05 to 1.5 wt% of basic aluminum lactate, 0.01 to 1 wt% of PVA short fibers and alumina cement are added in an outer ratio,
In addition, 75% or less of the magnesia particle in the entire refractory aggregate is 1 to 15% by weight of the cast refractory irregular shaped refractory.

It is known, for example, from JP-A-7-257978 that the addition of basic aluminum lactate to amorphous refractories is effective in preventing digestion. The basic nature aluminum lactate coats the surface of magnesia to prevent digestion.

The basic aluminum lactate gels by the addition of construction water, and forms fine cracks in the refractory structure due to volume shrinkage accompanying the gelation. And at the time of heating and drying of the cast material construction body, the fine cracks promote the escape of water vapor generated from construction water to the outside of the refractory structure,
It turned out to be more effective in preventing digestion.
However, there is a problem in that the stress of shrinkage due to the gelation of aluminum lactate is concentrated in some places, resulting in large cracks, which lowers the durability.

On the other hand, it is disclosed in Japanese Unexamined Patent Publication No.
-265572. Organic fibers form an escape path for water vapor in the refractory structure, and have the effect of preventing swelling and dry explosion of the construction.

On the other hand, in the present invention, the durability is remarkably improved by adding basic properties aluminum lactate and PVA short fibers at a specific ratio. Although the detailed mechanism is unknown, it is considered as follows.

The fine cracks formed by the gelling of the basic aluminum lactate have the effect of preventing digestion, but the cracks are concentrated in a part to generate large cracks. In the present invention, the shrinkage stress accompanying the gelation of basic aluminum lactate is dispersed by the susa effect of the PVA short fiber, and the occurrence of large cracks is prevented.

Moreover, after the PVA staple fiber acts on the reinforcement during the casting of the casting material, it shrinks in a relatively low temperature range during heating and drying, and then dissolves to form voids in the refractory structure. Easier escape of water vapor from the water, making digestion more reliable. Short fibers other than PVA, such as polypropylene and polyethylene, do not shrink under heating, soften and melt, close fine cracks in the refractory structure, do not easily escape water vapor, and have poor digestion resistance. Because of this, a sufficient effect on corrosion resistance cannot be obtained.

It is known that the addition of an organic fiber such as PVA short fiber prevents the construction from swelling and dry explosion. P
The remarkable effect in the present invention by the combination of the VA short fiber and the basic aluminum lactate is not due to the prevention of swelling and dry explosion of the construction body, but to the effect of digestion prevention in the alumina-magnesia pouring material. Conceivable.

[0016]

DETAILED DESCRIPTION OF THE INVENTION Alumina is a refractory raw material having both corrosion resistance and volume stability. In the present invention, if the proportion of alumina is less than 70 wt%, the spalling resistance is poor, and
If it exceeds 9 wt%, the slag penetration resistance is inferior.

As the type of alumina, either a sintered product or an electrofused product can be used, and the purity of Al ₂ O ₃ is preferably 90% or more.
About ₁ to 8 wt% of TiO2 or 5 to 10 of MgO
What contained about wt% can be used. In addition, low-purity products such as sand shale, sillimanite, and mullite may be used, but it is preferable to use high-purity products in the fine powder portion.

The particle size of alumina is less than 10 mm, preferably 8 mm or less. In order to obtain a dense construction, the particle size is appropriately adjusted to coarse, medium, and fine particles in consideration of the particle size of magnesia described later. A calcined product may be used for the fine particles.

Magnesia reacts with alumina to produce spinel (hereinafter referred to as spinel), and this spinel forms a solid solution of components such as FeO and MnO in the slag, thereby preventing slag from penetrating into the refractory structure. To prevent. Further, densification of the refractory structure by volume expansion accompanying the spinel generation also has an effect of preventing slag penetration.

Magnesia may be either a sintered product or an electrofused product. If the ratio is less than 1 wt%, the effect of slag penetration resistance is poor, and if it exceeds 30 wt%, the spalling resistance is poor.

The particle size of magnesia is less than 10 mm, and at the same time, 75 μm or less in the total refractory aggregate is 1-1.
It needs to be 5 wt%. 75 μm or less is 1 w
If it is less than t%, the effect of slag penetration resistance is inferior, and 15 wt%
If it exceeds 300, the volume expansion at the time of spinel generation becomes excessive and the spalling resistance is poor. On the other hand, when the proportion of magnesia exceeds 30 wt%, the spalling resistance is reduced due to the thermal expansion property of magnesia itself.

The particle size of 75 μm or less can be adjusted, for example, with a Tyler standard sieve 200 mesh. This 75 μm or less is the proportion of the entire refractory aggregate, and, for example, if a part of the sieve under 1 mm or less includes a part of 75 mesh or less, these are also added.

As the refractory aggregate, spinel, silicon carbide, chromite, carbon, volatile silica and the like may be further combined. Although a relatively large amount of spinel may be blended, the proportion in the refractory aggregate is preferably 20 wt% or less so as not to inhibit the formation of spinel due to the reaction between alumina and magnesia in the present invention.

Volatile silica is obtained, for example, as a by-product in the production of silicon or silicon alloys and is commercially available under the trade names such as silica flour or microsilica.
This has the effect of densifying the refractory structure and improving corrosion resistance. The proportion in the refractory aggregate is 3 wt% or less. If it exceeds 3% by weight, a low-melting substance is formed, and the corrosion resistance is reduced. The most preferred range is 0.05-1.5w
t%. It is preferred that

The basic aluminum lactate preferably has a molar ratio of Al ₂ O ₃ / lactic acid of 0.3 to ₂ . If the ratio is less than 0.05 wt% in the outer shell of the refractory aggregate, the effect of digestion resistance is not obtained, and if it exceeds 1.5 wt%, the corrosion resistance decreases. The addition to the refractory aggregate is in the form of powder in the examples described later, but may be added in advance with water.

PVA (polyvinyl alcohol) short fibers are soluble in hot water. Preferably, the size is 1 to 3 denier and the length is 1 to 10 mm. If the addition ratio is less than 0.01 wt% in the outer shell of the refractory aggregate, the effect of digestion resistance is poor, and if it exceeds 1 wt%, the corrosion resistance decreases.

Alumina cement has a role as a binder. The specific type and addition ratio are not particularly different from those of the conventional casting material. The preferred ratio is 10
If it is less than 3 wt%, sufficient strength of the construction body cannot be obtained, and if it exceeds 15 wt%, the corrosion resistance is reduced.

In addition, peptizers, refractory coarse particles, hardening modifiers, short metal fibers (for example, stainless steel fibers), glass powder, carbon powder, pitch powder, ceramic fibers, foams, which are known as additives for pouring materials. An agent may be added. .

In particular, the addition of a peptizer is effective in terms of workability. Specific examples include, for example, sodium tripolyphosphate,
Sodium hexametaphosphate, Ultra sodium polyphosphate,
Inorganic salts such as sodium acid hexametaphosphate, sodium borate, and sodium carbonate, sodium citrate, sodium tartrate, sodium polyacrylate, sodium sulfonate, and the like. The addition ratio is preferably 0.01 to 0.5% by weight based on the outer periphery of 100% by weight of the refractory aggregate.

The refractory coarse particles have a spalling resistance effect by disrupting the development of cracks generated in the refractory structure. Specific examples include alumina and spinel. In addition, brick waste, products after use of refractories, and the like may be used. The particle size is preferably from 10 to 50 mm. In addition, the ratio is preferably 40 wt% or less, more preferably 5 to 30 wt%, in an outer case with respect to 100 wt% of the refractory aggregate. 40
If it exceeds wt%, the strength of the construction body is reduced due to the imbalance in the particle size composition, and the corrosion resistance is reduced.

The addition of clay is effective for workability. However, if the amount of addition increases, the corrosion resistance is reduced. Therefore, it is preferable that the outer amount be 5 wt% or less relative to 100 wt% of the refractory aggregate. Construction is carried out as usual, and the above composition is
Approximately 8 wt% of construction water is added and mixed, and the construction is poured. At the time of pouring, vibration is generally applied to improve the filling rate.

[0032]

EXAMPLES Table 1 shows experimental examples, and Table 2 shows examples of the present invention and comparative examples. In each case, the composition shown in the table was kneaded at 5 wt% over the added water, poured into a mold, constructed, cured,
What was dried at 110 ° C. for 24 hours was used as a test piece.
The test method is as follows.

Flexural strength: In the experimental example, after drying at 110 ° C. for 24 hours, 500 ° C. assuming heating and drying during use.
× 3 hours after heating, 150 assuming contact with molten steel
The test after heating at 0 ° C. for 3 hours was performed.

Corrosion resistance; Steel slag by weight ratio: converter slag (Fe
(O content; 20 wt%) = 70:30
A rotary erosion test at 650 ° C. × 5 hours was performed to measure the erosion size.

Slag penetration resistance: After a rotational erosion test was performed under the above conditions, the slag penetration size was measured. Spalling resistance: After heating at 1550 ° C. × 15 minutes, the mixture was air-cooled, and this was repeated five times, and the state of crack generation was observed.

Practical machine test: Poured into a 200-ton molten steel ladle using a core, cured, heated and dried at about 1000 ° C. before use, and used, and the melting rate was measured by (mm / charge). .

[0037]

[Table 1]

Table 1 shows the alumina-magnesia pouring material to which basic aluminum lactate was added or the alumina-magnesia pouring material.
In the spinel cast material, the type and proportion of the refractory aggregate were made constant, and the presence or absence of short fibers and the type of short fibers were changed.

Experimental Examples 1 to 4 are alumina-magnesia cast materials, and Experimental Examples 5 to 8 are alumina-spinel cast materials. The degree of strength deterioration of the construction body due to digestion was measured by bending strength. In the case of alumina-magnesia, it was confirmed that Experimental Example 2 in which PVA short fibers and basic aluminum lactate were added in combination had high flexural strength and excellent digestibility. On the other hand, alumina-spinel does not show a large change in flexural strength because it is not digested.

[0040]

[Table 2]

Examples 1 to 5 all have high flexural strength and are excellent in corrosion resistance in combination with the slag penetration resistance of the alumina-magnesia cast material. This effect is also confirmed in the durability of the actual machine test.

Comparative Example 1 in which neither PVA short fiber nor basic aluminum lactate was added, Comparative Example 2 in which no PVA short fiber was added, Comparative Example 6 in which no basic aluminum lactate was added
Has low bending strength due to poor digestion resistance, and is also poor in corrosion resistance. Comparative Example 4 in which the addition amount of basic aluminum lactate was too large and Comparative Example 5 in which the addition amount of PVA short fiber was too large
The effect of the slag permeation resistance of the alumina-magnesia pouring material is not exhibited.

Although the actual machine test was performed on the lining of a molten steel ladle, the casting material of the present invention is not limited to this, and may be used for lining of a tundish, a vacuum degassing furnace, a converter, an electric furnace, etc. in contact with molten steel. Can be.

[0044]

As described above, in the present invention, the improvement of the durability resulting from the prevention of digestion by the combination of PVA short fibers and basic aluminum lactate is extremely clear as is clear from the test results of the above Examples. Notable.
And the operating rate of the molten steel container can be improved by the alumina-magnesia pouring material according to the present invention.

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[Procedure amendment]

[Submission date] April 18, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

Volatile silica is obtained, for example, as a by-product in the production of silicon or silicon alloys and is commercially available under the trade names such as silica flour or microsilica.
This has the effect of densifying the refractory structure and improving corrosion resistance. The proportion in the refractory aggregate is 3 wt% or less. If it exceeds 3% by weight, a low-melting substance is formed, and the corrosion resistance is reduced. The most preferred range is 0.05-1.5w
t%.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

[0040]

[Table 2]

Claims (2)

[Claims] (1) 70-99 wt% of alumina, magnesia 1
Refractory aggregate 100 having a particle size of less than 10 mm, containing up to 30 wt%
wt%, basic aluminum lactate 0.0
5 to 1.5 wt%, 0.01 to 1 wt% of PVA short fibers and alumina cement are added, and the particle size of magnesia is 75 μm or less in the total refractory aggregate.
A cast refractory of 15 wt%. 2. A molten steel container lined with the cast refractory according to claim 1.