JPH09183674A - Monolithic refractory for flowing-in working - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monolithic refractory for flowing-in working capable of attaining excellent durability as the lining of steelmaking furnace such as a vacuum degassing furnace, a ladle or a tundish, as a heat resistant protection member of a molten steel treating lance or the like and capable of attaining excellent durability in the use for a vigorous molten steel flow part. SOLUTION: This monolithic refractory is produced by externally adding 0.5-5wt.% Ba composition such as water-inactive barium titanate, barium aluminate, barium zirconate, barium sulfate and 0.5-5wt.% lightly burnt magnesia to 100wt.% refractory aggregate containing 5-60wt.% fine powdery alumina having <=0.15mm particle diameter. The water-inactive Ba composition does not react with water content for working, is prevented from lowering the strength of a worked body and is allowed to react with the fine powdery alumina to form barium aluminate to strengthen the combined structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast refractory for use as a lining of a steelmaking furnace such as a vacuum degassing furnace, a ladle, and a tundish, or as a heat-resistant protective member for a molten steel treatment lance. Is.

[0002]

2. Description of the Related Art At present, as a refractory for lining a molten steel ladle, alumina-based alumina cement is used as a binder.
Spinel or alumina-magnesia castings have been used.

To improve these materials, it has been proposed to add light burned magnesia. For example, JP-A-63
In JP-A-218586 and JP-A-64-87577, light burned magnesia is added to the joint portion, and the bond generated by hydration due to reaction with working water is utilized to improve corrosion resistance and slag infiltration resistance. I am trying. In addition, Japanese Unexamined Patent Publication No.
In No. -23275, magnesium hydroxide is produced by the reaction of light-burning magnesia with the working water at the time of binding, and after it is heated when the refractory is used, it changes to fine magnesia, and then it is quickly mixed with alumina of the aggregate. Al ₂ O ₃
-It is said that the effects of corrosion resistance and slag infiltration resistance are exhibited by producing MgO-based spinel.

[0004]

However, the refractory for casting by light-burning magnesia bonding cannot exhibit a sufficient effect depending on the part to be used, despite the above excellent characteristics. For example, when used in areas where molten steel flow is particularly strong,
The damage is great. It is considered that this is because the hot strength is low and the wear due to the molten steel flow cannot be endured.

The reason why the hot strength is low is that the refractory structure of the conventional material is so high in purity that there is almost no liquid phase at the boundaries of the refractory particles in the high temperature range during use. However, there is only a small amount of extremely low melting point liquid phase mainly composed of Na ₂ O. Therefore, even though it has high fire resistance, it is in a state of being bonded only by the cohesive force of the particles at the time of use, and the grain boundary is broken by a small stress, and when exposed to the molten steel flow, the refractory particles are It is considered that abrasion is promoted by easy separation.

The weakness of this refractory casting refractory due to the light-burning magnesia bond is the same not only in the high temperature region around 1500 ° C. but also in the intermediate temperature region around 1000 ° C. As a solution to this problem, Japanese Unexamined Patent Publication No. 5-306178 discloses S.
It has been proposed to add iO ₂ and glass. However, even if the strength of these additives increases in the middle temperature range,
In the high temperature region around 500 ° C., the addition of additives did not improve the hot strength due to the formation of low-viscosity glass.

Further, as seen in JP-A-6-277253, a method of using light burned magnesia and alumina cement in combination is being studied. However, due to the difference in the hydration rate between light burned magnesia and alumina cement, one of the binders hardens and the other hardens, so a slaking crack occurs during drying, and a good construction product is obtained. I can't get it.

[0008]

The present invention solves the above problems in a refractory for pouring construction using light burned magnesia as a binder, and has a particle size of 0.15 mm.
Refractory aggregate 10 containing 5 to 60 wt% of the following fine alumina powder
0 wt%, externally applied, water-inactive Ba composition 0.5
It is an amorphous refractory to which -5 wt% and light burned magnesia of 0.5-5 wt% are added. Further, a refractory aggregate 100 containing 5 to 40 wt% of fine alumina powder having a particle size of 10 μm or less.
Ba composition of 0.5 to 5 which is inert to water by wt% to the outside.
It is an amorphous refractory to which wt% and light burned magnesia of 0.5 to 5 wt% are added.

The water-inactive B used here is used.
Specific examples of the composition a include barium titanate, barium aluminate, barium zirconate, and barium sulfate. A water-inert Ba composition (hereinafter,
The inert Ba composition) significantly improves the hot strength by adding a small amount. As a result, combined with the corrosion resistance and slag penetration resistance of the light-burning magnesia bond,
Excellent durability is obtained even when used in places where the flow of molten steel is intense.

The reason may be as follows. That is, the inert Ba composition has no reaction with the applied water,
Does not reduce the strength of the construction body. Further, in the high temperature range during use, it reacts with finely divided alumina to form barium aluminate, and further strengthens the connective structure.

FIG. 1 shows a result obtained by measuring the transition of hot strength by hot bending strength by changing only the addition ratio of barium titanate with the basic composition of Example 1 described later.
It is a graph. It is confirmed that the hot strength is excellent when the ratio of barium titanate is in the range of 0.5 to 5 wt%.

FIG. 2 shows a basic composition of Example 2 described below, in which only the addition ratio of barium titanate is changed,
It is a graph obtained by measuring the erosion dimension (corrosion resistance) and the slag penetration dimension (slag penetration resistance). Note that the slag permeation size is shown as the total size together with the melt loss size for convenience.
It is confirmed that the corrosion resistance and the slag penetration resistance are excellent when the proportion of barium titanate is in the range of 0.5 wt% or more.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The refractory aggregate used in the present invention is 5 to 60 w of fine alumina powder having a particle size of 0.15 mm or less.
It is necessary to include t%. The fine alumina powder may be a sintered product, an electromelted product, or a calcined product.

It is further preferable that the finely divided alumina contains 5 to 40 wt% of ultrafine powder having a particle size of 10 μm or less in order to further enhance the reactivity with the inert Ba composition. Further, calcined alumina has high reactivity because it is fired at a relatively low temperature of about 1000 to 1400 ° C., and is obtained as ultrafine powder having an average particle size of 10 μm or less without pulverization,
Of the finely divided alumina, it is particularly preferable.

If the proportion of the fine alumina powder having a particle size of 0.15 mm or less contained in the refractory aggregate is less than 5 wt%, the effect of improving the hot strength becomes insufficient. If it exceeds 60 wt%, the balance of the grain size composition of the aggregate as a whole is disturbed, resulting in poor spalling resistance and corrosion resistance. When converted into ultrafine powder having a particle size of 10 μm or less, if it exceeds 40 wt%, the spalling resistance and the corrosion resistance are poor.

The type of refractory aggregate other than finely divided alumina is not particularly limited, but from the viewpoint of corrosion resistance, alumina, magnesia, magnesia-calcia, Al ₂ O ₃ .M
It is preferable to use gO-based spinel (hereinafter simply referred to as spinel) as a main material. Further, these may be electro-melted products or sintered products.

Specific examples of alumina include fused alumina, sintered alumina, shale shale, and bauxite. From the viewpoint of corrosion resistance, it is preferable to use a high-purity product. When a low-purity product is used, it is desirable to combine it with a high-purity product so that the average purity of the whole alumina is 90 wt% or more.

[0018] Magnesia or magnesia-calcia is excellent in slag resistance, but it is easily hydrated with working water, and therefore it is not preferable to use a large amount of fine particles having a large specific surface area. When a large amount of fine particles are used, those whose surface has improved slaking resistance by phosphoric acid treatment or carbonation treatment are used.

Spinel is excellent in slag penetration resistance. Since it is difficult to hydrate, it may be used as fine particles. M
The total amount of gO and Al ₂ O ₃ is preferably 95 wt% or more. M
The ratio of gO to Al ₂ O ₃ is not limited to the theoretical composition, and may be, for example, an Al ₂ O ₃ rich one in which the proportion of MgO is small.

Further, the refractory aggregate is made of the above materials such as mullite, chrome ore, zircon, zirconia, carbon, carbide,
Borides and nitrides may be combined. The particle size of the refractory aggregate is not particularly different from that of conventional materials, and the composition of coarse particles, medium particles, and fine particles is appropriately adjusted so that the irregular-shaped refractory material is densely packed by the construction. The maximum particle diameter is usually 10 mm or less, but coarse particles having a maximum particle diameter of 10 mm or more may be combined in order to improve the spalling resistance depending on the part where the refractory is used. The present invention is the above refractory aggregate 100w
An inert Ba composition and light burned magnesia are added together at t%.

Specific examples of the inert Ba composition are barium titanate, barium titanate, barium zirconate, barium sulfate and the like. If the addition amount is 0.5 wt% or less with respect to 100 wt% of the refractory aggregate, the effect of improving the hot strength of the present invention cannot be obtained. If it exceeds 5% by weight, the amount of low-melting substance is excessively produced, and the corrosion resistance is poor. Its particle size promotes a prompt reaction with alumina,
In order to further improve the strength of the connective tissue, fine powder is preferable.

Light burned magnesia is a fine powder in a state in which fine crystals obtained by firing magnesium hydroxide at about 800 to 1300 ° C. are agglomerated. Sintered magnesia is fired at a temperature lower than 1800 ° C or higher. It is preferable that the amount of iodine adsorbed is 1-120 mg / g iodine. The ratio of the refractory aggregate to 100 wt% is 0.
If it is less than 5 wt%, the role as a binder is inferior, and it is 5 wt%.
If it exceeds, the construction water content increases, the porosity increases, and the corrosion resistance decreases.

The refractory material of the present invention is composed of the above-mentioned compound, but in addition to this, a workability adjusting agent, a strength-developing agent, a dry explosion-proofing agent, etc. of an amorphous refractory material for pouring construction are suitable. You may add quantity. Examples of the workability adjusting agent include a dispersant for imparting fluidity during construction, fume silica, ultrafine zircon powder, and clay. Examples of the strength enhancer include glass powder, metal fiber, ceramic fiber and the like. Further, examples of the dry explosion-proof agent include organic fiber, metal powder, and foaming agent. As with conventional materials, it is particularly preferable to add a dispersant for imparting fluidity. Specific examples thereof include sodium hexametaphosphate, sodium tripolyphosphate, sodium polyacrylate, and the like. The ratio of addition is
0.01 to 3w with external coating on 100 wt% of refractory aggregate
It is about t%.

The work is carried out in the usual manner by adding 4 to 10 wt% of water to the whole composition of the irregular refractory, kneading, and then pouring using a form. The molten steel container or the heat-resistant equipment associated therewith may be cast directly, or may be lined with a precast product that has been cast beforehand. In addition, at the time of construction, it is preferable to apply vibration with a vibrator in order to improve the filling property.

[0025]

EXAMPLES Table 1 shows the chemical composition values of the finely divided alumina, binder and inert Ba composition used in each example. Table 2 is an example of the present invention, and Table 3 is a comparative example. Also, Tables 2 and 3
The test results are also shown in.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

In each of the examples, the amount of working water was adjusted so that the optimum fluidity was obtained in accordance with the material, and after kneading, it was poured into a mold and molded. Furthermore, this is 200 ℃ × 24Hr
After drying in, the test was conducted in the following manner.

Hot strength = 1 according to JIS-R2553
The hot bending strength at 500 ° C. heating was measured. Corrosion resistance = 1: 1 by weight ratio of billet and ladle slag
A rotary erosion test was performed at 1600 ° C. for 3 hours with the solvent combined with the above, and the erosion size was measured.

Slag penetration resistance = The slag penetration dimension was measured in the above rotary erosion test. Actual machine test = Used for the inner circumference of the immersion pipe of RH type vacuum degassing furnace,
The rate of erosion was measured.

From the test values shown in Table 2, all of the examples of the present invention to which the inert Ba composition is added have excellent hot strength and simultaneously have corrosion resistance and slag penetration resistance. As a result, in the actual machine test, Example 2 and Example 3 were
The durability was remarkably improved as compared with Comparative Example 1 corresponding to the conventional material, and the effect of the present invention was verified.

On the other hand, Comparative Example 1 in which the inert Ba composition is not added is inferior in hot strength. Comparative Example 2 is inactive B
Although the composition a is added, the binder is alumina cement, which is inferior in corrosion resistance and slag penetration resistance. Comparative Example 3
The amount of the inert Ba composition added is larger than the range of the limit of the present invention, and the corrosion resistance is poor. In Comparative Example 4, the amount of light-burned magnesia added was more than the range of the limit of the present invention, and the corrosion resistance was poor. In Comparative Example 5, the amount of finely divided alumina having a particle size of 0.15 mm or less is less than the limit range of the present invention, the hot strength is lowered, and the durability is poor even in the actual machine test. Comparative Example 6 uses alumina cement as a binder and is inferior in corrosion resistance.

Needless to say, the present invention is not limited to the above-mentioned embodiment, and various applications are possible.

[0035]

INDUSTRIAL APPLICABILITY The amorphous refractory for casting according to the present invention has the corrosion resistance and the slag permeation resistance of the material using light-burning magnesia as a binder, and is hot when used in combination with an inert Ba composition. As a result of improving the strength, excellent durability can be obtained especially when used in a portion where the molten steel flow is intense.
Therefore, the industrial value of the present invention is high in the recent trend toward severer operating conditions due to high-grade steel orientation or reduction of the refractory unit consumption.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of measuring changes in hot strength by hot bending strength.

FIG. 2 is a graph obtained by measuring a melt loss dimension (corrosion resistance) and a slag permeation dimension (slag permeation resistance).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C21C 7/10 C21C 7/10 B

Claims (3)

[Claims] 1. A 100 wt% refractory aggregate containing 5 to 60 wt% of finely divided alumina having a particle size of 0.15 mm or less is externally applied to 0.5 to 5 wt% of a water-inert Ba composition and 0 to lightly burned magnesia. An amorphous refractory containing 0.5 to 5 wt%. 2. Finely divided alumina having a particle size of 10 μm or less
An amorphous refractory obtained by adding 0.5 to 5 wt% of a water-inactive Ba composition and 0.5 to 5 wt% of light-burned magnesia to 100 wt% of a refractory aggregate containing 40 wt%. 3. A water inactive Ba composition comprising barium titanate, barium aluminate, barium zirconate,
The castable refractory according to claim 1 or 2, which is barium sulfate or the like.