JPH0676252B2 - Unfired alumina / magnesia brick - Google Patents

Description

TECHNICAL FIELD The present invention relates to an unburned alumina / magnesia brick used for lining metallurgical vessels such as hot metal gutters, blast furnaces, hot metal ladles, and molten steel ladles in blast furnaces.

[Conventional technology]

As a lining refractory for steelmaking such as blast furnace hot metal gutter, mixed piggy car, hot metal ladle, molten steel ladle, steelmaking metallurgical vessel, flake, zircon, high alumina, atsmina, silicon carbide, carbonaceous
Refractory materials such as magnesia and carbonaceous materials are used, but each of them has some drawbacks.

For example, high-alumina refractory materials have little erosion due to slag, but their penetration is deep and so-called structural spalling in which the penetration layer of components such as slag, hot metal, and molten steel peels off and peels off due to repeated heating and cooling during use. It has the drawback of being prone to occur.

Moreover, the pyrophyllic refractories are largely damaged by melting damage.

Zircon refractory has relatively excellent corrosion resistance, but its raw material is expensive because it cannot be produced in Japan, and the price has soared due to uncertainties in raw material supply. Zircon refractory has a small linear change rate before and after the treatment when it is heated to around the operating temperature and cooled, that is, the residual expansion coefficient, and shows a negative value, that is, shrinkability depending on this composition or the particle size composition. . Therefore, by subjecting it to cyclic heating and cooling at low and high temperatures, for example, joint opening and joint melting loss are large in a molten steel ladle, so-called "kamaboko-like melting loss" comes to be seen, and it may end in a short life. is there.

Carbon-containing refractories such as alumina / silicon carbide / carbon-based and magnesia-carbon-based have a high oxygen partial pressure because it is unavoidable that the brick structure becomes porous and weakened due to the disappearance of carbon oxidation. It has the drawback that it cannot be used in a place or atmosphere.

By the way, in order to prevent the joint opening and joint melting loss due to the contraction of the zircon refractory, it has been attempted to utilize the volume expansion associated with the so-called spinel formation reaction of MgO + Al ₂ O ₃ → MgO.Al ₂ O ₃ . However, I still haven't got what I want.

For example, JP-A-51-151705 discloses either one of magnesia or dolomite, or an aggregate composed of two or more kinds of silica-alumina-based substances having a magnesia-dolomite-alumina content of 40% or more, and a silica-alumina-based aggregate. Disclosed is a refractory material prepared by mixing a fine powder material prepared so that the silica content is 5 to 60% from the substance. This disclosure has the drawback that since the fine powder portion contains silica, the refractory degree of the matrix portion is low, and the range of use thereof is markedly restricted due to the large amount of melt formation.

That is, it is uneconomical as a refractory for a molten steel ladle used at a temperature of 1550 ° C. or higher and a container for a hot metal pretreatment in which a large amount of soda ash, quick lime, fluorite, etc. are used. Further, this invention uses dolomite for the aggregate grains, but in a refractory such that CaO is present alone in the brick structure, since the collapse of the brick structure due to the hydration reaction of CaO occurs, Careful attention is required for storage before use, or control of atmospheric conditions such as temperature and moisture during use, and the cost for that cannot be overlooked.

[Problems to be solved by the invention]

The present invention is intended to provide a refractory brick lining refractory iron for steelmaking, and steelmaking metallurgical container for solving the above problems, after heating to a working temperature range of 1400 ~ 1650 ℃. It is intended to provide a brick which has a positive residual expansion coefficient, that is, expandability, and is excellent in corrosion resistance and spall resistance.

[Means for solving problems]

The present invention is unavoidably 97-85 alumina raw material containing impurities
A resin or a resin and a phosphate as a binder are added to a mixture of 3 parts by weight of a magnesia-based raw material having a particle size of 0.1-1.0 mm and containing inevitable impurities, and the mixture is press-molded. It is an unfired alumina-magnesia brick.

. The brick of the present invention is a resin bond (resin bond) typified by a phenol resin, or a phosphate bond typified by aluminum phosphate or sodium hexametaphosphate, which is an alumina / magnesia unfired brick.

[Action]

The brick of the present invention does not impair the excellent corrosion resistance of alumina, and its strength is improved by resin bond or phosphate bond in the temperature range from room temperature to 1000 ° C., and by the formation of ceramic bond by sintering at higher temperatures. An Al ₂ O ₃ · MgO quality unfired brick designed to be maintained.

In addition, when exposed to high temperatures during use, the brick structure sinters moderately to form ceramic bonds, and the reaction of MgO + Al ₂ O ₃ → MgO.Al ₂ O ₃ (spinel) (1) results in the vicinity of the working surface. Since spinel is generated at this time, and volume expansion occurs at this time, leakage steel due to joint opening, and hull-like melting damage due to joint melting damage are prevented.

The first point of the present invention is to contain 3 to 15 parts by weight of an inevitable impurity-containing magnesia-based material having a particle diameter of 1 to 0.1 mm with respect to 97 to 85 parts by weight of an inevitable impurity-containing alumina-based material. An alumina / magnesia non-fired brick with a low silica content, characterized in that its bond is a resin bond or a resin and phosphate bond.

In the brick of the present invention, the presence of a specific amount of magnesia having a specific particle size in the alumina material causes sintering during use to form a durable wall surface of the refractory, and (1) above
By continuously imparting the residual expandability by the spinel-forming reaction of the formula, it is possible to maintain a stable wall surface against expansion and contraction accompanying the thermal cycle during use.

It is said that the residual expansion rate of bricks required to maintain a stable wall surface in a ladle, a tow truck, etc. is 0.1 to 1.0%, but the volume expansion due to the spinel formation reaction of the above formula (1) is about 8.9%. Is about 2.9% when converted to a linear expansion coefficient.

That is, the true specific gravities of alumina, magnesia, and spinel are 3.98, 3.60, and 3.55, respectively.
Since it is 3, 142.3, when spinel is generated by the reaction of equation (1), Therefore, the coefficient of linear expansion becomes about 2.9%.

This is a theoretical calculation value.In actual refractories, the expansion stress is absorbed and relaxed by the presence of pores and cracks, and the amount of spinel produced by the presence of impurities decreases, so this value is a little smaller. Become.

Furthermore, by setting the grain system of magnesia to 1.0 to 0.1 mm, the surface area is reduced as compared with the case of fine powder, so that the spinelization reaction is suppressed and the residual expansion coefficient can be maintained at an appropriate value.

Now, the residual expansion / shrinkage rate is slightly different depending on the place of use (lining container), but as described above, a value of 0.1 to 1.0% is necessary. If the residual expansion rate is 0.1% or less, joint openings and wall cracks will occur as described above, causing kamaboko-like melting loss and, if significant, steel leak accidents from joints. If it is 1.0% or more, the compressive stress generated cannot be completely absorbed in the refractory,
This may cause wall separation, peeling, or crushing, resulting in serious operational problems and damage.

The relationship between the particle size and addition amount of magnesia and the residual expansion / shrinkage ratio in resin-bonded alumina-magnesia bricks
Shown in the figure.

The basic composition of the brick shown in Fig. 1 is natural alumina particles (86% Al ₂ O ₃ ) 40% by weight sintered alumina (99.5% Al ₂ O ₃ ) 40-60% by weight sintered magnesia (98% MgO) 0 ~ 20% by weight. Moreover, the test method is 20mm × 20mm ×
The test piece was cut out to 120 mm, packed in a container made of SiC together with coke breeze, and heated at 1400 ° C. for 2 hours, and the rate of change in the length direction before and after the test is expressed as a percentage. When the particle size of the magnesia-based raw material is smaller than 0.1 mm, the generation of spinel is rapid, so the residual expansion rate becomes + 1% or more by adding 3% by weight of the magnesia-based raw material.
With 0.1 mm particles, the residual expansion rate is 3% by weight of magnesia-based raw material.
It is 0.1%, and it is clear that the residual expansion amount is 1% when the magnesia-based raw material is about 18% by weight. The amount of spinel produced and the rate of production are slightly affected by the amount of impurities contained in each of the alumina-based and magnesia-based raw materials in addition to the particle size of the raw materials, so that the addition amount of the magnesia-based raw material is 3 to 15 Weight percent is suitable.

The binder is preferably a resin or a combination of a resin and a phosphate. That is, the resin contains 30 to 60% by weight of carbon. Most of the resin dissipates at high temperatures,
Part of it remains in the brick structure and forms a small amount of amorphous carbon. This amorphous carbon is preferable because it impedes the penetration of slag, suppresses the generation of ceramic bonds, and suppresses the speed of spinel generation.

In addition, the presence of phosphate can prevent a sharp decrease in strength due to decarburization, and the highly viscous phosphate glass (melt) generated on the working surface suppresses the penetration of slag,
Improves slag resistance.

On the other hand, the presence of an excessive amount of phosphate lowers the fire resistance and spall resistance, which is not preferable. Therefore terms _of P ₂ O ₅ to 1.0% by weight or less addition amount of phosphate, preferably 0.2 to
0.5% by weight.

The amount of alumina used as the alumina-based raw material used in the present invention
Natural raw materials such as 60% by weight or more of natural corundum, bauxite, shale shale, sillimanite, and synthetic raw materials such as sintered alumina, fused alumina, synthetic mullite or fused mullite can be mentioned. Rather, it is preferable to use a mixture of two or more kinds.

As a magnesia-based raw material, the amount of magnesia is 80% by weight.
The above-mentioned natural or synthetic magnesia clinker and electro-melting magnesia can be used, but the particle size and the addition amount must be appropriately controlled as described in detail above.

Examples of the resin used in the present invention include phenolic resin, tar, pitch, petroleum pitch, and furan resin, which may be used alone or in a mixture of two or more kinds, and the amount thereof is usually 1 to 10% by weight based on the total amount of alumina and magnesia. %.

Examples of the phosphate used in the present invention include aluminum phosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate and the like.

Further, it is desirable to add an appropriate amount of metals such as silicon and aluminum, and carbides and nitrides such as SiC, B ₄ C and BN according to the place of use and atmosphere. These additives form an oxide film on the working surface of the bricks to prevent the penetration of slag, hot metal and molten steel components into the bricks, and to prevent a sudden decrease in strength due to decarburization, and to improve the durability of the bricks. It has the effect of remarkably improving the sex.

〔Example〕

Hereinafter, the usefulness of the present invention will be clarified by Examples and Comparative Examples.

Example 1 4.0 parts by weight of resole type phenolic resin was added to 100 parts by weight of the starting materials No. 1 to No. 3 and the comparative starting materials No. 1 to No. 3 each having the composition shown in Table 1. , Kneading at room temperature for 40 minutes, then using a 200-ton hydraulic press to form a normal brick shape (114
mm × 230 mm × 65 mm). Then, it was put into a hot air circulation type dryer and heat-treated at 240 ° C. for 24 hours.

Table 1 shows the qualities of the examples and comparative examples.

Examples No. 1 to No. 3, which contain 3 to 15% by weight of a magnesia-based raw material having a particle size of 1 to 0.1 mm and have a silica (SiO ₂ ) content of 3.5% by weight or less, are excellent in corrosion resistance and have a suitable amount. It is apparent that it has residual expansivity.

The test methods for physical properties are as follows.

(1) Apparent porosity and bulk specific gravity Measured according to JIS R2205-74.

(2) Residual expansion / shrinkage rate A test piece cut to a size of 20 mm × 20 mm × 120 mm was placed in a silicon carbide box with coke breeze and placed in an electric furnace.
The dimensional change rate in the longitudinal direction before and after heating when heat-treated at 1400 ° C. for 2 hours was expressed as a percentage.

(3) Softening point under load Measured according to JIS R2209-77.

(4) Corrosion resistance (melting loss index) 8 pieces of 114 mm long having a trapezoidal cross section with a short side of 60 mm, a long piece of 90 mm and a height (thickness) of 40 mm are assembled into a cylindrical shape, and the cylinder is 2
While rotating at 4 rpm, the inside is heated with an oxygen-propane burner and kept at 1700 ° C. Next, 60 parts of iron oxide (Fe ₂ O ₃ ),
Add 400 g of synthetic slag consisting of 20 parts of lime (CaO) and 20 parts of fluorspar (Ca ₂ F ₂ ). After 1 hour, the waste is discharged, and then 400 g of synthetic slag is added again. After repeating the above operation 4 times,
Cool, disassemble, and cut the center of each test piece in the vertical direction (114 mm direction) to measure the cross-sectional area. The difference in cross-sectional area before and after the test was taken as the amount of erosion, and the data was shown as an index with the amount of erosion of Comparative Example No. 7 described below as 100.

Example 2 40 parts by weight of shale shale, 55 parts by weight of sintered alumina, particle size 1 to
Based on a blend consisting of 5 parts by weight of 0.1 mm magnesia, Examples No. 4 to No. 9 using resin alone or a combination of resin and phosphate, and Comparative Examples No. 4 to No. using acid salt.
Table 2 shows the compounding raw materials and the product properties of Comparative Example No. 7, which is a sintered product prepared by mixing 6, shale shale, synthetic mullite, sintered alumina and clay.

The compounds shown in Table 2 were molded into a regular brick shape in the same manner as in the above example, and only Comparative Example No. 7 was fired at 1500 ° C. in a tunnel kiln. Further, Examples No. 4 to No. 9 and Comparative Examples No. 4 to No. 6 were heat-treated at 240 ° C. for 24 hours in the same manner as in Example No. 1.

From Table 2, it is clear that Examples No. 4 to No. 9 have a suitable residual expansion coefficient when the amount of silica (SiO ₂ ) is 3.5% by weight or less, and are excellent in corrosion resistance and spall resistance.

The test methods for porosity, bulk specific gravity, residual expansion coefficient, softening point under load, and corrosion resistance were the same as in Example 1, and the spall resistance was measured as follows.

Using an electric furnace, the surface of a 114 mm × 65 mm of normal bricks is
An operation of heating at 0 ° C. for 15 minutes and then air-cooling for 30 minutes was set as one cycle, and was performed up to 10 cycles. 5% of heating surface area
The number of cycles at the time of peeling and peeling was calculated and displayed.

Example 3 Examples No. 4 and No. 7 and Comparative Example No. 7 were attached to the ceiling part of a 250 ton mixed pig car and compared. The wear rate of Example No. 4
0.35 mm / heat, Example No. 7 was 0.32 mm / heat, and Comparative Example No. 7 was 0.48 mm / heat.

[Effects of the Invention] Not only can the wear rate be greatly reduced by using the brick of the present invention for the refractory lining of a metallurgical container, but since it is a non-fired brick, the firing step during manufacturing is unnecessary, which results in The production efficiency and the production yield were high, and the production cost could be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the relationship between the particle size of magnesia, the residual expansion of the addition amount, and the contraction rate.

Claims (1)

[Claims] 1. An inevitable alumina raw material 97 containing impurities.
~ 85 parts by weight and 3 to 15 parts by weight of magnesia-based raw material containing inevitable impurities and having a particle size of 0.1 to 1.0 mm, and a resin or a resin and a phosphate as a binder are added and press-molded. A non-fired alumina-magnesia brick that is characterized.