KR100213317B1 - Castable refractory composition - Google Patents

Abstract

The present invention relates to a composition of an alumina-magnesia-zirconia-based amorphous refractory used as a refractory material of various facilities for forcing such as ladle wall, hot reuse tundish, etc. The object is to provide an amorphous refractory composition excellent in spalling resistance have.

In order to achieve the above object, the present invention has a particle diameter of 1 mm or less, Al ₂ O ₃ -ZrO ₂ -based clinker containing 10-35% by weight of monoclinic zirconia: Magnesia powder of 10-35%, particle diameter of 45㎛ or less : 1-6% by weight, calcined alumina powder having a particle diameter of 5 μm or less: 5-15% by weight, alumina cement: 6-14% by weight, and alumina clinker having a particle size of 1 mm or more: 40-65% by weight The technical gist of an excellent amorphous refractory composition is set forth.

Description

Amorphous fire resistant composition with excellent spalling resistance

The present invention relates to an amorphous refractory composition used in various forced bath facilities such as ladle walls, tundish inner walls, and more particularly, to alumina-magnesia-zirconia-based amorphous refractory compositions having excellent spalling resistance, infiltration resistance and erosion resistance. It is about.

Conventional amorphous refractory materials for ladles include zirconium, silica-zirconium, alumina, magnesia, spinel, alumina-spinel, etc. Among them, alumina-spinel amorphous refractory is erosion and resistance to slag. It is known that the ladle using this material has a high temperature characteristic such as invasiveness and is higher in life than that of other materials.

The alumina-spinelyl amorphous refractory is mainly composed of alumina and spinel as aggregates and alumina cement having a high Al ₂ O ₃ content as a binder. However, the alumina-spinel amorphous amorphous refractories are somewhat better in resistance to slag infiltration than alumina amorphous refractory, but structural spalling due to insufficient penetration inhibitory effect of slag with high FeO content when used for a long time in ladle, hot reuse tundish, etc. There is a flaw in the vulnerability.

Therefore, recently, a method of using an alumina-rich (Al ₂ O ₃ rich) spinel clinker and a method of adding a part of magnesia powder have been proposed to suppress the penetration of FeO component, but these methods have been proposed to the slag containing a large amount of FeO component. Infiltration inhibition effect is not so large. In particular, the method of adding a part of the magnesia powder has the advantage of suppressing the infiltration of the slag due to densified amorphous refractory structure due to the volume expansion due to the reduction in the secondary spinel shape by the reaction of alumina and magnesia, but it controls the degree of volume expansion Since it is very difficult to perform, there is a problem in that the thermal spalling resistance is weak because a severe stress may occur in the structure due to excessive expansion of the amorphous refractory movable surface during heating. As a result, this causes structural spalling and lowers the durability of the internal refractories. Therefore, if the alumina-enriched secondary spinel is effectively produced by the reaction of alumina and magnesia, it is known that the penetration of FeO component can be actively inhibited, but stoichiometrically due to many variables such as the case of adding a large amount of magnesia powder. It was difficult to suppress the formation of 1: 1 spinel, so that effective slag penetration could not be suppressed.

Accordingly, the present inventors have conducted research and experiments to solve the above problems, and the thermal spalling resistance of these alumina or alumina-spinel amorphous refractory materials is highly dependent on the characteristics of the aggregate, particle size ratio, and type and content of the binder. It was confirmed that the present invention has been limited based on this.

It is an object of the present invention to provide a castable refractory composition having improved slag penetration resistance and thermal spalling resistance of conventional alumina or alumina-spinel refractories.

Hereinafter, the present invention will be described.

The present invention has an input of 1 mm or less, Al ₂ O ₃ -ZrO ₂ system clinker containing 10-30% by weight of monoclinic zirconia: 10-35%, magnesia powder having a particle diameter of 45㎛ or less: 1-6% by weight Amorphous refractory composition having excellent spalling resistance composed of calcined alumina powder having a particle diameter of 5 μm or less: 5-15 wt%, alumina cement: 6-14 wt%, and alumina clinker having a particle diameter of 1 mm or more: 40-65 wt% will be.

Hereinafter, the present invention will be described in detail.

The present invention is characterized by using 10-35% by weight of Al ₂ O ₃ -ZrO ₂ based klinger having a particle diameter of 1mm or less by including 10-35% by weight of zirconia having a monoclinic structure comprising monoclinic zirconia Al ₂ O ₃ -ZrO ₂ -based clinker refers to a ceramic material having a structure in which monoclinic zirconia is dispersed inside corundum crystal grains. These materials are manufactured by mixing zirconia and alumina raw materials, followed by sintering or melting, and have a property of hardly expanding at a temperature of 1200-1500 ° C. due to hot abnormal line change of zirconia dispersed in alumina particles.

Therefore, by adding a part of this material, the volume change due to the temperature change of the entire amorphous refractory composition is reduced, thereby improving heat spalling resistance. This effect is obtained when using this material with a particle diameter of 1 mm or less because it must be sintered or melted in a uniformly mixed state.

In addition, if the monoclinic zirconia content of this material is less than 10% by weight, it is difficult to expect a hot volume expansion buffering effect, and if it is 35% by weight or more, it is not effectively dispersed inside the zirconia alumina particles and is united together so that it can be used for hot abnormal line conversion of monoclinic zirconia. As a result, not only the spalling resistance is lowered, but also the strength of the Al ₂ O ₃ -ZrO ₂ -based clinker itself is low, so that the hot strength of the amorphous refractory composition is lowered. If the amount of Al ₂ O ₃ -ZrO ₂ -based clinker is less than 10% by weight, the effect of addition is insignificant. If it exceeds 35% by weight, the closest packing structure can be achieved due to the particle size composition.

In the present invention, in order to suppress the penetration of FeO component in the slag, without adding a spinel clinker to the fine powder magnesia powder having a particle size of 45㎛ or less and ultrafine calcined alumina powder having a particle size of 5㎛ or less is added to the amorphous refractory composition in hot In use, secondary spinels were allowed to form. At this time, the particle size was limited to 45 µm and 5 µm or less, respectively, in order to prevent the expansion of the partial abnormality by easily occurring and evenly dispersed throughout the entire tissue.

In addition, by limiting the amount of each powder added, an alumina-enriched spinel having a cationic lattice defect structure of Mg ²⁺ sites was formed, so that Fe ions in the slag were easily dissolved into the lattice defects, thereby preventing further penetration.

When the amount of the magnesia powder added is less than 1% by weight or the amount of the calcined alumina powder added is less than 5% by weight, the secondary spinel formation effect is too small. Particularly, the calcined alumina reduces the added moisture of the amorphous refractory composition and under low cement content. It should be added at least 5% by weight because it acts as an ultra fine binder to exhibit strength. In addition, when the amount of the magnesia powder added exceeds 6% by weight, not only the formation of the alumina-enriched spinel is difficult, but also the amount of water required for kneading increases, thereby decreasing the strength and erosion resistance of the amorphous refractory composition. The addition amount of the calcined alumina powder should not exceed 15% by weight. If this is exceeded, the amount of the ultrafine portion of the amorphous refractory composition particle size is too large, so that the amount of moisture required for kneading is large and the structure of the amorphous refractory composition is not dense and shrinks after firing. Show a tendency. Also, after firing, the spalling resistance is also poor because of locally oversintering in the structure of the amorphous refractory composition.

In the present invention, the addition of Al ₂ O ₃ -ZrO ₂ -based clinker is characterized in that the alumina-enriched spinel solid solution is stably produced by exceeding the secondary spinel formation reaction. That is, calcined alumina powder and magnesia powder react to form an alumina-enriched spinel, and the excess magnesia is absorbed by monoclinic zirconia in Al ₂ O ₃ -ZrO ₂ clinker so that tetragonal and cubic zirconia having a more stable structure at high temperature The Al ₂ O ₃ -ZrO ₂ -based clinker is stable and spalled, while the alumina-enriched spinel employs more magnesia to stoichiometrically 1; Suppresses the change to 1 spinichiometric spinel.

The monoclinic zirconia can employ up to about 10% by weight of magnesia, and spinel clinker can employ up to about 28.4% by weight of magnesia, but it can act as a lattice-defective spinel at 25% by weight or less, so the amount of magnesia powder added is amorphous. If the weight is more than the sum of 1/10 of the ZrO ₂ content added and 1/3 of the added calcined alumina powder content, the spinel structure moves to the stoichiometric 1: 1 structure, and thus effective slag penetration inhibition is achieved. it's difficult. That is, the content of magnesia powder is preferably (the amount of magnesia powder added ≤ ZrO ₂ content in castable x 1/10 + calcined alumina powder added x ⅓). If the alumina cement added as a binder is less than 6% by weight, the bond strength is too small. If the alumina cement is more than 14% by weight, the erosion resistance is lowered and the thermal spalling resistance is low due to excessive sintering. It is preferable to use.

The portion other than the above raw material is filled with an alumina clinker having a particle diameter of 1 mm or more, but the content of the alumina clinker at this time is preferably limited to 40-65 wt%. If the content of the alumina clicker is out of the above condition range, the particle size composition ratio is not appropriate, so that the amount of moisture required for kneading is increased, so the strength is lowered.

The present invention will be described in more detail with reference to the following Examples.

EXAMPLE

Table _{2 using} Al ₂ O ₃ -ZrO ₂ clinker having a composition as shown in Table 1, sintered alumina clinker, purity 98% grade magnesia powder, calcined alumina and Al ₂ O ₃ content 80% grade alumina cement, etc. The mixture was kneaded under the same conditions to obtain a blended raw material.

The blended raw materials were kneaded with water so that the flow value was 200, and then the following specimens were molded.

Specimen for measuring strength and line change rate (cuboid): 40 mm x 40 mm x 160 mm

Specimen for erosion test (cross-edge type): 110 mm x 40 mm x 88 mm x 116 mm

Specimen for spalling test (cube): 60 mm x 60 mm x 60 mm

The molded specimens were cured for 24 hours in a constant temperature and humidity chamber maintained at 25 ℃ and then dried for 24 hours at a temperature of 110 ℃ after compressive strength, hot bending strength, residual line change rate after firing, spalling resistance And re-characteristics such as bedroom depth, and the results are shown in Table 3 below.

The specific temperature was measured by repeating the spalling resistance of 1400 ° C. and water cooling by water, and measuring the repeated number of times of temperature rise and cooling until the specimen was broken.

In the erosion and infiltration test, a slag and a steel having a basicity of 2.5 and a total Fe 15% in a rotary erosion tester were mixed at a ratio of 1: 1 and melted at 1550 ° C., followed by six times of solidifying the slag and steel with a new one every hour. The erosion depth and infiltration depth of the specimens were then measured.

* 1: Moisture content (weight%) at 200 flow

* 2: Number of repetitions of 1400 ℃ ↔ water cooling until falling

* 3: {Delay slag (base degree of 2.5, T.Fe15%) + steel} = 1: Erosion depth (mm) after rotary erosion test (1550 ° C x 1 hour x 6 times)

As shown in Tables 2 and 3, in the case of the invention (1-4), it is an amorphous refractory composition that satisfies the conditions of the present invention, and has superior volumetric safety, erosion resistance, and infiltration resistance as compared with the conventional example (1-3). It was found that spalling resistance was also greatly improved.

In the case of Comparative Example (1), the AlO-ZrO-based clinker having a higher Zro content than the condition range of the present invention was used, and the spalling resistance and the hot strength were low, and in the case of Comparative Example (2), the present invention It can be seen that the spalling resistance is weak when the AlO-ZrO-based clinker having a lower ZrO content than the condition range of is used.

In addition, the comparative example (3) in the content of AlO-ZrO-based clinker is less than the range of the present invention, the effect is weak, and the content of the AlO-ZrO-based clinker is more than the range of the present invention In the case of (4), the strength is low, the corrosion resistance is weak, and the effect of improving the spalling resistance is also weak.

In addition, in the case of Comparative Example (5) (7) in which the amount of magnesia powder or calcined alumina added is less than the condition range of the present invention, the erosion and infiltration are severe. It can be seen that low.

In addition, in the case of Comparative Example (6) it can be seen that the addition of the magnesia powder exceeds the condition range of the present invention, the strength is low and the corrosion resistance is not improved.

In addition, in the case of Comparative Example (8) it can be seen that when the addition amount of the calcined alumina powder exceeds the condition range of the present invention, the amount of moisture required for kneading is large, the strength is low, and the spalling resistance is also weak.

In addition, in the case of the comparative example (9), it can be seen that the strength is very low when the addition amount of the alumina cement is less than the condition range of the present invention.

In addition, in the case of the comparative example (10) it can be seen that the hot strength and erosion resistance are weak when the addition amount of the alumina cement exceeds the condition range of the present invention.

In addition, in the case of Comparative Example (11) and many Comparative Examples (12) where the content of the alumina clinker is less than the condition range of the present invention, the total particle size composition ratio is not appropriate, it can be seen that the amount of moisture required for kneading is high and the strength is low.

In addition, in the case of Comparative Example 13, it was found that the spalling resistance was very weak when monoclinic zirconia powder was added alone instead of the AlO-ZrO-based clinker.

In the case of Inventive Example (5-6), the composition range of the present invention is satisfied, but the magnesia content is greater than (ZrO content in amorphous refractory x 1/10 + calcined alumina powder x 1/3). It was found that the infiltration resistance was slightly worse than that of 4), but was superior to the conventional and comparative examples. As a result, when the magnesia content rate (ZrO 2 × 1/10 + calcined alumina powder × 1/3) is less, it can be seen that a better amorphous type refractory composition is obtained.

In addition, in the case of the conventional example (1) which is an alumina amorphous refractory material, the spalling resistance and infiltration resistance are very poor, and in the case of the prior art example (2) which is an alumina-spinel amorphous amorphous refractory material, also the spalling resistance and infiltration resistance of this invention It is poor in comparison with the case.

In addition, in the case of the prior art example (3), which is an alumina-magnesia amorphous amorphous refractory material, it can be seen that the spraying resistance is weaker than that of the present invention, and the coefficient of hot linear expansion is large.

As described above, the amorphous refractory composition according to the present invention has high hot strength and stable line change characteristics, and in particular, has excellent spalling resistance, infiltration and corrosion resistance, so that it can be used for ladle walls, hot reuse tundish, etc. If there is an effect that greatly extends the life of the refractory material.

Claims (2)

Al ₂ O ₃ -ZrO ₂ -based clinker having a particle diameter of 1 mm or less and containing 10-35% by weight of monoclinic zirconia: 10-35%, magnesia powder having a particle size of 45 μm or less: 1-6% by weight, 5 μm in particle size An amorphous fire resistant composition having excellent spalling resistance, comprising: calcined alumina powder: 5-15 wt%, alumina cement: 6-14 wt%, and alumina clinker: 40-65 wt% having a particle diameter of 1 mm or more. The amorphous refractory composition having excellent spalling resistance according to claim 1, wherein the amount of the magnesia powder added is not more than 1/10 of the ZrO ₂ content in the amorphous refractory composition plus 1/3 of the added calcined alumina powder. .