KR940006431B1 - Unshaped refractories of calcium-zirconium - Google Patents

Abstract

The composition of calcium zirconate based unshaped refractories comprises 2.0-5.0 wt.% cement binder containing more than 65.0 wt.% Alite (C3S), 89.0-96.0 wt.% or 40.0-95.0 wt.% calcium zirconate clinker including 40.0-53.0 mol% calcium oxide, less than 56.0 wt.% zirconia clinker, and 2.0-6.0 wt.% superfine silica powder which has less than 1 μm of the particle size. This refractories have good workability, corrosion resistance and spalling resistance

Description

Calcium Zirconate Irregular Refractory Composition

The present invention relates to refractory materials used throughout the urinary tract, such as steelmaking facilities and cement kilns for the production of blue and blue steel, and more particularly, to a calcium zirconate amorphous refractory composition.

Recently, as the necessity of making steel with high cleanliness increases, the use of refractory which is advantageous for the production of clean steel has emerged as an important problem. Among them, the calcinated refractory has a very high melting temperature of 2572 ° C. and a spalling resistance compared to the magnesia refractory. It is known as an excellent refractory material that has excellent spattering properties and low vapor pressure under reduced pressure. It also has excellent properties as a refractory and CaO component reacts with non-metallic inclusions in molten steel to adsorb or separate the inclusions. . In addition, when the calcinated refractory material is used in a cement kiln, the liquid component of the cement clinker and the CaO component in the refractory react with each other to increase the viscosity of the liquid component, thereby improving the surface coating (coating) of the refractory brick in the kiln. .

In spite of the above advantages, calciasium refractory is very difficult to practically use due to the slaking phenomenon in which CaO component reacts rapidly with water or water and becomes Ca (OH) ₂ . Therefore, the method of improving the fire resistance of the clinker itself, such as calcia clinker which partially regulated the fire resistance with additives and the surface coated with CaCO ₃ and protective film, and hot pressing of CaO and CaCl ₂ at eutectic production temperature The method of improving fire resistance of refractory bricks is known, but refractory clinker has long term fire resistance and CaCl ₂ has high hygroscopicity. In particular, in order to manufacture amorphous refractory material using calciasyl clinker, non-aqueous binders such as pitch and phenol resin should be used, which has improved fire resistance but limited time to use. There is a disadvantage that requires careful consideration.

The calcium zirconate (CaO.ZrO ₂ ) nitride refractories have recently been developed. Calcium zirconate is a compound composed of about 31.5% by weight of CaO and about 68.5% by weight of ZrO ₂ , which has a very high melting point of 2325 ° C. and high corrosion resistance due to its difficult wettability on molten metal and slag of zirconia. Not only does it have the function of manufacturing clean steel that refractory has (in addition, according to Japanese Patent Application Publication No. 88-233072, Ca ₂ Z ₃ has about 18 times the Al ₂ O ₃ adsorption capacity than CaO), It is evaluated as an excellent refractory raw material with characteristics.

Therefore, calcium zirconate is stable upon contact with water, and thus an amorphous refractory material using an aqueous binder may be prepared and kneaded with water.

On the other hand, alumina cement whose main component is CaO · Al ₂ O ₃ is a representative material of amorphous refractory, especially castable refractory, but calcium zirco is produced by LIDDLE (Br. Ceramic Trans. J. 84, 166-169, 1985). When more than 1% of CaO · Al ₂ O ₃ is added to Nate, the heat resistance is sharply lowered, and the thermal kinetic (1600 ℃) falls below 1/10. As a binder of castable refractory material using calcium zirconate clinker as a main raw material Cannot be used. Therefore, currently, other binders such as clay, sodium silicate, phenol resin, etc. are used, but due to the reaction between the components of the binder and calcium zirconate, the corrosion resistance is poor or the workability is inferior to that of alumina cement.

Therefore, the present invention is advantageous in the manufacture of clean steel by adding a binder and ultra fine silica to a cement containing calcium zirconate clinker as a main raw material and 3CaO.SiO ₂ (Alite) as a main ingredient, and to provide corrosion resistance, spalling resistance and work. It is an object of the present invention to provide an ultrafine bonded cemented amorphous refractory composition having excellent properties.

Hereinafter, the present invention will be described in detail.

The present invention is a cement binder containing 65.0 wt% or more of 3CaOSiO ₂ (Alite): 2.0 to 5.0 wt%, and calcium zirconate clinker containing 40.0 to 53.0 mol% of CaO: 89.0 to 96.0 wt% and the average particle diameter Ultra fine powder silica of less than 1㎛: relates to a calcium zirconate amorphous amorphous refractory composition. In addition, the present invention is a cement binder containing 65.0% by weight or more of 3CaOSiO ₂ (Alite): 2.0 to 5.0% by weight, calcium zirconate clinker containing 40.0 to 53.0 mol% of CaO: 40.0 to 95.0% by weight, and Zirconia clinker: Ultrafine powdered silica of less than 56.0% by weight and less than 1 µm in average particle size: 2.0-6.0% by weight.

The reason for the numerical limitation will be described below.

In the present invention, calcium zirconate clinker may be used alone or in combination with zirconia clinker as the main aggregate (main raw material).

Calcium zirconate clinker that can be used in the present invention is preferably prepared so that the CaO content is 40.0 ~ 53.0mol%, the reason is that when the CaO content is 53.0mol% or more, the digestion of free CaO has the characteristics of the whole clinker As it is dominant, amorphous refractory materials that are kneaded with water may be collapsed during curing or drying. When CaO content is 40.0 mol% or less, relatively porous ø ₁ (CaZr ₄ O ₉ ) or This is because the formation of the ø ₂ (Ca ₆ Zt ₁₉ O ₄₄ ) phase is large, making it difficult to obtain a compact sintered body. .

When calcium zirconate clinker is used alone as the main aggregate, it is preferable to limit the amount of clinker added to 89.0 to 96.0% by weight. The reason is that when the amount of calcium zirconate clinker added is 96.0% by weight or more, If the amount of cement and ultrafine silica, which is a binder with silica, is too small to provide sufficient curing and dry strength for amorphous refractory materials, and the addition amount is less than 89.0% by weight, the content of cement binder, ultrafine silica or other impurities It is because too much heat resistance and erosion resistance of amorphous refractory material.

In addition, when the zirconate clinker is used in combination with the calcium zirconate clinker as a main aggregate, the corrosion resistance of the amorphous refractory is slightly improved. Since it is 40 weight% or less and cannot fully exhibit the ability to manufacture clean steel, the addition amount of the zirconia clinker which can be added in combination with calcium zirconate is preferably 56.0 weight% or less. In addition, when zirconia clinker is used in combination with calcium zirconia clinker as a coarse aggregate, the amount of calcium zirconate clinker added is limited to 40-95.0% by weight.

The calcium zirconate clinker does not disintegrate when contacted with water, so a cement binder that is easy to handle may be used. Alumina cement, which is mainly used as a binder of a castable refractory material, may be used as an amorphous refractory mainly composed of a calcium zirconate clinker. When used as a binder, calcium zirconate forms eutectic melts with Al ₂ O ₃ components at very low temperatures of 1550 ° C. or lower, thereby greatly lowering the heat resistance and erosion resistance of amorphous refractory materials. The use of alumina cement is not suitable, whereas calcium zirconate has relatively high heat resistance upon contact with the SiO ₂ component, so in the present invention, calcium silicate-based cement containing 5.0 wt% or more of 3CaO.SiO ₂ as a binder. Preference is given to using.

In addition, in the present invention, the coagulation principle of ultra-fine powder widely used in low cement dense castable refractory to express dry strength of amorphous refractory (particle-to-particle distance is the minimum of potential energy which is the sum of London-Vander Waals manpower and electrostatic repulsion force) Ultrafine powder having an average particle diameter of less than 1 µm, such as silica flowers, was used as the ultrafine powder, and calcium silicate cement was used as the binder and the ultrafine powder coagulant.

The addition amount of the finely divided silica is preferably 2.0-6.0 wt%, and the inuine cannot express sufficient dry strength when the addition amount is 2.0 wt% or less, and when it is 6.0 wt% or more, the SiO ₂ content of the amorphous refractory becomes high. This is because the heat resistance and erosion resistance of the amorphous refractory material are lowered.

In general, in Al ₂ O ₃ -SiO ₂ -based low cement castable refractory, an alumina cement having an effect of coagulating a dispersion system by slowly eluting polyvalent ions such as Al ³⁺ and Ca ²⁺ as an ultra fine flocculant is used. In the Al ₂ O ₃ component of the alumina cement, the heat resistance of the castable is very low, so calcium silicate-based cement containing polyvalent ions such as Ca ²⁺ and Si ⁴⁺ is used.

The ordinary potent cement used for construction has calcium silicate minerals such as 3CaO · SiO ₂ , 2CaO · SiO _2, and the calcium zirconate is more than about 80% by weight and the Al ₂ O ₃ content is within 10% by weight. Although the temperature for forming the solution by reacting with the clinker is relatively high, the coagulation of ultrafine powder does not occur effectively because of the slow elution rate of polyion after short-term (1 day) curing.

Therefore, in the present invention, it is preferable to use a cement containing at least 65% of 3CaO.SiO ₂ (Alite), which is eluted relatively early at the time of water addition, in the potent cement constituent mineral as a coagulant, for 3CaO · SiO. If ₂ is not more than 65.0% by weight, because they can not be a sufficient role as the binder for monolithic refractories does not have sufficient dry strength after curing a day.

In addition, the amount of the binder and the ultrafine powder coagulant is preferably added in an amount of 2.0 to 5.0% by weight, because when the amount is less than 2.0% by weight, sufficient dry strength cannot be expressed. This is because the content of SiO ₂ and its impurities in the refractory composition is increased to lower the heat resistance and erosion resistance of the amorphous refractory.

In addition, in order to increase the dissolution rate of the polyvalent ions in the cement to increase the curing strength of the castable, it is desirable that the specific surface area of the cement is about 6000 cm ² / g or more, and the secondary agglomeration of ultra fine powder and cement is performed. It is desirable to add high performance dispersants, such as naphthalin sulfonic acid formaldehyde high condensate salts, to prevent) and to enhance the initial strength.

The ultrafine silica-calcium silicate cement binders as described above not only show relatively high strength after 1 day curing but also have a high temperature of solution formation with CaO · ZrO _2. You can expect.

When using the calcium zirconate amorphous amorphous refractory composition of the present invention to the wall of tundish, ladle, etc., the non-metallic inclusions in the molten steel react with the CaO component in the calcium zirconate, which is the main aggregate, thereby adsorbing or floating on the wall. It is advantageous to clean steel and CaO dissolved in slag from CaO · ZrO ₂ increases the viscosity of slag, thereby preventing the slag from penetrating into the castable and causing structural spalling. In addition, when the castable refractory of the present invention is used in a cement kiln, CaO decomposed from the calcium zirconate and the binder is dissolved in the cement clinker to increase the viscosity of the liquid component, thereby forming a cement coating layer having a stable corrosion coating on the wall, and generating decomposition. Since ZrO ₂ exhibits high refractories, it is advantageous not only for cement production but also for the durability of walls.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

Calcium zirconate clinker having a composition as shown in Table 1 below, a binder having a composition as shown in Table 2 below, calcia stabilized zirconia clinker, 1 type of alumina cement, etc. Prepared. By adding water to the refractory composition prepared as described above, the flow rate was adjusted to about 200, and kneading, molding, curing and drying were performed to measure the bending strength, erosion resistance, fire resistance, spalling resistance and inclusion trapping ability. , The measurement results are shown in Table 4 below.

In Table 4, erosion resistance was tested using a ladle slag having a CaO / SiO ₂ ratio of about 2.5 in a high frequency induction furnace, and the relative erosion amount thereof was calculated using the conventional example as 100, and the fire resistance was shown. The specimen was placed in a constant temperature and humidity chamber at 20 ° C and a relative capability of 95%, and the weight change was measured after maintaining a constant time. The spalling resistance was repeated by heating (1300 ° C) and water cooling to determine the number of cracks in the specimen. will shown by measurements, inclusion trapping function is then held the molten steel of 50kg to 1650 ℃ in the high-frequency induction melting furnace, and the addition of Al ₂ O ₃ fine powder 150g 40 × 40 × 160mm specimens for 20 minutes immersion a Al ₂ O of the following: remove the specimen The increase of ₃ is measured and shown.

TABLE 1

TABLE 2

TABLE 3

As shown in Table 4, Inventive Example (1-5), which is an amorphous (castable) refractory prepared by kneading with a raw material and a blending ratio according to the present invention, is compared with the conventional example prepared with calcia clinker as a main component. Not only does it have an equivalent inclusion capturing ability, it is also excellent in spalling resistance and fire resistance, and in particular, Example (1-5) of the present invention is excellent in workability because the cement binder is used, and the binder is heat resistant of the castable refractory. It does not fall sharply and it turns out that it is excellent in corrosion resistance.

On the other hand, Comparative Example (a) was prepared by using a CZ ₁ clinker having a CaO content of 53.0 mol% or more in the calcium zirconate clinker as aggregate, collapsed during drying due to the digestion of free CaO.

Comparative Example (b) is prepared by using the CZIV clinker in the calcium zirconate clinker is out of the scope of the present invention as an aggregate, the structure of the clinker itself is not dense, the corrosion resistance is relatively inferior to CaO content in the clinker It can be seen that the lower the inclusion trapping ability is lower.

Comparative Example (c) is a case where the content of the zirconia clinker in the castable refractory composition is larger than the scope of the invention, the content of calcium zirconate clinker that can adsorb the inclusions is relatively inferior to the inclusion capturing ability. . Comparative Example (d) is a commercially available ordinary portland cement as a binder, hardly expressing strength after one day curing, it can be seen that the practical use is difficult. In Comparative Example (e), one type of alumina cement was used as the binder, and the CaO · Al ₂ O ₃ component in the alumina cement rapidly lowered the heat resistance of the castable, indicating that the hot strength and corrosion resistance were very poor.

Comparative Example (f) is the addition amount of the binder is smaller than the range of the present invention, the dry strength was low, Comparative Example (g) is the addition amount of the binder is more than the range of the present invention and the low melting point between the binder and the aggregate Due to the large amount of product, it can be seen that the hot strength is low and the corrosion resistance is relatively inferior.

Comparative Example (h) is the addition amount of the ultra fine silica is smaller than the range of the present invention, it can be seen that the dry strength is low.

Comparative Example (i) is the addition amount of the ultra fine silica is more than the scope of the present invention, it can be seen that since the SiO ₂ content of the castable is too high to form a solution at a low temperature, the hot strength and corrosion resistance is low, Comparative Example (j) is using the calcia clinker as the main aggregate and the cement within the scope of the present invention as a binder, it can be seen that the fire resistance is poor, careful consideration is required during the operation.

As described above, the present invention not only has excellent workability but has superior workability than amorphous calciasyl refractories using conventional structure or non-aqueous binder, and also has a conventional refractory material using amorphous calcium zirconate clinker. It is more effective to provide a calcium zirconate amorphous amorphous refractory composition which is more excellent in workability, corrosion resistance and spalling resistance.

Claims (2)

Cement binder containing 65.0 wt% or more of 3CaOSiO ₂ (Alite): 2.0 to 5.0 wt%, calcium zirconate clinker containing 40.0 to 53.0 mol% of CaO: 89.0 to 96.0 wt%, and an average particle diameter of less than 1 μm Ultra-fine powder silica: Calcium zirconate amorphous form refractory composition, characterized in that the composition is 2.6-6.0% by weight. Cement binder containing 65.0 wt% or more of 3CaOSiO ₂ (Alite): 2.0-5.0 wt%, calcium zirconate clinker containing 40.0-53.0 mol% of CaO: 40.0-95.0 wt%, and zirconia clinker: 56.0 wt% Ultrafine powder silica of less than%, and an average particle diameter of less than 1㎛: calcium zirconate amorphous form refractory composition, characterized in that the composition.