KR100332917B1 - Graphite-containing castable refractory composition - Google Patents

Abstract

PURPOSE: A graphite-containing castable refractory is provided, to improve the heat resistance, the heat impact resistance and the corrosion resistance with maintaining the strength and the water content to be constant within a certain range by employing the graphite whose surface is modified by using a synthetic resin and a hydrophilic particle. CONSTITUTION: The graphite-containing castable refractory comprises 75-95 wt% of a mixture consisting of 1-30 wt% of the surface-modified graphite and 70-99 wt% of aggregate; 2-15 wt% of alumina cement; and 15 wt% or less of super micropowder. The surface-modified graphite is obtained by coating graphite with 5-40 wt% of a synthetic resin and coating it with a hydrophilic particle. Preferably the surface-modified graphite has a particle size of 3 mm or less.

Description

Graphite-containing castable refractory composition

The present invention relates to a castable refractory composition that can be used in furnace equipment, such as ladle wall, ladle bottom, ladle well block, blast furnace barrel, crossroad car, etc., more specifically, heat resistance, heat resistance It relates to a graphite-containing castable refractory composition excellent in impact resistance and corrosion resistance.

Graphite-containing refractory containing graphite is widely used in the field of steelmaking and steelmaking because it has excellent properties such as heat resistance and thermal shock resistance, and is difficult to get wet with molten iron, molten steel, and molten slag and thus shows excellent corrosion resistance. However, in the case of graphite-containing orthogonal refractory, it requires a lot of work in manufacturing and construction, but requires a lot of cost and working time as a whole. As a result, in recent years, in the field of refractory, manufacturing and construction are simple, so that the portion of the amorphous refractory, which is relatively low in cost and independent of the shape of the construction site, is gradually increasing.

Amorphous refractory is to construct the composition of the powder mixed in the field by adding water in the field, when containing graphite, the graphite is hydrophilic when mixed with water will increase the water content. This increase in water content causes a decrease in physical properties such as increasing porosity and lowering strength after drying.

Therefore, many methods have been studied to solve the weakness of the graphite-containing amorphous refractory, among which, for example, surface treatment of graphite or coating synthetic resin, acid treatment method, alumina and carbonization And a method of coating hydrophilic particles such as silicon.

However, the method of increasing the hydrophilicity by coating the graphite powder with the surfactant has a limit on the amount of graphite that can maintain the strength, so that when a large amount is added to form amorphous refractory, no bond is formed in the matrix so that the strength is increased. There is a problem of low. In addition, the method of coating the synthetic resin on the graphite has a disadvantage in that the resin coating itself has a hydrophobic property, so that the resin coating is subjected to a surface treatment with a surfactant, and the acid treatment method penetrates the interlayer compound by infiltrating the crystalline layer of the graphite. When the graphite is expanded and mixed with water, the residual acid component in the graphite particles is dissolved in water to change pH and inhibit dispersion, thereby preventing high specific gravity refractory. In addition, the method of coating the hydrophilic particles is a method of coating the graphite surface with alumina particles by colliding graphite and alumina in the air rotating at high speed, the graphite and the hydrophilic particles are weakly bonded by physical force in the actual process The disadvantage is that hydrophilic particles are easily separated when handling graphite.

Thus, the present inventors have repeatedly conducted research and experiments to solve the above problems, and based on the results, the present invention proposes a synthetic resin and hydrophilic particles on the surface of graphite added to the amorphous refractory material. It is intended to provide a graphite-containing castable refractory composition excellent in heat resistance, thermal shock resistance and corrosion resistance, while maintaining the strength and moisture content in a predetermined range by adding a multi-coated surface.

In order to achieve the above object, the present invention contains 75-95% of the total weight of the surface-modified graphite and aggregate raw material in the ratio of 1-30% by weight and 70-99% by weight, respectively, and the remainder is alumina cement: 2-15% by weight, 0 ∠ ultra-fine powder ≤ 15% by weight, wherein the surface-modified graphite is coated with hydrophilic particles after coating 5-40% by weight of synthetic resin on the surface It relates to a graphite-containing castable refractory composition.

Hereinafter, the present invention will be described in more detail.

In general, castable refractory composition is known in many kinds, the representative of which is 75-95% by weight of the aggregate raw material and 2-15% by weight of alumina cement as the main raw material, and other ultra fine raw materials of less than 15% by weight Castable refractory compositions. Such castable refractory composition is usually used by adding 4-15% by weight of water, kneading, pouring into a mold of a desired form, curing and drying.

In the present invention, the surface-modified graphite is contained in an amount of 1-30% by weight in 100% by weight of the aggregate raw material, which accounts for 75-95% by weight in the castable refractory composition.

In this case, the surface-modified graphite is coated with 5-40% by weight of synthetic resin on the graphite surface, dried to obtain a resin coating, and then sprayed a slurry composed of an organic solvent and hydrophilic particles on the resin coating to form a hydrophilic particle It refers to what is obtained by coating the coating surface, which will be described in more detail as follows.

First, after curing, the surface of the graphite is coated with 5 to 40% by weight of synthetic resins such as phenol resin, frans resin, xylene resin, melamine resin, acrylic resin, which are hard to dissolve in water to obtain a resin coating. In this case, when the amount of the synthetic resin is less than 5% by weight, it is difficult to completely coat the graphite surface, and when it exceeds 40% by weight, it is difficult to uniformly coat the graphite particles and control the particle size of the resin coating. Moreover, it is more preferable to use resin with a high residual carbon amount as resin which coat | covers the said graphite.

Next, an organic solvent such as alcohol and the like, and hydrophilic particles such as metal oxides, metal carbides, metal nitrides, metal borides and metal particles having a smaller hydrophilicity than the average particle diameter of graphite particles are mixed to prepare a spray solution in a slurry state. . At this time, the hydrophilic particles may be mixed with one or more. In addition, the size of the hydrophilic particles is preferably 50% or less of the average particle diameter of the resin coating, the addition amount of the hydrophilic particles is suitable 5-50% by weight relative to the resin coating.

Next, the slurry of hydrophilic particles is sprayed onto the surface of the resin coating by using a spray. The surface of the resin coating is melted by the organic solvent by the spraying and the hydrophilic particles are coated. When the resin is dried again, the molten resin is cured and the hydrophilic particles are bonded to the surface of the resin coating.

In the present invention, the content ratio of the graphite with the surface-modified aggregate material is 1-30% by weight and 70-99% by weight.

If the content of the surface-modified graphite is less than 1% by weight, the effect of addition is insignificant, and if it is more than 30% by weight, dispersibility is poor, so that a dense sintered body cannot be formed.

In addition, the particle size of the surface-modified graphite contained in the above content is not particularly limited, but is preferably 3mm or less. The reason is that when larger than 3mm, the particles are broken when kneading, and the portion where the resin and the hydrophilic particles are not coated may be exposed to reduce fluidity.

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

Example

Phenolic resin was coated on the surface of natural graphite with the content shown in Table 1 and dried to obtain a resin coating having an average particle diameter of 150 μm. Further, the hydrophilic particles having an average particle diameter of 40 μm were mixed with alcohols by taking the amounts shown in Table 1 below with respect to the content of the resin coating, thereby obtaining a slurry. The slurry was sprayed onto the obtained resin coating, followed by drying to obtain graphite powder having a modified surface.

Inventive Example Comparative example One 2 3 4 One 2 3 Resin coating (average 150㎛) Natural graphite 80 80 80 80 80 80 - Phenolic Resin 20 20 20 20 20 20 - Hydrophilic Particles (Average 40㎛) Alumina 10 - - - - - - Silica - 10 - - - - - Silicon Carbide - - 10 40 10 10 -

Using the surface-modified graphite powder obtained above, the mixture was added in the mixing ratio as shown in Table 2 below, kneaded with water and the flow rate (flow value) 150, and then poured into a mold 40x40x160mm (porosity, bending strength test), 110 (length) x40 ( Height) x87.8 (upper side) x 115.9 (lower side) mm sized cross-cut type (for erosion test) and 60x60x60 mm (for oxidation test). The molded article was cured at room temperature for 24 hours, and then dried at 100 ° C for 24 hours. Further, the dried product was reduced and calcined at 1400 ° C. for 3 hours to prepare a fired product. The apparent porosity and the bending strength of the dried product and the fired product were obtained and shown in Table 2 below.

In addition, by repeating the temperature increase ↔ water cooling up to 1400 ℃ to repeat the number of times until some of the specimen is dropped to the spalling resistance and the results are shown in Table 1 below.

In addition, after performing the rotary erosion test with ladle slag (CaO / SiO ₂ : 6.0, Al ₂ O ₃ : 21%) at 1600 ℃ cross-section specimens were measured erosion depth and slag penetration depth. The rotary erosion test measures the slag penetration depth and erosion depth after repeating 1600 ℃ x 1 hour x 10 times in a rotary erosion tester, and the following formula (1) and (2) based on Comparative Example (3) The infiltration index and the erosion index were calculated, and their values are shown in Table 2 below.

Inventive Example Comparative example One 2 3 4 One 2 3 Compounding ratio (% by weight) Surface modified graphite powder 10 10 10 20 0.5 35 - Natural graphite - - - - - - 10 Alumina (<5mm) 73 73 73 63 78 48 73 Alumina cement 5 5 5 5 5 5 5 Calcined alumina 10 10 10 10 10 10 10 Silica flower 2 2 2 2 2 2 2 Hexametha sodium phosphate (extrapolation) 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Amount of added water (%) 8.6 8.3 7.4 8.7 5.8 13.8 12.6 Apparent porosity (%) 100 ℃ x24hr 16.9 16.7 14.6 18.0 11.6 25.4 23.1 1400 ℃ x3hr 21.7 20.8 19.9 22.5 17.1 29.2 25.8 Bending bending strength (MPa) 100 ℃ x24hr 3.9 4.5 5.5 4.2 7.5 1.1 1.2 1400 ℃ x3hr 4.0 4.9 6.2 4.7 9.9 1.5 2.1 Spalling resistance (1400 ℃ ↔water cooling) 60 60 60 60 32 33 28 Slag Infiltration Index 190 197 218 213 87 104 100 Slag erosion index 178 183 204 182 108 82 100

As shown in Table 2, Inventive Example (1-4) was changed within the scope of the present invention, Comparative Example (1-3) using a castable prepared in a content outside the scope of the present invention It was.

Inventive Example (1-4) is generally excellent in strength compared to Comparative Example (1-3), it can be seen that the penetration and erosion of the slag is greatly suppressed, and also characteristics such as spalling resistance and slag infiltration index Excellent.

As described above, according to the present invention, by including the surface-modified graphite in the castable refractory composition, compared with the conventional graphite-containing castable refractory composition, the strength, spalling resistance, and the penetration and erosion resistance against slag, etc. Since it improves more than the equivalent, when the obtained refractory material is applied to a ladle wall, a ladle bottom, a ladle well block, a blast furnace, a crossroad car, etc., the effect of increasing the refractory life is provided.

Claims (2)

The surface-modified graphite and aggregate raw material are contained in a ratio of 1-30% by weight and 70-99% by weight, respectively, and contain 75-95% of the total weight, and the rest is alumina cement: 2-15% by weight and 0∠ s. It is contained in a fine powder ≤ 15% by weight, wherein the surface-modified graphite is coated with hydrophilic particles after coating 5-40% by weight of synthetic resin on the surface, the graphite-containing castable refractory composition The method of claim 1, The surface-modified graphite is a graphite-containing castable refractory composition, characterized in that the particle size is 3mm or less