KR100332904B1 - A Method for Manufacturing Carbon Cotaining Castable - Google Patents

Abstract

PURPOSE: An amorphous refractory composition containing carbon is provided, to improve the physical properties and the corrosion resistance by reducing the required water content compared with that of the carbon-containing amorphous refractory using the pulverized natural crystalline graphite. CONSTITUTION: The amorphous refractory composition containing carbon comprises a blending source material comprising 77-82 wt% of a magnesia clinker, 5-10 wt% of alumina super micropowder, and 3-8 wt% of the pulverized artificial graphite; and 1-2 wt% of alumina cement, 1-3 wt% of silica super micropowder, and 0.1 wt% or less of a phosphate salt as a binder. Preferably the pulverized artificial graphite has a volume density of 1.8 g/cm3 or more or is obtained by pulverizing the artificial graphite by-product generated in the preparation of high purity silica single crystal. More preferably the pulverized artificial graphite has a particle size of 0.025-0.5 mm.

Description

A Method for Manufacturing Carbon Cotaining Castable}

The present invention relates to amorphous refractory materials used in the field of steelmaking and steelmaking, and more particularly, to amorphous refractory materials containing artificial graphite.

In general, physical and chemically stable inorganic oxides are used as main raw materials for steel and steel refractories.

However, inorganic oxides have the drawback that slag is easily wettable and spattering occurs due to thermal expansion at high temperatures. In order to compensate for this, the use of carbon having an excellent wettability against slag and having high thermal conductivity and thermal expansion together with an inorganic oxide is the mainstream of steel and steel refractories. In other words, the carbon-containing refractory has the inorganic oxide, its main raw material, corrosion resistance and abrasion resistance to molten steel, and carbon prevents the slag wetting of the inorganic oxide, thereby suppressing the erosion and reaction erosion of the inorganic oxide by the slag, and the high thermal conductivity It has the advantage of forming the mutual protection mechanism by improving the spalling resistance.

Normally, the amount of carbon used is less than 20w% in the form of refractory, and less than 10w% in the case of amorphous refractory. When the amount of carbon is large, the oxidation effect of carbon is large, which acts as a disadvantage of lowering the properties of the refractory.

These carbon-containing refractories are classified into various types according to their carbon form. In the case of amorphous carbon, it is mainly used only in a field used for special purposes. Otherwise, crystalline natural graphite phosphate (flake graphite) having a purity of 85% or more as a carbon raw material ) Is mainly used. This is because impression graphite has better oxidation resistance and corrosion resistance than crystalline artificial graphite.

However, in the refractory for inflow containing carbon containing magnesia (MgO), spinel or alumina (Al ₂ O ₃ ) as the main raw materials, the use of impression graphite is restricted because kneading and construction are performed using water. The reason is that carbon is not hydrophilic, and the graphite particles have a large specific surface area as a plate, and due to the layered structure of graphite, the amount of water consumed during kneading increases about twice as much as without using carbon, which greatly reduces the properties of the refractory material. Because.

There is also a method using a surface-modified carbon treated surface to have a hydrophilic to compensate for this disadvantage. However, when the surface-modified carbon is used, the required amount of water is reduced, but the surface-modified carbon itself is expensive, and the mass production is inefficient, and there are many restrictions on commercialization.

Accordingly, an object of the present invention is to provide a carbon-containing amorphous refractory material having a high content by using a small amount of water during kneading while using artificial graphite properly milled to solve the above disadvantages.

The present invention for achieving the above object in the carbon-containing amorphous refractory composition, magnesia clinker: 77-82% by weight, ultra fine alumina: 5-10% by weight, and crushed artificial graphite: 3-8% by weight of a blended raw material The present invention relates to a carbon-containing amorphous refractory composition which is added as a binder in an alumina cement: 1-2% by weight, ultrafine silica: 1-3% by weight and 0∠ phosphate≤0.1% by weight.

Hereinafter, the present invention will be described in detail.

Magnesia clinker according to the present invention is a refractory main raw material capable of withstanding high temperatures. If the content is less than 77% by weight, the corrosion resistance is lowered. If the content is more than 82%, the spalling resistance is lowered and the fluidity is lowered, which is not preferable.

The ultra-fine alumina serves to increase the fluidity as a refractory side material. If the content is less than 5% by weight, the effect of improving workable fluidity is lowered and corrosion resistance is lowered at 10% or more by weight.

The pulverized artificial graphite contained in the refractory material of the present invention prevents wettability of magnesia clinker or ultra fine alumina with slag, as well as has high thermal conductivity and low thermal expansion, thereby inhibiting the erosion and reaction erosion of the inorganic oxide. Do it. However, when the content of the pulverized artificial graphite is less than 3% by weight, the effect of inhibiting the erosion of the inorganic oxides by the slag infiltration is inferior, and when the content of more than 8% by weight increases the amount of water required during construction, the physical properties of the refractory are deteriorated. Not desirable The pulverized artificial graphite suitable for the present invention preferably has a high density, low porosity and is not thin in shape. This is because the use of thin man-made graphite, such as high graphite, increases the amount of water required, as in the case of using graphite. Corresponding artificial graphite is artificial graphite powder obtained by crushing by-products generated during the production of high purity silica single crystal. Preferably, the bulk density of the artificial graphite is about 1.8 g / cm ³ or more.

For example, pulverized artificial graphite suitable for the present invention is obtained as a by-product during the following high purity silicon single crystal manufacturing process. In other words, high-purity silicon single crystals used for semiconductor integrated circuit boards are manufactured by the Czochralski method in which polycrystalline silicon is heated and melted to 1700 ° C. or higher, and then the silicon solution is recrystallized into a single crystal. The polycrystalline silicon powder is filled in a silica (SiO ₂ ) quality container, and the filled polycrystalline silicon powder is melted by heating by an artificial graphite electrode located at the outer diameter of the silica container. When the silicon powder is completely melted, single crystal silicon can be obtained by bonding seed crystals located above the silica container with the molten silicon solution and gradually raising the seed crystals, wherein the silicon solution in the silica container is obtained. In order to prevent the cooling of the silica container, an artificial graphite container is used to insulate the silica container. In addition, an artificial graphite container for thermal insulation is also used for the electrode outer diameter portion. In addition, artificial graphite rods for supporting the vessels and artificial graphite rods are used for shanghaidong. Therefore, the artificial graphite container and the heat insulating material used to manufacture high purity silicon single crystal as described above are used in an argon (Ar) gas atmosphere to prevent oxidation of graphite because they are used at high temperature, but if used for a period of time, the artificial graphite container And the heat insulating material is oxidized and becomes impossible to reuse so that it is discarded as a by-product.

Such ground artificial graphite by-products are preferably ground to have a particle size of 0.5 mm or less. In the case of using artificial graphite having a particle size of 0.5 mm or more, large pores are formed in the refractory structure due to oxidation at a high temperature, thereby reducing the corrosion resistance of the refractory. In addition, in the case of using artificial graphite having a particle size of 0.025 mm or less, the amount of water used during kneading increases, and since oxidation resistance is lowered, there is a disadvantage of lowering the physical properties of the refractory.

Above all, the pulverized artificial graphite of the present invention preferably has a spherical shape or a shape close to a spherical shape that is not thin.

The pulverized artificial graphite powder thus obtained is blended with magnesia clinker and ultrafine alumina, which are refractory aggregates, and a binder is added thereto to obtain a carbon-containing amorphous refractory that requires less moisture.

The binder is suitable for alumina cement, ultrafine silica and phosphate, about 1-2 wt% for alumina cement, about 1-3 wt% for ultrafine silica, and about 0.1 wt% or less for phosphate. .

Hereinafter, the present invention will be described in detail through examples.

Example

3-10wt each of artificial graphite powder (0.5mm-0.025mm) pulverized by-products generated in the silicon single crystal manufacturing process as shown in Table 1 and natural impression graphite (average particle diameter, 0.18mm) of the quality as shown in Table 2 below % And magnesia clinker with 95% purity of magnesia (MgO) is 25wt% for 5-3mm, 23wt% for 3-1mm, 12-19wt% for less than 1mm, 15wt% for less than 0.075mm, and alumina (Al2O3) 2 wt% alumina cement (70% Al2O3 purity), 3 wt% silica ultrafine powder, 0.1 wt% phosphate was added as a binder to a raw material mixture composed of 10 wt% of alumina ultrafine powder (5 μm) having a purity of 95% or more. 6.5-12wt% of the total weight was added and kneaded at room temperature for 3 minutes using a kneader. Then, 40 × 40x160mm sized mold kneaded material was added to perform vibration inlet molding for 15 seconds, and the molded body was cured for 24 hours. Drying was performed for 24 hours in a drier.

In addition, in order to compare the corrosion resistance of the artificial graphite and the impression graphite used in the present invention, when vibration inflow molding was not possible in order to produce a specimen having the same amount of water, forced embossing was performed.

As a test method, the flow measurement measured the spread length (mm) after putting the kneaded sample on the fluidity measurement table and hitting 15 times.

Corrosion resistance is a drum-type rotary erosion machine using oxygen-propane as a heat source, injecting slag (CaO / SiO ₂ = 2.5) to melt, reacting at 1650 ° C for 30 minutes, and then discharging it. After repeated times, the center of the specimen was cut to measure the length of erosion and the length of slag penetration.

Erosion rate at this time was calculated by the following equation.

In addition, the other properties such as porosity, bending strength and hot bending strength were measured according to the inflow refractory and physical properties measurement method.

division Chemical composition Average particle diameter Particle shape C SiC Si SiO ₂ Content (wt%) 99.7 Tr Tr Tr 0.15mm Crushing Sphere

division Chemical composition Average particle diameter Particle shape C SiO ₂ Fe ₂ O ₃ CaO MgO Al ₂ O ₃ Content (wt%) 94.7 2.5 1.3 0.4 0.3 1.2 0.18mm Lamination

division Inventive Example Comparative example One 2 3 One 2 3 4 Compounding rate (wt%) Magnesia clinker 5-3mm 25 25 25 25 25 25 25 3-1mm 23 23 23 23 23 23 23 1-mm 19 17 14 12 17 17 19 0.075mm- 15 15 15 15 15 15 15 Artificial Graphite (0.5-0.025mm) 3 5 8 10 Impression Graphite (0.18mm) 5 5 3 Ultrafine Alumina (5㎛) 10 10 10 10 10 10 10 Alumina Cement (70%) 2 2 2 2 2 2 2 Ultrafine Silica Powder 3 3 3 3 3 3 3 phosphate 0.1 0.1 0.1 0.1 0.1 0.1 0.1 water 6.5 6.5 6.5 6.5 6.5 12 9.5 Properties Porosity (5) 14.3 14.8 15.2 15.3 * 15.1 23.4 21.6 Bending strength (kg / ㎠) 41 38 38 33 * 37 10.6 14.3 Hot bending strength (1400 ℃ x30m) 15.2 18.3 19.7 19.8 * 17.9 4.7 7.2 Characteristics of use Erosion Rate (%) 14.6 17.1 20.3 22.7 * 16.7 33.2 27.6 Slag Penetration (mm) 0.9 0 0 0 *0 0 1.4 Flow rate (mm) 165 155 147 130 ** 100 170 165 * Measured value of specimen forcedly molded by vibrating molding. ** Inflow construction is impossible.

As shown in Table 3, Inventive Example (1-3), as the amount of artificial graphite used increased, the bending strength decreased, and the porosity and hot bending strength increased. In addition, when kneading with the same water content, the flow rate decreased as the amount of artificial graphite increased, but the flow rate within the range of flowability (145-180mm) that can be introduced is shown. Corrosion resistance declined with increasing artificial graphite.

On the contrary, in Comparative Example (1), the flow rate decreased due to the increase in the amount of artificial graphite, and the inflow construction was difficult. Due to the extremely poor quality, the inflow construction was impossible, and when the flow rate was increased by increasing the amount of water, the physical properties as well as the corrosion resistance were significantly lower than those of the artificial graphite.

In addition, in the case of the comparative example (2) in which the forced graphite was formed by vibrating melt molding using the same amount of impression graphite and water as in the case of using artificial graphite, the physical properties similar to those of the invention example (2) using artificial graphite and Use characteristics are shown.

As described above, the carbon-containing amorphous refractory material of the present invention has better physical properties and corrosion resistance due to less water content than carbon-containing amorphous refractory material using pulverized phosphorus graphite, and is similar to the amorphous refractory material using impression graphite even when the same moisture content is required. Corrosion resistance was also shown, and by using waste by-products as raw materials, it can be produced at a low price, and in particular, there is an effect that is suitable as inflow refractory.

Claims (3)

Magnesia clinker: 77-82% by weight, ultra fine alumina: 5-10% by weight, and pulverized artificial graphite: 3-8% by weight, as a binder alumina cement: 1-2% by weight, ultrafine silica: 1 A carbon-containing amorphous refractory composition composed of -3 wt% and 0 'phosphate ≤0.1 wt%. The amorphous graphite-containing refractory composition according to claim 1, wherein the pulverized artificial graphite is an artificial graphite powder having a bulk density of 1.8 g / cm ³ or more, or a powder obtained by pulverizing artificial graphite by-products generated during the production of high-purity silica single crystals. 3. The carbon-containing fire resistant composition according to claim 2, wherein the pulverized artificial graphite has a particle size of 0.025-0.5 mm.