KR20040016493A - High intensity castable refractories with good adiabatic and high thermal shock resistance - Google Patents

Abstract

PURPOSE: Provided is a high strength castable refractory excellent in insulating property and heat impact resistance, which contains ceramic fiber and increases an insulating effect between an iron ware and a refractory in a high temperature furnace facility. CONSTITUTION: The high strength castable refractory comprises 40-64wt% of fused alumina, 5-12wt% of calcined alumina, 3-6wt% of silica ultrafine powder, 20-30wt% of ceramic fiber, 3-5wt% of vinyl fiber, and 5-7wt% of alumina cement. The ceramic fiber increases a buffer action of the refractory and the insulating effect by forming fine pores.

Description

HIGH INTENSITY CASTABLE REFRACTORIES WITH GOOD ADIABATIC AND HIGH THERMAL SHOCK RESISTANCE}

The present invention relates to a high-strength castable refractory having excellent thermal insulation and thermal shock resistance containing ceramic fibers filled between the gap between the shell and the refractory to increase the thermal insulation effect in various high temperature furnace equipment such as general heating furnaces, crosstalk cars and steelmaking ladles. will be.

In general, furnace equipment used at high temperatures has a lot of heat loss, so in order to reduce heat loss, it is blocked with heat by filling with a heat insulating brick or similar material between the shell and the interior refractories, and refractory material with a thin filling thickness and excellent heat insulation. Is required.

Japanese Patent Laid-Open Nos. Hei 6-279129 and Hei 9-142944 are mentioned as examples of the prior art disclosed regarding filling refractory materials.

Publication No. 6-279129 discloses a mortar used when a molten metal container is constructed using a high thermally expansible lead and is 10% by weight or more of powders of one or two or more kinds of carbonates and hydroxides such as magnesium and aluminum, and hydroxides. Regarding powdered refractory mortar, No. 9-142944 is a press-fitting repair material press-fitted into the gap between steel bar and internal refractories of an industrial furnace or between refractory materials, consisting of a mixture of powdered aggregate and aromatic hydrocarbon resin liquid. It relates to a crevice press-fitting material characterized in that the volume reduction rate is 2.0% or less and not thermally cured after holding at 24 ° C. for 24 hours.

However, although all of the fields of the present invention are refractory materials used for repairing molten metal containers and industrial furnaces that are used for long periods of time, these disclosed technologies have low strength and thermal insulation effect even though the strength to suppress expansion by refractory bricks should be strong. Because of their small size, their use has been severely limited, and their use is not well known.

The present invention was created in view of the above-mentioned problems of the prior art, and has been created to solve this problem, and after many years of research and experiments, based on the results, using ceramic fibers and organic fibers, It is an object of the present invention to overcome such problems by providing a castable refractory material having a high plastic strength with high plastic strength at high temperatures.

In order to achieve the above object, the present invention provides a castable refractory refractory composition containing ceramic fiber, in terms of weight% of an all-hot alumina: 40-64, calcined alumina: 5-12, silica ultrafine powder: 3-6, ceramic fiber: 20-30, organic fibers: 3-5, alumina cement: 5-7 is achieved by providing a high-strength castable refractory excellent in insulation and thermal shock resistance.

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

Alumina in the composition of the present invention is used as a main raw material and serves to increase the plastic strength by promoting the fire resistance and erosion resistance of the refractory used at high temperatures.

These raw materials include sintered alumina and fusing alumina (FUSED ALUMINA) according to the production method. In the present invention, fused alumina having low impurities and good sinterability was used.

When the amount of the molten alumina used is less than 40% by weight, the refractory degree of the refractory is low, which is unsuitable for use at high temperatures. When the amount of the molten alumina used is more than 64% by weight, the refractory degree is too high and the sinterability is not sufficient. % Is preferred.

Since calcined alumina is active as an ultra fine powder, it acts to improve the sinterability of the refractory and to increase the high temperature strength.

When the amount of the calcined alumina is 5 wt% or less, the amount of the calcined alumina is insufficient, and the sinterability is lowered. When the amount of the calcined alumina is 12 wt% or more, the shrinkage is severe due to oversintering, so the suitable amount of the calcined alumina is preferably 5-12 wt%.

The ultrafine silica powder increases the dispersibility of the refractory and has a sintering promoting effect at an intermediate temperature, that is, about 1000 ° C., thereby increasing the plastic strength at an intermediate temperature.

When the amount of the ultrafine silica is less than 3% by weight, the amount of the ultrafine powder is not only insufficient, so the dispersing effect of the refractory is not only small, but the sinterability is insufficient, so that the effect of enhancing the plastic strength is small. Due to excessive use of the furnace, the kneading property is lowered and the sintering promoting effect is too large, thus reducing the livestock property.

Therefore, the ultrafine silica powder is preferably added in the range of 3-6% by weight.

Ceramic fiber increases the buffering effect of the refractory and forms a micro-pores to increase the thermal insulation effect.

There are various kinds of ceramic fibers according to the components, but in the present invention, the alumina content is in the range of 30-60 wt% and the fiber length is 1-5 mm.

This is because the fiber length is too fine at 1 mm or less, which is not effective for increasing toughness, and when the fiber length is 5 mm or more, the fibers are entangled and do not loosen well, and kneading is difficult. It is because it is not suitable for use at high temperatures because it is low, and at 60% by weight or more, the alumina content is excessive, and the adhesion between the main material and the alumina surrounding the fiber is poor.

By the way, the ceramic fiber in the range of 30-60% by weight used in the present invention and the fiber length in the range of 1-5mm should be limited to 20-30% by weight, which is less than 20% by weight of the ceramic fiber This is because the amount of fibers is small and the animal properties are small and the toughness-promoting effect is inadequate, and when the amount of use is more than 30% by weight, the animal properties are good, but the amount of fibers is large, and the fibers are not entangled with each other and are not suitable for forming micropores.

Therefore, the ceramic fiber added in the present invention is most preferably about 20-30% by weight.

Organic fibers (vinyl fiber) is added in the refractory is lost at a temperature above 500 ℃ to form a micro-pores to play a role to increase the thermal insulation.

It is preferable that the length of the organic fiber is 1-3mm, which is too fine when the length of the organic fiber is less than 1mm, so that it is less effective in forming micropores. This is because the pore diameter generated later is not suitable to obtain a uniform refractory structure.

In addition, when the amount of the organic fibers added is less than 3% by weight, the amount of use thereof is insufficient, so that the pore-forming effect is small, and in the case of 5% by weight or more, it is preferable to add about 3-5% by weight because the formed pore area is excessive and the strength is lowered.

Alumina cement plays a role of increasing the plastic strength at room temperature strength and 1200 ℃ or more of the refractory.

When the amount of the alumina cement is less than 5% by weight, the amount is insufficient to enhance the strength, and when the amount is more than 7% by weight, the amount is excessive, the curing speed is too high and the strength is not suitable for use.

Therefore, a suitable amount of alumina cement is 5-7% by weight.

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

EXAMPLE

In order to manufacture a castable refractory having a composition ratio as shown in Table 1 below, the powder raw material is first mixed with water in a universal mixer for castable refractory kneading, and then kneaded in advance to uniformly add ceramic fibers and organic fibers little by little. It was kneaded.

The sample prepared in this way was molded into a size of 40 × 40 × 160 mm, and then the specimen was calcined at 1200 ° C. for 3 hours, and then the linear change rate, bending strength, specific gravity, and porosity were measured, and the results were shown.

Evaluation of workability was determined by spreading the raw material after 15 blows to the kneaded specimen using a flow meter (flow meter).

The thermal shock resistance is applied to a 50 × 50mm specimen prepared in an electric furnace heated to 1300 ℃, taken out again after 30 minutes, cooled in air, and then again cracked in the specimen during 20 times of heating and cooling. The appearance state such as edge dropping was observed.

As shown in Table 1, Inventive Example (1-5), which satisfies the scope of the present invention, has a relatively small line change rate, a large plastic strength, and a specific gravity, which is relatively low as compared with Comparative Examples (1-4) and conventional materials. This excellence could be confirmed.

As described in detail above, the ceramic fiber-containing castable refractory according to the present invention has excellent thermal insulation resistance and thermal shock resistance and has high temperature strength, thereby increasing thermal insulation effect between the shell and the refractory in a high-temperature furnace, thereby reducing heat loss. .

Claims (1)

In weight percent, Electrolytic alumina: 40-64, Calcined alumina: 5-12, Ultrafine silica: 3-6, Ceramic fiber: 20-30, Organic fiber: 3-5, Alumina Cement: 5-7 High strength castable refractory with excellent thermal insulation and thermal shock resistance.