KR960004393B1 - Castable composition - Google Patents

Abstract

The high-strength refractory and thermal insulating castable is composed of 50-70 wt% lightweight aggregate such as porous alumina, a mixture of porous alumina and perlite, which has the particle size of 1-3mm, 5-15 wt% refractory clay, 7-20 wt% fine spinel powder having the particle size of less than 40 micrometer, 2-7 wt% ultrafine silica powder having the particle size of less than 10 micrometer, 5-15 wt% alumina cement as a binder and 2-5 wt% sodium hexametaphosphate such as sodium pyrophosphate.

Description

High Strength Fire Resistant Castable Composition

The present invention relates to a high-strength refractory insulating castable composition for use in interiors of various heating furnaces, powder transport pipes, etc., which have high wear and tear at high temperatures and temperatures.

Recently, irregular refractory materials such as refractory insulating cascades have been used for various energy in urinary tracts.

Refractory insulation castable mainly used chamotte, bentonite, etc. as aggregate to make the structure of the refractory porous in consideration of thermal insulation. Recently, some porous alumina is used and alumina cement and clay are mainly used as binders. .

In addition, metal A1 powder, sawdust, organic materials, etc. may be added or foamed or lost during use to artificially form pores, which may be uniformly dispersed throughout the refractory structure to reduce the weight. In recent years, Japanese Patent Laid-Open No. 61-77675 As in the case of the arc, ceramics may be added to increase the insulation effect.

As a method for improving the strength in fire-resistant insulation castables mainly composed of lightweight aggregates, fine powders of silicate-based, alumina- or alumina-silica-based fire-resistant raw materials are added as in JP-A-74-2098920. To densify the refractory structure.

However, in the case of the above method, the strength is increased to some extent, but the heat insulation is remarkably lowered, the fire resistance is lowered due to the formation of a low melting portion at the joining portion, and the structure is too densely susceptible to door cracks, and the spalling resistance is lowered. There is this.

Accordingly, the present inventors have conducted research and experiments to improve the problems of the conventional method described above, and based on the results, the present invention proposes the present invention. To provide a composition, the purpose is.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention is a weight percent, lightweight aggregate; 50-70%, spinal powder: 7-20%, refractory clay: 5-15%, ultrafine silica: 2-7%, alumina cement: 5-15%, and hexametaphosphate: 2-5% It relates to a high strength fire resistant insulating castable composition to be formed.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The lightweight aggregate is preferably a porous alumina or a mixture of porous alumina and pearlite, and when the content is 50% or less, the heat insulating property is low, and thus the raw material itself is low in specific gravity. Because the volume is too large, the amount of addition is not kneaded properly, and the sintering property is also poor, so that the structure of the refractory becomes weak even after firing, so that it is difficult to maintain the strength. Therefore, the content of the light aggregate is preferably limited to 50-70%. .

The particle size of the lightweight aggregate is preferably 1-3mm, because when the particle size is less than 1mm, the mixture is agglomerated because the binding material is fine particles in a powder state, and the mixture is not sufficiently mixed. This is because the required strength does not come out.

The spinal is a high refractory raw material and is a component added due to its high melting point (2135 ° C.), volume stability against atmospheric changes, and excellent spalling resistance. It is hardly effective in improving strength, and in case of more than 20%, the strength of the refractory joints is increased, and the plastic strength and hot strength are significantly increased. However, as the production of low-rate materials is significantly reduced compared to that of silicate-based or alumina-based raw materials, Although there is little deterioration, since thermal sputtering property falls and heat insulating property which is a main characteristic of a heat insulating castable falls, it is preferable to limit the addition amount of the said spinal to 7-20%.

There are various kinds according to the spinal, alumina and magnesia component ratios, and the characteristics thereof are also various. In the present invention, the effect of the present invention can be exhibited by using any of them, and the particle size is preferably 40 mu m or less.

The spinal may have a zirconia or chrome light as the same.

The addition amount of the refractory clay is preferably limited to 5-15%, because when the addition amount is 5% or less, the bonding strength is lowered and the strength after drying and at a high temperature is low, and when it is 15% or more, at room temperature and high temperature This is because the strength is high but shrinkage is severe and there are many cracks.

In addition, when the addition amount of the ultrafine silica powder is 2% or less, there is no effect on the development of dry strength, and when the ultrafine silica powder is 7% or more, a low melt is formed and the thermal insulation and spalling resistance due to over sintering are reduced. The amount of added is preferably limited to 2-7%.

Moreover, 5 micrometers or less are preferable for the particle size of the said ultrafine silica powder, since workability and sintering property fall remarkably at 5 micrometers or more.

The alumina cement is a component to be added as a binder when the addition amount is 5% or less, the effect of castable strength is not effective and poor workability, when the alumina cement is more than 15%, the room temperature strength is good, but at 1,000 ℃ by evaporation of crystal water It is preferable to limit the amount of the alumina cement added to 5-15% because the strength of the alumina cement is low and the low temperature melt is generated due to excessive CaO component contained in the cement even at a high temperature and the high temperature strength is also reduced.

The hexametaphosphate is preferably a diacid salt such as sodium pyrophosphate, sodium tripolyphosphate, and the like. When the amount of the hexametaphosphate is 2% or less, the strength enhancing effect is small. Since a low melt is formed to lower the fire resistance and high temperature strength, it is preferable to limit the amount of the hexametaphosphate added to 2-5%.

The refractory insulating castable of the present invention, which is prepared as described above, has a high fire-resistant raw material spinal powder and sinterability at the joining portion of a lightweight castable using porous alumina and pearlite as a main raw material to improve high temperature strength while maintaining heat insulation. The addition of this fine ultrafine silica powder results in a high melting point, dense and firm structure resulting in increased high temperature strength and improved spalling resistance.

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

EXAMPLE

After mixing and curing the amorphous refractory composition having a composition ratio as shown in Table 1 below, molding and curing to a size of 40 × 40 × 160mm, linear change rate at room temperature and 1500 ℃, plastic strength (bending strength), thermal conductivity and spalling resistance The sex was measured and the results are shown in Table 2 below.

In Table 2, the spalling resistance is the result of observing the appearance state of the specimen by repeatedly performing 3-8 times of air cooling after maintaining at 1400 ° C. for 30 minutes using an electric furnace, and thermal conductivity using bottle-shaped lead and specimen. It is the value obtained by testing at 300 degreeC and 900 degreeC.

As shown in Table 1 and Table 2, in the case of Inventive Example (1-4) according to the present invention, it can be seen that the plastic strength and the hot strength are excellent while having the same thermal conductivity as the conventional example.

Comparative Example 1 is a composition in which the amount of porous alumina clinker is greater than the range of the present invention, the porous alumina itself is light and the amount of use is high, so that the kneading is not proper, the uniform structure is not good, and the structure of the refractory is fragile due to poor sintering.

In Comparative Example 2, the amount of porous alumina used was less than that of the present invention, and the heat insulating property was very low.

In Comparative Example 3, as the composition of spinal fine powder is larger than the range of the present invention, the fine powder content is too high, so close packing is difficult and the sintering property is poor, and thus cracks tend to occur due to a decrease in bonding strength between aggregates.

In Comparative Example 4, the fine amount of spinal is less than the range of the present invention, and the bonding portion is not dense, and thus the strength expression is not sufficient.

In Comparative Example 5, the amount of refractory clay used is higher than the range of the present invention, but the strength at room temperature and high temperature is high, but the shrinkage is severe and cracks are generated.

In Comparative Example 6, the amount of refractory clay used is less than that of the present invention, and the drying and high temperature strength are low, and the coking force is lowered, so that the construction is not good.

In Comparative Example 7, the workability was good due to the excessive amount of ultrafine silica, but the shrinkage during drying was high, and there were many cracks caused by over-sintering at high temperatures, and the plastic strength was high, but the hot strength was lowered due to the formation of low melt in the hot.

Comparative Example 8 does not use the ultrafine silica powder, the strength could not be expressed.

In Comparative Example 9, the amount of alumina cement used was high, and the room temperature strength was high, but the high temperature strength was low due to the reaction with CaO contained in the alumina cement in a large amount.

In Comparative Example 10, the amount of hexametaphosphate used was excessive, which did not adversely affect the plastic strength, but the hot strength was lowered because hot melt produced low melt.

As described above, the present invention has a high fire resistance and excellent heat resistance and plastic strength compared to the fire resistant material using the conventional porous alumina clinker as the main aggregate and only clay and alumina cement as binders, and thus require heat insulation and high temperature strength in the heat. There is an effect that can provide a high-strength refractory heat insulating castable composition that can be effectively used for the interior of the furnace hearth and powder transport pipe.

Claims (3)

By weight, lightweight aggregate: 50-70%, spinal fine powder: 7-20%, refractory clay: 5-15%, ultrafine silica: 2-7%, alumina cement: 5-15%, and hexametaphosphate Soda: high-strength fire-resistant insulating castable composition, characterized in that the composition is 2-5%. The high-strength fire-resistant insulating castable composition according to claim 1, wherein the particle size of the light aggregate is 1-3 mm, the particle size of spinal fine powder is 40 µm or less, and the particle size of the ultrafine silica powder is 5 µm or less. The high-strength refractory insulating castable composition according to claim 1 or 2, wherein the lightweight aggregate is porous alumina or a mixture of porous alumina and pearlite.