JPS5811388B2 - Amorphous fireproof composition for pouring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to minimize the adverse effects of castable refractory compositions, specifically alumina cement mixed as a binder, and which has high density and strength, and is resistant to steam explosion. This invention relates to a monolithic fire-resistant composition for pouring that has excellent workability and ease of construction.

Alumina cement-based refractories develop strength through hydration of alumina cement, but this hydrate has a
Since the strength reaches its lowest point during the heating and dehydration process at 00 to 1000° C. and causes structural deterioration, for example, a frit may be added to easily form a sintering or glass phase in such a temperature range.

However, this had the disadvantage that high heat resistance was significantly impaired.

In addition, CaO in alumina cement, whose main mineral is calcium aluminate, easily forms anorthite (CaO-A12O3-2SiO2) and gehlenite (
2CaO-A12O3.5iO2) is produced, so it is not desirable to use a large amount of alumina cement because it impairs the high heat resistance of the refractory.

Nevertheless, in order to ensure the strength of the cured product itself, it has been considered unavoidable to add 10% or more of it to the fire-resistant aggregate.

On the other hand, the denser the structure of the hardened material, the more difficult it is for the contained moisture to turn into water vapor and escape to the outside through the pores of the hardened material, resulting in a higher water vapor pressure. When the temperature was exceeded, the phenomenon of peeling together with an explosion sound often occurred.

Conventionally, metal aluminum or fibers were added to loosen the structure.
Efforts have been made to make it easier for water vapor to escape, but it has been difficult to obtain a dense structure using such means.

An object of the present invention is to provide a castable monolithic refractory composition that can eliminate the above-mentioned drawbacks.

The present invention consists of two inventions. The first invention is a fire-resistant material comprising 5% by weight or less of alumina cement, 2 to 10% by weight of ultrafine silica powder, and the remainder being refractory aggregate whose particle size has been adjusted. To the clay, 0.05 to 0.5% by weight of a phosphate compound and 0.05 to 1.0% by weight of a lithium salt were added, and the ratio of the silica-based ultrafine powder to alumina cement was 1. Or, it is an amorphous fireproof composition for pouring, characterized in that it is more dog-like than 1.

The refractory aggregate used in the present invention may be appropriately selected depending on the purpose of use, regardless of its basicity or acidity, as long as the particle size has been adjusted to enable close packing.

Conventionally used alumina cement is also sufficient.

As mentioned above, the amount of alumina cement added is preferably as small as possible.

The reason why the amount of alumina cement added in the present invention is 5% by weight or less is because if it exceeds 5% by weight, strength will deteriorate near 1000°C or heat resistance and corrosion resistance will be impaired, making it impossible to obtain the effects of the present invention. It is.

In order to develop strength at room temperature, the content is preferably 2% by weight or more.

Next, let's talk about silica-based ultrafine powder. When used in combination with other additives described below, it can significantly increase fluidity and therefore reduce the amount of added water, making it extremely effective for obtaining high-density cured products. .

The particle size of the ultrafine powder is preferably 5μ or less; if the particle size becomes large, it is impossible to pour it with the small amount of moisture mentioned above, and as a result, a higher amount of moisture than before is required. You must be careful because you will not be able to obtain high-density products.

Silica-based ultrafine powders can be obtained in natural products containing 50% or more of real silica by conventional techniques, or in artificial amounts, such as silica ultrafine powder, technical Kibushi clay ultrafine powder, vaporizable silica, silica flour, etc. One kind or a combination of two or more kinds can be used.

The reason why the amount of silica-based ultrafine powder added in the present invention is specified as 2 to 10% by weight is that if the amount added is less than 2% by weight, the above-mentioned effect of significantly increasing fluidity will not be achieved. This is because if it exceeds this, heat resistance will deteriorate.

In the present invention, the ratio of silica-based ultrafine powder to alumina cement is specified to be 1 or more than 1, but if this ratio is less than 1, the curing speed is too fast, and this tendency is particularly This is because the higher the value, the more noticeable it becomes, and this impedes workability.

Next, I will explain about the phosphate compound.It has a synergistic effect with the silica-based ultrafine powder mentioned above and the lithium salt mentioned below, which improves the fluidity of the composition even at low moisture levels, and improves the bonding strength of the cured product. It plays a role in making this happen.

Since this phosphate compound is a low melting point substance, it goes without saying that heat resistance deteriorates when used in large amounts, but it also has the property of deteriorating workability and fluidity when used in large amounts or in small amounts.

The reason why the amount of the phosphate compound added in the present invention is set to 0.05 to 0.5% by weight based on the fire-resistant clay is as follows.

That is, if the amount of the phosphate compound added is less than 0.05% by weight, there is no improvement in the bonding strength of the cured product, the workability is poor, and a large amount of water is required, which is not preferable.

If the amount exceeds 0.5% by weight, the bonding strength can be improved, but the workability deteriorates, and as a result, a large amount of water is required, making it impossible to obtain a high-density product, and the heat resistance also deteriorates.

This is because only when the amount added is in the range of 0.05 to 0.5% by weight, fluidity, strength, and heat resistance can be satisfied.

There are various phosphate compounds represented by the general formula xM2O・yP2O5 depending on x/y or M, but those that are easily soluble in water include sodium hexametaphosphate, sodium pyrophosphate, sodium tetrapolyphosphate, and sodium tripolyphosphate. , soluble phosphate glass, etc. are suitable.

In the present invention, a lithium salt is further added to the above-mentioned mixture.

Addition of lithium salt can be expected to increase the strength of the cured product.

The details of the mechanism by which lithium salt increases the strength of the cured product are unknown, but experiments have shown that addition of lithium salt alone does not produce any significant effect.

If the amount of lithium salt added is less than 0.05% by weight, no improvement in strength will be observed, and if it exceeds 1.0% by weight, heat resistance will be impaired, so it should be in the range of 0.05 to 1.0% by weight. be.

As the lithium salt, lithium carbonate, lithium borate, lithium fluoride, etc. can be used.

The first invention described above reduces the amount of alumina cement to 5
By setting the content to less than 1% by weight, the high heat resistance and corrosion resistance of the obtained refractory are not impaired, and the synergistic effect of the ultrafine silica powder, phosphate compound, and lithium salt increases the strength of the cured product itself. It is extremely superior in that it can ensure a high density product and can reduce the amount of added water due to the remarkable improvement in fluidity.

The second invention is an invention in which all of the essential features of the first invention are the main parts of the composition, and the composition of the first invention includes: Furthermore, a phenol resin is added in a range of 0.1 to 1.0% by weight.

The phenol resin can be either a resol type or a novolac type, but a powdered one is preferable.

If the amount of phenol resin used is less than 0.1% by weight, the desired effect cannot be expected.

Moreover, if it exceeds 1.0% by weight, the porosity increases and hot strength is inhibited.

The second invention has high density and high strength without impairing workability, and because of the relationship between the softening and decomposition of phenolic resin and steam pressure, the detailed reason is unknown, but it is effective in preventing steam explosions. It can exhibit excellent properties.

Examples are shown below.

Example 1 Table 1 shows the blending ratio and test results.

Each test specimen was poured into a shape of 40 x 40 x 160 mm,
After curing for 24 hours, the frames were removed and heat treated at various temperatures.

Comparing products A and B of the present invention with conventional product F, it is found that although the amount of added water is approximately 10% less, the flow value, which is a guide for workability, is not significantly different, and the porosity is small, and the product is high density and high strength. It is understood that this can be obtained.

In addition, the test results for comparative quantities show that in comparative quantity C, where the ratio of silica flour to alumina cement is less than 1, the flow value after 30 minutes is 100, that is, there is no flow, and there is a problem in workability. It can be seen that the strength after drying is extremely low in the comparative weighing without it, and the hot strength is extremely low in the comparative amount E, which contains a large amount of silica flour and alumina cement, which is unfavorable from the standpoint of heat resistance and corrosion resistance.

Example 2 A test was conducted according to Example 1 using the blending ratios shown in Table 2, and the results shown in the table below were obtained.

Although the amount of added water in the product G of the present invention is reduced by about 10% compared to the conventional product K, the flow value is not significantly different;
As in the case of , it can be seen that the porosity is small, and it is a high-density and high-strength product.

On the other hand, from the comparative amounts H1■ and J, it can be seen that even if any one of the technical Kibushi clay, sodium pyrophosphate, and lithium borate is missing, a high-density and high-strength product cannot be obtained.

Example 3 Tests were conducted according to Example 1 using the blending ratios shown in Table 3, and the results shown in the table below were obtained.

From the table above, it can be seen that the products of the present invention, M and N, are dense and have a large improvement in strength, and that as the amount of alumina cement increases, the hot strength decreases.

Example 4 In addition to testing in accordance with Example 1 using the blending ratios shown in Table 4, an explosion test was also conducted.

For the explosion test, it was poured into a 200 x 230 x 130 mm shape using a vibrator, and after one day of curing, it was removed from the frame, and then set in an explosion furnace so that the 200 x 230 mm surface became the heating surface. 8 at surface temperature using heavy oil burner
1000 while adjusting the speed to 00℃/hr.
The temperature was raised to ℃.

None of the products Q, R, and S of the present invention to which 0.1 to 1.0% by weight of phenolic resin powder was added caused steam explosion.

On the other hand, when the comparative amount U was less than 0.1% by weight, it exploded after 40 minutes, and when the comparative amount T was more than 1.0% by weight, it did not explode, but the strength decreased and the porosity increased, which is undesirable. All I got was results.

Claims (1)

[Claims] 0.05 to 0.05 to 0.05 to 0.05 to 0.05 to 0.05 to 0.05 to 0.05 to 0.05 to 0.5% by weight of a phosphate compound and 0.05 to 1.0% by weight of a lithium salt are added, and the ratio of the silica-based ultrafine powder to alumina cement is 1 or less than 1. A monolithic refractory composition for pouring. 0.05 to 0.5% by weight of a refractory clay consisting of 25% by weight or less of alumina cement, 2 to 10% by weight of ultrafine silica powder, and the remainder being refractory aggregate with adjusted particle size. In addition to adding a phosphate compound and 0.05 to 1.0% by weight of lithium salt, the ratio of the silica-based ultrafine powder to alumina cement is 1 or greater than 1, and further 0.1 to 1.0% by weight.
A monolithic fireproof composition for pouring, characterized in that 0% by weight of phenolic resin is added.