JPH07106949B2 - Irregular refractories - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement-free amorphous refractory suitable for use in iron and steel, cupola and induction furnace in the field of casting.

[0002]

2. Description of the Related Art Conventionally, as an irregular refractory, for example, a castable refractory, an alumina-silica based aggregate in which alumina cement is mixed as a binder has been generally used. However, when the content of alumina cement is high (more than 5% by weight), anorthite (CaO.Al2 O3 .2SiO2) is formed by the use of calcia (CaO), which is the main component of cement, when using molded refractories.
) And other low melting point compounds are produced in a considerable amount,
There is a problem that the hot strength at a high temperature is significantly reduced. In addition, since the amount of water added during construction is large, the compactness of the structure of the molded refractory is not sufficient and the strength against physical and chemical erosion is poor.

On the other hand, a so-called cementless castable refractory having a reduced amount of alumina cement has been provided in recent years. This product contains 4% by weight or less of alumina cement and, in order to improve the fluidity at the time of construction and to obtain the denseness of the structure, ultrafine silica (Si
O2) is added.

However, even such cementless castable refractories are still inferior in hot strength at high temperature due to the formation of anolsite by alumina cement, and they are used especially for cupola and induction furnaces in the field of steel and castings. in the case that, with the contact between the molten slag and the molten metal, silica content tends primarily by reaction with iron (Fe) to produce low-melting compounds undergoing erosion, as is very poor corrosion resistance Was becoming.

[0005]

Therefore, in recent years, a so-called non-cementable castable refractory has been considered which does not contain cement component at all and which contains ultrafine silica component as much as possible. In this product, hydraulic alumina is used as a hardening agent and a flocculant in place of alumina cement to obtain sufficient hot strength at high temperature and a small amount of ultrafine powder such as carbon (C). By adding, it is intended to improve the corrosion resistance.

However, in such a non-cement castable refractory, since the silica component is reduced and carbon is added, the fluidity is extremely deteriorated and the construction becomes difficult. In order to solve this fluidity problem, it is conceivable to add ultrafine powder of silicon carbide (SiC), but in this case, the ultrafine powder of silicon carbide is oxidized to generate silica. It was not adopted because it was expected to cause problems.

As described above, hitherto, no non-cement castable refractories capable of sufficiently improving hot strength, corrosion resistance and fluidity have not been obtained.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a sufficient hot strength at a high temperature of a molded refractory and to prevent chemical corrosion by molten metal or molten slag. (EN) It is intended to provide an amorphous refractory material which can enhance corrosion resistance and can obtain sufficient fluidity during construction.

[0009]

The amorphous refractory material of the present invention comprises, as a whole, 64-78% by weight of alumina and 1% of silica.
% By weight, 20 to 30% by weight of silicon carbide and 2 to 5% by weight of carbon, and a dispersant of 0.0
1 to 0.2 wt% is added, and the particle size in fine powder is 10μ
The following ultrafine powder portion is 2 to 20% by weight of the whole, and the ultrafine powder portion is 1% by weight or less of silica, 1 to 2% by weight of silicon carbide, 1 to 5% by weight of carbon, and 2% of hydraulic alumina. ~ 7
It is characterized in that it is composed of at least one component selected from alumina, chromia, titania, and zirconia, in addition to the component composition by weight.

[0010]

The present inventors have conducted various experiments and researches, and as a result, in the so-called cementless amorphous refractory composed of aggregates, intermediate particles and fine powders, By configuring the addition amount, the ratio of the ultrafine powder part to the whole, and the composition of the ultrafine powder part containing hydraulic alumina as a binder as described above, all of the hot strength, corrosion resistance and fluidity are sufficient. Therefore, they have completed the present invention by finding that they can be improved.

Particularly, regarding silicon carbide and carbon in the ultrafine powder portion, an appropriate amount has not been clarified in the past, but in the present invention, the corrosion resistance of the molded refractory material and the fluidity at the time of construction are determined. The composition can be configured so as to obtain an appropriate balance between the components, and as a result, the composition of the component can be such that no inconvenience occurs even if the content of silica is 1% by weight or less.

That is, first, the hydraulic alumina in the ultrafine powder portion functions as a binder, thereby making it cementless. This hydraulic alumina requires 2% by weight or more in order to enhance the hardenability at the time of construction, and the content of 7% by weight or less ensures good fluidity at the time of construction.

Corrosion resistance can be sufficiently improved by making the overall composition of the aggregate, the intermediate particles and the fine powder mainly composed of alumina, silicon carbide and carbon. In particular, when the silica component that reacts with iron or the like to form a low melting point compound is set to 1% by weight or less, the above-mentioned cementless formation and extremely high hot strength and corrosion resistance are achieved. In this case, it is desirable to use bauxite, chamotte, high-purity alumina, zircon, chromia, silicon carbide or the like as the material of the aggregate and the intermediate particles.

By containing 2 to 20% by weight of the ultrafine powder portion having a particle size of 10 μ or less in the fine powder, the gaps between the aggregates and the intermediate grains can be almost completely filled, and the structure is dense. It is possible to obtain an excellent molded refractory. Here, if the ultrafine powder portion is 2% by weight or more, the effect of sufficient structure densification is not exhibited if the amount is less than that, and if it is 20% by weight or more, the fluidity at the time of construction is increased. Because it gets worse.

Further, since the ultrafine powder portion contains silicon carbide and carbon, it is further excellent in corrosion resistance as a whole. In this case, since the ultrafine powder of silicon carbide easily oxidizes, 2% by weight is added in order to prevent the oxidation as much as possible.
It is necessary to do the following. Similarly, from the viewpoint of preventing oxidation and achieving good corrosion resistance, it is desirable that the particle size be 1 μm or more. On the other hand, it is desirable that the carbon contains 80% by weight or more of fixed carbon that does not volatilize and ash-differentiate even in a high temperature oxidizing atmosphere.

Here, it is conceivable that the ultrafine powder portion contains a small amount of silica component of 1% by weight or less and contains carbon, which deteriorates the fluidity during construction. In addition, the superfine powder of silicon carbide is contained by 1% by weight or more to cover it, and the dispersant also improves the overall fluidity.

As the dispersant, it is desirable to use a metal chelate compound or an alkali metal carbonate. When the dispersant is added in an amount of 0.01% by weight or more, the dispersion of each composition component is promoted, the workability such as fluidity and curability at the time of construction is improved, and the content is 0.2% by weight or less. The reason is that if it is added in an amount exceeding this range, excessive dispersibility will be exhibited and the curability will deteriorate.

The amount of added water at the time of construction is 4.
It is desirable to set it to 0 to 7.0% by weight. This is to balance the fluidity and the curability at the time of construction to improve the workability.

[0019]

EXAMPLES Examples of the present invention will be described below. First,
Example 2 is an amorphous refractory having a composition of ingredients as claimed. The second embodiment is composed of aggregates, intermediate particles, and fine powder containing ultrafine powder, and does not contain cement. 65% by weight of alumina (Al2 O3) and silica (SiO2)
Of 1% by weight, silicon carbide (SiC) of 27% by weight and carbon (C) of 3% by weight, and a predetermined amount (0.05% by weight) of a dispersant consisting of carboxylate soda salt was added. There is.

The ultrafine powder portion having a particle size of 10 μm or less in the fine powder is made up to 15% by weight with respect to the whole, and its component composition is, as shown in Table 2 below, 2% by weight of silicon carbide, Carbon is 3% by weight, silica is 1% by weight, and hydraulic alumina as a binder is 4% by weight.

Water was added to the above component composition in an amount of 6.2% by weight, and the characteristics of molded refractories were shown in the following Table 1 in comparison with conventional products and reference examples. Here, the conventional example is a cementless product described in the section of the prior art, which contains 3% by weight of an alumina cement component and 2% by weight of ultrafine silica (SiO2). The silicon carbide (SiC) component contained in 15% by weight is an aggregate and an intermediate grain, not an ultrafine powder, but a carbon (C)
It does not include at all. The reference example is a so-called non-cement product, in which hydraulic alumina is used instead of alumina cement, and 1% by weight of ultrafine carbon (C) powder is added. The silicon component is not ultrafine.

[0022]

[Table 1] As is clear from Table 1, according to the amorphous refractory material of Example 2, the hot strength was significantly improved as compared with the conventional example, and good hot strength was obtained as compared with the reference example. To be It is considered that this is because the production of the low melting point compound was suppressed by eliminating the cement component and reducing the silica component.

Further, in Example 2, even though the silica component was as small as 1% by weight or less and the carbon content was 3% by weight in the ultrafine powder portion, good fluidity at the time of construction was obtained and workability was improved. Was excellent. This is because 2% by weight of silicon carbide was added to the ultrafine powder portion, as will be described later.

Further, the state of the cut surface of the above-mentioned three types of molded refractories as a result of the corrosion resistance test (crucible test) is shown in the figure. FIG. 1 is a diagram of an example product (example 2), FIG . 2 is a diagram of a conventional product (conventional example), and FIG .
FIG. 4 is a diagram of another conventional product (reference example). The test condition was 1550 ° C. for 24 hours, and the slag amount was 35 g.
I am trying.

As a result, the height of the remaining molten slag was 16 mm in this example product and 1 mm in the other conventional product (reference example), and no molten slag remained in the conventional product. As is clear from the figure, according to the second embodiment, it is difficult to be corroded by the slag and extremely good corrosion resistance can be obtained.

Next, the suitability of the component composition of the ultrafine powder portion will be illustrated by several examples including the above-mentioned example 2. Examples 1 to 8 are amorphous refractories having the composition of components as set forth in the claims, and are composed of aggregates and intermediate grains, and fine powder containing ultrafine powder, and no cement. It is said that. The total composition of these components is such that alumina (Al2 O3) is 64-78% by weight,
Silica (SiO2) is less than 1% by weight, silicon carbide (Si
C) is adjusted to 20 to 30% by weight and carbon (C) is adjusted to 2 to 5% by weight, and further, a predetermined amount of a dispersion material composed of carboxylate soda salt is added.

The ultrafine powder portion having a particle size of 10 μm or less in the fine powder is 15% by weight with respect to the whole, and the component composition thereof is as shown in Table 2. In this case, silicon carbide is adjusted to 1 or 2% by weight, carbon is 2 to 5% by weight, silica is 0 to 1% by weight, and hydraulic alumina as a binder is adjusted to 4 or 7% by weight.
1 of alumina, chromia, titania and zirconia
It contains 2 to 6% by weight of one or more components.

On the other hand, in Comparative Examples 1 to 14,
The composition of the ultrafine powder or the amount of the dispersant is an irregular refractory material which deviates from the scope of claims. That is, Comparative Example 1
In Comparative Example 2, the amount of the dispersant added was set, in Comparative Examples 3 to 5, the amount of hydraulic alumina component was set, and in Comparative Example 6 and Comparative Example 7.
Is the amount of the carbon component, Comparative Examples 8 to 11 are the amounts of the silicon carbide component, Comparative Examples 12 and 13 are the amounts of the silica component, and Comparative Example 14 is the composition for the entire ultrafine powder portion. It is prepared to deviate from the scope of claims.

Now, with respect to these Examples 1 to 8 and Comparative Examples 1 to 14, construction was carried out by adding an appropriate amount (4 to 7% by weight) of water to obtain workability (fluidity and curability). ) And corrosion resistance were tested. The test results are shown in Table 2 below. In the column of evaluation in the table, particularly good ones are indicated by ⊚, good ones by ∘, ordinary ones by Δ, bad ones by x, and non-evaluable ones by −.

[0030]

[Table 2] As is clear from Table 2, the powder refractories of Examples 1 to 8 all showed excellent test results in terms of workability and corrosion resistance.

On the other hand, in Comparative Examples 1 and 2 in which the dispersant was not added or was excessive, the dispersion of each composition component was insufficient and the fluidity was deteriorated, or the excessive dispersibility was exerted to cure. It takes a long time, which causes deterioration of workability. Further, in Comparative Examples 3 to 5 in which the hydraulic alumina that functions as a binder is excessive or excessive,
The fluidity or the curability is lowered, and the workability is deteriorated.

In Comparative Example 6 in which the carbon component was excessive, the fluidity was also extremely deteriorated, and in Comparative Example 7 in which carbon was not added, the corrosion resistance was poor. Further, in Comparative Examples 8 and 9 in which the silicon carbide component was excessive, the fluidity was good, but the corrosion resistance was poor. this is,
It is considered that this is because the ultrafine powder of silicon carbide is oxidized to generate silica. Comparative Example 1 in which ultrafine silicon carbide is 0
At 0 and 11, the fluidity was normal or deteriorated, and the corrosion resistance was poor. Further, in Comparative Examples 12 and 13 in which the silica component was excessive, the workability (fluidity) was good, but the corrosion resistance was poor. Then, Comparative Example 14 in which the ultrafine powder portion exceeds 20% by weight of the whole.
Then, the fluidity during construction deteriorated.

As described above, according to the present embodiment, sufficient hot strength at a high temperature of the molded refractory material can be obtained, and the corrosion resistance to chemical corrosion by molten metal or molten slag can be enhanced, and It was possible to obtain a very useful powder refractory that could not be obtained in the past, that is, sufficient workability could be obtained.

[0034]

As is clear from the above description, according to the amorphous refractory of the present invention, the cement component is eliminated and the silica component is reduced, so that the molded refractory has sufficient heat at high temperature. It is possible to obtain inter-strength strength, and further improve the corrosion resistance against chemical erosion by molten metal or molten slag by appropriately adjusting the component composition of ultrafine powder such as carbon or silicon carbide, and at the time of construction It has an excellent effect that fluidity can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing a cut surface of a crucible after a corrosion resistance test of a molded product of an irregular shaped refractory according to an embodiment of the present invention .

FIG. 2 is a view corresponding to FIG . 1 of a conventional product .

FIG. 3 is a view corresponding to FIG . 1 of another conventional product .

Claims (1)

[Claims] 1. A non-cemented refractory composed of aggregate, intermediate particles and fine powder, which contains 64-78% by weight of alumina, 1% by weight or less of silica, and 20% by weight of silicon carbide. .About.30 wt%, carbon 2 to 5 wt%, and the dispersant is 0.01 to 0.
2 wt% is added, and further, the ultrafine powder portion having a particle size of 10 μ or less in the fine powder is 2 to 20% by weight of the whole, and the ultrafine powder portion contains 1 wt% or less of silica and 1 to 1% of silicon carbide. 2% by weight, 1 to 5% by weight of carbon, 2 to 2% of hydraulic alumina.
An amorphous refractory material characterized by comprising at least one component selected from alumina, chromia, titania, and zirconia in addition to the composition of 7% by weight.