JP3046119B2 - Lightweight magnesia coating material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory coating material, and more particularly to a lightweight magnesia coating material used as a coating material for a molten steel container or the like.

[0002]

2. Description of the Related Art Magnesia coating materials include, for example,
It is used as a coating material to be coated on a wall refractory of a molten steel container in order to suppress inclusion of inclusions in steel in the molten steel container and to facilitate residual steel treatment. However, since the conventional magnesia coating material has a large bulk specific gravity, the amount used in one coating is large, and the basic unit for producing steel accounts for about 50% of the basic unit for refractory used for continuous casting. I have.

[0003] In order to reduce the unit consumption, the weight of the coating material is reduced. As a method, a surfactant is added and the magnesia coating material is foamed to increase the volume and to increase the bulk specific gravity. A method of reducing the size is used.

[0004]

However, in the above-mentioned conventional method, the surfactant added to the magnesia coating material is expensive, and is susceptible to water properties such as hardness. However, there is a problem that the intended effect cannot be obtained without foaming.

An object of the present invention is to solve the problems of the conventional magnesia coating material and to provide a lightweight magnesia coating material which is economical and is not affected by conditions such as water properties. .

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventors have utilized carbon dioxide gas generated when an acidic substance such as an acid or an acidic salt is added to a carbonate compound (carbonate). We thought that we could reduce the bulk specific gravity (reduce the weight), and as a result of various experiments, by adding an acidic substance to a refractory material containing a carbonate compound, adding water at the time of use, and kneading it. The present inventors have found that bubbles can be included in a refractory material (magnesia coating material) to reduce the weight in the same manner as when a surfactant is used, and the present invention has been completed.

That is, the light-weight magnesia coating material of the present invention comprises 20 to 50% by weight of dolomite having a particle size of 0.1 to 2.5 mm with respect to magnesia clinker as a main component.
And 0.1 to 3.0% by weight of an acidic substance capable of decomposing a carbonic acid compound in the raw material to generate carbon dioxide gas, and a binder.

In the lightweight magnesia coating material of the present invention, the amount of dolomite added to the magnesia clinker as a main component is preferably in the range of 20 to 50% by weight. This is because the amount of dolomite added is 20% by weight.
If the amount is less than the above, the amount of carbon dioxide gas generated is insufficient, the purpose of reducing the weight (reducing the bulk specific gravity) cannot be sufficiently achieved, and if the addition amount of dolomite exceeds 50% by weight, After the generation of carbon dioxide, the content of CaO increases, which reacts with iron oxide, silica, alumina, etc. in the steel to produce low-melting substances, and the coating material burns with the wall refractory, making it difficult to treat the remaining steel. This is not preferable because of the problem of

[0009] The particle size of the dolomite is 0.1 to 2.5 mm.
Is desirably within the range. It has a particle size of 2.5mm
If it exceeds, the reaction rate will be slow, and the kneading time when adding and kneading water at the time of use will decrease the efficiency of construction, and if it is less than 0.1 mm, the activity will be too large and the steel content will be too large. This is because the reaction with impurities proceeds to generate a low-melting-point substance, which causes burning.

The acidic substance is a substance capable of decomposing a carbonic acid compound (mainly derived from dolomite) in a coating material containing a basic magnesia clinker to generate carbon dioxide gas. is necessary.
Substances satisfying these requirements include various organic acids, inorganic acids, and acidic bases thereof, and oxalic acid, citric acid, and sodium phosphate are exemplified as preferred acidic substances. Also, this acidic substance
It is preferably a powdery substance.

The amount of the acidic substance varies depending on the strength of the acid of the acidic substance. As described above, since the magnesia clinker is basic and consumes the acid, the acidic substance is added in a certain amount. Need to be added. Therefore, the acidic substance is preferably added in the range of 0.1 to 3.0% by weight. When the amount is less than 0.1% by weight, the effect of the addition, that is, the amount of generated carbon dioxide gas becomes insufficient, and even if the amount exceeds 3.0% by weight, the effect of the addition is remarkably improved. Because it is unacceptable and uneconomical.

In order to sufficiently generate carbon dioxide gas (that is, to cause a sufficient reaction), it is desirable to lengthen the kneading time after adding water. However, if the kneading time is long, bubbles are broken. Then, carbon dioxide gas is released to the outside of the system (outside of the coating material), and the effect of volume expansion is hindered. To prevent this, it is effective to add a thickener.

As the thickener, organic paste, magnesium sulfate and the like can be used. Also, the amount of addition
It is preferably in the range of 0.1 to 2.0%. 0.1
If the amount is less than 10% by weight, the effect of the addition becomes insufficient.
This is because even if the content exceeds 2.0% by weight, no improvement is observed in the effect of the addition.

Further, the effect can be further improved by using a surfactant in combination.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be described below in more detail with reference to embodiments.

In this example, magnesia clinker, dolomite, oxalic acid, citric acid, and the like, which are acidic substances, were mixed in the mixing ratios shown in Table 1 to prepare a lightweight magnesia coating material.

[0017]

[Table 1]

As shown in Table 1, Example A had a particle size of 1
A mixture of 30% by weight of dolomite of less than mm is added, and sodium oxyphosphate is added as a binder, magnesium sulfate is added as a thickener, and oxalic acid is added as an acidic substance.

In Example B, 37% by weight of dolomite having a particle size of 1 mm or less was blended, sodium phosphate was added as a binder, organic glue was added as a thickener, and citric acid was added as an acidic substance. Has been added.

Further, in Example C, the particle size of the magnesia clinker was adjusted to increase the ratio of the magnesia clinker having a small particle size, and 30% by weight of dolomite having a particle size of 1 mm or less was added to the binder. And sodium sulphate as a thickener, organic glue and magnesium sulfate as a thickener, and oxalic acid as an acidic substance.

Further, as a comparative example, a magnesia coating material to which dolomite and an acidic substance were not added was prepared.

Water was added to the samples of Examples A, B, and C and the comparative example and kneaded, and the relationship between kneading time and bulk specific gravity was examined. The result is shown in FIG.

As is clear from FIG. 1, the lightweight magnesia coating material of the present invention has a bulk specific gravity that decreases immediately after kneading, and is about 2.7 in 1 minute after the start of kneading, and 5 minutes after kneading. , About 2.0. On the other hand, in the magnesia coating material of the comparative example, no change (decrease) in the bulk specific gravity was observed even after 5 minutes had passed since the start of kneading.

<Actual use example> The lightweight magnesia coating material of Example C was coated on a molten steel container, and as a result of comparison with a conventional magnesia coating material having the same construction thickness (25 mm), about 20% The specific gravity was reduced, that is, the amount of the coating material used was reduced by about 20%.

Further, when the state of permeation of the slag was measured, the slag permeation resistance was substantially the same as that of the conventional magnesia coating material. In addition, there was no welding to the side wall refractories, and the residual steel treatment could be easily performed.

In the case of a lightweight magnesia coating material using a surfactant, even if hard water is used that does not foam and loses the effect of reducing bulk specific gravity, the lightweight magnesia coating of the embodiment of the present invention can be used. When the material was used, weight reduction (reduction in bulk specific gravity) could be achieved without any influence.

In the above embodiment, a light-weight magnesia coating material to which a thickener has been added has been described. However, the basic effects of the present invention can be obtained without adding a thickener.

[0028]

As described above, the lightweight magnesia coating material of the present invention has a particle size of 0.1 to 2.5 mm with respect to magnesia clinker, which is a main component of magnesia clinker.
% By weight, and 0.1 to 3.0% by weight of an acidic substance capable of decomposing a carbonic acid compound in the raw material to generate carbon dioxide gas.
And a binder, so that without using expensive surfactants, and therefore, without being affected by water quality such as hardness, weight reduction is realized and one coating , Ie, the unit consumption can be reduced.

The effect can be further improved by adding a thickener.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between kneading time and bulk specific gravity of a lightweight magnesia coating material according to an embodiment of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-71134 (JP, A) JP-A-5-125303 (JP, A) JP-A-63-99267 (JP, A) JP-A-60-1985 67567 (JP, A) JP-A-2-133512 (JP, A) JP-A-48-64125 (JP, A) JP-A-47-17836 (JP, A) JP-A-48-102134 (JP, A) JP-A-49-106534 (JP, A) JP-A-51-147536 (JP, A) JP-A-51-34227 (JP, A) JP-A-60-127372 (JP, A) JP-B-47-11588 (JP, B1) JP 48-40851 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 1/00 C09D 7/12

Claims (2)

(57) [Claims] 1. A dolomite having a particle size of 0.1 to 2.5 mm in an amount of 20 to 50% by weight based on magnesia clinker as a main component.
A light weight magnesia coating material comprising: 0.1 to 3.0% by weight of an acidic substance capable of decomposing a carbonic acid compound in a raw material to generate carbon dioxide gas; and a binder. 2. A lightweight magnesia coating material, characterized in that 0.1 to 2.0% by weight of a thickener is added to the lightweight magnesia coating material of claim 1.