JPH05163059A - Unburned magnesia-carbonaceous refractory - Google Patents

Abstract

PURPOSE:To improve oxidation resistance and strength of unburned magnesia- carbonaceous refractory by adding a binder prepared by blending one or more aqueous solutions of bittern and MgSO4 with a phenol resin soluble in the same amount of water. CONSTITUTION:100 pts.wt. phenol resin having properties of being dissolved in the same amount of water such as liquid resol type phenol resin having 68-72% nonvolatile component, 1.17-1.19 specific gravity and 250-350cPs viscosity is blended with 5-100 pts.wt. aqueous solution of bittern or MgSO4 having 18 deg.-26 deg. Baume concentration to prepare a binder. Then a composition obtained by blending a magnesia raw material such as natural magnesia clinker with a carbonaceous raw material such as scaly graphite and metal Si in a given weight ratio is mixed with a given amount of the prepared binder to give unburned magnesia carbonaceous refractory having excellent oxidation resistance and strength.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to refractories, and more particularly to unfired magnesia-carbonaceous refractories.

[0002]

2. Description of the Related Art Unfired refractories are prepared by adding a binder such as a phenol resin or a furan resin when kneading the kneaded clay, instead of firing at a high temperature.
The carbon bond generated at a relatively low temperature is used to impart a predetermined strength. Furthermore, carbon-containing unfired refractories mixed with carbonaceous raw materials such as graphite, tar, and pitch can improve spalling resistance and slag resistance, and can be used in various types of metal melting furnaces, electric furnaces, converters, etc. It is used for the furnace wall of molten metal containers.

However, since such a carbon-containing unfired refractory material contains a relatively large amount of carbon component, the carbon component in the tissue is subjected to an oxidizing action from a low temperature range of about 500 ° C. to form carbon monoxide. And volatilize into the air. In particular, the unfired refractory has a bond in the tissue at the initial stage of its operation and a carbon bond formed by the condensation of the above-mentioned binder, so that the porosity of the tissue proceeds from the early stage of the operation and further oxidation is promoted. However, the durability was deteriorated due to deterioration of strength and deterioration of structure.

Therefore, in order to improve the oxidation resistance of such a carbon-containing unfired refractory, various antioxidation measures have been proposed. For example, in JP-A-53-6312, in order to improve the oxidation resistance, one or more kinds of metal silicon, silicon nitride and silicon carbide and one or more kinds of phenol resin and furan resin may be added, if necessary. A carbonaceous non-fired refractory containing a binder containing one or more of sodium pyrophosphate, sodium hexametaphosphate, and sodium phosphate is disclosed, and the chemical bond by the silicon component compensates for the disappearing carbon bond. However, we are trying to prevent the weakening of the organization in the early stages of operation.

In addition to the above, the oxidation resistance can be improved by various means and methods such as coating or impregnating the surface of the refractory material with an antioxidant, or adding an easily oxidizable substance to the kneaded clay before kneading. I am trying.

However, although the above-mentioned means and methods can obtain a certain effect of improving the oxidation resistance, they are still insufficient, and the oxidation resistance of such an unburned magnesia-carbon refractory is improved. Is still required.

The present invention has been proposed in view of the above conventional circumstances, and prevents deterioration of the refractory structure due to oxidation / disappearance of the carbonaceous binder and carbon-containing components in the magnesia-carbonaceous unfired refractory. The purpose is to do.

[0008]

To achieve the above object, the present invention employs the following means in a magnesia-carbonaceous unfired refractory material. That is, the binder is prepared by adding at least one of bitter juice and magnesium sulfate to a phenol resin having a property of dissolving in the same amount of water.

[0009]

In the above structure, it is presumed that bittern or magnesium sulfate mixed with the phenol resin has the following effects.

(1) Bittern or magnesium sulfate forms a film, which covers carbon bonds and graphite. (2) In addition to the above carbon bond, a chemical bond that guarantees the strength and compactness of the refractory in the initial stage of operation is separately formed by the bitter juice or magnesium sulfate mixed with the binder.

The water-soluble phenolic resin in the present invention is required to have the property of being dissolved in the same amount of water. 19. Similarly, a liquid resol type phenol resin having a physical property value of viscosity 250 to 350 cps can be used.

When bitter or magnesium sulfate is added to the above-mentioned phenol resin, an aqueous solution having a concentration range of 18 ° to 26 ° Baume is used, and strength and oxidation resistance are not exhibited at a concentration of 18 ° Baume or lower. Two
At 6 ° Baume or higher, the effect of increasing bitter juice or magnesium sulfate is not observed.

The water-soluble phenolic resin usually contains 5 to 6% of water, and an aqueous solution of bitter juice or magnesium sulfate dissolved in water contains 18 ° to 26 °.
It is also possible to mix the amount to form a bowl and add it to the kneaded material during kneading, and this method is easier to handle and more practical.

When the bitter broth or magnesium sulfate is mixed with the aqueous solution, the bitter broth or magnesium sulfate aqueous solution having the above concentration is added to 100 parts by weight of the phenol resin.
It is desirable to mix it in an amount of 100 parts by weight. If the amount of bitter or magnesium sulfate aqueous solution exceeds 100 parts by weight, the mixed solution becomes a gel and is not uniformly dispersed as a binder, the graphite and the binder do not fit well, and the strength of the carbon bond is insufficient. Firing magnesia
Loss of carbonaceous refractory properties. On the other hand, if it is 5 parts by weight or less, almost no chemical bond is formed, and the effect of the combined use is not recognized.

The unburned magnesia-carbonaceous refractory to which the present invention is applied contains at least a magnesia raw material such as natural magnesia clinker and electro-melted magnesia clinker, and a carbonaceous raw material such as graphite, tar and pitch. It does not hinder the combined use with the antioxidant.

[0016]

The present invention will now be described in detail by contrasting the examples of the present invention with the comparative examples containing conventional binders.

The unburned magnesia-carbonaceous refractory used as the base material was composed of magnesia clinker, scaly graphite and metallic silicon in the mixing ratios shown in the upper column of Table 1. Example 1 had a water content of 6%. To the liquid phenol resin containing the above, a binder, which was previously dissolved in an amount corresponding to an aqueous solution of 23 ° Baume with respect to the contained water and dissolved, was added to the above base material in an amount as indicated by external coating. Similarly, in Example 2, similarly, a binder containing magnesium sulfate instead of bitter juice was added, and in Example 3, similarly, the binder 1 used in Example 1 was added.
00 parts by weight and 80 parts by weight of the bitter aqueous solution prepared at 23 ° Baume were mixed and dissolved, and this was added as a binder. In Comparative Example 1, the same phenol resin as that used in Examples 1 to 3 was blended.

As shown in the quality characteristic values in the lower column of Table 1, Example 1
In Nos. 3 to 3, the results (strength (compressive strength, bending strength)) and oxidation resistance (weight loss rate by the oxidation test) were improved as compared with the comparative example.

From this, it can be said that bittern or magnesium sulfate develops strength separately from the phenol resin, and further has an antioxidant effect on scaly graphite and bonded carbon. The present invention is not limited to the embodiment described above, but can be applied to various types of unburned magnesia-carbonaceous refractory materials, and the use of bitter juice or magnesium sulfate in combination is not hindered.

[0020]

[Table 1]

[0021]

As described above, according to the present invention, by adding bittern or magnesium sulfate in addition to the conventional binder containing a phenol resin as a main component, a coating for coating carbon bonds and graphite is formed. In addition to the above, since the chemical bond is formed separately from the carbon bond by the condensation polymerization of the phenol resin, it is possible to improve the oxidation resistance and the strength of the unburned magnesia-carbonaceous refractory.

Claims (1)

[Claims] 1. An unfired magnesia characterized by comprising a binder prepared by mixing at least one of bitter broth or an aqueous magnesium sulfate solution with a phenol resin having a property of dissolving in the same amount of water. Carbon refractory.