JPH10245284A - Magnesian and calcian refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnesian and calcian refractory excellent in sintering properties, hydration resistance and productivity by coating titanium-based organic metal compound or a colloidal titania on the powder surfaces of magnesian and calcian raw materials, and drying and heat-treating the coated magnesian and calcian raw materials to provide titania layers. SOLUTION: This magnesian and calcian refractory is obtained by coating a titanium-based organic metal compound such as an alkoxide, an acylate and a chelate, or a colloidal titania of 0.1-2wt.% in terms of titania on the surfaces of magnesian and calcian powdery raw materials, and drying the coated magnesian and calcian powdery raw materials, compacting the obtained dried material and firing the compact at 1,400-1,700 deg.C. The refractory obtained by forming a titania layer on the surface of the magnesia and calcia powder and firing the powder with the titania layer has a more decreased pore ratio and a higher bulk density and further extremely improved hydration resistance compared with the one obtained without forming the coating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of basic refractories of magnesia and calcia.

[0002]

2. Description of the Related Art Magnesia and calcia have a high melting point and excellent slag erosion resistance. For this reason, refractories made from these materials are widely used as basic refractory materials in the steel industry and other industries.

However, the magnesia and calcia powders are difficult to sinter, so that it is difficult to obtain a dense sintered body, and because of their high coefficient of thermal expansion, when used as a refractory, grain boundaries are eroded by slag. In addition, there is a drawback such as a decrease in strength, which shortens the service life. In addition, magnesia and calcia are water-absorbing, and since these powders and the refractory which is a sintered body of the powder as a constituent are hydrated during production, transportation and use,
This is one of the factors for shortening the service life of refractories using these materials. Especially in the case of calcia which is easy to hydrate,
Its use is also limited and its application range is limited.

[0004] In order to improve the above-mentioned disadvantages, various studies have been made in recent years. As for magnesia, a high-density electrofused magnesia clinker is manufactured using a high-purity raw material. This fused magnesium clinker
Although the slag erosion resistance has a certain improvement effect, the hydration resistance has not been sufficiently improved. Further, a method of improving the sinterability by adding a sintering aid to magnesia is considered to be one of the effective methods. For example, a method by adding titania powder (see
2-62508). On the other hand, calcia is coated on its surface with a metal such as aluminum, chromium, titanium, zirconium or a semimetal such as silicon, boron or carbon for the purpose of improving its hydration resistance (Japanese Patent Laid-Open No. 8-104574). Gazette).

[0005]

However, since the magnesia refractory material obtained by the method of Japanese Patent Publication No. 2-62508 mentioned above uses powder, the amount of titania added is 4% by weight.
As mentioned above, a large amount of low melting point compounds MgTi ₂ O ₅ , MgTiO ₃ and Mg ₂ TiO ₄ are formed around the magnesia grains during firing, and the high temperature performance of the material, especially when used as a refractory, It is considered that the slag erosion resistance is impaired. Further, since titania is added in the form of powder, it is difficult to uniformly densify the structure, and it is difficult to obtain a sufficient effect of addition. For example, 4.87 titania powder
When the magnesia molded body added by weight% was baked at 1900 ° C., the bulk density was 3.53.
The effect is not so large compared to.

On the other hand, in the case of calcia powder coated with a metal or metalloid, hydration resistance cannot be obtained unless a heat treatment is performed in a predetermined atmosphere to form a coating layer of a metal reactant. However, the use of this coated calcia is limited depending on the type of metal reactant in the coating layer. Also, the cost of the treated calcia is expected to be high because the metal for coating is very expensive compared to the oxide.

As described above, although the prior art is somewhat improved, the sinterability, hydration resistance and manufacturability are still inadequate. There is a need for calcia refractories.

[0008]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have found that a uniform titania layer is formed on the surface of magnesia or calcia powder, and the sinterability and hydration resistance And excellent magnesia and calcia refractories were obtained. That is, the present invention is a magnesia and calcia refractory characterized in that a titania layer is formed on the surface of a magnesia and calcia material, and in particular, the titania layer is a titanium-based organometallic compound or a colloidal material. A magnesia and calcia refractory characterized by being obtained by coating, drying and heat treating titania.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The magnesia and calcia raw materials used in the present invention are obtained by decomposing magnesium hydroxide, magnesium carbonate, calcium hydroxide, calcium carbonate and the like, in addition to magnesia and calcia, which are ordinary refractory raw materials. And those obtained by sintering or electrofusion can be used. Alternatively, magnesium hydroxide, magnesium carbonate, calcium hydroxide, and calcium carbonate powder can be directly used, and the surface thereof can be coated with an organic titanium compound and then heated and sintered. The magnesia and calcia raw materials can be used alone or in combination to form a magnesia-calcia refractory.

In the present invention, a titania layer is formed on the surface of these raw materials.
Those using a titanium-based organometallic compound and an aqueous colloidal titania can provide a coating having good properties after coating. Titanium-based organometallic compounds include alkoxides, acylates and chelates, and any of them may be used. The colloidal titania may be simply a suspension of fine titania in water.

In the present invention, the coating amount is 0.1 to 2% by weight in terms of titania. If the amount is less than 0.1% by weight, sufficient effects such as sinterability and hydration resistance cannot be obtained. Further, even if the content exceeds 2% by weight, it is difficult to obtain a further effect, and as described above, a large amount of a compound having a low melting point is generated in the material, which is an adverse effect.

The method for producing magnesia and calcia refractories of the present invention is carried out in exactly the same manner as in the prior art except that a raw material coated with a titania layer is used as a raw material.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to embodiments. Magnesia and calcia obtained by calcining magnesium carbonate and calcium carbonate at 1000 ° C. for 1 hour were used.

As the titanium-based organometallic compound, di-i-propoxybis (acetylacetonato) titanium Ti [OCH (CH ₃ ) ₂ ] ₂ [OC (CH ₃ ) CHCOC
H ₃ ] ₂ was used.

A predetermined amount of the titanium-based organometallic compound was diluted with ethyl alcohol, and magnesia and calcia powders were added to the solution, stirred, desolvated, and uniformly coated on the surface. The coated magnesia and calcia powders were each dried at 100 ° C. for 5 hours, and then formed into a column of 50 × 20 mm. The molded body thus obtained was fired at 1400 ° C. to 1700 ° C. for 2 hours. In addition, what was similarly fired using uncoated powder as a comparative sample was also manufactured.

In the hydration test, magnesia samples fired at each temperature were placed in water at a temperature of 80 ° C., and the hydration resistance of each sample was evaluated based on the weight increase rate of each sample. The calcia samples were allowed to stand in saturated steam at a temperature of 40 ° C., and the hydration resistance was evaluated based on the weight increase rate of each sample. The results are shown in Tables 1 and 2. In addition, the sample of Comparative Example 4 using magnesia without coating collapsed.

The refractory of the present invention obtained by forming a titania layer on the surface of magnesia and calcia powder and firing it has a significantly reduced porosity and a higher bulk density than the comparative example in which no coating layer is formed. It can be seen that the hydration resistance is significantly improved.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

According to the present invention, a very uniform and dense structure can be formed as compared with the conventional magnesia and calcia refractories, so that the sinterability and hydration resistance of the refractories are greatly improved. It can be expected that the service life as a refractory can be extended and the range of application can be further expanded. Further, since the manufacturing means is simple and relatively low-temperature firing is possible, it is effective for improving the productivity of this material and reducing the cost.

Claims (2)

[Claims] 1. A magnesia and calcia refractory, wherein a titania layer is formed on the surface of a magnesia and calcia material. 2. The magnesia and calcia refractory according to claim 1, wherein the titania layer is obtained by coating, drying and heat-treating a titanium-based organometallic compound or colloidal titania.