JPH0788254B2 - Method for manufacturing silicon carbide refractory - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to carbonization used in places where alkali resistance, oxidation resistance, slag resistance, and wear resistance are required, such as refractory for blast furnace walls. The present invention relates to a method for manufacturing a silicon refractory material.

[Conventional technology]

As the silicon carbide refractory, one bonded with clay or silicate has been used for a long time, but as the use condition becomes severe, alkali resistance, heat resistance, etc. have become insufficient.

As a countermeasure against this, for example, as described in Japanese Patent Publication No. 60-6305, a method has been developed in which Si or Al is mixed into an aggregate and fired in a nitriding atmosphere to bond silicon carbide with sialon. It was

However, in such a method, the added Si or
Al remains as a metal in the core of the molded body, and a refractory having insufficient alkali resistance and steam oxidation resistance is liable to be produced, which limits the wall thickness that can be manufactured.

Further, as described in Japanese Patent Publication No. 60-47224, Al, Si and clay are added to the mixture and the mixture is calcined at 1300 to 1600 in a coke breeze to form Si-Al-O-N at the joint. A method for producing alumina, silicon nitride and silicon carbide has also been proposed.

However, this method also produces during firing.
Due to the pore-sealing effect of Si ₃ N ₄ , Si or Al is likely to remain unreacted in the core, and the wall thickness that can be manufactured is limited.

Furthermore, as a method of not limiting the wall thickness of such a refractory to be produced, Si is added together with the resin binder in the composition, and the carbon from the resin binder is reacted with Si to form β- Although a method of forming a bond of SiC has also been attempted, the alkali resistance and spalling resistance of the one produced by this method are insufficient because of only the bond of β-SiC.

[Problems to be solved by the invention]

The problem to be solved by the present invention is to solve the problems at the time of manufacturing such a conventional silicon carbide refractory material,
It is an object of the present invention to provide a method for producing a silicon carbide-based refractory material capable of sufficiently exhibiting alkali resistance, oxidation resistance, slag resistance, and wear resistance without limiting other physical properties without limiting the wall thickness.

[Means for solving problems]

The present invention provides a sialon, A, which imparts alkali resistance, oxidation resistance, slag resistance, and wear resistance to a silicon carbide refractory.
It was completed by elucidating the mechanism of wall thickness limitation by lN, SiC, and Si ₃ N ₄ .

For example, as described in Japanese Patent Publication No. 60-6305, the added Si forms Si ₃ N ₄ when firing in a nitriding atmosphere such as N ₂ or NH ₃ flow. This prevents the nitriding gas from entering the refractory, which limits the nitriding reaction in the deep part of the refractory and limits the thickness of the refractory.

Further, also in the manufacturing method which does not particularly flow N ₂ or NH ₃ gas described in JP-B-60-47224,
Since clay is used in the formulation, the added Al reduces the silica in the clay and the Si produced by this reduction
During firing in the coke breeze, reacts with the nitrogen gas present in the coke breeze to form Si ₃ N ₄ , which becomes a form that suppresses the ingress of nitrogen gas into the refractory,
Similarly, the thickness of refractory materials is regulated. Further, the added Al is oxidized by silica in the clay to become corundum, and the production amount of AlN is reduced, so that the alkali resistance, spalling resistance, and slag resistance of the manufactured refractory are deteriorated.

The present invention provides a method for producing a silicon carbide-based refractory material using a composition containing such metallic aluminum or metallic silicon,
The unreacted metallic aluminum and metallic silicon residues that regulate the thickness are due to the elucidation of the mechanism that the entry of the nitriding gas is restricted by the formation of Si ₃ N ₄ , which was completed. The conditions for preventing the formation of Si ₃ N ₄ that restricts invasion are found.

Specifically, the weight ratio of Al / Si is within the range of 10/1 to 1/4, the mixture of metal aluminum and metal or alloy powder 5
30 wt%, 3 to 20 wt% of alumina powder, and the balance of silicon carbide are kneaded and molded with a resin having a high carbonization yield, and fired in carbon powder at 1300 to 1650 ° C. , Which forms sialon, AlN, β-SiC in the joint, which allows the reaction to proceed to the deep part without the formation of Si ₃ N ₄ and enables the production of thick refractory materials. Is.

In order to form sialon, AlN, and β-SiC that enhance the alkali resistance, slag resistance and strength of the joint, the total amount of the above-mentioned metallic aluminum and metallic silicon must be 5% by weight or more. However, the total amount added is 30% by weight.
Alkali resistance, because the amount of more joints becomes too large,
Spalling resistance is reduced.

In order to form an appropriate amount of sialon, AlN, β-SiC, etc. in this joint, the most important thing is the compounding ratio of metallic aluminum and metallic silicon, and the weight ratio of Al / Si is 10/1 ~ 1
When it is in the range of / 4, sialon, AlN, and β-SiC are formed in the joint without forming Si ₃ N ₄ by firing under the above-mentioned specific treatment conditions, and alkali resistance and resistance SiC refractory with enhanced spalling resistance, oxidation resistance, and slag resistance, and capable of thickening.

However, if the weight ratio of Al / Si is 10/1, the amount of AlN produced becomes relatively larger than the amount of β-SiC, and the digestion resistance and alkali resistance deteriorate. On the other hand, if the Al / Si ratio is less than 1/4 by weight, the amount of AlN produced becomes relatively smaller than the amount of β-SiO, and the slag resistance, alkali resistance, and spalling resistance deteriorate. .

In the present invention, 3 to 20% by weight of alumina powder for forming sialon that contributes to binding is blended in the formulation. If the content is less than 3% by weight, sialon will not be produced, and improvement in wear resistance and slag resistance cannot be expected. If it is more than 20% by weight, the amount of corundum remaining will increase and the resistance to alkali and The spalling property deteriorates.

Also, although it will increase the cost as an alternative to alumina,
AlN and Sialon can be used. If the oxygen content of the alumina substitute is 3% by weight in terms of alumina, sialon is produced and wear resistance and slag resistance are improved.

Further, although silicon carbide is blended in the balance, silicon nitride can be used instead of silicon carbide. The use of silicon nitride has a higher porosity of the raw material than that of silicon carbide, which raises the porosity of the refractory, lowers the alkali resistance and oxidation resistance, and increases the cost, but is advantageous in terms of spalling resistance. Therefore, up to 20% by weight of the compounded silicon carbide can be substituted.

In the present invention, when kneading the above-mentioned compound prior to molding, a phenol resin is desirable as a resin having a high carbonization yield of about 40 to 70% from the viewpoint of cost workability.

The kneaded and molded body thus obtained was placed in a silicon carbide sheath, and the space was filled with carbon powder.
Bake at ~ 1650 ° C.

As the carbon powder used as the packing powder, coke powder, graphite, electrode powder, by-product scaly graphite powder and the like can be used. The carbon powder keeps the atmosphere in a reducing atmosphere and supplies it from the air held in the filling powder into the compact during N ₂ firing.

In such an atmosphere, the above kneaded mixture molded body is heated at 1300 to 1650 °
By firing at 1, a structure bonded by sialon, AlN, and β-SiC is obtained, whereby a silicon carbide refractory having excellent alkali resistance, acid resistance, and abrasion resistance can be obtained.

If the firing temperature is lower than 1300 ° C, Al ₄ C _{3 formed} from Al added during firing remains and the digestion resistance and alkali resistance deteriorate. Further, if the firing temperature is higher than 1650 ° C, the physical properties of the refractory that can be formed do not significantly change, and there is no merit in terms of quality. In addition, the durability of the SiC sheath that holds the carbon-filled powder is greatly reduced, which only increases the cost.

〔Example〕

600 x 400 x 120 m of the compound as shown in Table 1 and Table 2
It was molded with m and fired under the conditions shown in the table.

Each of the examples manufactured under the conditions falling within the requirements of the present invention has excellent mechanical properties and corrosion resistance.

On the other hand, as shown in Comparative Examples 1 and 2, the nitriding fired product was not nitrided at the central portion, metal aluminum and metallic silicon remained, and the central portion had alkali resistance and oxidation resistance higher than those of the outer peripheral portion. Remarkably inferior. Further, in Comparative Example 1 in which only silicon is added, the slag resistance, spalling resistance, and wear resistance are greatly reduced. The nitriding atmosphere fired product of Comparative Example 2 to which Al and Si were added showed a large decrease in spalling resistance as compared with the fired product in carbon powder.

From Comparative Example 3 and Example 4, it can be seen that the strength, alkali resistance, slag resistance, and wear resistance are remarkably improved when the added amount of the mixed powder of Al and Si exceeds 5% by weight. However, it is understood from Comparative Example 4 and Example 3 that when the amount of the mixed powder of Al and Si added is more than 30% by weight, the alkali resistance and the spalling resistance are greatly reduced.

From Comparative Example 5 and Example 4, if the amount of alumina added exceeds 3% by weight, slag resistance and wear resistance are significantly improved. However, from Comparative Example 6 and Example 5, when the amount of alumina added is more than 20% by weight, alkali resistance, slag resistance, and
It can be seen that the spalling resistance is greatly reduced. However, it can be seen from Comparative Example 7 and Example 6 that when the substitution amount of SiC to Si ₃ N ₄ is more than 20% by weight, the alkali resistance and the oxidation resistance are greatly reduced.

It is understood from Examples 7 to 10 that one or more kinds of AlN, sialon, and silicon oxynitride can be used as a substitute for alumina.

In addition, by comparing Comparative Example 8 with Example 7, it was confirmed that the wear resistance, slag resistance and digestion resistance of the product when the oxygen content in the alumina substitute exceeds 3% by weight in terms of alumina. Greatly improved.

The formulations shown in Table 3 were molded under the same conditions as in Tables 1 and 2 and fired in 1500 ° C. carbon powder.

From Comparative Example A and Example A, it is understood that when the weight ratio of Al / Si is smaller than 10/1, digestion resistance and alkali resistance are remarkably improved.

From Comparative Example B and Example C, it can be said that Al and Si may be added in the form of mixed powder or alloy.

From Comparative Example C and Example B, it is understood that the addition of clay powder deteriorates the alkali resistance, slag resistance and spalling resistance of the central part.

The green body shown in Example 2 in Table 1 was fired under the conditions shown in Table 4.

From Comparative Example 2A and Example 2A, it is understood that when the firing temperature is higher than 1300 ° C., Al ₄ C ₃ does not remain during the firing and the digestion resistance and alkali resistance are improved. However, it can be seen from Comparative Example 2B and Example 2B that even if the firing temperature is higher than 1650 ° C., there is no particular effect on the quality and the alkali resistance and digestion resistance are slightly reduced. Then, the durability of the SiC sheath holding the carbon-filled powder is significantly reduced, and its practicality is lost.

The composition shown in Table 5 is used for blast furnace wall (650 x 450 x 120 mm),
Molded as slag melting furnace for furnace wall (900 x 350 x 85 mm),
Firing was performed under the same conditions as in Table 1, Table 2 and Table 3.

The bricks tested on the wall of the blast furnace were used for one year and then bored to measure the residual thickness to determine the wear rate. It was found that the product of the present invention had a significantly lower wear rate than the comparative product.

The brick test-tightened in the slag melting furnace was disassembled after 6 months of use, and the wear rate after measurement was determined.

In Comparative Example 2, since the thickness of the brick was thin at 85 mm, the center portion of the brick was not deteriorated, and because of continuous operation, it was slightly inferior to the product of the present invention probably because the influence of the decrease in spalling resistance was small. The comparative product of No. 2 had a remarkable increase in wear rate.

The product of the present invention can have a larger wall thickness than the nitriding fired product and the clay-added product, can reduce the number of joints, and can improve the gas sealing property and the furnace construction efficiency. Became.

The use of the product of the present invention is not limited to the use shown in Table 5, and it can be used for all uses in which the alkali resistance, slag resistance, spalling resistance, and oxidation resistance of silicon carbide refractories can be utilized. Is.

For example, a non-ferrous smelting furnace, a non-ferrous calcination furnace, an iron powder calcination furnace, a ceramic calcination jig (shelf plate, sheath, etc.), a refuse incinerator, etc. may be mentioned.

[Effect of the Invention] According to the present invention, it is possible to obtain a compound having sufficient characteristics as a silicon carbide brick even if the thickness of the compounded and kneaded compound is increased to about 120 mm.

Claims (3)

[Claims] 1. An Al / Si ratio of 5 to 30% by weight of Al and Si powder mixed or alloyed in a weight ratio range of 10/1 to 1/4,
High wall thickness is possible by mixing 3-20% by weight of alumina powder and the balance of silicon carbide by kneading and molding with a resin having a high carbonization yield and firing at 1300-1650 ° C in carbon powder. Of manufacturing a new silicon carbide refractory. 2. The method for producing a high-thickness silicon carbide refractory material according to claim 1, wherein 20% by weight or less of silicon carbide is replaced by silicon nitride. 3. A part of alumina powder is AlN, sialon, The method for producing a silicon carbide refractory material having a high wall thickness according to claim 1 or 2, characterized in that the refractory material is replaced by one or more of the above.