JPS6138146B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to highly corrosion-resistant synthetic refractories and refractory raw materials. Specifically, the present invention has excellent corrosion resistance not only against molten slag but also against molten iron, has excellent oxidation resistance at high temperatures, and when used as a refractory. This invention relates to synthetic refractories and refractory raw materials that exhibit high strength. In recent industries that use refractories, demands for corrosion resistance of refractories have been increasing due to technological innovations and increasingly severe operating techniques. For example, in the steel industry, improvements are being made in the continuous casting ratio with the aim of reducing production costs and stabilizing quality, and in-ladle scouring is being adopted as the quality of steel becomes higher and more diverse. There is now a demand for greater durability and stability than ever before. To be more specific, it is expected that improvements in the continuous casting ratio will lead to multiple casting and high-speed casting in the future.
As these advances progress, higher durability is required of refractories. Furthermore, as the frequency of scouring in a ladle increases, the durability of refractories decreases significantly due to higher temperatures of steel or an increase in the use of special steels that are highly corrosive to furnace materials. It is desired that In response to these demands, attempts have been made to improve durability by using conventionally used refractory raw materials such as magnesia, chromium oxide, dolomite, spinel, alumina, silica, carbon, silicon carbide, and silicon nitride, either singly or in combination. However, basic materials do not necessarily meet the above requirements in terms of spalling resistance, carbon-based materials in terms of oxidation resistance and wear resistance, and other materials in terms of chemical corrosion resistance. At present, this has not been achieved. Improving corrosion resistance is one of the factors that improves durability, but the inventors paid attention to this point and conducted various studies to overcome the above drawbacks, and as a result they developed completely new refractories and refractory raw materials that were not available before. We found this idea and established a method for its synthesis. The synthetic refractories and refractory raw materials according to the present invention consist of silicon carbide, aluminum nitride, aluminum carbide, aluminum oxide, and excess carbon, and when viewed microscopically, they exist in a mixed state, and have excellent corrosion resistance and acid resistance. It has the property of exhibiting high strength when used in refractories. This aluminum-containing amorphous carbon-mixed silicon carbide material can be said to be excellent in terms of thermal properties, with a coefficient of thermal expansion close to that of ordinary silicon carbide. Aluminum nitride and aluminum carbide have very little use in the refractory industry, and the present inventors intend to make use of these properties to widely utilize them in this field. The method for producing highly corrosion-resistant synthetic refractories and refractory raw materials of the present invention will be explained in detail below. The fine powder A of the silicon source used in the present invention includes metal silicon, silicon alloys, organic silicon polymer compounds, etc., and one or more of these are selected. At this time, the silicon content of fine powder A is 80% by weight.
(The following % indicates weight % unless otherwise specified.) If it is less than 90% by weight, the composition of the refractory raw material to be synthesized will contain many impurities, such as silicate-based low melting substances. This is because the properties as a highly corrosion resistant raw material cannot be exhibited. The reason why the particle size of fine powder A was set to be 100 mesh or less (the same applies below Tyler) is that the reactivity of silicon with carbon or nitrogen is particularly important in the production of the present invention, and if the particle size is larger than 100 mesh, the reactivity decreases. This is because there is a high risk that unreacted silicon will remain and cause a decrease in corrosion resistance. From this point, the particle size of 100 mesh or less is 80%
It is desirable that the powder be as fine as above. Next, the fine powder B of the aluminum source includes atomized aluminum, stamped aluminum, aluminum paste, aluminum alloy, etc., and one or more of these are selected. At this time, the aluminum content of fine powder B must be 80% or more; if it is less than 80%, the absolute amount of aluminum carbide, aluminum nitride, and aluminum oxide in the refractory raw material composition to be synthesized will decrease. This not only impairs the characteristics of the present invention, but also increases the amount of low-melting-point impurities. The reason for setting the particle size of fine powder B to be 100 mesh or less is that the reactivity of aluminum with nitrogen, carbon, and oxygen is particularly important in the production of the present invention, and when the particle size becomes larger than 100 mesh, the reactivity decreases. This is because the microstructure of the synthetic raw material, which is a feature of the present invention, cannot be obtained, which ultimately causes a decrease in corrosion resistance. From this point, the particle size of 100 mesh or less is 80
% or more is desirable. The carbon source fine powder C may be one type of amorphous carbon, such as petroleum pitch coke, Seishi coke, anthracite, charcoal, carbon black, carbohydrate pyrolysis carbon, hydrocarbon pyrolysis carbon, etc. Or two or more types are selected. The carbon content of fine powder C is
A content of 80% or more is required, and if it is less than this, the absolute amount of metal carbide or surplus free carbon will decrease, free carbon structure will not be formed in the structure, and the corrosion resistance, which is a characteristic of a highly corrosion-resistant refractory raw material, will be impaired. Furthermore, the reason why the fine powder C is made of amorphous carbon with a mesh size of 100 or less is as follows. Looking at the solubility of carbon in molten iron, crystalline carbon, such as scaly graphite, earthy graphite, artificial graphite, wood graphite, and pyrolytic graphite, has the highest solubility, and the more it becomes an amorphous fine powder, the more soluble it becomes. It gets watery. Furthermore, if the particle size is larger than 100 mesh, the surface area of carbon becomes smaller, which not only reduces the reactivity with silicon or aluminum, but also reduces the reactivity with silicon or aluminum.
The degree of dispersion of excess carbon also decreases. Therefore, if a powder other than the amorphous carbon fine powder C of the claims is used, silicon carbide obtained from amorphous carbon having very low solubility in molten iron, which is a feature of the present invention, or The feature of the present invention, which is made of aluminum carbide and whose surplus carbon is uniformly distributed within the structure, will be impaired. Next, the above fine powder is mixed with A=20~60% and B=10~
50%, C = weight ratio in the range of 30 to 50%, and the total
Mix A, B, and C in proportions to make 100%. Which of the following is the basis for setting the weight ratio of fine powders A, B, and C as above? If the weight ratio of fine powders A, B, and C is less than 20, 10, or 30% separately, the resulting synthetic raw materials are silicon carbide, aluminum nitride, aluminum carbide, and aluminum oxide. If it exceeds 60 or 50%, the reaction products mentioned above become unevenly distributed, and as a result, the presence of other compounds decreases or disappears. This results in an inferiority in the expression of comprehensive properties by each reaction product, which is a feature of the invention. The two are mixed using an ordinary mixer such as a V-type mixer, a bottom kneader, a kneader with a pressurizing device, etc. At this time, a binder such as water glass and monoaluminum phosphate is added as necessary. Inorganic binders, natural resins, synthetic resins, petroleum-based and coal-based solvents, organosilicon polymer compounds, alcohol, water, molasses, dextrin, pulp waste liquid, etc. are optionally added. Although it is possible to obtain the synthetic refractories or refractory raw materials of the present invention by filling them in powder form or by tapping them without adding any binder and proceeding to the firing process, the density or structure of the synthetic raw materials to be obtained should be taken into consideration. If you do, Frixion
It is preferable to perform pressure molding using a press, oil press, void press, crank press, or the like. After forming, dry at room temperature or with a hair dryer.
Fire in a non-oxidizing atmosphere. As the non-oxidizing atmosphere, an argon stream, a nitrogen gas stream, a silicon gas stream such as silicon chloride, a reducing atmosphere in carbon, etc. can be used, but the mineral composition should be determined depending on the purpose of use of the synthetic raw material. Therefore, the firing atmosphere can be arbitrarily selected, but the reducing atmosphere firing method is most suitable from the viewpoint of firing cost. Furthermore, reduction firing in carbon often contains trace amounts of oxygen or nitrogen, resulting in the production of silicon oxynitride, trace amounts of silicon nitride, and cristopalite, but this does not impair the characteristics of the present invention. It plays a role in improving oxidation resistance. The firing temperature is usually 1200°C to 1700°C since β-SiC starts to be generated around 1200°C and α-SiC starts to generate around 1700°C. Next, in claim 3, the fine powder C has an average particle size of 50 mμ or less and a specific surface area of 50 m ₂ ^/
The reason why carbon black is limited to carbon black with a weight of more than 100 g is shown below. The above-mentioned carbon black is particularly difficult to dissolve in molten iron among amorphous carbons, and has properties that make it difficult to get wet. Moreover, it has ^{1018 to 19} functional groups per unit particle, making it extremely chemically active. Because it is active, it has properties that are completely different from ordinary carbon materials. Therefore, it exhibits particularly excellent properties among the amorphous carbons of the present invention. Carbon black is widely used in printing inks, paints, rubber, carbon resistors, etc., but it is rarely used in the refractory industry, and only a few patent applications have been filed since 1973.
The report in No. 123413 is to some extent. Synthetic clinker obtained by the above manufacturing method generally has a high porosity, which may be inconvenient depending on the application. As a countermeasure to this, it is necessary to use a conventional method to remove the The tissue is densified by impregnation with the same or similar impregnating agent. Examples of the impregnating agent in this case include pitch, tar, silica sol, alumina sol, synthetic resin, organic silicon polymer compound, etc., and one or more types are selected from these depending on the purpose. Since the impregnability of the material fired in the non-oxidizing atmosphere of the present invention is significantly reduced, impregnating the material at a stage after molding (base material) is quite effective in lowering the porosity. Moreover, if the material impregnated with the base material in this manner is impregnated again with a lower viscosity impregnating agent such as furan resin after firing, the effect will be doubled. Next, as shown in the later examples, the reason why the product of the present invention exhibits high corrosion resistance, high oxidation resistance, and exhibits high strength when used in refractories is unclear, but the following considerations are made. be done. The synthetic refractory raw material of the present invention has silicon carbide and aluminum carbide or aluminum nitride as main components,
Consists of minerals produced by reaction sintering of carbon as a subcomponent and trace components of aluminum oxide, silicon oxynitride, silicon nitride, sialon, and cristopalite (however, the composition of the minerals produced differs slightly depending on the firing conditions). It has a microstructure in which excess carbon covers these intricately intertwined minerals, making it extremely difficult to wet with molten iron and exhibiting excellent corrosion and oxidation resistance. Moreover, these reactive sintered minerals are chemically active and have fine unit particle shapes, so when the present invention is used as a raw material for refractories, it has good sinterability and hot strength. A refractory with high corrosion resistance and high corrosion resistance can be obtained. Next, the characteristics of each produced mineral will be explained. Silicon carbide (α-SiC) is generally known for its excellent properties such as high melting point, high strength, high thermal conductivity, low thermal expansion, and high corrosion resistance to molten slag, but it has the disadvantage of significantly poor solubility in molten iron. It was also on. However, although the reason is unknown, the inventors believe that silicon carbide with a non-stoichiometric composition obtained by using amorphous carbon in excess of the theoretical composition of silicon carbide is superior to molten iron. It was discovered that it has excellent corrosion resistance. The present invention utilizes this special silicon carbide.
The present invention is mainly based on the technical law and is characterized in that carbon and aluminum carbide or aluminum nitride are combined therewith. There is little literature on aluminum carbide and there are some unknown points, but it is thought to have a high melting point and properties almost similar to ordinary metal carbides. Also, when heated in air, an aluminum oxide film is formed on the surface, preventing further oxidation. Aluminum nitride is said to have excellent mechanical, thermal, and chemical properties, and is easily generated at relatively low temperatures, forming a film of aluminum oxide, Al ₂ OC, and being stable even in oxidizing and reducing atmospheres. As for carbon, as is well known, it can be said to be an especially excellent refractory material in a non-oxidizing atmosphere. The present invention is characterized in that surplus carbon is contained in the raw material composition after synthesis, and it is necessary to adjust the blended composition of the synthetic raw materials accordingly. Further, as described above, the solubility in molten iron is lower as the powder is amorphous and finer, and its characteristics are exhibited as the surplus carbon is more uniformly dispersed in the composition of the synthetic raw materials. Regarding minerals produced as trace components,
As is well known, aluminum oxide is an excellent refractory material, and silicon nitride and Sialon have been reported in many recent years and are also known as excellent refractory materials. When silicon oxynitride and cristopalite are heated in air, a glass phase with a fairly high viscosity forms on the surface in contact with the air, which acts to prevent oxidation from proceeding. It is generally said that refractories that easily generate a glass phase are weak in corrosion resistance, but in the case of the present invention, the glass phase does not occur unless it comes into contact with oxygen, and even when it does come into contact with oxygen and forms glass, it is said that the refractories have poor corrosion resistance. The excess carbon acts as a filler, creating a highly viscous glass that exhibits a coating effect. Therefore, the synthetic refractory raw material according to the present invention has a composite structure in which the synthetic minerals produced by reaction sintering having the above-mentioned characteristics are intricately intertwined, and exhibits the individual characteristics in a complementary manner. The synthetic refractories produced as described above are molded and fired products themselves that are highly corrosion-resistant synthetic refractories, and at the same time, the fired products are crushed to the required particle size and are used as raw materials for the highly corrosion-resistant parts of the synthetic refractories. It can also be used as a clay composition. A specific example will be explained below. Example 1 Table 1 shows the relationship between the mixing ratio of silicon, carbon, and aluminum and quality in the present invention. Code 1-4
To prepare the sample, mix the formulation shown in Table 1 in a high-speed Eirich mixer, add oil and
Standard bricks were molded using a press at a molding pressure of 880 kg/cm ² , embedded in coke, and fired at 1450°C for 10 hours. Subsequently, the fired bricks were pulverized to a particle size of 0.2 mm or less, phenolic resin was added and kneaded, and samples with a shape of 150 x 20 x 20 mm were molded at a molding pressure of 500 Kg/cm ² . This is heated to 1500℃ in coke.
A test sample was prepared by firing for 3 hours.

【table】

[Table] It is clear that the synthetic refractory of the present invention has extremely excellent corrosion resistance. Example 2 Table 2 shows the quality when amorphous carbon and crystalline carbon were used as carbon raw materials. The sample was manufactured according to the manufacturing method of Example 1.

[Table] It can be seen that there is a wide difference in corrosion resistance between amorphous carbon and crystalline carbon. Example 3 Table 3 shows the relationship between the firing atmosphere and the quality of the synthetic raw materials. The samples were prepared according to the manufacturing method of Example 1 except for the firing conditions, and the firing was performed according to Table 3.
The test was carried out under the conditions shown below.

[Table] Example 4 Table 4 shows the change in the low porosity of the synthetic raw material by the impregnation method using coal pitch as an impregnating agent after forming 15, after calcination 16, and both after forming and calcination 17.

【table】

[Table] Impregnation treatment is effective in reducing the porosity of synthetic raw materials. Example 5 Table 5 shows the quality of plate bricks for sliding nozzles using the synthetic refractory raw material of the present invention. The synthetic refractory raw materials used were mixed, molded, dried, reduced and fired at the compounding ratio shown in Example 1, and then pulverized to a particle size of 0.2 mm or less. It also shows the quality of the alumina-carbon and corundum plate bricks for sliding nozzles that are currently in common use.

【table】

[Table] The refractory bricks using the product of the present invention had excellent hot strength and corrosion resistance, and also showed high durability in practical results.

Claims (1)

[Scope of Claims] 1. A silicon-containing material fine powder (A) of 100 meshes or less (Tyler, the same shall apply hereinafter) containing 80% by weight or more as silicon, and 100 meshes or less of aluminum containing 80% by weight or more as aluminum. Containing material fine powder (B) and amorphous carbon fine powder of 100 mesh or less containing 80% by weight or more as carbon (C)
, A, B, and C are each 20 to 60% by weight and 10 to 50% by weight.
A mixture of 30 to 50% by weight and a total of 100% by weight is made, and a commonly used binder is added and mixed to form clay, which is fired in a non-oxidizing atmosphere. Highly corrosion-resistant synthetic refractories and refractory raw materials obtained by 2 Silicon-containing material fine powder (A) of 100 meshes or less (Tyler) containing 80% by weight or more of silicon and 100 meshes or less of aluminum-containing material fine powder (B) containing 80% or more of aluminum by weight ) and fine powder of amorphous carbon of 100 mesh or less containing 80% by weight or more of carbon (C)
, A, B, and C are each 20 to 60% by weight and 10 to 50% by weight.
A mixture of 30 to 50% by weight and a total of 100% by weight is made, and a commonly used binder is added to this mixture to form clay, which is then fired in a non-oxidizing atmosphere. Highly corrosion-resistant synthetic refractories and refractory raw materials obtained by adding a step of impregnating with a commonly used impregnating agent after forming or firing or both after forming and firing. 3. Claim 1, wherein the amorphous carbon fine powder C is carbon black with an average particle diameter of 50 mμ or less and a specific surface area of 50 m ² /g or more by N ₂ adsorption method.
Highly corrosion-resistant synthetic refractories and refractory raw materials according to paragraph 2 or paragraph 2.