JP5331077B2 - Carbon-containing refractories - Google Patents

Description

  The present invention relates to a carbon-containing refractory used in a blast furnace, a kneading wheel, a hot metal ladle, a converter, an electric furnace, a molten steel pan, a sliding nozzle, a nozzle for continuous casting, and the like.

  Since refractories used in iron making, steel making, etc. are used at high temperatures, alumina is used for the purpose of imparting thermal shock resistance by reducing the thermal expansion coefficient and elastic modulus, densifying the structure and preventing slag penetration. Carbon-containing refractories in which carbon is added to brick are widely used.

Further, Al ₄ O ₄ C, which is one of aluminum oxycarbides, is known as a material that has better corrosion resistance than alumina and has the same antioxidant effect as aluminum.

In Patent Document 1, by adding Al ₄ O ₄ C to carbon-containing brick, the oxidation of the carbonaceous material is prevented, the hot strength is improved, and the corrosion resistance is improved by preventing slag permeation. It has been reported to do. Patent Document 2 describes an example in which an Al ₄ O ₄ C-containing composition is applied as an aggregate, and as a result of application to a blast furnace tapping material, the corrosion resistance is improved and the life is 20-30. % Improvement is reported.

However, in Patent Document 1, Al ₄ O ₄ C is used instead of metal powder (sintered material), and since the amount of addition is limited, the effect of improving corrosion resistance due to the addition of Al ₄ O ₄ C is also limited. It is done. Moreover, since it is fine powder, the thermal expansion coefficient and the effect of reducing thermal stress are also low.

Patent Document 2 discloses that when carbon is added to Bayer method alumina and arc melting, Na ₂ O, which is an impurity causing deterioration in corrosion resistance, is greatly reduced, and Al ₄ O ₄ C which is difficult to wet with molten slag is formed. It is an invention based on the knowledge that it is produced, and the carbon content of the Al ₄ O ₄ C-containing composition is as small as 0.5 to 3.0 mass%. Carbon content of Al ₄ O ₄ C-containing composition is indicative of the _Al 4 _{O 4} C content of _Al 4 _{O 4} C-containing composition, when _Al 4 _{O 4} C is 100 wt%, Al _{Since the} carbon content of the ₄ O ₄ C-containing composition is C / Al ₄ O ₄ C = 6.5% by mass, the Al ₄ O ₄ C content is 0.5 to 3.0% by mass. There are few. For this reason, Patent Document 2 cannot provide sufficient effects due to Al ₄ O ₄ C such as reduction of thermal expansion coefficient (improvement of thermal shock resistance) and improvement of oxidation resistance and corrosion resistance.

Japanese Patent Laid-Open No. 9-295857 Japanese Patent Publication No.57-61708

  The problem to be solved by the present invention is to further improve the thermal shock resistance, oxidation resistance and corrosion resistance of the carbon-containing refractory.

Carbon-containing refractories according to the present invention is a carbon-containing refractories containing _Al 4 _{O 4} C below 95 wt% or more 15.5% by mass, the _Al 4 _{O 4} C is, the _Al 4 _{O 4} C The aluminum oxycarbide composition raw material is derived from a main component of the aluminum oxycarbide composition, and the aluminum oxycarbide composition raw material is a carbonaceous raw material and an alumina raw material, one or more of silicon carbide, boron carbide, aluminum nitride, boron nitride and metal. And is melted in an arc furnace, and contains 3.1% by mass to 6.5% by mass of carbon .

According to the present invention, by including Al ₄ O ₄ C in the carbon-containing refractory 15.5 mass% or more and 95 mass% or less, the thermal stress due to the reduction in the thermal expansion coefficient caused by Al ₄ O ₄ C. (Improvement of thermal shock resistance) and the effect of improving oxidation resistance and corrosion resistance are fully exhibited, thereby improving the durability of the carbon-containing refractory.

The carbon-containing refractory according to the present invention contains 15.5 mass% or more and 95 mass% or less of aluminum oxycarbide, especially Al ₄ O ₄ C.

  Here, the carbon-containing refractory generally refers to a refractory containing 0.5 to 30% by mass of a carbonaceous raw material. As a carbonaceous raw material, in addition to naturally occurring graphite, pitch, tar, anthracite, and the like, industrially produced resins such as carbon black, artificial graphite, phenol, furan, and epoxy can be used.

When the Al ₄ O ₄ C content is less than 15.5% by mass, the thermal shock resistance effect due to the effect of reducing the thermal expansion coefficient cannot be sufficiently obtained. In addition, sufficient effects cannot be obtained with respect to oxidation resistance and corrosion resistance. Incidentally, aluminum oxycarbide composition material containing _Al 4 _{O 4} C includes other _Al 4 _{O 4} C, which is a main component, generally _Al 2 OC and _{Al 2 O 3, Al 4 C} 3, impurities such as Al Therefore, even if the entire amount of the aluminum oxycarbide composition raw material containing Al ₄ O ₄ C is used as a raw material other than the carbonaceous raw material, the upper limit of the Al ₄ O ₄ C content is about 95% by mass.

In the present invention, as _Al 4 _{O 4} C source, to use the aluminum oxycarbide composition material mainly composed of _{Al 4 O} 4 C. As the aluminum oxycarbide composition raw material, one or more of silicon carbide, boron carbide, aluminum nitride, boron nitride and metal are added to the carbonaceous raw material and the alumina raw material in order to increase the carbon yield, and the arc to use those produced by melting in a furnace. In this case, silicon carbide, boron carbide, aluminum nitride, boron nitride, and metal are preferably added to the carbonaceous raw material and the alumina raw material, which are the main raw materials, in an amount of 0.2 to 10.0% by weight, Needs to have a higher oxygen affinity than carbon in a temperature range of 1000 ° C. or higher. In addition, the aluminum oxycarbide composition raw material is preferably a dense material having a low porosity in terms of corrosion resistance.

As the aluminum oxycarbide composition raw material, as proposed by the present applicant in PCT / JP2010 / 055554, the carbonaceous raw material fine powder and the alumina raw material fine powder are uniformly mixed and manufactured by melting in an arc furnace. However, it is difficult to industrially mass-produce with this manufacturing method. In order to increase the carbon yield even in an oxidizing atmosphere using an alumina raw material and a carbonaceous raw material as main raw materials, the present inventors include one of silicon carbide, boron carbide, aluminum nitride, boron nitride and metal as the main raw material. by adding more, it was found that the Al 4 _O 4 aluminum oxycarbide composition material _that the _C content does not contain little high and the Al ₄ C ₃ is capable mass production. In the present invention, to use an aluminum oxycarbide composition material manufactured by this manufacturing method.

The carbon content of the aluminum oxycarbide composition material is Ru der 6.5 mass% or more 3.1% by mass. The ideal carbon content of Al ₄ O ₄ C is 6.5% by mass. Also, if the carbon component of an aluminum oxycarbide composition in the raw material are all _{Al 4 O 4 C, Al 4} O 4 C content of the carbon content of 3.1 wt% of aluminum oxycarbide composition in the raw material is 46 It becomes mass%. When almost no free carbon such as carbide, oxycarbide composition, graphite or the like such as Al ₄ C ₃ or Al ₂ OC is contained, the higher the carbon content in the aluminum oxycarbide composition raw material, the greater the Al ₄ O ₄ C content. The content is large, and the thermal expansion coefficient of the raw material itself decreases. The thermal expansion coefficient of Al ₄ O ₄ C with an ideal composition is 4 × 10 ⁻⁶ , which is approximately half that of alumina (corundum). When the carbon content of the aluminum oxycarbide composition raw material is less than 3.1% by mass, not only the effect of reducing the thermal expansion coefficient is small and sufficient thermal shock resistance cannot be obtained, but also sufficient oxidation resistance. Moreover, the effect of corrosion resistance cannot be obtained. On the other hand, when it exceeds 6.5% by mass, since Al ₄ C ₃ exists, the raw material itself collapses due to a hydration reaction, so that application to a refractory is difficult.

In the present invention, the aluminum oxycarbide composition raw material is preferably contained as an aggregate having a particle size of at least 0.2 mm. When used as an aggregate in this manner, a microspace is formed due to a difference in thermal expansion coefficient from alumina or the like in the matrix. This microspace not only has the effect of reducing the elastic modulus of the refractory, but also has a high effect of reducing the coefficient of thermal expansion because it absorbs the expansion of the matrix at high temperatures. Furthermore, when used as an aggregate, Al ₂ O ₃ formation due to the reaction between Al ₄ O ₄ C and the carbon monoxide atmosphere in the matrix is less likely to occur during use at high temperatures, and for a long time, low thermal expansion The rate effect can be maintained.

  Hereinafter, the present invention will be described in detail with reference to examples.

The effect of the content of Al ₄ O ₄ C on the characteristics of the carbon-containing refractory was investigated.

The aluminum oxycarbide composition raw material used as the Al ₄ O ₄ C source was produced by the following method.

That is, as a starting material, calcined alumina (Al ₂ O ₃ component 99.9% by mass) and scaly graphite (C component 99% by mass) are weighed to a total of 500 kg, and metal Si is externally applied thereto. The aluminum oxycarbide composition was manufactured by slowly cooling as it was without being rapidly cooled such as pouring out and casting into a mold after melting in an arc furnace of 1000 KVA. .

The produced aluminum oxycarbide composition raw material has a carbon content of 5.6% by mass, and if all the carbon components are contained in Al ₄ O ₄ C, the calculated Al ₄ O ₄ C content is about 86% by mass. %. In addition, the carbon content of the aluminum oxycarbide composition raw material was a total carbon amount that is the sum of carbon described in JIS-R2205 and carbon in silicon carbide. That is, since Al ₄ O ₄ C ideally begins to oxidize at a temperature of 820 ° C. or higher, the carbon content is calculated from the sum of the carbon content in carbon measured at 900 ° C. and silicon carbide measured at 1350 ° C. Evaluated.

  A carbon-containing refractory was produced using the above aluminum oxycarbide composition raw material, and its characteristics were evaluated. Specifically, after mixing predetermined raw materials at a predetermined ratio, a phenol resin was added as a binder, kneaded, molded, and heated at a temperature of 300 ° C. to produce a carbon-containing refractory.

  The produced carbon-containing refractories were evaluated for bulk specific gravity, apparent porosity, bending strength, and thermal expansion coefficient by the methods described in JIS-R-2205, JIS-R-2213, and JIS-R-2207. .

For corrosion resistance, molten iron and iron oxide powder are melted using an induction furnace to produce a synthetic slag of CaO / Al ₂ O ₃ = 2 and the amount of erosion loss is determined by performing a test at 1600 ° C. for 2 hours in this synthetic slag. It was measured. And it was indexed by setting the amount of melting loss of Comparative Example 2 in Table 3 described later as 100. The smaller the value, the better the corrosion resistance.

  The oxidation resistance is evaluated by the so-called post-oxidation BS wear method, in which the sample is oxidized at 800 ° C. and shot blasted to evaluate the wear amount. did. The smaller the value, the better the oxidation resistance.

  Regarding thermal shock resistance, the cycle of water-cooling after immersing the sample in molten steel at 1600 ° C. for 3 minutes was repeated, and the quality was judged from the number of times until peeling off. Specifically, the evaluation was performed by the average number of times that the N = 2 sample was peeled off. The larger the value, the better the thermal shock resistance.

  The digestion resistance was evaluated by the pulverization rate according to the digestion test method for magnesia clinker according to Gakushin method 4.

In addition, the Al ₄ O ₄ C content of the carbon-containing refractory was analyzed by chemical component analysis because almost no mineral phases other than Al ₄ O ₄ C and Al ₂ O ₃ were detected in the evaluation by the X-ray diffraction method. Calculated based on the value. That is, the amount of Al ₄ O ₄ C was calculated from the C component on the assumption that all the C components in the chemical component analysis were Al ₄ O ₄ C. In addition, the calculation was performed assuming that portions other than Al ₄ O ₄ C were corundum.

Table 1 shows the amount of Al ₄ O ₄ C contained in the carbon-containing refractory by changing the blending amount and particle size distribution of the aluminum oxycarbide composition raw material (indicated as “AOC composition” in Tables 1 and 3). The result of having evaluated by changing 77.5 mass% is shown.

The aluminum oxycarbide composition raw material was replaced with sintered alumina from a coarse particle region having a particle size of 3-1 mm. Sintered alumina was 99.5% by mass of Al ₂ O ₃ component with a predetermined particle size, and scaly graphite was # 100 with a carbon content of 99% by mass.

In Examples 1 to 4 which are within the scope of the present invention, the Al ₄ O ₄ C content is changed in the range of 15.5 to 77.5% by mass, and the Al ₄ O ₄ C content is It can be seen that the greater the number, the lower the coefficient of thermal expansion and the better the corrosion resistance and oxidation resistance, both of which are superior to Comparative Example 1 which is outside the scope of the present invention. Furthermore, regarding thermal shock resistance, no clear correlation with the Al ₄ O ₄ C content is observed, but it can be seen that both are better than Comparative Example 1.

Table 2 shows an aluminum oxycarbide composition raw material (indicated as “AOC composition 1” in Table 2) manufactured by the arc melting method described above and an aluminum oxycarbide composition raw material (Table 2 manufactured by the sintering method). Then, the result of comparing the use of “AOC composition 2” is shown. In the above sintering method, calcined alumina (average particle size 1 μm, Al ₂ O ₃ content 99.9% by mass) and scaly graphite (average particle size 5 μm, carbon content 99.5%) are mixed with alumina. After mixing at a carbon molar ratio of 1.5 (Al ₂ O ₃ / C), firing in an electric furnace under an Ar gas atmosphere at 1850 ° C. to produce about 100 g of an aluminum oxycarbide composition raw material, Repeatedly, a test sample to be added to the refractory was obtained. The aluminum oxycarbide composition raw material produced by the sintering method has a carbon content of 5.6% by mass and a high Al ₄ O ₄ C content, but it can be produced only as a powder.

In Reference Example 6, an aluminum oxycarbide composition raw material produced by a sintering method was added at a particle size of 0.074-0 mm, and an aluminum oxycarbide composition raw material of the same particle size produced by an arc melting method was applied. Example 5 and its effect were evaluated.

Example 5 is superior in oxidation resistance and corrosion resistance compared to Reference Example 6, and it can be seen that the aluminum oxycarbide composition raw material by the arc melting method is more effective.

  Table 3 shows the results of investigating the influence of the particle size of the aluminum oxycarbide composition raw material used.

In Examples 1, 7 to 9, and 5, the aluminum oxycarbide composition produced by the arc melting method was added by 18% by mass, the content of Al ₄ O ₄ C was constant at 15.5% by mass, and the particle size was The effect was compared in the range of 3-1 mm to 0.074 mm-0. As a result, the coarser the particle size, the higher the effect of reducing the coefficient of thermal expansion, and the better the corrosion resistance and thermal shock resistance. On the other hand, the smaller the particle size, the better the oxidation resistance. Even if it adds with any particle size, compared with the additive-free Comparative Examples 1 and 2, it is excellent in oxidation resistance and corrosion resistance, and the effect more than equivalent is obtained also in thermal shock resistance.

However, regarding the effect of thermal shock resistance due to the low coefficient of thermal expansion, which is a characteristic of Al ₄ O ₄ C, Examples 1, 7, and 8 using aggregates of 0.2 mm or more were used as finer powders. It is better to use as an aggregate of 0.2 mm or more.

Claims (2)

A carbon-containing refractory containing 15.5% by mass to 95% by mass of Al ₄ O ₄ C ,
The Al ₄ O ₄ C is derived from an aluminum oxycarbide composition raw material containing Al ₄ O ₄ C as a main component, and the aluminum oxycarbide composition raw material includes carbon carbide, carbonized carbonaceous raw material and alumina raw material. A carbon-containing refractory material produced by adding one or more of boron, aluminum nitride, boron nitride and metal and melting in an arc furnace, and containing 3.1% by mass to 6.5% by mass of carbon object. The carbon-containing refractory according to claim 1 , wherein the aluminum oxycarbide composition raw material is contained as an aggregate having a particle size of at least 0.2 mm.