KR100239940B1 - method for manufacturing refractories material having SiC - Google Patents

Abstract

The present invention relates to a method for producing silicon carbide (SiC) refractory material having high strength properties, the configuration is 65 to 90% by weight of alpha-type silicon carbide (α-SiC), 5 to 25% by weight of silicon (Si), 5-10% by weight of aluminum (Al) and resin as a binder are kneaded, aged, and calcined at 1200 to 1500 ° C for 3 to 50 hours in an atmosphere where carbon monoxide (CO) and nitrogen (N ₂ ) coexist after molding. It is a technique regarding the manufacturing method of the silicon carbide refractory material.

Description

Method for manufacturing refractories material having SiC}

The present invention relates to a method for producing a silicon carbide (SiC) -quality refractory material, and more specifically, by mixing and reacting alpha-type silicon carbide (α-SiC) and sialon-producing raw materials, high strength, oxidation resistance and corrosion resistance to molten metal It's about improving.

Silicon carbide refractories have excellent thermal shock resistance, corrosion resistance, hot strength, abrasion resistance, thermal conductivity, etc. have.

In a conventional method for producing a silicon carbide refractory material, carbon (C) is added to a mixed bed (Bed) to react with metal silicon (Si) during firing to obtain beta-type silicon carbide (β-SiC).

Such a conventional method is difficult because of the long kneading time to prevent this due to local carbon density when kneading due to the addition of fine carbon and the reaction of the solid with the low Gibbs Free Energy state In order to produce beta silicon carbide by atomic diffusion, the firing temperature must be high. In this case, most beta silicon carbides generate local weak points due to the interfacial reaction between silicon and carbon.

Therefore, compressive strength and hot strength are not good.

In addition, carbonization reaction occurs at high temperature (above 1450 ℃) and beta silicon carbide is produced before melting beta silicon carbide (about 1400 ℃ or less) according to the temperature control, and then the temperature is raised again (about 1430 ℃) and maintained for a long time. It was necessary to grow the beta silicon carbide mat (Matte) in the matrix (Matte) to the strength characteristics because the temperature control and rise and the process was complicated.

In addition, due to the increase in the amount of the binder due to the binder and the small wettability carbon, there is also a difficulty in the process such as the change in the bed (Bed) is increased.

As a part of improving the above problems, the present applicant does not add carbon (C) and mixes alpha-type silicon carbide (α-SiC) and metal silicon (Si) in a CO gas atmosphere and a low firing temperature (1350 to 1420 ° C). Korean Patent Publication No. 91-1363 has been proposed for the silicon carbide refractory material which has been calcined at, but it has high porosity (12.6 ~ 14.5%), bending strength (kg / ㎠) and 560 ~ 620, hot bending strength (kg / Cm 2) 480 to 505, which do not provide sufficient characteristics.

On the other hand, a method for producing a ceramic sintered material based on sialon is known from Japanese Patent Laid-Open No. 59-69476.

It reacts during sintering to produce sialon (formula: Si _6-Z Al _Z O _Z N _8-Z ) and a raw material (Si ₃ N ₄ , Al ₂ O ₃ , SiO ₂ , AlN) and a sintering aid (Y ₂ O ₃ , MgO, CeO ₂ , ZrO ₂ ) and carbon powder were mixed and sintered at a nitrogen atmosphere and 1600-1800 ° C. to obtain a sintered material.

However, since the sialon complex method uses various oxides as starting materials, the reaction takes place at a high sintering temperature, and when the sialon is formed, the fiber diameter is large, the amount of fiber is generated, and the composition of the atmosphere gas is reduced. The amount taken into the fireproofing tissue is also small.

Therefore, after generating the sialon based on the temperature control, the temperature must be raised again and sintered for a long time so that the strength is expressed, which involves a complicated process including energy consumption.

In addition, the expressed flexural strength (kg / ㎠) is not an excellent characteristic as the average of about 850.

The present invention has been made in order to solve the above-mentioned problems, and the mixture is calcined by mixing the alpha-type silicon carbide (α-SiC) and the sialon-generating material, but is suitably blended with the sialon-generating material as a metal element rather than an oxide. In addition, the firing is carried out in an atmosphere in which carbon monoxide (CO) and nitrogen (N ₂ ) coexist to provide a silicon carbide refractory material having low porosity and improved strength.

1 is a micrograph showing a microstructure according to the present invention

The present invention for achieving the above object is kneading the resin system as a binder with 65 to 90% by weight of alpha-type silicon carbide (α-SiC), 5 to 25% by weight of metal silicon (Si), 5 to 10% by weight of metal aluminum (Al) After molding, the method is a method for producing a silicon carbide refractory material, characterized in that the carbon monoxide (CO) and the nitrogen (N ₂ ) is fired at a temperature of 1200 to 1500 ℃ and 3 to 50 hours in the coexistence atmosphere.

In the numerical limits of each composition, its composition ratio, and firing conditions (temperature, time), since they have mutually organic bonding relationships, they cannot be discussed solely for individual individual compositions. Is more than 90% by weight, more than 25% by weight of metal silicon (Si), or more than 10% by weight of metal aluminum (Al), the strength decrease due to the excess matrix (Matrix) and the distribution ratio of large particles and small particles is not good Physical properties are degraded.

The CO gas and N ₂ gas provided in the minor atmosphere react with metal silicon (Si) and metal aluminum (Al) to form beta silicon carbide (β-SiC) and sialon, which is a whisker between particles and in pores. As it is produced in the form of fiber, it is possible to obtain high density sintered body even if the firing temperature is lower than the method of adding oxide or nitride or producing large amount of sialon, and the amount of whisker generated is well dispersed and well dispersed. It exhibits superior strength properties than any method.

When the firing temperature is lower than 1200 ℃ or higher than 1500 ℃, high density sintered body according to whiskers or fibers cannot be obtained. When the firing time is lower than 3 hours or higher than 50 hours, small amounts of beta silicon carbide are produced or destroyed, and the sialon complex effect It was small and not only did not develop microstructure, but also had low strength characteristics.

In addition, the particle size of the metal silicon is 10 μm or less, and the aluminum particles are used in a large fiber phase having a ratio of 5 to 500 times the ratio of the length and the particle diameter and the size of the particle diameter of 10 μm to 500 μm.

When starting materials are used, whiskers are developed on the basis of aluminum fibers used as starting materials for the production of sialon, which does not generate sialon by interdiffusion of existing oxides or nitrides. Dense tissue can be obtained by generating a large amount of whiskers in the form of a large amount of whiskers at the place of the aluminum fiber used as a starting material due to the penetration of CO) and nitrogen (N ₂ ) gas.

In the case of beta silicon carbide is also produced by the same effect as the present inventors domestic patent publication No. 91-1363.

The whiskers of sialon and beta silicon carbide thus produced are well connected to the particles and serve as a cause of showing a much higher strength value than the conventional methods.

The following is described according to the embodiment.

Example 1

The raw materials are blended according to the compounding table as shown in Table 1, and then aged and naturally dried at room temperature after pressure kneading.

The naturally dried molded body is then dried again at 150 ° C.

The dried compacts are calcined for 3 to 50 hours at 1200-1500 ° C. in a Tunnel Kiln furnace to complete the firing while encouraging an atmosphere in which CO gas and nitrogen gas can be generated.

Raw material blending ratio: wtsilicon carbide 80wt%, metal silicon 15wt%, metal aluminum 5wt%

└ 1-10 wt% binder added (weight ratio of the whole)

Particle Size Distribution ┌Metal Silicon 10㎛

└Total particle size distribution 1mm or more 40wt%, 1-0.297mm 30wt%, 0.297 or less 30wt%

Firing condition: ┌Temperature 1395 ± 20 ℃

└Time: 20 ± 10 Hours

Physical properties shown in accordance with the embodiment of the above conditions are as shown in Table 2, the bending strength is 1300㎏ / ㎠, hot bending strength 1400㎏ / ㎠, the compressive strength is 4500㎏ / ㎠ as the conventional invention including the comparative invention (sample 5-7) It has excellent physical properties compared to the invention (Sample 8-10).

In the prior invention, Sample 8-9 is Korean Patent Publication No. 91-1363, and Sample 10 is Japanese Laid-Open Patent Publication No. 59-69476.

Example 2

It carried out under the conditions as shown in Table 1.

Raw material mixture ratio: silicon carbide 75wt%, metal silicon 20wt%, metal aluminum 5wt%

└1-10 wt% external addition (binder weight ratio of silicon carbide to metal silicon)

Particle Size Distribution ┌ Metal Silicon 10㎛

└Total particle size distribution 1mm or more 45wt%, 1-0.297mm 25wt%, 0.297 or less 35wt%

Firing Conditions ┌Temperature 1420 ± 20 ℃

└Time 20 ± 10 Hours

As shown in Table 2, the physical properties shown in the above conditions were superior to the prior art as bending strength 1200 kg / cm 2, hot bending strength 1100 kg / cm 2 and compressive strength 3800 kg / cm 2.

Porosity was also 12% or more in the case of the prior art, 5-10% was excellent in the present invention (Fig. 1 is a micrograph showing the microstructure accordingly).

Examples 3 and 4

It was set as the raw material mixture ratio of Table 1, and other conditions were made the same as Example 1.

As a result, physical properties as shown in Table 2 were obtained.

This embodiment also obtained excellent properties compared to the prior art.

As described above, in the present invention, the structure is dense and the whisker due to the gas phase reaction is large by using Al as the metal aluminum and Si (O) and nitrogen (N) as the atmosphere gas when generating the sialon. Compared with the previous technology using oxides and nitrides, the strength characteristics and the dense structure were greatly improved.

In Table 1, the case of producing sialon by using alumina (oxide) was tested by comparison. As shown in Table 2, the properties were superior to those of the prior art, but the physical properties such as strength were higher than those of metal aluminum. Appeared low.

It is considered that the cause superior to the conventional invention is the effect of Patent Publication No. 91-1363, which was invented by the inventor, and the cause of lower characteristics than the case of using metal aluminum is the oxygen (O) site of sialon. Is not effective in densification because oxygen of alumina (Al ₂ O ₃ ) is used instead of oxygen, where C of CO is the C-site of beta silicon carbide production. This is because

TABLE 1

Example Comparative example Conventional One 2 3 4 5 6 7 8 9 10 Volume specific gravity 2.76 2.77 2.72 2.75 2.67 2.74 2.69 2.69 2.75 Porosity (%) 5.7 7.8 7.2 9.8 10.9 12.5 11.2 13.9 13.7 Bending strength (㎏ / ㎠) 1300 1200 1020 940 850 580 810 600 580 800 Hot bending strength (㎏ / ㎠) 1400 1100 1025 930 910 560 780 500 500 Compressive strength (㎏ / ㎠) 4500 3800 3600 3150 3200 2200 2980

As described above, according to the present invention, carbon monoxide (CO) and nitrogen (N ₂ ) are mixed with the alpha-silicon carbide (α-SiC) with the appropriate combination of metal silicon (Si) and metal aluminum (Al), which are sialon synthetic materials. In the coexistence atmosphere, the gas (CO, N ₂ ) component infiltrates into the fired body during the firing process, increases the density, and increases the amount of whisker generated by the gas phase reaction, thereby obtaining a sintered body having high strength characteristics.

Claims (2)

65 to 90% by weight of alpha-type silicon carbide (α-SiC), 5 to 25% by weight of silicon (Si), 5 to 10% by weight of aluminum (Al) and a known resin as a binder are aged and aged to form carbon monoxide (CO) ) And a calcination treatment at 1200 to 1500 ° C. for 3 to 50 hours in an atmosphere where nitrogen and N 2 coexist. The method of claim 1, A method for producing silicon carbide refractory material, characterized in that the particle size of silicon (Si) is 10 µm or less, and the aluminum (Al) particle size is a fraction of 5 to 500 times the ratio of length and particle diameter.

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