A mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, its preparation method and application

Abstract

The application belongs to the technical field of refractory materials, and particularly relates to a mullite-whisker-reinforced alumina-silicon carbide-carbon unfired refractory material as well as a preparation method and application thereof. In the application, corundum or bauxite, silicon carbide, calcium aluminate cement, spherical pitch, silicon powder, aluminum powder and a catalyst are fully mixed and uniformly distributed, gamma-alumina and silicon dioxide are additionally added as raw materials of mullite whiskers, and due to the effect of the catalyst, the mullite whiskers can be catalytically grown in situ in the unfired refractory material matrix and pores at a high-temperature service temperature, so that the mechanical properties and oxidation resistance of the unfired refractory material can be significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, its preparation method, and its application. Background Technology

[0002] Silicon carbide and carbon possess excellent resistance to slag erosion and thermal conductivity. Adding silicon carbide and carbon to alumina-based non-burned refractories can significantly enhance their slag corrosion resistance and thermal shock stability. Therefore, alumina-silicon carbide-carbon non-burned refractories are widely used in blast furnace tapping troughs. However, as blast furnace volumes increase, tapping temperatures, tapping times, and molten iron flow rates also increase, intensifying the oxidation of carbon-containing refractories. Oxidation of carbon-containing refractories reduces their performance and significantly shortens their service life.

[0003] It has been reported that whiskers can improve the mechanical properties and high-temperature oxidation resistance of refractory materials. For example, patent CN116751033A discloses a silicon carbide whisker-reinforced magnesium oxide-alumina-carbon non-fired refractory material, its preparation method, and its application. Using silicon powder and graphite powder as raw materials for silicon carbide whisker preparation, in-situ growth of silicon carbide whiskers in non-fired refractory materials is achieved under the action of a metal catalyst, significantly enhancing the mechanical properties and high-temperature oxidation resistance of the refractory material. Patent CN112811917A discloses a whisker-reinforced lightweight alumina-carbon refractory material and its preparation method. Using elemental silicon powder, carbon powder, and modified thermosetting phenolic resin as whisker growth raw materials, in-situ growth of silicon carbide whiskers and carbon nanotubes is achieved under the action of a catalyst, improving the strength and oxidation resistance of the refractory material. However, these whiskers themselves are carbides, which are continuously consumed during high-temperature oxidation, offering limited improvement to the oxidation resistance of the refractory material. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, its preparation method and application. The mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by the present invention has excellent mechanical properties and oxidation resistance.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, comprising the following raw materials by mass percentage:

[0007] Corundum and / or bauxite 63-69%,

[0008] Silicon carbide 17-23%,

[0009] Spherical asphalt: 1.7–2.3%

[0010] Calcium aluminate cement: 0.7-1.3%

[0011] γ-alumina 4-10%,

[0012] Aluminum powder 0.2-0.8%,

[0013] Silicon powder 0.2-0.8%,

[0014] 2.7-3.3% silica and 0.1-6% catalyst;

[0015] The carbon content of the spherical asphalt is 40-80%.

[0016] Preferably, the alumina content in the corundum and bauxite is independently ≥40% by mass; and the alumina content in the calcium aluminate cement is ≥70% by mass.

[0017] Preferably, the catalyst is aluminum fluoride.

[0018] Preferably, the particle size of the corundum and bauxite is ≤8mm.

[0019] The particle size of the silicon carbide is ≤1mm;

[0020] The particle size of the spherical asphalt is ≤0.2mm;

[0021] The particle size of the calcium aluminate cement is ≤100nm;

[0022] The particle size of the γ-alumina is ≤0.1mm;

[0023] The aluminum powder has a particle size ≤ 0.1 mm;

[0024] The particle size of the silicon powder is ≤0.1mm;

[0025] The particle size of the silica is ≤100μm;

[0026] The particle size of the catalyst is ≤500nm.

[0027] This invention also provides a method for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material described in the above technical solution, comprising the following steps:

[0028] The raw materials are mixed with water, and the resulting mixture is placed in a mold and vibrated to form a preform.

[0029] The molded blank is sequentially cured, dried and heat-exchanged to obtain a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material.

[0030] The heat source for the heat exchange comes from the temperature at which the molten iron taps out of the furnace.

[0031] Preferably, the mass of the water is 2-8% of the mass of the raw materials used in the preparation.

[0032] Preferably, the vibration molding frequency is 2000-3000 times / min; the vibration molding time is 30-40 minutes.

[0033] Preferably, the curing temperature is 30–60°C; the curing humidity is 40–70%; and the curing time is 12–24 hours.

[0034] Preferably, the drying temperature is 120–200°C; and the drying time is 12–24 hours.

[0035] The present invention also provides the application of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material described in the above technical solution or the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared by the preparation method described in the above technical solution as a refractory material in metallurgy.

[0036] This invention provides a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, comprising, by mass percentage: 63-69% corundum and / or bauxite, 17-23% silicon carbide, 1.7-2.3% spherical pitch, 0.7-1.3% calcium aluminate cement, 4-10% γ-alumina, 0.2-0.8% aluminum powder, 0.2-0.8% silica powder, 2.7-3.3% silica, and 0.1-6% catalyst; wherein the carbon content of the spherical pitch is 40-80%.

[0037] This invention involves thoroughly mixing corundum or bauxite, silicon carbide, calcium aluminate cement, spherical asphalt, silica powder, aluminum powder, and a catalyst. γ-alumina and silica are additionally added as raw materials for mullite whiskers. Under the action of the catalyst, γ-alumina and silica form mullite whiskers on the surface of the molten catalyst spheres. The mullite whiskers grow in situ within the refractory matrix and pores using a VS (gas-solid) growth mechanism. Compared to mullite grains, mullite whiskers have a larger specific surface area, providing better encapsulation within the alumina-silicon carbide-carbon non-fired refractories and better protection of other easily oxidized substances within the alumina-silicon carbide-carbon non-fired refractories during oxidation. The prepared mullite whiskers also possess the characteristics of whiskers themselves, not only improving the oxidation resistance of the alumina-silicon carbide-carbon non-fired refractories but also enhancing their mechanical properties. Moreover, the raw materials used in this invention are widely available and inexpensive, and the preparation method is simple, highly reproducible, and has a short production cycle, making it suitable for industrial production.

[0038] The preparation method provided by this invention enables the large-scale preparation of alumina-silicon carbide-carbon non-fired refractories reinforced with in-situ growth of mullite whiskers by controlling the proportion of raw materials. Furthermore, by controlling the particle size of the catalyst, this invention achieves in-situ growth of mullite whiskers within the matrix and pores of the alumina-silicon carbide-carbon non-fired refractories, with controllable diameter, while simultaneously improving the mechanical properties and high-temperature oxidation resistance of the alumina-silicon carbide-carbon non-fired refractories. Attached Figure Description

[0039] Figure 1 SEM image of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 1;

[0040] Figure 2 EDS (line scan) image of mullite whiskers inside the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 1.

[0041] Figure 3 The image shows the XRD pattern of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 1.

[0042] Figure 4 SEM image of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 2;

[0043] Figure 5 SEM image of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 3;

[0044] Figure 6 SEM image of the alumina-silicon carbide-carbon non-fired refractory material prepared in Comparative Example 1. Detailed Implementation

[0045] This invention provides a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, comprising the following raw materials by mass percentage:

[0046] Corundum and / or bauxite 63-69%,

[0047] Silicon carbide 17-23%,

[0048] Spherical asphalt: 1.7–2.3%

[0049] Calcium aluminate cement: 0.7-1.3%

[0050] γ-alumina 4-10%,

[0051] Aluminum powder 0.2-0.8%,

[0052] Silicon powder 0.2-0.8%,

[0053] 2.7-3.3% silica and 0.1-6% catalyst;

[0054] The carbon content of the spherical asphalt is 40-60%.

[0055] Unless otherwise specified, the present invention does not have special requirements on the source of the raw materials used in the preparation, and commercially available products well known to those skilled in the art can be used.

[0056] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by the present invention include corundum and / or bauxite with a mass percentage of 63-69%, more preferably 64-68%, and most preferably 65-67%.

[0057] In this invention, the corundum and / or bauxite is preferably corundum; the corundum is preferably brown corundum; the bauxite is preferably high-alumina bauxite; the mass percentage of alumina in the corundum and bauxite is independently preferably ≥40%, more preferably ≥80%, and most preferably ≥96%; the particle size of the corundum and bauxite is independently preferably ≤8mm; the particle size of the brown corundum is preferably 5-8mm, 3-5mm, 1-3mm, and 0-1mm.

[0058] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by this invention include silicon carbide with a mass percentage of 17-23%, more preferably 18-22%, and most preferably 19-21%. In this invention, the particle size of the silicon carbide is preferably ≤1 mm, more preferably 0.05-1 mm, and most preferably 0.1-1 mm; the purity of the silicon carbide is preferably ≥90%, more preferably 95-99%, and most preferably 99%.

[0059] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by this invention include spherical asphalt with a mass percentage of 1.7-2.3%, more preferably 1.8-2.2%, and most preferably 1.9-2.1%. In this invention, the carbon content of the spherical asphalt is preferably 40-80%, more preferably 40-70%, and most preferably 40-60%; the particle size of the spherical asphalt is preferably ≤0.2 mm, more preferably 0.05-0.2 mm, and most preferably 0.1-0.2 mm; the purity of the spherical asphalt is preferably 50-90%, more preferably 60-90%, and most preferably 70-90%.

[0060] The spherical asphalt used in this invention has a higher bulk density and a smaller surface area compared to other forms of asphalt. It is less prone to agglomeration during use and can be uniformly dispersed in other materials.

[0061] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by this invention include calcium aluminate cement with a mass percentage of 0.7-1.3%, more preferably 0.8-1.2%, and most preferably 0.9-1.1%. In this invention, the particle size of the calcium aluminate cement is preferably ≤100 nm, more preferably 10-100 nm, and most preferably 20-100 nm; the mass percentage of alumina in the calcium aluminate cement is preferably ≥70%, more preferably ≥90%, and most preferably ≥96%.

[0062] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by this invention include 4-10% γ-alumina by mass, more preferably 5-9%, and most preferably 6-8%. In this invention, the particle size of the γ-alumina is preferably ≤0.1 mm, more preferably 0.01-0.1 mm, and most preferably 0.05-0.1 mm; the purity of the γ-alumina is preferably 95-99%, more preferably 96-99%, and most preferably 99%.

[0063] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by this invention include aluminum powder with a mass percentage of 0.2-0.8%, more preferably 0.3-0.7%, and most preferably 0.4-0.6%. In this invention, the particle size of the aluminum powder is preferably ≤0.1 mm, more preferably 0.01-0.1 mm, and most preferably 0.05-0.1 mm; the purity of the aluminum powder is preferably 95-99%, more preferably 98-99%, and most preferably 99%.

[0064] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by this invention include silicon powder with a mass percentage of 0.2-0.8%, more preferably 0.3-0.7%, and most preferably 0.4-0.6%. In this invention, the particle size of the silicon powder is preferably ≤0.1 mm, more preferably 0.01-0.1 mm, and most preferably 0.05-0.1 mm; the purity of the silicon powder is preferably ≥99%, more preferably 99-99.9%, and most preferably 99%.

[0065] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by this invention include silicon dioxide with a mass percentage of 2.7-3.3%, more preferably 2.8-3.2%, and most preferably 2.9-3.1%. In this invention, the particle size of the silicon dioxide is preferably ≤100 μm, more preferably 20-100 μm, and most preferably 50-100 μm; the purity of the silicon dioxide is preferably 95-99%, more preferably 96-99%, and most preferably 99%.

[0066] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material provided by this invention include a catalyst with a mass percentage of 0.1-6%, more preferably 1-5%, and most preferably 2-4%. In this invention, the catalyst is preferably aluminum fluoride; the particle size of the catalyst is preferably ≤500 nm; the particle size of the aluminum fluoride is preferably 0-10 nm, 10-100 nm, and 100-500 nm; the purity of the aluminum fluoride is preferably ≥98%, more preferably 98-99%, and most preferably 99%.

[0067] Refractory materials consist of two parts: granular material (particle size greater than 1 mm) and matrix fine powder (less than 1 mm). The matrix is ​​the weakest part of the refractory material and is most easily damaged during use. Therefore, improving the performance of refractory materials usually focuses on reinforcing the matrix. This invention thoroughly mixes corundum or bauxite, silicon carbide, calcium aluminate cement, spherical asphalt, silica powder, aluminum powder, and a catalyst. γ-alumina and silica are additionally added as raw materials for mullite whiskers. Under the action of the catalyst, mullite whiskers grow in situ within the refractory matrix and pores via a VS (gas-solid) growth mechanism. Specifically, the growth mechanism of mullite whiskers involves AlF3 transforming into a gaseous phase at high temperatures and reacting with SiO2 and Al2O3 respectively to generate SiF4 and AlOF. Subsequently, SiF4 and AlOF further react to form Al2O3-SiO2 (mullite). During the reaction, AlF3 can lower the surface formation energy of SiO2 and Al2O3, causing them to preferentially grow along the c-axis, forming mullite whiskers. The reaction equation is shown below:

[0068] 6AlF3 + 3O2 → 6AlOF + 12F (1)

[0069] Al₂O₃ + 2F → 2AlOF + 0.5O₂ (2)

[0070] 2SiO2 + 8F → 2SiF4 + 2O2 (3)

[0071] 6AlOF+2SiF4+3.5O2→3Al2O3·2SiO2+14F (4).

[0072] Compared to mullite grains, mullite whiskers have a larger specific surface area, resulting in better encapsulation within the alumina-silicon carbide-carbon non-fired refractories. This provides better protection for other easily oxidized substances within the alumina-silicon carbide-carbon non-fired refractories during oxidation. The prepared mullite whiskers also possess the characteristics of whiskers themselves, not only improving the oxidation resistance of the alumina-silicon carbide-carbon non-fired refractories but also enhancing their mechanical properties. Furthermore, the raw materials used in this invention are widely available and inexpensive, and the preparation method is simple, reproducible, and has a short production cycle, making it suitable for industrial production.

[0073] This invention also provides a method for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material described in the above technical solution, comprising the following steps:

[0074] The raw materials are mixed with water, and the resulting mixture is placed in a mold and vibrated to form a preform.

[0075] The molded blank is sequentially cured, dried and heat-exchanged to obtain a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material.

[0076] The heat source for the heat exchange comes from the temperature at which the molten iron taps out of the furnace.

[0077] The present invention involves mixing the raw materials and water, placing the resulting mixture in a mold, and vibrating it to form a molded blank.

[0078] In this invention, the mass of the water is preferably 2-8% of the mass of the raw materials, more preferably 3-6%, and most preferably 4%; the mixing is preferably carried out under stirring conditions; the stirring speed is preferably 100-300 rpm, more preferably 200 rpm; the mixing time is preferably 20-40 min, more preferably 30-40 min, and most preferably 30 min.

[0079] Before mixing with water, the present invention preferably dry-mixes the raw materials; the dry-mixing time is preferably 60-120 min, more preferably 60-100 min, and most preferably 80 min.

[0080] The present invention does not impose any special limitation on the size of the mold; it can be determined according to actual production needs.

[0081] In this invention, the frequency of vibration molding is preferably 2000-3000 times / min, more preferably 2500-2800 times / min, and most preferably 2600 times / min; the vibration molding time is preferably 30-40 minutes, more preferably 30-35 minutes, and most preferably 30 minutes.

[0082] After obtaining the shaped blank, the present invention sequentially cures, dries and heat-exchanges the shaped blank to obtain a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material.

[0083] In this invention, the curing temperature is 30-60°C, more preferably 30-50°C, and most preferably 40°C; the curing humidity is preferably 40-70%, more preferably 50-60%, and most preferably 55%; the curing time is preferably 12-24 hours, more preferably 18-20 hours, and most preferably 20 hours.

[0084] In this invention, the drying temperature is preferably 120-200°C, more preferably 130-180°C, and most preferably 140°C; the drying time is preferably 12-24 hours, more preferably 15-20 hours, and most preferably 16 hours.

[0085] After drying, the present invention preferably further includes demolding the dried molded blank. The present invention does not have any particular limitation on the demolding process; any demolding process well known in the art can be used.

[0086] In this invention, the heat source for the heat exchange comes from the tapping temperature of the molten iron; in an embodiment of this invention, the heat exchange specifically involves sintering with carbon buried in a muffle furnace for 3 hours at a simulated tapping temperature of 1450°C.

[0087] The diameter of the mullite whiskers in the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material is preferably 50-1200 nm, more preferably 500-1200 nm.

[0088] The preparation method provided by this invention achieves the large-scale preparation of in-situ grown mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractories by controlling the raw material ratio. During high-temperature use, under the action of a catalyst, mullite whiskers grow in large quantities in-situ within the alumina-silicon carbide-carbon non-fired refractories matrix and pores via a VS (gas-solid) growth mechanism. By controlling the particle size of the catalyst, the in-situ growth of mullite whiskers within the alumina-silicon carbide-carbon non-fired refractories matrix and pores is achieved with controllable diameter, while simultaneously improving the mechanical properties and high-temperature oxidation resistance of the alumina-silicon carbide-carbon non-fired refractories.

[0089] The present invention also provides the application of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material described in the above technical solution or the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared by the preparation method described in the above technical solution as a refractory material in metallurgy.

[0090] In this invention, the metallurgy is preferably iron smelting.

[0091] The present invention does not impose any particular limitation on the application of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material in ironmaking; any application method known in the art can be used.

[0092] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0093] In the following examples, the particle sizes of brown fused alumina are 0–1 mm, 1–3 mm, 3–5 mm, and 5–8 mm, and the alumina content in brown fused alumina is 96%; the particle size of silicon carbide is 1 mm, and the purity is 99%; the particle size of spherical asphalt is 0.2 mm, the purity is 70%, and the carbon content is 40%; the particle size of calcium aluminate cement is 50 nm, and the alumina content in calcium aluminate cement is 96%; the particle size of γ-alumina is 0.074 mm, and the purity is 99%; the particle size of aluminum powder is 0.074 mm, and the purity is 99%; the particle size of silicon powder is 0.074 mm, and the purity is 99%; the particle sizes of aluminum fluoride are 0–10 nm, 10–100 nm, and 100–500 nm, and the purity is 99%; and the particle size of silica is 50 μm, and the purity is 99%.

[0094] Example 1

[0095] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, by mass percentage, are: 63% brown corundum, 20% silicon carbide, 2% spherical asphalt, 1% calcium aluminate cement, 7% γ-alumina, 0.5% aluminum powder, 0.5% silicon powder, 3% silicon dioxide, and 3% aluminum fluoride with a particle size of 100-500 nm. The average diameter of the synthesized mullite whiskers is 1200 nm.

[0096] The preparation steps are as follows:

[0097] The raw materials were dry-mixed in a mixer for 80 minutes according to the specified ratio. Then, 4 wt.% water was added to the mixture and stirred at 200 rpm for 30 minutes. The mixture was then poured into a 40 mm × 40 mm × 160 mm mold. The mold was placed on a vibrating table and vibrated at a frequency of 2600 times / min for 30 minutes to form the shape. The resulting green body was cured at 40°C and 55% humidity for 20 hours and then dried in an oven at 140°C for 16 hours. After demolding, the green body was sintered in a muffle furnace at a simulated molten iron tapping temperature of 1450°C for 3 hours to obtain a mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material.

[0098] Example 2

[0099] The only difference from Example 1 is:

[0100] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, by mass percentage, are: 63% brown corundum, 20% silicon carbide, 2% spherical asphalt, 1% calcium aluminate cement, 7% γ-alumina, 0.5% aluminum powder, 0.5% silicon powder, 3% silicon dioxide, and 3% aluminum fluoride with a particle size of 10-100 nm. The average diameter of the synthesized mullite whiskers is 800 nm.

[0101] Example 3

[0102] The only difference from Example 1 is:

[0103] The raw materials for preparing the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material, by mass percentage, are: 63% brown corundum, 20% silicon carbide, 2% spherical asphalt, 1% calcium aluminate cement, 7% γ-alumina, 0.5% aluminum powder, 0.5% silicon powder, 3% silicon dioxide, and 3% aluminum fluoride with a particle size of 0-10 nm. The average diameter of the synthesized mullite whiskers is 50 nm.

[0104] Comparative Example 1

[0105] The difference from Example 1 is as follows:

[0106] The raw materials prepared by mass percentage are: 66% brown corundum, 20% silicon carbide, 2% spherical asphalt, 1% calcium aluminate cement, 7% γ-alumina, 0.5% aluminum powder, 0.5% silica powder and 3% silicon dioxide. The synthesized material does not contain mullite whiskers.

[0107] Performance testing

[0108] (1) Figure 1 The image shows a SEM image of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 1.

[0109] Depend on Figure 1 It is known that when aluminum fluoride with a particle size of 100-500 nm is used as a catalyst, mullite whiskers grow in large quantities in situ in the matrix and weak pore areas, with the whisker diameter being the largest. It can be observed that the surface of the catalytically grown mullite whiskers is smooth and there are no alloy catalyst spheres, which proves that the mullite whiskers are grown by a gas-solid catalytic mechanism. The large aspect ratio and specific surface area of ​​mullite whiskers give the alumina-silicon carbide-carbon non-fired refractories excellent mechanical properties and high-temperature oxidation resistance.

[0110] (2) Figure 2 EDS (line scan) image of mullite whiskers inside the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 1.

[0111] according to Figure 2The EDS (line scan) analysis results show that the mullite whiskers are composed of aluminum, silicon, oxygen and a small amount of carbon.

[0112] (3) Figure 3 The image shows the XRD pattern of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 1.

[0113] according to Figure 3 XRD test results prove that the present invention synthesizes mullite whiskers.

[0114] (4) Figure 4 SEM image of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 2.

[0115] Depend on Figure 4 It can be seen that when aluminum fluoride with a particle size of 10-100 nm is used as a catalyst, the aspect ratio of mullite whiskers is smaller compared with that in Example 1.

[0116] (5) Figure 5 SEM image of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 3.

[0117] Depend on Figure 5 It can be seen that when aluminum fluoride with a particle size of 0-10 nm is used as a catalyst, the aspect ratio of mullite whiskers is the smallest compared to Examples 1-2.

[0118] (6) Figure 6 SEM image of the alumina-silicon carbide-carbon non-fired refractory material prepared in Comparative Example 1.

[0119] Depend on Figure 6 It can be seen that when the raw material does not contain the catalyst aluminum fluoride, no mullite whiskers are formed.

[0120] (7) Table 1 shows the EDS line scan element content results of the mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared in Example 1.

[0121] Table 1. Elemental content from EDS line scan

[0122] Element name Element symbols Atomic percentage (%) Weight percentage (wt%) aluminum Al 27.30 37.19 oxygen O 64.46 52.08 silicon Si 7.07 10.02 carbon C 1.18 0.71

[0123] Depend on Figures 1-3 As shown in Table 1, during the sintering process, mullite whiskers grow in situ in the matrix and pores of the alumina-silicon carbide-carbon non-fired refractory.

[0124] (8) The refractory materials prepared in Examples 1-3 and Comparative Example 1 were subjected to room temperature compressive strength, room temperature flexural strength, and oxidation resistance tests. The room temperature compressive strength of the refractory materials was tested according to the standard test method of GB / T 5072-2008, and the room temperature flexural strength was tested according to the standard test method of GB / T 3001-2007. Both tests were performed on a YAW300D integrated compressive and flexural strength testing machine. The high-temperature oxidation resistance of the samples was tested in a muffle furnace at a temperature of 1500℃, a heating rate of 10℃ / min, and a testing time of 3 hours. The oxidation resistance of the material was evaluated based on the thickness of the oxide layer; a thicker oxide layer indicated poorer oxidation resistance. The test results are shown in Table 2.

[0125] Table 2 shows the properties of the refractory materials prepared in Examples 1-3 and Comparative Example 1.

[0126] sample room temperature compressive strength Flexural strength at room temperature Oxide layer thickness Example 1 58.21MPa 22.13MPa 3.7mm Example 2 54.74MPa 18.84MPa 5.9mm Example 3 48.37MPa 13.96MPa 8.6mm Comparative Example 1 41.54MPa 8.18MPa 19.8mm

[0127] As shown in Table 2, the in-situ grown mullite whisker-reinforced alumina-silicon carbide-carbon non-fired refractory material prepared by this invention has excellent mechanical properties and oxidation resistance. However, after omitting the catalyst, the mechanical properties and oxidation resistance of the resulting alumina-silicon carbide-carbon non-fired refractory material are significantly reduced.

[0128] Comparing the SEM results of Examples 1-3 and Comparative Example 1, it was found that changing the particle size of the aluminum fluoride catalyst resulted in different diameters of the mullite whiskers grown in situ within the alumina-silicon carbide-carbon non-fired refractory matrix and pores. Due to the high-temperature decomposition of the large-particle-size aluminum fluoride catalyst, the fluorine content inside the refractory material increased. According to the gas-solid whisker growth mechanism, the large-particle-size aluminum fluoride provided more catalytic sites for the in-situ growth of mullite whiskers. Therefore, the mullite whiskers prepared using aluminum fluoride with a particle size of 100-500 nm had the largest diameter. Furthermore, mullite could not grow into whiskers without a catalyst.

[0129] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A mullite whisker reinforced alumina-silicon carbide-carbon unfired refractory material, characterized in that, The raw materials are prepared by the following ingredients in mass percentage: corundum and / or bauxite 63-69%, silicon carbide 17-23%, spherical pitch 1.7-2.3%, calcium aluminate cement 0.7-1.3%, γ-alumina 7%, aluminum powder 0.2-0.8%, silicon powder 0.2-0.8%, silicon dioxide 3% and catalyst 3%; the carbon content of the spherical pitch is 40-80%; the catalyst is aluminum fluoride; the particle size of the catalyst is 100-500 nm; the diameter of the mullite whisker in the mullite whisker reinforced alumina-silicon carbide-carbon unfired refractory material is 50-1200 nm.

2. Mullite whisker reinforced alumina-silicon carbide-carbon unfired refractory material according to claim 1, characterized in that the mass percentage of alumina in the corundum and bauxite is independently ≥40%; the mass percentage of alumina in the calcium aluminate cement is ≥70%.

3. Mullite whisker reinforced alumina-silicon carbide-carbon unfired refractory material according to claim 1, characterized in that the particle size of the corundum and bauxite is independently ≤8 mm; the particle size of the silicon carbide is ≤1 mm; the particle size of the spherical pitch is ≤0.2 mm; the particle size of the calcium aluminate cement is ≤100 nm; the particle size of the γ-alumina is ≤0.1 mm; the particle size of the aluminum powder is ≤0.1 mm; the particle size of the silicon powder is ≤0.1 mm; the particle size of the silicon dioxide is ≤100 μm.

4. Process for the production of mullite whisker reinforced alumina-silicon carbide-carbon unfired refractory material according to any one of claims 1 to 3, characterized in that comprising the following steps: mixing the raw materials and water, placing the mixture in a mold, and performing vibration molding to obtain a molded body; sequentially curing, drying, and heat exchanging the molded body to obtain a mullite whisker reinforced alumina-silicon carbide-carbon unfired refractory material; the heat source for the heat exchange comes from the tapping temperature of molten iron.

5. The production method according to claim 4, characterized by, the mass of the water is 2-8% of the mass of the raw materials.

6. The preparation method according to claim 4, characterized in that, the frequency of the vibration molding is 2000-3000 times / min; the time of the vibration molding is 30-40 min.

7. The preparation method according to claim 4, characterized in that, the temperature of the curing is 30-60 °C; the humidity of the curing is 40-70%; the time of the curing is 12-24 h.

8. The preparation method according to claim 4, characterized in that, the temperature of the drying is 120-200 °C; the time of the drying is 12-24 h.

9. The mullite whisker reinforced alumina-silicon carbide-carbon unfired refractory material of any one of claims 1-3 or the mullite whisker reinforced alumina-silicon carbide-carbon unfired refractory material prepared by the preparation method of any one of claims 4-8 as a refractory material in metallurgy.

Images