Silicon carbide crucible for melting aluminum alloy and method for manufacturing the same

Abstract

The present application relates to a kind of carbonized silicon crucible for aluminum alloy smelting and its preparation method.The technical scheme is: carbonized silicon particle A, carbonized silicon particle B, carbonized silicon fine powder A, carbonized silicon fine powder B and xylitol are mixed, immersed in silica sol, dried, heat treated;Silicon dioxide coated carbonized silicon obtained by heat treatment is mixed with alumina powder, vanadium pentoxide and deionized water, to obtain mixed slurry, additional binder, sintering aid, polyacrylamide and gum arabic, mix, ball mill, to obtain carbonized silicon slurry.After exhausting, carbonized silicon slurry is placed in gypsum mold for preparing crucible, stand, pour out excess carbonized silicon slurry, continue to stand, take out the carbonized silicon body after standing, indoor curing, drying, heat treatment at 1300-1500 DEG C, to obtain carbonized silicon crucible for aluminum alloy smelting.The carbonized silicon body prepared by the present application is not easy to break, the sintering temperature of the product is low, the compressive strength is large, the thermal shock stability is high, and the resistance to aluminum alloy melt erosion is strong.

Description

Technical Field

[0001] This invention belongs to the technical field of silicon carbide crucibles. Specifically, it relates to a silicon carbide crucible for aluminum alloy melting and its preparation method. Background Technology

[0002] Aluminum alloys, due to their low density, high strength, good corrosion resistance, and excellent electrical and thermal conductivity, are widely used in aerospace, automotive manufacturing, construction, and energy fields, making them the second most used metallic material in industry after steel. Crucibles are indispensable tools in the aluminum alloy melting process, ensuring the smooth melting of aluminum alloys at high temperatures. Crucibles used for melting aluminum alloys are typically cast iron crucibles, refractory knotted crucibles, and graphite crucibles. However, the service conditions during aluminum alloy melting are extremely harsh. Crucibles must withstand high-temperature oxidation, rapid heating and cooling, and corrosion from molten aluminum. They are also prone to reacting with aluminum alloys during melting, contaminating the melt and reducing the service life of the crucible.

[0003] Silicon carbide has a high melting point, high thermal conductivity, low coefficient of thermal expansion, and strong resistance to erosion by high-temperature melts such as molten aluminum, making it an ideal crucible material for smelting aluminum alloys. It has attracted widespread attention from those skilled in the art.

[0004] The patented technology "A fused silica-silicon carbide ceramic product and its preparation method" (CN202310128456.5) uses silicon carbide particles and quartz particles as the skeleton and clay and quartz fine powder as the powder. Although the fused silica-silicon carbide ceramic product prepared has a low sintering temperature and high thermal conductivity, it has problems such as poor resistance to aluminum alloy melt erosion and low compressive strength.

[0005] The patented technology, “Silicon Carbide Crucible and its Manufacturing Process (CN201110395843.2),” combines carbon fiber with silicon carbide. Although the resulting crucible has good thermal shock stability, it still suffers from problems such as high sintering temperature and low compressive strength.

[0006] The patented technology "A silicon carbide crucible and its preparation method (CN201710386625.X)" produces silicon carbide crucibles with high bending strength and good thermal shock stability. However, the crucible blanks prepared by compression molding are difficult to prepare with complex geometric shapes and are prone to cracking.

[0007] The patented technology "A silicon carbide slurry casting production process (CN201910304581.0)" produces silicon carbide crucible blanks with high strength and resistance to cracking. However, the silicon carbide bonding is poor at high temperatures, resulting in low compressive strength and thermal shock stability. The crucibles are prone to breakage under rapid heating and cooling conditions.

[0008] In summary, existing silicon carbide crucibles are limited by the formulation and preparation method, resulting in problems such as easy cracking of the silicon carbide crucible blank, high sintering temperature, low compressive strength, low thermal shock stability, and weak resistance to aluminum alloy melt erosion. Summary of the Invention

[0009] The present invention aims to overcome the technical defects of the prior art and provides a method for preparing a silicon carbide crucible for aluminum alloy melting that is not prone to cracking of silicon carbide billets. The silicon carbide crucible for aluminum alloy melting prepared by this method has a low sintering temperature, high compressive strength, high thermal shock stability and strong resistance to aluminum alloy melt erosion.

[0010] To achieve the above objectives, the specific steps of the technical solution adopted by the present invention are as follows:

[0011] Step 1: Mix 20-30 wt% of silicon carbide particles A with a particle size of 0.5-1.0 mm, 5-15 wt% of silicon carbide particles B with a particle size of 0.1-0.5 mm, 30-40 wt% of silicon carbide fine powder A, 20-30 wt% of silicon carbide fine powder B, and 3-7 wt% of xylitol to obtain mixture A; place mixture A in silica sol and immerse it under a vacuum of -0.08 to -0.10 MPa for 20-40 min to obtain mixture B; dry mixture B at 90-110℃ for 8-10 h and heat treat it at 400-600℃ for 2-4 h to obtain silicon dioxide-coated silicon carbide.

[0012] The silicon carbide particles A, B, A, and B have the same chemical composition: SiC content greater than 97.0 wt% and Fe2O3 content less than 0.5 wt%.

[0013] The second step involves mixing 55–75 wt% of the aforementioned silicon dioxide-coated silicon carbide, 10–20 wt% of alumina micro powder, 1–5 wt% of vanadium pentoxide, and 10–30 wt% of deionized water to obtain a mixed slurry. Then, 0.5–1.0 wt% of a binder, 0.5–1.0 wt% of a sintering aid, 0.5–1.0 wt% of polyacrylamide, and 0.2–0.5 wt% of gum arabic are added to the mixed slurry, and the mixture is ball-milled for 12–20 hours to obtain a silicon carbide slurry.

[0014] Step 3: Exhaust the silicon carbide slurry under a vacuum of -0.08 to -0.10 MPa for 10 to 30 minutes. Pour the slurry into a plaster mold for preparing the crucible, let it stand for 20 to 40 minutes, pour out the excess slurry, and let it stand for another 30 to 60 minutes to obtain a silicon carbide billet. Remove the billet from the plaster mold and cure it indoors at 20 to 30°C for 20 to 30 hours. Then dry it at 80 to 110°C for 8 to 12 hours, and finally heat treat it at 1300 to 1500°C for 2 to 4 hours to obtain a silicon carbide crucible for aluminum alloy smelting.

[0015] The particle size of silicon carbide fine powder A is <0.075 mm, and the particle size of silicon carbide fine powder B is <0.030 mm.

[0016] C5H in xylitol 12 The O5 content is >99.0 wt%.

[0017] The silica sol has the following characteristics: SiO2 content >30.0 wt%, Na2O content <0.3 wt%, pH 8.5–9.5, and average particle size of 10–30 nm.

[0018] The alumina micro powder has an Al2O3 content >97.0 wt% and a particle size <0.005 mm.

[0019] The vanadium pentoxide has a V2O5 content >99.0 wt%.

[0020] The adhesive is lignin sulfate or polyvinyl alcohol.

[0021] The sintering aid is a mixture of yttrium oxide and aluminum oxide, with a molar ratio of yttrium oxide to aluminum oxide of 1 to 1.2:1.

[0022] The ball mill has a rotation speed of 60-80 r / min, a ball-to-material ratio of 3-3.5:1, and the grinding balls are agate balls.

[0023] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0024] (1) This invention utilizes the in-situ carbon nanoparticles formed by the thermal decomposition and carbonization of xylitol to adjust the interface structure between the silicon carbide preform and the plaster mold used to prepare the crucible during the dehydration process, thereby stabilizing the surface structure of the silicon carbide preform after demolding. Simultaneously, by strictly limiting the particle size distribution, additives, and water content of the silicon carbide raw materials, the prepared silicon carbide slurry exhibits high solid content, good fluidity, and good stability. Consequently, the prepared silicon carbide preform has high strength and is less prone to cracking during demolding and drying.

[0025] (2) The silicon dioxide coated silicon carbide obtained in this invention forms mullite whiskers in situ with alumina micro powder under the condition of 1300-1500℃. The micropores formed by the oxidation of nano carbon particles during the high temperature heat treatment process provide an effective space for the in situ formation of mullite whiskers, avoiding the volume expansion effect generated during the formation of mullite whiskers. Furthermore, a stable mullite bond is formed between the raw material particles, giving the silicon carbide crucible for aluminum alloy melting high mechanical properties. Therefore, the silicon carbide crucible for aluminum alloy melting prepared in this invention has a low sintering temperature and high compressive strength.

[0026] (3) This invention makes full use of the high thermal conductivity and strong erosion resistance of silicon carbide and the high thermal shock stability of mullite. Since the micropores generated after the oxidation of nano carbon particles are filled by the mullite whiskers formed in situ, the internal pore structure of the silicon carbide crucible for aluminum alloy melting is adjusted and the pore volume is reduced. The pore characteristics after this adjustment improve the thermal shock resistance of the silicon carbide crucible for aluminum alloy melting. Therefore, the prepared silicon carbide crucible for aluminum alloy melting has high thermal shock stability and strong resistance to aluminum alloy melt erosion.

[0027] The silicon carbide crucible for aluminum alloy smelting prepared according to this invention was tested and found to have a bulk density of 2.60–3.00 g / cm³. 3 The compressive strength is 100–120 MPa; the thermal shock resistance is ≥20 cycles (1100℃, air-cooled); the coefficient of thermal expansion (20–1000℃) is (4.0–4.5) × 10⁻⁶. -6 / ℃; No obvious corrosion or penetration was observed in the aluminum alloy melt erosion test.

[0028] Therefore, the silicon carbide billet prepared by this invention is not easy to crack, and the silicon carbide crucible for aluminum alloy melting has a low sintering temperature, high compressive strength, high thermal shock stability and strong resistance to aluminum alloy melt erosion. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the scope of protection thereof.

[0030] A silicon carbide crucible for aluminum alloy melting and its preparation method. The preparation method described in this specific embodiment is as follows:

[0031] Step 1: Mix 20-30 wt% of silicon carbide particles A with a particle size of 0.5-1.0 mm, 5-15 wt% of silicon carbide particles B with a particle size of 0.1-0.5 mm, 30-40 wt% of silicon carbide fine powder A, 20-30 wt% of silicon carbide fine powder B, and 3-7 wt% of xylitol to obtain mixture A; place mixture A in silica sol and immerse it under a vacuum of -0.08 to -0.10 MPa for 20-40 min to obtain mixture B; dry mixture B at 90-110℃ for 8-10 h and heat treat it at 400-600℃ for 2-4 h to obtain silicon dioxide-coated silicon carbide.

[0032] The second step involves mixing 55–75 wt% of the aforementioned silicon dioxide-coated silicon carbide, 10–20 wt% of alumina micro powder, 1–5 wt% of vanadium pentoxide, and 10–30 wt% of deionized water to obtain a mixed slurry. Then, 0.5–1.0 wt% of a binder, 0.5–1.0 wt% of a sintering aid, 0.5–1.0 wt% of polyacrylamide, and 0.2–0.5 wt% of gum arabic are added to the mixed slurry, and the mixture is ball-milled for 12–20 hours to obtain a silicon carbide slurry.

[0033] Step 3: Exhaust the silicon carbide slurry under a vacuum of -0.08 to -0.10 MPa for 10 to 30 minutes. Pour the slurry into a plaster mold for preparing the crucible, let it stand for 20 to 40 minutes, pour out the excess slurry, and let it stand for another 30 to 60 minutes to obtain a silicon carbide billet. Remove the billet from the plaster mold and cure it indoors at 20 to 30°C for 20 to 30 hours. Then dry it at 80 to 110°C for 8 to 12 hours, and finally heat treat it at 1300 to 1500°C for 2 to 4 hours to obtain a silicon carbide crucible for aluminum alloy smelting.

[0034] The pH of the silica sol is 8.5–9.5.

[0035] The adhesive is lignin sulfate or polyvinyl alcohol.

[0036] The sintering aid is a mixture of yttrium oxide and aluminum oxide, with a molar ratio of yttrium oxide to aluminum oxide of 1 to 1.2:1.

[0037] The ball mill has a rotation speed of 60-80 r / min, a ball-to-material ratio of 3-3.5:1, and the grinding balls are agate balls.

[0038] In this specific implementation:

[0039] The silicon carbide particles A, B, A, and B have the same chemical composition: SiC content greater than 97.0 wt% and Fe2O3 content less than 0.5 wt%.

[0040] The particle size of silicon carbide fine powder A is <0.075 mm, and the particle size of silicon carbide fine powder B is <0.030 mm.

[0041] C5H in xylitol 12 The O5 content is >99.0 wt%.

[0042] The silica sol has the following characteristics: SiO2 content >30.0 wt%, Na2O content <0.3 wt%, and the average particle size of the silica sol is 10–30 nm.

[0043] The alumina micro powder has an Al2O3 content >97.0 wt% and a particle size <0.005 mm.

[0044] The vanadium pentoxide has a V2O5 content >99.0 wt%.

[0045] The details will not be repeated in the examples.

[0046] Example 1

[0047] A silicon carbide crucible for aluminum alloy melting and its preparation method. The preparation method described in this specific embodiment is as follows:

[0048] Step 1: Mix 20 wt% of silicon carbide particles A with a particle size of 0.5-1.0 mm, 15 wt% of silicon carbide particles B with a particle size of 0.1-0.5 mm, 40 wt% of silicon carbide fine powder A, 20 wt% of silicon carbide fine powder B, and 5 wt% of xylitol to obtain mixture A; place mixture A in silica sol and impregnate it under a vacuum of -0.08 MPa for 20 min to obtain mixture B; dry mixture B at 90°C for 8 h and heat treat it at 400°C for 2 h to obtain silicon dioxide coated silicon carbide.

[0049] The second step involves mixing 55 wt% of the aforementioned silicon dioxide-coated silicon carbide, 14 wt% of alumina micro powder, 1 wt% of vanadium pentoxide, and 30 wt% of deionized water to obtain a mixed slurry. Then, 0.5 wt% of a binder, 1.0 wt% of a sintering aid, 0.5 wt% of polyacrylamide, and 0.2 wt% of gum arabic are added to the mixed slurry, and the mixture is ball-milled for 12 hours to obtain a silicon carbide slurry.

[0050] The third step involves venting the silicon carbide slurry under a vacuum of -0.08 MPa for 10 minutes, pouring the vented silicon carbide slurry into a plaster mold for preparing the crucible, letting it stand for 20 minutes, pouring out the excess silicon carbide slurry, and letting it stand for another 30 minutes to obtain a silicon carbide blank. The silicon carbide blank is then removed from the plaster mold, cured indoors at 20°C for 20 hours, dried at 80°C for 8 hours, and then heat-treated at 1300°C for 2 hours to obtain a silicon carbide crucible for aluminum alloy smelting.

[0051] The pH of the silica sol is 8.5.

[0052] The binder is lignin sulfate.

[0053] The sintering aid is a mixture of yttrium oxide and aluminum oxide, with a molar ratio of yttrium oxide to aluminum oxide of 1:1.

[0054] The ball mill has a rotation speed of 60 r / min, a ball-to-material ratio of 3:1, and uses agate balls.

[0055] The silicon carbide crucible for aluminum alloy melting prepared in this invention was tested and found to have a bulk density of 2.62 g / cm³. 3 The compressive strength is 100 MPa; the thermal shock resistance is 25 cycles (1100℃, air-cooled); the coefficient of thermal expansion (20~1000℃) is 4.0×10⁻⁶. -6 / ℃; No obvious corrosion or penetration was observed in the aluminum alloy melt erosion test.

[0056] Example 2

[0057] A silicon carbide crucible for aluminum alloy melting and its preparation method. The preparation method described in this specific embodiment is as follows:

[0058] Step 1: Mix 23 wt% of silicon carbide particles A with a particle size of 0.5-1.0 mm, 10 wt% of silicon carbide particles B with a particle size of 0.1-0.5 mm, 38 wt% of silicon carbide fine powder A, 22 wt% of silicon carbide fine powder B, and 7 wt% of xylitol to obtain mixture A; place mixture A in silica sol and impregnate it under a vacuum of -0.09 MPa for 25 min to obtain mixture B; dry mixture B at 100°C for 9 h and heat treat it at 500°C for 3 h to obtain silicon dioxide coated silicon carbide.

[0059] The second step involves mixing 60 wt% of the aforementioned silicon dioxide-coated silicon carbide, 20 wt% of alumina micro powder, 3 wt% of vanadium pentoxide, and 17 wt% of deionized water to obtain a mixed slurry. Then, 0.7 wt% of a binder, 0.9 wt% of a sintering aid, 0.7 wt% of polyacrylamide, and 0.3 wt% of gum arabic are added to the mixed slurry, and the mixture is ball-milled for 15 hours to obtain a silicon carbide slurry.

[0060] The third step involves venting the silicon carbide slurry under a vacuum of -0.09 MPa for 15 minutes, pouring the vented silicon carbide slurry into a plaster mold for preparing the crucible, letting it stand for 30 minutes, pouring out the excess silicon carbide slurry, and letting it stand for another 40 minutes to obtain a silicon carbide blank. The silicon carbide blank is then removed from the plaster mold, cured indoors at 25°C for 24 hours, dried at 90°C for 10 hours, and then heat-treated at 1400°C for 3 hours to obtain a silicon carbide crucible for aluminum alloy smelting.

[0061] The pH of the silica sol is 8.8.

[0062] The binder is lignin sulfate.

[0063] The sintering aid is a mixture of yttrium oxide and aluminum oxide, with a molar ratio of yttrium oxide to aluminum oxide of 1.1:1.

[0064] The ball mill has a rotation speed of 70 r / min, a ball-to-material ratio of 3.2:1, and uses agate balls.

[0065] The silicon carbide crucible for aluminum alloy smelting prepared in this invention was tested and found to have a bulk density of 2.76 g / cm³. 3 The compressive strength is 106 MPa; the thermal shock resistance is 23 cycles (1100℃, air-cooled); the coefficient of thermal expansion (20~1000℃) is 4.2×10⁻⁶. -6 / ℃; No obvious corrosion or penetration was observed in the aluminum alloy melt erosion test.

[0066] Example 3

[0067] A silicon carbide crucible for aluminum alloy melting and its preparation method. The preparation method described in this specific embodiment is as follows:

[0068] Step 1: Mix 27 wt% of silicon carbide particles A with a particle size of 0.5-1.0 mm, 8 wt% of silicon carbide particles B with a particle size of 0.1-0.5 mm, 35 wt% of silicon carbide fine powder A, 26 wt% of silicon carbide fine powder B, and 4 wt% of xylitol to obtain mixture A; place mixture A in silica sol and impregnate it under a vacuum of -0.09 MPa for 30 min to obtain mixture B; dry mixture B at 105℃ for 9.5 h and heat treat it at 550℃ for 3.5 h to obtain silicon carbide coated with silica.

[0069] The second step involves mixing 65 wt% of the aforementioned silicon dioxide-coated silicon carbide, 11 wt% of alumina micro powder, 4 wt% of vanadium pentoxide, and 20 wt% of deionized water to obtain a mixed slurry. Then, 0.9 wt% of a binder, 0.7 wt% of a sintering aid, 0.9 wt% of polyacrylamide, and 0.4 wt% of gum arabic are added to the mixed slurry, and the mixture is ball-milled for 18 hours to obtain a silicon carbide slurry.

[0070] The third step involves venting the silicon carbide slurry under a vacuum of -0.09 MPa for 20 minutes, pouring the vented silicon carbide slurry into a plaster mold for preparing the crucible, letting it stand for 35 minutes, pouring out the excess silicon carbide slurry, and letting it stand for another 50 minutes to obtain a silicon carbide blank. The silicon carbide blank is then removed from the plaster mold, cured indoors at 28°C for 27 hours, dried at 100°C for 11 hours, and then heat-treated at 1450°C for 3.5 hours to obtain a silicon carbide crucible for aluminum alloy smelting.

[0071] The pH of the silica sol is 9.2.

[0072] The adhesive is polyvinyl alcohol.

[0073] The sintering aid is a mixture of yttrium oxide and aluminum oxide, with a molar ratio of yttrium oxide to aluminum oxide of 1.1:1.

[0074] The ball mill has a rotational speed of 75 r / min, a ball-to-material ratio of 3.4:1, and uses agate balls.

[0075] The silicon carbide crucible for aluminum alloy smelting prepared in this invention was tested and found to have a bulk density of 2.85 g / cm³. 3 The compressive strength is 113 MPa; the thermal shock resistance is 22 cycles (1100℃, air-cooled); the coefficient of thermal expansion (20~1000℃) is 4.4×10⁻⁶. -6 / ℃; No obvious corrosion or penetration was observed in the aluminum alloy melt erosion test.

[0076] Example 4

[0077] A silicon carbide crucible for aluminum alloy melting and its preparation method. The preparation method described in this specific embodiment is as follows:

[0078] Step 1: Mix 30 wt% of silicon carbide particles A with a particle size of 0.5-1.0 mm, 5 wt% of silicon carbide particles B with a particle size of 0.1-0.5 mm, 32 wt% of silicon carbide fine powder A, 30 wt% of silicon carbide fine powder B, and 3 wt% of xylitol to obtain mixture A; place mixture A in silica sol and impregnate it under a vacuum of -0.10 MPa for 40 min to obtain mixture B; dry mixture B at 110℃ for 10 h and heat treat it at 600℃ for 4 h to obtain silicon dioxide coated silicon carbide.

[0079] The second step involves mixing 75 wt% of the aforementioned silicon dioxide-coated silicon carbide, 10 wt% of alumina micro powder, 5 wt% of vanadium pentoxide, and 10 wt% of deionized water to obtain a mixed slurry. Then, 1.0 wt% of a binder, 0.5 wt% of a sintering aid, 1.0 wt% of polyacrylamide, and 0.5 wt% of gum arabic are added to the mixed slurry, and the mixture is ball-milled for 20 hours to obtain a silicon carbide slurry.

[0080] The third step involves venting the silicon carbide slurry under a vacuum of -0.10 MPa for 30 minutes, pouring the vented silicon carbide slurry into a plaster mold for preparing the crucible, letting it stand for 40 minutes, pouring out the excess silicon carbide slurry, and letting it stand for another 60 minutes to obtain a silicon carbide blank. The silicon carbide blank is then removed from the plaster mold, cured indoors at 30°C for 30 hours, dried at 110°C for 12 hours, and then heat-treated at 1500°C for 4 hours to obtain a silicon carbide crucible for aluminum alloy smelting.

[0081] The pH of the silica sol is 9.5.

[0082] The adhesive is polyvinyl alcohol.

[0083] The sintering aid is a mixture of yttrium oxide and aluminum oxide, with a molar ratio of yttrium oxide to aluminum oxide of 1.2:1.

[0084] The ball mill has a rotation speed of 80 r / min, a ball-to-material ratio of 3.5:1, and uses agate balls.

[0085] The silicon carbide crucible for aluminum alloy smelting prepared in this invention was tested and found to have a bulk density of 3.00 g / cm³. 3 The compressive strength is 118 MPa; the thermal shock resistance is 20 cycles (1100℃, air-cooled); the coefficient of thermal expansion (20~1000℃) is 4.5×10⁻⁶. -6 / ℃; No obvious corrosion or penetration was observed in the aluminum alloy melt erosion test.

[0086] This specific implementation method has the following advantages compared with the prior art:

[0087] (1) This specific embodiment utilizes the in-situ carbon nanoparticles formed by the thermal decomposition and carbonization of xylitol to adjust the interface structure between the silicon carbide preform and the plaster mold of the preparation crucible during the dehydration process, thereby stabilizing the surface structure of the silicon carbide preform after demolding. Simultaneously, by strictly limiting the particle size distribution, additives, and water content of the silicon carbide raw materials, the prepared silicon carbide slurry exhibits high solid content, good fluidity, and good stability. Therefore, the prepared silicon carbide preform has high strength and is less prone to cracking during demolding and drying.

[0088] (2) The silicon dioxide coated silicon carbide obtained in this specific embodiment forms mullite whiskers in situ with alumina micro powder under the condition of 1300-1500℃. The micropores formed by the oxidation of nano carbon particles during the high temperature heat treatment process provide an effective space for the in situ formation of mullite whiskers, avoiding the volume expansion effect generated during the formation of mullite whiskers. Furthermore, a stable mullite bond is formed between the raw material particles, giving the silicon carbide crucible for aluminum alloy melting high mechanical properties. Therefore, the silicon carbide crucible for aluminum alloy melting prepared in this specific embodiment has a low sintering temperature and high compressive strength.

[0089] (3) This specific embodiment makes full use of the characteristics of high thermal conductivity and strong erosion resistance of silicon carbide and high thermal shock stability of mullite. Since the micropores generated after the oxidation of nano carbon particles are filled by mullite whiskers formed in situ, the internal pore structure of silicon carbide crucible for aluminum alloy melting is adjusted and the pore volume is reduced. The pore characteristics after this adjustment improve the thermal shock resistance of silicon carbide crucible for aluminum alloy melting. Therefore, the prepared silicon carbide crucible for aluminum alloy melting has high thermal shock stability and strong resistance to aluminum alloy melt erosion.

[0090] The silicon carbide crucible for aluminum alloy melting prepared in this specific embodiment was tested and found to have a bulk density of 2.60–3.00 g / cm³. 3 The compressive strength is 100–120 MPa; the thermal shock resistance is ≥20 cycles (1100℃, air-cooled); the coefficient of thermal expansion (20–1000℃) is (4.0–4.5) × 10⁻⁶. -6 / ℃; No obvious corrosion or penetration was observed in the aluminum alloy melt erosion test.

[0091] Therefore, the silicon carbide billet prepared in this specific embodiment is not easy to crack, and the silicon carbide crucible for aluminum alloy melting has a low sintering temperature, high compressive strength, high thermal shock stability and strong resistance to aluminum alloy melt erosion.

Claims

1. A method for producing a silicon carbide crucible for smelting an aluminum alloy, characterized by The specific steps of the preparation method are: In the first step, 20-30wt% of silicon carbide particles A with a particle size of 0.5-1.0mm, 5-15wt% of silicon carbide particles B with a particle size of 0.1-0.5mm, 30-40wt% of silicon carbide fine powder A, 20-30wt% of silicon carbide fine powder B and 3-7wt% of xylitol are mixed to obtain a mixture A; the mixture A is placed in a silica sol and impregnated for 20-40min under a vacuum degree of-0.08--0.10MPa to obtain a mixture B; the mixture B is dried at 90-110℃ for 8-10h and heat treated at 400-600℃ for 2-4h to obtain silica-coated silicon carbide; The chemical compositions of the silicon carbide particles A, the silicon carbide particles B, the silicon carbide fine powder A and the silicon carbide fine powder B are the same: the SiC content is greater than 97.0wt% and the Fe2O3 content is less than 0.5wt%. The particle size of the silicon carbide fine powder A is <0.075mm and the particle size of the silicon carbide fine powder B is <0.030mm. In the second step, 55-75wt% of the silica-coated silicon carbide, 10-20wt% of alumina micro powder, 1-5wt% of vanadium pentoxide and 10-30wt% of deionized water are mixed to obtain a mixed slurry, and then 0.5-1.0wt% of a binder, 0.5-1.0wt% of a sintering aid, 0.5-1.0wt% of polyacrylamide and 0.2-0.5wt% of gum arabic are added to the mixed slurry, mixed and ball milled for 12-20h to obtain a silicon carbide slurry; In the third step, the silicon carbide slurry is degassed for 10-30min under a vacuum degree of-0.08--0.10MPa, the degassed silicon carbide slurry is poured into a gypsum mold for preparing a crucible, and then the excess silicon carbide slurry is poured out after being left to stand for 20-40min, and the silicon carbide body is obtained by continuing to stand for 30-60min; the silicon carbide body is taken out of the gypsum mold, cured in a room at 20-30℃ for 20-30h, dried at 80-110℃ for 8-12h and then heat treated at 1300-1500℃ for 2-4h to obtain a silicon carbide crucible for melting aluminum alloy.

2. The method of producing a silicon carbide crucible for melting an aluminum alloy according to claim 1, characterized by, The content of C5H 12 O5 in the xylitol is > 99.0 wt%.

3. The method of producing a silicon carbide crucible for melting an aluminum alloy according to claim 1, characterized by, The silica sol has a SiO2 content of >30.0wt%, a Na2O content of <0.3wt% and a pH of 8.5-9.5, and the average particle size of the silica sol is 10-30nm.

4. The method of producing a silicon carbide crucible for melting an aluminum alloy according to claim 1, characterized by, The alumina micro powder has an Al2O3 content of >97.0wt%, and the particle size of the alumina micro powder is <0.005mm.

5. The method of producing a silicon carbide crucible for melting an aluminum alloy according to claim 1, characterized by, The vanadium pentoxide has a V2O5 content of >99.0wt%.

6. The method of producing a silicon carbide crucible for melting an aluminum alloy according to claim 1, characterized by, The binder is lignin sulfate or polyvinyl alcohol.

7. The method of producing a silicon carbide crucible for melting an aluminum alloy according to claim 1, characterized by, The sintering aid is a mixture of yttrium oxide and alumina, and the molar ratio of yttrium oxide to alumina is 1-1.2:

1.

8. The method of producing a silicon carbide crucible for melting an aluminum alloy according to claim 1, characterized by, The ball milling is performed at a rotation speed of 60-80r / min and a ball-to-material ratio of 3-3.5:1, and the grinding balls are made of agate.

9. A silicon carbide crucible for smelting an aluminum alloy, characterized by The silicon carbide crucible for melting aluminum alloy is prepared according to the method for preparing the silicon carbide crucible for melting aluminum alloy according to any one of claims 1-8.