Silica-based ceramic material, foamed ceramic filter, manufacturing method and use

Abstract

The present invention relates to the field of casting technology, and provides a silica-based ceramic material, a foamed ceramic filter, a manufacturing method and uses thereof. The silica-based ceramic material provided by the present invention includes ceramic powder and auxiliary materials. The ceramic powder contains, by mass fraction, 40-80% silica, 8-30% aluminum oxide, and 8-30% silicon carbide. The auxiliary materials include an adhesive and a dispersant. The foamed ceramic filter manufactured from the silica-based ceramic material of the present invention has silica as the main component, has a wide source of silica, low cost, and the cost of the obtained silica-based foamed ceramic filter is significantly reduced compared to general silicon carbide and zirconia-based foamed ceramic filters in this field. In addition, the silica-based foamed ceramic filter provided by the present invention has excellent heat resistance, the maximum use temperature reaches 1600 °C, and fills the gap of foamed ceramic filters in the range of 1500-1600 °C.

Description

Technical Field

[0001] This application claims the priority of a Chinese patent application filed with the China National Intellectual Property Administration on May 10, 2023, with the application number CN202310517405.1 and the title of the invention "Silica-based Ceramic Material, Foamed Ceramic Filter, Manufacturing Method and Use", the entire content of which is incorporated herein by reference.

[0002] The present invention relates to the field of casting technology, and in particular, to silica-based ceramic materials, foamed ceramic filters, manufacturing methods and uses.

Background Art

[0003] With the rapid development of the casting industry, the requirements for the performance and appearance of castings are becoming increasingly strict. Non-metallic inclusions in castings are the most important factor causing casting defects, affecting the surface finish, mechanical and machining properties of castings, and leading to an increase in the rejection rate. Therefore, it is necessary to filter the inclusions in molten metal before filling the mold.

[0004] Currently, in the casting industry, iron and steel castings are generally filtered using foamed ceramic filters. Foamed ceramic filters have a three-dimensional mesh skeletal structure that effectively removes inclusions from the molten metal, reduces turbulence, and allows the molten metal to reach the filling flow rate quickly and stably, thereby improving the quality of the casting. Currently, the foamed ceramic filters commonly used are silicon carbide foamed ceramic filters or zirconia foamed ceramic filters. The main raw materials used in these two types of foamed ceramic filters are silicon carbide powder or zirconia powder, which are expensive, with zirconia foamed ceramic filters being even more expensive (about five times more expensive than silicon carbide foamed ceramic filters). Foamed ceramic filters are disposable consumables, which places a significant economic burden on users. Furthermore, the maximum operating temperature for silicon carbide foamed ceramic filters is 1500°C, while the maximum operating temperature for zirconia foamed ceramic filters is 1700°C. For some molten metals with temperatures between 1500 and 1600°C, only zirconia foamed ceramic filters can be used for filtering. Currently, there are no foamed ceramic filters in this field that can reach a maximum operating temperature of 1600°C and are also low-cost. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In view of this, the present invention provides a siliceous ceramic material, a foamed ceramic filter, a method for manufacturing it, and its use. The siliceous ceramic material provided by the present invention has silica as its main component, and the siliceous foamed ceramic filter manufactured using it is low-cost, has a maximum operating temperature of 1600°C, and is suitable for molten metals with a filtration temperature of 1600°C or less. [Means for solving the problem]

[0006] To achieve the objectives of the above invention, the present invention provides the following technical solutions.

[0007] A siliceous ceramic material comprising ceramic powder and auxiliary materials, The aforementioned ceramic powder contains, by mass fraction, 40-80% silica, 8-30% aluminum oxide, and 8-30% silicon carbide. The auxiliary material comprises an adhesive and a dispersant, wherein the mass of the adhesive is 1-5% of the mass of the ceramic powder, and the mass of the dispersant is 0.5-1% of the mass of the ceramic powder.

[0008] Preferably, the aluminum oxide is α-aluminum oxide, the mesh count of the aluminum oxide is 200 mesh or more, and the purity is 98% or more. The silica has a mesh count of 1000 mesh or more and a purity of 95% or more. The silicon carbide has a mesh count of 200 mesh or more and a purity of 95% or more.

[0009] Preferably, the adhesive comprises one or more of silica sol, methylcellulose, white latex, sodium carboxymethylcellulose, polyvinyl alcohol, polyvinyl butyral, phenolic resin, and ethyl silicate, and the dispersant comprises sodium hexametaphosphate and / or sodium tripolyphosphate.

[0010] Preferably, the concentration of the silica sol is 30 to 50 wt%.

[0011] The present invention further provides a silica-based foamed ceramic filter manufactured from the silica-based ceramic material described in the above solution.

[0012] Preferably, the silica crystalline phase in the siliceous foamed ceramic filter is one or more of the following: β-quartz, α-quartz, γ-tiolite, β-tiolite, α-tiolite, β-cristobalite, α-cristobalite, and quartz glass.

[0013] Preferably, the porosity of the open voids of the silica-based foamed ceramic filter is 80-83%.

[0014] The present invention further provides a method for manufacturing a silica-based foamed ceramic filter as described above, The steps include: mixing ceramic powder, auxiliary materials, and water to obtain a ceramic slurry; The steps include immersing the foam matrix in the ceramic slurry, then removing the excess slurry adsorbed on the foam matrix to obtain a foam immersion substrate, The present invention provides a method for manufacturing a silica-based foamed ceramic filter according to the above solution, which includes the step of sequentially drying and sintering the foamed immersion substrate to obtain the silica-based foamed ceramic filter.

[0015] Preferably, the amount of water used is 15 to 25% of the mass of the ceramic powder.

[0016] Preferably, the viscosity of the ceramic slurry is 20,000 to 50,000 MPa·s.

[0017] Preferably, the foam matrix is ​​a porous polyurethane foam.

[0018] Preferably, the porous polyurethane foam has 10 to 20 PPI pores, and the dimensions of the porous polyurethane foam are (75 to 100) mm × (75 to 100) mm × 22 mm.

[0019] Preferably, the drying is oven drying or natural drying, with the oven drying temperature being 100-120°C and the time being 60-90 min, and the natural drying time being 6-12 h.

[0020] Preferably, the sintering temperature is 1150-1300°C, and the holding time is 2-4 hours. The process of raising the temperature to the sintering temperature involves raising the temperature to a first temperature at a first heating rate, then raising the temperature to a second temperature at a second heating rate, and then raising the temperature to the sintering temperature at a third heating rate, wherein the first heating rate is 70-90°C / h, the first temperature is 500-550°C, the second heating rate is 200-250°C / h, the second temperature is 1000-1100°C, and the third heating rate is 70-90°C / h.

[0021] The present invention further provides the use of a silica-based foamed ceramic filter described in the above solution or a silica-based foamed ceramic filter manufactured by the manufacturing method described in the above solution in casting.

[0022] Preferably, the operating temperature of the silica-based foamed ceramic filter is 1600°C or lower.

[0023] The present invention provides a siliceous ceramic material comprising ceramic powder and auxiliary materials, wherein the ceramic powder contains, by mass fraction, 40-80% silica, 8-30% aluminum oxide, and 8-30% silicon carbide, and the auxiliary materials comprise an adhesive and a dispersant, wherein the mass of the adhesive is 1-5% of the mass of the ceramic powder, and the mass of the dispersant is 0.5-1% of the mass of the ceramic powder. The siliceous ceramic material provided by the present invention has silica as its main component, has a wide range of raw material sources, is low in cost, and has good high-temperature resistance.

[0024] The present invention further provides a silica-based foamed ceramic filter made of the silica-based ceramic material described in the above solution means. The silica-based foamed ceramic filter provided by the present invention has silica as the main component, a wide source of silica, low cost, and the price is about 50% of that of silicon carbide powder. The cost of the obtained foamed ceramic filter is significantly reduced compared with general silicon carbide and zirconia-based foamed ceramic filters in this field. Moreover, the silica-based foamed ceramic filter provided by the present invention has good heat resistance, and the maximum use temperature reaches 1600 °C, filling the blank of the foamed ceramic filter within the range of 1500-1600 °C. In addition, the silica-based foamed ceramic filter provided by the present invention has good filtration performance and can effectively filter inclusions in molten metal.

Brief Description of the Drawings

[0025] [Figure 1] It is a process flow chart for manufacturing a silica-based foamed ceramic filter in an embodiment of the present invention.

Modes for Carrying Out the Invention

[0026] The present invention provides a silica-based ceramic material, which includes ceramic powder and auxiliary materials. The ceramic powder contains, by mass fraction, 40-80% silica, 8-30% aluminum oxide, and 8-30% silicon carbide. The auxiliary materials include an adhesive and a dispersant. The mass of the adhesive is 1-5% of the mass of the ceramic powder, and the mass of the dispersant is 0.5-1% of the mass of the ceramic powder.

[0027] Unless otherwise specified, all raw materials used in the present invention are commercially available products.

[0028] [[ID=The silica-based ceramic material provided by the present invention includes ceramic powder and auxiliary materials, which will be described in detail below respectively.

[0029] The ceramic powder contains 40-80%, preferably 40-75%, of silica by mass fraction. In the present invention, the mesh count of the silica is preferably 200 mesh or more (i.e., the particle size of the silica is 74 μm or less), and the purity is preferably 95% or more. In the present invention, there are no special requirements for the silica, and general silica powder in the art can be used. In the present invention, the silica mainly acts as a framework and is beneficial in improving the impact resistance of foamed ceramic filters at high temperatures. In the art, silica is often added to silicon carbide foamed ceramic filters as a sintering aid to lower the sintering temperature and improve the sintering effect, but the amount added is small. The present invention provides a siliceous ceramic material with silica as the main raw material, and foamed ceramic filters manufactured using the ceramic material of the present invention not only have good filtration performance and heat resistance, but also significantly reduce costs.

[0030] The ceramic powder contains 8-30%, preferably 10-25%, of aluminum oxide by mass fraction. In the present invention, the aluminum oxide is preferably α-aluminum oxide, the mesh count of the aluminum oxide is preferably 1000 mesh or more (i.e., the particle size of the aluminum oxide is 13 μm or less), and the purity is preferably 98% or more. The aluminum oxide acts as a matrix, which is beneficial in improving the sintering strength of the foamed ceramic filter and lowering the firing temperature of the product.

[0031] The ceramic powder contains, by mass fraction, 8-30%, preferably 10-20%, and more preferably 10-15% silicon carbide. In the present invention, the mesh count of the silicon carbide is preferably 1000 mesh or more (i.e., the particle size of the silicon carbide is 13 μm or less), and the purity is preferably 95% or more. The silicon carbide can improve the thermal conductivity of the foamed ceramic filter, reduce the coefficient of expansion, and further improve the thermal stability of the product.

[0032] In the present invention, the auxiliary material preferably includes an adhesive and a dispersant, wherein the mass of the adhesive is 1 to 5%, preferably 2 to 4%, of the mass of the ceramic powder, and the mass of the dispersant is 0.5 to 1%, preferably 0.6 to 0.8%, of the mass of the ceramic powder.

[0033] In the present invention, the adhesive preferably contains one or more of silica sol, methylcellulose, white latex, sodium carboxymethylcellulose, polyvinyl alcohol, polyvinyl butyral, phenolic resin, and ethyl silicate, the concentration of the silica sol is preferably 30 to 50 wt%, more preferably 40 wt%, and the dispersant preferably contains sodium hexametaphosphate and / or sodium tripolyphosphate.

[0034] The present invention further provides a siliceous foamed ceramic filter manufactured from the siliceous ceramic material described in the above solution, wherein the crystalline phase of silica in the siliceous foamed ceramic filter is preferably one or more of β-quartz, α-quartz, γ-tridiolite, β-tridiolite, α-tridiolite, β-cristobalite, α-cristobalite, and quartz glass, and the present invention makes it possible to obtain a foamed ceramic filter with good filtration performance and heat resistance when silica is the main raw material by strictly controlling the mixing ratio of ceramic powder and auxiliary materials in the siliceous ceramic material, thereby satisfying the requirements for molten metal filtration. In the present invention, the total porosity of the siliceous foamed ceramic filter is preferably 78-85%, and the open porosity is preferably 80-83%.

[0035] The present invention further provides a method for manufacturing a silica-based foamed ceramic filter as described above, The steps include: mixing ceramic powder, auxiliary materials, and water to obtain a ceramic slurry; The steps include immersing the foam matrix in the ceramic slurry, then removing the excess slurry adsorbed on the foam matrix to obtain a foam immersion substrate, The present invention provides a method for manufacturing a silica-based foamed ceramic filter according to the above solution, which includes the step of sequentially drying and sintering the foamed immersion substrate to obtain the silica-based foamed ceramic filter.

[0036] The present invention provides a method for obtaining a ceramic slurry by mixing ceramic powder, an auxiliary material, and water. In this invention, the amount of water used is preferably 15-25% of the mass of the ceramic powder, more preferably 18-22%, the mixing is preferably carried out using a high-speed mixer, and the viscosity of the ceramic slurry is preferably 20,000-50,000 MPa·s, more preferably 20,000-30,000 MPa·s or 40,000-50,000 MPa·s.

[0037] In this invention, after obtaining a ceramic slurry, a foam matrix is ​​immersed in the ceramic slurry, and then excess slurry adsorbed on the foam matrix is ​​removed to obtain a foam immersion substrate. In the present invention, the foam matrix is ​​preferably a porous polyurethane foam, the number of pores of the porous polyurethane foam is preferably 10 to 20 PPI, the dimensions of the porous polyurethane foam are preferably (75 to 100) mm × (75 to 100) mm × 22 mm, in a specific embodiment of the present invention, in order to obtain a porous polyurethane foam that satisfies the dimensional requirements, the porous polyurethane foam further includes the steps of preparation slicing and punching before immersion, in the present invention, the immersion temperature is preferably room temperature, the immersion time is preferably 1 to 3 min, in the present invention there are no special requirements for the specific operating conditions of the immersion, the porous polyurethane foam is simply placed in the ceramic slurry and immersed sufficiently, in the present invention the method for removing excess slurry adsorbed on the foam matrix is ​​preferably extrusion, the extrusion is preferably performed using a roll press, the gap of the roll press is preferably 2 to 10 mm, in the present invention by controlling the gap of the roll press to extrude about 60% of the slurry immersed in the foam matrix and obtain a foam immersion base.

[0038] The present invention provides a silica-based foamed ceramic filter by first obtaining a foamed immersion substrate, and then sequentially drying and sintering the foamed immersion substrate. In the present invention, the drying is preferably oven drying or natural drying, the oven drying temperature is preferably 100-120°C, more preferably 105-110°C, the drying time is preferably 60-90 min, more preferably 60-70 min, and the natural drying time is preferably 6-12 h, more preferably 8-10 h.

[0039] In the present invention, the sintering temperature is preferably 1150 to 1300°C, more preferably 1200 to 1250°C, the heat retention time for sintering is preferably 2 to 4 hours, more preferably 2.5 to 3.5 hours, the process of raising the temperature to the sintering temperature is preferably raising the temperature to a first temperature at a first heating rate, then raising the temperature to a second temperature at a second heating rate, and then raising the temperature to the sintering temperature at a third heating rate, the first heating rate is preferably 70 to 90°C / h, more preferably 75 to 85°C / h, and the first temperature is preferably 500 to 550°C, more preferably 500 to The temperature is 520°C, the second heating rate is preferably 200-250°C / h, more preferably 230-250°C / h, the second temperature is preferably 1000-1100°C, more preferably 1000-1050°C, and the third heating rate is preferably 70-90°C / h, more preferably 75-85°C / h. The present invention prefers to heat the material in the above manner, which is beneficial for uniformly heating the foamed immersion substrate and improving the sintering effect. During the sintering process, the foam matrix is ​​decomposed by heat, leaving behind a foamed ceramic product, i.e., the silicate foamed ceramic filter of the present invention. After the heating is complete, the obtained product can be removed after cooling it to 100°C together with the furnace.

[0040] The present invention further provides the use of a silica-based foamed ceramic filter described in the above solution or a silica-based foamed ceramic filter manufactured by the manufacturing method described in the above solution in casting. In the present invention, the silica-based foamed ceramic filter is used for filtering molten metal in the casting process, and the operating temperature of the silica-based foamed ceramic filter is preferably 1600°C or lower, and more preferably 1500 to 1600°C.

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Clearly, the embodiments described are only a subset of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art without creative work based on embodiments of the present invention are all within the technical scope of the present invention.

[0042] Figure 1 is a process flowchart for manufacturing a silicate foamed ceramic filter in an embodiment of the present invention. First, porous polyurethane foam (i.e., polyurethane sponge) is loaded, sliced, punched, and molded. Next, ceramic slurry is immersed in it, followed by drying and firing. The resulting product passes inspection and is then packaged and stored.

[0043] Example 1 40 kg of commercially available 95% purity, 200 mesh silica, 30 kg of 98% purity, 1000 mesh α-aluminum oxide, 30 kg of 95% purity, 1000 mesh silicon carbide, and 15 kg of pure water were mixed with 5 kg of silica sol (40 wt%) and 1.0 kg of sodium hexametaphosphate. The mixture was then uniformly stirred using a high-speed mixer to form a thixotropic slurry with a viscosity of 40,000 MPa·s, i.e., a ceramic slurry. A 100×100×22mm polyurethane foam with 10 PPI was immersed in a manufactured ceramic slurry. After sufficient immersion in the slurry, approximately 60% of the slurry was extruded using a roll press to obtain a foamed immersion substrate. The obtained foamed immersion substrate was dried at 110°C for 1 hour. Next, the substrate was placed in a sintering furnace and heated to 500°C at a heating rate of 90°C / h, then to 1000°C at a heating rate of 250°C / h, and then to 1150°C at 90°C / h. After holding the temperature for 2 hours, the substrate was cooled to approximately 100°C along with the furnace and removed to obtain a silicate foamed ceramic filter with specifications of 100×100×22mm-10 PPI. After detection, the porosity of the silicate foamed ceramic filter was found to be 82%. When molten steel at a temperature of 1527°C was filtered using the silica-based foamed ceramic filter manufactured in Example 1, inclusions in the molten steel were effectively filtered, achieving a filtration efficiency of 95%, and the filtered 800 kg of molten steel was not washed away. Even after filtering 800 kg of molten steel using the silica-based foamed ceramic filter manufactured in Example 1, the filter remained intact, demonstrating its good impact resistance. When molten steel at a temperature of 1527°C was filtered using a general silicon carbide foam ceramic filter, the filter was already crushed when filtering 500 kg of molten steel. This indicates that general silicon carbide foam ceramic filters are not suitable for filtering molten metal at temperatures above 1500°C. The silica foam ceramic filter provided by the present invention is not only low-cost but also has good high-temperature resistance and impact resistance, making it suitable for filtering molten metal at 1500-1600°C.

[0044] Example 2 75 kg of commercially available silica with a purity of 98% and a mesh size of 325, 10 kg of α-aluminum oxide with a purity of 99% and a mesh size of 2000, 15 kg of silicon carbide with a purity of 96% and a mesh size of 3000, and 18 kg of pure water were mixed with 3 kg of polyvinyl alcohol and 0.5 kg of sodium tripolyphosphate. The mixture was then uniformly stirred using a high-speed mixer to obtain a thixotropic slurry with a viscosity of 30,000 MPa·s, i.e., a ceramic slurry. A 75×75×22mm polyurethane foam with a density of 20 PPI was immersed in a manufactured ceramic slurry. After sufficient immersion, approximately 60% of the slurry was extruded by roll pressing to obtain a foamed immersion substrate. The obtained foamed immersion substrate was air-dried for 12 hours. The substrate was then placed in a sintering furnace and heated to 500°C at a heating rate of 90°C / h, then to 1000°C at a heating rate of 250°C / h, and finally to 1250°C at 90°C / h. After holding the temperature for 2 hours, the substrate was cooled to 100°C along with the furnace and then removed to obtain a silica foamed ceramic filter with specifications of 75×75×22mm-20 PPI. After detection, the porosity of the silica foamed ceramic filter was found to be 81%. When molten steel at a temperature of 1600°C is filtered using the silica-based foamed ceramic filter manufactured in Example 2, inclusions in the molten steel can be effectively filtered, achieving a filtration efficiency of 96%, and 500 kg of filtered molten steel is not washed away.

[0045] The above are merely preferred embodiments of the present invention, and those skilled in the art can make some improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should be considered within the scope of protection.

Claims

1. A siliceous ceramic material comprising ceramic powder and auxiliary materials, The aforementioned ceramic powder contains, by mass fraction, 40-80% silica, 8-30% aluminum oxide, and 8-30% silicon carbide. The auxiliary material comprises an adhesive and a dispersant, wherein the mass of the adhesive is 1 to 5% of the mass of the ceramic powder, and the mass of the dispersant is 0.5 to 1% of the mass of the ceramic powder. The adhesive comprises one or more of silica sol, methylcellulose, white latex, sodium carboxymethylcellulose, polyvinyl alcohol, polyvinyl butyral, phenolic resin, and ethyl silicate, and the dispersant comprises sodium hexametaphosphate and / or sodium tripolyphosphate, characterized in that the silicate ceramic material is such that the adhesive comprises one or more of these, and the dispersant comprises sodium hexametaphosphate and / or sodium tripolyphosphate.

2. The aluminum oxide is α-aluminum oxide, and the mesh count of the aluminum oxide is 200 mesh or more, and the purity is 98% or more. The silica has a mesh count of 1000 mesh or more and a purity of 95% or more. The silicate ceramic material according to claim 1, characterized in that the silicon carbide has a mesh count of 200 mesh or more and a purity of 95% or more.

3. A siliceous foamed ceramic filter, characterized in that it is manufactured from the siliceous ceramic material described in claim 1.

4. The silica foamed ceramic filter according to claim 3, characterized in that the silica crystalline phase in the silica foamed ceramic filter is one or more of β-quartz, α-quartz, γ-tridiolite, β-tridiolite, α-tridiolite, β-cristobalite, α-cristobalite, and quartz glass.

5. The steps include: mixing ceramic powder, auxiliary materials, and water to obtain a ceramic slurry; The steps include immersing the foam matrix in the ceramic slurry, then removing the excess slurry adsorbed on the foam matrix to obtain a foam immersion substrate, A method for producing a silicate foamed ceramic filter according to claim 3, characterized by comprising the step of sequentially drying and sintering the foamed immersion substrate to obtain the silicate foamed ceramic filter.

6. The manufacturing method according to claim 5, characterized in that the amount of water used is 15 to 25% of the mass of the ceramic powder.

7. The manufacturing method according to claim 5, characterized in that the viscosity of the ceramic slurry is 20,000 to 50,000 MPa·s.

8. The manufacturing method according to claim 5, characterized in that the drying is oven drying or natural drying, the oven drying temperature is 100 to 120°C and the time is 60 to 90 min, and the natural drying time is 6 to 12 h.

9. A method for using a silicate foamed ceramic filter manufactured by the method described in Claim 3 or Claim 5 in casting.

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