Preparation method of ceramic particle combined filter

Abstract

According to the preparation method of the ceramic particle combined filter, a sodium alginate solution is adopted as a matrix solution, electrostatic interaction between the sodium alginate solution and calcium ions is utilized to form a stable cross-linked structure, a chelating agent is supplemented to form a three-dimensional network structure, the cross-linked structure is further consolidated, and a prepared biscuit is high in strength, smooth in surface and high in strength. On the basis, a required structure can be processed. In the high-temperature sintering process, the boron source can fully react in an aluminum oxide-rich environment to generate 9Al2O3. 2B2O3 fibers, and the 9Al2O3. 2B2O3 fibers have the advantages of high strength, high modulus and good fatigue resistance and serve as a binding phase in a filter to tightly connect the granular sand; the calcium element in the curing agent is attached to the periphery of the fiber and is converted into a liquid phase to protect the 9Al2O3. 2B2O3 fiber during service, and scouring of high-temperature liquid can be effectively slowed down. The ceramic filter prepared through the technical route has excellent high-temperature performance and can effectively resist high-temperature liquid scouring in the service process.

Description

Technical Field

[0001] The invention belongs to the field of filter manufacturing, and in particular relates to a method for preparing a ceramic particle combined filter. Background Art

[0002] Ceramic particle bonded filter is a filter formed by combining corundum or silicon carbide particles of fixed particle size with a binder. It mainly uses the tortuous gaps between particles to remove solid inclusions from the metal melt. Currently, there are two main types of filters: tubular filters (including cartridge filters and chute tube filters) and vertical door filters.

[0003] Ceramic particle combined filter is a new type of material that is different from foam ceramic filters and honeycomb ceramic filters. The filter uses large-sized ceramic particles as the main structure. The particles themselves have high hardness, strong resistance to melt thermal shock, high thermal conductivity, small temperature gradient between the head and tail, low filtration starting pressure head and fast speed. When in service, the filter has a large filtration area, high pore tortuosity and good filtration effect. Therefore, it is widely used in large-scale continuous melting and casting processes for high-end products such as cans, aluminum plates and foils, and hard drives.

[0004] Currently, there is little research and documentation on this type of filter in China. The paper "Application and Research Direction of Aluminum Melt Filtration Technology" (author Su Peng, published in "Light Alloy Processing Technology", 2009, Vol. 37, No. 9) introduces this filter but does not provide a preparation method. Patent CN 115283658 A uses polyvinyl acetate as a binder, high-alumina cement and powdered glass as raw materials, adding water, stirring, and then casting and molding. After sintering at 1100°C, it produces a ceramic filter for use in a molten aluminum environment. The binding phase generated in this patent is mA12O3·nSiO2, which has low strength during service and is prone to collapse. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a method for preparing a ceramic particle bonded filter.

[0006] The present invention adopts the following technical solutions to achieve the above-mentioned purpose: A method for preparing a ceramic particle-bonded filter, characterized in that the raw material components and proportions are: 75-90% granular sand; 1-8% alumina powder; 4-16% boron source; 3-5% sodium alginate; 0.1-2% chelating agent; 0.5-3% curing agent; 1-4% water; and 0.1-2% adipic acid. A sodium alginate solution is used as a matrix solution, and electrostatic interaction between the sodium alginate and calcium ions is utilized to form a stable cross-linked structure. The chelating agent is used to form a three-dimensional network structure to further consolidate the cross-linked structure. The green blank prepared in this manner has high strength and a smooth surface, and can be processed into a desired structure. The boron source can fully react in an alumina-rich environment to generate 9Al2O3·2B2O3. Fiber, 9Al2O3·2B2O3 fiber acts as a binding phase in the filter to tightly connect the granular sand; the calcium element in the curing agent adheres to the fiber and is converted into a liquid phase to protect the 9Al2O3·2B2O3 fiber during service; the method specifically includes the following steps: placing sodium alginate in water, stirring evenly, and then keeping the mixture warm at a certain temperature to obtain a sodium alginate solution; adding granular sand, a boron source, alumina powder, a curing agent, and a chelating agent to the sodium alginate solution, and uniformly mixing to obtain a slurry; adding adipic acid to the mixed slurry, and then injecting it into a mold, and pressing and forming a green body; drying the green body and sintering it to obtain a ceramic particle-bound filter with a 9Al2O3·2B2O3 fiber content greater than 5%.

[0007] The granular sand is one of silicon carbide and corundum, with a particle size of 500 microns to 2800 microns. 90 / d 50 ≤1.45.

[0008] The boron source is one or more of boron oxide, boron carbide, boron nitride, boric acid, and calcium hexaboride.

[0009] The chelating agent is one or both of trisodium citrate and sodium hexametaphosphate.

[0010] The curing agent is one or more of calcium carbonate, calcium hydrogen phosphate, calcium phosphate and calcium lactate.

[0011] The sodium alginate solution heat preservation process refers to heat preservation at 40-90° C. for 1-80 hours; pressure forming refers to hydraulic forming, vibration forming, isostatic pressing, hot pressing, and ramming forming.

[0012] The sintering atmosphere is air or oxygen, and the sintering temperature is between 900°C and 1700°C.

[0013] The present invention uses a sodium alginate solution as the matrix solution, leveraging its electrostatic interaction with calcium ions to form a stable cross-linked structure. A chelating agent is then added to form a three-dimensional network structure to further consolidate the cross-linked structure. The resulting green blank has high strength and a smooth surface, which can then be processed into a desired structure. During the high-temperature sintering process, organic matter and sodium are gradually burned away, allowing the boron source to fully react in an alumina-rich environment to form 9Al2O3·2B2O3 fibers. These fibers exhibit high strength, high modulus, and excellent fatigue resistance, serving as a binding phase in the filter to tightly connect the sand particles. The calcium in the curing agent adheres to the fibers and, during service, transforms into a liquid phase to protect the 9Al2O3·2B2O3 fibers, effectively mitigating the erosion of high-temperature liquids. The matrix, made of sand particles of similar particle size, forms uniform pores with a narrow pore size range, effectively filtering out inclusions in the melt. The ceramic filter produced using this technical route exhibits excellent high-temperature performance and effectively resists the erosion of high-temperature liquids during service. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the SEM (scanning electron microscope) image of Example 1 of the present invention. DETAILED DESCRIPTION

[0015] The present invention is further described below in conjunction with the embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, rather than to limit the present invention.

[0016] Example 1. A ceramic particle bonded filter and its preparation method, prepared from the following raw materials by mass fraction: corundum particle sand 85%, average particle size of 900 microns, d 90 / d 50 =1.30; 2% alumina powder; 5% boron carbide; 3% sodium alginate; 0.9% trisodium citric acid, 2% calcium lactate, 2.1% water, and 0.5% adipic acid; sodium alginate is placed in water, stirred evenly, and then kept warm at 70°C for 40 hours to obtain a sodium alginate solution. Corundum particles, alumina powder, boron carbide, trisodium citric acid, and calcium lactate are added to the sodium alginate solution and mixed evenly to obtain a slurry; adipic acid is added to the mixed slurry, which is then injected into a mold and hydraulically formed to obtain a blank; the blank is dried and sintered in an air atmosphere at 1150°C to obtain a corundum ceramic particle-bonded filter having a 9Al2O3·2B2O3 fiber content of 6%, uniform pores, and a narrow pore size range, which can effectively filter out inclusions in the melt. The SEM (scanning electron microscope) image of this embodiment is shown in FIG. Figure 1 shown.

[0017] Example 2. A ceramic particle combined filter and its preparation method, prepared from the following raw materials by mass fraction: corundum particle sand 78%, average particle size of 1500 microns, d90 / d 50 =1.40; 6% alumina powder; 6% boron oxide; 5% sodium alginate; 1.2% sodium hexametaphosphate; 1.8% calcium hydrogen phosphate; 4% water; and 1.2% adipic acid. Sodium alginate is placed in water, stirred evenly, and then kept at 50°C for 60 hours to obtain a sodium alginate solution. Corundum particles, alumina powder, boron carbide, trisodium citric acid, and calcium hydrogen phosphate are added to the sodium alginate solution and mixed evenly to obtain a slurry. Adipic acid is added to the mixed slurry, which is then poured into a mold and hydroformed to obtain a green body. The green body is then dried and sintered at 1500°C in an oxygen atmosphere to obtain a corundum ceramic particle-bonded filter. The filter has a 9Al2O3·2B2O3 fiber content of 11%, uniform pores, and a narrow pore size range, effectively filtering out inclusions from the melt.

[0018] Example 3. A ceramic particle bonded filter and its preparation method, prepared from the following raw materials by mass fraction: 78% silicon carbide granular sand, with an average particle size of 1300 microns, d 90 / d 50 =1.44; 8% alumina fine powder; 6% calcium hexaboride; 5% sodium alginate; 1.2% sodium hexametaphosphate; 1.8% calcium carbonate; 4% water; and 1.2% adipic acid. Sodium alginate is placed in water, stirred evenly, and then kept warm at 50°C for 60 hours to obtain a sodium alginate solution. Silicon carbide granular sand, alumina fine powder, boron carbide, trisodium citric acid, and calcium carbonate are added to the sodium alginate solution and mixed evenly to obtain a slurry. Adipic acid is added to the mixed slurry, which is then injected into a mold and hydroformed to obtain a green body. The green body is dried and sintered at 950°C in air to obtain a silicon carbide ceramic particle-bonded filter having a 9% 9Al2O3·2B2O3 fiber content, uniform pores, and a narrow pore size range, and can effectively filter out inclusions in the melt.

Claims

1. A method for preparing a ceramic particle bonded filter, characterized in that: The raw material components and proportions are 75-90% granular sand; 1-8% alumina powder; 4-16% boron source; 3-5% sodium alginate; 0.1-2% chelating agent, 0.5-3% curing agent, 1-4% water, and 0.1-2% adipic acid. Sodium alginate solution is used as the matrix solution, and the electrostatic interaction between it and calcium ions is utilized to form a stable cross-linking structure, and the chelating agent is used to form a three-dimensional network structure to further consolidate the cross-linking structure. The green blank prepared in this way has high strength and smooth surface, and can be processed into the desired structure on this basis. The boron source can fully react in an alumina-rich environment to generate 9Al2O3·2B2O3 fibers, 9Al2O3·2 B2O3 fibers act as a binding phase in the filter to tightly connect the granular sand; the calcium element in the curing agent adheres to the fibers and transforms into a liquid phase to protect the 9Al2O3·2B2O3 fibers during service; the method specifically comprises the following steps: placing sodium alginate in water, stirring it evenly, and then keeping it warm at a certain temperature to obtain a sodium alginate solution; adding granular sand, a boron source, alumina powder, a curing agent, and a chelating agent to the sodium alginate solution, and uniformly mixing them to obtain a slurry; adding adipic acid to the mixed slurry, and then injecting it into a mold and pressing it to obtain a green body; and drying the green body and sintering it to obtain a ceramic particle-bound filter with a 9Al2O3·2B2O3 fiber content greater than 5%.

2. The method for preparing a ceramic particle-bonded filter according to claim 1, wherein: The granular sand is one of silicon carbide and corundum, with a particle size of 500 microns to 2800 microns. 90 / d 50 ≤1.

45.

3. The method for preparing a ceramic particle-bonded filter according to claim 1, wherein: The boron source is one or more of boron oxide, boron carbide, boron nitride, boric acid, and calcium hexaboride.

4. The method for preparing a ceramic particle-bonded filter according to claim 1, wherein: The chelating agent is one or two of trisodium citric acid and sodium hexametaphosphate; the curing agent is one or more of calcium carbonate, calcium hydrogen phosphate, calcium phosphate and calcium lactate.

5. The method for preparing a ceramic particle-bonded filter according to claim 1, wherein: The sodium alginate solution is held at 40-90°C for 1-80 hours. Pressure forming can be performed by hydraulic pressure, vibration, isostatic pressing, hot pressing, or ramming. The sintering atmosphere is either air or oxygen, and the sintering temperature is between 900°C and 1700°C.

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