A method for producing a porous filter

Abstract

The application provides a preparation method of a porous filter, which comprises the following steps: granulating and preparing granular materials; mixing the granular materials and a curing agent to form printing raw materials; laying the printing raw materials and spraying a binder at a preset position, and repeating the laying and the spraying process to obtain a green body; and sintering the green body to form the porous filter. The filter prepared by the preparation method has high strength at the green body stage and after sintering, has high strength and high thermal stability when used for casting, and has a faster casting time and a higher casting capacity compared with the prior art. Therefore, the possibility of internal fine, fragile, slagging and damage of the filter is reduced, and the working needs of daily transportation and high-temperature filtration can be well met.

Description

Technical Field

[0001] This technology belongs to the field of additive manufacturing, specifically involving a molding technology and method for a novel porous high-temperature resistant ceramic material. Background Technology

[0002] 3D printing, also known as additive manufacturing, is a rapid prototyping manufacturing method. Depending on the forming method, 3D printing includes various forming processes. Among them, binder jetting 3D printing technology (also known as 3DP or BJ printing) is a forming process that combines precision and efficiency. This process is based on the principle of using piezoelectric nozzles to jet binder to bind powder particles into a shape. Currently, the forming accuracy of 3DP printing equipment can reach ±0.3mm, meeting the precision requirements of molds. In recent years, binder jetting 3D printing technology has developed rapidly in China and has become one of the most dynamic rapid prototyping technologies.

[0003] Molten liquid metal often contains various oxides and impurities, which can affect the metal's crystal structure, ultimately leading to a significant reduction in the mechanical properties of the formed metal—a desirable outcome in the casting industry. Currently, foam ceramic filters and straight-pore pressed filters are mainly used to achieve this filtration purpose, removing impurities from the molten metal and serving rectification and adsorption functions. These foam ceramic filters are further classified into silicon carbide filters and zirconia filters based on their high-temperature resistance. The current preparation method for foam ceramic filters primarily utilizes the structure of polyurethane foam. A high-temperature resistant slurry is coated evenly onto the surface of the polyurethane foam, and then the organic portion is sintered in a high-temperature furnace to remove it, leaving a foam ceramic body with different high-temperature resistance properties to achieve the purpose of preparing the foam ceramic filter. However, some parts of the internal structure of current foam ceramic filters are relatively delicate and fragile, and there is a possibility of slag shedding and damage during the transportation and casting of molten metal. The slag or defects can have an immeasurable impact on the casting. Summary of the Invention

[0004] To address the issues of numerous defects in existing filters and the tendency for the filter skeleton to fall off during the molten iron filtration process, this application employs binder jet 3D printing technology to fabricate a novel porous ceramic high-temperature resistant filter. This filter has a robust and complete skeleton structure, exhibits excellent high-temperature resistance during the molten metal filtration process, and avoids defects and slag shedding, thereby improving the yield and quality of castings.

[0005] The specific technical solution of this application is as follows:

[0006] A method for preparing a porous filter, wherein the method includes:

[0007] Granulation: Fine refractory granules, binder, solvent and additives are mixed in a mass ratio of (90~100):(1~5):(5~15):(0.5~10) and then granulated to prepare granules;

[0008] Printing material: Mix granular material and curing agent to form printing material;

[0009] A three-dimensional model of the blank to be printed is created, and then the three-dimensional model is input into the computer to obtain the number of printing material layers required for the blank to be printed and the corresponding bonding areas between the layers, i.e., the preset positions for adhesive spraying.

[0010] The printing material is laid flat, and adhesive is sprayed at preset positions. The process of laying and spraying adhesive is repeated to obtain a blank.

[0011] The blank is sintered to form a porous filter.

[0012] In one embodiment of this application, the fine refractory granules are selected from one or more of mullite, silicon carbide, silicon dioxide, alumina, and zirconium oxide; preferably silicon dioxide and alumina, more preferably, the ratio of silicon dioxide to alumina is 1:(0.6~1.5) by mass; and / or

[0013] The adhesive is selected from one or more of the following: furan resin, phenolic resin, urea-formaldehyde resin adhesive, polyvinyl alcohol acetal adhesive, polyvinyl acetate (PVAc) emulsion, acrylic water-based adhesive, rubber emulsion adhesive, polyurethane water-based adhesive, cement, gypsum, water glass, lime, and clay; and / or

[0014] The solvent is selected from one or more of water, methanol, ethanol, ethylene glycol, acetone, chloroform, carbon tetrachloride, diethyl ether, gasoline, benzene, toluene, and xylene; the solvent is preferably water or methanol; and / or

[0015] The additive is selected from one or more of sulfates, sulfonates, phosphates, amines, and polyethylene glycol.

[0016] In one embodiment of this application, the ratio of the fine refractory granules to the binder is 100:(1~3) by mass; and / or

[0017] The sphericity of the granules is 0.95-1.

[0018] In one embodiment of this application, the particle size distribution of the granules is 40-245 micrometers.

[0019] In one embodiment of this application, during the formation of the printing raw material, the mass ratio of the curing agent to the granules is (0.20~0.65):100.

[0020] In one embodiment of this application, the curing agent is selected from one or more of sulfate esters, p-toluenesulfonic acid, xylenesulfonic acid, benzenesulfonic acid, sulfuric acid, phosphoric acid, mixed xylenesulfonic acid, lactic acid, citric acid, maleic anhydride, and oxalic acid.

[0021] In one embodiment of this application, a sintering aid is added to the printing material before tiling, wherein the mass ratio of the printing material to the sintering aid is 100:(1.8~23).

[0022] In one embodiment of this application, the sintering aid is selected from one or more of amorphous silica, carbides, borides, oxides, spherical calcium aluminate, and aluminum fluoride granules, preferably in combination of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules.

[0023] In one embodiment of this application, the D50 particle size of the amorphous silica is 0.5-3 μm.

[0024] In one embodiment of this application, the adhesive is selected from one or more of polyvinyl alcohol (PVA), polyvinyl ketone, polyacrylic acid (PAA), furan resin, phenolic resin, epoxy resin, urea-formaldehyde resin adhesive, polyvinyl alcohol acetal adhesive, polyvinyl acetate (PVAc) emulsion, acrylate water-based adhesive, polyurethane water-based adhesive, water glass, phosphate, and polyurethane acrylate, wherein the adhesive is preferably furan resin.

[0025] In one embodiment of this application, the tensile strength of the blank is 2.0-5.0 MPa.

[0026] In one embodiment of this application, before sintering the blank, a post-processing step is further included, the post-processing step comprising the following steps:

[0027] The green body is immersed in a fine powder solution to increase its bulk density.

[0028] In one embodiment of this application, during the sintering process, the blank is sintered for the first time at temperature T1, and after the first sintering is completed, it is sintered for the second time at temperature T2, thereby obtaining the porous filter.

[0029] In one embodiment of this application, during the first sintering process, the temperature T1 is 800-900℃, and the sintering time is 2-4 hours; the pressure during the sintering process is atmospheric pressure; and / or

[0030] During the second sintering process, the T2 temperature is 1200-1750℃, the sintering time is 4h-6h, and the pressure during the sintering process is atmospheric pressure.

[0031] In one embodiment of this application, the porous filter has a compressive strength of 1.3-2.5 MPa at temperature T3 and a compressive strength of 0.6-1.5 MPa at temperature T4.

[0032] The temperature range of T3 is 10-30 ℃, and the temperature range of T4 is 900-1200 ℃.

[0033] In one embodiment of this application, the preparation is carried out using the method described above.

[0034] Invention Effects

[0035] This application employs binder jet 3D printing technology to prepare a novel porous ceramic high-temperature resistant filter. By selecting, synthesizing, and proportioning the printing material, and by impregnating the printed blank to make it dense, the prepared filter possesses high stress strength and compressive strength.

[0036] The novel ceramic filter prepared by the method described in this application has high strength at both room temperature and high temperature, which solves the problems of easy slag shedding and uneven particle size in traditional foam filters, and ensures that the molten iron is not contaminated by slag during the casting process.

[0037] The novel ceramic filter prepared by the method of this application can be modeled and designed to be suitable for the internal structure of high-temperature molten iron fluid. This can ensure the flow rate of molten iron in its channels and effectively filter out the impurities in the molten iron, thus ensuring the casting quality. Detailed Implementation

[0038] The embodiments described below provide a detailed description of this application. While specific embodiments of this application are shown, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0039] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0040] The following embodiments of this application are only used to illustrate specific implementation methods of this application, and these embodiments should not be construed as limitations on this application. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this application shall be considered equivalent substitutions and fall within the protection scope of this application.

[0041] The specific embodiments of this application will now be described in more detail. However, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0042] As used in this specification, "a" or "an" may mean one or more. As used in the claims, when used with the word "comprising," the word "a" or "an" may mean one or more.

[0043] The term “or” is used in the claims to mean “and / or” unless it is explicitly stated that it refers only to an alternative or that the alternatives are mutually exclusive, although this disclosure supports the definitions of referring only to an alternative and “and / or”. As used herein, “another” can mean at least a second or more.

[0044] This application relates to a method for preparing a porous filter, wherein the method includes:

[0045] Granulation involves mixing fine refractory granules, binders, solvents, and additives in a mass ratio of (90~100):(1~5):(5~10):(0.5~10), and then granulating the mixture to produce granules.

[0046] Printing material: Mix granular material and curing agent to form printing material;

[0047] Specifically, the printing material is first laid flat on the material box in one layer, and adhesive is sprayed at a preset position. At this time, one layer of spray printing is completed. After one layer of spray printing is completed, the material box is lowered by one layer, and the process of laying flat and spraying adhesive is repeated to obtain a blank. The blank is then sintered to form a porous filter.

[0048] In one embodiment of this application, during the granulation process, the ratio of the fine refractory granules to the binder can be 100:(1~3) by mass.

[0049] In one embodiment of this application, during the granulation process, the ratio of the fine refractory granules to the binder can be 100:(1~5) by mass.

[0050] Specifically, in the granulation process, the ratio of the fine refractory granules to the binder, by mass, can be 90:1, 90:2, 90:3, 90:4, 90:5, 91:1, 91:2, 91:3, 91:4, 91:5, 92:1, 92:2, 92:3, 92:4, 92:5, 93:1, 93:2, 93:3, 93:4, 93:5, 94:1, 94:2, 94:3, 94:4, 94 ... 4:5, 95:1, 95:2, 95:3, 95:4, 95:5, 96:1, 96:2, 96:3, 96:4, 96:5, 97:1, 97:2, 97:3, 97:4, 97:5, 98:1, 98:2, 98:3, 98:4, 98:5, 99:1, 99:2, 99:3, 99:4, 99:5, 100:1, 100:2, 100:3, 100:4, 100:5.

[0051] In one embodiment of this application, during the granulation process, the ratio of the fine refractory particles to the solvent by mass can be 90:5, 90:10, 90:15, 91:5, 91:10, 91:15, 92:5, 92:10, 92:15, 93:5, 93:10, 93:15, 94:5, 94:10, 94:15, 95:5, 95:10, 95:15, 96:5, 96:10, 96:15, 97:5, 97:10, 97:15, 98:5, 98:10, 98:15, 99:5, 99:10, 99:15, 100:5, 100:10, or 100:15.

[0052] In one embodiment of this application, during the granulation process, the ratio of the fine refractory particles to the additive, by mass, can be 90:0.5, 90:1, 90:5, 90:10, 91:0.5, 91:1, 91:5, 91:10, 92:0.5, 92:1, 92:5, 92:10, 93:0.5, 93:1, 93:5, 93:10, 94:0.5, 94:1, 9 4:5, 94:10, 95:0.5, 95:1, 95:5, 95:10, 96:0.5, 96:1, 96:5, 96:10, 97:0.5, 97:1, 97:5, 97:10, 98:0.5, 98:1, 98:5, 98:10, 99:0.5, 99:1, 99:5, 99:10, 100:0.5, 100:1, 100:5, 100:10.

[0053] In one embodiment of this application, the fine refractory granules are selected from one or more of mullite, silicon carbide, silicon dioxide, alumina, and zirconium oxide; the fine refractory granules are preferably silicon dioxide and alumina. The ratio of silicon dioxide to alumina is 1:(0.6~1.5) by mass, for example, it can be 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1.0, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, or 1:1.5.

[0054] The adhesive is selected from one or more of furan resin, phenolic resin, urea-formaldehyde resin adhesive, polyvinyl alcohol acetal adhesive, polyvinyl acetate (PVAc) emulsion, acrylate water-based adhesive, rubber emulsion adhesive, polyurethane water-based adhesive, cement, gypsum, water glass, lime, and clay; the adhesive is preferably phenolic resin.

[0055] The solvent is selected from one or more of water, methanol, ethanol, ethylene glycol, acetone, chloroform, carbon tetrachloride, diethyl ether, gasoline, benzene, toluene, and xylene; the solvent is preferably water or methanol.

[0056] The additive is selected from one or more of sulfates, sulfonates, phosphates, amines, and polyethylene glycol, with polyethylene glycol being the preferred additive.

[0057] It should be understood that any one of the fine refractory granules, binder, solvent and additives can be composed of multiple substances in any proportion. For example, the fine refractory granules can be made by mixing two or more substances in any proportion, or by using only one substance.

[0058] For example, the solvent can be selected from two or more solvents miscible in any proportion, or only one solvent can be used. In one embodiment of this application, the solvent is entirely water. In one embodiment of this application, the solvent is only an alcohol. In one embodiment of this application, the solvent is a mixture of ethanol and methanol, and in one embodiment of this application, the mass ratio of ethanol to methanol in the solvent is 1:9.

[0059] In this application, the granulation can be carried out using any granulation method well known to those skilled in the art, such as wet granulation, one-step granulation, spray granulation, dry granulation, etc., and no restrictions are imposed in this application.

[0060] In this application, "sphericity" refers to a parameter characterizing particle morphology. The closer a particle's morphology is to a sphere, the closer its sphericity is to 1. It is calculated as the ratio of the surface area of ​​a sphere of the same volume to the surface area of ​​the object. A sphere has a sphericity of 1, while other objects have a sphericity less than 1. In this application, the sphericity of the particle size is determined using a dynamic image particle analysis system (Dandong Better Instruments Co., Ltd.). In one embodiment of this application, the sphericity of the granular material is 0.95-1; for example, the sphericity of the granular material can be 0.95, 0.951, 0.952, 0.953, 0.954, 0.955, 0.956, 0.957, 0.958, 0.959, 0.96, 0.97, 0.98, 0.99, or 1.

[0061] In this application, "particle size" is also called "particle size" or "diameter". When a certain physical property or physical behavior of a particle being tested is most similar to that of a homogeneous sphere (or combination) of a certain diameter, the diameter (or combination) of that sphere is taken as the equivalent particle size (or particle size distribution) of the particle being tested. Particle size is generally divided into a single particle size representing the size of an individual particle and an average particle size representing a group of particles of different sizes. Since the shape of actual particles is usually non-spherical, it is difficult to directly represent their size using diameter. Therefore, in the field of particle size testing, for non-spherical particles, the equivalent particle size (generally referred to as particle size) is usually used to characterize the particle size. The equivalent particle size refers to the diameter (or combination) of a sphere (or combination) of a certain diameter that is most similar to the physical property or physical behavior of a particle being tested. In this application, D50 refers to the particle size corresponding to a sample whose volumetric cumulative particle size distribution percentage reaches 50%. Its physical meaning is that particles larger than its diameter account for 50% and particles smaller than its diameter also account for 50%. D50 is also called median diameter or median particle size. In this application, the particle size can be determined by the Malvern Mastersizer 3000 particle size analyzer.

[0062] The particle size distribution of the granules was determined using a Malvern Mastersizer 3000 particle size analyzer. In this document, the particle size distribution refers to the range comprised of the smallest and largest particle sizes measured by the Mastersizer 3000.

[0063] In one embodiment of this application, the particle size distribution of the granules is 40-245 micrometers, for example, the particle size can be 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, or 245 micrometers. Those skilled in the art will understand that in this case, the smallest particle size is 40 micrometers and the largest particle size is 245 micrometers.

[0064] In one embodiment of this application, the particle size distribution of the granules is 50-180 micrometers, for example, the particle size of the granules is 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, or 180 micrometers. In another embodiment of this application, the particle size of the granules conforms to a normal distribution pattern, and the minimum particle size confirmed by detection is 50 micrometers, and the maximum particle size is 180 micrometers.

[0065] In one embodiment of this application, during the formation of the printing raw material, the particulate material is mixed with the curing agent. The ratio of the curing agent to the particulate material, by mass, is (0.20~0.65):100. For example, the ratio of the curing agent to the particulate material, by mass, can be: 0.20:100, 0.25:100, 0.30:100, 0.35:100, 0.40:100, 0.45:100, 0.50:100, 0.55:100, 0.60:100, or 0.65:100.

[0066] In one embodiment of this application, the curing agent is selected from one or more of the following: sulfate ester, p-toluenesulfonic acid, xylenesulfonic acid, benzenesulfonic acid, sulfuric acid, phosphoric acid, mixed xylenesulfonic acid, lactic acid, citric acid, maleic anhydride, and oxalic acid. Preferably, the curing agent is a mixture of p-toluenesulfonic acid and sulfuric acid. In one embodiment of this application, the ratio of p-toluenesulfonic acid to sulfuric acid is (65~70):(0.5~2.0) by mass.

[0067] In one embodiment of this application, a sintering aid is added to the printing raw material. In another embodiment, the sintering aid is selected from one or more of amorphous silica, carbides, borides, oxides, spherical calcium aluminate, and aluminum fluoride granules, preferably a combination of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules. The amorphous silica can be prepared by refining zirconium oxide or by chemical reaction products of silica, silica, etc. The amorphous silica can also be obtained by methods well known to those skilled in the art.

[0068] The amorphous silica has a D50 particle size of 0.5-3 μm. For example, the particle size of the amorphous silica can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, or 3 μm. Preferably, the amorphous silica has a D50 particle size of 1 μm.

[0069] In this application, the spherical calcium aluminate is prepared by mixing alumina and calcium oxide in a certain proportion. The particle size of the spherical calcium aluminate is 55-150 μm. For example, the particle size of the spherical calcium aluminate can be 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, or 150 μm. Preferably, the D50 particle size of the spherical calcium aluminate is 150 μm.

[0070] The aluminum fluoride granules have a particle size of 60-185 μm. For example, the particle size can be 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, 155 μm, 160 μm, 165 μm, 170 μm, 175 μm, 180 μm, or 185 μm. Preferably, the D50 particle size of the aluminum fluoride granules is 185 μm.

[0071] In this application, the spherical calcium aluminate is prepared by mixing alumina and calcium oxide in a certain proportion and then preparing it by electrofusion.

[0072] The particle sizes of the spherical calcium aluminate, aluminum fluoride granules, and amorphous silica were determined using a Malvern Mastersizer 3000 particle size analyzer.

[0073] When amorphous silica, spherical calcium aluminate, and aluminum fluoride granules are used as sintering aids, the ratio of the printing raw material to the sintering aid is 100:(1.2~10) by mass. Specifically, the ratio of the printing raw material to the sintering aid by mass can be 100:1.2, 100:1.3, 100:1.4, 100:1.5, 100:1.6, 100:1.7, 100:1.8, 100:1.9, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, or 100:10.

[0074] The ratio of the printing material to amorphous silica by mass is 100:(0.2~2.2), preferably 100:(0.3~1). Specifically, the ratio of the printing material to the sintering aid by mass can be 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.7, 100:0.8, 100:0.9, or 100:1.

[0075] The ratio of the printing material to the spherical calcium aluminate by mass is 100:(0.2~0.8), specifically, the ratio of the printing material to the spherical calcium aluminate by mass is 100:(0.4~0.6), and more preferably, the ratio of the printing material to the spherical calcium aluminate by mass is 100:0.5.

[0076] The ratio of the printing raw material to the aluminum fluoride granules is 100:(0.8~7) by mass. Preferably, the ratio is 100:(1~6) by mass. Specifically, the ratio is 100:1, 100:2, 100:3, 100:4, 100:5, or 100:6 by mass.

[0077] In this application, the sintering aid is used to further improve the flowability of the artificial granulated material, promote the sintering of the ceramic phase, and reduce the sintering temperature.

[0078] In one embodiment of this application, the blank is prepared using binder jetting 3D printing technology. Specifically, a three-dimensional model of the blank to be printed is first established, and then the three-dimensional model is input into a computer. At this time, the number of printing material layers required for the blank to be printed and the corresponding bonding areas between the layers can be obtained in the computer, i.e., the preset positions for binder jetting. Specifically, the printing material is laid flat, and then the binder is jetted into the preset positions set by the computer. The process of laying flat and jetting binder is repeated. After printing, the blank is cleaned to obtain the blank that is identical to the three-dimensional model. Therefore, the role of the binder is to bond and fix two adjacent layers of printed material, improve the bonding strength between the printed material, and increase the overall strength of the printed blank.

[0079] The adhesive is selected from one or more of polyvinyl alcohol (PVA), polyvinyl ketone, polyacrylic acid (PAA), furan resin, phenolic resin, epoxy resin, urea-formaldehyde resin adhesive, polyvinyl alcohol acetal adhesive, polyvinyl acetate (PVAc) emulsion, acrylate water-based adhesive, polyurethane water-based adhesive, water glass, phosphate, and polyurethane acrylate, with furan resin being the preferred adhesive.

[0080] In one embodiment of this application, after obtaining the billet, a strength test is performed on the billet. The tensile strength of the billet is 2.0-5.0 MPa. For example, the tensile strength of the billet can be 2.0 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, 3.0 MPa, 3.1 MPa, 3.2 MPa, 3.3 MPa, 3.4 MPa, 3.5 MPa, 3.6 MPa, 3.7 MPa, 3.8 MPa, 3.9 MPa, 4.0 MPa, 4.1 MPa, 4.2 MPa, 4.3 MPa, 4.4 MPa, 4.5 MPa, 4.6 MPa, 4.7 MPa, 4.8 MPa, 4.9 MPa, or 5.0 MPa.

[0081] The tensile strength is measured by printing a sand mold figure-eight test block. The measurement method and standard can be found in industry standard JB / T 7526-2008.

[0082] Before immersion, the printed blank needs to be cleaned of powder. In this application, the cleaning method used is compressed air purging (equipment model: oil-free air compressor JB1680-35). During this process, compressed air or airflow is used to blow away excess powder material from the printed blank. If the blank has low strength, its weak parts are easily damaged; therefore, the blank needs to have high strength to ensure that the powder cleaning process does not cause damage.

[0083] In some embodiments of this application, the powder cleaning process can also be performed manually, vibratingly, by vacuuming, or using specialized 3D printing powder cleaning equipment or machines.

[0084] The large porosity among granular materials leads to insufficient bulk density in the green body, hindering subsequent ceramic sintering and posing significant challenges to the sintering process. Addressing the low density of 3D-printed ceramic green bodies requires post-processing to increase bulk density. A common method is to introduce fine powder into the voids. This involves preparing a solution of fine powder at a specific concentration, immersing the printed green body in the solution under normal or pressurized pressure to allow the powder to penetrate the voids and increase the green body's bulk density. In one embodiment of this application, before sintering, a post-processing step is included, comprising immersing the green body in a fine powder solution to further increase its bulk density.

[0085] The soaking time is 3 to 60 minutes.

[0086] In one embodiment of this application, the strength test of the blank is performed after the blank is printed and before the blank is soaked.

[0087] In this application, bulk density refers to the mass per unit volume of a material in its natural state (including the material solid and its open and closed pores), commonly known as bulk weight. Bulk density is an inherent property of any substance. That is, the value of bulk density varies depending on the type and characteristics of the material, but it does not actually affect the material's condition. Therefore, the value of bulk density is constant. Thus, to calculate the bulk density of an object, it can be calculated by dividing the object's mass by its volume. The bulk density of the blank is 0.4% to 0.7%.

[0088] In one embodiment of this application, the fine powder solution is a solution of a certain concentration prepared by mixing fine powder and a fine powder solvent. The fine powder is selected from one or more of mullite, silicon carbide, silicon dioxide, alumina, zirconium oxide, or silicon carbide; mullite is preferred. The fine powder solvent is selected from one or more of water, methanol, ethanol, ethylene glycol, acetone, chloroform, carbon tetrachloride, diethyl ether, gasoline, benzene, toluene, and xylene; methanol is preferred.

[0089] The concentration of the fine powder solvent is 30-70 wt%, for example, it can be 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, or 70 wt%. In one embodiment of this application, during the sintering process, the green body undergoes a first sintering at temperature T1, and after the first sintering, a second sintering is performed at temperature T2, thereby obtaining the porous filter.

[0090] In one embodiment of this application, during the first sintering process, the sintering temperature T1 is 800-900℃, and the sintering time is 2h-4h. During the first sintering process, the sintering pressure is atmospheric pressure.

[0091] For example, during the first sintering process, the sintering temperature can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, or 900℃; and the sintering time can be 2h, 2.5h, 3h, 3.5h, or 4h.

[0092] During the second sintering process, the sintering temperature T2 is 1200-1750℃, the sintering time is 4h-6h, and / or the sintering pressure is atmospheric pressure.

[0093] For example, during the second sintering process, the sintering temperature can be 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃, 1600℃, 1650℃, 1700℃, or 1750℃; and the sintering time can be 4h, 4.5h, 5h, 5.5h, or 6h.

[0094] In this application, after sintering is completed, the porous filter produced by sintering needs to be tested for mechanical strength. The porous filter has a compressive strength of 1.3MPa-2.5MPa at temperature T3 and a compressive strength of 0.6MPa-1.5MPa at temperature T4.

[0095] Preferably, the porous filter has a compressive strength of 1.5 MPa-1.8 MPa at temperature T3 and a compressive strength of 0.7 MPa-1.2 MPa at temperature T4.

[0096] The compressive strength test method shall refer to the compressive strength test method in GB / T 25319-2010 standard.

[0097] In one embodiment of this application, the temperature range of T3 is 10-30 ℃, and the temperature range of T4 is 900-1200 ℃.

[0098] For example, the T3 temperature can be 10, 15, 20, 25, or 30 °C. For example, the T4 temperature can be 900, 950, 1000, 1050, 1100, 1150, or 1200 °C.

[0099] This application also provides a porous filter, characterized in that it is prepared using the method described in any of the preceding claims.

[0100] Example

[0101] This application provides a general and / or specific description of the materials and test methods used in the experiments. In the following examples, unless otherwise specified, % represents wt%, i.e., mass percentage. Reagents or instruments used, unless otherwise specified, are all commercially available conventional reagent products.

[0102] Example 1

[0103] Example 1-1

[0104] Step 1: Silica, alumina, phenolic resin, ethanol, methanol and polyethylene glycol are mixed in a mass ratio of 40:60:1:1:9:0.5, and then granulated by spray granulation to prepare granules with a sphericity of 0.95-1 and a particle size range of 40-245 micrometers.

[0105] The sphericity test method was performed using a dynamic image particle analysis system (Dandong Better Instruments Co., Ltd.) in accordance with GB / T 39251-2020.

[0106] The particle size testing method was determined using a Malvern Mastersizer 3000 particle size analyzer.

[0107] Step 2: Mix the granules with the curing agent (a mixture of p-toluenesulfonic acid and sulfuric acid in a mass ratio of 68:1.5) at a mass ratio of 100:0.3 to form the printing material.

[0108] Step 3: Create a three-dimensional model of the sample to be printed, then input the three-dimensional model into the computer, add sintering aid (a mixture of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules) to the printing material, spread it evenly, and spray adhesive at the preset position. Repeat the spreading and adhesive spraying process to obtain the green body.

[0109] The binder is furan resin, the particle size D50 of the amorphous silica used is 1μm, the particle size of the spherical calcium aluminate used is 150μm, and the particle size of the aluminum fluoride granules used is 185μm.

[0110] Amorphous silica, spherical calcium aluminate, and aluminum fluoride granules are mixed in a mass ratio of 0.3:0.5:1.

[0111] Step 4: After obtaining the blank, perform a strength test on the blank, record the tensile strength data, and compile the statistics in Table 1.

[0112] The tensile strength was measured by printing sand castings of figure-eight blocks, according to JB / T 7526-2008.

[0113] Step 5: Immerse the obtained printed blank in a 50wt% mullite powder solution for 60 minutes.

[0114] Step 6: The densified blank is sintered for the first time at a temperature of 800℃ for 2 hours at atmospheric pressure.

[0115] Subsequently, a second sintering process was carried out under air conditions. The second sintering temperature was 1450℃, the time was 4 hours, and the pressure was atmospheric pressure.

[0116] Step 7: After sintering, the obtained ceramic product needs to be tested for mechanical strength. The test method should refer to the compressive strength test method in GB / T25319-2010 standard. The results are summarized in Table 2. T3 temperature is room temperature, and T4 temperature is 1000 degrees Celsius.

[0117] Step 8: Perform high-temperature casting tests to characterize the obtained ceramic filter product.

[0118] Based on the aforementioned seven steps, a spherical ceramic filter with a diameter of 100 mm and a thickness of 22 mm was prepared. The spherical filter was placed into a suitable metal gating port, and gray iron was melted to a temperature of 1500±20℃. A casting test platform was set up, and the molten gray iron was transported to the casting platform using a ladle. The molten iron was directly poured through the filter, and the application performance of the filter was characterized by statistically analyzing the quality of the cast iron and the casting time.

[0119] Method for testing the quality of molten iron: When using the direct pouring method, the ladle is tilted at a certain angle to ensure that the molten iron passes through the filter at a uniform speed during the pouring process. The filter is monitored in real time. When the filter is damaged, pouring is stopped, and the quality of the poured molten iron is recorded as the maximum pouring volume. The results are recorded in Table 3.

[0120] Casting time test method: Take another filter prepared according to the above 7 steps and use 300 kg of molten iron. In the direct casting method, use the same angle to tilt the ladle as in the casting time test method to ensure that the molten iron passes through the filter at the same or similar speed as in the casting time test method. Calculate the time required for all the molten iron to pass through the filter and record the results in Table 4.

[0121] Examples 1-2

[0122] The operation is the same as in Example 1-1, except that the mass ratio of silicon dioxide to aluminum oxide in step 1 is changed to 45:55, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0123] Examples 1-3

[0124] The operation is the same as in Example 1-1, except that the mass ratio of silicon dioxide and aluminum oxide in step 1 is changed to 50:50, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0125] Examples 1-4

[0126] The operation is the same as in Example 1-1, except that the mass ratio of silicon dioxide to aluminum oxide in step 1 is changed to 55:45, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0127] Examples 1-5

[0128] The operation is the same as in Example 1-1, except that the mass ratio of silicon dioxide to aluminum oxide in step 1 is changed to 60:40, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0129] Examples 1-6

[0130] The operation is the same as in Example 1-1, except that the mass ratio of silicon dioxide to aluminum oxide in step 1 is changed to 30:70, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0131] Examples 1-7

[0132] The operation is the same as in Example 1-1, except that the mass ratio of silicon dioxide to aluminum oxide in step 1 is changed to 70:30, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0133] Examples 1-8

[0134] The operation is the same as in Example 1-1, except that in step 1, silicon dioxide and aluminum oxide are replaced with only silicon dioxide, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0135] Examples 1-9

[0136] The operation is the same as in Example 1-1, except that in step 1, silicon dioxide and aluminum oxide are replaced with only aluminum oxide, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0137] Examples 1-10

[0138] The operation is the same as in Example 1-1, except that silicon dioxide and aluminum oxide in step 1 are replaced with only silicon carbide, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0139] Examples 1-11

[0140] The operation is the same as in Example 1-1, except that the ratio of silicon dioxide, aluminum oxide and phenolic resin in step 1 is changed to 40:60:3, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0141] Examples 1-12

[0142] The operation is the same as in Example 1-1, except that the ratio of silicon dioxide, aluminum oxide and phenolic resin in step 1 is changed to 40:60:5, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0143] Examples 1-13

[0144] The procedure was the same as in Examples 1-3, except that the adhesive in step 3 was changed from furan resin to phenolic resin. The results are summarized in Tables 1, 2, 3, and 4.

[0145] Examples 1-14

[0146] The procedure was the same as in Examples 1-3, except that the adhesive in step 3 was changed from furan resin to polyvinyl alcohol. The results are summarized in Tables 1, 2, 3, and 4.

[0147] Examples 1-15

[0148] The procedure was the same as in Examples 1-3, except that the binder in step 3 was changed from furan resin to silicate powder. The results are summarized in Tables 1, 2, 3, and 4.

[0149] Examples 1-16

[0150] The procedure was the same as in Examples 1-3, except that the mass ratio of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules was changed in step 3. The results are summarized in Tables 1, 2, 3, and 4.

[0151] Examples 1-17

[0152] The procedure was the same as in Examples 1-3, except that the mass ratio of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules was changed in step 3. The results are summarized in Tables 1, 2, 3, and 4.

[0153] Examples 1-18

[0154] The procedure was the same as in Examples 1-3, except that the mass ratio of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules was changed in step 3. The results are summarized in Tables 1, 2, 3, and 4.

[0155] Examples 1-19

[0156] The procedure was the same as in Examples 1-3, except that the mass ratio of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules was changed in step 3. The results are summarized in Tables 1, 2, 3, and 4.

[0157] Examples 1-20

[0158] The procedure was the same as in Examples 1-3, except that the mass ratio of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules was changed in step 3. The results are summarized in Tables 1, 2, 3, and 4.

[0159] Examples 1-21

[0160] The procedure was the same as in Examples 1-3, except that the mass ratio of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules was changed in step 3. The results are summarized in Tables 1, 2, 3, and 4.

[0161] Examples 1-22

[0162] The procedure was the same as in Examples 1-3, except that the mass ratio of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules was changed in step 3. The results are summarized in Tables 1, 2, 3, and 4.

[0163] Examples 1-23

[0164] The procedure was the same as in Examples 1-3, except that no sintering aids were added. The results are summarized in Tables 1, 2, 3, and 4.

[0165] Examples 1-24

[0166] The procedure was the same as in Examples 1-3, except that the first sintering temperature was changed to 900℃. The results are summarized in Tables 1, 2, 3, and 4.

[0167] Examples 1-25

[0168] The operation was the same as in Examples 1-3, except that the first sintering temperature was changed to 700℃. The results are summarized in Tables 1, 2, 3, and 4.

[0169] Examples 1-26

[0170] The operation was the same as in Examples 1-3, except that the first sintering temperature was changed to 1100℃. The results are summarized in Tables 1, 2, 3, and 4.

[0171] Comparative Example 1-1

[0172] The operation is the same as in Example 1-1, except that the ratio of silicon dioxide, aluminum oxide and phenolic resin in step 1 is changed to 40:60:0.5, and the results are statistically recorded in Tables 1, 2, 3 and 4.

[0173] Comparative Examples 1-2

[0174] The procedure was the same as in Example 1-1, except that no phenolic resin was added during the granulation process in step 1. The results are summarized in Tables 1, 2, 3, and 4.

[0175] Comparative Examples 1-3

[0176] The operation is the same as in Example 1-1, except that steps 1 to 6 are omitted, and in step 8, the ceramic filter prepared in Example 1-1 is replaced with a traditional foam silicon carbide filter produced by Shengquan CF-2BA. The results are statistically summarized in Tables 1, 2, 3 and 4.

[0177] Comparative Examples 1-4

[0178] The operation is the same as in Example 1-1, except that steps 1 to 6 are omitted, and in step 8, the ceramic filter prepared in Example 1-1 is replaced with an alumina filter FCF-3 produced by Shengquan. The results are statistically recorded in Tables 1, 2, 3 and 4.

[0179] Table 1 Performance parameters for printing figure-eight blocks

[0180] Note: Comparative Examples 1-3 and 1-4 are finished filters. Only pressure resistance tests and high-temperature casting tests were conducted for characterization. Therefore, the composition and tensile strength data are not statistically analyzed.

[0181] In this application, as shown in Table 1, examples 1-3 and 1-13 to 1-15 demonstrate that the choice of binder significantly affects the tensile strength of the printed blank. Increasing the amount of amorphous silica and aluminum fluoride granules slightly reduces the tensile strength. When the fine refractory granules are composed of silica and alumina, their tensile strength is generally higher than that of single-component materials (Examples 1-1 to 1-10). Conversely, insufficient binder content leads to lower tensile strength (Comparative Example 1-1). Examples 1-1 to 1-8, 1-11 to 1-12, and 1-16 to 1-22 all show a blank tensile strength greater than 2 MPa. This indicates that the porous filter preparation method disclosed in this application can well meet the requirements of the powder cleaning method and will not cause powder blowing cracking due to insufficient strength.

[0182] Table 2 Performance parameters of ceramic filters after green body sintering

[0183]

[0184] Note: Comparative Examples 1-3 and 1-4 are finished filters. Only pressure resistance tests and high-temperature casting tests were conducted for characterization. Therefore, sintering temperature data are not included in the statistics.

[0185] After sintering, the filter is required to have a certain strength at room temperature. Those skilled in the art believe that when the compressive strength at room temperature is above 1.38 MPa, the filter is not easily damaged during operation and transportation, thus avoiding the situation where the filter cannot be used due to physical damage. At the same time, at high temperature, it is also necessary to ensure that the compressive strength is greater than 0.65 MPa so that it can withstand the impact of molten iron casting on the filter skeleton and ensure its performance at high temperature.

[0186] As the content of added silica increases, the tensile strength in Table 1 and the compressive strength at room temperature in Table 2 both increase. Although it can be seen from Examples 1-8 in Table 1 that the tensile strength can reach 2.80 MPa when only silica and phenolic resin are used, alumina is more stable than silica at high temperatures. Therefore, it can be seen from Table 2 that adding too much silica will cause the filter to drop sharply at high temperatures (as in Examples 1-7 to 1-9).

[0187] As can be seen from Examples 1-6 and 1-7, with the increase of the amount of phenolic resin added, the physical properties of the filter in Tables 1 and 2 all show an initial increase followed by a decrease. This indicates that excessive phenolic resin has a negative effect on the transformer performance.

[0188] At the sintering temperature specified in this application, aluminum fluoride, as a sintering aid, becomes a liquid phase at a certain temperature. This liquid phase promotes dense sintering of the ceramic and eliminates air bubbles between particles. Excessive use of aluminum fluoride has a negative effect on ceramic sintering. Insufficient use results in insufficient sintering kinetics, making it difficult to promote dense sintering of the ceramic.

[0189] Comparative Examples 3 and 4 are existing technologies, and their compressive strength at temperatures T3 and T4 is barely sufficient or not sufficient to meet the requirements. Examples 1-1 to 1-5, 1-11 to 1-12, and 1-16 to 1-21 are all superior to existing technologies.

[0190] Table 3 Performance characteristics of ceramic filters in high-temperature casting test (maximum casting volume)

[0191]

[0192]

[0193] Note: 1. In Table 3, the blank area represents that during the statistical stage of the results in Tables 1 and 2, this embodiment could not be printed into a blank or sintered into a shape, so the high-temperature casting test in step 8 could not be carried out, and therefore there is no data in the blank area;

[0194] 2. Other data are rounded to the nearest integer.

[0195] Table 4. Performance Characterization Table of Ceramic Filters in High-Temperature Casting Test (Casting Time)

[0196]

[0197]

[0198] Note: 1. In Table 4, the blank area represents that during the result statistics stage of Tables 1 and 2, this embodiment could not be printed into a blank or sintered into a shape, so the high-temperature casting test in step 8 could not be carried out, and therefore there is no data in the blank area;

[0199] 2. Mid-cast failure refers to the situation where the filter is damaged during the casting of 300kg of molten iron. Casting must be stopped at this time. In this embodiment, the casting time is not recorded and is considered as failing the casting time test.

[0200] 3. Other casting times are rounded to the nearest integer.

[0201] It should be understood that once the filter is sintered, the width, shape, and length of its internal channels are immediately fixed. During the sintering process, due to the temperature difference between the internal and surface temperatures, even if the internal structure is fixed, incomplete sintering or residue blockage of the filter channels may occur. In actual production, this leads to a longer residence or passage time of molten metal in the filter, prolonging the casting time. Furthermore, the high temperature of the molten metal can even damage the internal structure of the filter, causing it to lose its intended filtration effect. Therefore, the casting time should be as short as possible. Similarly, in actual production, the filter needs to pass through as much molten metal as possible, i.e., ensuring the highest possible casting volume, to ensure the filter's service life.

[0202] Therefore, the formulation of the filter preparation material will directly affect the quality of the filter after sintering (whether the filter channel is intact, whether the channel is blocked, whether there are fragments and slag inside the filter after sintering, etc.), which in turn affects the casting time and the maximum casting volume.

[0203] In Table 3, the highest casting yield was best when the alumina content was 60% (Example 2-1), reaching 752 kg. When the alumina content was increased to 70% (Example 2-6), the highest casting yield decreased to 483 kg, but it was still better than the highest casting yield of the prior art (Comparative Examples 2-3 and 2-4). Among them, Examples 2-1 to 2-5, Examples 2-11, 2-12, and Examples 2-16 to 2-21 all showed better performance than the other examples. Their highest casting yield was approximately 1.5 to 2 times that of the prior art, indicating that the filters prepared by the preparation methods provided in Examples 1-1 to 1-5, Examples 1-11, 1-12, and Examples 1-16 to 1-21 have very good thermal stability, and their performance can fully meet production needs.

[0204] Table 4 combines the data from Table 3. In Table 3, filters with a casting volume of less than 300 kg will fail the casting time test. Therefore, such filters will be damaged during the casting process and are counted as "damaged during casting" in Table 4. Examples 2-6 and 2-7, which performed well in Table 3, had shorter casting times than the prior art. It is speculated that the filters prepared by the preparation methods provided in Examples 1-6 and 1-7 may have residue clogging the filter channels. This indicates that the filters prepared in Examples 1-6 and 1-7 are not as robust as those prepared in Examples 1-1 to 1-5, 1-11, and 1-12, or the filters prepared in Examples 1-16 to 1-21. This also explains the phenomenon that the highest casting volume in Table 3 did not exceed 500 kg, but its performance is still slightly better than the prior art. Examples 2-1 to 2-5, 2-11, 2-12, 2-16 to 2-21 still exhibit excellent performance, generally between 60-70 seconds, which greatly shortens the casting time compared with the prior art.

[0205] In summary, the filter prepared by the method provided in this application can achieve a tensile strength of over 2 MPa in the green body stage, which is sufficient to overcome the pressure exerted by the cleaning machine during the cleaning process. After sintering, although silica and alumina in the composition will affect the compressive strength at room temperature and high temperature, respectively, both can fully meet the production requirements, and there will be no situation where one performance is too high while the other is too low, leading to damage to the ceramic filter during use. Furthermore, the filter prepared according to the method of this application can have a maximum casting volume exceeding 750 kg, which is 1.5-2 times that of the prior art. At the same time, the casting time is significantly improved compared to the prior art, increasing the filtration efficiency and production efficiency of the filter. This indicates that the filter prepared by the method provided in this application has excellent performance in all aspects, possessing high strength and high thermal stability, while also having a faster casting time and a higher casting volume compared to the prior art. Therefore, the possibility of the filter being fine, fragile, prone to slag shedding, and damaged is greatly reduced, which can well meet the needs of daily transportation and high-temperature filtration.

[0206] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the protection scope of this application.

Claims

1. A method of making a porous filter, wherein, The method includes: Granulation: Fine refractory granules, binder, solvent and additives are mixed in a mass ratio of (90~100):(1~5):(5~15):(0.5~10) and then granulated to prepare granules; Printing material: Mix granular material and curing agent to form printing material; A three-dimensional model of the blank to be printed is established, and then the three-dimensional model is input into the computer to obtain the number of printing material layers required for the blank to be printed and the corresponding bonding area between the layers, that is, the preset position of the adhesive spraying. The printing material is laid flat, and adhesive is sprayed at a preset position. The process of laying flat and spraying adhesive is repeated to obtain a blank. The blank is sintered to form a porous filter.

2. The method according to claim 1, wherein the fine refractory granules are selected from one or more of mullite, silicon carbide, silicon dioxide, alumina, and zirconium oxide; and / or The adhesive is selected from one or more of the following: furan resin, phenolic resin, urea-formaldehyde resin adhesive, polyvinyl alcohol acetal adhesive, polyvinyl acetate (PVAc) emulsion, acrylic water-based adhesive, rubber emulsion adhesive, polyurethane water-based adhesive, cement, gypsum, water glass, lime, and clay; and / or The solvent is selected from one or more of water, methanol, ethanol, ethylene glycol, acetone, chloroform, carbon tetrachloride, diethyl ether, gasoline, benzene, toluene, and xylene; and / or The additive is selected from one or more of sulfates, sulfonates, phosphates, amines, and polyethylene glycol.

3. The method of claim 2, wherein, The fine refractory granules are composed of silicon dioxide and alumina, and the ratio of silicon dioxide to alumina is 1:(0.6~1.5) by mass. The solvents are water and methanol.

4. The method of claim 2, wherein, The ratio of the fine refractory granules to the binder is 100:(1~3) by mass; and / or The sphericity of the granules is 0.95-1.

5. The method of claim 1, wherein, The particle size distribution of the granules is 40-245 micrometers.

6. The method of claim 1, wherein, In the process of forming the printing raw material, the mass ratio of the curing agent to the granules is (0.20~0.65):

100.

7. The method of claim 6, wherein, The curing agent is selected from one or more of the following: sulfate ester, p-toluenesulfonic acid, xylenesulfonic acid, benzenesulfonic acid, sulfuric acid, phosphoric acid, mixed xylenesulfonic acid, lactic acid, citric acid, maleic anhydride, and oxalic acid.

8. The method according to claim 1, wherein, Before tiling, a sintering aid is added to the printing material, and the mass ratio of the printing material to the sintering aid is 100:(1.2~10).

9. The method according to claim 8, wherein, The sintering aid is selected from one or more of carbides, borides, oxides, spherical calcium aluminate, and aluminum fluoride granules.

10. The method according to claim 9, wherein, The sintering aid is a combination of amorphous silica, spherical calcium aluminate, and aluminum fluoride granules.

11. The method according to claim 10, wherein, The amorphous silica has a D50 particle size of 0.5-3 μm.

12. The method according to claim 1, wherein, The adhesive is selected from one or more of the following: polyvinyl alcohol (PVA), polyvinyl ketone, polyacrylic acid (PAA), furan resin, phenolic resin, epoxy resin, urea-formaldehyde resin adhesive, polyvinyl alcohol acetal adhesive, polyvinyl acetate (PVAc) emulsion, acrylate water-based adhesive, polyurethane water-based adhesive, water glass, phosphate, and polyurethane acrylate.

13. The method according to claim 12, wherein, The adhesive is furan resin.

14. The method according to claim 1, wherein, The tensile strength of the blank is 2.0-5.0 MPa.

15. The method according to claim 1, wherein, Before sintering the green body, a post-processing step is included, which includes the following steps: The green body is immersed in a fine powder solution to increase its bulk density.

16. The method according to claim 1, wherein, During the sintering process, the green body is sintered for the first time at temperature T1, and after the first sintering is completed, it is sintered for the second time at temperature T2, thereby obtaining the porous filter.

17. The method according to claim 16, wherein, During the first sintering process, the T1 temperature is 800-900℃, the sintering time is 2-4 hours, the pressure during the sintering process is atmospheric pressure, and / or During the second sintering process, the T2 temperature is 1200-1750℃, the sintering time is 4h-6h, and the pressure during the sintering process is atmospheric pressure.

18. The method according to any one of claims 1-17, wherein, The porous filter has a compressive strength of 1.3-2.5 MPa at temperature T3 and 0.6-1.5 MPa at temperature T4. The temperature range of T3 is 10-30 ℃, and the temperature range of T4 is 900-1200 ℃.

19. A porous filter, wherein, Prepared using the method described in any one of claims 1-18.

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