A method for preparing alumina grinding balls with a gradient structure

Abstract

This invention discloses a method for preparing alumina grinding balls with a gradient structure. The method includes: preparing alumina; preparing sintering aid powder; configuring a three-layer structural material layer; spraying atomized slurry with different components, continuously mixing the materials during spraying, resulting in three layers of powder; aging the three layers of powder to obtain three layers of aged material; using a rolling method for molding, sequentially adding the three layers of aged material while continuously spraying molding slurry, finally obtaining an alumina ball blank; drying the alumina ball blank, and then sintering to obtain alumina grinding balls with a gradient structure. In this invention, tetrabutyl titanate is coated onto the surface of the alumina powder particles, and adsorption bonding is achieved using a dispersant. The composition and pH of the slurry are designed to induce cross-linking of tetrabutyl titanate and control its cross-linking rate, achieving uniform distribution of the titanium dioxide precursor in the ball blank. Through temperature range design during sintering, alumina grinding balls with a gradient structure are finally prepared.

Description

Technical Field

[0001] This invention relates to the field of ceramic industry technology, and in particular to a method for preparing alumina grinding balls with a gradient structure. Background Technology

[0002] With the increasing demand for high-precision and high-wear-resistant grinding materials in industrial production, traditional alumina grinding balls are prone to wear, pulverization, and strength reduction during long-term use, making it difficult to meet the higher requirements of modern industry for grinding efficiency and service life. Therefore, developing a new type of alumina grinding ball with excellent impact resistance and high strength has become a research hotspot.

[0003] Driven by the need to improve the performance of alumina grinding balls, researchers have attempted to optimize their performance through gradient structure design. Existing gradient structure materials are mostly constructed by sequentially layering materials based on their composition. The bonding between these layers is significantly affected by the differences in the properties of the different components, leading to defects that can easily occur between layers during actual production, resulting in a substantial decrease in the mechanical properties of the product.

[0004] To meet the industrial demand for high-impact, high-strength abrasive materials, it is necessary to develop an alumina abrasive ball with a gradient structure. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing alumina grinding balls with a gradient structure.

[0006] The innovation of this invention lies in combining a specific slurry system to coat the surface of alumina powder particles with tetrabutyl titanate through an atomization step. A dispersant is used to achieve adsorption and bonding during the process. During the molding process, the molding slurry is used to form the green body into spheres. The composition and pH of the slurry are designed to induce cross-linking of tetrabutyl titanate and control its cross-linking rate, achieving a uniform distribution of the titanium dioxide precursor in the green body. Subsequently, during sintering, the in-situ growth of nano-titanium dioxide, the fine-grained growth of alumina, and the densification of the ceramic green body are completed sequentially through temperature range design. Finally, alumina grinding balls with a gradient structure are prepared, where the combination of fine and coarse grains achieves a synergistic effect of strength and toughness.

[0007] To achieve the above-mentioned objectives, the technical solution of this invention is: a method for preparing alumina grinding balls with a gradient structure, comprising the following steps:

[0008] (1) Alumina preparation: Alumina is ground and dried to obtain alumina powder with a fine D98 of 1.2-2 μm;

[0009] (2) Preparation of sintering aid powder: Take the following raw materials by mass fraction: 40-65% calcium oxide, 5-10% barium oxide, 20-30% silicon oxide, and 10-20% magnesium oxide, mix them, grind and dry them to obtain sintering aid powder with D98 of 1.2-2μm;

[0010] (3) Mixing and Aging: Three layers of structural material are prepared as the innermost, second outermost, and outermost layers. Each of the three layers is mixed for 1-2 hours. The mass fraction of the raw materials for the innermost layer is: 95-96% alumina powder and 4-5% sintering aid powder; the mass fraction of the raw materials for the second outermost layer is: 96-97% alumina powder and 3-4% sintering aid powder; the mass fraction of the raw materials for the outermost layer is: alumina powder...

[0011] 96-98%, with sintering aid powder accounting for 2-4%;

[0012] (4) Atomization: Atomized slurry with different components is sprayed onto the three-layer structural material layer. The mixture is continuously mixed during the spraying process. After the mixture is completed, three layers of powder are obtained. The solid content of the three layers of powder is controlled at 88-92%. The atomized slurry composition of the three-layer structural material layer is as follows: the innermost layer's atomized slurry composition is 83.5-91.5% anhydrous ethanol, 8-16% tetrabutyl titanate, and 0.2-0.5% dispersant; the next outermost layer's atomized slurry composition is 75.5-87.5% anhydrous ethanol, 12-24% tetrabutyl titanate, and 0.2-0.5% dispersant; the outermost layer's atomized slurry composition is 67.5-75.5% anhydrous ethanol, 24-32% tetrabutyl titanate, and 0.2-0.5% dispersant. The proportion of tetrabutyl titanate in the atomized slurry gradually increases from the innermost layer to the outermost layer.

[0013] (5) Aging: The three-layer powder is aged at 20-30℃ for 2-3 days to obtain three-layer aged material; (6) Molding: The rolling method is used for molding, in the order of the innermost layer, the second outermost layer and the outermost layer.

[0014] Add the three layers of aged material in step (4), and continuously spray molding slurry during the molding process to finally obtain alumina spherical blanks. The three layers of aged material are sprayed with different molding slurries. The molding slurry of the innermost layer is prepared by dissolving the following raw materials in water at the following mass percentages: 75-85% PVA,

[0015] 10-15% silane coupling agent KH-570, 4-8% hydroxyethyl cellulose, 1-4% sodium citrate; the molding slurry for the outermost layer is prepared by dissolving the following raw materials in water in the following mass percentages:

[0016] The outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 70-80% PVA, 15-20% silane coupling agent KH-570, 4-8% hydroxyethyl cellulose, and 1-4% sodium citrate; 65-75% PVA, 20-25% silane coupling agent KH-570, 4-8% hydroxyethyl cellulose, and 1-4% sodium citrate; the total mass of the raw materials in the three molding slurries...

[0017] The amount is 0.5% to 2% of the water mass;

[0018] (7) Drying and sintering: After drying the alumina spherical blanks, they are placed in a kiln for sintering. The sintering process is as follows:

[0019] a. The temperature is raised from room temperature to 200℃ at a rate of 10℃ / min, and the holding time at 200℃ is 30 minutes.

[0020] min;

[0021] b. Then raise the temperature to 1250-1300℃ at a rate of 5℃ / min and hold for 60-90min.

[0022] c. Increase the temperature to 1350-1400℃ for the second time, at a rate of 5℃ / min, and hold for 40-80min.

[0023] d. Use segmented cooling, lowering the temperature from the highest point to 1000℃, with a cooling rate of 3-5℃ / min;

[0024] e. When cooling from 1000℃ to room temperature, the cooling rate is 5~8℃ / min.

[0025] Alumina grinding balls with a gradient structure are obtained by firing.

[0026] Further, the dispersant in step (4) comprises, by mass fraction, 35-70% tricresylphenol phosphate polyoxyester and 30-65% polyacrylamide.

[0027] Furthermore, in step (4), the size of the spray droplets of the atomized slurry is controlled to be 50-80 μm.

[0028] Furthermore, the pH of the molding slurry in step (6) is 4 to 5.

[0029] Furthermore, in step (6), the innermost layer diameter is controlled to be in the range of 1.5 to 5 mm, the second outermost layer thickness is in the range of 2.5 to 5 mm, and the outermost layer thickness is in the range of 2 to 4 mm during molding.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention adopts a three-step process of "atomization-forming-sintering": introducing and dispersing tetrabutyl titanate into alumina-inducing cross-linking of tetrabutyl titanate to form a precursor-sintering self-grown titanium dioxide nanocrystals. Compared with the conventional method of directly adding titanium dioxide particles, the self-grown titanium dioxide grains are finer, the dispersion effect is better, and the growth-promoting effect on alumina grains is better during the sintering process.

[0032] 2. In the atomization process, the present invention designs the spray slurry, adds a dispersant to improve the functional groups on the surface of alumina, optimizes the surface compatibility between tetrabutyl titanate and alumina powder, and ensures that tetrabutyl titanate can be uniformly dispersed on the surface of alumina and bond with alumina.

[0033] 3. In this invention, the atomized slurry is sprayed during the atomization process to introduce tetrabutyl titanate. During the molding process, molding slurry is added to simultaneously complete the molding of alumina spheroids and the hydrolysis of tetrabutyl titanate. The hydrolysis rate of tetrabutyl titanate is controlled by controlling the pH of the slurry to avoid excessive titanium dioxide segregation due to excessively fast reaction.

[0034] 4. This invention designs a temperature curve to achieve in-situ growth of titanium dioxide nanocrystals in the spherical blank during the low-temperature stage, and to promote alumina development by maintaining a relatively long temperature in the medium-high temperature stage (below 1350℃). The high-temperature stage involves rapid heating to achieve densification of the alumina ceramic. This ensures the complete development of alumina grains in each layer while reducing the possibility of byproduct formation (such as aluminum titanate). The cooling stage controls the cooling rate to ensure the strength of the finished product while controlling shrinkage, reducing the gas-solid interface, and improving the mechanical strength of the material.

[0035] 5. In the gradient structure design of this invention, alumina is used as the main material. The chemical compatibility between the main materials and the physical properties of the surface have good stability, and no obvious defects are likely to occur between the layers during the grain growth process.

[0036] 6. This invention enables the in-situ growth of titanium dioxide nanocrystals within the alumina billet through formulation and process design. By utilizing the difference in the amount of titanium dioxide generated between different layers, the size of the alumina grains is controlled to complete the overall material design. The final product has a gradient structure with fine-grained to coarse-grained grains of increasing size. The former has strong grain boundary strength that inhibits crack propagation, while the latter has good resistance to plastic deformation, ultimately achieving synergistic enhancement of the strength and toughness of the alumina grinding ball. Attached Figure Description

[0037] Figure 1 This is an electron microscope image of the innermost layer structure of the alumina grinding ball prepared in Example 1.

[0038] Figure 2 This is an electron microscope image of the sub-outer layer structure of the alumina grinding ball prepared in Example 1.

[0039] Figure 3 This is an electron microscope image of the outermost layer structure of the alumina grinding ball prepared in Example 1.

[0040] Figure 4 The image shows the morphology of the alumina obtained in Example 1 after grinding.

[0041] Figure 5 The image shows the morphology of ordinary alumina ceramic after grinding and ball milling. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0043] Example 1: A method for preparing alumina grinding balls with a gradient structure, comprising the following steps:

[0044] (1) Alumina preparation: Alumina is ground and dried to obtain alumina powder with a fine D98 of 1.2-2 μm;

[0045] (2) Preparation of sintering aid powder: Take the following raw materials according to the mass fraction: 40% calcium oxide, 10% oxygen

[0046] Barium hydroxide, 30% silicon dioxide, and 20% magnesium oxide were mixed, ground, and dried to obtain a sintering aid powder with a D98 of 1.2–2 μm.

[0047] (3) Mixed aging: The three-layer structure material is configured as the innermost layer, the second outermost layer, and the outermost layer, for...

[0048] The three structural material layers were mixed for 1 hour each, and the mass fractions of the raw materials for the innermost layer were as follows:

[0049] The raw materials of the second outermost layer consist of 95% alumina powder and 5% sintering aid powder. The mass fractions of the raw materials in the third outermost layer are: 96% alumina powder and 4% sintering aid powder. The mass fractions of the raw materials in the outermost layer are: 96% alumina powder and 4% sintering aid powder.

[0050] 4%;

[0051] (4) Atomization: Spray atomized slurry with different components onto the three-layer structural material layers respectively.

[0052] The water spray droplet size is controlled between 50 and 80 μm. Mixing is continuous during spraying, resulting in three layers of powder. The solid content of each powder layer is controlled at 88%. The atomized slurry composition corresponding to the three structural material layers is as follows: The innermost layer's atomized slurry composition is...

[0053] The atomized slurry consists of 83.8% anhydrous ethanol, 16% tetrabutyl titanate, and 0.2% dispersant; the second outermost layer consists of 75.5% anhydrous ethanol, 24% tetrabutyl titanate, and 0.5% dispersant; the outermost layer consists of 67.5% anhydrous ethanol, 32% tetrabutyl titanate, and 0.5% dispersant; the dispersant, by mass fraction, includes 35% styrene phosphate polyoxyethylene ester and 65% polyacrylamide, with the proportion of tetrabutyl titanate in the atomized slurry gradually increasing from the innermost to the outermost layer;

[0054] (5) Aging: The three-layer powder is aged at 20°C for 2 days to obtain three-layer aged material;

[0055] (6) Molding: The rolling method is used for molding, in the order of the innermost layer, the second outermost layer, and the outermost layer.

[0056] Add the three layers of aged material from step (4), and continuously spray molding slurry during the molding process. The pH of the molding slurry is 4, and finally, alumina spherical blanks are obtained. The three layers of aged material are sprayed with different molding slurries. The innermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 75% PVA, 15% silane coupling agent KH-570, 8% hydroxyethyl cellulose, and 2% sodium citrate. The next outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages:

[0057] The outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 70% PVA, 20% silane coupling agent KH-570, 8% hydroxyethyl cellulose, and 2% sodium citrate.

[0058] The slurry contains 65% PVA, 25% silane coupling agent KH-570, 8% hydroxyethyl cellulose, and 2% sodium citrate. The total mass of the raw materials in the three molding slurries is 0.5% of the water mass. During molding, the innermost layer diameter is controlled at 1.5 mm, the second outermost layer thickness at 2.5 mm, and the outermost layer thickness at 2 mm.

[0059] mm;

[0060] (7) Drying and sintering: After drying the alumina spherical blanks, they are placed in a kiln for sintering. The sintering process is as follows:

[0061] a. The temperature is raised from room temperature to 200℃ at a rate of 10℃ / min, and the holding time at 200℃ is 30 minutes.

[0062] min;

[0063] b. Then raise the temperature to 1250℃ at a rate of 5℃ / min and hold for 60min;

[0064] c. Increase the temperature to 1350℃ a second time, at a rate of 5℃ / min, and hold for 40min;

[0065] d. A staged cooling method is used, lowering the temperature from the highest point to 1000℃ at a rate of 3℃.

[0066] / min;

[0067] e. When cooling from 1000℃ to room temperature, the cooling rate is 5℃ / min.

[0068] Alumina grinding balls with a gradient structure are obtained by firing.

[0069] According to SEM test results, the innermost layer of alumina particles is about 100nm in size, the next outermost layer of alumina particles is about 0.5-1μm in size, and the outermost layer of alumina particles has an alternating structure of small and large grains, with small grains ranging from 200-500nm in size and large grains ranging from 4-6μm in size.

[0070] Example 2: A method for preparing alumina grinding balls with a gradient structure, comprising the following steps:

[0071] (1) Alumina preparation: Alumina is ground and dried to obtain alumina powder with a fine D98 of 1.2-2 μm;

[0072] (2) Preparation of sintering aid powder: Take the following raw materials according to the mass fraction: 65% calcium oxide, 5% oxygen

[0073] Barium hydroxide, 20% silicon dioxide, and 10% magnesium oxide were mixed, ground, and dried to obtain a sintering aid powder with a D98 of 1.2–2 μm.

[0074] (3) Mixed aging: The three-layer structure material is configured as the innermost layer, the second outermost layer, and the outermost layer, for...

[0075] The three layers of structural materials were mixed for 1.2 hours each. The mass fraction of the raw materials in the innermost layer was 95.3% alumina powder and 4.7% sintering aid powder. The mass fraction of the raw materials in the next outermost layer was 96.3% alumina powder and 4.7% sintering aid powder.

[0076] 3.7%; the mass fractions of the outermost raw materials are: alumina powder 96.3%, sintering aid powder 3.7%;

[0077] (4) Atomization: Spray atomized slurry with different components onto the three-layer structural material layers respectively.

[0078] The water spray droplet size is controlled between 50 and 80 μm. Mixing is continuous during spraying, resulting in three layers of powder. The solid content of each powder layer is controlled at 89%. The atomized slurry composition corresponding to the three structural material layers is as follows: The innermost layer's atomized slurry composition is...

[0079] The atomized slurry consists of 91.5% anhydrous ethanol, 8% tetrabutyl titanate, and 0.5% dispersant; the second outermost layer consists of 87.5% anhydrous ethanol, 12% tetrabutyl titanate, and 0.5% dispersant; the outermost layer consists of 75.5% anhydrous ethanol, 24% tetrabutyl titanate, and 0.5% dispersant; the dispersant, by mass fraction, includes 40% styrene phosphate polyoxyethylene ester and 60% polyacrylamide, with the proportion of tetrabutyl titanate in the atomized slurry gradually increasing from the innermost layer to the outermost layer;

[0080] (5) Aging: The three-layer powder was aged at 23°C for 2.5 days to obtain three-layer aged material;

[0081] (6) Molding: The rolling method is used for molding, in the order of the innermost layer, the second outermost layer, and the outermost layer.

[0082] Add the three layers of aged material from step (4), and continuously spray molding slurry during the molding process. The pH of the molding slurry is 4.2. Finally, alumina spherical blanks are obtained. The three layers of aged material are sprayed with different molding slurries. The innermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 85% PVA, 10% silane coupling agent KH-570, 4% hydroxyethyl cellulose, and 1% sodium citrate. The next outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages:

[0083] The outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 80% PVA, 15% silane coupling agent KH-570, 4% hydroxyethyl cellulose, and 1% sodium citrate.

[0084] The slurry contains 75% PVA, 20% silane coupling agent KH-570, 4% hydroxyethyl cellulose, and 1% sodium citrate. The total mass of the raw materials in the three molding slurries is 1% of the water mass. During molding, the innermost layer diameter is controlled at 3mm, the second outermost layer thickness at 3mm, and the outermost layer thickness at [missing value].

[0085] 3mm;

[0086] (7) Drying and sintering: After drying the alumina spherical blanks, they are placed in a kiln for sintering. The sintering process is as follows:

[0087] a. The temperature is raised from room temperature to 200℃ at a rate of 10℃ / min, and the holding time at 200℃ is 30 minutes.

[0088] min;

[0089] b. Then raise the temperature to 1260℃ at a rate of 5℃ / min and hold for 70min.

[0090] c. Increase the temperature to 1360℃ a second time, at a rate of 5℃ / min, and hold for 50min;

[0091] d. A segmented cooling method is adopted, reducing the temperature from the highest point to 1000℃ at a cooling rate of 3.5℃ / min;

[0092] e. When cooling from 1000℃ to room temperature, the cooling rate is 6℃ / min.

[0093] Alumina grinding balls with a gradient structure are obtained by firing.

[0094] Example 3: A method for preparing alumina grinding balls with a gradient structure, comprising the following steps:

[0095] (1) Alumina preparation: Alumina is ground and dried to obtain alumina powder with a fine D98 of 1.2-2 μm;

[0096] (2) Preparation of sintering aid powder: Take the following raw materials by mass fraction: 55% calcium oxide, 7% sintering agent powder.

[0097] Barium, 25% silicon dioxide, and 13% magnesium oxide were mixed, ground, and dried to obtain a sintering aid powder with a D98 of 1.2–2 μm.

[0098] (3) Mixed aging: The three-layer structure material is configured as the innermost layer, the second outermost layer, and the outermost layer, for...

[0099] The three layers of structural materials were mixed for 1.5 hours each. The mass fraction of the raw materials in the innermost layer was: 95.8% alumina powder and 4.2% sintering aid powder. The mass fraction of the raw materials in the next outermost layer was: 96.8% alumina powder and 4.2% sintering aid powder.

[0100] 3.2%; the mass fractions of the outermost raw materials are: alumina powder 96.8%, sintering aid powder 3.2%;

[0101] (4) Atomization: Spray atomized slurry with different components onto the three-layer structural material layers respectively.

[0102] The water spray droplet size is controlled between 50 and 80 μm. Mixing is continuous during spraying, resulting in three layers of powder. The solid content of each powder layer is controlled at 90%. The atomized slurry composition corresponding to the three structural material layers is as follows: The innermost layer's atomized slurry composition is...

[0103] The atomized slurry consists of 83.5% anhydrous ethanol, 16% tetrabutyl titanate, and 0.5% dispersant; the second outermost layer consists of 82% anhydrous ethanol, 17.7% tetrabutyl titanate, and 0.3% dispersant; the outermost layer consists of 70% anhydrous ethanol, 29.8% tetrabutyl titanate, and 0.2% dispersant; the dispersant, by mass fraction, includes 60% styrene phosphate polyoxyethylene ester and 40% polyacrylamide, with the proportion of tetrabutyl titanate in the atomized slurry gradually increasing from the innermost to the outermost layer;

[0104] (5) Aging: The three-layer powder is aged at 28℃ for 3 days to obtain three-layer aged material;

[0105] (6) Molding: The rolling method is used for molding, in the order of the innermost layer, the second outermost layer, and the outermost layer.

[0106] Add the three layers of aged material from step (4), and continuously spray molding slurry during the molding process. The pH of the molding slurry is 4.8, and finally alumina spherical blanks are obtained. The three layers of aged material are sprayed with different molding slurries. The innermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 78% PVA, 12% silane coupling agent KH-570, 6% hydroxyethyl cellulose, and 4% sodium citrate. The next outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages:

[0107] The outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 73% PVA, 18% silane coupling agent KH-570, 5% hydroxyethyl cellulose, and 4% sodium citrate.

[0108] The mixture consists of 68% PVA, 22% silane coupling agent KH-570, 6% hydroxyethyl cellulose, and 4% sodium citrate. The total mass of the raw materials in the three molding slurries is 1.5% of the water mass. During molding, the innermost layer diameter is controlled to be 4 mm, the second outermost layer thickness is 4 mm, and the outermost layer thickness is 3.5 mm.

[0109] (7) Drying and sintering: After drying the alumina spherical blanks, they are placed in a kiln for sintering. The sintering process is as follows:

[0110] a. The temperature is raised from room temperature to 200℃ at a rate of 10℃ / min, and the holding time at 200℃ is 30 minutes.

[0111] min;

[0112] b. Then raise the temperature to 1280℃ at a rate of 5℃ / min and hold for 80min.

[0113] c. Increase the temperature to 1380℃ a second time at a rate of 5℃ / min, and hold for 70min.

[0114] d. A segmented cooling method is adopted, reducing the temperature from the highest point to 1000℃ at a cooling rate of 4.5℃ / min;

[0115] e. When cooling from 1000℃ to room temperature, the cooling rate is 7℃ / min.

[0116] Alumina grinding balls with a gradient structure are obtained by firing.

[0117] Example 4: A method for preparing alumina grinding balls with a gradient structure, comprising the following steps:

[0118] (1) Alumina preparation: Alumina is ground and dried to obtain alumina powder with a fine D98 of 1.2-2 μm;

[0119] (2) Preparation of sintering aid powder: Take the following raw materials by mass fraction: 50% calcium oxide, 8% calcium oxide

[0120] Barium, 27% silicon dioxide, and 15% magnesium oxide were mixed, ground, and dried to obtain a sintering aid powder with a D98 of 1.2–2 μm.

[0121] (3) Mixed aging: The three-layer structure material is configured as the innermost layer, the second outermost layer, and the outermost layer, for...

[0122] The three layers of structural materials were mixed for 1-2 hours respectively. The mass fraction of the raw materials in the innermost layer was: 96% alumina powder and 4% sintering aid powder; the mass fraction of the raw materials in the second outermost layer was: 97% alumina powder and 3% sintering aid powder; and the mass fraction of the raw materials in the outermost layer was: 98% alumina powder and 4% sintering aid powder.

[0123] Powder content: 2%;

[0124] (4) Atomization: Spray atomized slurry with different components onto the three-layer structural material layers respectively.

[0125] The water spray droplet size is controlled between 50 and 80 μm. Mixing is continuous during spraying, resulting in three layers of powder. The solid content of each powder layer is controlled at 92%. The atomized slurry composition corresponding to the three structural material layers is as follows: The innermost layer's atomized slurry composition is...

[0126] The atomized slurry consists of 90.7% anhydrous ethanol, 9% tetrabutyl titanate, and 0.3% dispersant; the second outermost layer consists of 78% anhydrous ethanol, 21.8% tetrabutyl titanate, and 0.2% dispersant; the outermost layer consists of 74% anhydrous ethanol, 25.6% tetrabutyl titanate, and 0.4% dispersant; the dispersant, by mass fraction, includes 70% styrene phosphate polyoxyethylene ester and 30% polyacrylamide, with the proportion of tetrabutyl titanate in the atomized slurry gradually increasing from the innermost to the outermost layer;

[0127] (5) Aging: The three-layer powder is aged at 30°C for 3 days to obtain three-layer aged material;

[0128] (6) Molding: The rolling method is used for molding, in the order of the innermost layer, the second outermost layer, and the outermost layer.

[0129] Add the three layers of aged material from step (4), and continuously spray molding slurry during the molding process. The pH of the molding slurry is 5, and finally, alumina spherical blanks are obtained. The three layers of aged material are sprayed with different molding slurries. The innermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 77% PVA, 13% silane coupling agent KH-570, 5% hydroxyethyl cellulose, and 3% sodium citrate. The next outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages:

[0130] The outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 75% PVA, 16% silane coupling agent KH-570, 6% hydroxyethyl cellulose, and 3% sodium citrate.

[0131] The slurry contains 72% PVA, 20% silane coupling agent KH-570, 5% hydroxyethyl cellulose, and 3% sodium citrate. The total mass of the raw materials in the three molding slurries is 2% of the water mass. During molding, the innermost layer diameter is controlled at 5mm, the second outermost layer thickness at 5mm, and the outermost layer thickness at 4mm.

[0132] mm;

[0133] (7) Drying and sintering: After drying the alumina spherical blanks, they are placed in a kiln for sintering. The sintering process is as follows:

[0134] a. The temperature is raised from room temperature to 200℃ at a rate of 10℃ / min, and the holding time at 200℃ is 30 minutes.

[0135] min;

[0136] b. Then raise the temperature to 1300℃ at a rate of 5℃ / min and hold for 90min;

[0137] c. Increase the temperature to 1400℃ a second time, at a rate of 5℃ / min, and hold for 80min;

[0138] d. A staged cooling method is used, lowering the temperature from the highest point to 1000℃ at a rate of 5℃.

[0139] / min;

[0140] e. When cooling from 1000℃ to room temperature, the cooling rate is 8℃ / min.

[0141] Alumina grinding balls with a gradient structure are obtained by firing.

[0142] High-speed self-polishing was performed using a high-energy mill on ordinary alumina ceramic grinding balls (grain size range approximately 3-5 μm) and the alumina ceramic grinding balls prepared according to Examples 1-3 of this invention. The high-energy mill has an internal volume of 0.2 m³. 3 The filling rate was approximately 40%, the maximum linear velocity inside the device was approximately 7 m / s, and the surface condition of the sample was observed after 48 hours of continuous operation. The wear test results are shown below.

[0143]

[0144]

[0145] The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing alumina grinding balls with a gradient structure, characterized in that, Includes the following steps: (1) Alumina preparation: Alumina is ground and dried to obtain alumina powder with a fine D98 of 1.2-2 μm; (2) Preparation of sintering aid powder: Take the following raw materials by mass fraction: 40-65% calcium oxide, 5-10% barium oxide, 20-30% silicon oxide, and 10-20% magnesium oxide, mix them, grind and dry them to obtain sintering aid powder with D98 of 1.2-2μm; (3) Mixing: Prepare three layers of structural material, namely the innermost layer, the second outermost layer, and the outermost layer. Mix the three layers of structural material for 1-2 hours respectively. The mass fraction of the raw material in the innermost layer is as follows: The alumina powder accounts for 95-96%, and the sintering aid powder accounts for 4-5%; the mass fraction of the raw materials in the second outermost layer is: alumina powder 96-97%, and sintering aid powder 3-4%; the mass fraction of the raw materials in the outermost layer is: alumina powder accounting for... 96-98%, with sintering aid powder accounting for 2-4%; (4) Atomization: Atomized slurry with different components is sprayed onto the three-layer structural material layer. The mixture is continuously mixed during the spraying process. After the mixture is completed, three layers of powder are obtained. The solid content of the three layers of powder is controlled at 88-92%. The atomized slurry composition of the three-layer structural material layer is as follows: the innermost layer's atomized slurry composition is 83.5-91.5% anhydrous ethanol, 8-16% tetrabutyl titanate, and 0.2-0.5% dispersant; the next outermost layer's atomized slurry composition is 75.5-87.5% anhydrous ethanol, 12-24% tetrabutyl titanate, and 0.2-0.5% dispersant; the outermost layer's atomized slurry composition is 67.5-75.5% anhydrous ethanol, 24-32% tetrabutyl titanate, and 0.2-0.5% dispersant. The proportion of tetrabutyl titanate in the atomized slurry gradually increases from the innermost layer to the outermost layer. (5) Aging: The three-layer powder is aged at 20-30℃ for 2-3 days to obtain three-layer aged material; (6) Molding: The rolling method is used for molding. The three layers of aged material from step (5) are added in the order of the innermost layer, the second outermost layer, and the outermost layer. Molding slurry is continuously sprayed during the molding process to finally obtain alumina spherical blanks. Different molding slurries are sprayed on the three layers of aged material. The molding slurry for the innermost layer is prepared by dissolving the following raw materials in water at the following mass percentages: 75-85% PVA, 10-15% silane coupling agent KH-570, 4-8% hydroxyethyl cellulose, 1-4% sodium citrate; the molding slurry for the outermost layer is prepared by dissolving the following raw materials in water in the following mass percentages: The outermost molding slurry is prepared by dissolving the following raw materials in water at the following mass percentages: 70-80% PVA, 15-20% silane coupling agent KH-570, 4-8% hydroxyethyl cellulose, and 1-4% sodium citrate; the total mass of the raw materials in the three molding slurries is 0.5-2% of the mass of water. (7) Drying and sintering: After drying the alumina spherical blanks, they are placed in a kiln for sintering. The sintering process is as follows: a. The heating rate from room temperature to 200℃ is 10℃ / min, and the holding time at 200℃ is 30min; b. Then raise the temperature to 1250-1300℃ at a rate of 5℃ / min and hold for 60-90min. c. Increase the temperature to 1350-1400℃ for the second time, at a rate of 5℃ / min, and hold for 40-80min. d. Use segmented cooling, lowering the temperature from the highest point to 1000℃, with a cooling rate of 3-5℃ / min; e. When cooling from 1000℃ to room temperature, the cooling rate is 5-8℃ / min; Alumina grinding balls with a gradient structure are obtained by firing.

2. The method for preparing alumina grinding balls with a gradient structure according to claim 1, characterized in that, The dispersant in step (4) comprises, by mass fraction, 35-70% tricresylphenol phosphate polyoxyester and 30-65% polyacrylamide.

3. The method for preparing alumina grinding balls with a gradient structure according to claim 1, characterized in that, In step (4), the size of the spray droplets of the atomized slurry is controlled to be 50-80 μm.

4. The method for preparing alumina grinding balls with a gradient structure according to claim 1, characterized in that, The pH of the molding slurry in step (6) is 4 to 5.

5. The method for preparing alumina grinding balls with a gradient structure according to claim 1, characterized in that, In step (6), the innermost layer diameter is controlled to be in the range of 1.5 to 5 mm, the second outermost layer thickness is in the range of 2.5 to 5 mm, and the outermost layer thickness is in the range of 2 to 4 mm during molding.

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