High-strength impact-resistant gradient material ceramic grinding ball and method of making same

Abstract

The application relates to a high-strength impact-resistant gradient ceramic grinding ball material, which comprises N material layers, N>=4; in each material layer, alumina accounts for 35wt%-95wt% in percentage by mass, and the rest is a composite auxiliary material. The application has the beneficial effects that: the powder materials of different layers can all reach the best sintering temperature area to be sintered to be dense, the layer interface defects are few, the specific gravity range of the multi-gradient material grinding ball is wide, basically covering the grinding ball demand range of the high-energy-density ore grinding method; the overall toughness, strength and impact resistance of the material can be greatly improved; the production cost is low, and the application is suitable for industrialized batch production; compared with ordinary grinding balls, the application can avoid the obvious wear and tear conditions such as peeling, notching and broken ball in severe working conditions, greatly reduces the consumption of grinding balls used in large mine semi-milling and other new high-efficiency energy-saving technologies, and has very obvious economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic non-metallic ceramic materials, and in particular relates to a high-strength, impact-resistant gradient material ceramic grinding ball and a preparation method thereof. Background Art

[0002] Functionally gradient materials (FGMs) are a new type of composite material composed of two or more materials whose composition and structure exhibit a continuous gradient. The gradient distribution of composition between different materials allows for a smooth transition from one material to another within the same component, thereby alleviating interfacial failure. FGMs can improve the connection mechanism between different materials, resulting in a smoother microstructural transition and effectively reducing stress at the interface. FGMs can be combined with ceramic materials with different specific properties to impart properties such as high temperature resistance, high wear resistance, and high impact resistance. These properties have attracted widespread attention from researchers and have become a research hotspot in the ceramics field.

[0003] The preferred crushing and grinding technology for modern mineral processing plants is the semi-autogenous grinding mill (SAG) mill. The grinding balls used have the greatest impact on SAG mill production efficiency. However, due to the often harsh operating conditions of SAG mills, existing grinding balls are prone to significant wear and tear, such as ball breakage, spalling, and excessive wear. Consequently, ceramic grinding balls have a short service life and are consumed at high rates, significantly impacting their efficiency and economic benefits. Therefore, the development of high-strength, high-impact, and low-wear ceramic grinding balls is needed to mitigate the wear and tear caused by ball breakage and spalling in high-energy-density operating conditions.

[0004] Most existing methods for preparing functionally gradient materials (FGMs) involve sequentially layering powder materials with varying ratios and then sintering the entire material. However, because the optimal sintering temperatures for powder materials with varying ratios vary during sintering of ceramic grinding balls, existing FGM preparation methods cannot guarantee high density across all layers of the ceramic material, especially in multi-layer gradient materials. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a high-strength, impact-resistant, gradient material ceramic grinding ball and a preparation method thereof.

[0006] This high-strength, impact-resistant gradient ceramic grinding ball material comprises N material layers, N being ≥ 4. In each material layer, aluminum oxide accounts for 35wt% to 95wt% by weight, with the remainder being composite auxiliary materials. The composite auxiliary materials account for 5wt% to 60wt% by weight in the innermost layer. The mass percentage of the composite auxiliary materials in each material layer from the innermost layer to the outermost layer of the N material layers increases layer by layer within a certain range of variation, and finally, the mass percentage of the composite auxiliary materials in the outermost layer increases to 20wt% to 65wt%.

[0007] The thickness of each material layer is 0.5mm to 5mm;

[0008] The composite auxiliary materials include kaolin, coal gangue, heavy calcium, magnesium carbonate, zirconium silicate, silicon oxide, zirconium oxide, cerium oxide, yttrium oxide and lanthanum oxide.

[0009] Preferably, the composite auxiliary material increases in weight percentage in each material layer from the innermost layer to the outermost layer, and the variation range is 1wt% to 10wt%.

[0010] Preferably, the thickness of the innermost material layer is 1 to 3 times the thickness of the second material layer.

[0011] Preferably, among the composite auxiliary materials, kaolin, coal gangue, heavy calcium carbonate and magnesium carbonate account for 4wt% to 40wt% of the total mass of the ceramic grinding ball material, zirconium silicate, silicon oxide, zirconium oxide, cerium oxide, yttrium oxide and lanthanum oxide account for 0wt% to 65wt% of the total mass of the ceramic grinding ball material, and aluminum oxide accounts for 35wt% to 95wt% of the total mass of the ceramic grinding ball material.

[0012] Preferably, the fineness D98 of alumina and composite auxiliary materials is 1-3 microns; among N material layers, the difference in fineness D50 between two adjacent material layers is ≤0.15 microns, and the fineness D50 is used to control the median particle size; the difference in fineness D98 between two adjacent material layers is ≤0.7 microns, and the fineness D98 is used to control the maximum particle size; the purpose of double fineness control is to ensure the fineness difference of powder in two adjacent material layers.

[0013] The method for preparing ceramic grinding balls using high-strength, impact-resistant gradient ceramic grinding ball material comprises the following steps:

[0014] Step 1, material preparation: prepare N parts of raw materials according to the proportion of each component of the ceramic grinding ball material, use a ball mill to coarsely grind the N parts of raw materials, and then use a sand mill to finely grind them as needed. After drying the finely ground raw materials, number them from 1 to N according to the mass percentage of the composite auxiliary materials contained in each part of the finely ground raw materials from low to high for later use;

[0015] Step 2: The N portions of finely ground raw materials obtained in step 1 are molded layer by layer in increasing order by a rolling method or an injection molding method, and a binder is sprayed during the molding process to obtain a spherical ceramic blank;

[0016] Step 3, drying, debinding and sintering: drying, debinding and sintering the ceramic green body obtained in step 2 to obtain high-strength and impact-resistant gradient material ceramic grinding balls.

[0017] As a preference:

[0018] In step 1, the purity of the prepared N parts of raw materials is ≥99.5% and the particle size is ≤50 microns;

[0019] In step 1, N portions of raw materials are coarsely ground in a ball mill, wherein the coarse grinding medium is water and alumina balls, the weight ratio of alumina balls to raw materials is (5:2) to (4:1), the coarse grinding time is 12 to 48 hours, and the fineness D98 of the discharge material is 1.5 to 10 μm;

[0020] In step 1, when the coarsely ground material is finely ground using a sand mill, the fine grinding medium is water and zirconium oxide balls, and the fineness D98 of the material is 1 to 3 microns.

[0021] As a preference:

[0022] In step 2, when spraying the binder, among the N material layers of the spherical ceramic blank, the binder concentration of the outer material layer in any two adjacent material layers is 1.05 to 1.2 times the binder concentration of the inner material layer;

[0023] In step 2, the binder includes at least one of PVA, glycerol and polyacrylamide;

[0024] When the injection molding method is used for molding in step 2, vacuum sludge refining is performed first and then injection molding is performed: N parts of finely ground raw materials are added to the injection molding machine mold of the previous layer of raw materials in sequence. After the injection molding of the previous layer is completed, the raw materials are transferred to the injection molding machine mold of the next layer of raw materials to continue molding; the injection molding pressure is 0.2-0.7 MPa, and the injection molding temperature is 60-70°C; the thickness of the interval between the injection molding machine mold of the previous layer of raw materials and the injection molding machine mold of the next layer of raw materials is 0.5-6 mm; the injection molding pressure at the injection molding machine mold of the next layer of raw materials is 1.05-1.2 times the injection molding pressure at the injection molding machine mold of the previous layer of raw materials.

[0025] In step 2, when the rolling method is used for forming, the thickness of each material layer of the spherical ceramic blank is 0.55 mm to 6.1 mm; among the N material layers of the spherical ceramic blank, the forming speed of the outer material layer of any two adjacent material layers is 1.05 to 1.2 times the forming speed of the inner material layer.

[0026] Preferably, in step 3, when the ceramic green body after drying and debinding is sintered, the low temperature stage is as follows: first, the temperature is raised to 200°C at a rate of 2-5°C / min and kept warm for 2-5 hours; the medium temperature stage is as follows: the temperature is raised to 500-600°C at a rate of 2-10°C / min and kept warm for 1-3 hours; the high temperature stage is as follows: the temperature is raised to 1350-1550°C at a rate of 5-10°C / min and kept warm for 3-5 hours; and then cooled to room temperature.

[0027] As preferred: the high-strength anti-impact gradient material ceramic grinding ball prepared in step 3 has a density of 3.3-5 g / cm3, a Vickers hardness of 1000-1350 GPa, a self-abrasion of 0.1-1.5 g / hr kg, and a belt abrasion of 0.1-1 g / hr kg.

[0028] The present application has the following advantages:

[0029] The present application designs a ceramic grinding ball material including N layers of material layers, N>=4, taking alumina as a main phase, introducing different gradient proportions of auxiliary agents to sinter the alumina main phase with other phases, and enabling the powder materials of different layers to reach the best sintering temperature region so as to be sintered to be dense, have few layer interface defects, and have a wide range of specific gravity of the multi-gradient material grinding ball, which basically covers the demand range of the grinding ball for high energy density grinding methods.

[0030] The ceramic grinding ball material of the present application introduces mullite phase, zirconium silicate phase and tetragonal zirconium phase by adopting a layered gradient formula, adopts rolling forming and injection molding, has the effects of mullite whisker toughening, zirconia phase change toughening and micro-crack toughening caused by stress between different layers, can greatly improve the overall toughness, strength and impact resistance of the material, has low production cost and is suitable for industrialized mass production.

[0031] The high-strength anti-impact gradient material ceramic grinding ball prepared in the present application mainly has point damage and furrow plowing wear when subjected to external strong impact and severe friction, can avoid obvious wear conditions such as peeling, notching and broken ball in severe working conditions compared with ordinary grinding balls, greatly reduces the consumption of grinding balls used in large mine semi-autogenous grinding and other new energy-efficient technologies, and has very obvious economic benefits.

[0032] In the present application, the fineness difference range of the adjacent layers of materials is controlled, so that the prepared ceramic grinding ball material has uniform particle distribution, good compatibility at the junction of different layers, and can match different layer body forming slurry proportion and forming speed parameters according to different ball blank sizes, so that the ball blank has high body strength, prevents cracks in the transfer and sintering stages, maintains consistent shrinkage rate inside and outside, and ensures high strength of the gradient material grinding ball. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A cross-sectional view of the product prepared in Example 2 is shown in Figure 2.

[0034] Figure 2 A cross-sectional view of the product prepared in Example 3 is shown in Figure 3.

[0035] Figure 3 A cross-sectional view of the product prepared in Example 4 is shown in Figure 4. DETAILED DESCRIPTION

[0036] The application will be further described in connection with the following examples. The following examples are intended to help understand the application. It should be noted that for those skilled in the art, without departing from the principles of the application, several modifications can be made to the application, and these improvements and modifications also fall within the scope of the claims of the application. Example 1:

[0037] A high-strength impact-resistant gradient ceramic grinding ball material, comprising N layers of material layers, N=4; in each layer of material layers, the proportion of alumina from the inside to the outside is 84wt%, 80wt%, 77wt%, and 75wt% respectively, and the rest is a composite auxiliary material; the mass percentage of the composite auxiliary material in the innermost layer is 16wt%, and in each layer of material layers from the innermost layer to the outermost layer in the N layers of material layers, the mass percentage of the composite auxiliary material in each layer of material layers increases by a certain range, and the change amount of the composite auxiliary material in each layer of material layers from the innermost layer to the outermost layer is increased by 2-4wt% layer by layer; the mass percentage of the composite auxiliary material in the outermost layer is increased to 25wt%.

[0038] The thickness of the first layer of material layer is 3mm; the thickness of the outer layer of material layer is 1.5 times the thickness of the adjacent inner layer of material layer;

[0039] The composite auxiliary material includes kaolin, coal gangue, heavy calcium, magnesium carbonate, zirconium silicate, silicon oxide, zirconium oxide, cerium oxide, yttrium oxide and lanthanum oxide; the kaolin, coal gangue, heavy calcium and magnesium carbonate in the composite auxiliary material account for 4wt%-10wt% of the total mass of the ceramic grinding ball material, the zirconium silicate, silicon oxide, zirconium oxide, cerium oxide, yttrium oxide and lanthanum oxide account for 3wt%-20wt% of the total mass of the ceramic grinding ball material, and the alumina accounts for 75wt%-84wt% of the total mass of the ceramic grinding ball material;

[0040] The fineness D98 of alumina and composite auxiliary material is 1-3 microns; in the N layers of material layers, the fineness D50 of the adjacent two layers of material layers differs by ≤0.15 microns, and the fineness D50 is used to control the median particle size; the fineness D98 of the adjacent two layers of material layers differs by ≤0.7 microns, and the fineness D98 is used to control the maximum particle size; the purpose of double fineness control is to ensure the fineness difference of the powders in the adjacent two layers of material layers. Example 2:

[0041] A method for preparing a high-strength impact-resistant gradient ceramic grinding ball material for ceramic grinding ball, specifically comprising the following steps:

[0042] Step S1-1: 5 groups of materials are prepared according to the mass percentage formula in Table 1, and the serial numbers 1-5 are identified. The fineness of alumina is 35 microns, and the fineness of the rest of the powders is 1.5-20 microns.

[0043] Table 1 Material formula of high strength impact resistant gradient ceramic grinding balls in Example 2

[0044]

[0045] The five composite auxiliary materials were coarsely ground in a ball mill for 6-8 hours using water and alumina balls as the media, with a ball-to-material weight ratio of 4:2. The five composite auxiliary materials had a D98 fineness of 6-7.5 microns. They were then ultrafine ground using a sand mill, using 0.6-0.8mm zirconia balls as the media. The D98 finenesses of the composite auxiliary materials 1-5 were 2.1μm, 1.9μm, 1.7μm, 1.85μm, and 1.9μm, respectively. The maximum difference in D50 between adjacent layers was 0.11 microns. Finally, the powders were dried and collected in sequence using a spray dryer for later use.

[0046] Step S1-2: Grinding ball blank forming:

[0047] Five parts of composite auxiliary material were added to the molding machine's hopper, starting with the smallest part and ending with the largest. Rolling molding was performed using a rolling method. The binder solution sprayed during the rolling process consisted of a PVA solution with a mass percentage of 0.05wt%, 0.06wt%, 0.07wt%, 0.075wt%, and 0.075wt%, respectively. The first core layer had a thickness of 1.5mm, the second layer had a thickness of 1mm, the third layer had a thickness of 2mm, the fourth layer had a thickness of 2mm, and the fifth layer had a thickness of 4mm. During the molding process, the feed rate for each layer was 1.1 times, 1.2 times, 1.3 times, and 1.5 times that of the previous layer, respectively. At the end of the molding process, the ball was tightened, the surface finished, and then shipped out of the machine.

[0048] Step S1-3: Drying, debinding and sintering:

[0049] The ceramic blank prepared in S1-2 was placed in a kiln and heated to 200°C at a rate of 2°C / min and kept at that temperature for 2 hours. Then, the temperature was raised to 500°C at a rate of 5°C / min and kept at that temperature for 1 hour. Then, the temperature was raised to 1450°C at a rate of 10°C / min and kept at that temperature for 3 hours. Then, the ceramic grinding balls with high strength and impact resistance and gradient material were obtained. The density was 3.93 g / cm 3 , Vickers hardness is 1134GPa, self-wear is 0.56g / hr•kg, and strip wear is 0.31g / hr•kg.

[0050] The cross-sectional view of the high-strength impact-resistant gradient material ceramic grinding ball prepared in this embodiment is shown in FIG. Figure 1 ,Depend on Figure 1 It can be seen that the gradient ceramic layers obtained by grinding, drying, rolling and firing the powders of different components designed in this embodiment have very good bonding and no cracks. Example 3

[0051] A method for preparing a high-strength impact-resistant gradient ceramic grinding ball material, specifically comprising the following steps:

[0052] Step S2-1: 6 groups of materials are prepared according to the mass percentage formulations in Table 2, and are identified as serial numbers 1-6. The fineness of the alumina is 35 microns, and the fineness of the remaining powders is 1.5-20 microns.

[0053] Table 2 Formulation table of high-strength impact-resistant gradient ceramic grinding ball material in Example 3

[0054]

[0055] The 6 kinds of composite auxiliary materials are sequentially mixed and coarsely ground for 20-24 hours using a ball mill, with water and alumina balls as the medium, and the ball-to-material weight ratio being 4:1. The outfeed fineness D98 of the 6 kinds of composite auxiliary materials is: 3.2-5 microns. Then, ultrafine grinding is performed using a sand mill, with 0.6-0.8 mm zirconium oxide balls added as the medium. The outfeed fineness D98 of the 1-6 kinds of composite auxiliary materials is 1.63 microns, 1.81 microns, 2.23 microns, 1.96 microns, 2.03 microns, and 2.49 microns, respectively. The maximum difference in D50 between adjacent two materials is 0.13 microns. Finally, the powders are sequentially dried and collected using a spray dryer, for standby use.

[0056] Step S2-2: Forming of the grinding ball green body:

[0057] The 6 kinds of composite auxiliary materials are sequentially mixed and coarsely ground for 20-24 hours using a ball mill, with water and alumina balls as the medium, and the ball-to-material weight ratio being 4:1. The outfeed fineness D98 of the 6 kinds of composite auxiliary materials is: 3.2-5 microns. Then, ultrafine grinding is performed using a sand mill, with 0.6-0.8 mm zirconium oxide balls added as the medium. The outfeed fineness D98 of the 1-6 kinds of composite auxiliary materials is 1.63 microns, 1.81 microns, 2.23 microns, 1.96 microns, 2.03 microns, and 2.49 microns, respectively. The maximum difference in D50 between adjacent two materials is 0.13 microns. Finally, the powders are sequentially dried and collected using a spray dryer, for standby use.

[0058] Step S2-3: Drying, glue removal, and sintering:

[0059] The ceramic blank prepared in S2-2 was placed in a kiln and heated at 5°C / min to 200°C and kept at this temperature for 3 hours. Then, the temperature was raised at 5°C / min to 600°C and kept at this temperature for 2 hours. Then, the temperature was raised at 8°C / min to the sintering temperature of 1500-1550°C, kept at this temperature for 3.5 hours, and then naturally cooled to room temperature. Finally, a high-strength, impact-resistant gradient material ceramic grinding ball with a density of 3.76g / cm 3 , Vickers hardness is 1036GPa, self-wear is 0.32g / hr•kg, and strip wear is 0.17g / hr•kg.

[0060] The cross-sectional view of the high-strength impact-resistant gradient material ceramic grinding ball prepared in this embodiment is shown in FIG. Figure 2 The gradient ceramic layers obtained by grinding, drying, rolling and firing the designed different component powders are very well bonded and free of cracks. Example 4:

[0061] Step S3-1: 5 groups of materials are prepared according to the mass percentage formula in Table 3 below and numbered 1 to 5. The fineness of the alumina is 35 microns, the fineness of the coal gangue powder is 45 microns, and the fineness of the remaining powders is 1.5-20 microns.

[0062] Table 3 Material formula of high strength impact resistant gradient ceramic grinding balls in Example 4

[0063]

[0064] The five components of the composite auxiliary materials were mixed and coarsely ground in a ball mill for 40-48 hours. The medium was water and alumina balls, and the ball-to-material weight ratio was 5:2. The fineness D98 of the two composite auxiliary materials were 2.03μm, 2.26μm, 2.81μm, 2.98μm, and 2.23μm, respectively, and the maximum difference in D50 between two adjacent layers of materials was 0.14 microns. The powders were then dried and collected in sequence using a spray dryer for later use.

[0065] Step S3-2: Grinding ball blank forming:

[0066] Six parts of composite auxiliary materials, ranked from smallest to largest, were added to the molding machine's hopper and rolled into shape. The binder solution sprayed during the rolling process consisted of a 1:1 ratio of PVA to polyacrylamide (0.05wt%, 0.06wt%, 0.07wt%, 0.075wt%, and 0.075wt% respectively. The first layer of the ball core had a molding size of 1mm, the second layer had a molding size of 0.5mm, the third layer had a molding thickness of 1mm, the fourth layer had a molding thickness of 1.2mm, and the fifth layer had a molding thickness of 1mm. During the molding process for layers 1-6, the subsequent layer feed rate was 1.1 times, 1.1 times, 1.1 times, 1.2 times, and 1.2 times that of the previous layer, respectively. At the end of the molding process, the ball was tightened, the surface finished, and then shipped out of the machine.

[0067] Step S3-3: Drying, debinding and sintering:

[0068] The ceramic blank prepared in S3-2 was placed in a kiln and heated at 2.5°C / min to 200°C and kept at this temperature for 2 hours. Then, the temperature was raised to 500°C at 10°C / min and kept at this temperature for 1 hour. Then, the temperature was raised to 1550°C at 10°C / min and kept at this temperature for 4-5 hours. Then, the ceramic grinding ball with high strength and impact resistance was obtained. The density was 3.48g / cm 3 , Vickers hardness is 1083GPa, self-wear is 1.42g / hr•kg, and strip wear is 0.89g / hr•kg.

[0069] The cross-sectional view of the high-strength impact-resistant gradient material ceramic grinding ball prepared in this embodiment is shown below. Figure 3 The gradient ceramic layers obtained by grinding, drying, rolling and firing the designed different component powders are very well bonded and free of cracks. Example 5:

[0070] Example 5 Referring to Example 2, four kinds of materials were prepared according to the proportions in Table 4 below.

[0071] Table 4 Material formula of high strength impact resistant gradient ceramic grinding balls in Example 5

[0072]

[0073] Four raw materials were respectively super-fined by ball milling and sand mill in sequence, the slurry fineness D98 was 1.4 μm, 1.2 μm, 1.4 μm, 1.65 μm, respectively, and the maximum difference of D50 between adjacent two layers of materials was 0.08 microns, then dried and rolled into shape, using a solution of glycerol: polyacrylamide = 1:2 as a binder, the binder solution sprayed in the rolling process was 0.075wt%, 0.08wt%, 0.085wt%, 0.07wt% in turn. The molding size of the first layer of core was 5mm, the molding size of the second layer was 2mm, the molding thickness of the third layer was 1.5mm, and the molding thickness of the fourth layer was 1.5mm. The feeding speed of the last layer in the molding process was 1.1 times, 1.1 times, 1.1 times of the speed of the previous layer, respectively, and the surface was collected at the end of the molding process. The high-strength impact-resistant gradient material ceramic grinding ball was obtained by sintering the molded green body. 3 , the density was 3.86 g / cm Example 6

[0074] Referring to Example 2, six materials were prepared according to the following Table 5.

[0075] Table 5 High-strength impact-resistant gradient ceramic grinding ball material formula table in Example 6

[0076]

[0077] The molding process adopted an injection molding machine. First, the powder was vacuum kneaded for 60 minutes, and then the six raw materials were added to the mold in sequence. After the inner layer was injection molded, the outer layer was continuously molded in the next material injection mold. The molding injection pressure from small to large was 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.52 MPa, 0.58 MPa, and 0.6 MPa, respectively. The injection molding temperature was 60℃. The thickness interval between adjacent two molds was 2mm, and the ceramic green body was obtained.

[0078] The injection molded green body was dried and degreased, and then sintered to obtain a high-strength impact-resistant gradient material ceramic grinding ball. The density was 4.96 g / cm 3 , the Vickers hardness was 1339 GPa, the self-abrasion was 0.11 g / hr•kg, and the belt abrasion was 0.12 g / hr•kg.

Claims

1. A high-strength, impact-resistant gradient ceramic grinding ball material, characterized in that: The method comprises N material layers, where N is greater than or equal to 4; in each material layer, aluminum oxide accounts for 35 wt% to 95 wt% by weight, and the rest is composite auxiliary material; The mass percentage of the composite auxiliary material in the innermost layer is 5wt% to 60wt%, and the mass percentage of the composite auxiliary material in each material layer increases gradually from the innermost layer to the outermost layer in the N material layers within a range of 1wt% to 10wt%, and finally the mass percentage of the composite auxiliary material in the outermost layer increases to 20wt% to 65wt%; The thickness of each material layer is 0.5mm to 5mm; The composite auxiliary material comprises kaolin, coal gangue, heavy calcium carbonate, magnesium carbonate, zirconium silicate, silicon oxide, zirconium oxide, cerium oxide, yttrium oxide and lanthanum oxide; in the composite auxiliary material, kaolin, coal gangue, heavy calcium carbonate and magnesium carbonate account for 4wt% to 40wt% of the total mass of the ceramic grinding ball material, zirconium silicate, silicon oxide, zirconium oxide, cerium oxide, yttrium oxide and lanthanum oxide account for 0wt% to 65wt% of the total mass of the ceramic grinding ball material, and aluminum oxide accounts for 35wt% to 95wt% of the total mass of the ceramic grinding ball material; The fineness D98 of alumina and composite auxiliary materials is 1-3 microns; in the N-layer material layer, the difference in fineness D50 between two adjacent material layers is ≤0.15 microns, and the fineness D50 is used to control the median particle size; the difference in fineness D98 between two adjacent material layers is ≤0.7 microns, and the fineness D98 is used to control the maximum particle size.

2. The high-strength, impact-resistant gradient ceramic grinding ball material according to claim 1, characterized in that: The thickness of the innermost material layer is 1 to 3 times the thickness of the second material layer.

3. A method for preparing ceramic grinding balls using the high-strength, impact-resistant gradient ceramic grinding ball material according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1, material preparation: prepare N parts of raw materials according to the proportion of each component of the ceramic grinding ball material, coarsely grind the N parts of raw materials through a ball mill, and then finely grind them with a sand mill. After drying the finely ground raw materials, number them from 1 to N according to the mass percentage of the composite auxiliary materials contained in each part of the finely ground raw materials from low to high for later use; Step 2: The N portions of finely ground raw materials obtained in step 1 are molded layer by layer in increasing order by a rolling method or an injection molding method, and a binder is sprayed during the molding process to obtain a spherical ceramic blank; Step 3, drying, debinding and sintering: drying, debinding and sintering the ceramic green body obtained in step 2 to obtain high-strength and impact-resistant gradient material ceramic grinding balls.

4. The method for preparing ceramic grinding balls from the high-strength, impact-resistant gradient ceramic grinding ball material according to claim 3, characterized in that: In step 1, the purity of the prepared N parts of raw materials is ≥99.5% and the particle size is ≤50 microns; In step 1, N portions of raw materials are coarsely ground in a ball mill, wherein the coarse grinding medium is water and alumina balls, the weight ratio of alumina balls to raw materials is (5:2) to (4:1), the coarse grinding time is 12 to 48 hours, and the fineness D98 of the discharge material is 1.5 to 10 μm; In step 1, when the coarsely ground material is finely ground using a sand mill, the fine grinding medium is water and zirconium oxide balls, and the fineness D98 of the material is 1 to 3 microns.

5. The method for preparing ceramic grinding balls from the high-strength, impact-resistant gradient ceramic grinding ball material according to claim 3, characterized in that: In step 2, when spraying the binder, among the N material layers of the spherical ceramic blank, the binder concentration of the outer material layer in any two adjacent material layers is 1.05 to 1.2 times the binder concentration of the inner material layer; In step 2, the binder includes at least one of PVA, glycerol and polyacrylamide; When the injection molding method is used in step 2, vacuum mud refining is performed first and then injection molding is performed: N portions of finely ground raw materials are added to the injection molding machine mold of the upper layer of raw materials in sequence. After the injection molding of the upper layer is completed, the raw materials are transferred to the injection molding machine mold of the next layer to continue molding; The injection pressure is 0.2-0.7 MPa, and the injection temperature is 60-70°C. The thickness of the gap between the upper layer of raw material injection molding machine mold and the lower layer of raw material injection molding machine mold is 0.5-6 mm. The injection pressure at the lower layer of raw material injection molding machine mold is 1.05-1.2 times the injection pressure at the upper layer of raw material injection molding machine mold. In step 2, when the spherical ceramic blank is roll-formed, the thickness of each material layer is 0.55 mm to 6.1 mm; among the N material layers of the spherical ceramic blank, the forming speed of any two adjacent material layers is 1.05 to 1.2 times the forming speed of the inner material layer.

6. The method for preparing ceramic grinding balls from the high-strength, impact-resistant gradient ceramic grinding ball material according to claim 3, characterized in that: In step 3, when the ceramic green body after drying and debinding is sintered, the low temperature stage: first, the temperature is raised to 200°C at a rate of 2-5°C / min and kept warm for 2-5 hours; the medium temperature stage: the temperature is raised to 500-600°C at a rate of 2-10°C / min and kept warm for 1-3 hours; the high temperature stage: the temperature is raised to 1350-1550°C at a rate of 5-10°C / min and kept warm for 3-5 hours; and then cooled to room temperature.

7. The method for preparing ceramic grinding balls from the high-strength, impact-resistant gradient ceramic grinding ball material according to claim 3, characterized in that: The high-strength impact-resistant gradient material ceramic grinding balls prepared in step 3 have a density of 3.3-5 g / cm 3 , Vickers hardness is 1000~1350GPa, self-wear is 0.1~1.5g / hr•kg, and strip wear is 0.1~1g / hr•kg.

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