Preparation method of hollow ATZ ceramic balls for bearings and hollow grouting gypsum mold

Abstract

The present invention discloses a preparation method of hollow ATZ ceramic balls for bearings and a hollow grouting gypsum mold. According to empirical formulas and data, the present invention obtains the solid content of the ATZ injection slurry to be configured and the spherical cavity size of the gypsum mold, then adds the configured ATZ injection slurry into the prepared gypsum mold, and fixes the assembled mold in a planetary ball mill. By high-speed rotation and the water absorption of the mold for water, ATZ ceramic green balls with specific spherical hollows are formed. After demolding, sintering, polishing and sorting, hollow ATZ ceramic balls for bearings are obtained, which have the characteristics of lower density than silicon carbide and higher hardness and strength than zirconia, thereby reducing the high-speed inertial force and impact force of the bearing balls on the bearings, improving the service life and durability of the bearings. Through hollow grouting, high roundness and high consistency of the hollow ATZ ceramic balls are achieved, and the impact force during the rotation of the ceramic balls is reduced, thereby improving the stability of the bearings.

Description

Technical Field

[0001] The present invention relates to the technical field of structural ceramic bearings, and particularly relates to a preparation method for hollow ATZ ceramic balls for bearings and a hollow grouting gypsum mold. Background Art

[0002] With the rapid development of industrial technology, the requirements for bearings are also getting higher and higher, specifically reflected in: precision in size, high speed in speed, high temperature in temperature, high vacuum, anti-corrosion and other more demanding working conditions are increasing day by day. The bearings made of steel materials cannot meet some performances. A large number of tests have proved that the precision bearing balls working in a high-speed environment are the weakest parts in the bearings, and about 60% - 70% of the failures of high-speed bearings are caused by different degrees of fatigue damage of the steel balls. The research results at home and abroad show that the application of structural ceramics to manufacture spheres or other bearing parts can significantly improve the service performance and life of high-speed bearings.

[0003] In the fields of aerospace, navigation, nuclear industry, petroleum, chemical industry, light textile industry, machinery, metallurgy, electric power, new energy, food, locomotive, subway, high-speed machine tools, etc., bearings are required to work under special working conditions such as high temperature, high speed, cryogenic, flammable, explosive, strong corrosion, vacuum, electrical insulation, non-magnetic, dry friction, easy to rust, etc. The irreplaceable role of ceramic bearings is being gradually recognized. With the continuous progress of processing technology and the increasing improvement of process level, the cost of ceramic bearings is continuously decreasing. It has gradually spread from being only used in a small range in some high-precision and high-tech fields in the past to various industrial fields of the national economy. Through the batch and long-term use tests in different industries. Many successful cases have realized the advantages of maintenance-free, long life, high stability and low cost brought by ceramic bearing balls and all-ceramic bearings. Ceramic bearings and ceramic bearing balls have moved from the research and trial production stage to the stage of batch production, and the wave of large-area application has come.

[0004] The commonly used materials for existing ceramic bearings are zirconia and silicon nitride;

[0005] Characteristics of silicon nitride ceramics: The density of silicon nitride ceramics is only 3.2 - 3.2 g / cm3, the high-temperature service temperature reaches 1000 °C, it has low-temperature insulation, non-magnetic, the hardness is up to more than HV11600, and it has good low-temperature insulation. When the temperature exceeds 1000 °C, it will have strong conductivity. Due to the relatively high preparation cost of silicon nitride ceramic bearings, specifically, the equipment used in the preparation of powder requires high temperature, high pressure and air isolation, and the subsequent ceramic forming and sintering also require relatively harsh conditions. Finally, the processing cost of the hard ceramic is also relatively high. Therefore, the scope of its application and promotion is restricted to a certain extent.

[0006] Characteristics of zirconia ceramics: The density of zirconia bearing beads is 6.08g / cm 3 , the operating temperature is 800-900℃, with strong corrosion resistance; high bending strength and toughness. Compared with silicon nitride materials, the preparation process is relatively simple, the cost of the blank is low, and it is easy to apply in the market. At the same time, the toughness of zirconium oxide is higher than that of silicon nitride, which is conducive to the stable use of bearings. In addition, the thermal expansion coefficient of zirconium oxide is close to that of steel, which improves its stability in mechanical structures. However, the high density of zirconium oxide ceramics leads to a large centrifugal force on the bearing, which is not conducive to high-speed rotation and limits its application field.

[0007] Characteristics of zirconia ceramics (ATZ ceramics) with 20%A mass fraction of alumina added, density 5.4-5g / cm 3 The flexural strength is close to that of zirconia ceramics, the toughness and hardness are higher than those of zirconia ceramics, and the hydrothermal aging resistance is also better.

[0008] The density of zirconium oxide is 6.08, which is much higher than that of silicon nitride ceramics, which is 3.2. This means that when it is used as a rolling element, the centrifugal force generated by the rotating body during the rotation of the bearing increases, and the weight of the bearing itself increases, which limits its application in high-speed environments. The present invention is to develop a larger-sized hollow ATZ ceramic precision bead for bearings, which has high hardness, low density, and excellent mechanical properties in all aspects. It is inexpensive and can be used in bearings in higher speed and harsher environments. Summary of the invention

[0009] The purpose of the present invention is to provide a preparation method of hollow ATZ ceramic balls for bearings and a hollow grouting gypsum mold. The hollow ceramic balls made of ATZ material have a lower density than silicon nitride and do not require the same stringent preparation conditions as silicon nitride. They only need to be sintered at normal pressure, and the sintering temperature is much lower than that of silicon nitride balls and is close to that of zirconia ceramics. The hollow ceramic balls made of ATZ material have a higher hardness than zirconia ceramic beads, a slightly higher strength than zirconia ceramic beads, and good roundness, which improves the wear resistance and stability of ceramic bearings, thereby improving the overall performance of ceramic bearings.

[0010] The present invention adopts the following technical solution:

[0011] A method for preparing a hollow ATZ ceramic ball for a bearing comprises the following steps:

[0012] S1. Determine the shrinkage ratio according to the empirical formula based on the size of the hollow ATZ ceramic ball, and calculate the spherical cavity size of the water-absorbing gypsum mold and the solid content of the ATZ slurry to be configured according to the shrinkage empirical formula;

[0013] S2. Take the ATZ powder and perform material ratio according to the solid content of the ATZ slurry to be prepared calculated by the empirical formula, and grind to obtain an ATZ slurry with uniform fineness; prepare a hollow spherical gypsum mold, assemble it according to the usage method of the gypsum mold, take the ATZ slurry with uniform fineness in an amount equal to the volume of the spherical cavity in the gypsum mold and add it into the cavity of the gypsum mold through the slurry filling port, and seal the gypsum mold well;

[0014] S3. Fix the sealed gypsum mold in a planetary ball mill, and then rotate it at high speed for 2 - 3 hours. Through the rotation of the planetary ball mill, the slurry is evenly contacted with the inner surface of the gypsum mold. As the rotation time of the planetary ball mill extends, the gypsum mold continuously absorbs water. Eventually, the ATZ slurry with uniform fineness inside the gypsum mold completely adheres to the wall uniformly and solidifies to form a hollow ATZ ceramic green ball;

[0015] S4. Remove the gypsum mold with the hollow ATZ ceramic green ball for drying. Due to the different shrinkages of the two materials, delamination occurs and the hollow ATZ ceramic green ball falls off. Then disassemble the gypsum mold according to the disassembly method of the gypsum mold and take out the hollow ATZ ceramic green ball inside;

[0016] S5. Take one of the hollow ATZ ceramic green balls from the same batch and break it open to observe whether there are any slurry hard lumps with water not completely absorbed by the gypsum mold; if not, it is judged as qualified;

[0017] S6. For the qualified batch of hollow ATZ ceramic green balls, sinter them according to a certain atmospheric air atmosphere sintering system. After sintering, polish them according to a certain polishing method. The polished hollow ATZ ceramic green balls are sorted according to a certain sorting method to obtain the finally qualified hollow ATZ ceramic balls for bearings.

[0018] Preferably, the empirical formula in step S1 is

[0019] Formula (1)

[0020] Formula (2)

[0021] Formula (3)

[0022] Formula (4)

[0023] ρ 空 : The density of the hollow ATZ ceramic ball, unit g / cm 3 ; The smaller this density is, the better, but D 空 / D 外The value should be less than 0.77 to ensure that the wall thickness is thick enough to maintain its mechanical properties under high-speed operation.

[0024] ρ 实 : The theoretical or sintering optimal density of ATZ ceramic material, unit g / cm 3 , for example, 20wt% ATZ is generally sintered densely at 5.45 - 5.5 g / cm 3 ;

[0025] ρ 生坯层 : The density of the dense part of the hollow ATZ ceramic green ball after demolding during slip casting, unit g / cm 3 ; This data can be obtained through small experiments and is a constant when the particle size of the slip casting slurry and the addition ratio of organic solutes are relatively stable, unit g / cm 3 ;

[0026] ρ 水 : The density of pure water, unit g / cm 3 ;

[0027] D 外 : The outer diameter of the qualified hollow ATZ ceramic ball after final polishing, unit mm;

[0028] D 外生坯 : The outer diameter of the hollow ATZ ceramic green ball, which is the inner diameter size of the cavity of the gypsum mold, unit mm;

[0029] D 空生坯 : The hollow cavity diameter of the hollow ATZ ceramic green ball, unit mm;

[0030] D 空 : The inner diameter of the qualified hollow ATZ ceramic ball after final polishing, unit mm;

[0031] K1: The shrinkage ratio of the hollow ATZ ceramic green ball after sintering, which is the ratio of the diameter of the sintered ball to the diameter before sintering. This coefficient can be simply obtained through experiments and is a fixed value when the particle size of the slurry and the solute formula therein are relatively stable;

[0032] K2: The water content of the hollow ATZ ceramic green ball, that is, grinding a hollow green ball into powder and then measuring the water content in a moisture analyzer. This is a fixed value when the particle size of the slurry and the solute formula therein are relatively stable, and this data can also be simply obtained through experiments;

[0033] K3: The polishing compensation coefficient, unit mm, which is the diameter of the sintered hollow ATZ ceramic ball minus the diameter of the qualified hollow ATZ ceramic ball after polishing;

[0034] SC: The solid content of the ATZ slurry to be configured;

[0035] Through the above 4 empirical formulas and related empirical constants, the solid content of the ATZ slurry to be configured during the slip casting of the designed hollow ATZ ceramic balls and the spherical cavity size of the gypsum mold can be calculated.

[0036] Preferably, in the step S2, the proportion of 3Y zirconia in the ATZ powder is 80 parts by mass, and the proportion of alumina is 20 parts by mass.

[0037] Preferably, in the step S2, 0.3 - 0.5% of a dispersion stabilizer is added to the ATZ slurry during grinding, and the dispersion stabilizer is CE64 or polyacrylic acid.

[0038] Preferably, the rotation speed of the planetary ball mill is 300 - 400 r / min.

[0039] Preferably, in the step S4, the drying temperature is between 30 - 40 °C, and the drying time is 3 - 6 h.

[0040] Preferably, in the step S6, a certain atmospheric air atmosphere sintering regime is as follows: when the temperature is 0 - 120 °C, the heating rate is 1.5 - 2 °C / min; when the temperature is 120 - 350 °C, the heating rate is 0.4 - 0.6 °C / min; when the temperature is 350 - 650 °C, the heating rate is 0.3 - 0.5 °C / min; keep the temperature at 650 °C for 120 min; when the temperature is 650 - 1450 °C, the heating rate is 1.0 - 1.2 °C / min; keep the temperature at 1450 °C for 180 min; when the temperature is 1450 - 1000 °C, the cooling rate is 1.5 - 2.0 °C / min.

[0041] Preferably, in the step S6, a certain polishing method is as follows: first, perform rough polishing: add 60 - 70 wt% of hollow ATZ beads, 20 - 25 wt% of pure water, 4 - 5 wt% of 20 - 50 µm white corundum particles, and 0.5 wt% of polyacrylic acid - type dispersant into a vertical sand mill; then, perform fine polishing: add 50 - 60 wt% of the hollow ATZ beads after rough polishing, 25 - 30 wt% of pure water, and 6 - 8 wt% of 1 - 5 µm alumina fine powder into a vertical sand mill.

[0042] Preferably, in the step S6, a certain sorting method is as follows: first, use a roughness detector to sort out the hollow ATZ ceramic balls with a roughness less than 0.05 μm as roughness qualified products; then use a laser particle size analyzer to test the roundness of each hollow ATZ ceramic ball, and take the hollow ATZ ceramic balls with a roundness greater than or equal to 99.9% as roundness qualified products; then conduct a density test, and sort out the hollow ATZ ceramic balls with a density less than or equal to 3 g / cm3 as qualified products; then conduct a quality classification, and put the hollow ATZ ceramic balls with a mass deviation less than 0.05 g into the same box for storage; then sort the hollow ATZ ceramic balls with a mass difference within 0.05 g according to their sizes, and finally sort out the hollow ATZ ceramic balls with a diameter error within ±0.05 mm of the designed size as the final qualified products.

[0043] A hollow grouting gypsum mold includes a plug component, an upper mold convex component, a lower mold concave component and a lower mold convex and concave component. The upper mold convex component is spliced and assembled with the lower mold concave component and the lower mold convex and concave component. After assembly, a spherical cavity is formed between the upper mold convex component and the lower mold concave component and the lower mold convex and concave component. A slurry filling port is opened on the upper mold convex component to communicate with the spherical cavity, and the plug component is hermetically sealed on the slurry filling port.

[0044] The beneficial effects of the present invention are as follows:

[0045] (1) By the method of the present invention, ATZ ceramic balls with a specific hollow size can be obtained, which have the characteristics of lower density than silicon nitride balls, higher hardness than zirconia balls, and higher toughness and strength than zirconia balls, improving the durability of ceramic bearings, etc., can broaden the application limitations of ceramic bearings, and the preparation cost is lower than that of silicon nitride balls;

[0046] (2) The present invention further reduces the density of ATZ ceramic balls by adopting a certain hollow method, so that the density of the final hollow ATZ ceramic balls is slightly lower than that of silicon nitride without affecting their mechanical properties. This can improve the durability of the bearings because if the bearing balls are solid, then at high speeds, the inertia of the bearing balls will be very large, and huge inertial forces and impact forces will be generated during acceleration and deceleration, easily causing bearing damage. Therefore, the hollow design of the bearing balls is to reduce the inertia and weight of the bearings, improve the operating efficiency and service life of the bearings, and this can also increase the rotational speed of the motor;

[0047] (3) The larger the radius of the bearing, the faster the angular velocity, and the greater the mass, the greater the force exerted by its ball bearings on the bearing wall. Under the condition of a certain angular velocity and radius, the mass of the bearing balls is proportional to the centrifugal force. The hollow ATZ ceramic balls made by the present invention have a small mass, a small centrifugal force, a small force between the balls and the bearing wall, and the frictional loss of the balls, etc. will also be reduced, improving the durability of the bearings;

[0048] (4) The ceramic balls for bearings need to have a high degree of roundness and a smooth surface. When making them hollow, the roundness of the balls must also be ensured. Slip casting is the best choice. The formed green body has fewer surface defects, and it is easier to make the surface smooth during subsequent polishing. The higher the roundness, the more uniform the rotational force on the bearing, the better the rotational effect, and the durability and reliability under high-speed rotation are improved. Brief Description of the Drawings

[0049] Figure 1 is a schematic cross-sectional view of the hollow ATZ ceramic ball of the present invention;

[0050] Figure 2 is a process flow chart of the preparation of the hollow ATZ ceramic ball of the present invention;

[0051] Figure 3 is an inlaid cross-sectional view of the 30mm hollow ATZ beads prepared in the embodiment of the present invention;

[0052] Figure 4 is a schematic overall view of the hollow slip casting gypsum mold of the present invention;

[0053] Figure 5 is a schematic structural view of the plug assembly of the hollow slip casting gypsum mold of the present invention;

[0054] Figure 6 is a schematic structural view of the upper mold convex assembly of the hollow slip casting gypsum mold of the present invention;

[0055] Figure 7 is a schematic structural view of the lower mold concave assembly of the hollow slip casting gypsum mold of the present invention;

[0056] Figure 8 is a schematic structural view of the lower mold concave-convex assembly of the hollow slip casting gypsum mold of the present invention;

[0057] In the figures: 1. Plug assembly, 2. Upper mold convex assembly, 3. Lower mold concave assembly, 4. Lower mold concave-convex assembly, 1-1. Spherical concave surface, 1-2. Convex block, 1-3. Cylindrical plug rod, 2-1. Limit boss, 2-2. Hemispherical hollow cavity, 2-3. Slurry filling port, 3-1. Concave limit card slot 1, 3-2. Limit groove, 3-3. One-quarter hollow spherical cavity 1, 4-1. Concave limit card slot 2, 4-2. Limit protrusion, 4-3. One-quarter hollow spherical cavity 2. Detailed Embodiments

[0058] The technical solutions of the present invention will be further specifically described below through specific embodiments in conjunction with the drawings:

[0059] Embodiment: To fabricate the hollow ATZ ceramic balls for bearings as shown in Figure 1 In this embodiment, through the method as shown in Figure 2Perform according to the following step process:

[0060] First, calculate according to the empirical formula: Design a hollow ATZ ceramic ball with an outer diameter of 30 mm. Corresponding to D in the empirical formula 外 = 30 mm. Set ρ for 20% Al2O3 ATZ material 实 to be 5.5 g / cm 3 , ρ 空 is set to 3.0 g / cm 3 , substitute into the empirical formula (1) to get D 空 = D = 23.066 mm, D 空 / D 外 = 0.769 < 0.77, meeting the composite design requirements; According to the empirical polishing compensation coefficient K3, it is set to 0.5 mm. According to experience, the sintering shrinkage coefficient K1 is set to 0.72. Then, according to the empirical formula (2), the diameter D of the hollow green body is obtained 外生坯 = 42.361 mm. According to the empirical formula (3) D 空生坯 = 32.036 mm. In the empirical formula (4), according to experimental experience, set ρ 生坯层 to be 3.6 g / cm 3 , the environmental temperature is 25 °C. Take ρ 水 to be 0.99705 g / cm 3 , according to empirical tests, the water content K2 of the hollow green body ATZ ball is 0.25. Substitute these parameters into formula (4) to obtain the solid content SC of the ATZ slurry to be configured = 0.619.

[0061] Secondly, mix and grind, and pour the slurry: According to the SC data, take ATZ dry powder, pure water, and a dispersion stabilizer for batching, and add 0.3% of the dispersion stabilizer. Ball mill to obtain an ATZ slurry with uniform fineness. According to D 外生坯 obtain the spherical cavity diameter of the water-absorbing gypsum mold, assemble the accessories according to the usage method of the hollow gypsum mold, take a uniform slurry in an amount equal to the volume of the spherical cavity of the gypsum mold and add it to the cavity of the gypsum mold, and assemble and seal the gypsum mold well.

[0062] Then, rotate at high speed in a planetary ball mill: Fix the assembled and sealed gypsum mold in the planetary ball mill, and then rotate at 500 r / min for 2 h. Through the rotation of the planetary ball mill, the slurry is evenly contacted on the inner surface of the hollow gypsum mold. As the rotation time of the planetary ball mill continues and the gypsum mold continuously absorbs water, the slurry inside the gypsum mold is finally completely and evenly adhered to the wall and solidified to form a hollow ATZ ceramic green body ball.

[0063] Then, dry, disassemble the mold, and take out the hollow ATZ ceramic green body balls: Remove the gypsum mold of the hollow ATZ ceramic green body balls and place it in an oven. Set the temperature to 35°C and dry for 3 hours. Due to the different shrinkages of the two materials, delamination occurs and the hollow ATZ ceramic green body balls fall off. Then, disassemble the mold according to the disassembly method of the gypsum mold and take out the hollow ATZ ceramic green body balls inside.

[0064] Then, check whether the hollow ATZ ceramic green body balls of the same batch are qualified: Take one of the hollow ATZ ceramic green body balls of the same batch and break it open to observe. Confirm whether there are any slurry hard lumps with unabsorbed moisture by the gypsum mold and whether a spherical cavity is formed. If not and a spherical cavity is formed, it is judged as qualified.

[0065] Finally, sinter, polish, and sort the qualified balls: For the green body hollow ATZ balls of the qualified batch, the heating rate is 1.5°C / min when the temperature rises from 0 to 120°C, 0.6°C / min when the temperature rises from 120 to 350°C, 0.4°C / min when the temperature rises from 350 to 650°C, keep the temperature at 650°C for 120 minutes, the heating rate is 1.5°C / min when the temperature rises from 650 to 1450°C, keep the temperature at 1450°C for 180 minutes, and the cooling rate is 1.7°C / min when the temperature drops from 1450 to 1000°C. Sinter under the normal pressure air atmosphere sintering system; Take 65 parts by mass of the sintered hollow ATZ ceramic balls and add them to a vertical sand mill. Then add 30 parts by mass of pure water and 5 parts by mass of white corundum particles with an average particle size of 30μm. Add 0.5 parts by mass of polyacrylic acid as an auxiliary agent for rough polishing; The balls after rough polishing are then polished finely. The conditions for fine polishing are: Add 55 parts by mass of the hollow ATZ ceramic balls after rough polishing, 30 parts by mass of pure water, 8 parts by mass of 3μm alumina fine powder, and add 0.5 parts by mass of polyacrylic acid as an auxiliary polishing agent; The hollow ATZ ceramic balls after fine polishing are sorted. First, sort according to the surface roughness, and screen out the hollow ATZ ceramic balls with a roughness less than 0.05μm as roughness qualified products; Then, conduct a roundness test on the hollow ATZ ceramic balls with qualified roughness through a laser particle size analyzer, and sort out the hollow ATZ ceramic balls with a sphericity of 99.9% as sphericity qualified products; The sorted hollow ATZ ceramic balls are then tested for density, and the hollow ATZ ceramic balls with a density less than 3g / cm 3 are sorted out as qualified products: Then, sort by quality. For the hollow ATZ ceramic balls with a mass difference within 0.05g, put them in the same box for storage. For the hollow ATZ ceramic balls with a mass within 0.05g, sort them by size again, and sort out the hollow ATZ ceramic balls with a diameter error of 30 ± 0.05mm as the final hollow ATZ ceramic balls for bearings with close density, close mass, close size, high roundness, and small roughness. The central cross-section inlay structure of the hollow ATZ ceramic balls is asFigure 3 as shown

[0066] As Figure 4 shown, a hollow grouting gypsum mold includes a plug component 1, an upper mold convex component 2, a lower mold concave component 3, and a lower mold concave-convex component 4. The upper mold convex component 2 is spliced and assembled with the lower mold concave component 3 and the lower mold concave-convex component 4. After assembly, a spherical cavity is formed between the upper mold convex component 2, the lower mold concave component 3, and the lower mold concave-convex component 4. A slurry filling port 2-3 is opened on the upper mold convex component 2 to communicate with the spherical cavity, and the plug component 1 is hermetically sealed on the slurry filling port 2-3.

[0067] As Figure 5 shown, the plug component 1 includes a convex block 1-2 and a cylindrical plug rod 1-3. The cylindrical plug rod 1-3 is cooperatively sealed on the slurry filling port 2-3. A spherical concave surface 1-1 is provided at the end of the cylindrical plug rod 1-3, and the spherical concave surface 1-1 is arranged in cooperation with the spherical cavity.

[0068] As Figure 6 shown, a hemispherical hollow cavity 2-2 is provided at the bottom of the upper mold convex component 2, and a slurry filling port 2-3 is provided at the upper part. The slurry filling port 2-3 communicates with the hemispherical hollow cavity 2-2. A circular limiting boss 2-1 is provided at the bottom of the upper mold convex component 2 along the outer edge of the hemispherical hollow cavity.

[0069] As Figure 7 shown, a quarter hollow spherical cavity one 3-3 is provided at the upper right side of the lower mold concave component 3. A semi-circular concave limiting card slot one 3-1 is provided at the top of the lower mold concave component 3 along the outer edge of the quarter hollow spherical cavity one 3-3. The semi-circular concave limiting card slot one 3-1 is correspondingly and cooperatively clamped and connected to the limiting boss 2-1. A limiting groove 3-2 is provided on the right side surface of the lower mold concave component 3.

[0070] As Figure 8 shown, a quarter hollow spherical cavity two 4-3 is provided at the upper left side of the lower mold concave-convex component 4. A semi-circular concave limiting card slot two 4-1 is provided at the top of the lower mold concave-convex component 4 along the outer edge of the quarter hollow spherical cavity two 4-3. The semi-circular concave limiting card slot two 4-1 is correspondingly and cooperatively clamped and connected to the limiting boss 2-1. A limiting protrusion 4-2 is provided on the left side surface of the lower mold concave-convex component 4, and the limiting protrusion 4-2 is correspondingly and cooperatively clamped and connected to the limiting groove 3-2.

[0071] The above-described embodiments are only a preferred solution of the present invention, and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. A preparation method of a hollow ATZ ceramic ball for bearings, characterized in that, It includes the following steps: S1. Determine the shrinkage ratio according to the empirical formula based on the size of the hollow ATZ ceramic ball, and calculate the spherical cavity size of the water-absorbing gypsum mold and the solid content of the ATZ slurry to be configured according to the shrinkage empirical formula; S2, taking ATZ powder and proportioning the materials according to the solid content of the ATZ slurry to be prepared according to the empirical formula, and grinding to obtain ATZ slurry of uniform fineness; Prepare a hollow spherical plaster mold, assemble it according to the method of using the plaster mold, take an amount of ATZ slurry with uniform fineness corresponding to the volume of the spherical cavity in the plaster mold, add it into the cavity of the plaster mold through the slurry filling port, and seal the plaster mold; S3, fix the sealed gypsum mold in a planetary ball mill, and then rotate it at high speed for 2-3 hours. The rotation of the planetary ball mill allows the slurry to evenly contact the inner surface of the gypsum mold. As the rotation time of the planetary ball mill increases, the gypsum mold continuously absorbs moisture. Finally, the ATZ slurry with uniform fineness inside the gypsum mold is completely and evenly adhered to the wall and solidified to form a hollow ATZ ceramic green ball; S4, removing the gypsum mold with the hollow ATZ ceramic green ball and drying it, because the two materials shrink differently and produce delamination, the hollow ATZ ceramic green ball falls off, and then disassembling the gypsum mold according to the disassembly method of the gypsum mold, and taking out the hollow ATZ ceramic green ball; S5. Take one of the hollow ATZ ceramic green balls from the same batch and knock it open to observe whether there is any slurry lump that has not been completely absorbed by the gypsum mold; if not, it is judged to be qualified; S6. The qualified batch of hollow ATZ ceramic green balls are sintered according to a certain normal pressure air atmosphere sintering system, and then polished according to a certain polishing method after sintering. The polished hollow ATZ ceramic green balls are sorted according to a certain sorting method to obtain the final qualified hollow ATZ ceramic balls for bearings.

2. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1, characterized in that, The empirical formula in step S1 is: Formula (1) Formula (2) Formula (3) Formula (4) ρ 空 : The density of the hollow ATZ ceramic balls, unit: g / cm 3 ; ρ 实 : The theoretical or sintering optimal density of ATZ ceramic material, unit: g / cm 3 ; ρ 生坯层 : The density of the dense part of the hollow green ATZ ceramic balls after demolding from the slip casting, in g / cm 3 ; ρ 水 : Density of pure water, unit g / cm 3 ; D 外 : The outer diameter of the qualified hollow ATZ ceramic balls after final polishing, unit: mm; D 外生坯 : The outer diameter of the green body ball of hollow ATZ ceramics, which is also the inner diameter size of the cavity of the gypsum mold, unit: mm; D 空生坯 : The hollow cavity diameter of the green ball of hollow ATZ ceramics, unit: mm; D 空 : Inner diameter of the qualified hollow ATZ ceramic ball after final polishing, unit: mm; K1: shrinkage ratio of hollow ATZ ceramic green balls after sintering; K2: moisture content of hollow ATZ ceramic green balls; K3: polishing compensation coefficient, unit: mm; SC: solid content of ATZ slurry to be prepared; The above four empirical formulas and related empirical constants can be used to calculate the solid content of the ATZ slurry and the spherical cavity size of the gypsum mold required for grouting of the hollow ATZ ceramic ball to be designed.

3. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1, characterized in that, In the step S2, the proportion of 3Y zirconium oxide in the ATZ powder is 80 parts by mass, and the proportion of aluminum oxide is 20 parts by mass.

4. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1, characterized in that, In the step S2, 0.3-0.5% of a dispersion stabilizer is added to the grinding ATZ slurry, and the dispersion stabilizer is CE64 or polyacrylic acid.

5. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1, characterized in that, The rotation speed of the planetary ball mill is 300-400r / min.

6. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1, characterized in that, In step S4, the drying temperature is between 30-40° C. and the drying time is 3-6 hours.

7. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1, characterized in that, In the step S6, a certain atmospheric pressure air atmosphere sintering system is as follows: when the temperature ranges from 0 to 120 °C, the heating rate is 1.5 - 2 °C / min; when the temperature ranges from 120 to 350 °C, the heating rate is 0.4 - 0.6 °C / min; when the temperature ranges from 350 to 650 °C, the heating rate is 0.3 - 0.5 °C / min; keep the temperature at 650 °C for 120 min; when the temperature ranges from 650 to 1450 °C, the heating rate is 1.0 - 1.2 °C / min; keep the temperature at 1450 °C for 180 min; when the temperature ranges from 1450 to 1000 °C, the cooling rate is 1.5 - 2.0 °C / min.

8. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1, characterized in that, In the step S6, a certain polishing method is as follows: first, perform rough polishing: add 60 - 70 wt% of hollow ATZ beads, 20 - 25 wt% of pure water, 4 - 5 wt% of 20 - 50 µm white corundum particles, and 0.5 wt% of polyacrylic acid dispersant into a vertical sand mill; then, perform fine polishing: add 50 - 60 wt% of the hollow ATZ beads after rough polishing, 25 - 30 wt% of pure water, and 6 - 8 wt% of 1 - 5 µm alumina fine powder into a vertical sand mill.

9. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1, characterized in that, In the step S6, a certain sorting method is as follows: first, use a roughness detector to sort out the hollow ATZ ceramic balls with a roughness less than 0.05 µm as roughness qualified products; then, use a laser particle size analyzer to test the roundness of each hollow ATZ ceramic ball, and take the hollow ATZ ceramic balls with a roundness greater than or equal to 99.9% as roundness qualified products; Then, perform density testing, and sort out the hollow ATZ ceramic balls with a density less than or equal to 3 g / cm³ as qualified products; Then, perform quality classification, and put the hollow ATZ ceramic balls with a mass deviation less than 0.05 g into the same box for storage; then sort the hollow ATZ ceramic balls with a mass difference within 0.05 g according to size, and finally sort out the hollow ATZ ceramic balls with a diameter error within ±0.05 mm of the designed size as the final qualified products.

10. The preparation method of a hollow ATZ ceramic ball for bearings according to claim 1 or 2, characterized in that, The gypsum mold includes a plug component, an upper mold convex component, a lower mold concave component, and a lower mold convex - concave component. The upper mold convex component is spliced and assembled with the lower mold concave component and the lower mold convex - concave component. After assembly, a spherical cavity is formed between the upper mold convex component and the lower mold concave component and the lower mold convex - concave component. A slurry filling port is opened on the upper mold convex component to communicate with the spherical cavity, and the plug component seals and plugs the slurry filling port.

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