A method for surface modification of large-size ceramic ball blanks

Abstract

The present invention discloses a method for surface modification of large-sized ceramic ball blanks, which mainly includes the following steps: low-temperature primary firing, rough polishing, surface pretreatment, surface repair, and secondary sintering. The present invention utilizes low-temperature firing to make the ceramic ball blanks vitrified to a certain extent and have a certain strength, thereby reducing the difficulty of processing the surface; on the premise that the surface of the ball blank is not damaged, the surface is processed by low-speed polishing to improve its roundness and roughness; then, the surface of the ceramic ball blank is functionalized using surface treatment slurry to facilitate fine polishing of the surface of the ball blank, and finally the secondary sintering adopts a rapid sintering process. While ensuring that the ceramic grinding balls are completely sintered, rapid sintering is beneficial to preventing abnormal grain growth, thereby improving the wear resistance of the ceramic balls. The surface of the large-sized ceramic balls modified by the method of the present invention is smooth and flat, which is a significant improvement over the directly fired balls.

Description

Technical Field

[0001] The invention relates to the field of ceramic ball blanks, and in particular to a method for surface modification of a large-size ceramic ball blank. Background Art

[0002] Ceramic grinding balls are widely used in metallurgy, mining, chemical industry and other fields, and are the most common grinding media currently used. As an engineering ceramic, it has the characteristics of wear resistance, high temperature resistance and corrosion resistance, and has good application prospects in the field of grinding. The current mainstream grinding balls are alumina composite balls, zirconium aluminum composite balls, cerium zirconium composite balls, etc. Take grinding balls with high alumina content as an example: high-alumina ceramic balls, the specific gravity is usually 3.5~3.9, and it has the characteristics of high strength, high hardness, good wear resistance at room temperature. The products after ultra-fine grinding and dispersion using this ceramic ball introduce less impurities and have high grinding efficiency.

[0003] The conventional preparation processes for ceramic balls are rolling and pressing. When using the rolling method to process ceramic ball blanks, collisions will occur between the balls. This collision is conducive to the adhesion and bonding between powder particles, but the surface defects cannot be controlled. This problem is particularly serious in large-sized ball blanks. One of the main reasons for the high wear of ceramic balls during grinding is that due to the presence of surface defects of the ceramic balls, the epidermis in some areas is more likely to fall off. Large-sized grinding balls are more likely to cause peeling on the surface due to their own high impact momentum. The increase in impurities in the grinding material will eventually hinder the stable progress of experiments or production.

[0004] At present, conventional polishing methods generally use water or the addition of polishing agents to achieve the surface finish of ceramic balls. For balls that have been sintered, the densification of the surface has been completed, so the difficulty of accurately modifying the defects of the ball blank in the subsequent polishing process is also greatly increased. Especially for large-sized ceramic balls, surface defects are more likely to become local pits under polishing conditions. Therefore, this patent proposes a simple and easy surface modification method for large-sized ceramic balls. Summary of the invention

[0005] The purpose of the invention is to provide a method for surface modification of large-size ceramic ball blanks.

[0006] The innovation of the present invention is that the surface of the large-sized ceramic ball is smooth and flat through low-temperature primary firing, rough polishing, surface treatment, surface modification and secondary sintering, which is a significant improvement over the directly fired ball.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0008] A method for surface modification of a large-size ceramic ball blank comprises the following steps:

[0009] (1) Low-temperature one-time firing: Adjust the temperature of the ceramic ball blank by 100~400℃ and set it as the target temperature. During sintering, when the room temperature rises to 500℃, the heating rate k1=2~3℃ / min is used to prevent the ball blank from bursting due to uneven evaporation of water. Keep it at 500℃ for 60~240min, then continue to heat it to the target temperature at a heating rate k2=2~3℃ / min. Keep it at the target temperature for 60~120min. After the insulation is completed, cool it down naturally to obtain a ceramic ball blank. The purpose of low-temperature one-time firing is to discharge the water inside the ball blank and to perform preliminary sintering to reduce pores. In the preliminary sintering and dense state, the ceramic ball blank has a certain degree of vitrification but is not completely dense. The ball blank has a certain strength and has better machinability in the subsequent polishing process. If the firing and holding time is too long, the ceramic ball blank will have too large a vitrification effect, and large-scale brittle peeling is likely to occur during polishing. If the firing and holding time is too short, the rough ceramic ball will not be sufficiently vitrified, and will have low strength and many pores. The ceramic ball will have more defects during the polishing process, and the surface modification effect of the ball blank cannot be achieved.

[0010] (2) Rough polishing: zirconium silicate powder and water are mixed into a slurry with a solid content of 3-5%. The ceramic ball blank and the slurry are mixed in a volume ratio of 1:1-2 and added to a ball mill for rough polishing. The speed of the ball mill is set to 0.3-1.2 m / s and the rough polishing time is set between 12-24 h. After polishing, the slurry on the surface of the ceramic ball blank is rinsed with clean water to obtain the pretreated ceramic ball blank;

[0011] (3) Surface pretreatment: 0.1-1 parts of stearic acid, 0.05-1 parts of polyvinyl alcohol and 98-99.85 parts of water are prepared into a surface treatment slurry. The pretreated ceramic ball blank and the surface treatment slurry are added into a ball mill at a volume ratio of 1:1-2. After the treatment, the water is dried to obtain a primary ceramic ball blank. The ball mill speed is set to 0.3-1.0 m / s and the treatment time is 60-90 min. The porcelain surface of the pretreated ceramic ball blank that is destroyed during the first firing and rough polishing process is functionalized, and then the raw materials used to make the ceramic ball blank are used to process the ceramic surface, and the surface pits can be repaired.

[0012] (4) Surface repair: Add the primary ceramic ball blank into the rolling forming machine, set the speed of the rolling forming machine to 20-25 rpm, and evenly add the raw materials for making the ceramic ball blank 10-20 times within 3 minutes after the rolling forming machine is turned on. The mass of each feed is 0.02-0.1% of the mass of the primary ceramic ball blank. During the process, the bonding slurry is continuously sprayed on the primary ceramic ball blank in the rolling forming machine. The mass ratio of the total amount of the bonding slurry sprayed to the total amount of the raw materials for making the ceramic ball blank is 1:4-8. After 3 minutes of starting the machine, stop adding the raw materials for making the ceramic ball blank and stop spraying the bonding slurry. The primary ceramic ball blank is continuously self-polished in the rolling forming machine for 20-30 min. After the self-polishing is completed, put the primary ceramic ball blank into an oven for low-temperature drying to obtain a low-temperature dried ball blank. The temperature of low-temperature drying is 40-80 °C. ℃; avoid adhesion. The raw materials for making the ceramic ball blank will show obvious cracking and peeling due to excessively high drying temperature and rapid water loss. At the same time, the primary ceramic ball blank is in an incompletely sintered state and absorbs a certain amount of moisture during the rough polishing and surface treatment process. Low-temperature drying can also help avoid cracks in the blank itself due to rapid water loss.

[0013] (5) Secondary sintering: The low-temperature dried ball blank is sintered to obtain a large-sized ceramic ball; during sintering, the temperature is raised to the direct sintering temperature at a rate of k3 = 4-6 °C / min, and the temperature is maintained at the direct sintering temperature for 30-90 min.

[0014] Furthermore, the raw material for making the ceramic ball blank used for surface repair in step (4) has a D98 fineness of 1-2.5 μm.

[0015] Furthermore, the ball mill in step (2) and step (3) has a soft lining of ≥5 MM, and the filling volume does not exceed 2 / 3 of the ball mill when used in step (2) and step (3). The ball mill has a soft lining of ≥5 MM, which can avoid excessive damage caused by collision between the ball blank and the ball mill. The filling volume does not exceed 2 / 3 of the ball mill when used to ensure the rough polishing effect of the ceramic ball rough blank after one firing and the surface pretreatment effect of the primary ceramic ball blank.

[0016] Furthermore, the adhesive slurry is prepared by 0.05 to 1 parts of polyvinyl alcohol and 99 to 99.95 parts of water.

[0017] Furthermore, the D98 fineness of the zirconium silicate powder is between 50 and 200 μm.

[0018] The beneficial effects of the present invention are:

[0019] 1. The present invention uses low-temperature primary firing, rough polishing, surface treatment, surface modification and secondary sintering to make the ceramic ball blank vitrified to a certain extent but not completely dense and have a certain strength, thereby reducing the difficulty of surface processing; on the premise that the surface of the ball blank is not damaged, the surface is processed by low-speed polishing to improve its roundness and roughness, which greatly improves the processing efficiency and saves energy compared with polishing the ceramic ball directly after sintering; then, the surface of the ceramic ball blank is treated with surface treatment slurry to achieve functionalization of the vitrified surface of the pre-treated ceramic ball blank destroyed in the primary firing and rough polishing process, which is beneficial to the adsorption of the vitrified surface destroyed in the rough polishing process on the raw materials for making the ceramic ball blank, thereby achieving the repair of surface pits; finally, the secondary sintering adopts a rapid sintering process, which ensures that the ceramic grinding ball is completely sintered, and rapid sintering is beneficial to preventing abnormal growth of grains, thereby improving the wear resistance of the ceramic ball. In particular, the secondary sintering also sintered the raw powder of the ceramic ball blank adhered to the surface repair process onto the ceramic ball, thus filling some of the surface defects caused by the rough polishing process. SEM showed that the surface of the ceramic ball was smooth and flat after surface modification, which was a significant improvement compared to the directly fired ball. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a flow chart of the surface modification method of ceramic ball blank.

[0021] Figure 2 This is the SEM image of the large-sized ceramic ball of Example 1;

[0022] Figure 3 This is the SEM image of large-sized ceramic balls obtained by direct sintering. Implementation

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0024] Embodiment 1: A method for surface modification of a large-sized ceramic ball blank comprises the following steps:

[0025] Low-temperature one-time firing: adjust the direct firing temperature of the ceramic ball blank down by 100℃ and set this temperature as the target temperature. During sintering: when the room temperature rises to 500℃, the heating rate k1=2℃ / min, keep at 500℃ for 60 min, then continue to heat to the target temperature, the heating rate k2=2℃ / min, keep at the target temperature for 60 min, and naturally cool down after the insulation to obtain the ceramic ball rough blank;

[0026] Rough polishing: zirconium silicate powder and water are mixed into slurry, the D98 fineness of zirconium silicate powder is 50μm, the solid content of the slurry is 3%, the ceramic ball rough blank and the slurry are mixed in a volume ratio of 1:1 and added into a ball mill for rough polishing, the ball mill speed is set to 0.3m / s, and the rough polishing time is set to between 12h. After polishing, the slurry on the surface of the ceramic ball rough blank is rinsed with clean water to obtain the pretreated ceramic ball blank;

[0027] Surface pretreatment: 0.1 parts of stearic acid, 0.05 parts of polyvinyl alcohol and 99.85 parts of water are prepared into surface treatment slurry, and the pretreated ceramic ball blank and the surface treatment slurry are added into the ball mill at a volume ratio of 1:1. After the treatment, the water is dried to obtain the primary ceramic ball blank. The ball mill speed is set to 0.3 m / s and the treatment time is 60 min.

[0028] During rough polishing and surface pretreatment, there is a 5 MM soft lining in the ball mill. When the ball mill is in use, the filling volume is 2 / 3 of the ball mill.

[0029] Surface repair: Add the primary ceramic ball blank to the rolling forming machine, set the speed of the rolling forming machine to 20rpm, and evenly add the raw materials for making the ceramic ball blank 10 times within 3 minutes after the rolling forming machine is turned on. The mass of each feed is 0.02% of the mass of the primary ceramic ball blank. During the process, the bonding slurry is continuously sprayed on the primary ceramic ball blank in the rolling forming machine. The mass ratio of the total amount of the bonding slurry sprayed to the total amount of the raw materials for making the ceramic ball blank is 1:4; the bonding slurry is prepared by 0.05 parts of polyvinyl alcohol and 99.95 parts of water. After 3 minutes of starting the machine, stop adding the raw materials for making the ceramic ball blank and stop spraying the bonding slurry. The primary ceramic ball blank continues to self-polish in the rolling forming machine for 20min. After the self-polishing is completed, the primary ceramic ball blank is placed in an oven for low-temperature drying to obtain a low-temperature dried ball blank. The temperature of low-temperature drying is 40℃; the raw materials for making the ceramic ball blank used for surface repair have a D98 fineness of 1μm.

[0030] Secondary sintering: The low-temperature dried ball blank is sintered to obtain a large-sized ceramic ball; during sintering, the temperature is raised to the direct sintering temperature at 4 °C / min, and the temperature is kept at the direct sintering temperature for 30 minutes.

[0031] Embodiment 2: A method for surface modification of a large-sized ceramic ball blank comprises the following steps:

[0032] Low-temperature one-time firing: Based on the direct firing temperature of the ceramic ball blank, adjust 250℃ downward and set this temperature as the target temperature. During sintering: when the room temperature rises to 500℃, the heating rate k1=2.5℃ / min, keep at 500℃ for 150min, then continue to heat to the target temperature, the heating rate k2=2.5℃ / min, keep at the target temperature for 90min, and naturally cool down after the insulation to obtain the ceramic ball blank;

[0033] Rough polishing: zirconium silicate powder and water are mixed into slurry, the D98 fineness of zirconium silicate powder is 100μm, the solid content of the slurry is 4%, the ceramic ball rough blank and the slurry are mixed in a volume ratio of 1:1.5 and added into a ball mill for rough polishing, the ball mill speed is set to 0.7 m / s, and the rough polishing time is set to between 18 h. After polishing, the slurry on the surface of the ceramic ball rough blank is rinsed with clean water to obtain the pretreated ceramic ball blank;

[0034] Surface pretreatment: 0.5 parts of stearic acid, 0.5 parts of polyvinyl alcohol and 99 parts of water were prepared into surface treatment slurry. The pretreated ceramic ball blank and the surface treatment slurry were added into the ball mill at a volume ratio of 1:1.5. After the treatment, the water was dried to obtain the primary ceramic ball blank. The ball mill speed was set to 0.7 m / s and the treatment time was 85 min.

[0035] During rough polishing and surface pretreatment, there is a 6 MM soft lining in the ball mill. When the ball mill is in use, the filling volume is 1 / 2 of the ball mill.

[0036] Surface repair: Add the primary ceramic ball blank to the rolling forming machine, set the speed of the rolling forming machine to 22rpm, and evenly add the raw materials for making the ceramic ball blank 15 times within 3 minutes after the rolling forming machine is turned on. The mass of each feed is 0.05% of the mass of the primary ceramic ball blank. During the process, the bonding slurry is continuously sprayed on the primary ceramic ball blank in the rolling forming machine. The mass ratio of the total amount of the bonding slurry sprayed to the total amount of the raw materials for making the ceramic ball blank is 1:6; the bonding slurry is prepared by 0.5 parts of polyvinyl alcohol and 99.5 parts of water. After 3 minutes of starting the machine, stop adding the raw materials for making the ceramic ball blank and stop spraying the bonding slurry. The primary ceramic ball blank is continuously self-polished in the rolling forming machine for 25 minutes. After the self-polishing is completed, the primary ceramic ball blank is placed in an oven for low-temperature drying to obtain a low-temperature dried ball blank. The low-temperature drying temperature is 60℃; the raw materials for making the ceramic ball blank used for surface repair have a D98 fineness of 2μm.

[0037] Secondary sintering: The low-temperature dried ball blank is sintered to obtain a large-sized ceramic ball; during sintering, the temperature is raised to the direct sintering temperature at a rate of k3=5°C / min, and the temperature is kept at the direct sintering temperature for 60 minutes.

[0038] Embodiment 3: A method for surface modification of a large-sized ceramic ball blank comprises the following steps:

[0039] Low-temperature one-time firing: Based on the direct firing temperature of the ceramic ball blank, adjust 400℃ downward and set this temperature as the target temperature. During sintering: when the room temperature rises to 500℃, the heating rate k1=3℃ / min, keep at 500℃ for 240min, then continue to heat to the target temperature, the heating rate k2=3℃ / min, keep at the target temperature for 120min, and naturally cool down after the insulation is completed to obtain the ceramic ball rough blank;

[0040] Rough polishing: zirconium silicate powder and water are mixed into slurry, the D98 fineness of zirconium silicate powder is 200 μm, the solid content of the slurry is 5%, the ceramic ball blank and the slurry are mixed in a volume ratio of 1:2 and added into a ball mill for rough polishing, the ball mill speed is set to 1.2 m / s, and the rough polishing time is set to between 24 h. After polishing, the slurry on the surface of the ceramic ball blank is rinsed with clean water to obtain the pretreated ceramic ball blank;

[0041] Surface pretreatment: 1 part of stearic acid, 1 part of polyvinyl alcohol and 98 parts of water were prepared into surface treatment slurry, and the pretreated ceramic ball blank and the surface treatment slurry were added into the ball mill at a volume ratio of 1:2. After the treatment, the water was dried to obtain the primary ceramic ball blank. The ball mill speed was set to 1.0 m / s and the treatment time was 90 min.

[0042] During rough polishing and surface pretreatment, there is a 7 MM soft lining in the ball mill. When the ball mill is in use, the filling volume is 2 / 5 of the ball mill.

[0043] Surface repair: Add the primary ceramic ball blank to the rolling forming machine, set the speed of the rolling forming machine to 25rpm, and evenly add the raw materials for making the ceramic ball blank 20 times within 3 minutes after the rolling forming machine is turned on. The mass of each feed is 0.1% of the mass of the primary ceramic ball blank. During the process, the bonding slurry is continuously sprayed on the primary ceramic ball blank in the rolling forming machine. The mass ratio of the total amount of the bonding slurry sprayed to the total amount of the raw materials for making the ceramic ball blank is 1:8; the bonding slurry is prepared by 1 part of polyvinyl alcohol and 99 parts of water. After 3 minutes of starting the machine, stop adding the raw materials for making the ceramic ball blank and stop spraying the bonding slurry. The primary ceramic ball blank is continuously self-polished in the rolling forming machine for 30 minutes. After the self-polishing is completed, the primary ceramic ball blank is placed in an oven for low-temperature drying to obtain a low-temperature dried ball blank. The low-temperature drying temperature is 80℃; the raw materials for making the ceramic ball blank used for surface repair have a D98 fineness of 2.5 μm.

[0044] Secondary sintering: The low-temperature dried ball blank is sintered to obtain a large-sized ceramic ball; during sintering, the temperature is raised to the direct sintering temperature at a rate of k3=6°C / min, and the temperature is kept at the direct sintering temperature for 90 minutes.

[0045] Test: According to the combination of low-temperature primary firing, rough polishing, surface treatment, surface repair and secondary sintering, the surface modification of large-sized ceramic balls is achieved to obtain ceramic balls with good surface finish. From the SEM image, it can be seen that the surface finish of large-sized ceramic balls using this method is greatly improved compared with the balls polished after direct firing, and the pore defects are significantly reduced. After the anti-wear test is completed by self-polishing using a ball pin machine, the reflected wear is lower than that of the balls polished after direct firing, and the anti-wear stability is better.

[0046] Ball pin machine test method: prepare two groups of balls, one is the ceramic ball obtained in Example 1 and the other is the large-sized ceramic ball obtained after direct firing and polishing (the raw materials used for the large-sized ceramic ball obtained after direct firing and polishing are the same as those in Example 1). Use a polyurethane-lined ball pin machine with a capacity of 1 L, add about 350 g of large-sized ceramic balls, add 150 g of water, use the ball pin machine to self-polish for 1 H, take out and dry after self-polishing, record the data after weighing, and then repeat the above process 5 times, without adding large-sized ceramic balls during the process. Arrange the data to obtain Table 1.

[0047] Table 1 Comparison of quality data of two types of ceramic grinding balls and bottle machines

[0048] Note: SY001 is a large-sized ceramic ball treated by the present invention;

[0049] SY002 is a large-sized ceramic ball obtained by direct firing;

[0050] Total wear rate = (mass of the initial machine - mass of the 5th machine) / mass of the initial machine.

[0051] The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for surface modification of a large-size ceramic ball blank, characterized in that: The following steps are involved: (1) Low-temperature one-time firing: Based on the direct firing temperature of the ceramic ball blank, adjust 100-400°C downward and set this temperature as the target temperature. During sintering: when the room temperature rises to 500°C, the heating rate k1=2-3°C / min, and the temperature is kept at 500°C for 60-240min, and then the temperature is continued to rise to the target temperature, the heating rate k2=2-3°C / min, and the temperature is kept at the target temperature for 60-120min. After the insulation is completed, the temperature is naturally lowered to obtain a ceramic ball blank; (2) Rough polishing: zirconium silicate powder and water are mixed into a slurry with a solid content of 3-5%. The ceramic ball blank and the slurry are mixed in a volume ratio of 1:1-2 and added to a ball mill for rough polishing. The speed of the ball mill is set to 0.3-1.2 m / s, and the rough polishing time is set to between 12 and 24 hours. After polishing, the slurry on the surface of the ceramic ball blank is rinsed with clean water to obtain a pretreated ceramic ball blank; (3) Surface pretreatment: 0.1-1 parts of stearic acid, 0.05-1 parts of polyvinyl alcohol and 98-99.85 parts of water are prepared into a surface treatment slurry, and the pretreated ceramic ball blank and the surface treatment slurry are added into a ball mill at a volume ratio of 1:1-2 for treatment. After the treatment, the water is dried to obtain a primary ceramic ball blank. The speed of the ball mill is set to 0.3-1.0 m / s, and the treatment time is 60-90 min. (4) Surface repair: Add the primary ceramic ball blank to a rolling forming machine, set the speed of the rolling forming machine to 20-25 rpm, and evenly add the raw materials for making the ceramic ball blank 10-20 times within 3 minutes after the rolling forming machine is turned on, and the mass of each feed is 0.02-0.1% of the mass of the primary ceramic ball blank. During the process, the primary ceramic ball blank in the rolling forming machine is continuously sprayed with adhesive slurry, and the mass ratio of the total amount of the adhesive slurry sprayed to the total amount of the raw materials for making the ceramic ball blank is 1:4-8; 3 minutes after the machine is turned on, stop adding the raw materials for making the ceramic ball blank and stop spraying the adhesive slurry, and the primary ceramic ball blank is continuously self-polished in the rolling forming machine, and the self-polishing time is 20-30 minutes. After the self-polishing is completed, the primary ceramic ball blank is placed in an oven for low-temperature drying to obtain a low-temperature dried ball blank, and the low-temperature drying temperature is 40-80°C; (5) Secondary sintering: The low-temperature dried ball blank is sintered to obtain a large-sized ceramic ball; during sintering, the temperature is raised to the direct sintering temperature according to k3 = 4-6°C / min, and the direct sintering temperature is kept at this temperature for 30-90 minutes.

2. The method for surface modification of large-size ceramic ball blanks according to claim 1, characterized in that: The raw material for making the ceramic ball blank used for surface repair in step (4) has a D98 of 1 to 2.5 μm.

3. The method for surface modification of large-size ceramic ball blanks according to claim 1, characterized in that: The ball mill in step (2) and step (3) has a soft lining of ≥5MM, and the filling volume does not exceed 2 / 3 of the ball mill when used in step (2) and step (3).

4. The method for surface modification of large-size ceramic ball blanks according to claim 1, characterized in that: The adhesive slurry is prepared by mixing 0.05 to 1 parts of polyvinyl alcohol and 99 to 99.95 parts of water.

5. The method for surface modification of large-size ceramic ball blanks according to claim 1, characterized in that: The D98 fineness of the zirconium silicate powder is between 50 and 200 μm.

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