Pressureless sintered silicon carbide grinding medium and preparation method thereof
The preparation of silicon carbide grinding media by pressureless sintering solves the problems of fragility and high cost in existing technologies, and realizes the preparation of silicon carbide grinding media with high hardness, high toughness and low wear, which simplifies the process and reduces costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHAANXI KEGU NEW MATERIAL TECH CO LTD
- Filing Date
- 2025-12-30
- Publication Date
- 2026-05-12
AI Technical Summary
Existing silicon carbide grinding media are prone to breakage during the grinding process, and their preparation process is complex and costly, making it difficult to meet the needs of ultrafine grinding.
Silicon carbide grinding media were prepared by pressureless sintering. Through steps such as ball milling, spray granulation, green blank drying, wax removal and high-temperature sintering, silicon carbide grinding media with high hardness, high toughness and low wear were prepared.
It simplifies the preparation process, reduces production costs, improves the sphericity, density, and strength of silicon carbide grinding media, extends service life, and has ultra-high wear resistance.
Smart Images
Figure CN122010571A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a pressureless sintered silicon carbide grinding media and its preparation method. Background Technology
[0002] With the development of ultrafine grinding technology, sand mills are increasingly being used in industries such as paint and printing inks, high-quality automotive paints, pigments and dyes, environmentally friendly thermal insulation materials, nano-ceramics, electronic materials, lithium batteries, barium carbonate, barium sulfate, food processing, chocolate, abrasives, biological agents, suspension pesticides, papermaking, submicron grinding, and pharmaceuticals. The principle involves using a pump to input a solid-liquid mixture, pre-dispersed and wetted by a mixer, into the mill. The material and the grinding media within the mill are agitated by a high-speed rotating disperser, resulting in stronger collisions, friction, and shearing between the solid particles and the grinding media, thus accelerating the grinding of fine particles and dispersing aggregates. The ground and dispersed material then passes through a dynamic separator to separate the grinding media and flows out through the discharge pipe. Because sand mills rely on the strong collisions, friction, and shearing between solid particles and grinding media to accelerate the grinding of fine particles and disperse aggregates, the wear of grinding media is very severe. In order to reduce the wear of grinding media and the contamination of materials, and to improve grinding efficiency, the higher the hardness and toughness of grinding media, the better, and the smaller the diameter of the balls, the better.
[0003] Silicon carbide has a hardness second only to diamond and cubic boron nitride. It is chemically stable, resistant to strong acids and alkalis, has high thermal conductivity, and a small coefficient of thermal expansion, making it the best material for making abrasive media.
[0004] Chinese patent CN1552936A relates to a grinding ball used in a ball mill and its manufacturing method, primarily addressing the problem of low fracture toughness in existing grinding media, which easily leads to breakage during the grinding process. The product of this invention comprises 55–99 parts of silicon carbide and boron carbide powders, 0.5–25 parts of Al-Y additives, and 0.5–30 parts of CeO2 or La2O3. The manufacturing method involves preparing raw balls using dry pressing or cold isostatic pressing, placing them in a vacuum sintering furnace, rinsing with argon gas, and sintering at a heating rate of 5–30 °C / min. After reaching 1750–2100 °C, the temperature is held for 240–480 minutes, and sintering is carried out under argon gas. The hardness of the product from this invention is adjustable from HV2420 to 3000, with improved wear resistance (10-50% higher than current technology) and reduced costs by 20-40%. Toughness can be increased to 7 MPa / cm1 / 2, about 30% higher than existing technologies, thus improving the material's resistance to breakage. This method is suitable for preparing grinding balls with a diameter >5 mm; however, it does not mention preparing grinding balls with a diameter of 0.2-5 mm.
[0005] Chinese patent CN10674758A relates to a production process for silicon carbide ceramic microspheres, belonging to the field of powder grinding. The ceramic raw materials are prepared by mass percentage as follows: α-SiC powder 75%-90%, SiO2 3%-7%, Al2O3 5%-7%, TiN 0.1%-3%, phenolic resin 0.5%-1%, HT resin 0.4%-5%, oleic acid 0.1%-1%, B4C 0.9%-1%. In the same rotating disk, a binder PVA is injected into the ceramic raw materials, and the PVA binder forms spheres and cures them in a medium, directly forming dense spheres with a particle size of 0.1-2 mm. The spheres filled in a sponge are then subjected to cold isostatic pressing for 2-10 minutes. The cold isostatically pressed spheres are placed in a degumming furnace to complete the degumming process. In a vacuum high-temperature sintering furnace, the resulting spheres are placed in a crucible for sintering to produce ceramic microsphere blanks. The obtained ceramic microsphere blanks are then ground and polished to produce ceramic microspheres. The silicon carbide ceramic microspheres produced by this method are first rolled into shape and then subjected to cold isostatic pressing. The production process is complicated, the production cost is high, and the selling price is expensive. Summary of the Invention
[0006] To address the above problems, the purpose of this invention is to provide a pressureless sintered silicon carbide grinding media and its preparation method.
[0007] The technical solution of this invention is: a method for preparing pressureless sintered silicon carbide polishing media, comprising the following steps: S1: Ingredients, by weight ratio, the base material for preparing silicon carbide grinding media includes: 98-99 wt% submicron silicon carbide and 1-2 wt% boron carbide; S2: Ball milling and mixing, the specific process is as follows: S21: The base material obtained in step S1 is put into a ball mill along with tetramethylammonium hydroxide and deionized water for stirring and ball milling. The tetramethylammonium hydroxide accounts for 0.2-1.5 wt% of the total weight of the base material, and the deionized water accounts for 65-75 wt% of the total weight of the base material, until the mixture is uniform. S22: Add water-soluble phenolic resin until thoroughly mixed, with the water-soluble resin accounting for 5-8 wt% of the total weight of the base material; S23: Add PEG400, which accounts for 1-3 wt% of the total weight of the base material. Stir until uniform, then start unloading, sieving, stirring and aging. S3: Spray granulation; S4: High-intensity mixing and granulation; S5: Drying of the green body, the specific process is as follows: The prepared grinding media blank balls were placed in a hot air oven and kept at 50-60℃ for 1-2 hours, and then heated to 120℃ and kept at 1-3 hours. S6: Wax removal from the unfinished body, the specific process is as follows: The dried grinding media blank is loaded into the wax removal furnace and heated to 850℃ at 1-5℃ / min. It is held for 1-4 hours, during which flowing argon gas is introduced for protection. After the holding period, it is cooled with the furnace. S7: High-temperature sintering completes the preparation.
[0008] In step S21, the rotational speed of the ball mill is in the range of 5-10 r / min.
[0009] In step S23, the specific process of unloading, sieving, stirring and aging is as follows: sieving is performed using a 250-mesh sieve, and then the slurry after sieving is poured into a slurry bucket for slow stirring and aging. The rotation speed of the stirring shaft is 10-25 r / min.
[0010] In step S3: spray granulation, the specific process is as follows: a centrifugal spray granulation tower is used for spray granulation. The aged slurry is poured into a storage tank. The inlet temperature is set to 200-250℃, the outlet temperature to 80-120℃, the atomizing disc speed to 6000-10000r / min, and the feed pump speed to 18-20HZ for spray granulation. The prepared spray granulated powder is sieved through an 80-mesh sieve and then sealed and aged for later use.
[0011] In step S4, the high-intensity stirring and granulation process is as follows: the spray granulation powder prepared in step S3 is added to the mixer, then deionized water is added to the container bottle, the air pressure is adjusted, the water is atomized into fine liquid and sprayed onto the surface of the granulation powder, and then high-intensity stirring and granulation is started. After the designed particle size is reached, the atomization and water spraying are stopped, and the granulated grinding media blank is allowed to run continuously for 10-30 minutes to enhance densification.
[0012] In step S5, the raw blank is dried. The specific process is as follows: the prepared grinding media raw blank balls are placed in a hot air oven and kept at 50-60℃ for 1-2 hours, and then the temperature is raised to 120℃ and kept at 1-3 hours.
[0013] In step S7, the high-temperature sintering process is as follows: the dewaxed green blank is placed into a graphite crucible, the graphite crucible is placed into a sintering furnace, and then a vacuum pump is turned on to evacuate the vacuum. The temperature is increased to 900℃ at 1-5℃ / min and held for 1-2 hours. The temperature is then increased to 1500℃ at 1-3℃ / min and held for 1-2 hours. Then the vacuum is turned off, argon gas is purged until the pressure gauge shows 0.1 bar, the temperature is increased to 2150℃ at 1-2℃ / min and held for 0.5-1.5 hours. Then the heating system is turned off, and the furnace is cooled to room temperature before being opened to complete the preparation.
[0014] A pressureless sintered silicon carbide abrasive media is prepared using the method described above. The pressureless sintered silicon carbide abrasive media has a particle size range of 3 mm to 20 mm, a bulk density ≥ 3.10 g / cm³, a crushing strength range of 8 KN to 20 KN, an abrasion value range of 0.275 to 0.350 g / (kg·h), and a Vickers hardness range of 22 to 30 GPa.
[0015] The technical advantages of this invention are as follows: 1. The preparation method of this invention has a simple process flow. Compared with the prior art, it does not require the use of large forming equipment such as dry presses and cold isostatic presses, which greatly reduces the production input cost. 2. The preparation method of this invention produces pressureless sintered silicon carbide grinding media spheres with good sphericity, high density, high strength, high toughness, ultra-high wear resistance, long service life, high temperature resistance, and good chemical stability.
[0016] The following will provide further explanation in conjunction with the accompanying drawings. Attached Figure Description
[0017] Figure 1 This is a schematic flowchart illustrating a method for preparing pressureless sintered silicon carbide polishing media according to an embodiment of the present invention. Detailed Implementation
[0018] Example 1 like Figure 1 As shown, a method for preparing pressureless sintered silicon carbide polishing media includes the following steps: S1: Ingredients, by weight ratio, the base material for preparing silicon carbide grinding media includes: 98-99 wt% submicron silicon carbide and 1-2 wt% boron carbide; S2: Ball milling and mixing, the specific process is as follows: S21: The base material obtained in step S1 is put into a ball mill along with tetramethylammonium hydroxide and deionized water for stirring and ball milling. The tetramethylammonium hydroxide accounts for 0.2-1.5 wt% of the total weight of the base material, and the deionized water accounts for 65-75 wt% of the total weight of the base material, until the mixture is uniform. S22: Add water-soluble phenolic resin until thoroughly mixed, with the water-soluble resin accounting for 5-8 wt% of the total weight of the base material; S23: Add PEG400, which accounts for 1-3 wt% of the total weight of the base material. Stir until uniform, then start unloading, sieving, stirring and aging. S3: Spray granulation; S4: High-intensity mixing and granulation; S5: Drying of the green body, the specific process is as follows: The prepared grinding media blank balls were placed in a hot air oven and kept at 50-60℃ for 1-2 hours, and then the temperature was raised to 120℃ and kept for 1-3 hours. S6: Wax removal from the unfinished body, the specific process is as follows: The dried grinding media blank is loaded into the wax removal furnace and heated to 850℃ at 1-5℃ / min. It is held for 1-4 hours, during which flowing argon gas is introduced for protection. After the holding period, it is cooled with the furnace. S7: High-temperature sintering completes the preparation.
[0019] In step S21, the rotational speed of the ball mill is in the range of 5-10 r / min.
[0020] In step S23, the specific process of unloading, sieving, stirring and aging is as follows: sieving is performed using a 250-mesh sieve, and then the slurry after sieving is poured into a slurry bucket for slow stirring and aging. The rotation speed of the stirring shaft is 10-25 r / min.
[0021] In step S3: spray granulation, the specific process is as follows: a centrifugal spray granulation tower is used for spray granulation. The aged slurry is poured into a storage tank. The inlet temperature is set to 200-250℃, the outlet temperature to 80-120℃, the atomizing disc speed to 6000-10000r / min, and the feed pump speed to 18-20HZ for spray granulation. The prepared spray granulated powder is sieved through an 80-mesh sieve and then sealed and aged for later use.
[0022] In step S4, the high-intensity stirring and granulation process is as follows: the spray granulation powder prepared in step S3 is added to the mixer, then deionized water is added to the container bottle, the air pressure is adjusted, the water is atomized into fine liquid and sprayed onto the surface of the granulation powder, and then high-intensity stirring and granulation is started. After the designed particle size is reached, the atomization and water spraying are stopped, and the granulated grinding media blank is allowed to run continuously for 10-30 minutes to enhance densification.
[0023] In step S5, the raw blank is dried. The specific process is as follows: the prepared grinding media raw blank balls are placed in a hot air oven and kept at 50-60℃ for 1-2 hours, and then the temperature is raised to 120℃ and kept for 1-3 hours.
[0024] In step S7, the high-temperature sintering process is as follows: the dewaxed green blank is placed into a graphite crucible, the graphite crucible is placed into a sintering furnace, and then the vacuum pump is turned on to evacuate the vacuum. The temperature is increased to 900℃ at 1-5℃ / min and held for 1-2 hours. The temperature is then increased to 1500℃ at 1-3℃ / min and held for 1-2 hours. Then the vacuum is turned off, argon gas is purged until the pressure gauge shows 0.1 bar, the temperature is increased to 2150℃ at 1-2℃ / min and held for 0.5-1.5 hours. Then the heating system is turned off, and the furnace is cooled to room temperature before being opened to complete the preparation.
[0025] The prepared pressureless sintered silicon carbide grinding media has a particle size range of 3 mm to 20 mm, a bulk density of ≥3.10 g / cm³, a crushing strength range of 8 KN to 20 KN, an abrasion value range of 0.275 to 0.350 g / (kg·h), and a Vickers hardness range of 22 to 30 Gp.
[0026] Example 2 A pressureless sintered silicon carbide abrasive media is prepared using the method described above. The pressureless sintered silicon carbide abrasive media has a particle size range of 3 mm to 20 mm, a bulk density ≥ 3.10 g / cm³, a crushing strength range of 8 KN to 20 KN, an abrasion value range of 0.275 to 0.350 g / (kg·h), and a Vickers hardness range of 22 to 30 GPa.
[0027] Example 3 The pressureless sintered silicon carbide polishing media as described in Example 1 is prepared using the same method, and the pressureless sintered silicon carbide polishing media as described in Example 2 is prepared by the following steps: S1: Ingredients, by weight, the base material for preparing silicon carbide grinding media includes: 99 wt% submicron silicon carbide, D50=0.7 μm, and 1 wt% boron carbide, D50=1.5 μm; tetramethylammonium hydroxide accounts for 0.8 wt% of the total weight of the base material, deionized water accounts for 70 wt% of the total weight of the base material, water-soluble resin accounts for 6 wt% of the total weight of the base material, and PEG400 accounts for 3 wt% of the total weight of the base material. S2: Ball milling mixture: Submicron silicon carbide, boron carbide, tetramethylammonium hydroxide, and deionized water were added to a ball mill in the above proportions and stirred and milled at a speed of 30 r / min for 4 h. Then add water-soluble phenolic resin and stir continuously at 30 r / min for 2 hours; Finally, add PEG400 and stir continuously at 30 r / min for 4 hours. Then start unloading and sieve the material through a 250 mesh screen. Pour the sieved slurry into a slurry bucket for slow stirring and aging. The stirring shaft rotates at 20 r / min. S3: Spray granulation: A centrifugal spray granulation tower was used for spray granulation. The aged slurry was poured into a storage tank. The inlet temperature was set to 240℃, the outlet temperature to 110℃, the atomizing disc speed to 10000r / min, and the pump speed to 20HZ. The spray granulation was carried out, and the prepared spray granulated powder was sieved through an 80-mesh sieve and then sealed and aged for later use. S4: High-intensity mixing and granulation: Using the R08 continuous high-intensity mixer manufactured by the German Erich Group GmbH, 50 kg of spray granulation powder was weighed and added to the mixer. Then, 2 kg of deionized water was added to the container bottle, and the pressure of the container bottle was adjusted to 0.2 kgf. The water was atomized into fine liquid and sprayed onto the surface of the granulation powder. First, the stirring paddle was turned on, and then the rotation button was started for high-intensity mixing and granulation. After the required particle size was achieved, the atomization and water spraying were stopped, and the granulated green body was allowed to run continuously for 10 minutes to enhance densification. S5: Drying of raw blanks: The prepared grinding media blank balls were placed in a hot air oven and kept at 60°C for 1 hour, and then the temperature was raised to 120°C and kept for 2 hours. S6: Waxing of unfinished blank: The dried grinding media blank is loaded into the wax removal furnace and heated to 850℃ at 2℃ / min. It is held for 1 hour, during which flowing argon gas is introduced for protection. After the holding period, it is cooled with the furnace. S7: High-temperature sintering: After dewaxing, the blank of the raw grinding media is placed into a graphite crucible, which is then placed into a sintering furnace. A vacuum pump is then turned on to evacuate the furnace, and the temperature is increased to 900℃ at a rate of 3℃ / min and held for 1 hour. The temperature is then increased to 1500℃ at a rate of 2℃ / min and held for 1 hour. The vacuum is then turned off, and argon gas is introduced until the pressure gauge shows 0.1 bar. The temperature is then increased to 2150℃ at a rate of 1℃ / min and held for 0.5 hours. The heating system is then turned off, and the furnace is allowed to cool to room temperature before being opened, thus completing the preparation of the pressureless sintered silicon carbide grinding media.
[0028] The crushing strength, Vickers hardness, and wear performance of the prepared pressureless sintered silicon carbide grinding media were tested as follows: 1. Bulk density: The bulk density of the pressureless sintered silicon carbide grinding media prepared by this method, measured by the water displacement method, is ≥3.10 g / cm³. The method of this invention produces pressureless sintered silicon carbide grinding media with high density.
[0029] 2. Crushing Strength: Twenty samples with acceptable dimensions (12mm each) were selected. Each sample was placed one by one at the center of the lower pressure plate of the material testing machine. The machine was adjusted so that the upper pressure plate slowly descended, applying pressure to the sample at a loading rate of 50 N / s until the sample was crushed. The maximum load value at crushing time for each sample was recorded. The arithmetic mean of the crushing strength of all samples was calculated to be 9.83 KN / sample. The preparation method of this invention produces high-strength pressureless sintered silicon carbide grinding media.
[0030] 3. Wear: Referring to industry standard JC / T848.1-2010, a grinding jar with an inner diameter of 200mm and lined with polyurethane was used, and the matching ball mill speed was 80 rpm, ensuring that the relative speed between the balls did not exceed 0.837m / s. First, 1000g of rolled ball samples with acceptable appearance quality and dimensional deviation were weighed and placed in the grinding jar, 1000g of water was added, and then the ball mill was started, allowing the rolled balls to undergo impact grinding under the specified speed and time conditions. After grinding for 48 hours, the ball mill was stopped, the rolled balls were removed, cleaned, and dried to constant weight. The mass of the rolled balls was weighed again, and the wear value was obtained by calculating the ratio of the difference in mass of the rolled balls before and after grinding to the grinding time, which was 0.341g / (kg·h). The preparation method of this invention produces pressureless sintered silicon carbide grinding media with ultra-high wear resistance and long service life.
[0031] 4. Vickers Hardness: The Vickers hardness (HV3) of the pressureless sintered silicon carbide abrasive media of this invention was measured to be 25.1 GPa according to the national standard GB / T16534-2009, "Test Method for Room Temperature Hardness of Fine Ceramics". The pressureless sintered silicon carbide abrasive media prepared by the method of this invention exhibits high hardness.
[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing pressureless sintered silicon carbide grinding media, characterized in that: Includes the following steps: S1: Ingredients, by weight ratio, the base material for preparing silicon carbide grinding media includes: 98-99 wt% submicron silicon carbide and 1-2 wt% boron carbide; S2: Ball milling and mixing, the specific process is as follows: S21: The base material obtained in step S1 is put into a ball mill along with tetramethylammonium hydroxide and deionized water for stirring and ball milling. The tetramethylammonium hydroxide accounts for 0.2-1.5 wt% of the total weight of the base material, and the deionized water accounts for 65-75 wt% of the total weight of the base material, until the mixture is uniform. S22: Add water-soluble phenolic resin until thoroughly mixed, with the water-soluble resin accounting for 5-8 wt% of the total weight of the base material; S23: Add PEG400, which accounts for 1-3 wt% of the total weight of the base material. Stir until uniform, then start unloading, sieving, stirring and aging. S3: Spray granulation; S4: High-intensity mixing and granulation; S5: Drying of the green body, the specific process is as follows: The prepared grinding media blank balls were placed in a hot air oven and kept at 50-60℃ for 1-2 hours, and then heated to 120℃ and kept at 1-3 hours. S6: Wax removal from the unfinished body, the specific process is as follows: The dried grinding media blank is loaded into the wax removal furnace and heated to 850℃ at 1-5℃ / min. It is held for 1-4 hours, during which flowing argon gas is introduced for protection. After the holding period, it is cooled with the furnace. S7: High-temperature sintering completes the preparation.
2. The method for preparing a pressureless sintered silicon carbide grinding media according to claim 1, characterized in that: In step S21, the rotational speed of the ball mill is in the range of 5-10 r / min.
3. The method for preparing a pressureless sintered silicon carbide grinding media according to claim 1, characterized in that: In step S23, the specific process of unloading, sieving, stirring and aging is as follows: sieving is performed using a 250-mesh sieve, and then the slurry after sieving is poured into a slurry bucket for slow stirring and aging. The rotation speed of the stirring shaft is 10-25 r / min.
4. The method for preparing a pressureless sintered silicon carbide grinding media according to claim 1, characterized in that: In step S3: spray granulation, the specific process is as follows: a centrifugal spray granulation tower is used for spray granulation. The aged slurry is poured into a storage tank. The inlet temperature is set to 200-250℃, the outlet temperature to 80-120℃, the atomizing disc speed to 6000-10000r / min, and the feed pump speed to 18-20HZ for spray granulation. The prepared spray granulated powder is sieved through an 80-mesh sieve and then sealed and aged for later use.
5. The method for preparing a pressureless sintered silicon carbide grinding media according to claim 1, characterized in that: In step S4, the high-intensity stirring and granulation process is as follows: the spray granulation powder prepared in step S3 is added to the mixer, then deionized water is added to the container bottle, the air pressure is adjusted, the water is atomized into fine liquid and sprayed onto the surface of the granulation powder, and then high-intensity stirring and granulation is started. After the designed particle size is reached, the atomization and water spraying are stopped, and the granulated grinding media blank is allowed to run continuously for 10-30 minutes to enhance densification.
6. The method for preparing a pressureless sintered silicon carbide grinding media according to claim 1, characterized in that: In step S5, the raw blank is dried. The specific process is as follows: the prepared grinding media raw blank balls are placed in a hot air oven and kept at 50-60℃ for 1-2 hours, and then the temperature is raised to 120℃ and kept at 1-3 hours.
7. The method for preparing a pressureless sintered silicon carbide grinding media according to claim 1, characterized in that: In step S7, the high-temperature sintering process is as follows: the dewaxed green blank is placed into a graphite crucible, the graphite crucible is placed into a sintering furnace, and then a vacuum pump is turned on to evacuate the vacuum. The temperature is increased to 900℃ at 1-5℃ / min and held for 1-2 hours. The temperature is then increased to 1500℃ at 1-3℃ / min and held for 1-2 hours. Then the vacuum is turned off, argon gas is purged until the pressure gauge shows 0.1 bar, the temperature is increased to 2150℃ at 1-2℃ / min and held for 0.5-1.5 hours. Then the heating system is turned off, and the furnace is cooled to room temperature before being opened to complete the preparation.
8. A pressureless sintered silicon carbide polishing medium, prepared by the method for preparing a pressureless sintered silicon carbide polishing medium as described in claim 1, characterized in that: The particle size range of the pressureless sintered silicon carbide grinding media is 3mm~20mm, the bulk density is ≥3.10g / cm³, the crushing strength ranges from 8KN to 20KN, the wear value ranges from 0.275 to 0.350g / (kg·h), and the Vickers hardness ranges from 22 to 30Gpa.