Preparation method of silicon carbide grinding beads

Abstract

The invention relates to a preparation method of silicon carbide grinding beads, which comprises the following steps: mixing silicon carbide powder, a sintering aid and a solvent to obtain silicon carbide slurry; carrying out spray granulation on the obtained silicon carbide slurry to obtain a granulated material; carrying out rolling forming on the obtained granulated material to obtain green pellets with target particle size distribution; sequentially carrying out constant-temperature and constant-humidity drying and drying on the obtained green pellets, and then carrying out pressureless sintering to obtain a sintered material; and grinding and polishing the obtained sintered material to obtain the silicon carbide grinding beads. The preparation method provided by the invention is suitable for industrial production, and the obtained silicon carbide grinding ball has the characteristic of particle size Gaussian distribution, and has the characteristics of high sphericity, excellent performance, low abrasion and difficulty in breaking.

Description

Technical Field

[0001] The invention belongs to the field of grinding technology and relates to a method for preparing grinding beads, in particular to a method for preparing silicon carbide grinding beads. Background Art

[0002] Grinding beads are an important engineering ceramic, widely used in cement, minerals, ceramics, electronic materials, magnetic materials, coatings, paints and other industries, and are a high-quality grinding medium. With the natural ball stone on the verge of exhaustion, the inferior and high-priced artificial ball stone seriously affects the quality of grinding materials and restricts the development of technology. In this context, silicon carbide grinding beads with extremely high hardness, small wear, corrosion resistance and oxidation resistance are used by more and more powder manufacturers.

[0003] The existing silicon carbide ball milling media include two types: Figure 1 The columnar grinding medium shaped silicon carbide shown in FIG. Figure 2 The spherical silicon carbide shown in the figure has different shapes, but they are both produced using similar processes, including the selection of molds of appropriate shapes for production. For example, when producing spherical silicon carbide, two unequal spherical molds are used, so the product will have a joint mark. Sintering and surface treatment are needed to eliminate this joint mark as much as possible.

[0004] CN115925425A discloses a process for making silicon carbide balls, comprising the following steps: (1) mixing quartz sand and coke, adding salt and sawdust, placing the mixture in an electric furnace, and heating to synthesize silicon carbide powder; (2) taking silicon carbide powder and carbon powder as raw materials, adding a sintering agent and a binder, and stirring the mixture into a slurry; (3) passing the slurry into a dryer for drying, and then sintering the slurry into a ball making machine to prepare a green ball; (4) placing the green ball into a vacuum press, and performing static pressing at a pressure of 140-160 MPa to obtain a green body.

[0005] CN109678518A discloses high-strength and high-sphericity silicon carbide grinding beads for preparing high-purity ultrafine powders. The raw material formula includes: black silicon carbide, green silicon carbide, beta silicon carbide and carbon. The powder is prepared through the steps of raw material pretreatment, batching, dry mixing, wet mixing, extrusion, cutting, kneading, ball selection, drying, screening, degreasing, sintering, selection, polishing, cleaning and drying.

[0006] However, the prior art has at least the following disadvantages when preparing silicon carbide ball milling media:

[0007] Due to the limitation of the size of the molding mold, the product size is single. For example, the sizes of grinding balls on the market are mostly 3mm, 5mm, 8mm and 12mm. Silicon carbide ball milling media of other sizes need to be customized with molding molds of appropriate sizes and then prepared separately. Moreover, it is very difficult to prepare grinding balls below 3mm.

[0008] Due to the limitation of the molding method, the molding efficiency is low, which makes the cost of the obtained silicon carbide grinding balls high;

[0009] Since the silicon carbide grinding balls produced are of a single size, it is necessary to match grinding balls of different sizes with the medium according to the type of grinding equipment and the target grinding particle size of the material during the grinding operation; and in order to improve the grinding efficiency, grinding balls of different sizes need to be graded and mixed to achieve a better grinding effect;

[0010] The surface of silicon carbide grinding balls prepared by existing processes is rough, which easily causes high wear and also contaminates the ground materials.

[0011] Therefore, it is necessary to provide a method for preparing silicon carbide grinding beads with high production efficiency and smooth surface. Summary of the invention

[0012] The object of the present invention is to provide a method for preparing silicon carbide grinding beads, which is suitable for industrial production, and the obtained silicon carbide grinding balls have the characteristics of Gaussian distribution of particle size, high sphericity, excellent performance, low wear and are not easy to break.

[0013] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0014] The present invention provides a method for preparing silicon carbide grinding beads, the preparation method comprising the following steps:

[0015] (1) mixing silicon carbide powder, a sintering aid and a solvent to obtain a silicon carbide slurry;

[0016] (2) spray granulating the silicon carbide slurry obtained in step (1) to obtain granulated material;

[0017] (3) using the granulated material obtained in step (2) to perform rolling molding to obtain green balls with a target particle size distribution;

[0018] (4) subjecting the green balls obtained in step (3) to constant temperature and humidity drying and oven drying in sequence, and then to pressureless sintering to obtain a sintered material;

[0019] (5) Grinding and polishing the sintered material obtained in step (4) to obtain the silicon carbide grinding beads.

[0020] The preparation method provided by the present invention is suitable for industrial production, and each step can achieve improved production efficiency; for example, the present invention adopts a rolling molding method to prepare green balls, which improves production efficiency and has a production speed better than compression molding; moreover, the preparation method provided by the present invention grinds and polishes the sintered material, reduces the surface wear of the obtained silicon carbide grinding beads during the application process, and improves its grinding performance; moreover, the preparation method can prepare silicon carbide grinding beads with a particle size range of 0.1-8mm, and the obtained product has the characteristics of high sphericity, excellent performance, low wear and not easy to break.

[0021] Preferably, the silicon carbide powder in step (1) is α-SiC powder.

[0022] Preferably, the average particle size of the α-SiC powder is 0.1-5 μm, for example, it can be 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 0.3-2 μm, and more preferably 0.3-1 μm.

[0023] Preferably, the sintering aid in step (1) includes boron powder, carbon powder or B4C powder.

[0024] Preferably, the average particle size of the sintering aid in step (1) is 0.05-3 μm, for example, it can be 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0.05-1 μm.

[0025] Preferably, the amount of the sintering aid in step (1) is 0.1-10wt% of the silicon carbide powder, for example, it can be 0.1wt%, 0.5wt%, 1wt%, 2wt%, 4wt%, 5wt%, 6wt%, 8wt% or 10wt%, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0.1-5wt%.

[0026] Preferably, the solvent in step (1) comprises water or an organic solvent, preferably water.

[0027] The present invention does not impose any further limitation on the amount of the solvent used in step (1), as long as the silicon carbide powder and the sintering aid can be uniformly mixed to form a slurry.

[0028] Preferably, the mixing in step (1) also includes mixing an organic additive.

[0029] Preferably, the organic additive includes any one of a dispersant, a binder, a plasticizer or a defoamer or a combination of at least two thereof. Typical but non-limiting combinations include a combination of a dispersant and a binder, a combination of a binder and a plasticizer, a combination of a plasticizer and a defoamer, a combination of a dispersant and a defoamer, a combination of a dispersant, a binder and a plasticizer, a combination of a binder, a plasticizer and a defoamer, or a combination of a dispersant, a binder, a plasticizer and a defoamer.

[0030] The present invention uses organic additives to facilitate uniform mixing of silicon carbide powder and sintering aid in silicon carbide slurry, and is also beneficial to the stability of silicon carbide slurry. The present invention does not further limit the specific types of dispersants, binders, plasticizers or defoamers, and those skilled in the art can reasonably select them according to needs.

[0031] Preferably, the amount of the organic additive is 0.1-5wt% of the silicon carbide powder, for example, it can be 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt% or 5wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the mixing method in step (1) comprises grinding.

[0033] Exemplarily, the grinding is performed in a grinding device, and the grinding device includes any one of a drum ball mill, a stirring ball mill, a vertical sand mill or a horizontal sand mill.

[0034] Preferably, the average particle size of the silicon carbide slurry obtained after grinding is below 1 μm, for example, it can be 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm or 1 μm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 0.3-1 μm.

[0035] Preferably, the average particle size of the granulated material in step (2) is 30-200 μm, for example, 30 μm, 50 μm, 80 μm, 100 μm, 150 μm or 200 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Exemplarily, the rolling molding in step (3) includes: adding granules to a rolling molding disk, spraying a water-soluble adhesive conventional in the art to form a ball core; then repeating the process of adding granules and spraying the water-soluble adhesive, so that the granules continue to grow during the rolling process until raw balls with a target particle size distribution are obtained.

[0037] Exemplarily, the adhesive used in the water-soluble glue includes, but is not limited to, any one of sodium methyl cellulose, phenolic resin, polyethylene glycol, polyvinyl alcohol or polyacrylic acid, or a combination of at least two thereof, and those skilled in the art can make a reasonable selection according to needs.

[0038] Through the rolling forming of the present invention, the particle size distribution of the obtained granulated material can present Gaussian distribution characteristics.

[0039] Preferably, the particle size of the granulated material in step (2) satisfies the numerical range of (D90-D10) / D50 of 0.8-1.8, for example, it can be 0.8, 1, 1.2, 1.5, 1.6 or 1.8, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, during the rolling forming process, the size of the ball core needs to be controlled to be less than 1 / 2 of the size of the raw ball.

[0041] Preferably, the average particle size of the raw ball core in step (3) is 0.03-3 mm, for example, it can be 0.03 mm, 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the particle size of the raw balls in step (3) is in the range of 0.3-10 mm, for example, 0.3 mm, 0.5 mm, 1 mm, 3 mm, 6 mm, 8 mm or 10 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the particle size of the raw balls in step (3) satisfies the numerical range of (D90-D10) / D50 of 1-2, for example, it can be 1, 1.2, 1.5, 1.6, 1.8 or 2, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0044] Preferably, the preparation method also includes selecting the green balls before constant temperature and humidity drying so that the sphericity of the green balls is above 0.9, for example, it can be 0.9, 0.91, 0.92, 0.93, 0.95, 0.98 or 0.99, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the temperature of the constant temperature and humidity drying in step (4) is 25-35°C, for example, it can be 25°C, 28°C, 30°C, 32°C or 35°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the relative humidity of the constant temperature and humidity drying in step (4) is 50-90%, for example, it can be 50%, 60%, 70%, 80% or 90%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, the constant temperature and humidity drying time in step (4) is 24-168 hours, for example, it can be 24 hours, 48 ​​hours, 96 hours, 120 hours or 168 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] Preferably, the drying temperature in step (4) is 45-120°C, for example, 45°C, 55°C, 75°C, 100°C, 110°C or 120°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0049] Preferably, the drying time in step (4) is 24-168 hours, for example, it can be 24 hours, 60 hours, 84 hours, 120 hours or 168 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] Preferably, the pressureless sintering in step (4) includes vacuuming, first heating, first heat preservation, second heating, second heat preservation and cooling performed in sequence.

[0051] Preferably, the first heating rate is 0.5-3°C / min, for example, 0.5°C / min, 1.5°C / min, 2.5°C / min or 3°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] Preferably, the endpoint temperature of the first heating is 480-520°C, for example, 480°C, 490°C, 500°C, 510°C or 520°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] Preferably, the first insulation time is 1-4h, for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] Preferably, the second heating rate is 1-5°C / min, for example, 1°C / min, 1.5°C / min, 3°C / min, 3.5°C / min or 5°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] Preferably, the endpoint temperature of the second heating is 1950-2150°C, for example, it can be 1950°C, 1980°C, 2000°C, 2050°C, 2100°C or 2150°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] Preferably, the second insulation time is 2-4h, for example, 2h, 2.5h, 3h, 3.5h or 4h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] Exemplarily, the pressureless sintering is carried out in a sintering furnace, and the temperature reduction is furnace cooling. When the temperature drops below 300° C., the sintering furnace is opened to obtain the sintering material.

[0058] Preferably, the preparation method further comprises hot isostatic pressing after pressureless sintering to obtain a sintered material.

[0059] The present invention can further improve the density and mechanical strength of the obtained silicon carbide grinding beads through hot isostatic pressing after pressureless sintering.

[0060] Preferably, the temperature of the hot isostatic pressing is 1800-2000°C, for example, 1800°C, 1850°C, 1900°C, 1950°C or 2000°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] Preferably, the hot isostatic pressing pressure is 120-180 MPa, for example, 120 MPa, 150 MPa, 160 MPa or 180 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0062] Preferably, the heat preservation and pressure holding time of the hot isostatic pressing is 0.8-3.6 h, for example, it can be 0.8 h, 1 h, 2 h, 2.5 h or 3.6 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0063] The present invention reduces the surface roughness of silicon carbide grinding beads by grinding and polishing, thereby reducing the wear of the grinding balls and avoiding the generation of broken corners and debris during the grinding process.

[0064] Preferably, the polishing time in step (5) is ≥ 24 h, for example, it can be 24 h, 40 h, 50 h, 60 h, 80 h, 100 h or 120 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0065] Preferably, the surface roughness of the silicon carbide grinding beads obtained after polishing in step (5) is ≤0.5μm, for example, it can be 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm or 0.5μm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably ≤0.3μm, and more preferably ≤0.1μm.

[0066] Illustratively, the silicon carbide grinding beads prepared by the present invention are screened to obtain silicon carbide grinding beads with particle sizes ranging from 0.3-0.6 mm, 0.6-0.8 mm, 0.8-1.2 mm, 2-4 mm, 3-6 mm and 4-8 mm, and other unlisted values ​​within the numerical range are also applicable.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] The preparation method provided by the present invention is suitable for industrial production, and each step can achieve improved production efficiency; for example, the present invention adopts a rolling molding method to prepare green balls, which improves production efficiency and has a production speed better than compression molding; moreover, the preparation method provided by the present invention grinds and polishes the sintered material, reduces the surface wear of the obtained silicon carbide grinding beads during the application process, and improves its grinding performance; moreover, the preparation method can prepare silicon carbide grinding beads with a particle size range of 0.1-8mm, and the obtained product has the characteristics of high sphericity, excellent performance, low wear and not easy to break. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a schematic diagram of silicon carbide in the shape of a columnar grinding medium in the prior art;

[0070] Figure 2 is a schematic diagram of spherical silicon carbide in the prior art;

[0071] Figure 3 This is the particle size distribution diagram of the silicon carbide grinding beads obtained in Example 1. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0073] Example 1

[0074] This embodiment provides a method for preparing silicon carbide grinding beads, the preparation method comprising the following steps:

[0075] (1) grinding and mixing α-SiC powder, a sintering aid, an organic additive, and water to obtain a silicon carbide slurry with an average particle size of 0.4 μm;

[0076] The average particle size of the α-SiC powder is 0.5 μm;

[0077] The sintering aid is B4C powder with an average particle size of 0.5 μm; the amount of the sintering aid is 1wt% of the α-SiC powder;

[0078] The organic additives include a dispersant (polymethacrylic acid, Kemik, 54193-36-1), a binder (polyvinyl alcohol, Mingxin Chemical, 5421), a plasticizer (polyethylene glycol, PEG-4000) and a defoamer (dimethyl silicone oil), wherein the dispersant is added in an amount of 0.2wt% of the α-SiC powder, the binder is added in an amount of 1.5wt% of the α-SiC powder, the plasticizer is added in an amount of 0.5wt% of the α-SiC powder, and the defoamer is added in an amount of 0.1wt% of the α-SiC powder;

[0079] (2) Spray granulation step (1) to obtain a granulated material with an average particle size of 50 μm from the silicon carbide slurry, and the particle size of the granulated material satisfies the value of (D90-D10) / D50 of 1.2;

[0080] (3) rolling the granulated material obtained in step (2) to obtain green balls with an average particle size of 2.2 mm, wherein the particle size of the green balls satisfies the value of (D90-D10) / D50 of 1.6; the average particle size of the ball core of the green balls is 1 mm; and the green balls are selected so that the sphericity of the green balls is greater than 0.9;

[0081] (4) subjecting the green balls obtained in step (3) to constant temperature and humidity drying and oven drying in sequence, and then to pressureless sintering to obtain a sintered material;

[0082] The constant temperature and humidity drying temperature is 30°C, the relative humidity is 70%; the drying time is 120h;

[0083] The drying temperature is 60°C and the drying time is 48h;

[0084] The pressureless sintering includes vacuuming, first heating, first heat preservation, second heating, second heat preservation and furnace cooling in sequence, and the material is taken out after the furnace is cooled to 300°C;

[0085] The first heating rate is 1.5°C / min, and the end temperature is 500°C;

[0086] The first insulation time is 2h;

[0087] The heating rate of the second heating is 2.5°C / min, and the end temperature is 2050°C;

[0088] The second insulation time is 3h;

[0089] (5) Grinding and polishing the sintered material obtained in step (4) to obtain silicon carbide grinding beads with a surface roughness of ≤0.5 μm.

[0090] The particle size distribution of the silicon carbide grinding beads obtained in this example is as follows: Figure 3 As shown by Figure 3 It can be seen that the particle size of the silicon carbide grinding beads obtained in this example has a Gaussian distribution characteristic.

[0091] Example 2

[0092] This embodiment provides a method for preparing silicon carbide grinding beads, the preparation method comprising the following steps:

[0093] (1) grinding and mixing α-SiC powder, a sintering aid, an organic additive, and water to obtain a silicon carbide slurry with an average particle size of 0.3 μm;

[0094] The average particle size of the α-SiC powder is 0.3 μm;

[0095] The sintering aid is B4C powder with an average particle size of 0.08 μm; the amount of the sintering aid is 0.5 wt% of the α-SiC powder;

[0096] The composition of the organic additive is the same as that of Example 1, wherein the amount of the dispersant added is 0.1wt% of the α-SiC powder, the amount of the binder added is 3wt% of the α-SiC powder, the amount of the plasticizer added is 1wt% of the α-SiC powder, and the amount of the defoamer added is 0.2wt% of the α-SiC powder;

[0097] (2) Spray granulation of the silicon carbide slurry obtained in step (1) to obtain granules with an average particle size of 35 μm, and the particle size of the granules satisfies the value of (D90-D10) / D50 of 0.9;

[0098] (3) rolling the granulated material obtained in step (2) to obtain green balls with an average particle size of 0.5 mm, wherein the particle size of the green balls satisfies the value of (D90-D10) / D50 of 1.1; the average particle size of the ball core of the green balls is 0.1 mm; and the green balls are selected so that the sphericity of the green balls is greater than 0.9;

[0099] (4) subjecting the green balls obtained in step (3) to constant temperature and humidity drying and oven drying in sequence, and then to pressureless sintering to obtain a sintered material;

[0100] The constant temperature and humidity drying temperature is 35°C, the relative humidity is 60%; the drying time is 72h;

[0101] The drying temperature is 45°C and the drying time is 120h;

[0102] The pressureless sintering includes vacuuming, first heating, first heat preservation, second heating, second heat preservation and furnace cooling in sequence, and the material is taken out after the furnace is cooled to 300°C;

[0103] The heating rate of the first heating is 0.5°C / min, and the end temperature is 480°C;

[0104] The first insulation time is 4h;

[0105] The second heating rate is 1°C / min, and the end temperature is 1950°C;

[0106] The second insulation time is 4h;

[0107] (5) Grinding and polishing the sintered material obtained in step (4) to obtain silicon carbide grinding beads with a surface roughness of ≤0.5 μm.

[0108] Example 3

[0109] This embodiment provides a method for preparing silicon carbide grinding beads, the preparation method comprising the following steps:

[0110] (1) grinding and mixing α-SiC powder, a sintering aid, an organic additive, and water to obtain a silicon carbide slurry with an average particle size of 0.5 μm;

[0111] The average particle size of the α-SiC powder is 0.7 μm;

[0112] The sintering aid is B4C powder with an average particle size of 1 μm; the amount of the sintering aid is 2wt% of the α-SiC powder;

[0113] The organic additives include a dispersant (polymethacrylic acid, Kemik, 54193-36-1), a binder (polyvinyl alcohol, Mingxin Chemical, 5421) and a defoamer (dimethyl silicone oil), wherein the dispersant is added in an amount of 1wt% of the α-SiC powder, the binder is added in an amount of 3wt% of the α-SiC powder, and the defoamer is added in an amount of 0.5wt% of the α-SiC powder;

[0114] (2) Spray granulation step (1) to obtain a granulated material with an average particle size of 60 μm from the silicon carbide slurry, and the particle size of the granulated material satisfies the value of (D90-D10) / D50 of 1.4;

[0115] (3) rolling the granulated material obtained in step (2) to obtain green balls with an average particle size of 7 mm, wherein the particle size of the green balls satisfies the value of (D90-D10) / D50 of 1.9; the average particle size of the ball core of the green balls is 2 mm; and the green balls are selected so that the sphericity of the green balls is greater than 0.9;

[0116] (4) subjecting the green balls obtained in step (3) to constant temperature and humidity drying and oven drying in sequence, and then to pressureless sintering to obtain a sintered material;

[0117] The constant temperature and humidity drying temperature is 32°C, the relative humidity is 80%; the drying time is 168h;

[0118] The drying temperature is 70°C and the drying time is 48h;

[0119] The pressureless sintering includes vacuuming, first heating, first heat preservation, second heating, second heat preservation and furnace cooling in sequence, and the material is taken out after the furnace is cooled to 300°C;

[0120] The heating rate of the first heating is 3°C / min, and the end temperature is 520°C;

[0121] The first insulation time is 1h;

[0122] The heating rate of the second heating is 5°C / min, and the end temperature is 2150°C;

[0123] The second insulation time is 2h;

[0124] (5) Grinding and polishing the sintered material obtained in step (4) to obtain silicon carbide grinding beads with a surface roughness of ≤0.5 μm.

[0125] Example 4

[0126] This embodiment provides a method for preparing silicon carbide grinding beads, the preparation method comprising the following steps:

[0127] (1) grinding and mixing α-SiC powder, a sintering aid, an organic additive, and water to obtain a silicon carbide slurry with an average particle size of 0.7 μm;

[0128] The average particle size of the α-SiC powder is 2 μm;

[0129] The sintering aid is B4C powder with an average particle size of 0.05 μm; the amount of the sintering aid is 0.1 wt% of the α-SiC powder;

[0130] The organic additives include a dispersant (polymethacrylic acid, Kemik, 54193-36-1), a binder (polyvinyl alcohol, Mingxin Chemical, 5421) and a defoamer (dimethyl silicone oil), wherein the dispersant is added in an amount of 1wt% of the α-SiC powder, the binder is added in an amount of 3wt% of the α-SiC powder, and the defoamer is added in an amount of 0.5wt% of the α-SiC powder;

[0131] (2) Spray granulation of the silicon carbide slurry obtained in step (1) to obtain granules with an average particle size of 70 μm, and the particle size of the granules satisfies the value of (D90-D10) / D50 of 1.5;

[0132] (3) rolling the granulated material obtained in step (2) to obtain green balls with an average particle size of 8 mm, wherein the particle size of the green balls satisfies the value of (D90-D10) / D50 of 2; the average particle size of the ball core of the green balls is 2.5 mm; and selecting the green balls so that the sphericity of the green balls is greater than 0.9;

[0133] (4) subjecting the green balls obtained in step (3) to constant temperature and humidity drying and oven drying in sequence, and then to pressureless sintering to obtain a sintered material;

[0134] The constant temperature and humidity drying temperature is 25°C, the relative humidity is 50%; the drying time is 168h;

[0135] The drying temperature is 70°C and the drying time is 128h;

[0136] The process steps of the pressureless sintering are the same as those in Example 1;

[0137] (5) Grinding and polishing the sintered material obtained in step (4) to obtain silicon carbide grinding beads with a surface roughness of ≤0.5 μm.

[0138] Example 5

[0139] This embodiment provides a method for preparing silicon carbide grinding beads, the preparation method comprising the following steps:

[0140] (1) grinding and mixing α-SiC powder, a sintering aid, an organic additive, and water to obtain a silicon carbide slurry with an average particle size of 0.7 μm;

[0141] The average particle size of the α-SiC powder is 5 μm;

[0142] The sintering aid is B4C powder with an average particle size of 3 μm; the amount of the sintering aid is 5wt% of the α-SiC powder;

[0143] The composition of the organic additive is the same as that of Example 1, wherein the amount of the dispersant added is 1wt% of the α-SiC powder, the amount of the binder added is 3wt% of the α-SiC powder, and the amount of the plasticizer added is 1wt% of the α-SiC powder;

[0144] (2) Spray granulation of the silicon carbide slurry obtained in step (1) to obtain granules with an average particle size of 100 μm, and the particle size of the granules satisfies the value of (D90-D10) / D50 of 1.8;

[0145] (3) rolling the granulated material obtained in step (2) to obtain green balls with an average particle size of 10 mm, wherein the particle size of the green balls satisfies the value of (D90-D10) / D50 of 2; the average particle size of the ball core of the green balls is 3 mm; and the green balls are selected so that the sphericity of the green balls is greater than 0.9;

[0146] (4) subjecting the green balls obtained in step (3) to constant temperature and humidity drying and oven drying in sequence, and then to pressureless sintering to obtain a sintered material;

[0147] The constant temperature and humidity drying temperature is 35°C, the relative humidity is 90%; the drying time is 24h;

[0148] The drying temperature is 120°C and the drying time is 24h;

[0149] The process steps of the pressureless sintering are the same as those in Example 1;

[0150] (5) Grinding and polishing the sintered material obtained in step (4) to obtain silicon carbide grinding beads with a surface roughness of ≤0.5 μm.

[0151] Example 6

[0152] This embodiment provides a method for preparing silicon carbide grinding beads, the preparation method comprising the following steps:

[0153] (1) grinding and mixing α-SiC powder, a sintering aid, an organic additive, and water to obtain a silicon carbide slurry with an average particle size of 0.4 μm;

[0154] The average particle size of the α-SiC powder is 0.5 μm;

[0155] The sintering aid is B4C powder with an average particle size of 0.5 μm; the amount of the sintering aid is 1wt% of the α-SiC powder;

[0156] The composition of the organic additive is the same as that of Example 1, wherein the amount of the dispersant added is 0.2wt% of the α-SiC powder, the amount of the binder added is 1wt% of the α-SiC powder, the amount of the plasticizer added is 0.5wt% of the α-SiC powder, and the amount of the defoamer added is 0.1wt% of the α-SiC powder;

[0157] (2) Spray granulation of the silicon carbide slurry obtained in step (1) to obtain granules with an average particle size of 50 μm, and the particle size of the granules satisfies the value of (D90-D10) / D50 of 1.2;

[0158] (3) rolling the granulated material obtained in step (2) to obtain green balls with an average particle size of 2.2 mm, wherein the particle size of the green balls satisfies the value of (D90-D10) / D50 of 1.6; and selecting the green balls so that the sphericity of the green balls is above 0.9;

[0159] (4) subjecting the green balls obtained in step (3) to constant temperature and humidity drying and oven drying, and then to pressureless sintering and hot isostatic pressing to obtain sintered materials;

[0160] The process parameters of the constant temperature and humidity drying, baking and pressureless sintering are the same as those in Example 1;

[0161] The hot isostatic pressing temperature is 1900°C, the pressure is 150MPa, and the time is 1.5h;

[0162] (5) Grinding and polishing the sintered material obtained in step (4) to obtain silicon carbide grinding beads with a surface roughness of ≤0.5 μm.

[0163] Example 7

[0164] This embodiment provides a method for preparing silicon carbide grinding beads, which is the same as Example 6 except that the temperature of hot isostatic pressing in step (4) is 1800°C, the pressure is 120 MPa, and the time is 3.6 hours.

[0165] Example 8

[0166] This embodiment provides a method for preparing silicon carbide grinding beads, which is the same as Example 6 except that the temperature of hot isostatic pressing in step (4) is 2000°C, the pressure is 180 MPa, and the time is 0.8 h.

[0167] Comparative Example 1

[0168] This comparative example provides a method for preparing silicon carbide grinding beads, which is the same as Example 4 except that in step (3), the beads are not rolled but pressed into a column shape, and polishing is not performed after sintering.

[0169] Comparative Example 2

[0170] This comparative example provides a method for preparing silicon carbide grinding beads, which is the same as Example 4 except that in step (3), the beads are not rolled but molded into balls.

[0171] Comparative Example 3

[0172] This comparative example provides a method for preparing silicon carbide grinding beads, which is the same as Example 4 except that in step (3), the beads are not rolled but pressed into balls, and the surface is not polished after sintering.

[0173] Performance Characterization

[0174] The purity, density, maximum compressive strength, sphericity and abrasion of the silicon carbide grinding beads obtained in the above examples and comparative examples were measured, and the results are shown in Table 1.

[0175] Among them, the purity is determined by ICP-OES; the density is determined by the Archimedes drainage method; the maximum compressive strength is determined by the universal testing machine compressive strength test; the sphericity is determined by the high-speed camera imaging method; and the abrasion is determined by the ball mill water grinding test.

[0176] Table 1

[0177] purity(%) <![CDATA[Density (g / cm 3 )]]> Sphericity(%) Maximum compressive strength (MPa) Wear (% / h) Example 1 99.2 3.14 0.99 2350 0.13 Example 2 99.2 3.16 0.92 2480 0.14 Example 3 98.8 3.12 0.99 2330 0.12 Example 4 98.8 3.12 0.99 2210 0.1 Example 5 98.8 3.10 0.99 2160 0.8 Example 6 99.5 3.20 0.99 2680 0.05 Example 7 99.4 3.18 0.99 2550 0.08 Example 8 99.8 3.20 0.99 2600 0.03 Comparative Example 1 98.5 3.12 none 2450 3 Comparative Example 2 98.5 3.12 0.99 2420 0.3 Comparative Example 2 98.5 3.12 0.99 2420 1.2

[0178] In summary, the preparation method provided by the present invention is suitable for industrial production, and each step can achieve improved production efficiency; for example, the present invention adopts a rolling molding method to prepare green balls, which improves production efficiency, and the production speed is better than compression molding; moreover, the preparation method provided by the present invention grinds and polishes the sintered material, reduces the surface wear of the obtained silicon carbide grinding beads during the application process, and improves its grinding performance; moreover, the preparation method can prepare silicon carbide grinding beads with a particle size range of 0.1-8mm, and the obtained product has the characteristics of high sphericity, excellent performance, low wear and not easy to break.

[0179] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing silicon carbide grinding beads, characterized in that: The preparation method comprises the following steps: (1) mixing silicon carbide powder, a sintering aid and a solvent to obtain a silicon carbide slurry; (2) spray granulating the silicon carbide slurry obtained in step (1) to obtain granulated material; (3) using the granulated material obtained in step (2) to perform rolling molding to obtain green balls with a target particle size distribution; (4) subjecting the green balls obtained in step (3) to constant temperature and humidity drying and oven drying in sequence, and then to pressureless sintering to obtain a sintered material; (5) Grinding and polishing the sintered material obtained in step (4) to obtain the silicon carbide grinding beads.

2. The preparation method according to claim 1, characterized in that: The silicon carbide powder in step (1) is α-SiC powder; Preferably, the average particle size of the α-SiC powder is 0.1-5 μm, preferably 0.3-2 μm, and more preferably 0.3-1 μm; Preferably, the sintering aid in step (1) comprises boron powder, carbon powder or B4C powder; Preferably, the average particle size of the sintering aid in step (1) is 0.05-3 μm, preferably 0.05-1 μm; Preferably, the amount of the sintering aid in step (1) is 0.1-10wt%, preferably 0.1-5wt% of the silicon carbide powder.

3. The preparation method according to claim 1 or 2, characterized in that: The solvent in step (1) includes water or an organic solvent; Preferably, the mixing in step (1) further comprises mixing an organic additive; Preferably, the organic additive includes any one or a combination of at least two of a dispersant, a binder, a plasticizer or a defoamer; Preferably, the amount of the organic additive is 0.1-5 wt % of the silicon carbide powder.

4. The preparation method according to any one of claims 1 to 3, characterized in that The mixing method in step (1) includes grinding; Preferably, the average particle size of the silicon carbide slurry obtained after grinding is less than 1 μm, preferably 0.3-1 μm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The average particle size of the granulated material in step (2) is 30-200 μm; Preferably, the particle size of the granulated material in step (2) satisfies the numerical range of (D90-D10) / D50 of 0.8-1.

8.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The average particle size of the raw balls in step (3) is 0.3-10 mm; Preferably, the particle size of the raw balls in step (3) satisfies the numerical range of (D90-D10) / D50 of 1-2.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The temperature of the constant temperature and humidity drying in step (4) is 25-35°C; Preferably, the relative humidity of the constant temperature and humidity drying in step (4) is 50-90%; Preferably, the constant temperature and humidity drying time in step (4) is 24-168 hours; Preferably, the drying temperature in step (4) is 45-120°C; Preferably, the drying time in step (4) is 24-168 hours.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The pressureless sintering in step (4) includes vacuuming, first heating, first heat preservation, second heating, second heat preservation and cooling in sequence; Preferably, the first heating rate is 0.5-3°C / min; Preferably, the terminal temperature of the first heating is 480-520°C; Preferably, the first insulation time is 1-4h; Preferably, the second heating rate is 1-5°C / min; Preferably, the end point temperature of the second heating is 1950-2150°C; Preferably, the second insulation time is 2-4 hours.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The preparation method further comprises performing hot isostatic pressing after pressureless sintering to obtain a sintered material; Preferably, the temperature of the hot isostatic pressing is 1800-2000°C; Preferably, the hot isostatic pressing pressure is 120-180 MPa; Preferably, the heat preservation and pressure holding time of the hot isostatic pressing is 0.8-3.6h.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The polishing time in step (5) is ≥ 24 h; Preferably, the surface roughness of the silicon carbide grinding beads obtained after polishing in step (5) is ≤0.5 μm, preferably ≤0.3 μm, and more preferably ≤0.1 μm.

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