CN110483056B - Preparation method of silicon carbide ceramic ball - Google Patents

Preparation method of silicon carbide ceramic ball Download PDF

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CN110483056B
CN110483056B CN201910811801.9A CN201910811801A CN110483056B CN 110483056 B CN110483056 B CN 110483056B CN 201910811801 A CN201910811801 A CN 201910811801A CN 110483056 B CN110483056 B CN 110483056B
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silicon carbide
degreasing
powder
binder
carbide powder
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CN110483056A (en
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史秀梅
曹剑武
张立君
郑顺奇
任丽宏
陈刚
郑阳升
程英晔
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China Weapon Science Academy Ningbo Branch
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Abstract

A preparation method of silicon carbide ceramic balls comprises the following steps: spraying and granulating silicon carbide powder, boron carbide powder, a half of surfactant, a sintering aid and a binder to obtain silicon carbide granulated powder; heating and stirring the silicon carbide granulation powder, the residual surfactant and the high polymer binder, mixing and crushing to obtain injection granules; and (3) injection molding the injection particles, and degreasing and sintering the obtained spherical biscuit to obtain the silicon carbide ceramic ball. The invention is carried out by adopting a ceramic injection molding method, has the characteristics of simple process, high efficiency and low cost, and the prepared silicon carbide ceramic ball has high sphericity, small expectation of subsequent grinding processing and higher production efficiency, can greatly save the production and processing cost and promote the wide application of the silicon carbide ceramic ball.

Description

Preparation method of silicon carbide ceramic ball
Technical Field
The invention relates to a preparation method of ceramic balls, in particular to a preparation method of silicon carbide ceramic balls.
Background
Silicon carbide (SiC) is an advanced structural ceramic material with the advantages of high hardness, high strength, good chemical stability and the like, and has wide application prospect in the fields of machinery, chemical engineering, energy, aerospace and military protection due to unique high-temperature resistance, oxidation resistance and corrosion resistance. Based on the advantages, the silicon carbide ceramic ball has wide application prospect as a key part of protection, grinding, ceramic bearings and ball valves in severe service environments such as high strength, high hardness, acid and alkali corrosion resistance, impact resistance and the like.
The silicon carbide ceramic ball has not been produced in batch, and mainly comes from the following two reasons: firstly, in large-scale production, a short cylindrical or sphere-like mold is usually adopted for biscuit pressing, and a silicon carbide ball blank prepared after normal pressure or hot pressing sintering needs to be subjected to a large amount of mechanical processing and grinding to obtain a product with good sphericity. Because of the extremely high hardness of silicon carbide ceramics, the machining is very difficult (usually, a diamond machining tool must be used), and the efficiency is low, so that the preparation cost of the silicon carbide ball is too high. Secondly, even if the ceramic ball is ground, because the preparation sphericity of the biscuit is very low, the error of the sphericity of the ceramic ball processed in batches is large, and the use requirements of precision parts such as ceramic bearings or ball valves cannot be met, so that the wide application of the silicon carbide ceramic ball is limited to a large extent. Therefore, there is a need to find a new method for preparing silicon carbide ceramic balls, which reduces the production cost, realizes mass high-quality preparation, and expands the application of silicon carbide ceramic balls.
Disclosure of Invention
The invention aims to solve the technical problem of providing the preparation method of the silicon carbide ceramic ball, which has simple process, high efficiency and low cost, and can realize batch high-quality preparation and small subsequent grinding allowance.
The technical scheme adopted by the invention for solving the technical problems is as follows: a preparation method of silicon carbide ceramic balls is characterized by comprising the following steps:
1) silicon carbide powder, boron carbide powder, a surfactant, a sintering aid, a binder and a high polymer binder are used as raw materials, the raw materials are proportioned and weighed according to a proportion, and the silicon carbide powder, the boron carbide powder, half of the surfactant, the sintering aid and the binder are subjected to spray granulation to obtain silicon carbide granulated powder;
2) heating and stirring the silicon carbide granulation powder, the residual surfactant and the high polymer binder, mixing and crushing to obtain injection granules;
3) and (3) injection molding the injection particles, and degreasing and sintering the obtained spherical biscuit to obtain the silicon carbide ceramic ball.
Preferably, the raw materials in the step 1) are as follows in parts by weight: 85-100 parts of silicon carbide powder, 1-7 parts of boron carbide powder, 5-10 parts of sintering aid, 1-2.5 parts of surfactant, 0.5-1 part of binder and 15-45 parts of high polymer binder.
Further, the silicon carbide powder D in the step 1)50Less than or equal to 1.1 μm, maximum particle size less than or equal to 3 μm, and specific surface area of about 12m2(ii)/g; boron carbide powder D50Less than or equal to 1.0 μm and a specific surface area of about 10m2(ii)/g; the sintering aid is Y2O3With Al2O3Combination of powders, Y2O3With Al2O3The mass ratio of (A) to (B) is 1: 1-3: 5; the surfactant is one or more of stearic acid, polyethylene glycol, ammonium polyacrylate or tetramethyl ammonium hydroxide; the binder is one or two of carboxymethyl cellulose and water-based phenolic resin.
Further, the high polymer binder is formed by combining paraffin, high-density polyethylene, polypropylene and stearic acid, wherein the mass ratio of the paraffin, the high-density polyethylene, the polypropylene and the stearic acid is 15:3:3: 1-20: 3:3: 1.
Further, the specific process of the step 1) is as follows: silicon carbide powder and boron carbide powder are used as main raw materials, deionized water and half of surfactant are added, after ball milling and mixing are carried out for 2-5 hours, sintering aid and binder are added, after nodular graphite mixing is carried out for 10-20 hours, the mixture is sieved by a 500-mesh sieve, uniform slurry is obtained, the solid content is more than or equal to 40 percent, the obtained slurry is dried by a spray dryer, the air inlet temperature is 100-160 ℃, the air outlet temperature is 80-140 ℃, the slurry flow is 5 kg/h-80 kg/h, and silicon carbide granulation powder is obtained by spray granulation.
Further, the heating temperature of the heating and stirring in the step 2) is 50-150 ℃, the mixing temperature is 50-150 ℃, and the crushing refers to crushing to obtain the master batch with the diameter of about 1mm (the maximum particle size is less than or equal to 1.5 mm).
Further, the injection molding process of the step 3) comprises the following steps: injecting the injection particles into a mold containing a spherical mold cavity at the heating temperature of 110-150 ℃ and the pressure of 50-150 MPa, wherein the diameter of the spherical mold cavity is 2-20 mm; the injection molding die is provided with a hot runner, and after injection is finished, the spherical biscuit is obtained by cooling.
Further, the degreasing in the step 3) comprises solvent degreasing and then thermal degreasing; the solvent used for solvent degreasing is gasoline, kerosene or n-heptane degreasing, the degreasing time is 10-40 hours, and the solvent degreasing temperature is 30-50 ℃; the thermal degreasing is carried out under vacuum (100mbar), the thermal degreasing temperature is 400-800 ℃, and the degreasing time is 30-60 hours.
And finally, sintering the sintered material in the step 3) under the inert atmosphere at normal pressure and in vacuum, wherein the sintering temperature is 2100-2200 ℃, preserving the heat for 100-150 min, and cooling along with the furnace.
Compared with the prior art, the invention has the advantages that: the silicon carbide ceramic ball is prepared by adopting a ceramic injection molding method, and the injection molding is a near-net-size molding technology, so that the silicon carbide ceramic ball can be applied to the preparation of the silicon carbide ball, the rapid and precise production of the silicon carbide ceramic ball can be realized, the follow-up processing is few, the cost is low, the batch production can be realized, and the silicon carbide ceramic ball has the characteristics of simple process, high efficiency and low cost.
Drawings
FIG. 1 is a photograph of a silicon carbide ceramic ball prepared by the method of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples.
Example 1:
a preparation method of silicon carbide ceramic balls comprises the following steps:
(1) weighing the following raw materials in parts by mass:
silicon carbide powder: 90 portions of
Boron carbide powder: 3 portions of
Sintering aid: 7 portions of
Surfactant (b): 2 parts (used in two parts on average)
Adhesive: 0.8 portion of
High polymer binder: 30 parts of silicon carbide powder D50Less than or equal to 1.1 μm, and the maximum grain diameter less than or equal to 3 μm, as a proportion tableArea of about 12m2/g；
Boron carbide powder D50Less than or equal to 1.0 μm and a specific surface area of about 10m2/g；
The sintering aid is Y2O3With Al2O3The powder composition is 3:4 in percentage by mass;
the surfactant is stearic acid;
the binder is water-based phenolic resin;
the high polymer binder is a composition of paraffin, high-density polyethylene, polypropylene and stearic acid, and the mass ratio is 18:3:3: 1. Paraffin wax has a small molecular weight, a low softening point, good flowability and good wettability with powders, and is therefore selected as a basic component of binder systems. Stearic acid is a good dispersant for ceramic powder, one end of a molecule is a polar end with carboxyl, and the other end of the molecule is oil-soluble alkyl, so that the uniform mixing is ensured, and the good forming performance is usually shown in the process. The high-density polyethylene has higher molecular weight, generally 40000-300000, high melting point and good forming process, and can be used together with injection polypropylene resin to maintain the shape of a blank as a framework and obtain better elastic modulus and lower thermal expansion coefficient.
(2) Taking silicon carbide powder and boron carbide powder as main raw materials, adding deionized water and a surfactant (the adding amount is 50% of the total mass), performing ball milling and mixing for 4 hours, then adding a sintering aid and a binder, performing ball milling and mixing for 15 hours, and sieving by a 500-mesh sieve to obtain uniform slurry with the solid content of 55%; the obtained slurry is dried by a spray dryer, the air inlet temperature is 130 ℃, the air outlet temperature is 100 ℃, and the slurry flow is 20 kg/h. And spray granulating to obtain silicon carbide granulated powder.
(3) Heating and uniformly stirring the silicon carbide granulated powder prepared in the step (2), the residual surfactant and the high polymer binder at the heating temperature of 80 ℃, mixing and feeding the materials at the mixing temperature of 120 ℃, and cooling and crushing the materials until the diameter is about 1mm (the maximum particle size is less than or equal to 1.5mm) to obtain an injection granule material;
(4) molding the injection granules on an injection molding machine: injecting the injection granules into a mold containing a spherical mold cavity with the diameter of 10mm at the temperature of 130 ℃ and the pressure of 80MPa, and cooling to obtain the spherical biscuit after the injection molding mold is provided with a hot runner. Placing the spherical biscuit in kerosene for solvent degreasing, wherein the degreasing time is 30 hours, and the degreasing temperature is 40 ℃; the biscuit degreased by the solvent is subjected to thermal degreasing in a vacuum furnace (100mbar), wherein the thermal degreasing temperature is 500 ℃, and the degreasing time is 50 hours. And (3) sintering the silicon carbide ceramic balls subjected to thermal degreasing in vacuum at normal pressure under an inert atmosphere, wherein the sintering temperature is 2200 ℃, preserving the heat for 120min, and cooling along with the furnace.
The silicon carbide ceramic ball blank disclosed by the embodiment of the invention has the advantages of good sphericity, less subsequent grinding processing and higher production efficiency, can greatly save the production and processing cost, and promotes the wide application of the silicon carbide ceramic ball.
Example 2:
the preparation method of the silicon carbide ceramic ball comprises the following steps:
(1) weighing the following raw materials in parts by mass:
silicon carbide powder: 100 portions of
Boron carbide powder: 7 portions of
Sintering aid: 10 portions of
Surfactant (b): 2 parts (used in two parts on average)
Adhesive: 1 part of
High polymer binder: 45 portions of
Wherein, the silicon carbide powder D50Less than or equal to 1.1 μm, maximum particle size less than or equal to 3 μm, and specific surface area of about 12m2(ii)/g; the boron carbide powder D50Less than or equal to 1.0 μm and a specific surface area of about 10m2(ii)/g; the sintering aid is Y2O3With Al2O3The powder composition is 3:5 in percentage by mass; the surfactant is a combination of polyethylene glycol and stearic acid; the binder is water-based phenolic resin; the high polymer binder is a composition of paraffin, high-density polyethylene, polypropylene and stearic acid, and the mass ratio is 20:3:3: 1.
The high polymer binder is a combination of paraffin, high-density polyethylene, polypropylene and stearic acid, and the mass ratio is 20:3:3: 1. Paraffin wax has a small molecular weight, a low softening point, good flowability and good wettability with powders, and is therefore selected as a basic component of binder systems. Stearic acid is a good dispersant for ceramic powder, one end of a molecule is a polar end with carboxyl, and the other end of the molecule is oil-soluble alkyl, so that the uniform mixing is ensured, and the good forming performance is usually shown in the process. The high-density polyethylene has higher molecular weight, generally 40000-300000, high melting point and good forming process, and can be used together with injection polypropylene resin to maintain the shape of a blank as a framework and obtain better elastic modulus and lower thermal expansion coefficient.
(2) Taking silicon carbide powder and boron carbide powder as main raw materials, adding deionized water and a surfactant (the adding amount is 50% of the total mass) into the main raw materials, performing ball milling and mixing for 5 hours, then adding a sintering aid and a binder, performing ball milling and mixing for 20 hours, and sieving the mixture by a 500-mesh sieve to obtain uniform slurry with the solid content of 55%; and drying the obtained slurry by using a spray dryer, wherein the air inlet temperature is 160 ℃, the air outlet temperature is 140 ℃, the flow rate of the slurry is 80kg/h, and spray granulation is carried out to obtain silicon carbide granulation powder.
(3) And (3) heating and uniformly stirring the silicon carbide granulated powder prepared in the step (2), the residual surfactant and the high polymer binder at the heating temperature of 150 ℃, mixing and feeding, cooling and crushing at the mixing temperature of 140 ℃ until the diameter is about 1mm (the maximum particle size is less than or equal to 1.5mm) to obtain the injection granule.
(4) Molding the injection granules on an injection molding machine: injecting the injection granules into a mold containing a spherical mold cavity at 150 ℃ and 150MPa, wherein the diameter of the spherical mold cavity is 20mm, the injection molding mold is provided with a hot runner, and after injection is finished, cooling to obtain a spherical biscuit; putting the spherical biscuit into n-heptane for solvent degreasing, wherein the degreasing time is 40 hours, and the degreasing temperature is 50 ℃; carrying out hot degreasing on the biscuit subjected to solvent degreasing in a vacuum furnace (100mbar), wherein the hot degreasing temperature is 800 ℃, and the degreasing time is 60 hours; and (3) carrying out vacuum sintering on the silicon carbide ceramic balls subjected to thermal degreasing under the inert atmosphere at normal pressure, keeping the sintering temperature at 2100 ℃ for 150min, and cooling along with the furnace.
The silicon carbide ceramic ball prepared by the embodiment has good blank sphericity, less subsequent grinding processing and higher production efficiency, can save the production and processing cost to a greater extent, and promotes the wide application of the silicon carbide ceramic ball.
Example 3
The preparation method of the silicon carbide ceramic ball comprises the following steps:
(2) weighing the following raw materials in parts by mass:
silicon carbide powder: 85 portions of
Boron carbide powder: 1 part of
Sintering aid: 5 portions of
Surfactant (b): 1 part (used in two parts on average)
Adhesive: 0.5 portion
High polymer binder: 15 portions of
Wherein, the silicon carbide powder D50Less than or equal to 1.1 μm, maximum particle size less than or equal to 3 μm, and specific surface area of about 12m2(ii)/g; the boron carbide powder D50Less than or equal to 1.0 μm and a specific surface area of about 10m2(ii)/g; the sintering aid is Y2O3With Al2O3The powder composition comprises 1:1 by mass; the surfactant is stearic acid; the binder is carboxymethyl cellulose; the high polymer binder is a combination of paraffin, high-density polyethylene, polypropylene and stearic acid, and the mass percentage is 15:3:3: 1.
The high polymer binder is a composition of paraffin, high-density polyethylene, polypropylene and stearic acid, and the mass ratio is 15:3:3: 1. Paraffin wax has a small molecular weight, a low softening point, good flowability and good wettability with powders, and is therefore selected as a basic component of binder systems. Stearic acid is a good dispersant for ceramic powder, one end of a molecule is a polar end with carboxyl, and the other end of the molecule is oil-soluble alkyl, so that the uniform mixing is ensured, and the good forming performance is usually shown in the process. The high-density polyethylene has higher molecular weight, generally 40000-300000, high melting point and good forming process, and can be used together with injection polypropylene resin to maintain the shape of a blank as a framework and obtain better elastic modulus and lower thermal expansion coefficient.
(2) The preparation method comprises the following steps of taking silicon carbide powder and boron carbide powder as main raw materials, adding deionized water and a surfactant (the adding amount is 50% of the total mass), carrying out ball milling and mixing for 2 hours, then adding a sintering aid and a binder, carrying out ball milling and mixing for 10 hours, and then sieving with a 500-mesh sieve to obtain uniform slurry with the solid content of 55%. The obtained slurry is dried by a spray dryer, the air inlet temperature is 100 ℃, the air outlet temperature is 80 ℃, and the slurry flow is 20 kg/h. And spray granulating to obtain silicon carbide granulated powder.
(3) And (3) heating and uniformly stirring the silicon carbide granulated powder prepared in the step (2), the residual surfactant and the high polymer binder, heating to 50 ℃, mixing and feeding, mixing to 60 ℃, cooling and crushing to obtain the injection granules with the diameter of about 1mm (the maximum particle size is less than or equal to 1.5 mm).
(4) Molding the injection granules on an injection molding machine: injecting the injection granules into a mold containing a spherical mold cavity at 110 ℃ and 50MPa, wherein the diameter of the spherical mold cavity is 4mm, the injection molding mold is provided with a hot runner, and after injection is finished, cooling to obtain a spherical biscuit; placing the spherical biscuit in kerosene for solvent degreasing, wherein the degreasing time is 15 hours, and the degreasing temperature is 30 ℃; carrying out hot degreasing on the biscuit subjected to solvent degreasing in a vacuum furnace (100mbar), wherein the hot degreasing temperature is 400 ℃, and the degreasing time is 30 hours; and (3) sintering the silicon carbide ceramic balls subjected to thermal degreasing in vacuum at normal pressure in an inert atmosphere, wherein the sintering temperature is 2100 ℃, preserving the heat for 100min, and cooling along with the furnace.
The carbonization ceramic ball prepared by the embodiment has good sphericity of the body, less subsequent grinding processing and higher production efficiency, can save the production and processing cost to a greater extent and promotes the wide application of the silicon carbide ceramic ball.
Ceramic powder Injection Molding (CIM) is a net-close Molding technique, and if an Injection Molding mold is designed and manufactured to be a proper powder material and the service performance is qualified, uniform shrinkage can achieve high dimensional accuracy, and the dimensional accuracy can be kept within 0.3%. And the utilization rate of the powder material is high, and high-density and high-precision parts with very complicated shapes can be produced in large quantity.

Claims (7)

1. A preparation method of silicon carbide ceramic balls is characterized by comprising the following steps:
1) silicon carbide powder, boron carbide powder, a surfactant, a sintering aid, a binder and a high polymer binder are used as raw materials, the raw materials are proportioned and weighed according to a proportion, and the silicon carbide powder, the boron carbide powder, half of the surfactant, the sintering aid and the binder are subjected to spray granulation to obtain silicon carbide granulated powder;
2) heating and stirring the silicon carbide granulation powder, the residual surfactant and the high polymer binder, mixing and crushing to obtain injection granules;
3) injection molding the injection particles, and degreasing and sintering the obtained spherical biscuit to obtain a silicon carbide ceramic ball;
the raw materials in the step 1) are as follows in parts by weight: 85-100 parts of silicon carbide powder, 1-7 parts of boron carbide powder, 5-10 parts of sintering aid, 1-2.5 parts of surfactant, 0.5-1 part of binder and 15-45 parts of high polymer binder;
the high polymer binder is composed of paraffin, high-density polyethylene, polypropylene and stearic acid, and the mass ratio of the paraffin, the high-density polyethylene, the polypropylene and the stearic acid is 15:3:3: 1-20: 3:3: 1.
2. The method of claim 1, wherein: the silicon carbide powder D in the step 1)50Less than or equal to 1.1 mu m, the maximum grain diameter less than or equal to 3 mu m, and the specific surface area of 11-13 m2(ii)/g; boron carbide powder D50Less than or equal to 1.0 mu m, and the specific surface area of 9-11 m2(ii)/g; the sintering aid is Y2O3With Al2O3Combination of powders, Y2O3With Al2O3The mass ratio of (A) to (B) is 1: 1-3: 5; the surfactant is one or more of stearic acid, polyethylene glycol, ammonium polyacrylate or tetramethyl ammonium hydroxide; the binder is one or two of carboxymethyl cellulose and water-based phenolic resin.
3. The method of claim 1, wherein: the specific process of the step 1) is as follows: silicon carbide powder and boron carbide powder are used as main raw materials, deionized water and half of surfactant are added, after ball milling and mixing are carried out for 2-5 hours, sintering aid and binder are added, after nodular graphite mixing is carried out for 10-20 hours, the mixture is sieved by a 500-mesh sieve, uniform slurry is obtained, the solid content is more than or equal to 40 percent, the obtained slurry is dried by a spray dryer, the air inlet temperature is 100-160 ℃, the air outlet temperature is 80-140 ℃, the slurry flow is 5 kg/h-80 kg/h, and silicon carbide granulation powder is obtained by spray granulation.
4. The method of claim 1, wherein: the heating temperature of the heating and stirring in the step 2) is 50-150 ℃, the mixing temperature is 50-150 ℃, and the crushing refers to crushing the master batch with the diameter of 1mm, wherein the maximum grain diameter of the master batch is less than or equal to 1.5 mm.
5. The method of claim 1, wherein: the injection molding process of the step 3) comprises the following steps: injecting the injection particles into a mold containing a spherical mold cavity at the heating temperature of 110-150 ℃ and the pressure of 50-150 MPa, wherein the diameter of the spherical mold cavity is 2-20 mm; the injection molding die is provided with a hot runner, and after injection is finished, the spherical biscuit is obtained by cooling.
6. The method of claim 1, wherein: the degreasing in the step 3) comprises solvent degreasing and then thermal degreasing; the solvent used for solvent degreasing is gasoline, kerosene or n-heptane degreasing, the degreasing time is 10-40 hours, and the solvent degreasing temperature is 30-50 ℃; the thermal degreasing is carried out under vacuum, the thermal degreasing temperature is 400-800 ℃, and the degreasing time is 30-60 hours.
7. The method of claim 1, wherein: and 3) sintering in vacuum at normal pressure in an inert atmosphere at the sintering temperature of 2100-2200 ℃ for 100-150 min, and cooling along with the furnace.
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