Preparation method of ceramic green body

Abstract

The invention relates to a preparation method of a ceramic green body, which comprises the following steps: (1) ceramic powder with the sphericity degree of 0.9-1 is sequentially subjected to dry pressing molding and crushing granulation treatment to obtain pretreated powder; and (2) sequentially carrying out die-filling treatment, heating and pressurizing treatment and sintering treatment on the pretreated powder obtained in the step (1) to obtain the ceramic green body. According to the method, the ceramic powder is subjected to dry pressing, crushing and granulation, and heating and pressurizing treatment is added before sintering treatment, so that the ceramic powder is dense in the sintering treatment process, powder overflow caused by heating is avoided, the size abnormal conditions such as edge unfilled corners of a product are reduced, and the yield is effectively improved; and the risk that the sintering furnace body is polluted due to overflowing of the powder is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of hot pressing and sintering ceramic preparation, and in particular to a method for preparing a ceramic green body. Background Art

[0002] Ceramic materials are a type of inorganic non-metallic material made from natural or synthetic compounds through molding and high-temperature calcination. They have the advantages of high melting point, high hardness, high wear resistance and oxidation resistance. Due to the wide variety of ceramic materials, their uses are also very wide. Some ceramic materials can be used as functional materials in the field of high-end manufacturing.

[0003] Large-sized and simple-shaped ceramics are usually molded directly after powder mixing, and finally sintered at high temperature and high pressure. The molding process and sintering process are the key factors that determine the sintering and molding of ceramic products, and directly determine the sintering quality of ceramic products and the yield rate of machining. At present, the more mature ceramic powder molding process is to directly fill the mixed powder into the mold, and then use the molding tool to flatten the powder, and then press the partition on the product, stuff the graphite paper around the partition, and then perform subsequent sintering molding after layer by layer molding.

[0004] CN 110078528A discloses a high-strength ceramic product and a preparation process thereof. The specific steps of the preparation process are as follows: S1: preparing fiber ceramic balls; S2: mixing: according to weight fractions, 40-50 parts of ceramic powder, 5-10 parts of magnetite, 6-12 parts of chromite and 3-7 parts of phenolic resin are put into a ball mill and ground for 1 hour, and then 30-40 parts of the fiber ceramic balls in step 1 are added, and the ball milling is continued for 9-10 hours to prepare a ceramic blank; S3: molding: filling the ceramic blank in step S2 into a mold, extruding and molding, and demolding into a blank; S4: sintering: the prepared blank is first dried in a drying chamber, and then sintered in a sintering furnace to obtain a ceramic product.

[0005] CN 111320478A discloses a method for preparing a carbon-silicon ceramic target. The method comprises the following steps: (1) according to the carbon-silicon ratio of the target to be prepared, weigh graphite powder, silicon powder and SiC powder, wherein the silicon powder accounts for 5-15at% of the total amount of the three; (2) crushing and mixing the graphite powder and silicon powder by horizontal axis ball milling to obtain carbon-silicon pre-ball milled powder; (3) adding the weighed SiC powder to the carbon-silicon pre-ball milled powder, placing the mixture in a horizontal axis ball mill for 2 hours to obtain a composite raw material powder; (4) sieving the composite raw material powder, loading it into a graphite mold, placing the mold in a hot pressing furnace, filling it with argon gas when the vacuum is less than 500Pa, and adopting front-stage rapid heating, middle-stage liquid phase sintering and high-temperature argon protection sintering; (5) cooling to obtain a carbon-silicon ceramic target blank, and processing, cleaning and drying to obtain a carbon-silicon ceramic target.

[0006] The above inventions all directly mold the ceramic raw material powder and then sinter it, which will cause the ceramic powder to flow out during the sintering process, resulting in abnormal product size and edge chipping. It will also cause contamination of the sintering furnace body, making cleaning difficult and the maintenance cycle short.

[0007] Therefore, in view of the shortcomings of the prior art, it is necessary to provide a method for preparing a ceramic green body with high powder filling density and no overflow risk. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing a ceramic green body. By combining powder dry pressing, crushing and granulation with a low-temperature pressurization process, the mold density of the ceramic powder is significantly improved. The ceramic powder will not overflow during the subsequent high-temperature sintering process, thereby improving the yield and reducing the risk of furnace contamination.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for preparing a ceramic body, the method comprising the following steps:

[0011] (1) Ceramic powder with a sphericity of 0.9-1 is subjected to dry pressing and crushing and granulation treatment in sequence to obtain pretreated powder;

[0012] (2) The pretreated powder obtained in step (1) is subjected to mold loading, temperature and pressure treatment, and sintering treatment in sequence to obtain the ceramic body.

[0013] The preparation method of the ceramic green body provided by the present invention comprises the following steps: dry-pressing and crushing the ceramic powder into granules, and further adding a heating and pressurizing treatment before the sintering treatment, so that the ceramic powder is kept dense during the sintering treatment, and the powder does not overflow due to the temperature increase, thereby reducing dimensional anomalies such as chipping on the edges of the product, and at the same time reducing the risk of sintering furnace contamination caused by powder overflow.

[0014] The sphericity of the ceramic powder is 0.9-1, for example, 0.9, 0.95 or 1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] Preferably, the dry pressing pressure in step (1) is 50-100 MPa, for example, 50 MPa, 60 MPa, 80 MPa, 90 MPa or 100 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] If the pressure of the dry pressing molding is too high or too low, it will have an adverse effect on the structure of the ceramic powder and further affect the mold density. Therefore, the pressure range of the dry pressing molding needs to be strictly controlled.

[0017] Preferably, the dry pressing time in step (1) is 1-3 min, for example, 1 min, 1.5 min, 2 min, 2.5 min or 3 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] Preferably, the crushing and granulation in step (1) is performed to a particle size of less than 100 μm, for example, 90 μm, 80 μm, 70 μm, 60 μm or 50 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] In the present invention, the particle size range of the pre-treated powder obtained by the crushing and granulation process needs to be controlled to ensure the mold density of the powder in the subsequent mold processing.

[0020] Preferably, the crushing and granulation process in step (1) is carried out in a roller extrusion granulator.

[0021] Preferably, the molding process in step (2) is to lay the pretreated powder flat into the mold and compact it.

[0022] Preferably, the compacting is to place the mold horizontally in a sintering furnace and use a pressing head to press the mold.

[0023] Preferably, the pressure exerted by the pressing head on the mold is 8-10t, for example, 8t, 8.5t, 9t, 9.5t or 10t, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the pressing time is 5-8 min, for example, 5 min, 6 min, 7 min or 8 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the temperature of the heating and pressurizing treatment in step (2) is less than 1000°C, for example, it can be 950°C, 900°C, 850°C, 800°C or 700°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the pressure of the heating and pressurizing treatment in step (2) is 250-300t, for example, it can be 250t, 260t, 280t, 290t or 300t, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the pressurization time of the heating and pressurizing treatment in step (2) is 0.8-1.2 h, for example, it can be 0.8 h, 0.9 h, 1 h, 1.1 h or 1.2 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the heating and pressurizing treatment in step (2) is repeated 3-4 times, for example, 3 times or 4 times.

[0029] The temperature and pressure treatment is performed multiple times at relatively low temperature and pressure, so that the density of the pretreated powder is maintained during the subsequent sintering treatment, and the powder does not overflow due to temperature increase, thereby ensuring that the shape and size of the product out of the furnace are consistent with the designed shape and size, which is beneficial to subsequent grinding processing, effectively improves the yield rate, and reduces the risk of furnace contamination.

[0030] Preferably, the temperature of the sintering treatment in step (2) is 1500-1600°C, for example, it can be 1500°C, 1520°C, 1550°C, 1580°C or 1600°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the sintering time in step (2) is 1.5-2.5 h, for example, 1.5 h, 1.8 h, 2 h, 2.2 h or 2.5 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0033] (1) Ceramic powder with a sphericity of 0.9-1 is dry pressed at 50-100 MPa for 1-3 min, and crushed and granulated in a roller extrusion granulator to a particle size of less than 100 μm to obtain a pretreated powder;

[0034] (2) The pretreated powder obtained in step (1) is flatly loaded into a mold, and the mold is kept horizontally placed in a sintering furnace. A pressure head is used to generate a pressure of 8-10 tons on the mold and press it down for 5-8 minutes; then the temperature is increased and pressurized to <1000°C, and the pressure is increased at 250-300 tons for 0.8-1.2 hours, and the pressurization is repeated 3-4 times; and the ceramic body is sintered at 1500-1600°C for 1.5-2.5 hours to obtain the ceramic body.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The preparation method of the ceramic green body provided by the present invention comprises the following steps: dry-pressing, crushing and granulating the ceramic powder, and further adding a heating and pressurizing treatment before the sintering treatment, so that the ceramic powder is kept dense during the sintering treatment, and the powder does not overflow due to the temperature increase, thereby reducing dimensional abnormalities such as chipping on the edges of the product, ensuring that the shape and size of the product out of the furnace are consistent with the designed shape and size, which is beneficial to the subsequent grinding process, and at the same time effectively improving the yield, reducing the risk of sintering furnace body contamination caused by powder overflow, and extending the maintenance cycle. DETAILED DESCRIPTION

[0037] 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.

[0038] Example 1

[0039] This embodiment provides a method for preparing a ceramic body, the method comprising the following steps:

[0040] (1) Ceramic powder with a sphericity of 0.95 was dry pressed at 80 MPa for 2 min and crushed and granulated in a roller extrusion granulator to a particle size of 80 μm to obtain a pretreated powder;

[0041] (2) The pretreated powder obtained in step (1) is flatly loaded into a mold, and the mold is kept horizontally placed in a sintering furnace. A pressure head is used to generate a pressure of 9 tons on the mold and press it down for 6 minutes; then the temperature is increased and pressurized to 900°C, and pressurized at 280 tons for 1 hour, and the pressurization is repeated 4 times; and sintered at 1550°C for 2 hours to obtain the ceramic body.

[0042] Example 2

[0043] This embodiment provides a method for preparing a ceramic body, the method comprising the following steps:

[0044] (1) Ceramic powder with a sphericity of 0.9 was dry pressed at 50 MPa for 3 min and crushed and granulated in a roller extrusion granulator to a particle size of 90 μm to obtain a pretreated powder;

[0045] (2) The pretreated powder obtained in step (1) is flatly loaded into a mold, and the mold is kept horizontally placed in a sintering furnace. A pressure head is used to generate a pressure of 8 tons on the mold and press it down for 8 minutes; then the temperature is increased and pressurized to 800°C, and pressurized at 250 tons for 1.2 hours, and the pressurization is repeated 3 times; sintering is performed at 1500°C for 2.5 hours to obtain the ceramic green body.

[0046] Example 3

[0047] This embodiment provides a method for preparing a ceramic body, the method comprising the following steps:

[0048] (1) The ceramic powder with a sphericity of 1 was subjected to dry pressing at 100 MPa for 1 min and crushed and granulated in a roller extrusion granulator to a particle size of 70 μm to obtain a pretreated powder;

[0049] (2) The pretreated powder obtained in step (1) is flatly loaded into a mold, and the mold is kept horizontally placed in a sintering furnace. A pressure head is used to generate a pressure of 10 tons on the mold and press down for 5 minutes; then the temperature is increased and pressurized to 700°C, and pressurized at 300 tons for 0.8 hours, and the pressurization is repeated 4 times; and sintering treatment is performed at 1600°C for 1.5 hours to obtain the ceramic green body.

[0050] Example 4

[0051] This embodiment provides a method for preparing a ceramic body, which is different from Embodiment 1 in that, except that the pressure of the dry pressing molding in step (1) is adjusted to 40 MPa, the rest is the same as Embodiment 1.

[0052] Example 5

[0053] This embodiment provides a method for preparing a ceramic body, which is different from Embodiment 1 in that, except that the pressure of the dry pressing molding in step (1) is adjusted to 120 MPa, the rest is the same as Embodiment 1.

[0054] Example 6

[0055] This embodiment provides a method for preparing a ceramic body, which is different from Embodiment 1 in that, except for adjusting the terminal temperature of the heating in step (2) to 1000° C., the rest is the same as Embodiment 1.

[0056] Example 7

[0057] This embodiment provides a method for preparing a ceramic green body, which is different from Embodiment 1 in that, except for adjusting the pressure exerted by the pressing head on the mold in step (2) to 5t, the rest is the same as Embodiment 1.

[0058] Example 8

[0059] This embodiment provides a method for preparing a ceramic green body, which is different from Embodiment 1 in that, except for adjusting the pressure exerted by the pressing head on the mold in step (2) to 12t, the rest is the same as Embodiment 1.

[0060] Example 9

[0061] This embodiment provides a method for preparing a ceramic body, which is different from Embodiment 1 in that, except for adjusting the number of repeated pressurization in step (2) to 1, the rest is the same as Embodiment 1.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing a ceramic body, which is different from Example 1 in that step (1) does not involve dry pressing and crushing and granulation, but directly subjects the ceramic powder to a mold, and the rest is the same as Example 1.

[0064] Comparative Example 2

[0065] This comparative example provides a method for preparing a ceramic body, which differs from Example 1 in that step (2) does not involve temperature increase and pressure treatment, and the rest is the same as Example 1.

[0066] Comparative Example 3

[0067] This comparative example provides a method for preparing a ceramic body, which differs from Example 1 in that the sphericity of the ceramic powder in step (1) is adjusted to 0.8, and the rest is the same as Example 1.

[0068] The ceramic bodies provided in Examples 1-9 and Comparative Examples 1-3 were tested for density using a range solid density tester, and then: 测 / ρ 理论 ×100% is calculated; by visually observing the product appearance to see if there are any dimensional anomalies or edge chippings, the structure is divided into "intact appearance" and "edge chippings". The results are shown in Table 1.

[0069] Table 1

[0070] Density(%) Product Appearance Example 1 99.7 Good appearance Example 2 99.4 Good appearance Example 3 99.5 Good appearance Example 4 98.7 Good appearance Example 5 99.2 Good appearance Example 6 98.6 Good appearance Example 7 98.3 Good appearance Example 8 98.8 Good appearance Example 9 97.6 Edge chipping Comparative Example 1 95.2 Edge chipping Comparative Example 2 94.3 Edge chipping Comparative Example 3 96.8 Edge chipping

[0071] It can be seen from Table 1 that the method for preparing a ceramic body provided by the present invention has a high density of the obtained ceramic body and a high yield rate of the finished product;

[0072] By comparing Example 1 with Examples 4 and 5, it can be seen that if the pressure of dry pressing is too large or too small, it will have an adverse effect on the structure of the ceramic powder, and thus affect the mold density; by comparing Example 1 with Examples 6-9, it can be seen that the temperature, pressure, and number of pressurization times during the heating and pressurization process have a certain effect on the density of the ceramic body. If the temperature, pressure, and pressurization times exceed the specified range, the density of the finished product will decrease, and the appearance quality will be reduced;

[0073] By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that if the dry pressing and crushing granulation treatment or the heating and pressurizing treatment in the present invention are not adopted, the density of the obtained ceramic green body will be greatly reduced and the yield rate will be significantly reduced; by comparing Example 1 with Comparative Example 3, it can be seen that if the sphericity of the ceramic powder raw material is too small, the uniformity of the paving during molding will be reduced, resulting in a decrease in appearance quality.

[0074] In summary, the preparation method of the ceramic green body provided by the present invention, through dry-pressing and crushing the ceramic powder into granules, and further adding a heating and pressure treatment before the sintering treatment, the ceramic powder is kept dense during the sintering treatment, and the powder does not overflow due to the temperature increase, thereby reducing dimensional abnormalities such as edge chipping of the product, ensuring that the shape and size of the product out of the furnace are consistent with the designed shape and size, which is beneficial to the subsequent grinding process, and at the same time effectively improves the yield, reduces the risk of sintering furnace contamination caused by powder overflow, and extends the maintenance cycle.

[0075] 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 a ceramic body, characterized in that: The preparation method comprises the following steps: (1) Ceramic powder with a sphericity of 0.9-1 is subjected to dry pressing and crushing and granulation treatment in sequence to obtain pretreated powder; (2) The pretreated powder obtained in step (1) is subjected to mold loading, temperature and pressure treatment, and sintering treatment in sequence to obtain the ceramic body.

2. The preparation method according to claim 1, characterized in that: The pressure of the dry pressing in step (1) is 50-100 MPa.

3. The preparation method according to claim 1 or 2, characterized in that: The dry pressing time in step (1) is 1-3 minutes.

4. The preparation method according to any one of claims 1 to 3, characterized in that The crushing and granulation process in step (1) is performed to a particle size of less than 100 μm; Preferably, the crushing and granulation process in step (1) is carried out in a roller extrusion granulator.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The mold filling process in step (2) is to lay the pretreated powder flat into the mold and compact it; Preferably, the compacting is to place the mold horizontally in a sintering furnace and use a pressing head to press the mold.

6. The preparation method according to claim 5, characterized in that: The pressure exerted by the pressure head on the mold is 8-10t; Preferably, the pressing time is 5-8 min.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The temperature of the heating and pressurizing treatment in step (2) is less than 1000°C.

8. The preparation method according to claim 7, characterized in that: The pressure of the heating and pressurizing treatment in step (2) is 250-300t; Preferably, the pressurization time of the heating and pressurization treatment in step (2) is 0.8-1.2h; Preferably, the heating and pressurizing treatment in step (2) is repeated 3-4 times.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The sintering temperature in step (2) is 1500-1600° C. Preferably, the sintering time in step (2) is 1.5-2.5 hours.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: (1) Ceramic powder with a sphericity of 0.9-1 is dry pressed at 50-100 MPa for 1-3 min, and crushed and granulated in a roller extrusion granulator to a particle size of less than 100 μm to obtain a pretreated powder; (2) The pretreated powder obtained in step (1) is flatly loaded into a mold, and the mold is kept horizontally placed in a sintering furnace. A pressure head is used to generate a pressure of 8-10 tons on the mold and press it down for 5-8 minutes; then the temperature is increased and pressurized to <1000°C, and the pressure is increased at 250-300 tons for 0.8-1.2 hours, and the pressurization is repeated 3-4 times; and the ceramic body is sintered at 1500-1600°C for 1.5-2.5 hours to obtain the ceramic body.