A large-size alumina ceramic forming method

Abstract

The present invention discloses a large-size alumina ceramic forming method, aiming to solve the problem that it is difficult to successfully form long strips with long sizes and certain internal features by dry pressing or cold isostatic pressing. The invention includes the following steps: S1, mixing alumina powder, dispersant and water to obtain a mixed slurry; S2, placing the mixed slurry in a vacuum degassing machine for vacuum degassing to remove bubbles in the mixed slurry; S3, loading the mixed slurry into a pressure grouting machine; S4, injecting the mixed slurry into a porous resin mold through the pressure grouting machine for continuous pressure molding; S5, drying after demoulding to obtain a ceramic green body; S6, loading the ceramic green body into a sintering furnace for firing and molding. This patent application uses pressure grouting to form ceramic products, which can form ceramic products with large sizes and internal features, overcoming the current situation that large-size products are difficult to form and internal features are difficult to process.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and more particularly to a method for forming large-size alumina ceramics. Background Art

[0002] From traditional ceramics to advanced ceramics, ceramic products have always been part of human life and modernization. There are many ways to form ceramic products. At present, our company uses dry pressing and cold isostatic pressing in the ceramic production process. In the forming process, it is difficult to use dry pressing or cold isostatic pressing for long ceramic strips with large size and certain internal characteristics. On the one hand, dry pressing will cause stratification, cracking and uneven density of the green body due to uneven radial and axial pressure distribution. The strength of the green body is not too high, and dry pressing cannot be used for ceramics with internal characteristics; on the other hand, cold isostatic pressing may cause uneven density of the green body due to different shrinkage rates of different parts of the green body, resulting in the phenomenon that the green body is thin in the middle and relatively thick at both ends. In addition, the capacity of cold isostatic pressing is limited, and the depth does not meet the requirements. For ceramics with complex structures, cold isostatic pressing is easy to destroy the structural characteristics, and it is not easy to demold after forming. Summary of the invention

[0003] In order to overcome the above-mentioned shortcomings, the present invention provides a large-size alumina ceramic forming method, which adopts pressure grouting to form ceramic products, which can not only reduce the drying shrinkage of the green body and the moisture of the green body after demolding, but also can form large-size ceramic products with internal features, overcoming the current situation that large-size products are difficult to form and internal features are difficult to process.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solution: a large-size alumina ceramic forming method, comprising the following steps:

[0005] S1, mixing alumina powder, dispersant and water to obtain a mixed slurry;

[0006] S2, placing the mixed slurry in a vacuum degassing machine for vacuum degassing to remove bubbles in the mixed slurry;

[0007] S3, loading the mixed slurry into a pressure grouting machine;

[0008] S4, injecting the mixed slurry into a porous resin mold for molding by a pressure grouting machine;

[0009] S5, demoulding and drying to obtain a ceramic green body;

[0010] S6, loading the ceramic green body into a sintering furnace for firing and forming.

[0011] The mixed slurry is more uniform after stirring, and the dispersant can improve the fluidity of the slurry, making it easier to inject the slurry into the porous resin mold. The mixed slurry is placed in a vacuum degassing machine for vacuum degassing to avoid residual bubbles in the mixed slurry that affect the product quality. The porous resin mold is used for pressure grouting molding. The mold has high strength, strong pressure shock resistance, long mold service life, and can be used continuously without drying. The mold has a microporous structure, which is more conducive to drainage and improves grouting efficiency. With pressure grouting molding, the force at each position of the product is uniform, so that the density at each position of the product is uniform, and large-sized ceramic green bodies with internal features can be formed.

[0012] This patent application uses pressure grouting to form ceramic products, which can not only reduce the drying shrinkage of the green body and the moisture of the green body after demolding, but also can form large-sized ceramic products with internal features, overcoming the current situation that large-sized products are difficult to form and internal features are difficult to process.

[0013] Preferably, in parts by mass, the content of alumina powder in the mixed slurry is 80-85 parts, the content of water is 15-20 parts, and the content of dispersant is 0.5-1 part.

[0014] The reasonable proportion of the mixed slurry ensures the product quality.

[0015] Preferably, the purity of the alumina powder is 99.9% and the average particle size is between 0.5 and 1 um.

[0016] Selecting the appropriate alumina powder particle size ensures that the slurry does not deposit, facilitates the flow of the slurry, and prevents the alumina powder from being too fine and entering the micropores of the mold, causing blockage.

[0017] Preferably, the S5 ceramic blank is dried in an oven, the oven temperature is set at 110-120°C, and the heating rate is 3-5°C / min.

[0018] Adopting appropriate drying temperature and heating rate for drying is beneficial to the drying of ceramic green body, preventing the green body from cracking during the drying process and improving the qualified rate.

[0019] Preferably, the S6 sintering furnace is filled with fine sintering sand, and the ceramic green body is placed in the fine sintering sand for sintering.

[0020] The use of fine sintering sand for isolation is conducive to smooth sintering shrinkage of the ceramic green body.

[0021] Preferably, the grouting pressure of the S4 pressure grouting machine is 0.8-1.2 MPa, and the pressure is maintained for 15-25 minutes.

[0022] Set appropriate grouting pressure and holding time to ensure that the density and strength of the ceramic green body meet the requirements.

[0023] Preferably, the sintering process of S6 ceramic green body includes degreasing stage, grain growth stage and cooling stage in sequence. In the degreasing stage, the temperature is slowly increased to 580-600℃ for 110-130h and kept at temperature for 4.5-5.5h; in the grain growth stage, the temperature is first increased to 1250-1350℃ for 40-50h and kept at temperature for 1.5-2.5h, and then the temperature is further increased to 1550-1650℃ for 20-30h and kept at temperature for 2.5-3.5h; in the cooling stage, the temperature is first slowly decreased to 580-600℃ for 60-70h and then naturally cooled to room temperature.

[0024] The degreasing stage is to remove the binder and degrease the ceramic products. The grain growth stage is to grow the grains and form the green body into porcelain. The cooling stage is to cool down slowly to prevent extreme cold or heat from causing the product to crack.

[0025] Preferably, the porous resin mold is covered with a metal shaping sleeve, the upper end of the porous resin mold is covered with a metal cover plate, and the metal cover plate is connected to the upper end of the metal shaping sleeve; a plurality of drainage holes are densely distributed on the outer wall of the metal shaping sleeve.

[0026] The metal shaping sleeve plays a role in shaping the porous resin mold to prevent the porous resin mold from being deformed by the high pressure of grouting. The setting of the drainage hole facilitates the rapid discharge of the water discharged from the porous resin mold.

[0027] Preferably, the porous resin mold includes a mold barrel and a mold core, the mold core is installed in the mold barrel, a mold cover is installed on the upper end of the mold barrel, a pressure plug is arranged on the lower surface of the mold cover, the pressure plug is sleeved between the outer wall of the mold core and the inner wall of the mold barrel, the pressure plug is connected to a plurality of push rods, and the push rods pass through the mold cover; a vibration mechanism is arranged under the metal molding sleeve, and the metal molding sleeve is installed on the vibration mechanism, and the vibration mechanism works to drive the metal molding sleeve to vibrate at S4; after S4 and before S5, pressure is applied to the pressure plug through the push rod until the pressure reaches the set value and then the pressure is stopped.

[0028] At the beginning of grouting, the metal shaping sleeve is driven to vibrate by the vibration mechanism, which is conducive to rapid drainage. The vibration mechanism stops working during the pressure holding stage. After the pressure holding is completed, pressure is applied to the pressure plug to further compact the ceramic product, which is conducive to improving product quality. When the pressure reaches the set value, the pressure is stopped and demoulding is performed afterwards.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: the present patent application adopts the pressure grouting method to form ceramic products, which can not only reduce the drying shrinkage of the green body and the moisture of the green body after demolding, but also can form ceramic products with large size and internal features, overcoming the current situation that large-size products are difficult to form and internal features are difficult to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1is a schematic diagram of a porous resin mold of Example 1 of the present invention;

[0031] Figure 2 is an exploded view of a porous resin mold of Example 1 of the present invention;

[0032] Figure 3 is a cross-sectional view of a porous resin mold according to Embodiment 2 of the present invention;

[0033] In the figure: 1. metal shaping sleeve, 2. metal cover plate, 3. drainage hole, 4. mold cylinder, 5. mold core, 6. mold cover, 7. jack, 8. convex ring, 9. grouting hole, 10. through hole, 11. pressure plug, 12. push rod, 13. pressure plate, 14. positioning screw sleeve, 15. workbench, 16. vibration plate, 17. vibration motor, 18. push block, 19. push plate, 20. push block, 21. vibration spring, 22. installation groove. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings:

[0035] Embodiment 1: A method for forming a large-size alumina ceramic, comprising the following steps:

[0036] S1, alumina powder, dispersant and water are mixed and stirred to obtain a mixed slurry; in parts by mass, the content of alumina powder in the mixed slurry is 80-85 parts, the water content is 15-20 parts, and the dispersant content is 0.5-1 part; in this embodiment, the content of alumina powder in the mixed slurry is 82 parts, the water content is 18 parts, and the dispersant content is 0.8 parts; the mixed slurry is put into a ball mill and stirred appropriately, and then put into a planetary ball mill for half an hour at a speed of 20r / min to obtain a mixed slurry; the purity of the alumina powder is 99.9%, and the average particle size is between 0.5 and 1um;

[0037] S2, placing the mixed slurry in a vacuum degassing machine for vacuum degassing to remove bubbles in the mixed slurry; when the vacuum degassing machine is vacuum degassing, the vacuum degree is -0.09MPa ~ -0.1MPa, and the vacuum degree in this embodiment is -0.095MPa, and the mixed slurry is slowly stirred at the same time; stirring and degassing at the same time is conducive to improving the degassing effect;

[0038] S3, loading the mixed slurry into a pressure grouting machine;

[0039] S4, injecting the mixed slurry into a porous resin mold for molding by a pressure grouting machine; the grouting pressure of the pressure grouting machine is 0.8-1.2 MPa, and the pressure is maintained for 15-25 minutes. In this embodiment, the grouting pressure is 1 MPa, and the pressure is maintained for 20 minutes;

[0040] S5, drying after demoulding to obtain a ceramic green body; the ceramic green body is dried in an oven, the oven temperature is set at 110-120°C, and the heating rate is 3-5°C / min. In this embodiment, the oven temperature is set at 115°C, and the heating rate is 4°C / min;

[0041] S6, loading the ceramic green body into a sintering furnace for sintering and forming. The sintering furnace is filled with fine sintering sand, and the ceramic green body is placed on the fine sintering sand for sintering. A table is built in the sintering furnace, and a layer of fine sintering sand is laid on the surface of the table, and the ceramic green body is placed on the table for sintering. The ceramic green body sintering process includes a degreasing stage, a grain growth stage, and a cooling stage in sequence.

[0042] During the degreasing stage, the temperature slowly rises to 580-600℃ for 110-130h and is kept warm for 4.5-5.5h; during the grain growth stage, the temperature first rises to 1250-1350℃ for 40-50h and is kept warm for 1.5-2.5h, and then the temperature continues to rise to 1550-1650℃ for 20-30h and is kept warm for 2.5-3.5h; during the cooling stage, the temperature first slowly decreases to 580-600℃ for 60-70h and then naturally cools to room temperature.

[0043] In this embodiment, the temperature in the degreasing stage is slowly increased to 600°C for 120 hours and kept at this temperature for 5 hours; in the grain growth stage, the temperature is first increased to 1300°C for 45 hours and kept at this temperature for 2 hours, and then the temperature is further increased to 1600°C for 25 hours and kept at this temperature for 3 hours; in the cooling stage, the temperature is first slowly decreased to 600°C for 65 hours and then naturally cooled to room temperature.

[0044] like Figure 1 , Figure 2 As shown, the porous resin mold is coated with a metal shaping sleeve 1, and the upper end of the porous resin mold is covered with a metal cover plate 2, which is connected to the upper end of the metal shaping sleeve; the outer wall of the metal shaping sleeve is densely covered with a number of drainage holes 3. The porous resin mold includes a mold barrel 4 and a mold core 5, the mold core is installed in the mold barrel, a mold cover 6 is installed on the upper end of the mold barrel, a slot is provided at the bottom of the mold barrel, and a plug hole 7 is provided on the mold cover, the lower end of the mold core is inserted in the slot, and the upper end of the mold core is inserted in the plug hole. A convex ring 8 is provided at the upper end of the mold barrel, and a groove is provided on the lower end surface of the mold cover, and the groove is adapted to be connected with the convex ring. A grouting hole 9 is provided on the mold cover, and a through hole 10 is provided on the metal cover, and the through hole is aligned with the grouting hole. The slurry is injected into the mold cavity between the outer wall of the mold core and the inner wall of the mold barrel from the through hole and the grouting hole.

[0045] The mixed slurry is more uniform after ball milling and stirring. The dispersant can improve the fluidity of the slurry, making it easier to inject the slurry into the porous resin mold. The mixed slurry is placed in a vacuum degassing machine for vacuum degassing to avoid residual bubbles in the mixed slurry that affect the product quality. The porous resin mold is used for pressure grouting molding. The mold has high strength, strong pressure shock resistance, long mold service life, and can be used continuously without drying. The mold has a microporous structure, which is more conducive to drainage and improves grouting efficiency. With pressure grouting molding, the force at each position of the product is uniform, so that the density at each position of the product is uniform, and large-sized ceramic green bodies with internal features can be formed.

[0046] Example 2: A method for forming a large-size alumina ceramic, the steps of which are similar to those of Example 1, the main difference being that the porous resin mold in this embodiment includes a mold barrel and a mold core, the mold core is installed in the mold barrel, and a mold cover is installed at the upper end of the mold barrel, such as Figure 3 As shown, a pressure plug 11 is arranged on the lower surface of the mold cover, and grouting holes are arranged on the pressure plug corresponding to the grouting holes. The pressure plug is sleeved between the outer wall of the mold core and the inner wall of the mold barrel. The pressure plug is connected to a plurality of push rods 12, and the push rods pass through the mold cover and the metal cover plate; a pressure plate 13 is arranged above the metal cover plate, and the push rods are all connected to the pressure plate. A positioning screw sleeve 14 is threadedly connected to the push rod, and the positioning screw sleeve abuts against the metal cover plate, and the positioning screw sleeve positions the pressure plug. A vibration mechanism is arranged below the metal shaping sleeve, and the metal shaping sleeve is installed on the vibration mechanism. At S4, the vibration mechanism works to drive the metal shaping sleeve to vibrate; after S4 and before S5, the positioning screw sleeve is loosened, and pressure is applied to the pressure plug through the push rod until the pressure reaches the set value and then the pressure is stopped. The vibration mechanism includes a workbench 15, a vibration disk 16 and a vibration motor 17. A plurality of top blocks 18 are evenly distributed circumferentially on the lower surface of the vibration disk, and the lower surface of the top blocks is tilted circumferentially. A push disk 19 is installed on the output shaft of the vibration motor, and a plurality of push blocks 20 are arranged on the upper surface of the push disk. The push blocks and the top blocks are arranged one by one, and the upper surface of the push blocks is tilted circumferentially so that the push blocks fit the vibration disk. The vibration disk can be lifted and installed on the workbench, and a vibration spring 21 is installed between the vibration disk and the workbench. An installation groove 22 is arranged on the workbench corresponding to the vibration disk, and the vibration disk is adapted to be connected with the installation groove, and a metal shaping sleeve is installed on the vibration disk. The vibration motor drives the push disk to rotate when it is working, and the push blocks on the push disk cooperate with the top blocks on the vibration disk to contact and realize the up and down vibration of the vibration disk. The other steps are the same as those in Example 1.

[0047] At the beginning of grouting, the metal shaping sleeve is driven to vibrate by the vibration mechanism, which is conducive to rapid drainage. The vibration mechanism stops working during the pressure holding stage. After the pressure holding is completed, pressure is applied to the pressure plug to further compact the ceramic product, which is conducive to improving product quality. When the pressure reaches the set value, the pressure is stopped and demoulding is performed afterwards.

[0048] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A method for forming large-size alumina ceramics, characterized in that: The following steps are involved: S1, mixing alumina powder, dispersant and water to obtain a mixed slurry; S2, placing the mixed slurry in a vacuum degassing machine for vacuum degassing to remove bubbles in the mixed slurry; S3, loading the mixed slurry into a pressure grouting machine; S4, injecting the mixed slurry into the porous resin mold for molding through a pressure grouting machine; the grouting pressure of the pressure grouting machine is 0.8-1.2 MPa, and the pressure is maintained for 15-25 minutes; after the pressure is maintained, pressure is applied to the pressure plug through the ejector rod until the pressure reaches the set value and then the pressure is stopped; S5, demoulding and drying to obtain a ceramic green body; S6, loading the ceramic green body into a sintering furnace for sintering and forming; The porous resin mold is covered with a metal shaping sleeve, and a plurality of drainage holes are densely distributed on the outer wall of the metal shaping sleeve; the porous resin mold comprises a mold barrel and a mold core, the mold core is installed in the mold barrel, a mold cover is installed on the upper end of the mold barrel, a pressure plug is arranged on the lower surface of the mold cover, the pressure plug is sleeved between the outer wall of the mold core and the inner wall of the mold barrel, the pressure plug is connected to a plurality of push rods, and the push rods pass through the mold cover; a vibration mechanism is arranged below the metal shaping sleeve, the vibration mechanism comprises a workbench, a vibration disk and a vibration motor, a plurality of push blocks are evenly distributed circumferentially on the lower surface of the vibration disk, the lower surface of the push blocks is inclined along the circumferential direction, a push disk is installed on the output shaft of the vibration motor, a plurality of push blocks are arranged on the upper surface of the push disk, and the push blocks and the push blocks are arranged one by one; a vibration spring is installed between the vibration disk and the workbench, and the metal shaping sleeve is installed on the vibration disk; in S4, the vibration mechanism works to drive the metal shaping sleeve to vibrate.

2. A large-size alumina ceramic forming method according to claim 1, characterized in that: In parts by mass, the content of alumina powder in the mixed slurry is 80-85 parts, the content of water is 15-20 parts, and the content of dispersant is 0.5-1 part.

3. A large-size alumina ceramic forming method according to claim 1, characterized in that: The purity of alumina powder is 99.9%, and the average particle size is between 0.5 and 1 um.

4. A large-size alumina ceramic forming method according to claim 1, characterized in that: The S5 ceramic green body was dried in an oven, the oven temperature was set at 110-120°C, and the heating rate was 3-5°C / min.

5. A large-size alumina ceramic forming method according to claim 1, characterized in that: The S6 sintering furnace is filled with fine sintering sand, and the ceramic green body is placed in the fine sintering sand for sintering.

6. A large-size alumina ceramic forming method according to any one of claims 1 to 5, characterized in that: The sintering process of S6 ceramic green body includes degreasing stage, grain growth stage and cooling stage in sequence.

7. A large-size alumina ceramic forming method according to claim 6, characterized in that: During the degreasing stage, the temperature slowly rises to 580-600℃ for 110-130h and is kept warm for 4.5-5.5h; during the grain growth stage, the temperature first rises to 1250-1350℃ for 40-50h and is kept warm for 1.5-2.5h, and then the temperature continues to rise to 1550-1650℃ for 20-30h and is kept warm for 2.5-3.5h; during the cooling stage, the temperature first slowly decreases to 580-600℃ for 60-70h and then naturally cools to room temperature.

8. A large-size alumina ceramic forming method according to claim 1, characterized in that: The upper end of the porous resin mold is covered with a metal cover plate, and the metal cover plate is connected to the upper end of the metal shaping sleeve.

Images