A high-precision alumina ceramic injection molding process
By controlling the particle size of alumina powder and the ratio of organic binder, a high-precision alumina ceramic injection molding process was developed, which solved the problem of debinding and sintering deformation of Al2O3 ceramic injection molded parts with a wall thickness of less than 0.5 mm, and achieved the preparation of ceramic products with low deformation and high density.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DONGGUAN XY PRECISION TUNGSTEN CARBIDE CO
- Filing Date
- 2024-02-03
- Publication Date
- 2026-07-17
AI Technical Summary
In existing technologies, Al2O3 ceramic injection molding for injection molded parts with a wall thickness of less than 0.5 mm is prone to debinding, sintering, and deformation problems.
The process employs a high-precision alumina ceramic injection molding process, which includes steps such as powder preparation, internal mixing and feeding, injection molding, thermal debinding and sintering. By controlling the particle size distribution of the alumina powder and the ratio of organic binder, the consistency of powder arrangement is ensured and deformation during the sintering process is reduced.
The prepared alumina ceramic products with a wall thickness of 0.2 mm have a diameter deformation as low as 0.02-0.03 mm and a sintering density of 3.85-3.92 g/cm3, which solves the debinding sintering deformation defect of injection molded parts with a wall thickness of less than 0.5 mm in the prior art.
Abstract
Description
Technical Field
[0001] This invention relates to the field of ceramic materials technology, and specifically to a high-precision alumina ceramic injection molding process. Background Technology
[0002] Compared with other manufacturing processes for Al2O3 ceramic parts, Al2O3 ceramic injection molding can mass-produce complex, high-precision fine parts such as electronic substrates, dental trays, and micro gears at low cost, and has broad research and application prospects both domestically and internationally. Currently, Al2O3 ceramic injection molding is mainly used to produce injection molded parts with a wall thickness greater than 0.5 mm. However, for injection molded parts with a wall thickness less than 0.5 mm, debinding and sintering deformation are prone to occur. Summary of the Invention
[0003] To overcome the shortcomings of existing technologies where Al2O3 ceramic injection molding is prone to debinding and sintering deformation when used for injection molded parts with a wall thickness of less than 0.5 mm, this invention provides a high-precision alumina ceramic injection molding process, which includes the following steps:
[0004] Step (1):
[0005] Preparation of powder: Take alumina raw powder and put it into a ball mill jar, then add alumina grinding balls and ball mill. The powder obtained after ball milling is spray granulated, and then the powder obtained by spray granulation is sieved to obtain the powder for use.
[0006] Step (2):
[0007] Internal mixing feed: Take the spare powder from step (1) and add it into the internal mixer, then add the organic binder and internal mix. After internal mixing, the material obtained is cooled and crushed, and then injected under high pressure and cooled by the injection molding machine to obtain feed.
[0008] Step (3):
[0009] Injection molding: The feed material obtained in step (2) is injected into the mold through an injection molding machine to obtain a ceramic green body;
[0010] Step (4):
[0011] Hot degreasing: The ceramic green body obtained in step (3) is placed in a closed sagger with holes on the top and placed in a degreasing furnace to remove the glue and obtain the green body;
[0012] Step (5):
[0013] Sintering: The green body obtained in step (4) is placed in a closed sagger for sintering to complete the preparation of alumina ceramic.
[0014] Further, in step (1), the alumina grinding balls comprise the following parts by weight: 10-20 parts of alumina grinding balls with a particle size of 4-8 mm, 20-30 parts of alumina grinding balls with a particle size of 2-6 mm, and 50-70 parts of alumina grinding balls with a particle size of 1-3 mm. The total mass of the alumina grinding balls to the mass ratio of the alumina powder is (1.5-3):1.
[0015] Alumina balls of different sizes must be mixed according to the set ratio. Too many or too few balls can easily lead to poor ball milling effect, affect ball milling time, increase workload, and make it impossible to control the particle size of the powder.
[0016] Furthermore, in step (1), the particle size of the obtained spare powder is 0.1-0.5 μm. The powder obtained by sieving can pass through a 110-mesh sieve but cannot pass through a 120-mesh sieve. The present invention selects alumina powder with a mesh size of 110-120. Powder within the same mesh range can ensure the consistency of powder arrangement during mixing and injection molding. The narrow particle size distribution of the powder can effectively reduce problems such as uneven coating, thermal flow, and pore filling caused by particle gradation due to the rearrangement of organic matter and powder particles during injection molding. This is beneficial to the consistency of subsequent sintering and can reduce deformation during the sintering process.
[0017] Further, in step (2), the organic binder comprises the following components in parts by weight: 1.3-2.4 parts stearic acid, 1.4-2.5 parts oleic acid, 13-15.6 parts refined wax, 20.3-27.5 parts polypropylene, 35.3-41.3 parts acrylic resin, 2.1-3.7 parts ethylene-vinyl acetate copolymer, and 4-7 parts SP-60 emulsifier.
[0018] Furthermore, in step (2), the mass ratio of the organic binder to the spare powder is (15-20):100.
[0019] Furthermore, in step (2), the mixture is stirred at 160-200℃ for 100-140 minutes.
[0020] Furthermore, in step (2), the high-pressure injection pressure of the injection molding machine is 120-160 bar, the injection speed is 20-40%, and the injection temperature is 170-190℃.
[0021] Furthermore, in step (3), the injection temperature is 180-190℃, the injection pressure is 80-120 bar, and the injection speed is 35-50%.
[0022] Furthermore, in step (5), the sintering temperature is 1600-1650℃ and the sintering time is 1.5-3h.
[0023] Furthermore, in step (5), the sintering curves are RT-600℃, 500-700min; 600-1050℃, 1000-1400min; 1050℃ for 100-140min; 1050-1610℃, 1000-1400min; 1610℃ for 100-140min.
[0024] The mechanism by which the process of this invention achieves low deformation is as follows:
[0025] The present invention sieves the alumina powder, resulting in a narrow particle size distribution. This effectively reduces problems such as uneven coating, thermal flow, and pore filling caused by particle gradation due to the rearrangement of organic matter and powder particles during the injection molding process. This is beneficial to the consistency of sintering and can reduce deformation during the sintering process.
[0026] During sintering, the large amount of organic matter discharged, the channels for colloid discharge, and the in-situ voids left after discharge are the main factors leading to large deformation in the injection molding process. Channels and voids are mainly discharged through subsequent powder particle rearrangement and neck-binding shrinkage between particles. Powders with narrow particle size distribution have a uniform internal structure, ensuring isotropic consistency during shrinkage. Therefore, sintering deformation is greatly reduced.
[0027] The beneficial effects of this invention are as follows:
[0028] This invention involves sieving alumina powder, then mixing it in an intensive kneading process, high-pressure injection molding it into a feedstock, injection molding the feedstock, and finally debinding and sintering it in a sagger. The resulting alumina ceramic product (0.2 mm wall thickness) exhibits a diameter deformation as low as 0.02 mm and a sintering density of 3.85-3.92 g / cm³. 3 This solves the problem that in existing technologies, Al2O3 ceramic injection molding is prone to debinding and sintering deformation when used for injection molded parts with a wall thickness of less than 0.5mm. Detailed Implementation
[0029] In the following embodiments, unless otherwise specified, the raw materials or processing techniques used are conventional commercially available raw materials or conventional processing techniques in the art.
[0030] Example 1
[0031] This embodiment provides a high-precision alumina ceramic injection molding process, which includes the following steps:
[0032] Step (1):
[0033] Powder preparation: Alumina raw powder (99.8% purity) was placed in a ball mill jar, and then three types of alumina grinding balls of different particle sizes were added (the total mass ratio of the three types of grinding balls to the raw alumina powder was 2:1). The mixture was ball-milled, and the resulting powder was spray-granulated. The spray-granulated powder was then sieved to obtain the final powder. The three types of alumina grinding balls were: 6mm, 4mm, and 2mm in diameter, with a ratio of 15:25:60. The sieved powder passed through a 110-mesh sieve but not a 120-mesh sieve. Powder within the 110-120 mesh range was selected (powder within the same mesh range ensures consistent powder distribution during mixing and injection molding). The particle size of the spare powder is 0.1-0.5μm.
[0034] Step (2):
[0035] Internal mixing feed: Take the spare powder from step (1) and add it to the internal mixer, then add the organic binder and internal mix. Mix at 180°C for 120 minutes. After internal mixing, the resulting material is cooled and crushed, and then injected under high pressure and cooled to obtain a denser feed. The injection pressure of the injection molding machine is 140 bar, the speed is 30%, and the injection temperature is 170°C.
[0036] The components and their weight parts of the organic binder are as follows: stearic acid 2.0 parts, oleic acid 2.1 parts, refined wax 14.6 parts, polypropylene 25.3 parts, acrylic resin 40.1 parts, ethylene-vinyl acetate copolymer 2.9 parts, and SP-60 emulsifier 6 parts. The mass ratio of the organic binder to the spare powder is 18:100.
[0037] The refined wax used in the internal mixing process is Japanese refined wax HNP-10, with a melting point of 74.8 (°C) and a penetration of 5 mm. The acrylic resin is Mitsubishi acrylic resin MB2478, with a molecular weight of 80,000 and a purity of ≥99%.
[0038] Step (3):
[0039] Injection molding: The feed material obtained in step (2) is injected into the mold through an injection molding machine to obtain a ceramic green body.
[0040] The injection temperature is 185℃, the injection pressure is 100 bar, and the injection speed is 40%.
[0041] The mold is a thin cap mold with a diameter of D4mm, an inner diameter of D3.6mm, a height of 4mm, and a wall thickness of 0.2mm.
[0042] Step (4):
[0043] Hot degreasing: The ceramic green body obtained in step (3) is placed in a closed sagger with holes on the top and then placed in a degreasing furnace to remove the glue and obtain the green body.
[0044] The glue removal curves are as follows: RT (room temperature) - 180℃ for 90 min, 180-220℃ for 120 min, 220℃ for 60 min, 220-240℃ for 120 min, 240℃ for 60 min, 240-330℃ for 1320 min, 330℃ for 60 min, and 330-600℃ for 180 min.
[0045] The glue-removing sagger has a square bowl-shaped structure, with the top and bottom fitting together. The upper sagger has a round hole with a diameter of 1mm.
[0046] Step (5):
[0047] Degreasing and sintering: The green body obtained in step (4) is placed in a closed sagger for sintering to complete the preparation of alumina ceramic.
[0048] The sintering temperature is 1610℃.
[0049] The sintering curves are as follows: RT (room temperature) - 600℃, 600 min; 600-1050℃, 1200 min; 1050℃, 120 min; 1050-1610℃, 1200 min; 1610℃, 120 min.
[0050] The alumina ceramic product prepared by the above method has a diameter deformation of 0.02 mm and a density of 3.90 g / cm³. 3 .
[0051] Example 2
[0052] This embodiment provides a high-precision alumina ceramic injection molding process, which includes the following steps:
[0053] Step (1):
[0054] Powder preparation: Alumina raw powder (99.8% purity) was placed in a ball mill jar, and then three types of alumina grinding balls of different particle sizes were added (the total mass of the three types of grinding balls to the mass of the alumina raw powder was in the ratio of 1.5:1). The mixture was ball-milled, and the resulting powder was spray-granulated. The spray-granulated powder was then sieved to obtain the final powder. The three types of alumina grinding balls were: 8mm, 6mm, and 3mm in diameter, with a ratio of 10:20:50. The sieved powder passed through a 110-mesh sieve but not a 120-mesh sieve. Powder within the 110-120 mesh range was selected (powder within the same mesh range ensures consistent powder distribution during mixing and injection molding). The particle size of the spare powder is 0.1-0.5μm.
[0055] Step (2):
[0056] Internal mixing feed: Take the spare powder from step (1) and add it to the internal mixer, then add the organic binder and internal mix. Mix at 160°C for 100 minutes. After internal mixing, the resulting material is cooled and crushed, and then injected under high pressure and cooled to obtain a denser feed. The injection pressure of the injection molding machine is 120 bar, the speed is 20%, and the injection temperature is 190°C.
[0057] The components and their mass fractions of the organic binder are as follows: stearic acid 1.3 parts, oleic acid 1.4 parts, refined wax 13 parts, polypropylene 20.3 parts, acrylic resin 35.3 parts, ethylene-vinyl acetate copolymer 2.1 parts, and SP-60 emulsifier 4 parts. The mass ratio of the organic binder to the spare powder is 15:100.
[0058] The refined wax used in the internal mixing process is Japanese refined wax HNP-10, with a melting point of 74.8 (°C) and a penetration of 5 mm. The acrylic resin is Mitsubishi acrylic resin MB2478, with a molecular weight of 80,000 and a purity of ≥99%.
[0059] Step (3):
[0060] Injection molding: The feed material obtained in step (2) is injected into the mold through an injection molding machine to obtain a ceramic green body.
[0061] The injection temperature is 180℃, the injection pressure is 80 bar, and the injection speed is 35%.
[0062] The mold is a thin cap mold with a diameter of D4mm, an inner diameter of D3.6mm, a height of 4mm, and a wall thickness of 0.2mm.
[0063] Step (4):
[0064] Hot degreasing: The ceramic green body obtained in step (3) is placed in a closed sagger with holes on the top and then placed in a degreasing furnace to remove the glue and obtain the green body.
[0065] The glue removal curves are as follows: RT (room temperature) - 180℃ for 90 min, 180-220℃ for 120 min, 220℃ for 60 min, 220-240℃ for 120 min, 240℃ for 60 min, 240-330℃ for 1320 min, 330℃ for 60 min, and 330-600℃ for 180 min.
[0066] The glue-removing sagger has a square bowl-shaped structure, with the top and bottom fitting together. The upper sagger has a round hole with a diameter of 1mm.
[0067] Step (5):
[0068] Degreasing and sintering: The green body obtained in step (4) is placed in a closed sagger for sintering to complete the preparation of alumina ceramic.
[0069] The sintering temperature is 1600℃.
[0070] The sintering curves are as follows: RT (room temperature) - 600℃, 500 min; 600-1050℃, 1000 min; 1050℃, 100 min; 1050-1610℃, 1000 min; 1610℃, 100 min.
[0071] The alumina ceramic product prepared by the above method has a diameter deformation of 0.02 mm and a density of 3.92 g / cm³. 3 .
[0072] Example 3
[0073] This embodiment provides a high-precision alumina ceramic injection molding process, which includes the following steps:
[0074] Step (1):
[0075] Powder preparation: Alumina raw powder (99.8% purity) was placed in a ball mill jar, and then three types of alumina grinding balls of different particle sizes were added (the total mass ratio of the three types of grinding balls to the raw alumina powder was 3:1). The mixture was ball-milled, and the resulting powder was spray-granulated. The spray-granulated powder was then sieved to obtain the final powder. The three types of alumina grinding balls were: 4mm, 2mm, and 1mm in diameter, with a ratio of 20:30:70. The sieved powder passed through a 110-mesh sieve but not a 120-mesh sieve. Powder within the 110-120 mesh range was selected (powder within the same mesh range ensures consistent powder distribution during mixing and injection molding). The particle size of the spare powder is 0.1-0.5μm.
[0076] Step (2):
[0077] Internal mixing feed: Take the spare powder from step (1) and add it to the internal mixer, then add the organic binder and internal mix. Mix at 200℃ for 140 minutes. After internal mixing, the resulting material is cooled and crushed, and then injected under high pressure and cooled to obtain a denser feed. The injection pressure of the injection molding machine is 160 bar, the speed is 40%, and the injection temperature is 180℃.
[0078] The components and their mass fractions of the organic binder are as follows: stearic acid 2.4 parts, oleic acid 2.5 parts, refined wax 15.6 parts, polypropylene 27.5 parts, acrylic resin 41.3 parts, ethylene-vinyl acetate copolymer 3.7 parts, and SP-60 emulsifier 7 parts. The mass ratio of the organic binder to the spare powder is 20:100.
[0079] The refined wax used in the internal mixing process is Japanese refined wax HNP-10, with a melting point of 74.8 (°C) and a penetration of 5 mm. The acrylic resin is Mitsubishi acrylic resin MB2478, with a molecular weight of 80,000 and a purity of ≥99%.
[0080] Step (3):
[0081] Injection molding: The feed material obtained in step (2) is injected into the mold through an injection molding machine to obtain a ceramic green body.
[0082] The injection temperature is 190℃, the injection pressure is 120 bar, and the injection speed is 50%.
[0083] The mold is a thin cap mold with a diameter of D4mm, an inner diameter of D3.6mm, a height of 4mm, and a wall thickness of 0.2mm.
[0084] Step (4):
[0085] Hot degreasing: The ceramic green body obtained in step (3) is placed in a closed sagger with holes on the top and then placed in a degreasing furnace to remove the glue and obtain the green body.
[0086] The glue removal curves are as follows: RT (room temperature) - 180℃ for 90 min, 180-220℃ for 120 min, 220℃ for 60 min, 220-240℃ for 120 min, 240℃ for 60 min, 240-330℃ for 1320 min, 330℃ for 60 min, and 330-600℃ for 180 min.
[0087] The glue-removing sagger has a square bowl-shaped structure, with the top and bottom fitting together. The upper sagger has a round hole with a diameter of 1mm.
[0088] Step (5):
[0089] Degreasing and sintering: The green body obtained in step (4) is placed in a closed sagger for sintering to complete the preparation of alumina ceramic.
[0090] The sintering temperature is 1650℃.
[0091] The sintering curves are as follows: RT (room temperature) - 700℃, 600 min; 600-1050℃, 1400 min; 1050℃, 140 min; 1050-1610℃, 1400 min; 1610℃, 140 min.
[0092] The alumina ceramic product prepared by the above method has a diameter deformation of 0.03 mm and a density of 3.85 g / cm³. 3 .
[0093] Comparative Example 1
[0094] Compared with Example 1, most aspects are the same, except that the powder obtained by spray granulation is not sieved in step (1). The product prepared in this example has a diameter deformation of 0.12 mm and a density of 3.92 g / cm³. 3 .
[0095] Comparative Example 2
[0096] Compared to Example 1, most aspects are the same, except that in step (2), the feedstock is obtained directly after cooling and crushing, without high-pressure injection cooling in an injection molding machine to obtain a denser feedstock. The product obtained in this example has a diameter deformation of 0.10 mm and a density of 3.86 g / cm³. 3 .
[0097] Comparative Example 3
[0098] Compared with Example 1, most aspects are the same, except that debinding and sintering in a sagger is not performed. The product obtained in this comparative example has a diameter deformation of 0.13 mm and a density of 3.90 g / cm³. 3 .
[0099] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.
Claims
1. A high-precision alumina ceramic injection molding process, characterized in that, The injection molding process includes the following steps: Step (1): Preparation of powder: Take alumina raw powder and put it into a ball mill jar, then add alumina grinding balls and ball mill. The powder obtained after ball milling is spray granulated, and then the powder obtained by spray granulation is sieved to obtain the powder for use. Step (2): Internal mixing feed: Take the spare powder from step (1) and add it to the internal mixer, then add the organic binder and internal mix. After internal mixing, the resulting material is cooled and crushed, and then injected under high pressure and cooled through an injection molding machine to obtain feed; Step (3): Injection molding: The feed material obtained in step (2) is injected into the mold through an injection molding machine to obtain a ceramic green body; Step (4): Hot degreasing: The ceramic green body obtained in step (3) is placed in a closed sagger with holes on the top and placed in a degreasing furnace to remove the glue and obtain the green body; Step (5): Sintering: The green body obtained in step (4) is placed in a closed sagger for sintering to complete the preparation of alumina ceramic.
2. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (1), the alumina grinding balls include the following parts by weight: 10-20 parts of alumina grinding balls with a particle size of 4-8 mm, 20-30 parts of alumina grinding balls with a particle size of 2-6 mm, and 50-70 parts of alumina grinding balls with a particle size of 1-3 mm. In step (1), the total mass of the alumina grinding balls and the mass ratio of the alumina powder are (1.5-3):
1.
3. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (1), the particle size of the prepared powder is 0.1-0.5 μm.
4. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (2), the organic binder comprises the following components in parts by weight: 1.3-2.4 parts stearic acid, 1.4-2.5 parts oleic acid, 13-15.6 parts refined wax, 20.3-27.5 parts polypropylene, 35.3-41.3 parts acrylic resin, 2.1-3.7 parts ethylene-vinyl acetate copolymer, and 4-7 parts SP-60 emulsifier.
5. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (2), the mass ratio of the organic binder to the spare powder is (15-20):
100.
6. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (2), the mixture is intensively mixed at 160-200℃ for 100-140 minutes.
7. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (2), the high pressure of the injection molding machine is 120-160 bar, the injection speed is 20-40%, and the injection temperature is 170-190℃.
8. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (3), the injection temperature is 180-190℃, the injection pressure is 80-120 bar, and the injection speed is 35-50%.
9. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (5), the sintering temperature is 1600-1650℃.
10. The high-precision alumina ceramic injection molding process according to claim 1, characterized in that, In step (5), the sintering curves are RT-600℃, 500-700min; 600-1050℃, 1000-1400min; 1050℃ for 100-140min; 1050-1610℃, 1000-1400min; 1610℃ for 100-140min.