Low-deformation 95 aluminum oxide ceramic material for hot die casting as well as preparation method and application of 95 aluminum oxide ceramic material

Abstract

The invention discloses a low-deformation 95 aluminum oxide ceramic material for hot die casting as well as a preparation method and application thereof. The ceramic material is prepared from an inorganic substance and an organic binder, the inorganic matter is prepared from the following components in parts by weight: 75 to 85 parts of high-purity fused corundum sand, 5 to 10 parts of flaky aluminum oxide, 5 to 10 parts of aluminum oxide powder fine material, 0 to 5 parts of quasi-nano magnesium aluminate spinel and 1 to 5 parts of calcined kaolin fine material; the organic binder comprises 12-15% of paraffin, 0.1-3% of TPE (thermoplastic elastomer) and 0.3-1% of oleic acid according to the total mass of inorganic matters. By optimizing an inorganic matter formula and an organic binder system and combining an AB two-section ball milling simplified process, the slurry fluidity, the blank rigidity and the finished product performance are synergistically improved, and the technical bottleneck of hot die-casting forming of the thin-wall 95 aluminum oxide ceramic part is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of alumina ceramic technology, specifically to a low-deformation 95 alumina ceramic material suitable for hot die casting process and its preparation method, which is particularly suitable for the mass production of thin-walled, precision-structured ceramic parts and can be widely used in electronic components, mechanical parts, medical devices and other fields. Background Technology

[0002] As is well known, 95% alumina ceramics are one of the most widely used ceramic categories in hot die casting processes due to their high strength, good insulation, and cost-effectiveness.

[0003] However, the following technical challenges still exist in the preparation process of existing 95% alumina ceramic materials for hot pressing:

[0004] 1. Deformation and cracking problems are prominent: Traditional formulas use single-grain corundum sand as the main raw material. The blank is prone to deformation due to uneven stress distribution during the forming, wax removal and sintering stages. Especially for thin-walled parts with a thickness of <1mm, the roundness deviation often exceeds 0.1mm, which cannot meet the assembly requirements of precision parts.

[0005] 2. High sintering energy consumption and limited strength: It relies on liquid phase sintering aids such as calcium carbonate and silicon dioxide, and needs to be sintered at a high temperature of 1650-1720℃, which consumes a lot of energy. In addition, too much liquid phase can easily lead to a decrease in grain boundary bonding force, and the ceramic strength is mostly lower than 300MPa.

[0006] 3. Difficulty in balancing slurry flowability and green body rigidity: In order to improve slurry flowability, the amount of organic binder is often increased, which leads to a decrease in green body rigidity and warping after molding. If the binder is reduced, the slurry flow will be obstructed and it will be unable to fill the complex mold cavity.

[0007] Based on the aforementioned technical problems, there is an urgent need to innovate the existing preparation process of 95% alumina ceramics. Summary of the Invention

[0008] To address the technical problems existing in the prior art, the present invention aims to provide a low-deformation 95% alumina ceramic material for hot die casting, its preparation method, and its application. The present invention optimizes the inorganic formulation and organic binder system, and combines the simplified process of "AB two-stage ball milling" to achieve a synergistic improvement in slurry fluidity, blank rigidity, and finished product performance, effectively solving the technical bottleneck of hot die casting of thin-walled 95% alumina ceramic parts.

[0009] The objective of this invention is achieved through the following technical solution: a 95% alumina ceramic material for low-deformation hot die casting, composed of inorganic materials and an organic binder; the inorganic materials, by weight, include 75-85 parts of high-purity molten corundum sand, 5-10 parts of flaky alumina, 5-10 parts of fine alumina powder, 0-5 parts of quasi-nano magnesium aluminum spinel, and 1-5 parts of fine calcined kaolin; the organic binder, by percentage of the total mass of the inorganic materials, includes 12-15% paraffin wax, 0.1-3% TPE, and 0.3-1% oleic acid.

[0010] Furthermore, the high-purity molten corundum sand... Purity ≥99%, particle size 20-50μm; the aspect ratio of the flake alumina is 10-20:1, particle size 5-15μm; the fine alumina powder... Purity ≥ 99.9%, particle size 0.5-2μm.

[0011] To address the aforementioned technical problems, this invention also provides another technical solution: a method for preparing a 95% alumina ceramic material for low-deformation hot die casting, comprising the following steps:

[0012] S1. Ingredients;

[0013] S2.AB Two-stage ball mill,

[0014] Section A ball milling: The weighed high-purity molten corundum sand, flaky alumina and all the oleic acid are added to the ball mill for ball milling, and the particle size D50 is controlled to be 3-10μm.

[0015] B-stage ball milling: Add alumina powder, quasi-nano magnesium aluminum spinel, and calcined kaolin powder to the slurry after A-stage ball milling, and continue ball milling. The particle size distribution after ball milling should meet the requirements of D50=2-7μm, and the ratios D90 / D50 and D50 / D10 <4. Dry the discharged material and set it aside for later use.

[0016] S3. Preparation of wax cake;

[0017] S4. Hot pressing molding;

[0018] S5. Powder embedding and wax removal;

[0019] S6. Sintering: Heat from room temperature to 1600-1630℃ at a rate of 1-8℃ / min, hold at that temperature for a period of time, and then cool to room temperature with the furnace.

[0020] Specifically, during the ball milling of section A, high-purity alumina balls with a particle size of 10-15mm are selected as the grinding medium, the material-to-ball ratio is controlled at 1:3-1:5, the rotation speed is 200-300r / min, and the ball milling time is 3-8h; during the ball milling of section B, the material-to-ball ratio and rotation speed are kept constant, and the ball milling continues for 1-2h, and the discharged material is dried until the moisture content is <0.5%.

[0021] Specifically, in step S3, the powder is dried at 110-140℃ until the moisture content is <0.2%, and then passed through a 120-mesh sieve; the paraffin wax and TPE are melted and stirred at 100-130℃ to form a binder solution; the powder is added to the binder solution and stirred at 100-130℃ for 30-120 minutes, and then cooled to form cakes.

[0022] Furthermore, in step S3, the waxing process is performed using a vacuum treatment with a vacuum degree of ≤-0.09Mpa to remove air bubbles from the solution.

[0023] Specifically, in step S4, the wax cake is melted at 60-80℃, injection molded under a pressure of 0.5-0.8MPa, and held under pressure for 10-30s to obtain a green blank.

[0024] Specifically, in step S5, industrial alumina powder is embedded in the green blank, the temperature is increased to 600℃ at 0.2-1℃ / min and held for 2-4 hours, and then the temperature is increased to 900-1000℃ at 0.5-2℃ / min and held for 1-3 hours.

[0025] Furthermore, the industrial alumina powder is 50-150 mesh. Purity ≥ 90%.

[0026] A thin-walled circular tube with a diameter of 20 mm × height of 50 mm × thickness of 0.5 mm was prepared according to the preparation method of the low-deformation hot die casting 95 alumina ceramic material, with a roundness deviation of <0.05 mm and a ceramic strength of ≥320 MPa.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] 1. Low deformation design enhances precision molding capabilities.

[0029] This invention uses high-purity molten corundum sand as the main framework, combined with lamellar alumina to form a composite reinforcement system: the high-purity molten corundum sand provides basic rigidity, resisting molding stress, wax removal, and stress deformation during sintering; the lamellar alumina, during the flow of hot-pressed casting slurry, is oriented along the low-resistance direction (similar to a "layered stacking" structure), further improving the billet's resistance to warping. In the embodiments, the roundness deviation of the thin-walled round tube is <0.05mm, solving the problem of severe deformation of thin-walled parts in traditional formulations and meeting the dimensional requirements of precision components.

[0030] 2. No traditional liquid phase additives are needed to achieve synergistic effects of low-temperature sintering and high strength.

[0031] This invention abandons traditional liquid-phase sintering aids such as calcium carbonate and silicon dioxide. Relying on the high surface energy and close packing effect of fine alumina powder (0.5-2μm particle size), it can be sintered at 1600-1630℃ without the need to introduce a low-viscosity liquid phase. This simultaneously reduces deformation. Furthermore, the fine alumina powder fills the voids between high-purity molten corundum sand and flake alumina, increasing the ceramic density to over 96%. Combined with the reinforcing effect of the flake alumina, the ceramic strength reaches over 320MPa, and CPK > 1.67, exhibiting significantly better performance stability than traditional products.

[0032] 3. The synergistic effect of organic binders reduces the molding and wax removal defect rate.

[0033] In organic binder systems, the addition of TPE (thermoplastic elastomer) significantly improves the plasticity and crack resistance of the preform: during the molding stage, it buffers the stress generated by die casting pressure, preventing micro-cracks in the preform; in the early stage of wax removal, it suppresses the difference in preform shrinkage caused by uneven temperature, reducing the risk of cracking. In the examples, the product qualification rate increased from the traditional 85% to 95%-97%, while the dispersing effect of oleic acid made the slurry fluidity reach over 1650 mm, ensuring the complete filling of complex mold cavities.

[0034] 4. Simplified process, suitable for mass production.

[0035] The "AB two-stage ball milling" process can achieve precise control of particle size distribution (D90 / D50 and D50 / D10<4) without the need for additional dispersion equipment, which shortens the ball milling time by 2-3 hours compared to the traditional single ball milling process. At the same time, the entire process has no special equipment requirements and can be directly adapted to existing hot die casting production lines, reducing the cost of technological transformation for enterprises and making it suitable for large-scale mass production. Detailed Implementation

[0036] To facilitate understanding of the present invention, the technical solutions and advantages of the invention are further described in detail below with reference to embodiments. Any mechanisms or methods not elaborated in this invention can be referred to in the prior art. The specific structures and features of the present invention are described below by way of example and should not be construed as limiting the present invention in any way. Furthermore, any of the technical features mentioned below (including implicit or explicit) can be arbitrarily combined or deleted from these technical features to form more other embodiments that may not be directly or indirectly mentioned in this invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0037] The low-deformation hot die casting 95% alumina ceramic material of the present invention is composed of inorganic substances and organic binders.

[0038] a. The components of the inorganic substance, by weight, include:

[0039] High-purity molten corundum sand ( ≥ 99%, particle size 20-50 μm, D50 = 8–15 μm) 75–85 parts;

[0040] 5–10 parts of flake-shaped alumina (aspect ratio ≥ 10–20:1, particle size 5–15 μm, D50 = 5–12 μm);

[0041] Fine alumina powder (specific surface area ≥ 10 m² / g, particle size 0.5-2 μm, D50 ≤ 0.8 μm) 5–10 parts;

[0042] Quasi-nano magnesium aluminum spinel ( (D50 ≤ 1.0 μm) 0–5 portions;

[0043] Calcinated kaolin fines ( 1–5 portions (D50 ≤ 2.0 μm).

[0044] b. Organic binders, by percentage of the total mass of the inorganic formulation, include:

[0045] Paraffin wax (melting point 52–58°C) 12–15%;

[0046] Thermoplastic elastomer (TPE, Shore hardness 40A–70A) 0.1–3%;

[0047] Oleic acid (analytical grade) 0.3–1%.

[0048] Among them, high-purity molten corundum sand is a type of high-purity alumina (… Artificial corundum material, with α-alumina as its main component, is produced through an electrofusion process and possesses high hardness, high melting point, and excellent chemical stability. In contrast, commercially available alumina has several crystal forms; the alumina mentioned here is α-alumina. Commercially available α-alumina typically has an α-phase content of <95%, while commercially available corundum sand has an α-phase content greater than 98%, produced through melt sintering at temperatures around 2000℃, while alumina is generally calcined at around 1400℃. High-purity molten corundum sand calcined at 2000℃–2200℃, due to its high calcination temperature and low reactivity, is more stable as a framework material during the liquid-phase sintering of alumina ceramics, absorbing the stress caused by liquid-phase flow and reducing deformation.

[0049] The preparation method of the low-deformation hot-pressing 95% alumina ceramic material of the present invention adopts a simplified process flow of "batch preparation - two-stage ball milling (A and B stages) - wax mixing - hot-pressing molding - powder embedding and wax removal - sintering", including the following steps:

[0050] S1. Ingredients.

[0051] According to the weight proportions of the above inorganic formulation, accurately weigh high-purity fused corundum sand, flaky alumina, fine alumina powder, quasi-nano magnesium aluminum spinel, and fine calcined kaolin; according to the percentage of the total inorganic mass, weigh paraffin wax, TPE, and oleic acid, and set aside. The accuracy of the batching should be controlled within ±0.1% to avoid affecting the slurry performance due to component deviations.

[0052] S2.AB Two-stage ball mill.

[0053] A two-stage ball milling process is employed to achieve precise control of particle size distribution and improve dispersion uniformity. Specific parameters are as follows:

[0054] Stage A Ball Milling: Weigh out high-purity molten corundum sand, flaky alumina, and all oleic acid, and add them to a planetary ball mill. Use high-purity alumina balls with a particle size of 10-15mm as the grinding media, controlling the material-to-ball ratio at 1:3-1:5, the rotation speed at 200-300 r / min, and the milling time at 3-8 hours. The purpose of this stage is to break up agglomerated high-purity molten corundum sand particles and simultaneously ensure that oleic acid is uniformly coated on the surface of the flaky alumina, improving its directional alignment. After ball milling, use a laser particle size analyzer to measure the particle size, controlling the D50 to be 3-10μm.

[0055] B-stage ball milling: Add alumina powder, quasi-nano magnesium aluminum spinel, and calcined kaolin powder to the slurry after A-stage ball milling. Maintain the material-to-ball ratio and rotation speed, and continue ball milling for 1-2 hours. The purpose of this stage is to uniformly disperse the ultrafine powder into the coarse particle system to form a compact packing structure. After ball milling, test the particle size distribution. It should meet the following requirements: D50 = 2-7 ​​μm, ratios D90 / D50 and D50 / D10 < 4, reasonable particle size distribution, and no agglomeration of ultrafine powder due to over-grinding. Finally, place the slurry in an oven and dry it at 80-100℃ until the moisture content is <0.5%, and set aside for later use.

[0056] S3. Preparation of wax cake.

[0057] Wax cake preparation is a key step in ensuring the fluidity of hot-press casting slurry. Specific steps include:

[0058] ① Slurry drying: Place the powder after the two-stage ball milling (AB) into a hot air circulating oven and dry it at 110-140℃ until the moisture content is <0.2%. If the moisture content is too high, it will cause air bubbles to form inside the wax cake, affecting the molding quality. After drying, crush it with a universal pulverizer and pass it through a 120-mesh standard sieve to remove impurities and remove incompletely dispersed agglomerated particles.

[0059] ② Wax melting: Add the weighed paraffin wax and TPE to a stainless steel reactor and heat to 100-130℃. This temperature needs to be 40-60℃ higher than the melting point of paraffin wax to ensure that the TPE is completely melted. Turn on the agitator and stir at 300-500 rpm for 15-30 minutes to prepare a uniform binder solution.

[0060] ③ Adding wax: Slowly add the dried inorganic powder to the binder solution, maintaining a temperature of 100-130℃, a stirring speed of 200-300 r / min, and a stirring time of 30-120 min. Avoid entrapping air during stirring; air bubbles can be removed by vacuuming (vacuum degree ≤ -0.09 MPa) to ultimately form a uniform wax slurry.

[0061] ④ Cooling and Molding: Pour the wax slurry into a custom-made metal mold. The size of the mold can be adjusted according to the hot die casting machine cylinder. Allow it to cool naturally to room temperature. This is because excessively rapid cooling can cause internal stress in the wax cake. The cooling time must be controlled to ≥2 hours. After demolding, a dense wax cake with a density of 1.8-2.0 g / cm³ is obtained and ready for use.

[0062] S4. Hot pressing casting.

[0063] The wax cake is placed in the barrel of the hot die-casting machine and heated to 60-80℃. This temperature needs to be controlled 5-20℃ above the melting point of paraffin wax to ensure the wax cake is completely melted and has good fluidity, forming a slurry. The die-casting system is started, and the slurry is injected into a pre-made thin-walled cylindrical mold at a pressure of 0.5-0.8MPa. For example, the mold cavity dimensions are: diameter 20mm × height 50mm × thickness 0.5mm. Pressure is held for 10-30 seconds. The holding time needs to be adjusted according to the thickness of the blank; the holding time should be shorter for thin-walled parts to avoid over-compaction and deformation. Finally, the mold is opened, and the formed green blank is removed. The surface of the green blank must be free of defects such as missing material, bubbles, and cracks.

[0064] S5. Embedding powder and removing wax.

[0065] The embedded powder dewaxing process is used to prevent the green body from deforming or cracking due to high temperature during the dewaxing process. The specific steps are as follows:

[0066] ① Place the formed green blank into an alumina crucible, and completely cover the green blank with 50-150 mesh industrial alumina powder, ensuring that there are no exposed parts of the green blank; wherein, the industrial alumina powder... Purity ≥ 90%, particle size must match the gap between the green body to prevent powder from penetrating into the pores of the green body;

[0067] ② Place the crucible in a box-type wax removal furnace and remove the wax according to the following heating curve: heat from room temperature to 600℃ at a rate of 0.2-1℃ / min. The heating rate should be slow in the low-temperature stage to avoid rapid decomposition of paraffin wax and the generation of a large amount of gas that could cause the blank to crack. Hold the temperature for 2-4 hours to allow the low-boiling-point organic matter such as paraffin wax to decompose completely. Then heat to 900-1000℃ at a rate of 0.5-2℃ / min and hold for 1-3 hours.

[0068] ③ After the wax removal is completed, the blank is cooled to below 200℃ in the furnace and then removed. At this time, the ash content of the blank must be <0.1%, and there should be no deformation or cracking.

[0069] S6. Sintering.

[0070] The dewaxed blank is placed in a high-temperature sintering furnace and subjected to a segmented heating process, specifically:

[0071] Heat from room temperature to 1600-1630℃ at a rate of 1-8℃ / min. The heating rate needs to be adjusted according to the size of the billet. Thin-walled parts can be heated faster, while thick-walled parts should be heated slower. Hold for 1-2 hours. The holding time needs to be controlled to avoid excessive grain growth due to prolonged holding. After holding, turn off the heating system and cool the furnace to room temperature.

[0072] To verify the technical effect of the present invention, three sets of examples with different formulations were selected and compared with the traditional 95% alumina ceramic formulation (control group). The slurry fluidity, finished product dimensional accuracy, mechanical properties and pass rate were tested, as follows.

[0073] Example 1

[0074] The low-deformation hot-die casting 95% alumina ceramic material of this embodiment 1 has the following raw material ratio:

[0075] a. Inorganic formulation: by weight, 80 parts high-purity fused corundum sand, 7 parts flaky alumina, 8 parts fine alumina powder, and 5 parts calcined kaolin fines, without the addition of quasi-nano magnesium aluminum spinel.

[0076] b. Organic binder: 14% paraffin, 1% TPE, and 0.5% oleic acid by weight percentage of total inorganic matter.

[0077] The preparation process parameters for the low-deformation hot-pressing 95% alumina ceramic material in Example 1 are as follows: Section A ball milling speed 250 r / min, time 5h; Section B ball milling time 1.5h; hot-pressing temperature 70℃, pressure 0.6MPa, holding pressure 20s; wax removal: heating rate from room temperature to 600℃ 0.5℃ / min (low temperature section), holding at 600℃ for 2h, then heating to 900℃ at 1℃ / min (high temperature section) and holding for 2h; sintering temperature 1600℃, holding for 1.5h.

[0078] Example 2

[0079] The low-deformation hot-die casting 95% alumina ceramic material of this embodiment 2 has the following raw material ratio:

[0080] a. Inorganic formulation: by weight, 78 parts high-purity fused corundum sand, 10 parts flaky alumina, 7 parts fine alumina powder, 3 parts quasi-nano magnesium aluminum spinel, and 2 parts calcined kaolin fines.

[0081] b. Organic binder: 15% paraffin, 2% TPE, and 0.8% oleic acid by weight percentage of total inorganic matter.

[0082] The preparation process parameters for the low-deformation hot-pressing 95% alumina ceramic material in Example 2 are as follows: Section A ball milling speed 280 r / min, time 6 h; Section B ball milling time 2 h; hot-pressing temperature 75℃, pressure 0.7 MPa, holding pressure 25 s; wax removal: heating rate from room temperature to 600℃ 0.5℃ / min (low temperature section), holding at 600℃ for 2 h, then heating to 1000℃ at 1℃ / min (high temperature section) and holding for 2 h; sintering temperature 1620℃, holding for 2 h.

[0083] Example 3

[0084] The low-deformation hot-die casting 95% alumina ceramic material of this embodiment 3 has the following raw material ratio:

[0085] a. Inorganic formulation: by weight, 75 parts high-purity fused corundum sand, 5 parts flaky alumina, 10 parts fine alumina powder, 5 parts quasi-nano magnesium aluminum spinel, and 5 parts calcined kaolin fines.

[0086] b. Organic binder: 12% paraffin, 3% TPE, and 1% oleic acid by weight percentage of total inorganic matter.

[0087] The preparation process parameters for the low-deformation hot-pressing 95% alumina ceramic material in Example 3 are as follows: Section A ball milling speed 300 r / min, time 8h; Section B ball milling time 2h; hot-pressing temperature 80℃, pressure 0.8MPa, holding pressure 30s; wax removal: heating rate from room temperature to 600℃ 0.5℃ / min (low temperature section), holding at 600℃ for 3h, then heating to 1000℃ at 1℃ / min (high temperature section) and holding for 2h; sintering temperature 1620℃, holding for 1h.

[0088] Control group (traditional formula)

[0089] The 95% alumina ceramic material used in this control group was commercially available 95% alumina wax cake. The hot pressing temperature was 75℃, the pressure was 0.7MPa, and the holding time was 25s. Wax removal: the temperature was increased from room temperature to 600℃ at a rate of 0.5℃ / min (low temperature section), held at 600℃ for 3 hours, and then increased to 1000℃ at a rate of 1℃ / min (high temperature section) and held for 2 hours. The sintering temperature was 1620℃ and held for 2 hours.

[0090] Performance testing

[0091] Performance tests were conducted on the finished products of Examples 1-3 of the present invention and the control group, and the test results are shown in Table 1.

[0092]

[0093] Table 1

[0094] As shown in Table 1 of the test results above, the slurry fluidity of Examples 1-3 of the present invention is ≥168mm, which is much higher than the 143mm of the control group, indicating that the slurry has good hot-press casting properties; the roundness deviation of the thin-walled round tubes is <0.05mm, which is significantly better than the 0.32mm of the control group, reflecting the advantage of low deformation; the ceramic strength is ≥328MPa and CPK>1.67, indicating that the product performance is stable; the pass rate is increased to 95%-97%, which fully achieves the expected effect of the invention.

[0095] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, it will be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-deformation 95% alumina ceramic material for hot die casting, characterized in that, It is composed of inorganic materials and an organic binder; the inorganic materials include, by weight, 75-85 parts of high-purity molten corundum sand, 5-10 parts of flaky alumina, 5-10 parts of fine alumina powder, 0-5 parts of quasi-nano magnesium aluminum spinel, and 1-5 parts of calcined kaolin fines; the organic binder includes, by weight percentage, 12-15% paraffin wax, 0.1-3% TPE, and 0.3-1% oleic acid.

2. The low-deformation 95% alumina ceramic material for hot die casting as described in claim 1, characterized in that, The high-purity molten corundum sand Purity ≥99%, particle size 20-50μm; the aspect ratio of the flake alumina is 10-20:1, particle size 5-15μm; the fine alumina powder... Purity ≥ 99.9%, particle size 0.5-2μm.

3. A method for preparing a low-deformation 95% alumina ceramic material for hot die casting as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Ingredients; S2.AB Two-stage ball mill, Section A ball milling: The weighed high-purity molten corundum sand, flaky alumina and all the oleic acid are added to the ball mill for ball milling, and the particle size D50 is controlled to be 3-10μm; B-stage ball milling: Add alumina powder, quasi-nano magnesium aluminum spinel, and calcined kaolin to the slurry after A-stage ball milling, and continue ball milling. The particle size distribution after ball milling should meet the requirements of D50=2-7μm, D90 / D50 and D50 / D10 <4, and reasonable particle size distribution. Dry the discharged material and set it aside for later use. S3. Preparation of wax cake; S4. Hot pressing molding; S5. Powder embedding and wax removal; S6. Sintering: Heat from room temperature to 1600-1630℃ at a rate of 1-8℃ / min, hold at that temperature for a period of time, and then cool to room temperature with the furnace.

4. The method for preparing the low-deformation hot die-casting 95% alumina ceramic material as described in claim 3, characterized in that, During the A-stage ball milling, high-purity alumina balls with a particle size of 10-15mm are used as the grinding medium. The material-to-ball ratio is controlled at 1:3-1:5, the rotation speed is 200-300r / min, and the ball milling time is 3-8h. During the B-stage ball milling, the material-to-ball ratio and rotation speed are kept constant, and the ball milling continues for 1-2h. The discharged material is dried until the moisture content is <0.5%.

5. The method for preparing the low-deformation hot die-casting 95% alumina ceramic material as described in claim 3, characterized in that, In step S3, the powder is dried at 110-140℃ until the moisture content is <0.2%, and then passed through a 120-mesh sieve; the paraffin wax and TPE are melted and stirred at 100-130℃ to form a binder solution; the powder is added to the binder solution and stirred at 100-130℃ for 30-120 minutes, then cooled and formed into cakes.

6. The method for preparing the low-deformation hot die-casting 95% alumina ceramic material as described in claim 5, characterized in that, In step S3, the waxing process is performed using a vacuum process with a vacuum degree of ≤-0.09Mpa to remove air bubbles from the solution.

7. The method for preparing the low-deformation hot die-casting 95% alumina ceramic material as described in claim 3, characterized in that, In step S4, the wax cake is melted at 60-80℃ and injection molded under a pressure of 0.5-0.8MPa for 10-30s to obtain a green blank.

8. The method for preparing the low-deformation hot die-casting 95% alumina ceramic material as described in claim 3, characterized in that, In step S5, industrial alumina powder is embedded in the green blank, and the temperature is increased to 600℃ at 0.2-1℃ / min and held for 2-4 hours, and then increased to 900-1000℃ at 0.5-2℃ / min and held for 1-3 hours.

9. The method for preparing the low-deformation hot die-casting 95% alumina ceramic material as described in claim 8, characterized in that, The industrial alumina powder is 50-150 mesh. Purity ≥ 90%.

10. A thin-walled circular tube with a diameter of 20 mm × height of 50 mm × thickness of 0.5 mm is prepared by the method of preparing low-deformation hot die casting 95 alumina ceramic material according to any one of claims 3-9, with a roundness deviation of <0.05 mm and a ceramic strength of ≥320 MPa.

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