A ceramic core material for magnesium alloy precision casting and preparation method thereof

Abstract

A ceramic core material for magnesium alloy precision casting and a preparation method thereof. The purpose of the present invention is to solve the problems that the existing casting core is easy to react chemically with the magnesium alloy metal liquid, the ceramic core strength is insufficient, and the molding size accuracy is low. The casting ceramic core material of the present invention is prepared from carbon-coated aluminum nitride powder, sintering aid, ethanol solvent and binder. The carbon-coated aluminum nitride powder is prepared by drying, calcining and grinding a mixed slurry of fructose and aluminum nitride; the carbon-coated aluminum nitride powder and the sintering aid are mixed and dried to prepare a mixed powder, and then an ethanol solvent and a binder are added to obtain a slurry, and the slurry is pressed into a core blank, and the core blank is then subjected to cold isostatic pressing and debonding treatment, and finally sintering treatment. The present invention can achieve low-temperature sintering preparation of ceramic core density and strength, and the prepared ceramic core has the advantages of high thermal conductivity, no interface reaction with metal magnesium liquid, good high temperature stability, easy sintering, easy core removal, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision casting, and relates to a ceramic core material for precision casting of magnesium alloys and a preparation method thereof. Background Art

[0002] The precision casting technology of magnesium alloys is widely used in the aerospace field, such as the hollow blades of aero-engines, the hubs, rims in turbine blades, and the casings of aero-engines. For the narrow or complex-shaped inner cavities of these castings, cores are required to ensure the dimensional accuracy of the castings. The cores for precision casting of magnesium alloys are different from those for precision casting of aluminum alloys. Magnesium alloys have lower corrosion resistance and more active chemical properties compared with aluminum alloys. Since magnesium reacts with most refractory materials to varying degrees, the reference value of the core materials for aluminum alloy casting to the core materials for magnesium alloy casting is not great. Selecting a suitable core material has become the key to determining the quality of the finished products with complex cavities.

[0003] Generally, precision casting cores need to meet some basic properties, including sufficient room temperature strength, high temperature stability, low thermal expansion coefficient, certain porosity and chemical activity, and no excessive phase changes during sintering and casting. In addition to meeting the above requirements, compared with the commonly used resin sand cores, the ceramic cores have higher surface finish and more accurate dimensional accuracy of the castings. Compared with salt cores, the ceramic cores have better room temperature strength and high temperature stability.

[0004] There is little introduction to the ceramic cores for magnesium alloy casting in the existing literature. In the existing patent (CN106927798A) a water-soluble ceramic core and its preparation method, this patent solves the problem of difficult core removal by adding several water-soluble salts such as sodium chloride, potassium carbonate, and calcium carbonate to electrolytic corundum powder. However, the addition of sodium salts and potassium salts increases the hygroscopicity of the core material and is prone to corrode the surface of the casting, affecting the surface quality of the core. Patent (CN108484140A) a two-component layered ceramic core. This patent uses a double-layer ceramic core structure, with porous and loose silica as the main raw material inside and magnesium oxide, which is suitable for magnesium alloys and has good high-temperature performance, as the main material outside. The ceramic core prepared by this invention improves the collapsibility of the core on the premise of improving the surface quality. However, the thermal expansion coefficients of silica and magnesium oxide differ greatly, and the mismatch of thermal expansion coefficients at the double-layer junction of the core material will generate cracks during high-temperature sintering, greatly reducing the bending strength of the ceramic core.

[0005] For the ceramic core of precision casting of magnesium alloy, it is necessary to meet the conditions that the ceramic core does not undergo chemical reactions and does not break during long-term immersion contact with the magnesium alloy molten metal at temperatures above 700 °C, and the dimensional accuracy of the parts must be ensured. However, the existing ceramic cores are difficult to meet the above requirements. Aiming at the deficiencies of the existing technology, the present invention proposes a ceramic core material suitable for precision casting of magnesium alloy with zero interfacial reaction with magnesium alloy, good sintering performance and stable high-temperature performance. Using this material, complex ceramic cores with excellent comprehensive performance can be prepared. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems that the cores for precision casting of magnesium alloy are prone to chemical reactions with the magnesium alloy molten metal, the strength of the ceramic core is insufficient, and the forming dimensional accuracy is relatively low, and to provide a ceramic core material for precision casting of magnesium alloy and its preparation method.

[0007] The ceramic core material for precision casting of magnesium alloy of the present invention is prepared from carbon-coated aluminum nitride powder, sintering aids, ethanol solvent and binder. The mass ratio of carbon-coated aluminum nitride powder to sintering aids is 1:(0.01 - 0.055); the carbon-coated aluminum nitride powder is obtained by drying, calcining and grinding the mixed slurry of fructose and aluminum nitride; the sintering aids are composed of magnesium oxide, aluminum oxide, silicon dioxide and calcium oxide according to the mass ratio of 1:(1.8 - 2):(7 - 8):(4.5 - 5.5); ethanol solvent and binder are added to the mixed powder prepared by mixing and drying carbon-coated aluminum nitride powder and sintering aids and mixed evenly to obtain a slurry. The slurry is poured into a mold and pressed into a core blank. The core blank is then subjected to cold isostatic pressing treatment and debinding treatment, and finally sintered at a temperature of 1450 - 1600 °C to obtain the ceramic core material for precision casting of magnesium alloy.

[0008] The preparation method of the ceramic core material for precision casting of magnesium alloy of the present invention is realized according to the following steps:

[0009] 1. Mix aluminum nitride powder, fructose and absolute ethanol for ball milling wet mixing, where the mass ratio of aluminum nitride powder to fructose is 1:(0.4 - 0.7), to obtain a mixed slurry;

[0010] 2. Dry the mixed slurry, perform calcination treatment at a temperature of 150 - 180 °C, and grind to obtain carbon-coated aluminum nitride powder;

[0011] 3. Mix the carbon-coated aluminum nitride powder and sintering aids according to the mass ratio of 1:(0.01 - 0.055), add absolute ethanol, stir evenly and put it into a blast drying oven, and dry and volatilize the absolute ethanol at a temperature of 100 - 150 °C to obtain the dried mixed powder;

[0012] IV. Dissolve the binder in absolute ethanol to obtain a binder solution, mix the dried mixed powder with the binder solution evenly, and pour the mixture into a mold.

[0013] V. Place the mold filled with the slurry into a flat vulcanizing machine, perform pressing treatment under a pressure of 2 - 10 MPa, and obtain a core blank after demolding.

[0014] VI. Place the core blank into a cold isostatic press, maintain the pressure at 100 - 150 MPa for 60 - 90 s, and take out the compact after pressure relief.

[0015] VII. Perform drying treatment on the compact to obtain a green body of aluminum nitride ceramic.

[0016] VIII. Place the green body of aluminum nitride ceramic into a drying furnace, perform debinding treatment by heat preservation at a temperature of 400 - 500 °C, and obtain a ceramic core after debinding.

[0017] IX. Under the condition of vacuum or inert protective gas, sinter the ceramic core after debinding at a temperature of 1450 - 1600 °C for 1 - 3 h, and then cool it to room temperature with the furnace to obtain a ceramic core material for precision casting of magnesium alloy.

[0018] The sintering aid is composed of magnesium oxide, aluminum oxide, silicon dioxide and calcium oxide according to a mass ratio of 1:(1.8 - 2):(7 - 8):(4.5 - 5.5).

[0019] Compared with the traditional ceramic core for precision casting of magnesium alloy, the core material prepared by the present invention is composed of aluminum nitride, sintering aid, solvent and binder, and the mass ratio of aluminum nitride to sintering aid is 1:(0.01 - 0.055). The sintering aid components are magnesium oxide, aluminum oxide, silicon dioxide and calcium oxide, and the mass ratio is 1:(1.8 - 2):(7 - 8):(4.5 - 5.5) in turn. Mix aluminum nitride powder with fructose to obtain a slurry, and obtain carbon-coated aluminum nitride powder after drying, calcining and grinding. Then stir and mix the carbon-coated aluminum nitride powder with the sintering aid and ethanol solvent, and after evaporation and drying, add a mixed solution of binder and ethanol. The binder is polyvinylpyrrolidone, and the mass ratio of ethanol to binder is 1:(0.2 - 0.6). The forming method adopts pressing forming combined with cold isostatic pressing forming, and the formed blank is sintered at 1450 - 1600 °C under vacuum or inert gas protection to obtain a ceramic core material for precision casting of magnesium alloy.

[0020] The crystal structure of aluminum nitride is hexagonal close-packed. Aluminum nitride ceramics have a small thermal expansion coefficient, good high-temperature stability, do not react with magnesium alloys, and the strength changes little with increasing temperature. Therefore, magnesium alloy castings with high dimensional accuracy can be produced. Coating carbon on the surface of aluminum nitride can reduce the bonding force between grains after the core is sintered, improve the collapsibility of the core material, and make the core easier to remove; the introduction of carbon on the surface of aluminum nitride can also enhance the thermal conductivity of the core material. At the same time, the added sintering aids react with each other to form a low-temperature liquid phase, reducing the sintering temperature of the core material, so that the aluminum nitride ceramic core can be sintered below 1600 °C.

[0021] The present invention can realize the low-temperature sintering preparation of the density and strength of the ceramic core. The prepared ceramic core has unique advantages such as high thermal conductivity, no interfacial reaction with molten magnesium, good high-temperature stability, easy sintering, and easy core removal, providing a new choice for the ceramic core material of magnesium alloy complex castings with high dimensional accuracy and surface quality in precision casting. Description of the Drawings

[0022] Figure 1 It is a physical diagram of the ceramic core block for precision casting of magnesium alloy obtained in the example;

[0023] Figure 2 It is a scanning diagram of the fracture surface of the ceramic core for precision casting of magnesium alloy obtained in the example. Detailed Embodiments

[0024] Detailed Embodiment 1: The ceramic core material for precision casting of magnesium alloy in this embodiment is prepared from carbon-coated aluminum nitride powder, sintering aids, ethanol solvent and binder. The mass ratio of carbon-coated aluminum nitride powder to sintering aids is 1:(0.01 - 0.055); the carbon-coated aluminum nitride powder is obtained by drying, calcining and grinding the mixed slurry of fructose and aluminum nitride; the sintering aids are composed of magnesium oxide, aluminum oxide, silicon dioxide and calcium oxide according to the mass ratio of 1:(1.8 - 2):(7 - 8):(4.5 - 5.5); ethanol solvent and binder are added to the mixed powder prepared by mixing and drying carbon-coated aluminum nitride powder and sintering aids and mixed evenly to obtain a slurry. The slurry is poured into a mold and pressed into a core blank. The core blank is then subjected to cold isostatic pressing treatment and degumming treatment, and finally sintered at a temperature of 1450 - 1600 °C to obtain the ceramic core material for precision casting of magnesium alloy.

[0025] This embodiment can ensure the low-temperature sintering preparation of the density and strength of the ceramic core. The prepared aluminum nitride ceramic core has unique advantages such as high thermal conductivity, no interfacial reaction with molten magnesium, good high-temperature stability, easy sintering, and easy core removal, providing a new choice for the ceramic core material of magnesium alloy complex castings with high dimensional accuracy and surface quality in precision casting.

[0026] Embodiment 2: The difference between this embodiment and Embodiment 1 is that the particle size of the carbon-coated aluminum nitride powder is 8 - 20 μm, and the particle size of the sintering aid is 10 - 30 μm.

[0027] Embodiment 3: The preparation method of the ceramic core material for precision casting of magnesium alloy is implemented according to the following steps:

[0028] 1. Mix aluminum nitride powder, fructose and absolute ethanol and carry out ball milling wet mixing, where the mass ratio of aluminum nitride powder to fructose is 1:(0.4 - 0.7), to obtain a mixed slurry;

[0029] 2. Dry the mixed slurry, perform calcination treatment at a temperature of 150 - 180 °C, and obtain carbon-coated aluminum nitride powder after grinding;

[0030] 3. Mix the carbon-coated aluminum nitride powder and the sintering aid according to a mass ratio of 1:(0.01 - 0.055), add absolute ethanol, stir evenly and then put it into a blast drying oven, and dry and volatilize the absolute ethanol at a temperature of 100 - 150 °C to obtain the dried mixed powder;

[0031] 4. Dissolve the binder in absolute ethanol to obtain a binder solution, and mix the dried mixed powder with the binder solution evenly and pour it into a mold;

[0032] 5. Put the mold filled with the slurry into a flat vulcanizing machine, perform pressing treatment at a pressure of 2 - 10 MPa, and obtain a core blank after demolding;

[0033] 6. Put the core blank into a cold isostatic press, maintain the pressure at 100 - 150 MPa for 60 - 90 s, and take out the pressed blank after pressure relief;

[0034] 7. Perform drying treatment on the pressed blank to obtain a green aluminum nitride ceramic blank;

[0035] 8. Put the green aluminum nitride ceramic blank into a drying furnace, perform debinding treatment at a temperature of 400 - 500 °C for heat preservation to obtain a debound ceramic core;

[0036] 9. Under vacuum or inert protective gas conditions, perform sintering treatment on the debound ceramic core at a temperature of 1450 - 1600 °C for 1 - 3 h, and then cool it to room temperature with the furnace to obtain the ceramic core material for precision casting of magnesium alloy;

[0037] The sintering aid is composed of magnesium oxide, aluminum oxide, silicon dioxide and calcium oxide according to a mass ratio of 1:(1.8 - 2):(7 - 8):(4.5 - 5.5).

[0038] Embodiment 4: The difference between this embodiment and Embodiment 3 is that in Step 2, it is calcined at a temperature of 150 - 180°C for 3 - 4 hours.

[0039] Embodiment 5: The difference between this embodiment and Embodiment 3 or 4 is that in Step 4, the mass ratio of absolute ethanol to the binder is 1:(0.2 - 0.6).

[0040] Embodiment 6: The difference between this embodiment and any one of Embodiments 3 to 5 is that in Step 4, the binder is polyvinylpyrrolidone.

[0041] Embodiment 7: The difference between this embodiment and any one of Embodiments 3 to 6 is that in Step 5, it is pressed at a pressure of 2 - 10 MPa for 20 - 60 s.

[0042] Embodiment 8: The difference between this embodiment and any one of Embodiments 3 to 7 is that in Step 7, the green compact is first dried at 20 - 50°C for 48 - 72 h, and then placed in a forced - air drying oven and dried at 70 - 100°C for 24 - 72 h.

[0043] Embodiment 9: The difference between this embodiment and any one of Embodiments 3 to 8 is that in Step 8, it is heat - insulated and degummed at a temperature of 400 - 500°C for 2 - 5 h.

[0044] Embodiment 10: The difference between this embodiment and any one of Embodiments 3 to 9 is that in Step 9, it is heated at a heating rate of 5 - 10°C / min to 1450 - 1600°C.

[0045] Example 1: The preparation method of the ceramic core material for precision casting of magnesium alloy in this example is implemented according to the following steps:

[0046] I. Mix aluminum nitride powder (particle size of 10 μm), fructose and absolute ethanol and carry out ball - milling wet - mixing for 4 h, where the mass ratio of aluminum nitride powder to fructose is 1:0.6 to obtain a mixed slurry;

[0047] II. Place the mixed slurry in a vacuum drying oven and dry it at 65°C for 3 h, then calcine it at a temperature of 150°C for 3.5 h, and after grinding, obtain carbon - coated aluminum nitride powder;

[0048] III. Mix the carbon - coated aluminum nitride powder and the sintering aid according to a mass ratio of 1:0.053, add absolute ethanol, stir evenly, and then place it in a forced - air drying oven and dry at a temperature of 150°C to volatilize the absolute ethanol to obtain the dried mixed powder;

[0049] IV. Dissolve polyvinylpyrrolidone in absolute ethanol according to a mass ratio of 0.4:1 to obtain a binder solution, mix the dried mixed powder with the binder solution evenly and pour it into a mold;

[0050] V. Place the mold filled with the slurry into a flat vulcanizing machine and press it at a pressure of 8 MPa for 20 s. After opening the mold, a core blank is obtained;

[0051] VI. Place the core blank into a cold isostatic press and keep the pressure at 100 MPa for 60 s. After releasing the pressure, take out the compacted blank;

[0052] VII. Dry the compacted blank at 40 °C for 72 h, then place it in a forced-air drying oven and dry it at 75 °C for 24 h to obtain a green body of aluminum nitride ceramic;

[0053] VIII. Place the green body of aluminum nitride ceramic into a drying furnace and heat it to 500 °C at a rate of 5 °C / min, and keep it at this temperature for 2 h for degumming treatment to obtain a degummed ceramic core;

[0054] IX. Under vacuum conditions, heat it to 1500 °C at a rate of 10 °C / min, keep it at this temperature for 2 h for sintering treatment, and then cool it to room temperature with the furnace to obtain a ceramic core material for precision casting of magnesium alloy;

[0055] Among them, the sintering aid is composed of magnesium oxide, aluminum oxide, silicon dioxide (30 μm), and calcium oxide (15 μm) according to a mass ratio of 1:1.85:7.5:5.1.

[0056] Example 2: The preparation method of the ceramic core material for precision casting of magnesium alloy in this example is implemented according to the following steps:

[0057] I. Mix aluminum nitride powder (particle size of 10 μm), fructose, and absolute ethanol and carry out wet ball milling for 4 h. The mass ratio of aluminum nitride powder to fructose is 1:0.6 to obtain a mixed slurry;

[0058] II. Place the mixed slurry into a vacuum drying oven and dry it at 65 °C for 3 h, then calcine it at 150 °C for 3.5 h, and grind it to obtain carbon-coated aluminum nitride powder;

[0059] III. Mix the carbon-coated aluminum nitride powder and the sintering aid according to a mass ratio of 1:0.041, add absolute ethanol, stir evenly, and then place it in a forced-air drying oven and dry it at 150 °C to volatilize the absolute ethanol to obtain a dried mixed powder;

[0060] IV. Dissolve polyvinylpyrrolidone in absolute ethanol according to a mass ratio of 0.4:1 to obtain a binder solution, and mix the dried mixed powder with the binder solution evenly and pour it into a mold;

[0061] V. Place the mold filled with the slurry into a flat vulcanizing machine and press it at a pressure of 8 MPa for 20 s. After opening the mold, a core blank is obtained;

[0062] VI. Place the core blank into a cold isostatic press, maintain the pressure at 100 MPa for 60 s, and take out the compact after pressure relief;

[0063] VII. Dry the compact at 40 °C for 72 h, then place it in a forced-air drying oven and dry it at 75 °C for 24 h to obtain a green body of aluminum nitride ceramic;

[0064] VIII. Place the green body of aluminum nitride ceramic into a drying furnace, heat it to 500 °C at a rate of 5 °C / min, and hold for 2 h for debinding treatment to obtain a debound ceramic core;

[0065] IX. Under vacuum conditions, heat it to 1600 °C at a rate of 10 °C / min, hold for 2 h for sintering treatment, and then cool it to room temperature with the furnace to obtain a ceramic core material for precision casting of magnesium alloy;

[0066] Among them, the sintering aid is composed of magnesium oxide, aluminum oxide, silicon dioxide (30 μm), and calcium oxide (15 μm) according to a mass ratio of 1:1.85:7.5:5.1.

[0067] Example 3: The preparation method of the ceramic core material for precision casting of magnesium alloy in this example is implemented according to the following steps:

[0068] I. Mix aluminum nitride powder (particle size of 10 μm), fructose, and absolute ethanol and carry out ball milling and wet mixing for 4 h, where the mass ratio of aluminum nitride powder to fructose is 1:0.6 to obtain a mixed slurry;

[0069] II. Place the mixed slurry into a vacuum drying oven and dry it at 65 °C for 3 h, then calcine it at 150 °C for 3.5 h, and grind it to obtain carbon-coated aluminum nitride powder;

[0070] III. Mix the carbon-coated aluminum nitride powder and the sintering aid according to a mass ratio of 1:0.031, add absolute ethanol, stir evenly, and then place it in a forced-air drying oven to dry and volatilize the absolute ethanol at a temperature of 150 °C to obtain a dried mixed powder;

[0071] IV. Dissolve polyvinylpyrrolidone in absolute ethanol according to a mass ratio of 0.4:1 to obtain a binder solution, and mix the dried mixed powder with the binder solution evenly and pour it into a mold;

[0072] V. Place the mold filled with the slurry into a flat vulcanizing machine, press it at a pressure of 8 MPa for 20 s, and obtain a core blank after opening the mold;

[0073] VI. Place the core blank into a cold isostatic press, maintain the pressure at 100 MPa for 60 s, and take out the compact after pressure relief;

[0074] VII. Dry the green compact at 40°C for 72 h, place it in a forced-air drying oven, and dry it at 75°C for 24 h to obtain a green body of aluminum nitride ceramic;

[0075] VIII. Place the green body of aluminum nitride ceramic in a drying furnace, heat it to 500°C at a rate of 5°C / min, and hold for 2 h for debinding treatment to obtain a debound ceramic core;

[0076] IX. Under vacuum conditions, heat it to 1600°C at a rate of 10°C / min, hold for 2 h for sintering treatment, and then cool it to room temperature with the furnace to obtain a ceramic core material for precision casting of magnesium alloy;

[0077] Among them, the sintering aid is composed of magnesium oxide, aluminum oxide, silicon dioxide (30 μm), and calcium oxide (15 μm) according to a mass ratio of 1:1.85:7.5:5.1.

[0078] Example 4: The preparation method of the ceramic core material for precision casting of magnesium alloy in this example is implemented according to the following steps:

[0079] I. Mix aluminum nitride powder (particle size of 10 μm), fructose, and absolute ethanol and carry out ball milling and wet mixing for 4 h. The mass ratio of aluminum nitride powder to fructose is 1:0.6 to obtain a mixed slurry;

[0080] II. Place the mixed slurry in a vacuum drying oven and dry it at 65°C for 3 h, then calcine it at 150°C for 3.5 h, and grind it to obtain carbon-coated aluminum nitride powder;

[0081] III. Mix the carbon-coated aluminum nitride powder and the sintering aid according to a mass ratio of 1:0.02, add absolute ethanol, stir evenly, and place it in a forced-air drying oven to dry and volatilize the absolute ethanol at a temperature of 150°C to obtain a dried mixed powder;

[0082] IV. Dissolve polyvinylpyrrolidone in absolute ethanol according to a mass ratio of 0.4:1 to obtain a binder solution, and mix the dried mixed powder with the binder solution evenly and pour it into a mold;

[0083] V. Place the mold filled with the slurry in a flat vulcanizing machine, press it at a pressure of 8 MPa for 20 s, and after opening the mold, obtain a core blank;

[0084] VI. Place the core blank in a cold isostatic press, maintain the pressure at 100 MPa for 60 s, and take out the green compact after depressurization;

[0085] VII. Dry the green compact at 40°C for 72 h, place it in a forced-air drying oven, and dry it at 75°C for 24 h to obtain a green body of aluminum nitride ceramic;

[0086] VIII. Place the green body of aluminum nitride ceramic into a drying furnace, heat it to 500 °C at a rate of 5 °C / min, and hold for 2 h for debinding treatment to obtain a ceramic core after debinding;

[0087] IX. Under vacuum conditions, heat it to 1500 °C at a rate of 10 °C / min, hold for 3 h for sintering treatment, and then cool it to room temperature in the furnace to obtain a ceramic core material for precision casting of magnesium alloy;

[0088] The sintering aid is composed of magnesium oxide, aluminum oxide, silicon dioxide (30 μm), and calcium oxide (15 μm) in a mass ratio of 1:1.85:7.5:5.1.

[0089] Perform strength tests on the ceramic core materials for precision casting of magnesium alloy in Examples 1 to 4, and the three-point bending strength values are shown in Table 1 below.

[0090] Table 1 Three-point bending strength test results of Examples 1-4

[0091] Example 1 Example 2 Example 3 Example 4 Three-point bending strength (MPa) 31.86 34.2 32.26 28.7 。

Claims

1. Ceramic core material for magnesium alloy precision casting, characterized by The ceramic core material for magnesium alloy precision casting is prepared from carbon-coated aluminum nitride powder, a sintering aid, an ethanol solvent and a binder, wherein the mass ratio of the carbon-coated aluminum nitride powder to the sintering aid is 1:(0.01-0.055); the carbon-coated aluminum nitride powder is prepared by drying, calcining and grinding a mixed slurry of fructose and aluminum nitride; the sintering aid is composed of magnesium oxide, aluminum oxide, silicon dioxide and calcium oxide in a mass ratio of 1:(1.8-2):(7-8):(4.5-5.5); an ethanol solvent and a binder are added to a mixed powder prepared by mixing and drying the carbon-coated aluminum nitride powder and the sintering aid to obtain a slurry, the slurry is poured into a mold, and a core blank is pressed to form the core blank, the core blank is then subjected to a cold isostatic pressing treatment and a degumming treatment, and finally sintered at a temperature of 1450-1600° C. to obtain the ceramic core material for magnesium alloy precision casting.

2. The ceramic core material for magnesium alloy precision casting according to claim 1, characterized in that The particle size of the carbon-coated aluminum nitride powder is 8-20 μm, and the particle size of the sintering aid is 10-30 μm.

3. The method for preparing a ceramic core material for magnesium alloy precision casting according to claim 1, characterized in that The preparation method is achieved by the following steps:

1. Mix aluminum nitride powder, fructose and anhydrous ethanol and perform ball milling wet mixing, wherein the mass ratio of aluminum nitride powder to fructose is 1:(0.4-0.7), to obtain a mixed slurry; 2. Drying the mixed slurry, calcining it at 150-180°C, and grinding it to obtain carbon-coated aluminum nitride powder; 3. Mix the carbon-coated aluminum nitride powder and the sintering aid in a mass ratio of 1:(0.01-0.055), add anhydrous ethanol, stir evenly, put into a blast drying oven, dry and volatilize the anhydrous ethanol at a temperature of 100-150° C., and obtain a dried mixed powder; 4. Dissolve the binder in anhydrous ethanol to obtain a binder solution, mix the dried mixed powder and the binder solution evenly and pour them into a mold; 5. Place the mold containing the slurry into a flat vulcanizer and press it at a pressure of 2-10MPa to obtain a core blank after the mold is opened; 6. Place the core blank into a cold isostatic press, maintain the pressure at 100-150 MPa for 60-90 seconds, and take out the pressed blank after the pressure is released; 7. Drying the compact to obtain an aluminum nitride ceramic green compact; 8. Put the aluminum nitride ceramic green body into a drying furnace and perform degumming treatment at a temperature of 400-500° C. to obtain a degummed ceramic core; 9. Under vacuum or inert protective gas conditions, sinter the debonded ceramic core at 1450-1600° C. for 1-3 hours, and then cool it to room temperature with the furnace to obtain a ceramic core material for magnesium alloy precision casting; The sintering aid is composed of magnesium oxide, aluminum oxide, silicon dioxide and calcium oxide in a mass ratio of 1:(1.8-2):(7-8):(4.5-5.5).

4. The method for preparing a ceramic core material for magnesium alloy precision casting according to claim 3, characterized in that In step 2, the calcination treatment is carried out at a temperature of 150-180° C. for 3-4 hours.

5. The method for preparing a ceramic core material for magnesium alloy precision casting according to claim 3, characterized in that In step 4, the mass ratio of anhydrous ethanol to the binder is 1:(0.2-0.6).

6. The method for preparing a ceramic core material for magnesium alloy precision casting according to claim 3, characterized in that The binder described in step 4 is polyvinyl pyrrolidone.

7. The method for preparing a ceramic core material for magnesium alloy precision casting according to claim 3, characterized in that In step 5, the pressing process is performed at a pressure of 2-10 MPa for 20-60 seconds.

8. The method for preparing a ceramic core material for magnesium alloy precision casting according to claim 3, characterized in that In step seven, the pressed green body is first dried at 20-50°C for 48-72 hours, and then placed in a forced air drying oven and dried at 70-100°C for 24-72 hours.

9. The method for preparing a ceramic core material for magnesium alloy precision casting according to claim 3, characterized in that In step eight, the degumming treatment is carried out at a temperature of 400-500° C. for 2-5 hours.

10. The method for preparing a ceramic core material for magnesium alloy precision casting according to claim 3, characterized in that In step nine, the temperature is increased to 1450-1600° C. at a heating rate of 5-10° C. / min.

Images