Thin-walled part casting method, ceramic mold shell and method of making

Abstract

This application discloses a casting method for thin-walled parts, its ceramic mold shell, and a preparation method thereof. The preparation method includes: S1. uniformly coating a surface layer slurry onto the surface of the investment mold; S2. applying a surface layer of sand to the surface layer slurry; S3. uniformly coating a back layer slurry, wherein the back layer slurry is an Al2O3-SiO2 based slurry; S4. applying a back layer of sand to the back layer slurry, wherein the sand used for the back layer sand application includes calcium carbonate and mullite, with a mass ratio of calcium carbonate to mullite of 0.2-2:1. After casting, after water immersion or a high-temperature, high-humidity environment for static treatment, the calcium oxide particles inside the ceramic mold shell undergo hydration and expansion, thereby enabling the ceramic mold shell to spontaneously crack, significantly reducing its collapse strength and making the shell cleaning operation very easy.

Description

Technical Field

[0001] This application relates to the field of casting, and more specifically, to a method for casting thin-walled parts and a ceramic mold shell thereof and a method for preparing it. Background Technology

[0002] Ceramic shells are crucial in high-temperature alloy investment casting, and their properties are vital to the yield, quality, and dimensional accuracy of the castings. In terms of strength, the ceramic shell before casting needs high strength to prevent cracking during preparation, transportation, and handling. During casting, the ceramic shell needs high high-temperature strength to resist the stress, thermal stress, and deformation generated during the injection and solidification of the alloy solution. After casting, the ceramic shell needs low collapse strength to ensure smooth shell removal. Excessive collapse strength significantly increases the difficulty of shell removal, increases workload, and may even reduce the surface quality of the casting.

[0003] Currently, ceramic shells made from aluminosilicate refractory materials such as corundum, bauxite, mullite, kaolin, and quartz are bonded using silica sol or ethyl silicate, exhibiting high wet strength and strength after baking. During high-temperature casting, the shell's interior generates high-temperature strength through ceramic sintering, effectively meeting the strength requirements of alloy casting. However, due to the high-temperature ceramic sintering process, the collapse strength of the shell after casting is generally too high, resulting in poor collapsibility. Especially for large-sized, thin-walled, complex, and irregularly shaped castings, existing shells present problems such as difficulty in shell removal and the potential for deformation and surface damage in thin-walled areas of the casting during mechanical shell removal.

[0004] Therefore, how to cast thin-walled parts and successfully remove them from the shell is the technical problem that this application needs to solve. Summary of the Invention

[0005] In view of this, this application proposes a method for preparing a ceramic mold shell for casting thin-walled parts, so as to prepare a ceramic mold shell suitable for casting thin-walled parts.

[0006] This application provides a method for preparing a ceramic mold shell for casting thin-walled parts, wherein the preparation method includes: S1. uniformly coating a surface layer slurry on the surface of the investment mold; S2. applying a surface layer of sand to the surface layer slurry; S3. uniformly coating a back layer slurry on the surface of the investment mold after applying the surface layer of sand, wherein the back layer slurry is an Al2O3-SiO2 based slurry; S4. applying a back layer of sand to the back layer slurry, wherein the sand used for applying the back layer of sand includes calcium carbonate and mullite, and the mass ratio of calcium carbonate to mullite is 0.2-2:1.

[0007] Optionally: In step S2, the sand used for the surface coating includes calcium carbonate and mullite, with a mass ratio of calcium carbonate to mullite of 0.2-2:1; and / or, the particle size of calcium carbonate is 16-100 mesh, and the particle size of mullite is 16-100 mesh.

[0008] Optionally: the sand particle size used for the surface sand coating in step S2 is 80-100 mesh; and / or, steps S3 and S4 are repeated multiple times, with the sand particle size used for the first back layer sand coating being 30-60 mesh, and the sand particle size used for the other back layer sand coatings being 16-30 mesh.

[0009] Optionally, the backing slurry includes mullite powder, silica sol, dispersant, wetting agent, defoamer and mineralizer, and organic explosion-proof fiber.

[0010] Optionally: the mullite powder has a particle size distribution of 10μm~75μm; the amorphous SiO2 content in the silica sol is 20~30wt.%; the dispersant is carboxymethyl cellulose, and the wetting agent is fatty alcohol polyoxyethylene ether; the mineralizer includes at least one of calcined kaolin powder and light calcium carbonate, both with a particle size range of 0.5μm~10μm; the organic explosion-proof fiber is polypropylene fiber with a diameter of 10μm~50μm and a length of 200μm~3000μm; and / or, the mass ratio of mullite powder to silica sol is (1.5~2.5):1; the dispersant, wetting agent, and defoamer are all 0.05%~0.2% of the total mass of the backing slurry; the mass ratio of mineralizer to mullite powder is (0.05~0.3):1.

[0011] Optionally, the surface slurry comprises white fused alumina powder, silica sol, dispersant, wetting agent, defoamer, and mineralizer, wherein: the white fused alumina powder has a particle size distribution of 10μm~75μm and an Al2O3 content greater than 99%; the silica sol has an amorphous SiO2 content of 20wt.~30wt.%; the dispersant is carboxymethyl cellulose; the wetting agent is fatty alcohol polyoxyethylene ether; the mineralizer is light calcium carbonate with a purity greater than 95% and a particle size range of 0.5μm~10μm; and / or, the mass ratio of white fused alumina powder to silica sol is (2.5~4.0):1; the dispersant, wetting agent, and defoamer are all 0.05%~0.2% of the total mass of the surface slurry; and the mass ratio of mineralizer to white fused alumina powder is (0.02~0.2):1.

[0012] Optionally, the preparation method includes: S5. sealing the surface of the back layer after sand coating with a back layer slurry to obtain a ceramic shell wet blank; S6. dewaxing and firing the ceramic shell wet blank to obtain a ceramic shell.

[0013] Optionally, in step S6, the roasting temperature is 950℃-1050℃, and the roasting time is 3 hours-6 hours.

[0014] This application also provides a ceramic shell, wherein the ceramic shell is prepared using the preparation method of this application.

[0015] This application also provides a casting method for thin-walled parts, wherein the casting method includes: A1. casting thin-walled parts using the ceramic mold shell of this application; A2. immersing the cast ceramic mold shell in water or placing it in an environment with a temperature of 30℃-40℃ and a humidity of 60%-99% to allow the ceramic mold shell to self-collapse.

[0016] According to the technical solution of this application, calcium carbonate / mullite composite sand is used as the backing sand material for the ceramic shell. After high-temperature firing, the calcium carbonate particles in the coated ceramic shell can decompose in situ to form calcium oxide particles. At the casting temperature, the surface of the calcium oxide particles easily sinters with the Al2O3-SiO2 backing coating encapsulated within them, thus forming a strong ceramic bond, which improves the high-temperature strength of the shell and ensures smooth alloy casting. After casting, because the sintering effect only occurs on the surface of the calcium oxide particles, the interior of the particles remains pure calcium oxide. After water immersion or high-temperature and high-humidity environment treatment, the calcium oxide particles inside the ceramic shell undergo hydration expansion, which allows the ceramic shell to spontaneously crack, greatly reducing the collapse strength and making the shell cleaning operation very easy.

[0017] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application, and the illustrative embodiments and descriptions thereof are used to explain this application. In the drawings:

[0019] Figure 1 A flowchart illustrating a casting method for a thin-walled part according to one embodiment of this application;

[0020] Figure 2 The image shows a thin-walled part after it has been de-shelled, serving as a comparative example.

[0021] Figure 3 This is a picture of the thin-walled part after it has been uncoated, as shown in Example 1. Detailed Implementation

[0022] The technical solution of this application will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] According to one aspect of this application, a method for preparing a ceramic mold shell for casting thin-walled parts is provided, wherein the preparation method includes: S1. uniformly coating a surface layer slurry on the surface of the investment mold;

[0024] S2. Apply surface sand coating to the surface slurry; S3. Apply back layer slurry evenly to the surface of the casting mold after surface sand coating, wherein the back layer slurry is an Al2O3-SiO2 system slurry; S4. Apply back layer sand coating to the back layer slurry to obtain a ceramic shell wet blank, wherein the sand used for back layer sand coating includes calcium carbonate and mullite, and the mass ratio of calcium carbonate to mullite is 0.2-2:1.

[0025] According to another aspect of this application, a ceramic shell is provided, wherein the ceramic shell is prepared using the preparation method of this application.

[0026] This application also provides a casting method for thin-walled parts, wherein the casting method includes: A1. casting thin-walled parts using the ceramic mold shell of this application; A2. immersing the cast ceramic mold shell in water or placing it in an environment with a temperature of 30℃-40℃ and a humidity of 60%-99% to allow the ceramic mold shell to self-collapse.

[0027] In this application, calcium carbonate / mullite composite sand is used as the backing sand material for the ceramic shell. After high-temperature firing, the calcium carbonate particles in the coated ceramic shell decompose in situ to form calcium oxide particles. At the casting temperature, the surface of the calcium oxide particles easily sintersects with the Al2O3-SiO2 backing coating, forming a strong ceramic bond. This improves the high-temperature strength of the shell and ensures smooth alloy casting. After casting, because the sintering only occurs on the surface of the calcium oxide particles, the interior remains pure calcium oxide. After water immersion or high-temperature and high-humidity environment treatment, the calcium oxide particles inside the ceramic shell undergo hydration and expansion, allowing the ceramic shell to spontaneously crack. This significantly reduces the collapse strength, making shell cleaning very easy.

[0028] To further improve the self-collapse properties of the ceramic shell, preferably, calcium carbonate / mullite composite sand can also be used when applying sand to the surface layer. Specifically, in step S2, the sand used for applying sand to the surface layer may include calcium carbonate and mullite, with a mass ratio of calcium carbonate to mullite of 0.2-2:1.

[0029] In addition, the particle size of the sand can be selected as needed. Preferably, the particle size of calcium carbonate is 16-100 mesh, and the particle size of mullite is 16-100 mesh. Specifically, the sand used for the first layer of sand application can be smaller, and the sand used for the later layer of sand application can be larger. That is, the particle size of the sand used for the surface layer of sand application is smaller than that used for the back layer of sand application. Preferably, the particle size of the sand used for the surface layer of sand application in step S2 is 80-100 mesh. In addition, steps S3 and S4 can be repeated multiple times, that is, the back layer slurry is applied multiple times, and the back layer sand application is performed after each application, with the particle size of the sand used for the first layer of back layer sand application being smaller than that used for the later layer of back layer sand application. Preferably, the particle size of the sand used for the first layer of back layer sand application is 30-60 mesh, and the particle size of the sand used for the other layers of back layer sand application is 16-30 mesh.

[0030] Specifically, when applying the surface layer slurry, the mold can be immersed in the slurry to ensure even coating. This is done 1-2 times, with the viscosity controlled at 25s-35s. Then, during the surface layer sanding process, calcium carbonate / mullite composite sand is sprinkled onto the slurry, and the mixture is allowed to dry naturally for 3-12 hours to obtain the shell surface layer. Next, the back layer slurry is applied to the shell surface layer, with the viscosity controlled at 10s-15s. 30-60 mesh calcium carbonate / mullite composite sand is used for the initial back layer sanding, and the mixture is allowed to dry naturally for 3-8 hours to obtain the first back layer. The back layer coating process is repeated several times using 16-30 mesh calcium carbonate / mullite composite sand until the desired ceramic shell thickness is achieved. Finally, the back layer slurry is used for sealing and drying to obtain the wet ceramic shell blank.

[0031] In this application, the backing slurry can be selected with appropriate components to form an Al2O3-SiO2 based slurry. Specifically, the backing slurry may include mullite powder, silica sol, dispersant, wetting agent, defoamer, mineralizer, and organic explosion-proof fiber. The specific specifications and types of each component can be selected as needed. Preferably, the mullite powder has a particle size distribution of 10μm to 75μm; the silica sol has an amorphous SiO2 content of 20 to 30 wt.%; the dispersant may be carboxymethyl cellulose; the wetting agent may be fatty alcohol polyoxyethylene ether; the mineralizer may include at least one of calcined kaolin powder and light calcium carbonate, both with a particle size range of 0.5μm to 10μm; and the organic explosion-proof fiber is polypropylene fiber with a diameter of 10μm to 50μm and a length of 200μm to 3000μm. Additionally, a suitable heat-resistant and stable defoamer can be used, such as JC-5 high-efficiency defoamer.

[0032] Furthermore, the components of the backing slurry can be set in appropriate proportions to obtain the required strength after sintering. For example, the mass ratio of mullite powder to silica sol can be (1.5~2.5):1; the dispersant, wetting agent, and defoamer can all be 0.05%~0.2% of the total mass of the backing slurry; and the mass ratio of mineralizer to mullite powder can be (0.05~0.3):1.

[0033] Furthermore, because organic explosion-proof fibers are added to the backing slurry, they will burn off during dewaxing, leaving narrow, elongated pores inside the ceramic mold. On one hand, these pores provide channels for the release of free water, silica sol, and gases generated from the decomposition of organic additives and calcium carbonate in the slurry during the firing process of the ceramic mold, preventing the formation of cracks within the coating. On the other hand, these interconnected pores greatly improve the permeability of the ceramic mold, which is beneficial to improving the quality of alloy casting.

[0034] In the preparation of the backing slurry, silica sol is poured into a slurry tank. First, dispersant, wetting agent, defoamer and organic explosion-proof fiber are added in proportion and stirred for 0.5 hours to 1 hour. Then, mullite powder is slowly added under stirring conditions and stirred for 1 hour to 2 hours. Finally, mineralizer is added and stirring is continued for 1 hour to 2 hours to obtain the backing slurry. The viscosity of the backing slurry is controlled at 10s to 15s.

[0035] In this application, the surface layer slurry can be selected with appropriate components to achieve suitable high-temperature strength and chemical stability. For example, the surface layer slurry may include white fused alumina powder, silica sol, dispersant, wetting agent, defoamer, and mineralizer. The specific specifications and types of each component can be selected as needed. Preferably, the white fused alumina powder has a particle size distribution of 10μm~75μm and an Al2O3 content greater than 99%; the silica sol has an amorphous SiO2 content of 20wt.~30wt.%; the dispersant can be carboxymethyl cellulose; the wetting agent can be fatty alcohol polyoxyethylene ether; and the mineralizer can be light calcium carbonate with a purity greater than 95% and a particle size range of 0.5μm~10μm. Furthermore, a suitable heat-resistant and stable defoamer can be used, such as JC-5 high-efficiency defoamer.

[0036] Furthermore, the components of the surface slurry can be set in appropriate proportions to obtain the required strength after sintering. For example, the mass ratio of white fused alumina powder to silica sol can be (2.5~4.0):1; the dispersant, wetting agent, and defoamer can all be 0.05%~0.2% of the total mass of the surface slurry; the mass ratio of mineralizer to white fused alumina powder can be (0.02~0.2):1.

[0037] Furthermore, because the surface slurry contains light calcium carbonate, on the one hand, the calcium mineralizer ensures the chemical stability of the surface layer, solving the problem of reactions between other mineralizers such as silicon and active metals in the alloy solution. On the other hand, under the synergistic effect of the highly active CaO obtained from the decomposition of calcium carbonate and the small amount of amorphous SiO2 introduced by silica sol, the sintering performance of the alumina surface layer during the casting process is significantly improved, the surface layer bonding strength is greatly enhanced, and the problem of easy peeling of pure alumina surface layers is solved.

[0038] In preparing the surface slurry, the silica sol is poured into the slurry tank. First, the dispersant, wetting agent and defoamer are added in proportion and stirred for 5 to 15 minutes. Then, white corundum powder is slowly added under stirring conditions. After stirring for 1 to 2 hours, the mineralizer is added and stirring is continued for 3 to 5 hours to obtain the surface slurry. The viscosity of the surface slurry is controlled at 25s to 35s.

[0039] In addition, to obtain the ceramic shell, the preparation method may further include: S5. Sealing the surface after the back layer sand coating (i.e., after the last back layer sand coating) with a back layer slurry to obtain a wet ceramic shell blank; S6. Dewaxing and firing the wet ceramic shell blank to obtain the ceramic shell. Depending on the required high-temperature strength, appropriate dewaxing methods and firing process parameters can be selected. For example, the wet ceramic shell blank can be placed in a high-pressure steam dewaxing kettle for steam dewaxing, with the pressure controlled at 0.6MPa-0.7MPa, the temperature at 165℃-175℃, and the dewaxing time at 15-30 minutes. Preferably, in step S5, the firing temperature can be 950℃-1050℃, and the firing time is 3-6 hours.

[0040] The preparation and casting methods of this application are illustrated below through examples and comparative examples.

[0041] Example 1

[0042] (1) Preparation of composite sand

[0043] Three types of heavy calcium carbonate sand (calcium carbonate content > 95%) with particle sizes of 24 mesh, 60 mesh, and 100 mesh, and sintered mullite sand (M70) were prepared respectively. Calcium carbonate and mullite sand of the same particle size were added to a mixer in batches at a mass ratio of 0.5:1 and mixed for 30 minutes to obtain three types of calcium carbonate / mullite composite sand with particle sizes of 24 mesh, 60 mesh, and 100 mesh.

[0044] (2) Preparation of surface slurry

[0045] Weigh 100 parts of silica sol (brand name Shellbond 107, amorphous SiO2 content 20~30 wt.%) and pour it into a paint tank equipped with stirring blades. Turn on the mixer and add 0.5 parts of dispersant (hydroxymethyl cellulose), 0.3 parts of wetting agent (fatty alcohol polyoxyethylene ether), and 0.3 parts of JC-5 high-efficiency defoamer in sequence. After all additives are added and stirred for 15 minutes, slowly add 350 parts of white fused alumina powder (320 mesh, alumina content 99.6%) while stirring. After the white fused alumina powder is added and stirred for 1 hour, finally add 35 parts of light calcium carbonate (purity greater than 99%, particle size distribution 3μm~8μm) and continue stirring for 3 hours. Pour the mixture into a slurry tank for later use. During this period, use a viscosity cup to test the viscosity of the surface slurry. The viscosity should be controlled between 30s and 35s.

[0046] (3) Preparation of back layer slurry

[0047] Prepare 200 parts of M70 sintered mullite powder, 30 parts of calcined kaolin powder (mineralizer, particle size 0.5μm~10μm), 0.3 parts of hydroxymethyl cellulose (dispersant), 0.2 parts of fatty alcohol polyoxyethylene ether (wetting agent), 0.2 parts of JC-5 high-efficiency defoamer (defoamer), and 0.1 parts of polypropylene fiber (diameter 20μm~30μm, length 1mm~2mm). Add 100 parts of silica sol (brand name Shellbond 107, amorphous SiO2 content 20~30%). Pour the wt.% of the mixture into the paint bucket, turn on the mixer, and add the weighed dispersant, wetting agent, defoamer and organic explosion-proof fiber in sequence. After stirring for 1 hour, slowly add mullite powder under stirring conditions. After stirring for 1 hour, add calcined kaolin powder and continue stirring for 2 hours. Pour the mixture into the slurry bucket for later use. During this period, use a viscosity cup to test the viscosity of the back layer slurry. The viscosity of the back layer slurry should be controlled between 10s and 15s.

[0048] (4) Coated shell

[0049] Topcoat application: Using a robotic arm, grip the handle of the casting mold assembly and slowly immerse it into the prepared topcoat paint. After complete immersion in the slurry for 10-15 seconds, remove the casting mold from the slurry surface and perform slurry control and spraying operations to ensure the slurry is evenly coated on the casting mold surface. Then, transfer the assembly to a sandblasting machine for topcoat sanding. Evenly sprinkle the prepared 100-mesh calcium carbonate / mullite composite sand onto the topcoat paint on the casting mold surface for 10-15 seconds. Allow the sand-coated assembly to air dry for 3-10 hours to complete the topcoat preparation.

[0050] Back coating: First, the naturally dried module surface layer is sprayed to remove loose sand from the surface coating. Then, the module is immersed in the back coating for 2-3 seconds, after which it is removed from the slurry surface for slurry control and spraying. The module is then immersed in a sand-coating machine for sand coating, following the same procedure as the surface sand coating. After sand coating, the module is thoroughly dried under ventilated conditions for 3-10 hours. The back coating (back coating slurry) and sand coating process is repeated 5 times. After the 5th back coating sand coating, a final back coating and sealing process is performed, followed by drying. The first back coating sand is 60-mesh calcium carbonate / mullite composite sand, while the second to fifth back coatings are all 24-mesh calcium carbonate / mullite composite sand.

[0051] (5) Dewaxing and roasting

[0052] The dried shell blank is placed in a high-pressure steam dewaxing kettle for steam dewaxing. The pressure is controlled at 0.7 MPa, the temperature at 170℃, and the dewaxing time is 20 minutes.

[0053] The dewaxed ceramic shell is placed in an electric resistance furnace and fired in an air atmosphere at a temperature of 950℃~1050℃ for 4 to 6 hours. After firing, it is cooled to below 500℃ in the furnace and then removed.

[0054] (6) Casting thin-walled parts

[0055] Nickel-based high-temperature alloy hollow turbine blade material is cast using the ceramic shell from step (5) at a casting temperature of 1380-1450℃.

[0056] (7) Collapse

[0057] The ceramic mold and the cast part were immersed in water for 1 hour. The ceramic mold collapsed spontaneously. The image shows the cleaned thin-walled part. Figure 3 As shown.

[0058] Example 2

[0059] Using the method of Example 1,

[0060] (1) Preparation of composite sand

[0061] Specifically, three types of heavy calcium carbonate sand (calcium carbonate content > 95%) with particle sizes of 18 mesh, 60 mesh, and 100 mesh and sintered mullite sand (M70) are prepared respectively. Calcium carbonate and mullite sand are poured into the mixer at a mass ratio of 0.2:1.

[0062] (2) Preparation of surface slurry

[0063] The mixture contains 100 parts silica sol, 0.5 parts dispersant, 0.3 parts wetting agent, 0.3 parts JC-5 high-efficiency defoamer, 350 parts white corundum powder, and 35 parts light calcium carbonate.

[0064] (3) Preparation of back layer slurry

[0065] The mixture includes 250 parts of M70 sintered mullite powder, 10 parts of calcined kaolin powder, 10 parts of light calcium carbonate (kaolin powder and light calcium carbonate are both mineralizers with a particle size of 0.5μm~10μm), 0.4 parts of hydroxymethyl cellulose (dispersant), 0.3 parts of fatty alcohol polyoxyethylene ether (wetting agent), 0.3 parts of JC-5 high-efficiency defoamer (defoamer), 0.1 parts of polypropylene fiber (diameter of 30μm~50μm and length of 1000μm~3000μm), and 100 parts of silica sol.

[0066] (4) Coated shell

[0067] Among them, the back layer sand of the second to fifth layers is 18-mesh calcium carbonate / mullite composite sand.

[0068] (7) Collapse

[0069] Specifically, when the ceramic shell and the cast parts are placed together in a constant temperature and humidity workshop at 35°C and 80%, the ceramic shell will spontaneously collapse.

[0070] Example 3

[0071] Using the method of Example 1,

[0072] (1) Preparation of composite sand

[0073] Specifically, three types of heavy calcium carbonate sand (calcium carbonate content > 95%) with particle sizes of 16 mesh, 60 mesh, and 100 mesh and sintered mullite sand (M70) are prepared respectively. Calcium carbonate and mullite sand are poured into the mixing machine at a mass ratio of 2:1.

[0074] (2) Preparation of surface slurry

[0075] Add 100 parts of silica sol, 0.3 parts of dispersant, 0.3 parts of wetting agent, 0.3 parts of JC-5 high-efficiency defoamer, 150 parts of white corundum powder, and 45 parts of light calcium carbonate.

[0076] (3) Preparation of back layer slurry

[0077] The mixture includes 150 parts of M70 sintered mullite powder, 10 parts of light calcium carbonate (particle size 0.5μm~10μm), 0.3 parts of hydroxymethyl cellulose (dispersant), 0.2 parts of fatty alcohol polyoxyethylene ether (wetting agent), 0.2 parts of JC-5 high-efficiency defoamer (defoamer), 0.1 parts of polypropylene fiber (diameter 10μm~25μm, length 200μm~1500μm), and 100 parts of silica sol.

[0078] (5) Coated shell

[0079] Among them, the back layer sand of the second to fifth layers is all 16-mesh calcium carbonate / mullite composite sand.

[0080] Comparative Example

[0081] (1) Sand preparation

[0082] Three types of sintered mullite sand (M70) with particle sizes of 24 mesh, 60 mesh, and 100 mesh were prepared as backing and surface layer sanding materials.

[0083] (2) Prepare the surface slurry

[0084] Weigh 100 parts of silica sol (brand name Shellbond 107, amorphous SiO2 content 20wt.%~30wt.%) and pour it into a paint tank equipped with stirring blades. Turn on the mixer and add 0.5 parts of dispersant (hydroxymethyl cellulose), 0.3 parts of wetting agent (fatty alcohol polyoxyethylene ether), and 0.3 parts of JC-5 high-efficiency defoamer in sequence. After all additives are added and stirred for 15 minutes, slowly add 350 parts of white corundum powder (320 mesh, alumina content 99.6%) while stirring. After the white corundum powder is added and stirred for 1 hour, finally add 35 parts of calcined kaolin powder (particle size distribution 0.5μm~10μm) and continue stirring for 3 hours. Pour the mixture into a slurry tank for later use. During this period, use a viscosity cup to test the viscosity of the surface slurry. The viscosity should be controlled between 30s and 35s.

[0085] (3) Prepare the back layer slurry

[0086] Prepare 180 parts of M70 sintered mullite powder, 0.3 parts of hydroxymethyl cellulose (dispersant), 0.2 parts of fatty alcohol polyoxyethylene ether (wetting agent), and 0.2 parts of JC-5 high-efficiency defoamer (defoamer). Pour 100 parts of silica sol (brand name Shellbond107, amorphous SiO2 content 20wt.%~30wt.%) into the coating bucket. Turn on the mixer and add the weighed dispersant, wetting agent and defoamer in sequence. After stirring for 1 hour, slowly add mullite powder under stirring conditions. After stirring for 1 hour, add calcined kaolin powder and continue stirring for 2 hours. Pour into the slurry bucket for later use. During this period, use a viscosity cup to test the viscosity of the back layer slurry. The viscosity of the back layer slurry should be controlled between 10s and 15s.

[0087] (4) Coated shell

[0088] Topcoat application: Using a robotic arm, grip the handle of the casting mold assembly and slowly immerse it into the prepared topcoat paint. After complete immersion in the slurry for 10-15 seconds, remove the casting mold from the slurry surface and perform slurry control and spraying operations to ensure the slurry is evenly coated on the casting mold surface. Then, transfer the assembly to a sandblasting machine for topcoat sanding. Evenly sprinkle the prepared sand onto the topcoat paint on the casting mold surface for 10-15 seconds. Allow the sand-coated assembly to air dry for 3-10 hours to complete the topcoat preparation.

[0089] Back coating: First, spray the naturally dried module surface layer to remove loose sand from the surface coating. Then, immerse the module in the back coating for 2-3 seconds, then remove it from the slurry surface for slurry control and spraying. Next, immerse the module in a sandblasting machine for sand coating, following the same procedure as the surface sand coating. After sand coating, allow it to dry thoroughly under ventilation for 3-10 hours. Repeat the back coating (back coating slurry) and sand coating process 5 times. After the 5th back sand coating, perform another back coating, then allow it to dry.

[0090] (5) Dewaxing and roasting

[0091] The dried shell blank is placed in a high-pressure steam dewaxing kettle for steam dewaxing. The pressure is controlled at 0.7 MPa, the temperature at 170℃, and the dewaxing time is 20 minutes.

[0092] The dewaxed ceramic shell is placed in an electric resistance furnace and fired in an air atmosphere at a temperature of 950℃~1050℃ for 4 to 6 hours. After firing, it is cooled to below 500℃ in the furnace and then removed.

[0093] (6) Casting thin-walled parts

[0094] The nickel-based high-temperature alloy hollow turbine blade material was cast using the ceramic mold shell from step (5) at a casting temperature of 1380℃-1450℃. The image of the cleaned thin-walled part is shown below. Figure 2 As shown.

[0095] The wet strength, room temperature strength after baking, high temperature strength at 1400℃, and room temperature strength after casting at 1450℃ of the ceramic shells prepared in Examples 1-3 and the comparative examples are shown in Table 1 below.

[0096] Among them, the wet strength of the shell refers to the strength of the shell after dewaxing; the room temperature strength after baking refers to the strength of the shell after cooling to room temperature after firing; the high temperature strength at 1400℃ refers to the strength of the prepared ceramic shell at 1400℃; and the room temperature strength after casting at 1450℃ refers to the strength of the ceramic shell after casting at 1450℃ and cooling to room temperature.

[0097] Table 1

[0098]

[0099] As shown in Table 1, the ceramic shells of Examples 1-3 exhibit good strength at high temperatures, making them suitable for high-temperature casting. However, their strength at room temperature after casting is relatively low (all below 12 MPa), making them prone to crumbling. In contrast, the comparative examples show higher strength at room temperature after casting, but poor resilience and are difficult to clean.

[0100] from Figure 2 and Figure 3 The comparison also shows that in Example 1, the ceramic shell self-collapses, resulting in a clean and powder-free part surface with an intact part surface. In contrast, the part in the comparative example still has ceramic shell powder attached to it after cleaning, and the part surface has surface defects (such as scratches) caused by insufficient clearance of the ceramic shell.

[0101] The preferred embodiments of this application have been described in detail above. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0102] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not describe the various possible combinations separately.

[0103] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, they should also be regarded as the content disclosed in this application.

Claims

1. A method for preparing a ceramic mold shell for casting thin-walled parts, characterized in that, The preparation method includes: S1. A topcoat slurry is uniformly applied to the surface of the investment mold. The topcoat slurry comprises white fused alumina powder, silica sol, dispersant, wetting agent, defoamer, and mineralizer. The mineralizer is light calcium carbonate. The mass ratio of white fused alumina powder to silica sol is (2.5~4.0):

1. The dispersant, wetting agent, and defoamer are all 0.05%~0.2% of the total mass of the topcoat slurry. The mass ratio of mineralizer to white fused alumina powder is (0.02~0.2):

1. S2. Apply a surface layer of sand to the surface layer slurry. The sand used for the surface layer sand application includes calcium carbonate and mullite, and the mass ratio of calcium carbonate to mullite is 0.2-2:

1. S3. Uniformly coat the surface of the casting mold after the surface sand is applied with a backing slurry. The backing slurry is an Al2O3-SiO2 based slurry, comprising mullite powder, silica sol, dispersant, wetting agent, defoamer, mineralizer, and organic explosion-proof fiber. The mineralizer comprises at least one of calcined kaolin powder and light calcium carbonate. The mass ratio of mullite powder to silica sol is (1.5~2.5):

1. The dispersant, wetting agent, and defoamer are each 0.05%~0.2% of the total mass of the backing slurry. The mass ratio of mineralizer to mullite powder is (0.05~0.3):

1. S4. Apply backing sand to the backing slurry. The sand used for backing sand application includes calcium carbonate and mullite, and the mass ratio of calcium carbonate to mullite is 0.2-2:

1.

2. The method for preparing a ceramic mold shell for casting thin-walled parts according to claim 1, characterized in that: In step S2, the particle size of calcium carbonate is 16-100 mesh, and the particle size of mullite is 16-100 mesh.

3. The method for preparing ceramic mold shells for casting thin-walled parts according to claim 2, characterized in that: In step S2, the sand used for the surface coating has a particle size of 80-100 mesh; and / or, Repeat steps S3 and S4 multiple times. The sand particle size used for the first back layer sand coating is 30-60 mesh, and the sand particle size used for the other back layer sand coatings is 16-30 mesh.

4. The method for preparing a ceramic mold shell for casting thin-walled parts according to claim 1, characterized in that: In step S3, the mullite powder has a particle size distribution of 10μm to 75μm; the amorphous SiO2 content in the silica sol is 20 to 30 wt.%; the dispersant is carboxymethyl cellulose, and the wetting agent is fatty alcohol polyoxyethylene ether; the particle size range of the calcined kaolin powder and light calcium carbonate is 0.5μm to 10μm; the organic explosion-proof fiber is polypropylene fiber with a diameter of 10μm to 50μm and a length of 200μm to 3000μm.

5. The method for preparing a ceramic mold shell for casting thin-walled parts according to any one of claims 1, characterized in that, In step S1, the white corundum powder has a particle size distribution of 10μm~75μm and an Al2O3 content greater than 99%; the silica sol has an amorphous SiO2 content of 20wt.~30wt.%; the dispersant is carboxymethyl cellulose and the wetting agent is fatty alcohol polyoxyethylene ether; the light calcium carbonate has a purity greater than 95% and a particle size range of 0.5μm~10μm.

6. The method for preparing a ceramic mold shell for casting thin-walled parts according to any one of claims 1-4, characterized in that, The preparation method includes: S5. Seal the surface of the back layer after sand coating with back layer slurry to obtain a ceramic shell wet blank; S6. Dewax and fire the ceramic shell wet blank to obtain a ceramic shell.

7. The method for preparing a ceramic mold shell for casting thin-walled parts according to claim 6, characterized in that, In step S6, the roasting temperature is 950℃-1050℃, and the roasting time is 3 hours-6 hours.

8. A ceramic shell, characterized in that, The ceramic shell is prepared using the preparation method described in any one of claims 1-7.

9. A casting method for thin-walled parts, characterized in that, The casting method includes: A1. Casting thin-walled parts using the ceramic mold shell as described in claim 8; A2. Immerse the cast ceramic shell in water or place it in an environment with a temperature of 30℃-40℃ and a humidity of 60%-99% to allow the ceramic shell to self-collapse.

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