Preparation method of large-size ceramic core for titanium alloy casting

Abstract

According to the preparation method of the large-size ceramic core for titanium alloy casting, the inner cavity structure of the metal mold is designed through reverse modeling of the target ceramic core, the wax coating thickness of the surface of the metal mold is accurately controlled, a stable and accurate mold inner cavity is provided for subsequent ceramic core forming, the size precision of a wax mold is guaranteed, and the production efficiency is improved. The size precision of the prepared ceramic core reaches CT3-CT6; by means of the design that a metal mold is subjected to block wax dipping, a splicing face is cleaned, the heating temperature of the metal mold is controlled to range from 80 DEG C to 100 DEG C, heat preservation is conducted for not less than 4 h, and then demolding is conducted, the metal mold and the ceramic core are separated more easily, and compared with the situation that adhesion is prone to occurring in traditional high-temperature demolding and damage is prone to occurring in mechanical demolding, the demolding yield of the method is larger than or equal to 98%; when the ceramic core is prepared, specific slurry and sand are used for different layers, the drying environments of the layers are different, the structure of the ceramic core is more stable, and the surface defect rate is smaller than or equal to 7%.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy casting, and in particular, to a method for preparing a large-sized ceramic core for titanium alloy casting. Background Art

[0002] The commonly used preparation techniques for ceramic cores mainly include the grouting molding method, the hot pressing injection molding method, and the isostatic pressing molding method, and their respective characteristics are as follows: The grouting molding method uses a mold to grout and form a ceramic core, and after drying, it is demolded and sintered to obtain a finished ceramic core, which is suitable for the preparation of ceramic cores with simple structures, such as ceramic filter cores, etc.; The hot pressing injection molding method uses a mold to hot press and inject, and after cooling and demolding, high-temperature dewaxing, and sintering, a finished ceramic core is obtained, which is suitable for medium-sized and medium-complexity ceramic cores, such as turbine blades of aeroengines; The isostatic pressing molding method uses a rubber mold to obtain a finished ceramic core through high-pressure isostatic pressing molding, demolding, and sintering, which is suitable for the preparation of high-density and high-strength ceramic cores, such as high-temperature resistant stoves.

[0003] For the production of large-sized ceramic cores, the grouting molding method is generally used, that is, reverse grouting in a wax mold with an open mold is the current mainstream process. However, when using this process to prepare large-sized ceramic cores, there are problems such as wax mold deformation and difficult-to-guarantee dimensional accuracy. There are also publicly disclosed patents showing that ceramic cores are prepared by directly grouting and sanding multiple layers into a mold, but this is suitable for the preparation of ceramic cores with simple structures and no complex shapes. For large-sized ceramic cores, there are problems such as low demolding efficiency, easy adhesion between the mold and the ceramic core in a high-temperature demolding environment, easy breakage of the ceramic core by traditional mechanical demolding, and short service life of the mold.

[0004] Chinese Patent Application with Publication No. CN118237538A discloses a sand mold-ceramic composite mold for titanium or titanium alloy casting, a casting method and applications thereof, which need to go through the preparation of a metal mold, molding a wax mold by metal mold pressing, preparing a green ceramic core, and sintering to obtain a mature ceramic core. Not only is the shrinkage process difficult to control, but there are also problems such as shrinkage deformation, self-weight deformation, and difficult removal of the wax mold. At the same time, since a wax injection machine is required for the preparation of the wax mold, the specifications of the wax mold are limited, and it cannot be used for large and complex castings. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for preparing a large-sized ceramic core for titanium alloy casting to solve the problems of low demolding efficiency, adhesion between the metal mold and the ceramic core, and poor dimensional accuracy in the prior art when preparing large-sized ceramic cores.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A method for preparing a large-sized ceramic core for titanium alloy casting, comprising the following steps:

[0008] S1: Mold design. Reverse model the target ceramic core and design the inner cavity structure of the metal mold.

[0009] S2: Wax coating inside the mold. Immerse the metal mold in wax in sections. After uniform coating, lift it to drain the wax. When there are no obvious wax drops flowing down, cool it down. The cooling temperature is 10 - 18°C. After cooling, the surface of the metal mold is evenly coated with wax, and the wax layer thickness is 0.15 - 0.2 mm.

[0010] S3: Mold assembly. Clean the wax layer on the mating surface of the metal mold and assemble the individual blocks of the metal mold together.

[0011] S4: Prepare the ceramic core. Coat a high-viscosity surface layer slurry on the wax layer surface of the metal mold, then sprinkle surface layer sand on the surface of the high-viscosity surface layer slurry. After drying, form a surface layer. Then prepare a transition layer on the surface of the surface layer. The preparation process of the transition layer is the same as that of the surface layer. Then coat a low-viscosity slurry on the surface of the transition layer, sprinkle bauxite sand on the surface of the low-viscosity slurry, and after drying, form a reinforcement layer. Then coat a low-viscosity slurry on the surface of the reinforcement layer and dry it to form a sealant layer.

[0012] S5: Demolding. Heat the metal mold to a temperature of 80 - 100°C and keep it warm for no less than 4 hours, then separate the metal mold from the ceramic core.

[0013] S6: Roasting. Heat it at a rate of 5 - 8°C / min to 850 - 950°C and keep it warm for 120 - 240 minutes. Then, heat it at a rate of 10 - 15°C / min to 1050°C and keep it warm for 240 - 360 minutes.

[0014] S7: Obtain the ceramic core blank.

[0015] This setting improves the dimensional accuracy of the wax mold, the demolding qualified rate, and reduces the surface defect rate.

[0016] Further, in step S2, before wax dipping, preheat the metal mold. The preheating temperature is 80 - 100°C, and the preheating time is not less than 2 hours. When wax dipping, the surface temperature of the metal mold is not less than 65°C, and the wax dipping time is 3 - 5 s.

[0017] This process is applicable to batch operations of more than ten metal molds, and can realize simultaneous preheating and heat preservation of multiple metal molds and rapid wax dipping in a production line, with high efficiency.

[0018] Further, in step S2, immerse a single metal mold in wax liquid at 80 - 100°C, and the heat preservation time in the wax liquid is not less than 180 s.

[0019] This process is applicable to the wax dipping of a small quantity of single-piece metal molds. Its advantages are a short process flow, high efficiency, and low production costs.

[0020] Furthermore, in step S4, the high-viscosity surface layer slurry is prepared from yttrium oxide powder with a mesh size of 200 - 400 and neutral silica sol, at a weight ratio of 2.5:1 - 5.5:1. The hanging slice viscosity of the high-viscosity surface layer slurry is 18 - 25, and the surface layer sand is zirconia sand with a mesh size of 40 - 100.

[0021] This setting enables the slurry to have good bonding properties, ensuring that the yttrium oxide powder and the neutral silica sol are fully mixed and tightly bonded together. At the same time, it enables the slurry to firmly bond with the wax layer of the metal mold and the surface layer sand, ensuring the stability of each layer structure of the ceramic core and avoiding problems such as delamination and peeling.

[0022] Furthermore, in step S4, the low-viscosity slurry is prepared from bauxite powder with a mesh size of 100 - 300 and silica sol, at a weight ratio of 5:1 - 7:1. The hanging slice viscosity of the low-viscosity slurry is 6 - 15, and the particle size of the bauxite sand is 30 - 60 mesh.

[0023] This setting enhances the bonding force between the layers, ensuring the stability of the overall structure of the ceramic core.

[0024] Furthermore, in step S4, the process preparation environments of the surface layer and the transition layer are the same, with a temperature of 23 ± 2°C, a humidity of 65 - 85%, and a drying time of not less than 4h; the process preparation environments of the reinforcement layer and the sealant layer are the same, with a temperature of 23 ± 2°C, a humidity of 45 - 55%, and a drying time of not less than 6h.

[0025] This setting enables the moisture in the high-viscosity surface layer slurry to volatilize slowly and evenly, allowing the yttrium oxide powder and the neutral silica sol to fully react and solidify, and tightly bond with the surface layer sand. The formed surface layer and transition layer have a uniform and dense structure, and can reduce defects such as pores and cracks, improving the surface quality and bonding strength.

[0026] The relatively low humidity and long drying time are beneficial for the better solidification and shrinkage of the bauxite powder and silica sol in the low-viscosity slurry, enhancing the strength of the reinforcement layer and the sealant layer. At the same time, it enables the bauxite sand to fully bond with the slurry, improving the overall structural stability of the ceramic core.

[0027] Further, in step S6, before baking, check the micropores, cracks and local non-uniform defects on the surface of the ceramic core, and coat the micropores, cracks and local non-uniform defects on the surface of the ceramic core with a repair slurry. The repair slurry is prepared from yttrium oxide powder with a mesh size of 200-400 and neutral silica sol in a weight ratio of 3.5:1-5.5:1. The hanging viscosity of the repair slurry is 22-28, and it is polished flat after natural drying.

[0028] Checking and repairing micropores, cracks and local non-uniform defects can effectively improve the finished product quality of the ceramic core and make the final product more in line with the use requirements.

[0029] Further, in step S1, the inner cavity structure of the metal mold is complementary to the outer shape of the target ceramic core. Except for the inner cavity structure, the rest of the metal mold is set as a hollow structure to reduce the weight of the metal mold.

[0030] Setting the rest of the metal mold except the inner cavity structure as a hollow structure greatly reduces the weight of the mold on the premise of not affecting the mold strength and service performance. On the one hand, it reduces the usage amount of metal materials and the manufacturing cost of the mold. On the other hand, the lighter mold is more convenient in the processes of handling, installation and operation, can improve production efficiency, and reduce equipment energy consumption at the same time.

[0031] Compared with the prior art, the preparation method of the large-size ceramic core for titanium alloy casting of the present invention has the following advantages:

[0032] 1) The dimensional accuracy is significantly improved;

[0033] 2) The demolding qualification rate is greatly improved;

[0034] 3) The surface defect rate is significantly reduced. Specific embodiments

[0035] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0036] Embodiment 1

[0037] This embodiment provides a preparation method of a large-size ceramic core for titanium alloy casting, including the following steps:

[0038] S1: Mold design, perform reverse modeling on the target ceramic core and design the inner cavity structure of the metal mold;

[0039] S2: Wax the inner cavity of the mold. Immerse the metal mold in wax in parts. After uniform immersion, lift it to drain the wax. When there are no obvious wax drops flowing down, cool it down. The cooling temperature is 10 - 18°C. After cooling, the surface of the metal mold is uniformly waxed, and the wax layer thickness is 0.15 - 0.2 mm.

[0040] S3: Assemble the mold. Clean the wax layer on the mating surface of the metal mold, and assemble the various parts of the metal mold together.

[0041] S4: Prepare the ceramic core. Coat a high-viscosity surface layer slurry on the wax layer surface of the metal mold, then sprinkle surface layer sand on the surface of the high-viscosity surface layer slurry. After drying, a surface layer is formed. Then, prepare a transition layer on the surface of the surface layer. The preparation process of the transition layer is the same as that of the surface layer. Then, coat a low-viscosity slurry on the surface of the transition layer, sprinkle bauxite sand on the surface of the low-viscosity slurry, and after drying, a reinforcement layer is formed. Then, coat a low-viscosity slurry on the surface of the reinforcement layer and dry it to form a sealant layer.

[0042] S5: Demold. Heat the metal mold to a temperature of 80 - 100°C, and the holding time is not less than 4 h. Then, separate the metal mold from the ceramic core.

[0043] S6: Bake. Heat it at a rate of 5 - 8°C / min to 850 - 950°C, hold for 120 - 240 min. Then, heat it at a rate of 10 - 15°C / min to 1050°C and hold for 240 - 360 min.

[0044] S7: Obtain the ceramic core blank.

[0045] Specifically, by reverse modeling the inner cavity structure of the metal mold for the target ceramic core and precisely controlling the wax coating thickness on the surface of the metal mold, a stable and precise mold inner cavity is provided for the subsequent ceramic core forming, ensuring the dimensional accuracy of the wax mold and making the dimensional accuracy of the prepared ceramic core reach CT3 - CT6, much higher than CT10 - CT12 of the traditional grouting forming method.

[0046] By designing to immerse the metal mold in wax in parts, clean the mating surface, and control the heating temperature of the metal mold at 80 - 100°C and demold after holding for not less than 4 h, it is easier to separate the metal mold from the ceramic core. Compared with the traditional high-temperature demolding that is prone to adhesion and mechanical demolding that is prone to breakage, the demolding qualification rate of this method is ≥98%, while that of the traditional grouting forming method is ≤62%.

[0047] When preparing the ceramic core, specific slurries and sands are used for different layers, and the drying environment for each layer is different. This design can make the structure of the ceramic core more stable, and the surface defect rate is ≤7%, while that of the traditional method is ≥85%.

[0048] Preferably, in step S5, the metal mold is placed in a resistance furnace for heating. After heat preservation, the metal mold is taken out, the fixed connection pins of the metal mold are disassembled, and then a thimble mechanism is used to separate the mold from the ceramic core.

[0049] As a preferred example of the present application, in step S2, before dipping in wax, the metal mold is preheated to a temperature of 80 - 100°C for at least 2 hours. When dipping in wax, the surface temperature of the metal mold is not lower than 65°C, and the dipping time is 3 - 5 seconds.

[0050] Specifically, preheating makes the temperature of the metal mold uniform. When the surface temperature is not lower than 65°C during wax dipping, the wax liquid can better infiltrate the surface of the mold. In this way, within a short time of 3 - 5 seconds of wax dipping, the wax liquid can be evenly attached to the surface of the mold. After cooling, a wax layer with a uniform thickness is formed, providing a stable basis for the subsequent preparation of the ceramic core, helping to improve the dimensional accuracy and surface quality of the ceramic core. This process is applicable to batch operations of more than ten metal molds, and can realize simultaneous preheating and heat preservation of multiple metal molds and rapid wax dipping in a production line, with high efficiency.

[0051] Preferably, the metal mold is placed in a resistance furnace for preheating.

[0052] As a preferred example of the present application, in step S2, a single metal mold is immersed in wax liquid at 80 - 100°C, and the heat preservation time in the wax liquid is not less than 180 seconds.

[0053] Specifically, the wax liquid temperature of 80 - 100°C enables the wax liquid to have good fluidity. A single mold is immersed in it and heat-preserved for more than 180 seconds, which can ensure that the wax liquid evenly wraps the surface of the mold, forming a wax layer with a uniform thickness, providing a guarantee for the subsequent preparation of high-precision ceramic cores. This process is applicable to wax dipping of a small number of single-piece metal molds. The advantages are short process, high efficiency, and low production cost.

[0054] As a preferred example of the present application, in step S4, the high-viscosity surface layer slurry is prepared from yttrium oxide powder with 200 - 400 meshes and neutral silica sol according to a weight ratio of 2.5:1 - 5.5:1. The hanging viscosity of the high-viscosity surface layer slurry is 18 - 25, and the surface layer sand is zirconia sand with 40 - 100 meshes.

[0055] Specifically, the yttrium oxide powder with 200 - 400 meshes has good high-temperature resistance. During the titanium alloy casting process, it can withstand high-temperature environments, ensuring the structural stability of the ceramic core at high temperatures and preventing the ceramic core from deforming due to high temperatures during the casting process.

[0056] The neutral silica sol and yttrium oxide powder are formulated in a weight ratio of 2.5:1 - 5.5:1, which can endow the slurry with good bonding properties. The viscosity of the high-viscosity surface layer slurry for hanging slices is 18 - 25, which can ensure that the yttrium oxide powder and the neutral silica sol are fully mixed and tightly bonded together. At the same time, the slurry can be firmly bonded to the wax layer of the metal mold and the surface layer sand, ensuring the stability of the structures of each layer of the ceramic core and avoiding problems such as delamination and shedding.

[0057] The zirconia sand with a particle size of 40 - 100 meshes is used as the surface layer sand. The finer particle size can make the surface of the ceramic core smoother, reduce surface defects and improve the surface quality.

[0058] Preferably, the surface layer sand can also be yttrium oxide sand with a particle size of 40 - 100 meshes.

[0059] As a preferred example of the present application, in step S4, the low-viscosity slurry is prepared from bauxite powder with a particle size of 100 - 300 meshes and silica sol in a weight ratio of 5:1 - 7:1. The viscosity of the low-viscosity slurry for hanging slices is 6 - 15, and the particle size of the bauxite sand is 30 - 60 meshes.

[0060] Specifically, the viscosity of the low-viscosity slurry for hanging slices is 6 - 15, and it has good fluidity. When coating, it can cover the surface of the transition layer more smoothly. Moreover, the bauxite powder with a particle size of 100 - 300 meshes and silica sol are formulated in a weight ratio of 5:1 - 7:1, which can make the slurry better penetrate into the lower layer structure, enhance the bonding force between each layer, and ensure the stability of the overall structure of the ceramic core.

[0061] The low-viscosity slurry formed by formulating bauxite powder with a particle size of 100 - 300 meshes and silica sol, combined with bauxite sand with a particle size of 30 - 60 meshes, can effectively improve the overall strength of the ceramic core after forming the reinforcement layer and the sealant layer, making it not easily damaged during subsequent processing and use.

[0062] As a preferred example of the present application, in step S4, the technological preparation environments of the surface layer and the transition layer are the same, with a temperature of 23 ± 2 °C, a humidity of 65 - 85%, and a drying time of not less than 4 h; the technological preparation environments of the reinforcement layer and the sealant layer are the same, with a temperature of 23 ± 2 °C, a humidity of 45 - 55%, and a drying time of not less than 6 h.

[0063] Specifically, this setting can make the water in the high-viscosity surface layer slurry volatilize slowly and evenly, enabling the yttrium oxide powder and the neutral silica sol to fully react and solidify, and tightly bond with the surface layer sand. The formed surface layer and transition layer structures are uniform and dense, and can reduce defects such as pores and cracks, improving the surface quality and bonding strength.

[0064] Relatively low humidity and a long drying time are conducive to better curing and shrinkage of bauxite powder and silica sol in the low-viscosity slurry, enhancing the strength of the reinforcement layer and the sealant layer. At the same time, it can enable the bauxite sand to fully bond with the slurry, improving the overall structural stability of the ceramic core.

[0065] As a preferred example of the present application, in step S6, before roasting, the micropores, cracks, and local non-uniform defects on the surface of the ceramic core are inspected, and the micropores, cracks, and local non-uniform defects on the surface of the ceramic core are coated with a repair slurry. Among them, the repair slurry is prepared from yttrium oxide powder with a mesh size of 200 - 400 and neutral silica sol according to a weight ratio of 3.5:1 - 5.5:1. The hanging slice viscosity of the repair slurry is 22 - 28, and it is polished flat after natural drying.

[0066] Specifically, inspecting and repairing micropores, cracks, and local non-uniform defects can effectively improve the finished product quality of the ceramic core, making the final product more in line with the usage requirements.

[0067] The repair slurry is prepared from yttrium oxide powder with a mesh size of 200 - 400 and neutral silica sol according to a ratio of 3.5:1 - 5.5:1, and the hanging slice viscosity is 22 - 28. This formulation gives the repair slurry good filling and bonding properties, enabling it to fully fill micropores and cracks, closely combine with the surface of the ceramic core, ensuring the strength and stability of the repaired part, and making the repair effect durable and reliable.

[0068] Preferably, a brush is used to dip the repair slurry and apply it to the micropores, cracks, and local non-uniform defects on the surface of the ceramic core.

[0069] Preferably, sandpaper with a mesh size of 400 - 800 is used for polishing.

[0070] As a preferred example of the present application, in step S1, the inner cavity structure of the metal mold is complementary to the outer shape of the target ceramic core. Except for the inner cavity structure, the rest of the metal mold is set as a hollow structure to reduce the weight of the metal mold.

[0071] Specifically, the complementary inner cavity structure of the metal mold and the outer shape of the target ceramic core provides an accurate mold cavity for the forming of the ceramic core. During the preparation process, it can ensure that the dimensions of each part of the ceramic core meet the design requirements, improving the quality of the ceramic core.

[0072] Setting the rest of the metal mold except the inner cavity structure as a hollow structure greatly reduces the weight of the mold on the premise of not affecting the strength and performance of the mold. On the one hand, it reduces the usage amount of metal materials and the manufacturing cost of the mold. On the other hand, the lighter mold is more convenient during handling, installation, and operation, can improve production efficiency, and reduce equipment energy consumption at the same time.

[0073] The hollow structure increases the heat dissipation area of the mold. During processes such as wax dipping, demolding, and heating, it enables the mold to dissipate heat or heat up more quickly, which helps to precisely control the temperature in the process, ensures that each process step is carried out according to the predetermined parameters, and improves the stability and reliability of the ceramic core preparation process.

[0074] Preferably, the metal mold is made of aluminum.

[0075] Using the traditional grouting molding method and the technical solution of Example 1, large-sized ceramic cores with a size of Φ660*550 were made respectively. The differences in their technical effects are shown in the following table:

[0076] Index Grouting forming method Example 1 Demolding qualification rate ≤62% ≥98% Dimensional accuracy CT10 - CT12 CT3 - CT6 Surface defect rate ≥85% ≤7%

[0077] In summary, the preparation method of the large-sized ceramic core for titanium alloy casting described in this application has the following advantages: 1) The dimensional accuracy is significantly improved; 2) The demolding qualification rate is greatly increased; 3) The surface defect rate is significantly reduced.

[0078] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A preparation method of a large-sized ceramic core for titanium alloy casting, characterized in that, It includes the following steps: S1: Mold design, reverse model the target ceramic core, and design the inner cavity structure of the metal mold; S2: Wax coating inside the mold, immerse the metal mold in wax in parts, lift it to drain the wax after uniform immersion, and cool it down when there are no obvious wax drops flowing down. The cooling temperature is 10 - 18°C. After cooling, the surface of the metal mold is evenly coated with wax, and the wax layer thickness is 0.15 - 0.2 mm; S3: Mold assembly, clean the wax layer on the mating surface of the metal mold, and assemble the various parts of the metal mold together; S4: Prepare the ceramic core, coat a high-viscosity surface layer slurry on the wax layer surface of the metal mold, then sprinkle surface layer sand on the surface of the high-viscosity surface layer slurry, dry to form a surface layer, then prepare a transition layer on the surface of the surface layer. The preparation process of the transition layer is the same as that of the surface layer. Then coat a low-viscosity slurry on the surface of the transition layer, sprinkle bauxite sand on the surface of the low-viscosity slurry, dry to form a reinforcement layer, and then coat a low-viscosity slurry on the surface of the reinforcement layer, dry to form a sealing slurry layer; S5: Demolding, heat the metal mold to a temperature of 80 - 100°C, keep it warm for no less than 4 h, and then separate the metal mold from the ceramic core; S6: Firing, heat up at 5 - 8°C / min to 850 - 950°C, keep it warm for 120 - 240 min, and then heat up at 10 - 15°C / min to 1050°C, keep it warm for 240 - 360 min; S7: Obtain the ceramic core blank.

2. The preparation method of the large-sized ceramic core for titanium alloy casting according to claim 1, wherein, In step S2, before wax immersion, preheat the metal mold, the preheating temperature is 80 - 100°C, and the preheating time is not less than 2 h. When wax immersion, the surface temperature of the metal mold is not less than 65°C, and the wax immersion time is 3 - 5 s.

3. The preparation method of the large-sized ceramic core for titanium alloy casting according to claim 1, characterized in that, In step S2, immerse a single-piece metal mold in wax liquid at 80 - 100°C, and keep it warm in the wax liquid for no less than 180 s.

4. The preparation method of the large-sized ceramic core for titanium alloy casting according to claim 1, characterized in that, In step S4, the high-viscosity surface layer slurry is prepared from yttrium oxide powder with a mesh size of 200 - 400 and neutral silica sol, according to a weight ratio of 2.5:1 - 5.5:

1. The hanging piece viscosity of the high-viscosity surface layer slurry is 18 - 25, and the surface layer sand is zirconia sand with a mesh size of 40 - 100.

5. The preparation method of the large-sized ceramic core for titanium alloy casting according to claim 1, characterized in that, In step S4, the low-viscosity slurry is prepared from bauxite powder with a mesh size of 100 - 300 and silica sol, according to a weight ratio of 5:1 - 7:

1. The hanging piece viscosity of the low-viscosity slurry is 6 - 15, and the particle size of the bauxite sand is 30 - 60 mesh.

6. The preparation method of the large-sized ceramic core for titanium alloy casting according to claim 1, characterized in that, In step S4, the process preparation environments of the surface layer and the transition layer are the same, the temperature is 23 ± 2°C, the humidity is 65 - 85%, and the drying time is not less than 4 h; the process preparation environments of the reinforcement layer and the sealing slurry layer are the same, the temperature is 23 ± 2°C, the humidity is 45 - 55%, and the drying time is not less than 6 h.

7. The preparation method of the large-sized ceramic core for titanium alloy casting according to claim 1, characterized in that, In step S6, before baking, check the micropores, cracks and local non-uniform defects on the surface of the ceramic core, and coat the micropores, cracks and local non-uniform defects on the surface of the ceramic core with a repair slurry. Among them, the repair slurry is prepared from yttrium oxide powder with a mesh size of 200-400 and neutral silica sol according to a weight ratio of 3.5:1-5.5:

1. The hanging slice viscosity of the repair slurry is 22-28, and it is polished flat after natural drying.

8. The preparation method of the large-sized ceramic core for titanium alloy casting according to claim 1, characterized in that, In step S1, the inner cavity structure of the metal mold is complementary to the outer shape of the target ceramic core. Except for the inner cavity structure, the rest of the metal mold is set as a hollow structure.