Preparation method of ceramic core for titanium alloy casting

Abstract

The invention belongs to the technical field of casting forming, and particularly relates to a preparation method of a ceramic core for titanium alloy casting. Comprising the following steps: designing a mold core mold according to a mold core structure, and obtaining the mold core mold through a photocuring 3D printing process; coating the working surface of the core mold with facing layer slurry, adjacent surface layer slurry and reinforcing layer slurry in sequence to obtain a core of a ceramic layer; the cavity of the mold core of the ceramic layer is filled with sodium silicate sand, roasting is carried out, the mold core mold is burnt out, the mold core is integrally sintered, and the ceramic mold core for titanium alloy casting is obtained. According to the method, the advantages of high precision of photo-curing printing and collapsibility of sodium silicate sand filling are combined, so that the problems of high cost, long period and complicated process flow caused by preparation of an existing metal mold and a wood mold and the problem of difficulty in cleaning caused by over-high strength of a ceramic core are effectively solved; the requirements for low surface roughness, high precision and easy core cleaning of the core mold are effectively met, and the core mold is suitable for casting titanium alloy castings with complex inner cavity structures.

Description

Technical Field

[0001] This invention belongs to the field of casting forming technology, and specifically relates to a method for preparing a ceramic core for titanium alloy casting. Background Technology

[0002] In the titanium alloy casting process, the core is crucial for forming the complex internal cavity structure of the casting, and its performance directly affects the dimensional accuracy and internal quality of the casting. Traditional ceramic core preparation often employs mold slip casting, which is challenging to design and costly to process for complex cores, and is also prone to defects such as bubbles and deformation during the forming process.

[0003] With the development of 3D printing technology, some studies have adopted the method of directly printing ceramic cores. However, it is difficult to balance the fluidity and curing performance of ceramic slurry, resulting in insufficient core density and high material cost.

[0004] Patent CN119175343A discloses a method for preparing ceramic cores for titanium alloy graphite mold casting. This method uses a wooden mold as the mold, requiring multiple processing steps before the core can be made. However, it suffers from problems such as high core surface roughness, long preparation cycle, and low dimensional accuracy. Patent CN111375731A discloses an integral preparation process for large-scale skeleton-type high-temperature titanium alloy castings. This process uses a prepared casting mold to integrally cast the required titanium alloy casting. The casting mold has a machined graphite outer shape and a ceramic core. The ceramic core is prepared using a metal mold, which suffers from high preparation costs, difficulty in demolding, and difficulty in preparing complex cores. Patent CN119187445A discloses a composite titanium alloy casting process using graphite and ceramic cores. The process employs a recyclable graphite mold for the outer shape and a ceramic core prepared using investment casting. After combining, melting, and casting the graphite mold and ceramic core, a high-quality titanium alloy casting with a short production cycle can be obtained. However, this process requires the preparation of a metal mold first, followed by the pressing of a wax pattern, and then the preparation of the ceramic core based on the wax pattern. The process is complex, time-consuming, and the wax pattern has low strength, making it prone to deformation for large cores.

[0005] In summary, the cores prepared in the above processes are all pure ceramic cores. Pure ceramic cores have problems such as excessive strength and difficulty in core removal in complex structural parts, which seriously affect the forming stability of the casting. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing ceramic cores for titanium alloy casting. This method ensures high-precision core forming while balancing structural strength. It improves the collapsibility of the core, reduces the difficulty of core removal, and provides a controllable preparation cycle and cost, while maintaining forming strength.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0008] The purpose of this invention is to provide a method for preparing a ceramic core for titanium alloy casting, comprising the following steps: S1. Based on the core structure, design the core mold and obtain the core mold through photopolymerization 3D printing process.

[0009] S2. Apply the surface layer slurry, adjacent surface layer slurry, and reinforcing layer slurry sequentially to the working surface of the core mold to obtain the ceramic core.

[0010] S3. Fill the cavity of the ceramic core with water glass sand and fire it. The core mold is burned off and the core is sintered as a whole to obtain a ceramic core for titanium alloy casting.

[0011] Furthermore, in the photopolymer 3D printing process, the three-dimensional model format is STL or STP, the printing layer height is 0.05mm to 0.15mm, and the printing material is photosensitive resin.

[0012] Furthermore, the surface roughness Ra of the core mold is less than 1.6 μm.

[0013] Furthermore, the water glass sand is composed of sand, water glass and organic grease hardener. The amount of water glass is 2wt.% to 10wt.% of the total amount of water glass sand, the amount of organic grease hardener is 10wt.% to 35wt.% of the total amount of water glass, and the sand is at least one of pearl sand, mullite sand and bauxite sand, with a particle size of 30 mesh to 100 mesh.

[0014] Furthermore, the surface layer slurry and the adjacent surface layer slurry are respectively composed of refractory powder and binder. The refractory powder is at least one of yttrium oxide powder and zirconium oxide powder, and the binder is at least one of yttrium sol, zirconium acetate and silica sol. The particle size of the refractory powder is 200 mesh to 400 mesh.

[0015] Furthermore, in the surface layer slurry, the ratio of refractory powder to binder is 3.5 to 5.5:1, and in the adjacent surface layer slurry, the ratio of refractory powder to binder is 1 to 4:1.

[0016] Furthermore, the reinforcing slurry is made of refractory powder and binder, with a ratio of refractory powder to binder of 1 to 2.5:1. The refractory powder is at least one of bauxite powder and mullite powder, with a particle size of 150 mesh to 250 mesh, and the binder is silica sol.

[0017] Furthermore, during the application of the reinforcing slurry, it is applied 1 to 3 times.

[0018] Furthermore, during the roasting process, the temperature is 900℃~1100℃ and the roasting time is 2h~4h.

[0019] Furthermore, after applying the topcoat slurry, adjacent surface slurry, or reinforcing layer slurry, sand is sprinkled and dried. When applying the topcoat slurry or adjacent surface slurry, the sand is at least one of yttrium oxide sand and zirconium oxide sand, with a particle size of 40 to 120 mesh. When applying the reinforcing layer slurry, the sand is at least one of bauxite sand and mullite sand, with a particle size of 16 to 60 mesh.

[0020] Compared with the prior art, the present invention has the following advantages: The method for preparing ceramic cores for titanium alloy casting provided by this invention is based on SLA high-precision 3D printing technology. The prepared mold has the characteristics of high strength, high precision, high surface quality, short cycle and low cost. It effectively solves the problems of high cost, long cycle and complicated preparation process caused by existing metal molds and wooden molds. The use of 3D printing technology can also solve the model deformation problem caused by other methods during dewaxing or demolding. It effectively ensures the requirements of low surface roughness, high precision and easy core cleaning of the core mold, and is suitable for casting titanium alloy castings with complex internal cavity structures. At the same time, this invention combines the ceramic core preparation process with the water glass sand process, which ensures the surface quality and strength of the core while taking into account the collapsibility of the core. It effectively solves the problem of excessive strength and difficulty in core removal of pure ceramic cores in complex structural parts. Attached Figure Description

[0021] Figure 1 This is a diagram showing the ceramic core prepared in Example 1 of the present invention and the composite assembly of the ceramic core and the machined graphite mold. Figure 1 In the diagram, a represents the ceramic core, and b represents the composite assembly diagram of the ceramic core and the machined graphite core.

[0022] Figure 2 This is an assembly diagram of the ceramic core and machined graphite shape prepared in Example 2 of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0025] Current core fabrication processes often employ metal molds and wooden molds. However, these methods suffer from high costs, long production cycles, and complex processes, while the high strength of ceramic cores leads to difficulties in cleaning. The lack of a fabrication method that can guarantee high-precision core forming, balance structural strength, improve core collapseability while ensuring forming strength, reduce core removal difficulty, and control the fabrication cycle and cost limits the application of titanium alloy casting in complex internal cavity castings.

[0026] Based on this, the present invention provides a method for preparing ceramic cores for titanium alloy casting. Based on SLA high-precision 3D printing technology, the prepared mold features high strength, high precision, high surface quality, short cycle time, and low cost, effectively solving the problems of high cost, long cycle time, and complex preparation process associated with existing metal and wooden molds. Using 3D printing technology for mold making also solves the model deformation problem caused by other methods during dewaxing or demolding. Simultaneously, the present invention combines the ceramic core preparation process with water glass sand processing, ensuring both the surface quality and strength of the core while also considering its collapsibility, effectively solving the problem of excessive strength and difficulty in core removal in complex structural parts of pure ceramic cores.

[0027] Specifically, the following steps are included: S1. Based on the core structure, design the core mold and obtain the core mold through photopolymerization 3D printing process.

[0028] In this invention, based on the characteristics of the core structure, a three-dimensional model of the core mold is designed. Using SLA high-precision 3D printing technology, the core mold is directly printed, effectively solving the problems of long cycles and high costs associated with existing technologies that require metal or wooden molds for core fabrication. During the photopolymerization 3D printing process, the three-dimensional model is in STL or STP format, the printing layer height is 0.05–0.15 mm, and the printing material is photosensitive resin. The surface roughness Ra of the prepared core mold is less than 1.6 μm, ensuring low surface roughness of the cast part. This effectively guarantees the requirements of low surface roughness, high precision, and easy core cleaning, making it suitable for casting titanium alloy castings with complex internal cavity structures.

[0029] S2. Apply the surface layer slurry, adjacent surface layer slurry, and reinforcing layer slurry sequentially to the working surface of the core mold to obtain the ceramic core.

[0030] In this invention, a core with a ceramic layer is prepared using a ceramic shell-making process. After applying a surface layer slurry, an adjacent layer slurry, or a reinforcing layer slurry, sand is sprinkled and dried. Specifically, after applying the surface layer slurry or adjacent layer slurry, the sand is at least one of yttrium oxide sand and zirconium oxide sand, with a particle size of 40-120 mesh. After applying the reinforcing layer slurry, the sand is at least one of bauxite sand and mullite sand, with a particle size of 16-60 mesh. The drying conditions after applying the surface layer slurry or adjacent layer slurry are: temperature 22℃-24℃, humidity 50%-65%, and drying time 8-24 hours. After drying, the surface layer and adjacent layer are obtained. During the application of the reinforcing layer slurry, it is applied 1-3 times. For different core sizes, different numbers of layers result in different strengths. Increasing the number of applications increases the strength. In practical applications, the appropriate number of applications is selected based on the core size and the required strength. After each application of the reinforcing layer slurry, sand is sprinkled and dried. The sand used for sprinkling is at least one of bauxite sand and mullite sand, with a particle size of 16-60 mesh. The drying conditions are: temperature 22℃-24℃, humidity 30%-45%, wind speed 3m / s-8m / s, and drying time 6h-24h, to obtain the reinforcing layer and form a ceramic layer.

[0031] S3. Fill the cavity of the ceramic core with water glass sand and fire it. The core mold is burned off and the core is sintered as a whole to obtain a ceramic core for titanium alloy casting.

[0032] In this invention, the water glass sand is composed of sand, water glass, and an organic grease hardener. The amount of water glass is 2wt.% to 10wt.% of the total water glass sand, and the amount of organic grease hardener is 10wt.% to 35wt.% of the total water glass. The organic grease hardener is of type WJ. The sand is at least one of alumina, mullite, and bauxite sand, with a particle size of 30 mesh to 100 mesh. After filling with water glass sand, drying is required. The drying conditions are: temperature 22℃ to 24℃, humidity less than 40%, and drying time 3h to 8h. This invention avoids the problem of difficult core removal from pure ceramic molds by filling the internal cavity with water glass sand, combined with the high precision of photopolymer printing and the collapsibility advantage of water glass sand filling.

[0033] In this invention, during the calcination process, the temperature is 900℃~1100℃ and the calcination time is 2h~4h. During the calcination process, the core mold is burned off, and the surface layer and the reinforcing layer are sintered together to obtain a ceramic core. This has the advantages of short process cycle, high core dimensional accuracy, good surface quality, and good core collapse resistance.

[0034] The following specific examples will provide further explanation.

[0035] Example 1 A method for preparing a ceramic core for titanium alloy casting includes the following steps: S1. Design a 3D model of the core mold based on the internal cavity structure of the shell, export the model in STP format, design the printing layer height to be 0.1mm, use photosensitive resin as the printing material, and print using an SLA printer to obtain the core mold. The surface roughness of the mold is 1.0μm.

[0036] S2. Apply a surface layer slurry to the working surface of the mold. The surface layer slurry is prepared by yttrium oxide powder and silica sol with a powder-to-liquid ratio of 4:1. The yttrium oxide powder has a particle size of 325 mesh. After the slurry is evenly applied, sprinkle yttrium oxide sand with a particle size of 100 mesh. Then dry it in a drying room at a drying temperature of 23°C and a humidity of 60% for 24 hours to obtain the surface layer.

[0037] S3. After the surface layer dries, the adjacent surface layer slurry is applied. The adjacent surface layer slurry is prepared by yttrium oxide powder and silica sol with a powder-to-liquid ratio of 2:1. The yttrium oxide powder has a particle size of 325 mesh. After the slurry is evenly applied, zirconium oxide sand with a particle size of 80 mesh is sprinkled on. Then, it is dried in a drying room at a temperature of 23°C and a humidity of 55% for 12 hours to obtain the adjacent surface layer.

[0038] S4. After the adjacent layer dries, a reinforcing layer slurry is applied. The reinforcing layer slurry is prepared by bauxite powder and silica sol with a powder-to-liquid ratio of 2:1. The bauxite powder has a particle size of 200 mesh. After the slurry is evenly applied, bauxite sand with a particle size of 60 mesh is sprinkled on top. Then, the material is dried in a drying room at a temperature of 23°C, a humidity of 40%, a wind speed of 5 m / s, and a drying time of 8 hours. This process is repeated twice to obtain a core with a ceramic layer.

[0039] S5. Fill the core with water glass sand, which is a mixture of granulated sand, water glass and organic grease hardener. The granulated sand has a particle size of 100 mesh, the amount of water glass is 8 wt.% of the sand, and the amount of organic grease hardener is 10 wt.% of the total amount of water glass. Dry for 4 hours at a temperature of 23℃ and a humidity of less than 40%.

[0040] S6. Place the core in a high-temperature furnace at 1000℃ for 2 hours. During the firing process, the mold is burned off, and the core is integrally sintered, finally obtaining a qualified ceramic core. The prepared ceramic core is as follows: Figure 1 As shown, it can be adapted to the height of machined graphite cavities.

[0041] Example 2 A method for preparing a ceramic core for titanium alloy casting includes the following steps: S1. Design a 3D model of the core mold based on the internal structure of the tubular part. Export the model in STL format, design the printing layer height to be 0.15mm, use photosensitive resin as the printing material, and print using an SLA printer to obtain the core mold. The surface roughness of the mold is 1.3μm.

[0042] S2. Apply a surface layer slurry to the working surface of the mold. The surface layer slurry is prepared by yttrium oxide powder and silica sol with a powder-to-liquid ratio of 5:1. The yttrium oxide powder has a particle size of 325 mesh. After the slurry is evenly applied, sprinkle yttrium oxide sand with a particle size of 80 mesh. Then dry it in a drying room at a temperature of 23°C and a humidity of 60% for 24 hours to obtain the surface layer.

[0043] S3. After the surface layer dries, the adjacent surface layer slurry is applied. The adjacent surface layer slurry is prepared by zirconium oxide powder and zirconium acetate with a powder-to-liquid ratio of 2:1. The yttrium oxide powder has a particle size of 300 mesh. After the slurry is evenly applied, zirconium oxide sand with a particle size of 80 mesh is sprinkled on it. Then, it is dried in a drying room at a drying temperature of 23℃ and a humidity of 60% for 12 hours to obtain the adjacent surface layer.

[0044] S4. After the adjacent layer dries, a reinforcing layer slurry is applied. The reinforcing layer slurry is prepared by mullite powder and silica sol with a powder-to-liquid ratio of 2:1. The mullite powder has a particle size of 200 mesh. After the slurry is evenly applied, mullite sand with a particle size of 30 mesh is sprinkled on. Then, it is dried in a drying room at a temperature of 23°C, a humidity of 40%, a wind speed of 8 m / s, and a drying time of 8 hours. This process is repeated 3 times to obtain a core with a ceramic layer.

[0045] S5. Fill the core with water glass sand, which is a mixture of mullite, water glass and organic grease hardener. The mullite has a particle size of 60 mesh, the amount of water glass is 5 wt.% of the sand, and the amount of organic grease hardener is 20 wt.% of the total amount of water glass. Dry for 6 hours at a temperature of 23℃ and a humidity of less than 40%.

[0046] S6. Place the core in a high-temperature furnace at 950℃ for 4 hours. During the sintering process, the mold is burned off, and the core is integrally sintered, ultimately obtaining a qualified ceramic core. The prepared ceramic core is highly compatible with the machined graphite cavity. Figure 2 As shown.

[0047] Example 3 A method for preparing a ceramic core for titanium alloy casting includes the following steps: S1. Design a 3D model of the core mold based on the internal cavity structure of the shell, export the model in STP format, design the printing layer height to be 0.05mm, use photosensitive resin as the printing material, and print using an SLA printer to obtain the core mold. The surface roughness of the mold is 0.8μm.

[0048] S2. Apply a surface layer slurry to the working surface of the mold. The surface layer slurry is prepared by yttrium oxide powder and silica sol with a powder-to-liquid ratio of 3.5:1. The yttrium oxide powder has a particle size of 325 mesh. After the slurry is evenly applied, sprinkle yttrium oxide sand with a particle size of 100 mesh. Then dry it in a drying room at a drying temperature of 23℃ and a humidity of 60% for 20 hours to obtain the surface layer.

[0049] S3. After the surface layer dries, the adjacent surface layer slurry is applied. The adjacent surface layer slurry is prepared by yttrium oxide powder and silica sol with a powder-to-liquid ratio of 1.5:1. The yttrium oxide powder has a particle size of 100 mesh. After the slurry is evenly applied, zirconium oxide sand with a particle size of 80 mesh is sprinkled on. Then, it is dried in a drying room at a drying temperature of 23℃ and a humidity of 60% for 20 hours to obtain the adjacent surface layer.

[0050] S4. After the adjacent layer dries, a reinforcing layer slurry is applied. The reinforcing layer slurry is prepared by bauxite powder and silica sol with a powder-to-liquid ratio of 1.5:1. The bauxite powder has a particle size of 200 mesh. After the slurry is evenly applied, bauxite sand with a particle size of 60 mesh is sprinkled on top. Then, the material is dried in a drying room at a temperature of 23°C, a humidity of 40%, a wind speed of 8 m / s, and a drying time of 12 hours to obtain a core with a ceramic layer.

[0051] S5. Fill the core with water glass sand, which is a mixture of bauxite sand, water glass and organic grease hardener. The bauxite sand has a particle size of 80 mesh, the amount of water glass is 10 wt.% of the sand, and the amount of organic grease hardener is 30 wt.% of the total amount of water glass. Dry for 8 hours at a temperature of 23℃ and a humidity of less than 40%.

[0052] S6. Place the core in a high-temperature furnace at 1100℃ for 2 hours. During the calcination process, the mold is burned off, and the core is integrally sintered, finally obtaining a qualified ceramic core. The prepared ceramic core is as follows: Figure 1 As shown, it can be adapted to the height of machined graphite cavities.

[0053] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0054] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a ceramic core for titanium alloy casting, characterized in that, Includes the following steps: Based on the core structure, a core mold is designed, and the core mold is obtained through photopolymerization 3D printing process; The surface layer slurry, adjacent surface layer slurry, and reinforcing layer slurry are sequentially applied to the working surface of the core mold to obtain a ceramic core. Water glass sand is filled into the cavity of the ceramic core, and then fired. The core mold is burned off, and the core is sintered as a whole to obtain a ceramic core for titanium alloy casting.

2. The method for preparing a ceramic core for titanium alloy casting according to claim 1, characterized in that, In the photopolymer 3D printing process, the three-dimensional model format is STL or STP, the printing layer height is 0.05mm to 0.15mm, and the printing material is photosensitive resin.

3. The method for preparing a ceramic core for titanium alloy casting according to claim 1, characterized in that, The surface roughness Ra of the core mold is less than 1.6 μm.

4. The method for preparing a ceramic core for titanium alloy casting according to claim 1, characterized in that, Water glass sand is composed of sand, water glass and organic grease hardener. The amount of water glass is 2wt.% to 10wt.% of the total amount of water glass sand, the amount of organic grease hardener is 10wt.% to 35wt.% of the total amount of water glass, and the sand is at least one of pearl sand, mullite sand and bauxite sand, with a particle size of 30 mesh to 100 mesh.

5. The method for preparing a ceramic core for titanium alloy casting according to claim 1, characterized in that, The surface layer slurry and the adjacent surface layer slurry are respectively composed of refractory powder and binder. The refractory powder is at least one of yttrium oxide powder and zirconium oxide powder, and the binder is at least one of yttrium sol, zirconium acetate and silica sol. The particle size of the refractory powder is 200 mesh to 400 mesh.

6. The method for preparing a ceramic core for titanium alloy casting according to claim 5, characterized in that, In the surface layer slurry, the ratio of refractory powder to binder is 3.5 to 5.5:1, and in the adjacent surface layer slurry, the ratio of refractory powder to binder is 1 to 4:

1.

7. The method for preparing a ceramic core for titanium alloy casting according to claim 1, characterized in that, The reinforcing slurry is made of refractory powder and binder, with a ratio of refractory powder to binder of 1 to 2.5:

1. The refractory powder is at least one of bauxite powder and mullite powder, with a particle size of 150 to 250 mesh, and the binder is silica sol.

8. The method for preparing a ceramic core for titanium alloy casting according to claim 1, characterized in that, During the application of the reinforcing slurry, apply it 1 to 3 times.

9. The method for preparing a ceramic core for titanium alloy casting according to claim 1, characterized in that, During the roasting process, the temperature is 900℃~1100℃ and the roasting time is 2h~4h.

10. The method for preparing a ceramic core for titanium alloy casting according to claim 1, characterized in that, After applying the topcoat slurry, adjacent surface slurry, or reinforcing layer slurry, sand is sprinkled and dried. When applying the topcoat slurry or adjacent surface slurry, the sand is made of at least one of yttrium oxide sand and zirconium oxide sand, with a particle size of 40 to 120 mesh. When applying the reinforcing layer slurry, the sand is made of at least one of bauxite sand and mullite sand, with a particle size of 16 to 60 mesh.

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