A filter for casting single-crystal blades, its preparation method and application

Abstract

This invention discloses a filter for casting single-crystal blades, its preparation method, and its application. The filter includes a main body with a threaded structure. The main body includes a first filter structure and a second filter structure arranged sequentially from top to bottom. The pore size of the first filter structure is larger than that of the second filter structure. The filter is formed by photopolymer ceramic 3D printing, and the printing material is alumina or zirconium oxide with a solid content greater than 50%. The printed filter is laid flat in the air for calcination. The filter is used for casting single-crystal blades and is installed on the casting mold shell of the single-crystal blade. This invention uses a graded, threaded filter printed by photopolymer ceramic 3D printing, which is screwed into the casting mold shell to prevent the filter from floating during the alloy liquid casting process. It is easy to operate and avoids the inclusions that may be introduced during the filter installation process, ensuring the purification effect of the alloy liquid during the casting of single-crystal blades and significantly reducing the scrap rate of aerospace single-crystal blades due to metallurgical inclusions.

Description

Technical Field

[0001] This invention relates to the field of single-crystal blade preparation technology, and in particular to a filter for casting single-crystal blades, its preparation method, and its application. Background Technology

[0002] High-temperature alloy single-crystal blades for aero-engines are hailed as the crown jewel of modern industrial technology by developed countries in Europe and America due to their complex manufacturing technology and significant application value. Single-crystal blades operate in extreme environments of high temperature, high pressure, and high load, requiring them to possess excellent comprehensive mechanical properties. Therefore, in addition to the control of materials and microstructure, single-crystal blades face extremely stringent requirements regarding metallurgical inclusions.

[0003] Generally, metallurgical inclusions are strictly prohibited in critical areas of single-crystal blades, such as the inlet edge, exhaust edge, blade body, and shroud transition. In other parts of the blade, only 1-3 inclusions with a size of 0.3-0.5 mm are allowed, making the overall requirements extremely stringent. In the entire blade manufacturing process, filter purification during alloy molten metal casting is one of the key steps in controlling metallurgical inclusions. The specifications, configuration, and installation of the filter have a significant impact on the effectiveness of metallurgical inclusion control.

[0004] Single-crystal blades typically employ 25-45 PPI (Pores Per Linear Inch) foam ceramic filters to purify molten alloy. Filters with a pore size below 25 PPI cannot meet the blade's control requirements for metallurgical inclusions due to their large pore size. Filters with a pore size above 25 PPI achieve better filtration as the pore size decreases. However, as the pore size decreases, the supporting framework for the pores also becomes increasingly smaller. These small supporting frameworks are highly susceptible to breakage and inclusion formation when impacted by molten alloy. Therefore, there is a contradiction in filter specifications: pore sizes that are too large cannot achieve the desired purification effect, while pore sizes that are too small are prone to breakage and inclusion formation.

[0005] Filters are typically placed directly within the mold shell or wrapped with refractory cotton and placed along the side. However, during the pouring of molten alloy, the filters are prone to floating, leading to filtration failure. Using refractory coatings to fix the filters is also problematic, as contamination of the coating and damage during operation can easily cause impurities to accumulate. Therefore, placing filters within the mold shell requires overcoming challenges such as filter floating, coating contamination, and filter damage.

[0006] Inclusion defects severely restrict the improvement of metallurgical quality and production qualification rate of single crystal blades. Therefore, the control of inclusions in single crystal blade metallurgy is very strict. As mentioned above, the existing technology of using filters to purify alloy liquid for single crystal blades has two drawbacks: First, in terms of filter specifications and configuration, if the pore size is too large, it cannot achieve the purification effect, and if the pore size is too small, it will be easily damaged and cause inclusions. Second, in terms of installation and use, it is very difficult to overcome filter floating, paint contamination and filter damage during operation, thus failing to achieve the ideal purification effect.

[0007] The application of filters requires technological innovation to address specific specifications, configurations, installation, and usage needs, overcoming contradictions and difficulties to achieve high-purity and high-efficiency purification of alloy molten metal. Therefore, this application proposes a filter for single-crystal blade casting, its preparation method, and its application to solve the aforementioned problems. Summary of the Invention

[0008] The main objective of this invention is to provide a filter for casting single-crystal blades, its preparation method, and its application, which can effectively solve the problems in the background art.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a filter for casting single crystal blades, comprising a main body, the main body having a threaded structure, the main body comprising a first filter structure and a second filter structure arranged sequentially from top to bottom, wherein the pore size of the first filter structure is larger than the pore size of the second filter structure.

[0010] Preferably, the first filter structure has a specification of 25-35 PPI.

[0011] Preferably, the second filter structure has a specification of 35-45 PPI.

[0012] Preferably, the outer side of the main body is provided with an edge-sealing structure, and the thickness of the edge-sealing structure is 0.45-1.5mm.

[0013] Preferably, the thread profile of the main body is arc-shaped and the number of thread teeth is 1-3.

[0014] Preferably, the difference between the outer diameter and the inner diameter of the thread of the main body is 3-15mm.

[0015] The present invention also provides a method for preparing the above-mentioned filter, which includes the following steps: the filter is formed by photocurable ceramic 3D printing, the printing material is alumina or zirconium oxide with a solid content of more than 50%, and the printed filter is placed flat in the air for calcination.

[0016] The above-mentioned filter is used in the casting of monocrystalline blades and is installed on the casting mold shell of the monocrystalline blades. The casting mold shell is provided with a threaded groove that matches the filter. The filter is screwed into the threaded groove of the mold shell and placed on the runner. The fit clearance between the filter and the threaded groove is 0.25-0.65mm.

[0017] Compared with traditional technologies, the beneficial effects of this invention are as follows: This invention uses a graded, threaded filter printed by photopolymer ceramic 3D printing. The filter has two filtration structures, one above the other. The first filtration structure can resist the alloy liquid and avoid turbulence, while the second filtration structure ensures a high-purity filtration effect. The threaded filter is matched with the shell structure and screwed into the casting shell, preventing the filter from floating during the alloy liquid casting process. It is also easy to operate and avoids the inclusions that may be introduced during the filter installation process. This ensures the purification effect of the alloy liquid during the casting of single crystal blades, thereby producing single crystal blades with qualified metallurgical quality and significantly reducing the scrap rate of aerospace single crystal blades due to metallurgical inclusions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the installation of the filter and the casting shell according to the present invention;

[0019] Figure 2 This is a schematic diagram of the filter structure of the present invention;

[0020] Figure 3 This is a schematic diagram of the casting shell structure of the present invention.

[0021] In the diagram: 1. Main body; 101. First filter structure; 102. Second filter structure; 103. Edge wrapping structure; 2. Casting shell; 3. Threaded groove; 4. Sprue; 5. Stepped structure; d1. Thread inner diameter; d2. Thread outer diameter; n. Thread tooth; g. Fit clearance. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0023] like Figure 1 As shown, this embodiment provides a filter for casting single-crystal blades. The filter adopts a graded, threaded structure. Specifically, the filter includes a main body 1, which has a threaded structure and is divided into upper and lower parts. The upper part is a first filter structure 101, and the lower part is a second filter structure 102. The pore size of the first filter structure 101 is larger than that of the second filter structure 102. The first filter structure 101 has a pore size of 25-35 PPI, which can resist the impact of molten alloy and prevent turbulence. The second filter structure 102 has a pore size of 35-45 PPI, which can achieve efficient filtration and purification of the molten alloy.

[0024] An edge-sealing structure 103 is provided on the outer side of the main body 1. The thickness of the edge-sealing structure 103 is 0.45-1.5mm. The edge-sealing structure 103 can effectively prevent slag from falling off.

[0025] The overall structure of the main body 1 is threaded. The thread n on the outer side of the main body 1 has an arc shape and the number of thread n is 1-3. In this example, the thread n is set to 1. Furthermore, the difference between the inner diameter d1 and the outer diameter d2 of the thread on the main body 1 is 3-15mm.

[0026] In the preparation of the above-mentioned filter, printing molding is adopted. The specific preparation method is as follows: the filter is formed by photopolymer ceramic 3D printing, which can realize the integrated molding of the filter's hierarchical structure, edge-wrapping structure and thread structure. The printing material is alumina or zirconium oxide with a solid content of more than 50%. The printed filter is laid flat in the air for baking.

[0027] The prepared filter is used in the casting of single-crystal blades, such as... Figure 1-3 As shown, the filter is installed on the casting mold shell 2 of the single crystal blade. The casting mold shell 2 is provided with a threaded groove 3 that matches the filter. The threaded groove 3 and the gating 4 form a stepped structure 5, which facilitates the limiting of the filter. The filter and the threaded groove of the casting mold shell 2 cooperate with each other, and the cooperation gap g is 0.25-0.65mm. The filter is screwed into the threaded groove 3 of the mold shell and placed on the gating 4, which effectively prevents the filter from floating during the alloy liquid pouring process. The operation is simple and avoids the risks of external contamination and filter damage.

[0028] The filter in this embodiment is applied to the batch production of thin-walled single-crystal blades for a certain type of light gas turbine in China. Compared with the use of traditional filters, the scrap rate of metallurgical inclusions in this batch of blades is reduced by 20%.

[0029] Its working principle is as follows: A graded, threaded filter is printed using photopolymer ceramic 3D printing. The filter employs two filtration structures: the first filtration structure 101 resists the molten alloy and prevents turbulence, while the second filtration structure 102 ensures high-purity filtration. The threaded filter mates with the casting mold 2, screwing into it to prevent the filter from floating during alloy casting. This design is easy to operate and avoids potential inclusions during filter installation, ensuring effective purification of the molten alloy during single-crystal blade casting. This results in metallurgically qualified single-crystal blades, significantly reducing the scrap rate of aerospace single-crystal blades due to metallurgical inclusions. It can be widely used in single-crystal blade casting and can also be applied in other precision casting and melting processes.

[0030] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above description is illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A filter for single crystal blade casting, characterized by: The filter includes a main body with a threaded structure. The main body includes a first filter structure and a second filter structure arranged sequentially from top to bottom. The pore size of the first filter structure is larger than that of the second filter structure. The first filter structure has a specification of 25-35 PPI, and the second filter structure has a specification of 35-45 PPI. The outer side of the main body is provided with an edge-sealing structure with a thickness of 0.45-1.5 mm. The thread profile of the main body is arc-shaped, and the number of thread teeth is 1-3. The difference between the outer diameter and the inner diameter of the thread of the main body is 3-15 mm.

2. A method of making a filter as claimed in claim 1, characterised by: It includes the following steps: the filter is formed by photocuring ceramic 3D printing, the printing material is alumina or zirconium oxide with a solid content of more than 50%, and the printed filter is laid flat in the air for baking.

3. An application of the filter as described in claim 1, characterized in that: The filter is used in the casting of monocrystalline blades and is installed on the casting mold shell of the monocrystalline blades. The casting mold shell is provided with a threaded groove that matches the filter. The filter is screwed into the threaded groove of the mold shell and placed on the runner. The fit clearance between the filter and the threaded groove is 0.25-0.65mm.

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