A method for supporting a large-size wax mold of a heavy gas turbine single crystal blade and controlling foreign crystals

Abstract

This invention discloses a method for supporting wax molds and controlling impurities in large-size monocrystalline blades for heavy-duty gas turbines, comprising the following steps: A bottom support is used for the large-size monocrystalline blades of the heavy-duty gas turbine. The bottom support structure is composed of a supporting process rib and a supporting rod. The monocrystalline blade has an extension section that follows its shape, and the extension section is connected to the starting section and the crystal selector in sequence. The supporting process rib is connected to the extension section, and the position of the supporting process rib is higher than that of the starting section. The bottom edge of the supporting process rib is connected to the bottom edge of the starting section. The supporting rod is connected to the high point of the supporting process rib. The blade is pulled vertically downwards. This invention ensures that no collapse or cracking occurs during the preparation of the wax mold and shell of the large-size heavy-duty gas turbine blade, achieves control of impurities in the bottom support scheme, and successfully prepares complete monocrystalline large-size monocrystalline blades for heavy-duty gas turbines. This method can be widely applied in the single-crystal casting process to achieve mass production of monocrystalline blades.

Description

Technical Field

[0001] This invention relates to the field of manufacturing technology for single-crystal blades of gas turbines and aero-engines, and particularly to a method for wax mold support and impurity control of large-size single-crystal blades for heavy-duty gas turbines. Background Technology

[0002] Single-crystal blades require a small single crystal, a few millimeters in size, to be obtained from the base using a spiral crystal selection or seed crystal method. Then, dendrites gradually grow and expand into the entire blade. Therefore, the connection between the entire blade wax model and the base is generally limited to a single location: the spiral (or seed crystal). In the fabrication of single-crystal blades for aero-engines, the spiral (or seed crystal) can support the weight of the entire blade wax model. Alternatively, the high-strength spiral combining resin and wax model as described in patent CN 107520403 B, or the lateral support wax model solution as described in patent CN206613990 U, can generally ensure that no collapse or cracking occurs during the fabrication, dendrite cleaning, and shell preparation of single-crystal blade wax models for aero-engines. However, for heavy-duty gas turbine single-crystal blades, the wax model size and weight are large. Practice has shown that neither high-strength spirals nor lateral supports can effectively guarantee support. Large-sized single-crystal blade wax models for heavy-duty gas turbines require direct support at the bottom. However, when supporting the bottom of the reburning blade wax model, if the wax model is used to connect a certain position on the bottom of the blade to the chassis, the grains formed on the chassis will grow into the blade body through the connection point, causing impurity defects. If the ceramic rod described in patent CN 115519071 A is used to support a certain position on the bottom of the blade, factors such as the structure, seam, surface roughness, and alloy wettability of the connection point between the ceramic rod and the blade can easily induce impurities. Controlling impurities is a key technical point in supporting single-crystal blade wax models. Therefore, reburning single-crystal blade wax models require direct bottom support, and clear and effective control measures are needed to address the impurity defects induced by the support.

[0003] Analogous to existing technologies in the wax mold preparation process for single-crystal blades of aero-engines, methods such as wax mold spirals, high-strength spirals combining resin and wax molds, and lateral support of wax molds can generally ensure that the wax molds for aero-engine single-crystal blades do not collapse or crack. However, these non-bottom support methods are still insufficient in strength and cannot prevent the collapse or cracking of wax molds for large-sized single-crystal blades in re-ignition. Large-sized single-crystal blades for re-ignition require direct bottom support, but existing support schemes using wax molds or ceramic rods at the bottom of single-crystal blades do not offer clear and effective control measures against impurity formation induced by the support, making it difficult to prevent the formation of impurities in large-sized single-crystal blades for re-ignition. Therefore, existing non-bottom support technologies are insufficient in providing strength for the wax molds of re-ignition blades, while existing bottom support technologies do not offer clear control measures against impurities.

[0004] For the support of wax molds for single-crystal blades of heavy-duty gas turbines, a sufficiently strong bottom support is a prerequisite, while impurity control is a key technical point in the support scheme. Therefore, this application proposes a method for supporting wax molds of large-size single-crystal blades of heavy-duty gas turbines and controlling impurities. This method ensures the strength of the bottom support of the wax mold for heavy-duty gas turbine blades and proposes clear and effective technical measures for controlling impurities in the support scheme, thus ensuring the preparation process of large-size single-crystal blade wax molds of heavy-duty gas turbines while effectively preventing the formation of impurities on the blades. Summary of the Invention

[0005] The main objective of this invention is to provide a method for supporting wax molds and controlling impurities in large-size single-crystal blades for heavy-duty gas turbines, which can effectively solve the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for supporting wax molds and controlling impurities in large-size single-crystal blades for heavy-duty gas turbines, comprising the following steps:

[0007] Support scheme design: The large-size single crystal blades of the re-ignition system adopt bottom support, which is composed of a combination of support process ribs and support rods. The bottom support structure is fixed on the chassis.

[0008] Blade wax mold processing: The single crystal blade is made with an extension section that follows the shape, and the extension section is connected to the starting section and the crystal selector in sequence;

[0009] Design of supporting process reinforcement: The supporting process reinforcement is connected to the extension section, the position of the supporting process reinforcement is higher than the position of the starting section, and the bottom edge of the supporting process reinforcement is connected to the bottom edge of the starting section;

[0010] Support rod design: The support rod is connected to the high point of the supporting process reinforcement;

[0011] Blade matrix dendrite growth control: The blade is pulled vertically downwards, and based on the design of the supporting process ribs, the matrix dendrites grow from the initial segment to the supporting process ribs.

[0012] Preferably, the bottom support structure is configured as multiple structures arranged around the single-crystal blade.

[0013] Preferably, the height of the extension section is 8-40mm.

[0014] Preferably, the slope of the bottom edge of the supporting reinforcement is not less than the slope of the bottom edge of the starting segment.

[0015] Preferably, the extension section, the starting section, and the supporting process rib are formed as a single mold.

[0016] Preferably, the connection method between the support rod and the support process rib is embedding, bonding, or integral molding.

[0017] Preferably, the material of the support rod is wax, silica ceramic or alumina ceramic, and the material of the support process rib is wax.

[0018] Preferably, the supporting process ribs and supporting rods are circular, elliptical, or square, with a diameter or side length of 8-30 mm.

[0019] Compared with traditional technologies, the beneficial effects of this invention are: this invention ensures that no damage such as collapse or cracking occurs during the preparation of wax molds and shells for large-size gas turbine blades, and achieves effective control of impurity crystals in the bottom support scheme, successfully preparing complete single-crystal large-size single-crystal blades for heavy-duty gas turbines. At the same time, this invention can be widely applied in the preparation process of single-crystal castings such as large-size multi-unit single-crystal guide blades and large-size single-crystal structural components. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the wax mold structure and bottom support scheme for the large-size single-crystal blades of the heavy-duty gas turbine of the present invention;

[0021] Figure 2 In this invention Figure 1 A partial schematic diagram.

[0022] In the diagram: 1. Spiral; 2. Starting segment; 2s. Bottom edge of starting segment; 3. Extension segment; 4. Single crystal blade; 5. Supporting process rib; 5s. Bottom edge of supporting process rib; 6. Support rod; 7. Base plate; 8. Gating; R. Pulling direction; a. Matrix dendrite; b. Impurity dendrite; c. Grain boundary. Detailed Implementation

[0023] 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.

[0024] A method for supporting wax molds and controlling impurities in large-size single-crystal blades for heavy-duty gas turbines includes the following steps:

[0025] Supporting scheme design: See Figure 1 , Figure 2 It was determined that the large-size single crystal blade 4 of the reburning device would adopt bottom support. The bottom support and other solutions such as high-strength spiral and lateral support of other crystal selectors can be implemented at the same time. The bottom support structure is composed of support process ribs 5 and support rods 6. The bottom support structure is fixed on the chassis 7. Specifically, the support rods 6 are fixedly connected to the chassis 7. Multiple bottom support structures are set and arranged around the single crystal blade 4. Generally, 1-5 bottom support structures are set.

[0026] Blade wax modeling: See Figure 1The single crystal blade 4 is shaped to form an extension section 3 with a height of 8-40mm. The extension section 3 is connected to the starting section 2 and the crystal selector in sequence. Specifically, the starting section 2 is connected to the spiral 1 of the crystal selector. The spiral 1 is a high-strength spiral. The upper end of the single crystal blade 4 is connected to a gating channel 8 for injecting alloy liquid.

[0027] Design of supporting process reinforcement 5: See Figure 1 , Figure 2 The supporting process rib 5 is connected to the extension section 3. The position of the supporting process rib 5 is higher than that of the starting section 2, and the bottom edge 5s of the supporting process rib is connected to the bottom edge 2s of the starting section. Specifically, the slope of the bottom edge 5s of the supporting process rib is not less than the slope of the bottom edge 2s of the starting section 2. The supporting process rib 5 is circular, elliptical, or square, with a diameter or side length of 8-30mm. The material of the supporting process rib 5 is wax. The extension section 3, the starting section 2, and the supporting process rib 5 are molded as a whole to form an integrated structure, which effectively ensures the surface quality and strength of the wax mold, thereby avoiding damage caused by impurities induced by surface quality and weak adhesion.

[0028] Design of support rod 6: The support rod 6 is connected to the high point of the support process rib 5. The connection method between the support rod 6 and the support process rib 5 can be embedding, bonding, or integral molding, or other connection methods can be used, with the goal of strong bonding. It is not necessary to consider whether it induces impurities. The material of the support rod 6 is wax, silicon oxide ceramic or alumina ceramic. The support rod 6 can be integrally molded with the support process rib 5, or it can be molded separately and then welded together. The shape of the support rod 6 can be circular, elliptical or square, with a diameter or side length of 8-30mm.

[0029] Impurity dendrite control induced by support rod 6: Since support rod 6 is connected at the high point of support process rib 5, the impurity dendrite b induced by support rod 6 will only spread upward or laterally and will not grow to the body of single crystal blade 4 through support process rib 5. Finally, the matrix dendrite a and impurity dendrite b of single crystal blade 4 converge at the support process rib 5 and away from single crystal blade 4 to form grain boundary c. The extension section 3 (including the starting section 2 and support) is cut off by wire cutting to obtain a complete single crystal re-ignition large-size single crystal blade 4.

[0030] Leaf matrix dendrite a growth control: See Figure 1 , Figure 2 The blade is pulled out vertically downwards; specifically, the pulling direction is... Figure 1 The direction R in the middle is designed based on the support process rib 5, so that the matrix dendrite a grows from the starting segment 2 to the support process rib 5.

[0031] Its working principle is as follows: The wax model of the large-size single-crystal blade 4 of a heavy-duty gas turbine is heavy and requires direct bottom support to ensure that the wax model does not collapse or crack during the preparation process. This invention adopts a bottom support method combining the supporting process rib 5 and the supporting rod 6. First, it ensures a reliable support effect for the wax model. At the same time, it utilizes the principle that dendrites in the directional solidification process can generally only grow upward or laterally under the action of temperature gradient. The connection method of the starting section 2, the supporting process rib 5, and the supporting rod 6 is designed as follows: ① The position of the supporting process rib 5 is designed to be higher than the position of the starting section 2 of the blade, and the mold is integrally formed, so that the matrix dendrites a of the single-crystal blade 4 can grow smoothly to the supporting process rib 5; ② The supporting rod 6 is connected to the high point of the supporting process rib 5. Because it is difficult to avoid the presence of impurities at the connection with the supporting rod 6, the impurities induced by the supporting rod 6 will not be able to grow to the blade body through the supporting process rib 5. Finally, the matrix dendrites a and impurity dendrites b converge at the supporting process rib 5, far from the blade body, to form a grain boundary c. The extension segment 3, the initial segment 2, and the support are removed by wire cutting to obtain a complete single-crystal large-size re-ignition turbine blade 4. This ensures that no damage such as collapse or cracking occurs during the preparation of the wax model and shell of the large-size re-ignition turbine blade, and effectively controls the impurities in the bottom support scheme, successfully fabricating a complete single-crystal large-size single-crystal blade 4 for heavy-duty gas turbines. Furthermore, this invention can be widely applied in the fabrication processes of large-size multi-unit single-crystal guide vanes, large-size single-crystal structural components, and other single-crystal castings.

[0032] 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 method for supporting wax molds and controlling impurities in large-size single-crystal blades for heavy-duty gas turbines, characterized in that, Includes the following steps: Support scheme design: The large-size single crystal blades of the re-ignition system adopt bottom support, which is composed of a combination of support process ribs and support rods. The bottom support structure is fixed on the chassis. Blade wax mold processing: The single crystal blade is made with an extension section that follows the shape, and the extension section is connected to the starting section and the crystal selector in sequence; Design of supporting process reinforcement: The supporting process reinforcement is connected to the extension section, the position of the supporting process reinforcement is higher than the position of the starting section, and the bottom edge of the supporting process reinforcement is connected to the bottom edge of the starting section. Support rod design: The support rod is connected to the high point of the supporting process reinforcement; Blade matrix dendrite growth control: The blade is pulled vertically downwards. Based on the design of the support process rib, the matrix dendrites grow from the starting section to the support process rib. The impurity dendrites induced by the support rod only grow upwards or laterally and cannot enter the single crystal blade body through the support process rib. The matrix dendrites and impurity dendrites converge to form grain boundaries at the position of the support process rib away from the blade body.

2. The method for supporting wax molds and controlling impurities in large-size single-crystal blades of heavy-duty gas turbines according to claim 1, characterized in that: The bottom support structure is configured as multiple structures arranged around the single crystal blade.

3. The method for supporting wax molds and controlling impurities in large-size single-crystal blades of heavy-duty gas turbines according to claim 1, characterized in that: The height of the extension section is 8-40mm.

4. The method for supporting wax molds and controlling impurities in large-size single-crystal blades of heavy-duty gas turbines according to claim 1, characterized in that: The slope of the bottom edge of the supporting reinforcement is not less than the slope of the bottom edge of the starting section.

5. The method for supporting wax molds and controlling impurities in large-size single-crystal blades of heavy-duty gas turbines according to claim 1, characterized in that: The extension section, the starting section, and the supporting process ribs are formed as a single mold.

6. The method for supporting wax molds and controlling impurities in large-size single-crystal blades of heavy-duty gas turbines according to claim 1, characterized in that: The connection between the support rod and the support process rib can be achieved by embedding, bonding, or integral molding.

7. The method for supporting wax molds and controlling impurities in large-size single-crystal blades of heavy-duty gas turbines according to claim 1, characterized in that: The material of the support rod is wax, silica ceramic or alumina ceramic, and the material of the support process rib is wax.

8. The method for supporting wax molds and controlling impurities in large-size single-crystal blades of heavy-duty gas turbines according to claim 1, characterized in that: The supporting process ribs and support rods are circular, elliptical, or square, with a diameter or side length of 8-30mm.

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