Method for controlling wall thickness size of single-crystal conjoined guide blade
By attaching core supports of different thicknesses to the core of the monocrystalline integrated guide vane and combining them with appropriate wax mold assembly design and core processing, the problem of controlling the wall thickness of the monocrystalline integrated guide vane was solved, achieving high-precision wall thickness control and low scrap rate.
Patent Information
- Application Number
- CN202511792772.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-02-17
AI Technical Summary
In the preparation of single-crystal integrated guide vanes, traditional methods are difficult to effectively control the wall thickness, especially during the directional solidification of the alloy. Due to the difference in gravity, the core floats or rotates, resulting in changes in the wall thickness. The deviation is particularly large at the exhaust edge, leading to the scrapping of a large number of castings.
Core supports of different thicknesses are attached to the blade core to compensate for the upward floating or rotation of the core during the directional solidification process of the blade. A suitable wax mold combination scheme is designed, and the free end of the core is treated to reduce the stress between the shell and the core. A wax mold with qualified wall thickness is obtained by pressing with a mold, followed by alloy directional solidification, shell removal, core removal and heat treatment.
It achieves precise control over the wall thickness of single-crystal integrated guide vanes, reduces the scrap rate, and improves the pass rate of castings. It is especially suitable for single-crystal integrated guide vanes with complex shapes and internal cavities and high wall thickness accuracy requirements.
Smart Images
Figure CN121538726A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of high-temperature alloy investment casting technology, specifically a method for controlling the wall thickness of single-crystal integrated guide vanes, which is mainly applicable to the preparation of single-crystal integrated guide vanes with complex external and internal dimensions and high requirements for wall thickness accuracy. Background Technology
[0002] With the rapid development of the aviation industry and the gradual improvement of the performance of aero engines, single-crystal hollow guide vanes have become one of the core components of engines. Their production methods have also gradually evolved from split casting to single-unit integral casting, and even multi-unit integral casting, which further increases the difficulty of controlling their dimensions, especially the thickness of the inner cavity wall.
[0003] In the fabrication of hollow single-crystal blades, the traditional method for controlling wall thickness involves attaching core supports of the same thickness as the theoretical blade wall to the blade head and back sides of the blade core, respectively, and then using a mold to press a wax model of the blade with acceptable wall thickness. However, the structural characteristics of single-crystal hollow integrated guide blades determine that their module arrangement differs from that of working blades. To ensure grain integrity, the blade head and back sides are not perpendicular to the horizontal plane in the module, but are often positioned with one side on top and the other on the bottom. This causes the core to float or rotate in the molten alloy due to gravity differences during the directional solidification process, resulting in changes in wall thickness, especially at the relatively thinner venting edge of the core. In addition, to reduce the stress between the core and the shell, the core end is usually treated as a free end, which further increases the freedom of the core to float or rotate in the molten alloy, leading to a large number of castings being scrapped due to wall thickness deviations. Summary of the Invention
[0004] The purpose of this invention is to provide a method for controlling the wall thickness of single-crystal coupled guide vanes. For single-crystal coupled guide vanes with complex external and internal dimensions and high requirements for wall thickness accuracy, problems such as eccentricity in the vane casting and unqualified wall thickness dimensions are prone to occur. This method is simple to operate, has high process consistency, and can achieve precise control of the wall thickness of each coupled vane.
[0005] The technical solution of this invention is: A method for controlling the wall thickness of a single-crystal integrated guide vane includes the following steps: (1) Module design: Based on the characteristics and technical requirements of the single crystal integrated guide vane, design the wax mold assembly scheme for the vane; (2) Paste core support: According to the tilt angle of each guide blade in the wax mold assembly scheme, paste core supports with different thicknesses on the blade basin side and blade back side, and with a gradual change in thickness from the air intake side to the exhaust side on the blade core, in order to compensate for the change in wall thickness caused by the blade core floating or rotating in the alloy liquid due to the difference in gravity during the directional solidification of the blade. (3) Wax mold pressing: Place the blade core with the core support attached into the mold, inject wax to complete the wax mold pressing, and inspect the wax mold to obtain a wax mold with the same wall thickness as the core support thickness; (4) Module preparation: After processing the free end of the blade core of the wax model, the wax model is assembled according to the designed wax model assembly scheme; (5) Blade preparation: The qualified modules are prepared by shell preparation, alloy directional solidification, shell removal, core removal and heat treatment to obtain single crystal integrated guide blade castings with qualified wall thickness.
[0006] In the method for controlling the wall thickness of the single crystal combined guide vane, in step (1), guide vanes are arranged sequentially from top to bottom between the outer edge plate and the inner edge plate of the single crystal combined guide vane, and the exhaust edge of each combined guide vane is higher than the air inlet edge of the vane.
[0007] In the method for controlling the wall thickness of the single-crystal interconnected guide vanes, in step (2), the number of core supports is as follows: when the blade width is ≤4cm, 6 pairs of core supports are pasted on each guide vane, one pair of core supports are pasted on the blade inlet edge, the relative position of the midpoint of the blade chord length, and the blade exhaust edge, close to the inner edge plate and the outer edge plate respectively; when the blade width is >4cm, 9 pairs of core supports are pasted on each guide vane, one pair of core supports are pasted on the blade inlet edge, the relative position of the midpoint of the blade chord length, and the blade exhaust edge, close to the inner edge plate, the outer edge plate, and the relative position of the midpoint between the inner edge plate and the outer edge plate respectively; each pair of core supports consists of one on the blade base and one on the blade back, and the positions are symmetrical.
[0008] The method for controlling the wall thickness of the single-crystal integrated guide vane uses a core support material that is either a plastic core support or a wax core support. The wax core support is made by pressing wax material through a mold or by cutting finished wax paper. The adhesive used to attach the core support is an organic paraffin wax or an organic adhesive.
[0009] The method for controlling the wall thickness of the single-crystal interconnected guide vane is described in which the bottom shape of each core support is: a square or rectangle with a side length of 3mm to 6mm, or a circle or ellipse with a diameter of 3mm to 6mm; the core support shape is cuboid, cylinder, boss-shaped, or hemispherical.
[0010] In the method for controlling the wall thickness of the single-crystal integrated guide vane, step (2) involves the following design of the core support thickness: When the inclination angle of the blade chord length direction relative to the horizontal plane in the wax mold assembly scheme is 0° < α ≤ 30°, the core support thickness ratio between the blade basin at the exhaust edge position and the blade back facing upwards and downwards is 1.3~1.4, the core support thickness ratio between the midpoint of the blade chord length and the relative position is 1.15~1.2, and the core support thickness ratio between the blade basin at the intake edge position and the blade back facing upwards and downwards is 1.0; when the inclination angle of the blade chord length direction relative to the horizontal plane is 30° < α ≤ 60°, the core support thickness ratio between the blade basin at the exhaust edge position and the blade back facing upwards and downwards is 1.0; The ratio of the core support thickness between the upper and lower sides of the blade back is 1.1 to 1.3; the ratio of the core support thickness between the midpoint of the blade chord length and the lower side is 1.05 to 1.15; and the ratio of the core support thickness between the blade basin at the air intake edge and the upper and lower sides of the blade back is 1.0. When the tilt angle of the blade chord length direction relative to the horizontal plane is 60° < α < 90°, the ratio of the core support thickness between the blade basin at the exhaust edge and the upper and lower sides of the blade back is 1.0 to 1.1; the ratio of the core support thickness between the midpoint of the blade chord length and the lower side of the blade back is 1.0 to 1.05; and the ratio of the core support thickness between the blade basin at the air intake edge and the upper and lower sides of the blade back is 1.0.
[0011] The method for controlling the wall thickness of the single-crystal integrated guide vane states that the sum of the thicknesses of the core supports on both sides of the blade base and blade back is the sum of the theoretical wall thicknesses of the cast blade base and blade back at that position.
[0012] The method for controlling the wall thickness of the single crystal combined guide blade, the wax model inspection method in step (3) is to inspect the integrity of the blade core inside the wax model by X-ray transmission. If the blade core is found to be broken or cracked, it shall be scrapped.
[0013] In the method for controlling the wall thickness of the single crystal combined guide blade, in step (4), the free end of the blade core is treated as the blade core end exposed outside the wax mold. Wax or paint is applied to the blade core end to keep a certain gap between the blade core end and the shell, so as to avoid excessive stress on the blade core due to the difference in expansion and contraction between the shell and the blade core in the high temperature to low temperature change environment during the directional solidification of the alloy, which would cause the blade core to break.
[0014] The method for controlling the wall thickness of the single-crystal integrated guide vane is described in which the vane core is a silicon-based ceramic core and the shell is an aluminum-based ceramic shell.
[0015] The design concept of this invention is: Before pressing the wax model, a suitable wax model assembly scheme is designed based on the characteristics and technical requirements of the single-crystal integrated guide blade. Then, according to the tilt angle of each guide blade in the wax model assembly scheme (the angle between the blade chord direction and the horizontal direction), a core support bonding scheme is set. Core supports with different thickness ratios on the blade base side and blade back side, a gradual change in thickness from the inlet side to the exhaust side, and a sum of thickness on the blade base side and blade back side equal to the theoretical sum of the wall thicknesses of the blade base and blade back of the casting are bonded to the blade core. This is to compensate for the changes in wall thickness caused by the blade core floating or rotating in the alloy liquid due to gravity differences during the directional solidification of the blade, especially at the relatively thin exhaust edge of the blade. The blade core with the core support attached is then placed in the mold, wax is injected, and pressed to obtain the blade wax model. Then, the free end of the blade core is treated to reduce the stress between the shell and the blade core during the melting and casting process. Finally, the wax model is assembled, the shell is made, the casting is melted, the shell is removed, the core is removed, and heat treatment is performed to obtain a blade casting with qualified wall thickness.
[0016] The present invention has the following advantages and beneficial effects: 1. This invention compensates for changes in wall thickness caused by the blade core floating or rotating in the molten alloy due to gravity differences by attaching core supports of different thicknesses to the blade core. The production process is simple and highly consistent.
[0017] 2. Through experimental verification, the method of the present invention can significantly reduce the scrap rate of the wall thickness dimension of single crystal combined guide blades, thereby improving the casting qualification rate.
[0018] 3. This invention is applicable to the preparation of single-crystal interconnected guide vanes with complex external and internal dimensions and high requirements for wall thickness accuracy. Attached Figure Description
[0019] Figures 1-2 This is a schematic diagram showing the single-crystal double-linked guide vane and its core support at different angles in the embodiment. In the figure, 1-guide vane outer edge plate, 2-guide vane inner edge plate, 3-blade basin of blade No. 1, 4-blade back of blade No. 1, 5-inlet edge of blade No. 1, 6-outlet edge of blade No. 1, 7-core of blade No. 1, 8-fixed end of core of blade No. 1, 9-free end of core of blade No. 1, 10-core support of blade basin of blade No. 1 at the outlet edge of ...
[0020] Figure 3 This is a schematic diagram of the wax model assembly scheme for the single-crystal double-linked guide vanes in the embodiment. In the figure, 16-single-crystal double-linked guide vane, 17-gating system, 18-crystal pulling system, 19-water cooling plate, 20-chord length of the first vane, 21-angle between the chord length direction of the first vane and the horizontal direction. Detailed Implementation
[0021] In the specific implementation process, before pressing the wax model, a wax model combination scheme suitable for the blade is designed based on the characteristics and technical requirements of the single-crystal integrated guide blade. Then, based on the angle between the chord length of each guide blade in the wax model combination scheme and the horizontal direction, a core support pasting scheme is set. Core supports with different thickness ratios on the blade basin side and blade back side, a gradual change in thickness from the intake side to the exhaust side, and a sum of thickness on the blade basin side and blade back side equal to the sum of the theoretical values of the blade basin and blade back wall thicknesses of the casting are pasted on the core to compensate for the wall thickness changes caused by the core floating or rotating in the alloy liquid due to the difference in gravity during the directional solidification of the blade. The core with the core support pasted is then placed into the mold, wax is injected, and pressed to obtain the blade wax model. Then, the free end of the core is treated to reduce the stress between the shell and the core during the melting and casting process. Finally, the wax model is assembled, shell is made, melting and casting is performed, shell is removed, core is removed, and heat treatment is carried out to obtain a blade casting with qualified wall thickness.
[0022] The present invention will now be described in further detail with reference to embodiments and accompanying drawings. Example
[0023] In this embodiment, a single-crystal twin-piece hollow guide vane is prepared using investment casting. Two hollow guide vanes, blade number two and blade number one, are positioned vertically between the outer edge plate 1 and the inner edge plate 2 of the guide vane, which are arranged in parallel. The blade wall thickness requires high precision (1.0 ± 0.1) mm, with a blade width of approximately 20 mm. The chord length of each guide vane is approximately 42.5 mm, and the venting edge of the blade core is relatively thin. If the traditional method is used to set the free end of the blade core, and core supports of the same thickness as the theoretical blade wall thickness are attached to the blade head and back sides of the blade core, the blade core is prone to floating and rotating, leading to eccentricity and non-compliant wall thickness in the blade casting. In previous production experience with this blade, the scrap rate due to non-compliant wall thickness was as high as 50% to 60%.
[0024] Taking blade number one as an example, the specific operating steps are as follows: (1) Module design like Figures 1-3 As shown, based on the characteristics and technical requirements of the single-crystal integrated guide vane, a suitable wax mold assembly scheme is designed for this vane. The hollow inner cavity of the first vane is equipped with a first vane core 7. One end of the first vane core 7 is equipped with a first vane core fixed end 8, and the other end is equipped with a first vane core free end 9. In the wax mold assembly scheme, the vane basin 3 of the first vane faces upward, and the vane back 4 of the first vane faces downward. Therefore, in the core support design process, the thickness ratio of the vane basin core support to the vane back core support is ≥1 to compensate for the wall thickness changes caused by the core floating or rotating in the alloy liquid due to gravity differences.
[0025] (2) Adhesive core support like Figures 1-3 As shown, in the wax model assembly scheme, the position of the exhaust edge 6 of the first blade is higher than that of the intake edge 5 of the first blade. The angle 21 between the chord length direction of the first blade and the horizontal direction is 42°. Six pairs of 12 plastic core supports are set opposite each other: the exhaust edge blade basin core support 10, the exhaust edge blade back core support 13, the chord length midpoint blade basin core support 11, the chord length midpoint blade back core support 14, the intake edge blade basin core support 12, and the intake edge blade back core support 15. The core support is hemispherical in shape, with a bottom diameter of 2mm. The distance between the 6 plastic core supports and the inner side of the guide vane outer edge plate 1 is 2mm, and the distance between the 6 plastic core supports and the inner side of the guide vane inner edge plate 2 is 2mm.
[0026] Among them, the two exhaust side blade core supports 10 and the two exhaust side blade back core supports 13 of the No. 1 blade are symmetrically positioned, and are both 2mm away from the exhaust side 6 of the No. 1 blade; the two midpoint blade core supports 11 and the midpoint blade back core supports 14 of the chord length of the No. 1 blade are symmetrically positioned, and are both at the corresponding projection position of the midpoint of the chord length 20 of the No. 1 blade on the single-crystal double-linked guide blade 16; the two intake side blade core supports 12 and the two intake side blade back core supports 15 of the No. 1 blade are symmetrically positioned, and are both 2mm away from the intake side 5 of the No. 1 blade.
[0027] The core support thickness is designed as follows: the core support 10 for the exhaust side blade basin of the two No. 1 blades is 1.1mm thick; the core support 13 for the exhaust side blade basin of the two No. 1 blades is 0.9mm thick; the core support 11 for the midpoint blade basin of the chord length of the two No. 1 blades is 1.05mm thick; the core support 14 for the midpoint blade basin of the chord length of the two No. 1 blades is 0.95mm thick; the core support 12 for the intake side blade basin of the two No. 1 blades is 1.0mm thick; and the core support 15 for the intake side blade basin of the two No. 1 blades is 1.0mm thick.
[0028] (3) Wax mold pressing The mold is preheated before pressing to a temperature of 35℃~50℃. The blade core with the core support attached is placed into the mold, and medium-temperature paraffin wax is used for wax injection to complete the wax mold pressing. The pressing process parameters are: injection pressure 1.7MPa~2.0MPa, temperature 70℃~75℃, and holding time 60s~70s.
[0029] A wax model inspection is conducted, using X-ray imaging equipment to check the integrity of the blade core inside the wax model. If the blade core is found to be broken or cracked, it is scrapped.
[0030] (4) Module preparation like Figures 1-2As shown, the free end of the blade core of the wax model is treated: molten low-temperature paraffin wax is brushed onto the free end 9 of the first blade core to form a wax cap with a thickness of 0.2mm~0.4mm.
[0031] like Figure 3 As shown, the wax model is assembled according to the designed combination scheme. A water-cooling plate 19 is horizontally set at the bottom of the casting system 17, and the single-crystal double guide vanes 16 are connected to the crystal pulling system 18, and the crystal pulling system 18 is vertically connected to the water-cooling plate 19.
[0032] (5) Leaf preparation The wax model assembly is coated with slurry and then sanded to create the mold shell. The materials used include corundum sand and silica sol. After drying, the mold shell is dewaxed and fired to obtain the finished mold shell. The dewaxing temperature is 150℃, and the firing temperature is 850℃.
[0033] The molten alloy is poured into a mold shell and undergoes directional solidification to obtain a single-crystal blade. The pouring temperature is 1500℃, and the directional solidification rate is 5mm / min. After shell removal, core removal, and heat treatment, a blade casting with acceptable wall thickness is obtained.
[0034] Using industrial CT equipment, the wall thickness of the single-crystal twin-blade casting prepared by this method was tested, and the wall thickness dimensional qualification rate reached 95%; at the same time, the single-crystal integrity of the casting was tested, and the qualification rate reached 90%; the dimensions of the casting were measured by a coordinate measuring machine, and the qualification rate reached 92%.
[0035] The results show that the method of the present invention has the advantages of simple operation and high process consistency. In particular, it can effectively improve the wall thickness accuracy of castings and reduce the wall thickness deviation caused by the directional solidification process of alloy for single crystal integrated guide blades with complex external shape and internal cavity dimensions and high requirements for wall thickness accuracy. This significantly improves the pass rate of single crystal integrated guide blade castings.
Claims
1. A method of controlling the wall thickness dimension of a single crystal ingot guide vane, characterized by, It comprises the following steps: (1) Module design: according to the characteristics and technical requirements of the single crystal joint guide vane, the wax mold combination scheme of the vane is designed; (2) Paste core support: according to the inclination angle of each joint guide vane in the wax mold combination scheme, the core support with different thickness of the vane basin side and the vane back side and gradually changing thickness from the inlet side to the exhaust side is pasted on the vane core, so as to reversely compensate the wall thickness size change caused by the floating or rotation of the vane core in the alloy liquid due to the gravity difference during the directional solidification of the vane; (3) Wax mold pressing: the vane core with pasted core support is put into the mold, the wax is shot to complete the wax mold pressing, and the wax mold inspection is carried out, so as to obtain the wax mold with the same thickness as the core support; (4) Module preparation: after the vane core free end treatment of the wax mold, the wax mold combination scheme is carried out according to the design; (5) Vane preparation: the qualified module is subjected to shell preparation, alloy directional solidification, shell removal, core removal and heat treatment, so as to obtain the single crystal joint guide vane casting with qualified wall thickness size.
2. The method of controlling the gauge of a single crystal ingot guide vane wall according to claim 1, wherein In step (1), the guide vane is arranged between the guide vane outer edge plate and the guide vane inner edge plate from top to bottom.
3. The method of controlling the gauge of a single crystal ingot guide vane wall according to claim 2, wherein In step (2), the number of pasted core supports is as follows: when the vane width is less than or equal to 4 cm, 6 pairs of core supports are pasted on each joint guide vane at the vane inlet edge position, the vane chord length midpoint position, the vane exhaust edge position, close to the inner edge plate and the outer edge plate; when the vane width is greater than 4 cm, 9 pairs of core supports are pasted on each joint guide vane at the vane inlet edge position, the vane chord length midpoint position, the vane exhaust edge position, close to the inner edge plate, the outer edge plate and the midpoint position between the inner edge plate and the outer edge plate; each pair of core supports has one vane basin and one vane back, and the positions are symmetrical.
4. The method of controlling the gauge of a single crystal ingot guide vane wall according to claim 3, wherein The core support material is plastic core support or wax core support, wherein the wax core support is wax material pressed by a mold or cut from finished wax paper; the adhesive used for pasting the core support is organic wax or organic adhesive.
5. The method of controlling the gauge dimension of a single crystal ingot guide vane wall as defined in claim 3, wherein The bottom surface shape of each core support is square or rectangular with a side length of 3-6 mm, or circular or elliptical with a diameter of 3-6 mm; the core support shape is rectangular, cylindrical, boss or hemispherical.
6. A method of controlling the gauge of a single crystal ingot guide vane wall according to one of claims 1 to 5, wherein In step (2), the core thickness is designed as follows: when the inclination angle of the blade chord length direction of the blade in the wax mold combination scheme relative to the horizontal plane is 0°<α≤30°, the ratio of the core thickness of the blade suction side position to the upper side and the lower side of the blade suction side and the blade pressure side is 1.3~1.4, the ratio of the core thickness of the blade chord length midpoint relative position is 1.15~1.2, and the ratio of the core thickness of the blade suction side position to the upper side and the lower side of the blade suction side and the blade pressure side is 1.0; when the inclination angle of the blade chord length direction relative to the horizontal plane is 30°<α≤60°, the ratio of the core thickness of the blade suction side position to the upper side and the lower side of the blade suction side and the blade pressure side is 1.1~1.3, the ratio of the core thickness of the blade chord length midpoint relative position is 1.05~1.15, and the ratio of the core thickness of the blade suction side position to the upper side and the lower side of the blade suction side and the blade pressure side is 1.0; when the inclination angle of the blade chord length direction relative to the horizontal plane is 60°<α<90°, the ratio of the core thickness of the blade suction side position to the upper side and the lower side of the blade suction side and the blade pressure side is 1.0~1.1, the ratio of the core thickness of the blade chord length midpoint relative position is 1.0~1.05, and the ratio of the core thickness of the blade suction side position to the upper side and the lower side of the blade suction side and the blade pressure side is 1.
0.
7. The method of controlling the gauge size of a single crystal ingot guide vane wall according to claim 6, wherein The sum of the core thicknesses of the two sides of the blade suction side and the blade pressure side is the sum of the theoretical wall thicknesses of the blade suction side and the blade pressure side of the casting at the position.
8. The method of controlling the gauge of a single crystal ingot guide vane wall according to claim 1, wherein The wax mold inspection method of step (3) is X-ray transillumination inspection of the blade core integrity in the wax mold, and if the blade core is found to be broken or cracked, it is discarded.
9. The method of controlling the gauge dimension of a single crystal ingot guide vane wall of claim 1, wherein In step (4), the blade core free end processing position is the blade core end head exposed outside the wax mold, and wax or paint is brushed on the blade core end head to leave a certain gap between the blade core end head and the mold shell, so as to avoid the blade core from being broken due to excessive stress caused by the expansion and contraction difference between the mold shell and the blade core in the high temperature to low temperature change environment during the alloy directional solidification process.
10. The method of controlling the gauge dimension of a single crystal ingot guide vane wall of claim 1, wherein The blade core is a silicon-based ceramic core, and the mold shell is an aluminum-based ceramic mold shell.