A method for optimizing the production quality of a hollow blade

Abstract

The application discloses a hollow blade production quality optimization method, and belongs to the technical field of aero-engine blade manufacturing. The method comprises the following steps: a limiting hole is arranged in the inner cavity of a wax mold, and a wax sheet is filled in the limiting hole; a core is assembled into the wax mold; a wax mold pressing operation is performed to obtain a blade wax mold with a wax mold boss; the boundary between the wax material on the top of the wax mold boss and the wax sheet is melted; shell making and directional blade pouring are performed to obtain a blade casting with a boss; and the boss of the blade casting is polished to ensure smooth transition of the profile. The application can avoid the surface scratch problem of the casting caused by traditional wax dripping and sandpaper polishing of the wax sheet and the risk of casting shell slag, and effectively improves the quality and efficiency of blade production and manufacturing.

Description

Technical Field

[0001] This application relates to the field of aero-engine blade manufacturing technology, and in particular, to a method for optimizing the production quality of hollow blades. Background Technology

[0003] Aero-engines are the "heart" of aviation equipment. Turbine blades, as core hot-end components, endure high temperatures, high pressures, alternating loads, and exhaust erosion over long periods. Their material microstructure directly determines the engine's ultimate performance. Traditional equiaxed crystal blades have complex grain boundaries, making them prone to crack initiation and creep failure at high temperatures. Promoting the evolution of blade microstructure from equiaxed crystals to columnar crystals and single-crystal ordered structures can minimize transverse grain boundaries, significantly improving high-temperature creep strength, fatigue resistance, and oxidation resistance. This technology is a key path to upgrading engine thrust-to-weight ratio and extending service life, and is widely used in advanced aircraft, high-bypass passenger aircraft, and gas turbine power plants. The technical specifications for the production of oriented columnar crystal blades clearly require that the blade blade grains grow in an orderly columnar morphology along the extension section throughout the entire process, strictly prohibiting the appearance of equiaxed impurities that deviate from the growth system of the extension section. This is also a core hard indicator for metallographic inspection and finished product quality assessment of blades. However, during actual manufacturing, due to the characteristics of directional solidification growth, adjacent columnar grains naturally form concave polygonal nested structures. The convergence of grain growth can create an illusion of equiaxed crystal structure in certain areas of the blade. This illusion is highly similar to the visual characteristics of non-compliant impurities, easily leading to misjudgments during quality inspection, misclassifying qualified blades as defective. Frequent such misjudgments not only result in the scrapping of large quantities of high-quality blades, raw material losses, and increased production costs, but also reduce the product qualification rate, slow down production delivery, and hinder the improvement of quality and efficiency in the mass production of directional solidification blades.

[0004] The hot-end blades of aero engines typically have complex three-dimensional curved surfaces and strict requirements for shape and position tolerances in terms of dimensional accuracy to achieve the expected aerodynamic performance of the blades. At the same time, in order to improve the blades' heat resistance, there are usually three mainstream technologies, among which the hollow air-cooled design of the blades is an important one. The cool air carries away the heat of the blades through complex channels inside the blades, thereby ensuring that the blades do not overheat and can operate normally.

[0005] In the investment casting industry, the production method of blades usually involves assembling a ceramic core with the same shape as the internal cavity of the blade into a wax mold, then pressing the wax mold to obtain a wax mold with a ceramic core; after that, the blades undergo shell making, melting and pouring, unpacking and cleaning, and core removal to finally obtain a hollow blade.

[0006] The ceramic core used in hollow blade wax molds is made from paraffin wax and ceramic powder through high-temperature sintering and strengthening. Its dimensions inevitably shrink by 1%-5% compared to the core mold. Therefore, to ensure the accurate positioning of the core in the wax mold, a wax sheet of a certain thickness is often used and adhered to the surface of the core to assist in positioning the ceramic core within the wax mold. After pressing the wax mold, the boundary between the wax material and the wax sheet is clearly visible at the adhered location. Please refer to the instruction manual. Figure 2 As shown, if the mold shell is prepared directly in this state, there will be a problem of missing material at the corresponding position of the casting. At the same time, the slurry used for shell making will also penetrate into the interior of the wax mold at the boundary of the wax sheet, which will create a hidden danger for the shell slag of the casting after pouring.

[0007] To address the boundary issues created by the wax sheet used for positioning the core of a hollow blade wax model, the common practice is to drip wax onto the wax sheet, cover it, and then polish it smooth with 400-grit sandpaper after the wax drop has cooled. However, this method leaves sandpaper scratches on the wax model, which will directly cause scratches on the same location in the subsequent casting. Furthermore, the sandpaper-polished surface of the wax model does not eliminate the risk of shell slag formation during shell making. Summary of the Invention

[0008] In view of at least one of the above technical problems, this application provides a method for optimizing the production quality of hollow blades, which can avoid the problems of surface scratches on castings and the risk of casting shell slag caused by traditional wax dripping + sandpaper polishing, and effectively improve the quality and efficiency of blade production and manufacturing.

[0009] According to one aspect of this application, a method for optimizing the production quality of hollow blades is provided, comprising the following steps: S100: A limiting hole is opened in the inner cavity of the wax mold, and the wax sheet is filled into the limiting hole; S200: Assemble the core into the wax mold; S300: Perform wax mold pressing operation to obtain blade wax mold, the blade wax mold has wax mold bosses formed by wax sheets and wax material wrapped around the outer periphery of the wax sheets; S400: The boundary between the wax material and the wax sheet at the top of the hot-melt wax mold boss; S500: Perform mold shell making and blade directional casting to obtain hollow blade castings with bosses in the blade shape; S600: Polishing the bosses of hollow blade castings to make the surface smooth and transition smoothly.

[0010] In some embodiments of this application, during step S300, when pressing the wax mold, the temperature range of the injected wax is 52-62°C, the injection pressure is 1.5-2.5 MPa, the injection flow rate is controlled at 80-200 cc / s, and the filling time is controlled at 20-60 s, to ensure that the molten wax fully fills the wax mold.

[0011] In some embodiments of this application, when pressing the wax mold, the temperature of the wax mold is kept at 20-30°C, and after the wax is filled, a holding pressure of 1.2-2.2 MPa is continuously applied for a holding time of 10-200 seconds to compensate for the volume shrinkage during the cooling and solidification process of the wax.

[0012] In some embodiments of this application, in step S500, when making the mold shell, a surface coating, a transition coating, and a back coating are prepared respectively. The blade wax model is immersed in the surface coating, the transition coating, and the back coating in sequence. After each immersion in a different coating, corundum sand is sprinkled on the surface of the blade wax model to form a mold shell model. The mold shell model is subjected to steam dewaxing treatment to obtain a hollow mold shell with the wax removed. The hollow mold shell after dewaxing treatment is fired to obtain the final blade mold shell.

[0013] In some embodiments of this application, the blades, sprue, top cover plate and pouring cup of the blade wax model are coated with six coats of topcoat, transition layer and backcoat in sequence, while the bottom plate of the blade wax model only needs to be coated with four coats of topcoat, transition layer and backcoat in sequence.

[0014] In some embodiments of this application, after the fourth coat of topcoat, transition coat and backcoat is applied to the blade wax model, the bottom plate of the blade wax model is held above the slurry surface to perform the fifth and sixth coats of coating. This achieves four layers for the bottom plate and the blade mold shell, while the remaining parts have six layers.

[0015] In some embodiments of this application, the viscosities of the topcoat, transition coating, and backcoat are 30-35s, 20-25s, and 10-12s, respectively. The particle size of the corundum sand sprinkled after immersion in the topcoat is 80#, the particle size of the corundum sand sprinkled after immersion in the transition coating is 46#, and the particle size of the corundum sand sprinkled after immersion in the backcoat is 24#.

[0016] In some embodiments of this application, during step S500, when casting the directional blade, the shape of the crystal-drawing segment of the blade wax model is consistent with the shape of the blade tip and is a contoured crystal-drawing segment. The directional blade crystal-drawing segment is divided into a lower crystal-drawing segment, a filter screen, and a grain shaper in sequence towards the blade tip. The filter screen is used to randomly screen the columnar crystals grown by the lower crystal-drawing segment to reduce the number of columnar crystals and increase the cross-sectional size of each columnar crystal. The grain shaper has multiple shaping channels inside, which are used to forcibly adjust the grain boundaries of the columnar crystals so that the columnar crystals obtain grain boundaries consistent with the shape of the channels after passing through the channels.

[0017] In some embodiments of this application, the shape and size of the lower crystal segment are consistent with the blade tip cross section, the filter screen is shaped like a blade tip and is 1-3 mm thicker on one side than the blade tip, the mesh density of the filter screen is 10-30 PPI, and the crystal shaper is consistent with the shape and size of the filter screen.

[0018] In some embodiments of this application, the pore inlet size near the filter screen of the shaping pore is small and the pore spacing is large, allowing only dendrites aligned with the pore inlet to enter and grow, while the misaligned parts are blocked to prevent further growth; the pore outlet size near the blade tip of the shaping pore is large and the pore spacing is small, avoiding abnormal growth of columnar crystals growing in adjacent pores due to excessive pore spacing, and excessive deviation in the shape of columnar crystals.

[0019] This application has the following beneficial effects: This application discloses a method for optimizing the production quality of hollow blades. A limiting hole is created within the cavity of a wax mold. Wax sheets are filled into the limiting hole, adjusting the thickness of the wax sheets from the original X to X + the depth of the limiting hole. A core is then assembled into the wax mold, and a wax molding operation is performed to obtain a blade wax mold with wax mold bosses. After molding, the boundary between the wax sheet and the blade wax mold shifts from the original blade wax mold surface to the top plane of the wax mold boss formed by the limiting hole. The wax material and wax sheet on the top plane of the wax mold boss are melted, and after re-solidification, the boundary between the wax sheet and the blade wax material is eliminated. Subsequently, a mold shell is made, and directional blade casting is performed to obtain a blade casting with bosses. After casting, corresponding bosses are formed at the corresponding positions, which can be removed after polishing, resulting in a smooth transition and a seamless surface. The processing method described in this application completely avoids the problems of surface scratches and casting slag caused by traditional wax dripping and sandpaper polishing. Furthermore, the use of limiting holes on the inner surface of the wax mold as wax sheet mounting holes clarifies the wax sheet pasting position, improves the consistency of the wax sheet pasting position, and helps to improve the overall processing efficiency.

[0020] Of course, any product implementing this application does not necessarily need to achieve all the advantages described above simultaneously. In addition to the purposes, features, and advantages described above, this application also has other purposes, features, and advantages. The following will provide a more detailed description of this application with reference to figures. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the overall structure of a preferred embodiment of this application; Figure 2 This is a schematic diagram showing the clear boundary between the wax material and the wax sheet in existing hollow blades; Figure 3 This is a schematic diagram of the wax sheet installation according to a preferred embodiment of this application; Figure 4 This is a schematic diagram of the multi-segment structure of the directional blade crystal-driving segment according to a preferred embodiment of this application; Figure 5 This is a schematic diagram of the structure of a grain shaper according to a preferred embodiment of this application.

[0022] Legend: 1. Blade wax model; 2. Wax model mold; 21. Limiting hole; 3. Core; 4. Wax sheet; 5. Crystal guide section; 6. Filter screen; 7. Grain shaper; 71. Shaping channel. Detailed Implementation

[0023] The following description provides specific application scenarios and requirements for this specification, intended to enable those skilled in the art to make and use the contents of this specification. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this specification. Therefore, this specification is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0024] Figure 1 This is a schematic diagram of the overall structure of a preferred embodiment of this application; Figure 2 This is a schematic diagram showing the clear boundary between the wax material and the wax sheet in existing hollow blades; Figure 3 This is a schematic diagram of the wax sheet installation according to a preferred embodiment of this application; Figure 4 This is a schematic diagram of the multi-segment structure of the directional blade crystal-driving segment according to a preferred embodiment of this application; Figure 5 This is a schematic diagram of the structure of a grain shaper according to a preferred embodiment of this application.

[0025] A method for optimizing the production quality of hollow blades includes the following steps: S100: A limiting hole 21 is opened in the inner cavity of the wax mold 2, and the wax sheet 4 is filled into the limiting hole 21; S200: Assemble the core 3 into the wax mold 2; S300: Perform wax mold pressing operation to obtain blade wax mold 1. The blade wax mold 1 has a wax mold boss formed by wax sheet 4 and wax material wrapped around the outer periphery of wax sheet 4. S400: The boundary between the wax material at the top of the hot-melt wax mold boss and the wax sheet 4; S500: Perform mold shell making and blade directional casting to obtain hollow blade castings with bosses in the blade shape; S600: Polishing the bosses of hollow blade castings to make the surface smooth and transition smoothly.

[0026] Here, "core 3" refers to the structure assembled with the inner cavity of the wax mold 2. In some embodiments, core 3 is a ceramic core that matches the shape of the internal cavity of the blade.

[0027] In some embodiments, the boundary between the wax material on the top of the wax mold boss and the wax sheet 4 is defined by using a soldering iron or an oxyhydrogen flame. The soldering iron or oxyhydrogen flame only provides heat to melt and re-solidify the wax itself. After the connection is completed, there are no excess residues. This avoids unclean or excess substances on the connection surface, which could affect the bonding between the mold shell and the wax model during subsequent shell making or dewaxing processes, or generate gas during dewaxing, ultimately leading to defects such as inclusions and porosity in the casting.

[0028] This application discloses a method for optimizing the production quality of hollow blades. A limiting hole 21 is opened inside the wax mold 2, and a wax sheet 4 is filled into the limiting hole 21, adjusting the thickness of the wax sheet 4 from the original X to X + the depth of the limiting hole 21. Then, a core 3 is assembled into the wax mold 2, and a wax mold pressing operation is performed to obtain a blade wax mold 1 with wax mold bosses. After pressing, the boundary between the wax sheet 4 and the blade wax mold 1 is transferred from the original surface of the blade wax mold 1 to the top plane of the wax mold boss formed by the limiting hole 21. The wax material and wax sheet 4 on the top plane of the wax mold boss are melted, and after re-solidification, the boundary between the wax sheet 4 and the blade wax material is eliminated. Subsequently, the mold shell is made, and the blade is cast in a directional manner to obtain a blade casting with bosses. After casting, corresponding bosses are formed at corresponding positions, which can be removed after polishing, resulting in a smooth transition and a seamless surface. The processing method described in this application completely avoids the problems of surface scratches on castings and the risk of casting shell slag caused by traditional wax dripping and sandpaper polishing. Furthermore, the limiting hole 21 is opened on the inner surface of the wax mold 2 as a wax installation hole, which can clearly define the pasting position of the wax sheet 4, improve the consistency of the pasting position of the wax sheet 4, and help improve the overall processing efficiency.

[0029] Preferably, in step S300, when pressing the wax mold, the temperature range of the injected wax is 52-62℃, the injection pressure is 1.5-2.5MPa, the injection flow rate is controlled at 80-200cc / s, and the filling time is controlled at 20-60s, to ensure that the molten wax fully fills the wax mold 2.

[0030] Understandably, to ensure good wax flowability while avoiding excessive shrinkage due to overheating and reduced dimensional accuracy, the wax temperature is controlled within the range of 52–62°C. This keeps the wax in a paste or semi-fluid state, while avoiding excessively low temperatures that result in poor wax flowability and an inability to accurately replicate the roughness of the mold's inner surface, leading to a rough wax mold surface. A wax injection pressure not exceeding 2.5 MPa prevents mold deformation, flash, or increased internal stress in the wax mold. An injection pressure not lower than 1.5 MPa ensures complete filling of complex structures with wax, preventing incomplete filling. Simultaneously, controlling the injection flow rate and filling time ensures sufficient filling of the wax mold 2 with molten wax.

[0031] Preferably, when pressing the wax mold, the temperature of the wax mold 2 is kept at 20-30°C. After the wax is filled, a holding pressure of 1.2-2.2 MPa is continuously applied for a holding time of 10-200 seconds to compensate for the volume shrinkage during the cooling and solidification process of the wax.

[0032] It should be noted that after the wax has basically filled the mold cavity, as the wax continues to cool and solidify and shrink further, a holding pressure, which is lower than the injection pressure, forces a small amount of extra wax to be added into the cavity. This effectively prevents surface pits, internal shrinkage cavities, or overall dimensional reduction caused by shrinkage. The temperature of the wax mold 2 is within the range of 20–30°C, which matches the temperature of the wax. This ensures sufficient fluidity of the injected wax for filling while avoiding defects caused by insufficient temperature difference leading to excessive cooling of the wax. This achieves an optimal balance between wax fluidity and shrinkage, thus guaranteeing the dimensional accuracy and surface quality of the wax mold.

[0033] Preferably, in step S500, when making the mold shell, a surface coating, a transition coating, and a back coating are prepared respectively. The blade wax model 1 is immersed in the surface coating, the transition coating, and the back coating in sequence. After each immersion in a different coating, corundum sand is sprinkled on the surface of the blade wax model 1 to make a mold shell model. The mold shell model is subjected to steam dewaxing treatment to obtain a hollow mold shell with the wax removed. The hollow mold shell after dewaxing treatment is fired to obtain the final blade mold shell.

[0034] It is understandable that immersing the blade wax model 1 sequentially in the top coat, transition coat, and back coat can meet the differentiated performance requirements of the shell at different structural levels, thereby ensuring the dimensional accuracy, surface quality, and yield of the final blade casting. The top coat directly determines the surface roughness and surface quality of the casting; the transition coat acts as a bonding agent, preventing paint delamination during subsequent drying, dewaxing, or pouring processes; and the back coat provides sufficient room-temperature strength and high-temperature stability to ensure the component does not deform and maintains dimensional accuracy.

[0035] In some embodiments, when the shell model is subjected to steam dewaxing, the pressure in the vessel is 0.5 to 0.7 MPa and the dewaxing time is 10 to 20 minutes to obtain a hollow shell with dewaxed material; the shell after dewaxing is then calcined in a high-temperature furnace at 850°C to 900°C for 1 to 2.5 hours to obtain the desired blade shell.

[0036] Preferably, the blades, sprue, top cover plate and pouring cup of the blade wax model 1 are coated with six coats of topcoat, transition layer and backcoat in sequence, while the bottom plate of the blade wax model 1 only needs to be coated with four coats of topcoat, transition layer and backcoat in sequence.

[0037] It should be noted that the base plate of the blade wax mold 1 can reduce the number of mold shell layers, increase the solidification temperature gradient during the directional solidification crystal pulling process, and also save material costs.

[0038] In this preferred embodiment, after the fourth coat of topcoat, transition coat and backcoat is applied to the blade wax mold 1, the bottom plate of the blade wax mold 1 is held above the slurry surface for the fifth and sixth coats of paint. This achieves four layers for the bottom plate and the blade mold shell, while the remaining parts have six layers.

[0039] Understandably, when preparing to apply the fifth layer of slurry after the fourth layer of the mold shell has dried, simply keeping the base plate above the slurry surface will ensure that the number of coating layers on the base plate is reduced. Similarly, when preparing to apply the sixth layer of slurry after the fifth layer of the mold shell has dried, it is also necessary to keep the base plate above the slurry surface to achieve four layers for the base plate and blade mold shell, and six layers for the remaining parts.

[0040] Preferably, the viscosities of the topcoat, transition coating, and backcoat are 30-35s, 20-25s, and 10-12s, respectively. The particle size of the corundum sand sprinkled after immersion in the topcoat is 80#, the particle size of the corundum sand sprinkled after immersion in the transition coating is 46#, and the particle size of the corundum sand sprinkled after immersion in the backcoat is 24#.

[0041] It should be noted that during shell making, the viscosity of each layer of slurry is selected to balance sufficient slurry fluidity and a suitable slurry coating thickness. The viscosity cannot be too high, resulting in poor slurry fluidity; nor can it be too low, leading to insufficient slurry coating thickness and the risk of grit penetrating the slurry during sand application. The principle for selecting the particle size of each layer of corundum sand is that the surface layer has a smaller particle size, which is beneficial for forming a smooth and delicate surface; the transition layer and back layer have a larger particle size, which is beneficial for providing sufficient strength to the mold shell.

[0042] In this application, the surface coating directly contacts the wax model surface, forming the surface of the casting after subsequent pouring. Using fine-grained sand allows the surface slurry to fully fill the gaps, resulting in a denser structure and a smooth, delicate surface. This ensures the accurate replication of the wax model's fine contours and prevents defects such as pitting and dents in the casting. The back layer, as the outer layer, requires coarse-grained sand. The large gaps between the sand grains provide sufficient breathability and improve the heat dissipation capacity of the mold shell. The transition layer, as the intermediate layer, needs a particle size between the two, capable of "interlocking" with the fine sand of the surface layer to prevent cracking due to insufficient strength. Simultaneously, the transition layer also needs to buffer the stress between the surface and back layers, preventing delamination and peeling of the mold shell during drying and firing processes.

[0043] In some embodiments, the composition and proportions of the topcoat, transition layer, and backcoat are shown in Table 1: Preferably, please refer to Figure 4 and 5 As shown, in step S500, during the casting of the directional blade, the shape of the directional blade crystal-drawing segment of the blade wax model 1 is consistent with the shape of the blade tip and is a contour-following crystal-drawing segment. The directional blade crystal-drawing segment is divided into a lower crystal-drawing segment 5, a filter screen 6, and a grain shaper 7 in sequence towards the blade tip. The filter screen 6 is used to randomly screen the columnar crystals grown in the lower crystal-drawing segment 5 to reduce the number of columnar crystals and increase the cross-sectional size of each columnar crystal. The grain shaper 7 has multiple shaping channels 71 inside. The shaping channels 71 are used to forcibly adjust the grain boundaries of the columnar crystals so that the columnar crystals obtain grain boundaries consistent with the shape of the channels after passing through the channels.

[0044] It should be noted that the shape of the directional blade's crystal-guiding section is consistent with the shape of the blade tip, and it is a contour-guided crystal-guiding section. The crystal-guiding section faces the direction of the blade tip (that is, from one end of the crystallizer to the other end of the blade tip). The crystal-guiding section consists of three parts: the lower crystal-guiding section 5, the filter screen 6, and the grain shaper 7. The lower crystal-guiding section 5 is used to achieve the transformation of randomly oriented equiaxed crystals into columnar crystals under a unidirectional temperature gradient after the liquid metal comes into contact with and condenses in the crystallizer. The filter screen 6 is a foam-type filter screen with a shape similar to the blade tip. It is used to randomly screen the columnar crystals grown by the lower crystal-guiding section 5, appropriately reducing the number of columnar crystals and increasing the cross-sectional size of each columnar crystal. The grain shaper is a porous component of refractory material, which consists of multiple shaping channels 71. The shaping channels 71 extend along the thickness direction of the grain shaper and can forcibly adjust the grain boundaries of the columnar crystals, so that the shape of the columnar crystals after passing through the channels is consistent with the shape of the channels, thus obtaining grain boundaries consistent with the shape of the channels.

[0045] Optionally, the shaping channel 71 is shaped as an equilateral triangle, a square, or a regular hexagon, with a smaller inlet size near the filter screen and a larger outlet size near the blade tip.

[0046] Preferably, please refer to Figure 4 and 5 As shown, the shape and size of the lower crystal segment 5 are consistent with the cross-section of the blade tip. The filter screen 6 is shaped like the blade tip and is 1-3 mm thicker on one side than the blade tip. The mesh density of the filter screen 6 is 10-30 PPI. The crystal shaper 7 has the same shape and size as the filter screen 6.

[0047] In this preferred embodiment, the pore inlet size of the shaping channel 71 near the filter screen 6 is small and the pore spacing is large, allowing only dendrites aligned with the pore inlet to enter and grow, while the misaligned parts are blocked to prevent further growth; the pore outlet size of the shaping channel 71 near the blade tip is large and the pore spacing is small, avoiding abnormal growth of columnar crystals growing in adjacent channels due to excessive pore spacing, and excessive deviation in the shape of columnar crystals.

[0048] It should be noted that the filter screen 6 is a foam-type filter screen, shaped like a blade tip but larger in size, which can randomly select the columnar crystals growing in the lower crystallization section 5. The filter screen 6 is thicker than the lower crystallization section 5, and the internal pore tunnels of the filter screen 6 can enhance heat conduction. The filter screen 6 can also slow down the flow rate of the molten metal flowing through the grain shaper 7, reducing the impact of the molten metal on the crystallizer, lifting the mold shell, and the risk of steel leakage from the bottom plate. The inlet size of the shaping channel 71 near the filter screen 6 is small and the channel spacing is large, allowing only dendrites aligned with the channel inlet to enter and grow, while the misaligned parts are blocked and prevented from growing further. The outlet size of the shaping channel 71 near the blade tip is large and the channel spacing is small. In some embodiments, the channel spacing is 0.1 to 0.2 mm, to avoid abnormal growth of columnar crystals growing in adjacent channels (due to local temperature field fluctuations) due to excessively large channel spacing, and excessive deviation of the columnar crystal shape.

[0049] The crystal-drawing section of the directional blade in this application is designed as a three-section structure (lower crystal-drawing section 5, filter screen 6, and grain shaper 7), which does not increase the crystal-drawing height. It can even shorten the crystal-drawing height while shaping the shape of columnar crystal grains and grain boundaries, avoiding the problem of blade scrapping caused by the nesting and intersecting growth of concave polygons at the grain boundaries of columnar crystals, which resembles equiaxed crystals.

[0050] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0051] It should be understood that in the foregoing description of the embodiments in this specification, various features are combined in a single embodiment, drawing, or description for the purpose of simplifying the description and aiding in the understanding of a feature. However, this does not mean that the combination of these features is necessary, and those skilled in the art may readily identify some of the devices as separate embodiments when reading this specification. That is, the embodiments in this specification can also be understood as an integration of multiple secondary embodiments. It is also valid when each secondary embodiment contains fewer than all the features of a single foregoing disclosed embodiment.

[0052] Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments described in this specification. Other modified embodiments are also within the scope of this specification. Therefore, the embodiments disclosed in this specification are merely examples and not limitations. Those skilled in the art can implement the applications described in this specification by adopting alternative configurations based on the embodiments in this specification. Therefore, the embodiments in this specification are not limited to the embodiments precisely described in the application. For those skilled in the art, several improvements, modifications, or changes can be made without departing from the principles of this application, and the above technical features can also be combined in an appropriate manner; these improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other occasions without modification, should all be considered as protection of this application.

Claims

1. A method for optimizing the production quality of hollow blades, characterized in that, Includes the following steps: S100: A limiting hole (21) is opened in the inner cavity of the wax mold (2), and the wax sheet (4) is filled into the limiting hole (21); S200: Assemble the core (3) into the wax mold (2); S300: Perform wax mold pressing operation to obtain blade wax mold (1). The blade wax mold (1) has a wax mold boss formed by wax sheet (4) and wax material wrapped around the outer periphery of wax sheet (4). S400: The boundary between the wax material at the top of the hot-melt wax mold boss and the wax sheet (4); S500: Perform mold shell making and blade directional casting to obtain hollow blade castings with bosses in the blade shape; S600: Polishing the bosses of hollow blade castings to make the surface smooth and transition smoothly.

2. The method for optimizing the production quality of hollow blades according to claim 1, characterized in that, In step S300, when pressing the wax mold, the temperature range of the injected wax is 52-62℃, the injection pressure is 1.5-2.5MPa, the injection flow rate is controlled at 80-200cc / s, and the filling time is controlled at 20-60s to ensure that the molten wax fully fills the wax mold (2).

3. The method for optimizing the production quality of hollow blades according to claim 2, characterized in that, When pressing the wax mold, ensure that the temperature of the wax mold (2) is between 20 and 30°C. After the wax is filled, apply a holding pressure of 1.2-2.2 MPa for 10-200 seconds to compensate for the volume shrinkage of the wax during the cooling and solidification process.

4. The method for optimizing the production quality of hollow blades according to claim 1, characterized in that, In step S500, when making the mold shell, the surface coating, transition coating and back coating are prepared respectively. The blade wax mold (1) is immersed in the surface coating, transition coating and back coating in sequence. After each immersion in different coatings, corundum sand is sprinkled on the surface of the blade wax mold (1) to make the mold shell model. The mold shell model is subjected to steam dewaxing treatment to obtain a hollow mold shell with dewaxed material. The hollow mold shell after dewaxing treatment is fired to obtain the final blade mold shell.

5. The method for optimizing the production quality of hollow blades according to claim 4, characterized in that, The blades, sprue, top cover and pouring cup of the blade wax model (1) are coated with six coats of top coat paint, transition coat paint and back coat paint in sequence. The bottom plate of the blade wax model (1) only needs to be coated with four coats of top coat paint, transition coat paint and back coat paint in sequence.

6. The method for optimizing the production quality of hollow blades according to claim 5, characterized in that, After the fourth coat of topcoat, transition coat and backcoat of the blade wax mold (1) is applied, the bottom plate of the blade wax mold (1) is held above the slurry surface for the fifth and sixth coats of coating. This will result in four layers for the bottom plate and the blade mold shell, and six layers for the rest of the parts.

7. The method for optimizing the production quality of hollow blades according to claim 4, characterized in that, The corresponding viscosities of the topcoat, transition layer, and backcoat are 30–35 s, 20–25 s, and 10–12 s, respectively. The particle size of the corundum sand sprinkled after immersion in the topcoat is 80#, the particle size of the corundum sand sprinkled after immersion in the transition layer is 46#, and the particle size of the corundum sand sprinkled after immersion in the backcoat is 24#.

8. The method for optimizing the production quality of hollow blades according to claim 1, characterized in that, In step S500, during the casting of the directional blade, the shape of the directional blade crystal-leading segment of the blade wax mold (1) is consistent with the shape of the blade tip and is a contour-following crystal-leading segment. The directional blade crystal-leading segment is divided into a lower crystal-leading segment (5), a filter screen (6), and a grain shaper (7) in the direction towards the blade tip. The filter screen (6) is used to randomly screen the columnar crystals grown by the lower crystal-leading segment (5) to reduce the number of columnar crystals and increase the cross-sectional size of the columnar crystals. The grain shaper (7) has multiple shaping channels (71) inside. The shaping channels (71) are used to force the adjustment of the grain boundaries of the columnar crystals so that the columnar crystals obtain grain boundaries consistent with the shape of the channels after passing through the channels.

9. The method for optimizing the production quality of hollow blades according to claim 1, characterized in that, The shape and size of the lower crystal section (5) are consistent with the cross section of the blade tip. The filter screen (6) is shaped like the blade tip and is 1-3 mm thicker on one side than the blade tip. The mesh density of the filter screen (6) is 10-30 PPI. The crystal shaper (7) is consistent with the shape and size of the filter screen (6).

10. The method for optimizing the production quality of hollow blades according to claim 8, characterized in that, The shaping channel (71) has a small inlet size and a large channel spacing near the filter screen (6), allowing only dendrites aligned with the inlet to grow, while the misaligned parts are blocked to prevent further growth; the shaping channel (71) has a large outlet size and a small channel spacing near the leaf tip, avoiding abnormal growth of columnar crystals growing in adjacent channels due to excessive channel spacing, resulting in excessive deviation of columnar crystal shape.

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