CN114799047A - Multilayer module superposed wax mold structure and method for efficiently preparing single crystal blade by using same - Google Patents

Abstract

The invention provides a multi-layer module superposed wax mold structure and a method for efficiently preparing a single crystal blade by using the same, and relates to the technical field of precision casting of aero-engine blades. The multilayer module superposed wax pattern structure provided by the invention comprises a casting system wax pattern, a blade wax pattern, a crystal selector wax pattern and a chilling plate wax pattern which are sequentially connected from top to bottom; the blade wax pattern comprises a plurality of layers of blade wax patterns which are sequentially connected from top to bottom. The invention effectively reduces the diameter of the die set and reduces the size requirements on the chilling plate and the die cavity of the directional solidification furnace under the condition of ensuring the same production capacity of the blades; the reduction of the diameter of the module obviously improves the temperature field distribution in the directional solidification process, improves the uniformity of a transverse temperature field, reduces the bending degree of an isotherm and improves the temperature gradient at the front edge of a solid-liquid interface; the defects of the single crystal blade are obviously reduced, including the reduction of the generation tendency of mixed crystals at the transition section and the platform, and the qualification rate of the mass production of the single crystal blade is effectively improved.

Description

A multi-layer module superimposed wax mold structure and a method for efficiently preparing a single crystal blade

technical field

The invention relates to the technical field of precision casting of aero-engine blades, in particular to a multi-layer module superimposed wax mold structure and a method for efficiently preparing single crystal blades.

Background technique

Single crystal blade is an important part of aero-engine, and single-crystal blade for aero-engine is generally prepared by investment casting method. First, the structural design of the module is carried out, the wax mold is pressed and assembled, the wax mold module is degreasing, and then the mold shell is prepared by coating, sanding, dewaxing, and roasting. Finally, the molten alloy liquid is poured and fixed on the In the mold shell of the high-vacuum directional solidification furnace, the mold is pulled to the cooling area, and the vacuum is broken after the solidification is completed.

Among them, the structural design of the module, as the initial step of single crystal blade production, will directly affect the quality of the single crystal blade. At present, the module structure for mass production of single crystal blades in the industry is generally a single-layer module, that is, the blade is arranged in a single layer; under the condition that the production capacity of single crystal blades remains unchanged, the diameter of the single-layer module is large, and a On the one hand, the size of the cavity of the chill plate and the directional solidification furnace is required to be large. On the other hand, the lateral temperature field distribution during the directional solidification process is uneven, the isotherm is bent, the temperature gradient at the front of the solid-liquid interface is small, and the transition section and platform miscellaneous crystals are prone to appear. and other solidification defects, which restrict the production qualification rate of single crystal blades.

The wax module trees disclosed in Chinese patents CN107931523A and CN210730902U are single-layer module structures commonly used in the current industry, that is, the blades are arranged in a single layer around the center of the module; when faced with the task of producing large quantities of single crystal blades, this kind of When the structure increases the number of blades in the module to improve the production capacity, it will inevitably lead to an increase in the diameter of the module, which in turn increases the requirements for the size of the chill plate and the cavity of the directional solidification furnace.

Xu et al. pointed out in "Multiscale Modeling and Simulation of Directional Solidification Process of Turbine Blade Casting with MCA Method" published in Metallurgical and Materials Transactions B in 2014 that when the number of blades in the module is large, the temperature field inside the blade during the directional solidification process will Tilt and bend.

Li Yafeng's doctoral dissertation "Research on Miscellaneous Crystal Defects in the Platform of Nickel-Based Single Crystal Superalloy Turbine Blades" pointed out that the curved isotherm will lead to preferential supercooling at the corners of the platform, and the miscellaneous crystals will nucleate and form The tendency increases with the degree of curvature of the isotherm.

To sum up, single-layer modules are commonly used in the mass production of single-crystal blades in the prior art. The diameter of such single-layer modules is relatively large. On the one hand, the chill plate and the cavity of the directional solidification furnace are required to have large dimensions; On the other hand, it causes the deterioration of the temperature field distribution during the directional solidification process, including the uneven temperature field in the transverse direction, the bending of the isotherm and the small temperature gradient at the front of the solid-liquid interface, which leads to the increase of the formation tendency of miscellaneous crystals and seriously reduces the size of the single crystal blade. Qualification rate of mass production.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a multi-layer module superimposed wax mold structure and a method for efficiently preparing a single crystal blade. Using the multi-layer module superimposed wax mold structure provided by the present invention can ensure that the production capacity of the blade remains unchanged. It can effectively reduce the diameter of the module, reduce the size of the chill plate and the cavity of the directional solidification furnace, improve the temperature field distribution during the directional solidification process, reduce the generation of solidification defects, and realize the efficient preparation of single crystal blades.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a multi-layer modular superimposed wax mold structure for preparing a single crystal blade, including a pouring system wax mold, a blade wax mold, a crystal selector wax mold and a chill plate wax mold connected in sequence from top to bottom ;

The blade wax mold includes multiple layers of blade wax molds connected sequentially from top to bottom.

Preferably, the casting system wax mold is composed of a sprue cup wax mold and a number of sprue wax molds distributed around the sprue cup wax mold; the bottom end of the sprue wax mold is connected to the top blade wax mold The tops of the molds are connected, the bottom end of the top-layer blade wax mold is connected with the top of the next-layer blade wax mold, and so on, the multi-layer blade wax molds are connected end to end in the vertical direction.

Preferably, it also includes a center pillar wax mold; the sprue cup wax mold, the center pillar wax mold and the chill plate wax mold are concentrically connected sequentially from top to bottom.

Preferably, the separator wax mold includes an upper spiral segment wax mold and a lower seeding segment wax mold.

Preferably, the number of layers of the blade wax model is two layers.

The invention provides a preparation method of a single crystal blade, comprising the following steps:

Provide the multi-layer module superimposed wax mold structure described in the above technical solution;

The multi-layer module superimposed wax mold structure is successively coated, sanded, dewaxed and roasted to obtain a mold shell;

The molten alloy liquid is poured into the mold shell, so that the molten alloy liquid is directional solidified from bottom to top, and the single crystal blade is obtained after shelling.

Preferably, both the casting and the solidification are performed in a directional solidification furnace; the directional solidification of the molten alloy liquid from bottom to top includes: during the solidification process, the mold shell is drawn downward to a cooling area.

Preferably, the pulling rate is 50-150 μm/s.

Preferably, the dewaxing is steam dewaxing.

Preferably, before the molten alloy liquid is poured into the mold shell, the mold shell is also preheated.

The invention provides a multi-layer modular superimposed wax mold structure for preparing a single crystal blade, including a pouring system wax mold, a blade wax mold, a crystal selector wax mold and a chill plate wax mold connected in sequence from top to bottom ; The blade wax pattern includes multiple layers of blade wax patterns connected in sequence from top to bottom. The multi-layer module superimposed wax mold structure provided by the present invention builds the multi-layer module superimposed wax mold structure in the manner of superimposing the blade wax mold up and down under the condition of ensuring the same blade production capacity, and the two-layer module superimposed wax mold structure is For example, the diameter of the module can be reduced to half of that of a single-layer module, effectively reducing the diameter of the module and reducing the size requirements for the chill plate and the cavity of the directional solidification furnace; the reduction in the diameter of the module significantly improves the directional solidification process. The medium temperature field distribution improves the uniformity of the transverse temperature field, reduces the bending degree of the isotherm, and increases the temperature gradient at the front of the solid-liquid interface; significantly reduces the generation of defects in single crystal blades, and can reduce the tendency of stray crystals at the transition section and platform. , effectively improve the qualification rate of mass production of single crystal blades.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the multi-layer module superimposed wax mold of Example 1; in Fig. 1, 1 is the wax mold of the pouring system; 1-1 is the sprue cup wax mold; 1-2 is the inclined runner wax mold; 3 is the wax model of the crystal selector; 3-1 is the wax model of the spiral section; 3-2 is the wax model of the seeding section; 4 is the wax model of the chill plate; 5 is the wax model of the central column;

Fig. 2 is the top view of Fig. 1;

FIG. 3 is a detailed display diagram of the double-layer superimposed blade in the multi-layer module superimposed wax mold structure of FIG. 1;

Figure 4 is a comparison chart of the temperature field simulation results of the single-layer module blade (a) and the double-layer module superimposed blade (b) and the upper blade (c) when the molten superalloy solidifies to the blade body. The lower limit temperature is the liquid and solidus temperature of the alloy, respectively;

Figure 5 is a comparison chart of the temperature field simulation results of the single-layer module blade (a) and the double-layer module superimposed blade (b) and the upper blade (c) when the molten superalloy solidifies to the blade platform. The lower limit temperature is the liquid and solidus temperature of the alloy, respectively;

Figure 6 is a comparison diagram of the simulation results of solidification grains of a single-layer module blade (a) and a double-layer module superimposed blade (b).

Detailed ways

The invention provides a multi-layer modular superimposed wax mold structure for preparing a single crystal blade, including a pouring system wax mold, a blade wax mold, a crystal selector wax mold and a chill plate wax mold connected in sequence from top to bottom ;

The blade wax mold includes multiple layers of blade wax molds connected sequentially from top to bottom.

The multi-layer module superimposed wax model structure provided by the present invention includes a casting system wax model and a blade wax model connected to the bottom end of the casting system wax model. As an embodiment of the present invention, the casting system wax mold is composed of a sprue cup wax mold and a plurality of ramped runner wax molds distributed around the sprue cup wax mold. As an embodiment of the present invention, the sprue wax mold is a radial structure uniformly distributed along the circumference of the sprue cup wax mold. In the present invention, the inclined angle of the inclined runner is preferably 20° to 70°. In the present invention, there are multiple sprue wax molds.

As an embodiment of the present invention, the bottom end of the sprue wax mold is connected to the top of the top blade wax mold, the bottom end of the top blade wax mold is connected to the top of the next layer blade wax mold, and so on , the multi-layer blade wax patterns are connected end to end in the vertical direction. As an embodiment of the present invention, the bottom end of a sprue wax mold is connected to two blade wax molds adjacent in the vertical direction, as shown in FIG. 3 .

In the present invention, the number of layers of the blade wax model is preferably two layers.

The multi-layer module superimposed wax mold structure provided by the present invention includes a crystallizer wax mold connected to the bottom end of the blade wax mold. As an embodiment of the present invention, the crystal separator wax mold includes an upper spiral segment wax mold and a lower seeding segment wax mold. In the present invention, the spiral segment wax model and the bottom end of the bottommost blade wax model are connected.

The multi-layer module superimposed wax mold structure provided by the present invention includes a chill plate wax mold connected to the bottom end of the crystal selector wax mold.

As an embodiment of the present invention, the multi-layer module superimposed wax mold structure further includes a center pillar wax mold; the sprue cup wax mold, center pillar wax mold and chill plate wax mold are coaxial from top to bottom in sequence Heart connection.

As an embodiment of the present invention, when the number of layers of the blade wax mold is two, the multi-layer module superimposed wax mold structure is: the wax mold of the gating system is composed of the sprue cup wax mold and the sprue around the gate. The cup wax mold is composed of several oblique runner wax molds distributed in a circle; the bottom end of the oblique runner wax mold is connected with the top end of the upper blade wax mold, and the bottom end of the upper blade wax mold is connected with the top of the lower blade wax mold connection; the bottom end of the lower blade wax mold is connected with the top end of the wax mold of the spiral segment, and the bottom end of the wax mold of the spiral segment is connected with the top end of the wax mold of the seeding segment; the bottom end of the wax mold of the seeding segment is connected; It is connected with the chill plate wax mold; the sprue cup wax mold, the center column wax mold and the chill plate wax mold of the wax mold of the pouring system are connected concentrically from top to bottom in sequence.

The present invention also provides a method for preparing a single crystal blade, comprising the following steps:

Provide the multi-layer module superimposed wax mold structure described in the above technical solution;

The multi-layer module superimposed wax mold structure is successively coated, sanded, dewaxed and roasted to obtain a mold shell;

The molten alloy liquid is poured into the mold shell, so that the molten alloy liquid is directional solidified from bottom to top, and the single crystal blade is obtained after shelling.

The present invention provides the multi-layer module superimposed wax mold structure described in the above technical solution. In the present invention, a pneumatic wax pressing machine is preferably used to obtain the multi-layer module superimposed wax mold structure described in the above technical solution. In the present invention, the temperature of the wax cylinder during the pressing is preferably 70-75° C., the temperature of the nozzle is preferably 60-65° C., and the injection pressure is preferably 0.1-0.6 MPa.

After the multi-layer module superimposed wax mold structure is obtained, the present invention sequentially performs coating, sanding, dewaxing and roasting on the multi-layer module superimposed wax mold structure to obtain a mold shell. In the present invention, the multi-layer modular superimposed wax mold structure preferably further includes degreasing and degreasing treatment before coating, hanging, and sanding. The invention adopts degreasing and degreasing treatment, which can remove the grease on the surface of the die and improve the ability of the coating to wet the surface of the wax die.

The present invention preferably adopts the dip coating method to coat and hang the multi-layer module superimposed wax mold structure. In the specific painting and hanging process, keep the surface of the multi-layer module superimposed wax mold structure evenly hung with paint to avoid blank and local accumulation; use a brush or special tools to brush the edges, grooves, and joints evenly to avoid bubbles. In the present invention, it is preferable to clean the floating sand on the previous layer before painting each layer of paint: stirring regularly during the painting and hanging process to master and adjust the viscosity of the paint. In the present invention, the sanding is preferably fluidized sanding or rain-type sanding. In the present invention, after the multi-layer module superimposed wax mold structure is taken out from the paint tank, sand can be sprinkled when the remaining paint on it flows uniformly and no longer drips continuously; the particle size of the sand is according to the paint level. Select and adapt to the viscosity of the paint, the surface layer sand has a finer particle size, and the reinforcement layer has a coarser sand particle size. In the present invention, drying and hardening are carried out after each coating and sanding layer. In a specific embodiment of the present invention, the multi-layer module is superimposed on the wax mold structure for 7-layer coating, hanging and sanding. The first layer is a surface layer, and 70# EC95 powder, silica sol and slurry are mixed and then coated. Hanging, self-drying for more than 8 hours; 2nd to 4th layers, mix 35#EC95 powder, silica sol and slurry, and then carry out 2-layer coating and hanging, self-drying for more than 6h; 5th to 6th layers, mix 22#EC95 powder, silicon After the sol and slurry are mixed, coat and hang, and dry for more than 6 hours; the seventh layer is the sealing layer, only the slurry is coated and hanged, and it will dry after the coating is completed; after 1 to 3 layers are dried, the lower layer is coated with silica sol before hanging. Strengthen and require good ventilation, ensure suitable temperature (21 ± 1.5 ℃) and humidity (40 ± 10%).

In the present invention, the dewaxing is preferably steam dewaxing. In the present invention, during the steam dewaxing, the steam pressure of the outer bladder is preferably 0.7-0.75MPa, the dewaxing time is preferably 12-14min, and the dewaxing temperature is preferably 160-170min. In the present invention, it is preferable to perform ventilation drying after the dewaxing.

In the present invention, the roasting is preferably carried out in a heating furnace; the roasting temperature is preferably 850° C.; the holding time is preferably 1.5 h. In the present invention, after the calcination, it is preferably taken out after being cooled to 500° C. with the furnace, and cooled to room temperature in the air to obtain a mold shell.

After the mold shell is obtained, the present invention pours the molten alloy liquid into the mold shell, so that the molten alloy liquid is directional solidified from bottom to top, and the single crystal blade is obtained after shelling. The present invention preferably further includes preheating the mold shell before pouring the molten alloy liquid into the mold shell. In the present invention, the temperature of the preheating is preferably 1530-1560°C. In the present invention, the pouring time is preferably less than 5s; the pouring temperature is preferably 1520-1540°C.

In the present invention, the casting and solidification are preferably performed in a directional solidification furnace; the directional solidification of the molten alloy liquid from bottom to top preferably includes: during the solidification process, the mold shell is drawn downward to a cooling area. In the present invention, the pulling rate is preferably 50-150 μm/s, more preferably 100 μm/s.

In the present invention, the casting and solidification are preferably performed under vacuum conditions.

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

The first step, the structural design and preparation of the wax model:

The structure of the double-layer module superimposed wax mold used in this embodiment is shown in Figures 1-2.

a. The design of the double-layer module superimposed wax mold structure and the wax mold pressing: the double-layer module superimposed wax mold structure consists of the casting system wax mold 1, blade wax mold 2, crystal selector wax mold 3, and chill plate wax The mold 4 and the central pillar wax mold 5 are composed of five parts; the pouring system wax mold 1 is composed of a sprue cup wax mold 1-1 and a number of inclined sprue wax molds 1-2 evenly distributed around it. The separator wax mold 3 is composed of the upper spiral section wax mold 3-1 and the lower seeding section wax mold 3-2; the wax mold of the above structure is pressed out by a pneumatic wax press; the temperature of the wax tank when the wax mold is pressed At 75℃, the nozzle temperature is 65℃, the injection pressure is 0.5MPa, and the pressed wax mold is deburred and trimmed;

b. The combination of the double-layer module superimposed wax mold structure: the above wax molds are combined in the following order: the bottom end of the sprue wax mold 1-2 is connected to the top of the upper blade wax mold, and the bottom end of the upper blade wax mold is connected to the lower blade. The top of the wax mold is connected; the bottom end of the lower blade wax mold is connected to the top of the crystal selector wax mold 3; the bottom end of the crystal selector wax mold 3 is connected to the chill plate wax mold 4; the wax mold of the pouring system wax mold 1- 2. The central pillar wax mold 5 and the chill plate wax mold 4 are connected concentrically from top to bottom in sequence;

c. Degreasing and degreasing: remove the grease on the surface of the double-layer module superimposed wax mold structure.

The second step, the preparation of the mold shell:

a. Coating and sanding: use dip coating method to coat and hang the degreasing double-layer module superimposed wax mold to keep the surface of the wax mold evenly coated with paint to avoid blank and local accumulation; edges, corners, grooves, Use a brush or special tool to brush the joints evenly to avoid air bubbles; clean the floating sand on the previous layer before painting each layer of paint: stir regularly during the painting process to master and adjust the viscosity of the paint. The sand is sprayed by rain; after the double-layer module superimposed wax mold is taken out of the paint tank, the remaining paint on it flows evenly and no longer drips continuously; the particle size of the sand is according to the paint level. Select and adapt to the viscosity of the paint, the surface layer sand has a finer grain size, and the reinforcement layer has a coarser grain size; after each layer of coating and sanding, it is fully dried and hardened; the double-layer module is superimposed on the mold shell for 7 layers Coating, hanging and sanding, (1) Surface layer, 70#EC95 powder + silica sol + slurry mixed in a mass ratio of 1:2:2, then coated and hanged, and self-drying for more than 8 hours; (2) 2 to 4 layers, 35 #EC95 powder + silica sol + slurry are mixed in a mass ratio of 1:2:2, and then coated in 2 layers, and self-drying for more than 6 hours; (3) 5 to 6 layers, 22#EC95 powder + silica sol + slurry press After mixing in a mass ratio of 1:2:2, coat and hang, and dry for more than 6 hours; (4) Sealing layer, only the slurry is coated and hanged, and it will dry after the coating is completed; After 1 to 3 layers are dried, the lower layer is coated before hanging It is strengthened with silica sol and requires good ventilation to ensure suitable temperature (21℃±1.5℃) and humidity (40%±10%);

b. Dewaxing: Open the end face mold shell of the sprue cup to facilitate wax removal and exhaust, and use the steam method to dewax. The steam pressure of the outer bladder is 0.7MPa, the dewaxing time is 13min, and the dewaxing temperature is 165min; after the dewaxing is completed, under ventilation conditions Fully dry for 12h;

c. Roasting: After the double-layer module superimposed mold shell is cooled to 300 ℃, it is put into a heating furnace for calcination at 850 ℃ for 1.5 hours, cooled to 500 ℃ with the furnace, taken out, and air-cooled to room temperature;

d. Inspection and shell repair: Check whether the mold shell has defects such as deformation, cracks, and damage; repair defects such as cracks and damage, and remove the excess mold shell edge of the gate.

The third step is to prepare the blades in the directional solidification furnace:

a. Check the equipment: Check whether the various valves of the equipment can operate normally, whether the water supply, power supply, and gas supply devices are normal, adjust the relative position of the temperature measuring device and the bottom of the crucible reasonably according to the amount of alloy material, clean the dust inside the furnace cavity and wipe the various observation window;

b. Loading the master alloy: knock out the large shrinkage cavity of the cut alloy material, grind it with sandpaper and clean it with alcohol, and then put it into the crucible;

c. Fixed mold shell: Fix the chill plate mold shell of the double-layer module superimposed mold shell on the chill plate of the directional solidification furnace with special clips or iron wires, and make the center position of the mold shell gate and the center of the liquid guide funnel. Coaxial to ensure that the alloy liquid is poured into the mold shell smoothly, and the furnace door is closed;

d. Vacuuming: first open the mechanical pump to rough vacuum to less than 1000Pa, open the roots pump to continue vacuuming to less than 20Pa, preheat the diffusion pump, and after the oil temperature of the diffusion pump rises to 300 ℃, open the valve of the diffusion pump to pump high Vacuum up to 6.67×10 ^{- 3} Pa;

e. Heating and heating: heating the heating body according to the set temperature curve, heating the double-layer module superimposed mold shell;

f. Alloy smelting: melting and refining of single crystal superalloy: slowly power on until the alloy is melted, and then superheat the alloy melt until only a small amount of scum exists in the edge area on the free surface of the alloy liquid; then perform the shaking furnace operation , preheat the edge of the crucible to prevent splashing during the pouring process; keep the temperature constant for 2 minutes after overheating to the set temperature;

g. Pouring and pulling: After the superheated melt is rapidly cooled to slightly higher than the pouring temperature, the temperature measuring thermocouple is raised, and the alloy liquid is poured into the double-layer module superimposed mold shell, and the pumping temperature is 100 μm/s. The pull rate pulls the mold into the cooling zone;

h. Sampling: After the solidification is completed, the temperature of the entire furnace body is cooled to below 100 ℃, and the vacuum sampling is broken, shelled and trimmed to obtain a large number of single crystal blades.

Taking the single-layer module for mass production of single-crystal blades using the same process as a comparative example, Figure 4 shows the comparison of the temperature field simulation results of the single-layer module blade and the double-layer module superimposed blade when the molten superalloy solidifies to the bottom of the blade body picture. It can be seen from Figure 4 that the bending degree of the isotherm in the double-layer module superimposed blade is low, and the degree of supercooling at the bottom and corner of the blade body is small, so it is difficult to achieve the critical nucleation and supercooling degree of the alloy, and the formation of heterocrystalline defects in the single crystal blade tends to be Small.

Figure 5 is a comparison diagram of the temperature field simulation results of the single-layer module blade and the double-layer module superimposed blade when the molten superalloy solidifies to the blade platform. It can be seen from Figure 5 that the bending degree of isotherm of the double-layer module superimposed blade is low, the degree of supercooling at the corners of the platform is small, and it is difficult to achieve the critical nucleation and supercooling degree of the alloy, and the formation tendency of miscellaneous crystal defects in the single crystal blade is small.

Figure 6 is a comparison diagram of the simulation results of solidification grains of a single-layer module blade and a double-layer module superimposed blade. It can be seen from Figure 6 that there are miscellaneous crystals formed in the single-layer module blade, which makes it difficult to produce qualified single-crystal blades. The double-layer module superimposed blade has no miscellaneous crystal formation, and the single-crystal blade is successfully prepared.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A multi-layer module superposed wax mould structure for preparing a single crystal blade comprises a casting system wax mould, a blade wax mould, a crystal selector wax mould and a chilling plate wax mould which are sequentially connected from top to bottom;

the blade wax pattern comprises a plurality of layers of blade wax patterns which are sequentially connected from top to bottom.

2. The multi-layer pattern assembly superimposed wax pattern structure according to claim 1, wherein the gating system wax pattern is composed of a sprue cup wax pattern and a plurality of inclined runner wax patterns distributed around the sprue cup wax pattern in a circle; the bottom of the inclined pouring channel wax mould is connected with the top end of the top layer blade wax mould, the bottom of the top layer blade wax mould is connected with the top end of the next layer of blade wax mould, and the like, and the multiple layers of blade wax moulds are connected end to end in the vertical direction.

3. The multi-layer pattern assembly superimposed wax pattern structure of claim 2, further comprising a king post wax pattern; the sprue cup wax mold, the center column wax mold and the chilling plate wax mold are sequentially connected with the same axle center from top to bottom.

4. The multi-layer pattern assembly superimposed wax pattern structure as claimed in claim 1, wherein the crystal selector wax pattern comprises an upper spiral segment wax pattern and a lower seeding segment wax pattern.

5. The multi-layer pattern assembly superimposed wax pattern structure of claim 1, wherein the number of layers of the blade wax pattern is two.

6. A method for preparing a single crystal blade, comprising the steps of:

providing a multi-layer module superimposed wax pattern structure as defined in any one of claims 1 to 5;

sequentially coating, sanding, dewaxing and roasting the multi-layer module superposed wax mold structure to obtain a mold shell;

and pouring the molten alloy liquid into the mold shell, so that the molten alloy liquid is directionally solidified from bottom to top, and removing the shell to obtain the single crystal blade.

7. The method according to claim 6, wherein the casting and the solidification are both performed in a directional solidification furnace; the step of directionally solidifying the molten alloy from bottom to top comprises the following steps: during solidification, the formwork is drawn down to a cooling zone.

8. The method according to claim 7, wherein the drawing rate is 50 to 150 μm/s.

9. The method of claim 6, wherein the dewaxing is steam dewaxing.

10. The method of claim 6, further comprising preheating the mold shell prior to pouring the molten alloy in the mold shell.

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