Upper box body of wind driven generator and preparation method

Abstract

The invention relates to the technical field of wind driven generator equipment, in particular to an upper box body of a wind driven generator and a preparation method, the upper box body comprises a box cover, the box cover is provided with a mounting cavity, and the end part of the box cover is provided with a mounting ring; and the installation supporting ring is installed in the middle of the installation cavity, the installation supporting ring and the installation cavity are concentrically arranged, the installation supporting ring is provided with an installation supporting cavity, and the installation supporting cavity extends out of the box cover. The device is compact in structure and high in preparation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine equipment, and particularly to an upper box body of a wind turbine and a preparation method thereof. Background Art

[0002] A wind turbine is a device that converts natural wind energy into electrical energy. Its basic working principle is to convert wind energy into mechanical energy and then convert mechanical energy into electrical energy.

[0003] China is rich in wind energy resources. The exploitable wind energy reserves are about 1 billion kW. Among them, the onshore wind energy reserves are about 253 million kW (calculated based on the data at a height of 10 m above the ground), and the exploitable and utilizable offshore wind energy reserves are about 750 million kW, totaling 1 billion kW. The operating environment of wind turbines is special. The box body of a wind turbine should have sufficient strength and stiffness to bear the weights of internal components, wind force, inertial force and other loads, and ensure that it will not deform or be damaged under various working conditions. However, at present, in order to meet the use requirements, the box body of the wind turbine is large in volume and complex in preparation process, resulting in a high manufacturing cost of the box body of the wind turbine, which is not conducive to market promotion.

[0004] Therefore, those skilled in the art are committed to developing an upper box body of a wind turbine and a preparation method thereof, which are not only structurally compact but also have high preparation efficiency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an upper box body of a wind turbine and a preparation method thereof, which are not only structurally compact but also have high preparation efficiency.

[0006] The technical solution of the present invention for solving the above technical problems is as follows: An upper box body of a wind turbine, comprising a box cover, the box cover having an installation cavity, and an installation ring at the end of the box cover; an installation support ring, the installation support ring being installed in the middle of the installation cavity and concentric with the installation cavity, the installation support ring having an installation support cavity, and the installation support cavity extending outside the box cover.

[0007] The beneficial effects of adopting the above scheme are as follows: The box cover has an installation cavity, and the installation support ring is installed in the middle of the installation cavity and concentric with the installation cavity. This structural design makes the internal space of the upper box body of the wind turbine more reasonably utilized, the component layout more compact, reduces the overall volume of the box body, and meets the requirement of developing a structurally compact upper box body of a wind turbine; The installation support ring has an installation support cavity, and the installation support cavity extends outside the box cover. This provides a more convenient channel and a more stable support structure for the installation of internal components of the wind turbine, which is beneficial to improving the installation efficiency and installation accuracy of components; The end of the box cover has an installation ring, and the installation support ring is concentrically arranged with the installation cavity and other structural features, which can enhance the overall strength and stiffness of the box body, enabling it to better bear the weights of various internal components, wind forces, inertial forces, etc., and ensuring that it will not deform or be damaged under various working conditions, meeting the special requirements of the usage environment of the wind turbine.

[0008] Based on the above technical solutions, the present invention can be further improved as follows.

[0009] Further, reinforcing ribs are installed between the installation support ring and the inner wall of the box cover, and through holes are also provided on the outer wall of the installation support ring.

[0010] The beneficial effect of adopting the above further solution is that installing reinforcing ribs between the installation support ring and the inner wall of the box cover can effectively enhance the structural stability of the box body, improve its load-bearing capacity, enable it to better resist the weights of internal components, wind forces, inertial forces, etc., and reduce the risk of deformation and damage.

[0011] Further, a concave platform is also provided at the end of the box cover, at least one positioning post and installation holes are provided on the outer periphery of the box cover, and the installation holes communicate with the installation cavity.

[0012] The beneficial effect of adopting the above further solution is that the concave platform provided at the end of the box cover can be used as a positioning reference surface during installation, ensuring the accuracy of the installation positions of internal components, improving the installation accuracy, and reducing the impact of installation errors on the operating performance of the wind turbine; The positioning posts and installation holes provided on the outer periphery of the box cover. The positioning posts facilitate quickly positioning and installing the upper box cover at the specified position, and the installation holes are used for installing accessory equipment such as wires.

[0013] A method for manufacturing the upper box body of a wind turbine, which is applied to the upper box body of the wind turbine as described above, includes the following steps: S100. Prepare the sand core and mold it. S200. Pour the molten metal into the cavity prepared by molding in step S100. S300. Cool the castings poured in step S200, the cooling time is greater than or equal to 2 hours, and the temperature for taking the parts is less than or equal to 200 °C. S400. Shot blast and polish the blank parts prepared in step S300.

[0014] The beneficial effect of adopting the above further solution is that by preparing the sand core and molding it, an accurate cavity can be formed, providing a good mold for the pouring of molten metal, which is conducive to obtaining castings with accurate shapes and qualified dimensions, and improving the quality and performance of the upper box body of the wind turbine; The shaping die has a compact layout, with 4 parts in 1 mold, greatly improving the production efficiency. The molten metal is poured into the cavity prepared by shaping. By using appropriate pouring process parameters, the product qualification rate is fully guaranteed to meet the market demand. When cooling the castings after pouring, controlling the cooling time and the pick-up temperature can avoid defects such as cracks and deformations caused by too fast cooling speed or too high temperature of the castings, ensuring the internal structure and mechanical properties of the castings. Shot blasting and grinding can remove impurities such as scale and sand grains and flash burrs on the surface of the castings, improving the surface finish and aesthetics, and applying anti-rust paint to enhance the corrosion resistance and service life of the castings.

[0015] Furthermore, in step S200, the components and mass ratios in the molten metal after melting are as follows: C: 3.7% - 3.9%, Si: 2.1% - 2.3%, Mn ≤ 0.2%, S ≤ 0.015%, P ≤ 0.05%, Mg: 0.035% - 0.055%, and the rest is Fe. The melting temperature is 1470°C to 1510°C.

[0016] The beneficial effects of adopting the above further scheme are as follows: Strictly controlling the mass ratios of the components in the molten metal after melting can ensure that the materials used have good mechanical properties such as strength and toughness, meeting the usage requirements of the upper box body of the wind turbine under complex working conditions. At the same time, the melting temperature is between 1470°C and 1510°C, which can make the molten metal fully melt and homogenize, reducing the generation of defects such as slag holes and gas holes, improving the quality of the molten iron, and providing guarantee for subsequent pouring and the quality of the castings.

[0017] Furthermore, in step S200, the pouring temperature of the molten metal is 1360°C to 1410°C, and the length of the spheroidizing wire is 21m to 23m.

[0018] The beneficial effects of adopting the above further scheme are as follows: Controlling the pouring temperature of the molten metal between 1360°C and 1410°C can ensure that the molten metal has good fluidity and filling property during pouring, fully filling every corner of the cavity, reducing defects such as cold shuts and misruns, and improving the density and surface quality of the castings. The length of the spheroidizing wire is 21m to 23m, which is beneficial to evenly distribute the spheroidizing agent in the molten metal during the spheroidizing treatment process, promoting graphite spheroidization, improving the spheroidization grade of the castings, and further enhancing the mechanical properties and good metallographic structure of the castings.

[0019] Furthermore, in step S100, preparing the sand core and shaping includes the following steps: S110. Mix the raw sand with resin and use a cold box core-making machine and a cold box mold to prepare the sand core. The sand shooting pressure of the cold box machine is 0.3mpa to 0.35mpa. S120. Place the external mold on the DISA molding machine for molding. The sand injection pressure of the molding machine is 1.5 Bar to 2.5 Bar, the extrusion pressure is 6 Bar to 10 Bar, and the target compaction rate is 20% to 25%. S130. Place the sand core into the molded cavity to form a casting mold.

[0020] The beneficial effect of adopting the above further solution is that when preparing the sand core and molding, first mix the raw sand and resin and use a cold box core shooter to prepare the sand core. The sand injection pressure of the cold box core shooter is controlled at 0.3 mpa to 0.35 mpa, which can make the surface of the sand core denser and smoother, improve the strength and dimensional accuracy of the sand core, and reduce problems such as collapse and deformation of the sand core during the casting process. When injecting sand into the cavity formed by the DISA molding machine and the external mold, reasonably controlling the sand injection pressure, extrusion pressure, and target compaction rate can make the molding sand fully fill and compact in the cavity, improve the density and surface quality of the cavity, and thus ensure the dimensional accuracy and surface finish of the casting.

[0021] Further, in step S110, the raw materials and components are 95% to 97% old sand, 1% - 2% new sand, 1% to 1.2% bentonite, and 0.4% to 0.6% pulverized coal.

[0022] The beneficial effect of adopting the above further solution is that the appropriate ratio of sand raw materials can make the molding sand have good properties such as air permeability, plasticity, strength, and refractoriness, meet the requirements of the casting process, and provide a basis for preparing a high-quality cavity.

[0023] Further, in step S120, after injecting sand into the mold cavity, high-frequency vibration compaction is required. Among them, the vibration frequency is 2000 Hz to 3000 Hz, the amplitude is 0.05 mm to 0.15 mm, and the duration is 30 seconds to 60 seconds.

[0024] The beneficial effect of adopting the above further solution is that after injecting sand into the mold cavity, high-frequency vibration compaction is carried out. By reasonably controlling the vibration frequency, amplitude, and duration, the molding sand can be more closely filled in the cavity, further improving the density and surface finish of the cavity, reducing defects such as sand holes and air holes on the surface of the casting, and improving the quality of the casting.

[0025] Further, in step S400, the shot peening time is 8 min to 10 min, and the diameter of the steel shot is 1.2 mm to 1.8 mm.

[0026] The beneficial effect of adopting the above further solution is that the shot peening cleaning is more thorough and uniform, effectively removing impurities such as oxide scales and sand grains on the surface of the casting, improving the surface roughness and finish. At the same time, it can also strengthen the surface of the casting, improving its fatigue strength and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of the upper box body of the wind turbine of the present invention; Figure 2 This is a schematic side view structural diagram of the upper box body of the wind turbine of the present invention; Figure 3 This is a schematic specific structural diagram of the second mold of the present invention.

[0028] In the drawings, the list of components represented by each reference numeral is as follows: 1. Box cover; 2. Installation cavity; 3. Installation ring; 4. Installation support ring; 5. Installation support cavity; 6. Reinforcing rib; 7. Through hole; 8. Concave platform; 9. Positioning column; 10. Installation hole; 11. Mold body; 12. Pouring cavity; 13. Core. DETAILED DESCRIPTION OF THE INVENTION

[0029] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0030] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "length", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "inner", "outer", "peripheral side", "circumferential direction", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0031] In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0032] In the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0033] As Figure 1 and Figure 2 shown, for a wind turbine upper box body, after the upper box body is integrally formed by pouring and then processed. It includes The lid 1 has an installation cavity 2. At the end of the lid 1, there is also a concave platform 8. At the outer periphery of the lid 1, there is at least one positioning post 9 and an installation hole 10. The installation hole 10 communicates with the installation cavity 2. At the end of the lid 1, there is an installation ring 3; The installation support ring 4 is installed in the middle of the installation cavity 2 and is concentric with the installation cavity 2. The installation support ring 4 has an installation support cavity 5. The installation support cavity 5 extends outside the lid 1. Between the installation support ring 4 and the inner wall of the lid 1, there are reinforcing ribs 6 installed. A plurality of reinforcing ribs 6 are arranged in a circle, and there are also through holes 7 on the outer wall of the installation support ring 4.

[0034] A preparation method for the upper box body of a wind turbine, which is applied to the upper box body of the wind turbine as described above, includes the following steps: S100. Prepare the sand core and mold. Specifically, preparing the sand core and mold includes the following steps: S110. Mix the molding sand raw materials to prepare the core and the mold body. After the core is prepared, sand shooting is carried out on the surface, and the sand shooting pressure is 0.3mpa to 0.35mpa; the raw materials and components are 95% to 97% of used sand, 1% - 2% of new sand, 1% to 1.2% of bentonite, and 0.4% to 0.6% of pulverized coal. Among them, used sand refers to the molding sand recovered after at least one casting, and new sand refers to the molding sand that has not been used. During the previous casting process, the used sand has experienced high temperature, and a dense oxide film will form on the surface of the sand grains. This oxide film can improve the refractoriness and strength of the molding sand, reduce the erosion and penetration of molten steel into the molding sand, thereby reducing the generation probability of defects such as sand holes. At the same time, during the use of the used sand, through repeated screening and treatment, its particle size distribution is more uniform, which can better meet the requirements of the molding sand for air permeability and fluidity during casting. Uniform particle size helps the gas to be discharged smoothly, reduces defects such as air holes, and at the same time enables the molding sand to better fill the mold cavity, improving the surface quality of the casting.

[0035] S120. Carry out sand shooting in the mold cavity of the mold body, the sand shooting pressure is 1.5Bar to 2.5Bar, the extrusion pressure is 6Bar to 10Bar, and the target compaction rate is 20% to 25%; After sand shooting in the mold cavity of the mold body, high-frequency vibration compaction is required. Among them, the vibration frequency is 2000Hz to 3000Hz, the amplitude is 0.05mm to 0.15mm, and the duration is 30 seconds to 60 seconds.

[0036] S130. Place the core into the mold cavity formed by the mold to form a casting mold.

[0037] S200. Pour the melted metal liquid into the cavity prepared by the molding in step S100; The components and mass ratios in the melted metal liquid are as follows: C: 3.7% - 3.9%, Si: 2.1% - 2.3%, Mn ≤ 0.2%, S ≤ 0.015%, P ≤ 0.05%, Mg: 0.035% - 0.055%, and the rest is Fe. The melting temperature is 1470°C to 1510°C. The pouring temperature of the metal liquid is 1360°C to 1410°C, and the length of the spheroidizing wire is 21m to 23m.

[0038] S300. Cool the castings poured in step S200. The cooling time is greater than or equal to 2 hours, and the picking temperature is less than or equal to 200°C. S400. Shot blast and polish the blank parts prepared in step S300. The shot blasting time is 8 min to 10 min, and the diameter of the steel shot is 1.2 mm to 1.8 mm. Example 1

[0039] S100. Prepare the sand core and mold S110. Prepare the core and mold body: Mix the molding sand raw materials in the proportion of 96.5% old sand, 2% new sand, 1% bentonite, coal powder, and 0.5%, and then mold them into a casting mold. Among them, Original sand: The particle size is 50 - 100 mesh, with an average fineness of 48 - 58; 70 - 140 mesh, with an average fineness of 68 - 78. The three - screen concentration is ≥75%; the mud content is ≤0.5%; the moisture content is ≤0.5%. Bentonite: The moisture content is ≤12%, the methylene blue adsorption (MB) is ≥35 g / 100 g, and the particle size is ≥80% passing through 200 mesh. Coal powder: The moisture content is ≤5%, the ash content is ≤12%, the sulfur content is ≤1%, the volatile matter is 30 - 38%, and the bright carbon is 10 - 16%.

[0040] The molding sand raw materials also contain 0.1% - 0.3% by mass of iron oxide powder, and the original sand is a mixed sand of chromite sand and silica sand, with a mixing ratio of 1:2 - 1:3, which improves the thermal stability of the sand core and reduces the sand adhesion defect of the casting.

[0041] And the overall particle size is ≥95% passing through a 140 - mesh sieve.

[0042] The core contains 0.65% of resin I and 0.65% of resin II. After the core is prepared, sand shooting treatment is carried out on its surface, and the sand shooting pressure is controlled at 0.32 mpa to enhance the surface strength and density of the core.

[0043] S120. Sand shooting and vibration compaction in the cavity: Carry out sand shooting operation in the cavity of the mold body. The sand shooting pressure is set at 2 Bar, the extrusion pressure is controlled at 8 Bar, and the target compaction rate is 22%.

[0044] Before sand shooting, preheat the mold body. The preheating temperature is 60 - 80°C, and the heat preservation time is 30 - 60 minutes.

[0045] After sand shooting, perform high-frequency vibration compaction on the cavity of the mold body. The vibration frequency is 2500 Hz, the amplitude is 0.1 mm, and the duration is 45 seconds to ensure that the molding sand is fully filled and compacted in the cavity, improving the density and surface finish of the cavity.

[0046] S130. Assemble the casting mold: Place the prepared sand core into the cavity of the processed mold body to form a complete casting mold. During the placement of the core, ensure its accurate and stable position to guarantee the smooth progress of the subsequent casting process. In other embodiments, the assembly gap between the core and the cavity of the mold body is 0.2 - 0.6 mm.

[0047] S200. Melting and pouring of molten metal Melting of molten metal: Select high-quality raw materials and charge according to the composition and mass ratio of C: 3.8%, Si: 2.2%, Mn: 0.15%, S: 0.01%, P: 0.03%, Mg%: 0.04%, and the rest is Fe.

[0048] In other embodiments, pig iron and scrap steel can be used. Among them, for pig iron, C% ≥ 4.0%, Si: 0.5 - 1.0%, S% < 0.03%, length ≤ 300 mm, surface quality: no rust, sediment, or oil stain. For scrap steel, C% ≤ 0.5%, Si ≤ 0.5%, Mn ≤ 0.2%, surface quality: no rust, sediment, or oil stain.

[0049] In the melting equipment, melt the mixed raw materials at a temperature not lower than 1490°C to ensure that the molten metal is fully melted and the composition is uniform. Subsequently, add a nodulizer for nodulizing treatment after the molten iron is tapped. The length of the nodulizing wire is controlled at 22 m to promote graphite nodulization and improve the nodulizing grade of the cast iron.

[0050] Pouring of molten metal: Control the pouring temperature of the melted molten metal to 1390 ± 10°C, and then pour it slowly and evenly into the cavity prepared in step S100. During the pouring process, control the pouring speed and pouring volume to ensure that the molten metal can fully fill every corner of the cavity and avoid defects such as cold shut and misrun.

[0051] S300. Cooling and part removal: Naturally cool the cast part in the mold. The cooling time is not less than 2 hours to ensure that the internal structure of the cast part is uniform and free of internal stress. When the original part cools to a part removal temperature less than or equal to 200°C, carefully remove the riser and runner to avoid damaging the cast part.

[0052] S400. Post-treatment of the blank: The blank prepared in step S300 is subjected to shot peening using a shot peening machine. The shot peening time is 9 min, and the diameter of the steel shot is 1.2 - 1.8 mm. Shot peening can effectively remove impurities such as scale and sand grains on the surface of the casting, improve the surface finish and roughness. At the same time, it can also strengthen the surface of the casting, improve its fatigue strength and corrosion resistance. Subsequently, manual grinding is carried out to remove flash and burrs.

[0053] Quality inspection and testing: The upper housing of the wind turbine after shot peening and grinding is subjected to strict quality inspection, including appearance inspection, dimensional measurement, internal defect detection, etc. Appearance inspection mainly checks whether there are defects such as cracks, sand holes, and air holes on the surface of the housing; high-precision measuring tools are used for dimensional measurement to ensure that the dimensions of each part of the housing meet the design requirements; internal defect detection can adopt methods such as ultrasonic flaw detection, X-ray flaw detection, and dissection to check whether there are defects such as porosity and shrinkage cavities inside the housing. The ultrasonic flaw detection frequency is 2.5 - 5 MHz, and the defect judgment standard is: the size of a single defect ≤ Φ3 mm, and the area of the dense defect area ≤ 5 cm². Products that fail the inspection are processed or reworked in a timely manner to ensure product quality.

[0054] Surface treatment and protection: According to the usage environment and requirements of the wind turbine, corresponding surface treatment and protection are carried out on the upper housing. For example, anti-rust paint, anti-corrosion coatings, etc. are applied to the surface of the housing to enhance its corrosion resistance and protection performance and extend its service life. For the parts that need to be connected to other components, fine machining is carried out to ensure the connection accuracy and reliability. Example 2

[0055] As Figure 3 shown, the mold in step S100 includes a mold body 11. The mold body 11 has a casting cavity 12, and a core 13 is provided in the casting cavity 12.

[0056] In the description of this specification, the description of reference terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0057] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A wind turbine upper box, characterized in that: include A box cover (1), the box cover (1) having a mounting cavity (2), and an end of the box cover (1) having a mounting ring (3); An installation support ring (4), the installation support ring (4) being installed in the middle of the installation cavity (2) and being arranged concentrically with the installation cavity (2), the installation support ring (4) having an installation support cavity (5), the installation support cavity (5) extending out of the box cover (1).

2. The upper box of the wind turbine generator according to claim 1 is characterized in that: A reinforcing rib (6) is installed between the mounting support ring (4) and the inner wall of the box cover (1), and a through hole (7) is also provided on the outer wall of the mounting support ring (4).

3. The upper box of the wind turbine generator according to claim 1 is characterized in that: The end of the box cover (1) is also provided with a recessed platform (8), and the outer periphery of the box cover (1) is also provided with at least one positioning column (9) and a mounting hole (10), wherein the mounting hole (10) is communicated with the mounting cavity (2).

4. A method for preparing an upper box of a wind turbine generator, applied to the upper box of a wind turbine generator as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: S100. Prepare sand core and shape; S200. pouring the smelted molten metal into the mold cavity prepared in step S100; S300. Cooling the original part cast in step S200, the cooling time is greater than or equal to 2 hours, and the temperature of the part is less than or equal to 200°C; S400. Shot blasting the blank prepared in step S300.

5. The method for preparing the upper box of a wind turbine generator according to claim 4, characterized in that: The components and mass ratios of the molten metal in step S200 are C: 3.7%-3.9%, Si: 2.1%-2.3%, Mn≤0.2%, S≤0.015%, P≤0.05%, and the rest is Fe. The smelting temperature is 1470°C to 1510°C.

6. The method for preparing the upper box of a wind turbine generator according to claim 5, characterized in that: In step S200, the water output of each bag is 1000KG, the length of the spheroidized wire is 21m to 23m, and the pouring temperature of the molten metal is 1360℃ to 1410℃.

7. The method for preparing the upper casing of a wind turbine according to claim 3, characterized in that: In step S100, preparing the sand core and molding it includes the following steps: S110. The raw sand mixed with resin is prepared into sand cores using a cold core making machine and a cold core mold, and the cold core machine sand shooting pressure is 0.3mpa to 0.35mpa; S120. Place the outer mold on the DISA molding machine for molding. The molding machine sand injection pressure is 1.5Bar to 2.5Bar, the extrusion pressure is 6Bar to 10Bar, and the target compaction rate is 20% to 25%; S130. Place the sand core into the molded cavity to form a casting mold.

8. The method for preparing the upper box of a wind turbine according to claim 7, characterized in that: In step S110, the raw materials and components are: 95% to 97% old sand, 1%-2% new sand, 1% to 1.2% bentonite, and 0.4% to 0.6% coal powder.

9. The method for preparing the upper casing of a wind turbine generator according to claim 7, characterized in that: In step S120, after the sand is shot into the mold cavity, high-frequency vibration compaction is required, wherein the vibration frequency is 2000 Hz to 3000 Hz, the amplitude is 0.05 mm to 0.15 mm, and the duration is 30 seconds to 60 seconds.

10. The method for preparing the upper box of a wind turbine according to claim 4, characterized in that: In step S400, the shot blasting time is 8 minutes to 10 minutes, and the steel shot is directly 1.2 mm to 1.8 mm.

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