Lower 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 a lower box body of a wind driven generator and a preparation method, the lower box body comprises a box body, the box body is provided with a mounting cavity, and the two ends of the box body are in outward flaring shapes; the two ends of the box body are connected with a first installation ring and a second installation ring respectively, and the side wall of the first installation ring is further connected with a fixing ring. The lower box body manufactured through the manufacturing method is compact in structure and high in manufacturing efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine equipment, and in particular to a lower 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 the mechanical energy into electrical energy. When the wind turbine is working, the wind wheel starts to rotate under the action of wind force, converting wind energy into mechanical energy. Then, the mechanical energy is transmitted to the generator through the transmission system, and further converted into electrical energy and connected to the power grid or stored for subsequent use. A wind turbine usually consists of a wind wheel, a generator, a nacelle, a tower, etc. Among them, the wind wheel is the key component for capturing wind energy, consisting of blades and a hub, and its design and performance directly affect the efficiency and stability of the wind turbine.

[0003] China is rich in wind energy resources, and the distribution of wind energy resources has obvious regional differences, mainly concentrated in the northern inland areas and coastal areas. These areas have rich and stable wind energy resources and have the potential for large-scale development. In recent years, the development of offshore wind power has been rapid and has gradually become an important part of China's wind power industry.

[0004] The operating environment of a wind turbine is special. The box body of the wind turbine should have sufficient strength and stiffness to bear the weights of internal components, wind force, inertial force and other loads, ensuring that it will not deform or be damaged under various working conditions. In actual operation, the wind turbine faces a complex and changeable natural environment, such as strong wind, heavy rain, lightning strikes, salt spray corrosion, etc. These factors put higher requirements on the performance of the box body. Especially in the offshore wind power environment, the box body not only has to bear huge wind force and wave impact force, but also has to resist the corrosion of seawater and the attachment of marine organisms. Therefore, special anti-corrosion materials and coatings, as well as a structural design with high strength and durability, are required. In addition, the wind turbine will generate vibration and noise during operation, and the structural design of the box body also needs to consider the functions of shock absorption and noise reduction to improve the reliability and operating stability of the equipment, and at the same time reduce the impact on the surrounding environment.

[0005] 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 wind turbine box body, which is not conducive to market promotion. In order to meet the requirements of strength and stiffness, the traditional box body of the wind turbine often adopts a thick steel plate structure, which makes the box body large in volume and heavy in weight, not only increasing the usage amount of raw materials, but also causing a substantial increase in transportation and installation costs. Moreover, due to the complex box body structure, involving welding, processing and assembly processes of multiple components, the preparation process requires high-precision equipment and professional technicians, further increasing the manufacturing cost and production cycle.

[0006] Therefore, those skilled in the art are committed to developing a lower box body of a wind turbine and a preparation method, which are not only structurally compact but also have high preparation efficiency. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a lower box body of a wind turbine and a preparation method, which are not only structurally compact but also have high preparation efficiency.

[0008] The technical solution of the present invention to solve the above technical problems is as follows: A lower box body of a wind turbine includes a box body main body, the box body main body has an installation cavity, and both ends of the box body main body are in a flared shape outward; A first installation ring and a second installation ring are respectively connected to both ends of the box body main body, and a fixing ring is further connected to the side wall of the first installation ring.

[0009] The beneficial effects of adopting the above scheme are: The box body main body has an installation cavity, which provides a spacious and centralized installation space for various internal components of the wind turbine, enabling the components to be arranged and fixed in the box body orderly, which is beneficial to improving the space utilization rate and the compactness of the overall structure. Different-sized and functional components can be concentrated in one cavity, avoiding the structural complexity and space waste problems caused by scattered installation of components, enhancing the space integration ability inside the box body, enabling more reasonable layout among components, and enhancing the practicality and functionality of the entire lower box body of the wind turbine; The flared design is beneficial for connecting and transitioning with other components at both ends of the box body, can provide a larger connection area and a more stable support structure, and enhance the connection strength and reliability between the box body and adjacent components. At the same time, the flared structure can also optimize the force distribution of the box body to a certain extent. When the wind turbine is operating under various loads, such as the weight of internal components, wind force, inertial force, etc., the flared part can better disperse and conduct these forces, reduce the stress concentration of the box body main body, thereby improving the overall structural stability and anti-deformation ability of the box body, and ensuring the safe and stable operation of the wind turbine under various working conditions; The settings of the first installation ring and the second installation ring provide a connection structure for the installation and fixation of the wind turbine, and can be accurately and firmly connected to other components or support structures of the wind turbine respectively, ensuring that the relative positions of all parts are accurate when the entire wind turbine system is assembled, and can withstand large installation loads and operating loads.

[0010] Further, a support ring is arranged in the installation cavity, and a plurality of annular grooves are arranged at intervals on the inner wall of the support ring.

[0011] The beneficial effect of adopting the above further solution is: arranging a support ring in the installation cavity can provide additional support and stabilization for the components in the installation cavity, ensure the stability of the position of the components during operation, reduce the displacement or shaking of the components caused by vibration or load, and improve the overall operation stability of the wind turbine; The annular groove is used to install the sealing ring, and can form multi-point contact and disperse the force between the support ring and the components in the installation cavity, effectively avoiding stress concentration, reducing the risk of damage to the components due to excessive local force, and extending the service life of the components.

[0012] Furthermore, the outer wall of the box body is also provided with a plurality of reinforcing ribs arranged at intervals.

[0013] The beneficial effect of adopting the above further scheme is that a plurality of spaced reinforcing ribs are arranged on the outer wall of the box body, which can significantly enhance the structural strength and rigidity of the box body, making it less likely to be deformed or damaged when subjected to loads such as the weight of internal components, wind force, inertial force, etc., thereby ensuring the stability and reliability of the box body under various working conditions.

[0014] A method for preparing a lower box of a wind turbine generator, applied to the lower box of the wind turbine generator as described above, comprises the following steps: S100. Prepare sand core and shape; S200. pouring the smelted molten metal into the mold cavity prepared in step S100; S300. Cool the casting poured in step S200, the cooling time is greater than or equal to 2 hours, and the temperature of the casting is less than or equal to 200°C; S400. Shot blasting the blank prepared in step S300.

[0015] The beneficial effects of adopting the above further scheme are: by preparing the sand core and shaping it, a precise cavity can be formed, which provides a good foundation for pouring the molten metal, is conducive to obtaining a casting with accurate shape and qualified size, and improves the quality and performance of the lower box of the wind turbine; The smelted metal liquid is poured into the mold cavity prepared by molding. The appropriate pouring process and parameters can quickly fill the mold cavity, shorten the production cycle, improve production efficiency, and meet market demand; The molding mold has a compact layout, with 4 pieces in one mold, which greatly improves production efficiency. The molten metal is poured into the mold cavity prepared for molding, and appropriate pouring process parameters are used to fully ensure the product qualification rate and meet market demand. When cooling the cast components, controlling the cooling time and the temperature of taking out the parts can avoid defects such as cracks and deformations caused by too fast cooling speed or too high temperature of the casting, ensure the internal structure and mechanical properties of the casting. Shot blasting and grinding can remove impurities such as scale and sand grains on the surface of the casting and flash burrs, improve the surface finish and aesthetics, and apply anti-rust paint to enhance the corrosion resistance and service life of the casting.

[0016] Further, in step S200, 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%, and the rest is Fe. The melting temperature is 1430°C to 1470°C.

[0017] The beneficial effects of adopting the above further scheme are: strictly controlling the mass ratios of the components in the melted metal liquid 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 between 1430°C and 1470°C can fully melt and homogenize the metal liquid, reduce the generation of defects such as slag holes and gas holes, improve the quality of the molten iron, and provide guarantee for subsequent pouring and casting quality.

[0018] Further, in step S200, the water output per ladle is 800 KG to 1200 KG, the pouring temperature of the metal liquid is 1320°C to 1370°C, and the length of the spheroidizing wire is 20 m to 25 m.

[0019] The beneficial effects of adopting the above further scheme are: controlling the pouring temperature of the metal liquid between 1320°C and 1370°C can ensure that the metal liquid has good fluidity and filling property during pouring, fully fills every corner of the cavity, reduces defects such as cold shut and misrun, and improves the density and surface quality of the casting; The length of the spheroidizing wire is 20 m to 25 m, which is beneficial to evenly distribute the spheroidizing agent in the metal liquid during the spheroidizing treatment process, promote graphite spheroidization, improve the spheroidization grade of the casting, and further enhance the mechanical properties and good metallographic structure of the casting.

[0020] Further, in step S100, preparing the sand core and molding includes the following steps: S110. Mix the raw sand with resin and use a cold box core making machine and cold box mold to prepare the sand core. The sand shooting pressure of the cold core machine is 0.4 mpa to 0.6 mpa; S120. Place the outer mold on a DISA molding machine for molding. The sand shooting pressure of the molding machine is 2 Bar to 4 Bar, the extrusion pressure is 8 Bar to 11 Bar, and the target compaction rate is 23% to 30%; S130. Place the sand core into the cavity after molding to form a casting mold.

[0021] The beneficial effects of adopting the above further scheme are as follows: When preparing the sand core and molding, first mix the raw sand and resin and then use a cold box core making machine to prepare the sand core. The sand injection pressure of the cold box core making machine is controlled between 0.4 mpa and 0.6 mpa, which can make the surface of the core more dense and smooth, 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 outer 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.

[0022] Further, in step S110, the raw materials and components are as follows: 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.

[0023] The beneficial effects of adopting the above further scheme are as follows: A suitable sand raw material ratio can endow the molding sand with good properties such as air permeability, plasticity, strength, and refractoriness, meet the requirements of the casting process, and provide a basis for preparing high-quality cavities.

[0024] Further, in step S120, after injecting sand into the cavity of the mold body, 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.

[0025] The beneficial effects of adopting the above further scheme are as follows: After injecting sand into the cavity of the mold body, 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.

[0026] 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.

[0027] The beneficial effects of adopting the above further scheme are as follows: Shot peening cleaning is more thorough and uniform, effectively removing impurities such as oxide scale 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. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of the lower box body of the wind turbine of the present invention; Figure 2This is a schematic side view structure of the lower box body of the wind turbine of the present invention.

[0029] In the drawings, the list of components represented by each reference numeral is as follows: 1. Box body main body; 2. Installation cavity; 3. First installation ring; 4. Second installation ring; 5. Fixed ring; 6. Support ring; 7. Annular groove; 8. Reinforcing rib. Detailed implementation manners

[0030] The principles and features of the present invention will be described below with reference to the drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0031] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "length", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "inner", "outer", "peripheral side", "circumferential direction", etc. is based on the orientation or positional relationship shown in the drawings, and is 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 a limitation to the present invention.

[0032] In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0033] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed", 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 circumstances.

[0034] As Figure 1 and Figure 2 shown, a lower box body of a wind turbine is integrally cast and then finely processed. It includes a box body main body 1, the box body main body 1 has an installation cavity 2, and both ends of the box body main body 1 are in a flared shape outward; Both ends of the box body main body 1 are respectively connected with a first installation ring 3 and a second installation ring 4. The side wall of the first installation ring 3 is also connected with a fixed ring 5, and a plurality of reinforcing ribs 8 are arranged at intervals on the outer wall of the box body main body 1.

[0035] A support ring 6 is arranged in the installation cavity 2, and a plurality of annular grooves 7 are arranged at intervals on the inner wall of the support ring 6.

[0036] A method for preparing the lower box body of a wind turbine, which is applied to the lower 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 original sand with resin and use a cold box core making machine and a cold box mold to prepare the sand core. The sand injection pressure of the cold core machine is 0.4 mpa to 0.6 mpa; raw materials and components, used sand 95% to 97%, new sand 1% - 2%, bentonite 1% to 1.2%, pulverized coal 0.4% to 0.6%.

[0037] S120. Place the outer mold on a DISA molding machine for molding. The sand injection pressure of the molding machine is 2 Bar to 4 Bar, the extrusion pressure is 8 Bar to 11 Bar, and the target compaction rate is 23% to 30%; After sand injection 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.

[0038] S130. Place the sand core into the molded cavity to form a casting mold.

[0039] S200. Pour the melted metal liquid into the cavity prepared in step S100 for molding; The components and mass ratios in the melted metal liquid 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 melting temperature is 1430 °C to 1470 °C. The pouring temperature of the metal liquid is 1320 °C to 1370 °C, and the length of the spheroidizing wire is 20 m to 25 m, and the water output per ladle is 800 KG to 1200 KG.

[0040] 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

[0041] S100. Prepare the sand core and mold S110. Prepare the core and mold body: After mixing used sand 96.5%, new sand 2%, bentonite 1%, and pulverized coal 0.5% in proportion, mold and prepare the casting mold.

[0042] Among them, the used sand refers to the sand recovered after at least one casting process, and the new sand refers to the sand that has not been used yet. During the previous casting process, the used sand has been subjected to high temperatures, 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 sand, reduce the erosion and penetration of molten steel into the sand, thereby reducing the 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 becomes more uniform, which can better meet the requirements for the gas permeability and fluidity of the sand during casting. Uniform particle size helps the gas to escape smoothly, reducing defects such as air holes, and at the same time enables the sand to better fill the mold cavity, improving the surface quality of the casting.

[0043] The sand core is prepared by mixing the raw sand with resin using a cold box core making machine and a cold box mold. Specifically, the raw sand uses a mixed sand of chromite sand and silica sand, and the mixing ratio is 1:2 - 1:3. This ratio can significantly improve the thermal stability of the sand core and reduce the sand sticking defect during the high-temperature pouring process of the casting. The particle size of the raw sand is controlled between 50 mesh - 100 mesh and 70 mesh - 140 mesh, with average finenesses of 48 - 58 and 68 - 78 respectively, and the three-screen concentration ≥ 75%, ensuring the fluidity and filling property of the sand. The moisture content of bentonite ≤ 12%, the methylene blue absorption (MB) ≥ 35 g / 100 g, and the particle size ≥ 80% passes through 200 mesh. These indexes ensure the bonding property and water absorption of bentonite, contributing to the molding and strength of the sand. The moisture content of pulverized coal ≤ 5%, the ash content ≤ 12%, the sulfur content ≤ 1%, the volatile matter 30% - 38%, and the bright carbon: 10% - 16%. These parameters ensure the stability and combustibility of pulverized coal in the sand, contributing to improving the surface quality of the sand core and reducing defects during the pouring process.

[0044] 0.85% of Resin ⅰ and 0.85% of Resin ⅱ are added to the core. The synergistic effect of these two resins further enhances the strength and high-temperature resistance of the core, solving problems such as sand washing, sand sticking, and sand inclusion during the product pouring process. After the core is prepared, the surface is subjected to sand shooting treatment, and the sand shooting pressure is controlled at 0.5 MPa. This step effectively improves the surface strength and density of the core, reducing the possibility of surface defects and sand particle shedding.

[0045] S120. Cavity Sand Shooting and Vibration Compaction Place the external mold on the DISA molding machine for molding. The sand injection pressure of the molding machine is set at 3 Bar, the extrusion pressure is controlled at 9 Bar, and the target compaction rate is 25%. Before sand injection, the mold body is preheated. The preheating temperature is 120°C - 150°C, and the heat preservation time is 30 minutes - 60 minutes. This helps improve the fluidity and filling property of the molding sand and reduces defects during the sand injection process. After sand injection, the cavity of the mold body is subjected to high-frequency vibration compaction treatment. The vibration frequency is 2500 Hz, the amplitude is 0.1 mm, and the duration is 45 seconds. The vibration compaction treatment ensures the full filling and compaction of the molding sand in the cavity, improves the density and surface finish of the cavity, and reduces defects such as sand holes and air holes that may occur during the pouring process.

[0046] S130. Assemble the pouring mold Place the sand core into the molded cavity to form a pouring mold and a complete pouring die. The mold body is made of HT250 material. During the placement of the core, ensure its accurate and stable position to guarantee the smooth progress of the subsequent pouring process. In other embodiments, the assembly gap between the core and the cavity of the mold body is 0.5 mm - 1.0 mm, and the gap is filled with refractory fiber felt to prevent the penetration of molten metal during pouring and improve the surface quality.

[0047] S200. Melting and pouring of molten metal The composition and mass ratio of the molten metal are C: 3.8%, Si: 2.2%, Mn: 0.15%, S: 0.01%, P: 0.03%, Mg%: 0.04%, and the rest is Fe. To improve the low-temperature impact toughness, 0.03% - 0.05% by mass fraction of Sb element is added to the molten metal, and Sb is added in the form of Cu-Sb master alloy. This helps inhibit the formation of pearlite in ductile iron and improves the toughness and impact resistance of the material. In the melting equipment, the mixed raw materials are melted at a temperature not lower than 1450°C to ensure that the molten metal is fully melted and the composition is uniform. At the same time, after the molten iron is tapped, a nodulizer is added for nodulizing treatment, and the length of the nodulizing wire is controlled at 22 m to promote graphite nodulization and improve the nodulizing grade of the cast iron.

[0048] Pouring of molten metal: Heat the melted molten metal to a pouring temperature of 1350°C ± 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 shuts and misruns. In other embodiments, pig iron and scrap steel can be used as raw materials. For pig iron, C% ≥ 4.0%, Si: 0.5 - 1.0%, S% < 0.03%, length ≤ 300 mm, and the surface quality has no rust, sediment, or oil; for scrap steel, C% ≤ 0.5%, Si ≤ 0.5%, Mn ≤ 0.2%, and the surface quality has no rust, sediment, or oil.

[0049] S300. Cooling and part removal Let the castings after pouring cool naturally in the mold. The cooling time shall be no less than 2 hours to ensure that the internal structure of the castings 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 gating system to avoid damaging the castings. In some embodiments, the cooling process is divided into two stages. In the first stage, the temperature is reduced at a rate of 5°C / min - 8°C / min to 500°C, and in the second stage, it is naturally air-cooled to below 200°C. By adopting this staged cooling gradient, the casting residual stress can be effectively reduced and the overall performance of the castings can be improved.

[0050] S400. Post-treatment of rough parts Use a shot blasting machine to perform shot blasting on the rough parts prepared in step S300. The shot blasting time is 9 minutes, and the diameter of the steel shot is 1.5 mm. Shot blasting can effectively remove impurities such as oxide scales and sand grains on the surface of the castings, improve the surface finish and roughness, and at the same time, it can also strengthen the surface of the castings and improve its fatigue strength and corrosion resistance. Subsequently, manual grinding is used to remove flash and burrs. In other embodiments, the shot blasting time can be adjusted to 8 min - 10 min, and the diameter of the steel shot can be selected as 1.2 mm - 1.8 mm to meet the requirements of castings with different specifications and thicknesses.

[0051] Quality inspection and testing Conduct strict quality inspection on the upper housing of the wind turbine after shot blasting and grinding, 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; dimensional measurement uses high-precision measuring tools 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, magnetic particle flaw detection, and dissection to check whether there are defects such as porosity and shrinkage in the housing. The ultrasonic flaw detection frequency is 2.5 MHz - 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. Timely handle or rework the unqualified products to ensure product quality.

[0052] 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 box body. For example, anti-rust paint, anti-corrosion coating, etc. are coated on the box body surface 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.

[0053] Subsequent steps also include Inspection: The appearance is smooth and defect-free; Material: Spheroidization rate ≥ 80%, Tensile strength ≥ 400 Mpa, Elongation ≥ 18%, Yield strength ≥ 250 Mpa, Hardness: HB120 - 175, Pearlite content ≤ 5%; Painting: Apply silver-gray paint at the specified position according to the customer's requirements. The subsequent baking temperature is 80 °C and the time is 30 min.

[0054] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. 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.

[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, 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 lower box of a wind turbine generator, characterized in that: It comprises a box body (1), the box body (1) having a mounting cavity (2), and both ends of the box body (1) are outwardly flared; The two ends of the box body (1) are respectively connected to a first mounting ring (3) and a second mounting ring (4), and the side wall of the first mounting ring (3) is also connected to a fixing ring (5).

2. The lower box of the wind turbine generator according to claim 1, characterized in that: A support ring (6) is arranged in the installation cavity (2), and the inner wall of the support ring (6) has a plurality of annular grooves (7) arranged at intervals.

3. The lower box of the wind turbine generator according to claim 1 is characterized in that: The outer wall of the box body (1) is also provided with a plurality of reinforcing ribs (8) arranged at intervals.

4. A method for preparing a lower box of a wind turbine generator, applied to the lower 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. Cool the casting poured in step S200, the cooling time is greater than or equal to 2 hours, and the temperature of the casting is less than or equal to 200°C; S400. Shot blasting the blank prepared in step S300.

5. The method for preparing the lower 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 1430°C to 1470°C.

6. The method for preparing the lower box of a wind turbine generator according to claim 5, characterized in that: In step S200, the water output of each bag is 800KG to 1200KG, the molten metal pouring temperature is 1320℃ to 1370℃, and the length of the spheroidized wire is 20m to 25m.

7. The method for preparing the lower box of a wind turbine generator 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 with a cold core making machine and a cold core mold, and the cold core machine sand shooting pressure is 0.4mpa to 0.6mpa; S120. The outer mold is placed on a DISA molding machine for molding. The molding machine has a sand injection pressure of 2 Bar to 4 bar, an extrusion pressure of 8 Bar to 11 Bar, and a target compaction rate of 23% to 30%; S130. Place the sand core into the molded cavity to form a casting mold.

8. The method for preparing the lower box of a wind turbine generator 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 lower box 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 lower box of a wind turbine generator 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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