Wind power main shaft and residual stress control method thereof

Abstract

The invention discloses a wind power main shaft and a control method for residual stress of the wind power main shaft, and belongs to the technical field of large-scale high-end equipment manufacturing. The method comprises the following steps: carrying out normalizing treatment and high-temperature tempering treatment on the wind power main shaft forging to obtain a first intermediate workpiece; the first intermediate workpiece is subjected to rough machining and first-time stress relief aging treatment, then semi-finish machining and second-time stress relief aging treatment are conducted, and a second intermediate workpiece is obtained; and finish machining is conducted on the second intermediate workpiece, and then vibration aging treatment and subzero treatment are conducted. According to the method, a stable and uniform residual compressive stress layer can be formed on the surface of the wind power main shaft, fatigue crack initiation and expansion can be effectively inhibited, and meanwhile the size stability, the abrasion resistance and the stress corrosion resistance are improved.

Description

Technical Field

[0001] This invention relates to the field of large-scale high-end equipment manufacturing technology, and more specifically, to a method for controlling the residual stress of a wind turbine main shaft. Background Technology

[0002] The wind turbine main shaft is the core transmission component of a wind turbine generator set. It operates in harsh environments, enduring complex alternating loads, torque, and wind impacts. Because wind turbine main shafts are typically manufactured from large forgings (such as alloy steels like 42CrMo4 and 34CrNiMo6) through multiple forging and heavy machining processes, a large amount of macroscopic and microscopic residual stress is inevitably generated during manufacturing. These residual stresses are the main causes of deformation after machining, poor dimensional stability, decreased fatigue performance during use, and even early stress corrosion cracking.

[0003] Currently, among the commonly used methods for eliminating residual stress in the industry, one is stress-relief annealing, and the other is natural aging. Although the former can eliminate some stress, it has problems such as long production cycle (usually requiring tens of hours), high energy consumption, and difficulty in controlling the overall heating uniformity of large workpieces, and it cannot effectively intervene in new stresses introduced by machining; the latter takes too long (months or even years), making it difficult to meet the needs of efficient production.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for controlling the residual stress of wind turbine main shafts, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows: In a first aspect, the present invention provides a method for controlling residual stress in a wind turbine main shaft, comprising the following steps: performing normalizing and high-temperature tempering on a wind turbine main shaft forging to obtain a first intermediate workpiece; performing rough machining and a first stress-relief aging treatment on the first intermediate workpiece, followed by semi-finishing and a second stress-relief aging treatment to obtain a second intermediate workpiece; performing finish machining on the second intermediate workpiece, followed by vibration aging treatment and deep cryogenic treatment.

[0007] In an optional embodiment, the normalizing treatment is carried out at 870℃~890℃ for 6h~10h.

[0008] In an optional embodiment, the high-temperature tempering treatment is carried out at 630℃~650℃ for 18h~22h.

[0009] In an optional embodiment, the first stress-relief aging treatment involves heating to 550°C to 600°C at a rate of 65°C / h to 75°C / h and holding at that temperature for 6 to 8 hours.

[0010] In an optional embodiment, the second stress-relieving aging treatment involves heating to 500°C to 550°C at a rate of 45°C / h to 55°C / h and holding at that temperature for 4h to 6h.

[0011] In an optional implementation, after the first stress-relief aging treatment, the furnace is cooled to 240°C~260°C before being removed from the furnace and air-cooled. And / or, after the second stress-relief aging treatment, the furnace is cooled to 170℃~190℃ before being removed from the furnace.

[0012] In an optional embodiment, the vibration aging treatment includes: performing multi-frequency vibration in the range of 20Hz to 200Hz, and maintaining the treatment for 25min to 35min when the dynamic stress reaches 30% to 40% of the material's theoretical yield strength.

[0013] In an optional embodiment, the cryogenic treatment includes cooling to -160°C to -190°C at a rate of 1.5°C / min to 2.5°C / min and holding at that temperature for 2 hours to 4 hours.

[0014] Secondly, the present invention provides a wind turbine main shaft, which is obtained by any of the control methods described in the foregoing embodiments.

[0015] In an optional implementation, the surface residual stress of the wind turbine main shaft is a compressive stress of -200MPa to -250MPa. And / or, the pressure distribution uniformity of the wind turbine main shaft should be ≥90%.

[0016] The beneficial effects of this invention include: The method provided by this invention achieves closed-loop management of residual stress through generation, elimination, regeneration, and re-elimination by placing stress control nodes at the forefront and integrating them throughout the entire process of forging, roughing, semi-finishing, and finishing, thus controlling stress accumulation at its source. Specifically, by combining vibration aging treatment with cryogenic treatment, the advantages of rapid stress homogenization by vibration and thorough stress elimination by cryogenic treatment are combined. Vibration aging treatment provides a more active microscopic state for cryogenic treatment, while cryogenic treatment consolidates and deepens the effect of vibration aging treatment. The two work together to achieve results far exceeding those of a single process in a short time. Compared to traditional single, long-duration thermal aging treatment, the method provided by this invention has a shorter overall cycle and significantly reduced energy consumption; moreover, the vibration aging treatment and cryogenic treatment processes are pollution-free, conforming to the concept of green manufacturing.

[0017] The method provided by this invention can ultimately form a stable and uniform residual compressive stress layer on the surface of the wind turbine main shaft, which can effectively suppress the initiation and propagation of fatigue cracks, while improving dimensional stability, wear resistance and stress corrosion resistance. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] The following is a detailed description of the wind turbine main shaft and its residual stress control method provided by the present invention.

[0020] This invention provides a method for controlling residual stress in wind turbine main shafts, comprising the following steps: S1: The wind turbine main shaft forging is subjected to normalizing and high-temperature tempering to obtain the first intermediate workpiece.

[0021] In some alternative embodiments, the wind turbine main shaft forging is obtained by forging an alloy steel ingot, wherein the alloy steel ingot may exemplary include a 42CrMo steel ingot. Forging can be carried out using forging methods and conditions commonly used for wind turbine main shafts, which will not be elaborated or limited here.

[0022] In some alternative embodiments, the normalizing treatment is carried out at 870°C to 890°C for 6 to 10 hours.

[0023] The normalizing temperature can be 870℃, 875℃, 880℃, 885℃ or 890℃, or other values ​​within the range of 870℃ to 890℃.

[0024] The normalizing time can be 6h, 8h, or 10h, or other values ​​within the range of 6h to 10h.

[0025] In some alternative implementations, the high-temperature tempering treatment is carried out at 630°C to 650°C for 18 to 22 hours.

[0026] The high-temperature tempering temperature can be 630℃, 635℃, 640℃, 645℃ or 650℃, or other values ​​within the range of 630℃ to 650℃.

[0027] The high-temperature tempering time can be 18h, 20h, or 22h, or other values ​​within the range of 18h to 22h.

[0028] If the tempering temperature is below 630℃, a low-temperature tempering treatment of 150℃~250℃ is not conducive to core toughness and service safety; a medium-temperature tempering treatment of 350℃~500℃ is not conducive to the matching of strength and toughness and the connection of surface hardening process.

[0029] In some alternative implementations, the normalizing treatment is followed by air cooling, and the tempering treatment is followed by furnace cooling.

[0030] Through the above-mentioned normalizing and high-temperature tempering treatments, a uniform sorbitic structure can be obtained, and forging stress can be initially eliminated.

[0031] S2: The first intermediate workpiece is rough-machined and subjected to a first stress-relieving aging treatment, followed by semi-finishing and a second stress-relieving aging treatment to obtain the second intermediate workpiece.

[0032] In some alternative implementations, roughing may involve rough turning the first intermediate workpiece to remove most of the machining allowance.

[0033] In some alternative implementations, the first stress-relief aging treatment involves heating to 550°C to 600°C at a rate of 65°C / h to 75°C / h and holding at that temperature for 6 to 8 hours.

[0034] The heating rate for the first stress-relief aging treatment can be 65℃ / h, 68℃ / h, 70℃ / h, 72℃ / h, or 75℃ / h, or other values ​​within the range of 65℃ / h to 75℃ / h.

[0035] If the heating rate of the first stress-relief aging treatment is lower than 65℃ / h, it is not conducive to improving production efficiency and process economy; if the heating rate of the first stress-relief aging treatment is higher than 75℃ / h, it is not conducive to avoiding thermal stress cracking.

[0036] The temperature for the first stress-relieving aging treatment can be 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃, or other values ​​within the range of 550℃ to 600℃.

[0037] If the temperature of the first stress-relief aging treatment is below 550℃, it is not conducive to stress relief efficiency; if the temperature of the first stress-relief aging treatment is above 600℃, it is not conducive to grain size control.

[0038] The time for the first stress-relieving aging treatment can be 6h, 6.5h, 7h, 7.5h or 8h, or other values ​​within the range of 6h to 8h.

[0039] After the first stress-relief aging treatment, the furnace is cooled to 240℃~260℃ (such as 240℃, 245℃, 250℃, 255℃ or 260℃, etc.) before being taken out of the furnace and air-cooled.

[0040] The aforementioned first stress-relieving aging treatment is a medium-high temperature thermal aging process, which can eliminate the macroscopic residual stress released and rebalanced after rough machining removes a large amount of material. It can also be understood as eliminating the stress redistribution caused by rough machining.

[0041] In some alternative implementations, semi-finishing can be performed by semi-finishing turning and initial grinding of the workpiece obtained from the first stress-relief aging treatment.

[0042] In some alternative embodiments, the second stress-relieving aging treatment involves heating to 500°C to 550°C at a rate of 45°C / h to 55°C / h and holding at that temperature for 4h to 6h.

[0043] The rate of the second stress-relieving aging treatment can be 45℃ / h, 48℃ / h, 50℃ / h, 52℃ / h or 55℃ / h, or other values ​​within the range of 45℃ / h to 55℃ / h.

[0044] If the heating rate of the second stress-relief aging treatment is lower than 45℃ / h, it is not conducive to the control of tissue stability; if the heating rate of the second stress-relief aging treatment is higher than 55℃ / h, it is not conducive to the control of thermal stress and dimensional stability.

[0045] The temperature for the second stress-relieving aging treatment can be 500℃, 510℃, 520℃, 530℃, 540℃ or 550℃, or other values ​​within the range of 500℃ to 550℃.

[0046] If the temperature of the second stress-relief aging treatment is below 500℃, it is not conducive to the effective elimination of residual stress; if the temperature of the second stress-relief aging treatment is above 550℃, it is not conducive to the maintenance of matrix hardness.

[0047] The second stress-relieving aging treatment can be performed for 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours, or other values ​​within the range of 4 hours to 6 hours.

[0048] After the second stress-relief aging treatment, the furnace is cooled to 170℃~190℃ (such as 170℃, 175℃, 180℃, 185℃ or 190℃, etc.) before being taken out of the furnace.

[0049] The aforementioned second stress-relieving aging treatment is a medium-temperature thermal aging process, which can eliminate the subsurface stress introduced by semi-finishing, stabilize the workpiece geometry, and provide a stable workpiece state for finishing.

[0050] S3: The second intermediate workpiece is precision machined, followed by vibration aging treatment and deep cryogenic treatment.

[0051] In some alternative implementations, finishing includes precision grinding and gear milling, etc.

[0052] In some optional implementations, the vibration aging treatment includes: clamping the vibration device onto the spindle flange end, starting the device to perform a full-frequency scan to find the first natural frequency. Multi-frequency vibration is then performed within the range of 20Hz to 200Hz, and dynamic stress is monitored using an accelerometer. When the dynamic stress reaches approximately 30% to 40% (e.g., 30%, 35%, or 40%) of the material's theoretical yield strength, the treatment is maintained for 25 to 35 minutes (e.g., 25 minutes, 30 minutes, or 35 minutes).

[0053] Maintaining the treatment for 25 to 35 minutes when the dynamic stress reaches approximately 30% to 40% of the material's theoretical yield strength is beneficial for the uniform elimination of residual stress.

[0054] In some alternative implementations, cryogenic treatment includes cooling to -160°C to -190°C at a rate of 1.5°C / min to 2.5°C / min and holding at that temperature for 2 hours to 4 hours.

[0055] The cooling rate of the cryogenic treatment can be 1.5℃ / min, 2℃ / min, or 2.5℃ / min, or other values ​​within the range of 1.5℃ / min to 2.5℃ / min.

[0056] By controlling the cooling rate of cryogenic treatment within the above range, it is beneficial to suppress thermal stress and the risk of cracking.

[0057] The temperature for cryogenic treatment can be -160℃, -165℃, -170℃, -175℃, -180℃, -185℃, or -190℃, or other values ​​within the range of -160℃ to -190℃.

[0058] If the cryogenic treatment temperature is higher than -160℃ (such as -150℃), it is not conducive to the full transformation of the retained austenite.

[0059] The holding time for cryogenic treatment can be 2h, 2.5h, 3h, 3.5h or 4h, or other values ​​within the range of 2h to 4h.

[0060] During operation, the workpiece after vibration aging treatment can be suspended into a liquid nitrogen cryogenic chamber and cooled to -160℃ to -190℃ at a rate of 1.5℃ / min to 2.5℃ / min, and held for 2h to 4h; then slowly warmed back to room temperature at a rate of 0.5℃ / min to 1.5℃ / min.

[0061] The above-mentioned cryogenic treatment can transform the residual austenite and produce microscopic coordinated deformation, further homogenizing and reducing residual stress.

[0062] Following the above, after finishing, a combined process of vibration aging and cryogenic treatment is performed. First, vibration aging is used to homogenize and reduce the machining stress on and near the surface of the workpiece. Then, cryogenic treatment is used to transform the retained austenite into martensite and generate uniform micro-plastic deformation, thereby further reducing deep stress and introducing uniform surface compressive stress, which significantly improves fatigue performance.

[0063] The roughing (such as rough turning), semi-finishing (such as semi-finish turning and initial grinding), and finishing (such as fine grinding and gear milling) mentioned in this invention are all conventional processes and can be performed according to conventional operations.

[0064] Furthermore, after the preparation is completed, an X-ray stress meter can be used to inspect key parts such as the spindle bearing stop and the flange transition fillet.

[0065] Accordingly, the present invention also provides a wind turbine main shaft, which is obtained by the above-described control method.

[0066] In some alternative implementations, the surface residual stress of the wind turbine main shaft is a compressive stress of -200MPa to -250MPa.

[0067] In some alternative implementations, the pressure distribution uniformity of the wind turbine main shaft should be ≥90%, such as 90%~95%.

[0068] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0069] Example 1 This embodiment provides a method for controlling residual stress in the main shaft of a 2MW wind turbine, including the following steps: S1: The wind turbine main shaft forging is subjected to normalizing and high-temperature tempering to obtain the first intermediate workpiece.

[0070] The wind turbine main shaft forging is made from 42CrMo alloy steel ingots. The normalizing treatment involves holding at 880℃ for 8 hours, followed by air cooling. The high-temperature tempering treatment involves holding at 640℃ for 20 hours, followed by furnace cooling.

[0071] S2: The first intermediate workpiece is rough-machined and subjected to a first stress-relieving aging treatment, followed by semi-finishing and a second stress-relieving aging treatment to obtain the second intermediate workpiece.

[0072] Specifically, the first intermediate workpiece is rough-turned, then loaded into a bogie-type resistance furnace, heated to 580°C at a rate of 70°C / h and held for 7 hours, then cooled in the furnace to 250°C and air-cooled; then semi-finish turning and initial grinding are performed; then it is put back into the furnace, heated to 520°C at a rate of 50°C / h and held for 5 hours, then cooled in the furnace to 180°C and removed from the furnace.

[0073] S3: The second intermediate workpiece is precision machined, followed by vibration aging treatment and deep cryogenic treatment.

[0074] Specifically, the second intermediate workpiece undergoes precision grinding and gear milling. Then, the vibration equipment is clamped to the spindle flange end and started to perform a full-frequency scan to find the first natural frequency (approximately 85Hz). Multi-frequency vibration is then performed within the range of 80Hz to 100Hz, and dynamic stress is monitored using an accelerometer. When the dynamic stress reaches approximately 35% of the material's theoretical yield strength (approximately 180MPa), the treatment is maintained for 30 minutes. Subsequently, the vibration-aged workpiece is suspended in a liquid nitrogen cryogenic chamber and cooled to -175℃ at a programmed rate of 2℃ / min, held at that temperature for 3 hours; then, it is slowly warmed back to room temperature at a rate of 1℃ / min.

[0075] Example 2 This embodiment provides a method for controlling residual stress in the main shaft of a 2MW wind turbine, including the following steps: S1: The wind turbine main shaft forging is subjected to normalizing and high-temperature tempering to obtain the first intermediate workpiece.

[0076] The wind turbine main shaft forging is made from 42CrMo alloy steel ingots. The normalizing treatment involves holding at 870℃ for 6 hours, followed by air cooling. The high-temperature tempering treatment involves holding at 630℃ for 18 hours, followed by furnace cooling.

[0077] S2: The first intermediate workpiece is rough-machined and subjected to a first stress-relieving aging treatment, followed by semi-finishing and a second stress-relieving aging treatment to obtain the second intermediate workpiece.

[0078] Specifically, the first intermediate workpiece is rough-machined, then loaded into a bogie-type resistance furnace, heated to 550°C at a rate of 65°C / h and held for 8 hours, then cooled in the furnace to 240°C and air-cooled; then semi-finished and first-grinded; then put back into the furnace, heated to 500°C at a rate of 45°C / h and held for 6 hours, then cooled in the furnace to 170°C and removed from the furnace.

[0079] S3: The second intermediate workpiece is precision machined, followed by vibration aging treatment and deep cryogenic treatment.

[0080] Specifically, the second intermediate workpiece undergoes precision grinding and gear milling. Then, a vibration device is clamped to the spindle flange end and started to perform a full-frequency scan to find the first natural frequency (approximately 90Hz). Multi-frequency vibration is then performed within the range of 85Hz to 110Hz, and dynamic stress is monitored using an accelerometer. When the dynamic stress reaches approximately 30% of the material's theoretical yield strength (approximately 154MPa), the treatment is maintained for 35 minutes. Subsequently, the vibration-aged workpiece is suspended in a liquid nitrogen cryogenic chamber and cooled to -160℃ at a programmed rate of 1.5℃ / min, held at that temperature for 4 hours. It is then slowly warmed back to room temperature at a rate of 0.5℃ / min.

[0081] Example 3 This embodiment provides a method for controlling residual stress in the main shaft of a 2MW wind turbine, including the following steps: S1: The wind turbine main shaft forging is subjected to normalizing and high-temperature tempering to obtain the first intermediate workpiece.

[0082] The wind turbine main shaft forging is made from 42CrMo alloy steel ingots. The normalizing treatment involves holding at 890℃ for 10 hours, followed by air cooling. The high-temperature tempering treatment involves holding at 650℃ for 22 hours, followed by furnace cooling.

[0083] S2: The first intermediate workpiece is rough-machined and subjected to a first stress-relieving aging treatment, followed by semi-finishing and a second stress-relieving aging treatment to obtain the second intermediate workpiece.

[0084] Specifically, the first intermediate workpiece is rough-machined, then loaded into a bogie-type resistance furnace, heated to 600°C at a rate of 75°C / h and held for 6 hours, then cooled in the furnace to 260°C and air-cooled; then semi-finished and first-grinded; then put back into the furnace, heated to 550°C at a rate of 55°C / h and held for 4 hours, then cooled in the furnace to 190°C and removed from the furnace.

[0085] S3: The second intermediate workpiece is precision machined, followed by vibration aging treatment and deep cryogenic treatment.

[0086] Specifically, the second intermediate workpiece undergoes precision grinding and gear milling. Then, the vibration equipment is clamped to the spindle flange end and started to perform a full-frequency scan to find the first natural frequency (approximately 80Hz). Multi-frequency vibration is then performed within the range of 60Hz to 95Hz, and dynamic stress is monitored using an accelerometer. When the dynamic stress reaches approximately 40% of the material's theoretical yield strength (approximately 205MPa), the treatment is maintained for 25 minutes. Subsequently, the vibration-aged workpiece is suspended in a liquid nitrogen cryogenic chamber and cooled to -190℃ at a programmed rate of 2.5℃ / min, held for 2 hours, and then slowly warmed back to room temperature at a rate of 1.5℃ / min.

[0087] Comparative Example 1 The difference between this comparative example and Example 1 is that in S1, the tempering temperature is 250°C, which means a low-temperature tempering process is performed.

[0088] Comparative Example 2 The difference between this comparative example and Example 1 is that in S1, the tempering temperature is 500°C, which is a medium-temperature tempering process.

[0089] Comparative Example 3 The difference between this comparative example and Example 1 is that in S2, the temperature of the first stress-relief aging treatment is 520°C.

[0090] Comparative Example 4 The difference between this comparative example and Example 1 is that in S2, the temperature of the first stress-relief aging treatment is 620°C.

[0091] Comparative Example 5 The difference between this comparative example and Example 1 is that no cryogenic treatment was performed in S3.

[0092] Comparative Example 6 The difference between this comparative example and Example 1 is that in S3, the temperature of the cryogenic treatment is -150°C.

[0093] Test case The wind turbine main shafts prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to surface residual stress tests. Specifically, the wind turbine main shafts were tested using an X-ray stress meter, and the results are shown in Table 1.

[0094] Table 1 Performance Results

[0095] As can be seen from Table 1, compared with Comparative Examples 1-6, the wind turbine main shafts prepared in Examples 1-3 of the present invention have significantly lower residual stress.

[0096] In summary, the method provided by this invention achieves closed-loop management of residual stress through generation, elimination, regeneration, and re-elimination by placing stress control nodes at the forefront and integrating them throughout the entire process of forging, roughing, semi-finishing, and finishing, thus controlling stress accumulation from the source. Specifically, by combining vibration aging treatment with cryogenic treatment, the advantages of rapid stress homogenization by vibration and thorough stress elimination by cryogenic treatment are combined. Vibration aging treatment provides a more active microscopic state for cryogenic treatment, while cryogenic treatment consolidates and deepens the effect of vibration aging treatment. The two work together to achieve results far exceeding those of a single process in a short time. Compared to traditional single long-term thermal aging treatment, the method provided by this invention has a shorter total cycle and significantly reduced energy consumption; moreover, the vibration aging treatment and cryogenic treatment processes are pollution-free, conforming to the concept of green manufacturing. The above-mentioned method of this invention can ultimately form a stable and uniform residual compressive stress layer on the surface of the wind turbine main shaft, effectively inhibiting the initiation and propagation of fatigue cracks, while improving dimensional stability, wear resistance, and stress corrosion resistance.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling residual stress in a wind turbine main shaft, characterized in that, Includes the following steps: The wind turbine main shaft forging is subjected to normalizing and high-temperature tempering to obtain the first intermediate workpiece; the first intermediate workpiece is subjected to rough machining and a first stress-relieving aging treatment, followed by semi-finishing and a second stress-relieving aging treatment to obtain the second intermediate workpiece; the second intermediate workpiece is subjected to finish machining, followed by vibration aging treatment and deep cryogenic treatment.

2. The control method according to claim 1, characterized in that, Normalizing treatment is carried out at 870℃~890℃ for 6h~10h.

3. The control method according to claim 1, characterized in that, High-temperature tempering treatment is carried out at 630℃~650℃ for 18h~22h.

4. The control method according to claim 1, characterized in that, The first stress-relieving aging treatment involves heating to 550℃~600℃ at a rate of 65℃ / h~75℃ / h and holding at that temperature for 6h~8h.

5. The control method according to claim 4, characterized in that, The second stress-relieving aging treatment involves heating to 500℃~550℃ at a rate of 45℃ / h~55℃ / h and holding at that temperature for 4h~6h.

6. The control method according to claim 5, characterized in that, After the first stress-relieving aging treatment, the furnace is cooled to 240℃~260℃ before being removed from the furnace and air-cooled. And / or, after the second stress-relief aging treatment, the furnace is cooled to 170℃~190℃ before being removed from the furnace.

7. The control method according to claim 1, characterized in that, Vibration aging treatment includes: multi-frequency vibration within the range of 20Hz to 200Hz first natural frequency, and maintaining the treatment for 25min to 35min when the dynamic stress reaches 30% to 40% of the material's theoretical yield strength.

8. The control method according to claim 1, characterized in that, Cryogenic treatment includes cooling to -160℃ to -190℃ at a rate of 1.5℃ / min to 2.5℃ / min and holding at that temperature for 2h to 4h.

9. A wind turbine main shaft, characterized in that, Obtained by the control method described in any one of claims 1 to 8.

10. The wind turbine main shaft according to claim 9, characterized in that, The residual stress on the surface of the wind turbine main shaft is a compressive stress of -200MPa to -250MPa; And / or, the pressure distribution uniformity of the wind turbine main shaft should be ≥90%.

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