Heat treatment process for high-strength bolt of wind power blade

Abstract

The invention relates to the technical field of bolt heat treatment, in particular to a wind power blade high-strength bolt heat treatment process which comprises the following steps: presetting a bolt heat treatment state, and performing impact treatment on the root of a bolt thread through a bolt heat treatment device to form a nanocrystalline layer; in the atmosphere of ammonia gas containing Ce-La mixed rare earth, three-section pulse type nitriding is carried out; and under the action of a transverse stable magnetic field, water-based atomized quenching liquid containing polyvinyl alcohol and graphene is adopted for gradient cooling. The method has the beneficial effects that through the synergistic effect of the multiple steps of surface mechanical nanocrystallization pretreatment, rare earth element gradient nitriding, magnetic field assisted gradient quenching, pulse current cryogenic composite tempering and the like, the comprehensive performance of the high-strength bolt of the wind power blade is remarkably improved through the technical scheme. And specifically, the surface hardness is greatly improved, meanwhile, good toughness of the core part is kept, the corrosion resistance of the bolt is remarkably improved, the fatigue life of the bolt is remarkably prolonged, and the service life of the bolt in an extreme marine environment is longer.

Description

Technical Field

[0001] The present invention relates to the technical field of bolt heat treatment, and specifically to a heat treatment process for high-strength bolts of wind turbine blades. Background Art

[0002] In the field of wind turbines, the performance of special fasteners for wind turbines, such as high-strength bolts of wind turbine blades, is crucial. To improve the performance of such bolts, the heat treatment process becomes a key link. Traditional heat treatment processes have certain limitations in improving bolt strength, wear resistance, etc. With the increasingly complex operating environment of wind turbines, the requirements for bolt performance are constantly increasing. It is urgent to develop a new and efficient heat treatment process for high-strength bolts of wind turbine blades to meet the long-term stable operation needs of wind turbines.

[0003] Currently, traditional heat treatment processes face many challenges in improving bolt performance, such as the matching problem between surface hardness and core toughness, the uniformity problem of nitrided layer depth and hardness, the cracking risk during quenching, and the limitations of tempering treatment in performance improvement. Especially in extreme marine environments, bolts need to withstand harsh working conditions such as high salt spray corrosion and alternating loads, which pose higher requirements for bolt strength, corrosion resistance, and fatigue life.

[0004] Therefore, developing a new and efficient heat treatment process for high-strength bolts of wind turbine blades to solve the performance bottleneck problems in the existing technology has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a heat treatment process for high-strength bolts of wind turbine blades to meet the higher requirements for bolt strength, corrosion resistance, and fatigue life in extreme marine environments where bolts need to withstand harsh working conditions such as high salt spray corrosion and alternating loads.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: A heat treatment process for high-strength bolts of wind turbine blades, comprising the following steps:

[0007] Preset the bolt heat treatment state, and perform impact treatment on the bolt thread root through a bolt heat treatment device to form a nanocrystalline layer;

[0008] Perform three-stage pulsed nitriding in an ammonia atmosphere containing Ce-La mixed rare earth;

[0009] Under the action of a transverse steady magnetic field, perform gradient cooling using an aqueous atomized quenching liquid containing polyvinyl alcohol and graphene;

[0010] Perform liquid nitrogen cryogenic treatment, and then apply pulsed current during the tempering process.

[0011] Further, the temperature in the first stage of the three-stage pulsed nitriding process is 520 °C, the nitriding time is 2 h, the temperature in the second stage is 580 °C, the nitriding time is 1.5 h, the temperature in the third stage is 500 °C, and the nitriding time is 3 h.

[0012] Further, the intensity of the transverse steady magnetic field is regulated in stages, including the initial stage, the main quenching stage, and the final cooling stage; the atomization pressure of the quenching liquid is regulated synchronously with each stage of the intensity of the transverse steady magnetic field.

[0013] Further, the liquid nitrogen cryogenic treatment includes gradient cooling in the first stage, the second stage, and the third stage;

[0014] The first stage: from 25 °C to -80 °C, the cooling rate is 3 °C / min, and it is maintained for 15 min;

[0015] The second stage: from -80 °C to -140 °C, the cooling rate is 2 °C / min, and it is maintained for 10 min;

[0016] The third stage: from -140 °C to -196 °C, the cooling rate is 1 °C / min, and it is maintained for 5 min.

[0017] Further, the bolt heat treatment device includes a fixing frame, on which a rotating workbench that can rotate periodically by 90° is installed. There are four bolt fixing components on the rotating workbench. A vibrating bracket that can move up and down is drivenly connected to the bolt fixing component. A driving bottom shaft is rotatably installed on the inner wall of the vibrating bracket. A magnetic attraction shaft is rotatably installed on the inner wall of the driving bottom shaft. A magnetic attraction groove for bolt magnetic attraction and positioning is opened at the top of the magnetic attraction shaft. The driving bottom shaft and the magnetic attraction shaft rotate coaxially in opposite directions. The fixing frame is sequentially provided with a loading and unloading station, a nano-treatment station, a negative pressure cleaning station, and a cleaning station in the clockwise direction. A treatment frame is installed on the fixing frame in a liftable manner. Nozzle mechanisms are arranged at positions corresponding to the nano-treatment station, the negative pressure cleaning station, and the cleaning station on the treatment frame. The bolts are subjected to nano-impact treatment at the nano-treatment station, negative pressure suction of nano-particles at the negative pressure cleaning station, and cleaning and low-temperature stress elimination of the bolts at the cleaning station.

[0018] Further, it further includes a servo motor installed at the bottom of the fixing frame. An output shaft end of the servo motor is installed with an incomplete gear. A transmission tooth surface is fixedly arranged on the incomplete gear. An intermittent shaft is installed on the bottom surface of the rotary working station frame. An intermittent gear meshing with the transmission tooth surface is fixedly installed on the intermittent shaft. A central angle corresponding to a meshing area of the transmission tooth surface is 90°. A radius of the incomplete gear is the same as a radius of the intermittent gear. A hollow tooth shaft is rotatably sleeved on the intermittent shaft. A driving gear ring is installed on the hollow tooth shaft. A belt is in transmission connection between an output shaft end of the servo motor and the hollow tooth shaft. A bottom cylinder is fixedly installed on the fixing frame. A shaft frame is fixedly installed on the bottom cylinder. A guiding shaft is rotatably installed at a position corresponding to a nano-treatment station, a negative-pressure cleaning station, and a cleaning station on the shaft frame. A transmission bevel gear and a driven gear in transmission connection with the driving gear ring are respectively installed on the guiding shaft. The bolt fixing component is adaptively connected with the transmission bevel gear. A vertically arranged screw rod lifting module is installed on the fixing frame. The screw rod lifting module is in transmission connection with the processing frame.

[0019] Further, the bolt fixing component includes a large circular shaft and a hollow shaft rotatably connected to the rotary working station frame. A driven bevel gear meshing with the transmission bevel gear is fixedly installed at one end of the large circular shaft. A first bevel gear is installed on both the hollow shaft and the large circular shaft. The two first bevel gears mesh with each other. A hollow groove with both ends open and slidably connected with a magnetic attraction shaft is fixedly opened inside the hollow shaft. Cross sections of the magnetic attraction shaft and the hollow groove are both regular hexagons. An eccentric wheel is installed on the large circular shaft. A follower wheel is rotatably installed on the vibration support. The follower wheel is in rolling contact with a contour surface of the eccentric wheel. The vibration support is slidably connected with the rotary working station frame. A vibration spring limited by the rotary working station frame is installed on a top surface of the vibration support.

[0020] Further, the bolt fixing component further includes a small circular shaft rotatably installed on the vibration support. A conical gear is installed on the small circular shaft. A second bevel gear is installed on both the magnetic attraction shaft and the transmission bottom shaft. The two second bevel gears are both in transmission connection with the conical gear. The two second bevel gears are respectively arranged on two sides of the conical gear.

[0021] Furthermore, the nozzle mechanism includes a conduit and a follower seat. The conduit is fixedly installed on the processing frame. Two T-shaped guide rods are installed on the top surface of the follower seat, and both T-shaped guide rods are slidably connected to the conduit. A rotary protective cylinder is rotatably installed on the inner wall of the follower seat. A sealing rubber ring connected to the transmission bottom shaft is fixedly installed at the bottom end of the rotary protective cylinder. A spray head is fixedly installed on the inner wall of the rotary protective cylinder, and the spray head faces the root of the bolt thread at an inclination angle of 45°. A through cavity is fixedly opened at the top of the rotary protective cylinder, and the tail end of the spray head is communicated with the through cavity. The bottom end of the conduit is rotatably communicated with the through cavity through a corrugated pipe. A vibration-following spring is sleeved on the corrugated pipe. At the top end of the conduit in the nano-treatment station, a nano-material connecting pipe communicated with the high-pressure nano-particle feeding device is fixedly arranged. At the top end of the conduit in the negative-pressure cleaning station, a negative-pressure suction pipe communicated with the negative-pressure suction device is fixedly arranged. At the top end of the conduit in the cleaning station, a cleaning joint communicated with the cleaning liquid feeding device is fixedly arranged. A heating coil is fixedly installed outside the rotary protective cylinder in the cleaning station.

[0022] Furthermore, it further includes a sleeve rotatably sleeved on the bottom cylinder. A sewage suction channel is fixedly opened inside the magnetic attraction shaft. The bottom end of the sewage suction channel is communicated with the sleeve through a sewage discharge pipe. A group of sewage suction holes distributed in a circumferential array and communicated with the sewage suction channel are opened on the magnetic attraction shaft. A sewage discharge cavity is fixedly opened inside the bottom cylinder. A sewage discharge hole communicated with the sewage discharge cavity is fixedly opened on the bottom cylinder at a position corresponding to the cleaning station. A sewage accumulation box communicated with the sewage discharge cavity is fixedly installed on the fixed frame.

[0023] Furthermore, the magnetic attraction shaft is made of permanent magnetic material, and the cross-section of the magnetic attraction groove is a regular hexagon.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. Through the synergistic action of multiple steps such as surface mechanical nanocrystallization pretreatment, rare earth element gradient nitriding, magnetic field-assisted gradient quenching, and pulsed current cryogenic complex tempering, this technical solution significantly improves the comprehensive performance of high-strength bolts for wind turbine blades. Specifically, the surface hardness is greatly improved, while maintaining good toughness at the core. The corrosion resistance and fatigue life of the bolts are also significantly improved, and the service life in extreme marine environments is longer.

[0026] 2. A number of innovations have been made on the basis of traditional heat treatment processes. For example, tungsten carbide cobalt particles with a particle size of 100 μm are used for impact treatment to form a nanocrystalline layer, rare earth elements Ce-La are introduced for gradient nitriding, a steady magnetic field is used to assist gradient quenching, and pulsed current is combined for cryogenic composite tempering, etc. These innovative processes not only improve the performance of the bolts but also significantly enhance the production efficiency. Magnetic field-assisted quenching realizes the control of the cooling rate gradient from the surface to the core by optimizing the magnetic field strength and the quenching liquid spraying speed, avoiding the cracking risk in traditional quenching processes. At the same time, the pulsed current cryogenic composite tempering technology further improves the strength and toughness of the bolts, making the entire heat treatment process more efficient and controllable.

[0027] 3. The present invention significantly improves the surface treatment uniformity of the bolts, enhances the shear resistance and fatigue life of the bolts. Through the dynamic vibration control mechanism, high-frequency micro-amplitude vibration combined with tungsten carbide cobalt particle impact forms a uniform nanocrystalline layer with a thickness of 50 - 80 μm and a grain size < 100 nm at the thread root. Compared with traditional static impact, the grain refinement efficiency is increased by 40%, and the deviation of the nanolayer thickness is reduced from ±15% to ±5%, solving the problems of weak shear resistance and short fatigue life caused by uneven particle distribution in traditional processes. This technology creatively introduces an eccentric wheel - follower wheel vibration structure and a regular hexagon magnetic attraction positioning to ensure no displacement deviation of the bolts during impact, which is applicable to extreme wind load conditions.

[0028] 4. The present invention adopts a three-stage pulsed nitriding process, combined with an ammonia atmosphere containing Ce-La rare earth, to form a rare earth element gradient penetration layer. Compared with the single-temperature nitriding process, the surface hardness uniformity is increased by 30%, and the salt spray corrosion test life is extended by more than 2 times, significantly adapting to the high-salt spray environment at sea. This gradient design breaks through the temperature control bottleneck of traditional nitriding processes, promotes the deep diffusion of rare earth elements through dynamic temperature adjustment, and has the dual advantages of high hardness and corrosion resistance.

[0029] 5. Under a 0.5 - 1.2 T transverse magnetic field, the present invention uses an atomized quenching liquid containing graphene for gradient cooling, and dynamically adjusts the magnetic field strength and cooling rate through a machine learning model, reducing the residual stress fluctuation from the traditional ±150 MPa to within ±50 MPa. This solution creatively introduces an intelligent control technology, combined with the enhanced thermal conductivity of the quenching liquid by graphene, effectively suppressing stress concentration. The fatigue life of the bolts under high-frequency alternating loads is significantly improved, and no manual debugging is required, reducing the process cost by 20%.

[0030] 6. The present invention can achieve high-precision multi-station collaboration, double improvement in production efficiency and consistency. Based on the incomplete gear intermittent gear structure driven by a servo motor, the positioning accuracy of the rotating station frame reaches ±0.1 mm. With the clamping by the regular hexagon magnetic suction groove, the circumferential sliding of the bolt is completely eliminated. Compared with the traditional continuous rotating station, the multi-process switching efficiency is increased by 50%, and the thickness consistency of the nano-layer is increased to 98%. The design of this equipment solves the industry problems of large positioning deviation and unstable clamping of traditional devices through the integration of mechanical structure and intelligent control, providing a reliable guarantee for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is the process flow chart of the heat treatment process for high-strength bolts of wind turbine blades

[0032] Figure 2 is the schematic diagram of the principle of the heat treatment process for high-strength bolts of wind turbine blades;

[0033] Figure 3 is the overall structure schematic diagram of the bolt heat treatment device of the present invention;

[0034] Figure 4 is the present invention Figure 1 's sectional structure schematic diagram;

[0035] Figure 5 is the present invention Figure 4 's partial enlarged structure schematic diagram at A;

[0036] Figure 6 is the present invention Figure 4 's partial enlarged structure schematic diagram at B;

[0037] Figure 7 is the present invention Figure 4 's partial enlarged structure schematic diagram at C;

[0038] Figure 8 is the structure schematic diagram of the negative pressure suction pipe, nano-material connection pipe and cleaning joint of the present invention;

[0039] Figure 9 is the structure schematic diagram of the bottom cylinder and the intermittent gear of the present invention;

[0040] Figure 10 is the structure schematic diagram of the shaft frame and the bottom cylinder of the present invention;

[0041] Figure 11 is the structure schematic diagram of the magnetic suction groove and the vibration spring of the present invention.

[0042] In the drawings, the list of components represented by each reference numeral is as follows:

[0043] 1. Bolt heat treatment device; 2. Fixed frame; 3. Rotary working station frame; 4. Vibration support; 5. Driving bottom shaft; 6. Magnetic attraction shaft; 7. Magnetic attraction groove; 8. Treatment frame; 9. Servo motor; 10. Incomplete gear; 11. Intermittent shaft; 12. Intermittent gear; 13. Hollow tooth shaft; 14. Active gear ring; 15. Bottom cylinder; 16. Shaft frame; 17. Guiding shaft; 18. Driven gear; 19. Screw rod lifting module; 20. Large round shaft; 21. Hollow shaft; 22. Eccentric wheel; 23. Follow-up wheel; 24. Vibration spring; 25. Small round shaft; 26. Follow-up seat; 27. T-shaped guide rod; 28. Rotating protection cylinder; 29. Sprinkler head; 30. Through cavity; 31. Bellows; 32. Vibration following spring; 33. Nano material connecting pipe; 34. Negative pressure suction pipe; 35. Cleaning joint; 36. Heating coil; 37. Sleeve; 38. Sewage suction channel; 39. Sewage suction hole; 40. Sewage discharge cavity; 41. Sewage discharge hole; 42. Sewage accumulation box; 43. Bolt; 44. Sewage discharge pipe; 45. Conduit. Detailed implementation mode

[0044] The principles and features of the present invention will be described below in conjunction with 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.

[0045] The present invention provides the following preferred embodiments

[0046] As Figure 1-2 shown, a heat treatment process for high-strength bolts of wind turbine blades includes the following steps:

[0047] SS01. Surface mechanical nanocrystallization pretreatment: Preset the heat treatment state of the bolt 43. The bolt heat treatment device 1 uses tungsten carbide cobalt particles with a particle size of 100 μm to impact the root of the bolt 43 thread at a speed of 300 m / s to form a nanocrystalline layer with a thickness of 80 μm and a grain size of less than 100 nm.

[0048] SS02. Rare earth element gradient nitriding: Perform three-stage pulse nitriding in an ammonia atmosphere containing 1.2 wt% Ce-La mixed rare earth.

[0049] The synergistic catalytic mechanism of rare earth elements (Ce-La) is as follows:

[0050] Surface activation effect: The atomic radii of Ce (cerium) and La (lanthanum) rare earth elements are relatively large (Ce: 0.182 nm, La: 0.187 nm). Their high surface energy characteristics can preferentially adsorb on the bolt surface, remove the oxide film and impurities, form active sites, and promote the decomposition of NH3 into active nitrogen atoms (N*).

[0051] Grain boundary diffusion acceleration: Rare earth elements segregate at grain boundaries during nitriding, reducing the diffusion activation energy of nitrogen atoms and accelerating the penetration of nitrogen into the matrix. Experiments show that adding 1.2 wt% Ce-La mixed rare earth can increase the nitrogen diffusion coefficient by 30%-40%.

[0052] Nitride refinement regulation: Rare earth elements inhibit the coarsening of Fe3N and promote the uniform precipitation of ε-Fe 23 N phase, forming a fine nitride layer, improving surface hardness (HV can reach 1200-1400) and corrosion resistance

[0053] In step SS02, the temperature in the first stage of three-stage pulse nitriding is 520 °C, the nitriding time is 2 h, the temperature in the second stage is 580 °C, the nitriding time is 1.5 h, the temperature in the third stage is 500 °C, and the nitriding time is 3 h;

[0054] The specific design of the three-stage pulse temperature gradient is as follows:

[0055] The first stage (520 °C × 2 h): In the medium-temperature stage, γ'-Fe4N formation is dominant. Rare earth elements are enriched on the surface, forming nano-scale CeN / LaN particles as nucleation sites, laying the foundation for a high-hardness base layer (thickness about 10-15 μm).

[0056] The second stage (580 °C × 1.5 h): Heating to above the austenitizing temperature accelerates the diffusion of nitrogen to the core. At the same time, rare earth elements migrate inward along the grain boundaries, forming a depth gradient transition layer (total nitrided layer reaches 0.3-0.4 mm), alleviating the stress concentration caused by the hardness mutation.

[0057] The third stage (500 °C × 3 h): During the cooling and tempering stage, the ε phase is stabilized. Rare earth elements react with the retained austenite to form LaFeO3 / Ce2O3 oxide films, sealing the micropores and improving the salt spray corrosion resistance (ASTM B117 salt spray test life > 1000 h).

[0058] Equipment: Controlled atmosphere pulse nitriding furnace (ammonia purity ≥ 99.99%), Ce-La mixed rare earth powder (Ce:La = 3:1).

[0059] Ammonia atmosphere: NH3 flow rate 1.8 L / min, mixed with 1.2 wt% Ce-La rare earth powder (200 mesh).

[0060] The temperature-time parameters are as follows:

[0061] The first stage: 520 °C × 2 h, furnace pressure 0.15 MPa;

[0062] The second stage: 580 °C × 1.5 h, furnace pressure 0.08 MPa (periodic pulse: switch between 0.12 MPa / 0.05 MPa every 10 min);

[0063] The third stage: 500 °C × 3 h, furnace pressure 0.20 MPa.

[0064] The performance test results are as follows:

[0065] Hardness gradient (HV0.3):

[0066] Depth (μm) 0 (surface) 50 100 200 300 Hardness value 1320 980 750 620 450

[0067] Through the depth segregation of Ce-La, the cross-scale performance matching of "super-hard surface - strong and tough core" is achieved; the three-stage variable-temperature coupled pulsed ammonia gas breaks through the diffusion kinetic limit of traditional isothermal nitriding, and the nitriding speed is increased by 40%; the synergistic effect of rare earth oxide film and gradient nitriding layer doubles the service life of bolts in the high-salt fog environment at sea.

[0068] SS03, magnetic field-assisted gradient quenching: Under the action of a 1.2 T transverse steady magnetic field, a liquid containing 20 wt% polyvinyl alcohol and 0.05 wt% graphene is used for gradient cooling; Water-based atomized quenching

[0069] The regulation mechanism of the transverse steady magnetic field is as follows:

[0070] Magnetostrictive effect: A 1.2 T transverse magnetic field induces anisotropic strain (ΔL / L ≈ 5×10 -6 ) in ferromagnetic materials (such as 42CrMo steel), promoting the preferential orientation of austenite lattice along the magnetic field direction and reducing the martensitic transformation resistance.

[0071] Lorentz force inhibits bubbles: During the atomization process of the quenching liquid, the Lorentz force (F = qv×B) generated by the magnetic field makes the charged droplets produce precessional motion, breaking through the steam film and increasing the heat transfer coefficient (up to 3800 W / m 2 ·K, 40% higher than traditional water quenching).

[0072] Dislocation oriented arrangement: Under the magnetic field, dislocation lines preferentially arrange along the {110} crystal plane slip system, forming a substructure parallel to the magnetic field direction and increasing the shear strength (τ_max increases by 18% - 22%).

[0073] The characteristics of graphene-enhanced quenching liquid include:

[0074] Thermal conductivity enhancement: 0.05 wt% graphene increases the thermal conductivity of the quenching liquid from 0.6 W / m·K to 1.8 W / m·K (a 200% increase), and the graphene sheets are oriented under the magnetic field (XRD shows that the orientation degree of the (002) plane > 85%), forming a fast heat conduction channel.

[0075] Wettability optimization: Graphene adsorbs on the surface of steel parts, the contact angle decreases from 78° to 32°, breaking through the Leidenfrost effect critical temperature (rising from 280°C to 450°C), and realizing the rapid transition from stable film boiling to nucleate boiling.

[0076] Stress buffering: Polyvinyl alcohol (20wt%) and graphene form a three-dimensional network structure, inhibiting the sudden change in the viscosity of the quenching liquid (η = 12mPa·s at 25°C, η = 3.2mPa·s at 300°C), and reducing the concentration of thermal stress.

[0077] The dynamic control of gradient cooling includes:

[0078] Magnetic field-cooling coupling: Through a magnetic field strength gradient of 0.5T → 1.2T (increasing by 0.1T every 30s), combined with the increase in the spraying speed of the quenching liquid from 2m / s to 5m / s, a cooling rate gradient from the surface to the core is achieved (surface: 220°C / s, core: 45°C / s).

[0079] Phase transformation timing regulation: Lath martensite is preferentially formed on the surface (lath width 50 - 80nm), and 10% - 15% retained austenite remains in the core, obtaining a "hard surface and tough core" structure (surface hardness HRC58 - 60, core impact work AKU = 75J).

[0080] The equipment includes: a transverse magnetic field quenching furnace (magnetic field strength adjustable from 0 to 2T), and a graphene-modified atomizing quenching system.

[0081] Magnetic field program:

[0082] Initial stage (0 - 30s): 0.5T steady magnetic field;

[0083] Main quenching stage (30 - 90s): Linearly increase to 1.2T;

[0084] Final cooling stage (90 - 120s): Maintain 1.2T.

[0085] Quenching liquid parameters:

[0086] Polyvinyl alcohol concentration: 20wt% (molecular weight 130,000);

[0087] Graphene content: 0.05wt% (flake diameter 5 - 10μm, number of layers < 5);

[0088] Atomizing pressure: 0.4 → 0.8MPa gradient boost.

[0089] It should be noted that the synergistic effect of the 1.2T transverse magnetic field and the graphene quenching liquid increases the heat transfer efficiency to 2.3 times that of traditional oil quenching, while avoiding the high cracking risk of water quenching, and improving the fatigue life.

[0090] Suitable for mass production of bolts for wind power spindles. Under extreme operating conditions of the wind turbine (alternating load ±250 kN, frequency 0.5 Hz), the service life is extended from 8 years to 15 years, and no intermediate maintenance or replacement is required.

[0091] SS04, cryogenic composite tempering with pulsed current: First, perform liquid nitrogen cryogenic treatment at -196 °C for 2 h, and then apply a pulsed current of 1000 A / cm 2 at 10 kHz during tempering at 450 °C for 4 h;

[0092] Equipment: Liquid nitrogen cryogenic box (-196 °C ± 2 °C), high-frequency pulsed tempering furnace (maximum current density 1500 A / cm 2 ).

[0093] Cryogenic treatment:

[0094] Temperature: -196 °C;

[0095] Time: 2 h (including 30 min stepwise cooling: 25 °C → -80 °C → -140 °C → -196 °C).

[0096] First stage: From 25 °C to -80 °C, cooling rate 3 °C / min, hold for 15 min;

[0097] Second stage: From -80 °C to -140 °C, cooling rate 2 °C / min, hold for 10 min;

[0098] Third stage: From -140 °C to -196 °C, cooling rate 1 °C / min, hold for 5 min.

[0099] Through three-stage gradient cooling (total time 30 min), microcracks caused by rapid cooling are inhibited (crack density reduced from 15 cracks / cm in the traditional process to ≤2 cracks / cm 2 ). 2

[0100] Pulsed tempering:

[0101] Temperature: 450 °C (furnace temperature uniformity ±5 °C);

[0102] Current parameters: 1000 A / cm 2 , 10 kHz square wave pulse (pulse width 50 μs, interval 450 μs);

[0103] Time: 4 h (divided into 2 cycles, each cycle 2 h with a 30 min air cooling interval).

[0104] Through the space-time coordination of cryogenic treatment and pulsed current, the strength and toughness of the wind power bolt are improved, enabling the wind power bolt to have a longer service life in extreme marine environments.

[0105] The heat treatment process for high-strength bolts of wind turbine blades according to the present invention further includes the following steps:

[0106] SS05. Real-time process control: Dynamically adjust the magnetic field strength and cooling rate in step SS03 through a machine learning model to control the surface residual stress fluctuation within the range of ±50 MPa;

[0107] By dynamically adjusting the magnetic field strength and cooling rate through a machine learning model, the problem of uneven residual stress distribution caused by fixed parameters in traditional heat treatment processes is solved. In the specific work process, the system collects data on temperature gradient, magnetic field strength, and coolant flow rate in the quenching stage in real time. Combining with the material properties of bolt 43, the optimal parameter combination is predicted through a trained neural network to strictly control the surface residual stress fluctuation within the range of ±50 MPa. Compared with the prior art, this solution significantly improves the fatigue life and stress corrosion resistance of bolt 43, especially suitable for the high-frequency alternating load conditions of wind turbine blades, avoiding early failure caused by stress concentration, reducing the manual debugging cost at the same time, and realizing intelligent and high-precision process control.

[0108] The inventor also found that in the heat treatment process of high-strength bolts for wind turbine blades, the surface treatment uniformity is poor; in the traditional mechanical impact treatment method, due to the lack of a dynamic vibration control mechanism, the distribution of nano-particles is uneven, resulting in poor consistency of the nano-crystalline layer thickness and grain size, affecting the shear resistance and fatigue life of the bolt thread root.

[0109] As Figure 3 - Figure 11 shown, the present invention also designs a bolt heat treatment device 1 for realizing impact treatment on the bolt thread root.

[0110] The bolt heat treatment device 1 according to the present invention includes a fixing frame 2. A rotating station frame 3 that can rotate periodically by 90° is rotatably installed on the fixing frame 2. Four bolt fixing components are provided on the rotating station frame 3. A vibrating bracket 4 that can move up and down is drivingly connected to the bolt fixing components. A driving bottom shaft 5 is rotatably installed on the inner wall of the vibrating bracket 4. A magnetic attraction shaft 6 is rotatably installed on the inner wall of the driving bottom shaft 5. A magnetic attraction groove 7 for magnetic attraction positioning of bolt 43 is provided at the top of the magnetic attraction shaft 6. The driving bottom shaft 5 and the magnetic attraction shaft 6 rotate coaxially and in opposite directions;

[0111] The magnetic attraction shaft 6 is made of permanent magnetic material, and the cross-section of the magnetic attraction groove 7 is a regular hexagon.

[0112] The hexagonal structure of the regular hexagonal magnetic suction groove 7 and the head of the bolt 43 are precisely matched to achieve zero-gap positioning. In the working process, the magnetic suction shaft 6 made of permanent magnet material quickly fixes the bolt 43 through magnetic force, and cooperates with the regular hexagonal cross-section of the hollow groove to prevent the circumferential sliding of the bolt 43 during the processing. Compared with the circular or square groove, the clamping efficiency of this design is increased by 60%, and it is adapted to the specifications of the standard wind power bolt 43, avoiding the deviation of the nano-layer thickness at the root of the thread due to loose clamping, and ensuring the process stability in mass production;

[0113] The fixed frame 2 is provided with loading and unloading stations, a nano-processing station, a negative pressure cleaning station and a cleaning station in a clockwise direction. A processing frame 8 is installed on the fixed frame 2 in a liftable manner. Nozzle mechanisms are provided on the processing frame 8 at positions corresponding to the nano-processing station, the negative pressure cleaning station and the cleaning station. The bolt 43 is subjected to nano-impact treatment at the nano-processing station, the nano-particles are suctioned away under negative pressure at the negative pressure cleaning station, and the bolt 43 is cleaned and low-temperature stress is eliminated at the cleaning station.

[0114] The servo motor 9 is also provided with an incomplete gear 10 installed at the bottom of the fixed frame 2. The output shaft end of the servo motor 9 is provided with an incomplete gear 10. A transmission tooth surface is fixedly provided on the incomplete gear 10. An intermittent shaft 11 is provided on the bottom surface of the rotating work station frame 3. An intermittent gear 12 meshing with the transmission tooth surface is fixedly provided on the intermittent shaft 11. The meshing area of ​​the transmission tooth surface corresponds to a central angle of 90°. The radius of the incomplete gear 10 is the same as the radius of the intermittent gear 12. A hollow gear shaft 13 is rotatably provided on the intermittent shaft 11. An active gear ring 14 is installed on the hollow gear shaft 13. The servo motor A belt is connected to the output shaft end of 9 and the hollow gear shaft 13, a bottom cylinder 15 is fixedly installed on the fixed frame 2, a shaft frame 16 is fixedly installed on the bottom cylinder 15, and a guide shaft 17 is rotatably installed on the shaft frame 16 and corresponding to the positions of the nano-processing station, the negative pressure cleaning station and the cleaning station. The guide shaft 17 is respectively equipped with a transmission bevel gear and a passive gear 18 connected to the active gear ring 14, the bolt fixing component is adapted to the transmission bevel gear, and a vertically arranged screw lifting module 19 is installed on the fixed frame 2, and the screw lifting module 19 is connected to the processing frame 8 in transmission.

[0115] When the heat treatment equipment for high-strength bolts 43 of wind turbine blades is in operation, the servo motor 9 starts and drives the hollow gear shaft 13 to rotate through a belt. The driving gear ring 14 on the hollow gear shaft 13 rotates accordingly. The driving gear ring 14 cooperates with the driven gear 18 to drive the guiding shaft 17 to rotate. At the same time, the incomplete gear 10 at the output shaft end of the servo motor 9 meshes with the intermittent gear 12. Since the meshing area of the transmission tooth surface corresponds to a central angle of 90°, and the radius of the incomplete gear 10 is the same as that of the intermittent gear 12, the rotary working station frame 3 realizes accurate periodic 90° rotation, ensuring seamless switching of the nano-treatment, cleaning, and washing workstations. The screw rod lifting module 19 precisely lifts and lowers the treatment frame 8. The traditional rotary working station frame 3 often causes positioning deviation due to mechanical clearance, affecting the coherence and accuracy of the heat treatment process. This design solves this problem. Cooperating with the screw rod lifting module 19, it significantly improves the collaborative efficiency of multiple processes, reduces the error during equipment operation, improves the overall efficiency and quality of the heat treatment of high-strength bolts 43 of wind turbine blades, and ensures the stability and reliability of production.

[0116] The bolt fixing component includes a large circular shaft 20 and a hollow shaft 21 rotatably connected to the rotary working station frame 3. One end of the large circular shaft 20 is fixedly installed with a driven bevel gear meshing with the transmission bevel gear. A first bevel gear is installed on both the hollow shaft 21 and the large circular shaft 20, and the two first bevel gears mesh with each other. A hollow groove with both ends open and slidably connected to the magnetic attraction shaft 6 is fixedly opened inside the hollow shaft 21. The cross-sections of the magnetic attraction shaft 6 and the hollow groove are both regular hexagons. An eccentric wheel 22 is installed on the large circular shaft 20. A follower wheel 23 is rotatably installed on the vibration support 4. The follower wheel 23 rolls on the contour surface of the eccentric wheel 22. The vibration support 4 is slidably connected to the rotary working station frame 3. A vibration spring 24 limited by the rotary working station frame 3 is installed on the top surface of the vibration support 4.

[0117] When performing surface mechanical nanocrystallization pretreatment on the high-strength bolt 43 of a wind turbine blade, the large circular shaft 20 rotates driven by external power. The passive bevel gear at one end thereof meshes with the transmission bevel gear, thereby driving the large circular shaft 20 to rotate. The eccentric wheel 22 on the large circular shaft 20 rotates accordingly. The eccentric wheel 22 pushes the follower wheel 23, causing the vibration support 4 to slide along the rotating station frame 3. The vibration spring 24 plays an elastic resetting role, realizing the high-frequency and small-amplitude vibration of the bolt 43 during nano-impact treatment. The first bevel gears on the hollow shaft 21 and the large circular shaft 20 mesh with each other, and the hollow groove inside the hollow shaft 21 is slidably connected to the magnetic attraction shaft 6. The cross-sections of the magnetic attraction shaft 6 and the hollow groove are both regular hexagons, enhancing the clamping stability of the bolt 43. In traditional static impact, the particle distribution is uneven, affecting the uniformity of the nanocrystalline layer. This structure enables the root of the bolt 43 thread to be in full contact with the tungsten carbide cobalt particles through the rolling contact between the eccentric wheel 22 and the follower wheel 23 and the elastic resetting of the vibration spring 24. The nanocrystalline layer is formed more uniformly, and the grain refinement efficiency is increased by 40%. At the same time, displacement deviation during the treatment process is avoided, ensuring that the anti-shear performance of the wind turbine blade bolt 43 meets the standard under extreme wind loads, and improving the mechanical properties and service life of the bolt 43.

[0118] The bolt fixing component further includes a small circular shaft 25 rotatably installed on the vibration support 4. A conical tooth is installed on the small circular shaft 25. Second bevel gears are installed on both the magnetic attraction shaft 6 and the transmission bottom shaft 5. Both second bevel gears are in transmission connection with the conical tooth, and the two second bevel gears are respectively arranged on both sides of the conical tooth.

[0119] Through the meshing of the conical tooth on the small circular shaft 25 with the second bevel gears on the magnetic attraction shaft 6 and the transmission bottom shaft 5, the coaxial reverse rotation of the transmission bottom shaft 5 and the magnetic attraction shaft 6 is realized. During the working process, the magnetic attraction shaft 6 drives the bolt 43 to rotate, and at the same time, the transmission bottom shaft 5 reversely drives the rotary protection cylinder 28 in the nozzle mechanism to rotate. When the rotary protection cylinder 28 rotates, the nozzle 29 always accurately covers the root of the thread at an angle of 45°. Through the coaxial reverse rotation setting of the nozzle 29 and the bolt 43 during nano-treatment, the coverage uniformity of the nano-particles at the root of the bolt 43 thread can be effectively improved. Through the setting of the protection cylinder, the overflow rate of the nano-particles can be effectively reduced, thereby improving the safety during nano-treatment operation. Through the vibration structure setting of the protection cylinder and the bolt 43 during treatment, the residual rate of the non-consolidated nano-particles on the inner wall of the root of the bolt 43 thread and the protection cylinder can be effectively reduced, thereby effectively improving the inner wall cleanliness of the protection cylinder.

[0120] The nozzle mechanism includes a conduit 45 and a follower seat 26. The conduit 45 is fixedly installed on the processing rack 8. Two T-shaped guide rods 27 are installed on the top surface of the follower seat 26. Both of the two T-shaped guide rods 27 are slidably connected to the conduit 45. A rotary protective cylinder 28 is rotatably installed on the inner wall of the follower seat 26. A sealing rubber ring connected to the driving bottom shaft 5 is fixedly installed at the bottom end of the rotary protective cylinder 28. A nozzle 29 is fixedly installed on the inner wall of the rotary protective cylinder 28. The nozzle 29 faces the thread root of the bolt 43 at an inclination angle of 45°. A through cavity 30 is fixedly opened at the top of the rotary protective cylinder 28. The tail end of the nozzle 29 communicates with the through cavity 30. The bottom end of the conduit 45 is rotationally communicated with the through cavity 30 through a corrugated pipe 31. A vibration following spring 32 is sleeved on the corrugated pipe 31.

[0121] During the working process, the rotary protective cylinder 28 is connected to the driving bottom shaft 5 through the sealing rubber ring. The corrugated pipe 31 compensates for the lifting displacement under the buffering of the vibration following spring 32. Finally, the rotary protective cylinder 28 undergoes driven vibration rotation following the vibration rotation of the driving bottom shaft 5. And through the setting of the sealing rubber ring, the sealing performance at the connection between the driving bottom shaft 5 and the rotary protective cylinder 28 can be effectively guaranteed.

[0122] At the top end of the conduit 45 in the nano-treatment station, a nano-material connecting pipe 33 connected to the high-pressure nano-particle feeding device is fixedly arranged. At the top end of the conduit 45 in the negative-pressure cleaning station, a negative-pressure suction pipe 34 connected to the negative-pressure suction device is fixedly arranged. At the top end of the conduit 45 in the cleaning station, a cleaning joint 35 connected to the cleaning liquid feeding device is fixedly arranged. A heating coil 36 is fixedly installed outside the rotary protective cylinder 28 in the cleaning station.

[0123] In different stations of the heat treatment of the high-strength bolt 43 of the wind turbine blade, the nozzle mechanism plays an important role. In the nano-treatment station, high-pressure nano-particles enter the conduit 45 through the nano-material connecting pipe 33, then enter the through cavity 30 at the top end of the rotary protective cylinder 28 through the corrugated pipe 31, and finally are sprayed out from the nozzle 29 facing the thread root of the bolt 43 at an inclination angle of 45° to perform impact treatment on the thread root of the bolt 43. At this time, the follower seat 26 can slide on the conduit 45 through the T-shaped guide rods 27 to adjust the distance between the nozzle 29 and the bolt 43. The rotary protective cylinder 28 can rotate to enable the nozzle 29 to better cover the thread root of the bolt 43. In the negative-pressure cleaning station, the negative-pressure suction pipe 34 is connected to the negative-pressure suction device to suck out the residual nano-particles after nano-treatment. In the cleaning station, the cleaning liquid enters through the cleaning joint 35, and the nozzle 29 sprays out the cleaning liquid to clean the bolt 43. The heating coil 36 outside the rotary protective cylinder 28 in the cleaning station can heat the cleaning liquid to improve the cleaning effect. It is difficult for the traditional nozzle mechanism to accurately process and clean the thread root of the bolt 43, and it has a single function. This nozzle mechanism is ingeniously designed, can realize different functions in different stations, improves the accuracy and efficiency of the heat treatment process, ensures the surface treatment quality of the bolt 43, and enhances the overall performance of the high-strength bolt 43 of the wind turbine blade.

[0124] When the heat treatment equipment for high-strength bolts 43 of wind turbine blades is in operation, in the nano-treatment station, the nano-material connecting pipe 33 is connected to the high-pressure nano-particle feeding device, and can stably transport tungsten carbide cobalt microparticles with a particle size of 50 - 100 μm to the nozzle 29 at a speed of 200 - 300 m / s to impact the root of the thread of the bolt 43, forming a high-quality nano-crystalline layer. In the negative-pressure cleaning station, the negative-pressure suction pipe 34 is connected to the negative-pressure suction device, and can timely and effectively suck out the nano-particles remaining after nano-treatment to avoid the influence of these particles on subsequent processes. In the cleaning station, the cleaning joint 35 is connected to the cleaning liquid feeding device to provide sufficient cleaning liquid for cleaning the bolt 43. After cleaning, the heating coil 36 outside the rotating protection cylinder 28 can perform low-temperature thermal stress relief on the treated bolt 43.

[0125] The high-pressure nano-particle feeding device can adopt the spraying system of Sulzer Metco or the powder feeding device of Praxair, which can be selected or replaced according to the actual situation, and will not be elaborated here.

[0126] It also includes a sleeve 37 rotatably sleeved on the bottom cylinder 15. A sewage suction channel 38 is fixedly opened inside the magnetic attraction shaft 6. The bottom end of the sewage suction channel 38 is connected to the sleeve 37 through a sewage discharge pipe 44. A group of sewage suction holes 39 distributed in a circumferential array and communicating with the sewage suction channel 38 are opened on the magnetic attraction shaft 6. A sewage discharge cavity 40 is fixedly opened inside the bottom cylinder 15. A sewage discharge hole 41 communicating with the sewage discharge cavity 40 is fixedly opened on the bottom cylinder 15 at the position corresponding to the cleaning station. A sewage accumulation box 42 communicating with the sewage discharge cavity 40 is fixedly installed on the fixed frame 2.

[0127] The directional collection of cleaning waste liquid is realized by the communication between the sewage suction holes 39 inside the magnetic attraction shaft 6 and the sewage discharge cavity 40 of the bottom cylinder 15.

[0128] 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 in the protection scope of the present invention.

Claims

1. A heat treatment process for high-strength bolts of wind turbine blades, characterized in that, It includes the following steps: Preset the heat treatment state of the bolt, and perform impact treatment on the root of the bolt thread through a bolt heat treatment device to form a nanocrystalline layer; Perform three-stage pulse nitriding in an ammonia atmosphere containing Ce-La mixed rare earths; Under the action of a transverse steady magnetic field, use an aqueous atomized quenching liquid containing polyvinyl alcohol and graphene for gradient cooling; Perform liquid nitrogen cryogenic treatment, and then apply a pulsed current during the tempering process.

2. The heat treatment process of a high-strength bolt for a wind turbine blade according to claim 1, wherein, For the first stage of the three-stage pulse nitriding, the temperature is 520 °C and the nitriding time is 2 h; for the second stage, the temperature is 580 °C and the nitriding time is 1.5 h; for the third stage, the temperature is 500 °C and the nitriding time is 3 h.

3. A heat treatment process for high-strength bolts of a wind turbine blade according to claim 1, characterized in that, The intensity of the transverse steady magnetic field is regulated in stages, including the initial stage, the main quenching stage, and the final cooling stage; the atomization pressure of the quenching liquid is regulated synchronously with each stage of the intensity of the transverse steady magnetic field.

4. A heat treatment process for high-strength bolts of a wind turbine blade according to claim 1, characterized in that, The liquid nitrogen cryogenic treatment includes gradient cooling in the first stage, the second stage, and the third stage; The first stage: from 25 °C to -80 °C, the cooling rate is 3 °C / min, and it is maintained for 15 min; The second stage: from -80 °C to -140 °C, the cooling rate is 2 °C / min, and it is maintained for 10 min; The third stage: from -140 °C to -196 °C, the cooling rate is 1 °C / min, and it is maintained for 5 min.

5. A heat treatment process for high-strength bolts of a wind turbine blade according to any one of claims 1-4, characterized in that, The bolt heat treatment device includes a fixing frame (2), on which a rotating workbench frame (3) that can rotate periodically by 90° is rotatably installed. There are four bolt fixing components on the rotating workbench frame (3). A vibrating support (4) that can move up and down is drivingly connected to the bolt fixing components. A driving bottom shaft (5) is rotatably installed on the inner wall of the vibrating support (4). A magnetic attraction shaft (6) is rotatably installed on the inner wall of the driving bottom shaft (5). A magnetic attraction groove (7) for magnetic attraction positioning of the bolt (43) is opened at the top of the magnetic attraction shaft (6). The driving bottom shaft (5) and the magnetic attraction shaft (6) rotate coaxially in opposite directions. A loading and unloading station, a nano-treatment station, a negative pressure cleaning station, and a cleaning station are sequentially arranged on the fixing frame (2) in the clockwise direction. A treatment frame (8) is liftably installed on the fixing frame (2). Nozzle mechanisms are arranged on the treatment frame (8) corresponding to the positions of the nano-treatment station, the negative pressure cleaning station, and the cleaning station.

6. A heat treatment process for high-strength bolts of a wind turbine blade according to claim 5, characterized in that, It further includes a servo motor (9) installed at the bottom of the fixed frame (2). An output shaft end of the servo motor (9) is provided with an incomplete gear (10). A transmission tooth surface is fixedly arranged on the incomplete gear (10). An intermittent shaft (11) is installed on the bottom surface of the rotary station frame (3). An intermittent gear (12) meshing with the transmission tooth surface is fixedly installed on the intermittent shaft (11). A central angle corresponding to a meshing area of the transmission tooth surface is 90°. A radius of the incomplete gear (10) is the same as a radius of the intermittent gear (12). A hollow tooth shaft (13) is rotatably sleeved on the intermittent shaft (11). A driving gear ring (14) is installed on the hollow tooth shaft (13). A belt is in transmission connection between an output shaft end of the servo motor (9) and the hollow tooth shaft (13). A bottom cylinder (15) is fixedly installed on the fixed frame (2). A shaft frame (16) is fixedly installed on the bottom cylinder (15). A guiding shaft (17) is rotatably installed on the shaft frame (16) corresponding to positions of a nano-treatment station, a negative-pressure cleaning station, and a cleaning station. A transmission bevel gear and a driven gear (18) in transmission connection with the driving gear ring (14) are respectively installed on the guiding shaft (17). The bolt fixing component is adaptively connected with the transmission bevel gear. A screw rod lifting module (19) arranged vertically is installed on the fixed frame (2). The screw rod lifting module (19) is in transmission connection with the treatment frame (8).

7. A heat treatment process for high-strength bolts of a wind turbine blade according to claim 6, characterized in that, The bolt fixing component includes a large circular shaft (20) and a hollow shaft (21) rotatably connected to the rotary station frame (3). A driven bevel gear meshing with the transmission bevel gear is fixedly installed at one end of the large circular shaft (20). A first bevel gear is installed on each of the hollow shaft (21) and the large circular shaft (20). The two first bevel gears mesh with each other. A hollow groove with two open ends and slidably connected to the magnetic attraction shaft (6) is fixedly formed inside the hollow shaft (21). Cross sections of the magnetic attraction shaft (6) and the hollow groove are both regular hexagons. An eccentric wheel (22) is installed on the large circular shaft (20). A follower wheel (23) is rotatably installed on the vibration support (4). The follower wheel (23) is in rolling contact with a contour surface of the eccentric wheel (22). The vibration support (4) is slidably connected to the rotary station frame (3). A vibration spring (24) limited by the rotary station frame (3) is installed on a top surface of the vibration support (4).

8. A heat treatment process for high-strength bolts of a wind turbine blade according to claim 7, characterized in that, The bolt fixing component further includes a small circular shaft (25) rotatably installed on the vibration support (4). A conical tooth is installed on the small circular shaft (25). A second bevel gear is installed on each of the magnetic attraction shaft (6) and the transmission bottom shaft (5). The two second bevel gears are both in transmission connection with the conical tooth. The two second bevel gears are respectively arranged on two sides of the conical tooth.

9. A heat treatment process for high-strength bolts of a wind turbine blade according to claim 6, characterized in that, The nozzle mechanism includes a conduit (45) and a follower seat (26). The conduit (45) is fixedly installed on the processing frame (8). Two T-shaped guide rods (27) are installed on the top surface of the follower seat (26). Both of the two T-shaped guide rods (27) are slidably connected to the conduit (45). A rotary protection cylinder (28) is rotatably installed on the inner wall of the follower seat (26). A sealing rubber ring connected to the driving bottom shaft (5) is fixedly installed at the bottom end of the rotary protection cylinder (28). A spray head (29) is fixedly installed on the inner wall of the rotary protection cylinder (28). The spray head (29) faces the thread root of the bolt (43) at an inclination angle of 45°. A through cavity (30) is fixedly opened at the top of the rotary protection cylinder (28). The tail end of the spray head (29) is communicated with the through cavity (30). The bottom end of the conduit (45) is rotatably communicated with the through cavity (30) through a corrugated pipe (31). A vibration-following spring (32) is sleeved on the corrugated pipe (31). At the top end of the conduit (45) in the nano-treatment station, a nano-material connecting pipe (33) communicated with the high-pressure nano-particle feeding device is fixedly arranged. At the top end of the conduit (45) in the negative-pressure cleaning station, a negative-pressure suction pipe (34) communicated with the negative-pressure suction device is fixedly arranged. At the top end of the conduit (45) in the cleaning station, a cleaning joint (35) communicated with the cleaning liquid feeding device is fixedly arranged. A heating coil (36) is fixedly installed on the outside of the rotary protection cylinder (28) in the cleaning station.

10. A heat treatment process for high-strength bolts of a wind turbine blade according to claim 7, characterized in that, It further includes a sleeve (37) rotatably sleeved on the bottom cylinder (15). A sewage suction channel (38) is fixedly opened inside the magnetic attraction shaft (6). The bottom end of the sewage suction channel (38) is communicated with the sleeve (37) through a sewage discharge pipe (44). A group of sewage suction holes (39) distributed in a circumferential array and communicated with the sewage suction channel (38) are opened on the magnetic attraction shaft (6). A sewage discharge cavity (40) is fixedly opened inside the bottom cylinder (15). A sewage discharge hole (41) communicated with the sewage discharge cavity (40) is fixedly opened on the bottom cylinder (15) at a position corresponding to the cleaning station. A sewage accumulation box (42) communicated with the sewage discharge cavity (40) is fixedly installed on the fixing frame (2).

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