A method for induction quenching of an inner ring of a wind turbine

Abstract

The present application relates to the technical field of metal heat treatment, and discloses a wind power inner gear ring induction quenching method, which comprises the following steps: preparing an epoxyethane and epoxypropane random copolymer aqueous solution as a main quenching liquid, and preparing a sodium xylene sulfonate aqueous solution as an auxiliary liquid; quenching along the axial direction of the workpiece from top to bottom, spraying only the main quenching liquid in the initial interval, and then injecting the auxiliary liquid into the main quenching liquid in an incremental manner for mixed spraying. The mixed waste liquid is collected and kept at a set separation temperature for stratification, and the crude polyether-rich phase and the auxiliary agent-containing water phase mother liquor are collected respectively; the crude polyether-rich phase is mixed with heated deionized water and subjected to constant-temperature centrifugal separation, and the pure polyether-rich phase is cooled and reused. The auxiliary agent is injected in an incremental manner to raise the dynamic cloud point, the axial heat accumulation lag is compensated, the workpiece hardness range and the deformation amount are reduced, the polyether and the auxiliary agent salt are deeply separated through high-temperature stratification and isothermal centrifugal washing, and the long-term stability of the rheological and thermodynamic parameters of the closed-loop circulation system is maintained.

Description

Technical Field

[0001] This invention relates to the field of metal heat treatment technology, specifically to an induction hardening method for internal gear rings in wind turbines. Background Technology

[0002] The internal gear ring of a wind turbine is a core transmission component in a wind turbine generator set, and it typically requires induction scanning hardening to achieve high surface hardness and wear resistance. In conventional vertical induction scanning hardening processes, polymer aqueous solutions (such as polyether polymers) with reverse solubility are commonly used as the quenching fluid. When the quenching fluid comes into contact with the high-temperature workpiece surface, the fluid temperature rises above its natural cloud point, and polymer macromolecules precipitate and adhere to the workpiece surface, forming a polymer insulating film. The cooling rate of the workpiece is controlled by the thickness of this insulating film and the timing of its precipitation.

[0003] However, in the top-down vertical induction scanning quenching process, the sprayed quenching fluid inevitably flows downwards along the workpiece surface due to gravity. This continuous downward fluid flow carries the high-temperature waste liquid and heat from the upper part into the middle and lower regions of the workpiece, causing severe heat accumulation lag. The increased fluid background temperature in the middle and lower regions causes the polymer polymer to reach its phase transition turbidity point prematurely, precipitating a thick insulating film on the tooth surface and reducing the convective heat transfer coefficient in this region. This thermal imbalance results in a highly uneven cooling rate along the axial direction of the workpiece. The huge temperature difference between hot and cold induces a complex martensitic phase transformation stress and thermal stress alternation network inside the large thin-walled annular part, ultimately causing severe deviations in surface hardness in the upper, middle, and lower parts of the workpiece and triggering macroscopic mechanical deformation exceeding the safety threshold, significantly increasing the machining allowance and scrap rate in subsequent machining.

[0004] To regulate the cooling rate, existing technologies sometimes premix salt additives into the polymer base to alter the overall cloud point of the quenching fluid. However, a quenching fluid with a constant global concentration still cannot offset the axial thermal resistance imbalance caused by gravity. Furthermore, in closed-loop recycling systems for quenching fluids, the deep separation of high-molecular-weight polyethers from polar small-molecule salt additives presents a physicochemical challenge. Conventional natural sedimentation or low-temperature separation processes cannot disrupt the high-temperature hydrated hydrogen bond network of polymer macromolecules, causing some incompletely dehydrated and shrunken polymers to remain in the aqueous phase through the phase interface. This accumulation and entanglement in subsequent dehydration and concentration stages leads to an exponential increase in the system's hydrodynamic viscosity, ultimately causing blockage and failure of fluid transport equipment. Simultaneously, residual salts physically entrained within the crude polyether phase, if not eluted, will accumulate with the polymer reflux in the main quenching fluid system, causing an irreversible unidirectional shift in the background cloud point of the main quenching fluid. This long-term cross-contamination disrupts the baseline stability of the thermodynamic and rheological parameters of the quenching system, making it impossible to maintain the quenching process based on precise cloud point control in long-term continuous production across multiple batches. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an induction hardening method for wind turbine internal gear rings, which solves the problems of uneven axial cooling rate, surface hardness deviation, and macroscopic mechanical deformation caused by the downward flow of quenching fluid due to gravity in the lower part of the workpiece during vertical induction scanning hardening of wind turbine internal gear rings.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for induction hardening of internal gear rings in wind turbines, comprising the following steps: The random copolymer of ethylene oxide and propylene oxide is dissolved in water to prepare an aqueous solution with a mass fraction of 10.0%-15.0%, which is used as the main quenching fluid. Sodium xylenesulfonate is dissolved in water to prepare an aqueous solution with a mass fraction of 20.0%-30.0%, which is used as the stock solution for the auxiliary agent. The sensor and sprayer are used to perform scanning quenching from top to bottom along the axial direction of the wind turbine's internal gear ring. Within the range of 0%-L1 of the total axial length of the wind turbine internal gear ring, the sprayer only sprays the main quenching liquid, where L1 is 15%-30%; When the sensor scans to the L1 position, the auxiliary agent stock solution is injected into the main quenching liquid in an incremental manner to form a mixed fluid, which is then sprayed out by the sprayer. When the scan reaches position L2, which is the total axial length of the wind turbine internal gear ring, the instantaneous mass flow rate of sodium xylenesulfonate in the mixed fluid accounts for 2.0%-5.0% of the total mass flow rate of the mixed fluid, of which L2 is 90%-100%. Collect the mixed waste liquid flowing down from the surface of the wind turbine inner gear ring, and perform heat preservation and stratification at a set separation temperature to separately extract the crude polyether-rich phase and the aqueous mother liquor containing additives. Heated deionized water is mixed with the extracted crude polyether-rich phase and centrifuged to obtain a pure polyether-rich phase; the pure polyether-rich phase is cooled to 25°C and then returned to be used as the main quenching fluid.

[0007] As a further limitation of the technical solution of the present invention, the separation temperature is set to 90℃-95℃; the temperature of the deionized water mixed with the crude polyether is 90℃-95℃; and the centrifugal separation is carried out under constant temperature conditions of 90℃-95℃.

[0008] As a further limitation of the technical solution of the present invention, in the random copolymer of ethylene oxide and propylene oxide, the mass ratio of ethylene oxide to propylene oxide is 25:75-35:65. The natural cloud point of the main quenching fluid is 70℃-75℃; when scanning to the L2 position, the dynamic cloud point of the mixed fluid sprayed by the sprayer is 82℃-88℃.

[0009] As a further limitation of the technical solution of the present invention, the axial feed speed of the sensor and the sprayer is set to 1.0 mm / s-3.5 mm / s; the spray pressure of the main quenching fluid is maintained at 0.15 MPa-0.30 MPa.

[0010] As a further limitation of the technical solution of the present invention, the auxiliary agent stock solution is injected into the inlet end of the tubular static mixer through a diaphragm variable frequency metering pump, and mixed with the main quenching liquid delivered by the main liquid supply pump to form a mixed fluid. The length-to-diameter ratio of the tubular static mixer is 15-25.

[0011] As a further limitation of the technical solution of the present invention, the heat preservation and stratification are carried out in a continuous clarifier separator, and the average residence time of the mixed waste liquid in the continuous clarifier separator is controlled at 30 min-60 min; the volume ratio of deionized water to the crude polyether-rich phase is set at 1:1-3:1, and the centrifugal separation is carried out in a liquid-liquid centrifugal extractor with a rotation speed set at 1500 rpm-3000 rpm. The centrifugal separation simultaneously separates the washed aqueous phase; the collected aqueous mother liquor containing the auxiliary agent is combined with the washed aqueous phase and introduced into a low-temperature vacuum flash evaporator for reduced pressure concentration and dehydration.

[0012] As a further limitation of the technical solution of the present invention, the absolute operating pressure of the low-temperature vacuum flash evaporator is set to 5.0 kPa-20.0 kPa, and the jacket heating temperature is set to 60℃-80℃; the dehydration is stopped when the mass fraction of sodium xylenesulfonate in the bottom liquid is 20.0%-30.0%, and the concentrated bottom liquid is returned for use as the auxiliary agent stock solution. The pure water produced by the dehydration is condensed and heated to 90℃-95℃ and returned for use as the deionized water mixed with the crude polyether rich phase; the sprayer is a ring sprayer with a downward tilt angle of 30°-45°.

[0013] The induction hardening method for internal gear rings in wind turbines provided by this invention has the following working mechanism and technical effects: First, a mechanism of dynamically gradient-injecting additive stock solution to regulate the local dynamic cloud point is adopted to offset and compensate for the axial heat accumulation delay caused by the downward flow of the quenching fluid. In the initial stage at the top of the workpiece (0%-L1 interval), only pure polyether aqueous solution is sprayed, utilizing its natural cloud point of 70℃-75℃ to promote the rapid precipitation of polymer on the tooth surface and form a complete insulating film, inhibiting the top-end cooling cracking. In the stage where the sensor moves down to the middle and lower part (L1-L2 interval), sodium xylenesulfonate stock solution is continuously and incrementally injected. The hydrophobic groups in the sodium xylenesulfonate molecular structure associate with the polyether molecular chain, and its hydrophilic sulfonic acid groups enhance the hydration capacity of the polyether macromolecules at high temperatures, pushing the macroscopic dynamic cloud point of the mixed fluid from top to bottom to 82℃-88℃. The rise in dynamic cloud point delays the precipitation time of polymer macromolecules on the high-temperature tooth surface and forcibly thins the physical thickness of the insulating film, causing the convective heat transfer coefficient at the contact interface to increase nonlinearly along the axial direction. The aforementioned method of increasing cooling capacity by intervening in the critical point of physicochemical phase transformation balances the heating temperature gradient in the lower part of the gear ring, enabling the entire workpiece to achieve an equivalent cooling rate across all axial sections. This mechanism controls the hardness difference between the upper, middle, and lower parts of the gear ring after quenching to within 1.5 HRC, while simultaneously eliminating the thermal stress alternation network induced by the non-uniform martensitic phase transformation, and controlling the maximum ellipticity deformation to below 1.30 mm.

[0014] Secondly, a dual isothermal control mechanism of separation temperature and extraction / washing temperature is employed to prevent cross-permeation and enrichment of the polymeric main agent and polar low-molecular-weight salt auxiliaries in the closed-loop circulation system. The separation temperature of the continuous clarification separator is set at 90℃-95℃, a temperature range strictly higher than the highest dynamic turbidity point of the mixed fluid. The high temperature, far exceeding the turbidity point, breaks the hydrogen bond network of the polyether macromolecules, forcing the polyether molecular chains to contract and coil violently and forcibly expel bound water molecules. This transforms the polymer from a hydrated and stretched state into a dense condensed phase with a density greater than that of the aqueous phase. The density difference and interfacial tension are used to achieve physical separation of the two phases of the mixed waste liquid, reducing the polyether loss rate in the aqueous mother liquor to below 0.42%, preventing the accumulation of polymeric components at the vacuum concentration and dehydration end and the resulting surge in the dynamic viscosity of the auxiliary raw solution. Simultaneously, isothermal deionized water heated to 90℃-95℃ is used for centrifugal extraction of the crude polyether-rich phase. At this thermodynamic temperature, deionized water loses its ability to dissolve polyether macromolecules, maintaining the hydrophobic droplet state of the polyether; while sodium xylenesulfonate, as a polar small molecule salt, maintains high solubility in high-temperature pure water. This isothermal extraction and washing step relies on the concentration difference to remove the small molecule salts physically entrained in the crude polyether phase into the washing aqueous phase, reducing the residual sodium xylenesulfonate in the pure polyether-rich phase to 0.06%. The combination of the phase change separation and high-temperature elution mechanism maintains the constancy of the natural cloud point baseline of the main quenching liquid and the rheological parameters of the auxiliary agent stock solution after multiple batches of system operation.

[0015] This invention provides a method for induction hardening of internal gear rings in wind turbines. It has the following beneficial effects: 1. This invention involves spraying only the main quenching fluid in the initial scanning zone of the induction hardening of the wind turbine internal gear ring, and then injecting the auxiliary agent stock solution in an incremental manner in the subsequent middle and lower scanning zones. This causes the dynamic cloud point of the mixed fluid sprayed by the sprayer to gradually increase with the quenching process. By utilizing the increase in the dynamic cloud point, the precipitation time of the polymer in the quenching fluid on the workpiece surface is delayed, and the thickness of the insulating film is forcibly thinned. This compensates for the lag in heat accumulation in the middle and lower parts caused by the downward flow and accumulation of the quenching fluid due to gravity, achieving an axial isothermal phase transformation on the workpiece surface. This effectively reduces the hardness difference at various axial positions of the gear ring after quenching and controls the amount of macroscopic mechanical deformation of the workpiece.

[0016] 2. This invention sets the insulation and stratification temperature of the continuous clarifier to a thermodynamic range higher than the highest dynamic turbidity point of the mixed waste liquid, forcing the polyether molecular chains to undergo a thermodynamic phase transition. This causes them to contract and coil violently, expelling bound water molecules and forming a dense condensed phase with a density greater than water. This mechanism achieves deep physical separation between the high-molecular-weight polyether-rich phase and the aqueous mother liquor containing additives, reducing the polyether loss rate in the aqueous mother liquor. It also prevents insufficiently dehydrated and shrunken polymers from penetrating the phase interface into the aqueous phase and accumulating in subsequent vacuum dehydration and concentration processes, thus maintaining the dynamic viscosity stability of the additive stock solution during the closed-loop circulation process.

[0017] 3. This invention employs heated deionized water mixed with a crude polyether-rich phase and centrifugally extracted and separated the phase under constant high-temperature conditions. Utilizing the thermodynamic property that deionized water cannot dissolve the large polyether molecules within this high-temperature, constant-temperature range, the hydrophobic droplet state of the polyether is maintained. Simultaneously, relying on the high solubility of polar small-molecule salts in high-temperature pure water, auxiliary salts physically entrained within the polyether-rich phase are reverse-extracted and removed into the washing aqueous phase. This reduces the residual rate of auxiliary agents in the polyether-rich phase, prevents the continuous accumulation of residual salts in the main quenching fluid circuit, and ensures that the baseline natural cloud point of the main quenching fluid remains constant during multiple batches of continuous operation. Attached Figure Description

[0018] Figure 1 This is a graph showing the change of the absolute value of the macroscopic dynamic turbidity point with mass fraction in an embodiment of the present invention. Figure 2 This is a graph showing the change in the relative basic turbidity point in an embodiment of the present invention. Figure 3 This is a line graph showing the change in polyether loss rate with separation temperature in an embodiment of the present invention. Figure 4 This is a bar chart showing the residual rate of sodium xylenesulfonate under different washing conditions in the embodiments of the present invention; Figure 5 This is a line graph showing the distribution of surface hardness at different axial positions in an embodiment of the present invention. Figure 6 This is a comparative bar chart showing the maximum macroscopic ellipticity deformation of the gear ring under various process schemes in the embodiments of the present invention. Figure 7 This is a line graph showing the variation of the natural cloud point temperature of the main quenching fluid under different cycle batches in this embodiment of the invention; Figure 8 This is a line graph showing the change in dynamic viscosity of the additive stock solution under different cycle batches in this embodiment of the invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing a random copolymer of ethylene oxide and propylene oxide, comprising the following steps: Ethylene glycol and potassium hydroxide were added to a high-pressure reactor, which was then sealed and purged three times with nitrogen. The temperature was raised to 110°C, and vacuum dehydration was carried out for 2 hours under an absolute pressure of 5 kPa. After releasing the vacuum, the reactor temperature was raised to 120°C, and a mixture of ethylene oxide and propylene oxide monomers in a mass ratio of 25:75 was continuously injected into the reactor. The pressure inside the reactor was controlled between 0.3 MPa and 0.4 MPa, and the reaction was carried out at a constant temperature until the pressure no longer decreased. Aging was continued at this temperature for another 2 hours. The temperature was then lowered to 80°C, and glacial acetic acid was added to neutralize the system to a pH of 7. Vacuum devolatilization was carried out for 1 hour under an absolute pressure of 5 kPa. The product was then cooled and discharged to obtain a random copolymer of ethylene oxide and propylene oxide. The weight-average molecular weight of this random copolymer was determined to be 12000 g / mol by gel permeation chromatography.

[0021] Preparation Example 2: This preparation example provides a method for preparing a random copolymer of ethylene oxide and propylene oxide, comprising the following steps: Ethylene glycol and potassium hydroxide were added to a high-pressure reactor, which was then sealed and purged three times with nitrogen. The temperature was raised to 110°C, and vacuum dehydration was carried out for 2 hours under an absolute pressure of 5 kPa. After releasing the vacuum, the reactor temperature was raised to 120°C, and a mixture of ethylene oxide and propylene oxide monomers in a mass ratio of 30:70 was continuously injected into the reactor. The pressure inside the reactor was controlled between 0.3 MPa and 0.4 MPa, and the reaction was carried out at a constant temperature until the pressure no longer decreased. Aging was continued at this temperature for another 2 hours. The temperature was lowered to 80°C, and glacial acetic acid was added to neutralize the system to a pH of 7. Vacuum devolatilization was carried out for 1 hour under an absolute pressure of 5 kPa. The product was then cooled and discharged to obtain a random copolymer of ethylene oxide and propylene oxide. The weight-average molecular weight of this random copolymer was determined to be 15000 g / mol by gel permeation chromatography.

[0022] Preparation Example 3: This preparation example provides a method for preparing a random copolymer of ethylene oxide and propylene oxide, comprising the following steps: Ethylene glycol and potassium hydroxide were added to a high-pressure reactor, which was then sealed and purged three times with nitrogen. The temperature was raised to 110°C, and vacuum dehydration was carried out for 2 hours under an absolute pressure of 5 kPa. After releasing the vacuum, the reactor temperature was raised to 120°C, and a mixture of ethylene oxide and propylene oxide monomers in a mass ratio of 35:65 was continuously injected into the reactor. The pressure inside the reactor was controlled between 0.3 MPa and 0.4 MPa, and the reaction was carried out at a constant temperature until the pressure no longer decreased. Aging was continued at this temperature for 2 hours. The temperature was lowered to 80°C, and glacial acetic acid was added to neutralize the system to a pH of 7. Vacuum devolatilization was carried out for 1 hour under an absolute pressure of 5 kPa. The product was then cooled and discharged to obtain a random copolymer of ethylene oxide and propylene oxide. The weight-average molecular weight of this random copolymer was determined to be 18000 g / mol by gel permeation chromatography.

[0023] Examples 1-3: Example 1: This embodiment provides a method for induction hardening of wind turbine internal gear rings, including the following steps: The random copolymer of ethylene oxide and propylene oxide prepared in Preparation Example 1 was dissolved in water to prepare an aqueous solution with a mass fraction of 10.0%, which was used as the main quenching liquid. The natural cloud point of the main quenching liquid was determined to be 70°C. Sodium xylenesulfonate was dissolved in water to prepare an aqueous solution with a mass fraction of 20.0%, which was used as the auxiliary agent stock solution. The wind turbine internal gear ring is installed on a rotary table, and the rotational linear speed of the rotary table is set to 100 mm / min. The inductor and an annular sprayer with a downward tilt angle of 30° are used to perform scanning quenching from top to bottom along the axial direction of the wind turbine internal gear ring. The axial feed speed of the inductor and the sprayer is 1.0 mm / s. Within the range of 0% to 15% of the total axial length of the wind turbine internal gear ring, the sprayer only sprays the main quenching liquid, and the spraying pressure is maintained at 0.15 MPa. When the sensor scans to 15% of the total axial length of the wind turbine's internal gear ring, the additive stock solution is injected into the inlet of the tubular static mixer in an incremental manner through a diaphragm-type variable frequency metering pump. It mixes with the main quenching liquid delivered by the main liquid supply pump to form a mixed fluid. The length-to-diameter ratio of the tubular static mixer is 15, and the mixed fluid is sprayed out by a sprayer. When the sensor scans to 90% of the total axial length of the wind turbine's internal gear ring, the instantaneous mass flow rate of sodium xylenesulfonate in the mixed fluid accounts for 2.0% of the total mass flow rate of the mixed fluid, and the dynamic cloud point of the mixed fluid is 82℃. The mixed waste liquid flowing down from the surface of the wind turbine's internal gear ring is collected and pumped into a continuous clarifier. The separation temperature is set at 90℃ and the average residence time is controlled at 30 minutes. The mixture is kept warm and separated into layers. The crude polyether-rich phase and the aqueous mother liquor containing additives are collected separately. Deionized water heated to 90°C was mixed with the extracted crude polyether-rich phase at a volume ratio of 1:1 and introduced into a liquid-liquid centrifugal extractor. The mixture was centrifuged at a constant temperature of 90°C and the speed of the liquid-liquid centrifugal extractor was set to 1500 rpm. The pure polyether-rich phase and the washed aqueous phase were separated simultaneously. The polyether-rich phase was cooled to 25°C and then returned to be used as the main quenching liquid. The collected aqueous mother liquor containing additives was combined with the washed aqueous phase and introduced into a low-temperature vacuum flash tank for vacuum concentration and dehydration. The absolute operating pressure of the low-temperature vacuum flash tank was set to 5.0 kPa, and the jacket heating temperature was set to 60℃. Dehydration was stopped when the mass fraction of sodium xylenesulfonate in the bottom liquid was 20.0%. The concentrated bottom liquid was returned for use as the additive stock solution. The pure water produced by vacuum concentration and dehydration was condensed and heated to 90℃ and returned for use as deionized water for mixing with the crude polyether-rich phase.

[0024] Example 2: This embodiment provides a method for induction hardening of wind turbine internal gear rings, including the following steps: The random copolymer of ethylene oxide and propylene oxide prepared in Preparation Example 2 was dissolved in water to prepare an aqueous solution with a mass fraction of 12.5%, which was used as the main quenching liquid. The natural cloud point of the main quenching liquid was measured to be 72°C. Sodium xylenesulfonate was dissolved in water to prepare an aqueous solution with a mass fraction of 25.0%, which was used as the auxiliary agent stock solution. The wind turbine internal gear ring is installed on a rotary table, and the rotational linear speed of the rotary table is set to 200 mm / min. The inductor and an annular sprayer with a downward tilt angle of 35° are used to perform scanning quenching from top to bottom along the axial direction of the wind turbine internal gear ring. The axial feed speed of the inductor and the sprayer is 2.0 mm / s. Within the range of 0% to 20% of the total axial length of the wind turbine internal gear ring, the sprayer only sprays the main quenching liquid, and the spraying pressure is maintained at 0.20 MPa. When the sensor scans to 20% of the total axial length of the wind turbine's internal gear ring, the additive stock solution is injected into the inlet of the tubular static mixer in an incremental manner through a diaphragm-type variable frequency metering pump. It mixes with the main quenching liquid delivered by the main liquid supply pump to form a mixed fluid. The length-to-diameter ratio of the tubular static mixer is 20, and the mixed fluid is sprayed out by a sprayer. When the sensor scans to 95% of the total axial length of the wind turbine's internal gear ring, the instantaneous mass flow rate of sodium xylenesulfonate in the mixed fluid accounts for 3.5% of the total mass flow rate of the mixed fluid, and the dynamic cloud point of the mixed fluid is 85℃. The mixed waste liquid flowing down from the surface of the wind turbine's internal gear ring was collected and pumped into a continuous clarifying separator. The separation temperature was set at 92℃ and the average residence time was controlled at 45 min. The mixture was kept warm and separated into layers. The crude polyether-rich phase and the aqueous mother liquor containing additives were collected separately. Deionized water heated to 92°C was mixed with the extracted crude polyether-rich phase at a volume ratio of 2:1 and introduced into a liquid-liquid centrifugal extractor. The mixture was centrifuged at a constant temperature of 92°C with the centrifugal extractor speed set to 2000 rpm. The pure polyether-rich phase and the washed aqueous phase were separated simultaneously. The polyether-rich phase was cooled to 25°C and then returned to be used as the main quenching liquid. The collected aqueous mother liquor containing additives was combined with the washed aqueous phase and introduced into a low-temperature vacuum flash tank for vacuum concentration and dehydration. The absolute operating pressure of the low-temperature vacuum flash tank was set to 10.0 kPa, and the jacket heating temperature was set to 70℃. The vacuum concentration and dehydration was stopped when the mass fraction of sodium xylenesulfonate in the bottom liquid was 25.0%. The concentrated bottom liquid was returned as the additive stock solution. The pure water produced by vacuum concentration and dehydration was condensed and heated to 92℃ and returned as deionized water for mixing with the crude polyether-rich phase.

[0025] Example 3: This embodiment provides a method for induction hardening of wind turbine internal gear rings, including the following steps: The random copolymer of ethylene oxide and propylene oxide prepared in Preparation Example 3 was dissolved in water to prepare an aqueous solution with a mass fraction of 15.0%, which was used as the main quenching liquid. The natural cloud point of the main quenching liquid was determined to be 75°C. Sodium xylenesulfonate was dissolved in water to prepare an aqueous solution with a mass fraction of 30.0%, which was used as the auxiliary agent stock solution. The wind turbine internal gear ring is installed on a rotary table, and the rotational linear speed of the rotary table is set to 300 mm / min. The inductor and an annular sprayer with a downward tilt angle of 45° are used to perform scanning quenching from top to bottom along the axial direction of the wind turbine internal gear ring. The axial feed speed of the inductor and the sprayer is 3.5 mm / s. Within the range of 0% to 30% of the total axial length of the wind turbine internal gear ring, the sprayer only sprays the main quenching liquid, and the spraying pressure is maintained at 0.30 MPa. When the sensor scans to 30% of the total axial length of the wind turbine's internal gear ring, the additive stock solution is injected into the inlet of the tubular static mixer in an incremental manner through a diaphragm-type variable frequency metering pump. It mixes with the main quenching liquid delivered by the main liquid supply pump to form a mixed fluid. The length-to-diameter ratio of the tubular static mixer is 25, and the mixed fluid is sprayed out by a sprayer. When the sensor scans to 100% of the total axial length of the wind turbine's internal gear ring, the instantaneous mass flow rate of sodium xylenesulfonate in the mixed fluid accounts for 5.0% of the total mass flow rate of the mixed fluid, and the dynamic cloud point of the mixed fluid is 88℃. The mixed waste liquid flowing down from the surface of the wind turbine's internal gear ring was collected and pumped into a continuous clarifying separator. The separation temperature was set at 95℃, and the average residence time was controlled at 60 minutes. The mixture was kept at a constant temperature and separated into crude polyether-rich phase and aqueous mother liquor containing additives. Deionized water heated to 95℃ was mixed with the collected crude polyether-rich phase at a volume ratio of 3:1 and introduced into a liquid-liquid centrifugal extractor. The mixture was centrifuged at a constant temperature of 95℃ and the speed of the liquid-liquid centrifugal extractor was set at 3000 rpm. The pure polyether-rich phase and the washed aqueous phase were separated simultaneously. The polyether-rich phase was cooled to 25℃ and returned to be used as the main quenching liquid. The collected aqueous mother liquor containing additives was combined with the washed aqueous phase and introduced into a low-temperature vacuum flash tank for vacuum concentration and dehydration. The absolute operating pressure of the low-temperature vacuum flash tank was set to 20.0 kPa, and the jacket heating temperature was set to 80℃. The vacuum concentration and dehydration was stopped when the mass fraction of sodium xylenesulfonate in the bottom liquid was 30.0%. The concentrated bottom liquid was returned as the additive stock solution. The pure water produced by vacuum concentration and dehydration was condensed and heated to 95℃ and returned as deionized water for mixing with the crude polyether-rich phase.

[0026] Comparative Examples 1-4: Comparative Example 1: Compared with Example 2, the difference is that the diaphragm frequency conversion metering pump is not started during the entire induction scanning quenching process. That is, only the main quenching liquid is sprayed throughout the process, and no auxiliary agent stock solution is injected. Everything else is the same.

[0027] Comparative Example 2: Compared with Example 2, the difference is that the step of dynamically gradient injection of auxiliary agent stock solution was not adopted. Instead, the main quenching liquid and auxiliary agent stock solution were pre-mixed to prepare a mixed quenching liquid with a constant sodium xylenesulfonate mass fraction of 3.5%. This constant concentration of mixed quenching liquid was sprayed throughout the entire process from 0% to 100% of the total axial length of the wind turbine internal gear ring. The rest were the same.

[0028] Comparative Example 3: Compared with Example 2, the difference is that the separation temperature of the continuous clarifier, the heating temperature of the deionized water, and the constant temperature conditions in the liquid-liquid centrifugal extractor are all changed from 92°C to 78°C, while the rest are the same.

[0029] Comparative Example 4: Compared to Example 2, the difference lies in the absence of the isothermal centrifugal washing step. Specifically, after separating and collecting the crude polyether-rich phase in a continuous clarifier, it is not mixed with deionized water, nor is it subjected to liquid-liquid centrifugal extraction. Instead, the crude polyether-rich phase is directly cooled to 25°C and returned for use as the main quenching liquid. Everything else remains the same.

[0030] Test Examples 1-4: Test Example 1: Feasibility Test of Dynamic Regulation Mechanism for Cloud Point Take 500 mL of each of the main quenching fluids prepared in Examples 1 to 3 as the basic test solution.

[0031] Sodium xylenesulfonate solid powder was added to each of the above basic test solutions to prepare mixed test solutions with sodium xylenesulfonate mass fractions of 1.0%, 2.0%, 3.5%, and 5.0%, respectively. The solutions were stirred at 300 rpm at room temperature for 20 minutes until completely dissolved. The 0% stock solution without added sodium xylenesulfonate was used as the baseline control.

[0032] Each mixed test solution was transferred to a jacketed glass-jacketed reactor and heated by a circulating constant temperature water bath at a rate of 1°C / min.

[0033] Immerse the probe of the transmittance meter 5 cm below the surface of the test liquid, set the test wavelength to 500 nm, and record the transmittance change curve during the heating process. Record the system temperature corresponding to the point where the transmittance drops sharply to 50% as the macroscopic dynamic turbidity point of the mixture. Perform three parallel tests for each concentration gradient and take the arithmetic mean.

[0034] Table 1. Macroscopic dynamic cloud point test data of the mixed fluid under different mass fractions of sodium xylenesulfonate in conclusion: Figure 1 This study demonstrates the physical phenomenon that the macroscopic dynamic cloud point of the mixed fluid monotonically increases with increasing sodium xylenesulfonate mass fraction in three example systems with different base polyether concentrations and molecular weights. The grayscale trends of different marker lines show that no phase separation instability occurred in any of the example systems within the 0% to 5.0% additive addition range, and the curve slopes remained relatively consistent, confirming that sodium xylenesulfonate has a wide range of applicability in raising the cloud point of polyether macromolecular aqueous solutions.

[0035] Figure 2The net intervention of sodium xylenesulfonate on the thermodynamic phase transition was demonstrated. When the instantaneous injection mass flow rate of sodium xylenesulfonate reached 5.0%, the cloud point elevation of the three example systems was concentrated in the range of 13.9℃ to 15.7℃. This trend indicates that the charge effect and hydration of the co-solvent have a stable synergistic effect within a specific polymer concentration window, providing precise thermodynamic data support for achieving axial isothermal control of quenching cooling rate by adjusting the flow rate of the variable frequency metering pump.

[0036] According to the data in Table 1, sodium xylenesulfonate has a direct effect on raising the phase transition temperature of the aqueous solution of the random copolymer of ethylene oxide and propylene oxide, and the increase is positively correlated with the mass fraction of sodium xylenesulfonate. As the mass fraction of sodium xylenesulfonate increases from 0% to 5.0%, the cloud points of the systems in Examples 1 to 3 rise from the initial 70.2℃, 72.1℃, and 74.6℃ to 85.6℃, 87.8℃, and 88.5℃, respectively. As a co-solvent, the hydrophobic groups in the molecular structure of sodium xylenesulfonate associate with the polyether molecular chains. The hydrophilic sulfonic acid groups enhance the hydration capacity of the polyether macromolecules at high temperatures, thereby increasing the critical thermodynamic energy required for the polyether molecules to overcome hydrogen bond breaking and undergo reverse solubility phase separation.

[0037] This data verifies that injecting sodium xylenesulfonate stock solution via a metering pump at a preset gradient during the quenching scanning process can raise the local turbidity point of the sprayed liquid in real time during the lower and middle quenching stages. This increased turbidity point inhibits premature precipitation of the polymer insulation film on the workpiece surface, reduces the film thickness, and directly improves the convective heat transfer coefficient at the contact interface. This physicochemical phase change intervention mechanism compensates for the delayed heat accumulation in the lower part caused by the downward flow and accumulation of the upper quenching liquid due to gravity in the later stages of the wind turbine internal gear ring scanning quenching, achieving balanced control of the cooling rate at different axial heights of the same workpiece. The data also show that sodium xylenesulfonate maintains a stable thermodynamic intervention effect for main quenching liquid systems with different monomer ratios and weight-average molecular weights, with a maximum adjustment window of 13°C to 15°C.

[0038] Test Example 2: Feasibility Test of High-Temperature Deep Separation and Isothermal Washing Mechanism According to the composition ratio of Example 2, a mixture containing 12.5% ​​by mass of ethylene oxide and propylene oxide random copolymer and 3.5% by mass of sodium xylenesulfonate was prepared to simulate the mixed waste liquid after scanning quenching.

[0039] The mixed waste liquid was divided into five equal portions and placed in separate sedimentation tanks equipped with temperature control and stirring devices. The constant temperature settling temperatures of the five sedimentation tanks were set to 78.2℃, 83.1℃, 87.6℃, 92.3℃, and 96.5℃, respectively. The sedimentation tanks were allowed to stand at the constant temperature for 45 minutes to separate into layers.

[0040] Extract the mother liquor containing additives from the bottom of each settling tank. Measure the total organic carbon content in the mother liquor using a total organic carbon analyzer. Calculate the mass of polyether retained in the mother liquor based on the carbon content, and divide this mass by the total mass of polyether in the initial mixed waste liquid to obtain the polyether loss rate.

[0041] The crude polyether-rich phase precipitated from the upper layer of the sedimentation tank at 92.3℃ was extracted. The mass fraction of sodium xylenesulfonate in the unwashed crude polyether-rich phase was determined using high performance liquid chromatography.

[0042] The crude polyether-rich phase extracted in step 4 was divided into three equal portions, and each portion was mixed with twice the volume of deionized water. The preheating temperatures of the three sets of deionized water were set to 25.4℃, 65.8℃, and 92.1℃, respectively. At the corresponding set temperatures, a liquid-liquid centrifuge was used for centrifugation at a speed of 2000 rpm.

[0043] The purified polyether-rich phase after centrifugation was removed, and the residual mass fraction of sodium xylenesulfonate in the polyether-rich phase was determined again using high performance liquid chromatography.

[0044] Table 2. Test data on polyether loss rate at different separation temperatures Table 3. Test data on sodium xylenesulfonate residue rate after washing with different deionized water temperatures. in conclusion: Figure 3 This study demonstrates the direct physical impact of separation temperature on the aggregation compactness of polymeric polyethers after the mixed waste liquid has passed the dynamic cloud point phase transition. The line graph shows that in the mid-to-low temperature range of 78.2℃ to 87.6℃, the polyether loss rate remains at a high level, indicating that the two-phase interface is blurred and separation is extremely incomplete. Once the separation temperature exceeds the 90℃ threshold, the curve shows a sharp downward convergence trend, with the polyether loss rate approaching zero at 92.3℃ and 96.5℃. This trend confirms that the separation temperature must be higher than the highest dynamic cloud point to completely destroy the polymer's hydrogen bond network through thermodynamic phase transition, achieving deep two-phase separation of the waste liquid.

[0045] Figure 4The washing and extraction capabilities of deionized water within different thermodynamic ranges for residual salts in the polyether-rich phase were compared. The results show that the unwashed polyether contains a high proportion of small-molecule salts. When washing with deionized water at 25.4℃, the system underwent reverse dissolution due to the temperature being below the natural cloud point of the polyether, leading to the merging and failure of the two phases. While washing with warm water at 65.8℃ preserved the stratified state, the impurity removal efficiency was limited. When washing with hot water at 92.1℃, the residual rate column height showed a sharp drop. This column distribution verifies that isothermal washing, while ensuring the stability of the hydrophobic droplet morphology of the polyether, enhances the mass transfer driving force for the transfer of polar small-molecule salts to the aqueous phase, making it a key operational step for achieving high-purity reuse of the main quenching fluid.

[0046] According to the data in Tables 2 and 3, the separation temperature must be set within a thermodynamic range much higher than the highest dynamic turbidity point to achieve two-phase separation of the waste liquid. The highest dynamic turbidity point of the mixed waste liquid in Example 2 was 85°C. Table 2 shows that when the separation temperatures were 78.2°C and 83.1°C, the polyether loss rate in the aqueous mother liquor was as high as 41.27% and 18.54%, respectively. When the separation temperature was close to or below the highest dynamic turbidity point, the hydrogen bonds of the polyether macromolecular chains were not completely broken, and the polymers maintained a certain degree of hydration and expansion, resulting in a large amount of polyether remaining in the aqueous phase. When the separation temperature was increased to 92.3°C, the polyether loss rate dropped sharply to 0.42%. The high temperature forced the polyether molecular chains to contract and coil violently, expelling bound water molecules and forming a dense condensed phase with a density much greater than that of water. This density difference and interfacial tension facilitated deep phase separation.

[0047] Table 3 data verifies the impurity removal effect of the isothermal centrifugal washing step in the closed-loop cycle. The unwashed crude polyether-rich phase physically carried 7.18% sodium xylenesulfonate. When washing with room temperature water at 25.4℃, because the water temperature is below the natural cloud point of the polyether, the polyether re-bonded with water, resulting in complete miscibility between the two phases and rendering the washing and purification process ineffective. When washing with water at 65.8℃, although the stratified state was maintained, the residual sodium xylenesulfonate rate was still 1.83%. When washing with hot water at 92.1℃, the washing temperature was isothermal to the separation temperature and far exceeded the cloud point. Deionized water could not dissolve the polyether macromolecules at this temperature, maintaining the hydrophobic droplet state of the polyether. Sodium xylenesulfonate, as a polar small molecule salt, has high solubility in high-temperature water. The 92.1℃ hot water, relying on the concentration gradient, efficiently extracted the sodium xylenesulfonate molecules entrained within the oil phase polyether into the washing aqueous phase, reducing the residual sodium xylenesulfonate rate in the polyether-rich phase to 0.06%. The test results demonstrate that the process matching of setting the separation temperature to a high temperature and the washing conditions to an isothermal temperature is a necessary thermodynamic boundary condition for maintaining the high purity closed-loop circulation of the main quenching fluid.

[0048] Test Example 3: Quenching Cooling Rate Uniformity and Macroscopic Mechanical Properties Test Wind turbine internal gear rings that underwent induction hardening according to Examples 1 to 3 and Comparative Examples 1 to 2 were selected as test objects. All gear rings under test maintained the same material, initial state, and geometric dimensions before hardening.

[0049] Using wire cutting equipment, along the axial direction of each wind turbine internal gear ring, cut tooth test blocks with dimensions of 20mm×20mm×15mm at the upper position, 50% of the total length from the top, and 90% of the top.

[0050] The cut tooth test blocks were subjected to surface grinding and polishing. Using a Rockwell hardness tester, five points were randomly selected on the working area of ​​each test block's tooth surface for hardness testing. The maximum and minimum values ​​were discarded, and the arithmetic mean was recorded as the macroscopic surface hardness value at that location. The range of hardness values ​​at the upper, middle, and lower positions of the same tooth ring was calculated.

[0051] Before and after the quenching process, a coordinate measuring machine was used to scan the roundness of the inner diameter of each wind turbine internal gear ring. Circumferential scan data from three different heights of the gear ring cross-section were selected, and the absolute value of the maximum radial dimensional deviation before and after quenching was extracted and recorded as the maximum macroscopic ellipticity deformation of the gear ring.

[0052] Table 4. Test data on hardness and deformation of the internal gear ring of the wind turbine in the examples and comparative examples. in conclusion: Figure 5 This intuitively reflects the intervention effect of the quenching fluid cloud point control strategy on the axial cooling rate of the workpiece. The broken line trend shows that in Comparative Example 1, without the addition of additives, the heat accumulation caused by the downward flow of the quenching fluid due to gravity resulted in a severe decrease in cooling rate at the lower part of the gear ring, leading to a steep downward trend in the hardness curve. Comparative Example 2 used a globally constant high concentration of additives, which, while increasing the overall cooling limit of the quenching fluid, caused a rapid increase in hardness in the initial quenching section at the top due to the lack of an insulating film, and still could not offset the sluggish heat accumulation at the bottom. In contrast, the hardness distribution curves of Examples 1 to 3 were nearly horizontal. The gradient injection strategy utilizes the low cloud point of pure polyether to form a thick insulating film for slow cooling in the upper part, while gradually increasing the additive concentration in the middle and lower parts to raise the local dynamic cloud point and thin the insulating film to enhance convective heat transfer. This physicochemical mechanism precisely compensates for the cooling temperature difference caused by heat accumulation in terms of heat transfer, achieving an isothermal phase transition on the workpiece surface.

[0053] Figure 6The cumulative effect of the microscopic cooling rate difference on macroscopic mechanical deformation is demonstrated. The stark contrast in the height of the bar charts indicates that the hardness difference of 9.2 HRC to 11.3 HRC in Comparative Examples 1 and 2 induced a highly non-uniform martensitic phase transformation stress and thermal stress alternation network within the large, thin-walled annular component, ultimately causing the maximum ellipticity deformation of the gear ring to exceed the safety threshold of 2.90 mm. Examples 1 to 3, through precise dynamic control of the thermodynamic boundary, compressed the hardness difference to below 1.5 HRC, effectively eliminating the source of asymmetric internal stress, stabilizing the maximum deformation below 1.30 mm, and reducing subsequent machining allowances and scrap rates. The test data rigorously confirms the engineering effectiveness of dynamically altering the phase transformation characteristics of polymer aqueous solutions in solving the problem of thermal resistance imbalance in large vertical quenching processes.

[0054] According to the data in Table 4, Comparative Example 1 used only a single concentration of polyether aqueous solution throughout the entire process. The downward flow of the quenching fluid caused severe heat accumulation in the lower part of the gear ring. This heat retention increased the local fluid temperature, causing the polyether polymer in the lower part to reach the phase transition turbidity point prematurely and precipitate on the tooth surface to form a thick insulating film, reducing the convective heat transfer coefficient. Therefore, the hardness of the lower part of Comparative Example 1 decreased sharply to 45.8 HRC, and the hardness difference between the upper, middle and lower parts was as high as 11.3 HRC. This extreme uneven cooling rate generated huge internal structural stress and thermal stress, resulting in a maximum elliptic deformation of 3.52 mm in the gear ring. Comparative Example 2 used a constant high turbidity point quenching fluid with globally premixed high concentration of additives. Although the overall heat transfer efficiency was improved, the top 10% of the quenching area lacked heat accumulation and had a low fluid temperature in the initial stage of quenching. The high turbidity point meant that an effective polymer insulating protective film could hardly be formed in this area, resulting in a rapid cooling phenomenon. The hardness of the upper part soared to 62.4 HRC. Meanwhile, due to the lack of gradient compensation for the downward flow of heat, the hardness still declines in a step-like manner along the axial direction, with a hardness range of 9.2 HRC and a deformation of 2.94 mm, which cannot meet the dimensional accuracy requirements of wind turbine gear rings.

[0055] The hardness data of Examples 1 to 3 remained highly stable along the axial direction, with the hardness range between the upper, middle, and lower parts all controlled within 1.5 HRC. During the initial quenching stage (approximately 0% to 20% of the upper part), the low natural cloud point of the pure polyether aqueous solution facilitated rapid polymer precipitation, forming a complete insulating film and preventing top-end cooling cracking and excessive hardness. As the sensor moved downwards, the continuous increase in sodium xylenesulfonate concentration simultaneously raised the local dynamic cloud point of the mixed fluid. The increase in phase change temperature delayed the polymer precipitation time on the high-temperature tooth surface and forcibly thinned the insulating film, resulting in a non-linear enhancement of the cooling capacity of the spray liquid along the axial direction. This incremental increase in cooling capacity, achieved through dynamic control of the physicochemical phase change critical point, precisely offset the heat accumulation lag caused by the high-temperature waste liquid scouring in the lower part of the gear ring. The entire workpiece achieved a highly consistent equivalent cooling rate across all axial sections, eliminating structural internal stress induced by uneven heating and cooling. The maximum deformation in all examples was suppressed to below 1.30 mm. The test results verified the engineering feasibility of the dynamic cloud point control mechanism in solving the problem of thermal resistance imbalance in large-scale vertical quenching.

[0056] Test Example 4: Mass Balance Stability Test of Closed-Loop System During Long-Term Operation A miniature closed-loop circulation test system was constructed, comprising a quenching mixing flow path, a continuous clarifying separator, a liquid-liquid centrifugal extractor, and a low-temperature vacuum flash evaporator. The initial main quenching liquid and the initial auxiliary agent stock solution corresponding to Examples 1 to 3, Comparative Example 3, and Comparative Example 4 were quantitatively injected into their respective storage tanks.

[0057] The cyclic testing system was started, and 50 consecutive batches of simulated quenching and separation recovery cyclic operations were carried out according to the temperature, pressure, and flow parameters set in each embodiment and comparative example. The single batch operation included mixing the main quenching liquid and the auxiliary agent stock solution according to the set gradient, heating the mixed waste liquid to a constant temperature for stratification, extracting and washing the crude polyether with pure water, and concentrating and dehydrating the aqueous mother liquor containing the auxiliary agent under reduced pressure. The separated and purified polyether and the concentrated auxiliary agent solution were respectively returned to the corresponding storage tanks.

[0058] After the first, 25th, and 50th batches of the cycle were completed and the system liquid level stabilized, samples were taken from the sampling valves at the bottom of the main quenching liquid storage tank and the auxiliary agent stock liquid storage tank, respectively.

[0059] A sample of the main quenching fluid was extracted and placed in a glass interlayer transmittance test chamber. The temperature was programmed to rise at a rate of 1℃ / min, and the system temperature at which the transmittance decreased to 50% was recorded as the background natural cloud point temperature of the main quenching fluid without any added additives.

[0060] Samples of the additive stock solution were extracted and placed in a 25°C water bath. The absolute dynamic viscosity (mPa·s) of the additive stock solution was measured using a rotational viscometer. The test points for each batch were sampled and measured three times, and the arithmetic mean was taken.

[0061] Table 5. Test data of the natural cloud point temperature of the main quenching fluid under different cycle batches Table 6. Dynamic viscosity test data of additive stock solution under different cycle batches in conclusion: Figure 7 This reflects the system's control effect in preventing the enrichment of polar small molecule salts into the polymeric agent system during multiple batches of recycling. As can be seen from the line trend, in Comparative Example 4, due to the absence of a high-temperature water washing extraction step, the sodium xylenesulfonate physically entrained in the crude polyether formed an irreversible accumulation in the main quenching liquid loop with increasing number of recycling batches, resulting in a significant upward shift of the natural cloud point baseline (from 72.1℃ to 83.2℃). The cloud point curves of Examples 1 to 3 remained consistently stable, verifying that isothermal centrifugal water washing above 90℃ can utilize the polarity difference under thermodynamic phase separation conditions to wash away residual salts in the polymeric phase, ensuring the long-term stability of the background cloud point parameter of the quenching agent.

[0062] Figure 8 This study revealed the role of setting the separation temperature in preventing the escape of polymers into the aqueous phase system. The line graph shows that in Comparative Example 3, under the set low-temperature separation conditions of 78°C, a large amount of insufficiently dehydrated and shrunk polyether polymers penetrated the phase interface and entered the aqueous phase, continuously accumulating during the subsequent vacuum dehydration and concentration process. The physical entanglement effect of the long polymer chains caused the dynamic viscosity of the additive stock solution to increase exponentially with each batch, ultimately leading to system fluid transport failure. In contrast, Examples 1 to 3, by strictly controlling the separation temperature above the highest dynamic cloud point (≥90°C), relied on high temperature to force the polyether molecular chains to contract and curl violently, expelling bound water, thus achieving deep phase separation. After 50 batches, the increase in the dynamic viscosity of the additive stock solution was minimal, demonstrating that this high-temperature deep separation process effectively avoids the malignant accumulation of polymer components at the concentration and dehydration end, maintaining the rheological stability of the closed-loop dosing system.

[0063] According to the data in Tables 5 and 6, the thermodynamic range of the separation temperature setting and the presence or absence of the isothermal centrifugal extraction step directly determine the batch-to-batch mass balance stability of the polyether macromolecules and the sodium xylenesulfonate small molecule salt in the closed-loop system. Comparative Example 3 used 78℃ as the operating temperature of the continuous clarification separator, which is below the thermodynamic threshold required for phase separation of the polyether system. At this temperature, the polyether molecular chains were not completely dehydrated and coiled, resulting in a high proportion of polymer penetrating the separation interface in a hydrated state and remaining in the aqueous mother liquor containing the additives. During the subsequent vacuum concentration and dehydration process, water evaporation caused the penetrating polyether to continuously accumulate in the high-concentration additive stock solution. The entangled network of the long chains of the polyether macromolecules caused the dynamic viscosity of the additive stock solution to increase exponentially with each batch, reaching 56.27 mPa·s by the 50th batch. This high fluid viscosity exceeded the rated delivery limit of the variable frequency metering pump, leading to physical blockage and failure of the dynamic injection system.

[0064] Comparative Example 4 eliminated the liquid-liquid centrifugal extraction and washing step, preventing the physical removal of sodium xylenesulfonate physically trapped within the crude polyether-rich phase. The polyether containing residual additives was directly cooled and returned to the main quenching liquid storage tank, causing sodium xylenesulfonate to continuously accumulate in the main quenching liquid loop. Table 5 shows that the continuously increasing concentration of sodium xylenesulfonate unilaterally increased the background cloud point of the main quenching liquid, which had drifted from an initial 72.1℃ to 83.2℃ by the 50th batch. This significant increase in the background cloud point compressed the thermodynamic window for local cooling rate control through additional additive injection during subsequent quenching scans, rendering the dynamic gradient compensation mechanism of the lower quenching section ineffective.

[0065] In Examples 1 to 3, the maximum drift of the natural cloud point of the main quenching fluid after 50 cycles was only 0.8℃, and the increase in dynamic viscosity of the additive stock solution was controlled within 0.07 mPa·s. High-temperature separation above 90℃ forced the polyether to expel bound water and precipitate to form a dense phase, cutting off the path of polymer transfer to the aqueous phase loop. Washing with deionized water under the same high-temperature conditions utilized the high solubility of polar small-molecule salts in high-temperature pure water and the insolubility of polymers at high temperatures to remove salt impurities from the polyether-rich phase through reverse extraction into the aqueous system. The matching of the physical phase transition point and the extraction temperature prevented cross-contamination between the polymeric main agent and the low-molecular-weight additive in the two independent reflux pipelines, maintaining a constant physicochemical baseline for the entire quenching fluid system during long-term operation.

Claims

1. A method for induction hardening of an internal gear ring for wind turbines, characterized in that, Includes the following steps: The random copolymer of ethylene oxide and propylene oxide is dissolved in water to prepare an aqueous solution with a mass fraction of 10.0%-15.0%, which is used as the main quenching fluid. Sodium xylenesulfonate is dissolved in water to prepare an aqueous solution with a mass fraction of 20.0%-30.0%, which is used as the stock solution for the auxiliary agent. The sensor and sprayer are used to perform scanning quenching from top to bottom along the axial direction of the wind turbine's internal gear ring. Within the range of 0%-L1 of the total axial length of the wind turbine internal gear ring, the sprayer only sprays the main quenching liquid, where L1 is 15%-30%; When the sensor scans to the L1 position, the auxiliary agent stock solution is injected into the main quenching liquid in an incremental manner to form a mixed fluid, which is then sprayed out by the sprayer. When the scan reaches position L2, which is the total axial length of the wind turbine internal gear ring, the instantaneous mass flow rate of sodium xylenesulfonate in the mixed fluid accounts for 2.0%-5.0% of the total mass flow rate of the mixed fluid, of which L2 is 90%-100%. Collect the mixed waste liquid flowing down from the surface of the wind turbine inner gear ring, and perform heat preservation and stratification at a set separation temperature to separately extract the crude polyether-rich phase and the aqueous mother liquor containing additives. Heated deionized water is mixed with the extracted crude polyether-rich phase and centrifuged to obtain the polyether-rich phase; the polyether-rich phase is cooled and returned to be used as the main quenching liquid.

2. The induction hardening method for wind turbine internal gear rings according to claim 1, characterized in that, The separation temperature is set to 90℃-95℃; The temperature of the deionized water mixed with the crude polyether-rich phase is 90℃-95℃; The centrifugation was carried out under constant temperature conditions of 90℃-95℃.

3. The induction hardening method for wind turbine internal gear rings according to claim 1, characterized in that, In the random copolymer of ethylene oxide and propylene oxide, the mass ratio of ethylene oxide to propylene oxide is 25:75-35:

65.

4. The induction hardening method for wind turbine internal gear rings according to claim 1, characterized in that, The natural cloud point of the main quenching fluid is 70℃-75℃; When the scan reaches the L2 position, the dynamic cloud point of the mixed fluid sprayed by the sprayer is 82℃-88℃.

5. The induction hardening method for wind turbine internal gear rings according to claim 1, characterized in that, The axial feed speed of the sensor and the sprayer is set to 1.0 mm / s-3.5 mm / s; The spray pressure of the main quenching fluid is maintained at 0.15MPa-0.30MPa.

6. The induction hardening method for a wind turbine internal gear ring according to claim 1, characterized in that, The auxiliary agent stock solution is injected into the inlet of the tubular static mixer through a diaphragm-type variable frequency metering pump, and mixed with the main quenching liquid delivered by the main liquid supply pump to form a mixed fluid. The length-to-diameter ratio of the tubular static mixer is 15-25.

7. The induction hardening method for wind turbine internal gear rings according to claim 1, characterized in that, The heat preservation and stratification are carried out in a continuous clarifier and separator, and the average residence time of the mixed waste liquid in the continuous clarifier and separator is controlled to be 30 min-60 min. The volume ratio of deionized water to the crude polyether-rich phase is set to 1:1-3:1, and the centrifugal separation is carried out in a liquid-liquid centrifugal extractor with a rotation speed set to 1500rpm-3000rpm.

8. The induction hardening method for a wind turbine internal gear ring according to claim 1, characterized in that, The centrifugation process simultaneously separates the washed aqueous phase. The collected aqueous mother liquor containing the additives was combined with the washed aqueous phase and introduced into a low-temperature vacuum flash tank for depressurization concentration and dehydration.

9. The induction hardening method for a wind turbine internal gear ring according to claim 8, characterized in that, The absolute operating pressure of the low-temperature vacuum flash evaporator is set to 5.0 kPa-20.0 kPa, and the jacket heating temperature is set to 60℃-80℃. Dehydration is stopped when the mass fraction of sodium xylenesulfonate in the base liquid is 20.0%-30.0% under reduced pressure. The concentrated base liquid is then returned to be used as the original solution for the auxiliary agent.

10. The induction hardening method for a wind turbine internal gear ring according to claim 8, characterized in that, The purified water produced by vacuum concentration and dehydration is condensed and then heated to 90°C-95°C and returned to be used as the deionized water mixed with the crude polyether-rich phase. The sprayer is an annular sprayer with a downward tilt angle of 30°-45°.

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