A manufacturing method for improving fatigue life of split flywheel ring gear

Abstract

The application relates to the technical field of metal heat treatment, and discloses a manufacturing method for improving the fatigue life of a split flywheel gear ring, which comprises the following steps: preparing a water-based quenching medium containing polyether, disodium sebacate, sodium molybdate, sodium polyacrylate and a block copolymer defoaming agent and adjusting the pH value; inductively heating the tooth profile surface of the gear ring to form an internal-external temperature gradient; dropping the gear ring into a quenching tank, initially establishing a turbulent flow, injecting nitrogen to form a gas-liquid two-phase flow to flush the surface, and using mechanical action to break the steam film; in the later period, the flow field is transitioned to a laminar flow to control the cooling speed, the polymer is stably formed into a film on the surface to control the martensite phase change, and the liquid surface micro-bubbles are overflowed and scraped off; and finally, tempering treatment is carried out. Through the cooperation of the specific formula medium and the dynamic flow field control, a uniform residual compressive stress layer is formed on the tooth profile surface, soft spots and micro-cracks are avoided, and the fatigue life of the gear ring is improved.

Description

Technical Field

[0001] This invention relates to the field of metal heat treatment technology, specifically to a manufacturing method for improving the fatigue life of a split flywheel gear ring. Background Technology

[0002] Split flywheel ring gears are frequently subjected to alternating loads from engine starting and transmission systems during service, and the fatigue resistance of their tooth profile surfaces determines the component's service life. Currently, existing technologies typically employ surface induction heating combined with water-based polymer medium quenching to strengthen the ring gear.

[0003] However, conventional heat treatment processes struggle to precisely control the continuous cooling transformation process in actual production. When a high-temperature gear ring is immersed in a quenching tank, the surrounding liquid vaporizes on the workpiece surface, forming a vapor film. This vapor film's insulating effect hinders heat exchange between the fluid and the metal surface, leading to differences in cooling rates across different areas of the gear ring. This, in turn, easily results in soft spots with lower local hardness on the gear profile surface. As the workpiece temperature decreases and enters the austenite-to-martensite transformation temperature range, the cooling rate is often difficult to control due to the difficulty in dynamically intervening in the quenching flow field. Excessive cooling at this point causes the volume expansion accompanying the martensitic phase transformation, generating structural stress. With asynchronous internal and external cooling, the core cannot provide stable mechanical restraint for the surface phase transformation expansion. This imbalance in stress release easily induces quenching microcracks and heat treatment distortion, making it difficult to form a uniform macroscopic residual compressive stress layer on the gear ring surface.

[0004] Furthermore, to maintain temperature uniformity within the quenching tank, the equipment typically requires the operation of a circulating pump for fluid agitation. This mechanical shearing process leads to the introduction and accumulation of microbubbles within the water-based medium. The continuous accumulation of microbubbles on the liquid surface and in the flow field alters the overall density and specific heat capacity of the quenching fluid, causing fluctuations in heat transfer efficiency and affecting the uniformity of the cooling process. Existing treatment methods often rely on single chemical defoamers, but these are prone to failure under high temperature and intense circulation conditions, making it difficult to maintain the long-term stability of the medium's physicochemical properties. The aforementioned uneven cooling and medium degradation issues during the heat treatment process ultimately limit the improvement of the flywheel gear ring's fatigue life. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a manufacturing method for improving the fatigue life of a split flywheel gear ring. This method solves the technical problem that the cooling rate is difficult to accurately match the material transformation curve during the quenching process of existing flywheel gear rings, which leads to soft spots and microcracks on the workpiece surface and thus affects its fatigue life.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a manufacturing method for improving the fatigue life of a split flywheel ring gear, comprising the following steps: Add 8-10% by mass of polyether, 0.5-1.2% by mass of disodium sebate, 0.1-0.3% by mass of sodium molybdate, 0.2-0.5% by mass of sodium polyacrylate and 0.05-0.15% by mass of high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer to the remaining deionized water, and adjust the pH to 8.5-9.5 to obtain a water-based quenching medium; The tooth profile surface of the gear ring is induction heated so that the surface layer of the tooth profile reaches 860-880℃, while the core temperature is below 400℃. The induction-heated gear ring is dropped into a quenching tank containing water-based quenching medium. The circulation pump of the quenching tank is controlled to establish turbulence. The bypass Venturi jet of the quenching tank is turned on to inject nitrogen gas. The gas content of the fluid is controlled to be 3-5% to maintain the gas jet scouring. Turn off the nitrogen ejector, reduce the frequency of the circulating pump to transition the flow field to laminar flow, control the cooling rate of the gear ring to 15-25℃ / s, and the microbubbles on the liquid surface enter the bypass settling defoaming tank through the overflow weir of the quenching tank. After the temperature of the gear ring drops below 80℃, it is removed from the quenching tank. Temper the gear ring removed from the quenching tank at 180–200°C for 1.5–2 hours, then air cool to room temperature.

[0007] By adopting the above technical solution, the present invention mainly achieves the expected technical effect through the following mechanism: In terms of regulating the physicochemical properties of quenching media, polyether components provide fundamental anti-solution properties. When in contact with high-temperature metal surfaces, they precipitate and form a polymer film, thereby adjusting the interfacial thermal conductivity of the medium. To address the problem of easy foaming during fluid circulation, high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymers are used as steric hindrance defoamers. The hydrophobic segments of polyoxypropylene and the hydrophilic segments of polyoxyethylene in their molecular structure can be oriented at the gas-liquid interface. When bubbles are generated at room temperature, the hydrophobic segments adsorb onto the bubble interface, while the hydrophilic segments extend into the aqueous phase to form a steric hindrance layer, preventing bubbles from approaching each other and coalescing. During the quenching heating stage, the block copolymer undergoes cloud point phase separation, and the precipitated polymer droplets enter the bubble liquid film, reducing local surface tension, thinning the bubble wall, and causing it to rupture, thus achieving defoaming at the chemical level. In addition, disodium sebate and sodium molybdate form a composite corrosion inhibition system, in which molybdate ions undergo anodic polarization on the metal surface to form an iron-molybdenum oxide deposition layer, while disodium sebate undergoes chemisorption on the metal surface. This dual mechanism protects the gear ring surface from oxidative corrosion.

[0008] Besides the properties of the quenching fluid itself, the heating method also affects the final stress distribution. By applying medium- to high-frequency induction heating to the tooth profile surface, the surface microstructure transforms into austenite, while the core microstructure remains in its original state. This temperature gradient distribution formed on the cross-section promotes martensitic transformation and volume expansion in the surface layer during subsequent quenching and cooling. Since the core hinders this expansion process, macroscopic residual compressive stress will inevitably form on the tooth profile surface, thereby macroscopically improving the fatigue life of the gear ring under alternating loads.

[0009] In the actual cooling process, when the high-temperature gear ring is initially immersed in water, the polymer medium easily forms a stable vapor film on the metal surface, which usually hinders heat transfer. This solution introduces nitrogen injection and establishes a turbulent field, allowing nitrogen microbubbles to impact the gear ring surface at high speed with the fluid. When the gas-filled jet contacts the high-temperature surface, the gas inside the bubble undergoes violent heating and expansion, followed by cavitation collapse under the combined action of surrounding fluid pressure and turbulent shear force. The microjet generated by the collapse directly acts on the vapor film, disrupting the continuity of the gas film and causing the nucleation boiling stage to arrive earlier, thereby increasing the cooling rate of the high-temperature zone and eliminating surface hardness unevenness and soft spot defects. At the same time, using nitrogen as an inert gas does not participate in the chemical reaction, avoiding oxidation and decarburization of the high-temperature metal surface.

[0010] As the temperature drops into the martensitic transformation temperature range, the nitrogen ejector is shut off and the circulation pump frequency is reduced, causing the flow field in the quenching tank to transition from turbulent to gentle laminar flow. In laminar flow, the fluid shear force decreases, allowing the polymer film to uniformly and stably coat the gear ring surface. By increasing the thermal resistance of the thickened polymer film, the cooling rate is precisely limited to 15–25 °C / s. This cooling rate control slows down the strain rate released during the phase transformation and reduces thermal stress caused by the internal and external temperature differences, preventing gear ring deformation and cracking. Combined with the physical surface skimming design of the overflow weir, residual microbubbles collected on the liquid surface are continuously scraped into the bypass settling tank, preventing bubbles from being re-entrained into the circulating flow field and ensuring system stability in the later stages of cooling.

[0011] Preferably, the water-based quenching medium is prepared from raw materials comprising the following mass fractions: 9.0% polyether, 0.85% disodium sebate, 0.2% sodium molybdate, 0.35% sodium polyacrylate, and 0.1% block copolymer, with the balance being deionized water, and the system pH is 9.0.

[0012] By adopting the above technical solution and defining the specific medium formulation ratio, the precipitation thickness of the polymer film and the interfacial activity of the defoamer can be optimally balanced, thereby maintaining the stability of the thermophysical properties of the fluid system.

[0013] Preferably, the specific implementation method for preparing water-based quenching medium is as follows: Deionized water is injected into the liquid preparation vessel, the water temperature is maintained at 25-35℃, the stirrer is turned on and the speed is controlled at 60-80 rpm, polyether, disodium sebacate, sodium molybdate and sodium polyacrylate are added in sequence, and after stirring until homogeneous, the block copolymer is added, and finally a 10% sodium hydroxide aqueous solution is added dropwise to adjust the pH value of the system.

[0014] By adopting the above technical solutions and controlling the feeding sequence and stirring parameters of the materials, it is possible to ensure that various polymers are fully dissolved and dispersed, prevent local agglomeration of sodium polyacrylate and block copolymers, and maintain the uniform distribution of the fluid properties of the medium.

[0015] Preferably, when performing induction heating, the gear ring is made of 50Mn medium carbon steel forging; induction heating is performed using a medium-high frequency induction heating device with a working frequency of 30-50kHz; and the surface layer of the tooth profile is a region extending 2.0-3.0mm from the tooth tip to the tooth root of the gear ring.

[0016] By adopting the above technical solution, the heating frequency and depth are matched to the phase transformation characteristics of 50Mn material, and the effective hardened layer thickness under stress concentration is controlled to meet the mechanical requirements of torque transmission and resistance to contact fatigue.

[0017] Preferably, when maintaining the gas-containing jet scouring in the quenching tank, the turbulent flow velocity established by the circulating pump is 1.0 to 1.2 m / s; the nitrogen is industrial nitrogen with a purity of 99.99%; and the duration of the gas-containing jet scouring is 2.0 to 4.0 seconds.

[0018] By adopting the above technical solution, the fluid flow rate and impact time are set to provide sufficient kinetic energy to cause the complete collapse and rupture of the vapor film in the high-temperature stage. At the same time, the introduction of high-purity industrial nitrogen is controlled to prevent impurity gases from contaminating the water-based quenching fluid.

[0019] Preferably, when the frequency of the circulating pump is reduced, the flow field transitions to laminar flow with a velocity of 0.2 to 0.3 m / s; the surface velocity of the microbubbles on the liquid surface scraped into the bypass static defoaming tank through the overflow weir is 0.5 to 1.0 m / s.

[0020] By adopting the above technical solution, a stable flow field velocity is defined in the low-temperature zone, ensuring the integrity and thickness uniformity of the polymer film layer on the metal surface. At the same time, the control of the surface flow velocity decouples the physical removal action of microbubbles from the main fluid circulation, improving the stability of the medium during long-term use.

[0021] This invention provides a manufacturing method for improving the fatigue life of a split flywheel ring gear. It has the following beneficial effects: 1. This invention establishes turbulence and injects nitrogen gas through a circulating pump during the initial quenching stage, creating a specific gas-liquid two-phase flow within the quenching tank to scour the workpiece surface. When nitrogen microbubbles contact the high-temperature workpiece, they expand and collapse upon heating, mechanically breaking the stable vapor film formed on the workpiece surface during the initial quenching stage. This film-breaking method facilitates rapid cooling across the vapor film barrier, allowing for boiling cooling. This not only avoids soft spots caused by uneven local cooling but also utilizes the chemical inertness of nitrogen to prevent oxidation and decarburization of the workpiece surface at high temperatures.

[0022] 2. In the later stages of quenching and cooling, this invention controls the pump group to transition the flow field to laminar flow, thereby reducing the shear erosion of the workpiece surface by the fluid. This allows the polyether precipitated from the water-based medium due to its reverse solubility properties to stably adhere to the workpiece surface and form an insulating film. This film-forming mechanism slows down the cooling process of the workpiece, ensuring that the volume expansion during the transformation of the surface austenite to martensite is mechanically constrained by the core that has not undergone phase transformation. It is this difference in phase transformation time and volume change between the internal and external structures that ultimately translates into macroscopic residual compressive stress on the tooth profile surface, thereby offsetting the alternating tensile stress borne by the gear ring during service and improving its fatigue life.

[0023] 3. This invention introduces a specific molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer as a defoamer into the water-based quenching medium, and combines it with the overflow weir structure of the quenching tank for comprehensive defoaming treatment. The block copolymer utilizes the steric hindrance effect to disrupt the liquid film of bubbles on the liquid surface, while the overflow weir promptly introduces the floating microbubbles into a bypass static defoaming tank for physical separation. This combination of chemical defoaming and physical removal prevents excessive accumulation of microbubbles in the tank during quenching, which could lead to a decrease in the overall fluid density and specific heat capacity, thus maintaining the stability of the heat exchange area and cooling performance within the main quenching tank. Attached Figure Description

[0024] Figure 1 This is a bar chart comparing the local flow field gas content test results of the present invention. Figure 2 This is a kinetic curve of the foam volume change over time after gas is stopped for each test sample of the present invention; Figure 3 This is a biaxial graph showing the test results of the tooth root vapor film collapse temperature and the difference in cooling time between the tooth tip and tooth root according to the present invention. Figure 4 This is a diagram showing the distribution of residual stress along the depth direction in the root region of the gear ring of the present invention. Figure 5 The graphs showing the changes in bubbling characteristics and quenching hardness uniformity under different cyclic aging times are shown below. (a) is a line graph showing the change in bubbling volume with cyclic time; (b) is a line graph showing the change in surface hardness range of the workpiece with cyclic time. Figure 6 The graphs show the changes in heat transfer characteristics inside the blind hole under different ejector gas volumes according to the present invention. (a) is a line graph showing the change in vapor film collapse time at the bottom of the blind hole with the ejector gas volume; (b) is a line graph showing the change in maximum cooling rate at the bottom of the blind hole with the ejector gas volume. Detailed Implementation

[0025] The technical solutions in 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.

[0026] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing a high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer (a hysteretic defoamer), comprising the following steps: In an anhydrous high-pressure reactor equipped with a stirrer and temperature control system, propylene glycol was used as the initiator, and potassium hydroxide (0.3% by mass of the expected total feed amount) was added as a catalyst. After purging the reactor with nitrogen to replace the air, the temperature was raised to 110°C and vacuum was applied for dehydration. Subsequently, the pressure was restored to atmospheric pressure and the temperature was maintained at 110°C. Propylene oxide monomer was slowly added dropwise to the reactor, and the pressure inside the reactor was controlled at 0.2 MPa. Polymerization produced hydrophobic polyoxypropylene segments, and the weight-average molecular weight of the polyoxypropylene segments was controlled to be 6800. The reactor temperature was then maintained at 115°C, and ethylene oxide gas was continuously introduced into the reaction system to induce ring-opening block copolymerization at both ends of the polyoxypropylene segments. The amount of ethylene oxide grafting was controlled so that the hydrophilic polyoxyethylene segments accounted for 20% of the total mass of the copolymer. After the reaction was completed, the temperature was lowered to 80°C, and glacial acetic acid was added to neutralize the catalyst in the system to pH 6.0. The resulting inorganic salts were removed by vacuum dehydration and filtration, thus obtaining a high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer with a weight average molecular weight of 8500.

[0027] Preparation Example 2: This preparation example provides a method for preparing a high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer (a hysteretic defoamer), comprising the following steps: In an anhydrous high-pressure reactor equipped with a stirrer and a temperature control system, propylene glycol was used as the initiator, and potassium hydroxide with a mass fraction of 0.4% of the expected total feed amount was added as a catalyst. After nitrogen gas was introduced to replace the air in the reactor, the temperature was raised to 115°C and vacuum was applied for dehydration. Then, the pressure was restored to normal and the temperature was maintained at 115°C. Propylene oxide monomer was slowly added dropwise into the reactor while the pressure inside the reactor was controlled at 0.3 MPa. Polymerization was carried out to generate hydrophobic polyoxypropylene segments, and the weight average molecular weight of the polyoxypropylene segments was controlled at 7400. The reactor temperature was then maintained at 120°C, and ethylene oxide gas was continuously introduced into the reaction system to induce ring-opening block copolymerization at both ends of the polyoxypropylene segments. The amount of ethylene oxide grafting was controlled so that the hydrophilic segments of polyoxyethylene accounted for 22% of the total mass of the copolymer. After the reaction is complete, the temperature is lowered to 80°C, and glacial acetic acid is added to neutralize the catalyst in the system to pH 6.5. After vacuum dehydration and filtration to remove the generated inorganic salts, a high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer with a weight average molecular weight of 9500 is obtained.

[0028] Preparation Example 3: This preparation example provides a method for preparing a high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer (a hysteretic defoamer), comprising the following steps: In an anhydrous high-pressure reactor equipped with a stirrer and a temperature control system, propylene glycol was used as the initiator, and potassium hydroxide with a mass fraction of 0.5% of the expected total feed amount was added as a catalyst. After nitrogen gas was introduced to replace the air in the reactor, the temperature was raised to 120°C and vacuum was applied for dehydration. Then, the pressure was restored to normal and the temperature was maintained at 120°C. Propylene oxide monomer was slowly added dropwise into the reactor, and the pressure inside the reactor was controlled at 0.4 MPa. Polymerization was carried out to generate hydrophobic polyoxypropylene segments, and the weight average molecular weight of the polyoxypropylene segments was controlled at 8000. The reactor temperature was then maintained at 125°C, and ethylene oxide gas was continuously introduced into the reaction system to induce ring-opening block copolymerization at both ends of the polyoxypropylene segments. The amount of ethylene oxide grafting was controlled so that the hydrophilic segments of polyoxyethylene accounted for 25% of the total mass of the copolymer. After the reaction is complete, the temperature is lowered to 80°C, and glacial acetic acid is added to neutralize the catalyst in the system to pH 7.0. After vacuum dehydration and filtration to remove the generated inorganic salts, a high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer with a weight average molecular weight of 10,700 is obtained.

[0029] Examples 1-5: Example 1: This embodiment provides a manufacturing method for improving the fatigue life of a split flywheel ring gear, including the following steps: The first step is to prepare the water-based quenching medium: inject the remaining proportion of deionized water into the mixing vessel, maintain the water temperature at 30°C, turn on the stirrer and control the speed at 70 rpm, and add 9.0% polyether, 0.85% disodium sebate, 0.2% sodium molybdate and 0.35% sodium polyacrylate by mass fraction in sequence. After stirring until homogeneous, add 0.1% of the high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer obtained in Preparation Example 2 by mass fraction, and finally add 10% sodium hydroxide aqueous solution by mass fraction to adjust the pH value of the system to 9.0.

[0030] The second step is the machining and austenitization of the gear ring: 50Mn medium carbon steel forgings are selected and machined to prepare a split flywheel gear ring blank. The tooth profile surface is heated by a medium-high frequency induction heating device with a working frequency of 40kHz, so that the area of ​​the gear ring extending 2.5mm from the tooth tip to the tooth root reaches the austenitization temperature of 870℃, while the core temperature is kept below 400℃.

[0031] The third step, dynamic cavitation quenching stage: The gear ring is dropped into the quenching tank equipped with a bypass Venturi jet. At the moment the gear ring enters the water, the circulating pump of the quenching tank is controlled to run at full load to establish turbulence with a flow velocity of 1.1 m / s. At the same time, the Venturi jet is turned on to quantitatively inject industrial nitrogen gas with a purity of 99.99%. The injection amount is controlled to make the gas content of the local fluid reach 4.0%, and the gas-containing jet is maintained for 3.0 seconds.

[0032] The fourth step, mesoscopic regulation cooling and auxiliary defoaming stage: turn off the nitrogen ejector, reduce the frequency of the circulating pump to transition the flow field to a laminar flow state with a flow velocity of 0.25 m / s, and use the thermal conductivity limitation of the polymer film to control the cooling rate at 20℃ / s. Microbubbles that escape to the liquid surface are scraped into the bypass static defoaming tank through the overflow weir at the top of the quenching tank at a surface flow velocity of 0.75 m / s. After the overall temperature of the gear ring drops below 80℃, it is removed from the quenching tank.

[0033] Step 5, tempering treatment: The gear ring is sent into the tempering furnace and held at 190℃ for 1.75 hours, and then air-cooled to room temperature.

[0034] Example 2: This embodiment provides a manufacturing method for improving the fatigue life of a split flywheel ring gear, including the following steps: The first step is to prepare the water-based quenching medium: inject the remaining proportion of deionized water into the mixing tank, maintain the water temperature at 25°C, turn on the stirrer and control the speed at 60 rpm, and add 8.0% polyether, 0.5% disodium sebate, 0.1% sodium molybdate and 0.2% sodium polyacrylate by mass fraction in sequence. After stirring until homogeneous, add 0.05% of the high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer obtained in Preparation Example 1 by mass fraction, and finally add 10% sodium hydroxide aqueous solution by mass fraction to adjust the pH value of the system to 8.5.

[0035] The second step is the machining and austenitization of the gear ring: 50Mn medium carbon steel forgings are selected and machined to prepare a split flywheel gear ring blank. The tooth profile surface is heated by a medium-high frequency induction heating device with a working frequency of 30kHz, so that the area of ​​the gear ring extending 2.0mm from the tooth tip to the tooth root reaches an austenitization temperature of 860℃, while the core temperature is kept below 400℃.

[0036] The third step, dynamic cavitation quenching stage: The gear ring is dropped into the quenching tank equipped with a bypass Venturi jet. At the moment the gear ring enters the water, the circulating pump of the quenching tank is controlled to run at full load to establish turbulence with a flow velocity of 1.0 m / s. At the same time, the Venturi jet is turned on to quantitatively inject industrial nitrogen gas with a purity of 99.99%. The injection amount is controlled to make the gas content of the local fluid reach 3.0%, and the gas-containing jet is maintained for 2.0 seconds.

[0037] The fourth step, mesoscopic regulation cooling and auxiliary defoaming stage: turn off the nitrogen ejector, reduce the frequency of the circulating pump to transition the flow field to a laminar flow state with a flow velocity of 0.2 m / s, and use the thermal conductivity limitation of the polymer film to control the cooling rate at 15℃ / s. Microbubbles that escape to the liquid surface are scraped into the bypass static defoaming tank through the overflow weir at the top of the quenching tank at a surface flow velocity of 0.5 m / s. Remove the gear ring from the quenching tank when the overall temperature drops below 80℃.

[0038] Step 5, tempering treatment: The gear ring is sent into the tempering furnace and held at 180°C for 1.5 hours, and then air-cooled to room temperature.

[0039] Example 3: This embodiment provides a manufacturing method for improving the fatigue life of a split flywheel ring gear, including the following steps: The first step is to prepare a water-based quenching medium: inject the remaining proportion of deionized water into the mixing vessel, maintain the water temperature at 35°C, turn on the stirrer and control the speed at 80 rpm, and add 10.0% polyether, 1.2% disodium sebate, 0.3% sodium molybdate and 0.5% sodium polyacrylate by mass fraction in sequence. After stirring until homogeneous, add 0.15% of the high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer obtained in Preparation Example 3 by mass fraction, and finally add 10% sodium hydroxide aqueous solution by mass fraction to adjust the pH value of the system to 9.5.

[0040] The second step is the machining and austenitization of the gear ring: 50Mn medium carbon steel forgings are selected and machined to prepare a split flywheel gear ring blank. The tooth profile surface is heated by a medium-high frequency induction heating device with a working frequency of 50kHz, so that the area of ​​the gear ring extending 3.0mm from the tooth tip to the tooth root reaches an austenitization temperature of 880℃, while the core temperature is kept below 400℃.

[0041] The third step, dynamic cavitation quenching stage: The gear ring is dropped into the quenching tank equipped with a bypass Venturi jet. At the moment the gear ring enters the water, the circulating pump of the quenching tank is controlled to run at full load to establish turbulence with a flow velocity of 1.2 m / s. At the same time, the Venturi jet is turned on to quantitatively inject industrial nitrogen gas with a purity of 99.99%. The injection amount is controlled to make the gas content of the local fluid reach 5.0%, and the gas-containing jet is maintained for 4.0 seconds.

[0042] The fourth step, mesoscopic regulation cooling and auxiliary defoaming stage: turn off the nitrogen ejector, reduce the frequency of the circulating pump to transition the flow field to a laminar flow state with a flow velocity of 0.3 m / s, and use the thermal conductivity limitation of the polymer film to control the cooling rate at 25℃ / s. Microbubbles that escape to the liquid surface are scraped into the bypass static defoaming tank through the overflow weir at the top of the quenching tank at a surface flow velocity of 1.0 m / s. Remove the gear ring from the quenching tank when the overall temperature drops below 80℃.

[0043] Step 5, tempering treatment: The gear ring is sent into the tempering furnace and held at 200℃ for 2.0 hours, and then air-cooled to room temperature.

[0044] Example 4: This embodiment provides a manufacturing method for improving the fatigue life of a split flywheel ring gear, including the following steps: The first step is to prepare a water-based quenching medium: inject the remaining proportion of deionized water into the mixing vessel, maintain the water temperature at 30°C, turn on the stirrer and control the speed at 70 rpm, and add 9.5% polyether, 1.0% disodium sebate, 0.25% sodium molybdate and 0.4% sodium polyacrylate by mass fraction in sequence. After stirring until homogeneous, add 0.12% of the high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer obtained in Preparation Example 3 by mass fraction, and finally add 10% sodium hydroxide aqueous solution by mass fraction to adjust the pH value of the system to 9.2.

[0045] The second step is the machining and austenitization of the gear ring: 50Mn medium carbon steel forgings are selected and machined to prepare a split flywheel gear ring blank. The tooth profile surface is heated by a medium-high frequency induction heating device with a working frequency of 35kHz, so that the area of ​​the gear ring extending 2.2mm from the tooth tip to the tooth root reaches the austenitization temperature of 865℃, while the core temperature is kept below 400℃.

[0046] The third step, dynamic cavitation quenching stage: The gear ring is dropped into the quenching tank equipped with a bypass Venturi jet. At the moment the gear ring enters the water, the circulating pump of the quenching tank is controlled to run at full load to establish turbulence with a flow velocity of 1.05 m / s. At the same time, the Venturi jet is turned on to quantitatively inject industrial nitrogen gas with a purity of 99.99%. The injection amount is controlled to make the gas content of the local fluid reach 3.5%, and the gas-containing jet is maintained for 2.5 seconds.

[0047] The fourth step, mesoscopic regulation cooling and auxiliary defoaming stage: turn off the nitrogen ejector, reduce the frequency of the circulating pump to transition the flow field to a laminar flow state with a flow velocity of 0.22 m / s, and use the thermal conductivity limitation of the polymer film to control the cooling rate at 18℃ / s. Microbubbles that escape to the liquid surface are scraped into the bypass static defoaming tank through the overflow weir at the top of the quenching tank at a surface flow velocity of 0.6 m / s. Remove the gear ring from the quenching tank when the overall temperature drops below 80℃.

[0048] Step 5, tempering treatment: The gear ring is sent into the tempering furnace and held at 185°C for 1.6 hours, and then air-cooled to room temperature.

[0049] Example 5: This embodiment provides a manufacturing method for improving the fatigue life of a split flywheel ring gear, including the following steps: The first step is to prepare the water-based quenching medium: inject the remaining proportion of deionized water into the mixing tank, maintain the water temperature at 30°C, turn on the stirrer and control the speed at 70 rpm, and add 8.5% polyether, 0.6% disodium sebate, 0.15% sodium molybdate and 0.25% sodium polyacrylate by mass fraction in sequence. After stirring until homogeneous, add 0.08% of the high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer obtained in Preparation Example 1 by mass fraction, and finally add 10% sodium hydroxide aqueous solution by mass fraction to adjust the pH value of the system to 8.8.

[0050] The second step is the machining and austenitization of the gear ring: 50Mn medium carbon steel forgings are selected and machined to prepare a split flywheel gear ring blank. The tooth profile surface is heated by a medium-high frequency induction heating device with a working frequency of 45kHz, so that the area of ​​the gear ring extending 2.8mm from the tooth tip to the tooth root reaches the austenitization temperature of 875℃, while the core temperature is kept below 400℃.

[0051] The third step, dynamic cavitation quenching stage: The gear ring is dropped into the quenching tank equipped with a bypass Venturi jet. At the moment the gear ring enters the water, the circulating pump of the quenching tank is controlled to run at full load to establish turbulence with a flow velocity of 1.15 m / s. At the same time, the Venturi jet is turned on to quantitatively inject industrial nitrogen gas with a purity of 99.99%. The injection amount is controlled to make the gas content of the local fluid reach 4.5%, and the gas-containing jet is maintained for 3.5 seconds.

[0052] The fourth step, mesoscopic regulation cooling and auxiliary defoaming stage: turn off the nitrogen ejector, reduce the frequency of the circulating pump to transition the flow field to a laminar flow state with a flow velocity of 0.28 m / s, and use the thermal conductivity limitation of the polymer film to control the cooling rate at 22℃ / s. Microbubbles that escape to the liquid surface are scraped into the bypass static defoaming tank through the overflow weir at the top of the quenching tank at a surface flow velocity of 0.8 m / s. After the overall temperature of the gear ring drops below 80℃, it is removed from the quenching tank.

[0053] Step 5, tempering treatment: The gear ring is sent into the tempering furnace and held at 195℃ for 1.8 hours, and then air-cooled to room temperature.

[0054] Comparative Examples 1-6: Comparative Example 1: Compared with Example 1, the difference is that this comparative example uses the existing water-based quenching process. Its water-based quenching medium consists only of 9.0% polyether (PAG) by mass and the balance deionized water. No disodium sebacate, sodium molybdate, sodium polyacrylate, or high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer is added. In addition, in the third step of dynamic cavitation quenching, the venturi jet injector is not turned on to inject nitrogen gas. Only pure liquid phase flushing with a flow rate of 1.1 m / s is maintained. All other aspects are the same.

[0055] Comparative Example 2: Compared with Example 1, the difference is that in the third step of dynamic cavitation quenching, the Venturi jet injector is not turned on to inject nitrogen gas, and only pure liquid phase scouring with a flow rate of 1.1 m / s is maintained. All other aspects are the same.

[0056] Comparative Example 3: Compared with Example 1, the difference is that the water-based quenching medium in this comparative example consists only of 9.0% polyether (PAG) by mass and the balance deionized water, without the addition of disodium sebacate, sodium molybdate, sodium polyacrylate and high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer, while all other components are the same.

[0057] Comparative Example 4: Compared with Example 1, the difference is that sodium molybdate is not added to the water-based quenching medium in this comparative example, but all other aspects are the same.

[0058] Comparative Example 5: Compared with Example 1, the difference is that in this comparative example, 0.1% by mass of high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer is replaced by an equal amount of commercial fast-acting silicone defoamer (polyether modified siloxane), and all other aspects are the same.

[0059] Comparative Example 6: Compared with Example 1, the difference is that no high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer (i.e., no defoamer) is added to the water-based quenching medium in this comparative example, while all other aspects are the same.

[0060] Test Examples 1-6: Test Example 1: This test aims to verify whether, under a specific flow rate, opening a Venturi jet and using the sodium sebacic acid and sodium polyacrylate formulation of this invention can stably generate a gas-liquid two-phase flow with a gas content of 3.0%-5.0% in a local flow field within a very short pulse aeration period of 2-4 seconds. The test subjects are the water-based quenching medium stock solutions prepared in Examples 1-5 and Comparative Examples 2 and 3.

[0061] The testing process is as follows: 1. In a simulated quenching tank with a volume of 500L, an industrial Venturi jet injector is connected in series with the outlet bypass of the guide pipe. A high-frequency conductivity probe (sampling frequency 1000Hz) is rigidly installed at the center of the pipe cross-section 15cm downstream of the jet injector outlet to capture the volume fraction change of microbubbles flowing through that point.

[0062] 2. Pour each set of test solutions into the tank to the standard liquid level, keep it cold (30℃) and do not put in the gear ring.

[0063] 3. Turn on the variable frequency circulation pump of the quenching tank and adjust it to the steady-state flow rate set in each embodiment or comparative example.

[0064] 4. After the liquid flow stabilizes, the solenoid valve instantly opens the Venturi ejector and quantitatively ejects industrial nitrogen gas with a purity of 99.99%, with the ejection time set to 3 seconds, and then the gas valve is closed. The conductivity signal is continuously recorded from 0 to 5 seconds throughout the entire process, and the time-domain conductivity signal is converted into local volumetric gas content using Maxwell's equations.

[0065] 5. Extract the average gas content during the inflation period (1.0-4.0 seconds) and the residual gas content 1.0 second after the valve is closed (i.e., the 5.0 second). To ensure data reliability, each test is repeated three times, and the arithmetic mean is taken as the final recorded data.

[0066] Table 1. Test data of local flow field gas content of each group of quenching media during and after pulse aeration. Figure 1 The horizontal axis represents Examples 1-5, Comparative Examples 2 and 3, respectively, and the vertical axis represents the percentage of gas content. Dark gray bars represent the average gas content during the aeration period (1.0-4.0 s), and light gray bars represent the residual gas content 1.0 s after aeration. (Based on Table 1 and...) Figure 1 According to the data from Examples 1 to 5, during the pulse air injection period of 1.0 to 4.0 seconds, the average gas content of the local flow field remained between 3.12% and 4.88%. This indicates that by using a Venturi jet injector in conjunction with the aforementioned chemical formula, the designed gas content target of 3.0% to 5.0% can be achieved in a short time. Under this gas content condition, the microbubbles can acquire sufficient kinetic energy to disrupt the vapor film formed on the high-temperature tooth root surface, while avoiding flow field resistance caused by excessive gas volume. After the gas valve is closed for 1 second, the gas content of each example drops back to close to 1% (the specific residual value is between 0.65% and 1.04%), indicating that the microbubbles generated by this system have the characteristic of rapid dissipation and can meet the cooling control requirements of subsequent frequency reduction and laminar flow conversion.

[0067] Compared with the examples, the test results of the comparative examples further verified the necessity of the synergistic effect of the formulation of the present invention. In Comparative Example 2, due to the absence of gas introduction, the measured trace gas content was only a small amount of gas entrained by the background turbulence of the fluid (test values ​​were only 0.05% and 0.02%, respectively), making it impossible to form a membrane-breaking two-phase flow. In Comparative Example 3, under the same flow rate and aeration conditions, because disodium sebate and sodium polyacrylate, which act as rapid diffusion membrane-breaking inducers, were removed from the system, the average gas content during the aeration period was only 1.83%, and the residual gas content 1.0 second after the aeration ended dropped to 0.14%. This indicates that in the absence of small-molecule surfactants to stabilize the nascent gas-liquid interface, the nitrogen microbubbles generated by the Venturi tube coalesced after leaving the nozzle. After coalescence, the bubble volume increased, and due to buoyancy, it deviated from the central region of the guide tube, resulting in a reduction in the number of microbubbles reaching the root region, failing to meet the kinetic energy and density requirements for breaking the vapor film. These experimental phenomena indicate that it is difficult to establish a stable phase change flow field by relying solely on mechanical gas supply. It is necessary to use small molecule foam stabilizers to maintain the morphology of physical cavitation microbubbles, which is the basis for achieving this process goal.

[0068] Test Example 2: This test case aims to verify, through static foam decay measurement, whether the high molecular weight block copolymer defoamer synthesized in this invention possesses an interfacial diffusion lag effect of more than 15 seconds in a water-based quenching medium, thereby achieving time window control for early foam retention and later foam destruction. The experimental subjects were the water-based quenching media prepared in Examples 1, 3, and 5, as well as the water-based quenching media of Comparative Example 5 (containing a commercially available fast-acting silicone defoamer) and Comparative Example 6 (containing no defoamer).

[0069] The experimental procedure is as follows: 1. Build a Roche foam test platform that meets industry standards. The temperature inside the glass measuring cylinder is strictly controlled at 30℃ through a constant temperature water bath jacket to simulate the basic properties of the quenching medium in a cold state.

[0070] 2. Pour 200mL of the quenching medium stock solution to be tested into the test measuring cylinder and let it stand for 5 minutes to eliminate internal air bubbles.

[0071] 3. Start the miniature air pump connected to the standard porous glass gas distributor at the bottom of the measuring cylinder, set the gas flow meter to a constant flow rate of 2.5 L / min, and continue bubbling for 60 seconds to allow the system to fully foam.

[0072] 4. Turn off the air pump and simultaneously press the stopwatch to read and record the static macroscopic foam volume in the graduated cylinder at the instant the air pump stops (i.e., second 0).

[0073] 5. Keep the environment vibration-free, continue to observe and record the residual foam volume at 3 seconds, 15 seconds, and 30 seconds. Repeat the test three times with a new sample for each liquid, and take the arithmetic mean of the results and round it to the nearest integer.

[0074] Table 2. Macroscopic foam volume changes of each test sample at different times after gas shut-off Figure 2 The five broken lines with different line types and markings represent the water-based quenching media of Examples 1, 3, 5, and Comparative Examples 5 and 6, respectively, and the decay process of foam volume over time within the 0 to 30 seconds after the bubbling ends. Specifically, the solid line marked with a dark gray filled circle represents Example 1, the dashed line marked with a medium gray filled square represents Example 3, the dotted line marked with a light gray filled upward triangle represents Example 5; the dotted line marked with a hollow diamond represents Comparative Example 5, and the solid line marked with an asterisk represents Comparative Example 6.

[0075] According to Table 2 and Figure 2 The data from the examples and comparative examples show different trends in the foam volume decay curves after gas depletion. The volume change processes of Examples 1, 3, and 5 are observed. Figure 2 The three broken lines in the middle section show that, within the 0-3 second time period, the foam volume of the fluid did not decrease, and the overall attenuation rate was controlled at around 5%, corresponding to the almost horizontal line segment in the 0-3 second interval of the figure. This initial foam retention characteristic is consistent with the time required for microbubbles to travel with the jet to the surface of the gear ring during quenching. In a real industrial quenching tank, it typically takes 1.5 to 2.5 seconds for microbubbles generated by the jet injector to be pumped to the surface of the heated workpiece. In the example system, the bubbles did not burst in large numbers during this stage, ensuring that a sufficient number of microbubbles existed in the gas-liquid two-phase flow reaching the root region of the gear.

[0076] As the settling time continued for 15 seconds, the foam volume of the sample in the example decreased, and dropped to approximately 50 mL after 30 seconds. Figure 2 The line segment slopes downwards after 15 seconds. This is because the spread of block copolymers with a weight-average molecular weight of 8000 to 10000 or higher at the water / air interface requires overcoming certain resistance, resulting in a time delay in the adsorption of macromolecules at the microbubble interface, which macroscopically manifests as a delayed start of the defoaming effect. As the microbubbles complete their disturbance of the vapor film and float to the surface of the tank with the liquid flow, the lag-type defoamer is gradually adsorbed to the gas-liquid interface, replacing the small-molecule surfactant disodium sebate that originally played a foam-stabilizing role. The instability of the bubble double layer then triggers bubble collapse.

[0077] In contrast to Comparative Example 5 Figure 2The bottom line closest to the horizontal axis uses a conventional fast-acting silicone defoamer, which initially produces only 145 mL of foam at 0 seconds, decreasing to 82 mL at 3 seconds. Due to the rapid defoaming speed, most microbubbles break down before contacting the tooth root area, reducing the scouring effect of the gas-liquid two-phase flow. Comparative Example 6 corresponds to... Figure 2 The topmost flat solid line, lacking any added defoaming component, showed almost no volume loss of foam within 30 seconds. Test results indicate that controlling the onset time of the defoamer avoids foam accumulation problems in continuous quenching processes.

[0078] Test Example 3: This test case primarily verifies the intervention effect of water-based quenching media on the vapor film collapse behavior in the narrow root region of the gear ring after introducing microbubble two-phase flow and components such as sodium molybdate. The experimental subjects included the quenching media prepared in Examples 1, 2, and 4, as well as the conventional PAG aqueous solution in Comparative Example 1 (without gas ejection) and the quenching media in Comparative Example 4 (with gas ejection but without sodium molybdate).

[0079] The experimental procedure is as follows: 1. A split flywheel gear ring made of 50Mn medium carbon steel was selected as the standard test sample. Temperature measurement blind holes with a diameter of 1.5mm were machined in the tooth tip area and the bottom of the tooth root fillet, respectively, and the hole depth was controlled to be 2mm below the surface.

[0080] 2. Insert the K-type armored thermocouple into the temperature measurement blind hole, use an energy storage spot welder to firmly weld the thermocouple measuring end to the metal substrate at the bottom of the hole, and seal the hole with high-temperature inorganic adhesive.

[0081] 3. Place the gear ring sample equipped with a thermocouple into a medium-frequency induction heating furnace and heat it to 880℃ at the set heating rate. Hold it at this temperature for 5 minutes to homogenize the temperature of the sample cross-section.

[0082] 4. Start the circulation pump and data acquisition system of the quenching tank, set the acquisition frequency to 100Hz, quickly immerse the heated sample into the quenching medium to be tested at a constant temperature of 30℃, execute the quenching program according to the parameters of each embodiment or comparative example, and record the temperature data of the entire process of the sample cooling to room temperature.

[0083] 5. Extract the inflection point where the slope of the cooling curve at the tooth root changes abruptly from the output temperature-time data, record it as the vapor film collapse temperature, and extract the time difference between the tooth tip and tooth root when the temperature drops to 650℃, which is recorded as the time difference. Three parallel samples are tested for each group of media, and the arithmetic mean is taken as the recorded data.

[0084] Table 3. Test data on the vapor film breakdown temperature at the tooth root and the difference in cooling time between the tooth tip and tooth root for each group of quenching media. Figure 3The horizontal axis represents different test objects (Example 1, Example 2, Example 4, Comparative Example 1, Comparative Example 4), the left vertical axis and the light gray bar chart represent the root vapor film collapse temperature (unit: °C), and the right vertical axis and the broken line with dark gray square marks represent the time difference between the tooth tip and the tooth root dropping to 650 °C (unit: s).

[0085] According to Table 3 and Figure 3 Data, the root vapor film rupture temperature in Examples 1, 2, and 4 are as follows: Figure 3 The three taller pillars on the left side of the image show temperatures concentrated between 638℃ and 652℃. Under conventional liquid-phase quenching conditions, due to the limited geometric space at the root of the gear ring, the fluid exchange capacity is weak, and the vapor film formed by the vaporization of the liquid quenching medium adheres to the metal surface and remains at a relatively low temperature. Taking Comparative Example 1 as an example, when using a readily available pure PAG aqueous solution for quenching, the fracture temperature in the gear root region is only 421.6℃ (corresponding to...). Figure 3 The lowest column in the middle, resulting in a time difference of 4.75 seconds between the tooth tip and root dropping to the critical phase transition temperature of 650°C. Figure 3 The highest peak of the broken line. This asynchronous cooling causes differences in martensitic transformation time, resulting in residual tensile stress at the tooth root.

[0086] In this embodiment, the introduction of a Venturi jet and a specific gas content provided the physical kinetic energy to break the gas film, raising the breakup temperature by over 200°C. To verify the effect of sodium molybdate on the film-breaking behavior, Comparative Example 4, while maintaining the same flow rate and aeration conditions as Example 1, removed the inorganic salt component, sodium molybdate. The measured breakup temperature was 518.2°C, with a time difference of 2.81 seconds. Figure 3 The results show that the height of the column and the position of the broken line point are both between those of Example 1 and Comparative Example 1. This result is an improvement over Comparative Example 1 with pure liquid phase, but it still fails to achieve synchronization of the cooling curves of the tooth tip and tooth root. In this scheme, the precipitation of locally supersaturated sodium molybdate at the high-temperature transient gas-liquid-solid three-phase interface provides a low-energy-barrier heterogeneous nucleation site, reducing the difficulty for the liquid phase to break through the vapor film and undergo nucleation boiling, thus preventing the gas film structure from becoming unstable. Comparing the test results of Example 1 and Comparative Example 4, it can be seen that the microbubbles generated by physical cavitation and the chemical nucleating agent sodium molybdate work together to raise the vapor film collapse temperature to around 650°C. This temperature is above the nose temperature of the pearlite transformation of medium carbon steel, and the test data shows that the time difference between the tooth tip and tooth root in the phase transformation sensitive region is controlled within 1.2 seconds (e.g., ...). Figure 3 (The broken line segments corresponding to the Chinese embodiments are all at low positions), which proves the effectiveness of the process and formula parameters of this solution in eliminating the cooling hysteresis of structural components from the perspective of heat transfer.

[0087] Test Example 4: This test aims to evaluate the effect of gas-liquid co-firing quenching process on improving the final macroscopic mechanical properties of complex-shaped structural parts by testing the residual stress depth distribution. Five 50Mn medium carbon steel split flywheel gear ring samples from the aforementioned quenching batches were selected as experimental subjects, corresponding to Examples 1, 3, and 5, respectively, as well as Comparative Example 1 (pure PAG medium without gas injection) and Comparative Example 3 (with the rapid foam stabilizer removed).

[0088] The experimental procedure is as follows: 1. Extract the cooled gear ring sample from the corresponding processing batch, and use a CNC wire EDM machine to cut a 15mm × 15mm metal block from the tooth root fillet of the sample. Coolant flushing is maintained throughout the cutting process to prevent secondary tempering from affecting internal residual stress.

[0089] 2. The cut sample was cold-mounted with epoxy resin, then placed on an automatic polishing machine, and water-polished with silicon carbide sandpaper of different grits in sequence. Finally, 3μm diamond polishing paste was applied to the surface to complete mechanical polishing and remove the cutting damage layer on the surface.

[0090] 3. The residual stress distribution of the surface and subsurface layers of the tooth root of the sample was determined using an X-ray diffractometer. Cr-Kα radiation and the (211) crystal plane were selected as the diffraction planes during the test, and sin... 2 Stress calculation is performed using the ψ method.

[0091] 4. To obtain stress data at different depths, a constant current electropolishing method was used to peel off the metal layer layer by layer. The electrolyte formula and corrosion current parameters were set, and the metal was peeled off to depths of 0.05 mm, 0.15 mm, 0.30 mm and 0.50 mm from the surface in sequence. X-ray diffraction measurements were performed immediately after each peeling.

[0092] 5. For each test object, three different tooth root locations are randomly selected and the above peeling and measurement process is repeated. After removing outliers with excessive dispersion, the arithmetic mean of the residual stress data at the same depth is taken as the final record.

[0093] Table 4: Residual stress distribution data of different depth layers in the root region of the gear ring after quenching medium treatment. (Note: Negative values ​​in the data represent residual compressive stress, and positive values ​​represent residual tensile stress) Figure 4The horizontal axis represents the detection depth from the tooth root surface, and the vertical axis represents the residual stress value. The horizontal solid line in the figure is the zero-stress baseline. The solid line marked with a dark gray filled circle represents Example 1, the dashed line marked with a medium gray filled square represents Example 3, and the dotted line marked with a light gray filled upward triangle represents Example 5. The dotted line marked with a hollow diamond represents Comparative Example 1, and the solid line marked with an asterisk represents Comparative Example 3.

[0094] According to Table 4 and Figure 4 The data show that the distribution of residual stress depth at the tooth root varies after treatment with different quenching media. The test results for Examples 1, 3, and 5 correspond to... Figure 4 The three broken lines in the lower region exhibit stable compressive stress in the subsurface region from 0.05 mm to 0.50 mm, and are distributed below the zero baseline in the figure. These three curves all show extreme points at a depth of 0.15 mm, corresponding to compressive stress peaks exceeding 400 MPa. Combined with the cooling rate evolution observed in previous tests, when the phase transformation time difference between the tooth tip and root is controlled within 1 second, the order of martensitic transformation within the cross-section changes. After the surface material preferentially undergoes volume expansion, the subsequent phase transformation in the core exerts pressure on it. This combined effect of structural stress and thermal stress is the mechanical basis for the formation of surface compressive stress. The existence of surface compressive stress can offset the alternating loads borne by the gear ring during service, playing a practical role in extending the fatigue life of the component.

[0095] For the traditional pure liquid phase quenching method, Comparative Example 1 corresponds to Figure 4 The uppermost dotted line, failing to overcome the vapor film barrier at the tooth root region, resulted in a slower local cooling rate and delayed phase transformation. This uneven thermal distribution meant that Comparative Example 1 failed to achieve compressive stress in the 0.05mm and 0.15mm surface layers, instead exhibiting residual tensile stresses of 85MPa and 12MPa, respectively. The presence of tensile stress in the surface layer makes the workpiece prone to microcracks during subsequent assembly or grinding. Comparative Example 3 corresponds to... Figure 4 Although the solid line marked with an asterisk indicates that gas ejection has been initiated, the lack of surfactants such as disodium sebate to stabilize the nascent gas-liquid interface causes microbubbles to coalesce and deviate from the target scouring area during transport. The residual stress curve is generally higher than that of the example, and rapidly approaches zero as it extends inward, indicating low surface compressive stress that decays quickly towards the interior. By controlling bubble size through chemical composition and combining it with the fluid dynamics design of the Venturi tube, uniform cooling of surfaces with complex geometries can be achieved. The stress distribution test results verify the effectiveness of this phase change flow field control process in heat treatment quality control.

[0096] Test Example 5: This test case primarily verifies the shear stability of water-based quenching media under continuous air jet conditions, and evaluates the impact of long-term high-speed fluid circulation on the media's foaming control capability and the uniformity of hardness in quenched workpieces. The experimental subjects included the quenching media prepared in Examples 1 and 5, as well as Comparative Example 5 using a commercially available conventional silicone defoamer and Comparative Example 6 without any added defoaming components.

[0097] The experimental procedure is as follows: 1. Take 50 liters of each group of prepared water-based quenching media and inject them into the simulation tanks equipped with Venturi ejectors and circulating pumps. Set the outlet flow rate of the circulating pump to 5 m / s and the air intake of the ejector to 0.5 L / min. Turn on the equipment to conduct a continuous and uninterrupted cyclic shear aging test, during which the temperature of the tank liquid is controlled to be stable at 35℃.

[0098] 2. At four time points—0 hours, 48 ​​hours, 96 hours, and 144 hours—500 mL samples were taken from the outlet of each simulation tank. The samples were transferred to a standard graduated cylinder, and aeration was carried out at the standard flow rate for 30 seconds. The maximum macroscopic foam volume generated by the medium at the moment of gas cessation was recorded.

[0099] 3. While taking the above-mentioned foaming amount sample, a standard round bar sample of 50Mn medium carbon steel with a diameter of 20mm and a length of 100mm, which has been preheated to 880℃ in an electric furnace and held for 30 minutes, is vertically placed into the running simulation tank and quenched and cooled to room temperature.

[0100] 4. Take out the cooled round bar sample, cut off the middle section along the radial direction, grind and mechanically polish it, and use a Rockwell hardness tester to uniformly select 8 test points in the circumferential direction of the cross-section edge to determine the hardness.

[0101] 5. Calculate the difference between the maximum and minimum hardness values ​​of these 8 test points on the same cross section, and count it as the surface hardness range. Use this index to evaluate the uniformity of the cooling capacity of the medium at different aging stages.

[0102] Table 5. Data on foam volume and hardness range of each test medium after different cyclic aging times. Figure 5 The figures are arranged vertically into two sub-figures: (a) shows the maximum foam volume (mL) on the ordinate; and (b) shows the hardness range (HRC) on the ordinate. In both sub-figures, solid lines marked with dark gray filled circles represent Example 1, dashed lines marked with light gray filled squares represent Example 5, dotted lines marked with hollow rhombuses represent Comparative Example 5, and solid lines marked with asterisks represent Comparative Example 6.

[0103] According to Table 5 and Figure 5Data shows that different quenching media exhibit varying foam suppression capabilities and cooling uniformity after prolonged cyclic shearing. In conventional heat treatment industrial settings, the circulating pumps within the quenching tank typically require continuous operation to maintain a uniform overall flow field, placing the medium under constant physical shearing. For example... Figure 5 (a) As shown by the smooth zigzag line at the bottom, in Examples 1 and 5, the maximum foaming volume remained between 140 and 155 mL during continuous fluid circulation for up to 144 hours. The corresponding hardness difference of the round bar cross-section was controlled within 1.6 HRC. Figure 5 (b) The low-lying, gently folded line at the bottom. The block copolymer defoamer selected in this scheme has a long-chain polymer structure, which mainly regulates the interfacial tension through the physical spreading of molecular chain segments at the water-air interface. This physical adsorption mechanism, which relies on macromolecular steric hindrance and conformational changes, has strong resistance to mechanical shearing, ensuring the long-term interfacial activity of the medium under continuous aeration conditions.

[0104] The performance of Comparative Example 5, using a commercially available silicone defoamer, decreased with increasing cycle time. At the initial stage of the test (0 h), Comparative Example 5 produced 144.6 mL of foam, comparable to the initial defoaming ability of the examples. However, after cycling for 96 hours, the foam production increased, reaching 392.7 mL at 144 hours. Figure 5 (a) The upward curve with a gradually increasing slope. This is mainly related to the state of organosilicon in the water-based system. Silicone oil components usually need to be dispersed in water with the help of emulsifiers to form tiny emulsion droplets. Long-term pumping and high-frequency fluid impact inside the Venturi tube will gradually destroy the surface protective layer of these latex particles, causing the effective components to agglomerate and precipitate locally in the bath. The precipitation of defoaming components causes the medium to generate a large amount of macroscopic foam that cannot be broken in time, causing a regional imbalance in quenching cooling capacity. In terms of workpiece cooling quality, the hardness difference of Comparative Example 5 widened to 4.67 HRC in the later stage of the test ( Figure 5 (b) The corresponding dotted lines show a synchronous upward trend, indicating that the disorderly accumulation of unbroken bubbles on the metal surface interferes with the local boiling heat transfer process.

[0105] Comparative Example 6 serves as a reference system without added defoaming components; its data are... Figure 5 The foam layer was at its highest position in both (a) and (b). Throughout the test cycle, the foam volume remained above 500 mL, and the workpiece hardness range fluctuated around 4.0 HRC. The stable foam layer blocked the contact erosion of the fluid, resulting in uneven temperature distribution along the circumference of the workpiece. The test results confirm that large-scale continuous production requires the use of polymeric interface control components with shear stability to maintain flow field stability and phase change heat uniformity.

[0106] Test Example 6: This test case aims to investigate the effect of gas flow rate (gas content) of a Venturi ejector on the heat transfer characteristics inside a complex confined space, and to evaluate the actual ability of different quenching media to break the vapor film and increase the local cooling rate in dead flow areas such as blind holes. Example 2 prepared as described above, Example 4 with sodium molybdate removed, and Comparative Example 1 using pure PAG aqueous solution were selected as test subjects.

[0107] The experimental steps are as follows: 1. Select a cylindrical sample made of 42CrMo material, with dimensions of 30mm in diameter and 80mm in length. Machin a blind hole with a diameter of 10mm and a depth of 60mm at the center of the sample end face. Drill a temperature measuring hole along the side wall of the sample, embed the measuring end of the K-type thermocouple in the subsurface area 5mm from the bottom of the blind hole, and seal and fix it with high-temperature resistant putty.

[0108] 2. Prepare 100-liter volumes of quenching media for Examples 2, 4, and Comparative Example 1, respectively, and inject them sequentially into test tanks equipped with variable-speed circulating pumps and Venturi ejectors. Turn on the temperature control system to maintain the tank temperature at a stable 40°C.

[0109] 3. Adjust the gas flow rate of the Venturi ejector using the flow control valve, selecting five different gas flow rates of 0, 2.0, 4.0, 6.0, and 8.0 L / min sequentially during the test. After adjusting to each flow rate, allow the circulation equipment to run unloaded for 15 minutes to allow the flow field to reach a dynamically stable state.

[0110] 4. Place the sample with the thermocouple in a box-type resistance furnace, heat it to 860℃ and hold it at that temperature for 45 minutes. Then quickly transfer it to the test tank, keeping the blind hole opening facing upwards, and immerse it vertically above the ejector area for quenching.

[0111] 5. Use a data acquisition instrument to record the temperature and time data of the sample from liquid immersion to cooling to room temperature. Differentially process the cooling curve to extract the starting point of the rising edge of the cooling rate curve corresponding to the vapor film collapse time at the bottom of the blind hole, and the maximum cooling rate. Use this as a cooling evaluation index under different operating conditions. Repeat the above steps after changing the medium to obtain multiple sets of data.

[0112] Table 6. Test data of heat transfer characteristics at the bottom of the blind hole for each medium under different ejector gas rates Figure 6 The graph contains two subgraphs arranged vertically: (a) has the vertical axis representing the collapse time (in seconds); and (b) has the vertical axis representing the maximum cooling rate (in °C / s). In both subgraphs, the solid line marked with a dark gray circle represents Example 2, the dashed line marked with a light gray square represents Example 4, and the dotted line marked with a hollow triangle represents Comparative Example 1.

[0113] According to Table 6 and Figure 6 The data shows that the Venturi ejector gas flow rate has a nonlinear effect on the local heat transfer efficiency of deep blind hole structures. In heat treatment engineering practice, geometrically confined spaces such as blind holes and deep cavities, due to obstructed fluid exchange, are often the regions with the longest vapor film residence time and are most prone to phase transition hysteresis. Under pure liquid phase circulation conditions with an ejector gas flow rate of 0 L / min, the vapor film breakdown time at the bottom of the blind hole in both the example and the comparative example exceeded 12 seconds, corresponding to... Figure 6 (a) The high-level region of the starting point of the vertical axis, and Figure 6 (b) The maximum cooling rates are all at a low level. The test results indicate that liquid jets relying solely on circulating pumps cannot penetrate deep into the bottom of narrow orifices, and conventional heat transfer methods are insufficient to disrupt stable vapor films.

[0114] When the ejector gas flow rate increased to the range of 4.0 to 6.0 L / min, the cooling rate at the bottom of the blind hole in Example 2 was improved. The rupture time was shortened to about 4 seconds, and the maximum cooling rate increased to nearly 96°C / s, which is significant. Figure 6 (a) and (b) represent the minimum valley and maximum peak of the curve, respectively. Under the action of surfactants such as disodium sebate, the drawn-in air is dispersed into uniformly sized microbubbles. The microbubble community enters the depths of the blind hole with the fluid, undergoing volume expansion and collapse upon contact with the high-temperature metal wall. Simultaneously, supersaturated sodium molybdate particles precipitated from the solution adhere to the bubble boundaries, providing low-barrier chemical nucleation sites for nucleated boiling. Example 4, lacking this chemical component, exhibits a slightly longer collapse time and limited increase in cooling rate at the same gas content. Figure 6 (a) and (b) are represented by dashed lines located above and below the curve of Example 2, respectively, illustrating the synergistic effect of inorganic salts in the gas-liquid-solid three-phase heat exchange process.

[0115] When the gas flow rate reached 8.0 L / min, the cooling performance of Example 2 did not continue to improve with the increase of gas flow; instead, a slight decrease in heat transfer occurred. Figure 6 The end of the broken line is shown as Figure 6 (a) The curve curves upwards and Figure 6 (b) Curve decline. Excess gas input exceeds the bubble stabilization threshold of the polymer system, causing a large number of bubbles to coalesce inside the blind holes. The resulting gas jamming effect blocks the heat exchange channels, hindering the continuous replenishment of the cryogenic liquid phase. In Comparative Example 1, due to the lack of specific bubble stabilization and nucleation formulations, the bubbles are difficult to maintain a diffuse state in the early stages of transport, resulting in the worst overall heat exchange efficiency. In the two sub-graphs, it occupies the uppermost position of the collapse time and the lowermost position of the cooling rate, respectively. When the ejector gas flow rate exceeds 4.0 L / min, large-sized bubbles accumulate at the blind hole opening. Instead of penetrating to the bottom of the hole to provide kinetic energy, they increase the fluid ingress resistance, causing its cooling rate curve to decline. Figure 6(b) shows a decreasing trend with increasing gas volume. Comprehensive test results indicate that when designing a gas-liquid mixing quenching process, it is necessary to set a reasonable gas content range based on the characteristics of the workpiece, and rely on a dedicated quenching medium chemical system to maintain bubble stability and ensure that microbubbles can enter the dead zone area to achieve film rupture.

Claims

1. A manufacturing method for improving the fatigue life of a split flywheel ring gear, characterized in that, Includes the following steps: Add 8-10% by mass of polyether, 0.5-1.2% by mass of disodium sebate, 0.1-0.3% by mass of sodium molybdate, 0.2-0.5% by mass of sodium polyacrylate and 0.05-0.15% by mass of high molecular weight polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer to the remaining deionized water, and adjust the pH to 8.5-9.5 to obtain a water-based quenching medium; The tooth profile surface of the gear ring is induction heated so that the surface layer of the tooth profile reaches 860-880°C and the core temperature is below 400°C. The induction-heated gear ring is dropped into a quenching tank containing the water-based quenching medium. The circulation pump of the quenching tank is controlled to establish turbulence. The bypass Venturi jet of the quenching tank is turned on to inject nitrogen gas. The gas content of the fluid is controlled to be 3-5% to maintain the gas-containing jet scouring. Turn off the nitrogen ejector, reduce the frequency of the circulating pump to transition the flow field to laminar flow, control the cooling rate of the gear ring to 15-25℃ / s, and allow the microbubbles on the liquid surface to enter the bypass settling defoaming tank through the overflow weir of the quenching tank. After the temperature of the gear ring drops below 80℃, remove it from the quenching tank. The gear ring removed from the quenching tank is tempered at 180-200°C for 1.5-2 hours and then air-cooled to room temperature.

2. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 1, characterized in that, The water-based quenching medium is prepared from raw materials containing the following mass fractions: The system comprises 9.0% of the polyether, 0.85% of the disodium sebate, 0.2% of the sodium molybdate, 0.35% of the sodium polyacrylate, and 0.1% of the block copolymer, with the balance being deionized water, and the pH of the system is 9.

0.

3. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 1, characterized in that, The specific implementation method for preparing the water-based quenching medium is as follows: Inject the deionized water into the mixing vessel, adjust the water temperature, turn on the stirrer, and add the polyether, disodium sebate, sodium molybdate and sodium polyacrylate in sequence. After stirring until homogeneous, add the block copolymer, and finally add sodium hydroxide aqueous solution to adjust the pH value of the system.

4. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 1, characterized in that, When performing the induction heating, the gear ring is made of 50Mn medium carbon steel forging; The induction heating is performed using a medium-to-high frequency induction heating device with a working frequency of 30-50kHz; The surface layer of the tooth profile is a region extending 2.0 to 3.0 mm from the tooth tip to the tooth root of the tooth ring.

5. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 1, characterized in that, When the gas-containing jet is maintained in the quenching tank, the turbulent flow velocity established by the circulating pump is 1.0 to 1.2 m / s; The nitrogen gas mentioned is industrial nitrogen gas; The duration of the gas-filled jet scouring is 2.0 to 4.0 seconds.

6. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 1, characterized in that, When the frequency of the circulating pump is reduced, the flow field transitions to the laminar flow with a velocity of 0.2 to 0.3 m / s after the frequency reduction. The surface flow velocity of the liquid surface microbubbles scraped into the bypass static defoaming tank through the overflow weir is 0.5 to 1.0 m / s.

7. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 1, characterized in that, The weight-average molecular weight of the block copolymer is 8500 to 10700; The block copolymer contains hydrophobic segments of polyoxypropylene and hydrophilic segments of polyoxyethylene, and the hydrophilic segments of polyoxyethylene account for 20% to 25% of the total mass of the block copolymer.

8. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 7, characterized in that, The block copolymer is prepared in advance through the following steps: In an anhydrous high-pressure reactor, propylene glycol is used as an initiator, potassium hydroxide is added as a catalyst, nitrogen gas is introduced to replace the air in the anhydrous high-pressure reactor, and then the temperature is raised and a vacuum is drawn for dehydration treatment. The pressure is restored to normal and the temperature of the anhydrous high-pressure reactor is maintained. Propylene oxide monomer is slowly added dropwise into the anhydrous high-pressure reactor to polymerize and generate the hydrophobic polyoxypropylene segments. The temperature of the anhydrous high-pressure reactor is raised and maintained, and ethylene oxide gas is continuously introduced into the reaction system, so that the ethylene oxide gas undergoes ring-opening block copolymerization at both ends of the hydrophobic polyoxypropylene chain segment. After the reaction is completed, the temperature is lowered, glacial acetic acid is added to neutralize the catalyst in the reaction system, and the generated inorganic salts are removed by vacuum dehydration and filtration to obtain the block copolymer.

9. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 8, characterized in that, During the polymerization process of slowly adding propylene oxide monomer to the anhydrous high-pressure reactor, the pressure inside the anhydrous high-pressure reactor is controlled at 0.2 to 0.4 MPa, and the weight-average molecular weight of the generated polyoxypropylene hydrophobic segments is controlled at 6800 to 8000. During the continuous introduction of ethylene oxide gas into the reaction system, the grafting amount of the ethylene oxide gas is controlled so that the proportion of the hydrophilic polyoxyethylene segments in the final block copolymer is 20% to 25%.

10. The manufacturing method for improving the fatigue life of the split flywheel gear ring according to claim 8, characterized in that, The amount of potassium hydroxide added is 0.3% to 0.5% of the expected total feed mass; Perform the heating and vacuum dehydration process; After the reaction is complete, cool down and add glacial acetic acid to neutralize the reaction system until the pH value is 6.0-7.0.

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