Carburizing and quenching process for reducing deformation of thin-wall gear

Abstract

The invention provides a carburizing and quenching process for reducing deformation of a thin-wall gear. The carburizing and quenching process comprises the steps that S200, the multiple thin-wall gears are stacked on the stacking frame in the axial direction with the positioning end faces of the thin-wall gears as the reference; s300, the thin-wall gear is heated to the carburizing temperature of 920 + / -10 DEG C in a multi-stage stepped mode; s400, the thin-wall gear is subjected to heat preservation for 1320 min and then enters a carburizing procedure; s500, the thin-wall gear treated through the carburizing procedure is subjected to tempering treatment and then cooled; s600, measuring the ellipse deformation of each thin-wall gear subjected to slow cooling in the carburizing process; s700, the thin-wall gears on the stacking frame are rearranged according to the ellipse deformation amount; and S800, the thin-wall gears stacked again are subjected to multi-section stepped heating quenching. The carburizing and quenching stepped heating process relieves thermal stress concentration and reduces the risk of thermal deformation, so that the production quality of the thin-wall gear can be ensured while the production efficiency of the thin-wall gear is ensured.

Description

Technical Field

[0001] This invention relates to the field of gear processing and manufacturing technology, and in particular to a carburizing and quenching process for reducing the deformation of thin-walled gears. Background Technology

[0002] Thin-walled gears are key load-bearing components in high-end transmission equipment. Their small wall thickness-to-outer diameter ratio and weak structural rigidity make deformation control during carburizing and quenching extremely difficult. Existing carburizing and quenching processes for thin-walled gears have the following shortcomings: The heating method often adopts "rapidly reaching the carburizing temperature", which concentrates thermal stress in the thin-walled matrix and easily causes tooth surface warping and gear body elliptical deformation. The loading method is mostly single-piece suspension or disordered stacking. The gears have poor support stability under hot conditions and are prone to additional plastic deformation. The aforementioned problems result in excessive deformation of thin-walled gears after carburizing and quenching under existing processes (ovalness often reaches 1.3-2.3mm). Subsequent tooth grinding is prone to exceed the allowable range of the machining process, and prolongs the subsequent processing time. The yield rate is only about 60%, which greatly increases production and rework costs.

[0003] Current technologies do not address the structural characteristics of thin-walled gears by coordinating and optimizing the heating process and furnace loading method, thus failing to balance deformation control, machining accuracy, and production efficiency. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a carburizing and quenching process for reducing the deformation of thin-walled gears, which overcomes or at least partially solves the above problems. This process can solve the problem that the existing carburizing process for thin-walled gears cannot simultaneously achieve deformation control, machining accuracy and production efficiency, thereby improving the production efficiency and quality of thin-walled gears.

[0005] Specifically, the present invention provides a carburizing and quenching process for reducing the deformation of thin-walled gears. The carburizing and quenching process for reducing the deformation of thin-walled gears includes: Multiple thin-walled gears are stacked on a stacking frame along the axial direction with their positioning end faces as a reference. The thin-walled gear is heated in multiple stages to a carburizing temperature of 920±10℃, and the holding time is the same after each stage of heating to the preset temperature of the corresponding stage. The carburizing process is completed after the thin-walled gear is kept at a temperature for 1320 minutes. The thin-walled gear, after undergoing carburizing, is then tempered and cooled. The elliptical deformation of each thin-walled gear after slow cooling following the carburizing process was measured. The thin-walled gears on the stacking frame are rearranged according to the amount of elliptical deformation, and the thin-walled gears with smaller elliptical deformation are stacked on the upper and lower sides of the thin-walled gears with larger elliptical deformation. The thin-walled gears, after being reassembled, are subjected to multi-stage stepped temperature quenching.

[0006] Optionally, the step of progressively heating the thin-walled gear to a carburizing temperature of 920±10℃ in multiple stages, with the same holding time after each stage reaches its preset temperature, includes: The thin-walled gear is heated to 450±10℃ at a rate of 5-8℃ / min and held at that temperature for 120-150min. The thin-walled gear is then heated to 600±10℃ at a rate of 3-5℃ / min and held at that temperature for 120-150min. The thin-walled gear is then heated to 800±10℃ at a rate of 3-5℃ / min and held at that temperature for 120-150min. Finally, the thin-walled gear is heated to a carburizing temperature of 920±10℃ at a rate of 2-3℃ / min.

[0007] Optionally, the cooling step after tempering of the thin-walled gear that has undergone the carburizing process includes: After the carburizing process, the thin-walled gear is cooled to 800±10℃ and held for 90-120 minutes. The thin-walled gear is then placed in a slow-cooling furnace and cooled to 300~400℃; The thin-walled gear is then placed in a tempering furnace and heated to 650°C, held at that temperature for 180-240 minutes, and then air-cooled.

[0008] Optionally, the step of performing multi-stage stepped temperature quenching on the re-stacked thin-walled gears includes: The thin-walled gear is heated to 410±10℃ at a rate of 5-8℃ / min and held at that temperature for 120-150min. The thin-walled gear is then heated to 600±10℃ at a rate of 3-5℃ / min and held at that temperature for 120-150min. Finally, the thin-walled gear is heated to a quenching temperature of 820±10℃ at a rate of 2-3℃ / min. The thin-walled gear is then subjected to a quenching process.

[0009] Optionally, the step prior to stacking the plurality of thin-walled gears axially on the stacking frame with their positioning end faces as a reference includes: A carburizing-resistant coating is applied to the surface of the parts of the thin-walled gear that require specific manufacturing processes.

[0010] Optionally, the step of stacking the plurality of thin-walled gears in the axial direction on the stacking frame with their positioning end faces as a reference includes: 16-22 of the thin-walled gears are stacked on the stacking rack.

[0011] Optionally, the step of rearranging the thin-walled gears on the stacking frame according to the elliptical deformation amount, and stacking the thin-walled gears with smaller elliptical deformation amounts on the upper and lower sides of the thin-walled gears with larger elliptical deformation amounts, includes: The 15-17 thin-walled gears are vertically re-stacked on the stacking rack according to the elliptical deformation.

[0012] Optionally, the step of stacking the plurality of thin-walled gears along the axial direction on the stacking frame with their positioning end faces as a reference further includes: The adjacent thin-walled gears naturally fit together through the cylindrical surfaces of the root of their respective external teeth.

[0013] Optionally, the stacking rack includes stacking mandrels, a top auxiliary tooling, a bottom auxiliary tooling, and a base; The stacked mandrel is vertically arranged and fixedly installed on the base; both the bottom auxiliary tooling and the top auxiliary tooling can be sleeved on the stacked mandrel; the thin-walled gear is sleeved on the stacked mandrel and is located between the bottom auxiliary tooling and the top auxiliary tooling.

[0014] In the carburizing and quenching process for reducing deformation of thin-walled gears in this invention, the direct and rapid heating is replaced with a multi-stage stepped controlled heating. The fundamental purpose is to "control the temperature difference and heat evenly, thereby minimizing thermal stress." The multi-stage stepped heating can release residual stress and avoid stress concentration. Because thin-walled gears have residual stress inside after machining, directly heating them from room temperature to 920°C will cause these residual stresses to superimpose with the rapidly increasing thermal stress, easily leading to stress concentration in the weak parts of the thin-walled gear (such as the thin wall and tooth root), directly causing plastic deformation (warping, ellipticing).

[0015] Each stage of the stepped heating process acts as a window for stress relaxation and redistribution. At relatively lower temperatures, material plasticity increases, internal micro-defects are repaired, and stress is partially released and homogenized, creating a more relaxed starting point for the next stage of heating. Simultaneously, stepped heating ensures uniform heating over time, eliminating the internal and external temperature differences in thin-walled gears. The direct driving force of thermal deformation is the temperature difference (thermal stress) across the part's cross-section. The thicker the gear and the faster the heating, the greater the internal and external temperature difference. Stepped heating, through a "heating-holding (uniform temperature)-reheating" pattern, forces sufficient time for heat to conduct from the surface to the core. For example, after the first stage reaches 450℃ and is held for a long time, the gear achieves a near-uniform 450℃ temperature from the inside out before the next stage of heating begins. In this way, each stage of temperature rise occurs on a relatively uniform temperature field, thereby controlling the maximum instantaneous temperature difference throughout the heating process to an extremely low level, fundamentally suppressing thermal deformation.

[0016] Setting the holding time for each stage within the same or similar range serves not only to achieve "temperature homogenization," but also, at specific temperature points (especially in the 600℃-800℃ range), to facilitate the recovery and recrystallization of the material's internal structure and further stress relaxation. This consistent time range aligns with the overall production line cycle time, the heating capacity of the carburizing furnace, and the production plan, representing an optimal balance between ensuring quality (sufficient temperature homogenization) and balancing efficiency. Therefore, a unified holding time design ensures that the gears receive sufficient and consistent "temperature homogenization treatment" and "stress relaxation opportunities" at each critical temperature point. This guarantees the machining quality and efficiency of thin-walled gears. Similarly, the multi-stage heating in the S800 step serves the same purpose.

[0017] In summary, the stepped heating process alleviates the thermal stress concentration of thin-walled gears, and the orderly stacking of the predicted deformation amount before quenching improves the support stability under hot conditions. The two work together to suppress problems such as tooth surface warping and elliptical deformation of the gear body.

[0018] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0019] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a carburizing and quenching process for reducing the deformation of thin-walled gears according to an embodiment of the present invention. Figure 2 This is a schematic flowchart of step S300 in the carburizing and quenching process for reducing the deformation of thin-walled gears according to an embodiment of the present invention. Figure 3 This is a schematic flowchart of step S500 in the carburizing and quenching process for reducing the deformation of thin-walled gears according to an embodiment of the present invention. Figure 4 This is a schematic flowchart of step S800 in the carburizing and quenching process for reducing the deformation of thin-walled gears according to an embodiment of the present invention. Figure 5 This is a schematic structural diagram of a stacking rack in a carburizing and quenching process for reducing the deformation of thin-walled gears according to an embodiment of the present invention. Figure 6 This is a schematic line diagram of the carburizing and quenching process in reducing the deformation of thin-walled gears according to an embodiment of the present invention.

[0020] In the diagram: 100, stacked mandrel; 200, top auxiliary tooling; 300, bottom auxiliary tooling; 400, base; 500, thin-walled gear. Detailed Implementation

[0021] The following reference Figures 1 to 6 This invention describes a carburizing and quenching process for reducing deformation of thin-walled gears according to embodiments of the present invention. In this description, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature, that is, include one or more of that feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. When a feature "includes or contains" one or more of the features it encompasses, unless otherwise specifically described, this indicates that other features are not excluded and may be further included.

[0022] Unless otherwise expressly specified and limited, the terms "set up," "install," "connect," "link," "fix," and "couple" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art should be able to understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Furthermore, in the description of this embodiment, "above" or "below" the second feature can include direct contact between the first and second features, or it can include contact between the first and second features through another feature between them. That is, in the description of this embodiment, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," or "below" of the second feature can mean the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0024] In the description of this embodiment, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0025] Figure 1 This is a schematic structural diagram of the carburizing and quenching process to reduce the deformation of thin-walled gears, such as... Figure 1 As shown, and with reference Figures 2 to 6 The carburizing and quenching process to reduce the deformation of thin-walled gears includes: S200: Multiple thin-walled gears 500 are stacked on the stacking frame along the axial direction with their positioning end faces as a reference. S300, the thin-walled gear 500 is heated in multiple steps to the carburizing temperature of 920±10℃, and the holding time is the same after each step is heated to the preset temperature of the corresponding stage. S400, after holding the thin-walled gear 500 at a temperature for 1320 minutes, the carburizing process is completed; S500, after being carburized, thin-walled gear 500 is tempered and then cooled. S600, Measure the elliptical deformation of each thin-walled gear 500 after slow cooling following the carburizing process; S700: According to the amount of elliptical deformation, rearrange the thin-walled gears 500 on the stacking frame, and stack the thin-walled gears 500 with smaller elliptical deformation on the upper and lower sides of the thin-walled gears 500 with larger elliptical deformation. S800, the thin-walled gear 500 after being re-stacked is subjected to multi-stage stepped temperature rise quenching.

[0026] Specifically, in step S200, multiple thin-walled gears 500 are stacked axially with their positioning end faces as a reference. Adjacent gears achieve radial self-positioning through the natural contact of the cylindrical surfaces of their respective external tooth roots. Auxiliary tooling is placed at the bottom and top of the stacking frame, and the stacked assembly is loaded into the heat treatment furnace. Further, in S300, the direct and rapid heating is changed to multi-stage stepped controlled-speed heating. The fundamental purpose is to "control the temperature difference, heat evenly, and thus minimize thermal stress." Multi-stage stepped heating can release residual stress and avoid stress concentration. Because the thin-walled gears 500 have residual stress inside after machining, directly and rapidly heating them from room temperature to 920°C will cause these residual stresses to superimpose with the rapidly increasing thermal stress, easily leading to stress concentration in the weak parts of the thin-walled gears 500 (such as the thin walls and tooth roots), directly causing plastic deformation (warping, ellipticing).

[0027] Each stage of the stepped heating process acts as a window for stress relaxation and redistribution. At relatively lower temperatures, material plasticity increases, and stress is partially released and homogenized, creating a more relaxed starting point for the next stage of heating. Simultaneously, stepped heating ensures uniform heating over time, eliminating the internal and external temperature difference in the thin-walled gear 500. The direct driving force of thermal deformation is the temperature difference (thermal stress) across the part's cross-section. The thicker the gear and the faster the heating, the greater the internal and external temperature difference. Stepped heating, through a "heating-holding (uniform temperature)-reheating" pattern, forces sufficient time for heat to conduct from the surface to the core. For example, after the first stage reaches 450℃ and is held for a long time, the gear achieves a near-uniform 450℃ temperature from the inside out before the next stage of heating begins. In this way, each stage of temperature rise occurs on a relatively uniform temperature field, thus controlling the maximum instantaneous temperature difference throughout the heating process to a low level and fundamentally suppressing thermal deformation.

[0028] Setting the holding time for each stage within the same or similar range serves not only to achieve "temperature homogenization," but also, at specific temperature points (especially in the 600℃-800℃ range), to facilitate the recovery process of the material's internal structure and further stress relaxation. This consistent time range aligns with the overall production line cycle time, the heating capacity of the carburizing furnace, and the production plan, representing an optimal balance between ensuring quality (sufficient temperature homogenization) and balancing efficiency. Therefore, the uniform holding time design ensures that the gears receive sufficient and consistent "temperature homogenization treatment" and "stress relaxation opportunities" at each critical temperature node. This guarantees the machining quality and efficiency of the thin-walled gear 500. Similarly, the multi-stage heating in the S800 step serves the same purpose.

[0029] In summary, the stepped heating process alleviates the thermal stress concentration of the thin-walled gear 500, and the orderly stacking method of the predicted deformation amount before quenching improves the support stability under hot conditions. The two work together to suppress problems such as tooth surface warping and elliptical deformation of the gear body.

[0030] Furthermore, in step S700, the elliptical deformation of each thin-walled gear 500 is pre-detected. Based on the pre-detected elliptical deformation data, with the center of the stacking frame in the vertical direction as the axis of symmetry, the gear with the largest elliptical deformation is placed in the central area. Gears with decreasing deformation are arranged sequentially on both sides along the vertical axis, forming a symmetrical distribution sequence of "large deformation in the middle and small deformation at both ends". Therefore, the rigidity of the low-deformation thin-walled gears 500 on both sides can provide symmetrical support, forming a "mechanical bridge" effect during the pressing process, suppressing further deformation of the thin-walled gear 500 in the middle. The bottom and top of the mounting assembly are equipped with auxiliary tooling rings with dimensions similar to those of the thin-walled gears 500 to keep the contact surface flat and the pressure uniform, ensuring that each thin-walled gear 500 in axial adjacent contact is a gear of the same specification. This ensures that all thin-walled gears 500 are under similar thermal flow and heat dissipation conditions during heating and cooling, reducing the temperature difference deformation caused by the mounting position, and ensuring the hardness and quality of the thin-walled gears 500 after quenching.

[0031] In this embodiment, production verification of this process shows that after carburizing and quenching, the ellipticity of the gear is reduced from 1.3-2.3 mm in the existing process to 0.2-0.7 mm, and the deformation is reduced by 69-84%.

[0032] Subsequent mass production verification showed that the tooth grinding amount was stably controlled within the range of 0.2-0.6mm, fully meeting the processing requirements; the yield rate increased from 60% of the existing process to over 95%, significantly reducing production rework costs.

[0033] Table 1. Dimensional changes of thin-walled gears after heat treatment before optimization.

[0034] Table 2. Dimensional changes of the optimized thin-walled gears after heat treatment. In some embodiments of the present invention, such as Figure 1 , Figure 2 and Figure 6 As shown, the step of multi-stage stepped heating of the thin-walled gear 500 to the carburizing temperature of 920±10℃, with the same holding time after each stage of heating to the preset temperature, includes: S310, heat the thin-walled gear 500 to 450±10℃ at a rate of 5-8℃ / min, and hold for 120-150min; S320, then heat the thin-walled gear 500 to 600±10℃ at a rate of 3-5℃ / min, and hold for 120-150min; S330, then heat the thin-walled gear 500 to 800±10℃ at a rate of 3-5℃ / min, and hold for 120-150min; S340, and finally, the thin-walled gear 500 is heated to the carburizing temperature of 920±10℃ at a rate of 2-3℃ / min.

[0035] Specifically, the temperature platforms are set at 450℃, 600℃, and 800℃, with the holding time uniformly set at 120-150 minutes. The first platform, 450℃±10℃, is the "low-temperature stress relaxation and safety zone." Below approximately 400℃, the material has poor thermal conductivity and low plasticity. If the temperature rises too quickly, the thermal stress generated by the huge internal and external temperature difference cannot be released through plastic deformation, easily leading to cracking or permanent deformation. This allows the gear as a whole (especially the thick-walled or core parts) to slowly and evenly pass through this "low-temperature danger zone."

[0036] The second platform's 600℃±10℃ is the "recovery zone." For most alloy carburized steels, around 600℃ is the recovery range. At this temperature, metal atoms gain sufficient mobility to release the stress introduced by machining, allowing lattice distortion to be largely restored.

[0037] The third platform, at 800℃±10℃, serves as the "austenitization outpost and precise isothermal zone." The purpose of this stage is to "create an absolutely uniform temperature field for the phase transformation." 800℃ is near the austenitic phase transformation initiation temperature (Ac1 point) of most carburized steels. Temperature uniformity is crucial at the threshold of the impending phase transformation (pearlite to austenite). This is the most critical step in preventing significant structural stress during subsequent phase transformation. If a temperature difference is introduced into the phase transformation zone, the asynchronous transformation of different parts will lead to uncontrollable deformation due to the resulting stress. Insulating at this platform ensures that every point on the gear, from the surface to the core, precisely and consistently reaches the same state before the phase transformation.

[0038] The same holding time is set for the three heating plateaus because 120-150 minutes is a sufficient and conservative time. It not only ensures that "complete temperature uniformity" is achieved at any plateau, but also provides ample time windows for processes such as tissue recovery at 600℃ and pre-phase transition equilibration at 800℃, ensuring stable results. It is the best balance between "ensuring quality" and "considering efficiency".

[0039] In some embodiments of the present invention, such as Figure 1 , Figure 3 and Figure 6As shown, the cooling step after tempering of the thin-walled gear 500, which has undergone the carburizing process, includes: S510. After the carburizing process, cool the thin-walled gear 500 to 800±10℃ and hold for 90-120 minutes. S520, then place the thin-walled gear 500 into a slow-cooling furnace to cool to 300~400℃; S530, then place the thin-walled gear 500 into a tempering furnace and heat it to 650℃, hold it at that temperature for 180-240 minutes, and then air cool it.

[0040] Specifically, in step S510, the thin-walled gear 500 is cooled from the carburizing temperature of 920℃ to this temperature, still in the austenitic state. Holding at this temperature for 90-120 minutes aims to achieve a very high and potentially uneven carbon content in the austenite after carburizing. Holding at 800℃ allows the supersaturated carbon to precipitate from the austenite in the form of fine, uniform carbides, avoiding the formation of harmful, coarse, or network-like carbides distributed along grain boundaries during subsequent cooling.

[0041] Furthermore, after the carburizing process, the thin-walled gear 500 is held at 800±10℃ for 90-120 minutes in a slow cooling furnace, then cooled in the slow cooling furnace to 300~400℃, and then held at 650℃ for a period of time before air cooling. This process can achieve a uniform microstructure, reduce stress concentration in the subsequent cooling process, lower the cooling rate, and allow for more complete release of thermal and structural stresses, further reducing the deformation of the thin-walled gear 500 caused by uneven cooling.

[0042] Furthermore, the slow-cooling furnace reduces the cooling rate of the thin-walled gear 500. Slow cooling makes the phase transformation process gentle, resulting in less structural stress, while thermal stress is also reduced due to the small temperature difference.

[0043] In some embodiments of the present invention, such as Figure 1 , Figure 4 and Figure 6 As shown, the step of performing multi-stage stepped temperature quenching on the re-stacked thin-walled gear 500 includes: S810, heat the thin-walled gear 500 to 410±10℃ at a rate of 5-8℃ / min, and hold at that temperature for 120-150min; S820, then heat the thin-walled gear 500 to 600±10℃ at a rate of 3-5℃ / min, and hold for 120-150min; S840, and finally, the thin-walled gear 500 is heated to a quenching temperature of 820±10℃ at a rate of 2-3℃ / min. S850, the thin-walled gear 500 is then sent to the quenching process.

[0044] In some embodiments of the present invention, such as Figure 1 As shown, the step before stacking multiple thin-walled gears 500 along the axial direction on the stacking frame with their positioning end faces as a reference includes: S100. Apply an anti-carburization coating to the surface of the part of the thin-walled gear that requires process specifications.

[0045] Specifically, in step S100, an anti-carburizing coating is applied only to the parts of the thin-walled gear that require process specifications (outside the teeth as required by the gear process card) to ensure the hardness and machinability of the non-carburized parts, while also preventing adhesion to auxiliary tooling.

[0046] In some embodiments of the present invention, the step of stacking multiple thin-walled gears 500 along the axial direction on a stacking frame with their positioning end faces as a reference includes: S210. Stack 16-22 thin-walled gears 500 on the stacking rack.

[0047] Specifically, the thin-walled gears 500 are stacked in 16-22 layers on the stacking rack. Considering the efficiency requirements of mass production and the fact that carburizing causes less deformation than quenching, the number of stacking layers is controlled to 16-22 layers to ensure that the adjacent press-fit surfaces of the gears fit tightly together.

[0048] In some embodiments of the present invention, the step of rearranging the thin-walled gears 500 on the stacking frame according to the amount of elliptical deformation, and stacking the thin-walled gears 500 with smaller elliptical deformation on the upper and lower sides of the thin-walled gears 500 with larger elliptical deformation, includes: S710. Apply an anti-stick carbon coating again to the surface of the stacking rack; S720, stack 15-17 thin-walled gears 500 vertically on the stacking rack according to the elliptical deformation amount.

[0049] Specifically, an anti-sticking carbon coating is applied again to the stacking rack to prevent gears from sticking to the rack's clamps. Furthermore, by re-stacking the gears according to the amount of elliptical deformation, the number of layers is reduced, and the stacking height is lowered. This allows the protective atmosphere or heat radiation from the heating elements within the furnace to act more evenly on each gear, reducing "air pockets" or temperature dead zones. During furnace quenching, fewer layers and a lower rack height allow quenching oil (or other media) to more quickly and evenly coat and wash each gear, reducing deformation differences caused by different cooling sequences (cooling the outer ring first, then the center).

[0050] In some embodiments of the present invention, such as Figure 5 As shown, the step of stacking multiple thin-walled gears 500 along the axial direction using their positioning end faces as a reference also includes: S220, adjacent thin-walled gears 500 naturally fit together through the cylindrical surfaces of their respective external tooth roots.

[0051] In some embodiments of the present invention, such as Figure 5 As shown, the stacking rack includes a stacking mandrel 100, a top auxiliary fixture 200, a bottom auxiliary fixture 300, and a base 400. The stacking mandrel 100 is vertically arranged and fixedly mounted on the base 400. Both the bottom auxiliary fixture 300 and the top auxiliary fixture 200 can be fitted onto the stacking mandrel 100. A thin-walled gear 500 is fitted onto the stacking mandrel 100 and is located between the bottom auxiliary fixture 300 and the top auxiliary fixture 200.

[0052] Specifically, the bottom auxiliary tooling 300, the thin-walled gear 500 and the top auxiliary tooling 200 can be coaxially mounted on the stacked mandrel in sequence, so that the adjacent thin-walled gears 500 or the thin-walled gears 500 and the auxiliary tooling can be radially positioned by naturally fitting the cylindrical surface of the tooth root or the positioning surface, thereby achieving better positioning.

[0053] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A carburizing and quenching process for reducing distortion in thin- walled gears, characterized by, include: Multiple thin-walled gears are stacked on a stacking frame along the axial direction with their positioning end faces as a reference. The thin-walled gear is heated in multiple stages to a carburizing temperature of 920±10℃, and the holding time is the same after each stage of heating to the preset temperature of the corresponding stage. The carburizing process is completed after the thin-walled gear is kept at a temperature for 1320 minutes. The thin-walled gear, after undergoing carburizing, is then tempered and cooled. The elliptical deformation of each thin-walled gear after slow cooling following the carburizing process was measured. The thin-walled gears on the stacking frame are rearranged according to the amount of elliptical deformation, and the thin-walled gears with smaller elliptical deformation are stacked on the upper and lower sides of the thin-walled gears with larger elliptical deformation. The thin-walled gears, after being reassembled, are subjected to multi-stage stepped temperature quenching.

2. The carburizing and quenching process for reducing deformation of thin-walled gears according to claim 1, characterized in that, The step of progressively heating the thin-walled gear to a carburizing temperature of 920±10℃ in multiple stages, with each stage holding at the preset temperature for the same duration, includes: The thin-walled gear is heated to 450±10℃ at a rate of 5-8℃ / min and held at that temperature for 120-150min. The thin-walled gear is then heated to 600±10℃ at a rate of 3-5℃ / min and held at that temperature for 120-150min. The thin-walled gear is then heated to 800±10℃ at a rate of 3-5℃ / min and held at that temperature for 120-150min. Finally, the thin-walled gear is heated to a carburizing temperature of 920±10℃ at a rate of 2-3℃ / min.

3. The carburizing and quenching process for reducing deformation of thin-walled gears according to claim 2, characterized in that, The cooling step following tempering of the thin-walled gear after the carburizing process includes: After the carburizing process, the thin-walled gear is cooled to 800±10℃ and held for 90-120 minutes. The thin-walled gear is then placed in a slow-cooling furnace and cooled to 300~400℃; The thin-walled gear is then placed in a tempering furnace and heated to 650°C, held at that temperature for 180-240 minutes, and then air-cooled.

4. The carburizing and quenching process for reducing deformation of thin-walled gears according to claim 1, characterized in that, The step of performing multi-stage stepped temperature quenching on the re-stacked thin-walled gears includes: The thin-walled gear is heated to 410±10℃ at a rate of 5-8℃ / min and held at that temperature for 120-150min. The thin-walled gear is then heated to 600±10℃ at a rate of 3-5℃ / min and held at that temperature for 120-150min. Finally, the thin-walled gear is heated to a quenching temperature of 820±10℃ at a rate of 2-3℃ / min. The thin-walled gear is then subjected to a quenching process.

5. The carburizing and quenching process for reducing deformation of thin-walled gears according to claim 1, characterized in that, The step prior to stacking the plurality of thin-walled gears axially on the stacking frame with their positioning end faces as a reference includes: A carburizing-resistant coating is applied to the surface of the parts of the thin-walled gear that require specific manufacturing processes.

6. The carburizing and quenching process for reducing deformation of thin-walled gears according to claim 1, characterized in that, The step of stacking multiple thin-walled gears along the axial direction on a stacking frame with their positioning end faces as a reference includes: 16-22 of the thin-walled gears are stacked on the stacking rack.

7. The carburizing and quenching process for reducing deformation of thin-walled gears according to claim 1, characterized in that, The step of rearranging the thin-walled gears on the stacking frame according to the elliptical deformation amount, and stacking the thin-walled gears with smaller elliptical deformation amounts on the upper and lower sides of the thin-walled gears with larger elliptical deformation amounts, includes: The 15-17 thin-walled gears are vertically re-stacked on the stacking rack according to the elliptical deformation.

8. The carburizing and quenching process for reducing deformation of thin-walled gears according to claim 1, characterized in that, The step of stacking multiple thin-walled gears along the axial direction on the stacking frame with their positioning end faces as a reference also includes: The adjacent thin-walled gears naturally fit together through the cylindrical surfaces of the root of their respective external teeth.

9. The carburizing and quenching process for reducing deformation of thin-walled gears according to claim 1, characterized in that, The stacking rack includes stacking mandrels, top auxiliary fixtures, bottom auxiliary fixtures, and a base; The stacked mandrel is vertically arranged and fixedly installed on the base; both the bottom auxiliary tooling and the top auxiliary tooling can be sleeved on the stacked mandrel; the thin-walled gear is sleeved on the stacked mandrel and is located between the bottom auxiliary tooling and the top auxiliary tooling.

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