A method for processing a disc type carburized gear

Abstract

The application relates to the field of gear machining, and discloses a machining method of a disc type carburized gear, which is used for solving the problem of size over tolerance of the inner tooth cross-pitch caused by the superposition of factors such as forging organization uniformity fluctuation, hot tooth insertion fluctuation and heat treatment distortion in the heat treatment production process. In the rough and fine machining treatment, the upper and lower ends of the outer gear ring and the upper end of the inner gear ring of the gear blank are reserved for machining, so that the intermittent turning of the end face after heat treatment can be effectively avoided, the hot tooth insertion operation before heat treatment is carried out to ensure that the size will not exceed the upper tolerance required by the product drawing, and the rework of the subsequent inner tooth is more facilitated.

Description

Technical Field

[0001] This invention relates to the field of gear processing, specifically to a method for processing a disc-shaped carburized gear. Background Technology

[0002] Carburizing heat treatment is the most commonly used surface strengthening method in the gear transmission field. However, due to the high-temperature thermal cycling of this heat treatment method, the drastic change in the surface chemical composition of the parts after carburizing, and the rapid cooling during the quenching stage, thermal stress and structural stress inevitably cause certain distortions in the parts, i.e., heat treatment deformation. In addition, fluctuations in hardenability of different batches of materials before heat treatment, the pre-heat treatment process (the external environment has a significant impact on pre-heat treatment), and the dimensions before hot machining will exacerbate the distortion after heat treatment.

[0003] For different application areas and design concepts, designers have different requirements for the allowable manufacturing tolerances or precision of products. When heat treatment deformation causes some product dimensions to exceed the design tolerance, the handling method is to rework or scrap.

[0004] The main methods for controlling or reducing heat treatment distortion are as follows:

[0005] (1) Strengthen production process control: This mainly involves comprehensive control over the processes of materials, forging technology, pre-heat treatment, carburizing heat treatment, and machining to ensure the production stability of each step, thus resulting in relatively small cumulative deformation. However, this control method reflects the macro-level industrial capability and is difficult to improve.

[0006] (2) Shape-limiting quenching: This is the process of applying reverse pressure to the part using a pressure quenching die during the part quenching process to prevent the part from being over-deformed.

[0007] (3) Post-heat finishing: This mainly includes reserving machining allowance and using post-heat finishing to reduce heat treatment distortion after heat treatment, such as gear grinding and post-heat turning. However, this method is not applicable to some teeth that cannot be machined.

[0008] like Figure 1 The image shows an irregularly shaped disc gear. The material of this part is 17NiCrMo6-4, which has high hardenability. The main problems encountered during the production of this part are as follows:

[0009] (1) Internal tooth ball pitch out of tolerance: The required internal tooth ball pitch is 184.624~184.844mm, that is, the tolerance of internal tooth ball pitch is 0.22mm. However, due to the poor uniformity of the forging structure at the internal tooth (see details...), Figure 3 The superposition of problems such as internal tooth forging normalized structure, hot pre-welded tooth size fluctuation, and heat treatment distortion makes this tolerance dimension easy to exceed the tolerance;

[0010] (2) Out-of-tolerance height chain dimensions and discontinuous cutting of tooth surfaces: This finished part needs to simultaneously meet the following requirements. Figure 1 As shown in the diagram, the three height chain dimensions indicate that severe warping of the part can lead to black burrs on the cross-section after hot machining. Furthermore, the end face of the part may exhibit intermittent machining, resulting in burrs on the external gear end face. Summary of the Invention

[0011] In order to overcome the defects of the prior art, the present invention aims to provide a machining method for disc-shaped carburized gears, so as to solve the technical problem of burrs caused by the discontinuous turning of the external tooth end face due to the superposition of factors such as the uniformity of forging structure, the pre-heat shaping fluctuation and the distortion of heat treatment during the heat treatment production process, which leads to the out-of-tolerance of the internal tooth ball pitch and the discontinuous end face machining.

[0012] This invention is achieved through the following technical solution:

[0013] A method for machining a disc-shaped carburized gear includes the following steps:

[0014] Step 1: After induction heating, the bar stock is pre-forged and then forged to obtain a gear blank with an internal gear ring and an external gear ring.

[0015] Step 2: Perform preheating treatment on the gear blank. After testing the normalized structure and hardness of the internal and external gear rings of the gear blank, perform rough and fine machining, carburizing and slow cooling treatment and pressure quenching treatment in sequence to obtain a disc-shaped carburized gear sample.

[0016] Step 3: Perform heat treatment and gear grinding on the end face of the disc-shaped carburized gear sample to obtain the finished disc-shaped carburized gear, thus completing the processing of the disc-shaped carburized gear.

[0017] Preferably, in step 2, the pre-heat treatment process for the gear blank is as follows:

[0018] The gear blanks are stacked in an orderly manner and heated to 930℃±10℃, held at that temperature, then rapidly cooled, and transferred to an isothermal normalizing furnace, where the temperature is set to 650℃±10℃ and held to complete the preliminary heat treatment of the gear blanks.

[0019] Preferably, in step 2, the normalizing structure of the inner and outer gear rings of the gear blank mainly includes metallographic structure detection and banded structure detection.

[0020] Preferably, in step 2, the roughing and finishing processes are as follows:

[0021] S1, the upper and lower ends of the outer gear ring and the upper end of the inner gear ring of the gear blank are pre-machined, with the pre-machining size being 0.43±0.03mm;

[0022] S2, perform hot gear shaping operation, where the ball pitch of the gear blank is 184.64±0.03mm.

[0023] Preferably, the specific process of carburizing and slow cooling treatment in step 2 is as follows:

[0024] L1, place the large end of the gear blank to be carburized and slowly cooled flat on the heat-resistant steel tray.

[0025] L2 sequentially performs the strong carburizing stage, the first cooling and carbon potential reduction stage, the first diffusion stage, the second cooling and carbon potential reduction stage, the second diffusion stage, and the slow cooling stage to complete the carburizing and slow cooling treatment of the gear blank.

[0026] Furthermore, in L2, the temperature during the strong permeation stage is set to 920±5℃, the carbon potential is set to 1.15±0.05%, and the cycle is 360±5min;

[0027] In the first cooling and carbon potential reduction stage, the temperature is reduced from 920±5℃ to 860±5℃, and the carbon potential is reduced from 1.15±0.05% to 0.95±0.05%. The cycle of this stage is 120±10min.

[0028] In the first diffusion stage, the temperature was set to 860±5℃, the carbon potential was set to 0.95±0.05%, and the cycle was 150±5min.

[0029] In the second cooling and carbon potential reduction stage, the temperature is reduced from 860±5℃ to 830±5℃, and the carbon potential is reduced from 0.95±0.05% to 0.85±0.05%. The cycle of this stage is 30±10min.

[0030] In the second diffusion stage, the temperature was set to 830±5℃, the carbon potential was set to 0.85±0.05%, and the cycle was 30±5min.

[0031] During the slow cooling stage, the carburized gear blank is pulled to the front chamber of the carburizing equipment and the temperature is slowly reduced to 150°C under nitrogen protection and oil wall cooling conditions. The cycle of this stage is set to 120±5min.

[0032] Preferably, in step 2, the pressure quenching process is as follows:

[0033] K1 involves reheating the carburized and slowly cooled gear blank in a rotary hearth furnace.

[0034] K2, after secondary heating, uses an outer pressure ring and an outer support ring to restrict the deformation of the large end face, and an inner pressure ring and an inner support ring to restrict the deformation of the small end face and groove.

[0035] K3, measure the tooth span and ball pitch. If the dimensions and metallographic indicators of the tooth span and ball pitch are all qualified, proceed to the next cleaning and shot blasting process; otherwise, perform pressure quenching and rework.

[0036] Furthermore, in K1, the secondary heating temperature is 860±5℃, the carbon potential is 0.9±0.05%, and the holding time is 100-120min.

[0037] Furthermore, in K3, during the pressure quenching rework process, the parts with inclined supports are placed in reverse into the furnace for secondary heating. The parts that have undergone secondary heating are then adjusted in terms of the internal tooth span ball pitch until the tooth span ball pitch dimensions and metallographic indicators are met.

[0038] Preferably, after step 3, the finished disc-shaped carburized gears that have completed all processes are subjected to dimensional inspection, and then oiled, packaged, and stored.

[0039] Compared with the prior art, the present invention has the following beneficial technical effects:

[0040] This invention provides a method for machining disc-shaped carburized gears. By sequentially performing rough and finish machining, carburizing and slow cooling, and pressure quenching on the gear blank, the method addresses the issue of out-of-tolerance dimensional tolerances in the internal tooth pitch caused by the combined effects of fluctuations in forging microstructure, pre-heat shaping fluctuations, and heat treatment distortion during the heat treatment process. In the rough and finish machining, pre-machining is performed at the upper and lower ends of the outer gear ring and the upper end of the inner gear ring on the gear blank. This effectively avoids intermittent turning during the post-heat finishing end face process and ensures that the dimensions do not exceed the product drawing requirements during pre-heat shaping. The upper tolerance is more conducive to subsequent rework of the internal gears. The pressure quenching stage includes primary pressure quenching and pressure quenching rework. Primary pressure quenching is carried out using an automated production line. This production line has simple pressure quenching molds, high production efficiency, and low risk of bumps and pressure damage. However, the internal gears are in a free expansion and contraction state, and a certain proportion of the ball pitch dimensions will be out of tolerance after quenching. Pressure quenching rework is a secondary pressure quenching process for parts with internal gear ball pitch exceeding the lower tolerance. In this method, because the internal gears face downwards, they are prone to bumping with the mold. Therefore, manual loading is required. This method has relatively low production efficiency and is limited to the rework of individual parts. Through these two steps, it can be guaranteed that the ball pitch and height difference dimensions of the internal gears are 100% qualified. Attached Figure Description

[0041] Figure 1 Schematic diagram of a certain irregularly shaped disc gear structure

[0042] Figure 2 This is a flowchart of the machining method for the disc-shaped carburized gear in this invention;

[0043] Figure 3 This is a schematic diagram of the internal tooth-like structure after preheating treatment;

[0044] Figure 4This is a schematic diagram of the detection position of the forging blank in this invention;

[0045] Figure 5 This is to allow for the end face allowance during precision machining in this invention.

[0046] In the diagram: 1 - Internal gear ring; 2 - External gear ring. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0048] The present invention will now be described in further detail with reference to the accompanying drawings:

[0049] The purpose of this invention is to provide a machining method for disc-shaped carburized gears, in order to solve the technical problem of burrs caused by the discontinuous turning of the external tooth end face due to the superposition of factors such as fluctuations in the uniformity of forging structure, fluctuations in pre-heat shaping, and distortion during heat treatment production, which lead to out-of-tolerance dimensions of the internal tooth span ball pitch and discontinuous end face machining.

[0050] This invention provides a method for machining disc-shaped carburized gears, which involves the following steps: forging → pre-heat treatment → rough and finish turning → gear shaping → drilling → gear hobbing → carburizing and slow cooling → pressure quenching (including pressure quenching rework) → hot turning → gear grinding → inspection, packaging, and warehousing. The key processes involved in this invention are forging, pre-heat treatment, rough and finish turning, carburizing and slow cooling, and pressure quenching. See [link to relevant documentation]. Figure 2 Specifically, it includes the following steps:

[0051] Step 1: After induction heating, the bar stock is pre-forged and then forged to obtain a gear blank with an internal gear ring 1 and an external gear ring 2.

[0052] Specifically, the forging method of the present invention is die forging.

[0053] Step 2: Perform preheating treatment on the gear blank. After testing the normalized structure and hardness of the inner gear ring 1 and outer gear ring 2 of the gear blank, perform rough and fine machining, carburizing and slow cooling treatment and pressure quenching treatment in sequence to obtain the disc-shaped carburized gear sample.

[0054] Specifically, the pre-heat treatment process for the gear blank is as follows:

[0055] The gear blanks are stacked in an orderly manner and heated to 930℃±10℃, held at that temperature, then rapidly cooled, and transferred to an isothermal normalizing furnace at 650℃±10℃ for holding. This completes the preliminary heat treatment of the gear blanks. Figure 3 As shown.

[0056] Specifically, the normalizing structure of the inner gear ring 1 and outer gear ring 2 of the gear blank mainly includes metallographic structure detection and banded structure detection.

[0057] Specifically, the roughing and finishing processes are as follows:

[0058] S1, the upper and lower ends of the outer gear ring 2 and the upper end of the inner gear ring 1 of the gear blank are pre-machined, and the pre-machined size is 0.43±0.03mm;

[0059] S2, perform hot gear shaping operation, where the ball pitch of the gear blank is 184.64±0.03mm.

[0060] Specifically, the carburizing slow cooling treatment process is as follows:

[0061] L1, place the large end of the gear blank to be carburized and slowly cooled flat on the heat-resistant steel tray.

[0062] L2 sequentially performs the strong carburizing stage, the first cooling and carbon potential reduction stage, the first diffusion stage, the second cooling and carbon potential reduction stage, the second diffusion stage, and the slow cooling stage to complete the carburizing and slow cooling treatment of the gear blank.

[0063] In L2, the temperature during the strong permeation stage is set to 920±5℃, the carbon potential is set to 1.15±0.05%, and the cycle is 360±5min.

[0064] In the first cooling and carbon potential reduction stage, the temperature is reduced from 920±5℃ to 860±5℃, and the carbon potential is reduced from 1.15±0.05% to 0.95±0.05%. The cycle of this stage is 120±10min.

[0065] In the first diffusion stage, the temperature was set to 860±5℃, the carbon potential was set to 0.95±0.05%, and the cycle was 150±5min.

[0066] In the second cooling and carbon potential reduction stage, the temperature is reduced from 860±5℃ to 830±5℃, and the carbon potential is reduced from 0.95±0.05% to 0.85±0.05%. The cycle of this stage is 30±10min.

[0067] In the second diffusion stage, the temperature was set to 830±5℃, the carbon potential was set to 0.85±0.05%, and the cycle was 30±5min.

[0068] During the slow cooling stage, the carburized gear blank is pulled to the front chamber of the carburizing equipment and the temperature is slowly reduced to 150°C under nitrogen protection and oil wall cooling conditions. The cycle of this stage is set to 120±5min.

[0069] Specifically, the pressure quenching process is as follows:

[0070] K1 involves reheating the carburized and slowly cooled gear blank in a rotary hearth furnace.

[0071] The secondary heating temperature is 860±5℃, the carbon potential is 0.9±0.05%, and the holding time is 100-120min.

[0072] K2, after secondary heating, uses an outer pressure ring and an outer support ring to restrict the deformation of the large end face, and an inner pressure ring and an inner support ring to restrict the deformation of the small end face and groove.

[0073] K3, measure the tooth span and ball pitch. If the dimensions and metallographic indicators of the tooth span and ball pitch are all qualified, proceed to the next cleaning and shot blasting process; otherwise, perform pressure quenching and rework.

[0074] In the pressure quenching rework process, the parts with inclined supports are placed in the furnace in reverse for secondary heating. The parts that have been heated for the second time are then adjusted to meet the size and metallographic parameters of the tooth span ball pitch.

[0075] Step 3: Perform heat treatment and gear grinding on the end face of the disc-shaped carburized gear sample to obtain the finished disc-shaped carburized gear, thus completing the processing of the disc-shaped carburized gear.

[0076] Specifically, the finished disc-shaped carburized gears that have completed all processes are subjected to dimensional inspection, and then coated with oil, packaged, and put into storage.

[0077] Example

[0078] This invention provides a method for machining disc-shaped carburized gears, comprising the following steps: forging → pre-heat treatment → rough and finish turning → gear shaping → drilling → gear hobbing → carburizing and slow cooling → pressure quenching (including pressure quenching rework) → hot turning → gear grinding → inspection, packaging and warehousing. Specifically, the process includes the following steps:

[0079] Forging: The forging method in this embodiment is die forging. First, the φ180mm bar is induction heated to 1080℃±10℃, pre-forged into φ460×40mm by a 4000T press, and then finally forged into shape by a 10000T press.

[0080] Preliminary heat treatment: The final forged blanks are stacked in an orderly manner and heated to 930℃±10℃, held for 4 hours, then rapidly cooled using four fans, and transferred to an isothermal normalizing furnace at 650℃±10℃ for 6.5 hours. After this process, the normalized microstructure and hardness of the inner and outer gear rings of the blanks after isothermal normalizing need to be tested simultaneously. Figure 3 As shown, the metallographic structure conforms to grades 1-3 of GB / T13320-2007, the banded structure conforms to grades 0-3 of GB / T13299-1991, and the hardness requirement is 156-207HB.

[0081] Rough and finish turning: To avoid interrupted turning during the post-heat finishing process, a 0.43±0.03mm step needs to be left at both ends of the external gear ring and at the upper end of the internal gear ring during the finish turning process. Figure 4 and Figure 5 Within the dashed circle shown.

[0082] Tooth shaping: The required ball pitch for pre-heat shaping is 184.64±0.03mm. After testing, it has been verified that this dimension can ensure that the dimension will not exceed the upper limit of the product drawing after pressure quenching and tempering, which is more conducive to the rework of the internal teeth.

[0083] Carburizing and slow cooling:

[0084] Step 1: Place the carburized and slowly cooled parts directly flat on the heat-resistant steel tray with the large end facing down;

[0085] Step 2, the strong infiltration stage, the temperature is set at 920±5℃, the carbon potential is set at 1.15±0.05%, and the cycle is 360±5min;

[0086] Step 3: Cooling and carbon potential reduction stage 1, the temperature is reduced from 920±5℃ to 860±5℃, and the carbon potential is reduced from 1.15±0.05% to 0.95±0.05%, the cycle of this stage is 120±10min;

[0087] Step 4: Diffusion stage 1, temperature set at 860±5℃, carbon potential set at 0.95±0.05%, cycle at 150±5min;

[0088] Step 5: Cooling and carbon potential reduction stage 2, the temperature is reduced from 860±5℃ to 830±5℃, and the carbon potential is reduced from 0.95±0.05% to 0.85±0.05%, the cycle of this stage is 30±10min;

[0089] Step 6: Diffusion stage 2, temperature set at 830±5℃, carbon potential set at 0.85±0.05%, cycle time 30±5min;

[0090] Step 7: Slow cooling stage. The carburized parts are pulled to the front chamber of the carburizing equipment and the temperature is slowly reduced to about 150°C under nitrogen protection and oil wall cooling conditions. The cycle of this stage is set to 120±5min.

[0091] Pressure quenching:

[0092] The pressure quenching stage includes primary pressure quenching and pressure quenching rework. Primary pressure quenching is performed on an automated production line. This line uses simple quenching dies, has high production efficiency, and low risk of impact and damage. However, the internal teeth are in a free expansion and contraction state, resulting in a certain percentage of parts having out-of-tolerance ball pitch dimensions after quenching. Pressure quenching rework is a secondary pressure quenching process for parts with excessive ball pitch. Because the internal teeth face downwards, they are prone to collisions with the die, thus requiring manual loading. This method has relatively low production efficiency and is limited to the rework of individual parts. These two steps ensure 100% compliance with the ball pitch and height difference dimensions of the internal teeth. The main steps of pressure quenching are as follows:

[0093] Step 1: The carburized and slowly cooled parts are reheated in a rotary hearth furnace at a temperature of 860±5℃ and a carbon potential of 0.9±0.05%, and held for 100-120 minutes.

[0094] Step 2: The parts that have undergone secondary heating are automatically transferred to a location using a robotic arm. Figure 5 The pressure quenching mold uses an outer pressure ring and an outer support ring to restrict the deformation of the large end face, and an inner pressure ring and an inner support ring to restrict the deformation of the small end face and the groove (the groove can indirectly control the deformation of the small end face). The pressure quenching process is divided into three stages as shown in Table 1 below. The two stages work together to ensure that the height difference of the product fluctuates within a reasonable range.

[0095] Table 1. Press-quenching process for disc gears

[0096]

[0097] Step 3: After pressure quenching and low-temperature tempering, measure the 100% internal tooth span ball pitch of the part. If the dimensions and metallographic indicators are all qualified, proceed to the next cleaning and shot blasting process. If the dimensions are not qualified, perform pressure quenching and rework.

[0098] Step 4: Perform a second heating on the part with the internal gear dimension exceeding the tolerance as in Step 1. It is worth mentioning that during the second heating, the part needs to be placed in the furnace in reverse with the inclined support. This can effectively prevent excessive collapse or warping of the inner and outer end faces.

[0099] Step 5: Manually transfer the reheated parts to the rework quenching mold. The mold's mandrel is an expansion block type, which expands uniformly under the machine tool's expansion pressure. Following the quenching rework process in Table 2, the internal tooth pitch of parts with dimensional defects can be effectively increased, ultimately meeting the drawing's tolerance requirements. It is worth noting that the expansion pressure needs to be adjusted appropriately based on the dimensions before rework, while its parameters remain unchanged.

[0100] Table 2 Rework and quenching process for disc gears

[0101]

[0102] After the car is heated:

[0103] The end faces are heat-treated to ensure the height difference meets the drawing requirements. Batch experiments have verified that by pre-reserving steps before heat treatment, the internal and external tooth end faces can be effectively prevented from intermittent turning while ensuring the height chain dimensions, thus preventing burr formation.

[0104] Grinding teeth:

[0105] The outer tooth surface is ground to achieve the tooth surface accuracy required by the drawing.

[0106] Inspection, packaging, and warehousing:

[0107] The finished parts that have completed all processes are inspected for dimensions, coated with oil, packaged, and put into storage.

[0108] This embodiment performs batch process verification.

[0109] One hundred blanks were randomly selected and manufactured according to the above process. The first-pass yield of the pressure quenching process was 95%. Among them, the internal tooth span ball pitch of 5 products exceeded the lower tolerance in some positions, but there was no upper tolerance. The pressure quenching rework process was used to rework them. The data is shown in Table 3.

[0110] Table 3 Rework Data Statistics Process

[0111]

[0112]

[0113] In summary, this invention provides a method for machining disc-shaped carburized gears. By sequentially performing rough and finish machining, carburizing and slow cooling, and pressure quenching on the gear blank, the method addresses the issue of out-of-tolerance dimensional tolerances in the internal tooth pitch caused by the combined effects of fluctuations in forging microstructure, pre-heat shaping fluctuations, and heat treatment distortion during the heat treatment process. By pre-machining the upper and lower ends of the outer gear ring and the upper end of the internal gear ring in the rough and finish machining process, interrupted turning during the post-heat finishing end face process can be effectively avoided, and the pre-heat shaping operation ensures that the dimensions do not exceed the product specifications. The drawing requires an upward deviation, which facilitates subsequent rework of the internal gears. The pressure quenching stage includes primary pressure quenching and pressure quenching rework. Primary pressure quenching is performed on an automated production line. This line has simple quenching dies, high production efficiency, and low risk of bumps and damage. However, the internal gears are in a free expansion and contraction state, resulting in a certain percentage of out-of-tolerance ball pitch dimensions after quenching. Pressure quenching rework is a secondary pressure quenching process for parts with excessively low ball pitch. Because the internal gears face downwards, they are prone to bumping against the die, so manual loading is required. This method has relatively low production efficiency and is limited to the rework of individual parts. Through these two steps, 100% compliance of the ball pitch and height difference dimensions of the internal gears can be guaranteed.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for machining a disc-shaped carburized gear, characterized in that, Includes the following steps: Step 1: After induction heating of the bar stock, pre-forging and final forging are performed sequentially to obtain a gear blank with an internal gear ring (1) and an external gear ring (2); Step 2: Perform preheating treatment on the gear blank, and after testing the normalized structure and hardness of the inner gear ring (1) and outer gear ring (2) of the gear blank, perform rough and fine machining, carburizing and slow cooling treatment and pressure quenching treatment in sequence to obtain a disc-shaped carburized gear sample. Step 3: Perform heat treatment and gear grinding on the end face of the disc-shaped carburized gear sample to obtain the finished disc-shaped carburized gear, thus completing the processing of the disc-shaped carburized gear. The specific process of carburizing and slow cooling treatment is as follows: L1, place the large end of the gear blank to be carburized and slowly cooled flat on the heat-resistant steel tray. L2, sequentially performs the strong carburizing stage, the first cooling and carbon potential reduction stage, the first diffusion stage, the second cooling and carbon potential reduction stage, the second diffusion stage, and the slow cooling stage, to complete the carburizing and slow cooling treatment of the gear blank. In L2, the temperature during the strong permeation stage is set to 920±5℃, the carbon potential is set to 1.15±0.05%, and the cycle is 360±5min. In the first cooling and carbon potential reduction stage, the temperature decreased from 920±5℃ to 860±5℃, and the carbon potential decreased from 1.15±0.05% to 0.95±0.05%. The cycle of this stage is 120±10min. In the first diffusion stage, the temperature was set to 860±5℃, the carbon potential was set to 0.95±0.05%, and the cycle was 150±5min. In the second cooling and carbon potential reduction stage, the temperature is reduced from 860±5℃ to 830±5℃, and the carbon potential is reduced from 0.95±0.05% to 0.85±0.05%. The cycle of this stage is 30±10 min. In the second diffusion stage, the temperature was set at 830±5℃, the carbon potential was set at 0.85±0.05%, and the cycle was 30±5min. During the slow cooling stage, the carburized gear blank is pulled to the front chamber of the carburizing equipment and the temperature is slowly reduced to 150°C under nitrogen protection and oil wall cooling conditions. The cycle of this stage is set to 120±5min.

2. The method for machining a disc-shaped carburized gear according to claim 1, characterized in that, In step 2, the pre-heat treatment process for the gear blank is as follows: The gear blanks are stacked in an orderly manner and heated to 930℃±10℃, held at that temperature, then rapidly cooled, and transferred to an isothermal normalizing furnace, where the temperature is set to 650℃±10℃ and held to complete the preliminary heat treatment of the gear blanks.

3. The method for machining a disc-shaped carburized gear according to claim 1, characterized in that, In step 2, the normalizing structure of the inner gear ring (1) and outer gear ring (2) of the gear blank mainly includes metallographic structure detection and banded structure detection.

4. The method for machining a disc-shaped carburized gear according to claim 1, characterized in that, In step 2, the roughing and finishing processes are as follows: S1, make a reserved machining at the upper and lower ends of the outer gear ring (2) and the upper end of the inner gear ring (1) of the gear blank, wherein the reserved size is 0.43±0.03mm; S2, perform hot gear shaping operation, where the ball pitch of the gear blank is 184.64±0.03mm.

5. The method for machining a disc-shaped carburized gear according to claim 1, characterized in that, In step 2, the pressure quenching process is as follows: K1 involves reheating the carburized and slowly cooled gear blank in a rotary hearth furnace. K2, after secondary heating, uses an outer pressure ring and an outer support ring to restrict the deformation of the large end face, and an inner pressure ring and an inner support ring to restrict the deformation of the small end face and groove. K3, measure the tooth span and ball pitch. If the dimensions and metallographic indicators of the tooth span and ball pitch are all qualified, proceed to the next cleaning and shot blasting process; otherwise, perform pressure quenching and rework.

6. The method for machining a disc-shaped carburized gear according to claim 5, characterized in that, In K1, the secondary heating temperature is 860±5℃, the carbon potential is 0.9±0.05%, and the holding time is 100-120min.

7. The method for machining a disc-shaped carburized gear according to claim 5, characterized in that, In K1 and K3, during the pressure quenching rework process, the parts with inclined supports are placed in reverse into the furnace for secondary heating. The parts that have undergone secondary heating are then adjusted to adjust the internal tooth span and ball pitch until they meet the required dimensions and metallographic indicators.

8. The method for machining a disc-shaped carburized gear according to claim 1, characterized in that, In K1, after step 3, the finished disc-shaped carburized gears that have completed all processes are inspected for dimensions, oiled, packaged, and put into storage.

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