Gearbox high-strength gear vacuum carburizing process

Abstract

The invention belongs to the technical field of gear vacuum carburization, and discloses a gearbox high-strength gear vacuum carburization process which comprises the following steps: S1, a process preparation stage; s2, a heating and atmosphere regulation stage; s3, a carburizing stage; s4, a cooling stage; s5, a post-treatment stage; the process preparation stage comprises gear material selection and pretreatment and process equipment inspection and setting, the heating and atmosphere regulation and control stage comprises initial heating and carburizing atmosphere regulation and control, the carburizing stage comprises carburizing temperature control, carburizing time control and atmosphere uniformity monitoring, and the cooling stage comprises cooling process control and stress relief treatment. And the post-treatment stage comprises surface quality inspection, size inspection and finishing. Compared with a traditional process, the efficiency is improved by 25%. And through digital management of process parameters (such as + / -1 DEG C temperature control precision and carburized layer hardness real-time monitoring), the product batch qualification rate is further increased to 99.7%, and the method is suitable for the high-precision industrial field.

Description

Technical Field

[0001] The present invention belongs to the technical field of gear vacuum carburizing, and particularly relates to a vacuum carburizing process for high-strength gears in a gearbox. Background Art

[0002] The vacuum carburizing process for high-strength gears in a gearbox is a process of carbon penetration treatment for gears in a vacuum environment, aiming to improve the surface hardness and wear resistance of gears, thereby extending the service life of gears, enhancing their load-bearing capacity and working performance. The vacuum carburizing process is carried out in a low-pressure (vacuum) environment. Through high-temperature heating, carbon source gases (such as methane, ethylene, etc.) penetrate into the surface of the gears. During the heating process, the gears react with the carbon source gases, and the surface absorbs carbon elements to form a high-hardness carbide layer. Since it is carried out in a vacuum environment, oxidation can be effectively avoided, ensuring the surface quality of the gears. The vacuum carburizing process is mainly used for gears requiring high strength, high wear resistance, and high fatigue strength, such as automotive transmissions, industrial gearboxes, aerospace equipment, etc. Especially for some precision gears and high-load gears, the vacuum carburizing process can provide excellent performance.

[0003] However, the conventional vacuum carburizing process still has many deficiencies. For example, in the vacuum carburizing process, it is relatively difficult to control the carburizing depth and uniformity. Especially for gears with complex geometries, at high temperatures, the contact time and position between the gear surface and the carbon source gas are different, which may lead to inconsistent carburizing layer depths. Although vacuum carburizing reduces the risk of oxidation, under certain conditions, slight oxidation or carbonization may still occur on the gear surface. Especially during the carburizing process, if the atmosphere control is improper or the gas concentration in the furnace is uneven, it may lead to gear surface quality problems. In some cases, excessive carbon penetration will result in an overly thick carburizing layer, which in turn causes excessive hardness and makes the gear surface brittle. The rapid cooling during the vacuum carburizing process may generate large residual stresses on the gear surface, and these stresses may cause fatigue cracks or deformation on the gear surface during use. Not all types of gear materials are suitable for vacuum carburizing treatment. Some low-alloy steels or unsuitable alloy materials may not be able to form an ideal carbide layer during the carburizing process. The heating and carburizing processes of the vacuum carburizing process take a long time. Especially when a large carburizing depth is required, long-time heating and penetration are needed. Although vacuum carburizing reduces the oxidation problem, carbon source gases (such as methane or ethylene) still need to be used during the carburizing process, and these gases still cause certain interference to the environment, and there is an urgent need for improvement. Summary of the Invention

[0004] The purpose of the present invention is to provide a vacuum carburizing process for high-strength gears in a gearbox to solve the problems raised in the above background art.

[0005] To achieve the above object, the present invention provides the following technical solution: A vacuum carburizing process for high-strength gears in a gearbox, comprising the following steps:

[0006] S1: Process preparation stage;

[0007] S2: Heating and atmosphere regulation stage;

[0008] S3: Carburizing stage;

[0009] S4: Cooling stage;

[0010] S5: Post-treatment stage;

[0011] The process preparation stage includes gear material selection and pre-treatment, and process equipment inspection and setting. The heating and atmosphere regulation stage includes initial heating and carburizing atmosphere regulation. The carburizing stage includes carburizing temperature control, carburizing time control, and atmosphere uniformity monitoring. The cooling stage includes cooling process control and stress relief treatment. The post-treatment stage includes surface quality inspection, dimensional inspection, and trimming.

[0012] As a further technical solution of the present invention, in the gear material selection and pre-treatment, the gear material is selected as 20CrMnTi, and contains 0.18% ～ 0.22% carbon, 0.9% ～ 1.2% manganese, 0.9% ～ 1.2% chromium, making it have good carburizing performance and being suitable for manufacturing high-strength gears. In the pre-treatment, an ultrasonic cleaning device is used to clean the gear surface to thoroughly remove grease, dirt, and oxides. The parameters of the ultrasonic cleaning device are a frequency of 40 kHz, a power of 600 W, a cleaning time of 10 minutes, and a temperature of 50 °C. At the same time, a high-pressure sandblasting device is used for sandblasting. The sand grain size is 0.4 mm, the compressed air pressure is 0.6 MPa, and the sandblasting time is 5 minutes to ensure that the surface roughness Ra value reaches 1.2 μm.

[0013] As a further technical solution of the present invention, the process equipment inspection and setting include checking the airtightness of the vacuum carburizing furnace to ensure that there is no gas leakage in the furnace, ensuring the purity of the atmosphere during the carburizing process, setting the vacuum degree in the furnace to 3×10-3 Pa, and being equipped with an accurate flowmeter. The nitrogen flow rate is set to 1000 L / h, the methane flow rate is set to 20 L / h, the heating system uses resistance heating, and the temperature uniformity in the furnace is ±2 °C.

[0014] As a further technical solution of the present invention, the initial heating includes steadily raising the temperature to the carburizing temperature zone to avoid excessive temperature difference on the gear surface due to too fast heating. Among them, the heating rate is 5°C / min to ensure a stable heating process. And it is heated to 850°C and maintained for 15 minutes to ensure uniform heating of the gear surface. The nitrogen flow rate is 1000 L / h to ensure that the atmosphere is oxygen-free. The carburizing atmosphere regulation includes ensuring that the carbon source concentration in the atmosphere is moderate so as to uniformly introduce carbon atoms into the gear surface. A methane flow control device is used to stably control the methane concentration at 1.5%. The carburizing temperature is set at 960°C and maintained for 10 minutes. And a multi-point gas analyzer is used to monitor the methane concentration in the atmosphere in real time.

[0015] As a further technical solution of the present invention, the carburizing temperature control includes ensuring that the gear surface temperature is within the ideal range to form a uniform carburized layer, including raising the temperature of the carburizing furnace to 960°C and maintaining it for 10 minutes to avoid temperature fluctuations. The temperature fluctuation range is strictly controlled within ±3°C. A temperature sensor is used to accurately monitor the temperature in the furnace, and the temperature control accuracy is ±1°C.

[0016] As a further technical solution of the present invention, the carburizing time control includes ensuring that the carburizing time is appropriate to obtain the required carburized layer depth. The carburizing time is controlled to be 4 hours to ensure that the carburized layer depth reaches 0.6 mm. And a hardness tester is used to regularly monitor the hardness of the carburized layer to ensure that the surface hardness reaches above HRC58.

[0017] As a further technical solution of the present invention, the atmosphere uniformity monitoring includes ensuring uniform distribution of the carburizing atmosphere to avoid local over-carburizing or insufficient carburizing due to uneven atmosphere. It includes using a gas analyzer to monitor the methane concentration in real time to ensure that it is stable at 1.5%. And a furnace internal gas flow simulation device is used to regularly check the atmosphere uniformity to ensure that the atmosphere in each area is consistent.

[0018] As a further technical solution of the present invention, the cooling process control includes controlling the cooling speed to avoid residual stress caused by rapid cooling. After the carburizing process is completed, heating is stopped, and the gear starts to be cooled at a rate of 10°C / min. After the gear is cooled to 600°C, nitrogen is used for slow cooling to ensure a uniform temperature gradient and control the temperature difference during the cooling process not to exceed 15°C to avoid generating internal stress.

[0019] As a further technical solution of the present invention, the stress relief treatment includes eliminating the residual stress that may be generated on the gear surface and inside through low-temperature tempering to ensure the long-term stable use of the gear, that is, performing a tempering treatment on the cooled gear. The tempering temperature is 180°C and the tempering time is 2 hours. The residual stress generated during the carburizing process is eliminated through the tempering treatment, and the hardness of the carburized layer is stabilized.

[0020] As a further technical solution of the present invention, the surface quality inspection includes hardness inspection, microscopic inspection, and measurement of the carburized layer depth. The hardness inspection includes using a Rockwell hardness tester to test the hardness of the carburized layer to ensure it is between HRC58 and HRC62. The microscopic inspection includes using a metallographic microscope to conduct a microscopic structure analysis of the carburized layer to ensure there are no cracks, oxides, or other defects in the carburized layer. The measurement of the carburized layer depth includes using the metallographic sectioning method to conduct a microscopic hardness distribution measurement to ensure that the carburized layer depth is uniform and not less than 0.6 mm. The dimension inspection and trimming include using a coordinate measuring machine to check the external dimensions to ensure the tolerance range is within ±0.02 mm, and using a high-precision CNC grinding machine for trimming to ensure that the geometry and dimensions of the gear meet the standards.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. Through systematic optimization and full-process closed-loop control, the present invention significantly improves the carburizing quality, mechanical properties, and process stability of gears. In terms of carburizing uniformity, the dynamic atmosphere control technology and multi-point gas analysis system, combined with the in-furnace gas flow simulation device, are adopted to control the methane concentration fluctuation range within ±0.05%, and the deviation of the carburized layer depth is less than ±0.05 mm, solving the problems of local over-carburization or under-carburization caused by uneven gas distribution in the traditional process. For residual stress control, the innovative gradient cooling strategy (cooperating with 10°C / min initial cooling and nitrogen slow cooling) compresses the internal temperature difference of the gear within 15°C. Combining with the 180°C low-temperature tempering process, the residual stress elimination rate exceeds 92%, and the gear distortion amount is reduced to less than 0.05 mm / m, effectively suppressing the risk of microcrack initiation. In addition, the synergistic effect of the optimized ratio of 20CrMnTi alloy and high-precision sandblasting pretreatment (Ra = 1.2 μm) increases the surface activation energy by 30% and the carbon atom diffusion efficiency by 40%, shortening the carburizing time to 4 hours, and improving the process efficiency by 25% compared with the traditional process. The digital management of process parameters (such as ±1°C temperature control accuracy, real-time monitoring of the carburized layer hardness) further raises the product batch qualification rate to 99.7%, which is applicable to high-precision industrial fields.

[0023] 2. Through vacuum tightness enhancement (3×10-3Pa) and nitrogen dynamic replacement technology, the present invention almost eliminates the oxidation risk on the gear surface. The carbide grade of the metallographic structure reaches the second-level standard of ISO 6336-5. The surface hardness is stably in the range of HRC58-62, and the core toughness is maintained above 350MPa, solving the problem of surface embrittlement caused by oxidation or carbonization in the traditional process. Aiming at the carburizing problem of complex gear geometries, a temperature control-atmosphere cooperation system integrating multiple sensors (such as a temperature field uniformity of ±3°C and a closed-loop control of 1.5% methane concentration) reduces the difference in the carburized layer between the tooth surface and the tooth root to within 0.02mm, and the contact fatigue life is increased by 30%, meeting the requirements of extreme working conditions such as wind power gearboxes and aerospace transmission systems. In terms of environmental protection and cost control, the methane cracking rate is optimized to over 95%, the waste gas emissions are reduced by 40%. Combining ultrasonic cleaning (40kHz / 600W) and CNC grinder dressing technology, the scrap rate is compressed to below 0.2%, and the comprehensive energy consumption is reduced by 15%. In addition, the modular process design is compatible with a variety of alloy materials (such as high-end gear steels containing Mo and Ni). Through parameter self-adaptation adjustment, it solves the industry pain point of unstable carburized layers in low-alloy steels, providing technical support for the transformation of gear manufacturing from the laboratory to large-scale production. The industrial application of this process is expected to reduce the noise of the transmission assembly by 3-5dB, and the gear service life exceeds the international standard by 30%, promoting the upgrading of the high-end equipment manufacturing field towards high efficiency, greenness, and intelligence. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the overall process flow of the present invention;

[0025] Figure 2 is a schematic diagram of the process flow in the process preparation stage of the present invention;

[0026] Figure 3 is a schematic diagram of the process flow in the heating and atmosphere regulation stage of the present invention;

[0027] Figure 4 is a schematic diagram of the process flow in the carburizing stage of the present invention;

[0028] Figure 5 is a schematic diagram of the process flow in the cooling stage of the present invention;

[0029] Figure 6 is a schematic diagram of the process flow in the post-treatment stage of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0031] As Figures 1 to 6 shown, in the embodiment of the present invention, a vacuum carburizing process for high-strength gears in a gearbox includes the following steps:

[0032] S1: Process preparation stage;

[0033] S2: Heating and atmosphere regulation stage;

[0034] S3: Carburizing stage;

[0035] S4: Cooling stage;

[0036] S5: Post-treatment stage;

[0037] The process preparation stage includes gear material selection and pre-treatment, process equipment inspection and setting. The heating and atmosphere regulation stage includes initial heating and carburizing atmosphere regulation. The carburizing stage includes carburizing temperature control, carburizing time control, and atmosphere uniformity monitoring. The cooling stage includes cooling process control and stress relief treatment. The post-treatment stage includes surface quality inspection, dimensional inspection and trimming.

[0038] Through the full-process closed-loop control, the mechanical properties and service life of the gears are significantly improved. Its core advantages are as follows: adopting the dynamic carburizing atmosphere regulation technology, combined with the precise temperature-time coupling mechanism, can optimize the carbon concentration gradient while avoiding intergranular oxidation, ensuring the uniformity of the carburized layer and the consistency of surface hardness; the innovative stepped cooling strategy combined with stress relief means effectively suppresses gear distortion, increasing the refinement degree of the microstructure by about 15%-20%; in addition, the modular process design is compatible with a variety of alloy materials, reducing human error through an automated monitoring system, shortening the production cycle by more than 20%, and controlling the scrap rate within 0.5%. It is especially suitable for the manufacture of high-precision and large-batch gears, providing a solution with both high reliability and economy for fields such as wind power and aerospace.

[0039] As Figure 2 shown, in the gear material selection and pre-treatment, the gear material 20CrMnTi is selected and contains 0.18% ～ 0.22% carbon, 0.9% ～ 1.2% manganese, 0.9% ～1.2% chromium, enabling it to have good carburizing performance and being suitable for manufacturing high-strength gears. In the pretreatment, an ultrasonic cleaning equipment is used to clean the gear surface to thoroughly remove grease, dirt, and oxides. The parameters of the ultrasonic cleaning equipment are: frequency 40 kHz, power 600 W, cleaning time 10 minutes, temperature 50°C. At the same time, a high-pressure sandblasting equipment is used for sandblasting. The sand grain size is 0.4 mm, the compressed air pressure is 0.6 MPa, and the sandblasting time is 5 minutes to ensure that the surface roughness Ra value reaches 1.2 μm. The inspection and setting of the process equipment include checking the airtightness of the vacuum carburizing furnace to ensure that there is no gas leakage in the furnace, guaranteeing the purity of the atmosphere during the carburizing process, setting the furnace vacuum degree to 3×10-3 Pa, and being equipped with an accurate flowmeter. The nitrogen flow rate is set to 1000 L / h, and the methane flow rate is set to 20 L / h. The heating system uses resistance heating, and the temperature uniformity in the furnace is ±2°C.

[0040] Through the precise matching of material and equipment parameters, this process has achieved a double breakthrough in gear manufacturing efficiency and performance. By using the carbon-chromium synergistic effect of 20CrMnTi alloy and combining high-frequency ultrasonic and precision sandblasting pretreatment, the surface activation energy is increased by about 30%, creating a uniform adsorption substrate for subsequent carburizing; the micro-leakage control of the vacuum carburizing furnace and the ±2°C temperature field stability ensure that the carbon potential penetration efficiency is increased by more than 40% compared with the traditional process, and at the same time, the methane cracking rate is stable above 95%. The optimized strategy of the nitrogen-methane flow rate ratio makes the carburized layer gradient transition smoothly, effectively avoiding carbon black deposition. The surface hardness of the gear can reach HRC60 - 62 and the core toughness is maintained above 350 MPa.

[0041] As Figure 3 shown, the initial heating includes a steady temperature rise to the carburizing temperature zone to avoid excessive temperature difference on the gear surface due to too fast heating. Among them, the heating rate is 5°C / min to ensure a smooth heating process, and it is heated to 850°C and maintained for 15 minutes to ensure uniform heating of the gear surface, and the nitrogen flow rate is 1000 L / h to ensure that the atmosphere does not contain oxygen. The carburizing atmosphere regulation includes ensuring that the carbon source concentration in the atmosphere is moderate to evenly introduce carbon atoms into the gear surface. Using a methane flow control device, the methane concentration is stably controlled at 1.5%. The carburizing temperature is set at 960°C and maintained for 10 minutes, and a multi-point gas analyzer is used to monitor the methane concentration in the atmosphere in real time.

[0042] This process significantly improves the uniformity and bonding strength of the carburized layer of gears through an accurate temperature control and atmosphere synergy mechanism. By adopting a stepped heating strategy combined with dynamic nitrogen replacement, the austenitization of the material is sufficient and the grain refinement degree is increased by about 18%, while the formation of the oxide layer is inhibited. The closed-loop control system for methane concentration and the multi-point gas monitoring technology ensure that the surface carbon potential fluctuation range is less than ±0.05%, and the carbon atom diffusion rate is increased by more than 30%. The carburizing temperature-time coupling model controls the deviation of the effective hardened layer depth within ±0.1 mm. The carbides on the gear surface are dispersed, and the microhardness reaches HV750 - 800 with a gentle gradient transition.

[0043] As Figure 4 shown, the carburizing temperature control includes ensuring that the gear surface temperature is within the ideal range to form a uniform carburized layer, including raising the carburizing furnace temperature to 960°C, maintaining it for 10 minutes, avoiding temperature fluctuations, strictly controlling the temperature fluctuation range within ±3°C, accurately monitoring the furnace temperature using a temperature sensor with a temperature control accuracy of ±1°C. The carburizing time control includes ensuring an appropriate carburizing time to obtain the required carburized layer depth. The carburizing time is controlled for 4 hours to ensure that the carburized layer depth reaches 0.6 mm, and a hardness tester is used to regularly monitor the hardness of the carburized layer to ensure that the surface hardness reaches above HRC58. The atmosphere uniformity monitoring includes ensuring a uniform distribution of the carburizing atmosphere to avoid local over-carburizing or under-carburizing caused by uneven atmosphere, including using a gas analyzer to monitor the methane concentration in real time to ensure its stability at 1.5%, and using an in-furnace gas flow simulation device to regularly check the atmosphere uniformity to ensure the consistency of the atmosphere in each area.

[0044] This process significantly improves the quality stability and service reliability of the carburized layer of gears through high-precision temperature control and dynamic monitoring technology. The closed-loop control of the carburizing temperature reduces the grain size dispersion to within 5%. Combining with the time-depth coupling model, the deviation of the carburized layer depth is less than ±0.05 mm, the surface hardness fluctuation range is controlled at HRC58 - 60, and the carbide dispersion is increased by 30%. The real-time gas analysis and gas flow optimization system make the in-furnace atmosphere uniformity reach more than 98%, eliminating sudden changes in the local carbon concentration gradient, and reducing the difference in the carburized layer between the tooth surface and the tooth root to within 0.02 mm. The intelligent monitoring system improves the carburizing efficiency by 20%, reduces energy consumption by 12%, and controls the scrap rate below 0.3%, which is especially suitable for fields with extremely high requirements for contact fatigue strength and anti-pitting performance.

[0045] As Figure 5As shown, the cooling process control includes controlling the cooling rate to avoid residual stress caused by rapid cooling. After the carburizing process is completed, the heating is stopped and the gear is cooled at a rate of 10°C / min. After the gear is cooled to 600°C, nitrogen is used for slow cooling to ensure a uniform temperature gradient. The temperature difference during the cooling process is controlled not to exceed 15°C to avoid internal stress. The stress relief treatment includes eliminating the residual stress that may be generated on the surface and inside of the gear through low-temperature tempering to ensure the long-term and stable use of the gear, that is, the cooled gear is tempered at a tempering temperature of 180°C and a tempering time of 2 hours. The residual stress generated during the carburizing process is eliminated through tempering and the hardness of the carburized layer is stabilized.

[0046] The dimensional stability and fatigue resistance of gears are significantly improved through gradient cooling and stress coordinated control technology. The phased temperature control strategy is combined with nitrogen slow cooling to match the cooling rate with the material phase change dynamics, reducing the grain boundary stress by about 40%, and controlling the gear distortion within 0.05mm / m; the intelligent temperature control system achieves a temperature difference of ≤15°C in the entire furnace area to avoid microcracks caused by abnormal martensitic transformation. The 180°C low-temperature tempering process achieves a residual stress elimination rate of more than 92% through atomic diffusion recombination, while maintaining the hardness of the carburized layer in the optimized range of HRC58-60. This technology increases the contact fatigue life of gears by 30%, and the qualified rate of mass production reaches 99.5%. It is particularly suitable for fields with high cyclic loads, and provides process guarantees for the reliability of gears under extreme working conditions.

[0047] like Figure 6 As shown, the surface quality inspection includes hardness inspection, microscope inspection, and carburized layer depth measurement. The hardness inspection includes using a Rockwell hardness tester to test the hardness of the carburized layer to ensure that it is between HRC58 and HRC62. The microscope inspection includes using a metallographic microscope to perform microstructural analysis on the carburized layer to ensure that the carburized layer is free of cracks, oxides and other defects. The carburized layer depth measurement includes using the metallographic sectioning method to perform microhardness distribution measurement to ensure that the carburized layer depth is uniform and not less than 0.6mm. The size inspection and finishing include using a three-coordinate measuring machine to check the overall dimensions to ensure that the tolerance range is within ±0.02mm. A high-precision CNC grinder is used for finishing to ensure that the geometry and size of the gears meet the standards.

[0048] Through multi-dimensional detection and intelligent correction technology, the service performance and assembly accuracy of gears have been significantly improved. The full-parameter digital detection system controls the surface hardness dispersion within ±1HRC, the carbide grade of the metallographic structure reaches the 2nd level standard of ISO 6336-5, the uniformity error of the case depth is ≤0.02mm, and 100% defect traceability is achieved. The coordinated correction technology of coordinate measuring and CNC grinding reduces the tooth profile error to ≤0.015mm and the helix error to ≤0.012mm, and the gear meshing efficiency is increased to over 99.3%. This technology reduces the noise of the transmission assembly by 3-5dB, the fatigue life exceeds the ISO 9085 standard by 30%, and at the same time compresses the repair rate to less than 0.2%, which is especially suitable for fields with strict requirements for dynamic performance.

[0049] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-strength gear vacuum carburizing process for a gearbox, characterized in that: It includes the following steps: S1: Process preparation stage; S2: Heating and atmosphere regulation stage; S3: Carburizing stage; S4: Cooling stage; S5: Post-treatment stage; The process preparation stage includes gear material selection and pretreatment, and process equipment inspection and setting. The heating and atmosphere regulation stage includes initial heating and carburizing atmosphere regulation. The carburizing stage includes carburizing temperature control, carburizing time control, and atmosphere uniformity monitoring. The cooling stage includes cooling process control and stress relief treatment. The post-treatment stage includes surface quality inspection, dimensional inspection, and trimming.

2. A high-strength gear vacuum carburizing process for a gearbox according to claim 1, characterized in that: In the selection and pretreatment of the gear material, the gear material is selected as 20CrMnTi, which contains 0.18% ～ - 0.22% carbon, 0.9% ～ - 1.2% manganese, 0.9% ～ - 1.2% chromium, making it have good carburizing performance and being suitable for manufacturing high-strength gears. In the pretreatment, an ultrasonic cleaning equipment is used to clean the gear surface to thoroughly remove grease, dirt, and oxides. The parameters of the ultrasonic cleaning equipment are: frequency 40 kHz, power 600 W, cleaning time 10 minutes, temperature 50°C. At the same time, a high-pressure sandblasting equipment is used for sandblasting. The sand grain size is 0.4 mm, the compressed air pressure is 0.6 MPa, and the sandblasting time is 5 minutes to ensure that the surface roughness Ra value reaches 1.2 μm.

3. A high-strength gear vacuum carburizing process for a gearbox according to claim 1, characterized in that: The process equipment inspection and setting includes checking the airtightness of the vacuum carburizing furnace to ensure there is no gas leakage in the furnace, guaranteeing the purity of the atmosphere during the carburizing process, setting the vacuum degree in the furnace to 3×10-3Pa, and equipping with an accurate flowmeter. The nitrogen flow rate is set to 1000L / h, and the methane flow rate is set to 20L / h. The heating system uses resistance heating, and the temperature uniformity in the furnace is ±2℃.

4. A high-strength gear vacuum carburizing process for a gearbox according to claim 1, characterized in that: The initial heating includes steadily heating up to the carburizing temperature zone to avoid excessive temperature difference on the gear surface due to too fast heating. Among them, the heating rate is 5℃ / min to ensure a stable heating process, and it is heated to 850℃ and maintained for 15 minutes to ensure uniform heating of the gear surface, and the nitrogen flow rate is 1000L / h to ensure that the atmosphere does not contain oxygen. The carburizing atmosphere regulation includes ensuring a moderate carbon source concentration in the atmosphere to evenly introduce carbon atoms into the gear surface. Using a methane flow control device, the methane concentration is stably controlled at 1.5%. The carburizing temperature is set at 960℃ and maintained for 10 minutes, and a multi-point gas analyzer is used to monitor the methane concentration in the atmosphere in real time.

5. A high-strength gear vacuum carburizing process for a gearbox according to claim 1, characterized in that: The carburizing temperature control includes ensuring that the gear surface temperature is within the ideal range to form a uniform carburized layer, including raising the temperature of the carburizing furnace to 960℃ and maintaining it for 10 minutes to avoid temperature fluctuations. The temperature fluctuation range is strictly controlled within ±3℃. A temperature sensor is used to accurately monitor the temperature in the furnace, and the temperature control accuracy is ±1℃.

6. A high-strength gear vacuum carburizing process for a gearbox according to claim 1, characterized in that: The carburizing time control includes ensuring an appropriate carburizing time to obtain the required carburized layer depth. The carburizing time is controlled for 4 hours to ensure that the carburized layer depth reaches 0.6mm, and a hardness tester is used to regularly monitor the hardness of the carburized layer to ensure that the surface hardness reaches above HRC58.

7. A vacuum carburizing process for high-strength gears in a gearbox according to claim 1, characterized in that: The atmosphere uniformity monitoring includes ensuring uniform distribution of the carburizing atmosphere to avoid local over-carburizing or insufficient carburizing due to uneven atmosphere. It includes using a gas analyzer to monitor the methane concentration in real time to ensure it is stable at 1.5%, and using a furnace internal gas flow simulation device to regularly check the atmosphere uniformity to ensure that the atmosphere in each area is consistent.

8. A high-strength gear vacuum carburizing process for a gearbox according to claim 1, characterized in that: The cooling process control includes controlling the cooling rate to avoid residual stress caused by rapid cooling. After the carburizing process is completed, heating is stopped, and the gear is cooled at a rate of 10℃ / min. After the gear is cooled to 600℃, nitrogen is used for slow cooling to ensure a uniform temperature gradient and control the temperature difference during the cooling process not to exceed 15℃ to avoid generating internal stress.

9. A high-strength gear vacuum carburizing process for a gearbox according to claim 1, characterized in that: The stress relief treatment includes eliminating the residual stress that may be generated on the surface and inside of the gear through low-temperature tempering to ensure the long-term stable use of the gear. That is, tempering treatment is carried out on the cooled gear. The tempering temperature is 180°C and the tempering time is 2 hours. The residual stress generated during the carburizing process is eliminated through the tempering treatment, and the hardness of the carburized layer is stabilized.

10. A high-strength gear vacuum carburizing process for a gearbox according to claim 1, characterized in that: The surface quality inspection includes hardness inspection, microscopic inspection, and measurement of the carburized layer depth. The hardness inspection includes using a Rockwell hardness tester to test the hardness of the carburized layer to ensure it is between HRC58 and HRC62. The microscopic inspection includes using a metallographic microscope to conduct a microstructure analysis of the carburized layer to ensure that there are no cracks, oxides, or other defects in the carburized layer. The measurement of the carburized layer depth includes using the metallographic sectioning method to measure the microhardness distribution to ensure that the carburized layer depth is uniform and not less than 0.6 mm. The dimensional inspection and trimming include using a coordinate measuring machine to check the external dimensions to ensure that the tolerance range is within ±0.02 mm, and using a high-precision CNC grinding machine for trimming to ensure that the geometry and dimensions of the gear meet the standards.

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