Machining process of stainless steel gear for small-tooth-difference planet gear transmission mechanism

Abstract

The invention relates to the technical field of alloy smelting, heat treatment and machining, and discloses a machining process of a stainless steel gear for a small-tooth-difference planet gear transmission mechanism, which comprises the following steps: S1, refining a stainless steel ingot, carrying out desulfurization and dephosphorization treatment, and then pouring into a stainless steel rod; s2, roughly turning the stainless steel rod and dividing the stainless steel rod into gear blank sections; s3, the gear blank section is subjected to heat treatment, after solution treatment and heat preservation of the gear blank section are completed, the gear blank section is rapidly cooled to 32 DEG C or below in a water quenching or oil quenching or air cooling mode, then precipitation hardening aging treatment is conducted on the gear blank section, and then the gear blank section is air-cooled to the room temperature; s4, finish turning of the gear blank section; s5, gear manufacturing is conducted, specifically, the gear blank section is machined into a gear through a gear shaping or gear hobbing machining method; s6, low-temperature annealing is conducted, and then the gear is air-cooled to the room temperature; s7, accurate grinding is conducted, specifically, the surface except the tooth part is accurately ground to the design size; and S8, gear grinding is conducted, specifically, the tooth profile of the gear is ground to the finished product size.

Description

Technical Field

[0001] The invention relates to the technical field of alloy smelting, heat treatment and processing, and more specifically to a processing technology of a stainless steel gear for a planetary gear transmission mechanism with a small tooth difference. Background Art

[0002] The small tooth difference planetary gear transmission mechanism is a special planetary gear transmission mechanism, which consists of internal gears and external gears meshing with each other, as well as an output mechanism, and the number of teeth of the internal gears and external gears is very small. The small tooth difference planetary gear transmission mechanism has the advantages of small size, light weight, compact structure, wide transmission ratio range, high transmission efficiency, etc., and is currently widely used in aerospace, shipbuilding, engineering machinery and other fields.

[0003] The core parts of the planetary gear transmission mechanism with small tooth difference are the meshing internal gears and external gears. Under normal use conditions, the internal gears and external gears processed by conventional gear materials can meet the use requirements after heat treatment such as carburizing and quenching or nitriding. However, under certain special use conditions, such as high temperature and strong radiation conditions, in order to ensure accuracy and reduce thermal deformation and corrosion loss, parts such as internal gears and external gears need to have properties such as high temperature resistance and corrosion resistance. Among the materials commonly used in the mechanical field, stainless steel materials have excellent properties such as high temperature resistance and corrosion resistance. However, stainless steel materials cannot be heat treated by carburizing, quenching or nitriding like conventional gear materials. The internal gears and external gears directly processed by stainless steel on the market are prone to hot brittleness and cold brittleness, and the mechanical properties, high temperature resistance and corrosion resistance cannot meet the use requirements. In addition, stainless steel materials themselves have high hardness and strength, and are difficult to process. If the tools and processing parameters used to process conventional gear materials are used, the chips are easy to stick to the tools, and it is also easy to cause problems such as tool chipping, insufficient processing accuracy and surface finish. There is no suitable or mature process in the prior art for processing stainless steel to produce gears suitable for use under high temperature and strong radiation conditions. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies in the prior art, the present invention provides a processing technology for stainless steel gears used in a planetary gear transmission mechanism with a small tooth difference. The present invention achieves the above-mentioned purpose through the following technical solutions.

[0005] A processing technology for stainless steel gears for a small-tooth-difference planetary gear transmission mechanism comprises the following steps: S1, refining stainless steel ingots, remelting the stainless steel ingots for desulfurization and dephosphorization treatment, and then casting them into stainless steel bars, with each furnace of molten steel casting one batch of stainless steel bars; S2, rough turning of stainless steel bars, using tungsten-cobalt carbide turning tools to turn stainless steel bars, and dividing the stainless steel bars into several gear billets, each batch of stainless steel bars is divided into a batch of gear billets, the rake angle α is in the range of 16-18°, the back angle β is in the range of 6-9°, the main deflection angle is in the range of 40-80°, the secondary deflection angle is in the range of 11-14°, the blade inclination angle λs is in the range of -4-6°, the cutting speed is in the range of 40-80m / min, the feed rate is in the range of 0.2-0.5mm / r, the back cutting amount is in the range of 3-5mm, and the cutting allowance relative to the single side of the finished product is in the range of 6.5-8.5mm, and the cutting fluid is continuously poured on the contact position between the turning tool and the workpiece, and the cutting fluid adopts an emulsion with an oil-water dilution ratio in the range of 1:20-1:18; S3, heat treatment of the gear billet, firstly subjecting the gear billet to solid solution treatment, the holding temperature of the solid solution treatment is 1025-1055°C, the holding time is 30-45 minutes, after the holding is completed, the gear billet is quickly cooled to below 32°C by water quenching, oil quenching or air cooling, and then the gear billet is subjected to precipitation hardening aging treatment, the holding temperature of the precipitation hardening aging treatment is in the range of 480-620°C, the holding time is in the range of more than 2 hours, and then the gear billet is air-cooled to room temperature; S4, precision turning of gear blanks, using tungsten-cobalt carbide turning tools to turn gear blanks, the rake angle α is in the range of 20-25°, the back angle β is in the range of 11-12°, the main deflection angle is in the range of 4-6°, the secondary deflection angle is in the range of 4-6°, the cutting edge angle λs is in the range of 0-4°, the cutting speed is in the range of 40-80m / min, the feed rate is in the range of 0.1-0.4mm / r, the back cutting amount is in the range of 0.1-0.3mm, and the cutting fluid is continuously poured at the contact position between the turning tool and the workpiece. The cutting fluid adopts an emulsion with an oil-water dilution ratio of 1:10-1:8; S5, gear making, gear blanks are processed into gears by gear shaping or gear hobbing. The gear tooth top height coefficient ranges from 0.6 to 0.8. Tungsten-cobalt carbide tools are used for gear shaping or gear hobbing. S6, low temperature annealing, placing the gear in an annealing furnace for heat preservation at a temperature of 220-280°C for 1.5-2 hours, and then air cooling the gear to room temperature; S7, fine grinding, fine grinding of the surface other than the tooth part to the designed size; S8, gear grinding, grinding the gear tooth profile to the finished size.

[0006] This solution first remelts the stainless steel ingots for desulfurization and dephosphorization, and then casts them into stainless steel rods to avoid hot brittleness and cold brittleness, and improve mechanical properties, high temperature resistance and corrosion resistance. Tungsten-cobalt carbide tools are used during cutting to effectively avoid chipping, and the chips and tools are not easy to stick together, which better ensures processing accuracy and surface finish. After rough turning, the gear billet is subjected to solid solution, precipitation hardening and aging treatments to enhance the hardness and strength of the gear billet. The various process parameters during cutting are different from the various process parameters for processing conventional gear materials, and after a large number of practical tests, high-precision gears can be processed. The various steps in this solution are combined to form a set of suitable and mature processes for processing stainless steel to produce gears suitable for use under high temperature and strong radiation conditions.

[0007] As an optimized processing technology, in the above step S5, a gear shaping method is adopted for the internal gear, and the nominal parameters of the gear shaping cutter are selected according to the GB / T 6081-2001 standard. During gear shaping, the rake angle of the gear shaping cutter is in the range of 5 to 10°, and the clearance angle is in the range of 0 to 8°. For the external gear, a gear hobbing method is adopted, and the nominal parameters of the gear hobbing cutter are selected according to the GB / T6083-2016 standard. During gear hobbing, the rake angle of the gear hobbing cutter is in the range of -1° to -2°, the top edge clearance angle αp is in the range of 10° to 12°, the side edge clearance angle is ≥3°, and the gear hobbing cutter installation angle Φ=β±λ, wherein β is the gear helix angle, λ is the gear hobbing cutter helix angle, and when the rotation direction of the gear hobbing cutter is the same as the rotation direction of the cut gear, "+" is taken, and when the rotation direction of the gear hobbing cutter is opposite to the rotation direction of the cut gear, "-" is taken. Both internal gears and external gears can be formed by gear shaping and gear hobbing. However, in order to ensure processing accuracy, this scheme adopts gear shaping for internal gears and gear hobbing for external gears. In addition, the various process parameters during cutting are different from those for processing conventional gear materials. After a large number of practical tests, high-precision gears can be processed.

[0008] As an optimized processing technology, the above step S1 includes step S1a after step S1, chemical composition analysis, sampling for chemical composition smelting analysis during casting, sampling for chemical composition finished product analysis of each batch of stainless steel bars after casting, chemical composition analysis is performed according to ASTM A751-2021 standard, and the stainless steel bars of the batch that meet the set chemical composition requirements in both smelting analysis and finished product analysis proceed to the next step. This further ensures that the processed gears meet the use requirements.

[0009] As an optimized processing technology, the above step S3 includes step S3a, etching test analysis, where at least one gear billet is randomly selected from each batch of gear billets and subjected to a macro-etching test according to the provisions of ASTM E340. The gear billets of the batch to which the macro-etching test data meets the set requirements proceed to the next step, so as to further ensure that the processed gears meet the use requirements.

[0010] As an optimized processing technology, the above step S3 includes step S3b after the liquid penetrant test and ultrasonic flaw detection. Each gear billet is subjected to 100% surface liquid penetrant test according to the test method specified in CAP-NDE-V7-032; each gear billet is subjected to 100% volume ultrasonic flaw detection according to the test method specified in CAP-NDE-V7-032; the gear billet that passes the liquid penetrant test and ultrasonic flaw detection enters the next step. Only the gear billet that has been inspected and tested can proceed to the subsequent steps such as fine turning and gear making, which can save process costs on the one hand and improve the yield rate on the other.

[0011] As an optimized processing technology, the above step S3 includes step S3c after step S3c, sampling test; measuring the Brinell hardness of each gear billet, then selecting 2% and at least one gear billet with the highest hardness from each batch of gear billets, and cutting a room temperature tensile test specimen, a high temperature tensile test specimen, and three impact test specimens at the large diameter end of the selected gear billet by a machining method; selecting 2% and at least one gear billet with the lowest hardness from each batch of gear billets, and cutting a room temperature tensile test specimen, a high temperature tensile test specimen, and three impact test specimens at the large diameter end of the selected gear billet by a machining method; When cutting, the longitudinal axis of the sample is parallel to the main processing direction of the gear billet. When the diameter of the gear billet is φ≤25mm, the longitudinal axis of the sample is at the center line of the gear billet; when 25mm<the diameter of the gear billet is φ≤50mm, the longitudinal axis of the sample is located at 12.5mm from the heat-treated surface of the gear billet; when the diameter of the gear billet is φ>50mm, the longitudinal axis of the sample is located at half the radius of the gear billet. Three impact specimens should be cut side by side; room temperature tensile specimens and high temperature tensile specimens are standard circular section specimens with a gauge length of 50mm and a diameter of 12.5mm as specified in ASTMA370. The specimens are cut according to ASTM The room temperature tensile test and high temperature tensile test are carried out according to the provisions of ASTM A370; the impact specimen is prepared according to the Charpy V-notch standard impact specimen specified in the ASTM A370 standard, and the V-notch axis of the specimen should be consistent and perpendicular to the nearest heat-treated surface of the gear billet. The impact specimen is subjected to the Charpy V-notch impact test according to the provisions of ASTM A370; the selected gear billet is subjected to a hardness test according to the provisions of ASTM A370, and the hardness test is carried out at the adjacent part of the room temperature tensile specimen or the high temperature tensile specimen, or at half the radius of the end of the gear billet; the gear billet of the batch to which the data of the Brinell hardness measurement, room temperature tensile test, high temperature tensile test, impact test and hardness test meet the set requirements can enter the next step. The gear billet of the batch to which the measurement and test data meet the set requirements can proceed to the subsequent steps such as fine turning and gear making, which can save process costs on the one hand and improve the yield rate on the other hand.

[0012] Compared with the prior art, the present invention mainly has the following beneficial effects: the present invention first remelts the stainless steel ingot for desulfurization and dephosphorization treatment, and then casts it into a stainless steel rod to avoid hot brittleness and cold brittleness tendency, and improves mechanical properties, high temperature resistance and corrosion resistance. Tungsten-cobalt carbide tools are used during cutting to avoid chipping, and the chips and tools are not easy to stick together, so as to better ensure the processing accuracy and surface finish. After rough turning, the gear billet is subjected to solid solution, precipitation hardening and aging treatment to enhance the hardness and strength of the gear billet. The various process parameters during cutting are different from the various process parameters for processing conventional gear materials, and after a large number of practical tests, high-precision gears can be processed. The various steps in the present invention are combined together to form a set of suitable and mature processes for processing stainless steel to produce gears suitable for use under high temperature and strong radiation conditions. After the corresponding steps in the whole process, component analysis, quality inspection and detection, sampling test, etc. are respectively carried out to improve the yield rate and ensure that the processed gears are suitable for use under high temperature and strong radiation conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the cross-sectional structure of the internal gear and the external gear in the embodiment when they are in meshing state. Implementation

[0014] The present invention is further described below in conjunction with the accompanying drawings. The accompanying drawings are only used for exemplary description and cannot be understood as limiting the present invention. In order to more concisely describe the present embodiment, some parts that are well known to those skilled in the art but not related to the main content of the present invention will be omitted in the accompanying drawings or descriptions. In addition, for the convenience of description, some parts in the accompanying drawings will be omitted, enlarged or reduced, but they do not represent the size or entire structure of the actual product.

[0015] Examples, such as Figure 1 As shown, it is an internal gear 1 and an external gear 2 in a planetary gear transmission mechanism with a small tooth difference used in a nuclear power equipment, the working temperature is 150-200°C, the number of teeth of the internal gear 1 is 64, the number of teeth of the external gear 2 is 63, and the module is 2.25. This embodiment takes these two gears as an example to introduce a processing technology of stainless steel gears for a planetary gear transmission mechanism with a small tooth difference, including the following steps: S1, refined stainless steel ingot. This embodiment adopts a stainless steel ingot with a steel grade of 05Cr17Ni4Cu4Nb under the GB / T 20878-2007 standard, and adopts the "arc furnace + electroslag remelting" smelting method to remelt the stainless steel ingot for precipitation desulfurization and precipitation dephosphorization treatment, and then cast it into stainless steel rods, with one batch of stainless steel rods cast from each furnace of molten steel. In other embodiments, the "vacuum arc remelting" smelting method can also be adopted. During casting and forming, a cut-off amount is left at the head and tail of the stainless steel rod to remove shrinkage cavities and major segregation.

[0016] S1a, chemical composition analysis. When each furnace of molten steel is poured, samples are taken for chemical composition smelting analysis. After casting, samples are taken from each batch of stainless steel bars for chemical composition analysis. The chemical composition analysis is carried out in accordance with ASTM A751-2021. The chemical composition of the smelting analysis is required by mass percentage as follows: C≤0.07%, Mn≤1%, P≤0.02%, S≤0.015%, Si≤1%, 15%≤Cr≤17.5%, 3%≤Ni≤5%, 3%≤Cu≤5%, 0.15%≤Nb+Ta≤0.45%, Co≤0.05%. The chemical composition of the finished product analysis is required by mass percentage: C≤0.08%, Mn≤1.03%, P≤0.02%, S≤0.015%, Si≤1.05%, 14.85%≤Cr≤17.7%, 2.93%≤Ni≤5.07%, 2.9%≤Cu≤5.15%, 0.1%≤Nb+Ta≤0.5%, Co≤0.05%. The batch of stainless steel bars that meet the set chemical composition requirements in both smelting analysis and finished product analysis will enter the next step to further ensure that the processed gears meet the use requirements.

[0017] S2, rough turning of stainless steel rods. Use tungsten-cobalt carbide turning tools to turn stainless steel rods, specifically YG6X carbide turning tools. Divide the stainless steel rods into several gear billets, and divide one batch of gear billets from each batch of stainless steel rods. During turning, the front angle α is 18°, the back angle β is 9°, the main rake angle is 50°, the secondary rake angle is 13°, the blade inclination angle λs is 0°, the cutting speed is 55m / min, the feed rate is 0.3mm / r, the back cutting amount is 3mm, and the cutting allowance is 7.5mm relative to the single side of the finished product. The cutting fluid is continuously poured on the contact position between the turning tool and the workpiece. The cutting fluid uses an emulsion with an oil-water dilution ratio of 1:20. After turning, the turning tool immediately leaves the cutting surface.

[0018] S3, heat treatment of the gear billet. First, the gear billet is subjected to a solution treatment at a holding temperature of 1025-1055°C for 30-45 minutes. After the insulation is completed, the gear billet is quickly cooled to below 32°C by oil quenching. In other embodiments, water quenching or air cooling can also be used to quickly cool the gear billet. The gear billet is then subjected to precipitation hardening and aging treatment at a holding temperature of 595°C for at least 4 hours, and then the gear billet is air-cooled to room temperature. The oxide scale produced by the heat treatment is removed by pickling or other appropriate methods.

[0019] S3a, Etching test analysis. Randomly select at least one gear billet from each batch of gear billets for macro-etching test according to ASTM E340. On the acid etched test pieces taken from the full cross section of both ends of the gear billet, there shall be no visible defects such as shrinkage cavities, bubbles, cracks, inclusions, white spots and peeling. The gear billets of the batch to which the macro-etching test data meets the set requirements shall proceed to the next step.

[0020] S3b, liquid penetrant testing and ultrasonic flaw detection. Perform 100% surface liquid penetrant testing on each gear billet according to the testing method specified in CAP-NDE-V7-032. Perform 100% volume ultrasonic flaw detection on each gear billet according to the testing method specified in CAP-NDE-V7-032. Gear billets that pass the liquid penetrant testing and ultrasonic flaw detection will proceed to the next step. Gear billets that have passed the inspection and testing can proceed to the subsequent steps of fine turning and gear making, which can save process costs on the one hand and improve the yield rate on the other.

[0021] S3c, sampling test. The Brinell hardness of each gear billet is measured, and then 2% and at least 1 gear billet with the highest hardness is selected from each batch of gear billets, and a room temperature tensile specimen, a high temperature tensile specimen, and three impact specimens are cut from the large diameter end of the selected gear billet by machining. 2% and at least 1 gear billet with the lowest hardness is selected from each batch of gear billets, and a room temperature tensile specimen, a high temperature tensile specimen, and three impact specimens are cut from the large diameter end of the selected gear billet by machining. When cutting, the longitudinal axis of the sample is parallel to the main processing direction of the gear billet, that is, the direction of grain flow, that is, longitudinal sampling. When the gear billet diameter φ≤25mm, the longitudinal axis of the sample is at the center line of the gear billet; when 25mm<gear billet diameter φ≤50mm, the longitudinal axis of the sample is located 12.5mm away from the heat treatment surface of the gear billet; when the gear billet diameter φ>50mm, the longitudinal axis of the sample is located at half the radius of the gear billet. Three impact specimens should be cut side by side.

[0022] The room temperature tensile specimens and high temperature tensile specimens are standard circular section specimens with a gauge length of 50mm and a diameter of 12.5mm as specified in the ASTM A370 standard. The specimens are subjected to room temperature tensile tests and high temperature tensile tests as specified in the ASTM A370 standard. The impact specimens are prepared according to the Charpy V-notch standard impact specimens specified in the ASTM A370 standard. The V-notch axis of the specimens should be consistent and perpendicular to the nearest heat-treated surface of the gear billet. The impact specimens are subjected to the Charpy V-notch impact test as specified in the ASTM A370 standard. The selected gear billet is subjected to a hardness test as specified in the ASTM A370 standard. The hardness test is conducted at the adjacent part of the room temperature tensile specimen or the high temperature tensile specimen, or at half the radius of the end of the gear billet.

[0023] The batch of gear billets whose data of Brinell hardness measurement, room temperature tensile test, high temperature tensile test, impact test and hardness test meet the set requirements can enter the next step. The batch of gear billets whose measurement and test data meet the set requirements can proceed to the subsequent steps of fine turning and gear making, which can save process costs on the one hand and improve the yield rate on the other.

[0024] S4, precision turning of gear blanks. Use tungsten-cobalt carbide turning tools to turn gear blanks, specifically YG6X carbide turning tools. During turning, the front angle α is 22°, the back angle β is 11°, the main deflection angle is 5°, the secondary deflection angle is 5°, the cutting angle λs is 0°, the cutting speed is 75m / min, the feed rate is 0.1mm / r, the back cutting amount is 0.2mm, and the cutting fluid is continuously poured at the contact position between the turning tool and the workpiece. The cutting fluid uses an emulsion with an oil-water dilution ratio of 1:10.

[0025] S5, gear making. The gear blank is processed into a gear by gear shaping or gear hobbing. The gear tooth top height coefficient is 0.75. The gear shaping cutter or gear hobbing cutter uses tungsten-cobalt carbide tools. The gear shaping method is used for the internal gear 1. The gear shaping accuracy is level 5. The nominal parameters of the gear shaping cutter are selected according to the GB / T 6081-2001 standard. The gear shaping cutter uses a YG6X carbide gear shaping cutter. The front angle of the gear shaping cutter is 6° and the back angle is 8° during gear shaping. Among the main process parameters of gear shaping, the stroke number is 60st / min, the stroke length is 58mm, the circumferential feed is 0.15mm / st, and the radial cut-in amount is 0.1~0.15mm per feed. The hobbing method is used for the external gear 2, and the hobbing accuracy is level 5. The nominal parameters of the hobbing cutter are selected according to the GB / T6083-2016 standard. The hobbing cutter adopts the YG6X carbide hobbing cutter. During hobbing, the hobbing cutter rake angle is -2°, the top edge clearance angle αp is 10°, and the side edge clearance angle is 5°. The hobbing cutter installation angle Φ=β±λ, where β is the gear helix angle, λ is the hobbing cutter helix angle, and the hobbing cutter rotation direction is "+" when the hobbing cutter rotation direction is the same as the cut gear rotation direction, and the hobbing cutter rotation direction is "-" when the hobbing cutter rotation direction is opposite to the cut gear rotation direction. Among the main process parameters of hobbing, the tooth width feed is 0.15mm per gear rotation, the radial cut-in amount is 0.1~0.15mm per feed, and the hobbing cutter speed is 15m / min.

[0026] S6, low temperature annealing. The working temperature of the inner gear 1 and the outer gear 2 processed in this embodiment is 150-200°C, so the gears are placed in an annealing furnace for insulation at a temperature of 220-280°C for 1.5-2 hours, and then the gears are air-cooled to room temperature.

[0027] S7, fine grinding. Align with the pitch circle of the gear and fine grind the surface outside the gear to the designed size.

[0028] S8, Gear Grinding. Gear grinding is performed by forming method. The grinding wheel is trimmed to the finished tooth profile. Attention is paid to trimming the shape and edge. The reference runout of the ground outer circle is aligned to <0.01. The gear tooth profile is ground to the finished size. The tooth root is not ground. After grinding, the surface usually needs to be inspected and the tooth surface polished. The roughness Ra<0.2.

[0029] In addition, at each stage of stainless steel bar or gear billet processing, the surface of the bar should be carefully checked. The surface of the finished bar is not allowed to have scaling, cracks, folds, spots, looseness or other defects that may damage the use of the bar.

[0030] In this embodiment, the stainless steel ingot is first remelted for desulfurization and dephosphorization treatment, and then cast into a stainless steel rod to avoid hot brittleness and cold brittleness tendency, and improve mechanical properties, high temperature resistance and corrosion resistance. Tungsten-cobalt carbide tools are used during cutting to avoid chipping, and the chips and tools are not easy to stick together, which better ensures processing accuracy and surface finish. After rough turning, the gear billet is treated with solid solution, precipitation hardening and aging to enhance the hardness and strength of the gear billet. The various process parameters during cutting are different from the various process parameters for processing conventional gear materials, and after a large number of practical tests, high-precision gears can be processed. The various steps in this embodiment are combined to form a set of suitable and mature processes for stainless steel processing to produce gears suitable for use under high temperature and strong radiation conditions. After the corresponding steps in the whole process, component analysis, quality inspection and testing, sampling tests, etc. are carried out respectively to improve the yield rate and ensure that the processed gears are suitable for use under high temperature and strong radiation conditions.

[0031] The above is only a specific embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using the concept of the present invention fall within the protection scope of the present invention.

Claims

1. A processing technology for stainless steel gears for a planetary gear transmission mechanism with a small tooth difference, characterized in that: The steps include: S1, refining stainless steel ingots, remelting the stainless steel ingots for desulfurization and dephosphorization treatment, and then casting them into stainless steel bars, with each furnace of molten steel casting one batch of stainless steel bars; S2, rough turning of stainless steel bars, using tungsten-cobalt carbide turning tools to turn stainless steel bars, and dividing the stainless steel bars into several gear billets, each batch of stainless steel bars is divided into a batch of gear billets, the rake angle α is in the range of 16-18°, the back angle β is in the range of 6-9°, the main deflection angle is in the range of 40-80°, the secondary deflection angle is in the range of 11-14°, the blade inclination angle λs is in the range of -4-6°, the cutting speed is in the range of 40-80m / min, the feed rate is in the range of 0.2-0.5mm / r, the back cutting amount is in the range of 3-5mm, and the cutting allowance relative to the single side of the finished product is in the range of 6.5-8.5mm, and the cutting fluid is continuously poured on the contact position between the turning tool and the workpiece, and the cutting fluid adopts an emulsion with an oil-water dilution ratio in the range of 1:20-1:18; S3, heat treatment of the gear billet, firstly subjecting the gear billet to solid solution treatment, the holding temperature of the solid solution treatment is 1025-1055°C, the holding time is 30-45 minutes, after the holding is completed, the gear billet is quickly cooled to below 32°C by water quenching, oil quenching or air cooling, and then the gear billet is subjected to precipitation hardening aging treatment, the holding temperature of the precipitation hardening aging treatment is in the range of 480-620°C, the holding time is in the range of more than 2 hours, and then the gear billet is air-cooled to room temperature; S4, precision turning of gear blanks, using tungsten-cobalt carbide turning tools to turn gear blanks, the rake angle α is in the range of 20-25°, the back angle β is in the range of 11-12°, the main deflection angle is in the range of 4-6°, the secondary deflection angle is in the range of 4-6°, the cutting edge angle λs is in the range of 0-4°, the cutting speed is in the range of 40-80m / min, the feed rate is in the range of 0.1-0.4mm / r, the back cutting amount is in the range of 0.1-0.3mm, and the cutting fluid is continuously poured at the contact position between the turning tool and the workpiece. The cutting fluid adopts an emulsion with an oil-water dilution ratio of 1:10-1:8; S5, gear making, gear blanks are processed into gears by gear shaping or gear hobbing. The gear tooth top height coefficient ranges from 0.6 to 0.

8. Tungsten-cobalt carbide tools are used for gear shaping or gear hobbing. S6, low temperature annealing, placing the gear in an annealing furnace for heat preservation at a temperature of 220-280°C for 1.5-2 hours, and then air cooling the gear to room temperature; S7, fine grinding, fine grinding of the surface other than the tooth part to the designed size; S8, gear grinding, grinding the gear tooth profile to the finished size.

2. The processing technology of stainless steel gears for planetary gear transmission mechanism with small tooth difference according to claim 1 is characterized in that: In the step S5, a gear shaping method is used for the internal gear, and the nominal parameters of the gear shaping cutter are selected according to the GB / T 6081-2001 standard. During gear shaping, the rake angle of the gear shaping cutter is in the range of 5 to 10°, and the clearance angle is in the range of 0 to 8°. For the external gear, a gear hobbing method is used, and the nominal parameters of the gear hobbing cutter are selected according to the GB / T 6083-2016 standard. During gear hobbing, the rake angle of the gear hobbing cutter is in the range of -1° to -2°, the top edge clearance angle αp is in the range of 10° to 12°, the side edge clearance angle is ≥3°, and the gear hobbing cutter installation angle Φ=β±λ, wherein β is the gear helix angle, λ is the gear hobbing cutter helix angle, and when the rotation direction of the gear hobbing cutter is the same as the rotation direction of the cut gear, "+" is taken, and when the rotation direction of the gear hobbing cutter is opposite to the rotation direction of the cut gear, "-" is taken.

3. The processing technology of stainless steel gears for planetary gear transmission mechanism with small tooth difference according to claim 1 is characterized in that: The step S1 includes step S1a after step S1, chemical composition analysis, sampling for chemical composition smelting analysis during casting, sampling for chemical composition finished product analysis of each batch of stainless steel bars after casting, the chemical composition analysis is performed according to ASTM A751-2021 standard, and the stainless steel bars of the batch to which the smelting analysis and the finished product analysis meet the set chemical composition requirements enter the next step.

4. The processing technology of stainless steel gears for planetary gear transmission mechanism with small tooth difference according to claim 1 is characterized in that: The step S3 includes step S3a, etching test analysis, randomly selecting at least one gear billet from each batch of gear billets for macro etching test according to the provisions of ASTM E340, and the gear billets of the batch to which the macro etching test data meets the set requirements enter the next step.

5. The processing technology of stainless steel gears for planetary gear transmission mechanism with small tooth difference according to claim 1 is characterized in that: The step S3 includes step S3b, liquid penetrant testing and ultrasonic flaw detection, wherein each gear billet is subjected to 100% surface liquid penetrant testing according to the testing method specified in CAP-NDE-V7-032; each gear billet is subjected to 100% volume ultrasonic flaw detection according to the testing method specified in CAP-NDE-V7-032; the gear billet that passes the liquid penetrant testing and ultrasonic flaw detection proceeds to the next step.

6. The processing technology of stainless steel gears for planetary gear transmission mechanism with small tooth difference according to claim 1, characterized in that: The step S3c includes a sampling test after the step S3; performing Brinell hardness measurement on each gear billet segment, then selecting 2% and at least one gear billet segment with the highest hardness from each batch of gear billets, and cutting a room temperature tensile test specimen, a high temperature tensile test specimen, and three impact test specimens at the large diameter end of the selected gear billet segment by a machining method; selecting 2% and at least one gear billet segment with the lowest hardness from each batch of gear billets, and cutting a room temperature tensile test specimen, a high temperature tensile test specimen, and three impact test specimens at the large diameter end of the selected gear billet segment by a machining method. The specimens are cut with the longitudinal axis parallel to the main processing direction of the gear billet. When the diameter of the gear billet is φ≤25mm, the longitudinal axis of the specimen is at the center line of the gear billet. When the diameter of the gear billet is 25mm<the diameter of the gear billet is φ≤50mm, the longitudinal axis of the specimen is 12.5mm away from the heat-treated surface of the gear billet. When the diameter of the gear billet is φ>50mm, the longitudinal axis of the specimen is located at half the radius of the gear billet. The three impact specimens should be cut side by side. Both the room temperature tensile specimen and the high temperature tensile specimen are ASTM The A370 standard specifies standard circular section specimens with a gauge length of 50mm and a diameter of 12.5mm. The specimens are subjected to room temperature tensile tests and high temperature tensile tests in accordance with the provisions of ASTM A370. The impact specimens are prepared according to the Charpy V-notch standard impact specimens specified in the ASTM A370 standard. The V-notch axes of the specimens should be consistent and perpendicular to the nearest heat-treated surface of the gear billet. The impact specimens are subjected to Charpy V-notch impact tests in accordance with the provisions of ASTM A370. The selected gear billets are subjected to hardness tests in accordance with the provisions of ASTM A370. The hardness tests are carried out at the adjacent parts of the room temperature tensile specimens or high temperature tensile specimens, or at half the radius of the end of the gear billet. The gear billets of the batch to which the data of the Brinell hardness measurement, room temperature tensile test, high temperature tensile test, impact test and hardness test meet the set requirements proceed to the next step.

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