CN-121976149-A - Two-stage ion nitriding method for small-modulus gear

Abstract

The invention discloses a two-stage ion nitriding method for a small-modulus gear, which comprises the following steps of preprocessing the gear, nitriding the gear for the first stage, nitriding the gear for the second stage, and obtaining the nitrided gear. The gear deformation processed by the method is extremely small, namely the gear deformation is less than or equal to 0.02mm through the process steps of stress removal, sectional temperature control and slow cooling of the gear through pretreatment, so that the gear tooth directional error deformation is less than or equal to the precision transmission requirement. The treated gear has homogeneous permeated layer, the difference between the thickness of the permeated layer of the tooth root, tooth surface and tooth top is less than or equal to 0.02mm, the effective permeated layer depth is stabilized within the range of 0.05mm-0.15mm, and the wear resistance and the tooth root strength are both considered. The treated gear has high surface hardness, the compound layer and the diffusion layer cooperate, the surface hardness reaches HV950-1100, and the method is improved by 30-40% compared with the traditional process, and the treatment method has good process stability, and the fluctuation of the permeation layer performance of gears in different batches is less than or equal to 5% by precisely controlling parameters such as duty ratio, furnace pressure and the like, so that the method is suitable for batch production.

Inventors

• Qu Xuanyou
• WANG JIANGHUA
• WANG LINSEN

Assignees

• 贵州振华群英电器有限公司（国营第八九一厂）

Dates

Publication Date

20260505

Application Date

20260109

Claims (10)

1. 1. A method for two-stage ion nitriding of a small-modulus gear, which is characterized by comprising the following steps: s1, preprocessing a gear; S2, nitriding the gear in a first section; And S3, carrying out second-stage nitriding on the gear to obtain the gear subjected to nitriding treatment.
2. 2. A two-stage ion nitriding method for a small modulus gear is characterized in that the first-stage nitriding step comprises the steps of placing a pretreated gear in a vacuum glow ion nitriding furnace, vacuumizing the furnace to be less than or equal to 60Pa, introducing ammonia gas, controlling the pressure in the furnace to be 200-300Pa, heating to 470-480 ℃, and preserving heat for 10-20min.
3. 3. A method of ion nitriding a small module gear wheel according to claim 2, wherein the duty cycle in the nitriding of the first section is 20 to 30%.
4. 4. A method for two-stage ion nitriding of a small modulus gear as set forth in claim 2, wherein the flow rate of ammonia gas in the first-stage nitriding is 500-700mL/min.
5. 5. A two-stage ion nitriding method for a small modulus gear is characterized in that the second-stage nitriding step comprises the steps of placing the gear subjected to the first-stage nitriding treatment in a vacuum glow ion nitriding furnace, vacuumizing the furnace to be less than or equal to 60Pa, introducing ammonia gas, adjusting the pressure in the furnace to be 300-500Pa, heating to 490-510 ℃, preserving heat for 20-40min, cooling the gear to be below 150 ℃ along with the furnace, and discharging the gear subjected to nitriding treatment.
6. 6. A method of ion nitriding a small module gear wheel according to claim 5, wherein the duty cycle in the second-stage nitriding is 35-45%.
7. 7. A method for two-stage ion nitriding of a small modulus gear as set forth in claim 5, wherein the flow rate of ammonia gas in the second-stage nitriding is 600-900mL/min.
8. 8. The method for two-stage ion nitriding of a small modulus gear according to claim 1, wherein the pretreatment comprises the step of cleaning and degreasing the small modulus gear, ultrasonic cleaning is adopted for cleaning the small modulus gear, and cleaning medium is alkaline cleaning agent, and cleaning time is more than or equal to 15min.
9. 9. A method of ion nitriding a small module gear according to claim 1, wherein the module of the gear is 0.2 to 0.5.
10. 10. A method of ion nitriding a small modulus gear as set forth in claim 1 wherein said gear is 38CrMoAl.

Description

Two-stage ion nitriding method for small-modulus gear Technical Field The invention belongs to the technical field of heat treatment of gears, and particularly relates to a two-stage ion nitriding method of a small-modulus gear. Background The pinion with the modulus of 0.2-0.5 is widely applied to the fields of precision instruments, micro motors, aerospace and the like, and the working environment of the pinion requires high wear resistance, high fatigue strength and strict dimensional accuracy. Nitriding treatment is a key process for improving the surface performance of gears, and is a process used for nitriding treatment of vacuum glow ion nitriding process. The vacuum glow ion nitriding process includes vacuum pumping workpiece as cathode and container wall as anode inside a sealed vacuum container, introducing nitrogen-containing gas, such as nitrogen and ammonia, applying high voltage DC electric field to produce glow discharge to ionize nitrogen gas molecule into nitrogen ion, bombarding the surface of the workpiece with the nitrogen ion under the action of the electric field, sputtering the cathode to clean the surface and activate crystal lattice, adsorbing nitrogen ion and diffusing the nitrogen ion into the workpiece to form nitrogen-containing hardening layer on the surface of the workpiece. The existing small modulus gear nitriding process mostly adopts a one-section nitriding process, and has the following problems: 1. The deformation is large, the small modulus gear has small size (the tooth thickness is usually less than or equal to 1 mm), the one-stage nitriding temperature is too high or the heat preservation time is too long, the thermal deformation is easy to cause, the tooth direction error is out of tolerance (usually more than 0.02 mm), and the transmission precision is influenced; 2. The uneven seepage layer is that the difference of nitrogen adsorption capacity of tooth root, tooth top and tooth surface of the gear is large, the seepage layer thickness of each part is difficult to be considered by one-step technology, and the phenomena of too thin seepage layer (< 0.03 mm) of the tooth root and too thick seepage layer (> 0.2 mm) of the tooth top are easy to occur; 3. The quality of the nitriding layer structure and brittleness of the workpiece is difficult to control and is influenced by the parameters of gas components, temperature, pressure, time and the like, wherein the ion nitriding compound layer of 38CrMoAl steel is composed of gamma '+epsilon+alpha phases, the gamma' phases are mainly used, the phases are favorable for diffusing subsurface nitrogen, the formation of a diffusion layer is accelerated, the gear modulus is small, if the parameters are not reasonably regulated, the phenomenon of positive out-of-tolerance permeation is easy to occur in the permeation layer depth, and network nitride is easy to occur in the permeation layer structure, so that the brittleness of the small modulus gear is improved, and the quality risk of breakage is caused. Therefore, designing a nitriding method for precisely controlling the quality and deformation of a permeation layer aiming at the structural characteristics of a small-modulus gear becomes a problem to be solved. The publication number CN106191759a discloses a vacuum glow ion nitriding process for reducing deformation of precision gears of industrial robots, including cleaning and nitriding processes for parts. The patent application publication No. CN113930715A discloses a small module gear ion nitriding method for comparison analysis, which is used for nitriding gears with the modulus less than or equal to 1 mm. The patent application publication No. CN109023224A discloses a tooth surface shallow ion nitriding method of a thin-wall small-modulus gear for comparative analysis, and a process curve adopts a section of ion nitriding. The patent application publication No. CN113930716A discloses an ion nitriding method for ultra-high strength stainless steel gear for comparative analysis, and a process curve adopts a section of ion nitriding. None of the above patent application documents relates to the improvement of gear performance by a multistage nitriding process. Disclosure of Invention In order to solve the technical problems, the invention provides a two-stage ion nitriding method for a small module gear, so as to realize the technical effects of uniform diffusion layer, standard hardness and controllable deformation of the small module gear. The invention is realized by the following technical scheme. The invention provides a two-stage ion nitriding method for a small-modulus gear, which comprises the following steps of: s1, preprocessing a gear; S2, nitriding the gear in a first section; And S3, carrying out second-stage nitriding on the gear to obtain the gear subjected to nitriding treatment. Preferably, the first-stage nitriding step comprises the steps of placing the pretreated gear in a vacuum glow ion nitriding fur