阅读说明：本技术 一种汽车变速箱内齿圈的渗氮方法 (Nitriding method of inner gear ring of automobile gearbox ) 是由 胡大维 张雪梅 胡敬华 于 2020-12-28 设计创作，主要内容包括：本发明公开了一种汽车变速箱内齿圈的渗氮方法,其首先进行渗氮前处理：对高强度合金钢进行调质预处理,得到基体硬度为28-32HRC的内齿圈；然后进行渗氮处理：采用二段气体渗氮方法,将内齿圈装入渗氮炉中,第一阶段在520℃下保温进行强渗,第二阶段在500℃下保温进行扩散；最后进行冷却处理：所述渗氮处理结束后,随炉冷却到120℃出炉空冷,本发明采用非常规的二段气体渗氮方法,实现了在微变形条件下获得高硬度、高耐磨性和高抗疲劳性的渗氮层,能满足混合动力汽车变速箱内齿圈的要求。(The invention discloses a nitriding method of an inner gear ring of an automobile gearbox, which comprises the following steps of: carrying out quenching and tempering pretreatment on the high-strength alloy steel to obtain the inner gear ring with the matrix hardness of 28-32 HRC; then carrying out nitriding treatment: a two-stage gas nitriding method is adopted, the ring gear is arranged in a nitriding furnace, the first stage is subjected to heat preservation at 520 ℃ for strong penetration, and the second stage is subjected to heat preservation at 500 ℃ for diffusion; and finally, cooling treatment: after the nitriding treatment is finished, the nitriding layer is cooled to 120 ℃ along with the furnace and discharged from the furnace for air cooling, and the method adopts an unconventional two-stage gas nitriding method, so that the nitriding layer with high hardness, high wear resistance and high fatigue resistance can be obtained under the micro-deformation condition, and the requirement of the inner gear ring of the gearbox of the hybrid electric vehicle can be met.)

1. A nitriding method of an inner gear ring of an automobile gearbox is characterized by comprising the following steps:

s1, nitriding pretreatment: carrying out quenching and tempering pretreatment on the high-strength alloy steel to obtain the inner gear ring with the matrix hardness of 28-32 HRC;

s2, nitriding treatment: a two-stage gas nitriding method is adopted, the ring gear obtained in the step S1 is loaded into a nitriding furnace, the first stage is subjected to heat preservation at 520 ℃ for strong infiltration, and the second stage is subjected to heat preservation at 500 ℃ for diffusion;

s3, cooling treatment: and after the nitriding treatment is finished, cooling the inner gear ring to 120 +/-10 ℃ along with the furnace, and discharging and air cooling.

2. The nitriding method for the ring gear of automobile transmissions according to claim 1, characterized in that: the high-strength alloy steel is 42CrMo steel.

3. The nitriding method for the ring gear of automobile transmissions according to claim 1, characterized in that: the heat preservation time of the first stage is 4 +/-0.5 h, and the heat preservation time of the second stage is 7 +/-0.5 h.

4. The nitriding method for the ring gear of automobile transmissions according to claim 1, characterized in that: in step S2, the flow rate of the introduced ammonia gas is 800-1000mL/h and the gas pressure is 0.02-0.04MPa in the nitriding treatment process.

5. The nitriding method for the ring gear of automobile transmissions according to claim 1, characterized in that: in step S2, the nitriding furnace is a shaft type gas nitriding furnace or a hood type gas nitriding furnace.

6. The nitriding method for the ring gear of automobile transmissions according to claim 1, characterized in that: the automobile is a hybrid automobile.

7. An automotive transmission ring gear treated by the nitriding method according to any one of claims 1 to 6.

Technical Field

The invention belongs to the technical field of heat treatment, and particularly relates to a nitriding method of an inner gear ring of an automobile gearbox.

Background

The hybrid electric vehicle is a new energy vehicle. The internal combustion engine and the motor are used as a mixed power source, the engine has the advantages of good power performance of the fuel engine and long working time, has the advantages of no pollution and low noise of the motor, has the characteristics of energy conservation, low emission and the like, draws the attention of the automobile industry at home and abroad, and becomes a key point of the international automobile research and development.

The gear box is a core component of an automobile, the inner gear ring is a key part for transmitting power of the gear box, and the inner gear ring and other components such as gears are combined into a set of planetary gear mechanism to bear the functions of energy splitting and comprehensive power distribution, so that the precision, the wear resistance and the fatigue resistance of the inner gear ring need to meet high requirements. These highly required properties are in turn closely related to the nitriding process of the ring gear.

At present, three technical problems of gas nitriding treatment of the inner gear ring of the hybrid electric vehicle exist: firstly, the requirement on the nitriding deformation is strict; secondly, a high-wear-resistance compound layer (white layer) on the surface of the nitriding layer needs to reach a certain thickness and has no brittleness; thirdly, the large-scale production requires short nitriding production period, energy conservation and production cost reduction.

Disclosure of Invention

The invention aims to provide a nitriding method of an annular gear of an automobile gearbox, which can overcome the defects in the background technology.

Therefore, the invention adopts the following technical proposal,

a nitriding method of an annular gear of an automobile gearbox comprises the following steps:

s1, nitriding pretreatment: carrying out quenching and tempering pretreatment on the high-strength alloy steel to obtain the inner gear ring with the matrix hardness of 28-32 HRC;

s2, nitriding treatment: a two-stage gas nitriding method is adopted, the ring gear obtained in the step S1 is loaded into a nitriding furnace, the first stage is subjected to heat preservation at 520 ℃ for strong infiltration, and the second stage is subjected to heat preservation at 500 ℃ for diffusion;

s3, cooling treatment: and after the nitriding treatment is finished, cooling the inner gear ring to 120 +/-10 ℃ along with the furnace, and discharging and air cooling.

Further, the high-strength alloy steel is 42CrMo steel.

Further, the heat preservation time of the first stage is 4 +/-0.5 h, and the heat preservation time of the second stage is 7 +/-0.5 h.

Further, in step S2, the flow rate of the introduced ammonia gas is 800-.

Further, in step S2, the nitriding furnace is a shaft type gas nitriding furnace or a bell type gas nitriding furnace.

Further, the automobile is a hybrid automobile.

The invention also provides an automobile gearbox ring gear obtained by the nitriding method.

Compared with the background technology, the technical scheme at least has the following advantages:

1. the invention adopts an unconventional two-stage gas nitriding method, wherein the first stage uses 520 ℃ for strong nitriding and the second stage uses 500 ℃ for low-temperature diffusion, thereby realizing obtaining a nitriding layer with high hardness, high wear resistance and high fatigue resistance under the micro-deformation condition;

2. the invention adopts a nitriding method for effectively controlling the surface compound layer and the diffusion layer of the inner gear ring, namely, the time for adjusting the strong permeation and the diffusion is respectively 4 plus or minus 0.5h and 7 plus or minus 0.5h at lower temperature, a chemical layer (white layer) with certain thickness is obtained on the surface of the tooth part of the inner gear ring, and the nitriding method has no brittleness and simultaneously ensures that the nitriding deformation amount is minimum;

3. after the nitriding method provided by the invention is adopted for treatment, the surface hardness of the obtained nitriding layer of the inner gear ring is 734-750HV0.3, the depth/thickness of the nitriding layer is 0.26mm, the depth/thickness of the compound layer (white layer) is 10-12 mu m, the deformation is 1-2 wires of span rod distance reduction, and the diameter of the root circle is 3-5 wires of expansion. The brittleness grade of the nitriding layer reaches grade 1. The wear resistance and the fatigue resistance of the inner gear ring are obviously improved, so that the reliability and the fatigue life of the inner gear ring are ensured;

4. the total nitriding time of the invention is 11 hours, compared with the conventional two-stage nitriding time, the invention greatly shortens the time, consumes short time, saves energy and reduces the production cost. The invention can give consideration to both quality and efficiency, has reliable quality and stable process by mass production, and can meet the strict quality requirement of the inner gear ring of the gearbox of the hybrid electric vehicle.

Drawings

FIG. 1 is a route diagram of a nitriding process of the inner gear ring of the automobile gearbox provided by the invention.

Detailed Description

The gas nitriding treatment of the ring gear of the hybrid electric vehicle has three technical problems to be solved urgently: firstly, the requirement on the nitriding deformation is strict; secondly, a high-wear-resistance compound layer (white layer) on the surface of the nitriding layer needs to reach a certain thickness and has no brittleness; thirdly, the large-scale production requires short nitriding production period, energy conservation and production cost reduction.

Therefore, the invention provides a novel nitriding method for an annular gear of an automobile gearbox, and aims to solve the technical problem.

In order that the objects, features and advantages of the invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings, which are illustrated in detail in order to provide a thorough understanding of the invention, but which may be carried out in other ways than those described. Accordingly, the invention is not limited by the specific implementations disclosed below.

Examples

Referring to fig. 1, a nitriding method for an annular gear of a hybrid automobile gearbox comprises the following steps:

a nitriding method of an annular gear of an automobile gearbox comprises the following steps:

s1, nitriding pretreatment: carrying out quenching and tempering pretreatment on the high-strength alloy steel to obtain the inner gear ring with the matrix hardness of 28-32 HRC;

specifically, the high-strength alloy steel is 42CrMo steel, has the characteristics of high strength, high toughness and good hardenability, and the chemical components of 42CrMo specified in GB/T3077-: w (c) 0.38% -0.45%; w (si) 0.17% -0.37%; w (mn) 0.50% -0.80%; w (cr) 0.90% -1.20%; w (mo) 0.15% to 0.25%. According to the technical requirement of nitriding of the inner gear ring, quenching and tempering are adopted, the hardness reaches 28-32HRC, and a good base body is provided for nitriding.

S2, nitriding treatment: a two-stage gas nitriding method is adopted, the ring gear obtained in the step S1 is loaded into a nitriding furnace, the first stage is subjected to heat preservation at 520 ℃ for strong infiltration, and the second stage is subjected to heat preservation at 500 ℃ for diffusion;

specifically, referring to fig. 1, the invention adopts an unconventional two-stage gas nitriding treatment process, wherein the ring gear obtained in the step S1 is firstly loaded into a nitriding furnace, the nitriding furnace can be a well-type gas nitriding furnace or a bell-type gas nitriding furnace, the ring gear is heated along with the furnace, the temperature is kept at 520 ℃ for 4 +/-0.5 h, which is a first stage (strong-penetration stage), and then the temperature is kept at 500 ℃ for 7 +/-0.5 h, which is a second stage (diffusion stage), the flow of ammonia gas introduced into the furnace is 1000mL/h, and the gas pressure is 0.02-0.04MPa during the nitriding treatment process.

S3, cooling treatment: and after the nitriding treatment is finished, cooling to 120 +/-10 ℃ along with the furnace, discharging and air cooling.

The inner gear ring subjected to nitriding treatment of the embodiment is detected according to the provisions of GB/T11354-2005 'nitriding layer depth determination and metallographic structure inspection', and the surface hardness of a nitriding layer is 734-750HV0.3, the depth/thickness of the nitriding layer is 0.26mm, the depth/thickness of a compound layer (white layer) is 10-12 mu m, the deformation amount is 1-2 threads of span rod distance reduction, and the diameter of a tooth root circle is 3-5 threads of root circle expansion. The brittleness grade of the nitriding layer reaches grade 1. The invention obviously improves the wear resistance and the fatigue resistance of the inner gear ring, and ensures the reliability and the fatigue life of the inner gear ring.

The invention is characterized in that a compound layer (white layer) and a diffusion layer are formed by strong permeation and diffusion on the premise of micro-deformation and high precision, and the obtained nitriding layer has high surface hardness and small nitriding deformation (the span length is reduced to be less than 1-2 wires, and the diameter expansion of a gear root circle is less than 3-5 wires) due to the adoption of a low-temperature diffusion process, is thin, eliminates the brittleness of the nitriding layer, and can meet the strict quality requirement of the annular gear of the gearbox of the hybrid electric vehicle.

The total nitriding time of the invention is 11 hours, compared with the conventional two-stage nitriding time, the invention greatly shortens the time, consumes short time, saves energy and reduces the production cost. The invention can give consideration to both quality and efficiency, and the mass production shows that the quality is reliable, the process is stable, and the invention is beneficial to popularization.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.