阅读说明：本技术 航空发动机轴承高强韧复相热处理方法 (High-strength-toughness complex-phase heat treatment method for aeroengine bearing ) 是由 钱东升 王丰 冯玮 杜宇辰 左斯玉 夏舒航 周枢宇 韩悦 于 2021-06-11 设计创作，主要内容包括：本发明公开了一种航空发动机轴承高强韧复相热处理方法,包括以下步骤：根据套圈的内外径尺寸,在奥氏体化前将轴承套圈进行预热处理,预热后将套圈均匀浸入高温盐浴炉进行奥氏体化,通过控制奥氏体化温度和时间使奥氏体化组织均匀；将奥氏体化后的轴承套圈浸入低温盐浴炉进行等温淬火,通过控制等温淬火温度和时间,将贝氏体含量控制在指定区间范围内；将轴承套圈放入回火炉中进行回火处理。本发明提出的航空发动机轴承高强韧复相热处理方法,通过控制复相热处理工艺参数,实现定量调控马贝复相组织配比,从而优化热处理组织,提高了基体强韧性。(The invention discloses a high-strength and high-toughness complex phase heat treatment method for an aircraft engine bearing, which comprises the following steps of: according to the size of the inner diameter and the outer diameter of the bearing ring, the bearing ring is subjected to preheating treatment before austenitizing, the bearing ring is uniformly immersed into a high-temperature salt bath furnace for austenitizing after preheating, and the austenitizing structure is uniform by controlling the austenitizing temperature and time; immersing the bearing ring subjected to austenitizing in a low-temperature salt bath furnace for isothermal quenching, and controlling the bainite content in a specified interval range by controlling the isothermal quenching temperature and time; and putting the bearing ring into a tempering furnace for tempering treatment. The high-strength and high-toughness complex phase heat treatment method for the bearing of the aircraft engine realizes quantitative regulation and control of the proportion of the martensite complex phase structure by controlling the complex phase heat treatment process parameters, thereby optimizing the heat treatment structure and improving the strength and toughness of the matrix.)

1. A high-strength and high-toughness complex-phase heat treatment method for an aircraft engine bearing is characterized by comprising the following steps:

according to the size of the inner diameter and the outer diameter of the bearing ring, the bearing ring is subjected to preheating treatment before austenitizing, the bearing ring is uniformly immersed into a high-temperature salt bath furnace for austenitizing after preheating, and the austenitizing structure is uniform by controlling the austenitizing temperature and time;

immersing the bearing ring subjected to austenitizing in a low-temperature salt bath furnace for isothermal quenching, and controlling the bainite content in a specified interval range by controlling the isothermal quenching temperature and time;

and putting the bearing ring into a tempering furnace for tempering treatment.

2. The high-strength and high-toughness complex-phase heat treatment method for the aero-engine bearing as claimed in claim 1, wherein when the bearing ring is uniformly immersed in a high-temperature salt bath furnace for austenitizing treatment, the austenitizing temperature T is higher_A＝T_Ac3+k_TT_Ac1Time of austenitizing

Wherein D and D are respectively the outer diameter and inner diameter of the ferrule, T_Ac1For the austenitizing transformation starting temperature, T, of the bearing material_Ac3The austenite transformation end temperature, k, of the bearing material_TFor austenitizing temperature correction coefficient, k_T0.25 to 0.28.

3. The complex-phase heat treatment method for the high strength and toughness of the bearing of the aircraft engine as claimed in claim 1, wherein when the bearing ring is subjected to the preheating treatment, the preheating time is related to the size of the ring, and the preheating temperature is 200-350 ℃.

4. The high-toughness complex-phase heat treatment method for the aero-engine bearing as claimed in claim 3, wherein the preheating time of the bearing ring is t₁，t₁＝t₀(D-d)/d，t₀For preheating the ferrule for an initial time t₀Is 20min to 30 min.

5. The method for the complex-phase heat treatment of the high strength and toughness of the aero-engine bearing as set forth in claim 1, wherein the step of immersing the austenitized bearing ring in a low-temperature salt bath furnace for isothermal quenching further comprises the steps of:

after the isothermal quenching process is finished, quenching the bearing ring into an oil tank and uniformly stirring, taking out the bearing ring after the salt on the surface of the ring is condensed and crystallized, and washing and drying the bearing ring in warm water.

6. The high-strength and high-toughness complex-phase heat treatment method for the aero-engine bearing as claimed in claim 1, wherein when the bearing ring after austenitizing is immersed in a low-temperature salt bath furnace for isothermal quenching, the temperature T of isothermal quenching is_BComprises the following steps:

T_B＝[1+k_Bd/(D-d)]T_Ms，

wherein, T_MsIs the martensite transformation starting point, k, of the bearing material_BIs an austempering temperature correction coefficient, k_B0.05 to 0.1.

7. The high-toughness complex-phase heat treatment method for the aeroengine bearing as claimed in claim 6, wherein the time t of isothermal quenching_BThe numerical control is related to the inner and outer diameter sizes of the ferrule and the isothermal quenching temperature as follows:

t_A＝t₂[(D-d)/d]·[T_Ms/(T_B-T_Ms)]，

wherein, t₂Initial time of isothermal quenching, t₁Is 150 min-180 min.

8. The high-strength and high-toughness complex-phase heat treatment method for the aero-engine bearing as claimed in claim 1, wherein when the bearing ring is placed into a tempering furnace for tempering treatment, the tempering temperature is 535-550 ℃, and the cycle is carried out for three times.

9. The high-toughness complex-phase heat treatment method for the aeroengine bearing as claimed in claim 1, wherein the content of the quenched retained austenite is controlled to be between 20% and 30%, and the content of the tempered retained austenite is controlled to be below 4%.

10. The high-toughness complex-phase heat treatment method for the aero-engine bearing according to any one of claims 1 to 9, wherein when the bearing ring after austenitizing is immersed in a low-temperature salt bath furnace for isothermal quenching, the bainite content is controlled to be between 5% and 50%.

Technical Field

The invention relates to a bearing manufacturing technology, in particular to a high-strength and high-toughness complex-phase heat treatment method for an aircraft engine bearing.

Background

The bearing of the aircraft engine is used for supporting the most core rotor system of the engine, has extremely bad service working condition, requires high rotating speed, high precision, high bearing capacity and high reliability, and is a key part for guaranteeing the long service life of the aircraft engine. The bearing is composed of an inner ferrule, an outer ferrule, a rolling body and a retainer. Wherein, the ferrule is the core component of the bearing, the weight and the manufacturing cost account for 60% -70% of the bearing, the performance directly determines the service life and the reliability of the bearing, and the ferrule is the core of the bearing manufacturing. How to obtain the high-strength and high-toughness bearing ring and ensure the reliable service of the extreme working condition of the bearing is a leading-edge subject which is highly emphasized in the field of international bearing science and technology.

The main material of the bearing ring of the aeroengine is 8Cr4Mo4V, which is a typical high-temperature bearing steel, and in order to ensure the high-temperature hardness and the high dimensional stability of the bearing ring, the heat treatment process of martensitic quenching and multiple times of high-temperature tempering is usually adopted. However, the prior traditional process has extremely low content of residual austenite of a toughness phase and poor tissue toughness ratio, is difficult to ensure long-life service of the bearing in an extremely severe working environment, and has seriously hindered the development of the field of manufacturing of aviation equipment.

Disclosure of Invention

The invention mainly aims to provide a high-strength and high-toughness complex-phase heat treatment method for an aeroengine bearing, and aims to improve the strength and toughness of a matrix.

In order to achieve the aim, the invention provides a high-strength and high-toughness complex-phase heat treatment method for an aircraft engine bearing, which comprises the following steps:

according to the size of the inner diameter and the outer diameter of the bearing ring, the bearing ring is subjected to preheating treatment before austenitizing, the bearing ring is uniformly immersed into a high-temperature salt bath furnace for austenitizing after preheating, and the austenitizing structure is uniform by controlling the austenitizing temperature and time;

immersing the bearing ring subjected to austenitizing in a low-temperature salt bath furnace for isothermal quenching, and controlling the bainite content in a specified interval range by controlling the isothermal quenching temperature and time;

and putting the bearing ring into a tempering furnace for tempering treatment.

Preferably, the austenitizing temperature T is obtained when the ferrule is uniformly immersed into a high-temperature salt bath furnace for austenitizing treatment_A＝T_Ac3+k_TT_Ac1Time t of austenitization_A＝[(D-d)/1mm]·T_A/T_Ac1，

Wherein D and D are respectively the outer diameter and inner diameter of the ferrule, T_Ac1For the austenitizing transformation starting temperature, T, of the bearing material_Ac3The austenite transformation end temperature, k, of the bearing material_TFor austenitizing temperature correction coefficient, k_T0.25 to 0.28.

Preferably, when the bearing ring is subjected to preheating treatment, the preheating time is related to the size of the ring, and the preheating temperature is 200-350 ℃.

Preferably, the preheating time of the bearing ring is t₁，t₁＝t₀(D-d)/d，t₀For preheating the ferrule for an initial time t₀Is 20min to 30 min.

Preferably, the step of immersing the austenitized bearing ring in a low-temperature salt bath furnace for isothermal quenching further comprises the following steps:

after the isothermal quenching process is finished, quenching the bearing ring into an oil tank and uniformly stirring, taking out the bearing ring after the salt on the surface of the ring is condensed and crystallized, and washing and drying the bearing ring in warm water.

Preferably, when the austenitized bearing ring is immersed in a low-temperature salt bath furnace for isothermal quenching, the temperature T of the isothermal quenching_BComprises the following steps:

T_B＝[1+k_Bd/(D-d)]T_Ms，

wherein, T_MsIs the martensite transformation starting point, k, of the bearing material_BIs an austempering temperature correction coefficient, k_B0.05 to 0.1.

Preferably, the time t of austempering_BThe numerical control is related to the inner and outer diameter sizes of the ferrule and the isothermal quenching temperature as follows:

t_A＝t₂[(D-d)/d]·[T_Ms/(T_B-T_Ms)]，

wherein, t₂Initial time of isothermal quenching, t₁Is 150 min-180 min.

Preferably, when the bearing ring is placed into a tempering furnace for tempering treatment, the tempering temperature is 535-550 ℃, and the process is circulated for three times.

Preferably, the content of the quenched retained austenite is controlled to be between 20% and 30%, and the content of the tempered retained austenite is controlled to be less than 4%.

Preferably, when the bearing ring after austenitizing is immersed into a low-temperature salt bath furnace for isothermal quenching, the bainite content is controlled between 5% and 50%.

The high-strength and high-toughness complex-phase heat treatment method for the bearing of the aero-engine, provided by the invention, has the following beneficial effects:

(1) the preheating treatment is introduced before the austenitizing, so that the heat treatment deformation and stress of the ferrule are reduced, and the austenitizing is carried out by adopting a high-temperature salt bath method, so that the nonuniform heating of the ferrule is reduced, and the uniformity of the structure performance is improved;

(2) by reasonably controlling the austenitizing time and temperature, the austenitizing parameters are accurately matched with the size and the material characteristics, so that the austenitizing tissue is uniform and controllable;

(3) on the one hand, the bainite content is controlled in a specified interval range by controlling the isothermal quenching time and temperature and a fine lath structure is obtained by utilizing the segmentation effect of bainite on crystal grains based on the size and material characteristics of the bearing ring, so that the structure refining effect is increased; on the other hand, proper bainite is introduced, so that the residual austenite content is in a specified interval, the decomposition effect of proper residual austenite in the high-temperature tempering process improves the dislocation density after tempering, the dislocation strengthening effect is improved, and the strength and the toughness are promoted to be improved simultaneously;

(4) based on the optimized complex phase heat treatment process window, the whole process flow of the complex phase heat treatment is accurately designed and planned, the heat treatment efficiency and the quality of bearing products are guaranteed, and the final microstructure state is regulated and controlled through the quantitative control of the complex phase proportion and the process planning, so that the strength and the toughness of the bearing ring of the aeroengine are obviously improved.

Drawings

FIG. 1 is a schematic flow chart of a preferred embodiment of the high-toughness complex-phase heat treatment method for the aeroengine bearing.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1, in the preferred embodiment, a high-toughness complex-phase heat treatment method for an aircraft engine bearing comprises the following steps:

step S10, according to the inner and outer diameter sizes of the bearing ring, the bearing ring is preheated before austenitizing, the bearing ring is uniformly immersed into a high-temperature salt bath furnace for austenitizing after preheating, and the austenitizing structure is uniform by controlling the austenitizing temperature and time (the austenitizing temperature is related to the bearing material, and the austenitizing time is related to the bearing material and the size);

step S20, immersing the austenitized bearing ring into a low-temperature salt bath furnace for isothermal quenching, and controlling the bainite content in a specified interval range by controlling the isothermal quenching temperature and time;

and step S30, tempering the bearing ring in a tempering furnace.

The traditional austenitizing method adopts a resistance furnace or a vacuum furnace for heating, so that the heat conduction of the component is slow, the heating is not uniform, and the tissue uniformity is poor. And in the step S10, a high-temperature salt bath furnace is adopted for austenitizing, so that the condition of nonuniform heating of the ferrule is reduced, and the uniformity of the structure performance is improved.

In step S10, when the ferrule is uniformly immersed in the high-temperature salt bath furnace to be austenitized, the austenitizing temperature T is set to_A＝T_Ac3+k_TT_Ac1Time t of austenitization_A＝[(D-d)/1mm]·T_A/T_Ac1，

Wherein D and D are respectively the outer diameter and inner diameter of the ferrule, T_Ac1For the austenitizing transformation starting temperature, T, of the bearing material_Ac3The austenite transformation end temperature, k, of the bearing material_TFor austenitizing temperature correction coefficient, k_T0.25 to 0.28.

The austenitizing parameters adopted in the prior art are single and fixed, the size and the material characteristics of a ferrule cannot be considered, and the stability and the uniformity of a heat treatment structure of a component are seriously influenced. In this example, both the time and temperature of austenitization take into account ferrule dimensions and material properties.

In step S10, when the bearing ring is preheated, the preheating time is related to the size of the bearing ring, and the preheating temperature is 200 to 350 ℃.

Specifically, the preheating time of the bearing ring is t₁，t₁＝t₀(D-d)/d，t₀For preheating the ferrule for an initial time t₀Is 20min to 30 min.

Further, step S20 is followed by:

and step S21, after the isothermal quenching process is finished, quickly quenching the bearing ring into an oil tank and uniformly stirring, after the salt on the surface of the ring is condensed and crystallized, taking out the ring, putting the ring into warm water for cleaning and airing.

In step S20, when the austenitized bearing ring is immersed in a low-temperature salt bath furnace for austempering, the austempering temperature T is set to_BComprises the following steps:

T_B＝[1+k_Bd/(D-d)]T_Ms，

wherein, T_MsIs the martensite transformation starting point, k, of the bearing material_BIs an austempering temperature correction coefficient, k_B0.05 to 0.1.

In step S20, the time t for austempering_BThe numerical control is related to the inner and outer diameter sizes of the ferrule and the isothermal quenching temperature as follows:

t_A＝t₂[(D-d)/d]·[T_Ms/(T_B-T_Ms)]

wherein, t₂Initial time of isothermal quenching, t₁Is 150 min-180 min. Under the process condition, the bainite content can be strictly controlled in a designated interval, and the proportion of martensite and bainite complex phase structure is ensured to meet the requirements.

The key of the complex phase heat treatment is to control the contents of martensite and bainite, the ratio of martensite to bainite directly determines the performance of the final component, and the malted complex phase structure with improper mixture ratio can even cause serious deterioration of the performance. In the embodiment, the isothermal quenching time and temperature are accurately controlled according to different sizes and material characteristics of the ferrule, and the bainite content is controlled within a specified interval range.

In step S30, when the bearing ring is placed in a tempering furnace for tempering treatment, the tempering temperature is 535-550 ℃, the process is cycled for three times, and the tempering time is 2 hours each time.

Specifically, the content of the quenched retained austenite (i.e., the retained austenite content after step S20) is controlled to be between 20% and 30%, and the content of the tempered retained austenite (i.e., the retained austenite content after step S30) is controlled to be 4% or less. When the bearing ring after austenitizing is immersed into a low-temperature salt bath furnace for isothermal quenching, the bainite content is controlled between 5% and 50%.

The following specifically describes the process by taking a certain type of bearing (the outer diameter of the outer ring is 120mm, and the inner diameter is 102mm) made of 8Cr4Mo4V bearing steel as an example:

(1) homogeneous austenitization of the structure

Depending on the inner and outer diameter of the ferrule, prior to austenitizationPreheating the bearing ring for 5min at 300 deg.c. Subsequently, the ferrule was uniformly immersed in a high-temperature salt bath furnace for austenitization. T of 8Cr4Mo4V material_Ac1And T_Ac3Respectively taking 820 ℃ and 874 ℃, calculating the austenitizing temperature range to be 1079-1104 ℃, the austenitizing isothermal time to be 24min, the austenitizing temperature to be 1088 ℃ and the austenitizing isothermal time to be 24min based on the austenitizing isothermal temperature and isothermal time design formula.

(2) Complex phase structure accurate control quenching

Immersing the bearing ring after austenitizing into a low-temperature salt bath furnace, and carrying out T treatment on 8Cr4Mo4V material_MsAnd calculating the isothermal quenching temperature range of 206-252 ℃ and the time range of 47-114 min, the isothermal quenching temperature is set to 236 ℃ and the isothermal quenching time is set to 60min by using an isothermal quenching temperature and time design formula according to the martensite transformation starting point of the bearing material and the size characteristics of the ferrule at 161 ℃. After the isothermal quenching process is finished, the bearing ring is quickly quenched into a large-scale oil tank and is fully and uniformly stirred. After the salt on the surface of the ferrule is condensed and crystallized, the ferrule is taken out and put into warm water for cleaning and airing.

(3) Tissue tempering

And (3) uniformly loading the bearing ring into a high-temperature tempering furnace, wherein the temperature in the tempering furnace is ensured to be uniform in the process, the temperature is set to be 550 ℃, and the circulation is carried out for three times.

Comparing the technical effects of the obtained bearing ring with the traditional martensite heat treatment bearing ring, the bainite content of the 8Cr4Mo4V bearing ring of the embodiment is 13%, the average lath size is reduced from 1.95 μm to 1.06 μm, and the lath size is thinned by 45.6%; average dislocation density is 3.6 × 10¹⁵/m²Increased to 5.4X 10¹⁵/m²The dislocation density is improved by 50%. Meanwhile, the result of the mechanical property test shows that the tensile strength is increased from 2143MPa to 2248MPa, and the impact energy is increased from 56J to 93J. Thus illustrating that: by introducing a proper amount of bainite, the structure is effectively refined, dislocation is increased, and toughness of the aeroengine bearing is improved.

The high-strength and high-toughness complex-phase heat treatment method for the bearing of the aero-engine, provided by the invention, has the following beneficial effects:

(1) the preheating treatment is introduced before the austenitizing, so that the heat treatment deformation and stress of the ferrule are reduced, and the austenitizing is carried out by adopting a high-temperature salt bath method, so that the nonuniform heating of the ferrule is reduced, and the uniformity of the structure performance is improved;

(2) by reasonably controlling the austenitizing time and temperature, the austenitizing parameters are accurately matched with the size and the material characteristics, so that the austenitizing tissue is uniform and controllable;

(3) on the one hand, the bainite content is controlled in a specified interval range by controlling the isothermal quenching time and temperature and a fine lath structure is obtained by utilizing the segmentation effect of bainite on crystal grains based on the size and material characteristics of the bearing ring, so that the structure refining effect is increased; on the other hand, proper bainite is introduced, so that the residual austenite content is in a specified interval, the decomposition effect of proper residual austenite in the high-temperature tempering process improves the dislocation density after tempering, the dislocation strengthening effect is improved, and the strength and the toughness are promoted to be improved simultaneously;

(4) based on the optimized complex phase heat treatment process window, the whole process flow of the complex phase heat treatment is accurately designed and planned, the heat treatment efficiency and the quality of bearing products are guaranteed, and the final microstructure state is regulated and controlled through the quantitative control of the complex phase proportion and the process planning, so that the strength and the toughness of the bearing ring of the aeroengine are obviously improved.

The above description is only for the preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or any other related technical fields, are intended to be covered by the scope of the present invention.