High-carbon chromium bearing ring structure property distribution control method

Abstract

The invention provides a high-carbon-chromium bearing ring structure property distribution control method, relates to the technical field of bearings, and aims to solve the problem that the structure property requirement of a high-carbon-chromium bearing steel precision bearing cannot be well met in the related technology. The control method comprises the steps that overall quenching treatment is conducted on the first side and the second side of the bearing ring; gradient tempering heat treatment is conducted on the first side of the bearing ring, so that a tempering gradient temperature field is constructed on the radial wall thickness of the bearing ring, and a heat source is transmitted to the second side from the first side in a heat conduction mode; and performing cold treatment on the first side and the second side of the bearing ring. According to the method, it can be guaranteed that the quenched working face has enough retained austenite with the high carbon content, so that the working face has high heat stability and mechanical stability after gradient tempering and stable heat treatment, and asynchronous transformation of the retained austenite in the radial direction of the bearing ring is achieved; and the differentiated requirements of the raceway working surface and the radial whole on the retained austenite content are effectively met.

Description

Technical Field

[0001] This application relates to the technical field of bearings, and particularly to a method for controlling the tissue performance distribution of high-carbon chromium bearing rings. Background Art

[0002] Bearings are the supporting components of various major mechanical equipment, directly determining the development level of the entire equipment manufacturing industry. The basic structure of a bearing consists of a bearing matrix (including an inner ring and an outer ring), rolling elements, and a cage. Among them, the bearing matrix is the core component that actively bears the load and is most likely to fail in a rolling bearing. To improve the performance and lifespan of a bearing, the technical core lies in improving the tissue state of the bearing matrix.

[0003] Due to its good hardenability and comprehensive mechanical properties, high-carbon chromium bearing steel has become the most widely used bearing matrix material at present. Currently, the final heat treatment of high-carbon chromium bearing steel mainly involves conventional quenching and tempering, and a complex phase structure of high-carbon martensite, retained austenite, and carbides can be obtained after heat treatment. In related technologies, conventional low-temperature tempering, as the key process for determining the tissue performance of the bearing matrix, can only change the overall tissue content of the bearing matrix but cannot regulate its distribution, and cannot simultaneously meet the special requirements of wear resistance and dimensional stability for retained austenite.

[0004] Therefore, researching a method for controlling the tissue performance distribution of bearings has become an urgent problem to be solved. Summary of the Invention

[0005] The embodiments of this application provide a method for controlling the tissue performance distribution of high-carbon chromium bearing rings, realizing the asynchronous transformation of retained austenite in the radial direction of the bearing rings, and effectively solving the differential requirements of the raceway working surface and the radial integrity for the content of retained austenite.

[0006] To achieve the above objective, the embodiments of this application provide a method for controlling the tissue performance distribution of high-carbon chromium bearing rings, which is used for bearing rings. The bearing rings have a first side and a second side along their thickness. The first side is the working surface, and the working surface is configured to contact the rolling elements. The control method includes:

[0007] Performing overall quenching treatment on the first side and the second side of the bearing rings;

[0008] Performing gradient tempering treatment on the first side of the bearing rings to construct a tempering gradient temperature field on the radial wall thickness of the bearing rings, and enabling the heat source to be transferred from the first side to the second side through heat conduction;

[0009] Performing cold treatment on the first side and the second side of the bearing rings.

[0010] In a possible implementation, heat treatment of the first side of the bearing ring includes:

[0011] Induction heating of the first side.

[0012] In a possible implementation, induction heating of the first side of the bearing ring includes:

[0013] Control the heating rate range of the first side to be 50 - 90 °C / s, and the heat source conducts from the first side to the second side, with the heating rate range of the second side being 40 - 60 °C / s.

[0014] In a possible implementation, induction heating of the first side of the bearing ring includes:

[0015] Control the heating temperature range of the first side to be 350 - 400 °C, and the heat source conducts from the first side to the second side, with the heating temperature range of the second side being 250 - 350 °C.

[0016] In a possible implementation, induction heating of the first side of the bearing ring includes:

[0017] Control the induction power supply frequency range to be 10 - 60 KHz, the current density range to be 10 8 ~10 9 A / m 2 , and the induction heating time range to be 2 - 6 s.

[0018] In a possible implementation, overall quenching treatment of the first side and the second side of the bearing ring includes:

[0019] Control the austenitizing heating rate range to be 0.5 - 5 °C / s.

[0020] In a possible implementation, the overall quenching treatment of the first side and the second side of the bearing ring further includes:

[0021] When the austenitizing heating rate reaches 5 °C / s, control the holding temperature range to be 880 - 920 °C, and the holding time range to be 10 - 40 min;

[0022] After the holding is completed, cool to room temperature with oil at 60 - 70 °C.

[0023] In a possible implementation, cryogenic treatment of the first side and the second side of the bearing ring includes:

[0024] Control the lowest temperature range of the cryogenic treatment to be -79 ~ -110 °C;

[0025] When the lowest temperature of cryogenic treatment reaches -110°C, control the holding time within the range of 30 - 120 min, and after the holding is completed, heat up to room temperature.

[0026] In a possible implementation, after cryogenic treatment of the first side and the second side of the bearing ring, it further includes:

[0027] Perform low-temperature tempering treatment on the first side and the second side of the bearing ring.

[0028] In a possible implementation, control the tempering holding temperature range to be 120 - 140°C, and the holding time range to be 60 - 180 min.

[0029] The method for controlling the tissue performance distribution of the high-carbon chromium bearing ring provided by the embodiments of the present application, on the one hand, adopts a relatively high austenitizing temperature to match the holding time, ensuring that there is sufficient retained austenite with a high carbon content on the working surface of the bearing ring after quenching, so that it has high thermal stability and mechanical stability after gradient tempering and stabilization heat treatment, and at the same time ensuring that there are no coarsely aggregated carbides on the working surface of the raceway; on the other hand, by utilizing the skin effect of induction heating and the efficient heat conduction in the metal solid, a tempering gradient temperature field is constructed on the limited wall thickness of the precision bearing ring, making full use of the kinetic relationship between the transformation of the tempered structure of high-carbon chromium bearing steel and the change of tempering heating temperature - time, realizing the asynchronous transformation of retained austenite in the radial direction of the bearing ring, and effectively solving the differential requirements of the working surface of the bearing ring raceway and the whole radial direction for the content of retained austenite; on the other hand, the tempering heat treatment method provides a relatively fast overall heating rate for the gradient tempering of the bearing ring, making the tempered carbides finer and more dispersed, which not only provides a positive tissue state for improving the wear resistance of the working surface of the raceway, but also reduces the hardness deviation of the whole radial direction of the bearing ring after gradient tempering; on the other hand, the stabilization heat treatment improves the residual stress distribution of the bearing ring and further improves the thermal stability and mechanical stability of the retained austenite.

[0030] The structure of the present application and its other application purposes and beneficial effects will become more obvious and understandable through the description of the preferred embodiments in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1Schematic flow chart of the method for controlling the microstructure and property distribution of a high-carbon chromium bearing ring provided by the embodiments of the present application. Detailed implementation manners

[0033] Currently, in order to improve the precision life of high-carbon chromium bearing steel precision bearings, cryogenic treatment is usually supplemented before low-temperature tempering or stabilization tempering is supplemented after that. However, the traditional process has a long cycle and poor comprehensive effect. Through surface modification, the wear resistance and fatigue life of the working surface of the bearing ring can be significantly improved, but the influence on controlling the austenite content to improve dimensional stability can be ignored. In addition, different from the structural characteristics, performance requirements and microstructural characteristics of the parts material of high-nitrogen stainless steel threaded bearing parts, the wall thickness of the high-carbon chromium bearing steel precision bearing ring is relatively thin, and the overall hardness change range of the ring is narrow. After tempering treatment above 500 °C, the hardness and wear resistance of high-carbon chromium bearing steel decrease sharply, and the existing high-frequency induction local tempering process cannot meet the requirements of the microstructure and properties of high-carbon chromium bearing steel precision bearings.

[0034] Based on the above technical problems, the embodiments of the present application provide a method for controlling the microstructure and property distribution of a high-carbon chromium bearing ring. On the one hand, a relatively high austenitizing temperature is matched with the holding time to ensure that there is enough retained austenite with a high carbon content on the working surface of the bearing ring after quenching, so that it has high thermal stability and mechanical stability after gradient tempering and stabilization heat treatment, and at the same time ensures that there are no coarsely aggregated carbides on the working surface of the raceway. On the other hand, by using the skin effect of induction heating and the efficient heat conduction in the metal solid, a tempering gradient temperature field is constructed on the limited wall thickness of the precision bearing ring, and the kinetic relationship between the transformation of the tempered microstructure of high-carbon chromium bearing steel and the tempering heating temperature-time is fully utilized to realize the asynchronous transformation of retained austenite in the radial direction of the bearing ring, effectively solving the differential requirements for the content of retained austenite on the working surface of the bearing ring raceway and the overall radial direction. On the other hand, the tempering heat treatment method provides a relatively fast overall heating rate for the gradient tempering of the bearing ring, making the tempering carbides finer and more dispersed, which not only provides a positive tissue state for improving the wear resistance of the working surface of the raceway, but also reduces the hardness deviation of the overall radial direction of the bearing ring after gradient tempering. On the other hand, the stabilization heat treatment improves the residual stress distribution of the bearing ring and further improves the thermal stability and mechanical stability of the retained austenite.

[0035] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Refer toFigure 1 As shown in Figure 1 , an embodiment of the present application provides a method for controlling the tissue performance distribution of a high-carbon chromium bearing ring, which is used for a bearing ring. The bearing ring has a first side and a second side along its thickness, and the first side is the working surface, which is configured to contact with rolling elements.

[0037] Exemplarily, the type of high-carbon chromium bearing steel is not limited. For example, it can be GCr19SiMnMo, G8Cr15, GCr15, GCr15SiMn, GCr15SiMo, and GCr18Mo. This embodiment does not limit this.

[0038] It should be noted that the distribution control method provided in this embodiment can be applied to any of the above types of high-carbon chromium bearing steels.

[0039] It should be noted that the reduction of wear resistance and overall dimensional stability of the bearing ring working surface is the key factor leading to the loss of bearing accuracy. The tissue state of the bearing ring is the fundamental determinant of the bearing ring performance and the key factor affecting bearing accuracy and life. However, the microstructure of the bearing matrix, especially the content of retained austenite, has a significant difference in the influence on wear resistance and dimensional stability. Among them, considering the wear resistance of the bearing ring working surface, it is desired to retain a large amount of retained austenite and fine and dispersed carbides on the raceway working surface. From the perspective of the dimensional stability of the entire bearing ring in the radial direction, it is desired that only a small amount of retained austenite exists, and there are no special requirements for the size and morphology of carbides.

[0040] Among them, the surface area where the bearing ring directly contacts and relatively rolls with the rolling elements is called the raceway working surface. Here, it is desired to retain a large amount of retained austenite (volume fraction of 12 - 16%), and at the same time, the carbides present a fine and dispersed state. Retained austenite is an austenite structure that fails to transform into martensite during quenching and cooling. It has certain toughness and plasticity. The fine and dispersed carbides are distributed in the matrix, which can effectively hinder the movement of dislocations and improve the hardness and wear resistance of the material.

[0041] Among them, from the inner surface to the outer surface of the bearing ring, the entire range of the ring along the radial direction. From the perspective of dimensional stability, it is desired that the content of retained austenite is as small as possible (volume fraction ≤ 4%), and there are no special requirements for the size and morphology of carbides. Retained austenite will transform under certain conditions, and this transformation may cause volume changes, thus affecting the dimensional stability of the bearing ring.

[0042] In the above design, on the one hand, from the inner surface to the outer surface of the bearing ring, the entire range of the ring along the radial direction. Considering the dimensional stability, it is desirable that the retained austenite content be as low as possible (volume fraction ≤ 4%), and there are no special requirements for the size and morphology of the carbides. Retained austenite will transform under certain conditions, and this transformation may cause volume changes, thus affecting the dimensional stability of the bearing ring. An appropriate content (12 - 16 vol. %) of retained austenite can continuously provide this strengthening effect during the wear process, thereby improving the wear resistance of the raceway working surface. On the other hand, the finely dispersed carbides are like hard "particles", evenly embedded in the matrix. When the rolling elements roll on the raceway, these carbides can bear part of the load and prevent the matrix material from being worn too quickly. Moreover, the finely dispersed distribution method increases the interface area between the carbides and the matrix, making the strengthening effect more significant and further enhancing the wear resistance of the raceway working surface.

[0043] In order to simultaneously meet the special requirements of wear resistance and dimensional stability for retained austenite, change the overall tissue content of the bearing matrix and regulate its distribution, this embodiment provides a method for controlling the tissue performance distribution of a high-carbon chromium bearing ring. The control method includes:

[0044] S100: Perform overall quenching treatment on the first side and the second side of the bearing ring.

[0045] In this embodiment, quenching is a heat treatment process in which the metal material is heated above the critical temperature and rapidly cooled after holding for a certain time. The purpose of this step is to make the entire bearing ring obtain higher hardness and strength. By rapid cooling, the organizational structure of the metal changes to form strengthening phases such as martensite, thereby improving the basic mechanical properties of the ring and laying a foundation for subsequent processing.

[0046] Exemplarily, the way of quenching treatment can include: performing overall quenching treatment on the first side and the second side of the bearing ring.

[0047] Or, first put the heated bearing ring into a medium with stronger cooling ability (such as water) to cool for a period of time. When the ring cools to a certain temperature, quickly transfer it to a medium with weaker cooling ability (such as oil) to continue cooling.

[0048] Or, utilize the thermal effect generated by the induced current passing through the workpiece to quickly heat the surface of the workpiece to the quenching temperature, and then immediately spray water for cooling to achieve surface quenching. The induction heating speed is extremely fast and the heating time is short, which can make the surface of the workpiece obtain fine grain structure, thereby improving hardness, wear resistance and fatigue strength. At the same time, since the heating is only concentrated on the surface layer, the core of the workpiece still maintains good toughness.

[0049] Among them, the quenching treatment method of the bearing ring in this embodiment is not limited, and can be specifically selected according to actual needs.

[0050] In this way, through overall quenching, high hardness and strength are obtained, and then through gradient tempering, appropriate organizational structures and properties are constructed in different parts. Finally, cryogenic treatment further stabilizes the structure and improves the properties, enabling the bearing ring to have good wear resistance on the working surface, and at the same time having certain toughness and dimensional stability as a whole, being able to better withstand the load of the rolling elements and extend the service life.

[0051] In the specific experimental process: the effective wall thickness of the high-carbon chromium bearing steel bearing ring is 9.2 mm, and overall quenching treatment is carried out in an atmosphere furnace. Aiming at the phase transformation characteristics of the material, the austenitizing isothermal temperature and isothermal time are reasonably designed and controlled. The heating rate is selected as 3.0 °C / s. According to the design formula of the austenitizing isothermal temperature and isothermal time, the austenitizing isothermal temperature is calculated to be 889.1 - 891.5 °C, and the isothermal time is 16.6 - 23.7 min. In this preferred embodiment, the heating temperature is selected as 890 °C and the isothermal time is 20 min for austenitizing heat treatment of the bearing matrix. After the heat preservation is completed, it is immediately cooled to room temperature with oil at 60 - 70 °C. After quenching, the overall retained austenite content is 18 vol. %.

[0052] S200: Perform gradient tempering heat treatment on the first side of the bearing ring to construct a tempering gradient temperature field on the radial wall thickness of the bearing ring, and make the heat source transfer from the first side to the second side by heat conduction.

[0053] In this embodiment, tempering is a heat treatment process in which the quenched metal material is heated to a certain temperature range below the critical temperature, held for a certain time, and then cooled.

[0054] Exemplarily, the tempering methods can include: low-temperature tempering: heating the workpiece to 150 - 250 °C, holding for a certain time and then cooling. In this temperature range, quenched martensite begins to decompose, precipitating fine carbides, reducing the quenching stress and brittleness, while maintaining relatively high hardness and wear resistance.

[0055] Or, medium-temperature tempering: the heating temperature is 350 - 500 °C. At this time, martensite further decomposes to form tempered troostite structure, which has a relatively high elastic limit and yield strength, and the toughness is also improved; or, high-temperature tempering, heating to 500 - 650 °C, and the quenched structure transforms into tempered sorbite, which has good comprehensive mechanical properties, that is, relatively high strength, plasticity and toughness.

[0056] Here, through a special gradient tempering method, a tempering gradient temperature field is constructed on the radial wall thickness of the bearing ring. Due to the existence of a temperature gradient in the temperature distribution, heat will gradually transfer from the first side with a higher temperature (the side where the heat source is located) to the second side through heat conduction. This treatment method can enable different positions of the bearing ring from the first side to the second side to obtain different degrees of tempering effects, thereby forming different organizational structures and performance distributions in the radial wall thickness direction. For example, the tempering degree near the first side (the working surface) may be relatively low, maintaining a high hardness to meet the wear resistance requirements when contacting the rolling elements, and suppressing the transformation of austenite; while the tempering degree near the second side is relatively high, appropriately reducing the hardness but increasing the toughness to enhance the impact resistance of the entire ring, etc.

[0057] In this way, the gradient tempering heat treatment constructs a tempering gradient temperature field on the radial wall thickness, realizing a reasonable distribution of the performance of the bearing ring along the thickness direction. The working surface has a high hardness, ensuring the wear resistance when contacting the rolling elements; while the toughness is appropriately increased on the other side, enhancing the overall reliability and avoiding brittle failure caused by excessive local hardness.

[0058] During the specific experimental process: The high-carbon chromium bearing steel bearing ring processed in step S100 is subjected to gradient tempering heat treatment. The heating method is induction heating, the frequency of the induction power supply is 50 KHz, and the current density is about 3.8×10 8 A / m 2 , and the induction heating time is 4.5 s. Utilizing the skin effect in the high-frequency alternating electric field and the internal heat conduction of the ring, a gradient temperature field is constructed on the radial cross-section of the ring to achieve gradient tempering. The average heating rate of the raceway working surface is about 80 °C / s, and the highest temperature is about 373.4 °C. The average heating rate of the non-working surface of the ring is about 58 °C / s, and the highest temperature is about 313.1 °C. After heating, it is air-cooled to room temperature.

[0059] S300: Cold treatment is performed on the first side and the second side of the bearing ring.

[0060] In this embodiment, the cold treatment usually involves holding the quenched metal material at a low temperature (such as liquid nitrogen temperature, etc.) for a certain period of time, and then slowly heating it to room temperature. This step can further stabilize the organizational structure of the bearing ring, reduce the content of retained austenite, thereby improving performance such as dimensional stability and hardness. After the previous quenching and tempering treatments, a certain proportion of retained austenite may still exist. The cold treatment can promote the further transformation of retained austenite into stable phases such as martensite, thereby optimizing the comprehensive performance of the bearing ring.

[0061] In this way, the cold treatment reduces the content of retained austenite, effectively reducing the dimensional changes caused by the transformation of retained austenite during use, improving the dimensional accuracy of the bearing ring during operation, and ensuring the normal operation and assembly accuracy of the bearing.

[0062] During the specific experiment process: the high-carbon chromium bearing steel bearing rings processed in step S200 are cryogenically treated. The minimum cryogenic treatment temperature range is -79°C, the holding time is 80 min, and after the holding is completed, the temperature is raised to room temperature. Subsequently, the cryogenically treated bearing rings are subjected to low-temperature tempering treatment, the tempering holding temperature is 140°C, and the holding time is 90 min.

[0063] In one possible implementation, heat treatment of the first side of the bearing ring may include: induction heating of the first side.

[0064] Exemplarily, a pure copper circular profiling inductor is used.

[0065] Among them, induction heating utilizes the principle of electromagnetic induction and can quickly convert electrical energy into heat energy, heating the first side of the bearing ring to the required temperature in an extremely short time. Compared with traditional heating methods, the heating speed is greatly increased. This rapid heating reduces the residence time of the workpiece at high temperatures, reduces the possibility of oxidation and decarburization, helps to maintain the chemical composition and purity of the first side surface, and improves the surface quality.

[0066] Among them, by reasonably designing the shape, size and position of the induction coil, the heating area can be precisely controlled to heat only the first side of the bearing ring. This makes the heat treatment process highly targeted and can meet the performance requirements of different parts of the bearing ring. For example, for the first side working surface in contact with the rolling elements, precise strengthening treatment can be carried out on it without affecting the performance of the second side and other parts, realizing precise control of the performance of the ring.

[0067] Among them, induction heating can form an obvious temperature gradient on the first side of the bearing ring. Since it takes a certain time for heat to conduct from the surface to the inside, during the heating process, the surface temperature of the first side rises rapidly while the internal temperature is relatively low, thus forming a temperature gradient that gradually decreases from the surface to the inside. This temperature gradient is very crucial in subsequent heat treatment processes such as tempering, which helps to construct a tempering gradient temperature field, enabling different organizational structures and properties to be obtained at different depth positions on the first side to meet the different performance requirements of the working surface.

[0068] In one possible implementation, induction heating of the first side of the bearing ring may include: controlling the heating speed range of the first side to be 50 - 90°C / s, the heat source conducts from the first side to the second side, and the heating speed of the second side may range from 40 - 60°C / s.

[0069] Exemplarily, the heating speed of the first side can be controlled to be 50°C / s, 60°C / s, 70°C / s, 80°C / s, 85°C / s, 90°C / s or any value between 50 - 90°C / s.

[0070] Among them, the heating rate on the first side is greater than that on the second side, enabling the austenitization process on the first side to be completed rapidly. Under such fast heating conditions, the austenite grains reach the temperature required for quenching before they have time to grow sufficiently, thereby obtaining fine austenite grains. After subsequent quenching, fine martensite structures will be formed. The fine grains not only increase the hardness and strength of the first side but also improve its toughness and fatigue resistance, enabling the working surface of the first side to better withstand the impact and friction of the rolling elements and extending the service life of the bearing ring.

[0071] Exemplarily, the heating rate on the second side can range from 40 °C / s, 42 °C / s, 45 °C / s, 60 °C / s, or any value between 40 and 60 °C / s.

[0072] Among them, the heating rate on the second side is slightly slower, but it can still enable the second side to obtain appropriate tissue transformation. It can avoid the problem of coarse grains caused by too slow heating rate, and at the same time, the tissue on the second side can be strengthened to a certain extent. By obtaining heat from the first side through heat conduction for heating, the organizational structure of the second side can form a certain gradient change with that of the first side, enhancing the comprehensive performance of the entire bearing ring.

[0073] In addition, this heating rate helps to form a tissue with good toughness and certain strength on the second side. Compared with the first side which focuses more on hardness and wear resistance, the second side needs to have a certain degree of toughness to buffer and absorb energy to prevent brittle fracture of the bearing ring during operation. The heating rate of 40 - 60 °C / s can enable the second side to maintain good toughness while ensuring a certain strength, achieving a balance between strength and toughness.

[0074] Therefore, by reasonably controlling the heating rates of the first side and the second side, a performance gradient is formed in the radial direction of the bearing ring. The first side has the characteristics of high hardness and high wear resistance, suitable for working in contact with the rolling elements; the second side has better toughness and certain strength, which can support and protect the first side and withstand a certain load. This performance gradient enables the bearing ring to better adapt to complex working conditions and improves the overall reliability and service life.

[0075] In a possible implementation, induction heating of the first side of the bearing ring may include: controlling the heating temperature range of the first side to be 350 - 400 °C, and the heat source is conducted from the first side to the second side, and the heating temperature range of the second side is 250 - 350 °C.

[0076] Exemplarily, the heating temperature of the first side can be controlled to be 350 °C, 360 °C, 370 °C, 380 °C, 390 °C, 400 °C, or any value between 350 - 400 °C.

[0077] Among them, the heating temperature on the first side is relatively high, which helps to decompose or transform some retained austenite, and can also stabilize the remaining retained austenite to a certain extent. An appropriate amount of stable retained austenite can play a buffering role during the operation of the bearing, absorb energy, and improve the toughness and fatigue resistance of the first side. When the first side is subjected to the impact and friction of the rolling elements, the retained austenite can undergo a certain amount of plastic deformation, thereby alleviating stress concentration and reducing the generation and propagation of cracks.

[0078] Exemplarily, the heating temperature on the second side can be 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 350°C or any value between 250 - 350°C.

[0079] Among them, the heating temperature on the second side is relatively low, which can cause the structure to undergo a tempering transformation and gradually form tempered sorbite. Tempered sorbite has good comprehensive mechanical properties, with both a certain strength and hardness, as well as good toughness and plasticity. This enables the second side to withstand a certain load and is not prone to brittle fracture when subjected to impact, enhancing the reliability of the entire bearing ring.

[0080] Therefore, by controlling the different heating temperatures on the first side and the second side, the heat is slowly conducted from the first side to the second side, avoiding excessive thermal stress caused by too large a temperature difference. The smaller thermal stress can reduce the risk of deformation and cracking of the bearing ring during the heating process, improving the product qualification rate and quality stability.

[0081] In a possible implementation, the induction heating of the first side of the bearing ring includes: controlling the induction power supply frequency range to be 10 - 60 KHz, the current density range to be 10 8 ~10 9 A / m 2 , and the induction heating time range to be 2 - 6 s.

[0082] Exemplarily, the control induction power supply frequency range can be 10 KHz, 20 KHz, 30 KHz, 40 KHz, 50 KHz, 60 KHz or any value between 10 - 60 KHz. The current density range can be any value between 10 8 ~10 9 A / m 2 , and the induction heating time range can be any value between 2 - 6 s. This embodiment does not make any limitations in this regard.

[0083] In this way, the frequency range of 10 - 60 kHz can make the heat mainly concentrated within a certain depth range on the first side of the bearing ring. Lower frequencies can result in a relatively larger heating depth, while higher frequencies make the heating more concentrated on the surface. By reasonably selecting the frequency, the heating depth on the first side can be precisely controlled according to the specific requirements of the bearing ring to meet different performance needs. For example, for bearing rings that require a relatively deep hardened layer, a relatively lower frequency can be selected; while for cases where only surface strengthening is needed, a higher frequency can be chosen.

[0084] The appropriate current density (10 8 ~10 9 A / m²) and heating time (2 - 6 s) cooperate with the frequency to further optimize the heating depth and heating effect. At a certain frequency, an appropriate current density and heating time can ensure that the heat is evenly distributed within the target depth range, avoiding situations of insufficient heating or overheating.

[0085] During the rapid heating process with a short time (2 - 6 s), the austenite grains do not have enough time to fully grow before reaching the quenching temperature. This enables the first side to obtain a fine grain structure after quenching. The fine grains not only increase the hardness and strength of the material but also improve its toughness and fatigue resistance, enabling the first side of the bearing ring to better withstand the impact and load of the rolling elements during operation.

[0086] It should be noted that the frequency range of 10 - 60 kHz, the current density range of 10 8 ~10 9 A / m², and the heating time range of 2 - 6 s have a certain degree of adjustability. During the production process, these parameters can be flexibly adjusted according to bearing rings of different specifications and materials as well as specific performance requirements to obtain the best heat treatment effect and meet diverse production needs.

[0087] In a possible implementation, overall quenching treatment is performed on the first side and the second side of the bearing ring, including: controlling the austenitizing heating rate range to be 0.5 - 5 °C / s.

[0088] Exemplarily, the austenitizing heating rate can be controlled at 0.5 °C / s, 1 °C / s, 1.5 °C / s, 2 °C / s, 2.5 °C / s, 5 °C / s, or any value between 0.5 - 5 °C / s.

[0089] In this way, an appropriate heating rate can enable the carbides to dissolve fully during austenitization. The degree of carbide dissolution has a significant impact on the microstructure and properties after quenching. If the heating rate is too fast, the carbides may not dissolve fully, resulting in excessive carbide residues after quenching, which affects hardness and wear resistance; while a slower heating rate (0.5 - 5 °C / s) can make the carbides dissolve gradually, providing a good microstructure basis for subsequent quenching and tempering treatments. Additionally, during subsequent cooling and tempering processes, the carbon dissolved in austenite will precipitate in a suitable manner. Due to the uniform composition during austenitization, the precipitation of carbides will also be more uniform and finer, contributing to improving the hardness and wear resistance of the bearing ring.

[0090] Meanwhile, the slow heating rate enables the temperatures of the first side and the second side of the bearing ring to rise more evenly, reducing the thermal stress generated due to excessive temperature gradient. Thermal stress is one of the important reasons for workpiece deformation and cracking during quenching. By controlling the heating rate and reducing the thermal stress, the dimensional accuracy and yield rate of the bearing ring can be effectively improved, and the waste loss can be reduced.

[0091] In a possible implementation, the overall quenching treatment of the first side and the second side of the bearing ring further includes: when the heating rate for austenitization reaches 5 °C / s, controlling the holding temperature range to be 880 - 920 °C and the holding time range to be 10 - 40 min; after the holding is completed, cooling to room temperature with oil at 60 - 70 °C.

[0092] Exemplarily, the controlled holding temperature can be 880 °C, 890 °C, 900 °C, 920 °C or any value between 880 - 920 °C. The holding time can be 10 min, 20 min, 30 min, 40 min or any value between 10 - 40 min. This embodiment does not limit this.

[0093] In this way, during the holding process at 880 - 920 °C, the atoms have sufficient activity for diffusion. After the previous heating rate of 5 °C / s, the distribution of alloying elements and carbon in austenite already has a certain basis, and the 10 - 40 min holding time further promotes their uniform diffusion, making the composition of austenite more uniform. This helps to obtain a martensite microstructure with uniform properties during subsequent quenching, avoiding local property differences caused by composition segregation and improving the stability of the overall performance of the bearing ring.

[0094] Appropriate heat preservation temperature and time can control the growth of grains while ensuring the uniformity of austenite composition. The temperature range of 880 - 920 °C and the heat preservation time of 10 - 40 min can enable the grains to grow to a certain extent without becoming overly coarse. Fine and uniform austenite grains will transform into fine martensite structure after quenching, thereby improving the strength, hardness, toughness and fatigue resistance of the bearing rings.

[0095] In a possible implementation, the cryogenic treatment of the first side and the second side of the bearing ring may include: controlling the minimum temperature range of the cryogenic treatment to be -79~-110 °C; when the minimum temperature of the cryogenic treatment reaches -110 °C, controlling the heat preservation time range to be 30 - 120 min, and heating to room temperature after the heat preservation ends.

[0096] In this way, in the low-temperature environment of -79~-110 °C, the retained austenite in the bearing ring will transform into martensite. Retained austenite is a metastable phase and may continue to transform at room temperature, resulting in dimensional changes and unstable performance. Through cryogenic treatment, most of the retained austenite is transformed into martensite, which can significantly reduce the content of retained austenite. For example, when the minimum temperature of the cryogenic treatment reaches -110 °C and the heat preservation is 30 - 120 min, the content of retained austenite can be greatly reduced, thereby optimizing the organizational structure of the bearing ring.

[0097] At the same time, cryogenic treatment makes the structure more uniform and dense, reducing the stress concentration phenomenon caused by uneven distribution of retained austenite. Under the action of alternating loads, the uniform organizational structure can better disperse stress, delay the initiation and propagation of fatigue cracks, and thus significantly improve the fatigue resistance of the bearing ring.

[0098] It should be noted that controlling the minimum temperature range of the cryogenic treatment to be -79~-110 °C and controlling the heat preservation time range to be 30 - 120 min at -110 °C provides a certain degree of flexibility for process adjustment. Appropriate cryogenic treatment parameters can be selected according to factors such as the material, size and performance requirements of the bearing ring to achieve the best treatment effect and meet different production needs.

[0099] In a possible implementation, after the cryogenic treatment of the first side and the second side of the bearing ring, it may further include: performing low-temperature tempering treatment on the first side and the second side of the bearing ring.

[0100] Among them, there is a certain amount of residual stress inside the martensite structure formed after cryogenic treatment. During the low-temperature tempering process, atoms have a certain activity ability, which can relieve the lattice distortion part in the martensite, thereby reducing the residual stress. This helps to stabilize the martensite structure and prevent dimensional changes or performance fluctuations caused by stress release during subsequent use.

[0101] In addition, during low-temperature tempering, the carbon in the supersaturated martensite will precipitate in the form of fine dispersed carbides. The precipitation of these carbides can not only further improve the hardness and wear resistance of the bearing rings, but also refine the structure and improve the comprehensive properties of the material. For example, fine dispersed carbides can hinder dislocation movement and enhance the strength and hardness of the material.

[0102] In addition, low temperature tempering treatment makes the performance of bearing rings more stable and better adaptable to complex and changing working environments. Whether in high temperature, low temperature, humidity or corrosive media, low temperature tempered bearing rings can maintain good performance, ensure the normal operation of bearings, and improve the reliability and work efficiency of equipment.

[0103] In a possible implementation, the tempering and holding temperature range is controlled to be 120-140°C, and the holding time range is 60-180 minutes. It should be noted that the tempering and holding temperature and holding time can be controlled according to factors such as the material, size, and performance requirements of the bearing ring, and appropriate tempering and holding parameters can be selected to achieve the best treatment effect and adapt to different production needs.

[0104] In this way, during the low-temperature tempering process at 120-140°C, the supersaturated martensite begins to decompose. Carbon atoms will gradually precipitate from the martensite lattice to form transition phase carbides. This moderate decomposition process will not completely transform the martensite, but will optimize its internal structure while retaining a certain martensite structure, creating conditions for improving material properties.

[0105] Long-term heat preservation (60-180min) helps to fully release the internal stress generated during cold treatment and quenching. The reduction of internal stress improves the toughness of the material, which can better absorb impact energy and reduce the generation and expansion of cracks. In practical applications, bearing rings have better anti-destructive ability when subjected to impact and vibration of rolling elements.

[0106] Therefore, by controlling the tempering temperature and holding time, the organization of the bearing ring is made more stable. The decomposition of martensite and the stabilization of residual austenite reduce the volume change caused by organizational transformation. This is very important for high-precision bearing rings, which can ensure their dimensional accuracy during assembly and use, and ensure the normal operation of the bearing.

[0107] The following is a comparison of the microstructure and performance of the bearing rings of the embodiment of the present application with the microstructure and performance of the bearing rings of the conventional process in combination with specific experimental data.

[0108] Specifically, under the same test conditions, the structures of retained austenite content, hardness, and dimensional stability were compared.

[0109] Table 1 Comparison of the microstructure and properties of the bearing rings obtained in the embodiments of the present application and the traditional process

[0110]

[0111] It should be noted that the size stability test condition is to place the bearing ring in a constant temperature environment of 110°C, and measure the change rate of the equivalent diameter of the bearing ring after isothermal treatment for 400 h. The average life is the average value of the number of stress cycles until fatigue. The room temperature impact toughness uses a non-standard notchless rectangular specimen.

[0112] As can be seen from Table 1, under the same test conditions, the content of retained austenite at the working surface of the raceway in the traditional process is low, but the size stability of the bearing matrix is reduced instead, the average life of the bearing matrix is shortened, and the impact toughness is also greatly reduced.

[0113] Therefore, it can be seen that the traditional process reduces the content of retained austenite in the whole bearing matrix to improve the size stability and hardness, but fails to give full play to the positive role of retained austenite in wear resistance and fatigue life, which may cause problems such as low impact toughness of the bearing ring, weakening the potential of high-carbon chromium bearing steel. The present application can effectively control the content and distribution of retained austenite in the bearing ring. On the premise of reducing the overall content of retained austenite, it maintains a high content of retained austenite and appropriate hardness at the working surface of the raceway of the bearing ring, improves the wear resistance of the raceway of the bearing ring and the size stability of the radial whole, and finally improves the accuracy retention of precision bearings.

[0114] The method for controlling the microstructure and property distribution of the high-carbon chromium bearing ring provided by the embodiment of the present application realizes the asynchronous transformation of retained austenite in the radial direction of the bearing ring, and effectively solves the differential requirements of the working surface of the raceway and the radial whole for the content of retained austenite.

[0115] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0116] In the description of the present application, it should be understood that the terms "comprising", "having" and any variations thereof used herein are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0117] Unless otherwise clearly specified and defined, terms such as "installed", "connected", "linked", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal connection of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances. In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for controlling the tissue property distribution of a high-carbon chromium bearing raceway, characterized in that For a bearing ring having a first side and a second side along its thickness, the first side being the working surface configured to contact rolling elements, the control method includes: Performing integral quenching treatment on the first side and the second side of the bearing ring; Performing gradient tempering heat treatment on the first side of the bearing ring to construct a tempering gradient temperature field on the radial wall thickness of the bearing ring, and allowing the heat source to transfer from the first side to the second side by heat conduction; Performing cryogenic treatment on the first side and the second side of the bearing ring.

2. The method for controlling the microstructure and property distribution of the high-carbon chromium bearing ring according to claim 1, characterized in that, Performing heat treatment on the first side of the bearing ring, including: Performing induction heating on the first side.

3. The method for controlling the tissue property distribution of a high-carbon chromium bearing raceway according to claim 2, wherein Performing induction heating on the first side of the bearing ring, including: Controlling the heating speed range of the first side to be 50 - 90 °C / s, allowing the heat source to conduct from the first side to the second side, and the heating speed range of the second side to be 40 - 60 °C / s.

4. The method for controlling the tissue property distribution of a high-carbon chromium bearing raceway according to claim 2, characterized in that Performing induction heating on the first side of the bearing ring, including: Controlling the heating temperature range of the first side to be 350 - 400 °C, allowing the heat source to conduct from the first side to the second side, and the heating temperature range of the second side to be 250 - 350 °C.

5. The method for controlling the tissue property distribution of a high-carbon chromium bearing ring according to claim 2, wherein, Performing induction heating on the first side of the bearing ring, including: The control induction power supply has a frequency range of 10 - 60 KHz and a current density range of 10 8 ~10 9 A / m 2 , and the induction heating time range is 2 - 6 s.

6. The method for controlling the tissue property distribution of a high-carbon chromium bearing raceway according to any one of claims 1-5, characterized in that, Performing integral quenching treatment on the first side and the second side of the bearing ring, including: Controlling the austenitizing heating speed range to be 0.5 - 5 °C / s.

7. The method for controlling the tissue property distribution of a high-carbon chromium bearing raceway according to claim 6, characterized in that, Performing integral quenching treatment on the first side and the second side of the bearing ring further includes: When the austenitizing heating speed reaches 5 °C / s, controlling the holding speed range to be 880 - 920 °C and the holding time range to be 10 - 40 min; After the holding is completed, cooling to room temperature with oil at 60 - 70 °C.

8. The method for controlling the microstructure and property distribution of the high-carbon chromium bearing ring according to any one of claims 1-5, characterized in that, Performing cryogenic treatment on the first side and the second side of the bearing ring, including: Controlling the lowest temperature range of the cryogenic treatment to be -79 ~ -110 °C; When the lowest temperature of the cryogenic treatment reaches -110 °C, controlling the holding time range to be 30 - 120 min, and heating to room temperature after the holding is completed.

9. The method for controlling the distribution of the microstructure and properties of the high-carbon chromium bearing raceway according to any one of claims 1-5, characterized in that, After performing cryogenic treatment on the first side and the second side of the bearing ring, it further includes: Performing low-temperature tempering treatment on the first side and the second side of the bearing ring.

10. The method for controlling the tissue property distribution of a high-carbon chromium bearing raceway according to claim 9, characterized in that, Controlling the tempering holding temperature range to be 120 - 140 °C and the holding time range to be 60 - 180 min.

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