Rolling bearing and method for manufacturing same

Abstract

Provided is a rolling bearing in which the occurrence of white structure peeling and / or the occurrence of surface-starting peeling can be suppressed without applying carburizing and carburizing / nitriding treatments that cause environmental load and increase in manufacturing cost. A rolling bearing (radial ball bearing (1)) is provided with a pair of steel raceway rings (an outer ring (3) and an inner ring (5)) and a plurality of rolling elements (balls (6)) which are held between the pair of raceway rings so as to be capable of rolling. In the steel in the raceway ring, the proportion of a lower bainite structure is 35% to 90%, the proportion of a retained austenite structure is 5% to 40%, and the remainder is a martensite structure and a carbide.

Description

Technical Field

[0001] This invention relates to rolling bearings and methods for manufacturing the same. Background Technology

[0002] In rolling bearings, prolonged use under heavy loads can sometimes lead to metal fatigue, causing the raceway surface to peel off. One type of peeling is "inclusion-origin peeling," which originates from inclusions within the steel forming the inner ring, outer ring, and rolling elements. "Surface-origin peeling" occurs when foreign matter such as debris gets trapped inside the bearing, causing indentations on the raceway surface. "White structure peeling" results from hydrogen embrittlement caused by hydrogen produced during use, such as from lubricant decomposition, leading to changes in the microstructure known as white structure. This peeling originates from within the material and is accompanied by cracks, contributing to shortened bearing life. These various types of peeling occur with different mechanisms, thus requiring different countermeasures depending on the type.

[0003] For example, Patent Document 1 proposes a bearing steel that suppresses surface initiation-type peeling and exhibits excellent rolling life in environments with foreign matter contamination. Patent Document 1 describes that, in order to improve rolling life in environments with foreign matter contamination, the amount of retained austenite in the surface layer after quenching and tempering needs to be 20% to 45%. Furthermore, it describes that to obtain the aforementioned amount of retained austenite by eliminating the costly and time-consuming carburizing and nitriding treatment, compared to SUJ2 steel, a general bearing steel, it is necessary to increase the content of alloying elements and specify the surface hardness after quenching and tempering.

[0004] Furthermore, Patent Document 2 discloses a bearing steel that specifies the content of alloying elements in the steel, and specifies the total amount of elements dissolved in the parent phase composition and the residual γ amount in a specified region from the outermost surface after carburizing, quenching and tempering or carburizing and nitriding, quenching and tempering. In addition, Patent Document 3 discloses a bearing steel that, in addition to the provisions of Patent Document 2, specifies a predicted value √areamax of the maximum inclusion diameter in the non-metallic inclusions in the steel. The bearing steels described in Patent Documents 2 and 3 exhibit excellent rolling fatigue life even in environments where a white microstructure change caused by hydrogen occurs.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2004-124215

[0008] Patent Document 2: Japanese Patent No. 6846901

[0009] Patent Document 3: Japanese Patent No. 6639839 Summary of the Invention

[0010] The technical problem that the invention aims to solve

[0011] However, the bearing steel described in Patent Document 1, particularly in improving rolling life in environments with foreign matter contamination, hardly considers the peeling of white structures. Furthermore, the bearing steels described in Patent Documents 2 and 3 primarily suppress the occurrence of white structure peeling, without considering surface-starting peeling. In addition, carburizing, quenching, and tempering or carburizing and nitriding quenching and tempering processes involve longer heat treatment times compared to conventional quenching and tempering, thus increasing manufacturing costs. Moreover, when performing gas carburizing, modified gases with H2, CO, and N2 as their main components are used, which may restrict future use from an environmental perspective.

[0012] The present invention was made in view of the above-mentioned problems, and its object is to provide a rolling bearing and a method for manufacturing the same, which can suppress either the occurrence of white tissue peeling or surface origin peeling without performing carburizing or carburizing nitriding treatments that lead to environmental impact and increased manufacturing costs.

[0013] Technical means for solving problems

[0014] The rolling bearing of the present invention is as shown in the following [1].

[0015] [1] A rolling bearing comprising: a pair of steel raceway rings; and a plurality of rolling elements, wherein the plurality of rolling elements are rotatably held between the pair of raceway rings, wherein,

[0016] The steel in the raceway ring has a lower bainite structure of 35% to 90%, a retained austenite structure of 5% to 40%, and the remainder is martensite and carbides.

[0017] The preferred embodiment of the rolling bearing of the present invention is shown in the following [2].

[0018] [2] The residual stress of the rolling bearing described in [1] is below -50 MPa.

[0019] The method for manufacturing the rolling bearing of the present invention is shown in the following [3].

[0020] [3] A method for manufacturing a rolling bearing, for manufacturing the rolling bearing described in [1] or [2], the method comprising:

[0021] The austenitizing process involves heating the raceway material to a temperature above 820°C and below 950°C to austenitize it.

[0022] The cooling process involves rapidly cooling the austenitized raceway material to a temperature exceeding the Ms point but below 270°C; and

[0023] The isothermal phase change treatment process involves maintaining the raceway material after the cooling process at a temperature exceeding Ms point and below 270°C for a period of more than 2 hours and less than 24 hours.

[0024] Invention Effects

[0025] According to the present invention, by appropriately controlling the proportions of lower bainite, martensite, and retained austenite in the microstructure of the steel constituting the rolling bearing, it is possible to provide a rolling bearing and a method thereof capable of suppressing either the occurrence of white microstructure peeling or surface initiation-type peeling. Attached Figure Description

[0026] Figure 1 This is a cross-sectional view illustrating a rolling bearing according to an embodiment of the present invention. Detailed Implementation

[0027] Through repeated and in-depth research, the inventors discovered that controlling the microstructure of the steel constituting rolling bearings is important. Specifically, they found that appropriately controlling the ratio of lower bainite, martensite, and retained austenite is effective in suppressing white microstructure peeling caused by hydrogen intrusion and surface-starting-type peeling under foreign matter intrusion environments. Furthermore, the inventors investigated the relationship between heat treatment conditions and microstructure, clarifying the heat treatment conditions used to produce a composite microstructure with the desired ratio. This invention is based on the above insights.

[0028] The embodiments of the present invention will now be described in detail. However, the present invention is not limited to the embodiments described below.

[0029] [Rolling bearings]

[0030] Figure 1 This is a cross-sectional view illustrating a rolling bearing according to an embodiment of the present invention. In this invention, the type and structure of the rolling bearing are not particularly limited; therefore, in this embodiment, a radial ball bearing is used as an example for explanation. Figure 1As shown, the radial ball bearing (rolling bearing) 1 has a steel outer ring 3 with an outer ring raceway surface 2 on its inner circumferential surface and a steel inner ring 5 with an inner ring raceway surface 4 on its outer circumferential surface, forming a pair of raceway rings. Furthermore, a plurality of balls (rolling elements) 6 are arranged between the pair of raceway rings (between the outer ring raceway surface 2 and the inner ring raceway surface 4). These balls 6 are held in a cage 7 in a state of being equally spaced in the circumferential direction, allowing for free rolling.

[0031] In the rolling bearing of this embodiment, the phase structure of the steel constituting the raceway rings (outer ring 3 and inner ring 5) is appropriately controlled. Specifically, the steel constituting the rolling bearing has a composite structure consisting of lower bainite and retained austenite, with the remainder being martensite and carbides. The phase structure of the steel specified in this embodiment will be described in detail below.

[0032] <Proportion of lower bainite structure: 35% or more but less than 90%>

[0033] If the steel undergoes a bainitic transformation, compressive residual stress is introduced into the surface layer of the steel along with the bainitic transformation, thus suppressing the deformation of the resulting steel. Furthermore, the lower bainitic structure is considered to also influence white spalling. When the proportion of lower bainitic structure is less than 35%, it is difficult to ensure the hardness of the raceway ring, and white spalling is prone to occur. Therefore, the proportion of lower bainitic structure in the steel constituting the raceway ring of the rolling bearing is 35% or more, preferably 40% or more, and more preferably 50% or more.

[0034] On the other hand, when the proportion of lower bainite exceeds 90%, the austenite structure described later decreases, making surface-start type peeling more likely to occur. Therefore, the proportion of lower bainite in the steel constituting the raceway ring of the rolling bearing is 90% or less, preferably 85% or less, and more preferably 80% or less.

[0035] <Percentage of retained austenite: 5% or more but less than 40%>

[0036] Retained austenite is a microstructure that influences surface-initiated spalling. When the proportion of retained austenite is less than 5%, surface-initiated spalling is more likely to occur. Therefore, the proportion of retained austenite in the steel constituting the raceway ring of a rolling bearing is 5% or more, preferably 8% or more, and more preferably 10% or more.

[0037] On the other hand, if the proportion of retained austenite exceeds 40%, the hardness of the raceway ring cannot be sufficiently ensured. Therefore, the proportion of retained austenite in the steel constituting the raceway ring of the rolling bearing is 40% or less, preferably 35% or less, and more preferably 30% or less.

[0038] <Balance: Martensite and carbides>

[0039] In this embodiment, martensite is not a particularly desirable structure, and it is preferable that the steel contains little martensite. Furthermore, the carbides dispersed in the lower bainite structure are unavoidable during the manufacturing process of the rolling bearing and do not affect the peeling of the white structure or surface start-point peeling. Therefore, in the steel constituting the raceway ring of the rolling bearing, as long as the ratio of lower bainite to retained austenite is within the aforementioned range, and the balance is martensite and carbides, the ratio is not particularly limited.

[0040] However, if the proportion of carbides increases, the steel becomes softer, and it is sometimes difficult to obtain the desired hardness for the steel constituting the raceway ring of a rolling bearing. Therefore, the proportion of carbides in the steel constituting the raceway ring of a rolling bearing is preferably 20% or less, more preferably 15% or less, and even more preferably 12% or less. In addition, as mentioned above, the less martensite in the steel constituting the raceway ring of the rolling bearing, the more preferable it is; for example, preferably 40% or less, more preferably 25% or less, and even more preferably 20% or less. Furthermore, in the steel constituting the raceway ring of the rolling bearing of this embodiment, it is preferable that ferrite and pearlite are substantially absent, with both ferrite and pearlite being 0%.

[0041] (Methods for calculating the proportions of each organization)

[0042] The fractions of each microstructure can be calculated, for example, by the following method. After electrolytically grinding the test piece to a depth of 300 μm from the surface, X-rays are irradiated. The amount of retained austenite can be calculated based on the ratio of the integrated intensity of the diffraction peaks of the (211) plane of the bcc structure to the (220) plane of the fcc structure. The fractions of other microstructures can be determined using the EBSD method. The test piece, after mirror finishing, is irradiated with an electron beam using FE-SEM. Phase identification is performed based on the obtained diffraction pattern, and the area fraction of carbides is calculated. Furthermore, the orientation of martensite and bainite is identified from the diffraction pattern, and the orientation difference between the blocks is calculated, thereby allowing the calculation of the ratio of martensite to bainite.

[0043] <Residual stress: below -50MPa>

[0044] As described above, the lower bainite structure in steel is the microstructure that affects the residual stress of the steel. In this embodiment, by appropriately adjusting the proportion of lower bainite in the steel, the value of residual stress is controlled, and the occurrence of white microstructure peeling is suppressed. When the residual stress of the rolling bearing is below -MPa, excellent crack propagation characteristics can be obtained, deformation can be suppressed, and good bearing performance can be maintained. Therefore, the residual stress of the rolling bearing is preferably below -50MPa, more preferably below -70MPa, and even more preferably below -100MPa.

[0045] (Methods for determining residual stress)

[0046] Regarding residual stress, it can be determined, for example, by the following method: After electrolytically grinding the test piece to a depth of 300 μm from the surface, X-rays are irradiated, and the residual stress is determined by the Cosα method based on the diffraction peaks of the (211) plane of the bcc structure.

[0047] In the rolling bearing of this embodiment described above, the proportions of various microstructures in the steel are appropriately controlled, thereby suppressing the occurrence of white microstructure peeling and surface-starting point peeling. It should be noted that in this embodiment, the composition of the steel constituting the rolling bearing is not particularly limited. For example, SUJ2 steel as specified in JISG 4805:2019, or 100CrMnSi6-4 as specified in ISO 683-17, which are commonly used as bearing steels, can be used.

[0048] In addition, steel with adjusted alloying elements can also be used, relative to the steel raw materials mentioned above. For example, steel containing C: 0.60% by mass or more and 1.21% by mass or less, Si: 0.40% by mass or more and 1.02% by mass or less, Mn: 0.55% by mass or more and 1.51% by mass or less, Cr: 0.75% by mass or more and 3.00% by mass or less, Mo: 1.00% by mass or less, Ni: 0.20% by mass or less, Cu: 0.20% by mass or less, S: 0.025% by mass or less, P: 0.020% by mass or less, and O: 0.0015% by mass or less, with the balance being Fe and unavoidable impurities.

[0049] [Manufacturing method of rolling bearings]

[0050] Next, the manufacturing method of the rolling bearing of this embodiment will be described in the following process sequence.

[0051] <Austenitizing Process>

[0052] First, the steel material undergoes the following processes: it is machined into the shape of the raceway ring for the rolling bearing; the machined raceway ring material is then heated to a temperature above point A1 to perform austenitization. In this process, austenite becomes the dominant microstructure in the steel.

[0053] (Temperature of the austenitizing process)

[0054] For raceway rings in rolling bearings, the austenitizing process requires a temperature of 820°C or higher, preferably 840°C or higher, to achieve the desired hardness by dissolving carbon in the steel through heating. On the other hand, at 950°C, the carbides almost completely dissolve in the steel, thus eliminating the need for heating above 950°C, but also increasing manufacturing costs. Therefore, the austenitizing process temperature is 950°C or lower, preferably 880°C or lower.

[0055] Cooling Process

[0056] Next, the austenitized raceway material is quenched to a temperature exceeding the Ms point but below 270°C. In this specification, quenching refers to cooling at a rapid pace that does not reach the Ps line (the temperature at which pearlite begins to form) or the Bs line (the temperature at which bainitic phase transformation begins). For example, cooling using salt can be cited as a method of quenching.

[0057] It should be noted that if the temperature is cooled to below Ms point after the cooling process and before the following isothermal phase transformation treatment, the martensitic phase transformation begins, and the resulting raceway ring contains martensite. In this embodiment, the ratio of lower bainite to retained austenite is specified; if a large amount of martensite is present, the ratio of lower bainite to retained austenite changes. Furthermore, in this embodiment, martensite is not required. Therefore, it is preferable to perform the isothermal phase transformation treatment without cooling to below Ms point after the cooling process.

[0058] <Irothermal Phase Change Treatment Process>

[0059] Then, the raceway material after the cooling process is kept at a temperature above Ms point but below 270°C. Through this isothermal phase transformation treatment process, the austenite is transformed into a lower bainite structure.

[0060] (Holding time during isothermal phase change treatment)

[0061] If the holding time in the isothermal transformation treatment process is less than 2 hours, a lower bainite structure of more than 50% cannot be obtained. Therefore, the holding time in the isothermal transformation treatment process is set to 2 hours or more, preferably 3 hours or more, and more preferably 4 hours or more. On the other hand, if the holding time in the isothermal transformation treatment process exceeds 24 hours, the proportion of lower bainite structure in the steel exceeds 90%, and surface initiation-type peeling is prone to occur. Therefore, the holding time in the isothermal transformation treatment process is set to within 24 hours, preferably within 16 hours, and more preferably within 12 hours.

[0062] (The holding temperature during the isothermal phase change treatment process)

[0063] When the holding temperature in the isothermal transformation process is low, the desired hardness can be obtained. However, when it is below the Ms point, even with extended holding time, a portion of the austenite and martensite structures in the steel will not transform into lower bainite, making it impossible to obtain the desired proportion of lower bainite. Therefore, the holding temperature in the isothermal transformation process is set to a temperature above the Ms point, preferably at a temperature 10°C or higher than the Ms point, and more preferably at a temperature 20°C or higher than the Ms point. As a specific example of the holding temperature in the isothermal transformation process, it is preferably set to 180°C or higher, and more preferably to 200°C or higher.

[0064] On the other hand, if the temperature of the raceway material after the cooling process exceeds 270°C, upper bainite will be generated, which will adversely affect the mechanical properties of the steel. Therefore, the holding temperature in the isothermal phase transformation treatment process is set to a temperature of 270°C or below, preferably at a temperature of 250°C or below, and more preferably at a temperature of 240°C or below.

[0065] Then, after cooling the raceway material following the isothermal phase change treatment, it is ground to produce the raceway of the rolling bearing. Subsequently, the retainer and rolling elements are assembled onto a pair of raceway rings using conventional methods, thereby manufacturing the rolling bearing. Furthermore, in this embodiment, a pair of raceway rings is produced by heat-treating the raceway material already machined into the raceway ring shape, but the rolling elements can also be produced using the same method.

[0066] If a rolling bearing is manufactured using the manufacturing method of this embodiment, the proportions of various microstructures in the steel can be appropriately controlled without performing carburizing and carburizing-nitriding treatments that lead to increased environmental impact and manufacturing costs. Therefore, it is possible to manufacture rolling bearings that suppress the occurrence of white microstructure peeling and surface-starting peeling, thus achieving a long service life.

[0067] [Example]

[0068] The following describes an inventive example and a comparative example of the rolling bearing according to this embodiment. First, for test pieces that underwent heat treatment under various heat treatment conditions, the proportions of each microstructure were calculated, and the physical properties were measured to investigate the changes in microstructure and physical properties caused by the heat treatment conditions.

[0069] <Production of Experimental Films>

[0070] Prepare steel with the composition range shown in Table 1 below, perform various heat treatments under the heat treatment conditions shown in Table 2 below, and produce test pieces.

[0071] Specifically, symbol A in Table 2 represents the following heat treatment conditions: an austenitizing process in which the steel is heated to 860°C, followed by a cooling process to 210°C, and then an isothermal transformation process in which the temperature is maintained at 210°C for 6 hours without decreasing. Symbol B represents the heat treatment conditions of an 8-hour isothermal transformation process according to Invention Example No. 1, performed at 210°C. Symbol C represents the heat treatment conditions of a quenching process in which the steel is heated to 820°C, followed by tempering at 200°C.

[0072] Symbol D indicates a heat treatment condition where the steel is quenched to 820°C and then tempered at 240°C. Symbol E indicates a heat treatment condition where the steel is quenched to 860°C and then tempered at 180°C. Symbol F indicates the following heat treatment condition: the steel is heated to 860°C, cooled to 210°C, and then subjected to an isothermal phase transformation treatment at 210°C for 72 hours without lowering the temperature.

[0073] <Calculation of the proportion of each organization>

[0074] The microstructure of the obtained test pieces was calculated using the following method. The test pieces were electrolytically ground to a depth of 300 μm from the surface and then irradiated with X-rays. The amount of retained austenite was calculated from the integral intensity ratio of the diffraction peaks of the (211) plane of the bcc structure and the (220) plane of the fcc structure. The fractions of other microstructures were determined using the EBSD method. The test pieces that had undergone mirror finishing were irradiated with an electron beam using FE-SEM. Phase identification was performed using the obtained diffraction patterns, and the area fraction of carbides was calculated. Furthermore, the orientation of martensite and bainite was identified from the diffraction patterns, and the orientation difference between the blocks was calculated, thereby determining the ratio of martensite to bainite. The proportions of each microstructure are shown in Table 2 below.

[0075] <Determination of physical properties>

[0076] (Determination of residual stress)

[0077] After electrolytically grinding the test piece to a depth of 300 μm from the surface, it was irradiated with X-rays. The residual stress was determined by the Cosα method based on the diffraction peaks of the (211) plane of the bcc structure.

[0078] (Hardness Measurement)

[0079] Regarding the Vickers hardness after heat treatment, the test load was set to 1 kgf, and the test was performed at 5 points in the center of the test piece. The average value of these measurements was taken as the measured hardness value.

[0080] Next, rolling fatigue life tests were conducted on the bearings manufactured by heat treatment under the above-mentioned heat treatment conditions.

[0081] <Fabrication of Experimental Deep Groove Ball Bearings (Rolling Bearings)>

[0082] Raceway rings (inner and outer rings) for deep groove ball bearings, designated as JIS B1513-1995 (number 6206), were manufactured by turning steel with the composition shown in Table 1 below. Next, the raceway ring material was heat-treated under the conditions indicated by symbols A to F in Table 2 below, and then ground to produce the raceway rings. Finally, 3 / 8-inch steel balls made of SUJ2 steel as specified in JIS G 4805:2019 and a resin retainer were assembled onto the obtained raceway rings to manufacture a test deep groove ball bearing.

[0083] <Rolling fatigue life test>

[0084] The fabricated deep groove ball bearings were mounted on a radial fatigue life testing machine, and rolling fatigue life tests were conducted under the following conditions to determine the white tissue peeling life and surface initiation peeling life. Additionally, each test was performed 5 times, and the life at which the cumulative failure probability reaches 50% (L) was calculated. 50 The average value of ).

[0085] (Determination conditions for white tissue peel life)

[0086] Test load (radial load): 910 kgf

[0087] Rotation speed: 3000 min -1

[0088] Lubricating oil: A special type of lubricating oil that easily produces hydrogen due to its decomposition.

[0089] (Determination conditions for surface origin-type peeling lifetime)

[0090] Test load (radial load): 635 kgf

[0091] Rotation speed: 3000 min-1

[0092] Lubricating oil: RO68 (containing 0.05g / 1.2L of iron powder with a size of approximately 100μm and a hardness of 870HV)

[0093] The results of the physical property measurements and the rolling fatigue life test are shown in Table 3 below. It should be noted that in the white tissue peeling test and surface initiation type peeling test shown in Table 3 below, the results are compared with those of Comparative Example No. 1, which used the heat treatment conditions indicated by the general implementation symbol C.

[0094] [Table 1]

[0095]

[0096] [Table 2]

[0097]

[0098] [Table 3]

[0099]

[0100] As shown in Tables 2 and 3 above, the ratio of lower bainite and retained austenite in Invention Examples No. 1 and No. 2 is within the range specified in this invention, with the remainder being martensite and carbides. Therefore, it is possible to suppress the occurrence of white tissue peeling caused by hydrogen intrusion and to suppress surface-initiation type peeling in environments with foreign matter contamination. Furthermore, since Invention Examples No. 1 and No. 2 have lower bainite structures, the residual stress is negative, becoming compressive residual stress, thus exhibiting excellent crack propagation characteristics.

[0101] On the other hand, Comparative Example No. 1 did not undergo isothermal phase transformation treatment, and therefore no lower bainite structure was formed. Therefore, compared to Invention Examples No. 1 and No. 2, the lifespan of the white structure peeling test and the surface initiation type peeling test was shorter. Comparative Example No. 2 also did not undergo isothermal phase transformation treatment, and therefore no lower bainite structure was formed; furthermore, the proportion of retained austenite was extremely low. Therefore, the lifespan of the surface initiation type peeling test was shorter. Therefore, the white structure peeling test was not performed.

[0102] It is believed that Comparative Example No. 3, compared to Comparative Example No. 1, was heated at a higher temperature, resulting in the dissolution of more carbon in the steel and thus higher martensite hardness, leading to a longer lifespan in the surface initiation peel test. However, Comparative Example No. 3 did not undergo isothermal transformation treatment, and no lower bainite structure was formed. Therefore, the lifespan in the white structure peel test was particularly short. It should be noted that the residual stress in Comparative Examples No. 1 to No. 3 was positive, becoming tensile residual stress, and therefore, the crack propagation characteristics were considered poor. Comparative Example No. 4 underwent isothermal transformation treatment at 210°C for 72 hours, resulting in a lower bainite structure proportion exceeding the range specified in this invention. Therefore, the lifespan in the surface initiation peel test was extremely short.

[0103] Various embodiments have been described above with reference to the accompanying drawings, but the present invention is not limited to these examples. It will be apparent to those skilled in the art that various modifications or alterations will occur within the scope of the claims, and these modifications or alterations are also within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the invention.

[0104] Furthermore, this application is based on Japanese Patent Application No. 2023-141257, filed on August 31, 2023, the contents of which are incorporated herein by reference.

[0105] Explanation of reference numerals in the attached figures:

[0106] 1 Radial ball bearing

[0107] 2 Outer ring raceway surface

[0108] 3 Outer ring

[0109] 4 Inner ring raceway surface

[0110] 5 Inner Circle

[0111] 6 ball bearings

[0112] 7. Holder

Claims

1. A rolling bearing, characterized in that, It comprises: a pair of steel raceway rings; and a plurality of rolling elements, wherein the plurality of rolling elements are freely maintained between the pair of raceway rings, wherein, The steel in the raceway ring has a lower bainite structure of 35% to 90%, a retained austenite structure of 5% to 40%, and the remainder is martensite and carbides.

2. The rolling bearing according to claim 1, characterized in that, The residual stress is below -50 MPa.

3. A method for manufacturing a rolling bearing, characterized in that, A method for manufacturing the rolling bearing according to claim 1 or 2, comprising: The austenitizing process involves heating the raceway material to a temperature above 820°C and below 950°C to austenitize it. The cooling process involves rapidly cooling the austenitized raceway material to a temperature exceeding the Ms point but below 270°C; and The isothermal phase change treatment process involves maintaining the raceway material after the cooling process at a temperature exceeding Ms point and below 270°C for a period of more than 2 hours and less than 24 hours.

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