Manufacturing method of rolling bearing

Abstract

To provide a manufacturing method for a rolling bearing that is excellent in seizure resistance and improves indentation resistance.SOLUTION: A manufacturing method for a rolling bearing in which a plurality of rolling elements are rotatably held between bearing rings having a raceway surface, comprises carbonitriding or carburizing a material constituting the bearing ring, and after tempering at 250°C or higher, hardening the raceway surface by machining, where the material contains, in mass%, C: 0.2 to 1.2%, Si: 0.5 to 1.5%, Mn: 0.1 to 1.5%, Cr: 2.5% or less, Mo: 1.5% or less (including 0%), and the balance consisting of Fe and unavoidable impurities.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a rolling bearing. [Background technology]

[0002] It is known that when rolling bearings are fitted or subjected to excessive static loads while stationary, Hertzian contact occurs between the outer and inner raceways and the rolling elements, resulting in permanent deformation (indentations) at the contact points. If such indentations exist on the raceways, they affect the acoustic and vibration characteristics when the ball bearings are in use. For example, in machine tools used under high-temperature conditions and high-speed rotation, even minute indentations of about 1 μm can cause serious problems in terms of abnormal noise and vibration. For this reason, when designing rolling bearings, the basic static load rating is determined by the contact stress, and JIS B 1519 stipulates that the contact stress for radial ball bearings, excluding thrust ball bearings and self-aligning ball bearings, is 4.2 GPa.

[0003] In addition, with the background of improved performance such as fuel efficiency in automobiles, there is an increasing demand for smaller bearings, and plastic deformation resistance that can withstand excessive static loads is required. In order to improve the plastic deformation resistance of a bearing, it is important to balance the material hardness of the outer and inner rings of the bearing and the amount of retained austenite. Therefore, efforts have been made to improve the indentation resistance by improving the hardness of the outer and inner rings and reducing the soft retained austenite. For example, in Patent Document 1, the indentation resistance of a bearing is improved by reducing the retained austenite through sub-zero treatment and high-temperature tempering. In addition, in Patent Document 2, the indentation resistance is improved by subjecting high carbon chromium steel to carbonitriding treatment.

[0004] Furthermore, in operating environments such as high temperature and high speed rotation of machine tools, the formation of an oil film becomes insufficient, causing metal contact between the outer and inner rings and the rolling elements, which may lead to seizure. Therefore, in addition to the impression resistance of the material used in the bearing, seizure resistance must also be considered. For example, in Patent Document 3, by adjusting the composition, high temperature tempering after carbonitriding does not reduce functions such as hardness, and seizure resistance is ensured even under poor lubrication conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-274440 A [Patent Document 2] JP 2015-200351 A [Patent Document 3] Patent No. 3873741 Summary of the Invention [Problem to be solved by the invention]

[0006] However, there is a strong demand for further improvement in the indentation resistance, and there is a limit to how much the indentation resistance can be improved by the above-mentioned heat treatment and composition adjustment alone. On the other hand, there is also a demand for sufficient seizure resistance.

[0007] The present invention has been made in light of the above-mentioned problems, and has an object to provide a method for manufacturing a rolling bearing that has excellent seizure resistance and improved indentation resistance. [Means for solving the problem]

[0008] Here, the formation of the indentation is a plastic deformation of the raceway ring, and can be regarded as a simple material yield phenomenon, and there is a technique called work hardening. The inventors have found that in order to improve the indentation resistance while also improving the seizure resistance, it is effective to adopt a steel material having a predetermined chemical composition that is a material with excellent seizure resistance as the material constituting the raceway ring, and after subjecting the steel material to a specific heat treatment, i.e., a carbonitriding treatment or a carburizing treatment, to apply a work hardening treatment by machining to the raceway surface of the raceway ring.

[0009] The present invention is based on these findings, and provides a method for producing a rolling bearing as shown in (1) below in order to solve the above problems.

[0010] A method for manufacturing a rolling bearing in which a plurality of rolling elements are held between races having raceways, the method comprising the steps of: the material constituting the raceway contains, by mass%, C: 0.2 to 1.2%, Si: 0.5 to 1.5%, Mn: 0.1 to 1.5%, Cr: 2.5% or less, Mo: 1.5% or less (including 0%), with the balance being Fe and unavoidable impurities; A method for manufacturing a rolling bearing, comprising the steps of: subjecting the material to carbonitriding or carburizing treatment; tempering the material at 250°C or higher; and then subjecting the raceway surfaces to work-hardening treatment by machining.

[0011] Further, preferred embodiments of the present invention relating to a method for manufacturing a rolling bearing relate to the following (2) to (5).

[0012] (2) A method for producing a rolling bearing as set forth in (1) above, characterized in that Si carbonitrides or Si carbides are dispersed and precipitated in the surface layer of the raceway surface by the carbonitriding treatment or the carburizing treatment. (3) The method for producing a rolling bearing according to (2) above, wherein the Si carbonitride or the Si carbide contains at least one of Si-Mn, Si-Mo and Si-Cr. (4) The method for producing a rolling bearing according to any one of (1) to (3) above, characterized in that the machining is burnishing. (5) a first curve showing a yield shear stress in a depth direction of the raceway surface before the raceway surface is machined; and a second curve showing a static shear stress in a depth direction of the raceway surface in a state in which the raceway surface has been machined; a third curve showing a static shear stress in the depth direction of the raceway surface in a state in which the rolling elements are in contact with the raceway surface and a static load is applied; and The area enclosed by the first curve, the second curve, and the third curve is below the area A; If the area enclosed by the area above the first curve and below the third curve is S, The method for producing a rolling bearing according to any one of (1) to (4) above, characterized in that the machining is carried out under machining conditions that satisfy the relationship: area A<area S. Effect of the Invention

[0013] According to the manufacturing method of the present invention, in bearings, such as machine tool spindles, in which excessive static loads are applied to the raceways and which are prone to indentations, it is possible to suppress the formation of minute indentations of about 1 μm on the raceway surface, and to manufacture rolling bearings that are less susceptible to seizure even under high-speed rotation, i.e., rolling bearings that have excellent seizure resistance and improved indentation resistance. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a partially cutaway perspective view showing a radial ball bearing, which is an example of a rolling bearing. [Diagram 2] FIG. 2 is a schematic diagram for explaining a method for calculating the area S. [Diagram 3] FIG. 3 is a schematic diagram for explaining a method for calculating the area A. In FIG. [Figure 4] FIG. 4 is a graph showing the limit PV value until seizure occurs for the steel material (bearing material) used in the examples and SUJ2 steel (standard bearing steel). [Diagram 5]FIG. 5 is a graph showing the temper softening resistance performance of the steel material (relevant bearing material) used in the examples and SUJ2 steel (standard bearing steel). [Figure 6] FIG. 6 is a graph showing the relationship between the maximum surface pressure and the indentation depth in Examples 1 to 4 and the comparative example. [Figure 7] FIG. 7 is a graph showing the relationship between the maximum surface pressure and the deformation resistance improvement index RD in Examples 1 to 4 and the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied within the scope of the present invention.

[0016] In the present invention, there is no limitation on the type or configuration of the rolling bearing that can be obtained, and one example is the radial ball bearing shown in Fig. 1. As shown in the figure, the radial ball bearing 1 comprises an outer ring 3 having an outer ring raceway surface 2 on its inner peripheral surface, an inner ring 5 having an inner ring raceway surface 4 on its outer peripheral surface, and a plurality of balls 6, each of which is a rolling element, disposed between the outer ring raceway surface 2 and the inner ring raceway surface 4. These balls 6 are held by a cage 7 so as to be able to roll freely, with the balls 6 spaced at equal intervals in the circumferential direction.

[0017] In the manufacturing method of the rolling bearing according to this embodiment, first, a steel material having a predetermined chemical composition, which will be described later, is subjected to a carbonitriding or carburizing treatment as a material for forming the raceways (outer ring 3 and inner ring 5) to disperse and precipitate Si-containing carbonitrides (hereinafter referred to as "Si carbonitrides") or Si-containing carbides (hereinafter referred to as "Si carbides") in the surface layer of the raceway surface. Si carbonitrides and Si carbides have a self-lubricating effect, and significantly improve seizure resistance and wear resistance without impairing the rolling life. This is because they show the same effect as the self-lubricating action of molybdenum disulfide and the like, and can prevent metal contact and improve seizure life and wear life.

[0018] The content of the Si carbonitride or Si carbide in the surface layer is preferably 1 to 30 mass% in order to fully exert the self-lubricating effect. If the content is less than 1 mass%, the lubricating effect is insufficient, whereas if the content exceeds 30 mass%, not only the lubricating effect is saturated, but also toughness is reduced, which may shorten the rolling life.

[0019] The Si carbonitride or Si carbide in the surface layer is, for example, Si-Mn, Si-Mo or Si-Cr, and it is preferable that the surface layer contains at least one of these.

[0020] Furthermore, if the size (equivalent circle diameter) of the Si carbonitrides or Si carbides in the surface layer exceeds 10 μm, stress concentration increases, which may cause a decrease in rolling life. The substantial lower limit of the size of the Si carbonitrides or Si carbides in the surface layer is 0.5 μm.

[0021] The carbonitriding and carburizing treatments can be carried out according to conventional methods, and the heat treatment temperature and time can be adjusted to precipitate the appropriate amounts of Si carbonitrides and Si carbides. The heat treatment conditions can be varied, for example, in the range of 850 to 950°C and the time period between 1 and 24 hours.

[0022] The chemical composition of other elements in the steel material constituting the raceway preferably falls within the numerical ranges shown below.

[0023] [C:0.2~1.2% by mass] To obtain the cleanliness required for a rolling bearing, C (carbon) must be 0.2 mass% or more. If C exceeds 1.2 mass%, the amount of retained austenite increases, reducing the dimensional stability of the bearing and forming eutectic carbides, shortening the life of the bearing. Therefore, the C content is preferably 0.2 to 1.2 mass%. To improve cleanliness, prevent excessive retained austenite, and prevent the formation of eutectic carbides, the C content is more preferably 0.35 to 1.1 mass%.

[0024] [Si:0.5~1.5% by mass] Silicon (Si) is essential for forming Si carbonitrides and Si carbides that are effective against seizure and friction wear. With a Si concentration of 0.15 to 0.35 mass%, which is necessary for deoxidation during steelmaking, it is difficult to improve seizure resistance and wear resistance, so it is necessary to add 0.5 mass% or more. However, if the amount added is too large, the seizure resistance and wear resistance effects of Si carbonitrides and Si carbides will decrease, so the Si content is preferably 1.5 mass% or less.

[0025] [Mn:0.1~1.5% by mass] Mn (manganese), like Si, is an element necessary for deoxidation during steelmaking, and is added in an amount of 0.1 mass% or more. Mn also improves hardenability and contributes to improving strength after heat treatment and rolling fatigue life. However, if the amount added is too large, retained austenite, which is harmful to dimensional stability, is generated and workability is deteriorated, so the Mn content is preferably 1.5 mass% or less.

[0026] [Cr: 2.5% by mass or less] Cr (chromium) improves hardenability and contributes to improving strength after heat treatment and rolling fatigue strength. However, if the amount of Cr added is large, it may reduce workability or generate eutectic carbides, so the Cr content is preferably 2.5 mass% or less.

[0027] [Mo: 1.5 mass% or less (including 0 mass%)] Mo (molybdenum) is selectively added because it improves hardenability and contributes to improving strength and rolling fatigue life after heat treatment, but if a large amount is carbonized, the material cost increases and workability decreases, so the Mo content is preferably 1.5 mass% or less. Note that since the Mo content is selectively added, the case where the Mo content is 0 mass% is also included.

[0028] [Balance: Fe and unavoidable impurities] The balance of the steel material constituting the raceway, excluding the above chemical components, is Fe (iron) and unavoidable impurities, such as S (sulfur), P (phosphorus), O (oxygen), Cu (copper), and Ti (titanium).

[0029] Next, in the manufacturing method of the rolling bearing according to this embodiment, after the above-mentioned carburizing treatment or carbonitriding treatment, tempering at 250°C or higher is required. The tempering temperature is preferably 270°C or higher, and more preferably 290°C or higher. In addition, the upper limit of the tempering temperature is preferably 350°C or lower, taking into consideration the maintenance of bearing function and treatment efficiency. Note that a temperature in the vicinity of 300°C is particularly preferable, and is 290 to 310°C when specified as a numerical range.

[0030] When bearing steel used in rolling bearings is subjected to carbonitriding, the structure of the surface layer (surface portion) of the raceway becomes a composite structure having a strong structure called martensite and a soft structure called retained austenite. The specified tempering is then performed to stabilize the composite structure. Note that by performing the specified heat treatment, i.e., the carburizing or carbonitriding, and then tempering at 250°C or higher, the surface layer (depth of about 100 μm) of the raceway becomes approximately HV700 in hardness and the amount of retained austenite becomes 5% or less.

[0031] Here, the bearing steel targeted in the present invention (i.e., a steel material containing, by mass%, C: 0.2-1.2%, Si: 0.5-1.5%, Mn: 0.1-1.5%, Cr: 2.5% or less, Mo: 1.5% or less (including 0%), with the remainder being Fe and unavoidable impurities) has a much higher temper softening resistance than the high carbon chromium bearing steel SUJ2 of JIS G 4805 (hereinafter referred to as "SUJ2 steel"), and is characterized in that the hardness does not decrease significantly even when tempered. In other words, by subjecting the steel material to carbonitriding or carburizing treatment and then subjecting it to a specified high-temperature tempering, it is possible to impart excellent indentation resistance.

[0032] Furthermore, in the manufacturing method of the rolling bearing according to this embodiment, after the above-mentioned predetermined tempering, it is necessary to perform a work hardening treatment by machining on the raceway surface of the race. When performing machining, it is assumed that the greater and deeper the static shear stress distribution given by the processing load is, the higher the plastic deformation resistance will be. Therefore, it is preferable to obtain a large plastic deformation resistance by performing heat treatment and machining under appropriate conditions for the material used.

[0033] There is no particular restriction on the type of machining method, but vanishing and shot peening are preferred. Vanishing is a machining method in which a device having a spherical tip and a high-hardness part as a machining jig is pressed against the outer ring raceway surface 2 and the inner ring raceway surface 4, and the outer ring 3 and the inner ring 5 are rotated around their own axis to apply compressive stress to the outer ring raceway surface 2 and the inner ring raceway surface 4. Shot peening is a machining method in which high-hardness, approximately spherical projectiles are sprayed onto the outer ring raceway surface 2 and the inner ring raceway surface 4. The processing conditions, such as the size, material, and spray speed of the approximately spherical projectiles, can be adjusted to achieve the same quality as vanishing. Note that vanishing is preferably used as the machining process because it suppresses the deterioration of surface properties, unlike shot peening, and can suppress the amount of machining required during finishing processing, which is performed as necessary in a later process.

[0034] The work hardening treatment introduces a static shear stress exceeding the yield shear stress of the material forming the outer ring 3 and the inner ring 5 to the outer ring raceway 2 and the inner ring raceway 4. The working conditions can be determined, for example, as follows.

[0035] Figure 2 shows "Curve a" which indicates the yield shear stress of the steel material (the material forming the rolling bearing) in the depth direction of the raceway surface, and "Curve b" which indicates the static shear stress in the depth direction of the raceway surface that occurs inside the raceway ring when a certain maximum surface pressure (static load) is applied. As shown in the figure, there is an area (hatched area in the figure) where the static shear stress shown by curve b exceeds the yield shear stress of the material forming the rolling bearing shown by curve a, and the amount of plastic deformation of the raceway surface can be estimated from the size of this "area S". It can be said that the smaller this area S is, the more difficult it is to cause plastic deformation and the less likely it is to leave an indentation on the raceway surface.

[0036] Similarly, when the raceway surface is subjected to work hardening treatment, the processing tool (a part with a spherical tip in the case of burnishing, or a roughly spherical projectile in the case of shot peening) comes into contact with the raceway surface, so this can be considered to be Hertzian contact. Also, it can be considered that a static shear stress exceeding the yield shear stress of the material forming the rolling bearing is introduced before the static load is applied.

[0037] In FIG. 3, "curve c" is superimposed on FIG. 2, which shows the static shear stress generated inside the raceway due to Hertzian contact of the tip of the machining jig. It is considered that if the "area A" of the region surrounded by lines a, b, and c (hatched portion in the figure) is reduced, the indentation resistance will improve. In other words, in order to improve the indentation resistance of the bearing raceway by machining, it is necessary that "area A < area S." If "area A = area S," the strengthening by the burnishing process is insufficient and does not contribute to improving the indentation resistance. It is preferable to perform machining at the maximum contact pressure at which line c, which contributes to the reduction of area S, is applied inside the raceway.

[0038] In addition, lines a, b, and c can be determined by the following calculations.

[0039] Static shear stress τ occurring inside the raceway st At the contact point between the raceway and the rolling element, Normal stress σ occurring in the tangential direction of the rolling element x(unit: MPa), normal stress σ z (unit: MPa) is expressed by the following formula (1).

[0040]

number

[0041] Normal stress σ x and σ z In the case of point contact, the maximum contact pressure q of Hertzian contact can be calculated using, for example, Hanson's elastic theory solution (Hanson, MT and Johnson, T., "The Elastic Field for Spherical Hertzian Contact of Isotropic Bodies Revisited: Some Alternative Expressions", Transactions of the ASME, Journal of Tribology, Vol. 115 (1993), pp. 327-332). max , contact surface radius a, Using the Poisson's ratio ν, σ x and σ z is expressed by the following equations (2) to (7).

[0042]

number

[0043]

number

[0044]

number

[0045]

number

[0046]

number

[0047]

number

[0048] Here, x=rcosθ(r>0), and when x>0, θ=0, and when x<0, θ=π. The maximum contact pressure q of the Hertzian contact max The contact surface radius a can be calculated by referring to, for example, "Introduction to Ball Bearing Design Calculations" (Okamoto Junzo, 2011). In the case of line contact, calculations can be performed using, for example, Smith's elastic theory solution (Smith, JO, Liu, C K and Ill U., “Stress Due to Tangential and Normal Loads on an Elastic Solid With Application to Some Contact Stress Problems”, Transaction of the ASME, Journal of Applied Mechanics, Vol. 20 (1953), pp. 157-166).

[0049] In addition, the yield shear stress τ of the material forming the rolling bearing y (Unit: MPa) is 0.2% yield strength σ 0.2 If the Vickers hardness of the raceway is HV, it is expressed by the following formula (8).

[0050]

number

[0051] Then, each line is calculated from the above formula, and the difference between line a, line b, and curve c at the same depth from the surface is integrated in the depth direction from the surface, thereby obtaining the area A.

[0052] Also, for ease of calculation, it is possible to perform an approximation using the quadrature method. In other words, the contact point between the raceway and rolling element is used as a reference to divide the normal direction of the rolling element into multiple infinitesimal sections ΔZ, and the areas of these infinitesimal sections are added together. For more accurate calculations, it is desirable to make the infinitesimal section ΔZ smaller, but 0.01 mm is appropriate. Even if it is made smaller than this, the difference in the calculated area A is negligibly small.

[0053] After the above work hardening treatment, finishing is carried out in the usual manner, and balls 6 and a cage 7 are fitted to obtain a rolling bearing. EXAMPLES

[0054] The effects of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0055] <1. Manufacturing of rolling bearings> (Examples 1 to 4) The inner and outer rings of the bearing were made of steel with the chemical composition, in mass%, of C: 0.3-0.4%, Si: 0.9-1.1%, Mn: 0.6-0.8%, Cr: 1.5%, and Mo: 0.9-1.1%, and were subjected to carbonitriding by heat treatment at 890°C for 12 hours. After the treatment, 2 to 5% by area of ​​Si carbonitride was precipitated in the vicinity of a depth of 100 μm from the raceway surface (the above area percentage is the average value measured in five fields of view in the vicinity of a depth of 100 μm from the raceway surface using EDS analysis). After the carbonitriding treatment, high-temperature tempering at 300°C was carried out.

[0056] FIG. 4 is a graph showing the limit PV value until seizure occurs for the steel material (indicated as "relevant bearing material" in the figure) and SUJ2 steel (indicated as "standard bearing steel" in the figure) used in the examples. FIG. 5 is a graph showing the temper softening resistance performance of the steel material (relevant bearing material) and SUJ2 steel (standard bearing steel) used in the examples. As shown in FIG. 4, the "relevant bearing material" has a PV value, which is a guideline for the occurrence of surface damage such as seizure and wear, that is about 1.5 times higher than that of the "standard bearing steel," and is therefore superior in seizure resistance. As shown in FIG. 5, it is also shown that the material has excellent softening resistance (temper softening resistance) when held at high temperatures. The "relevant bearing material" in the results shown in FIGS. 4 and 5 was subjected to carbonitriding treatment under heat treatment conditions of 890°C x 12 hours, and then to high-temperature tempering at 300°C.

[0057] The bearing races were then subjected to a work-hardening treatment after high-temperature tempering, and then to a finishing process, in which burnishing was used as the machining process.

[0058] Regarding the burnishing conditions, the tip shape of the burnishing tool was φ6 mm, the peripheral speed was 150 m / min, and the tool feed rate was 0.1 mm / rev in Examples 1 and 2. In addition, in Examples 3 and 4, the tip shape of the burnishing tool was φ10 mm, and other parameters were the same as in Examples 1 and 2. The processing load was 6.2 GPa in Example 1, 6.7 GPa in Example 2, 5.5 GPa in Example 3, and 5.7 GPa in Example 4. The burnishing conditions mentioned above are processing conditions that satisfy the above-mentioned "area A < area S", and the maximum contact pressure that causes line c, which contributes to the reduction of area S, to be applied to the inside of the raceway is adopted as the processing condition.

[0059] (Comparative Example) The inner and outer rings were made of the same steel as in Examples 1 to 4, and were subjected to only the same heat treatment as above, but were not subjected to burnishing, and were subjected to finish processing.

[0060] <2. Indentation test> In order to verify the indentation resistance of the rolling bearings according to Examples 1 to 4 and Comparative Example, an indentation test was carried out using a tension and compression tester manufactured by Instron Japan. As the test conditions for indentation formation, a silicon nitride ball having a diameter of 12 mm was pressed against the races of Examples 1 to 4 and Comparative Example at a strain rate of 0.2 mm / min. After reaching a predetermined maximum surface pressure, the pressure was held for 30 seconds to form a clear indentation shape. The maximum surface pressure during indentation formation was 5.00 GPa, 5.38 GPa, and 5.75 GPa. The depth of the formed indentation was then measured using a three-dimensional surface texture measuring instrument Talysurf manufactured by Taylor Hobson.

[0061] The results are shown in Table 1 and FIG. 6. From these results, it was confirmed that all of Examples 1 to 4 had shallower indentation depths than the comparative examples. It was also confirmed that, among the Examples, Example 4 had the highest allowable maximum surface pressure and the shallowest indentation depth. Note that each plot in FIG. 6 is an actual measurement value, and each curve is an approximation curve based on the plot. Also, the indentation depths in Table 1 are the indentation depths at maximum surface pressures of 5.00 GPa, 5.38 GPa, and 5.75 GPa in the approximation curve in FIG. 6.

[0062] [Table 1]

[0063] Next, the above-mentioned "area A" (see FIG. 3) was calculated for each of Examples 1 to 4. For the comparative example, since there is no line c associated with the burnishing process shown in FIG. 3, the "area S" shown in FIG. 2 was calculated. Then, the difference was calculated by subtracting each area A from the area S when forming an indentation under three conditions of maximum surface pressures of 5.00 GPa, 5.38 GPa, and 5.75 GPa, and the difference was divided by the area S of the comparative example to obtain the "deformation resistance improvement index R D The results of these calculations are shown in Table 2.

[0064] [Table 2]

[0065] Furthermore, FIG. 7 shows the relationship between the maximum surface pressure and the deformation resistance improvement index R in Examples 1 to 4 and the comparative example. D The relationship between the deformation resistance improvement index R D indicates that the closer the value approaches 1, the smaller the indentation depth formed by the burnishing process becomes. In other words, the deformation resistance improvement index R D The closer the value is to 1, the better the plastic deformation resistance is.

[0066] Also, 0 <R D In addition, from the results of this test, it can be confirmed that the performance improvement by the burnishing process is within the range of the deformation resistance improvement index R D It was confirmed that the deformation resistance improvement index R D It can be said that Example 4, in which the value is the highest, is the most suitable. [Explanation of symbols]

[0067] 1 Radial ball bearing 2 Outer ring raceway 3 Outer ring 4 Inner ring raceway surface 5. Inner Circle 6 balls 7 Cage

Claims

1. A method for manufacturing a rolling bearing in which a plurality of rolling elements are held between races having raceways, the method comprising the steps of: a material constituting the raceway contains, by mass%, C: 0.2 to 1.2%, Si: 0.5 to 1.5%, Mn: 0.1 to 1.5%, Cr: 2.5% or less, Mo: 1.5% or less (including 0%), with the balance being Fe and unavoidable impurities; a step of subjecting the material to a carbonitriding treatment or a carburizing treatment, subjecting the material to a tempering treatment at 250°C or more, and then subjecting the raceway surface to a work hardening treatment by machining; a first curve showing a yield shear stress in a depth direction of the raceway surface before the raceway surface is machined; a second curve showing a static shear stress in a depth direction of the raceway surface in a state in which the raceway surface has been machined; a third curve showing a static shear stress in the depth direction of the raceway surface in a state in which the rolling elements are in contact with the raceway surface and a static load is applied; and The area enclosed by the first curve, the second curve, and the third curve is below the area A; When the area enclosed by the area above the first curve and below the third curve is defined as area S, A method for manufacturing a rolling bearing, characterized in that the machining is carried out under machining conditions that satisfy the relationship: area A < area S.

2. 2. A method for producing a rolling bearing according to claim 1, characterized in that Si carbonitrides or Si carbides are dispersed and precipitated in a surface layer of said raceway surface by said carbonitriding treatment or said carburizing treatment.

3. 3. The method for producing a rolling bearing according to claim 2, wherein the Si carbonitride or the Si carbide contains at least one of Si--Mn, Si--Mo, and Si--Cr.

4. The method for manufacturing a rolling bearing according to any one of claims 1 to 3, characterized in that the machining is a burnishing process.

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