JP5233171B2 - Rolling bearing - Google Patents

Description

  The present invention relates to a rolling bearing, in particular, a ball bearing, a cylindrical roller bearing, a tapered roller bearing, a self-aligning roller bearing, a needle bearing, etc. used for transmissions, engines, etc. of automobiles, agricultural machines, construction machines, and steel machines. This relates to the improvement of the service life of rolling bearings.

  In the above-described rolling bearing, foreign matter or the like is mixed in the lubricating oil, and an impression is generated due to the biting of the foreign matter on the transfer surface, so that there is a high possibility of causing early peeling starting from the indentation. As a means for solving this, for example, by subjecting inner and outer rings and rolling elements to carburizing or carbonitriding to deposit a predetermined amount of residual austenite, the stress concentration due to the indentation generated on the transfer surface is alleviated. It is known to extend the peeling life (see Patent Document 1). It is also known to increase the service life by increasing the hardness of the transfer surface by high-concentration carburizing treatment and improving the material strength (see Patent Document 2).

Japanese Patent Laid-Open No. 64-55423 Japanese Unexamined Patent Publication No. 7-41934

  However, in any of the above means, the inner and outer rings and the rolling elements are basically considered as individual parts, and each part is strengthened. For example, when it is desired to improve the life of the raceway, a predetermined The service life is extended. Today, the environment surrounding bearings in the market is becoming more severe as machines become smaller and faster, and the number of cases in which effective longevity cannot be achieved with conventional longevity technologies is increasing.

  On the other hand, in order to improve the material strength, high alloying and the like are also considered. However, the use of a special material causes a significant cost increase and is not the best means.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a rolling bearing that suppresses peeling of both the rolling elements and the raceway and extends the bearing life.

  The present inventors examined the life extension of the bearing and focused on the synergistic effect of the bearings and the rolling elements rather than individually strengthening them. For example, in order to improve the life of the raceway, conventionally, only the strength of the raceway material has been considered, but the physical properties of the rolling elements are taken into consideration.

  As a result, it has been found that the life of each of the raceway and the rolling element is greatly affected by the surface condition of the counterpart (shape collapse due to roughness, indentation, etc.). For example, it has been found that it is more advantageous to improve the surface condition of the rolling element than to improve the raceway material in order to improve the life of the raceway. Therefore, by improving the surface condition of both the race and the rolling element during the manufacture of the bearing, the life of the contact partner is improved, and the life of the entire bearing is improved.

  In addition, for the foreign object biting, it is possible to extend the life of the bearing as a whole by changing the pressure dent of the raceway ring and the pressure dent of the rolling element and forming a dent preferentially on one of them. I found. By forming an indentation on either the raceway or the rolling element, stress concentration due to the indentation does not occur on the other side, and the side where the indentation is not formed is shorter than the short life effect due to stress concentration on the side where the indentation is formed. The long life effect due to the good maintenance of the surface condition becomes larger, and as a result, the entire bearing has a long life.

  Furthermore, it was examined whether it is advantageous to prolong the life of the bearing if the impression is preferentially formed on the raceway or the rolling element. If the surface condition of the mating component is poor, the tangential force acting on the edge of the indentation becomes large and the service life is shortened. In addition, the surface state on the side (drive side) where the peripheral speed is faster (drive side) than the surface state on the side where the peripheral speed is slow (driven side) significantly affects the life. Therefore, it is more effective to improve the pressure-proof dent on the drive side than on the driven side and make it difficult to make a dent. In a ball bearing or a self-aligning roller bearing, the rolling element (ball or roller) is on the drive side in a region where the surface pressure is high. In addition, in cylindrical roller bearings and tapered roller bearings, there is basically no slip between the bearing ring and the rolling element in the region where the surface pressure is high (pure rolling), so there is no distinction between the driving side and the driven side. In many cases, the roller is provided with a crowning for the purpose of suppressing the edge load, in which case the roller is on the driven side. From these points, in both ball bearings and roller bearings, it is more effective to extend the life of the entire bearing by improving the pressure dent of the rolling element and making it difficult to make the dent.

  As a method for controlling the easiness of the indentation of the material and the difficulty of attaching it, it is conceivable to provide a difference in hardness. Therefore, if the hardness of the rolling element is increased and the hardness of the raceway ring is reduced, an indentation can be preferentially formed on the raceway ring, but the basic strength of the raceway ring is reduced and the shortness is reduced. There will be a problem of end of life. Therefore, in the present invention, the carbon concentration of the material is made lower than that of ordinary bearing steel, and the hardness of the raceway raceway surface is increased by carburizing or carbonitriding, and the hardness of the raceway ring core is reduced. .

  In addition to hardness, retained austenite can be cited as a material factor that affects the ease of indentation. Residual austenite is a softer structure than martensite, which is the main structure of the bearing material, and the greater the amount of retained austenite, the easier it is to form indentations. Furthermore, the retained austenite has an effect of extending the life in a foreign matter-mixed lubricating environment. Therefore, in the present invention, retained austenite on the raceway raceway surface is increased in order to make the raceway easily indented and to ensure the effect of extending the life of the raceway. However, when the amount of retained austenite is too large, not only the surface hardness, pressure scar resistance and wear resistance are lowered, but also the dimensional stability when used at high temperatures is deteriorated.

  On the other hand, in order to make it hard to make an indentation on a rolling element, in addition to hardness, the surface nitrogen concentration, the area ratio and size of nitride, and the number are specified as material factors.

In view of the above, the present invention provides the following rolling bearings.
(1) Rollable between an outer member having a raceway surface on the inner peripheral surface, an inner member having a raceway surface on the outer peripheral surface, and a rolling surface of the outer member and a rolling surface of the inner member. In a rolling bearing provided with a plurality of rolling elements arranged in
The inner member and the outer member are carburized or carbonitrided, and the amount of retained austenite on each raceway surface is 20 to 45% by volume,
The rolling element is carbonitrided or nitrided, the nitrogen concentration on the rolling surface is 0.2 to 2.0 mass%, and the area ratio of the nitride containing Si and Mn is 1% or more and 20 % Of the surface hardness is HV750 or more, and 100 or more nitrides having an average particle size of 0.05 μm to 1 μm are contained in an area of 375 μm ² .
When the depth from the rolling surface of the rolling element is Z and the diameter of the rolling element is d, the hardness of the rolling element at Z = 0.045d is HV650-850, and Z = 0.18d. A rolling bearing characterized by having a hardness of HV700 to 771.

  In the rolling bearing of the present invention, the physical properties of the respective materials forming the inner and outer rings and the rolling elements are relatively defined to improve the pressure scar resistance and wear resistance of the entire bearing. It has a long life against the indentation origin type peeling that occurs below.

  Hereinafter, the present invention will be described in detail.

  In the present invention, the type and structure of the rolling bearing are not limited, and for example, a deep groove ball bearing shown in a sectional view in FIG. 1 can be exemplified. The deep groove ball bearing includes an inner ring 1 (inner member) having a raceway surface 1a on an outer peripheral surface, an outer ring 2 (outer member) having a raceway surface 2a facing the raceway surface 1a of the inner ring 1 on an inner peripheral surface, A ball, which is a plurality of rolling elements 3 arranged so as to be capable of rolling between both raceway surfaces 1a, 2a, a retainer 4 that holds the rolling elements 3 between the inner ring 1 and the outer ring 2, and an inner ring 1 and an outer ring 2 Seals 5 and 5 covering the openings of the gaps between them, and lubrication between both raceway surfaces 1a and 2a and the rolling surface 3a of the rolling element 3 is performed by a lubricant 6 such as grease or lubricating oil. Has been done. Note that the cage 4 and the seal 5 may not be provided.

  Further, as shown in a sectional view in FIG. 2, a tapered roller as a rolling element 3 is held by a cage 4 between an inner ring 1 and an outer ring 2, and a tapered roller bearing having a nominal number L44649 / 610 is illustrated. You can also Further, although not shown, angular ball bearings, cylindrical roller bearings, self-aligning roller bearings, needle roller bearings, and the like are also possible.

  In the present invention, the inner ring and the outer ring are subjected to carburizing or carbonitriding so that the amount of retained austenite on the raceway surface is 20 to 45% by volume. As described above, as the amount of retained austenite increases, the indentation is more easily formed. Therefore, in the present invention, the amount of retained austenite is increased to 20% by volume or more. Preferably it is 30 volume% or more. However, if there is too much retained austenite, the surface hardness, pressure scar resistance, and wear resistance will decrease, and the dimensional stability at high temperatures will deteriorate, so it will be 45% by volume or less, preferably 40% by volume or less.

  In addition, carbonitriding or nitriding is performed to enrich the surface layer of the rolling element with predetermined nitrogen. Nitrogen, like carbon, not only acts to strengthen the solid solution of martensite and to ensure the stability of retained austenite, but also forms nitrides or carbonitrides to improve the pressure resistance and wear resistance. The higher the surface nitrogen concentration is, the better the wear resistance and pressure scar resistance are. When the surface nitrogen concentration exceeds 0.2% by mass, a remarkable effect appears, but preferably 0.45% by mass or more.

  On the other hand, if the nitrogen concentration is too high, there is a drawback that toughness and static strength are lowered. Since the toughness and static strength are necessary performances for rolling elements of a rolling bearing, it is not preferable that the nitrogen concentration is too high. Therefore, the upper limit of the nitrogen concentration in the present invention is 2.0% by mass.

  Further, even when the nitrogen concentration is the same, the pressure scar resistance and the wear resistance change depending on the presence of nitrogen inside the material. Nitrogen may be present as a solid solution in the material or may be precipitated as a nitride. In addition, when carbonitriding a material containing a large amount of Si and Mn, a nitride containing Si and Mn on the surface (hereinafter referred to as “Si · Mn”) rather than the amount of nitrogen present in solid solution in the material even at the same nitrogen concentration. The amount of nitrogen present by precipitation as "system nitride" increases. The higher the area ratio of the Si · Mn nitride, the better the wear resistance and the pressure scar resistance. When the area ratio of the Si · Mn nitride exceeds 1%, a remarkable effect appears. % Or more.

  However, as with the nitrogen concentration, if the amount of Si / Mn nitride deposited becomes too large, there is a drawback that the toughness and static strength decrease. Since the toughness and static strength are necessary performances for rolling elements of a rolling bearing, it is not preferable that the amount of Si / Mn nitride precipitates is excessive. In particular, when the area ratio of the Si · Mn nitride exceeds 20%, the toughness is drastically lowered. Therefore, the upper limit of the area ratio of the Si · Mn nitride is 20%, more preferably 10%.

  Further, nitrides exceeding 1 μm do not contribute much to the strengthening of the material. The one where fine nitride is dispersed is strengthened. The reason for this is that, in the theory of precipitation strengthening, the smaller the distance between the precipitate particles, the better the strengthening ability. Therefore, even if the area ratio of the Si / Mn nitride is the same, if the number of precipitated particles is large, the relative In addition, the interparticle distance is shortened and strengthened. That is, the number of fine nitrides having an average particle size of 0.05 μm or more and 1 μm or less is used in a range where the area ratio of Si · Mn nitride is 1 to 20%, using steel with a high content of Si and Mn. It is good to increase. Further, among the Si · Mn nitrides of 0.05 μm or more, the ratio of the number of Si · Mn nitrides of 0.05 to 0.50 μm is set to 20% or more, so that it can be further strengthened. Become.

Specifically, it is preferable that there are 100 or more Si · Mn nitrides having an area of 375 μm ² and 0.05 μm or more and 1 μm or less. It is preferable to set it to 800 degreeC or more and 870 degrees C or less. When this temperature is exceeded, the nitride becomes coarse and the number of fine Si · Mn nitrides decreases. Further, when the temperature is higher than the treatment temperature, the solid solubility limit of nitrogen is increased, so that the amount of nitride is reduced and a desired area ratio may not be obtained. From the initial stage of the carbonitriding process, it is preferable that the mixed gas atmosphere of RX gas, enriched gas, and ammonium gas is used, the CP value is 1.2 or more, and the flow rate of ammonia gas is at least 1/5 of the RX gas flow rate. Moreover, it is preferable to perform the quenching after carbonitriding in the range of oil temperature 60-120 degreeC. If it is higher than this temperature, sufficient hardness may not be obtained. Tempering is performed at a temperature of 160 to 270 ° C., and the range of surface hardness is Hv 740 or higher, preferably Hv 780 or higher. Moreover, you may perform a subzero process after a quenching process as needed.

  Furthermore, the surface hardness of the rolling element is HV750 or more, preferably HV800 or more, more preferably HV820 or more. Hardness is the most effective material factor for improving the indentation resistance. Types of indentations include foreign matter indentations caused by biting foreign matter, and Brinell indentations caused by rolling elements biting into the raceway when an excessive load is applied, and the raceway crushing the rolling element. In the case of foreign matter indentation, the formation of the indentation can be suppressed by increasing only the hardness in the vicinity of the surface, but in the case of Brinell indentation, it is important that the hardness is high not only on the surface but also on the core. The indentation is formed by static shear stress (shear stress in a direction of 45 ° with respect to the rolling direction) generated inside the material when the raceway and the rolling element come into contact with each other and a load is applied. The phenomenon that the indentation is formed is caused by plastic deformation of the material. Therefore, if the yield shear stress of the material is equal to or higher than the static shear stress, the indentation is not formed. Usually, since the load acting on the rolling bearing is designed to be equal to or less than the static load rating, it is important to maintain a material strength that does not form indentation even when the static load rating is applied. The static load rating is defined as a load that generates a contact surface pressure of 4200 MPa for ball bearings and 4000 MPa for roller bearings. The static shear stress generated when this surface pressure is applied is the yield of the bearing material. Indentation does not occur if the shear stress or less. On the other hand, the yield shear stress of the material is proportional to the hardness of the material, and the yield shear stress and the Vickers hardness have a relationship of τy = 1/6 × HV.

  Therefore, in order not to form the Brinell impression, it is important to define the hardness so that the shear yield stress distribution (hardness distribution) exceeds the static shear stress distribution at the time of static load application. On the other hand, if the hardness of the core is too large, the toughness is lowered and cracking becomes a problem.

Moreover, since the maximum static shear stress working depth (static shear stress distribution) has a correlation with the rolling element diameter, the hardness was defined as follows. That is , when the depth from the rolling surface of the rolling element is Z and the diameter of the rolling element is d, the hardness of the rolling element at Z = 0.045d is HV650-850, preferably HV770-816, Z = 0.18d hardness is set to HV700 to 771, more preferably HV718 to 771, so that formation of Brinell indentation due to contact between the raceway and the rolling element can be suppressed. It is possible to achieve a long life by suppressing the tangential force acting on the.

  In addition, it is preferable that a rolling element contains the element shown below. The balance is iron and inevitable impurities.

[C: 0.3 to 1.2% by mass]
Carbon is an important element for obtaining the strength and life required for steel. If the amount of carbon is too small, not only a sufficient strength cannot be obtained, but also the heat treatment time required to obtain the hardened layer depth required for carbonitriding described later will be increased, leading to an increase in the heat treatment cost. Therefore, the carbon content is 0.3% by mass or more, preferably 0.5% by mass or more. In order to obtain a hardness of Z = 0.18d, preferably Z> 0.06d, 0.95% by mass or more is preferable. In addition, if the carbon content is too large, giant carbides are produced during steelmaking, which adversely affects the subsequent quenching characteristics and rolling fatigue life, and the header property may be reduced, leading to an increase in cost. .2% by mass, preferably 1.10% by mass.

[Si: 0.3-2.2% by mass, Mn: 0.2-2.0% by mass]
As described above, in order to sufficiently precipitate Si · Mn nitride, it is necessary to use a steel material containing a large amount of Si and Mn. SUJ2, a common bearing material, has a Si content of 0.25% and a Mn content of 0.4%, and even if nitrogen is added excessively by carbonitriding, etc., the amount of Si / Mn nitride is small . For this reason, content of Si and Mn makes the following values critical values.

<Si: 0.3-2.2 mass%>
It is an element necessary for the precipitation of Si · Mn-based nitrides, and due to the presence of Mn, it effectively reacts with nitrogen and precipitates significantly when added in an amount of 0.3% by mass or more. Preferably it is 0.4-0.7 mass%.

<Mn: 0.2 to 2.0% by mass>
It is an element necessary for the precipitation of Si · Mn nitride, and has the effect of promoting the precipitation of Si · Mn nitride when added in an amount of 0.2% by mass or more by coexistence with Si. Further, since Mn has a function of stabilizing austenite, it is set to 2.0% by mass or less in order to prevent the problem that the retained austenite increases more than necessary after the heat treatment for curing. Preferably it is 0.9 to 1.15 mass%. More preferably, the Si / Mn ratio is set to 5 or less for the following reason.

  Unlike nitrides obtained by tempering, Si · Mn-based nitrides are formed by reacting with Si while incorporating Mn in the austenite region when nitrogen that has entered during carbonitriding treatment. Therefore, if the amount of Mn added is less than the amount of Si added, precipitation of Si / Mn nitride is not promoted even if nitrogen is sufficiently diffused. In the range of Si and Mn addition described above, and when the nitrogen content penetrates 0.2% by mass or more, by making the Si / Mn ratio 5 or less, the life is extended and the wear resistance and seizure resistance are improved. An effective precipitation amount of Si · Mn nitride having an area ratio of 1.0% or more can be ensured.

[Cr: 0.5 to 2.0% by mass]
Cr is a carbide forming element as well as improving hardenability, and promotes precipitation and further refines the carbide that strengthens the material. If it is less than 0.5% by mass, the hardenability is lowered and sufficient hardness cannot be obtained, or the carbides are coarsened during carbonitriding. If it exceeds 2.0% by mass, a Cr oxide film is formed on the surface during carbonitriding to inhibit the diffusion of carbon and nitrogen. Therefore, the Cr content is preferably 0.5% by mass or more and 2.0% by mass or less, and more preferably 0.9 to 1.2% by mass.

  On the other hand, the inner ring and the outer ring preferably contain the following elements. The balance is iron and inevitable impurities.

[C: 0.1 to 0.7% by mass]
If the carbon content is low, the time required for the carburizing treatment and carbonitriding treatment becomes longer, so 0.1 mass% or more is necessary, 0.3 mass% or more is preferable, and 0.41 mass% or more is more preferable. . However, in order for the inner ring and the outer ring not to be too hard than the rolling element, it is necessary to be 0.7 mass% or less, preferably 0.5 mass% or less, and more preferably 0.46 mass% or less. Moreover, by setting it as such carbon content, the average amount of retained austenite can be made into a defined range.

[Cr: 0.5 to 3.0% by mass]
By containing Cr in this manner, a large amount of carbides, carbonitrides and chromium nitrides can be precipitated by carburizing or carbonitriding, and these particle sizes can be made fine. If the Cr content is less than 0.5% by mass, the carbides are likely to become large during carburizing or carbonitriding. If the Cr content exceeds 3.0% by mass, chromium oxide is formed on the surface, making it difficult for carbon and nitrogen to enter, and the carburizing characteristics and carbonitriding characteristics deteriorate. The Cr content is preferably 1.0 to 1.6% by mass, and more preferably 1.1 to 1.3% by mass.

[Si: 0.15-1.0% by mass]
By including Si in this manner, mechanical properties and heat treatment characteristics are improved. When the Si content is less than 0.15% by mass, the toughness of the core part is lowered, and when it exceeds 1.0% by mass, it is difficult for carbon and nitrogen to enter from the surface, and the carburizing characteristics and carbonitriding characteristics are deteriorated. The Si content is preferably 0.15 to 0.6% by mass, and more preferably 0.3 to 0.45% by mass.

[Mn: 0.20 to 1.5% by mass]
By containing Mn in this way, hardenability is improved and toughness is increased after quenching. When the Mn content is less than 0.20% by mass, the effect is not sufficiently exhibited, and when it exceeds 1.5% by mass, the machinability and hot workability of the alloy steel are deteriorated. The Mn content is preferably 0.6 to 1.3% by mass, and more preferably 1.0 to 1% by mass.

  Moreover, you may add at least 1 or more types of Mo, Ni, and V to a rolling element, an inner ring | wheel, and an outer ring | wheel as needed.

[Mo: 0.2 to 1.2% by mass]
Mo is a carbonitride-forming element as well as improving hardenability, and has the effect of promoting precipitation and further refinement of carbides, carbonitrides, and nitrides that strengthen the material. The effect becomes remarkable when 0.2% by mass or more is added. If it exceeds 1.2% by mass, the effect is saturated and the cost increases. Therefore, the Mo content is preferably 0.2 to 1.2% by mass, and more preferably 0.9 to 1.1% by mass.

[Ni: 0.5 to 3.0% by mass]
Ni has an effect of improving hardenability and at the same time improving toughness, and the effect becomes remarkable when 0.5% by mass or more is added. It is an austenite stabilizing element. When 3.0% by mass or more is added, the retained austenite becomes excessive and the core hardness decreases. Therefore, the Ni content is preferably 0.5% by mass or more and 3.0% by mass or less.

[V: 0.5 to 1.5% by mass]
V has the effect of improving wear resistance by forming hard carbides and carbonitrides by carbonitriding. This effect becomes remarkable when 0.5% by mass or more is added. When it is added excessively exceeding 1.5% by mass, it is combined with the solid solution carbon of the material to form a carbide and the hardness is lowered. Accordingly, the V content is preferably 0.5% by mass or more and 1.5% by mass or less.

  Hereinafter, the present invention will be further described with reference to examples and comparative examples, but the present invention is not limited thereto.

(Example 1-21 and Comparative Example 1-7)
A tapered roller bearing L44649 / 610 (rolling element diameter d = 5.44 mm) was prepared as a test bearing. For the inner ring and the outer ring, carburized steel having the composition shown in Table 1 (the balance is iron and inevitable impurities) was used. This carburized steel is carbonitrided and quenched (940 ° C. × 4 hr, RX gas + enrich gas + ammonia gas atmosphere), then quenched (830 ° C. × 0.5 hr, RX gas, oil quenching), tempered (160-220 ° C. × 2 hr). Also, the rollers are manufactured by header processing and rough grinding processing of wire rods having the composition shown in Table 2 (remaining iron and inevitable impurities), and carbonitriding and quenching (830 ° C. × 5 to 20 hr, RX gas + enrich gas + ammonia gas atmosphere) ), 180-270 ° C. tempering heat treatment and post-process.

  About the rolling element, the amount of surface nitrogen was measured using the electron beam microanalyzer (EPMA), and the amount of retained austenite of the surface layer was measured by the X-ray diffraction method. Also, using a field emission scanning electron microscope (FE-SEM), the rolling surface was observed at an acceleration voltage of 10 Kv, and after taking a picture of at least three fields of view at a magnification of 5000 times, the picture was binarized. Then, the area ratio of the Si · Mn nitride was calculated using an image analyzer. Furthermore, the hardness of the rolling element at the surface, 0.045d, 0.18d was measured. Table 2 shows the measurement results.

And about the said tapered roller bearing, after applying the excessive surface pressure of 4000 MPa once, the life test was done under foreign material mixing lubrication. The test conditions were as follows. The time until peeling occurred was measured, a Weibull plot was created, and the L10 life was obtained from the results of the Weibull distribution. Each test was performed 12 times. The results are shown in the column of the rolling life ratio in Table 2, and are shown as relative values with the value of Comparative Example 1 having the shortest life as 1.
Test load: Fr = 12 kN, Fa = 3.5 kN
・ Rotation speed: 3000 min ^-1
・ Lubricant: VG68
・ Hardness of foreign matter: HV870
Foreign material size: 74-134 μm
-Foreign matter contamination: 0.1g

  As shown in Table 2, according to the present invention, carburizing or carbonitriding treatment, inner and outer rings having a retained austenite amount of 20 to 45% by volume on the raceway surface, carbonitriding or nitriding treatment, and nitrogen on the rolling surface Examples in which the concentration is 0.2 to 2.0% by mass, the area ratio of the Si · Mn nitride is 1% or more and 20% or less, and the surface hardness is HV750 or more are all combined. Long life.

It is sectional drawing of the deep groove ball bearing which is an example of a rolling device. It is sectional drawing of the tapered roller bearing which is another example of a rolling device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 1a Raceway surface 2 Outer ring 2a Raceway surface 3 Rolling element 3a Rolling surface 4 Cage

Claims (1)

An outer member having a raceway surface on the inner peripheral surface, an inner member having a raceway surface on the outer peripheral surface, and a rollable arrangement between the rolling surface of the outer member and the rolling surface of the inner member In a rolling bearing provided with a plurality of rolling elements,
The inner member and the outer member are carburized or carbonitrided, and the amount of retained austenite on each raceway surface is 20 to 45% by volume,
The rolling element is carbonitrided or nitrided, the nitrogen concentration on the rolling surface is 0.2 to 2.0 mass%, and the area ratio of the nitride containing Si and Mn is 1% or more and 20 % Of the surface hardness is HV750 or more, and 100 or more nitrides having an average particle size of 0.05 μm to 1 μm are contained in an area of 375 μm ² .
When the depth from the rolling surface of the rolling element is Z and the diameter of the rolling element is d, the hardness of the rolling element at Z = 0.045d is HV650-850, and Z = 0.18d. A rolling bearing characterized by having a hardness of HV700 to 771.

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