JP2012031456A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve rolling fatigue life of a rolling bearing, which is used under conditions where structure changing type peeling is likely to occur, such as a bearing for a wind turbine, and a bearing for a construction machine.SOLUTION: An inner ring 1 is formed by using a material, which is an alloy steel containing 0.95-1.1 mass% [C], 0.20-0.70 mass% [Si], 0.30-1.2 mass% [Mn], 0.90-1.6 mass% [Cr], 0.30 mass% or less [Mo], 0.20 mass% or less [Ni] and [Cu], 0.02 mass% or less [S], 0.02 mass% or less [P], and 12 ppm or less [O], and contains an oxide inclusion with a diameter 10 μm or more of 10 pieces/320 mm, and by carburizing or carbonitriding, and quenching and tempering. In a 1%D position of a raceway surface, [C+N] is 1.10-1.50 mass%; Hv is 700-800; a residual austenite amount is 20-40 vol.%; a compression residual stress is 50-200 MPa, and surface roughness is 1.0 μm or less at a maximum peak height (Rp) of a roughness curve.

Description

  The present invention relates to a rolling bearing.

Supports the rotating shaft of the wind turbine for wind power generation (hereinafter simply referred to as “wind turbine”) (the main shaft of the rotor to which the blades are attached, the input shaft and the output shaft of the transmission disposed between the rotor and the generator). As the rolling bearing to be used, for example, a large roller bearing having an outer diameter of 180 mm or more (particularly 280 mm or more) is used.
Since the bearing ring and the rolling element of the rolling bearing generate a high surface pressure at the contact portion between them, and a high shear stress is generated inside, it is necessary to have a hardness that can withstand this. In particular, large bearings are required to be hardened to a deep position because shear stress acts deep inside. Moreover, since the roller bearing has a large contact area between the race and the rolling element, a region where shear stress acts is large. Even in the case of a ball bearing, a large rolling bearing having a ball (rolling element) with a diameter of 30 mm or more has a large area on which shear stress acts.

  A windmill bearing is used under conditions where slippage is likely to occur between the race and the rolling elements. When a large slip occurs between the raceway and the rolling element, the lubricating oil (oil film) that exists in the form of a film between the rolling element and the raceway easily breaks, and metal contact occurs at the cut part. When metal contact occurs, a newly formed metal surface is temporarily formed and chemically active, so that the lubricating oil decomposes and hydrogen is likely to be generated, and the generated hydrogen forms steel that forms the race and rolling elements. It becomes easy to invade.

Further, the rotational speed of the wind turbine bearing is likely to change. In applications where the rotational speed is variable, synthetic oil such as polyalkylene glycol is sometimes used instead of mineral oil in order to stably form an oil film between the race and the rolling elements. Some synthetic oils are more prone to generate hydrogen than mineral oil.
It is considered that hydrogen generated from the lubricating oil penetrates into the steel forming the race and rolling elements, and is a factor that accelerates the structure change type separation of the rolling bearing. The structure change-type peeling is a phenomenon in which the metal structure of steel changes from martensite to ultrafine ferrite, and fatigue cracks are generated starting from the portion where the ferrite is formed, leading to peeling.

For example, large ball bearings and roller bearings having an outer diameter of 180 mm or more are used in rolling bearings that support an axle of a construction machine and an input / output shaft of a transmission.
Since construction machines are used while repeating forward and reverse, the rotational direction of the rolling bearing changes each time. If the direction of rotation changes frequently, the oil film between the rolling element and the raceway will be easily cut, and metal contact will occur at the cut part, and as described above, the lubricating oil will decompose and hydrogen will be generated easily. The generated hydrogen is likely to enter the steel forming the race and rolling elements.

As described above, the structure change-type peeling is likely to occur in the wind turbine bearing and the construction machine bearing.
2. Description of the Related Art Conventionally, proposals have been made to suppress the structure change type separation of rolling bearings (see Patent Documents 1 to 3, etc.). Patent Documents 1 and 2 relate to rolling bearings for engine accessories, and the chromium content of the steel used is as high as 2.5 to 17% and 3 to 9%, resulting in high costs and heat treatment. Productivity decreases with decreasing properties and processability.

Patent Document 3 discloses that any of an inner ring, an outer ring, and a roller as a roller bearing suitable for supporting a rotating shaft of a windmill is alloy steel satisfying the following configuration (a), or a configuration (a) and a configuration: A material obtained by processing a material made of alloy steel satisfying both of (b) into a predetermined shape and quenching and tempering without carburizing or carbonitriding is described.
(a) The carbon content [C] is 0.90% by mass or more and 1.2% by mass or less, the silicon content [Si] is 0.20% by mass or more and 0.70% by mass or less, and the manganese content [Mn] is 0.30 mass% or more and 1.2 mass% or less, chromium content [Cr] is 0.90 mass% or more and 1.6 mass% or less, molybdenum content [Mo] is 0.30 mass% or less, and the balance is iron (Fe) and inevitable impurities, the DI value represented by the following formula (1) satisfies 5.0 or more and 9.0 or less.
DI = (0.18 [C] +0.16) (0.7 [Si] +1.0) (3.4 [Mn] +1.0) (2.2 [Cr] +1.0) (3.0 [Mo] +1.0) (1)
(b) When the maximum thickness of the rolling part (the raceway surface part of the inner ring and the outer ring, the rolling surface part of the roller) is t (mm), the following formula (2) is satisfied. DI / t ≧ 0.20 (2)

  In the invention described in Patent Document 3, if there is an incompletely hardened structure inside the raceway and the rolling element, the hydrogen generated by the decomposition of the lubricating oil is trapped and the metal structure is likely to change. As a result of the occurrence of such peeling, the rolling fatigue life is reduced, so that an incompletely hardened structure is prevented from occurring in the race and the rolling element.

JP 2005-163893 A Japanese Patent No. 4273609 JP 2010-31307 A

However, the rolling bearing described in Patent Document 3 has room for further improvement in terms of extending the rolling fatigue life when used under conditions in which structure change-type separation is likely to occur.
An object of the present invention is to further increase the rolling fatigue life of a rolling bearing used under conditions in which structure change-type separation is likely to occur, such as a wind turbine bearing and a construction machine bearing.

In order to solve the above-described problems, the rolling bearing of the present invention is characterized in that at least one of an inner ring, an outer ring, and a rolling element has the following configurations (1) and (2). Moreover, it is preferable to have the following configurations (1) to (3).
(1) Carbon content [C] is 0.95 mass% or more and 1.10 mass% or less, Silicon content [Si] is 0.20 mass% or more and 0.70 mass% or less, and manganese content [Mn] is 0.30% by mass to 1.2% by mass, chromium content [Cr] of 0.90% by mass to 1.6% by mass, molybdenum content [Mo] of 0.25% by mass or less, nickel content [Ni] is 0.20 mass% or less, copper content [Cu] is 0.20 mass% or less, sulfur content [S] is 0.02 mass% or less, and phosphorus content [P] is 0.02 mass%. %, Oxygen content [O] is 12 mass ppm or less, the balance is iron (Fe) and an inevitable impurity alloy steel, and an oxide system having a diameter of 10 μm or more per 320 mm ² area at an arbitrary cut surface After processing a material with 10 or less inclusions into a predetermined shape, carburization or Obtained by performing carbonitride and quenching and tempering.
(2) Total content of carbon and nitrogen [C + N] at a position corresponding to 0.01 times the diameter of the rolling element from the surface of the rolling surface (the raceway surface of the inner and outer rings, the rolling surface of the rolling element) 1.10 mass% or more and 1.50 mass% or less, Vickers hardness (Hv) is 700 or more and 800 or less, residual austenite amount is 20 volume% or more and 40 volume% or less, and compressive residual stress is 50 MPa or more and 200 MPa. It is as follows.
(3) The surface roughness of the rolling surfaces (the raceway surfaces of the inner and outer rings, the rolling surfaces of the rolling elements) is 1.0 μm or less in terms of the maximum peak height (Rp) of the roughness curve.

[Composition of alloy steel used in configuration (1)]
The reason why [C] is 0.95 mass% or more and 1.10 mass% or less is as follows.
Carbon (C) is an element that strengthens steel by solid solution in matrix (matrix) by quenching and martensifying the structure. Moreover, it has the effect | action which combines with another alloy element and forms hard carbide | carbonized_material in steel, and improves abrasion resistance. Furthermore, since it is an element that stabilizes austenite, it also has the effect of increasing the amount of retained austenite.

Since hydrogen that has penetrated into the steel becomes difficult to diffuse due to the presence of residual austenite, the larger the amount of residual austenite, the more difficult it is for hydrogen to accumulate locally, and the occurrence of structural changes in the steel can be suppressed.
In order to obtain these effects, the carbon content is set to 0.95% by mass or more.
However, if the carbon content exceeds 1.10% by mass, coarse carbides are easily generated in the steel, and the toughness and workability become insufficient.

The reason why [Si] is 0.20 mass% or more and 0.70 mass% or less is as follows.
Silicon (Si) acts as a deoxidizer during refining. Moreover, it has the effect | action which improves hardenability by making it dissolve in a base. Furthermore, since it is an element that stabilizes martensite, it has the effect of suppressing the structural change from martensite to ferrite due to hydrogen. If the silicon content is less than 0.20% by mass, the action cannot be substantially obtained. Preferably it is 0.50 mass% or more.
However, when the silicon content exceeds 0.70% by mass, toughness, cold workability and machinability become insufficient.

The reason why [Mn] is 0.30 mass% or more and 1.2 mass% or less is as follows.
Manganese (Mn) has the effect of improving the hardenability by dissolving in the matrix. Moreover, since it is an element which stabilizes martensite, it has the effect | action which suppresses the structure change from the martensite to a ferrite by hydrogen. Furthermore, since it is also an element that stabilizes austenite, it also has the effect of increasing the amount of retained austenite that suppresses local accumulation of hydrogen, which causes the structural change of steel. If the manganese content is less than 0.30% by mass, the action cannot be substantially obtained. Preferably it is 0.90 mass% or more.
However, if the manganese content exceeds 1.2% by mass, the amount of retained austenite increases too much and the dimensional stability decreases.

The reason why [Cr] is 0.90 mass% or more and 1.6 mass% or less is as follows.
Chromium (Cr) has the effect of improving the hardenability by solid solution in the base. Moreover, it has the effect | action which combines with carbon and forms a hard carbide | carbonized_material in steel, and improves abrasion resistance. Moreover, since it is an element which stabilizes martensite, it has the effect | action which suppresses the structure change from the martensite to a ferrite by hydrogen. When the chromium content is less than 0.90% by mass, these effects are not substantially obtained.
However, since chromium is an expensive element, it is preferable that the content is small. On the other hand, when the chromium content exceeds 1.6% by mass, it is necessary to increase the quenching temperature in order to form a chemically stable carbide, and thus the productivity is lowered.

The reason for making [Mo] 0.25 mass% or less is as follows.
Molybdenum (Mo) has a function of improving the hardenability and temper softening resistance by dissolving in a matrix. Moreover, it has the effect | action which combines with carbon and forms a hard carbide | carbonized_material in steel, and improves abrasion resistance. Moreover, since it is an element which stabilizes martensite, it has the effect | action which suppresses the structure change from the martensite to a ferrite by hydrogen. Furthermore, since it is also an element that stabilizes austenite, it also has the effect of increasing the amount of retained austenite that suppresses local accumulation of hydrogen, which causes the structural change of steel.

Molybdenum is an expensive element and is not an essential component, but if its content is less than 0.01% by mass, these effects cannot be substantially obtained. Is 0.01% by mass or more.
However, if the molybdenum content exceeds 0.25% by mass, the cold workability and machinability become insufficient, and the productivity decreases.

The reason why [Ni] is 0.20 mass% or less is as follows.
Nickel (Ni) has the effect of improving the hardenability and toughness by dissolving in the matrix. Moreover, since it is an element which stabilizes austenite, it has the effect | action which increases the amount of retained austenite which suppresses local accumulation | storage of the hydrogen which causes the structure | tissue change of steel.
Since nickel is an expensive element, the content is made 0.20% by mass or less. Nickel is not an essential component, but if its content is less than 0.01% by mass, these effects cannot be substantially obtained. Not less than mass%.

The reason why [Cu] is 0.20 mass% or less is as follows.
Copper (Cu) has a function of improving the hardenability and grain boundary strength by dissolving in a matrix. Copper is not an essential component, but if the content is less than 0.02% by mass, these effects cannot be substantially obtained. Therefore, when copper is contained, the content is 0.02% by mass or more. And
However, if the copper content exceeds 0.20% by mass, the hot forgeability becomes insufficient and the productivity decreases.

The reason why [S] is 0.02 mass% or less is as follows.
Sulfur (S) combines with manganese (Mn) to form MnS and become inclusions, so the content is made 0.02% by mass or less.
The reason why [P] is 0.02 mass% or less is as follows.
Phosphorus (P) segregates at the crystal grain boundaries and lowers the grain boundary strength and fracture toughness, so the content is made 0.02% by mass or less.
The reason for making [O] 12 mass ppm or less is as follows.
Oxygen (O) combines with aluminum (Al), magnesium (Mg), calcium (Ca) and the like to form oxides such as Al ₂ O ₃ , MgO and CaO. Since these oxides become inclusions and serve as starting points for peeling, the content is made 12 mass ppm or less.

[About oxide inclusions in the material used in configuration (1)]
When large non-metallic inclusions are present in steel, stress concentrates around the inclusions, resulting in fatigue cracks starting from the inclusions and causing peeling. Further, since hydrogen that has penetrated into the steel is likely to accumulate in the stress concentration portion, the structure of the steel is likely to change around large non-metallic inclusions.
Among non-metallic inclusions, oxide inclusions such as Al ₂ O ₃ , MgO, CaO and the like having a diameter of 10 μm or more are likely to be the origin of cracks. When the size of the oxide inclusions is less than 10 μm, the base structure of the steel is changed by hydrogen before the cracks starting from the inclusions, and the accompanying cracks are generated. Therefore, even if oxide inclusions having a diameter of less than 10 μm are present, it is not substantially harmful.
From these viewpoints, in order to suppress the occurrence of fatigue cracks starting from inclusions, a material having 10 or less oxide inclusions having a diameter of 10 μm or more per 320 mm ² area at an arbitrary cut surface Is used.

[Configuration (2)]
Carburizing or carbonitriding and quenching and tempering are performed on the material having the structure (1), whereby carbon or carbon and nitrogen are introduced into the surface layer portion of the bearing component (inner ring, outer ring, or rolling element). Configuration (2) specifies the properties of the surface layer.
First, the position for specifying the properties of the surface layer portion is referred to as a depth corresponding to 0.01 times the diameter of the rolling element (maximum diameter in the case of rollers) from the surface of the rolling surface (hereinafter referred to as “1% D”). .) Is set.
The area around the 1% D position is the position where the shear stress generated inside the material at the contact portion between the race and the rolling element is maximized, and local accumulation of hydrogen is likely to occur. Identifies organizational changes.

The reason why the total content [C + N] of carbon and nitrogen at the 1% D position is 1.10% by mass or more and 1.50% by mass or less is as follows.
By making the total content [C + N] of carbon and nitrogen at the 1% D position 1.10% by mass or more, the necessary hardness for the rolling surface can be obtained, and the amount of retained austenite in the surface layer portion can be increased. Get the effect of suppressing changes. When the total content [C + N] of carbon and nitrogen at the 1% D position exceeds 1.50 mass%, the toughness necessary for the rolling surface is insufficient.

The reason why the Vickers hardness (Hv) at the 1% D position is 700 or more and 800 or less is as follows.
By setting the Vickers hardness (Hv) at the 1% D position to 700 or more, local plastic deformation is less likely to occur even when hydrogen enters the steel, so that structural changes due to hydrogen can be suppressed. This is based on the finding that the structural change caused by hydrogen is caused by local plastic deformation in steel. If the Vickers hardness at the 1% D position exceeds 800, the fracture toughness value required for the rolling surface cannot be obtained.

The reason why the amount of retained austenite at the 1% D position is 20% by volume or more and 40% by volume or less is as follows.
By setting the amount of retained austenite at the 1% D position to 20% by volume or more, an effect of suppressing the structural change of the steel due to retained austenite is obtained. If the amount of retained austenite at the 1% D position exceeds 40% by volume, the dimensional stability becomes poor.

The reason why the compressive residual stress at the 1% D position is 50 MPa or more and 200 MPa or less is as follows.
The compressive residual stress existing at the 1% D position has an action of suppressing the progress of cracks caused by the structural change caused by hydrogen. If the pressure is less than 50 MPa, this effect is not substantially obtained. If the pressure exceeds 200 MPa, the progress of the crack may be promoted by the action of the tensile residual stress generated in the interior in a size that is commensurate with the compressive residual stress.

[Configuration (3)]
If the rolling surface has a rough surface, the oil film is easily cut, and the raceway and the rolling element are in metal contact at the part where the oil film is cut, which makes it easier for the lubricant to break down and to invade hydrogen, which can cause structural changes. . Normally, the surface roughness of the rolling surface of a rolling bearing is controlled by arithmetic average roughness (Ra), but the maximum peak height (Rp) of the roughness curve is more suitable as an index of oil film breakability. Yes. And, when the surface roughness of the rolling surface exceeds 1.0 μm in the maximum peak height (Rp) of the roughness curve, the oil film is cut and partial metal contact is likely to occur.

  Setting the maximum peak height (Rp) of the roughness curve of the surface roughness of the rolling surface to 1.0 μm or less can be achieved by optimizing the processing conditions such as the type of grinding wheel and the grinding speed in the grinding process. In addition, the measurement is performed for 5 to 10 points on the rolling surface (in the circumferential direction when the rolling surface is the surface of the ball, and in the axial direction in other cases) (obtains a roughness curve), The maximum peak height (Rp) of the curvature curve is set to 1.0 μm or less.

[Preferred use]
A rolling bearing having a rolling element with a diameter of 30 mm or more has a large contact area between the bearing ring and the rolling element, so that it is difficult to form an oil film stably. Hydrogen is easily generated by decomposition, and the generated hydrogen easily enters the steel forming the race and rolling elements.
Also, in applications where the shaft of a transmission that transmits power with a gear is supported and the direction of the torque acting on the shaft changes temporarily, a large slip occurs between the rolling elements and the raceway. As a result, the lubricant is easily decomposed and hydrogen is easily generated, and the generated hydrogen easily enters the steel forming the race and the rolling elements.

In applications where the rolling direction of the rolling bearing changes frequently, the oil film between the rolling elements and the raceway ring is likely to break, and metal contact occurs at the cut portion, so that the lubricating oil decomposes and hydrogen is likely to be generated. The generated hydrogen is likely to enter the steel forming the race and rolling elements.
Since the rolling bearing according to the present invention is unlikely to cause structure change type separation, it is suitable as a large rolling bearing having a rolling element diameter (maximum diameter in the case of a roller) of 30 mm or more. It is suitably used in applications that support a rotating shaft and applications that support a rotating shaft of a construction machine. More specifically, it is suitably used in applications that support a main shaft of a wind turbine for wind power generation and a rotating shaft of a speed increaser (transmission), and applications that support an axle of a construction machine and a rotating shaft of a transmission.

  Also, the purpose of supporting the input / output shaft of the wind turbine transmission for wind power generation (the rotating shaft of the gearbox) is to support the shaft of the transmission that transmits power with gears, and the direction of the torque acting on the shaft is temporarily The application that supports the axle of the construction machine is included in the application in which the rotation direction of the rolling bearing frequently changes.

  According to the rolling bearing of the present invention, the rolling fatigue life can be extended when it is used under the condition that the structure change type separation is likely to occur, such as a windmill bearing or a construction machine bearing.

It is sectional drawing which shows the ball bearing corresponded to 1st Embodiment of this invention.

Embodiments of the present invention will be described below.
FIG. 1 is a cross-sectional view showing a ball bearing of this embodiment. The ball bearing includes an inner ring 1, an outer ring 2, a ball (rolling element) 3, and a cage 4.
As a ball bearing having the shape of FIG. 1, a ball bearing having an identification number “6317” (inner diameter: 85 mm, outer diameter: 180 mm, width: 41 mm, ball diameter: 30.2 mm) is manufactured.
The outer ring 2 and the ball 3 were made by a normal method using SUJ2 material. The inner ring 1 was produced by the following method. As the material for the inner ring 1, columnar materials made of steel types A to M in Table 1 were prepared. Steel type H is SUJ2.

In addition, by polishing the cut surface of each part with the radial direction of each material into 10 equal parts to a mirror surface and observing the polished surface with an optical microscope, the cross section exists at an area of 320 mm ² in an arbitrary cross section The number of “oxide inclusions having a diameter of 10 μm or more” was examined. And the maximum value in the cross section of this number of several places was shown in Table 1 as "the number of inclusions."

First, each cylindrical material was cut to a predetermined length, and then subjected to hot rolling, spheroidizing annealing, and turning to obtain the shape of the inner ring 1. Next, the following types of heat treatments indicated by A to U were performed. Next, grinding was performed.
<Heat treatment: carburization → quenching and tempering>
Carburizing treatment is performed for 8 hours in an Rx gas + enriched gas atmosphere adjusted to temperatures of 780 to 880 ° C., followed by quenching with oil cooling, and then tempering for 2 hours at temperatures of 160 to 240 ° C. After performing, air cool.

<Heat treatment a: carbonitriding → quenching and tempering>
After carbonitriding for 8 hours in an atmosphere of Rx gas + enriched gas + ammonia gas adjusted to each temperature of 780 to 880 ° C., quenching with oil cooling is performed, and then at each temperature of 160 to 240 ° C., 2 After tempering for a long time, air-cool.
<Heat treatment: Quenching and tempering>
After holding in an Rx gas atmosphere at 840 ° C. for 1 hour, quenching by oil cooling is performed, and then tempering by holding at 180 ° C. for 2 hours is performed, followed by air cooling.
Using the obtained inner ring 1, outer ring 2, ball 3 and general steel punched cage 4, each of the three ball bearings shown in FIG. 1 is assembled and subjected to a rotation test under the following conditions. The time (life) until breakage such as peeling occurred in any of 1, outer ring 2 and ball 3 was examined. Further, it was observed with an optical microscope whether or not there was a change in structure on the surface where peeling occurred.

<Test conditions>
Radial load: 66.2kN
Rotational speed: 2000 min ^-1
Lubricant: High traction oil (lubricating oil that is liable to decompose and generate hydrogen)
The average value (average life) of the bearing life of the three bodies of each sample was calculated, and the relative value with the average life of sample No. 1-11 as “1” was calculated from the average life of each sample. The results are also shown in Table 2.

Further, with respect to the obtained inner ring 1, the total content [C + N] of carbon and nitrogen at the 1% D position on the raceway surface was measured with an electron beam microanalyzer (EPMA).
Further, a part including the raceway surface of the obtained inner ring 1 was cut out, and the cut surface was polished into a mirror surface to prepare a test piece for measuring Vickers hardness. Using this test piece, the Vickers hardness at the 1% D position on the raceway surface was measured at 10 locations with a micro Vickers hardness measuring machine, and the average value of the measured values at 10 locations was calculated.

Moreover, a part including the raceway surface of the obtained inner ring 1 was cut out, the raceway surface was electropolished, and the amount of retained austenite (volume%) and compressive residual stress at the 1% D position were measured with an X-ray diffractometer. This measurement was performed at three or more locations at the 1% D position, and an average value was calculated.
Further, the surface roughness of the raceway surface of the obtained inner ring 1 was measured at 8 points in the axial direction with a length of 4 mm each in the axial direction, and the arithmetic average roughness (Ra) and the maximum peak height of the roughness curve were measured. (Rp) was examined.
These results are also shown in Table 2.
Note that “life (relative value): 5.0 or more” in Table 2 was terminated because no peeling occurred even after 5.0 times or more of the life of sample No. 1-11 passed. It shows that. Further, all the peeling occurred on the inner ring, and the change in the structure occurred on the raceway surface where the peeling occurred.

No. 1-1 to 1-10, No. 1-15 and No. 1-20 had a life of 3.0 times or more that of No. 1-11. Among these, No. 1-15 and No. 1-20 have a problem in terms of dimensional stability because the amount of retained austenite at the 1% D position of the inner ring raceway surface exceeds 40.
Nos. 1-1 to 1-10 satisfy the above-described configurations (1) and (2). Among these, Nos. 1-1 to 1-6 using a material made of steel types A to C are steel types. A to C are in a range where both [Si] and [Mn] are preferable (0.50 mass% ≦ [Si] ≦ 0.70 mass%, 0.90 mass% ≦ [Mn] ≦ 1.20 mass%). In order to satisfy, the life of 5.0 times or more of No. 1-11 was obtained.

  Among No. 1-1 to 1-6, the maximum peak height (Rp) of the roughness curve exceeds 1.0 μm (does not satisfy the configuration (3)) No. 1-1, 1-3, 1- No. 1-2, 1-4, No. 1-2, 1-4, in which a change in structure was observed on the raceway surface, but the maximum peak height (Rp) of the roughness curve was 1.0 μm or less (satisfying the configuration (3)). In 1-6, no structural change was observed on the raceway surface. Therefore, when the test is continued without being terminated, it is estimated that No. 1-1, 1-3, 1-5 has a shorter life than No. 1-2, 1-4, 1-6.

From the above results, the ball bearing of FIG. 1 in which the diameter of the ball 3 is 30.2 mm, and the bearing satisfying the configurations (1) and (2) is any of the configurations (1) and (2). Compared to bearings that do not satisfy the above conditions, the service life is longer when used under conditions that allow hydrogen to enter. Especially, bearings that satisfy all of the above-mentioned configurations (1) to (3) have conditions that allow hydrogen to enter (the type of lubricant). And that the rolling element has a diameter of 30 mm or more).
In this embodiment, the ball bearing is described, but it goes without saying that the rolling bearing of the present invention includes a roller bearing. In addition, the ball bearing of this embodiment or a ball bearing or roller bearing of the same size as this is used for supporting the rotating shaft of a wind turbine speed increaser (transmission), or rotating the axle of a construction machine and the transmission. Used in applications that support the shaft.

1 Inner ring 2 Outer ring 3 Ball (rolling element)
4 Cage

Claims (5)

At least one of the inner ring, the outer ring, and the rolling element is
The carbon content [C] is 0.95 mass% to 1.1 mass%, the silicon content [Si] is 0.20 mass% to 0.70 mass%, and the manganese content [Mn] is 0.30. % By mass to 1.2% by mass, chromium content [Cr] of 0.90% by mass to 1.6% by mass, molybdenum content [Mo] of 0.30% by mass or less, nickel content [Ni] Is 0.20 mass% or less, copper content [Cu] is 0.20 mass% or less, sulfur content [S] is 0.02 mass% or less, phosphorus content [P] is 0.02 mass% or less, The oxygen content [O] is 12 ppm or less, the balance is iron (Fe) and an inevitable impurity alloy steel, and there are 10 or less oxide inclusions having a diameter of 10 μm or more per 320 mm ^{2 in} an arbitrary cross section. After the material is processed into a predetermined shape, carburizing or carbonitriding and firing Obtained by performing tempering,
At a position corresponding to a depth corresponding to 0.01 times the diameter of the rolling element from the surface of the rolling surface, the total content of carbon and nitrogen [C + N] is 1.10 mass% or more and 1.50 mass% or less, Vickers hardness A rolling bearing characterized in that (Hv) is 700 or more and 800 or less, the amount of retained austenite is 20 volume% or more and 40 volume% or less, and the compressive residual stress is 50 MPa or more and 200 MPa or less.   The rolling bearing according to claim 1, wherein the surface roughness of the rolling surface is 1.0 μm or less in terms of the maximum peak height (Rp) of the roughness curve.   The rolling bearing according to claim 1 or 2, wherein the rolling element has a diameter of 30 mm or more.   The rolling bearing according to claim 1 or 2, which is used for supporting a rotating shaft of a wind turbine for wind power generation.   The rolling bearing according to claim 1 or 2, which is used for supporting a rotating shaft of a construction machine.

Images