WO1999063125A1

WO1999063125A1 - Rolling bearing

Info

Publication number: WO1999063125A1
Application number: PCT/JP1999/002944
Authority: WO
Inventors: Kenji Yamamura; Susumu Tanaka
Original assignee: Nsk Ltd.
Priority date: 1998-06-04
Filing date: 1999-06-02
Publication date: 1999-12-09
Also published as: JP3391345B2

Abstract

A rolling bearing suitably used as a ball bearing (3) to be inserted between a shaft (2) and a housing (4) of, for example, a HDD spindle motor unit, wherein a steel material for forming inner and outer rings has a composition in weight percentage within the following ranges, i.e. 0.80-1.20 wt.% of C, not more than 0.60 wt.% of Si, not more than 0.25 wt.% of Mn, 1.00-1.50 wt.% of Cr and 0.60-1.50 wt.% of Mo, the inner and outer rings formed of this steel material being subjected to quenching and tempering to set an amount of residual austenite to zero volume percent and a surface hardness to not lower than HRC62, rolling elements in use being formed of martensite stainless steel subjected to quenching and tempering, nitriding to form a nitriding layer of not less than 3 √m in thickness on surfaces thereof, and a finishing process to set a surface roughness to not more than 0.1 √m Ra.

Description

Description Rolling bearing technical field

The present invention relates to a rolling bearing, and more particularly to a rolling bearing having a very small size and requiring high rotational accuracy, such as a spindle for a magnetic disk drive (HDD). Background art

The inner ring, outer ring and rolling elements of rolling bearings are subjected to repeated shear stress under high surface pressure in use. Conventionally, in order to obtain the required rolling fatigue life to withstand such severe operating conditions, high carbon chromium bearing steel such as SUJ2 was used as the steel material, and quenching and tempering were performed after molding. The surface hardness of the inner ring, outer ring, and rolling elements is HRC 58-64.

On the other hand, demands for smaller, faster, and lower cost HDDs used as computer storage devices have been increasing in recent years. Of these, magnetic disks are being reduced in size and density to reduce the size of HDDs. In addition, in order to rotate the magnetic disk at high speed, it is required to improve the rotational accuracy of the rolling bearing for the spindle.

Here, in order to improve the rotational accuracy of the rolling bearing, it is necessary to minimize residual austenite, which is the most harmful to the accuracy characteristics, particularly on the raceway surfaces of the inner ring and the outer ring. Therefore, conventionally, the inner ring and the outer ring formed of SUJ 2 are subjected to quenching, followed by sub-zero treatment, or the tempering temperature is increased. However, although the amount of residual austenite can be reduced by sub-zero treatment after quenching, it is difficult to reduce the content to 0% by volume. Also, it is possible to reduce the amount of residual austenite to 0% by volume by high-temperature tempering. <High-temperature tempering reduces the surface hardness to about HRC57, so sufficient rolling fatigue life May not be obtained.

Therefore, when the inner ring and the outer ring are manufactured using SUJ2 as a steel material, there is a problem that a rolling bearing excellent in both rolling fatigue life and rotational accuracy cannot be obtained.

Examples of steel materials that can increase the surface hardness even when tempering at a high temperature such that the residual austenite amount becomes 0% by volume include high-speed steel M50 used for aircraft and the like. This high-speed steel M50 is a precipitation-hardened alloy steel containing a large amount of Cr, Mo, and V, and has over 10 giant carbides in the compact after tempering. There is a problem with acoustic characteristics. In addition, since large carbides are present from the raw material stage, workability is poor and there is a problem in productivity.

Also, the development of steel materials that can increase the surface hardness even if the residual austenite amount is reduced to 0% by volume by performing surface hardening treatment such as carburizing is being promoted. However, when performing surface hardening treatment on small compacts with a thickness of about 1 mm, such as the inner and outer rings of rolling bearings for HDD spindles, it is difficult to set processing conditions and allowances. It is. In addition, the cost is high because the processing cost is high.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and it is an object of the present invention to provide a low-cost rolling bearing suitable for HDD spindles, which is excellent in both rolling fatigue life and rotational accuracy. As an issue.

On the other hand, in recent years, in rolling bearings used for precision equipment, the amount of lubricant used has tended to be reduced as much as possible in order to suppress gas generated inside the bearings. Wear problems due to poor lubrication. As a countermeasure, the use of ceramic rolling elements is being studied to reduce the cohesive force between the inner and outer rings and the rolling elements or to reduce the contact area. However, when a ceramic rolling element is used, the contact stress between the inner and outer rings and the rolling element increases, and the impact resistance of the bearing may be reduced.

Another object of the present invention is to improve the impact resistance of a rolling bearing using a ceramic rolling element. Disclosure of the invention

In order to achieve the above object, according to the present invention, at least one of the inner ring, the outer ring, and the rolling element contains, as an alloy component, 0.80 to 1.20% by weight of C, and 0.60% of 31 as an alloy component. Iron and steel containing Mn in the range of 0.25% by weight or less, Mn in the range of 0.25% by weight or less, and 1 "in the range of 1 • 00 to 1.5% by weight,] 40 in the range of 0.60 to 1.5% by weight. After being formed from a material (steel material), it is quenched and tempered to reduce the amount of retained austenite to 0% by volume and the surface hardness to HRC (rock hardness for scale C) 62 or more. To provide a rolling bearing.

In this rolling bearing, as described above, the composition range of C, Si, Mn, Cr, and Mo is determined for the composition of the steel material forming at least one of the inner ring, the outer ring, and the rolling element. limit. The critical significance of each numerical limitation is described below.

[C: 0.80-: L. 20% by weight]

. Is an element that imparts hardness to steel by turning the base material into a martensite by quenching and tempering treatment. If the C content is less than 0.80, HRC 62 or more may not be secured. If the C content exceeds 1.2% by weight, the effect of improving the hardness due to C is not only saturated, but also the residual aus The amount of tenite is easily generated.

[S i: 0.60% by weight or less]

Si is an element necessary as a deoxidizing agent in steelmaking, and has the effect of increasing temper softening resistance and improving mechanical strength and rolling fatigue life after heat treatment. If the Si content exceeds 0.6% by weight, an effect of preventing the decomposition of the residual austenite is produced, and the machinability is reduced. If the content of Si is less than 0.1% by weight, the deoxidizing effect may not be sufficient. Therefore, the content of 31 is preferably 0.10% by weight or more.

(Mn: 0.25% by weight or less)

Like Si, Mn is an element necessary as a deoxidizing agent in steelmaking, and has the effect of improving hardenability and improving mechanical strength and rolling fatigue life after heat treatment. If the content of Mn exceeds 0.25% by weight, residual austenite is easily generated, and the machinability decreases. If the content of Mn is less than 0.15% by weight, the deoxidizing effect may not be sufficient. Therefore, the content of Mn is preferably 0.15% by weight or more. [Cr: 1.00 to: L. 50% by weight]

Cr has the effect of improving hardenability and improving mechanical strength and rolling fatigue life after heat treatment. It also has the effect of forming carbides in combination with C and spheroidizing the cementite. When the Cr content is less than 1.0% by weight, these effects are not substantially exerted. When the Cr content exceeds 1.50% by weight, these effects are saturated.

[Mo: 0.60 ~: L. 50% by weight]

Mo is an element that improves the hardenability and increases the tempering softening resistance, and has the effect of improving the mechanical strength after rolling and the rolling fatigue life. In order to raise the tempering temperature and reduce the amount of residual austenite to 0% by volume and achieve a surface hardness of HRC 62 or more, the Mo content should be 0.60% by weight or more. It is preferable that the content be 0.80% by weight or more. If the Mo content exceeds 1.5% by weight, not only the above effects are saturated, but also the machinability decreases. In addition, Mo is expensive, so if it is contained in a large amount, the cost increases.

By specifying the steel material as described above, the surface hardness can be increased to HRC 62 or more even when tempering is performed at a high temperature so that the residual austenite amount becomes 0% by volume. In addition, when this steel material is used, there is no large carbide such as high-speed steel M50, and there is no need to perform surface hardening treatment such as carburization, so that the processing cost can be reduced.

If the surface hardness is less than HRC 62, sufficient rolling fatigue life cannot be obtained, and sufficient impact resistance cannot be obtained as a rolling bearing for HDD spindles.

According to the present invention, at least one of the inner ring and the outer ring has, as alloy components, C of 0.80 to 1.20% by weight, 31 of 0.60% by weight or less, and Mn of 0. 25% by weight or less, Cr is 1.0-1.5% by weight, 1 ^ 0 is 0.60-: L. 50% by weight of steel material (steel material) After the quenching and tempering, the amount of residual austenite is reduced to 0% by volume and the surface hardness is HRC 62 or higher. 3 to 0.6% by weight, Si 0.3 to 1.5% by weight, Mn 0.3 to 1.7% by weight, Cr 0.5 to 2.5% by weight, Mo 0. It is formed of a steel material having a content of 6 to 3.0% by weight and a content of 0 of 9 ppm or less, and is subjected to carbonitriding treatment, then quenching and tempering, and remaining austenite. And the surface hardness is HRC 62 or more. To provide a gully bearing.

According to this rolling bearing, since the inner ring and / or the outer ring are formed of steel material, as described above, there is no residual hardening treatment, and no residual hardening is performed. A stenite amount of 0% by volume and a surface hardness of HRC 62 or more are achieved. In addition, the rolling element also has a residual austenite amount of 0% by volume and a surface hardness of HRC 62 or more. Therefore, this rolling bearing is excellent in both rolling fatigue life and rotational accuracy. .

In addition, the rolling elements are made of a steel material (steel material) that has a lower carbon content, a higher Mn content, and a lower oxygen content than steel material ①, and is carbonitrided. Accordingly, even at a high-speed rotation of, for example, about 1000 rpm to 1500 rpm, generation of vibration is suppressed, and the acoustic life at high-speed rotation is prolonged. In order to obtain such effects, the surface carbon concentration of the rolling elements is reduced to 0.8 to 1.2% by weight and the surface nitrogen concentration is reduced to 0.2 to 0.6% by carbonitriding. It is preferable that Further, in order to reduce the amount of residual austenite to 0% by volume and achieve a surface hardness of HRC 62 or more, the Mo content in the steel material should be 0.6% by weight or more, preferably 0.8% by weight or more. There is a need.

In addition, since the rolling elements have a small amount of deformation due to heat treatment, it is easier to set the processing conditions and the like by performing carbonitriding on the rolling elements than performing carbonitriding on the inner and outer rings. In addition, costs can be kept low.

As an embodiment of the rolling bearing of the present invention, at least one of the inner ring and the outer ring has, as alloy components, 0.80 to 1.20% by weight of C and 0.60% by weight or less of 3%. , Mn: 0.25% by weight or less, Cr: 1.0-1.5% by weight, Mo {). 60-1.5% by weight ) After being formed by quenching and tempering, the residual austenite amount is 0% by volume, the surface hardness is HRC 62 or more, and the rolling elements are formed of martensitic stainless steel. After the quenching and tempering, the surface is nitrided to a thickness of 3 m or more. Are formed and then finished to a surface roughness of 0.1 / mRa or less.

According to this rolling bearing, since the inner ring and / or the outer ring are formed of steel material, as described above, the residual austenite amount is 0% by volume and the surface hardness is HRC 6 without surface hardening treatment. Two or more are achieved. As a result, sufficient rolling fatigue life and sufficient impact resistance as a rolling bearing for HDD spindles can be obtained. The rolling elements are made of martensitic stainless steel, quenched and tempered, then nitrided to form a nitrided layer with a thickness of 3 m or more on the surface, and then finished. As a result, the surface roughness is 1 / mRa or less, so heat resistance and wear resistance are increased.

The use of martensitic stainless steel as the base material of the rolling elements prevents the base material from softening during nitriding. It is preferable to use 13Cr-based martensitic stainless steel from the viewpoint of acoustic characteristics and the like. In order for the nitrided layer to be uniformly present on the rolling element surface after finishing, it is necessary to perform nitriding so that the thickness of the nitrided layer is 3 or more.

As an embodiment of the rolling bearing of the present invention, at least one of the inner ring and the outer ring has, as alloy components, C of 0.80 to 1.20% by weight and 31 of 0.60% by weight or less. , Mn: 0.25% by weight or less, Cr: 1.0-1.5% by weight, 1 ^ 0: 0.60-1.5% by weight After being formed in ①), quenching and tempering are applied to reduce the amount of residual austenite to 0% by volume and the surface hardness to HRC 62 or more. The rolling elements are made of ceramics (for example, nitrided). Silicon, silicon carbide, alumina, zirconia, alumina nitride, etc.). According to this rolling bearing, the inner ring and / or the outer ring are formed of steel material ①. Therefore, as described above, a residual o-stenite amount of 0% by volume and a surface hardness of HRC 62 or more can be achieved without performing a surface hardening treatment. As a result, despite having the ceramic rolling elements, it is possible to obtain impact resistance equal to or higher than that of conventional rolling bearings (for example, the inner and outer rings and rolling elements are all made of SUJ 2). . BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view showing an HDD spindle motor unit in which a rolling bearing manufactured according to an embodiment of the present invention is incorporated and subjected to an impact resistance test. FIG. 2 is a graph showing the results of a heat treatment experiment performed to determine heat treatment conditions for the inner ring and the outer ring in the embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to specific experimental examples.

[First Embodiment]

First, a ball bearing having an inner diameter of 5 mm, an outer diameter of 13 mm, a width of 4 mm, and a ball diameter of 2 mm was produced as follows. For the inner ring and outer ring, after forming molded bodies of a predetermined shape using steel materials of each composition of symbols A to V shown in Table 1 below, each molded body was quenched at 860 ° C, And then tempered at 240 ° C. for 2 hours. Surface hardness (HRC) and residual austenite amount after the heat treatment the (y _R) be shown together in Table 1. All the rolling elements used were conventional SUJ2 balls.

The heat treatment conditions for the inner and outer rings were determined by conducting the following heat treatment experiments. That is, after quenching at 860 ° C for the formed body made of each of the steel materials A to P in Table 1, tempering was performed at 180 ° C to 240 ° C. The residual austenite value of each compact was measured. The results are shown in the graph of FIG.

As can be seen from this graph, if the tempering temperature when quenching is performed at 860 ° C is set to 230 ° C or less, all the retained austenite values of the compacts made of the steel materials of symbols A to P Becomes 0. Here, the tempering temperature was set to 240 ° C. to ensure that the residual austenite value of all these compacts was 0. Further, according to the heat treatment conditions, the surface hardness is HRC 62 or more. These heat treatment conditions are merely examples, and the heat treatment conditions performed in the present invention are not limited to these.

Next, this ball bearing was assembled into the HDD spindle motor unit shown in Fig. 1 with preload applied, and a test was conducted to examine the impact resistance of the ball bearing.

The HDD spindle motor unit shown in FIG. 1 includes a hub 1 rotating on which a magnetic disk is mounted, a shaft 2 having an upper end fixed to the hub 1, and two ball bearings 3 arranged in the axial direction. A housing 4 that rotatably supports the shaft 2 via these ball bearings 3 is provided. As the two ball bearings 3, each of the ball bearings manufactured as described above was used, and the same two were combined and assembled between the housing 4 and the shaft 2.

By dropping the motor unit at a predetermined drop distance, an impact load of 30 kgf was applied to the ball bearing 3, and the degree of deterioration in acoustic characteristics before and after the drop was measured. Specifically, the axial vibration (acceleration G value) of this motor unit was measured before and after the fall, and if the G value after the fall was 5 or more higher than the G value before the fall, the acoustic characteristics were degraded. (Poor impact resistance:); otherwise, no deterioration in acoustic characteristics was observed (good impact resistance: 〇). The deterioration of the acoustic characteristics due to the drop is caused by the deformation of the raceway surface of the ball bearing due to the drop. Good performance indicates that the deformation resistance of the raceway surface is sufficiently high, and that the rotation accuracy is unlikely to decrease. These results are also shown in Table 1.

As can be seen from the results, the composition of the steel material forming the inner ring and the outer ring

C: 0.80 to 1.20% by weight

S i: 0.60% by weight or less

Mn: 0.25% by weight or less

Cr: 1.00 to 1.50% by weight

Mo: 0.60 to 1.5% by weight

The ball bearings with the symbols A to P satisfying all of the above conditions have excellent impact resistance because the amount of residual austenite after heat treatment of the inner and outer rings is 0% by volume or less and the surface hardness is HRC 62 or more.

On the other hand, in the ball bearing with the symbol R, since the C content of the steel material forming the inner ring and the outer ring is lower than the range of the present invention, the amount of residual austenite after heat treatment of the inner ring and the outer ring is 0% by volume. However, the surface hardness was reduced to HRC 60.7. As a result, the impact resistance was poor.

In the ball bearing of symbol S, the surface hardness of the inner and outer rings after heat treatment was HRC 62.7 because the content of Si in the steel material forming the inner and outer rings was higher than the range of the present invention. The residual austenite was not completely decomposed by the high temperature tempering at 240 ° C. As a result, the impact resistance was poor.

In the ball bearing of symbol T, the Cr content of the steel material forming the inner ring and the outer ring is lower than the range of the present invention. Therefore, the residual austenite amount after heat treatment of the inner ring and the outer ring is 0% by volume. However, the surface hardness was reduced to HRC 60.5. As a result, the impact resistance was poor.

Symbol U ball bearings contain Mo in the steel material forming the inner and outer rings Since the ratio was lower than the range of the present invention, the residual ore-stenite amount after heat treatment of the inner ring and the outer ring was 0% by volume, but the surface hardness was as small as HRC 60.2. As a result, the impact resistance was poor.

The ball bearing of symbol V uses a composition equivalent to SUJ2 steel as the steel material forming the inner and outer rings. In this steel, the content of Mo is lower than the range of the present invention, and the content of Cr is higher than the range of the present invention. Therefore, the amount of residual austenite after heat treatment of the inner ring and the outer ring is 0% by volume. However, the surface hardness was reduced to HRC 57.0. As a result, the ball bearing of symbol V had poor impact resistance.

As described above, in the ball bearings of the symbols A to P corresponding to the embodiment of the present invention, since the composition of the steel material forming the inner ring and the outer ring is within the above range, the residual austenite of the inner ring and the outer ring by high-temperature tempering. The surface hardness of the inner ring and the outer ring can be increased to HRC 62 or more without performing surface hardening treatment such as carburizing while reducing the volume of the sample to 0% by volume. As a result, a rolling bearing excellent in both rotational accuracy and rolling fatigue life can be obtained at low cost.

In the first embodiment, only the inner ring and the outer ring have a residual o-stainate amount of 0% by volume and a surface hardness of HRC 62 or more, but the rolling bearing of the present invention is not limited to this. That is, in order to obtain a rolling bearing excellent in both rolling fatigue life and rotational accuracy, at least one of the inner ring, the outer ring, and the rolling element is formed of a steel material having a composition in the above range. It is sufficient that the residual austenite amount is 0% by volume and the surface hardness is HRC 62 or more by quenching and tempering.

[Second embodiment]

First, a ball bearing having an inner diameter of 5 mm, an outer diameter of 13 mm, a width of 4 mm, and a ball diameter of 2 mm was produced as follows. For the inner ring and outer ring, molded products of a predetermined shape were formed using the steel materials A to P and V shown in After the formation, each compact was quenched at 860 ° C., and then tempered at 240 ° C. for 2 hours. Hardness after heat treatment (HR C) and residual Osutenai preparative amounts (§ _R) is also shown in Table 1. For the rolling elements, balls with a diameter of 2 mm were formed using the steel materials X and Y shown in Table 2 below and the steel material A shown in Table 1 below. Thereafter, the ball formed of material X was carbonitrided at 870 ° C to 900 ° C for 1 to 5 hours, and then quenched at 840 ° C to 860 ° C. Subsequently, tempering was performed at 270 ° C. to 350 ° C. for 1.5 to 3.0 hours. The balls formed of material Y and material A were quenched at 860 ° C and subsequently tempered at 240 ° C for 1.5 to 3.0 hours. Material Y corresponds to JIS grade SUJ 2 steel.

Hardness after heat treatment of the ball which is formed of a material X and material Y (HRC) Contact and residual austenite amount (§ _R) shown in Table 2. The surface hardness (HRC) and the amount of residual austenite (rR) of the ball formed of material A after the heat treatment were the same as those shown in Table 1. The surface carbon concentration of the ball formed of the material X after the heat treatment was 0.9% by weight, and the surface nitrogen concentration was 0.3% by weight.

These inner and outer rings and rolling elements were assembled in the combinations shown in Table 3 below to obtain No. 1 to No. 19 ball bearings. For each bearing, the inner ring and the outer ring were made of the same material and subjected to the same heat treatment. These ball bearings were rotated under the following conditions, and an acoustic life test was performed during high-speed rotation. <Rotation condition>

Number of rotations: 1 0 0 0 0 r p m

Axial load: 2 kgf

Ambient temperature: 70 ° C

Lubricant: mineral oil grease Rotation time: 300 hours

For each ball bearing, the vibration is measured by an Anderometer immediately before the start of rotation and immediately after the end of rotation. In other words, the bearing is attached to the anderometer, the inner ring is rotated under specified conditions, the thrust load is applied to the outer ring, and the stylus of the converter is brought into contact with the outer ring in a stationary state. Measure the value (Anderon value) proportional to the effective value.

For the determination of the acoustic life, the value obtained by subtracting the Anderon value immediately before the start of the test from the Anderon value immediately after the end of the test is calculated as the Anderon rise value. If the value is 2.5 or less, the acoustic life is long (〇 ), The sound lifetime was judged to be slightly short (△) if it was 2.6 or more and 5.0 or less, and the sound life was judged to be short (X) if it was 5.1 or more. The results are shown in Table 3 below.

As can be seen from the results, the composition of the steel material forming the ball (rolling element) is

C: 0.3 to 0.6% by weight

S i: 0.3-1.5% by weight

Mn: 0.3 to 1.7% by weight

Cr: 0.5 to 2.5% by weight

Mo: 0.6 to 3.0% by weight

Content of 0: 9 ppm or less

No. 1 to No. 16 ball bearings using balls with the symbol X in which nitrogen is present on the surface due to carbonitriding have a long acoustic life at high speeds.

In contrast, the No. 17 and No. 18 ball bearings use balls with the symbol Y (surface hardness HRC 57) obtained using a steel material that does not contain Mo and without carbonitriding. The sound life at high speed rotation is short. there were. In addition, the No. 19 ball bearing uses the steel ball containing the symbol A (Mo is 1.0% by weight, so the surface hardness is HRC 62.5). Since the obtained ball was used, the acoustic life at high speed rotation was somewhat short. It should be noted that the ball bearing No. 19 has a sufficiently long acoustic life when the rotation speed is equal to or less than 700 rpm.

[Third embodiment]

First, a ball bearing having an inner diameter of 5 mm, an outer diameter of 13 mm, a width of 4 mm, and a ball diameter of 2 mm was produced as follows. For the inner ring and outer ring, after forming molded bodies of a predetermined shape using the steel materials A to V shown in Table 1, each molded body was quenched at 860 ° C, and then, It was produced by tempering for 2 hours. Hardness after heat treatment (HRC) Contact and residual austenite amount (§ _R) is also shown in Table 1.

For the rolling elements, coarse steel spheres with diameters larger than 2 mm were formed using the steel materials a and b whose alloy component contents are the values shown in Table 4 The quenching was carried out at a temperature of 110 ° C. to 110 ° C., followed by a tempering at a temperature of 43 ° C. to 550 ° C. for 2 to 4 hours. Next, the coarse spheres were polished until they reached a predetermined size, and were subjected to a gas nitriding treatment at 410 to 460 ° C. for 24 to 48 hours. Next, by performing finishing, a nitride layer having a thickness of 15 μm was formed on the surface, and a ball with a diameter of 2 mm and a surface roughness of 0.1 / mRa or less was obtained.

These inner rings, outer rings, and rolling elements were assembled in combinations shown in Table 5 below to obtain ball bearings No. 3-1 to No. 321. For each bearing, the inner ring and the outer ring were made of the same material and subjected to the same heat treatment. These ball bearings are assembled with a preload applied to the HDD spindle motor unit shown in Fig. 1, and the impact resistance of the ball bearings is determined in the same manner as in the first embodiment. A test was conducted to examine Table 5 shows the results.

As can be seen from this table, the ball bearings of Nos. 3-1 to 3-16 have excellent impact resistance because the inner and outer rings are the same as the ball bearings A to P in the first embodiment. Was. On the other hand, the ball bearings of Nos. 3-17 to 3-21 had poor impact resistance because the inner and outer rings were the same as the ball bearings of symbols R to V of the first embodiment.

That is, if the inner ring and the outer ring have the same configuration as the symbols A to P in the first embodiment, the rolling elements are formed of martensite stainless steel, quenched and tempered, and then subjected to nitriding. Even if a nitrided layer with a thickness of 3 m or more is formed on the surface and the surface roughness is 0.1 mRa or less, the same as in the first embodiment using the SUJ 2 rolling element is used. In addition, excellent impact resistance is obtained.

[Fourth embodiment]

First, a ball bearing having an inner diameter of 5 mm, an outer diameter of 13 mm, a width of 4 mm, and a ball diameter of 2 mm was produced as follows. For the inner ring and outer ring, after forming molded bodies of a predetermined shape using the steel materials of A and V (SUJ2) shown in Table 1, each molded body was quenched at 860 ° C, It was produced by performing tempering at 240 ° C. for 2 hours. Hardness after heat treatment (HRC) and residual austenite amount (§ _R) is also shown in Table 1. As shown in Table 6, the rolling elements were formed of ceramics (silicon nitride: Si ₃ N ₄ ) or SUJ 2.

Next, a test for examining the impact resistance of each ball bearing was performed. That is, after the impact load is applied stepwise to each ball bearing, the measurement of the acoustic level of each ball bearing is repeated, and the load when the acoustic level rises sharply is referred to as the impact resistance load. did. Based on the results, the relative value with the impact load of No. 4-3 (both inner and outer rings and rolling elements made of SUJ 2), which is the conventional example, was set to 1. Calculated. Table 6 shows the results.

As can be seen from this table, when the rolling elements are made of ceramics, the inner and outer rings are made of SUJ 2 (No. 4-2), and the impact resistance is lower than that of the conventional example (No. 43). However, if the inner and outer rings have the same configuration (No. 4-1) as the ball bearing with the symbol A in the first embodiment, the impact resistance will be equal to or higher than that of the conventional example (No. 4-3). Can be. Industrial applicability

As described above, according to the present invention, by forming at least one of the inner ring, the outer ring, and the rolling elements from the specific steel material (steel material), both the rolling fatigue life and the rotational accuracy are excellent. Rolled bearings can be provided at low cost.

In addition, at least one of the inner ring and the outer ring is formed of the specific steel material (steel material), and the rolling element is formed of another specific steel material (steel material) and subjected to carbonitriding. By doing so, it is possible to provide a low-cost rolling bearing that is excellent in both rolling fatigue life and rotational accuracy, and prolong the acoustic life at high speed rotation.

Further, by forming at least one of the inner ring and the outer ring with the specific steel material (steel material), even if a ceramic rolling element or a rolling element made of martensitic stainless steel and nitrided is used, A rolling bearing excellent in both rolling fatigue life and rotational accuracy can be provided at low cost. 1 Alloy component content (wt%) Hardness Impact resistance

C S i M n C r M o

A 1.01 0.11 0.20 1.31 1.00 62.5 0 〇

B 0.95 0.30 0.19 1.25 1.01 63.2 0 〇

C 0.80 0.35 0.21 1.30 0.97 62.2 0 〇

D 1.20 0.11 0.18 1.20 0.98 63.5 0 〇

E 1.05 0.15 0.21 1.32 1.01 62.3 0 〇

F 1.02 0.11 0.25 1.31 0.95 62.3 0 〇

G 1.05 0.12 0.22 1.00 1.02 62.1 0 〇

H 1.01 0.11 0.21 1.40 0.95 62.5 0 〇

I 1.02 0.12 0.19 1.50 1.01 62.4 0 〇

J 1.15 0.10 0.22 1.32 0.60 62.1 0 〇

K 1.10 0.11 0.21 1.31 0.80 62.40 〇〇 1.05 0.12 0.23 1.29 1.50 62.80 〇

M 1.02 0.11 0.25 1.30 1.05 62.7 0 〇

N 0.95 0.12 0.21 1.35 0.95 62.2 0 〇

0 0.98 0.50 0.20 1.33 0.98 63.5 0 〇

P 1.01 0.60 0.21 1.31 1.02 63.3 0 〇

R 0.71 0.12 0.22 1.31 1.01 60.7 0 X

S 1.02 0.82 0.21 1.30 1.05 62.73.2 X

T 1.03 0.21 0.23 0.82 1.01 60.5 0 X

U 1.01 0.18 0.22 1.28 0.51 60.2 0 X

V 1.02 0.22 0.24 1.51 57.0 0 X Table 2

* 〇 is ppm, other elements are wt%. Table 3

No. Raceway Rolling element Acoustic life

1 A X 〇

2 B X 〇

3 C X 〇

4 D X 〇

5 E X 〇

6 F X 〇

G G X 〇

8 H X 〇

9 I X 〇

10 J X 〇

11 K X 〇

12 L X 〇

13 M X 〇

14 N X 〇

15 0 X 〇

16 P X 〇

17 A Y X

18 V Y X

19 AA △ Table 4

C r S i C N

a 13.2 0.45 0.3 0.14 b 12.8 0.67 0.2 (unit: wt%) Table 5

No. Ring S! J Impact resistance

3-1 A a 〇

3-2 B b 〇

3-3 C a 〇

3-4 D b 〇

3-5 E a 〇

3-6 F b 〇

3-7 G a 〇

3-8 H b 〇

3-9 I a 〇

3-10 J b 〇

3-11 K a 〇

3-12 then b 〇

3-13 M a 〇

3-14 N b 〇

3-15 0 a 〇

3-16 P b 〇

3-17 R a X

3-18 S b X

3-19 T a X

3-20 u b X

3-21 V a X Table 6

No. Bearing ring Rolling element Impact resistance

4-1 AS i ₃ N ₄ 1.1

4-2 VS i 3 N ₄ 0.7

4-3 V S U J 2 1

Claims

The scope of the claims

1. For at least one of the inner ring, outer ring and rolling element, as an alloy component, C is 0.80 to 1.2% by weight, 31 is 0.60% by weight or less, and] ^ 11 is After being formed of a steel material containing 0.25% by weight or less, Cr in the range of 1.0% to 1.5% by weight, and Mo in the range of 0.6% to 1.5% by weight, A rolling bearing characterized by having been quenched and tempered to have a residual austenite amount of 0% by volume and a surface hardness of HRC 62 or more.

2. For at least one of the inner ring and the outer ring, as an alloying component, C is 0.8-1.2% by weight, 31 is 0.60% by weight or less, Mn is 0.25% by weight or less, Cr 1.0 to 1.5% by weight, 1 ^ 0 0.6 to 1.

After being formed from a steel material containing up to 50% by weight, it is quenched and tempered to reduce residual austenite to 0% by volume and surface hardness to HRC.

The rolling elements are as follows: C: 0.3 to 0.6% by weight, Si: 0.3 to: L. 5% by weight, Mn: 0.3 to 1. A steel material containing 7% by weight, 1 to 0.5 to 2.5% by weight, Mo in the range of 0.6 to 3.0% by weight, and having a 0 content of 9 ppm or less. Rolling characterized by being formed, subjected to carbonitriding, then quenching and tempering to reduce residual austenite to 0% by volume and surface hardness to HRC 62 or more. bearing.

3. For at least one of the inner ring and the outer ring, as alloy components, C is 0.80 to 1.2% by weight, 31 is 0.60% by weight or less, Mn is 0.25% by weight or less, Cr 1.0-1.5% by weight, 1 ^ 0.6-0.1.

After being formed from a steel material containing up to 50% by weight, it is quenched and tempered to reduce the amount of retained austenite to 0% by volume and the surface hardness to HRC.

6 2 or more, the rolling elements are made of martensite stainless steel After being quenched and tempered, it is subjected to a nitriding treatment to

A rolling bearing characterized in that a nitrided layer of 3 m or more is formed and then finished to have a surface roughness of 0.1 ^ mRa or less.

4. For at least one of the inner ring and the outer ring, as alloy components, C is 0.80 to 1.2% by weight, 31 is 0.60% by weight or less, Mn is 0.25% by weight or less, Cr is 1.0 to 1.5% by weight, 1 ^ is 0.6 to 1.0.

Rolling bearing characterized in that the rolling element is formed of ceramics.