JPH02277764A - Roller bearing - Google Patents

Abstract

PURPOSE:To prevent the generation of microcracks by forming at least one among the inner and outer rings and roller with an alloy steel having the specified contents of C, Cr, Ti, O, P, S and the balance Fe, carbonitriding the alloy and specifying the amts. of the fine carbide and retained austenite. CONSTITUTION:At least one among the inner and outer rings and roller constituting the bearing is formed with the following alloy steel. The alloy steel contains 0.3-0.6wt.% C, 3-14wt.% Cr, <=40ppm Ti, <=12ppm O, <=200ppm P, <=80ppm S and the balance Fe. The alloy steel is carburized or carbonitrided. The content of the fine carbide layer of the surface layer part is controlled to 20-50vol.%, and the amt. of the retained austenite is adjusted to 10-25vol.%. A bearing having a long service life can be provided by this method.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to rolling bearings used in automobiles, agricultural machinery, construction machinery, steel machinery, etc., and in particular, rolling bearings that have a long life required for transmissions and engines. Regarding rolling bearings.

[Prior art] Rolling bearings are used harshly, subjecting them to repeated shear stress under high surface pressure, so in order to withstand the shear stress and ensure rolling fatigue life (hereinafter also referred to as rolling life or service life), , high carbon chrome steel bearings (SUJ2
) was quenched and tempered to have a Rockwell hardness of HRC58-64. In addition, in rolling bearings using case hardened steel, it is necessary to set the hardness curve according to the internal shear force distribution caused by contact surface pressure, so we use low carbon case hardened @5CR420H, which has good hardenability. S.C.
Using M420H, 5AE8620H, 5AE4320H, etc., carburizing or carbonitriding, quenching, tempering,
By applying this, the surface hardness of the inner and outer rings and rolling elements is
RC5B~64, and its core hardness is HRC30
The required lifespan has been secured by increasing the lifespan to ~48.

However, in today's world where it is desired to extend the life of bearings, conditions are becoming more severe. For example, foreign matter mixed in bearing lubricating oil can cause scratches on the rolling elements and inner and outer rings.
There have been cases where the conventional bearing hardness described above is insufficient.

Therefore, it is necessary to improve the surface hardness of the bearing.

As a conventional example of improving bearing surface hardness, for example,
There is a conventional example of manufacturing bearings using precipitation hardening tool steel (SKH, 5KD) in which carbide-forming elements are added and a large number of carbides precipitate (Metal Handbook, edited by the Japan Institute of Metals, revised 3rd edition, 780- 797 pages).

[Problem to be solved by the invention]

However, bearings manufactured using the above-mentioned conventional tool steels have the advantage of having high surface hardness and being less prone to impressions caused by foreign matter in the lubricating oil, but they also contain alloying elements that form carbides. Depending on the amount, the carbide that precipitates becomes coarse, which causes stress concentration around the carbide, causing flaking starting from that area and shortening the service life.

In addition, by controlling the residual austenite ffl on the bearing surface within a predetermined range, stress concentration at the edge of the foreign matter indentation can be alleviated and the service life can be extended (Japanese Patent Application No. 62-209
No. 167), but in the high surface pressure conditions required for automobiles, for example, there is a demand for a further improvement in life than in the past.

In order to solve such conventional unresolved problems, the present invention aims to provide a rolling bearing that has a longer life than conventional rolling bearings.

[Means for solving the problem] A rolling bearing according to claim (1) for achieving the above object is a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, in which at least the inner ring, the outer ring, and the rolling element. One is C
:Q, 3-0.6% by weight, Cr: 3-14% by weight, Ti
:40ppm or less, O:12ppm or less, P:200p
pm or less, S: 80 ppm or less, and the balance is Fe, and the alloy steel is subjected to carburizing or carbonitriding heat treatment, and the amount of fine carbides in the surface layer is 20 to 50 vol%, and there is no residual austenite in the surface layer. HE is 10
It is characterized by a content of ~25 vol%.

Further, the rolling bearing according to claim (2) for achieving the above object is a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, in which at least one of the inner ring, outer ring, and rolling element has a C: 0.3 to 0.3. 0.6% by weight, Cr: 3-14% by weight
, Ti: 40ppm or less, Si: 0.9% by weight or less, M
o: 0.4 to 2.0% by weight, Mn: 2.0% by weight or less,
O: 12 ppm or less, P: 200 ppm or less, S: 8
0 ppm or less, the balance being Fe, the alloy steel is subjected to carburizing or carbonitriding heat treatment, the amount of fine carbides in the surface layer is 20 to 50 vol%, and the amount of retained austenite in the surface layer is 10 to 25 vol. %.

Further, the rolling bearing according to claim (3) for achieving the above object is a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, in which at least one of the inner ring, outer ring, and rolling element is C:O, 3-3. 0.6% by weight, Cr: 3-14% by weight,
Ti: 40ppm or less, Si: 0.9% by weight or less, Mn
: 2.0% by weight or less, ■=0°03-1% by weight, O:
12ppm or less, P: 200ppm or less, S: 80ppm
m or less, the balance is Fe, the alloy steel is subjected to carburizing or carbonitriding heat treatment, the amount of fine carbides in the surface layer is 20 to 50 vol%, and the amount of retained austenite in the surface layer is 10 to 25 vol. %.

Furthermore, the rolling bearing according to claim (4) for achieving the above object is a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, in which at least one of the inner ring, outer ring, and rolling element has a C: 0.3 to 0.3. 0.6% by weight, Cr: 3 to 14% by weight, Ti: 40ppm or less, Si: 0.9% by weight or less,
Mo: 0.4 to 2.0% by weight, Mn: 2.0% by weight
Hereinafter, V: 0.03 to 1, weight 0: 12 ppm or less, P: 200 ppm or less, S: 80 ppm or less, the balance is Fe, and the alloy steel is subjected to carburizing or carbonitriding heat treatment, and the surface layer The amount of fine carbides in is 20-5
0 vol%, and the retained austenite t-i in the surface layer portion is 10 to 25νO1%.

Furthermore, the rolling bearing according to claim (5) for achieving the above object is a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, in which at least one of the inner ring, outer ring, and rolling element has a C: 0.3. ~0.6% by weight, Cr: 3-14
Weight %, Si: 0.9 weight % or less, M n : 2.0
It is made of an alloy steel with weight% or less, Ti: 40 ppm or less, 0: 12 ppm or less, P: 200 ppm or less, S: 80 ppm or less, and the balance is Fe, and the alloy steel is subjected to carburizing or carbonitriding heat treatment to form fine carbides in the surface layer. amount is 20-5
0 vol%, and the retained austenite i in the surface layer portion is 10 to 25 vol%.

[Function] The present inventors have developed an alloy steel with a low impurity content. As a result of various studies on extending the life of rolling bearings manufactured using high-cleanliness steel, we found that the relationship between the fineness of carbides in the surface layer of the bearing, their abundance, and the relationship between retained austenite i in the surface layer of the bearing and life. , various findings have been obtained regarding the relationship between S content and cracking incidence during forging.
Based on this knowledge, we have arrived at the present invention as described in the claims.

The effects of the contained elements used in the present invention and the critical significance of their contents will be explained.

C, 0.3 to 0.6% by weight C is an element necessary to improve hardness after quenching and tempering.

If the carbon content exceeds 0.6% by weight, the toughness at the core will decrease and the fracture strength will decrease.

On the other hand, if it is less than 0.3% by weight, the carburizing or carbonitriding treatment time becomes longer and the heat treatment productivity decreases, so the carbon content was limited within the above range. In particular, 0.35 to 0.
Preferably it is 45% by weight.

Cr: 3 to 14% by weight The rolling bearing according to the present invention is intended to improve the surface hardness of the bearing by forming hard carbides on the surface layer of the bearing. At this time, Cr is necessary as a carbide-forming element, and Cr combines with C to form fine carbides.

If the Cr content is less than 3% by weight, the required surface hardness (
The amount of carbide required to obtain an HRC of 65 to 70) is reduced. On the other hand, if the Cr content exceeds 14, giant carbides will be formed in the material stage, stress concentration will occur around these carbides, and the life will be shortened. Therefore, the content of Cr should be kept within the above range. Limited. In particular, it is preferably 11.0 to 13.0% by weight.

Ti: 40 ppm or less Ti appears as a nonmetallic compound in the form of TiN. Since this TiN has high hardness and low plastic deformability, it becomes a stress concentration source and reduces the life span, so it is necessary to reduce the Ti content as much as possible. Therefore, the Ti content was limited to the above value.

Si: 0.9% by weight or less St in steel is effective for solid solution strengthening and improving temper softening resistance. However, as the content increases, decarburization due to heat treatment becomes significant and surface hardness decreases, so the upper limit of the content is limited to the above value. Therefore, in the inventions described in claims (2) to (5), by containing Si, solid solution strengthening and improvement in temper softening resistance are achieved.

Mo; 0-4 to 2-0% by weight Mo, like Cr, is necessary for forming carbides on the bearing surface and is effective because it improves hardenability.

The effect of fine carbide formation by Mo becomes remarkable when MO is contained in an amount of 0.4% by weight or more within the above-mentioned Cr content range, so this value was set as the lower limit of the MO content.

On the other hand, when the Mo content exceeds 2.0% by weight, giant carbides are formed in the material stage, similar to Cr, and the life of the bearing is reduced, so the upper limit was set to the above value. In particular, 1.
It is preferably 5 to 2.0% by weight.

Therefore, in the inventions described in claims (2), (4), and (5), molybdenum carbide is generated by containing MO to further improve the surface hardness of the bearing.

Mn; 2. O wt % or less Mn in steel plays a major role in improving hardenability, and is included because it is inexpensive.

However, when the Mn content increases, non-metallic inclusions tend to occur in large numbers, hardness improves, and machinability such as forgeability and machinability decreases, so the upper limit of the Mn content is set to the above value.

Therefore, in the inventions described in claims (2) to (5), M
By containing n, hardenability is improved.

V, 0.03 to 1% by weight (2) is an element that precipitates at grain boundaries to suppress coarsening of crystal grains and make them finer, and also combines with carbon in steel to form fine carbides. It is added because its addition improves the hardness of the bearing surface layer and improves wear resistance.

The effect becomes significant when the content is 0.03% by weight or more, so this value was set as the lower limit of the content.

On the other hand, if the upper limit of the content exceeds 1% by weight, the carbide (1) will precipitate at the grain boundaries, deteriorating workability and various mechanical properties, so the upper limit of the content was limited to the above value. In particular, it is preferably 0.8 to 1% by weight.

Therefore, in the invention described in claims (3) and (4),
By containing (2), the surface hardness of the bearing is further improved.

0; 12 ppm or less Since O reduces rolling fatigue life as an element that generates oxide-based nonmetallic inclusions (especially AIzOi), it is necessary to reduce its content as much as possible, so the upper limit is set to 12 ppm.
And so.

P: 200ppm or less P is an element that reduces the impact resistance of alloy steel.

Therefore, it is necessary to lower the content, and the upper limit is set to 2.
00 ppm.

S: 80 ppm or less S causes the formation of sulfide-based nonmetallic inclusions such as MnS. Since MnS has low hardness and high plastic deformability, it acts as a starting point for cracking during pre-processing such as rolling and forging. Therefore, in order to prevent cracking during pre-processing such as forging and to enable stronger processing, it is necessary to reduce the S content, and the upper limit was set at 80 ppm.

A cylindrical sample of φ20×30M was prepared using alloy steel having the composition described in the above claims, cold worked (forged) at an upsetting rate of 80%, and the crack occurrence rate was investigated. Figure 2 shows the relationship between the S content in steel and the cracking incidence. It can be seen from FIG. 2 that the cracking incidence decreases as the S content in the sample material decreases, and it can be seen that the cracking incidence is 0% when the S content is 180 ppm or less. Therefore, if the S content is 80 ppm or less, stronger processing becomes possible.

Next, the action of retained austenite, which is a feature of the present invention, and the critical significance of its abundance will be explained.

When a bearing is used under lubrication contaminated with foreign matter, concave impressions are generated on the rolling surfaces of the inner and outer races and rolling elements due to repeated contact with foreign matter. This impression has an edge portion.

Retained austenite is soft (for example, around Hv300 (however, it varies depending on the carbon content of the material), and unlike low-carbon martensite, which is simply low in hardness, it can be transformed into martensite through deformation-induced transformation. Therefore, the residual austenite present in a suitable amount in the bearing surface layer will deform the surface after a predetermined number of relative passes of the other member (for example, the raceway ring to the rolling element) passing through the indentations during rolling. It hardens by turning into martensite due to energy. During this process, the rolling load concentrated at the edge of the impression caused by foreign matter mixed in the lubricating oil is alleviated, preventing the occurrence of microcracks and extending the life.

The lifespan of bearing materials in foreign matter lubrication tests is
Bearing life and retained austenite γ shown in the graph in the figure
As is clear from the relationship with R (vol%), the life LIO indicated by the number of stress repetitions changes depending on the change in the amount of retained austenite.

That is, in a range where the amount of retained austenite is 40% or less, the life under lubrication with foreign matter increases as the amount increases.

On the other hand, in order to improve the hardness of the transfer surface, the amount of carbide in the surface layer is set to 20 to 5 Qvol%, but if the amount of retained austenite exceeds 25vol%, the mechanical strength of the material will decrease and it will not be practical. . Also, C
Since carbide-forming elements such as r, Mo, and V are added, there is little solid solution of C in the matrix, and it is difficult for retained austenite to exceed 25 vol%.

If the amount of retained austenite is less than 10 vol%, the effect of extending the life under lubrication with foreign matter is small, so the amount of retained austenite is set to 10 to 25 vol%.

In Fig. 1, the curves ■ and ■ are the lifespan L+o under clean lubrication. are shown respectively. Further, curves ■ and ■ indicate the lifespan LIO and LSO under lubrication with foreign matter, respectively.

The experimental conditions shown in FIG. 1 are as follows.

“Special Steel Handbook (1st edition)” edited by Electric Steel Research Institute, Rikogakusha,
On May 25, 1965, using the testing machine described on pages 1O to 21A, steel powder (hardness, HRC 66.3, hardness 80
Using a lubricant containing ~160 μm of Fe5C) at a mixing ratio of 300 ppm, the maximum surface pressure was 500 kgf 7 mm2.
The test was conducted at a stress repetition rate of 3000 cpm.

Next, the action of carbides present in the bearing surface layer and the critical significance of their content will be explained.

In the present invention, at least one surface layer of the inner ring ζ outer ring and the rolling ring is carburized or carbonitrided.

Fine carbides are produced by the quenching and tempering processes.

This carbide is hard and has excellent wear resistance, thereby increasing the life of the bearing. In addition, since the size is minute, the life of the bearing can be improved without causing stress concentration due to the applied load.

In the present invention, carbide refers to, for example, Cr7C3°C
r5Cb, MozC,vc, v4c3 and Fe,C
Or these double carbides are mentioned.

In the present invention, the size of the carbide (1/2 of the sum of the maximum diameter and the minimum diameter) is preferably 0.5 to 140 μm.

In the present invention, the amount of carbide present in the surface layer of the bearing is 20 to 5 Qvol%, and its critical significance is as follows.

In order to achieve long bearing life 4, the surface hardness is HRC6.
It is desirable to have a hardness of 5 to 70, but if the amount of carbide present is less than 20 vol%, the desired hardness cannot be obtained. On the other hand, if the amount exceeds 50 vol %, fine carbides will bond with each other, making the carbides coarser and causing stress concentration, which is not preferable. Therefore, the amount of carbide present in the surface layer was set within the above range.

By allowing fine carbides to exist in the surface layer of the bearing within the above range, a highly hard bearing with a surface hardness of HRC 65 to 70 can be obtained.

In the present invention, by carburizing or carbonitriding the alloy steel having the composition described in the claims, the amount of solute carbon or solute carbon nitrogen can be reduced to 0.0 as shown in FIG.
6 to 0.8% by weight (total carbon concentration on the surface 2.5 to 3.8% by weight), and by quenching and tempering it, the amount of retained austenite in the surface layer can be reduced to 10 to 25 vol.
%.

In addition, in the heat treatment process, A. Carbide nuclei are generated when heated above the transformation point, and fine spherical carbides can be precipitated on the surface layer in the subsequent quenching and tempering process. Moreover, the amount of solid solute carbon is 0.6
~0.8% by weight (total carbon concentration on the surface 2.5-3.8% by weight), the amount of carbides in the surface layer can be reduced to 20% by weight.
~5Qvol%.

〔Example〕

Next, examples of the present invention will be described.

By carburizing the alloy field of the test piece shown in Table 1 below, followed by soaking, quenching, and tempering, test piece 1
~12 were created.

(Hereafter, margin) Next, the heat treatment conditions in this example will be explained.

Direct quenching, which is part of carburizing heat treatment, involves heat treatment at 920 to 960°C for about 3 to 5 hours in an atmosphere of Rx gas + enriched gas, followed by soaking at 680°C for 1 hour, as shown in the graph shown in Figure 4. and then 84
Oil quenched for 1 hour at 0°C, then further quenched at 180'CX.
Tempering was performed for 2 hours.

Furthermore, as for carbonitriding heat treatment, as shown in the graph of FIG. 5, carbonitriding heat treatment was performed at 830 to 870°C for about 3 to 5 hours in an atmosphere of Rx gas + enriched gas + 5% ammonia gas, Thereafter, the same treatment as in the carburizing treatment described above was performed.

In Figure 4.5, when the A1 transformation point (approximately 726°C) is exceeded during the process from soaking to quenching, a carbide nucleus is generated, and then fine spherical carbides are formed around this nucleus in the specimen. Precipitates on the surface layer.

Then, the surface hardness (HRC) was determined for each specimen.

Presence of carbide present in the surface layer 51 (vol%) 1 The amount of retained austenite present in the surface layer and the average particle size of the carbide were measured. In addition, disk-shaped test pieces that can be applied to either the inner ring or the outer ring of a rolling bearing were created using each test piece subjected to the carburizing heat treatment, and the number of stress cycles (cycles) was determined for each disk-shaped test piece. The rolling life (L, .) indicated by was measured. These results are also shown in Table 1 above.

In addition, hardness (HRC) and rolling life (L,.) are shown in Figure 6.
The relationship between retained austenite 1 (vol%
) and rolling life (Ll.).

Note that the lifespan was measured based on the following conditions.

Bearing life test is carried out in R Special Steel Handbook, (1st edition) edited by Electric Steel Research Institute, Science and Engineering, May 25, 1965, p. 10~
Steel powder (hardness, H
RC66,3, 80-160 μm of Fe=C)
Using a lubricant added at a mixing ratio of 0.00 ppm, a maximum surface pressure of 500 kgf/mm2 and a stress repetition rate of 3000
Tested at cpm. The service life was determined to have expired when flaking occurred on the surface.

In Table 1, test piece 1 corresponds to the embodiment of the invention described in claim (1), and since the surface carbide concentration in the surface layer portion is a good value of 22 vol%, the surface hardness is also HRC66. This is a good value, and a good rolling life can be achieved even under lubrication contaminated with foreign matter. In addition, although it is inevitable that Si and Mn are contained as unavoidable impurities in the test piece l, even if the content of St and Mn is reduced to 0 as much as possible, the test piece Similar to No. 1, good surface hardness and rolling life can be obtained.

Test specimens 2 and 3 are examples of the invention described in claim (5), and it is possible to achieve good surface hardness and rolling life.

Test piece 4 is an embodiment of the invention as claimed in claim (2), test material 5 is an embodiment of the invention as claimed in claim (3), and test piece 6.7 is an embodiment of the invention as claimed in claim (3). This is an example of the invention described in 4), and can achieve good surface hardness and rolling life similarly to the above-mentioned test pieces.

Specimen 8 has a C content exceeding the range of the present invention, and also contains Cr.
This is a comparative example (SUJ-2) of the invention according to claim (5), characterized in that the content of is below the range of the present invention.

In this specimen 8, since the Cr content is low, the amount of Cr carbide produced in the surface layer is reduced to 8 vol %, and as a result, the surface hardness is insufficiently improved, reaching only about a little over 62 HRC. Therefore, L. The lifespan is lXl06, which is a small value compared to the above-mentioned test pieces. Furthermore, since the C content is high, the toughness in the deep part decreases and the fracture strength decreases.

Test piece 9 is a comparative example of the invention described in claim (5), similar to test piece 8, in which the content of Cr is below the range of the present invention.

In this specimen 9, the amount of Cr carbide produced in the surface layer portion was reduced to 1 vol % as in the specimen 8, and as a result, the surface hardness was insufficiently improved and the HRC was only about 64. Therefore, Ll. The lifespan is also a small value of 3.5×10′ compared to the above-mentioned test pieces.

Test piece 10 is a comparative example of the invention described in claim (2), characterized in that the content of Mo exceeds the range of the invention.

In this specimen 10, even if the MO content exceeds the range of the present invention, there is no significant difference in the effect of forming fine MO carbides on the rolling surface of the bearing, resulting in high cost and the carbides becoming large, which is claimed The rolling life tends to be lower than that of specimen 4 which is an example of the invention described in item (2).

Test piece 11 is a comparative example of the invention described in claim (3), characterized in that the content of (1) exceeds the range of the invention.

In this test piece 11, even if the content of (1) exceeds the range of the present invention, there is no difference in grain refining effect, which is not preferable because it increases cost and deteriorates workability and various mechanical properties.

Test piece 12 is a comparative example of the invention described in claim (4), characterized in that the content of Mo and V exceeds the range of the invention. In this specimen 12, even if the content of Mo and V exceeds the range of the present invention, there is no difference in the effect of forming fine carbides on the surface layer of the bearing, and the content of (3) exceeds the range of the present invention. Even if the range is exceeded, there is no difference in the grain refinement effect, and in either case, there is a cost disadvantage. Further, the carbide tends to become large, which reduces the rolling life, which is undesirable.

For each of the above specimens 1 to 7, 10 cylindrical specimens of φ20 x 30M were made, cold worked (forged) at an upsetting rate of 80, and the crack occurrence rate was investigated. Even in the sample, the cracking incidence was 0%.

Next, using each of test specimens 1, 2.4 to 6, and 8, a small ball bearing (686) having an inner diameter of 6 mm was fabricated, and a wear resistance test was conducted on this bearing. The test conditions are as follows.

Preload...2kgf, swing angle...8°, speed -2
0112, Grease lubrication, evaluation cycle - 2X107
times.

Temperature: normal temperature, number of prototypes: 8 The results of this abrasion resistance test are shown in Tables 2 and 3 below and will be explained.

(Presence or absence of flaking) Table 2 (Amount of wear due to fretting) Table 3 As shown in Table 2.3 above, sample 1.2 had surface carbide concentrations of 22 and 23 vol%, respectively. Since it is within the scope of the present invention, the surface carbide concentration is 8 vol.
%, which is lower than the range of the present invention, the number of fretting occurrences is small and the amount of wear is also small.

In addition, in specimens 4 to 6, in which the surface carbide concentration was higher than that of specimen 1.2, both the number of fretting occurrences and the amount of wear were smaller.

Next, the inner diameter 6fflII+ was prototyped using the test piece.
A test was conducted to confirm that 20 of the small ball bearings (686) were resistant to indentation (as a result, the acoustic characteristics were good).
It was carried out according to 8. FIG. 8 illustrates the results of this test.

As can be seen from FIG. 8, the average value X of the sound pressure (dB) of test pieces 1, 2.4 to 6 is lower than that of test piece 8. This is because test specimens 1°2.4 to 6 have a higher surface carbide concentration and transfer surface hardness than test specimen 8, making it difficult for impressions to form on the surface. In particular, specimen 4 to which the surface carbide concentration is higher than specimen 1.2
6 has a lower sound pressure level.

Note that the surface layer portion as referred to in the present invention is calculated from the contact pressure applied to the contact surfaces of the inner ring, outer ring, and raceway surfaces of the rolling elements that constitute the rolling bearing. That is, the maximum shear stress position (depth from the surface) is set to 2. Then, it refers to the part from the surface to a depth of Z0 to 2Z.

As an order, for example, 0.2 to 0.5 mm from the surface
It will be about the same depth.

In addition, in the rolling life test shown in Table 1 above, the life was shown for a disk-shaped test piece that can be applied to either the inner ring or the outer ring, but the rolling elements were formed from the same material and the rolling life was Similar results can be obtained by conducting tests.

Furthermore, in the wear resistance test and the acoustic property test, the entire rolling bearing, that is, the inner and outer rings and the rolling elements, were made from the above-mentioned test pieces, but at least one of the inner ring, outer ring, and rolling elements was made of the alloy according to the present invention. If it is made of steel, it will be possible to obtain good wear resistance and acoustic properties as in the previous embodiment.

[Effects of the Invention] As explained above, according to the rolling bearing according to the present invention, an appropriate amount of fine carbide is formed on the surface layer of at least one of the inner ring, the outer ring, and the rolling elements to improve the surface hardness. A suitable amount of retained austenite is present in the surface layer to prevent micro-cranks from occurring under lubrication contaminated with foreign matter.

Therefore, when using bearings under clean lubrication, they have a much longer lifespan than conventional bearings.
Furthermore, when the bearing is used under lubrication containing foreign matter, the life of the bearing is much longer than that of conventional bearings.

As a result, in both cases where the bearing is used under sliding conditions described above, it is possible to improve the life of the bearing under high rolling loads.

[Brief explanation of drawings]

Figure 1 shows bearing life and retained austenite) TR (vol%).
), Figure 2 is a characteristic diagram showing the relationship between the S content in steel and the cracking incidence, and Figure 3 is the relationship between the amount of solid solute carbon or solute carbon nitrogen and the amount of retained austenite. FIGS. 4 and 5 are process diagrams illustrating the heat treatment conditions for manufacturing the rolling bearing according to the present invention, and FIG. 6 is a characteristic diagram showing the relationship between
A characteristic diagram showing the relationship between the surface hardness (HRC) of the specimen and the bearing life L1° indicated by the number of stress repetitions. Figure 7 shows the relationship between the amount of retained austenite and the number of stress repetitions in the fatigue life of the bearing. Characteristic diagram, FIG. 8 is a characteristic diagram showing the acoustic characteristics of each test piece.

Claims (5)

[Claims] (1) In a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, at least one of the inner ring, outer ring, and rolling element is C
:0.3 to 0.6% by weight, Cr: 3 to 14% by weight, Ti
:40ppm or less, O:12ppm or less, P:200p
pm or less, S: 80 ppm or less, and the balance is Fe, the alloy steel is subjected to carburizing or carbonitriding heat treatment, the amount of fine carbides in the surface layer is 20 to 50 vol%, and the residual austenite in the surface layer is amount is 10
A rolling bearing characterized in that the content is ~25 vol%. (2) In a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, at least one of the inner ring, outer ring, and rolling element is C
:0.3 to 0.6% by weight, Cr: 3 to 14% by weight, Ti
:40ppm or less, Si:0.9% by weight or less, Mo:0
．． 4 to 2.0% by weight, Mn: 2.0% by weight or less, O: 1
2ppm or less, P: 200ppm or less, S: 80ppm
Hereinafter, the alloy steel is made of alloy steel with the balance being Fe, and the alloy steel is subjected to carburizing or carbonitriding heat treatment, and the amount of fine carbides in the surface layer is 20 to 50 vol%, and the amount of retained austenite in the surface layer is 10 to 25 vol%. A rolling bearing characterized by: (3) In a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, at least one of the inner ring, outer ring, and rolling element is C
:0.3 to 0.6% by weight, Cr: 3 to 14% by weight, Ti
: 40ppm or less, Si: 0.9% by weight or less, Mn: 2
．． 0% by weight or less, V: 0.03-1% by weight, O: 12p
pm or less, P: 200 ppm or less, S: 80 ppm or less, and the balance is Fe, and the alloy steel is subjected to carburizing or carbonitriding heat treatment to reduce the amount of fine carbides in the surface layer to 2.
A rolling bearing characterized in that the amount of retained austenite in the surface layer portion is 0 to 50 vol% and 10 to 25 vol%. (4) In a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, at least one of the inner ring, outer ring, and rolling element is C
:0.3 to 0.6% by weight, Cr: 3 to 14% by weight, Ti
:40ppm or less, Si:0.9% by weight or less, Mo:0
．． 4 to 2.0% by weight, Mn: 2.0% by weight or less, V: 0
．． 03-1% by weight, O: 12ppm or less, P: 200p
pm or less, S: 80 ppm or less, and the balance is Fe, the alloy steel is subjected to carburizing or carbonitriding heat treatment, the amount of fine carbides in the surface layer is 20 to 50 vol%, and the residual austenite in the surface layer is amount is 10
A rolling bearing characterized in that the content is ~25 vol%. (5) In a rolling bearing consisting of an inner ring, an outer ring, and a rolling element, at least one of the inner ring, outer ring, and rolling element is C
: 0.3 to 0.6 wt%, Cr: 3 to 14 wt%, Si
: 0.9% by weight or less, Mn: 2.0% by weight or less, Ti:
40ppm or less, O: 12ppm or less, P: 200pp
m or less, S: 80 ppm or less, balance Fe, the alloy steel is subjected to carburizing or carbonitriding heat treatment, and the amount of fine carbides in the surface layer is 20 to 50 vol%,
And the amount of retained austenite in the surface layer is 10~
A rolling bearing characterized in that it contains 25 vol%.