JP2011190921A - Thrust roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thrust roller bearing having a lace which can prevent crack generation at bending and can secure required durability. <P>SOLUTION: Each of an outer lace 4 and an inner lace 5 is formed of alloy steel which contains 0.68 to 0.88 mass% of C, 0.01 to 0.15 mass% of Si, 0.2 to 0.7 mass% of Mn, and 0.3 to 0.7 mass% of Cr, and has an oxygen concentration of 15 ppm or below. Furthermore, quenching, carburizing quenching, and carbonitriding quenching are applied to surfaces of the outer lace 4 and the inner lace 5, and thus a surface-hardened layer having a prescribed property is formed. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to a thrust roller bearing that is mounted on an electrical component such as an automobile transmission, a compressor for a car air conditioner, or a rotation support part of various machines for general industry and supports a thrust load applied to the rotation support part. Regarding improvement. Specifically, with regard to the improvement of the race that constitutes the thrust roller bearing, a race made of a steel material having a composition excellent in workability and durability is realized.
The thrust roller bearing that is an object of the present invention includes a thrust needle bearing that uses a needle (needle roller) having a larger axial dimension than the outer diameter as a rolling element. Therefore, the roller described in the present specification and claims includes the needle.

For example, a thrust roller bearing 1 as shown in FIG. 1 is mounted on a rotating portion of a transmission, a torque converter, a car cooler compressor, or the like to support a thrust load applied to a rotating shaft or the like (for example, Patent Document 1). reference). The thrust roller bearing 1 includes a plurality of rollers 2 arranged in a radial direction, a cage 3 that is formed in an annular shape as a whole, and holds the rollers 2 in a freely rolling manner, and the rollers 2 are pivoted. It consists of an outer race 4 and an inner race 5 that are clamped from both sides in the direction (left-right direction in FIG. 1). The outer race 4 or the inner race 5 corresponds to the race described in the claims.
Of these, the outer race 4 has a ring portion 7 having an outer ring raceway 6 on one side surface (left side surface in FIG. 1), and a state of projecting toward the outer ring raceway 6 in the axial direction from the outer peripheral edge of the ring portion 7. And a cylindrical outer flange 8 formed over the entire circumference. The inner race 5 has a ring portion 10 having an inner ring raceway 9 on one side surface (the right side surface in FIG. 1) and a state in which the inner ring race 5 projects toward the inner ring raceway 9 in the axial direction from the inner periphery of the ring portion 10 And the inner flange 11 formed over the entire circumference.

  The cage 3 is formed by combining a pair of elements 12a and 12b, each of which has a U-shaped cross section made of a metal plate and is formed in an annular shape as a whole. The same number of pockets 14 and 14 as the rollers 2 are provided in the radial direction in the ring portions 13 and 13 of the elements 12a and 12b, respectively. And the said holder | retainer 3 is comprised by combining each element 12a, 12b which provided such pockets 14 and 14 in the state in which the phases of these each pockets 14 and 14 correspond. In addition to the cage 3 formed by combining such a pair of elements 12a and 12b in the middle, for example, an annular main portion made of synthetic resin is passed through both axial side surfaces. A cage having a pocket is also known in the art.

Similarly, Patent Document 1 describes a thrust roller bearing 1a as shown in FIG. This thrust roller bearing 1a is provided with pockets 14 and 14 for holding a plurality of rollers 2 and 2 arranged in the radial direction in two rows in the radial direction at a plurality of locations in the circumferential direction of the cage 3a. Yes. Further, an outer ring race 4a and an inner ring race 5a are provided to hold the rollers 2 and 2 from both sides in the axial direction (vertical direction in FIG. 2). Of these, the outer race 4a is composed of an annular portion 7a having an outer raceway 6a on one side (the lower side in FIG. 2). The inner race 5a comprises an annular portion 10a having an inner ring raceway 9a on one side (the upper side in FIG. 2).
Incidentally, as the structure of the race constituting the thrust roller bearing, the structure as shown in FIGS. 3A to 3D including the structures of the outer ring races 4, 4a and the inner ring races 5, 5a is included. The race has been known for a long time.

  As shown in FIG. 1, the outer ring and the inner ring races 4 and 5 constituting the thrust roller bearing 1 are generally made of a plate-shaped steel plate, which is a material, by punching it into an annular first intermediate material. Get. Then, the first intermediate material is subjected to a bending process such as a burring process to obtain a second intermediate material in which the flanges 8 and 11 are formed. Further, the second intermediate material is subjected to a heat treatment such as quenching, and a hardened surface is formed on the surface of the second intermediate material to ensure the required hardness. This quenching process is soaked in quenching oil in a heated state, so-called soaking quenching, carburizing quenching after carburizing treatment, and quenching treatment after performing carbonitriding treatment. Various methods such as carbonitriding and quenching to be applied can be appropriately selected.

Further, as the material of the race constituting the thrust roller bearing, different materials are generally used depending on whether or not the manufacturing process includes bending. That is, when the manufacturing process includes a bending process for forming the outer and inner flanges 8 and 11 as in the structure of the outer races and inner races 4 and 5 shown in FIG. When alloy steel having a high carbon content, such as type 2 (SUJ2), is used, cracks are likely to occur at the root portions of the flanges 8 and 11 (portions indicated by chain lines A and B in FIG. 1). For this reason, alloy steels such as SK85 and SAE1074, which have a lower carbon content than SUJ2, are used. However, even with these alloy steels, cracks may occur during bending, although not as much as the SUJ2. In the case of the SK85, the quality after the heat treatment is not stable even if the carbonitriding process is performed, and it is difficult to secure a sufficient rolling fatigue life because the desired amount of retained austenite cannot be ensured.
On the other hand, when the manufacturing process does not include bending as in the structure of the outer races and inner races 4a and 5a shown in FIG. 2, the SUJ2 can be used, and sufficient durability can be easily secured.

By the way, when the thrust roller bearing 1 as shown in FIG. 1 is required to have a long life, the structure of the outer ring and the inner ring races 4, 5 of the SK85 is replaced by the structure of the SUJ2. It can be considered that the specification is changed to a flat lace structure as shown in FIG.
On the other hand, when the specification cannot be changed, SCM415, which has a lower carbon content than SK85 and has high bending workability, is used as a material, and a steel plate made of this material is punched and bent to obtain an intermediate material. After that, a method is used in which the intermediate material is subjected to heat treatment such as carburizing treatment to ensure durability. However, in this case, the occurrence of cracks can be prevented, but since the heat treatment takes a long time, the production efficiency is lowered and the processing cost is increased.

Further, the thickness of each outer ring and inner ring races 4 and 5 as shown in FIG. 1 is mainly 0.6 to 1.5 mm, and the SK85 is considered in consideration of workability and quality after heat treatment. Is generally used.
In order to ensure the durability of the race, when the thickness of the race is increased to 2 mm or more, if the inner race 5 is made using the SK85, the inner diameter φd of the first annular intermediate material before bending and If the value of the hole expansion parameter E (= φD / φd) derived based on the inner diameter φD of the second intermediate material after bending is large, cracks are likely to occur. For this reason, after performing an annealing process, it is necessary to perform the said bending process, manufacturing efficiency will fall and processing cost will increase. In order to omit the annealing process, a method is used in which the SCM415 having a carbon content lower than that of the SK85 is used as a material and heat treatment such as carburizing is performed to ensure durability. . However, since this heat treatment takes a long time, the production efficiency is lowered and the processing cost is increased.

  In view of the circumstances as described above, the present invention regulates the composition of the steel material for producing the race that constitutes the thrust roller bearing. The invention was invented to prevent the occurrence and to ensure the durability required as a thrust roller bearing.

  The thrust roller bearing of the present invention includes a plurality of rollers arranged in a radial direction and at least one race made of a metal plate in an annular shape and having one axial side surface as a thrust raceway surface.

  In particular, in the thrust roller bearing of the present invention, the race is composed of 0.68 to 0.88 mass% of C (carbon), 0.01 to 0.15 mass% of Si (silicon), and Mn (manganese). ) 0.2 to 0.7 mass%, Cr (chromium) 0.3 to 0.7 mass%, and the oxygen concentration is 15 ppm or less. The balance of the alloy steel is Fe and inevitable impurities.

Further, when the thrust roller bearing of the present invention is implemented, the thickness is preferably set to 0.4 to 6.0 mm as in the invention described in claim 2.
Moreover, hardness (Vickers hardness) shall be 100-300Hv.
Furthermore, the surface roughness (arithmetic average roughness) is set to 0.4 μmRa or less.

Further, when the invention described in claim 2 as described above is carried out, the surface formed by subjecting the race to quenching and tempering treatment, preferably as in the invention described in claim 3. It shall have a hardened layer.
Moreover, the hardness of this surface hardening layer shall be 650-850Hv.
Furthermore, the surface roughness of the surface hardened layer is set to 0.4 μmRa or less.

Alternatively, as in the invention described in claim 4, the race has a hardened surface layer formed by performing quenching / tempering after carburizing or carbonitriding. .
Moreover, this surface hardening layer shall contain C 0.8-1.2 mass% and N 0.05-0.50 mass%.
Moreover, the hardness of the said surface hardening layer shall be 700-900Hv.
Further, the retained austenite amount γ _R of the surface hardened layer is set to 15 to 45% by volume.
Furthermore, the surface roughness of the surface hardened layer is set to 0.4 μmRa or less.

According to the thrust roller bearing of the present invention configured as described above, by appropriately regulating the composition of the steel material that constitutes the race, it is possible to prevent cracks from occurring in the bent portion during the bending process. The improvement of sex can be aimed at.
Further, after forming into a lace shape by bending, an appropriate heat treatment is applied to the surface of the lace to form a hardened surface layer having a desired property on the surface of the lace. For this reason, sufficient durability can be secured without requiring an excessive heat treatment time.
Hereinafter, the composition of the steel material (alloy steel) which is the material of the lace and the properties of the surface hardened layer formed in the lace will be described together with the reasons for defining the components of the alloy steel.

(1) On the composition of the alloy steel constituting the race [C: 0.68 to 0.88 mass%]
C is added to ensure the rolling fatigue life and wear resistance of the raceway surface. That is, C is an element that improves the hardness required as a raceway surface of a rolling bearing by solid solution in the base by quenching. C also has a role of improving wear resistance by combining with other alloy elements to form hard carbides in the steel. However, if the amount of C added in the alloy steel is less than 0.68% by mass, the hardness required for a rolling bearing may not be ensured. Further, in order to improve the C concentration on the surface, a long time is required for the carburizing process or the carbonitriding process, which causes an increase in processing cost. On the other hand, if the amount of C exceeds 0.88% by mass, eutectic carbides are likely to be generated in the steel, and the rolling fatigue life of the raceway surface may be reduced. Sex is reduced. Therefore, the amount of C added to the alloy steel is restricted to a range of 0.68 to 0.88 mass%.

[Cr 0.3-0.7 mass%]
Cr is an element that dissolves in the base and improves hardenability, corrosion resistance, etc., and combines with C to form hard carbides in the steel, thereby improving wear resistance. However, when the amount of Cr added to the alloy steel is less than 0.3% by mass, the above effect cannot be obtained sufficiently. On the other hand, when the addition amount of Cr exceeds 0.7 mass%, the eutectic carbide in the steel becomes large and the average crystal grain becomes large. For this reason, workability may be reduced. Therefore, the amount of Cr added to the alloy steel is restricted to a range of 0.3 to 0.7 mass%.

[Mn is 0.2 to 0.7% by mass]
Mn is added for improving the hardenability and ensuring the amount of retained austenite on the surface (orbital surface). That is, Mn has the effect of improving the hardenability by dissolving in the base. Furthermore, Mn also has an effect of assisting formation of retained austenite on the surface. However, when the amount of Mn added to the alloy steel is less than 0.2% by mass, the above effect cannot be obtained sufficiently. On the other hand, when the amount of Mn added exceeds 0.7% by mass, not only the workability is deteriorated, but also the amount of retained austenite on the surface (the raceway surface) becomes excessive, and the hardness required as a rolling bearing I can't get it. Therefore, the amount of Mn added to the alloy steel is restricted to a range of 0.2 to 0.7% by mass.

[0.01 to 0.15 mass% of Si]
Si is added to improve the surface (orbital surface) hardness by quenching, improve the rolling fatigue life of the orbital surface, and reduce the oxygen content in the alloy steel. That is, Si dissolves in the base to improve the hardenability and improve the temper softening resistance to give the raceway the necessary hardness. It also strengthens the base structure and improves the rolling fatigue life of this raceway surface. Moreover, it reacts with oxygen in the alloy steel to produce an oxide, thereby reducing the amount of oxygen in the alloy steel. However, when the addition amount of Si is less than 0.01% by mass, the above effect cannot be obtained sufficiently. On the other hand, if the amount of Si added to the alloy steel exceeds 0.15% by mass, in addition to the deterioration of workability, carbon intrusion occurs during carburizing or carbonitriding. Inhibits. Therefore, the amount of Si added to the alloy steel was regulated to a range of 0.01 to 0.15 mass%.

[Reason for setting oxygen concentration to 15 ppm or less]
When the oxygen concentration in the alloy steel becomes high, an oxide-based intervening portion that becomes a starting point of peeling is formed on the hardened raceway surface, so that the rolling fatigue life is lowered. For this reason, it is preferable to reduce the oxygen concentration in the alloy steel in order to improve the rolling fatigue life. Therefore, this oxygen concentration was regulated to 15 ppm or less.

(2) Concerning the properties of the race surface (track surface) [C concentration of 0.8 to 1.2% by mass]
C is for obtaining the hardness required to ensure the rolling fatigue life of the raceway surface in a state after the surface layer portion of the raceway surface is polished after carburizing or carbonitriding the race. To contain. In order to give the surface layer portion the hardness necessary to ensure a sufficient rolling fatigue life, it is necessary to contain 0.8 mass% or more of C. On the other hand, when the content exceeds 1.2% by mass, it becomes easy to generate giant carbides in the surface layer portion, and it becomes easy to become a starting point for damage such as cracks. Therefore, the C content in the surface layer portion was regulated to 0.8 to 1.2% by mass. The concentration of C is adjusted by changing the conditions for carburizing or carbonitriding.

[N concentration of 0.05 to 0.5 mass%]
N is contained in order to improve the tempering resistance of the surface layer portion of the lace and to disperse and precipitate fine carbon and nitride to improve the strength. In order to obtain such an effect, the N content needs to be 0.05% by mass or more. On the other hand, when the N content exceeds 0.5% by mass, the wear resistance is excessively improved, and not only the polishing process as the finishing process of the race becomes difficult, but also the brittleness of the surface layer portion. Crack strength also decreases. Therefore, the N content is regulated to 0.05 to 0.5% by mass.

[Residual austenite amount is 15 to 45% by volume]
The amount of retained austenite in the surface layer portion of the race is regulated in order to improve the peeling resistance of the raceway surface. That is, retained austenite is a sticky metal structure, and a large amount of retained austenite contributes to an improvement in peeling resistance. However, when the amount of retained austenite in the surface layer portion is less than 15% by volume, the effect of improving the peeling resistance is small. On the other hand, when the amount of retained austenite in the surface layer portion exceeds 45% by volume, the surface hardness of the raceway surface is excessively lowered, and the rolling fatigue life of the raceway surface may be reduced. Therefore, in the invention according to claim 4, the amount of retained austenite in the surface layer portion of the race is regulated to a range of 15 to 45% by volume. The amount of retained austenite in the surface layer portion of the race is adjusted by appropriately combining the composition of the alloy steel constituting the race, carburizing treatment, or carbonitriding conditions, quenching conditions, and tempering conditions. .

(3) On the properties of the entire race [Race surface hardness]
The hardness of the hardened surface layer (track surface) formed on the race surface is a factor that affects the rolling fatigue life of the raceway surface. If this hardness is low, the rolling fatigue life decreases. However, if it is excessively high, not only does the cost for increasing the hardness increase, but also the possibility of insufficient toughness arises.
Then, regarding the invention which concerns on Claim 3, the hardness of the surface was controlled in the range of 650-850Hv.
Moreover, regarding the invention which concerns on Claim 4, the hardness of the surface was controlled in the range of 700-900Hv.

[Race surface roughness]
The roughness of the hardened surface layer (the raceway surface) formed on the race surface is a factor that affects the rolling fatigue life of the raceway surface. If this roughness is high, the rolling fatigue life decreases. Therefore, the surface roughness was regulated to 0.4 μmRa or less.

The fragmentary sectional view shown in the state which assembled | attached the thrust roller bearing of the conventional structure to the use location. Sectional drawing which shows another example of the conventional thrust roller bearing. Sectional drawing which shows another four examples of the structure of the conventional race.

  The feature of the present invention is that the composition of the steel material constituting the race and the surface of the race are subjected to heat treatment in order to improve the workability and durability of the race constituting the thrust roller bearing. It is in the point which controlled the property of the hardened surface layer. About the structure of the said thrust roller bearing and the race which comprises this thrust roller bearing, including the structure shown in above-mentioned FIGS. 1-3, various conventionally known thrust roller bearings, and a race, Since it is the same, illustration and description of a specific structure are omitted, and next, an example of a method of manufacturing a thrust roller bearing race which is an object of the present invention will be described.

First, a flat steel plate as a material is punched to obtain a first annular intermediate material, and then the flange is formed by bending the annular first intermediate material such as burring. A formed second intermediate material is obtained.
Next, heat treatment is performed on the second intermediate material. This heat treatment is a so-called so-called sukiyaki process performed in the order of quenching → tempering, or carburizing process or carbonitriding process → quenching → tempering, so-called carburizing quenching or carbonitriding process. A heat treatment called “putting” is applied.
By performing such a heat treatment, a surface hardened layer having desired properties is formed on the surface of the intermediate member. Thereafter, this hardened surface layer is polished to finish the finished shape of the race. Then, a roller that is a rolling element and a cage are combined with the race made in this manner to form a thrust roller bearing.

In the case of performing the above-described heat treatment by sukiyaki, quenching is performed at 800 to 880 ° C. and oil cooling. Tempering is performed at a temperature of 160 to 250 ° C. and furnace cooling or air cooling.
Moreover, when performing the heat treatment by the carburizing quenching or carbonitriding quenching, the carburizing treatment is performed at 800 to 880 ° C. using a mixed gas of RX gas and enriched gas as an atmosphere.
After holding for 20 to 90 minutes, it is performed by air cooling or oil cooling. On the other hand, the carbonitriding process is performed by using a mixed gas of RX gas, enriched gas, and ammonia gas as an atmosphere, holding at 800 to 880 ° C. for 20 to 90 minutes, and then cooling with air or oil. Do by. The subsequent quenching is carried out by holding at 800 to 880 ° C. and oil cooling. Tempering is performed at a temperature of 160 to 250 ° C. and furnace cooling or air cooling.

An experiment conducted for confirming the effect of the present invention will be described. This experiment is an experiment for bending the alloy steel having the composition shown in Table 1 and confirming the number of cracks generated. In addition, this experiment was conducted using 14 kinds of alloy steels of Examples 1 to 6 belonging to the technical scope of the present invention and Comparative Examples 1 to 8 not belonging to the technical scope of the present invention shown in Table 1 described later. A sample was used. Of the steel materials constituting these samples, Comparative Example 1 is SK85, Comparative Example 2 is SUJ2, Comparative Example 3 is SCM415, Comparative Example 4 is SAE1070, and Comparative Example 5 is SPCC.
The race manufactured by the experiment was performed under the following conditions.
“Conditions for manufacturing races”
Target thrust roller bearing: Inner diameter φ50 × Outer diameter φ100
Inner diameter before flange formation (φd): 35 mm
Inner diameter after flange formation (φD): 50 mm
Flange height (h): 5.0 mm
Plate thickness (t): 2.0mm
Hole expansion parameter (E): 1.43
As described above, the hole expansion parameter E is a guideline for occurrence of cracks, and is a value derived from the equation E = φD / φd. If the parameter E is large, cracks are likely to occur. There is a tendency.

As shown in Table 1, each sample of Examples 1 to 6 belonging to the technical scope of the present invention had Si of 0.15 mass% or less and C was 0.88 mass% or less. The ductility was increased and no cracks occurred during 10 experiments. Even when the number of experiments was increased to 100, no cracks occurred.
Moreover, since Si was 0.15 mass% or less in each sample of Comparative Examples 5 to 8, no crack was generated. In addition, although these materials do not generate cracks, as can be seen from Table 2 showing the results of the fatigue test of Example 2 described later, there are many cases where a sufficient rolling fatigue life cannot be obtained.
On the other hand, the samples of Comparative Examples 1, 2, and 4 were prone to cracking because of the large amount of C and Si and low ductility. In the sample of Comparative Example 3, although C was as small as 0.15% by mass, Si was as large as 0.2% by mass, so that cracking occurred.

Using the samples of Examples 1 to 6 and Comparative Examples 1 to 8 shown in Table 1 as materials, the steel plate made of these materials was subjected to the punching process → bending process described above and formed into a lace shape. After obtaining the intermediate material, heat treatment was performed to produce a race, which was used as a sample for this experiment.
The heat treatment was performed by the following two methods.
"Conditions for heat treatment (1)"
As described above, quenching was carried out by holding at 800 to 880 ° C. and oil cooling. Subsequently, tempering was performed at 160 to 250 ° C.
“Conditions for heat treatment (2)”
After carbonitriding by the method described above, quenching was performed at 800 to 880 ° C. after cooling. Subsequently, tempering was performed at 160 ° C to 250 ° C.
Table 2 shows the hardness, carbon concentration, nitrogen concentration, and retained austenite amount of the surface hardened layer formed on the surface of each race by the heat treatment.

A thrust roller bearing having an identification number of FH506502 (inner diameter = 65 mm, outer diameter = 85 mm, axial thickness = 4.81 mm, combining two races manufactured in this way, rollers, and a cage. A race plate thickness = 2 mm and a flange height = 0.81 mm) were produced, and a rolling fatigue test was performed on each of these thrust roller bearings under the following conditions to obtain a rolling fatigue life.
"Fatigue test conditions"
Load (P / C): 0.4
Rotational speed: 6000 min ^-1
Lubricating oil: ATF
Lubricating oil temperature: 120 ° C
Calculated life L _CAL : 60 hours (hr)
Hardness of foreign matter: 600 to 800 Hv
Foreign material size: 100 μm
Foreign matter was mixed only in the case of carbonitriding.

The results of fatigue tests performed under such conditions are shown in Table 2 below.

In the case of Examples 1 to 6 that were subjected to the heat treatment (1) and belong to the technical scope of the present invention, there was no contamination with foreign matter, and although the test was performed at a high temperature, as shown in Table 1, the oxygen concentration Is 15 ppm or less, a rolling fatigue life of 1.5 times or more of the calculated life L _CAL (60 hours) was obtained.
Further, among Examples 1 to 6, in the case of Examples 2 to 6 where the hardness of the surface hardened layer is 700 Hv or more, the rolling is even more favorable as being twice or more of the calculated life L _CAL (60 hours). A fatigue life was obtained.

On the other hand, in Comparative Examples 1 and 4, the oxygen concentration is high as shown in Table 1, but the hardness of the surface hardened layer is good, so that the rolling fatigue life is almost equal to the calculated life L _CAL (60 hours). Obtained.
In Comparative Examples 7 and 8, since the oxygen concentration was low as shown in Table 1, a rolling fatigue life longer than the calculated life L _CAL (60 hours) was obtained. In Comparative Examples 3, 5, and 6, since the hardness of the surface hardened layer was not sufficient, the rolling fatigue life was shorter than the calculated life L _CAL (60 hours). In addition, since the comparative example 2 is SUJ2, the hardness of the surface hardened layer was sufficient and the life was long.

Moreover, in the case of Examples 1-6 which performed the said heat processing (2) and belong to the technical scope of this invention, by performing a carbonitriding process, N is dissolved and the hardness of the said surface hardening layer, and Since the amount of retained austenite increases, a rolling fatigue life sufficiently longer than the calculated life L _CAL (60 hours) can be obtained even under the condition where the foreign matter is mixed. In particular, when the amount of retained austenite is in the range of 20 to 40% by volume as in Examples 1, 2, 4 to 6, a sufficient rolling fatigue life is often obtained.

On the other hand, Comparative Examples 1, 5, 7, and 8 had a rolling fatigue life shorter than the calculated life L _CAL (60 hours) because C was not sufficiently dissolved in the matrix and the amount of retained austenite was small. In Comparative Examples 3, 4, and 6, although the hardness of the surface hardened layer and the amount of retained austenite are large, the matrix is not strengthened. Indentation was likely to occur, and sufficient rolling fatigue life could not be obtained. In Comparative Example 2, since SUJ2 was carbonitrided, the hardness of the surface hardened layer was sufficient and the life was long.

As can be seen from Table 2 showing the results of the fatigue test conducted under the conditions as described above, it belongs to the technical scope of the present invention, that is, the composition of the alloy steel constituting the race, the oxygen concentration, and the surface hardened layer. Examples 1 to 6 in which all of the hardness, carbon concentration, nitrogen concentration, and retained austenite amount are within the range defined by the present invention have a longer rolling fatigue life than the calculated life L _CAL (60 hours). I can get it.
On the other hand, when any element deviates from the technical scope of the present invention as in Comparative Examples 1 to 6, a decrease in bending workability or a decrease in rolling fatigue life occurs. If only the result of the said Example 1 is seen, since the sample of Comparative Examples 5-8 shown in the said Table 1 does not have a crack, it has favorable workability, but the result of the said Example 2 is shown. As can be seen from Table 2 shown, sufficient rolling fatigue life cannot often be obtained. Further, Comparative Example 2 shown in Table 2 has a sufficient rolling fatigue life, but as can be seen from Table 1, the bending workability is low.

  As described above, according to the thrust roller bearing race of the present invention, it is possible to improve the bending workability by regulating the composition of the race. Furthermore, since the surface hardened layer is formed by heat treatment and the properties of the surface hardened layer are regulated, the life of the thrust roller bearing can be extended.

  The present invention is not limited to the thrust roller bearing as shown in FIG. 1 described above, but can be applied to various types of rolling bearings incorporated in a rotation support portion of a mechanical device or the like. For example, double row ball bearings, thrust ball bearings, (single row or double row) radial tapered roller bearings, thrust tapered roller bearings, and self-aligning roller bearings can be targeted.

DESCRIPTION OF SYMBOLS 1, 1a Thrust roller bearing 2 Roller 3, 3a Cage 4, 4a Outer ring race 5, 5a Inner ring race 6, 6a Outer ring raceway 7, 7a Ring portion 8 Outer flange 9, 9a Inner ring raceway 10, 10a Ring portion 11 Inside Flange 12a, 12b Element 13 Ring portion 14 Pocket

JP 2006-194292 A

Claims (4)

  A thrust roller bearing comprising a plurality of rollers arranged in a radial direction and at least one race made of a metal plate in a ring shape and having one axial side surface as a thrust raceway surface. C, 0.68 to 0.88 mass%, Si 0.01 to 0.15 mass%, Mn 0.2 to 0.7 mass%, and Cr 0.3 to 0.7 mass% A thrust roller bearing characterized by being made of alloy steel having an oxygen concentration of 15 ppm or less.   The thrust roller bearing according to claim 1, wherein the race has a thickness of 0.4 to 6.0 mm, a hardness of 100 to 300 Hv, and a surface roughness of 0.4 μmRa or less.   The lace has a surface hardened layer formed by performing quenching and tempering treatment, the hardness of the surface hardened layer is 650 to 850 Hv, and the surface roughness is 0.4 μmRa or less. 2. Thrust roller bearing described in 2. The lace has a surface hardened layer formed by performing a quenching and tempering treatment after carburizing or carbonitriding, and this surface hardened layer has a C of 0.8 to 1.2. In addition to containing 0.05 to 0.50 mass% of N, the hardness is 700 to 900 Hv, the retained austenite amount γ _R is 15 to 45 vol%, and the surface roughness is 0.4 μmRa or less. The thrust roller bearing according to claim 2, wherein the thrust roller bearing is provided.

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