JPH09228009A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stillness of a rolling bearing. SOLUTION: This is a ball bearing 1 provided with inner and outer both rings 2 and 3 and plural balls 4 arranged between the inner and outer both rings 2 and 3. The inner and outer both rings 2 and 3 and the balls 4 are respectively formed of steel contg., by weight, 0.60 to 0.80% C, 0.10 to 0.80% Si, 0.85 to 1.25% Mn and 9.0 to 14.0% Cr, and the balance Fe with inevitable impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as, for example, a spindle motor bearing incorporated in a hard disk drive device, a floppy disc device or the like, or a cylinder bearing incorporated in a video tape recorder, a digital audio tape recorder or the like. , A rolling bearing that requires quietness.

[0002]

2. Description of the Related Art Conventionally, as this type of rolling bearing, both the inner and outer wheels and rolling elements have C 0.60 to 0.80 wt% and Si 0.10 to 0.8, respectively.
0 wt%, Mn 0.30 to 0.80 wt% and Cr10.
It is known that a steel containing 5 to 13.5 wt% and the balance Fe and inevitable impurities is formed (Japanese Patent Publication No.
-2734).

However, in the above electric equipment, in recent years, the operating conditions of bearings have been increasing in the direction of increasing load load and increasing ambient temperature, and the above-mentioned conventional rolling bearings are operating under high load conditions. Causes microscopic indentation on the rolling surface, and under high temperature use conditions, the rolling surface becomes rough due to aging, resulting in insufficient quietness. It should be noted that the occurrence of such indentations and roughness on the raceway surface is particularly noticeable on the rotation side race ring.

Therefore, the inventors of the present invention have conducted various experiments and researches to find out the cause of the above-mentioned problems in the conventional rolling bearings, and as a result, the conventional steel has poor thermal stability of retained austenite. Therefore, it was found that the above-mentioned problem occurs. That is, if the thermal stability of the retained austenite is poor, the retained austenite in the structure of the steel may be decomposed due to the repeated stress load caused by the rolling elements passing through, and the surface accuracy of the raceway surface may decrease.
Further, when a preload of a light load is applied or an impact load is applied, residual austenite in the structure of steel is decomposed and an indentation may occur on the raceway surface. Then, the acoustic characteristics of the rolling bearing are easily affected by the deterioration of the surface accuracy on the raceway surface and the impression, and as a result, the quietness is deteriorated.

The object of the present invention is to solve the above problems and to improve the quietness as compared with the conventional rolling bearing even when used under high load and high temperature, when used with preload, when subjected to impact load, etc. It is to provide a rolling bearing.

[0006]

A rolling bearing according to the present invention is a rolling bearing provided with both inner and outer wheels and a plurality of rolling elements arranged between both inner and outer wheels, and at least the rotating side of both the inner and outer wheels and rolling elements. The bearing ring is C0.60
0.80 wt%, Si 0.10 to 0.80 wt%, Mn0.
It is formed of steel containing 85 to 1.25 wt% and 9.0 to 14.0 wt% Cr and the balance Fe and unavoidable impurities.

The reasons for limiting the alloy components in the above steel are as follows.

C: 0.60 to 0.80 wt% C has the property of increasing the quenching hardness, but if its content is less than 0.60 wt%, the quenching hardness becomes insufficient, There is a problem that wear resistance becomes insufficient and load capacity becomes small. On the other hand, when the content of C exceeds 0.80 wt%, a huge eutectic carbide is formed, and when it appears on the surface, the quietness of the rolling bearing is significantly reduced. That is, when a giant eutectic carbide appears on the surface, the precision of the finished surface is reduced, and the quietness is reduced in the initial stage of use, and due to the difference in wear resistance between the giant eutectic carbide and the surrounding portion. Quietness is reduced due to the surface shape being disturbed by use, or the giant eutectic carbide being cracked and falling off by use. Moreover, the rolling fatigue life of the rolling bearing is shortened, and the deformation resistance is increased to deteriorate the workability, especially the cold workability. Therefore, the content of C should be selected within the range of 0.60 to 0.80 wt%, and particularly preferably within the range of 0.65 to 0.75 wt%.

Si: 0.10 to 0.80 wt% Si has the property of shortening the time required for deoxidation in the steelmaking process, but if its content is less than 0.10 wt%, deoxidation takes a long time. Costly. On the other hand, if the Si content exceeds 0.80 wt%, the cleanliness of the steel is impaired, and the toughness decreases and the workability, especially cold workability, deteriorates. Therefore, the Si content is 0.10 to 0.80.
It should be selected within the range of wt%, but especially 0.20 to 0.
It is preferably in the range of 60 wt%.

Mn: 0.85-1.25 wt% Mn generally has the property of improving the hardenability and increasing the hardness of the steel after quenching. For this reason, Mn has the property of enabling tempering at a higher temperature, reducing the structural change during aging treatment, improving the accuracy of size and shape, and consequently improving the quietness of the rolling bearing. Further, Mn has the property of improving the thermal stability of the retained austenite and suppressing the decomposition of the retained austenite, thereby contributing to the maintenance of the surface accuracy of the raceway surface and improving the quietness of the rolling bearing. The present invention has been made with particular attention to the property of Mn to improve the thermal stability of retained austenite. However, the Mn content is 0.85 wt%
If it is less than the above range, the above effect is reduced. On the other hand, if the Mn content exceeds 1.25 wt%, the amount of retained austenite after quenching increases, the amount of retained austenite after tempering also increases, and the microstructural change during aging treatment increases, resulting in dimensional and shape accuracy. Deteriorates, and as a result, the quietness of the rolling bearing decreases. In addition, when the amount of retained austenite after tempering is large, the hardness becomes low, the material is easily worn and deformed, and the quietness of the rolling bearing is deteriorated. Therefore, the content of Mn should be selected within the range of 0.85 to 1.25 wt%, and particularly preferably within the range of 0.85 to 1.05 wt%.

Cr: 9.0 to 14.0 wt% Cr has the property of increasing the hardness of steel and improving the corrosion resistance, but if the content is less than 9.0 wt%, the above effects are reduced. On the other hand, the content of Cr is 14.0.
If it exceeds wt%, a huge eutectic carbide is formed, and the quietness of the rolling bearing is significantly reduced for the same reason as described for C. Moreover, the rolling fatigue life of the rolling bearing is shortened, and the deformation resistance is increased to deteriorate the workability, especially the cold workability. Therefore, the Cr content is 9.0.
〜14.0wt% should be selected, especially 1
It is preferably in the range of 0.0 to 13.0 wt%.

According to the rolling bearing of the present invention, at least the inner and outer wheels and the race ring on the rotating side of the rolling elements are made of the above-mentioned steel, so that the rolling bearing is quieter than the conventional one. improves.

In the above-mentioned rolling bearing, it is possible to further contain 0.20 to 2.0 wt% of Mo in the steel forming at least the rotating side race ring of both the inner and outer wheels and the rolling elements. Mo has the property of improving hardenability and corrosion resistance, but if its content is less than 0.20 wt%, its effect cannot be obtained, and if it exceeds 2.0 wt%, the effect of improving hardenability and corrosion resistance is obtained. Will not be better and will be more expensive. Therefore, the content of Mo is 0.
It should be selected within the range of 20 to 2.0 wt%, but particularly preferably within the range of 0.30 to 1.50 wt%.

Further, in the above rolling bearing, it is preferable that the residual austenite amount of steel is 7 vol% or less. If the amount of retained austenite exceeds 7 vol%, the hardness decreases due to the relative proportion with the martensite phase in the parent phase, and it becomes easy to wear, and indentation also easily occurs, and the quietness of the rolling bearing decreases. There is a risk.

In the rolling bearing of the present invention, both the inner and outer wheels and the rolling elements may be made of the above steel. In this case, the quietness is further improved as compared with the case where only the bearing ring on the rotation side is made of the above steel.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
This will be described with reference to the drawings.

FIG. 1 shows a ball bearing to which the present invention is applied.

In FIG. 1, the ball bearing (1) is the inner ring (2).
And an outer ring (3), and a plurality of balls (4) arranged between the inner and outer wheels (2) and (3). Inner ring (2), outer ring (3) and balls (4)
Are C 0.60 to 0.80 wt% and Si 0.10, respectively.
~ 0.80 wt%, Mn 0.85-1.25 wt% and C
steel containing r9.0 to 14.0 wt% and the balance Fe and unavoidable impurities, or Mo 0.20 to 2.0.
It is made of steel containing wt%.

The inner and outer wheels (2) (3) and the balls (4) are manufactured, for example, by the following method. That is, the inner and outer wheels (2) (3) are
After turning from the bar made of the above steel into the shape of both inner and outer wheels (2) and (3), the quenching temperature is 1020 to 1070 ° C, and the deep treatment temperature is −
It is manufactured by heat treatment under the conditions of 60 to -80 ° C and tempering temperature of 150 to 180 ° C, and further subjected to final polishing finish. Balls (4) are manufactured by cold forging a bar made of the above steel into a spherical shape, then subjecting it to the same heat treatment as in the case of both inner and outer wheels (2) and (3), and then applying a final polishing finish. To be done.

[0020]

EXAMPLES Specific examples of the present invention will be described below together with comparative examples.

[0021]

[Table 1] Eight types of steel having the compositions shown in Table 1 were used to produce both inner and outer wheels (2), (3) and balls (4) from each steel, and eight types of No. 600 series ball bearings (1) were produced. Both inner and outer wheels (2) and (3) were turned from a bar made of each steel into the shape of both inner and outer wheels (2) and (3), then the quenching temperature was 1050 ° C, the cryogenic treatment temperature was -60 ° C, and the tempering temperature was 1
It was manufactured by performing a heat treatment at 65 ° C. and further performing a final polishing finish. The balls (4) are manufactured by cold forging a bar made of each steel into a spherical shape, then subjecting it to the same heat treatment as for the inner and outer wheels (2) and (3), and then applying a final polishing finish. did. The surface hardness (Rockwell C hardness (HRC)) and the amount of retained austenite of the inner and outer wheels (2) (3) and the ball (4) are shown in Table 1, respectively.

Evaluation test 1 First, an arbor was inserted into the inner ring (2) of the ball bearing (1) made of each steel, and the outer ring (3) was rotated at a speed of 1800 rpm with a preload of 0.75 kgf in the thrust direction. The sound value was measured by rotating and picking up in the arbor. This is the acoustic value before being left at high temperature. Then, the acoustic value ratio when the acoustic value of the ball bearing made of steel of Comparative Example 3 was set to 1 was obtained. Then, the test jig (1
Two ball bearings (1) made of each steel were set in (0). The test jig (10) consists of a housing (11), a sleeve (12), a compression coil spring (13), and a shaft (14) with an external thread (14a).
And a nut (15) that is screwed into the male thread (14a) of the shaft (14) .The ball bearing (1) is screwed into the sleeve (12) and the spring (13). A predetermined thrust load is applied as a preload via the. Then, as a preload, a thrust load of 0.24C ₀ was applied to the ball bearing (1), and in this state, 2
After holding for 0 hour, the ball bearing (1) was removed from the test jig (10), and the acoustic value was measured by the same method as above. This is the acoustic value after being left at a high temperature. Next, the acoustic value ratio when the acoustic value before high temperature leaving of the ball bearing made of the steel of Comparative Example 3 was set to 1 was obtained. Here, C ₀ represents the static load rating of the ball bearing (the same applies hereafter). The test results are shown in FIG.

As is clear from FIG. 3, the acoustic value after being left at high temperature is higher than the acoustic value before being left at high temperature in all ball bearings, but the Mn contents are 0.70 wt% and 0.80 wt%. Whereas in the ball bearings of Comparative Examples 1 and 3 and the ball bearing of Comparative Example 2 in which the Mn content is 1.35 wt%, the acoustic value after being left at high temperature is about twice the acoustic value before being left at high temperature. , Mn content is 0.89 to 1.23
In the ball bearings of Examples 1 to 5 with wt%, the acoustic value after being left at high temperature was as small as about half that of Comparative Examples 1 to 3. Further, although indentations having a maximum depth of 0.02 μm were observed on the raceway surface of the bearing ring of the ball bearing made of the steel of Comparative Example 3 after being left at a high temperature, the ball bearings made of the steel of Examples 1 to 5 were observed. No indentation was observed on the raceway surface of the bearing ring after being left at high temperature. The reason why these results were obtained is that by increasing the Mn content, the thermal stability of retained austenite in the steel forming the bearing ring and balls under a constant load (such as a kind of micro creep) It is considered that this is because the resistance to the phenomenon) and, by extension, the thermal stability of the parent phase composed of the martensite phase and the retained austenite phase under a constant load is excellent. In the ball bearing made of the steel of Comparative Example 2 having a Mn content of 1.35 wt%, the acoustic value after being left at a high temperature is large because the retained austenite amount is 7.8 vol%.
It is considered that this is because the proportion of the low hardness phase in the matrix phase increased, so that abrasion and indentation were likely to occur. As described above, this evaluation test revealed that there is an appropriate value of the Mn content that can reduce the increase in the acoustic value due to being left at high temperature as compared with the cases of Comparative Examples 1 to 3.

Evaluation Test 2 Similar to Evaluation Test 1 above, two ball bearings (1) made of each steel shown in Table 1 were set on the test jig (10) shown in FIG. A thrust load of 0.24 C ₀ was applied as a preload to the shaft, and the shaft (14) was rotated for 100 hours in an oven at an ambient temperature of 60 ° C. and a rotation speed of 3200 rpm. Then, the ball bearing (1) was removed from the test jig (10), and the acoustic value was measured by the same method as in the above evaluation test 1. This is the acoustic value after rotation. Next, the acoustic value ratio of the ball bearing made of the steel of Comparative Example 3 when the acoustic value before high temperature standing in the above evaluation test 1 was set to 1 was determined. The acoustic value before being left at high temperature in the evaluation test 1 is the same as the acoustic value before rotation. The test results are shown in FIG.

As is clear from FIG. 4, in the ball bearings of Examples 1 to 5 in which the Mn content was 0.89 to 1.23 wt%, almost no change in the acoustic value due to the rotation test was observed. On the other hand, the Mn contents are 0.70 wt% and 0.80 wt%
%, The ball bearings of Comparative Examples 1 and 3 and the ball bearing of Comparative Example 2 having a Mn content of 1.35 wt% had a post-rotation acoustic value increased by about 30% of the pre-rotation acoustic value. The reason why such a result was obtained is that by increasing the Mn content, decomposition of retained austenite due to cyclic stress loading caused by balls passing through the bearing ring is suppressed,
It is considered that this is because the surface precision of the raceway surface did not deteriorate. That is, this is also one of the effects of increasing the thermal stability of retained austenite by increasing the Mn content.

Further, it is known that the hardness is increased by increasing the Mn content ("Steel and alloy elements (above)", P488, Japan Society for the Promotion of Science, Steelmaking 19th Committee, 1971). Issued by Seibundo Shinkosha). Therefore, tempering at a higher temperature is possible to obtain a certain required hardness. That is, when the Mn content is increased, the microstructural change is small up to a higher temperature. In the evaluation test 2, it is estimated that the temperature near the contact surface between the ball and the bearing ring rises considerably during the test, and the surface accuracy deteriorates due to the microstructure change due to this temperature rise, which causes the deterioration of the acoustic value after the test. However, if the Mn content is increased, the deterioration of the acoustic value due to the deterioration of the surface accuracy is also suppressed.
In the ball bearing made of the steel of Comparative Example 2 having a Mn content of 1.35 wt%, the acoustic value after rotation was large because the retained austenite amount was as high as 7.8 vol%,
It is considered that this is because the proportion of low hardness phase was increased, so that abrasion and indentation were easily generated.

Evaluation Test 3 A ball bearing made of each steel shown in Table 1 is loaded with a thrust load of 0 to
The load was increased by about 5 kgf in the range of 0.8 C ₀ kgf (the load time at each load was 10 seconds), and the acoustic value of the ball bearing at each load was measured in the same manner as in Evaluation Test 1 above. . Then, at each load, the acoustic value ratio was calculated when the acoustic value when the thrust load of the steel ball bearing of Comparative Example 3 was 0 was set to 1. The result is shown in FIG.
Shown in

As is apparent from FIG. 5, the Mn content of 0.
In the ball bearings of Examples 1 to 5, which are 89 to 1.23 wt%,
The acoustic value did not change so much until the thrust load was 0.6 C ₀ , and started to increase at 0.7 C ₀ or higher. On the other hand, in the ball bearings of Comparative Examples 1 and 3 having Mn contents of 0.70 wt% and 0.80 wt% and the ball bearing of Comparative Example 2 having Mn content of 1.35 wt%, 0.2 to 0. The acoustic value has already begun to increase with a thrust load of 3C ₀ . Thus, it was found that there is an appropriate value for the Mn content with respect to the load bearing capacity of the acoustic value. The effect of Mn content on load bearing can be explained by solid solution hardening and increase in work hardening rate of retained austenite itself. The Mn content is 1.35 wt.
%, The acoustic value after rotation is large in the ball bearing made of the steel of Comparative Example 2, which is 7.8 vol% of retained austenite, and the proportion of low hardness phase increases, resulting in wear and indentation. It is considered that this is because the occurrence of the phenomenon becomes easier.

Evaluation Test 4 Of the eight types of steel shown in Table 1, test pieces were formed from the steels of Example 3 and Comparative Example 3, respectively, and subjected to a JIS Z2371 salt spray test and a JIS K2246 wetting test to rust. The corrosion resistance was examined by measuring the area ratio of the parts. The test conditions are as shown in Table 2.

[0030]

[Table 2] The results of the salt spray test are shown in Table 3.

[0031]

[Table 3] As is clear from Table 3, the test piece made of the steel of Example 3 and the test piece made of the steel of Comparative Example 3 have almost the same area ratio of the rusted portion and have the same corrosion resistance. I understand.

Further, as a result of the wet test, no rusting was observed in the test piece made of the steel of Example 3 and the test piece made of the steel of Comparative Example 3, and it was judged that the corrosion resistance was the same for both. .

Evaluation test 5 Of the eight types of steel shown in Table 1, cylindrical rollers were formed from the steels of Example 3 and Comparative example 3, respectively, and heat treatment conditions for manufacturing both the inner and outer wheels and balls in the above evaluation test 1 were used. The heat treatment was performed under the same conditions as in. The surface hardness is the same as in Table 1. Then, a rolling life test was conducted under the conditions shown in Table 4 using a rolling life tester. A load was applied to the cylindrical roller by a coil spring via upper and lower rolls and a load roller. The cylindrical roller was rotated by rotating the drive roll with an electric motor. FIG. 6 shows the result.

[0034]

[Table 4] As is clear from FIG. 6, the cylindrical roller made of the steel of Example 3 and the cylindrical roller made of the steel of Comparative Example 3 have almost the same L ₁₀ life, and it is determined that the rolling life is the same for both. To be done.

[0035]

According to the rolling bearing of the present invention, as described above, the acoustic characteristics can be sufficiently enhanced by setting the Mn content to the newly found proper value.
Therefore, the quietness of the rolling bearing is improved as compared with the conventional one. Moreover, the corrosion resistance, rolling life, surface hardness, etc. are the same as conventional ones.

[Brief description of drawings]

FIG. 1 is a partially enlarged vertical sectional view of a ball bearing showing an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a state in which a ball bearing is set on a test jig used for an evaluation test.

FIG. 3 is a graph showing the results of evaluation test 1.

FIG. 4 is a graph showing the results of evaluation test 2.

FIG. 5 is a graph showing the results of evaluation test 3.

FIG. 6 is a graph showing the results of evaluation test 5.

[Explanation of symbols]

 (1) Ball bearing (2) Inner ring (3) Outer ring (4) Ball

Claims (3)

[Claims] 1. A rolling bearing provided with both inner and outer wheels and a plurality of rolling elements arranged between both inner and outer wheels, wherein at least the rotation-side bearing ring of both the inner and outer wheels and rolling elements has a C0.60 to 0.80 wt. %, Si 0.10 to 0.8
0 wt%, Mn 0.85-1.25 wt% and Cr 9.0
A rolling bearing made of steel containing ˜14.0 wt% and the balance Fe and unavoidable impurities. 2. The steel forming at least the rotation-side bearing ring of both the inner and outer wheels and the rolling elements further contains 0.20 Mo.
The rolling bearing according to claim 1, wherein the rolling bearing contains ˜2.0 wt%. 3. The rolling bearing according to claim 1, wherein the retained austenite amount of steel is 7 vol% or less.