JPH05125488A - Bearing parts - Google Patents

Abstract

PURPOSE:To provide superior toughness and sufficient surface hardness, to improve rolling fatigue life, and also to obtain excellent damping characteristic. CONSTITUTION:The parts are composed of a high damping steel having a composition consisting of, by weight, 0.2-0.6% C, 5.0-15.0% Cr, 0.2-1.3% Si, and the balance Fe with inevitable impurities. A hardened layer is formed on the surface of the above by means of carburizing treatment or carbonitriding treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing component such as a rolling element or a bearing ring of a bearing which is required to have a high vibration damping property.

[0002]

2. Description of the Related Art In recent mechanical devices, high performance,
Along with high precision, quietness is also an important factor in quality evaluation, and there is an increasing demand for bearings to cope with this quietness.

In order to obtain a bearing that meets the above requirements, C0.64 to 0.80% by weight and Cr5.0 to 10.
A bearing component containing 0% by weight, 0.20 to 0.90% by weight of Si, and the balance Fe and unavoidable impurities has been proposed (see Japanese Patent Laid-Open No. 2-93041).

[0004]

However, a bearing provided with the above-mentioned bearing component can obtain high vibration damping property, but under the condition that foreign matter is mixed in the lubricating oil such as a transmission. However, there is a problem that sufficient rolling fatigue life cannot be obtained when used in. That is, since the hardness of the above steel after normal quenching and tempering is as low as about 61 at the Rockwell C hardness (HRC) at the maximum, indentation is generated on the raceway due to the mixed foreign matter. When the rolling element passes through the indented portion, stress concentrates on the indented portion, and microcracks, which are the starting points of peeling, are generated and easily propagate, which shortens the rolling fatigue life.

An object of the present invention is to provide a bearing component that solves the above problems.

[0006]

A bearing component according to the present invention contains C0.2 to 0.6% by weight, Cr 5.0 to 15.0% by weight, Si 0.2 to 1.3% by weight, and the balance. It is made of damping steel made of Fe and unavoidable impurities, and has a hardened layer formed on its surface by carburizing or carbonitriding.

The reasons for limiting the alloy components are as follows.

C: 0.2 to 0.6% by weight If the content of C is less than 0.2% by weight, the carburizing treatment time and the carbonitriding treatment time become long, and the heat treatment productivity decreases. That is, in order to obtain a predetermined surface hardness, the C concentration in the hardened layer must be a certain value or more, but if the C content is less than 0.2% by weight, a long time is required for that. Moreover, carbonitriding case of processing, it is necessary to C content in the steel to increase the processing temperature if an attempt shorten a is despite treatment time less than 0.2 wt%, NH ₃
The decomposition rate of gas is so high that nitriding is not sufficiently performed, and the penetration depth is shallow, and sufficient hardness cannot be obtained. On the other hand, if the C content exceeds 0.6% by weight, in the steel containing the above amount of Cr, giant carbides are likely to be generated, sufficient toughness cannot be obtained, and microcracks that are the starting points of peeling occur, The rolling fatigue life is shortened due to easy progress. Moreover, the internal friction value decreases as the C content increases, and the vibration damping property is impaired. Therefore, the C content should be selected within the range of 0.2 to 0.6% by weight.

Cr: 5.0 to 15.0% by weight Cr has the property of improving the vibration damping property, but if the content of Cr is less than 5.0% by weight, this effect cannot be obtained.
If it exceeds 5% by weight, giant carbides are likely to be formed, sufficient toughness cannot be obtained, and microcracks that are the starting points of peeling tend to occur and propagate, resulting in a shorter rolling fatigue life. Therefore, C
The r content should be selected within the range of 5.0 to 15.0% by weight, preferably about 10% by weight.

Si: 0.2 to 1.3% by weight Si is an element necessary for deoxidation at the time of steel making, and is effective for extending the life of the bearing by improving solid solution strengthening and resistance to temper softening. Is an element. If the deoxidation is insufficient, oxide-based non-metallic inclusions increase, which serves as a stress concentration source to generate and propagate microcracks that act as the origin of peeling, leading to a reduction in rolling fatigue life. However, the Si content is 0.2
If it is less than wt%, deoxidation during steelmaking will not be carried out sufficiently,
If it exceeds 1.3% by weight, the mechanical strength is lowered and the carburizing and carbonitriding properties are lowered, and further, the workability such as forgeability and machinability is lowered. Therefore, S
The i content should be chosen within the range of 0.2 to 1.3% by weight.

Further, in the present invention, Mn, Cu, Ni, Mo and the like may be contained within a range that does not impair the characteristics of the above steel.

In the above, the surface hardness of the hardened layer is preferably about 63 to 65 in terms of Rockwell C hardness (HRC).

[0013]

Function: C 0.2 to 0.6% by weight, Cr 5.0 to 15.
0% by weight, Si 0.2 to 1.3% by weight, balance F
Since it is made of vibration-damping steel containing e and unavoidable impurities, the time required for carburizing or carbonitriding can be shortened and excellent toughness and vibration-damping properties can be obtained. In addition, since a hardened layer is formed on the surface by carburizing or carbonitriding, high surface hardness is obtained, and it is sufficient under conditions where foreign matter is mixed in lubricating oil such as transmission. A long rolling life can be obtained.

[0014]

EXAMPLES Examples of the present invention will be shown below together with comparative examples.

Six kinds of steels having the compositions shown in Table 1 were prepared, and the bearing rings of the rolling bearings were made from the steels by the usual method, and each bearing ring was also subjected to the heat treatment shown in Table 1. Then, the Rockwell C hardness (HRC) of the surface was measured. The results are also shown in Table 1.

[0016]

[Table 1]

The heat treatment conditions in the heat treatment column of Table 1 are as follows.

Carbonitriding and quenching: Carburizing at 930 ° C for 3 hours, nitriding at 850 ° C for 5 hours, oil cooling, and tempering at 180 ° C for 2 hours.

Normal quenching 1 ... Heating at 840 ° C. for 40 minutes to austenite, cooling with oil, and then tempering at 180 ° C. for 2 hours.

Carburizing and quenching ... Carburizing treatment at 930 ° C. for 4.5 hours, heating at 820 ° C. for 20 minutes and oil cooling, and then 180
Tempering for 2 hours at ℃.

Normal quenching 2 ... Heating at 970 ° C. for 40 minutes to austenite, oil cooling, then deep cooling treatment, and then tempering at 180 ° C. for 2 hours.

As is clear from Table 1, the surface hardness of Examples 1 and 2 is higher than the surface hardness of Comparative Examples 1 to 4.

Next, Examples 1, 2 and Comparative Examples 1, 3,
No. 4 bearing ring, cage made of SPB1 and SUJ2
Assembling a bearing using a rolling element consisting of a turbine oil VG68 containing 0.05% by weight of bearing steel powder having a particle diameter of about 100 μm as a lubricating oil, a radial load of 918 kgf,
A life test was conducted at a rotation speed of 2500 rpm. The result is shown in FIG. As is apparent from FIG. 1, the life of the bearings using the bearing rings of Examples 1 and 2 is much longer than the life of the bearings using the bearing rings of Comparative Examples 2 to 4. For example, when the bearing ring of Example 1 is used, it is about three times as large as when the bearing ring of Comparative Example 2 is used.

Further, vibration damping of each of the above bearings was examined by a rotation test. The vibration damping was obtained from the vibration input by the hammering of the rotating shaft and the output ratio (transfer function) from the pickup attached to the housing. The test conditions are
The preload is 2.5 kgf.cm and the rotation speed is 1000 rpm. The test results are shown in FIGS. 2 and 3. FIG. 2 shows the results of comparison between Example 1 and Comparative Examples 2 and 3, and FIG. 3 shows the results of comparison between Example 2 and Comparative Examples 2 and 4. Example 1 from FIG. 2 and FIG.
The vibration damping effect of the bearings using the bearing rings 2 and 2 is superior to the vibration damping effect of the bearings using the bearing rings of Comparative Examples 2 to 4. That is, 10d at maximum in the range of 2-3 kHz
About B, the damping effect is excellent.

[0025]

The bearing component of the present invention, as described above,
Since it has excellent toughness and sufficient surface hardness, rolling fatigue life is improved. Moreover, excellent vibration damping property is obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a life test result.

FIG. 2 is a graph showing vibration damping by a rotation test.

FIG. 3 is a graph showing vibration damping by a rotation test.

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Claims (1)

[Claims] 1. C0.2 to 0.6% by weight, Cr5.0 to
15.0% by weight, Si 0.2-1.3% by weight,
Made of damping steel consisting of balance Fe and unavoidable impurities,
Bearing parts that have been carburized or carbonitrided to form a hardened layer on the surface.