Rolling bearing and method manufacturing the same

Details Rolling bearing and method manufacturing the same Rolling bearing and method manufacturing the same

2000-12-14

2003-02-11

Yee, Deborah (Department: 1742)

Metal treatment

Stock

Ferrous

C148S906000, C148S589000, C148S334000, C148S335000, C148S328000, C148S320000, C492S055000

Reexamination Certificate

active

06517644

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a rolling bearing, in particular a rolling bearing suitable for engine auxiliary machines (alternator, electromagnetic clutch or intermediate pulley), and also relates to a method for manufacturing the same.
Conventionally, SUJ2 (high carbon chromium bearing steel—2nd category) has mainly been employed as materials of bearing rings and rolling elements of rolling bearings.
Recently, in company with making automobiles small sized and light weight, auxiliary machines of engines have also been demanded to provide high performance and high output together with making the small size and the light weight. For example, bearings for alternators are subjected to high vibration or high load (around 4 G to 20 G at the acceleration of gravity) through belts accompanying rotation of high speed simultaneously with working of the engine. Therefore, in the conventional bearing for the alternator, a problem has been present that exfoliation (so called as a premature peeling) is easy to occur at an premature period of service especially in the bearing face of the outer ring being a stationary ring.
There have been proposed many techniques for preventing the premature peeling/exfoliation so as to lengthen the life of the bearing to be served under the high vibration and high load.
For example, Japanese Patent Unexamined Publication No. Hei.4-28845 proposes the use of a steel containing low carbon (C) (0.65 to 0.90%) and high chromium (Cr) (2.0 to 5.0%) in comparison with SUJ2 which has hitherto been used. This publication discusses that the premature exfoliation is caused by generation of a white structure in steel which occurs by cohesion of carbon. Thus, by employing the above mentioned steel, the carbon is prevented from diffusion to be a cause of cohesion for attaining the long life.
Japanese Patent Unexamined Publication No. Sho.62-218542 proposes the technology that a blank material is made by adding Al or Si to SUJ2 or a steel following it to be 1 to 2% therein, a bearing ring is formed with this blank material, followed by an ordinary quenching and a tempering at high temperature, thereby decreasing a residual austenite to be 8 vol % or lower. According to this art, a softening resistance by tempering is heightened by adding Al or Si. By decreasing the residual austenite, it is possible to reduce a plastic deformation in the bearing face under the high vibration and high load. Thereby, the hardness in the bearing ring is maintained high to prevent the premature exfoliation for attaining the long life.
Further, Japanese Patent Examined Publication No. Hei.7-72565 discloses that the stationary ring formed with SUJ2 is carried out with the ordinary quenching and then a subzero treatment, followed by the high temperature tempering, for reducing the residual austenite to be 10 vol % or lower in the stationary ring. That is, by reducing the residual austenite in the stationary ring, the hardness in the bearing ring is maintained high to lower the plastic deformation in the bearing face of the stationary ring under the high vibration and high load to reduce the premature exfoliation.
However, the circumstances of using rolling bearing for engine auxiliary machines have recently been severer. Therefore, a problem has arisen that the technology set forth in JP-A-4-28845 could not sufficiently check the appearance of the white structure.
A further problem is that since the arts of Japanese Patent Examined Publication No. Hei.7-72565 and Japanese Patent Unexamined Publication No. Sho.62-218542 reduce the residual austenite by the tempering of high temperature, the hardness over the entire bearing ring is lowered accordingly. If the blank material is a steel of high Al or Si as 1 to 2%, oxides based inclusions are easily formed and a rolling fatigue life is probably shortened.
SUMMARY OF THE INVENTION
The invention has been realized, paying attentions to the problems of the prior arts, and accordingly it is an object of the invention to provide a rolling bearing served under the conditions of high vibration and high load, in which the premature exfoliation is prevented and a long life of the bearing is possible, and also to provide a method for manufacturing the same.
For accomplishing the above mentioned problems, the rolling bearing of the invention is characterized in that at least the stationary ring (the bearing ring of an inner ring and an outer ring, which is at a stationary side when using) is fabricated with a steel material containing as alloying elements carbon (C) 0.80 to 1.10 wt %, silicon (Si) 0.20 to 0.50 wt %, manganese (Mn) 0.2 to 1.0 wt %, and further containing any two kinds or more of chromium (Cr), molybdenum (Mo) and vanadium (V) at rates of Cr: 1.2 to 3.5 wt %, Mo: 0.5 to 1.5 wt % and V: 0.2 to 1.0 wt %, the containing rates of Cr, Mo and V satisfying the under mentioned formula (1), subsequently subjecting to the quenching and the tempering.
1.8≦[
Cr
]×0.6+[
Mo
]×
0.5+[
V
]≦3.0  (1)
(in the formula, [Cr] shows the containing rate (wt %) of Cr in the steel material, [Mo] shows the containing rate (wt %) of Mo in the steel material, and [V] shows the containing rate (wt %) of V in the steel material).
The above-mentioned object can also be achieved by a rolling bearing according tot he present invention comprising:
a stationary ring;
a rotating ring; and
a plurality of rolling elements disposed between the stationary ring and the rotating ring,
wherein the stationary ring is made of a steel material containing,
0.80 to 1.10% by weight of C,
0.20 to 0.50% by weight of Si,
0.20 to 1.0% by weight of Mn,
and further containing any two kinds or more of
1.2 to 3.5% by weight of Cr,
0.5 to 1.5% by weight of Mo, and
0.2 to 1.0% by weight of V wt %, and wherein containing rates of Cr, Mo and V satisfying a following formula (1),
1.8≦[
Cr
]×0.6+[
Mo
]×0.5+[
V
]≦3.0  (1)
where, [Cr] defines the containing rate (wt %) of Cr in the steel material, [Mo] indicates the containing rate (wt %) of Mo in the steel material, and [V] denotes the containing rate (wt %) of V in the steel material,
wherein the steel material is subsequently subjected to quenching and tempering.
In addition to this, the above-mentioned object can further be achieved by a method for manufacturing a component of rolling bearing comprising a stationary ring, a rotating ring and a plurality of rolling elements disposed between the stationary ring and the rotating ring, the method according to the present invention comprising:
forming a blank stationary ring with a steel material containing, as alloying elements
0.80 to 1.10% by weight of C,
0.20 to 0.50% by weight of Si, and
0.20 to 1.0% by weight of Mn,
and further containing any two kinds or more of
1.2 to 3.5% by weight of Cr,
0.5 to 1.5% by weight of Mo, and
0.2 to 1.0% by weight of V wt %, and wherein containing rates of Cr, Mo and V satisfying a following formula (1),
1.8≦[
Cr
]×0.6+[
Mo
]×0.5+[
V
]≦3.0  (1)
where, [Cr] defines the containing rate (wt %) of Cr in the steel material, [Mo] indicates the containing rate (wt %) of Mo in the steel material, and [V] denotes the containing rate (wt %) of V in the steel material;
quenching thus formed blank stationary ring;
tempering thus quenched blank stationary ring, to thereby provide the stationary ring.
In the rolling bearing of the invention, as the steel material for fabricating at least the stationary ring, the material contains any two kinds or more of Cr, Mo and V at the above mentioned rates such that the above formula (1) is satisfied. Thereby, lots of carbides different in kinds and sizes are diffused and precipitated in the steel after the heat treatment (quenching and tempering). These carbides check the diffusion of carbon, so that the appearance of the white struc

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