Bearing component

Details Bearing component Bearing component

1996-09-06

1999-06-01

Zimmerman, John J.

Metal treatment

Stock

Ferrous

420 11, 428544, 384912, C22C 3800, C22C 3822, C22C 3812

Patent

active

059085150

DESCRIPTION:

BRIEF SUMMARY
This application has been filed under 35 U.S.C. 371 from PCT International Application PCT/JP94/02149, filed on 20 Dec. 1994.


TECHNICAL FIELD

The present invention relates to bearing components for use in anti-friction bearings as bearing rings or rolling elements.


BACKGROUND ART

Conventionally, bearing components are prepared from high-carbon chromium steels typical of which is, for example, JIS SUJ2.
However, JIS SUJ2 has a great carbon content and therefore has the problem of being poor in workability and costly. Further because the carbide resulting from hardening and tempering is relatively great in particle size, the steel has another problem of being liable to fluctuations in life.
An object of the present invention is to provide a bearing component which is free of the above problems.


DISCLOSURE OF THE INVENTION

The present invention provides a bearing component made from a steel comprising 0.6 to 0.8 wt. % of C, 0.05 to 0.25 wt. % of Si, 0.2 to 0.9 wt. % of Mn, 0.4 to 1.2 wt. % of Cr, one or both of 0.10 to 0.30 wt. % of Mo and 0.03 to 0.10 wt. % of V, and the balance Fe and inevitable impurities, the bearing component as hardened and tempered containing carbide having a maximum particle size of up to 1.5 .mu.m, the amount of the carbide being 2 to 7% in area ratio.
The alloy components of the steel are limited for the following reasons.
C: 0.6 to 0.8 wt. %
C has the property of giving an enhanced hardness on quenching, but if the content thereof is less than 0.6 wt. %, there arises the problem that the steel has an insufficient hardness on quenching, unsatisfactory abrasion resistance and diminished load carrying capacity, whereas if the C content is in excess of 0.8 wt. %, difficulty is encountered in the particle size refinement of the carbide, resulting in fluctuations in rolling life and entailing impaired cold workability due to increased deformation resistance. Moreover, an increased cost will result. Accordingly, the C content should be within the range of 0.6 to 0.8 wt. %, more preferably within the range of 0.65 to 0.75 wt. %.
Si: 0.05 to 0.25 wt. %
Si has the property of shortening the time required for deoxidation. When the content thereof is less than 0.05 wt. %, deoxidation requires a longer period of time to result in an increased cost. If the Si content is over 0.25 wt. %, on the other hand, it becomes difficult to spheroidize the carbide, permitting formation of network carbide and leading to impaired cold workdability due to increased deformation resistance. Accordingly, the Si content should be within the range of 0.05 to 0.25 wt. %, more preferably within the range of 0.10 to 0.20 wt. %.
Mn: 0.2 to 0.9 wt. %
Mn has the property of giving improved hardenability. If the content thereof is less than 0.2 wt. %, this effect diminishes. On the other hand, Mn contents over 0.9 wt. % result in lower toughness and impaired workability. Accordingly, the Mn content should be within the range of 0.2 to 0.9 wt. %, more preferably within the range of 0.2 to 0.5 wt. %.
Cr: 0.4 to 1.2 wt. %
Cr has the property of affording improved strength. If the content thereof is less than 0.4 wt. %, it becomes difficult to spheroidize the carbide, permitting formation of network carbide. If the Cr content is over 1.2 wt. %, a higher cost results, while the effect to give increased strength levels off. For this reason, the Cr content should be within the range of 0.4 to 1.2 wt. %, more preferably within the range of 1.0 to 1.2 wt. %.
One or both of 0.10 to 0.30 wt. % of Mo and 0.03 to 0.10 wt. % of V
Mo and V compensate for the impairment of hardenability that is attributable to the contents of the foregoing alloy components which are made lesser than in the usual material JIS SUJ2, and also have the property of forming a structure of finer grains. When the Mo content is less than 0.10 wt. % with the V content below 0.03 wt. %, these effects are not fully available. When the Mo content is over 0.30 wt. % with the V content in excess of 0.10 wt. %, a higher cost will result. Accordingly, the Mo con

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