Micro-alloyed steel rolling bearings

Details Micro-alloyed steel rolling bearings Micro-alloyed steel rolling bearings

1998-04-29

2001-12-25

Yee, Deborah (Department: 1742)

Alloys or metallic compositions

Ferrous

Vanadium, tantalum or niobium containing

C148S906000, C148S320000, C384S492000, C384S912000

Reexamination Certificate

active

06333001

ABSTRACT:

BACKGROUND OF THE INVENTION
The performance and reliability of rolling bearings are determined to a large degree by the materials from which the bearing components are made. Steels used for rolling bearings must be capable of being adequately hardened and must have high fatigue strength and wear resistance. Also, the structural and dimensional stability of the bearing components must be satisfactory at the operating temperatures that can be expected.
In so-called hub bearing units (HBU) for cars and truck hub units (THU), the hub forms a bearing race for the rolling elements. For such HBU/THU forgings, a steel grade named SAE 1055 is commonly used. The composition of this steel grade is the following: 0.50-0.60% C, 0.60-0.90% Mn, 0.050% S max and 0.040% P max. The rest is iron and ordinary impurities. The bearing race is commonly induction hardened.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of this invention to avoid or alleviate the problems of the prior art.
It is further an object of this invention to provide a micro-alloyed steel for rolling bearings especially for HBU/THU forgings with improved strength.
It is an aspect of the invention to provide a new steel grade for rolling bearings and especially for forged HBU/THU with improved yield strength in “as forged” condition which will result in improved performance, such as an improved fatigue strength and resistance to axial clearance, and/or create the possibility for downsizing of the HBU/THU (weight reduction). The surface hardness after induction hardening should be sufficient for the above applications. These objects have been achieved by a micro-alloyed steel having the following composition:
0.5-0.7% C, 0-0.6% Si, 0.4-1.2% Mn, 0-0.035% S, 0.05-0.2% V, 80-160 ppm N, and the remainder iron and ordinary impurities.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The alloy of the presently claimed invention comprises: 0.5-0.7% C, 0-0.6% Si, 0.4-1.2% Mn, 0-0.035% S, 0.05-0.2% V, 80-160 ppm N, and the remainder iron and ordinary impurities. Among the main differences between the steel grade according to the presently claimed invention and the SAE 1055 are the relatively small addition of vanadium (V) and a controlled content of nitrogen. A significant increase in the yield strength has been obtained with such addition.
The invention is additionally illustrated in connection with the following Example which is to be considered as illustrative of the present invention. It should be understood, however, that the invention is not limited to the specific details of the Example.


REFERENCES:
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H. R. Lin et al., “The Prediction of Precipitation Strengthening in Microalloyed Steels,”Metallurgical Transactions A,vol. 19A, No. 6, ISSN 0360-2133, Jun. 1998, pp. 1471-1480.
Patent Abstract of Japan, vol. 095, No. 009, JP 07 150235, Jun. 13, 1995.
Patent Abstracts of Japan, vol. 012, No. 050, JP 62 196323, Aug. 29, 1987.

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