Metal treatment – Stock – Carburized or nitrided
Reexamination Certificate
1999-07-02
2001-06-19
Yee, Deborah (Department: 1742)
Metal treatment
Stock
Carburized or nitrided
C148S906000, C148S218000, C148S225000, C148S326000, C148S328000, C148S607000, C148S622000, C384S492000, C384S912000
Reexamination Certificate
active
06248186
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a ball-and-roller bearing and a method of manufacturing the same, particularly to a ball-and-roller bearing used in, for example, an aircraft and a method of manufacturing the same.
BACKGROUND ART
A high mechanical strength is required for a ball-and-roller bearing used under conditions of a high temperature and a high rotating speed like the ball-and-roller bearing used in an engine of an aircraft. Particularly, since only a slight damage done to a member is likely to bring about a serious accident in an aircraft, a very high mechanical strength and reliability is required for the ball-and-roller bearing for an aircraft.
For the same reasons, the ball-and-roller bearing for an aircraft is judged in general to have reached the life at the time when only a slight rust has been formed. Such being the situation, the ball-and-roller bearing for an aircraft is required to exhibit not only a high mechanical strength but also an excellent corrosion resistance.
It was customary to use a semihice series materials of AISI M50, M50NiL, etc. for forming the ball-and-roller bearing for an aircraft. The ball-and-roller bearing for an aircraft that is made of these materials exhibits a relatively high mechanical strength. However, in these materials, a content of chromium that is said to be most effective for improving the corrosion resistance of the steel is low.
In general, an airport is constructed near the coast, since the airport requires a tremendously large site and serious noises are generated by the aircraft around the airport. What should be noted is that the ball-and-roller bearing for an aircraft is used or stored under the environment in which rust tends to be caused by salt.
In the ball-and-roller bearing for an aircraft that is made of the semihice series material, the problem derived from the rust is not so serious in respect of the rolling body. This is because the rolling body has a small surface area, compared with other members. In addition, the most portion of the surface is brought into a rolling or sliding contact with other members. However, each of the inner ring and the outer ring has a large surface area, and the most portion of the surface is not brought into a rolling or sliding contact with other members. In addition, the ball-and-roller bearing for an aircraft including an inner ring or an outer ring made of the material described above fails to exhibit a sufficiently high corrosion resistance.
A martensite series stainless steel such as SUS440C is known to be suitable for use as a material of the ball-and-roller bearing excellent in corrosion resistance. However, in the case of using a martensite series stainless steel for forming the ball-and-roller bearing for an aircraft, coarse eutectic carbide particles are formed in the inner ring, outer ring, etc. As a result, it is not possible to obtain a hardness high enough to be used satisfactorily under the particularly severe conditions of a high temperature and a high rotating speed. Under the circumstances, it is important to improve further the rolling fatigue life characteristics of the ball-and-roller bearing.
DISCLOSURE OF INVENTION
The present invention, which has been achieved in view of the above-noted problems inherent in the prior art, is intended to provide a ball-and-roller bearing excellent in mechanical characteristics and corrosion resistance and a method of manufacturing the same.
According to the present invention, there is provided a ball-and-roller bearing, comprising an inner ring, an outer ring arranged on the co-axis of the inner ring and rotating around the axis relative to the inner ring, and a rolling body interposed between the inner ring and the outer ring and rolling on the inner ring and the outer ring in accordance with rotation of the outer ring relative to the inner ring, wherein at least one member selected from the group consisting of the inner ring, the outer ring, and the rolling body comprises a core member consisting essentially of an alloy containing iron, at least one of 0.2 to 1.0% by weight of silicon and 0.2 to 1.5% by weight of manganese, 7.0 to 11.0% by weight of chromium, 1.5 to 6.0% by weight of molybdenum, and 0.5 to 8.0% by weight of cobalt, and a case hardened layer formed by subjecting a surface region of the core member to a secondary hardening treatment and containing 0.9 to 1.5% by weight of carbon.
The present invention also provides a method of manufacturing a ball-and-roller bearing, comprising the steps of forming a core member consisting essentially of an alloy containing iron, at least one of 0.2 to 1.0% by weight of silicon and 0.2 to 1.5% by weight of manganese, 7.0 to 11.0% by weight of chromium, 1.5 to 6.0% by weight of molybdenum, and 0.5 to 8.0% by weight of cobalt, forming a case hardened layer containing 0.9 to 1.5% by weight of carbon in a surface region of the core member by applying to the core member a carborizing or carbonitriding treatment, a hardening treatment, and a tempering treatment under high temperatures in the order mentioned, and assembling an inner ring, an outer ring and a rolling body such that the inner ring and the outer ring are positioned on the same axis and that the rolling body is interposed between the inner ring and the outer ring, at least one of the inner ring, the outer ring, and the rolling body being formed of the core member having the case hardened layer formed on the surface.
REFERENCES:
patent: 5560787 (1996-10-01), Takagi et al.
Ohori Manabu
Tanaka Susumu
Yamamura Kenji
Christensen O'Connor Johnson & Kindness PLLC
NSK Ltd.
Yee Deborah
LandOfFree
Ball-and-roller bearing and method of manufacturing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ball-and-roller bearing and method of manufacturing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ball-and-roller bearing and method of manufacturing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2490277