Patent Application
20130084209
This application claims benefit, under 35 U.S.C. ยง119(e), of U.S. Provisional Application Ser. No. 61/541,395, filed 30 Sep. 2011, the entire contents and substance of which is hereby incorporated by reference.
1. Field
Embodiments and aspects of the present invention relate to tin based white metal alloys useful in various industrial applications, including the bushings of rolling mill oil film bearings.
2. Description of Related Art
The most prominent white metal alloy used in oil film bearings in the rolling mill field is described in ASTM B23 #2, (referred to here as ASTM #2) and is comprised primarily of tin, with antimony and copper, as alloying elements. ASTM #2 is well understood and is readily deposited onto bushing shells via centrifugal casting, spray deposition, or welding. Unfortunately, ASTM #2 has relatively low fatigue resistance, which limits load capacity of bearings made with this material.
Various versions of Nickel hardened white metal alloys have been used where common versions are referred to as Tuftin. These alloys can be cast and welded, but they contain Nickel, which is a heavy metal that is undesirable for environmental reasons.
U.S. Pat. No. 6,589,372 B1 (Roeingh et al.) discloses use of a known tin based white metal alloy consisting essentially of antimony, copper, zinc, silver, and tin. The alloy of Roeingh is suitable for centrifugal casting applications. But due to the brittleness of the zinc component, this alloy cannot be readily drawn into wire for use in spray and welding applications.
U.S. Pat. No. 4,140,835 (Goddard) and U.K. Application No. 2146354 A disclose cobalt as a component of tin based white metal alloys that also include cadmium. Cadmium is a known carcinogen that has been banned from most workplaces and thus is undesirable.
U.S. Pat. No. 4,150,983 (Mori) and U.S. Pat. No. 5,512,24 (Tanake et al.) disclose alloys cobalt is employed along with chrome. The inclusion of chrome is impractical as it is not readily soluble under normal alloying conditions.
U.S. Pat. No. 4,795,682 (Turner et al.) discloses a tin/cobalt alloy useful as a sacrificial coating designed to absorb particulates. Such coatings lack the toughness required for heavily loaded oil film bearing applications, and the disclosed use of cobalt at elevated percentage levels would inhibit the flow characteristics necessary in a casting or welding process.
Briefly described, aspects of the present invention relate to a tin based white metal alloy that is universally useful in centrifugal casting, spraying, and welding applications.
Aspects of the present invention also relate to a tin based white metal alloy having the elevated strength and fatigue resistance required for use in heavily loaded oil film bearings of the type commonly found in the metals industry.
Aspects of the present invention further relate to a tin based white metal alloy that is low in toxicity and generally free from carcinogenic components, including cadmium and the like.
In one embodiment, aspects of the present invention may be achieved by replacing zinc and silver components of the alloy disclosed in the above referenced U.S. Pat. No. 6,589,372 B1 with cobalt in amounts ranging between about 0.1%-0.7% by weight, with amounts ranging between 0.2% and 0.5% being considered optimal.
These and other objects, features and advantages of the present invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawing.
To facilitate an understanding of embodiments, principles, and features of the present invention, they are explained hereinafter with reference to implementation in illustrative embodiments. In particular, they are described in the context of being a novel and non-obvious tin-based white metal alloy.
Embodiments of the present invention, however, are not limited to use in the described systems.
The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present invention.
A tin based white metal alloy in accordance with the present invention includes as principal components tin, antimony, and copper, to which cobalt has been added. Addition of cobalt in amounts above approximately 0.7% by weight has been found to disadvantageously lower the fluidity of the resulting alloy. Thus, cobalt additions of between about 0.1%-0.7% by weight have been found to be effective in achieving the above-stated objectives, with additions of between about 0.2%-0.5% by weight being optimal.
Tin based white metal alloys of the present invention consist essentially of the components listed in the following examples:
The resulting alloys of the present invention may be centrifugally cast, and may also be drawn into wire for use in spraying or welding applications. Further, alloys of the present invention have the strength and fatigue resistance required for use in heavily loaded bearing applications, including the steel making industry applications, while being free of components that either are banned or otherwise detrimental.
Fatigue resistance of white metal alloys can be determined experimentally through the use of tension/compression specimens that are cycled until failure. Laboratory test data comparing the alloy of the present invention with commonly used alloys in the field are illustrated in
While embodiments of the present invention have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 61541395 | Sep 2011 | US |
