CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit, under 35 U.S.C. § 119(e), of U.S. Provisional Application Serial No. 61/541 ,395, filed 30 September 201 1, the entire contents and substance of which is hereby incorporated by reference.

BACKGROUND

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. Patent No. 6,589,372 Bl (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. Patent 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. Patent Nos. 4,150,983 (Mori) and 5,512,242 (Tanake et al.) disclose alloys in which cobalt is employed along with chrome. The inclusion of chrome is impractical as it is not readily soluble under normal alloying conditions.

U.S. Patent 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.

SUMMARY

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. Patent No. 6,589,372 Bl 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.

DETAILED DESCRIPTION

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:

EXAMPLE I

Antimony 5.0-9.0% by weight

Copper 3.0-8.0% by weight

Cobalt 0.1-0.7% by weight

Tin Balance

EXAMPLE II

Antimony 6.0-8.0% by weight

Copper 3.0-8.0% by weight

Cobalt 0.1-0.7% by weight

Tin Balance

EXAMPLE III

Antimony 6.0-8.0% by weight

Copper 6.0-7.0% by weight

Cobalt 0.1-0.7% by weight

Tin Balance

EXAMPLE IV

Antimony 6.0-8.0% by weight

Copper 6.0-7.0% by weight Cobalt 0.2-0.5% by weight

Tin Balance

EXAMPLE V

Antimony 6.0-8.0% by weight

Copper 6.0-7.0% by weight

Cobalt 0.2-0.5% by weight

Tin Balance

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 TABLE 1. Based on test data the fatigue strength of the alloy containing 0.3% to 0.5% cobalt has excellent fatigue resistance, exceeding that of other alloys commonly used in the rolling mill application. Test data shown was determined in accordance with ASTM E 466 with an applied load of 7,500 psi (51.7 MPa) and test frequency of 10 Hz. Axial Fatigue Resistance of Various White Metal Alloys

18000

16000

™ 1 ₄ 000

g 12000

to 10000

8000

6000

₄ 000

^" o 2000

υ

ASTM #2 Roeingh et al Tuftin Modified 0.3% - 0.5% Co Alloy

Alloy

TABLE 1 : Comparison of Fatigue Resistance, as measured in Cycles to Failure in accordance with ASTM E 466. specimens stresses to 7.500 psi (51.7 MPa)

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.