Bismuth Tin Bronze
Bismuth tin bronze is a copper alloy which typically contains 1-3% bismuth, although some can contain over 6% Bi. This bronze alloy is very corrosion-resistant, making it suitable for use in environments such as the ocean. Bismuth tin bronzes are more malleable, thermally conductive, and polish better than regular brasses. This line of no-lead bronze alloys includes C89320, C89325, C89831, C89833, C89835 and C89844.
Specifically, alloy C89835 is a C932 lead-free replacement alloy and is offered as a standard-stocked product. Randall Bearings provides an inventory of this alloy numbering over 90 items and in sizes up to 4.0” O.D. C89835 supports the market demand for lead-free material and compliance with the 3874 Reduction of Lead in Drinking Water Act (effective January 2014).
High Tin Bronze
The bronze alloys which are described as tin bronzes have long been recognized for their low lead content (less than .25% lead) and high strength characteristics. These alloys from C90300 through C91000 and C91300 are not materially different than those produced more than 3,500 years ago in Europe and China.
High tin bronze alloys are typically found in gears as well as high-strength bushing and bearing applications where high strength, low speeds and heavy loads are present. Other high-strength applications for these alloys are pump impellers, piston rings, steam fittings and valve bodies. High tin bronze castings are utilized in movable bridge components, turntables for bridges and other structures for fixed and expansion bearings with slow or intermittent movement with heavy loads.
Aluminum bronze is the highest strength standard copper-based alloy. Randall Bearings uses C95400, C95500 and C95900 in standard sizes of rounds, tubes and rectangles. Aluminum, in conjunction with iron and nickel in C95500, acts as a strengthener in these alloys. All of the aluminum bronzes can be heat treated, further increasing tensile strengths.
Lead-Free Bearing Bronze
Apart from providing excellent anti-friction and anti-wear properties for bearing alloys, lead is considered an environmentally hazardous material. Lead content in bearing bronze varies depending on the application and, in some cases, is fairly low. However, disposal of waste material from fabrication processes, disposal of used bearings, and contamination of lubricants can cause serious environmental and health concerns. Regulations prohibit the use of lead in plumbing applications as well as bearing materials.
As an answer to these concerns, another subcategory of lead-free replacement bronze alloys has been noted in the bronze industry, titled lead-free bearing bronze. This lead-free, environmentally friendly copper-based bearing material is designed for high speed/load applications. Bronzes in this group of alloys include C89835, C90300, C95400, C95500 and C95900.
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