The bronzes are a family of copper-based alloys traditionally alloyed with tin but can refer to alloys of copper and other elements (e.g., aluminum, silicon, and nickel). Bronzes are somewhat stronger than the brasses, yet they still have a high degree of corrosion resistance. Generally, they are used when good tensile properties are required, in addition to corrosion resistance. For example, beryllium copper attains any copper-based alloy’s greatest strength (to 1,400 MPa).
Historically, alloying copper with another metal, for example, tin, to make bronze was first practiced about 4000 years after the discovery of copper smelting and about 2000 years after “natural bronze” had come into general use. An ancient civilization is defined in the Bronze Age as producing bronze by smelting its copper and alloying it with tin, arsenic, or other metals. Bronze, or bronze-like alloys and mixtures, were used for coins over a longer period. Bronzes are still widely used today for springs, bearings, bushings, automobile transmission pilot bearings, and similar fittings and are particularly common in the bearings of small electric motors. Brass and bronze are common engineering materials in modern architecture and are primarily used for roofing and facade cladding due to their visual appearance.
Bell Metal – High-tin Bronze
In general, bell metals usually refer to high-tin bronzes that are a family of copper-based alloys traditionally alloyed with tin, commonly with more than 20% of tin (typically, 78% copper, 22% tin by mass). Bell metal is used for the casting of high-quality bells. The higher tin content increases the rigidity of the metal and the resonance. It has been found that increasing the tin content increases the decay time of the bell strike, thus making the bell more sonorous. High-tin bronzes are also found in gears and high-strength bushing and bearing applications where high strength and heavy loads are present.