Copper, Brass and Bronze Alloys

Copper, brass and bronze alloys are non-ferrous metals with excellent electrical and thermal conductivity as well as good corrosion resistance, ductility and strength. Pure copper (Cu) is an unalloyed metallic element. Low alloy copper contains very small amounts of alloying elements such as aluminum and titanium. Brass, bronze, leaded brass, nickel silver, copper nickel, aluminum bronze, tin bronze and silicon bronze are examples of copper alloys. Many copper, brass and bronze alloys are hardened or strengthened with cold working processes, solution treating, precipitation hardening, or spinodal decomposition. These materials are easy to fabricate and available in a variety of finished, semi-finished, and hollow stock shapes. Examples include anodes, billets, blooms, coils, flats, foils, ingots, nuggets, plates, powders, sheets, shims, slabs, strips, and wires. Square, rectangular, hexagonal, spherical and tubular products are also available. Important specifications for copper, brass and bronze alloys include outside width or outer diameter (OD), overlength, overall thickness, and inner diameter (ID).   

There are two basic types of copper, brass and bronze alloys: cast alloys and wrought alloys. Cast alloys are melted and then cast continuously, centrifugally, or statically into a mold. Wrought alloys are deformed mechanically during manufacturing in rolling, extrusion, or forging processes. Copper, brass and bronze alloys can also be fabricated through the pressing and sintering of copper powders. Often, materials such as lead, tellurium or other additives are used to improve chip breaking, which imparts free machining characteristics. Composite or reinforced materials with a matrix or continuous phase are also available. Typically, these products are reinforced with a secondary component in particulate, chopped fiber, continuous filament or fabric form.

Selecting copper, brass and bronze alloys requires an analysis of material grades and specifications. The Copper Development Association (CDA) defines compositional standards that adhere to the unified numbering system (UNS) for alloys. UNS was established in conjunction with the American Society for Testing and Materials (ASTM), the Society of Automotive Engineers (SAE), and several metal trade associations and societies. Other organizations that define specifications for copper, brass and bronze alloys include the Alloy Casting Institute (ACI), the Investment Casting Institute ICI), and the American Die Casting Institute (ADCI). Materials that are manufactured in accordance with U.S. military specifications (MIL-SPEC) receive a QQ or QQS designation. Metal and metal alloys that are suitable for aerospace applications meet criteria in the SAE’s aerospace material specification (AMS). In Europe, common EuroNorm (EN) specifications have superseded several older, national systems with lettered designations such as BS, DIN, NS and SS.

Applications for copper, brass and bronze alloys include architectural and building materials; automotive parts; consumer, recreational and household products; tubes, pipes, and fittings; food processing; energy and gas transport; and welding and thermal processing equipment. Pure copper and high copper alloys are used widely in electrical power, current carrying, electronics and telecommunications applications.  They are also used in heat sinks, radiators, chillers, chill rolls, crucibles, and other heat transfer or cooling applications. Copper alloys such as brass and bronze are used in structural components such as bearings, fittings, and wear plates.

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