Since around 3500 BC, people have been using bronze. One of the earliest alloys, it combines copper and tin. Some consider the best type to consist of 80% copper and 20% tin. Bronze may also contain other metals. Foundries and manufacturers may add them to improve the physical properties of the final product. Common metals, metalloids and non-metals include aluminum, manganese, zinc and phosphorous. However, one of the most common additions is lead. Leaded bronze is popular for its ability to improve certain properties innate to bronze.
Bronze Properties
Bronze is a hard and brittle metal. Its melting point varies according to the amount of tin. Shipbuilders prize bronze for its ability to resists corrosion from salt-water spray. Others praise it ability to repel metal fatigue and its role as an excellent conductor of heat and electricity.
By adding lead to bronze, companies improve and/or add certain properties. In the case of quality bushings & leaded bronze, the addition of this metal improves the machinability of the metal. Because lead has a higher melting point than solid copper, it and its alloys, solidifies before the lead. Lead then distributes itself throughout filling in cavities and other irregularities. This makes the material smoother and reduces friction allowing the machining process to occur at faster rates.
Applications
These qualities make lead containing bronze suitable for specific applications. Bearings in particular benefit. The solid lubrication quality enhances the ability of the bearings to perform. Until recently, components in many water applications benefited from bronze featuring lead. Other applications include:
* Airplane – bearings
* Boat fittings including submerged bearings
* Machine tools
* Home appliances – small electric motors
* Farm machinery
* Pumps
Leaded Bronze
Bronze has been in use for millenniums. An early alloy, it combines copper and tin in various percentages to produce a strong, desirable metal. With the addition of lead, the material is more machinable. Today, leaded bronze no longer permitted in certain applications, continues to be in demand in others.