The second most prevalent element in bronze is tin, which is also variable commonly composing between 12% and 40% of the alloy.
The mixture of tin and copper results in bronze, an alloy that is less brittle than tin and iron, but harder and more durable than pure copper. Additionally, bronze is more readily melted and easier to cast or work. Additional elements such as manganese, lead, zinc, silver, phosphorous, arsenic and more may also be added to enhance specific features of special-purpose bronzes. These and other less complex varieties of bronze are available to suit a wide range of industrial applications. Aluminum bronze, which offers high strength and resistance to corrosion, is used to make bearings, valves, and machine components.
Silicon bronze is used for telegraph wires and chemical containers, whereas phosphor bronze is used to make springs. Leaded bronze, a very strong type of bronze, is used in heavy-duty bushings and bearings. Bronze can also be used to cast bells. Other items that contain bronze include gunmetal, coins, castings, engravings, forgings, steam and water fittings, electrical connectors, gears, valves, and more. In general, industrial applications for bronze also take advantage of its good thermal and electrical conductivity, minimal metal-on-metal friction and non-sparking properties.
As aforementioned, bronze is more easily formed than either pure copper or tin. Though slightly less malleable than pure copper, a number of manufacturing methods are commonly employed in the processing of bronze parts and components. Before machining, however, bronze production begins much like that of any alloyed metal with the combination of copper, tin and any additional additives. These elements, often in the more of metal scrap, are weighed and appropriate amounts transported into a furnace, commonly electric. At this point the mixture is heated to temperatures in excess of 1700°F (950°C). Such temperatures allow for the homogenization of the molten materials.
Once this occurs the metal is poured or cast into stock shapes and allowed to cool before further processing. These billets and ingots are then formed as needed into bronze bars, plates, sheets, foils, strips, rods and other stock shapes via hot or cold rolling, extrusion, drawing, cutting or more. With a wide range to choose from, manufacturers select the stock shape most easily incorporated into the design of the final product which may then undergo several secondary processes. Though a lacquer may need to be applied to prevent the formation of patina, the natural dark amber hue of bronze is desirable in many applications and finishing is not often needed even for aesthetic components.