Brass is an alloy (mixture) of copper and zinc. Other elements may be added to the alloy for special uses. Brass is widely used in making hardware, electrical fixtures, inexpensive jewelry, metal decorations, military supplies, and musical instruments.
The amount of copper used in brass ranges from 55 percent to more than 95 percent. The color and properties of brass vary with its composition. When the alloy contains about 70 percent copper, it has a golden yellow color and is known as yellow brass, high brass, or cartridge brass. When it contains 80 percent or more copper, it has a reddish copper color and is known as red brass or low brass. Muntz metal contains 60 percent copper and 40 percent zinc. Alloys that have a high copper content are almost as soft as pure copper. But as zinc is added, they become stronger and tougher. Compositions of 55 percent copper and 45 percent zinc are hard and somewhat brittle.
To obtain special properties, brass makers often add other elements to the copper-zinc alloy. Lead is added to improve machinability (ease of cutting). The result is called leaded brass. Brass that contains 1 percent to 3 percent lead can be machined easily and is often used to make parts for clocks and other precision equipment. Tin and nickel are often added to increase the alloy’s resistance to corrosion or wear. Naval brass contains 1 percent tin. Nickel can be added to obtain a silvery-white color that makes the alloy a more suitable base for silver plating. Silver-plated flatware and hollowware often have a brass base. Other elements added to brass are iron, aluminum, and manganese. Aluminum helps prevent seawater from corroding brass.
Making brass.
The first step in making brass is to melt copper in an electric furnace. Solid pieces of zinc are then added to the melted copper. The zinc melts rapidly. A covering of charcoal is often placed over the liquid metals to reduce the loss of heat and to prevent an excessive loss of zinc by vaporization (see Vapor ). After the copper and zinc have been melted and thoroughly mixed, the brass is ready for pouring. It can be poured directly into forms to cast the wanted articles, or it can be made into bars called billets. Such bars make it easier to work with the brass or to store it. Workers may cut off the top of the brass bar. This portion, which became solid last, contains impurities and is porous. The billet is then placed in another furnace and reheated until it reaches the proper temperature for working.
After the reheating process, the brass can be rolled while it is still hot, and formed into the desired shape. A milling machine removes surface imperfections. The brass is then cold-rolled.
Almost any method for shaping metal can be used to shape brass. It can be rolled into sheets and plates; drawn or extruded (squeezed out) into rods, tubes, and wire; forged or pressed into complicated shapes; and spun to form deep receptacles (containers).
Brass articles are free from dirt, gas, and other defects, so they can be polished to a brilliant finish. Brass objects often are electroplated (see Electroplating ). Their surfaces are easily treated to obtain beautiful and useful effects.
History.
Both brass and bronze, the alloy of copper and tin, were probably first made accidentally when people heated copper ores that contained the alloying metals. But brass did not have the importance of bronze in ancient times. Brass was harder to produce because the zinc in brass, unlike the tin in bronze, evaporates soon after melting and is lost.
Brass was first used extensively by the Romans about 2,000 years ago. They made brass coins, kettles, and ornaments.
