Brass and Bronze are metal alloys used extensively in everyday objects. While brass is an alloy of copper and zinc, bronze is an alloy consisting mainly of copper, combined most often with tin, but at times also with other metals. Owing to their properties, these two alloys have various uses.
Brass has higher malleability than zinc or copper. It has a a low melting point (900 centigrade) and flows when melted making it easy to cast in molds. Combinations of iron, aluminum, silicon and manganese make brass wear and tear and corrosion resistant. Susceptible to stress cracking when exposed to ammonia.
Bronze is hard and brittle. It melts at a slightly higher temperature at 950 centigrade, but this depends on the amount of tin present in the alloy. Bronze resists corrosion (especially seawater corrosion) and metal fatigue more than steel and is also a better conductor of heat and electricity than most steels.
The composition of both alloys depends on the particular use. For instance, Cartridge brass contained 30% zinc and was used to make cartridges for firearms. Naval brasses had up to 39.7% Zinc and were used in various applications on ships. Bismuth bronze is a bronze alloy with a composition of 52 parts copper, 30 parts nickel, 12 parts zinc, 5 parts lead, and 1 part bismuth. It is able to hold a good polish and so is sometimes used in light reflectors and mirrors.
- Musical instruments:
The malleability and acoustic properties of brass have made it the metal of choice for brass musical instruments such as the trombone, tuba, trumpet, cornet, euphonium, tenor horn, and the French horn. Even though the saxophone is classified as a woodwind instrument and the harmonica is a free reed aerophone, both are also often made from brass.
Bronze is the most popular metal for top-quality bells, particularly bell metal, which is about 23% tin. Nearly all professional cymbals are made from a bronze alloy. The alloy used in drum kit cymbal bronze is unique in the desired balance of durability and timbre. Phosphor bronze is also used in guitar and piano strings.
- Sculptures and statues:
Brass is often used for decoration, statues and coins for its bright gold-like appearance and its relative resistance to tarnishing.
Many common bronze alloys have the unusual and very desirable property of expanding slightly just before they set, thus filling in the finest details of a mould so widely used for cast bronze sculpture.
- Machine parts:
Brass is used for applications where low friction is required such as locks, gears, bearings, doorknobs, ammunition, and valves. It is used for plumbing and electrical applications.
Bronze is ideally used today for springs, bearings, bushings, automobile transmission pilot bearings, and similar fittings, and is particularly common in the bearings of small electric motors. Phosphor bronze is particularly suited to precision-grade bearings and springs. Bronze was especially suitable for use in boat and ship fittings prior to the wide employment of stainless steel owing to its combination of toughness and resistance to salt water corrosion. Bronze is still commonly used in ship propellers and submerged bearings
The first known existence of bronze dates to about 3500 BC and the Sumerians and lends its name to the Bronze age. The discovery of bronze enabled people to create better metal objects than before. Tools, weapons, armor, and various building materials, like decorative tiles, made of bronze were harder and more durable than their stone and copper.
Brass came later dates back to about 500 BC. Zinc is practically never found naturally in its pure state, but people had realized that copper smelted with calamine -- a zinc ore -- produced a golden-colored tarnish-resistant metal that was useful for all sorts of things due in part to its low melting point and malleability. The zinc itself is not seen but is released from the calamine ore by heating and combines immediately with copper.