Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminium, or silicon. It was particularly significant in antiquity, giving its name to the Bronze Age. "Bronze" derives from the and, in turn, is perhaps ultimately taken from the Persian word "birinj," meaning "copper".

History

Bronze was significant to any culture that encountered it. It was one of the most innovative alloys of mankind. Tools, weapons, armor, and various building materials like decorative tiles made of bronze were harder and more durable than their stone and copper ("Chalcolithic") predecessors. Initially bronze was made out of copper and arsenic to form arsenic bronze. It was only later that tin was used, becoming the sole type of bronze in the late 3rd millennium BC. Tin bronze was superior over arsenic bronze in that the alloying process itself could more easily be controlled (as tin was available as a metal) and the alloy was stronger and easier to cast. Also, unlike arsenic, tin is not toxic.

The earliest tin-alloy bronzes date to the late 4th millennium BC in Susa (Iran) and some ancient sites in Luristan (Iran) and Mesopotamia (Iraq).

Copper and tin ores are rarely found together (exceptions include one ancient site in Thailand and one in Iran), so serious bronze work has always involved trade. In Europe, the major source for tin was Great Britain's deposits of ore in Cornwall. Phoenician traders visited Great Britain to trade goods from the Mediterranean for tin.Fact: date=September 2007

Though bronze is stronger (harder) than wrought iron,Fact: date=February 2008 the Bronze Age gave way to the Iron Age; this happened because iron was easier to find. Bronze was still used during the Iron Age, but for many purposes the weaker wrought iron was found to be sufficiently strong. Archaeologists suspect that a serious disruption of the tin trade precipitated the transition. The population migrations around 1200 – 1100 BC reduced the shipping of tin around the Mediterranean (and from Great Britain), limiting supplies and raising prices. As ironworking improved, iron became cheaper, and cultures learned how to make steel, which is stronger than bronze and holds a sharper edge longer.

Properties

Bronze can be superior to iron in many applications. It is considerably less brittle than iron. Bronze only oxidizes superficially; once the surface oxidizes, the thin oxide layer protects the underlying metal from further corrosion. Copper-based alloys have lower melting points than steel or iron, and are more readily produced from their constituent metals. They are generally about 10 percent heavier than steel, although alloys using aluminum or silicon may be slightly less dense. Bronzes are softer and weaker than steel, e.g. bronze springs are less stiff (and so store less energy) for the same bulk. Bronze resists corrosion (especially seawater corrosion) and metal fatigue better than steel and also conducts heat and electricity better than most steels. The cost of copper-base alloys is generally higher than that of steels but lower than that of nickel-base alloys such as stainless steel.