1 Notable characteristics
A typical iron atom has 56 times the mass of a typical hydrogen atom. Iron is the most abundant metal, and is believed to be the tenth most abundant element, in the universe. Iron is also the most abundant (by mass, 34.6%) element making up the Earth; the concentration of iron in the various layers of the Earth ranges from high at the inner core to about 5% in the outer crust; it is possible the Earth's inner core consists of a single iron crystal although it is more likely to be a mixture of iron and nickel; the large amount of iron in the Earth is thought to contribute to its magnetic field. Its symbol Fe is an abbreviation of ferrum, the Latin word for iron.
Iron is a metal extracted from iron ore, and is hardly ever found in the free (elemental) state. In order to obtain elemental iron, the impurities must be removed by chemical reduction. Iron is used in the production of steel, which is not an element but an alloy, a solution of different metals (and some non-metals, particularly carbon).
The nucleus of iron has the highest binding energy per nucleon, so it is the heaviest element that is produced exothermically through fusion and the lightest through fission. When a star that has sufficient mass to produce iron does so, it can no longer produce energy in its core and a supernova will ensue.
Cosmological models with an open universe predict that there will be a phase where as a result of slow fusion and fission reactions, everything will become iron.
2 Applications
Iron is the most used of all the metals, comprising 95 percent of all the metal tonnage produced worldwide. Its combination of low cost and high strength make it indispensable, especially in applications like automobiles, the hulls of large ships, and structural components for buildings. Steel is the best known alloy of iron, and some of the forms that iron takes include:
- Pig iron has 4% – 5% carbon and contains varying amounts of contaminants such as sulfur, silicon and phosphorus. Its only significance is that of an intermediate step on the way from iron ore to cast iron and steel.
- Cast iron contains 2% – 3.5% carbon and small amounts of manganese. Contaminants present in pig iron that negatively affect the material properties, such as sulfur and phosphorus, have been reduced to an acceptable level. It has a melting point in the range of 1420–1470 K, which is lower than either of its two main components, and makes it the first product to be melted when carbon and iron are heated together. It is extremely strong, hard and brittle. Working cast iron, even white hot cast iron, tends to break the object.
- Carbon steel contains between 0.5% and 1.5% carbon, with small amounts of manganese, sulfur, phosphorus, and silicon.
- Wrought iron contains less than 0.5% carbon. It is a tough, malleable product, not as fusible as pig iron. It has a very small amount of carbon, a few tenths of a percent. If honed to an edge, it loses it quickly.
- Alloy steel s contain varying amounts of carbon as well as other metals, such as chromium, vanadium, molybdenum, nickel, tungsten, etc.
- Iron (III) oxides are used in the production of magnetic storage in computers. They are often mixed with other compounds, and retain their magnetic properties in solution.
