Name | Characteristics | Found | Reactions | Uses

Iron (Fe) is a transition metal in Group VIIIB (Group 8). Other members of the iron group are ruthenium (Ru) and osmium (Os).

The name "iron" is the Anglo-Saxon word for the metal. The symbol Fe is an abbreviation of the Latin word, ferrum, for iron metal. Iron is of prehistoric discovery, and gives its name to one of the periods of prehistory.

Iron is the fourth most abundant element on earth, comprising about 6 percent of the earth's crust and it is the most abundant of the 4th period transition elements. Uncombined iron is very rare in nature except in a class of meteorites known as siderites. The core of the earth is thought to be largely composed of iron with about 10% occluded hydrogen. In the solid state the metal has a body-centered cubic structure.

The most common ore is hematite [iron(III) oxide], from which the metal is obtained by reduction with carbon. Iron is found in other widely distributed minerals, such as magnetite which is frequently seen as black sands along beaches and banks of streams.

Pure iron is very reactive chemically, reacting with air, acids, and halogens. It rapidly corrodes, especially in moist air or at elevated temperatures.

Taconite is becoming increasingly important as a commercial ore, and other common ores are limonite [hydrated iron(III) oxide], siderite [iron(II) carbonate], and iron pyrite (iron disulfide, "fool's gold").

Iron is a vital constituent of plant and animal life, and is a constituent of hemoglobin (heme) and of myoglobin. One cause of anemia is iron deficiency.

Pure iron has four allotropic forms with transition points at 770, 928, and 1530°C. The pure metal is not often encountered in commerce, but is usually alloyed with carbon or metals.

Iron is the cheapest and most abundant, useful, and important of all metals. Pig iron is an alloy containing about 30% carbon with varying amounts of S, Si, Mn, and P. It is hard, brittle, fairly fusible, and is used to produce other alloys, including steel. Commercial iron appears in three forms: cast iron, wrought iron, and steel.

Cast iron is made when pig iron is remelted in small cupola furnaces and poured into molds to make castings. It usually contains 92-94% iron, 2-6% carbon and small amounts of silicon, sulfur, manganese and phosphorus. Cast iron is used in making machine parts, cooking ranges, stoves, pipes, and radiators.

Wrought iron is made by purifying melted pig iron in a puddling furnace (a small reverberatory furnace).

Pig iron is refined in a "basic oxygen furnace", where oxygen is blown into molten pig iron to oxidize impurities containing P, C, S, and other elements. All are converted to oxides that then react with the basic lining of the furnace. For example, phosphorus is oxidized to P4O10, which then reacts with CaO.

P4O10 + 6 CaO 2 Ca3(PO4)2

The purified iron is then poured into a molten iron silicate slag, and the resulting semisolid mass is then passed between rollers that squeeze out most of the slag. The wrought iron obtained is tough, malleable, ductile, and corrosion resistant, and it melts only at high temperatures. It is used chiefly for rivets, bolts, water pipes, chains, anchors, and fire bars; it is used also for ornamental ironwork. Wrought iron contains only a few tenths per cent of carbon and has a "fibrous" structure.

Carbon steel is an alloy of iron with carbon, with small amounts of Mn, S, P, and Si. Alloy steels are carbon steels with other additives, such as nickel, chromium, and vanadium.