Probably one of the most important, being used on the largest scale of any metal. Its production in the blast furnace is well documented. When pure, iron is a lustrous white metal which is soft and very workable. However, it is reactive and easily forms a coating of hydrated oxide on its surface in the presence of moist air. This is non-coherent and flakes easily to reveal fresh surfaces for attack. Iron is soluble in dilute acids, where Fe(II) is produced in solution; more oxidising acids produce Fe(III) solutions and strongly oxidising agents (e.g. dichromate or concentrated nitric acid) produce a passive form of the metal, probably as a result of the formation of a coherent surface film of oxide. Depending upon the temperature, pure iron can exist in three forms, namely alpha-, gamma- and delta-iron; alpha iron is a polymorphic form of iron which is stable below 906°C; it has a body centred cubic lattice (bcc) and is magnetic up to 768°C. Gamma iron is a polymorphic form of iron which is stable between 906°C and 1403°C; it has a face centred cubic lattice (fcc) and is nonmagnetic (n.b. its range of stability is reduced by the presence of carbon, manganese and nickel and it is the basis of the austenite solid solutions). Delta iron is the polymorphic form of iron which is stable between 1403°C and the melting point; it has the same lattice structure as alpha iron. Iron is the basis for many types of steel, the properties being achieved by the alloying of iron with carbon, nickel, chromium and other elements in varying proportions which results in materials with vastly differing mechanical and physical properties. Iron is also an essential element for all life forms, the average human body containing 4 gmof the element. The majority of iron in the body is present within haemoglobin, the respiratory pigment which provides the mechanism for the transportation of oxygen by red blood cells. In Latin it is ferrum, hence the symbol Fe.
- 1400BC iron working is developed in the Middle East.
- One of the most abundant metals, 41000 ppm in the earth’s crust.
|Atomic / Molecular Weight||55.847||gmol-1||Clip|
|Crystal Structure||bcc / fcc at 1180K then fcc / bcc at 1670K||Clip|
|Tensile strength||100e6 to 370e6||Nm-2||Clip|
|Yield strength||150e6 to 160e6||Nm-2||Clip|
|Youngs modulus||110e9 to 206e9||Nm-2||Clip|
|Poissons ratio||0.27 to 0.29||Clip|
|Linear expansivity||11e-6 to 12e-6||K-1||Clip|
|Specific heat capacity||448||Jkg-1K-1||Clip|
|Latent heat of fusion||205000||Jkg-1||Clip|
|Thermal conductivity||60 to 84||Wm-1K-1||Clip|
|Acoustic wave velocity (longitudinal bulk waves)||4994 to 5957||ms-1||Clip|
|Acoustic wave velocity (Irrotational waves)||4477 to 5189||ms-1||Clip|
|Acoustic wave velocity (Shear waves)||2809 to 3224||ms-1||Clip|
|Acoustic wave velocity (Rayleigh waves)||2590 to 2986||ms-1||Clip|
|Bulk Modulus of Rigidity||169800000000||Nm-2||Clip|
See also: Alpha Iron, Angle Iron, Anthracite Iron, Austenite, Cast Iron, Delta Iron, Gamma Iron, Iron Foundry, Iron Hydroxide, Iron II Chloride, Iron II Hydroxide, Iron II Oxide, Iron II Sulphate, Iron II Sulphide, Iron III Chloride, Iron III Oxide, Iron Sulphide, Nonferrous, Periodic Table, Pig Iron, Rust, Silicon Iron, Steel, Wrought Iron.