Most common engineering materials are ferrous materials such as mild steel and stainless steel which are alloys of iron. It is truly said that gold is metal for kings and iron is king of metals. Otto Von Bismark of Germany once said that "for development of a nation, lectures and meetings are not important, but what is important are blood and steel". Incidentally, what is common in blood and steel is "Iron". Though iron is important, but it is mostly used in the form of its alloy, namely steel.
To a layman, words iron and steel convey the same meaning. But iron and steel are two different things. Iron is the name given to the metal, whose chemically symbol is Fe and refers to pure (or almost pure iron). Pure iron is relatively soft and less strong. Its melting point is about 1540°C. In industry, wrought iron is the material which is nearest to iron in purity; but is rarely used these days.
Steel on the other hand, is an alloy of iron and carbon,; the percentage of carbon theoretically varies from 0 to 2%. However in actual practice, carbon rarely exceeds 1.25 to 1.3%. Carbon forms anointermetallic compound called Cementite (Fe3C), which is very hard, brittle and strong. The presence of Cementite in steel makes steel much stronger and harder than pure iron.
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