Pig iron: It is the impurest form of iron. It is obtained directly from the blast furnace and contains about 4% carbon besides impurities of Mn, Si, S and P. Due to the presence of impurities its mp. is low (1473 K).
Cast iron: It contains 3% carbon. It is extremely hard but brittle. Its melting point is the same as that of pig iron.
Wrought iron: It is the purest form of iron. Carbon is partly present as graphite and partly as iron carbide.
Steel: The carbon content of various steels lies between those cast iron and wrought iron.
