Question

Describe the method for preparation of cast iron from pig iron.

Answer 1

Hint: The branch which deals with the study of extraction of metals from their ore is metallurgy. There are different forms of iron such as cast iron, pig iron, wrought iron. Generally metals are extracted from their ores.

Complete answer:
In the extraction of metal from its ore various processes are involved. There are various ores or iron and are mostly in the oxide form. Hematite is the most commonly used ore.
First the ores are concentrated by different methods. This involves removal of unwanted particles like sand, soil etc.
After concentration of ore, we need to remove the metal from it. The concentrated ore must be converted into a suitable form for reduction.
Oxides of iron after concentration are either roasted or calcined so as to remove water, decompose the carbonates.
After that the ore is mixed with limestone and coke and fed into a blast furnace. In a blast furnace oxide is reduced to metal. In a blast furnace reduction of oxides take place at different temperatures. The iron obtained from blast furnaces contains $4\% $ carbon and many impurities like phosphorus, silicon, sulphur in smaller amounts. This is known as pig iron and cast into a variety of shapes.
Cast iron is made from pig iron by smelting pig iron with scrap iron and coke using hot air blast.

Note: Cast iron has a low amount of carbon almost $3\% $ . it is extremely hard and brittle.
Wrought iron is the purest form of iron and is prepared from cast iron.
Coke is mostly carbon. Limestone is also known as calcium carbonate.