Iron is found everywhere on earth. It is not only present in the minerals but also in animals and plants. It is found even in the human body. Man began to use iron about 1200 B.C. after the Bronze Age.
Five per cent of the earth’s crust is iron. It is estimated that the earth’s core contains huge quantities of iron and nickel. It is not found in a free state but occurs in a combined state with other elements. Its chief ores are: magnetite, haematite, limonite, siderite and iron pyrites. In India, these ores are mainly found in Bihar and Orissa. To obtain the iron from these ores, they are first finely ground with coal and limestone and then heated to a high temperature in a blast furnace. The melted iron comes out from the bottom of the furnace which, on cooling, becomes solid. The iron so obtained is called ‘pig iron’ and ‘cast iron’. It contains 5% of carbon. After reducing the percentage of carbon from 2 to 0.2% it is converted into steel. The process of the manufacture of steel from cast or pig iron is called “Bessemer Process”, named after Sir Henry Bessemer, who invented it in 1850.
Iron and steel are very useful for us. They are used in all the industries in some form or the other. Appliances of our daily use such as knives, scissors, blades, locks, buckets, utensils are all made from iron. Ships, planes, trains, buses, cars, scooters etc. are also made from this useful metal. This is also used in the construction of bridges and buildings. Various kinds of nuts, bolts, pipes etc. are also made from iron.
Stainless steel which is a very useful metal contains 18% chromium, 8% nickel apart from steel. In India, for making stainless steel, manganese is used instead of nickel because availability of nickel is rare in our country. Stainless steel has some special characteristics – chromium stops it from rusting and it is also not affected by acids and alkalies. Other steels are made with manganese, nickel and tungsten. Iron compounds are used to make pigments, inks and film for cameras. Iron oxide is used to make the tapes for tape recorders.