Category Science

Modern construction work will be reduced to almost nothing if not for iron and steel. Want to know why? Let us take a look.

If you have visited a construction site, you will see a lot of large girders. The framework of steel girders that you see in the buildings under construction is designed to bear the weight of the building. Without this framework, buildings made from just stone or brick would have to have very thick walls at the bottom. This would limit their height.

Iron plays important roles in other construction activities too. Cast-iron is used to make buildings and fences, while railway tracks are made of steel. Iron is also an ideal material for building bridges.

The first iron bridge was built in 1778, and in 1818 the first iron ship was launched. You all know about Paris’s famous Eiffel Tower. This 300 metres tall tower is built of latticed iron. The uses for iron and steel in construction are many, and continue to expand as the years go by.

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You might have seen reddish orange patches on iron at times. These patches are known as rust. Rust forms on iron because of oxidization, when the oxygen of the air burns the surface of the iron. It can be rubbed off in the form of fine powder just like ash.

Rusting damages the iron; it spoils the appearance of cars and buildings and the damage it causes costs a lot of money to be set right. However, rust is not that bad. It is actually beneficial to us in many ways.

Rust mixes with the soil, giving it a good brown or red colour. When powdered rust dissolves in water, it is taken up by plants and this eventually contributes to their green colour. Finally, through water and plants, we take iron into our bodies to give us the red colour of our blood.

Let us now look at how iron is converted into steel. Steelmaking is a tedious task. In most of the iron ores, iron is found in the form of iron oxides. We have already discussed how iron is extracted by heating it with coke using a, blast furnace.

The extracted iron might contain other metal impurities that are further removed or reduced by mixing it with scrap iron, blowing pure oxygen into the mixture, and adding calcium oxide later.

Slag will be formed as a reaction and it is removed. The iron extract after removing the slag is used to make steel. Other elements like manganese, chromium and nickel are added to the sourced iron to make steel.

The practice of steelmaking is centuries-old. Steelmaking flourished in the 19th century; nowadays, there are different techniques for steelmaking.

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Tools and weapons were essential for the survival of ancient humans. Since blacksmiths were the ones who made weapons and tools out of iron, they were revered. There is a beautiful old tale that illustrates how important blacksmiths were to a community.

Thousands of years ago, the wise king Solomon built a beautiful temple in Jerusalem. To celebrate the completion of the temple, he held a feast for his men. At the feast, he asked whose contribution to the creation of the temple was the greatest.

Everyone was in a hurry to make themselves sound important. The mason, the carpenter and the digger all claimed that theirs had been the most significant contribution. It was then that the king pointed out, that though their work was important; the greatest contribution was made by the blacksmith who made their tools, for without their tools they could not work, and without the blacksmith there would be no tools!

The early knowledge of iron comes from meteorites as we already mentioned. Early humans thought that these huge stones fell from heaven. Iron was the prominent element in the meteorites that fell on Earth. Many of them were made of up to 90 per cent iron. Therefore, iron was referred to and was described as ‘celestial stone’ in many ancient texts.

Hundreds of meteorites hit the surface of the earth every year. Some of these meteorites were really huge. One of the heaviest meteorites ever found is called the Hoba. This meteorite weighed about 60 tons.

In 1894, the polar explorer Robert Peary found a meteorite weighing 33 tons in Greenland. A gigantic iron meteorite hit the Arizona desert in prehistoric times leaving a crater that is 1200 metres in diameter and over 175 metres deep. The crater exists in Arizona even today.

Till about 1500 BC, iron was not a popular metal. Why was this so though iron was abundant on Earth? This was because of the difficulty in extracting iron, though the Hittites in West Asia did learn how to use it.

The Hittites kept the secret of making iron for about 400 years! They found out that iron weapons were better than bronze ones and that is why they decided not to tell anybody else how to make iron. The secret of making iron came to India with the Aryans. The Aryans invaded India around 1500 BC. People who lived in China learned how to make iron by around 700 or 600 BC. By about 300 AD, people in West Africa and East Africa too had learned the secrets of making iron.

Some people treasured iron more than gold as it was a rarity. Iron jewellery was worn by only the wealthiest people, and in ancient Rome, even wedding rings were made of iron! Though iron gradually became more easily available and cheaper, some tribes still considered it precious.

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