How is Steel Made?

Steel is used every day in almost all aspects of our lives. It is strong, durable, versatile, and most importantly, sustainable. The sustainability of steel makes it eco-friendly and reliable for a long time. But, have you ever wondered how steel is made?

Steel is not a naturally occurring metal. It is manmade. Pure iron is no harder than pure gold. It is quite soft and not suitable for use. So it is integrated with other elements in varying proportions to improve its properties. When iron is mixed with carbon, the resulting metal is known as steel.

The carbon content in steel varies between 0.5%-2%. Apart from the carbon, steel also contains minute quantities of silicon, manganese, oxygen, phosphorus, and sulphur.

History of steel making

Iron was first produced around 2000 BC in the south-west or central Asia. It was heated and hammered to remove the impurities by blacksmiths. This metal was called wrought iron which was hard, yet malleable. The iron making process marked the beginning of iron age which replaced the use of bronze in tools and weapons.

During the middle ages, tougher iron was made by heating it at higher temperatures. It was called cast iron which was harder than wrought iron but brittle.

Coming to steel making in ancient times, evidence of steel in ironware has been discovered in regions of Turkey, South India, and Sri Lanka. The earliest known steel making can be dated back to the 6th century BC in South Asia and it was known as Seric iron back then. It was regarded as the finest quality of steel exported.

The ancient Sinhalese used wind furnaces to make steel. Soil containing iron was heated with firewood. The monsoon winds powered the furnace and generated high-carbon steel, known as wootz steel. It is said that this technique was taken from the Tamilians, and spread to China and the middle east.

Today, the method remains similar with few differences. Furnaces are still used to produce steel but come in two different types.

Steelmaking today

There are two methods by which steel is produced;

• Blast furnace

• Electric arc furnace

Blast furnace method: It is a large cylinder with bricks lining where iron ore, coke and limestones are fed into it from the top. Air is blown through molten iron to oxidise it.

Coke is cooked coal. The coal is powdered and heated at 982°C for 18-24 hours in the oven. Heating it removes impurities like oil, tar and sulphur. The resulting element when cooled is called coke, which is an important element in heating the iron because the energy and gases released from coke help the process.

So, the iron ore, coke and limestone (also known as flux) descends the cylinder and gets hotter as they do. In the top of the furnace, oxygen is released from the coke and in the bottom, where the temperature reaches 1650 °C, limestone reacts with the impurities separated from iron ore and coke, forming slag. The slag floats above the molten steel and is extracted via a slag notch. Molten steel is extracted with a separate notch.

This method was invented by an Englishman named Henry Bessemer in the 1850s.

Electric arc furnace: EAFs use scrap metal to produce steel. Scrap metal pieces are chugged down the furnace and is shut with a lid when full. The electrodes installed on the inside of the lid are lowered into the furnace. They are charged with high-current electricity which generates heat, melting the metal.

Oxygen is blown into the furnace to separate the impurities from the steel. Limestone is added to mix with the impurities which becomes slag and is separated.

As the metal melts, Ferro-alloys are added to it to get a desired kind of steel. It alerts the chemical composition of steel, so different qualities of steel can be made. For example, chromium and nickel are added to steel to make it corrosive-resistant.

Unlike blast furnaces which use hot metal, EAFs use scrap or recycled metals to produce steel.

Steelmaking in India

Being the second-largest producer of steel in the world, India owes many conglomerates in the steel industry such as Tata, JSW, and SAIL to the large production. Tata steel can produce about 33 million tons per annum. Tata steel products are of high-quality and follow the Indian standards. Tata steel in Bangalore has many dealers selling for reasonable prices.

JSW can produce about 18 million tons per annum. Steel price in Bangalore is becoming steady as steel demand is slowly picking up.