Steelmaking in a Blast Furnace
Making steel requires extreme heat. To produce steel from iron, the hot furnace-like structure known as a blast furnace is used. Inside an operating blast furnace, temperatures can reach up to 4000°F.
Blast furnaces convert iron ore into steel. They have been used for centuries, long before electricity and modern machinery. To operate a blast furnace, iron ore and coke (a fuel made from coal) are placed in the furnace and heated. The coke is burned, supplying heat and carbon monoxide to react with the ore to form molten iron. Limestone, which acts as a flux, is also added to the mix. The limestone helps to chemically transform the ore and remove impurities. As temperatures increase, the flux melts, releasing slag that floats on top of the molten iron. The slag is skimmed off the surface and disposed of. The molten iron is drained from the bottom of the blast furnace.
The molten iron still contains impurities, so a series of refining steps must occur to create high quality steel. First, the molten iron is transferred to secondary furnaces. Additional alloys are added to create specific types of steel. The alloying elements typically added are manganese, nickel, chromium, and silicon. After the steel cools and hardens, it is cut into a variety of shapes and sizes for production use.
Today, blast furnaces are also used to produce chemicals and pig iron for use in secondary production. By-products generated by the blast furnace are also harvested for use in other industries. Steel production using the blast furnace method is efficient and cost-effective. Even with the addition of modern production methods, such as electric arc furnaces and ladle metallurgy systems, blast furnaces are still a major contributor to steel production.
