Steel, an alloy of Iron, carbon and other materials, is the most widely used component used in the field of construction of buildings, automobiles, weapons and much more. Steel is manufactured from the steelmaking process. Steelmaking process has a long history since ancient times, although this procedure was commercialized in the late 19th century.
Steelmaking led to the production of high-grade steel types mainly mild steel, HYSD and the stronger Thermomechanically Treated (TMT) reinforced steel bars with grades of Fe 415, Fe 500, Fe 550, Fe 600.
The Modern steelmaking typically involves two types of procedures which are namely the primary steelmaking and secondary steelmaking. The modern process is however based on the Bessemer process. Usually pig iron and ingots are the raw materials in steelmaking, Even steel scraps can be used since Steel is a 100% recyclable component.
The primary steelmaking is a conventional process which involves the conversion of liquid iron produced from a blast furnace into steel or by using recycled scraps to manufacture into steel. Two methods commonly used in Primary steelmaking is basic oxygen steelmaking (BOS) and the electric arc furnace (EAF). These two methods account for virtually all steel production.
In the BOS process, the molten pig iron is poured into a large refractory-lined container called a ladle. High purity oxygen is introduced at supersonic speed onto the surface of the iron bath through a water-cooled lance, at a pressure between 700–1000 kilopascals (100–150 psi). The blowing of oxygen through the molten iron lowers the carbon content and changes it into steel. The process is named as basic due to the chemical nature of the refractories, namely calcium oxide and magnesium oxide that are able to withstand high temperatures and the corrosive nature of molten metal and slag in the vessel.
In the EAF process, the steel is produced from scrap steels. Scrap steel or the direct reduced iron is loaded into the furnace. Gas burners may be used to assist with the melting down the scrap in the furnace. Similar to BOS, fluxes are usually added to protect the lining of the vessel and improve the removal of impurities. The capacity of EAF is usually around 100 tonnes.
Secondary steelmaking involves the treating of the molten steel produced from both BOS and EAF processes to adjust the composition of the steel. This is achieved by adding or removing certain elements and manipulating the temperature and production environment. The following are the different secondary steelmaking processes which are used:
- Ladle furnace
- Ladle injection