Secondary Steelmaking

Modern steelmaking is classified into two categories: primary and secondary. Nowadays, secondary steelmaking units have become an essential part of the integrated steel plants to supply sophisticated grade of steel for continuous casting. Secondary steel refining homogenizes the temperature and composition of the steel bath; facilitates decarburization, desulfurization, dephosphorization, deoxidation, nitrogen and hydrogen removal, attainment of the required teeming temperature; controls the shape of the inclusions; and improves the cleanliness of the steel. In order to fulfill these requirements, one or more units like inert gas purging (IGP), ladle furnace (LF), injection metallurgy (IM), vacuum degassing, and so on may be employed. This chapter gives a brief account on IGP, LF, and IM, and discusses the physicochemical aspects of refining using synthetic slag, deoxidation, and degassing. It also explains stainless steelmaking, which involves melting in electric arc furnaces and decarburization and alloying in ladles either under argon or vacuum.