Properties and Uses of Steelmaking Slag...

Properties and Uses of Steelmaking Slag Steelmaking slag is an integral part of the steelmaking process. It is produced during the separation of the liquid steel from impurities in steelmaking furnace and is a non-metallic by-product of steelmaking process. It occurs as a molten liquid melt and is a complex solution of silicates and oxides which solidifies upon cooling. It primarily consists of silicates, alumina silicates, calcium aluminum silicates, iron oxides and crystalline compounds. During steelmaking, slag is produced in the hot metal pretreatment processes (desulphurization, desiliconization, and dephosphorization etc.), in the primary steelmaking processes (basic oxygen furnace, electric arc furnace, and induction furnace), slag formed during the secondary refining processes (this slag is sometimes called ?secondary refining slag? or ?ladle slag?), and slag formed in tundish during continuous casting of steel (also known as tundish slag). The slag generated in the basic oxygen furnace (BOF) and electric arc furnace (EAF) is of basic nature while the slag is of acidic nature in induction furnace because of the use of silica ramming mass as the lining material. Since most of the steel produced in the world is by BOF and EAF processes, hence slag from these processes is discussed in this article. The processing of the steelmaking slag (Fig 1) is normally carried out by (i) solidifying and cooling of the hot liquid slag, (ii) crushing and magnetic separation treatment of the slag to recover the scrap, (iii) crushing and classification of the slag for grain size adjustment to manufacture the slag product, and (iv) aging treatment of the slag product for improving its quality and volumetric stability. These processes are explained below.   Fig 1 Processing of steelmaking slag As steelmaking slag is formed, it is in a molten or red-hot state at...