Analysis of Steel Slag Composition and Properties to Facilitate the Search for Rational Slag Recycling Methods

Abstract

This paper is devoted to the challenging problem of steel slag recycling. This study considers the composition and properties of steel slag, namely, slag of electric and pneumatic steelmaking. Slag of the pneumatic and electric steelmaking was found to be composed of calcium silicate Ca2SiO4, while phosphorus is represented by a complex calcium silicophosphate. Iron is in oxidized forms of FeO, Fe2O3 and Fe3O4 with the following ratios to the total mass of iron oxides, %: 51.51:37.16:11.33 for pneumatic steelmaking slag, and 75.92:20.90:3.18 for electric steelmaking slag, respectively. Chemical composition study showed the following content of the main elements for electric steelmaking slag, mass %: 31.6 – 33.2 Fe; 0.330 – 0.383 P; 19.15 – 19.2 Ca; 4.62 – 5.39 Si; for pneumatic steelmaking slag, mass %: 18.7 – 20.5 Fe; 0.630 – 0.710 P; 27.8 – 28.0 Ca; 4.73 – 5.04 Si. Electron microprobe analysis of slag samples showed the presence of Fe, C, O, P, Ca, Si, Mn, Ti, Cr, and Mg heterogeneously distributed over the sample crosscut surface. Samples had low content of phosphorus, however, this element was found to be accumulated in clusters together with Si and Ca.