Quantitative phase analysis of exogenous nonmetallic inclusions in steel

Abstract

† Inclusions introduced in steel by the batch materials (scrap, hot metal, ferroalloys, etc.) are said to be exogenous. This is a relatively arbitrary definition, since it is not always possible to trace the origin of nonmetallic inclusions. Inclusions were systematized into groups (oxides, nitrides, carbides, sulfides, silicates) in [1]. In this brief academic study, a serious effort was made to establish the relation between the technology and the composition of the inclusions. The description of nonmetallic inclusions (an atlas, 227 figures) is an example of scrupulous and thorough experimental research, which remains valid today. However, the author wrote of slag inclusions. This term does not reflect the breadth of possible compositions and is not widely used today. In the present work, we calculate the phase composition of slag inclusions seen in melt smelted by various technologies [1]. The composition of such inclusions cannot be expressed as a sum of simple oxides. The reaction between the simple oxides (elements) is taken into account on the basis of thermodynamics and material-balance equations. By refining the phase composition of exogenous inclusions introduced in steel, we may correct the alloying and reduction technology on the basis of a deeper understanding. Special attention is paid to nonmetallic inclusions in ferroalloys, since such inclusions are supplied to the ingot when alloying steel in the ladle.