Non-metallic inclusions – Their Quantitative extraction from Steel

Abstract

With the rising tempo in iron and steel industry in respect of quantitative output, the emphasis on quality of steel is equally significant. The quality of steel is closely related to the nature, quantum and mode of occurrence of non-metallic inclusions in steel. Tiny globules scattered uniformly may do little direct harm, but elongated inclusion streaks are potential weak areas break as these do continuity of the mass and as such strictly speaking represent elongated cracks within the steel body. However, complete removal of inclusions from steel is practically unattainable. Any sample of steel will on microscope study reveal particles of material incongruent with the metal lattice, demonstrating either definite non-metallic or quasi-metallic properties. Some of these are of foreign origin and are physically entrained particles of refractory, slag and the like, that have been entrapped by the freezing steel and thus are exogenous inclusions; whilst others evidently have been precipitated from the melt following chemical reactions or solubility changes in the wake of solidification of the melt. Such inclusions are known as indigenous inclusions and are integral part of the heterogeneous and complex metal body i.e. steel.