Evolution of Inclusions and Associated Microstructure in Ti–Mg Oxide Metallurgy Steel

Abstract

Evolution of inclusions from laddle furnace (LF) to continuous casting in Ti–Mg oxide metallurgy treatment were studied. The resuluts suggested that the composition of inclusions changed from MnS-MnO·SiO₂ to (Ti–Ca–Mg–Al–O)–MnS. Furthermore, EDS results indicated that the content of Mg decreased because of reduction reaction, float and gasification. The average size of inclusions was decreased from 0.73 µm to 0.47 µm and the number density decreased from 977/mm² to 595/mm² after continuous casting. The microstructures changed from polygonal ferrite (PF) and ferrite side plate (FSP) to acicular ferrite (AF), PF and bainite (B) gradually after inclusion treatment (Ti–Mg oxide metallurgy) in LF furnace and Ca treatment in RH furnace. Heterogeneous nucleation of AF was observed on the surface of Ti–Mg oxides.