Influence of Oxygen Contamination on the Genesis of Nonmetallic Inclusions in a Microalloyed Steel

Nonmetallic inclusions are inherent to steelmaking processes, negatively affecting both mechanical properties and industrial productivity. The control of these inclusions is a determining factor in achieving high‐quality microalloyed steels. The objective of this study was to examine the evolution of nonmetallic inclusions in a microalloyed steel under adverse oxygen‐contamination conditions, simulating partially oxidizing atmospheres during melting. Controlled experiments with complete melting of the samples were conducted in an electric resistance furnace at 1575°C. After solidification, microstructural analyses were carried out using optical microscopy (OM) and scanning electron microscopy (SEM) using energy dispersive spectra (EDS) system. Moreover, some complementary study was carried out by thermodynamic simulations using Thermocalc software. Experimental results revealed the transformation of primary Al 2 O 3 (s) and CaO·Al 2 O 3 (s) inclusions into complex FeO–MnO types, indicating significant reoxidation during melting. Complementary thermodynamic simulations confirmed the stability of these mixed oxides at the investigated temperature. Systems subjected to oxidation favored the formation of alumina inclusions encapsulated by MnO–FeO oxides, demonstrating that controlling the melting atmosphere and the deoxidation process is essential for producing cleaner steels with improved microstructural reliability.