Interfacial Reactions and Inclusion Formations at an Early Stage of FeNb Alloy Additions to Molten Iron

Nb is an important microalloying element in steelmaking. Its interaction with liquid Fe during an early stage of the alloying process has a considerable influence on the Nb recovery. In the present work, the inclusions in FeNb alloys were characterized using the electrolytic extraction method combined with SEM-EDS. The interfacial reactions between FeNb alloy and liquid Fe, as well as inclusion formations, were studied during an early stage of an alloy addition using a liquid-metal-suction method. The results revealed that a diffusion zone consisting of different regions of Fe-Nb phases was formed and that the thickness of the zone increased with time. Based on the experimental findings, the mechanism of the early dissolution process of FeNb alloys in liquid Fe was discussed. Moreover, the Nb rich regions formed after the alloy contacted with liquid Fe could modify the existing inclusions in the alloy, also their evolution mechanisms were studied. The addition of FeNb alloys can introduce inclusions, such as Al-O and Al-Ti-Nb-O inclusions to the liquid steel. Overall, this study has contributed to the understanding the behaviour of impurities from the FeNb source at the early dissolution process during the microalloying process of steels containing Nb.