<p>High-Cr and Ti-bearing ferritic stainless steel (Ti-FSS) has superior corrosion resistance compared to other steel grades. Ti-FSS offers not only high corrosion resistance and formability but also superior cleanliness of the cold-rolled sheet. Specifically, the cleanliness of Ti-FSS is improved through vacuum oxygen decarburization (VOD) and ladle treatment (LT) processes. Nevertheless, there are unresolved problems such as large fluctuations in Ti-yield and formation-removal behavior of non-metallic inclusions (NMI) due to factors including Al deoxidation and slag-metal reactions after Ti alloying. Moreover, Mg(Al,Ti)₂O₄ spinel-type inclusions formed in molten steel after Ti alloying cause nozzle clogging and surface defects in the final products. Therefore, it is essential to design the slag refining process to ensure excellent removal of NMI and optimize deoxidation practice in VOD. In the present study, we investigated the Ti-yield and evolution behavior and number density (ND) of NMI in molten steel according to input conditions of aluminum and titanium in steel as well as TiO₂ and CaF₂ in slag during reactions between Ti-FSS melt and VOD slag. As the TiO₂ content in the slag increased, the Ti-yield in the molten steel and the average Ti₂O₃ content in the NMI both increased after the addition of titanium. When the Al/Ti input ratio increased, the Ti-yield in the molten steel slightly increased. Mg pick-up from the slag also increased with increasing Al/Ti input ratio, resulting in increased MgO content in NMI, and thus, spinel-type inclusions were modified into MgO particles. When the CaF₂ content in the slag increased, the total removal rate of NMI increased due to a decrease in slag viscosity, resulting in a concomitant decrease of the number density of NMI in Ti-FSS.</p>