Evolution Behavior of Inclusions During the Reoxidation of Titanium Microalloyed Steel

Titanium microalloyed steels are widely used in modern manufacturing industries. However, during steelmaking, air, protective slag, and refractory materials can all contribute to the reoxidation of molten steel, with air having the most pronounced effect. This study investigates the evolution of inclusions during reoxidation in titanium microalloyed steel by combining experimental work with thermodynamic calculations. The results show that as reoxidation intensifies, both the types and sizes of inclusions in steel increase, and the increase in T.O content promotes Al 2 O 3 , thereby reducing the effectiveness of Ca treatment. Additionally, the composite inclusions follow the evolution path: Al 2 O 3 → Al 2 O 3 ‐CaO → Al 2 O 3 (‐CaO)‐(Mn, Ca)S → Al 2 O 3 –CaO–(Mn, Ca)S–TiN. With increasing nitrogen content, both the quantity and size of TiN inclusions also show a significant increasing trend. The experimental observations were further confirmed by thermodynamic calculations, revealing the thermodynamic conditions for inclusion formation in steel at different degrees of reoxidation. Notably, the maximum generation of Al 2 O 3 , TiN, and CaS inclusions increases as reoxidation progresses. Therefore, controlling the reoxidation degree of molten steel is crucial for reducing the formation of large TiN inclusions and composite inclusions and improving the cleanliness of molten steel.