A Novel Nonmetallic Inclusion in High‐Mn and High‐Al Steel Caused by the Interfacial Reaction Between Steel and Ladle Filler Sand

The influence of chromium‐bearing filler sand on the transformation of inclusions in high‐Mn and high‐Al steel under various reaction times and Mn content levels is studied, and the mechanism of filler sand intrusion into the steel matrix is analyzed. It is demonstrated that an inclusion containing Cr 2 O 3 is discovered. The evolution pathway of oxide inclusions is identified as Al 2 O 3 –MnO → Al 2 O 3 –MnO–SiO 2 → Al 2 O 3 –MnO–SiO 2 –Cr 2 O 3 (Cr 2 O 3 + MnO–SiO 2 ) → Al 2 O 3 –MnO–Cr 2 O 3 –MgO·Al 2 O 3 . It is noteworthy that Cr 2 O 3 inclusions tend to diffuse from the outside inward, but the internal content remains almost unchanged, which is due to the strong diffusion hindrance of SiO 2 . The formation of a liquid phase in the filler sand is a necessary condition for its infiltration into the steel matrix. The critical liquid‐phase content that results in the formation of Cr 2 O 3 inclusions is 42%, which contains 5–8% of Cr 2 O 3 . The formation of pore channels provides favorable conditions for sand penetration, with the maximum penetration depth reaching up to 29 mm. Large sand inclusion particles reach millimeter scale in size and are distributed quite randomly. Chemical reactions at the steel/sand interface can lead to an increase in the total oxygen (T.O) content in the steel. The reaction time has little effect on the T.O content, while the Mn content in the steel has a significant impact, with an increase of up to 41 ppm. During the smelting stage, the filler sand can enter the molten steel, thereby affecting the quality of the product.