Thermodynamic and Kinetic Analysis for Transformation of Oxide Inclusions in Solid 304 Stainless Steels.

Inclusions in 304 stainless steels are transformed from manganese silicate to manganese chromite (spinel) upon heating in the range of 1000–1350 °C, while this transformation is not observed when heating temperature is 1400 °C. Thermodynamic analysis with software FactSage™ is applied in interpreting the transformation. Manganese chromite spinel, with light color under SEM, is deemed to be formed on the surface of MnO–SiO2 inclusions by the reaction between Cr in steel matrix and MnO–SiO2 in inclusions. Heating experiments with different time at 1235 °C (rolling insulation temperature) are carried out to confirm the kinetics of the transformation reaction. Mass transfer coefficients of inclusions' composition, SiO2, MnO, and Cr2O3 are ranging from 5 × 10−7 to 9 × 10−7 m s−1, depending on diameters and components of inclusions. [ABSTRACT FROM AUTHOR]