Mechanism of Interfacial Reactions Between Type 430 Stainless Steel and Complex MgO–Al₂O₃–SiO₂–CaO–MnO Oxide During Isothermal Heating

Abstract

To quantitatively study the mechanism of interfacial reactions between type 430 stainless steel and complex MgO–Al₂O₃–SiO₂–CaO–MnO oxide during the soaking process before hot-rolling, diffusion couple experiments at 1373 K and 1673 K (1100 °C and 1400 °C) with different MnO and SiO₂ contents were conducted. Experimental results showed that the “solid–liquid” and “solid–solid” steel–oxide reactions occurred between the Cr, Mn and Si in the steel and the MnO and SiO₂ in the MgO–Al₂O₃–SiO₂–CaO–MnO oxide during the heating at 1373 K and 1673 K (1100 °C and 1400 °C), respectively, resulting in a change of steel and oxide compositions. Calculations on the Gibbs free energy changes of those steel–oxide reactions before and after isothermal heating indicated the thermodynamic equilibrium at the interface of the steel and oxide were generally achieved after the heating at 1373 K and 1673 K (1100 °C and 1400 °C) for 240 min. Diffusion coefficients of related elements in type 430 stainless steel at 1373 K and 1673 K (1100 °C and 1400 °C) were calculated: Cr, Mn, and Si at 1673 K (1400 °C) are in the range of 1.44 to 3.40 × 10^–12, 0.42 to 1.19 × 10^–11 and 0.52 to 1.34 × 10^–11 m² m⁻¹, respectively, while Mn and Si at 1373 K (1100 °C) are in the range of 0.80 to 3.71 × 10⁻¹³ and 1.04 to 5.64 × 10⁻¹³ m² s⁻¹, respectively.