In-situ observation and crystallization kinetics during the solidification of Cr-containing stainless steel slags

Abstract

For a sustainable recycling process of Cr-containing stainless steel slags, high chromium recovery through selective crystallization could be achieved when thermophysical properties are controlled based on the crystallization kinetics. The in-situ observation and crystallization kinetics of synthesized Cr-containing slags has been studied. The crystallization characteristics in the CaO–SiO2–Al2O3–MgO–Cr2O3 slag system were investigated by using CLSM (confocal laser scanning microscopy) and DSC (differential scanning calorimetry). Analysis of crystallization kinetics was divided into spinel phase and calcium silicate phase. The growth mechanism of primary spinel phase has been demonstrated through CSD (crystal size distribution) theory with varying temperatures and cooling rates. The crystallization kinetic analysis of calcium silicate phase was performed using the modified Avrami equation and the combined Avrami and Ozawa equation. The Friedman differential isoconversional method was applied for determining the apparent activation energy during non-isothermal crystallization. Observations of crystalline phase morphologies and the precipitated phase was identified by using SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy) and XRD (X-ray diffraction) analyses. The change in the crystallization characteristics were compared with the slag melt structures analyzing by Raman spectroscopy.

Keywords

• Cr-containing slag
• Crystallization
• Confocal laser scanning microscope
• Spinel
• Raman spectroscopy