In-situ confocal microscopy study of the dissolution kinetics of calcium aluminate inclusions in CaO-Al2O3-SiO2 type steelmaking slags

Abstract

Dissolution kinetics of CaO∙2Al2O3 (CA2) particles in a synthetic CaO-Al2O3-SiO2 steelmaking slag system has been investigated using high-temperature confocal laser scanning microscope (HT-CLSM). Effects of temperatures (i.e., 1500, 1550, and 1600°C) and slag composition on the dissolution time of CA2 particles are investigated, along with the time dependency of the projection area of the particle during the dissolution process. It is found that the dissolution rate was enhanced by either an increase of temperature or a decrease of slag viscosity. Moreover, a higher ratio of CaO/Al2O3 (C/A) leads to an increased dissolution rate of CA2 particle at 1600°C. Thermodynamic calculations suggested that the dissolution product, i.e. melilite formed on the surface of the CA2 particle during dissolution in slag with a C/A ratio at 3.8 at 1550°C. SEM-EDS analysis of as-quenched samples confirmed the dissolution path of CA2 particles in slags with C/A ratio at 1.8 and C/A ratio at 3.8 as well as melilite formed on the surface of CA2 particle. The formation of this layer during the dissolution process was identified as a hindrance, impeding the dissolution of CA2 particle. The current study offers a valuable reference for designing or/and choosing the composition of top slag for clean steel production, especially using calcium treatment during the secondary refining process.