Crystallization Behavior, Viscosity and Structure of CaO–SiO2–MgO–(15 30 Mass Pct) Al2O3 Melts Representing the Oxide Inclusions in Si-Killed Steel

The crystallization behavior, viscosity and structure of CaO–SiO2–MgO–Al2O3 melts with different Al2O3 contents and CaO/SiO2 mass ratios were investigated. The local structures of oxide glasses were determined by Raman spectroscopy to correlate their crystallization behaviors. The crystallization temperature of the oxide melts increases as the Al2O3 content is increased from 15 to 30 mass pct, indicating an increased crystallization tendency. However, the crystallization ability of the oxide melts was lowered with the increase in the Al2O3 content. Since the polymerization degree of the aluminosilicate network increases, the viscosity of the oxide melts increases as the Al2O3 content is increased from 15 to 30 mass pct, resulting in suppressed crystallization ability. The reduction of the viscosity of oxide melts with increasing CaO/SiO2 mass ratio from 0.8 to 1.2 is dominated by a reduced polymerization degree of the oxide melts, resulting in the crystallization enhancement of oxide melts.