Crystallization Kinetics and Structure of CaF₂–CaO–Al₂O₃–MgO–TiO₂ Slag for Electroslag Remelting

Abstract

The crystallization kinetics and structure of CaF₂–CaO–Al₂O₃–MgO–TiO₂ slag for electroslag remelting (ESR) were investigated by differential scanning calorimetry and Raman spectroscopy, respectively. The results show that increasing TiO₂ content from 4.2 mass% to 16.8 mass% in the slag lowers the crystallization rate of the slag. The crystallization of the primary crystalline phase (11CaO·7Al₂O₃·CaF₂) in the slags with 4.2–12.6 mass% TiO₂, and primary crystalline phase (11CaO·7Al₂O₃·CaF₂ and CaTiO₃) in slag with 16.8 mass% TiO₂ originates from constant nucleation rate, interface reaction controlled and one-dimensional growth, irrespective of the TiO₂ contents of the slag. Raman spectroscopy study indicates that TiO₂ plays a network-modifier role in relatively more complex Al–O–Al band and Q⁴ units by forming Q² units and less complex Ti₂O₆^4- chain unit, resulting the decreasing of the polymerization degree of the slag. The variation in slag structure is in agreement with the analysis of crystallization kinetics.