Crystallization Kinetics and Structure of CaF_2-CaO-Al_2O_3-MgO-TiO_2 Slag for Electroslag Remelting

摘要

The crystallization kinetics and structure of CaF_2-CaO-Al_2O_3-MgO-TiO_2 slag for electroslag remelting (ESR) were investigated by differential scanning calorimetry and Raman spectroscopy, respectively. The results show that increasing TiO_2 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·7Al_2O_3-CaF_2) in the slags with 4.2-12.6 mass% TiO_2, and primary crystalline phase (11CaO-7Al_2O_3·CaF_2 and CaTiO_3) in slag with 16.8 mass% TiO_2 originates from constant nucleation rate, interface reaction controlled and one-dimensional growth, irrespective of the TiO_2 contents of the slag. Raman spectroscopy study indicates that TiO_2 plays a network-modifier role in relatively more complex Al-O-Al band and Q~4 units by forming Q~2 units and less complex Ti_2O_6~(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.