2015 Volume 55 Issue 4 Pages 830-836
Crystallization behaviors of new developed CaO–Al2O3 based mould fluxes with TiO2 addition for casting of high-Al steels were investigated by using DTA techniques combined with SEM-EDS and XRD analysis. XRD and SEM analyzed on the crystallized samples showed that the sequence of crystal precipitation for TiO2-free mould flux during cooling was MgO, and followed by Ca12Al14O33 during cooling. The sequence of crystal formation for TiO2-bearing mould fluxes during cooling is CaTiO3 to MgO, and then Ca12Al14O33. Continuous cooling transformation diagrams (CCT) were constructed for analysis of the crystallization behaviors. The Undercooling values for onset crystallization of various crystals were calculated by using liquidus temperature obtained by heating DTA and crystallization temperature of various crystals. The crystallization temperatures of CaO–Al2O3 based mould fluxes increased with increasing TiO2 content. The undercooling values for onset crystallization of CaTiO3 decreased with increasing TiO2 content, which indicating that the crystallization of CaTiO3 was enhanced with increasing TiO2 content. The undercooling values for onset crystallizations of Ca12Al14O33 and MgO only changed slightly with increasing TiO2. This indicated that crystallizations of Ca12Al14O33 and MgO crystals were only slightly influenced by TiO2 addition. The overall crystallization of mould fluxes was enhanced with increasing TiO2 content.