w(CaO)/w(Al2O3)对钙铝基保护渣结晶性能的影响

利用热丝法测试技术，结合扫描电镜和能谱分析，研究了不同w(CaO)/w(Al₂O₃)条件下钙铝基保护渣的结晶性能.结果表明，较低w(CaO)/w(Al₂O₃)下，保护渣结晶物相为LiAlO₂和CaO·Al₂O₃.其析出由渣中的Li⁺离子和Ca²⁺离子分别对高聚合度铝氧四面体结构的电荷补偿所致.而且，Li⁺离子优先参与，LiAlO₂优先析出.较高w(CaO)/w(Al₂O₃)下，结晶物相转变为LiAlO₂和3CaO·Al₂O₃.其变化原因为，CaO相对质量分数提高，保护渣聚合度降低，Ca²⁺离子和低聚合度铝氧四面体结构单元Q²结合而形成3CaO·Al₂O₃并析出.随着w(CaO)/w(Al₂O₃)由1.13提高至1.82，钙铝基保护渣析晶能力先减弱然后增强.在w(CaO)/w(Al₂O₃)为1.50和1.82时分别具有最弱和最强的析晶能力.

Effect of w( CaO)/w( Al2 O3 ) on the Crystallization Properties of CaO-Al2 O3-based Mold Flux

The crystallization properties of CaO-Al₂O₃-based mold fluxes with different values of w(CaO)/w(Al₂O₃) were studied by using single hot thermocouple technique(SHTT) and scanning electron microscope and energy dispersive spectrometer(SEM-EDS). The results showed that the crystalline phases were LiAlO₂ and CaO·Al₂O₃ with a lower w(CaO)/w(Al₂O₃). They were formed due to the charge compensation of Li⁺ions and Ca²⁺ ions to aluminum tetrahedral structure with high polymerization degree. Li⁺ions were preferentially involved， and LiAlO₂ preferentially precipitated. With higher w(CaO)/w(Al₂O₃)， the crystalline phase was transformed into LiAlO₂ and 3CaO·Al₂O₃. The reason for the change was that the relative mass fraction of CaO was increased， accordingly， the degree of polymerization of the mold flux was decreased and 3CaO·Al₂O₃ was formed and precipitated due to the combination of Ca²⁺ ions and low-polymerization tetrahedral structural unit Q². As the w(CaO)/w(Al₂O₃) was increased from 1.13 to 1.82， the crystallization ability was first weakened and then increased. The crystallization ability was the weakest and the strongest when the w(CaO)/w(Al₂O₃) was 1.50 and 1.82， respectively.