Study on the role of CaF2 in CaO-Al2O3-based mold fluxes with different acid-base property
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摘要: 采用新型CaO-Al2O3基结晶器保护渣进行高铝钢浇铸，可有效抑制钢液中Al与渣中组元的界面反应。但是，浇铸过程中仍存在着结晶性能强、传热不均等问题。助熔剂是调整熔渣理化性能的关键因素之一。基于此，系统研究了典型助熔剂CaF2对不同酸碱性CaO-Al2O3基保护渣微观结构、黏度及结晶物相的影响。结果表明，在近中性CaO-Al2O3基保护渣中加入CaF2后，析晶物相由Ca12Al14O33+Ca3Al2O6转变为Ca12Al14O32F2+LiAlO2+CaF2，LiAlO2的析出可导致转折点温度上升，升幅约175 ℃，熔渣高温段黏度基本保持不变。在偏碱性CaO-Al2O3基保护渣中加入CaF2后，析晶物相由Ca3Al2O6+CaO转变为Ca12Al14O32F2+LiAlO2+CaF2，单一CaO的过早析出得到有效抑制，转折点温度降低约70 ℃，高温段黏度明显减小。Abstract: The new CaO-Al2O3 based mold fluxes can effectively inhibit the interfacial reaction between Al and slag components in high-aluminum steel casting. However, there were still some problems in the casting process, such as strong crystallization performance and uneven heat transfer. Fluxing agent was one of the key factors to adjust the physical and chemical properties of slag. Based on this, the effects of typical flux CaF2 on the microstructure, viscosity and crystalline phase of CaO-Al2O3 based mold fluxes with different acid-base property were studied. The results show that in the near-neutral CaO-Al2O3-based mold flux, the crystallization phase changes from Ca12Al14O33+Ca3Al2O6 to Ca12Al14O32F2+LiAlO2+CaF2 after adding CaF2. The precipitation of LiAlO2 can lead to the increase of the breaking temperature by about 175 °C, and the viscosity of the high temperature section of the slag remains basically unchanged. In the alkaline CaO-Al2O3-based mold flux, the crystalline phase changed from Ca3Al2O6+CaO to Ca12Al14O32F2+LiAlO2+CaF2 after adding CaF2, and the premature precipitation of single CaO was effectively inhibited. The breaking temperature is reduced by about 70 °C, and the viscosity at high temperature is significantly reduced.
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Key words:
- continuous casting /
- high-aluminum steel /
- CaO-Al2O3 based mold flux /
- fluxing agent /
- viscosity /
- crystalline phase /
- melt structure
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图 5 不同温度下结晶物相的扫描电镜照片
Figure 5. SEM images of crystalline phases at different temperatures
图 7 S1与S3渣拉曼光谱曲线及拉曼光谱解谱
Figure 7. Raman spectra curves and solutions of S1 and S3 slags
图 10 不同温度下结晶物相的扫描电镜照片
Figure 10. SEM images of crystalline phases at different temperatures
图 12 S2与S4渣拉曼光谱曲线及拉曼光谱解谱
Figure 12. Raman spectra curves and solutions of S2 and S4 slags
表 1 保护渣的化学成分（摩尔分数）
Table 1. Chemical compositions of mold fluxes (mole fraction)
% 序号 CaO Al2O3 Li2O CaF2 C/A S1 59.8 32.2 8 1.86 S2 63.5 28.5 8 2.23 S3 59.8 32.2 8 10 1.86 S4 63.5 28.5 8 10 2.23 
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