The volatilization problem of mold fluxes extremely affects their physicochemical properties and then the quality of steel shells and casting process. Therefore, in this paper, the qualitative and quantitative analysis of volatiles in the most commonly used CaO–SiO₂–CaF₂–Na₂O slag was conducted with thermogravimetric analyzer–mass spectroscopy (TG–MS), X-ray diffraction (XRD), scanning electron microscope with energy-dispersive spectroscopy (SEM–EDS) and FactSage, followed by giving the mechanism of fluorine volatiles in mold fluxes during the actual casting process. The results showed that the fluorine volatiles were formed when the temperature was higher than 1000 °C. The species of fluorine volatiles were SiF₄ and NaF. Moreover, the total volatiles content of fluorine for sample B with Na₂O was 9.41%, being much larger than that of 1.53% for sample C without Na₂O. For sample B, the content of NaF was much larger than that of SiF₄. It was because of the reaction between Na₂O and CaF₂. SiF₄ with a low boiling point of − 65 °C could pass through the slag layer and enter air directly. However, when NaF passed through the sinter layer or powder slag layer, NaF would convert into liquid or solid state, reenter molten slag and continuously repeat this process due to their high melting point of 993 °C.

脱模剂的挥发问题极大地影响了它们的理化性能，进而影响了钢壳的质量和铸造工艺。因此，本文采用热重分析仪-质谱（TG-MS），X射线衍射仪（XRD）对最常用的CaO-SiO ₂ -CaF ₂ -Na ₂ O炉渣中的挥发物进行定性和定量分析。），带能量色散光谱仪（SEM-EDS）和FactSage的扫描电子显微镜，然后给出了实际铸造过程中结晶器熔剂中氟挥发物的机理。结果表明，温度高于1000℃时，会形成氟挥发物。氟挥发物的种类为SiF ₄和NaF。此外，含Na ₂ O的样品B中氟的总挥发物含量为9.41％，比不含Na ₂ O的样品C中氟的总挥发物含量大1.53％。对于样品B，NaF的含量远大于SiF的含量₄。这是由于Na ₂ O和CaF ₂之间的反应。低沸点为-65°C的SiF ₄可以穿过炉渣层并直接进入空气。但是，当NaF通过烧结层或粉末炉渣层时，NaF会因其993°C的高熔点而转变成液态或固态，重新进入熔融炉渣并连续重复此过程。