Effect of MgO on the fluoride vaporization and crystallization of CaF2–CaO–Al2O3–(MgO) slag for vacuum electroslag remelting

• Published in: Journal of thermal analysis and calorimetry Vol. 147; no. 20; pp. 11445 - 11455
• Main Authors: Li, Tengfei, Li, Guangqiang, Liu, Yu, Wang, Xijie, Tian, Yufeng
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.10.2022; Springer Nature B.V
• Subjects: Aluminum fluorides; Aluminum oxide; Analytical Chemistry; Calcium fluoride; Calcium oxide; Chemistry; Chemistry and Materials Science; Crystallization; Electroslag remelting; Inorganic Chemistry; Magnesium fluorides; Magnesium oxide; Measurement Science and Instrumentation; Melting; Physical Chemistry; Polymer Sciences; Slag; Vapor pressure; Vaporization; Viscosity; Vacuum electroslag remelting; Slag; MgO addition; Fluoride vaporization; Crystallization
• DOI: 10.1007/s10973-022-11347-y
• ISSN: 1388-6150

The vaporization and crystallization of CaF 2 –CaO–Al 2 O 3 slags with different MgO contents for electroslag remelting were investigated by various analytical methods. The results show that the main volatiles from investigated slag with 8.8 mass% MgO content at 1723 K are CaF 2 and AlF 3 and contain trace MgF 2 . The mass loss of CaF 2 –CaO–Al 2 O 3 –(MgO) slag decreases with the increase of MgO content. The addition of MgO within 8.8 mass% has little effect on the viscosity of investigated slag, implying that the viscosity change is not the reason to inhibit the fluoride vaporization. At 1723 K, the vapor pressures of CaF 2 and AlF 3 decrease with the increase of MgO content; thus, fluoride vaporization becomes weak. The fluoride vaporization of slag with MgO addition under vacuum at 1823 K is also inhibited. The MgO addition can decrease the crystallization temperature of 11CaO·7Al 2 O 3 ·CaF 2 , but excessive MgO addition can lead to the precipitation of MgO.