The relationship between crystallization and break temperature of mould flux

Abstract

Many researchers believe that crystallization is responsible for drastic viscosity changes near the break temperature of mould flux; however, there are no reasonable experimental data to support this view. In this study, the complete crystallization process is recorded in situ by inhibiting the volatilization of fluoride, and the relationship between viscosity change and crystallization near the break temperature is studied. Mould flux with a basicity of 0.65 had no break temperature, and no crystallization occurs within the temperature range of the viscosity test. The other three mould fluxes begin to crystallize before the break temperature, but the crystal volume fractions at the break temperature are different. The break temperature of mould flux is the crystallization temperature with a critical crystal volume fraction, which is related to the viscosity before the break temperature. The higher the viscosity, the smaller the critical crystal volume fraction. Therefore, break temperature ≤ initial crystallization temperature.

Designing mould fluxes to prevent longitudinal cracking for peritectic steel slab casting

“…The relationship between the break temperature measured at rotation viscometer, and the onset of crystallization measured with thermal analysis apparatus, was already studied; it was reported that the crystallization temperature agrees well with the break temperature in some cases, and in other cases does not [10]. Besides, it was also reported that crystallization temperature should be higher than break temperature measured with rotation viscometer, because the break point is not related to the first crystals precipitation, but instead to a critical volume fraction of crystals; depending on mould flux composition, this volume varies [11].…”

Effect of Interfacial Reaction between CaO–BaO–Al2O3‐Based Mold Fluxes and High‐Mn–High‐Al Steels on Fundamental Properties and Lubrication of Mold Flux

“…The decrease in Na 2 O content was likely to be attributed to the evaporation as gaseous species or was reduced by Al in the liquid steel. Our group has tested that the volatilization ratio ranged from 0.5 to 1.25 mass% for four CaO–SiO 2 –Al 2 O 3 –MgO–Na 2 O–F mold fluxes with about 6–12 mass% of Na 2 O content. Kim et al also reported that Na 2 O would be reduced by Al in the molten steel due to less SiO 2 or high Al in the steel.…”

Optimization of Mold Slag for Continuous Casting of Peritectic Steel

“…However, the in situ observation of the crystallization of mold slag with different basicities in this study indicated that when basicity exceeded 1.45, the temperature at which the cuspidine crystal started to precipitate was reduced. [30] Therefore, the break temperature initially increased and subsequently decreased, as shown in Figure 2a. The evolution of the melting temperature illustrated in Figure 2b exhibits the same trend as the break temperature.…”