TY - JOUR

T1 - New Mold Slag Compositions for the Continuous Casting of Soft Steels

AU - Kölbl, Nathalie

PY - 2021

Y1 - 2021

N2 - Several fluorine-free mold slag compositions have already been established in the literature. In all cases, the formation of a crystalline phase exhibiting behavior similar to that of cuspidine is emphasized to control horizontal heat transfer without influencing the lubrication performance for the casting of peritectic steel grades. In contrast, for casting soft steels, glassy solidification of the slag is required. Herein, different slag compositions involving the selected oxides are developed with the help of FactSage calculations. Mixtures of pure raw materials are melted at 1673 K and quenched to 295 K. It is observed that B2O3 increases the glass-forming ability of the slags. To obtain the glassy phase, the composition must satisfy the conditions (CaO+MgO)/(Al2O3+SiO2)<0.9 and (CaO+MgO)<30wt%. For TiO2 content <10 wt%, glassy solidification is detected after quenching to room temperature. However, this phenomenon-is not observed for slags with TiO2 content >15 wt%. Moreover, the addition of alumina and alkali oxides enhances crystallization. Based on these findings, promising mold slag compositions are designed and characterized in the laboratory using a furnace crystallization test, mineralogical investigations, and the single/double hot thermocouple technique. From the investigated mixtures, three compositions are suggested for use in continuous casting processes.

AB - Several fluorine-free mold slag compositions have already been established in the literature. In all cases, the formation of a crystalline phase exhibiting behavior similar to that of cuspidine is emphasized to control horizontal heat transfer without influencing the lubrication performance for the casting of peritectic steel grades. In contrast, for casting soft steels, glassy solidification of the slag is required. Herein, different slag compositions involving the selected oxides are developed with the help of FactSage calculations. Mixtures of pure raw materials are melted at 1673 K and quenched to 295 K. It is observed that B2O3 increases the glass-forming ability of the slags. To obtain the glassy phase, the composition must satisfy the conditions (CaO+MgO)/(Al2O3+SiO2)<0.9 and (CaO+MgO)<30wt%. For TiO2 content <10 wt%, glassy solidification is detected after quenching to room temperature. However, this phenomenon-is not observed for slags with TiO2 content >15 wt%. Moreover, the addition of alumina and alkali oxides enhances crystallization. Based on these findings, promising mold slag compositions are designed and characterized in the laboratory using a furnace crystallization test, mineralogical investigations, and the single/double hot thermocouple technique. From the investigated mixtures, three compositions are suggested for use in continuous casting processes.

U2 - 10.1002/srin.202100165

DO - 10.1002/srin.202100165

M3 - Special issue

SP - 1

EP - 7

JO - Steel research international

JF - Steel research international

SN - 1869-344X

ER -