Abstract
Mold powders are mainly formed of such oxides as SiO2, CaO, Al2O3, Na2O along with F and C. One of the main constitutional composes of mold powders is F, which is utilized in chemical composition of mold powders due to its features of controlling viscosity and producing desired lubrication between solidified steel shell and mold. However, the emission of F through such compositions as HF (g) causes health and environmental problems. The purpose of this research is to decrease, and subsequently substitute, F in chemical composition of a lubricating high speed powder, which is used in continuous casting of steel industry. A combination of Fe2O3 and TiO2 compositions to substitute F in chemical composition of a fluorine-free mold powder was used to meet the purposed of this research. In addition, nine powder samples (A-I) with laboratory scale were prepared. In order to evaluate the samples’ viscosity behavior, groove viscometer test and image analysis software was used and to evaluate the crystalline behavior of samples C and G, XRD and SEM analyses were conducted. The results of these analyses demonstrated that the fluorine-free sample, due to its viscosity resemblance in comparison with molten reference powder and through creation of such crystalline phases as Perovskite (CaTiO3) and Fayalite (Fe2SiO4), will result in viscosity control of the mold powder and therefore optimizing continuous casting conditions. Finally, it is possible to derive that this sample may be an appropriate substitution for the reference powder being utilized in steel continuous casting industry.
Highlights
Mold powders are generally composed of such oxides as SiO2, CaO, Al2O3, Na2O along with F− and C [1]
One of the main constitutional composes of mold powders is F−, which is utilized in chemical composition of mold powders due to its features of controlling viscosity and producing desired lubrication between solidified steel shell and mold
In order to evaluate the samples’ viscosity behavior, groove viscometer test and image analysis software was used and to evaluate the crystalline behavior of samples C and G, XRD and SEM analyses were conducted. The results of these analyses demonstrated that the fluorine-free sample, due to its viscosity resemblance in comparison with molten reference powder and through creation of such crystalline phases as Perovskite (CaTiO3) and Fayalite (Fe2SiO4), will result in viscosity control of the mold powder and optimizing continuous casting conditions
Summary
Mold powders are generally composed of such oxides as SiO2, CaO, Al2O3, Na2O along with F− and C [1]. One of the major constituents of mold powders is fluorine (CaF2), which is used to control viscosity and solidification temperature in the slag film through creation of crystalline sediment of Cuspidine (3CaO·2SiO2·CaF2) [6, 7] These properties are directly related to lubrication and heat transfer between the steel shell and copper mold walls [8,9]. The aim of this study is to decrease F− in the chemical composition of the mold powder and replace it with other compositions, and subsequently study the effects of its replacements on viscosity For that purpose, such compounds as iron oxide (Fe2O3), titanium oxide (TiO2), zinc oxide (ZnO), sodium oxide (Na2O), boron oxide (B2O3), lithium oxide (Li2O), were used as substitutes for fluorine (CaF2) in the produced powders.
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