Sls 573 Pdf Free Free Download
Considering the development of non-reactive F-free mold fluxes for the continuous casting of high aluminum steels, it is imperative to understand their crystallization behavior in the mold, since control of horizontal heat transfer is related to crystallization tendency. An inappropriate control of heat transfer in continuous casting process can result in breakout if heat transfer rate is too low, or longitudinal cracks if heat transfer rate is too high.
Sls 573 Pdf Free Download
Mold fluxes play a crucial role in the continuous casting of defect-free steel products, providing appropriate heat transfer control, lubrication, thermal insulation, inclusion absorption, and oxidation prevention.[1] It is well accepted that horizontal heat transfer rate can be controlled when controlling mold slag crystallization.[2,3]
In order to deal with these demands, in a previous study, several recipes of F-free CaO-Al2O3-based mold fluxes were proposed and evaluated. In this study,[5] it was reported that, for some compositions in the CaO-Al2O3-B2O3-Na2O-Li2O system, the viscosity and melting temperature were close to traditional CaO-SiO2-CaF2 mold fluxes. Besides, crystallization from mold slag was analyzed. The first crystal, which precipitates during continuous cooling, is Ca3Al2O6, followed by LiAlO2 and Ca3B2O6. It was found that crystallization temperatures got from differential thermal analysis (DTA) decreases when increasing B2O3 and Na2O contents. This work concluded that some recipes in the CaO-Al2O3-B2O3-Na2O-Li2O system are potential substitutes for traditional mold powders. Due to their non-reactive behavior (no SiO2), these new fluorine-free mold fluxes could be applied for casting of high Al steels.
Several techniques have been developed to study the crystallization behavior of mold fluxes, such as DTA.[12,13] Differential Scanning Calorimetry (DSC),[14,15,16] Single Hot Thermocouple Technique (SHTT),[17,18,19] Double Hot Thermocouple Technique (DHTT),[17,20] laser confocal microscopy,[21] and others.[22] However, most of these studies were performed above mold flux liquidus temperature and therefore mainly dealt with crystallization from molten slag. Few papers are found for mold flux devitrification.[12,13,23] The present authors investigated traditional glassy mold fluxes[13,24] and glassy fluoride-free mold fluxes based on CaO-SiO2-TiO2-B2O3 system using DTA.[25] Regarding devitrification of fluorine-free mold fluxes based on the CaO-Al2O3-B2O3 system, no report was found in the literature.
The present paper reports an investigation using DSC with multiple heating rates, considering non-isothermal crystallization kinetics for glassy fluorine-free mold fluxes in the CaO-Al2O3-B2O3-Na2O-Li2O system. Field-Emission Environmental Scanning Electron Microscope/Energy Dispersive Spectroscopy (FE-SEM/EDS) techniques were used to identify crystalline phases and observe the morphology of crystals. Crystallization mechanisms and activation energies for devitrification were determined for three mold flux samples, with the ratios w(CaO)/w(Al2O3) 0.9, 1.0, and 1.1.