Mold fluxes are complex oxides that, due to their chemical composition and structure, can be classified as glass-ceramics. These materials are used as lubricants in the continuous casting of steel at temperatures between 1200-1400°C. The rheology of these multicomponent oxide systems plays a fundamental role during the process, since the viscosity in the wall of the mold has to be adequate to maximize the lubrication capacity. For this reason, it is of technological interest to understand the relationship between this macroscopic property and the molecular/ionic structure, which strongly affects the performance of these materials in metallurgical processes. In this work, glassy layers from three commercial mold fluxes were obtained by quenching from 1300°C. Chemical compositions were analyzed by X-ray fluorescence spectroscopy (XRF). The layers were characterized by X-ray diffraction (XRD) and Raman spectroscopy. The viscosity of each of these materials was associated with a polymerization index of the silicate networks determined by the deconvolution of the Raman peak between 800-1200 cm-1 and the chemical composition. The parameter Q, defined as 4-NBO/T, obtained from the Raman spectra, presented a good correlation with the viscosity values measured at 1300ºC.
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