Thermal analysis techniques applied to study corrosion mechanisms of SEN used in the steel continuous casting process

Abstract

Recent advances in the technology of black refractories for steel continuous casting promote the development of materials that operate at extreme conditions. The effects of different damage mechanisms are critical, and it is necessary to provide detailed information about the thermal behaviour of the nozzle–mould flux system, at steel continuous casting process condition. Mould fluxes present a chemical composition that includes a complex mix of oxides, fluorite (CaF2) and carbonaceous materials (coke, graphite, etc.). Their physical properties [viscosity (η) and surface tension (γ)] are strongly dependent on chemical composition and temperature evolution at process conditions. For this reason, a complete characterization and deep knowledge of the thermal behaviour of the mould flux is the key to understand in detail the interaction phenomena present in the system (insert nozzle–mould flux), in order to identify the corrosion mechanisms. In these circumstances, the use of thermal analysis techniques (DTA-TG and dilatometry) can provide relevant information about nozzles and mould fluxes such as phase transformations, mass changes and volumetric variations, which occur in the system of study. In this paper, these results are correlated with a microstructural study of two samples: S1 (as received) and S2 (post-mortem) applying different microscopy techniques, X-ray diffraction and thermal simulation of the nozzle corrosion by FactSage 7.2 in order to identify the wear mechanisms and to obtain relevant information for the refractory and steelmaking industry.