The master’s thesis on The influence of the slag and high sulphur steel interactions on defects during ingot casting was carried out with the aim of determining the cause of the inclusion of slag into the casting system before the end of casting process, where there is still a significant amount of melt in the ladle. In doing so, we examined slag sample from rhizome of the casting system with SEM microscope, microstructural components were determined by EDS analysis. The chemical composition of the slag of PK339 steel was determined by ICP-OES and XRF methods, the composition of the samples was recalculated and they were alloyed with sulphur (0, 2,5, 5, 10 wt. %). We melted the samples in induction furnace, casted into a croning measuring cell, where we measured their temperature and electrical resistance. With thermodynamic calculations we characterized the phases in slag at certain temperatures and compared samples with one another. We also made XRD analysis of synthetic slag samples. With SEM analysis, we found that the steel droplets captured in slag are surrounded by a layer of CaS, which could be one of the causes of slag inclusion into the casting system. After measuring the electrical resistance of all four slag samples, we were also able to confirm the increase in the electrical resistance of the slag with increasing sulphur content, which means that as the sulphur content in the steel increases, the viscosity of the slag also increases, which, in addition to the aforementioned adhesion of CaS to the steel surface, is the reason for inclusion of slag in the casting system. We also performed Thermo-Calc calculations to determine the phases during solidification and cooling of slag.
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