Optimization And Industrial Experiment On Basic Tundish Fluxes Made Of Blast Furnace Slag

Basic tundish flux was produced by blast furnace slag. It gives not only savingresources and protecting environment, but also good economic and social benefit. Byanalyzing of the type and application provided a basic data for the research on thetundish covering flux.By using blast furnace slag as base material, and lime, limestone, fluorite andvermiculite as additives, special basic tundish flux for Longmen Iron and Steel Workswas prepared. Combining with the chemical composition of the raw materials, the seriesof experiments were carried out according to the phase diagram ofCaO-A12O3-SiO2-MgO8wt%.Melting temperature, melting rate, viscosity and thermalinsulation property were determined for each formulation with the method of Quadraticregression orthogonal design. The phase composition of the melted cover agents wereanalyzed by TG-DSC and XRD. Furthermore, quadric polynomial regression modelwas established to determine the effects of CaF2wt%and alkalinity on the meltingtemperature, melting rate and viscosity. The tundish covering agent formula wasoptimized finally.The results of melting temperature and melting rate indicated that meltingtemperature of tundish covering flux could be dramatically reduced by70℃with CaF2changing from10to20wt%and also reduced50℃with alkalinity varying from1.5to2.0.Melting rate respectively shorted up to23s and extended up to17s with theincreasing of CaF2wt%and the alkalinity. The best content of vermiculite was20wt%in the experiments of thermal insulation property. The viscosities of tundish fluxeswhich were between0.388Pa·s and0.743Pa·s at1450℃decreased gradually with the rise of temperature and influenced greatly by alkalinity varying from1.75to1.85.Themelting temperatures of cover agents varied with the different phase composition inmolten condition by TG-DSC and XRD. According to the above research results, thechemical components was optimized (CaF210~15wt%, alkalinity1.75~1.85,vermiculite20wt%and the utilization rate of blast furnace slag ranged from38to45wt%).Furthermore, industrial tests were carried out by using the optimal formula.(blastfurnace slag37.1wt%, lime stone35.1wt%, fluorite12.2wt%and vermiculite15.6wt%).The result indicated that the tundish flux spurted little dust, and it didn’tcongeal and sticked the long nozzle. In addition, the tundish covering flux had goodspreadability and thermal insulation property, which could spread smoothly and fully in5minutes and exposed less.