Per: SAMUEL L. S. MEDEIROS (UFC), JEFERSON LEANDRO KLUG (UFC), KLAUS SCHHULZ (Imerys Metalcasting Germany
GmbH), BRUNO TOUZO (IMERYS BELGIUM SA)
Abstract:
MOLD FLUXES MAIN FUNCTIONS DURING CONTINUOUS CASTING OF STEEL ARE LUBRICATION AND CONTROL OF HORIZONTAL HEAT TRANSFER RATE. BOTH FUNCTIONS ARE DEPENDENT ON MOLD FLUX CRYSTALLIZATION BEHAVIOR. REMOVING F FROM MOLD FLUXES IS BECOMING OBVIOUS DUE TO ENVIRONMENTAL AND HEALTH CONCERNS, AND DUE TO CORROSION OF THE CONTINUOUS CASTING MACHINE. HOWEVER, WHEN REPLACING F WITH OTHER MATERIALS, SUCH AS TIO2-BASED ONES, AMONG OTHERS, THERE IS A DRASTIC CHANGE IN MOLD FLUXES RECIPES. THE MOLD FLUXES TECHNOLOGICAL PARAMETERS CHANGE, INCLUDING CRYSTALLIZATION BEHAVIOR, WHICH IS CRITICAL FOR PERITECTIC STEEL SLAB CASTING. CONSIDERING THE NEED FOR INDUSTRIAL TRIALS WITH NEW RECIPES, IT IS IMPORTANT TO GET BASIC UNDERSTANDING ON CRYSTALLIZATION KINETICS TO OPTIMIZE TESTS, WHEN DEVELOPING F-FREE TIO2-BEARING MOLD FLUXES FOR PERITECTIC STEEL SLAB CASTING. THEREFORE, IT IS NECESSARY TO DEFINE THE BEST WAY TO EVALUATE CRYSTALLIZATION KINETICS. THE PRESENT WORK SHOWS A SURVEY OF THE LITERATURE ON HOW TO ASSESS CRYSTALLIZATION KINETICS FOR F-FREE MOLD FLUXES. THE TWO KINDS OF CRYSTALLIZATION PROCESSES WHICH ARE RELEVANT DURING CONTINUOUS CASTING ARE ANALYZED. REGARDING CRYSTALLIZATION FROM MELT, THE FRIEDMAN ISOCONVERSIONAL METHOD CAN BE USED TO DETERMINE ACTIVATION ENERGY. AND FOR CRYSTALLIZATION FROM GLASS (DEVITRIFICATION), THE MATUSITA-SAKKA MODEL SHOULD BE USED. THE SINGLE HOT THERMOCOUPLE TECHNIQUE CAN BE USED TO GET COMPLEMENTARY INFORMATION. IN THIS WAY, CRYSTALLIZATION KINETICS FOR NEW F-FREE RECIPES CAN BE COMPARED WITH STANDARD F-BEARING RECIPES WHICH ARE BEING USED AT STEELWORKS, FOR THE RELEVANT CRYSTALS WHICH PRECIPITATE DURING CONTINUOUS CASTING.
