Presentation on theme: "GTT-Technologies AVOIDING NOZZLE CLOGGING DURING CASTING OF STEELS Steels contain additions of Aluminium (grain refining) and Sulphur (machinability)."— Presentation transcript:
GTT-Technologies AVOIDING NOZZLE CLOGGING DURING CASTING OF STEELS Steels contain additions of Aluminium (grain refining) and Sulphur (machinability). In both cases, nozzle clogging can occur during continuous casting. o At what temperatures, O- and Ca- contents can a steel with a given Al- and S- content be cast without nozzle clogging?
GTT-Technologies AVOIDING NOZZLE CLOGGING DURING CONTINUOUS CASTING OF STEELS The figures show: Figure 1: From the phase diagram one can find which phases can coexist at 1600°C in the system Al 2 O 3 -CaO. Figure 2: Depending upon the O- and Ca- content of the steel, one can find at a given temperature either, solid aluminates, aluminate + liquid oxide, liquid oxide only, or liquid oxide + CaS precipitate in equilibrium with the liquid steel. Experimental findings are also shown in the diagram. Figures 3, 4 & 5 show the nozzle clogging behaviour in different perspective, e.g. when adding CaSi to a steel bath. The conclusion is, that by influencing thermochemical parameters, it is possible to find a “Slag-window” in which nozzle clogging does not occur.
GTT-Technologies F IGURE 1: CaO.2Al 2 O 3 + CaO.Al 2 O 3 3CaO.Al 2 O 3 + CaO.Al 2 O 4 CaO.6Al 2 O 3 +Al 2 O 3
GTT-Technologies F IGURE 2:
GTT-Technologies Figure 3: Phase Fields for T=1600 C and various wt ppm Oxgen
GTT-Technologies Figure 4: Precipitation phases as function of CaSi addition
GTT-Technologies Figure 5: Precipitation phases as function of CaSi addition, higher initial Al 2 O 3