THE DISSOLUTION OF NIOBIUM AND ZIRCONIUM IN LIQUID STEEL

The dissolution rates of niobium and zirconium cylinders in liquid steel have been measured in a 'dynamic way', with the help of a data acquisition and process control facility. Two distinct periods were identified; the steel shell period and the free dissolution period.; Lower bath superheats allowed a reaction to take place at the steel shell/niobium interface while higher superheats didn't; the intermetallic compounds Fe{dollar}sb 2{dollar}Nb and Fe{dollar}sb 2{dollar}Nb{dollar}sb 3{dollar} were identified as the reaction products. Niobium dissolved relatively slowly in liquid steel and its dissolution speed was increased under dynamic conditions (i.e., inductively stirred baths).; In the case of zirconium, an exothermic reaction occurred at the steel shell/zirconium interface and the intermetallics Fe{dollar}sb 2{dollar}Zr and FeZr{dollar}sb 2{dollar} were identified as the reaction products. This reaction was triggered at 1220 K by the formation of a liquid Fe-Zr (76 at% Zr) eutectic. For the experimental conditions under which this study was performed, the hydrodynamic conditions of the steel baths did not seem to influence the dissolution rates of zirconium.; A simplified mathematical model was used in order to simulate the coupled heat and mass transfer phenomena which take place during the two periods.