ACCELERATIVE EVAPORATION MECHANISM OF MOL TEN PURE COPPER AND HIGH-CARBON IRON BY UREA ADDITION

In order to obtain the fundamental information concerning accelerative evaporation of copper dissolved in molten steel with ammoniacal compo und, experiments were done by adding urea onto molten pure copper and high carbon iron containing 0.4% Cu at 1150 to 1450 degrees C under an argon atmosphere. Evaporated amount of the molten copper increased wi th the increase of urea amount. At constant urea amount, it increased with increasing temperature at 1150 to 1250 degrees C, while it became constant above 1250 degrees C. Based on the mass balance of evaporate d copper to added urea, it was concluded that the molten copper was ev aporated as Cu(N-3)(2) and this compound decomposed to liberate copper immediately after evaporation. In the case of high carbon iron contai ning 0.4% Cu, iron was preferentially evaporated, so that copper was c oncentrated in the molten iron. At constant urea amount, evaporated am ount of the molten iron increased abruptly with increasing temperature up to 1250 degrees C, while it reached almost constant value at 1250 to 1300 degrees C. After again increasing at 1300 to 1350 degrees C, i t remained unchanged above 1350 degrees C. X-ray diffraction analysis showed that the matter entrapped from exhaust gas was composed of grap hite, Fe3C and Fe3N. Based on this result and the mass balance, it was concluded that the high carbon iron was evaporated as Fe(CN), below 1 300 degrees C and Fe(CN)(2) above 1350 degrees C.