Abstract
In order to obtain the fundamental information concerning accelerative evaporation of copper dissolved in molten steel with ammoniacal compound, experiments were done by adding urea onto molten pure copper and high carbon iron containing 0.4%Cu at 1150 to 1450°C under an argon atmosphere.
Evaporated amount of the molten copper increased with the increase of urea amount. At constant urea amount, it increased with increasing temperature at 1150 to 1250°C, while it became constant above 1250°C. Based on the mass balance of evaporated copper to added urea, it was concluded that the molten copper was evaporated as Cu (N3) 2 and this compound decomposed to liberate copper immediately after evaporation.
In the case of high carbon iron containing 0.4%Cu, iron was preferentially evaporated, so that copper was concentrated in the molten iron. At constant urea amount, evaporated amount of the molten iron increased abruptly with increasing temperature up to 1250°C, while it reached almost constant value at 1250 to 1300°C. After again increasing at 1300 to 1350°C, it remained unchanged above 1350°C. X-ray diffraction analysis showed that the matter entrapped from exhaust gas was composed of graphite, Fe3C and Fe3N. Based on this result and the mass balance, it was concluded that the high carbon iron was evaporated as Fe (CN)3 below 1300°C and Fe (CN)2 above 1350°C.
