Article ID



Elimination of copper from the molten steel by NH3 blowing under reduced pressure



Katsutoshi Ono
Eiji Ichise
Ryosuke O.Suzuki
Toshitsugu Hidani


Steel Research, Vol.66, No.9, (1995) pp. 372-376.


Based on the finding that blowing of NH3 gas onto molten pure copper at atmospheric pressure causes its evaporation of enormously high rate, attempts have been made on elimination of copper dissolved in molten steel by NH3 gas blowing under reduced pressure. Typical behaviors of molten steel when attacked by NH3 gas are boiling, splashing and in a violent case slopping from the crucible. These phenomena are accompanied by an immense increase in the surface area from which volatile species are able to evaporate and may be useful for vacuum metallurgical process. In this investigation, the decuprization experiments have been conducted to measure the rate at which the copper level in the molten steel is reduced using a vacuum induction furnace and blowing NH3 gas through a vertical water-cooled copper nozzle. The data were represented in terms of the amount of copper transferred from the melt to the gaseous phase per unit surface area and time. According to these experiments, complete decuprization was attainable confirming selective evaporation of copper from molten steel under reduced pressure. So far as the mechanism of copper elimination by NH3 gas, beside the enhanced vacuum evaporation of metal by cooling effect due to endothermic decomposition of NH3, the formation of volatile copper compound was suggested from the fact that the copper could be removed down to extra-low level as several ppm even under residual gas pressure of order of 10 Torr.