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Elimination of copper from the molten steel by NH 3 blowing under reduced pressure
Author(s) -
Ono Katsutoshi,
Ichise Eiji,
Suzuki Ryosuke O.,
Hidani Toshitsugu
Publication year - 1995
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199501140
Subject(s) - copper , crucible (geodemography) , chemistry , metallurgy , evaporation , nozzle , boiling , boiling point , atmospheric pressure , brass , materials science , thermodynamics , computational chemistry , physics , oceanography , organic chemistry , geology
Based on the finding that blowing of NH 3 gas onto molten pure copper at atmospheric pressure causes an evaporation of an enormously high rate, attempts have been made to eliminate copper dissolved in molten steel by NH 3 gas blowing under reduced pressure. Typical behaviours of molten steel when attacked by NH 3 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 processes. 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 NH 3 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 NH 3 gas, besides the enhanced vacuum evaporation of metal by the cooling effect of endothermic decomposition of NH 3 , the formation of volatile copper compound was suggested from the fact that the copper could be removed down to an extra‐low level of several ppm, even under a residual gas pressure of the order of 10 Torr.