Article ID
96BEN41002
Title
Elimination of Copper from Molten Steel by Ammonia Gas Blowing
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Author(s)
Toshitsugu Hidani
Koji Takemura
Ryosuke O.
Suzuki
Katsutoshi Ono
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Publication/Publisher
Tetsu-to-Hagane, Vol. 82, No.2 (1996), pp.
135-140.
SΖ| ζ82ͺ ζ2 (1996), 135-140Ε
Abstract
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 by NH3
gas are boiling, splashing and in a violent case slopping from the
crucible.
Evaporation from liquid pure copper by top-blowing of NH3 was
observed by the laser-light sheet method and it was confirmed that a large
amount of copper smoke takes off from the molten surface attacked by NH3 gas.
The condensates of the smoke were fine copper particles.
The decuprization
experiments have been conducted to measure the rate at which the copper level in
the molten steel is reduced by using a vacuum induction furnace and blowing NH3
gas through a vertical water-cooled copper nozzle. For comparison, the rate of
copper elimination from a small molten steel droplet has also been determined.
From these experiments the rate constant for copper elimination from a flat and
smooth surface of molten steel was the order of 2x10-3 mEmin-1 at 1900 K and the
pressure range of 100 to 10000Pa.
Because the boiling phenomena are
accompanied by an immense increase in the surface area from which volatile
species are able to evaporate, NH3 gas blowing may be useful to reduce the
decuprization time. Nitrogen concentration in the molten steel increases with
increasing the flow rate of NH3 gas. It was reduced down to the initial level by
vacuum degassing after stopping NH3 gas blowing.