Chromium distribution between slag and non-carbon saturated metal phases under changin partial pressure of carbon monoxide

Slag-metal equilibrium experiments were conducted at 1500�C and 1580�C under 0.03 atm, 0.05 atm and 0.83 atm CO partial pressures using silica and Cr-oxide crucibles. The complex slags belonged to SiO2-CaO-Al2O3-MgO-FeOx-CrOx and the metal phase to the Cr-Fe-CSi-( S) systems. The carbon saturati...

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Bibliographic Details
Published in:Journal of the South African Institute of Mining and Metallurgy 2004-11, Vol.104 (10), p.583-587
Main Author: Pan, X. & Eric, R.H.
Format: Article
Language:English
Subjects:
carbon monoxide
carbon saturation
chromium distribution
equilibrium
high carbon ferrochromium
medium carbon ferrochromium alloys
non-carbon metal
non-carbon saturated metal phase
slag metal
slag metal phases
stainless steel
stainless steel manufacture
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Summary:Slag-metal equilibrium experiments were conducted at 1500�C and 1580�C under 0.03 atm, 0.05 atm and 0.83 atm CO partial pressures using silica and Cr-oxide crucibles. The complex slags belonged to SiO2-CaO-Al2O3-MgO-FeOx-CrOx and the metal phase to the Cr-Fe-CSi-( S) systems. The carbon saturation of the metal phase was avoided using oxide crucibles and thus the results are pertinent to ferrochromium refining slags and processes. From equilibrium data and thermodynamic calculations, the CrO /(CrO+Cr2O3) ratio in the slag was determined as 0.75, 0.80 and 0.86 under 0.83 atm and 0.05 atm of CO pressure at 1500�C and 0.03 atm and CO pressure at 1580�C, respectively. The results clearly demonstrated that a higher chromium content of the metal results in higher Cr in the slag, and chromium in slag decreases with increasing SiO2. The results were also sensitive to the crucibles used as these oxide crucibles saturated the slag either with respect to SiO2 or Cr-oxides. It was also demonstrated that the relative amount of CrO in the slag was higher when SiO2 crucibles were used in accord with thermodynamic calculations. Iso-concentration curves for carbon and chromium of the metal phase in equilibrium with the slag were drawn on a pseudo ternary SiO2 � (AI2O3+CaO+MgO) � (Cr2O3+Fe2O3) diagram. The activity coefficients and activities of carbon and chromium of the metal phase were also calculated from the experimental data and available thermodynamics information and were plotted as iso-activity curves in the same pseudo ternary diagram. Keywords: chromium, slag, equilibrium
ISSN:0038-223X