Kinetics of oxidation of carbon in liquid iron-carbon-silicon-manganese-sulfur alloys by carbon dioxide in nitrogen |
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Authors: | Haiping Sun Robert D Pehlke |
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Affiliation: | (1) Department of Materials Science and Engineering, Kyushu University, 813 Fukuoka, Japan;(2) Department of Materials Science and Engineering, University of Michigan, 48109 Ann Arbor, MI |
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Abstract: | The oxidation of carbon with the simultaneous oxidation of silicon, manganese, and iron of liquid alloys by carbon dioxide
in nitrogen and the absorption of oxygen by the alloys from the gas were studied using 1-g liquid iron droplets levitated
in a stream of the gas at 1575 °C to 1715 °C. Oxidation of carbon was favored over oxidation of silicon and manganese when
cast iron (3.35 pct C, 2.0 pct Si, 0.36 pct Mn, and 0.05 pct S) reacted with CO2/N2 gas at 1635 °C. An increase in the flow rate of CO2/N2 gas increased the decarburization rate of cast iron. The rate of carbon oxidation by this gas mixture was found to be independent
of temperature and alloying element concentrations (in the range of silicon = 0 to 2.0 pct manganese = 0 to 0.36 pct and sulfur
= 0 to 0.5 pct) within the temperature range of the present study. Based on the results of a kinetic analysis, diffusion of
CO2 in the boundary layer of the gas phase was found to be the rate-limiting step for the reactions during the earlier period
of the reaction when the contents of carbon, silicon, and manganese are higher. However, the limiting step changed to diffusion
of the elements in the metal phase during the middle period of the reaction and then to the diffusion of CO in the gas phase
during the later period of the reaction when the content of the elements in the metal were relatively low. For the simultaneous
oxidation reactions of several elements in the metal, however, the diffusion of CO2 in the gas phase is the primary limiting step of the reaction rate for the oxidation of carbon during the later period of
reaction.
Formerly Visiting Assistant Research Scientist, Department of Materials Science and Engineering, University of Michigan, Ann
Arbor, MI 48109 |
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