The rate of absorption of nitrogen into liquid iron containing oxygen and sulfur |
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Authors: | R J Fruehan L J Martonik |
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Affiliation: | (1) U. S. Steel Research Laboratory, 15146 Monroeville, PA |
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Abstract: | The rate of nitrogen absorption into and desorption from liquid iron containing sulfur and/or oxygen was measured by employing
a constant-volume technique with a highly sensitive pressure transducer. Critical evaluation of the results demonstrated conclusively
that the chemical rate at high oxygen or sulfur contents is second order with respect to nitrogen content in the metal and
probably controlled by the dissociation of the nitrogen molecule on the surface. The effect of sulfur on the rate is complex
because of the influence of 1) liquid-phase mass transfer at low sulfur contents, 2) the chemical rate on vacant iron sites
at intermediate sulfur contents, and 3) the rate on the adsorbed sulfur layer or the limiting rate at high sulfur contents.
However, at intermediate concentrations the limiting case for the adsorption isotherm for sulfur is adhered to and the rate
is inversely proportional to the sulfur concentration. For Fe-O melts the rate is inversely proportional to the oxygen content
except at low oxygen levels where mass transfer affects the rate. The rate for Fe-S-O melts can be calculated reasonably well
from the results for the Fe-S and Fe-0 alloys, assuming that oxygen does not effect the adsorption of sulfur andvice versa and that there is nearly complete coverage of the surface with oxygen and sulfur atoms. |
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