The rate of absorption of hydrogen into iron and of nitrogen into Fe-Cr and Fe-Ni-Cr alloys containing sulfur |
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Authors: | R J Fruehan L J Martonik |
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Affiliation: | (1) Carnegie-Mellon University, 15213 Pittsburgh, PA;(2) United States Steel Corporation, 15146 Monroeville, PA |
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Abstract: | The rate of absorption of hydrogen into liquid iron and of nitrogen into liquid Fe-Cr alloys containing various levels of
sulfur was measured by using a constant-volume Sieverts apparatus employing a sensitive pressure transducer. The rate for
the absorption of hydrogen was measured by using H2 containing a small amount of H2S(<0.2 pct) such that the activity of sulfur on the surface of the melt was the same as in the bulk metal. The hydrogen-absorption
rate for Fe-S melts containing up to 0.72 pet sulfur was virtually independent of sulfur content and controlled by liquid-phase
mass transfer. The liquidphase mass-transfer coefficient for hydrogen in liquid iron, calculated from the results, was comparable
to that for nitrogen transfer in liquid iron. The rate of absorption of nitrogen into Fe-Cr melts with low-sulfur contents
was controlled by liquid-phase mass transfer. For melts containing significant amounts of sulfur it was controlled by both
mass transfer and the chemical rate of the dissociation of nitrogen on the surface in series. Equations were developed to
calculate the chemical rate from the measured rate, correcting for mass transfer. The chemical rate decreased with increasing
sulfur content as expected, because sulfur is strongly adsorbed on the surface and increased with chromium content at constant
sulfur activity, possibly because available Cr sites promote nitrogen dissociation.
Formerly with United States Steel Corporation, Monroeville, PA |
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