Thermodynamics of Nitrogen in Liquid Manganese and Ferromanganese Alloys.

초록

The nitrogen solubility in pure Mn, Mn-C, Mn-Fe and Mn-Fe-C melts have been measured by the gas-liquid metal equilibration technique in the temperature range of 1350 - 1550 oC. The low nitrogen partial pressure of 0.03-0.2 atm by dilution with argon gas enabled us to obtain the reliable information on the nitrogen solubility in high manganese melts. The nitrogen dissolution followed the Sieverts law, and the standard free energy change for the dissolution of nitrogen in pure manganese melt has been determined as -16.070 +7.25T cal per g-atom of nitrogen. Carbon and iron in manganese melt significantly increase the activity coefficient of nitrogen. The first and second order interation parameters of nitrogen with iron and carbon in ferromanganese melt were determined. The activity coefficient of nitrogen in ferromanganese melt can be expressed as ; logf_N = 0.09[%C]-0.013[%C]^2 + 0.015[%Fe], in the temperature range of 1350 - 1550 oC. Therefore, the nitrogen solubility in ferromanganese melts at a given nitrogen partial pressure can be estimated as functions of melt composition and temperature.