Levitation Melting/Thermoconductometric Method for Determination of Nitrogen in Steel

A levitation melting/thermoconductometric method for determination of nitrogen in steel has been developed, in which metal samples are melted in a state of floatation by magnetic pressure. The present method needs no crucible, so it is free from contamination from crucibles. Nitrogen extracted from a steel sample in a state of floatation was measured quantitatively with a thermal conductivity detector. About 5 min was required for nitrogen to be sufficiently extracted, versus only about 2 min for hydrogen. This difference was explained in terms of their diffusion velocities in molten iron. The calibration curve for nitrogen was linear to 156 μg/g, with a relative standard deviation of 6.5% at the 20 μg/g level. The present method was applied to determination of nitrogen in certified reference material JSS GS-5a, and the analytical result (17.5 ± 1.1 μg/g) was in good agreement with the certified value (17.0 μg/g).