NEW FINDINGS IN THE SPECTROMETRIC DETERMINATION OF STEEL NITROGEN LEVELS

The efficiency of analyzing nitrogen by optical emission spectroscopy was put to test in a first publication by six German laboratories of t he iron and steel industry. Further experiences with this new method a ccumulated in the meantime will be reported here. By taking into accou nt interelement effects both the residual scatter and BEC (background equivalent concentration) values for alloy steels have clearly been im proved. The detection limit was determined at 6 mu g/g by using the re peatability standard deviation in the range of the spectral background . Precipitates of titanium nitrides or carbon nitrides lead to high sc atter of measured values. The long-term stability of the spectrometric measuring system is largely dependent on the purity of the argon gas, transmission conditions in the spectral apparatus, the properties of the excitation unit, and the quality of the specimen surface. To all t hese items recommendations for practice are given.