EFFECT OF MICRO-STRUCTURE OF STEEL SAMPLE ELECTRODES ON ARC TEMPERATURE AND VOLATILIZATION OF THE ELECTRODE IN SPECTRAL LIGHT SOURCES

Abstract

Further study of the effect of micro-structure of the sample electrode on the spectrochemical analysis of steels revealed that the effect on the analysis of W, Si and Ni all increases with the increase of the carbon content and for different analysis line pairs chosen, the effect not only differs in magnitude but also can be different in direction as was observed in the case of Cr in chromium steels. The effect on the analysis of Mn in all the steel samples studied is not significant. Structure effects observed under different excitation conditions show that under the same excitation condition, the arc temperature which is indicated by the log intensity ratio of two iron lines of different excitation potential is higher when the sample electrode is of annealed structure; and in light sources of the same arc temperature the relative concentration of alloying elements to iron is higher when the sample electrode is of quenched structure. Since these two factors have opposite effect on spectral line intensities, the result of analysis will be different for different line pairs chosen. If the analysis line pair is homologous, the effect observed is due to a difference of relative concentration of different elements in the arc column alone, and the result of analysis is always higher when the sample electrode is of quenched structure. This may he explained by the fact that the presence of carbon in solid solutions decreases the interatomic forces or shows a lowering of energy of volatilization. This lowering is different for different elements but all increases with the increase of carbon content.