On relative sensitivity coefficients of spark source mass spectrographic analysis of steels: Application of the mass spectrometry to the analysis of trace elements in steels. II

For improving accuracy in analyzing trace elements in steels by r-f spark source mass spectrography, an investigation was made about sample electrode shape, thermal hysteresis, matrix (steel grade) and also about the influence of content on relative sensitivity coefficient using standard samples of low alloy steel and stainless steel of NBS (National Bureau of Standards) etc., 25 samples in total. By keeping the cutting angle of the top end of sample electrode sharpened, it was found that the relative sensitivity of each element becomes lowered when the iron, main composition element is taken as internal standard. After making a comparison of relative sensitivity of various trace elements in a standard sample of S35C between the case of lead-quenching and slow cooling from 850°C, there was observed no significant difference between these 2 cases and it seemed that the influence on relative sensitivity due to the difference of thermal hysteresis of samples could be ignored. The comparison of relative sensitivity of various trace elements between low alloy steel and stainless steel showed that there was not any significant difference and, that the value in stainless steel could also be corrected by the same relative sensitivity of low alloy steel. However, as for C, Si, Ge and Ni they are influenced by content and in each case it was observed that the relative sensitivity coefficient was apt to get bigger if the content of C, Si, Ge and Ni became lower. After statistic investigation of the relationship between the average value of relative sensitivity obtained after making the above written 25 standard samples analyzed 2 times each and melting point, boiling point, heat of sublimation, temperature for vapor pressure of 10-6 Hg, rate of evaporation, relative ionization cross-section, ionization potential (I) and (II), it was found that the melting point and heat of sublimation correlates each other much and the multiple correlation coefficient which has these 2 physical properties as factors was 0.944 and the variation of the actually measured relative sensitivity coefficient from regression formula was 34% as coefficient of variation. From this, it is presumed that the relative sensitivity coefficient could fairly accurately be estimated.