APPROACH TO THE SOLUTION OF CARBON CONTENT INFLUENCE IN THE X-RAY-FLUORESCENCE ANALYSIS OF FERROMANGANESE

This work aimed to evaluate the influence of carbon on CrK(alpha) inte nsity measurements from ferromanganese test samples. Sample preparatio n was carried out by melting the ferroalloy, diluted with iron in prop ortions from 13 + 27 to 17 + 23, in an open induction furnace. Two che mically standardized ferromanganeses, one with a low carbon content (< 0.5%) and the other with a high carbon content (>6%), were used to pre pare the test samples. Samples for calibration were obtained from diff erent iron dilution proportions of both materials, with two calibratio n graphs resulting. The influence of carbon was evaluated by measuring samples prepared with a constant manganese content and with variable carbon contents, with suitable mixing of the two aforementioned ferrom anganeses. The correlation C% --> I(MnKalpha) was established and the correction factor was calculated. On application of the carbon correct ion factor, a single calibration graph is obtained, and the calculated Mn concentrations for all the samples prepared with the same Mn conte nt present an RSD value of 0.34%. The F-test was applied in order to e valuate the effects due to sample preparation, and to the variability throughout the analysis, on the total variance. Accuracy was tested by analyzing four ferromanganese Reference Materials: CRM 583-1; BCS 208 /2; BCS 280/2, and IRSID 502-1.