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) intensity measurements from ferromanganese test samples. Sample preparation was carried out by melting the ferroalloy, diluted with iron in proportions from 13 + 27 to 17 + 23, in an open induction furnace. Two chemically standardized ferromanganeses, one with a low carbon content (<0.5%) and the other with a high carbon content (>6%), were used to prepare the test samples. Samples for calibration were obtained from different iron dilution proportions of both materials, with two calibration 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 ferromanganeses. The correlation C% --> I(MnKalpha) was established and the correction factor was calculated. On application of the carbon correction factor, a single calibration graph is obtained, and the calculated Mn concentrations for all the samples prepared with the same Mn content present an RSD value of 0.34%. The F-test was applied in order to evaluate 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.