REMELTING TECHNIQUE FOR X-RAY-FLUORESCENCE ANALYSIS OF MAIN CONSTITUENT IN FERROMOLYBDENUM AND FERRONIOBIUM

A study was conducted of the main constituent determination in ferromo lybdenum and ferroniobium using X-Ray fluorescence by wavelength dispe rsion and energy dispersion. Ensuring a good sample preparation system and the availability of an appropriate set of calibration samples is the most important part of any instrumental analytical technique, havi ng an important bearing on the accuracy of the analytical results. The remelting technique is capable of dealing with the two major factors that cause difficulties in the practical application of X-ray fluoresc ence techniques to the analysis of ferroalloys: their unsuitability fo r direct instrumental analysis and the availability of accurately anal ysed standards in a suitable form and in sufficient quantities to adeq uately cover the required composition ranges. The remelting technique makes it possible to change the physical form of the ferroalloy sample into one appropriate for X-ray measurements, while at the same time d iluting with an appropriate quantity of pure iron (avoiding the proble m of sample fracturing during cooling, chilling or polishing), and all ows to prepare sets of calibration samples from appropriate proportion s of the main element and pure iron. Test samples were prepared by rem elting the ferroalloy diluted with iron using the following proportion s: 15 g of FeMo + 25 g of Fe for ferromolybdenum analysis and 12 g of FeNb + 28 g of Fe for ferroniobium analysis. Calibration samples were obtained in two different ways: from a commercial ferroalloy diluted w ith iron in different proportions and from adequate proportions of the main constituent pure metal and iron. Precisions (relative standard d eviations), influenced by the sample preparation system and by the ins trumental variability, better than 0.6% were obtained for both type of ferroalloys using both X-ray dispersive systems.