X-ray fluorescence (XRF) yield x-ray absorption fine structures (XAFS) have been investigated in terms of quantitative analysis for steel sheets containing 31-2 100 ppm of Nb. Nb concentrations in the samples were determined with high accuracy from the height of the K-edge jump. The detection limit was estimated down to the single digit ppm range. The combination of this technique with the conventional extended x-ray absorption fine structure (EXAFS) analysis for an identical XAFS spectrum provides both quantity and chemical state information of trace elements in the given volume of steel samples.

For the steel making control with micro-alloyed elements, it is essential to accurately analyze the distribution of those elements between different metallurgical phases in steel. The micro-alloyed elements contained in precipitates have been analyzed by conventional chemical or electrochemical procedures, selectively dissolving the Fe matrix by electrolysis, and separating precipitates as insoluble particles from the matrix by filtration. But this method has become inadequate to analyze the fine precipitates because some of the fine precipitates extracted are unavoidably uncollected. Hence, we have developed a quantitative analysis for micro-alloyed elements containing in the solid solution phase of steel, named solute elements, by using of analyzing a portion of the electrolytic solution. By electrolysis, solute elements are dissolved into the electrolyte, and the precipitates remain on the surface of the sample as insoluble particles. So, the analysis of the electrolytic solution during or after electrolysis enables the determination of solute elements directly. For certified reference materials, the sum total of concentration of solute element analyzed by this method and the precipitate analyzed by conventional method suits a certified value substantially on the micro-alloyed element. However, for the samples that contain fine precipitates, they are not in agreement with the total content obtained by the spark-OES. It is estimated that the precipitates not collected by filtration in the conventional method cause the disagreement. It shows the proposed method, which analyzes solute elements directly, is useful for estimating the distribution of the microalloyed elements between different metallurgical phases.

Synopsis : Manganese is one of the important elements for characterization of steel and its concentration is controlled in a steelmaking process. Recently, manganese ore can be used in a basic oxygen furnace blowing because the amount of slag is drastically reduced. Accordingly, if changes of the manganese concentration can be monitored more rapidly and accurately during the basic oxygen furnace operation, manganese ore can be utilized to control the final component of molten steel instead of expensive manganese alloy. In this work, we focus on the vapor generated naturally from the molten steel and investigated an on-line system for monitoring the manganese concentration applying the principle of an atomic absorption spectrometry. In using a lab-melting furnace, we confirmed good correlation between the absorption ratio (Mn/Fe) and the manganese concentration within 0.2% in the molten steel.

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