Investigation of the Parameters Influencing the Accuracy of Rapid Steelmaking Slag Analysis with Laser‐Induced Breakdown Spectroscopy

Abstract

Laser‐Induced Breakdown Spectroscopy (LIBS) is used for the analysis of steelmaking slags (EAF, Ladle Furnace (LF) and Vacuum Ladle Degasser (VLD)). In view of the potential industrial application of LIBS for rapid slag analysis, relatively simple criteria were employed in order to obtain calibration curves for the elements of interest. The LIBS experiments were performed on samples prepared after crushing and milling to a size less than 0.2 mm and on as delivered solidified slag samples. In general, the analysis of the solidified as delivered slag samples exhibited better results than the corresponding analysis of the pressed slag, mainly for the elements distributed in the matrix. Thus, for LIBS application, the time consuming sample preparation of the slag can be avoided. According to the results obtained, the potential of LIBS technique for in‐situ, multi‐element analysis of slag was examined at the 60t‐ EAF of Helliniki Halyvourgia SA (HH‐Greece). The most important parameters that influence slag analysis are the laser pulse energy, the number of accumulated laser shots, the laser beam focusing conditions and the gating conditions of the detector. LIBS accuracy was found to depend on both the distribution of elements in the slag and on their environment (i.e. if they are embedded in the matrix or in a specific crystallized phase) as well. LIBS limitations for quantitative slag analysis are also discussed.The accuracy of FeOn LIBS analysis for as delivered solidified EAF and VLD slags of the steel plant of Georgsmarienhütte was satisfactory showing a Regression Coefficient (RC) of 0.93 and 0.95 respectively. The accuracy of SiO2 and MgO analysis of VLD slags with RCs of 0.94 and 0.86 respectively was also satisfactory. In contrast, for the EAF slags the RC for MgO and SiO2, due to the observed non‐homogeneous crystallized phases have shown insufficient values, with 0.55 and 0.43 respectively. Similar results were gained for the FeOn, MgO and SiO2 analysis of the HH slags. Due to the higher intensity of scattering, the analysis of CaO, Al2O3 and Cr2O3 was of lower accuracy than for FeOn, MgO and SiO2.