1148 Susumu Imashuku et al.
luminescence colors of nonmetallic inclusions. It should, how- ever, be noted that detection of nonmetallic inclusions which do notemit lightisdifficult for both the XEOL analyzer and the portable EPMA–CL analyzer in the present circumstances.
CONCLUSIONS
We have demonstrated that we can identify MgAl2O4 spinel and Al2O3 particles in air by capturing the XEOL image of a model sample containing MgAl2O4 spinel and Al2O3 parti- cles in the size range from 20 to 50 μm. The X-ray intensity, irradiated from an X-ray tube of a few watts in power, was not sufficient to detect the luminescence of the particles below 30 μm in the model sample. All of the particles could be detected when using an X-ray tube with a few kW in power. Thus, XEOL analysis has potential in the on-line analysis of nonmetallic inclusions in steel if the luminescence colors of the nonmetallic inclusions are known. Thus, the acquisition of luminescence spectra of the nonmetallic inclusions is required to apply XEOL analysis to the practical on-line analysis of these inclusions, but the present study is important with respect to the fact that we first demonstrated that the major nonmetallic inclusions, MgAl2O4 spinel and Al2O3, can be distinguished by XEOL analysis. We also showed that our portable CL spectrometer can identify MgAl2O4 spinel and Al2O3 particles in the same model sample and that our portable EPMA can distinguish between MgAl2O4 spinel and Al2O3 particles whose luminescent colors were detected by the portable CL spectrometer. The beam current of the portable CL spectrometer was not sufficient to detect the luminescence of all the particles in the model sample. We propose that a beam current sufficient to detect the luminescence of particles with sizes above a dozen micrometers would be able to be obtained by optimizing the heating temperature and cooking rate of the LiTaO3 crystal. It would be, therefore, possible to carry out on-site analysis for screening the inclusions using the portable EPMA–CL before precise analysis without knowledge of luminescence colors of the nonmetallic inclusions. These two analyzers of XEOL and EPMA–CL will contribute to the improvement of productivity of steel because they would drastically reduce time for the analysis. We must note that only nonmetallic inclusions producing luminescence can be detected using the present XEOL analyzer and portable EPMA–CL analyzer.
ACKNOWLEDGMENTS
Financial support for the present study was provided by JSPS KAKENHI Grant Number 17H03435 for XEOL analysis and JFE 21st Century Foundation for analysis using the portable CL spectrometer and EPMA.
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