Characterization of Nonmetallic Inclusions in Ce‐Containing Steels at the Submicroscopic Level

This study aims to improve the characterization of nonmetallic inclusions with automated SEM/EDS analysis at the submicroscopic scale down to 0.5 µm. The specific focus of this research is on Ce‐containing steels. Ce modifies the nonmetallic inclusion population across the represented steel grades (ultralow‐carbon, high‐manganese, and electrical steels) in different ways, resulting in complex multiphase clusters or newly formed submicroscopic particles. Inclusions were quantified in terms of size, morphology, and chemistry. Due to the optimized submicroscopic settings, the determination of Ce‐containing nonmetallic inclusions in the 0.5–1 µm size range increased. The greatest increase was observed in high‐Mn steel, where the submicroscopic setting detected over 42.4% (especially +13.4% CeS) more inclusions. However, the characterization of multiphase particles also improved across all investigated steel grades. As a result of pixelization, a deviation of approximately 12.2% was observed in the measured sizes of particles and phases below 0.5 µm at 400x magnification, compared with 2% at 800x magnification. By adjusting the settings for automated SEM/EDS analysis, the study demonstrates significant improvements in the accuracy of NMI evaluation. The findings also highlight the need for continued advances in microscopy technology to address the growing importance of submicroscopic inclusions in steels.