APPLICATION OF NEW TECHNIQUES FOR CHARACTERIZATION OF NONMETALLIC INCLUSIONS IN STEEL

This research, aiming at a new approach to the characterization of non-metallic inclusions in steel, has revealed how to measure and specify them quantitatively. Inclusions to be measured are the ones near the surface or the center of continuously cast low carbon steel, and also those in two sorts of bearing steel after rolling. The specimens are prepared for microscopic observation of the sectioned inclusions, and SEM observation of the inclusions floating up on the surfaces after electron beam remelting of the specimens. Two new methods, which have been proposed in consideration of not only the particle sizes but also the shapes, are applied for the measurement, For the low carbon steel, the inclusions, as a whole or as limited only to alumina, are larger and more spherical in the central zone than those in the surface-near areas. Morphological differences between the inclusions in these bearing steels can be statistically clarified. The new approach shows that even the overlapping information can be individually separated and quantified by using approximate functions through the suitable choice of variable conversion. Examination and discussion on the present quantitative results can be enriched with various combinations of the specimens and the methods. The achievement can also suggest several remarks far further investigation on inclusions.