Chemical methods for the isolation and determination, and micro-analytical techniques of inclusions and precipitates in steels are reviewed. The several isolation and determination methods were recommended by the joint research societies (Iron and Steel Institute of Japan and Japan Society for the Promotion of Science) through above 30 years. Recently the quantitative isolation procedure of calcium aluminate (mCaO·nAl2O3), CaS and CaO in Ca-treated steels was carried out in a glovebox with an Ar atmosphere. Then the aqueous soluble inclusions (mCaO·nAl2O3 involved with high ratio of CaO) could be isolated quantitatively. On the other hand, the many micro-analytical techniques were applied to the characterization of inclusions and precipitates in several steels. For example, the distribution of Cu atomic cluster in Cu-added ultra-low carbon steels could be characterized by the atom-probe field-ion microscopy (AP-FIM) with 3-dimensional system.
