The Isolation, Separation, and Identification of Microconstituents in Steels

A general scheme relating the chemical and instrumental methods available for isolation and identification of microconstituents in steel is presented. Several techniques are discussed in more detail. These include electrolytic solution, selective centrifuging, and use of the petrological microscope. High-silica values were obtained when thiocyanate and citrate were used as electrolytes in electrolyses of the Klinger and Koch type. The anomalous values were traced to oxidation of silica in the steel to silicic acid. Washing the residue with sodium carbonate eliminated this problem. The authors describe use of a potentiostat for selective solution of complex austenitic 15Cr-25Ni steels containing additions of other metals. Use of the threshold centrifuge to separate residues by weight and size for X-ray diffraction analysis is discussed. An example of identification of spinels in a globular silicate inclusion by the petrological microscope is also presented. Throughout the paper the complementary nature of the various methods and the use of methods in combination are stressed.