In the study of non-metallic inclusions in steel, the methods of extracting them are recognized one of the important techniques of study. In the series of our investigation on the behavior of oxide inclusions in steel in hot-rolling process, we adopted the electrolytic extraction method using Koch-Sundermann (type) cells and with neutral sodium citrate solution as electrolyte. This is one of the methods by which it is possible to extract stably and reliably the oxide inclusions from steel. But, in our investigation, we thought that it was necessary to examine the adaptability of the electrolytic method in regard to extracting such inclusions as α-Al2O3, TiO2, SiO2, MnO2, FeO, (Mn, Fe) O, FeO·Al2O3, 2FeaTiO2, 2FeO-ESiO2, MnO-ESiO2 and 2MnO-ESiO2.
Therefore, the steel specimens containing uniformly a certain amount of particular oxide inclusions were prepared by means of powder metallurgy, and these specimens were dissolvedanodically at definite conditions. The extracted inclusions were examined by weighing and chemical as well as X-ray analysis, and the degree of extraction of the different inclusions were observed quantitatively.
The results were as follows:
(1)α Al2O3, TiO2, SiO2 and FeO could be extracted almost to the full, but MnO could scarcely be extracted.
(2) As for (Mn, Fe) O, oxides rich in MnO could not be extracted at all. What was extracted had changed their composition because MnO in (Mn, Fe) O dissolved selectively during the electrolytic extraction.
(3) FeO·Al2O3 and 2FeO·TiO2 could be extracted perfectly. The extraction percentages of 2FeO·SiO2, MnO·SiO2 and 2MnO·SiO2 were between 60 and 80%, but these extracted inclusions had not changed in quality.