This study was carried out to get fundamental informations on nonmetallic inclusions in order to make clear the relation betwee nonmetallic inclusions and properties of steel.To. study the behaviour of Mn oxide, Si oxide and manganese silicate in steel, electrolytic iron was melted in a high frequency induction furnace with varied addition of manganese, silicon or silicomanganese.Two kinds of rolling temperature (1250-1000°and below 1000°) and two kinds of rolling ratio (9 and 36) were selected.X-ray probe microanalyser was used to identifyinclusions and the eyepiece with micrometer was used to measure microscopically the quantity of inclusion deformation.The results were mainly as follows:
It appears that inclusions are classified into two typesaccording to course of formation, size, composition and distribution, namely: largeinclusions (5-25μ) and small inclusions (>5μ).Quantity of inclusion deformation increases as the volume of inclusion increases and rolling ratio becomes large.But the proportion of quantity of inclusion deformation to that of steel deformation decreases with increasing rolling ratio.In this experiment inclusions except sulfide, Mn silicate and silica are easier to deform at low rolling temperature than at high rolling temperature.In cases of sulfide and Mn silicate, the quantity of deformation is large at high rolling temperature.Quantity of deformation of inclusions which is produced by manganese deoxidation increases gradually with added manganese content.Quantity of deformation of inclusions in steel deoxidized with silicon increases rapidly with added silicon content, but it decreases rapidly as soon as SiO₂ begins to form and they are scarcely defo rmed by rolling. In case of inclusions in steel deoxidized with silicomanganese, the quantity of deformation increases with increasing added silicomanganese content.This deformation depends mainly on that of manganesesilicate.