Abstract: Two sets of RH furnaces were taken as the main objects. The specimens were sampled at different refining times. The composition， content， and size distribution of the inclusions in steels were analyzed by means of metallographic microscope， SEM and EDS， and the collision， growth and removal of the inclusions during RH refining process were discussed. The results showed that the inclusion removal was very obvious during RH refining process， and almost no inclusion with the dimension more than 10μm were observed after the soft blowing. With the increase of refining time， the average size of inclusions changed little， however the amount of inclusions significantly decreased. The area ratio of inclusions in two type steels increased at first and then reduced. In SiMn deoxidized steels， silicate inclusions had a certain capacity of the sulphur， the dual layer inclusions were therefore easier to form with the surface of sulphurrich phase and the inner core of silicate phase. As the strong mixture of the liquid steel in RH vacuum chamber， solid inclusions were always captured by the liquid calcium aluminate and formed a typical inlaid feature.

Key words: RH refining, nonmetallic inclusions, evolution, removal, inlaid feature