Abstract: From the summary on domestic and international development in special steels, it can be seen that the focal point for quality improvement has been transferred from cleansteel refining technology to largesizeinclusion controltechnology, especially to the sulfide control. The maximum size of inclusions affects the fatigue property of special steels obviously, and when the total oxygen content w(T.O)≤5×10^-6，the influence of sulfide is most serious. The large size inclusions are mainly originated from MgO-Al₂O₃ and CaO-Al₂O₃  by slagmelt reaction, as well as from CaO-SiO₂-Al₂O₃ by involved slag. To control the large-size inclusions, the following process technologies must be improve: lower down the operating load of refining process, optimize deoxidation process, control slag-involving strictly, and promote inclusions floating upward during continuous casting.

Key words: special steel, bearing steel, inclusion, refining