Abstract: To the question of the unsteadiness of the steel oxygen content at the end of RH vacuum treatment for the aluminium deoxidization nonoriented silicon steel refining, the oxygen potential of molten steel and slag was optimized during tapping and deoxidation alloying process. Results show that the oxygen mass fraction of nonoriented silicon steel is stably controlled below 650×10^-6 as it was (400－900)×10^-6 before optimization. Furthermore, T.O mass fraction is controlled below 450×10^-6 at the end of decarbonization in RH. With the optimization process, the mass fraction of T.Fe in slag is decreased from 10 %－25 % to less than 15 % at the beginning of RH, which is also decreased from 2 %－12 % to below 3 % at the end of RH, and the slag basicity is controlled above 3.0 during RH treatment process. T.O mass fraction at the end of RH is reduced from (15－30)×10^-6 to below 15×10^-6 using the optimization process, which indicated that the cleanliness of molten is significantly improved.

Key words: Al deoxidization silicon steel, total oxygen, ladle slag modification, secondary oxidation