| Recent years, for the excellent properties of corrosion resistance, oxidation resistance at high temperature, better ductibility at low temperature etc, the stainless steel is extensively used in many departments of the National Economy. The composition, size, quantities, shape and distribution of inclusions in steel are main factors which determined the properties of steel, and lots of researchers studied on inclusions by different kinds of the theories and tried to find the methods to control inclusions.The 304 austenitic stainless steel which is used widely was researched, and the AOD metallurgy process which is always used for stainless steel smelting industry was simulated. The typical FeSi was choosed as the deoxidizer, and the composition of slag is CaO-SiO2-Al2O3-MgO-CaF2. The influence of different refining slag basicity on nonmetallic inclusion compositions was studied.From the refining process of every experiment, the shapes of inclusions were changed from strip to globosity, and the average size, the quantities, the total area of inclusions are gradually decreased, and the final compositions of inclusions are compound inclusions mainly consisted of SiO2. All these indicated that it is very important to control the inclusions in 304 stainless steel by refining slag.From comparing the results of the first three experiments under the high oxygen supply condition, with the increasing of refining slag basicity, the total oxygen content is decreased, the average size, the quantities, and the total area of inclusions are also decreased. All these indicated that the high basicity refining slag can accelerate the adsorption of deoxidization product, which has the advantage of forming small size inclusions. Comparing the results, we can conclude that the size of inclusions is smaller when the refining slag R≥2。Comparing the following four experiments under low oxygen supply condition, with the increasing of refining slag basicity, the total oxygen content is also decreased, the average size, the quantities, and the total area of inclusions are decreased.The 430 ferritic stainless steel which is used widely was also researched, and the AOD metallurgy process which is always used for stainless steel smelting industry was simulated. The oxygen content of 430 stainless steel melt was controlled by aluminum deoxidation, the composition of slag was CaO-SiO2-Al2O3-MgO-CaF2. Also, the refining slag without SiO2 was used. The compositions of slags were controlled primarily according to the basicity and the ratio of Al2O3 and CaF2 of which, the influence of different refining slag on nonmetallic inclusion compositions were studied to 430 stainless steels.From the refining process of every experiment, the average size, the quantities, the total area of inclusions are gradually decreased. The final compositions of inclusions are mainly consisted of SiO2 in the first three experiments using refining slag bearing SiO2. Global Al2O3-MgO was got in the final sample refined using slag without SiO2.Comparing the results of the slags bearing SiO2, the much smaller inclusions is easily got for the slag of R=3, Al2O3=30%.
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