Influences of deoxidation and VOD slag on the behavior of inclusions in Fe–21Cr ferrite stainless steel

The influences of deoxidation process and VOD slag compositions on the behavior of inclusions during refining of Ti–Nb bearing Fe–21%Cr ferrite stainless steels were studied in the present work. The results indicated that the main oxide inclusions by the Al–Si complex deoxidization were MgO·Al2O3. And the main inclusions after Ti addition were MgO·Al2O3–TiOx and Al2O3–TiN complex inclusions. After calcium treatment, the main inclusions became spherical MgO·Al2O3–CaO and Al2O3–SiO2–CaO combined with TiOx and TiN. As the basicity of refining slag was increased from 2.5 to 4.0, the number density of inclusions in the steel reduced, while the average particle size of inclusions increased. When the basicity of CaO–SiO2–(15–20%) Al2O3–10%MgO–5%CaF2 refining slag was 3.5, the number of large inclusions would decrease with the deceasing of the Al2O3 content in the refining slag, and the amount of inclusions in molten steel decreased and the size of most inclusions was distributed within 1–2 μm.