Laboratory Study on Oxide Inclusions in High-Strength Low-Alloyed Steel Refined by Slag with Basicity 2-5

摘要

Non-metallic inclusions in high-strength low-alloyed steel refined by slag with basicity (B) 2-5 and Al_2O_3 content 20%-30% (in mass percent) were investigated by slag-metal equilibrium experiments in laboratory and thermodynamic calculations. Most inclusions in equilibrium were quasi-spherical CaO-MgO-Al_2O_3-SiO_2 system and the sizes were less than 5 um. The average content ratio, CaO/Al_2O_3 and CaO/SiO_2 of the inclusions, increased with slag basicity increasing when Al_2O_3 content in slag was around 25%, MgO/Al_2O_3 and CaO/Al_2O_3 increased with Al_2O_3 content in slag decreasing when slag basicity was around 3.3. The MgO/Al_2O_3 of the inclusions was influenced mainly by Al_2O_3 content in slag and CaO/Al_2O_3 was influenced mainly by slag basicity. To make the inclusions out of relative lower melting region (＜1,773 K), the values of CaO/Al_2O_3, MgO/Al_2O_3 and (CaO + MgO)/Al_2O_3 of the inclusions should be enhanced by increasing basicity and decreasing Al_2O_3 content in slag properly.