Control of Non-metallic Inclusions by Slag-metal Reactions for High Strength Alloying Steels

摘要

A laboratory study was carried out to investigate non-metallic inclusions in high strength alloying steel refined by high basicity slag. The results indicated that the inclusions were mainly of the CaO-MgO-Al_2O_3 system, Al_2O_3-MgO and MgO-based inclusions. The steel/slag reaction time and Al_2O_3 content in slag had a great effect on inclusions characteristics. With the reaction time increasing from 30 to 180 minutes, inclusions experienced a transformation process: from mainly Al_2O_3-MgO system and MgO-based inclusions to spherical CaO-MgOAl_2O_3 system inclusions surrounded by a lower melting temperature surface layer of CaO-Al_2O_3. Formation and transformation mechanisms of the inclusions were given based on the results. It was also found that with Al_2O_3 content in slag reduced from 40% to 30%, [Mg] contents in steel melts were increased and MgO in slag reached saturation, which contributed to the formation of more MgO-based inclusions and a more scattered inclusion composition distribution after 90 min reaction.