2018 Volume 58 Issue 5 Pages 886-891
Ferromanganese alloys are usually used for the manganese adjustment to meet the requirement of IF steel grade; and the formation and transformation of manganese-containing inclusions were closely relevant with the recovery yield of manganese in the melt and the morphologies of final deoxidation products. Characteristic transformation of manganese-containing inclusions during Al-killed process in ultra-low carbon interstitial-free steel were studied through the factory trial and hot crucible experiment. Factory trial showed that the manganese recovery yield fluctuated between 14% and 92% mainly due to the formation of manganese-containing inclusions. Hot crucible experiment revealed that three different groups of inclusions, including FeO·xMnO (FM), FeO–Al2O3 (FA) and Al2O3 (AO) inclusions, appeared after semi Al-killed; and five typical Al2O3 inclusions, including spherical Al2O3, polygonal Al2O3, cluster Al2O3, dendritic Al2O3 and aggregated Al2O3, appeared successively based on different formation mechanisms. Under homogenous nucleation condition, the spherical Al2O3 appeared firstly, and changed to be cluster Al2O3 by collision growth or transformed to be large dendrite Al2O3 by single-direction diffusion growth. Under heterogenous nucleation condition, the manganese-containing inclusions were transformed to Al2O3 inclusions in the following order: spherical FeO·xMnO → spherical FeO·xMnO with coarse surface → polygonal FeO·Al2O3 → polygonal Al2O3 → aggregated Al2O3.
