Effect of Ce on the Purifying Degree and Inclusion modification of Low Carbon and High-Strength Steel

In order to improve the refining process of low carbon and high-strength container plates,four steel samples were prepared by adding Ce into the molten steel containing 0.08C-0.60Si-0.45Mn-0.3Cu-0.09P(mass%) at 1 873 K in a 3.0 kg vacuum induction furnace under Ar atmosphere(800 Pa).The chemical composition,SEM and EDS analytic results were obtained to study the cleanliness of 0.08C-0.60Si-0.45Mn-0.3Cu-0.09P-xCe(mass%)steel and the change of inclusions.When content was 0,the inclusions were MnS-MgO-Al₂O₃ system;when content was in the range of 0.008%~0.020%,the inclusions were MgO-Al₂O₃-Ce₂₂O₃>O₂S system;when content was 0.043%,the inclusions became FePCe-Ce₂₂O₃>O₂S system and spherical inclusions of 2 μm or even smaller than 0.3 μm were transformed from 7 μm inclusions with irregular shape.The residual area of inclusions in the steel matrix was reduced by 58.1% and the size of inclusions was below 3 μm approximately.The liquid steel was cleaned profoundly due to the floating up and removal of inclusions which were formed by Ce deoxidation and desulfuration.The formation of different kinds of inclusions was relevant to the relative thermodynamic conditions.