Modification of Sulfide in a 303 Ton Carbon Manganese Steel Heavy Ingot with Cerium Treatment

Abstract

Herein, the cerium treatment is used to modify large MnS inclusions in a 303‐ton carbon manganese steel ingot. When the cerium content in steel in the tundish is 90 ppm, the inclusions are CeAlO3 with a small amount of Ce2O2S. The precipitation sequence of inclusions during the solidification and cooling process in the ingot is MgO·Al2O3 + CeAlO3→Ce2S3→MnS→MgS. Due to the inevitable macrosegregation, a small amount of elongated MnS inclusions is precipitated at the radial center. The maximum diameter is 257.80 μm, and the average aspect ratio is 3.28. For heterogeneously nucleated sulfide, the average diameter is less than 13.39 μm, and the average aspect ratio is less than 1.88. The morphology of MnS inclusion is well controlled when the mass ratio of Ce/S in steel is in the range of 0.7–2.8. The average aspect ratio of homogeneously nucleated MnS is less than 1.9. In addition, the formation of CeAlO3 clusters is avoided. According to the atomic mismatch obtained by the edge‐to‐edge matching model, the possibility of heterogeneous nucleation of MnS on the oxide core is CeAlO3 > Ce2O2S > MgO·Al2O3. The Ce2S3 inclusions are mainly precipitated with the core of MgO·Al2O3.