Formation and Evolution of Non-Metallic Inclusions in the Ladle Treatment - Ingot Casting - Electroslag Remelting Process Chain

The need for high-quality tool steel is ever rising in many applications. One factor which impacts the quality of tool steel is the cleanliness of the steel, which can be defined as the number, sizes, and types of nonmetallic inclusions present in the steel. Electroslag remelting is a process that is good at improving the cleanliness of steel. The final quality of the remelted ingot is influenced by a range of different factors, one being the quality of the electrode used for the remelting. In this study, the characteristics of the nonmetallic inclusions found in the ladle treatment and casting process were analyzed and compared to help map out the evolution of the non-metallic inclusions during these two steps in the process chain. The characteristics investigated were the size, morphology, and composition of the non-metallic inclusions, which were done using electrolytic extraction on several steel samples to gather the non-metallic inclusions and using a scanning electron microscope to investigate them. The results showed that the nonmetallic inclusions found in the electrode ingot were MgO – Al2O3 spinels and Al2O3. The inclusions found in the ladle were Al2O3 and inclusions composed of Al2O3 – MgO – CaO with S and SiO2. Additionally, the size of the inclusions was not affected by their location within the electrode ingot, but there were signs that clusters formed in higher numbers towards the center of the ingot, as well in the bottom part of the ingot.