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The objective of this research was to study non-metallic inclusions during vacuum degassing in an ASEA-SKF ladle furnace. Five steel and top slag samples were taken before, during and after vacuum degassing for chemical analysis and scanning electron microscopy. It was concluded that the average CaO/Al2O3 ratios in the top slags became close to the phase C3A. The average CaO/Al2O3 ratios in the inclusions of this study were close to the phase CA6, but at the end of degassing, the average CaO/Al2O3 ratios in the calcium aluminates by subtracting the Al amounts of the inclusions that were assumed to form spinel phases with the available Mg amounts in the inclusions were situated between the phases C12A7 and C3A. By decreasing the S and Al contents of molten steel and at [S]3.[Al]2 less than around 10-7 , the ratio of calcium aluminates to spinels increased continously. It was finally concluded that by increasing the Ca amount in inclusions, their equivalent circle diameters grew, and their aspect ratios went toward unity, and when the amount of Ca measured in the inclusions was more than ∼25 wt-%, inclusions with bigger equivalent circle diameters appeared. [ABSTRACT FROM AUTHOR]

This study sets out to compare the wt-% CaOslag and Al2Oslag3 in the binary system of CaO-Al2O3 that were measured in the top slag before teeming, the CaOincl and Al2Oincl3 in calcium aluminates that were analysed by scanning electron microscopy of the steel samples and the CaOcalc and Al2Ocalc3 that were achieved from theoretical calculations using the total measured elements in the top slag and steel before teeming. The CaOincl and Al2Oincl3 in all of the calcium aluminate inclusions of this study did not have the same ratio; in the opposite, they covered a large range. The average CaOincl and Al2Oincl3 in all samples had nearly similar compositions that were close to the border of the phase Ca12Al14O33 in the binary phase diagram of CaO-Al2O3. The CaOslag and Al2Oslag3 in all samples had almost similar compositions that were close to the border of the phase Ca3Al2O6 in the binary phase diagram of CaO-Al2O3. The results of theoretical calculations were close to the CaOslag and Al2Oslag3, but they did not follow the same maximum and minimum tendencies of CaOslag and Al2Oslag3. [ABSTRACT FROM AUTHOR]

This article sets out to study the development of oxide inclusions during the vacuum degassing process at the ASEA-SKF ladle furnace. During the degassing process, five steel and top slag samples were taken, and their chemical compositions were analysed. All steel samples were further analysed by scanning electron microscopy. It was concluded that the vacuum degassing process was a dynamic process during which spinel and calcium aluminate inclusions were dominant. In addition, it was seen that during this process, the percentage share of calcium aluminates compared with spinels, the Ca weight per cent content of the oxides, the average equivalent circle diameter (ECD) of the oxides and the percentage share of the oxides with bigger ECD were increasing, and the oxides tended to form more round shapes. [ABSTRACT FROM AUTHOR]