Morphology and composition changes of spinel (MgAl₂O₄) inclusions in steel

Abstract

In this study, spinel inclusions of close to stoichiometric MgO.Al₂O₃ composition and known size distribution were added to a liquid steel bath before assessing their reactivity. The inclusions were then tracked for changes in size, morphology and composition with time in an aluminium killed steel at 1600°C, by sampling of the melt followed by automatic SEM based inclusion analysis techniques. The majority of the inclusions in the melt were alumina and complex sulphide inclusions, with the added spinel inclusions being a small proportion of the total inclusions. The proportion of alumina inclusions increased with time. The spinel inclusions were found to be evenly distributed through the melt and there was little change in their average size during the reaction. However, the composition of the inclusions did change, with the Mg/Al mass-% ratio changing from ∼0·5 to 0·08.

Keywords:

• Inclusion modification
• Inclusion reactivity
• Spinel

Acknowledgements

The authors would like to acknowledge the support of BlueScope Steel Metallurgical Centre funding for this project. This research used equipment funded by Australian Research Council grant LE0882813 and located at the UOW Electron Microscopy Centre.