Rob Dekkers

Non-metallic inclusions in aluminium killed steels

Abstract Heats of medium carbon aluminium killed, low carbon silicon-aluminium killed, and low carbon aluminium killed steels were sampled with short time intervals during ladle metallurgy. Non-metallic inclusions were extracted from the steel matrix and investigated using scanning electron microscopy and energy dispersive spectrometry. Six inclusion morphologies were recognised, i.e. spherical, faceted, platelike, and dendritic shapes, as well as clusters and aggregates. For each sample also the total oxygen content was measured. Spherical inclusions were most abundant, but clusters, aggregates, and large faceted inclusions made up most of the oxide volume fraction. The present research shows that clusters, which are formed during the deoxidation operation, are removed within ~15 min after aluminium addition. Aggregates and large polyhedra appear after 5-10 min and their sizes increase with holding time. Small, mainly spherical and polyhedral, and to some extent also platelike, inclusions do not show evolution in size or in composition.

Morphology and growth of alumina inclusions in Fe–Al alloys at low oxygen partial pressure

Abstract The degree of supersaturation is a factor that influences the Al2O3 inclusion characteristics in steel. The influence of the addition of a large amount of Al in the molten steel on the formation, growth and morphology of Al2O3 inclusions was investigated by laboratory scale experiments. Consecutive steel samples were taken during the deoxidation process and subjected to chemical analysis (ICP-AES), automated image analysis (AIA) and scanning electron microscopy (SEM) assessment with respect to the extracted inclusions. The characterisation and quantification of Al2O3 particles show different growth processes, leading to variations in particle size distribution as well as in the morphology.