A Study of Cluster Characteristics in Liquid Stainless Steel and in a Clogged Nozzle. Issue 11 (12th February 2015) - Janis, Diana
Abstract : Clusters of Al2 O3 inclusions in a liquid stainless steel (18/8) and in a clogged ZrO2 nozzle after casting were studied during a pilot plant trial. Samples were taken from the melt at different holding times after an addition of 0.1 mass% Al. The characteristics (composition, size, number, and morphology) of clusters and clustered inclusions in the steel samples and in the clogged nozzle were investigated after electrolytic extraction and etching by using SEM. It was found that the Al2 O3 inclusions in the clusters are transformed from a spherical into irregular and regular (with sharp edges) shape during the holding time. Most of the inclusions in the clusters (>80%) after a 6 min holding time are regular inclusions, which have sharp edges and flat faces. The size of the inclusions in clusters in the melt increased on average from 1.0 μm at a 1 min to 5.2 μm at a 12 min holding time. While the sizes of different types of inclusions in the clogged nozzle correspond to those present in the liquid steel at respective time, the frequency of spherical inclusions in the clogged nozzle is about 2–4 times larger (particularly near the nozzle wall) compared to that in the melt. Growth and transformation of Al2 O3 clusters in the liquid steel at different holding times after an addition of Al and during casting were considered based on the obtained results. Abstract : Clusters of Al2 O3 inclusions in a liquid stainless steel and in a clogged ZrO2 nozzle after casting are studied during a pilot plant trial. It is found that most of the Al2 O3 inclusions (>80%) are transformed from a spherical into regular (with sharp edges) shape after 6 min of holding time. While the sizes of inclusions in the clogged nozzle and liquid steel are similar, the frequency of spherical inclusions in the clogged nozzle is 2–4 times larger compared to that in the melt.