Distribution of Inclusions in Continuously Cast AISI 316L Stainless Steel Blooms

摘要

Size distribution of inclusions to ascertain the mechanism of modification of inclusion distribution along the cross-section of continuously cast blooms of AISI 316L grade of stainless steel was studied. Specimens from various locations along perpendicular and diagonal directions of 0.16 mm square AISI 316L grade stainless steel blooms were used in the present study. Inclusion distribution on the surface of the specimens was studied by feature counting method using an optical microscope. Size distribution, mean size, mean distance of separation, and volume fraction of inclusions were investigated by measuring the sizes of inclusions using an image analyser and using the particle-size-distribution module of a computer program developed in this laboratory which was based on Schwartz-Saltykov method. Inclusions were characterised by SEM and EDS studies. Inclusion size was found to be finer near the surface of the bloom compared to that observed farther away from the surface towards centre where shell growth rate was lower than that at the surface. The number of inclusion per unit area was found to increase to a maximum value and again decreases from the surface to the centre of the bloom cross-section. Particle coarsening diffusional growth of bigger silica inclusion at the expense of the smaller ones is found to be operative during solidification. The coarsening rate constant matches fairly well to that derived from the physical parameters of the melt and the inclusions.