On Microstructure Development and Inclusion Generation in a Continuously Cast Resulphurised Steel

−− An experimental study on solidification structure development and on endogenous inclusion precipitation in a continuously cast resulphurised steel is presented. Results were obtained by investigating two heats of a free cutting C-Mn steel cast in billets with a diameter of 145 mm. The as cast structure was evaluated by macroand microscopic analyses. Primary and secondary dendrite arm spacing measurement allowed to estimate the solidification time experienced by the steel in different region of the billet section. Modification of the pearlite vs. ferrite fraction was also studied as a function of distance from billet surface and thus with reference to solidification conditions. Endogenous inclusions of the type MnS and CaO-Al2O3 were analysed. Their formation was discussed as a function of the composition of the heats. Also for the inclusions resulting after steel solidification, the data suggested that the effects of local solidification condition and of segregation played a role of primary importance. Keywords−− continuous casting, resulphurised steels, dendrite arm spacing, endogenous inclusions.