Experimental Study of Inclusion Modification by Ca in AHSS

The effects of different Ca and S contents of steel on the modification of endogenous Al 2 O 3 inclusions were studied in the laboratory. Three Ca levels (35, 20, 10 ppm) and two S levels (30, 20 ppm) were studied. An automated SEM-EDS system was used for the characterization of inclusions. It was found that the quantity of inclusions in steel increases with the amount of Ca and S contents in the melt. The mechanism of inclusion modification had been discussed based upon the obtained results and thermodynamics. Furthermore, a parameter named ‘dimensionless Ca’ was introduced, which can be used to estimate the extent of modification of inclusions based upon the Ca content of the steel. This parameter was validated against industrial heats.