SECONDARY STEEL REFINING FOR CONTINUOUS SEQUENCE BLOOM CASTING FOR HIGH OXIDE CLEANNESS FINAL PRODUCTS

Steelmaking and secondary refining process technology of resulphurized liquid steel with low content of total oxygen, assigned for continuous casting of strands for rolled and forged products for automotive industry was developed. The influence of secondary steel refining parameters on total oxygen content as well as amount and morphology of non-metallic inclusions was examined. It was found, that content of total oxygen and amount of non-metallic inclusions in steel decrease as steel refining time in the ladle becomes longer, and the chemical composition of non-metallic inclusions in steel changes from modified calcium aluminates to spinel inclusion of CaO·Al2O3·MgO type. The total oxygen content in steel from continuous casting in four cast sequence ranged from 6 to 25 ppm, with percentage share of non-metallic inclusions from 0.09 to 0.30 per cent and equivalent diameter 0.78 to 1.59 µm