Abstract: This study established a mathematical model of solidification and heat transfer for 220 mm×260 mm bloom, which was verified through the nail-shooting experiments in the narrow side of the bloom. The solidification heat transfer model was calculated for the pull down and soft reduction section and the results were applied to industrial test. The results show that the center segregation and shrinkage cavity significantly improve when the casting speed is adjusted to meet the required soft reduction zone as a matter of priority. Except for the internal crack, the internal quality of the bloom has not been improved obviously because of the unreasonable soft reduction position and distribution of reduction amount.

Key words: bearing steel, soft reduction, center segregation, nail-shooting