Abstract: To address center segregation and shrinkage cavities in GCr15 bearing steel continuous casting billets,a steel plant established a solidification heat transfer model for large billets by integrating principles of heat transfer,steel grade characteristics,and the spatial structure of the withdrawal and straightening equipment,employing the finite difference method.Leveraging the accuracy of this model,a final-stage reduction technology was developed and implemented on a seven-stand withdrawal and straightening system with 1 200 mm equal roller spacing,achieving safe and stable production with a total reduction of 22 mm.With this technology,the center carbon segregation index of high-carbon steel billets has been consistently maintained within 0.95-1.05,the proportion of billets with a carbon extreme deviation not exceeding 0.08% has increased to 98.4%,and 99.95% of billets now exhibit center shrinkage cavities of grade 0.5 or lower.This breakthrough enhancement in internal billet quality has enabled the plant to adopt a low compression ratio rolling process for producing large-size bars,which achieve an ultrasonic testing pass rate exceeding 99.95%in accordance with the AA grade of GB/T 4162.