CONTROL OF CENTERLINE SEGREGATION IN CONTINUOUSLY CAST BLOOMS BY CONTINUOUS FORGING PROCESS

The continuous forging equipment was constructed at No. 3 Continuous Casting Machine of Mizushima Works in 1990 to prevent the centerline segregation in continuously cast blooms. To clarify the mechanism of prevention of centerline segregation of blooms by this process, a mathematical model was developed by considering the discharge of the solute-enriched liquid between dendrites. The model shows that the segregation ratio in the central portion of the bloom decreases as the solid fraction at the forging point decreases. The solute concentration in the central portion of the bloom during forging calculated from the model is in good agreement with the observed values. The solute concentration in the central portion of the bloom can be predicted and controlled to a desired value by changing the solid fraction at the forging point by use of casting speed as a variable. As forging proceeds, a solute-enriched liquid region is formed in the upstream liquid region close to the forging point. The carbon concentration in the solute-enriched liquid region, where the solute accumulates, becomes constant after several meters from the forging point.