Effect of the Roll Surface Profile on Centerline Segregation in Soft Reduction Process

Abstract

This study investigates the effect of roll surface profile on the centerline segregation of the molten metal (bloom) being solidified in the soft reduction process, where the molten metal (bloom) thickness is reduced consecutively by a set of rolls. The roll surface profiles are convex and flat. Finite element analysis was performed to examine the variations in solidus line contour, the phase state across the bloom cross-section and stress state of the bloom in the mushy zone to the casting direction when high carbon bloom (400 mm in thickness and 500 mm in width) was solidified and plastically deformed at the same time. To verify the finite element analysis results, soft reduction test with an actual bloom caster was also carried out. Results reveal that a convex roll surface profile is much more effective than a flat roll surface profile in decreasing the centerline segregation and the internal cracks in the bloom. The convex roll surface profile compresses the mushy zone from both directions (bloom thickness and width) and subsequently compensates efficiently the solidification shrinkage of molten metal. In addition, the convex roll can save energy required in deforming the bloom in the soft reduction process.