Patent ID: 7086450
Filing Date: 2006-08-08
Classification: B22D

Abstract:
1. A continuous casting method, comprising the following steps of: guiding molten steel from an immersion nozzle into a mold; guiding a slab formed in said mold to a plurality of guide roll pairs; bulging said slab by providing an increased spacing between a select number of the guide roll pairs to produce a bulged slab with a liquid core; completing the solidification of a liquid core in a thickness-wise center part of said bulged slab at the position where the bulged slab is reduced, and reducing the thickness of said bulged slab to a predetermined thickness with a reduction roll pair comprising an upper reduction roll and a lower reduction roll, wherein the uppermost surface of said lower reduction roll is projected a distance higher than a lower pass line for the slab, wherein the projection distance of the uppermost surface of the lower reduction roll from the lower pass line for the slab is based on a bulging thickness of the slab and the projection distance is the same as or not more than a bulging thickness of the bulged slab, wherein by reducing the bulged slab, a Mn segregation index C/C where C: the Mn content (mass %) at the center part in the thickness direction of the slab, C W d: the thickness of the solidified shell (the distance between an area of the slab with a solid fraction of 0.8 and a surface layer on a narrow side at the position of thickness reduction) (mm).