SECONDARY COOLING DEVICE FOR CONTINUOUS CASTING MACHINE, AND SECONDARY COOLING METHOD THEREFOR

PROBLEM TO BE SOLVED: To provide a secondary cooling device for a continuous casting machine in which, when a slab produced by a mold is cooled, without performing equipment remodeling on a large scale, the cooling performance of a slab is improved, slab temperature can be stably controlled, and the improvement of casting speed can be attained while evading the surface cracks of the slab, and to provide a secondary cooling method therefor. SOLUTION: In the secondary cooling device 10 for a continuous casting machine comprising a plurality of rolls 17 carrying a slab 14 and a nozzle 18 for cooling arranged between the rolls 17, a forced cooling range is provided within a range in which the relation between the total thickness D of the thicknesses d1, d2 of solidified shells 21, 22 formed at the surface side 15 and the back surface side 16 in the slab 14, and the thickness D of the slab 14 reaches 0.25