Patent ID: 7981358

Claim:
A cooling method comprising constraining and conveying hot steel plate horizontally by a plurality of pairs of constraining rolls and spraying the top and bottom surfaces of the hot steel plate between adjoining pairs of constraining rolls with cooling water from respective pluralities of lines of spray nozzles so as to cool the hot steel plate, wherein said plurality of lines of spray nozzles between an adjoining pair of constraining rolls comprises one or more lines of a first type of spray nozzles each having a first range of cooling water impact pressure integrated value, wherein each said line of first type of spray nozzles is arranged in the width direction perpendicular to the conveyance direction, and one or more lines of a second type of cooling spray nozzles each having a second range of cooling water impact pressure integrated value which is higher than said first range of cooling water impact pressure integrated value, wherein each said line of second type of spray nozzles is arranged in the width direction perpendicular to the conveyance direction, said cooling water impact pressure integrated value being defined as the value of the n power of the cooling water impact pressure integrated in the steel plate conveyance direction between a pair of constraining rolls, where 0.05≦n≦0.2; wherein said first type and second type of spray nozzles are selected such that the maximum of said first range of cooling water impact pressure integrated value and the minimum of said second range of cooling water impact pressure integrated value are equal; and wherein said first type and second type of spray nozzles are arranged such that regions of fluctuation of cooling water impact pressure integrated values of the two types of lines of spray nozzles are continuous.