STEEL PLATE HAVING EXCELLENT FINE BLANKING WORKABILITY, AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a steel plate capable of continuous blanking on a commercial scale without causing the reduction in service life of a die, having excellent FB workability and further having excellent formability after FB working. SOLUTION: The steel plate has a composition comprising, by mass, 0.1 to 0.5% C, 0.2 to 1.5% Si and Mn, and Si, P and S controlled into an appropriate range, and comprising one or two kinds selected from 0.0005 to 0.005% Ca and 0.001 to 0.02% rare earth metals so as to satisfy the specified relation with the S content, and has a structure where the average particle diameter of ferrite is 1 to 10μm, the spheroidized rate of carbides is 80% or more, and the amount of carbides in grain boundaries of ferrite defined by the expression of Sgb(%)[=äSon/(Son+Sin)}×100 (wherein, Sonrepresents the total occupation area of carbides existing in the grain boundaries among the carbides existing in a unit area; and Sinrepresents the total occupation area of carbides existing in the grains among the carbides existing in the unit area)] is more than 40%. Then, the steel plate can be subjected to continuous blanking on a commercial scale, and acquires superior FB workability and formability after FB working. COPYRIGHT: (C)2008,JPO&INPIT