| 摘要 |
PROBLEM TO BE SOLVED: To provide a dual-phase steel sheet superior in formability such as elongation and stamped-hole expandability, and to provide a manufacturing method therefor. SOLUTION: The dual-phase steel sheet superior in the formability has a composition including, by mass%, 0.01 to 0.2% of C, 0.8 to 3.0% of Si, 0.5 to 3% of Mn, 0.1% or less of P, 0.01% or less of S, 0.005 to 2.0% of Al, 0.02% or less of N, and the balance Fe with unavoidable impurities, and has a structure including ferrite of 90% or more but less than 100% by a volume rate as a main phase, and martensite, bainite, or both of them as a second phase. The second phase exists in a density of less than 10,000 pieces per square millimeter in a cross section which is parallel to a rolling direction, and has the maximum major diameter of 20μm or smaller. The face intensity of a face ä100} at 1/2t part of the steel sheet is 2.5 or less. COPYRIGHT: (C)2009,JPO&INPIT
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