| 摘要 |
PROBLEM TO BE SOLVED: To provide a TRIP type high strength thin steel sheet having a structure more uniform than that of the conventional one, and having excellent formability, and to provide a method for producing the same. SOLUTION: The high strength thin steel sheet having excellent formability has a steel composition comprising, by mass, 0.05 to 0.25% C,≤2.0% Si, 0.8 to 3% Mn, 0.0010 to 0.1% P, 0.0010 to 0.05% S, 0.0010 to 0.010% N and 0.01 to 2.0% Al, and the balance iron with inevitable impurities, and in which Mn micro-segregation in the range of 1/8t to 3/8t of the sheet thickness t lies in the range satisfying formula (1), and its structure comprises retained austenite having a mean carbon content of≥0.9% by≥3%: 0.10≥σ/Mn (1); wherein, Mn denotes its additional amount, andσdenotes the standard deviation in Mn micro-segregation measurement. COPYRIGHT: (C)2007,JPO&INPIT
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