| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength thin steel sheet in which the hole expansibility and ductility of a high strength thin steel sheet having a tensile strength of≥850 MPa are both improved, and to provide its production method. SOLUTION: The high strength and high ductility thin steel sheet having excellent hole expansibility comprises, by mass, 0.001 to 0.3% C, 0.001 to 0.6% Si, 0.01 to 3% Mn, 0.001 to 4.0% Al, 0.001 to 1.0% Mo, 0.0001 to 0.3% P, 0.0001 to 0.1% S, 0.0001 to 0.0050% B and 0.0001 to 0.0070% N, and in which the space factor of the microstructure in the steel is composed of, by volume fraction,≥20% ferrite phase,≥10% bainite phase,≥5% martensite phase, and≤5% retained austenite phase, and has a tensile strength of≥850 MPa. The production method uses the same. COPYRIGHT: (C)2006,JPO&NCIPI
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