| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength steel product having a tensile strength of 600 MPa or higher and being excellent in delayed fracture resistance, and to provide a method for the production thereof. SOLUTION: The high strength steel product is characterized in that it has such a composition, in mass%, that: C: 0.02 to 0.25%, Si: 0.01 to 0.8%, Mn: 0.5 to 2.0%, Al: 0.005 to 0.1%, N: 0.0005 to 0.008%, P: 0.03% or less, S: 0.03% or less, also, one or more kinds of Mo, Nb, V and Ti, and, if required, one or more kinds of Cu, Ni, Cr, W, B, Ca, REM and Mg, and the balance: Fe and inevitable impurities, and it contains precipitates containing one or more kinds of Mo, Nb, V and Ti, and includes deposits having an average particle diameter of 20 nm or less in an amount of 5 pieces/250,000 nm<SP>2</SP>or more. Further, its microstructure contains retained austenite of 0.5 to 5% by a volume fraction. COPYRIGHT: (C)2007,JPO&INPIT
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