| 摘要 |
<p>A steel plate having more excellent fatigue crack progression resistance is provided to be applicable in the various fields such as ships, offshore structures, bridges, etc. A steel plate excellent in resistance against fatigue crack growth has a composition constituting, in mass percent, 0.03 to 0.30% of C, 0.5% or less(without including 0%) of Si, 0.8 to 2% of Mn, 0.01 to 0.1% of Al, 0.010% or less(without including 0%) of N, 0.03% or less(without including 0%) of P, and 0.01% or less(without including 0%) of S with the balance being Fe and inevitable impurities, wherein structure at a position of a depth t/4(t = plate thickness) when seen from a Z direction(plate thickness direction) is consisted essentially of a mixed structure of ferrite and rigid phase.</p> |
