| 摘要 |
<p>A high-strength steel plate has a chemical composition containing, % by mass: C: 0.05% or more and less than 0.10%; Si: 0.20% or more and 0.50% or less; Mn: 0.20% or more and less than 1.20%; Cr: 0.20% or more and 1.20% or less; Mo: 0.20% or more and 0.60% or less; Nb: 0.010% or more and 0.050% or less; Ti: 0.005% or more and 0.030% or less; Al: 0.01% or more and 0.10% or less; B: 0.0003% or more and 0.0030% or less; V: 0% or more and 0.10% or less; Cu: 0% or more and 0.50% or less; and Ca: 0% or more and 0.0030% or less; and limited to: Ni: 0.1% or less; P: 0.012% or less; S: 0.005% or less; and N: 0.0080% or less; and a balance consisting of Fe and inevitable impurities, wherein Pcm is equal to or less than 0.22%, "A" is equal to or less than 2.0, the sum of a structural fraction of a lower bainite and a structural fraction of a martensite is equal to or more than 90%, the structural fraction of the lower bainite is equal to or more than 70%, an aspect ratio of a prior austenite grain is equal to or more than 2, a yield strength is equal to or more than 885 MPa, and a tensile strength is equal to or more than 950 MPa and equal to or less than 1130 MPa.</p> |
