| 摘要 |
PROBLEM TO BE SOLVED: To provide a thick steel plate in which toughness in the plate thickness direction is satisfactory, and jumping energy cost is suppressed, and which can be inexpensively produced. SOLUTION: The thick steel plate has a composition comprising, by mass, 0.01 to 0.12% C,≤0.50% Si, 0.4 to 2.0% Mn,≤0.05% P,≤0.008% S, 0.003 to 0.10% Nb, 0.002 to 0.05% Al and≤0.010% N, and the balance Fe with impurities, and in which the value of [(9.238×C<SP>0.5</SP>)×(1+0.64×Si)×(1+4.1×Mn)×(1+0.27×Cu)×(1+0.5×Ni)×(1+2.33×Cr)×(1+3.14×Mo)] satisfies≤25. Further, the ratio of ferrite having the average crystal grain size of >3 to 20μm and the average aspect ratio of≤4 occupied in a microstructure is≥80%. COPYRIGHT: (C)2010,JPO&INPIT |
