| 摘要 |
PROBLEM TO BE SOLVED: To provide a thick high tensile strength steel plate having excellent brittle fracture propagation stopping properties and weldability, and having a yield strength of≥650 MPa and a tensile strength of≥750 MPa. SOLUTION: The thick high tensile strength steel plate has a composition comprising specified amounts of C, Si, Mn, P, S, Cu, Ni, Cr, Mo, Nb, V, Ti, sol.Al, B, N and O, and the balance Fe with impurities, and satisfying Mn/S≥1200, Cr/Mo≥2, C+(Si/30)+(Mn/20)+(Cu/20)+(Ni/60)+(Cr/20)+(Mo/15)+(V/10)+5B≤0.25%, and C<SP>0.5</SP>×(1+0.64×Si)×(1+4.1×Mn)×(1+0.27×Cu)×(1+0.52×Ni)×(1+2.33×Cr)≥150, and has a microstructure composed of a mixed structure of martensite and bainite, and in which the dimensions in the plate thickness direction of a packet are≤20μm, further, the dimensional ratio between the rolling direction and plate thickness direction of the packet is≥2 at the 1/4 position of the plate thickness and is≥1.2 at the central position of the plate thickness. COPYRIGHT: (C)2008,JPO&INPIT
|
