| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength steel sheet which has a TS of≥780 MPa and vE-80 of≥80 J and does not give rise to crack even if the preheating temperature during welding procedure is≤50°C. SOLUTION: The high-strength steel sheet has a chemical composition containing 0.03 to 0.15% C, 0.02 to 0.4% Si, 1.0 to 1.6% Mn, 0.6 to 7.0% Ni, 0.005 to 0.03% Ti, 0.002 to 0.070% sol.Al, 0.0005 to 0.0070 N,≤1.5% Cu,≤1.0% Cr,≤1.0% Mo,≤0.05% V,≤0.06 Nb and≤0.0025% B, composed of the balance Fe and impurities and having Pcm≤0.25% and Fnl≥3.0% and has SR of≤800 MPa, where Pcm=C+(Si/30)+(Mn/20)+(Cu/20)+(Ni/60)+(Cr/20)+(Mo/15)+(V/10)+5B, Fn1=Mn+2Ni, Sr=-ä1(Tr/830)}×Ys+2.45×(Tr-Th). In the formula of SR, Tr is the transformation point (°C) of the steel sheet; YS is the yield stress (MPa) of the steel sheet; and Th is the preheating temperature (°C) before welding. COPYRIGHT: (C)2005,JPO&NCIPI
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