| 摘要 |
PROBLEM TO BE SOLVED: To provide a thick high-strength steel plate by which excellent weld HAZ toughness can be achieved even when a welding is applied with an amount of welding heat input of 20 to 100 kJ/mm to a steel plate having a plate thickness of 50 to 80 mm and a base-material tensile strength of 490 to 570 MPa class. SOLUTION: The steel plate has a composition which consists of, by mass, 0.03 to 0.14% C,≤0.30% Si, 0.8 to 2.0% Mn,≤0.02% P,≤0.005% S, 0.8 to 4.0% Ni, 0.003 to 0.040% Nb, 0.001 to 0.040% Al, 0.0010 to 0.0100% N, 0.005 to 0.030% Ti and the balance iron with inevitable impurities and in which Ni and Mn satisfy inequality Ni/Mn≥10×Ceq-3 (where 0.36<Ceq<0.42 is satisfied), wherein Ceq is represented by Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15. COPYRIGHT: (C)2006,JPO&NCIPI
|
