THICK HIGH STRENGTH Ni-CONTAINING STEEL HAVING LOW TEMPERATURE TOUGHNESS IN HIGH HEAT INPUT WELD HEAT AFFECTED ZONE

摘要

PROBLEM TO BE SOLVED: To provide thick high strength Ni-containing steel having excellent low temperature toughness in the high heat input weld heat affected zone which has a thickness of 50 to 80 mm and a yield strength in a class of 390 to 460 MPa and capable of satisfying Charpy impact properties at -40°C in HAZ (Heat Affected Zone) subjected to single pass welding in a welding heat input volume of ≥20 kJ/mm.;SOLUTION: The thick high strength Ni-containing steel has a composition comprising, by mass, 0.03 to 0.08% C, 0.5 to 3% Ni, 0.5 to 2% Mn, 0.001 to 0.025% Nb and 0.001 to 0.05% Al, if required, further comprising prescribed amounts of one or more kinds of metals selected from Si, Cr, Mo, V and Cu, and also satisfying the expressions (1) to (4), and the balance iron with inevitable impurities; wherein, the expressions (1): 0.35≤Ceq≤0.45, the expressions (2): Mn≤-10C+2.3, the expressions (3): S≤-0.0014Mn+0.0057, and the expressions (4): Si+Cu+Cr+1.5Mo+15Nb+4V≤0.4.;COPYRIGHT: (C)2005,JPO&NCIPI