| 摘要 |
<p>A steel plate with high strength and high toughness which has 500 MPa or more of tensile strength at the center of thickness and has a ductile-brittle transition temperature of -50 deg.C or less as an ultra-thick steel plate for welded structure having a thickness of 50 mm or more, and a method of manufacturing the same are provided. As an ultra-thick steel plate for welded structure comprising, by weight percent, 0.05 to 0.10% of C, 0.10 to 0.35% of Si, 1.35 to 1.6% of Mn, 0.005 to 0.055% of soluble Al, 0.005 to 0.05% of Nb, 0.005 to 0.017% of Ti, 0.01% or less of N, and the balance of Fe and unavoidable impurities, an ultra-thick steel plate for welded structure having excellent strength and toughness at the center of thickness is characterized in that a polygonal ferrite area ratio in a thickness range of t/4 to 3t/4 when the plate has a thickness of t is 10% or less.</p> |
