| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-tensile strength steel wherein the base material has excellent strength and ductility, as well as excellent ductility in welding heated parts, even in thick high-strength steel plates, and a manufacturing method thereof. SOLUTION: Disclosed is a high-tensile strength steel comprising, in mass%, C: 0.03 to 0.10%, Si: 0.30% or less, Mn: 1.60 to 2.30%, P: 0.015% or less, S: 0.005% or less, Al: 0.005 to 0.06%, Nb: 0.004 to 0.05%, Ti: 0.005 to 0.02%, N: 0.001 to 0.005%, Ca: 0.0005 to 0.003%, as well as Ca, S, and O satisfy formula (1); 0<(Ca-(0.18+130×Ca)×O)/1.25/S<1: wherein the content (mass%) of each element Ca, S, and O is satisfied, and the remainder of which comprises Fe and unavoidable impurities. COPYRIGHT: (C)2010,JPO&INPIT |
