| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide high strength steel having a tensile strength of 590 MPa grade or more, which suppresses usage of Ni, Mo and Mn as much as possible, and is excellent in high heat input HAZ toughness. <P>SOLUTION: High strength steel excellent in toughness at a welding heat-affected zone has a composition including, by mass%, 0.025-0.050% of C, 0.3% or less of Si, 1.2-2.0% of Mn, 0.05% or less of P, 0.01% or less of S, 1.5-3.5% of Cr, 0.05% or less of Al, 0.005-0.050% of Ti, 0.5-2.0% of Ni and 0.0015-0.0060% of N, with the remainder being iron and unavoidable impurities, while satisfying the following expression (1). 2.3≤(Mn+0.4Cr)≤2.7 (1). In the expression, Mn and Cr represent the content (mass%) of the respective elements. <P>COPYRIGHT: (C)2012,JPO&INPIT</p> |
