| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high-strength steel sheet which is manufactured at a low cost without adding a large quantity of alloy elements, and is superior in low-temperature toughness and toughness in a weld heat-affected zone, and to provide a manufacturing method therefor. <P>SOLUTION: The high-strength steel sheet superior in the toughness in the weld heat-affected zone comprises, by mass%, 0.02% or more but less than 0.07% C, 0.01-0.5% Si, 0.5-1.8% Mn, 0.05-0.3% Mo, 0.005-0.025% Ti, 0.08% or less Al, 0.004-0.006% N, while controlling C/(Mo+Ti) to 0.5-3, Ti/N to 2-4, and Ceq shown by the expression (a): Ceq = C + Mn/6 + (Cu+Ni)/15 + (Cr+Mo+V)/5, to 0.38 or less, and the balance substantially Fe; and has a metallographic structure of a two-phase structure consisting substantially of ferrite and bainite, in which fine carbides containing Ti and Mo with particle sizes of less than 10 nm are dispersingly precipitated. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
