| 摘要 |
<p>A high strength thin steel sheet excellent in hole expansibility and ductility, characterized in that it has a chemical composition in mass %: C: 0.01 to 0.20 %, Si: 1.5 % or less, Al: 1.5 % or less, Mn: 0.5 to 3.5 %, P: 0.2 % or less, S: 0.0005 % to 0.009 %, N; 0.009 % or less, Mg: 0.0006 to 0.01 %, O: 0.005 % or less, one or both of Ti: 0.01 to 0.20 % and Nb: 0.01 to 0.10 %, and the balance: Fe and inevitable impurities, with the proviso that Mn %, Mg %, S % and O % satisfy the following formula: [Mg %] >= ([O %]/16 X 0. 8) X 24 -------(1) [S %] <= ([Mg %]/24 -[O %]/16 X 0.8 + 0.00012) X 32 --(2) [S %] <= 0.0075/[Mn %] -------(3), and has a steel structure comprising ferrite, bainite and martensite as main components.</p> |
