| 摘要 |
High-strength steel sheet excellent in hole-expandability and ductility, characterized by; comprising, in mass %, C: not less than 0.01% and not more than 0.20%, Si: not more than 1.5%, Al: not more than 1.5%, Mn: not less than 0.5% and not more than 3.5%, P: not more than 0.2%, S: not less than 0.0005% and not more than 0.009%, N: not more than 0.009%, Mg: not less than 0.0006% and not more than 0.01%, O: not more than 0.005% and Ti: not less than 0.01% and not more than 0.20% and/or Nb: not less than 0.01% and not more than 0.10%, with the balance consisting iron and unavoidable impurities, having Mn %, Mg %, S % and O % satisfying equations (1) to (3), and having the structure primarily comprising one or more of ferrite, bainite and martensite. [Mg %]≧([O %]/16×0.8)×24  (1) [S %]≦̸([Mg %]/24−[O %]/16×0.8+0.00012)×32  (2) [S %]≦̸0.0075/[Mn %]  (3) |
