Patent ID: 8192683
Filing Date: 2012-06-05
Classification: B21B,C21D,C22C

Abstract:
1. High-strength steel sheet excellent in hole-expandability and ductility, consisting essentially of, in mass %, C: not less than 0.01% and not more than 0.20%, Si: not more than 1.5%, Al: not less than 0.18% to 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 being iron and unavoidable impurities, having the Mn %, Mg %, S % and O % satisfying equations (1) to (3), allowing precipitation of Mg-sulfides while impeding the precipitation of Mn-sulfides, the Al % and Si % satisfying equation (4), and the Ti %, C %, Mn % and Nb % satisfying equations (5) to (7), and containing not less than 5.0×10 having a structure primarily comprising bainite, and