High strength steel excellent in uniform elongation properties and method of manufacturing the same

US8815025B2 · kind B2 · utility

Assignees

• JFE Steel Corporation · JP
• Thyssenkrupp Steel AG · DE

Inventors

• Takeshi Yokota · Tokyo, JP
• Akio Kobayashi · Tokyo, JP
• Kazuhiro Seto · Rifu, JP
• Yoshihiro Hosoya · Tokyo, JP
• Thomas Heller · Pittsburgh, US
• Brigitte Hammer · Voerde, DE
• Rolf Bode · Wesel, DE
• Günter Stich · Bochum, DE

Key dates

• Filing date: Nov 3, 2006
• Grant date: Aug 26, 2014
• Expiry date: Sep 25, 2028

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C22C38/14
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A high strength steel, including about 0.05 to about 0.25% of C, less than about 0.5% of Si, about 0.5 to about 3.0% of Mn, not more than about 0.06% of P, not more than about 0.01% of S, about 0.50 to about 3.0% of Sol. Al, not more than about 0.02% of N, about 0.1 to about 0.8% of Mo, about 0.02 to about 0.40% of Ti, and the balance of iron and unavoidable impurities, wherein the steel has a structure formed of at least three phases including a bainite phase, and a retained austenite phase in addition to a ferrite phase having a composite carbide containing Ti and Mo dispersed and precipitated therein, wherein the total volume of the ferrite phase and the bainite phase is not smaller than 80%, the volume of the bainite phase is about 5% to about 60%, and the volume of the retained austenite phase is about 3 to about 20%.