Title: A high strength steel excellent in uniform elongation properties and method of manufacturing the same
Application Number: 200610162827 Application Date: 2006.11.24
Publication Number: 1970812 Publication Date: 2007.05.30
Approval Pub. Date: Granted Pub. Date:
International Classifi-cation: C22C38/14;C21D8/02;C21D11/00;B21B37/74;B21D5/00
Applicant(s) Name: Jfe Steel Corp. Address:
Inventor(s) Name: Yokota Takeshi;Kobayashi Akio;Seto Kazuhiro;Hosoya
Attorney & Agent: wanghai chuan fanwei min
Abstract:
    The present invention is intended to provide a high strength steel sheet having a strength not lower than 780 MPa and exhibiting a high yield ratio, an excellent balance between the strength and the uniform elongation, and a good plating property in addition to a good balance between the strength and the stretch flangeability. The present invention provides a high strength steel, comprising 0.05 to 0.25 % of C, less than 0.5 % of Si, 0.5 to 3.0 % of Mn, not more than 0.06. % of P, not more than 0.01 % of S, 0.50 to 3.0 % of Sol. A1, not more than 0.02 % of N, 0.1 to 0.8 % of Mo, 0.02 to 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 5% to 60%, and the volume of the retained austenite phase is 3 to 20%.
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