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Title:
DUAL-PHASE HIGH-STRENGTH STEEL SHEET HAVING EXCELLENT DYNAMIC DEFORMATION PROPERTIES AND PROCESS FOR PREPARING THE SAME
Document Type and Number:
WIPO Patent Application WO/1998/041664
Kind Code:
A1
Abstract:
A dual-phase high-strength steel sheet for automobiles, which possesses excellent collision safety and excellent dynamic deformation properties and is used mainly for structural members and reinforcements of automobiles, and a process for preparing the same. The steel sheet is characterized in that the microstructure of the finally obtained steel sheet is a composite texture comprising a main phase of ferrite and a secondary phase of other low-temperature formed phase containing 3 to 50 %, in terms of volume fraction, of martensite after 5 % forming of the steel sheet, that the difference between the quasistatic deformation strength $g(s)s upon deformation in the strain range of from 5 x 10?-4� to 5 x 10?-3� (s?-1�) after application of predeformation of more than 0 to not more than 10 % in terms of corresponding strain and the dynamic deformation strength $g(s)d upon deformation in the strain range of from 5 x 10?2� to 5 x 10?3� (s?-1�) after the application of the predeformation, that is, $g(s)d-$g(s)s, is not less than 60 MPa, and that the work hardening index at a strain of 5 to 10 % is not less than 0.13.

Inventors:
Uenishi, Akihiro (Nippon Steel Corporation, Technical Development Bureau 20-1, Shintom, Futtsu City Chiba, 293-0011, JP)
Takahashi, Manabu (Nippon Steel Corporation, Technical Development Bureau 20-1, Shintom, Futtsu City Chiba, 293-0011, JP)
Kuriyama, Yukihisa (Nippon Steel Corporation, Technical Development Bureau 20-1, Shintom, Futtsu City Chiba, 293-0011, JP)
Sakuma, Yasuharu (Nippon Steel Corporation Kimitsu Works, 1 Kimits, Kimitsu City Chiba, 299-1193, JP)
Kawano, Osamu (Nippon Steel Corporation Oita Works, 1 Oaza-Nishinos, Oita City Oita, 870-8566, JP)
Wakita, Junichi (Nippon Steel Corporation Oita Works, 1 Oaza-Nishinos, Oita City Oita, 870-8566, JP)
Mabuchi, Hidesato (Nippon Steel Corporation Oita Works, 1 Oaza-Nishinos, Oita City Oita, 870-8566, JP)
Application Number:
PCT/JP1998/001101
Publication Date:
September 24, 1998
Filing Date:
March 16, 1998
Export Citation:
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Assignee:
NIPPON STEEL CORPORATION (6-3 Otemachi 2-chome, Chiyoda-ku, Tokyo, 100-8071, JP)
International Classes:
C21D8/02; C21D9/46; C22C38/00; C22C38/50; (IPC1-7): C22C38/00; C22C38/50; C21D8/02; C21D9/46
Foreign References:
JPH08176738A1996-07-09
JPH08176723A1996-07-09
JPH0790482A1995-04-04
JPH083677A1996-01-09
JPS59219473A1984-12-10
Other References:
See also references of EP 0969112A4
Attorney, Agent or Firm:
Ishida, Takashi (A. Aoki & Associates, Toranomon 37 Mori Building 5-1, Toranomon 3-chom, Minato-ku Tokyo, 105-8423, JP)
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