| (19) |
 |
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(11) |
EP 2 017 363 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
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05.08.2009 Bulletin 2009/32 |
| (43) |
Date of publication A2: |
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21.01.2009 Bulletin 2009/04 |
| (22) |
Date of filing: 04.06.2003 |
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| (51) |
International Patent Classification (IPC):
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| (84) |
Designated Contracting States: |
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DE SE |
| (30) |
Priority: |
14.06.2002 JP 2002173668
14.06.2002 JP 2002173669
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| (62) |
Application number of the earlier application in accordance with Art. 76 EPC: |
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03736017.9 / 1514951 |
| (71) |
Applicant: JFE Steel Corporation |
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Tokyo, 100-0011 (JP) |
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| (72) |
Inventors: |
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- Hasegawa, Kohei
c/o Intellectual Prop. Dept. JFE Steel corp.
Tokyo 100-0011 (JP)
- Matsuda, Hiroshi
c/o Intellectual Prop. Dept. JFE Steel corp.
Tokyo 100-0011 (JP)
- Kitano, Fusato
c/o Intellectual Prop. Dept. JFE Steel corp.
Tokyo 100-0011 (JP)
- Kawamura, Kenji
c/o Intellectual Prop. Dept. JFE Steel corp.
Tokyo 100-0011 (JP)
- Tsurumaru, Hideyuki
c/o Intellectual Prop. Dept. JFE Steel corp.
Tokyo 100-0011 (JP)
|
| (74) |
Representative: HOFFMANN EITLE |
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Patent- und Rechtsanwälte
Arabellastraße 4
81925 München
81925 München (DE) |
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| (54) |
High strength cold-rolled steel sheet and method for manufacturing the same |
(57) A high strength cold-rolled steel plate which has a chemical composition in mass%:
C: 0.04 to 0.10%, Si: 0.5 to 1.5%, Mn: 1.8 to 3%, P: 0.02% or less, S: 0.01% or less,
Sol.Al: 0.01 to 0.1%, N: 0.005% or less, and the balance: Fe and inevitable impurities,
and has a metal structure consisting substantially of a ferrite phase and a martensite
phase. The high strength cold-rolled steel plate exhibits good ductility of an elongation
of 18% or more and excellent stretch-flanging property of a bore expanding percentage
of 60% or more, in combination with a tensile strength of 780 MPa or more, and thus
can be suitably used for a structural member of an automobile.