METHOD FOR PRODUCING COLD ROLLED STEEL PLATE OF SUPER HIGH STRENGTH

Title:

METHOD FOR PRODUCING COLD ROLLED STEEL PLATE OF SUPER HIGH STRENGTH

Document Type and Number:

WIPO Patent Application WO/2003/104499

Kind Code:

A1

Abstract:

A method for producing a cold rolled steel plate of super high strength, which has a process of continuously annealing a cold rolled steel plate having a substantial chemical composition in wt %: C: 0.07 to 0.15 %, Si: 0.7 to 2 %, 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 %, B: 0.0003 to 0.003 %, and balance: Fe, wherein the continuous annealing process comprises a step of heating the cold rolled steel plate before annealing at 800 to 870°C for 10 sec, a step of slowly cooling the heated steel plate to 650 to 750°C, a step of rapidly cooling the steel plate after the slow cooling to 100°C or lower at a cooling rate of more than 500°C/sec, a step of re-heating the steel plate after the rapid cooling at 325 to 425°C for 5 to 20 min, and a step of cooling the steel plate after the re-heating to room temperature and winding it up. A steel plate produced by the method has a tensile strength of 980 MPa or more and is excellent in stretch-flamging property and spot welding property, and thus can be suitably used as a cold rolled steel plate of super high strength for a structural member of an automobile.

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Inventors:

HASEGAWA KOHEI (JP)
NAKAMURA NOBUYUKI (JP)
URABE TOSHIAKI (JP)

Application Number:

PCT/JP2003/007215

Publication Date:

December 18, 2003

Filing Date:

June 06, 2003

Export Citation:

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Assignee:

JFE STEEL CORP (JP)
HASEGAWA KOHEI (JP)
NAKAMURA NOBUYUKI (JP)
URABE TOSHIAKI (JP)

International Classes:

C21D8/02; C21D9/52; C22C38/00; C22C38/02; C21D9/46; C22C38/04; C22C38/06; C22C38/14; C21D1/19; (IPC1-7): C21D9/46; C21D8/02; C22C38/06; C22C38/14

Domestic Patent References:

WO2002022904A1

2002-03-21

Foreign References:

JPH0192317A	1989-04-11
JPS63241115A	1988-10-06
JPS6314817A	1988-01-22
JPS6213533A	1987-01-22

Other References:

See also references of EP 1512762A4
None

Attorney, Agent or Firm:

Ochiai, Kenichiro c/o Intellectual, Property Dept (JFE STEEL CORPORATION 2-3, Uchisaiwaicho 2-chom, Chiyoda-ku Tokyo, JP)

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