Title:
HIGH-STRENGTH COLD-ROLLED STEEL SHEET HAVING EXCELLENT WORKABILITY AND COLLISION CHARACTERISTICS AND HAVING TENSILE STRENGTH OF 980 MPa OR MORE, AND METHOD FOR PRODUCING SAME
Document Type and Number:
WIPO Patent Application WO/2016/158159
Kind Code:
A1
Abstract:
Provided are: a high-strength cold-rolled steel sheet having a tensile strength of 980 MPa or more, having good workability as evaluated by ductility and stretch-flangeability, and having excellent collision characteristics; and a method for producing said steel sheet. In this high-strength cold-rolled steel sheet, the metal structure at a position of ¼ sheet thickness satisfies (1)-(4) below. (1) The area ratio of ferrite is 0-10%, inclusive, and the balance is a hard phase comprising at least one selected from the group consisting of bainitic ferrite, bainite, and tempered martensite, said hard phase including quenched martensite and retained austenite. (2) The volume ratio Vγ of retained austenite is 5-30%, inclusive. (3) The area ratio VMA of an MA structure in which quenched martensite and retained austenite are combined is 3-25%, inclusive, and the average equivalent circle diameter of the MA structure is 2.0 μm or less. (4) The ratio VMA/Vγ of the area ratio VMA of the MA structure to the volume ratio Vγ of the retained austenite is 0.50-1.50.
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Inventors:
MURATA TADAO
FUTAMURA YUICHI
KASUYA KOJI
FUTAMURA YUICHI
KASUYA KOJI
Application Number:
PCT/JP2016/056168
Publication Date:
October 06, 2016
Filing Date:
March 01, 2016
Export Citation:
Assignee:
KK KOBE SEIKO SHO(KOBE STEEL LTD ) (JP)
International Classes:
C22C38/60; C21D8/02; C21D9/46
Domestic Patent References:
| WO2014092025A1 | 2014-06-19 | |||
| WO2009099079A1 | 2009-08-13 | |||
| WO2010029983A1 | 2010-03-18 | |||
| WO2015151427A1 | 2015-10-08 |
Other References:
See also references of EP 3279362A4
Attorney, Agent or Firm:
UEKI, Kyuichi et al. (JP)
Hisakazu Ueki (JP)
Hisakazu Ueki (JP)
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