Title:
STEEL SHEET, MEMBER, AND METHOD FOR MANUFACTURING SAME
Document Type and Number:
WIPO Patent Application WO/2020/129402
Kind Code:
A1
Abstract:
The present invention provides a steel sheet, a member, and a method for manufacturing the same, the steel sheet having: a specific component composition in which the contents of Ti and Nb satisfy a specific relationship; and a structure in which the total area ratio of martensite and bainite is 95% to 100%, the remainder being one or more phases selected from ferrite and residual austenite, and the density of inclusion grain groups in which the long-axis length of the inclusion grain groups is 20 µm to 80 µm is 5/mm2 or less, the inclusion grain groups comprising inclusion grains having a long-axis length of 20 µm to 80 µm and for which the shortest distance between inclusion grains is more than 10 µm, and two or more inclusion grains for which the shortest distance between the inclusion grains is 10 µm or less and which are inclusion grains having a long-axis length of 0.3 µm or greater; the local P concentration in a position range 1/4 to 3/4 of the thickness from the steel sheet surface being 0.060% by mass or less, the degree of segregation of Mn in said position range being 1.50 or less, the tensile strength being 1320 MPa or greater, and delayed fracture in a cut end surface also being suppressed to a superior degree in the steel sheet.
Inventors:
YOSHIOKA SHIMPEI (JP)
ONO YOSHIHIKO (JP)
HONDA YUMA (JP)
NAKAMURA NOBUYUKI (JP)
ONO YOSHIHIKO (JP)
HONDA YUMA (JP)
NAKAMURA NOBUYUKI (JP)
Application Number:
PCT/JP2019/041817
Publication Date:
June 25, 2020
Filing Date:
October 25, 2019
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C21D9/46; B22D11/124; C22C38/00; C22C38/14; C22C38/60
Domestic Patent References:
| WO2017138504A1 | 2017-08-17 | |||
| WO2016163469A1 | 2016-10-13 |
Foreign References:
| JP3514276B2 | 2004-03-31 | |||
| JP5428705B2 | 2014-02-26 | |||
| JPS5431019A | 1979-03-07 | |||
| JP5824401B2 | 2015-11-25 | |||
| JP4427010B2 | 2010-03-03 | |||
| JP6112261B2 | 2017-04-12 | |||
| JP2015155572A | 2015-08-27 | |||
| JP2016153524A | 2016-08-25 |
Other References:
See also references of EP 3875615A4
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JP)
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