Title:
HIGH-STRENGTH COLD-ROLLED STEEL SHEET
Document Type and Number:
WIPO Patent Application WO/2017/141953
Kind Code:
A1
Abstract:
The present invention provides a high-strength cold-rolled steel sheet having excellent delayed fracture resistance and chemical conversion properties and being characterized by having a tensile strength of 1180 MPa or more. Provided is a high-strength cold-rolled steel sheet that has a composition containing, by mass%, C: 0.10-0.6%, inclusive, Si: 1.0-3.0%, inclusive, Mn: more than 2.5% but at most 10.0%, P: 0.05% or less, S: 0.02% or less, Al: 0.01-1.5%, inclusive, N: 0.005% or less, and Cu: 0.05-0.50%, inclusive, wherein the balance consists of iron and inevitable impurities, the steel sheet surface coverage ratio of oxides mainly composed of Si is 1% or less, the steel sheet surface coverage ratio of iron oxides is 40% or less, CuS/CuB satisfies 4.0 or less (CuS is the Cu concentration of a surface layer of the steel sheet and CuB is the Cu concentration of a parent material), and the tensile strength is 1180 MPa or more.
Inventors:
YOSHIOKA SHIMPEI (JP)
ONO YOSHIHIKO (JP)
KIMATA YUSUKE (JP)
MASUOKA HIROYUKI (JP)
ONO YOSHIHIKO (JP)
KIMATA YUSUKE (JP)
MASUOKA HIROYUKI (JP)
Application Number:
PCT/JP2017/005467
Publication Date:
August 24, 2017
Filing Date:
February 15, 2017
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C22C38/00; C22C38/16; C22C38/60; C21D9/46
Foreign References:
| JP2012132092A | 2012-07-12 | |||
| JP2012172183A | 2012-09-10 | |||
| JP2013173976A | 2013-09-05 | |||
| JP2015193907A | 2015-11-05 | |||
| JP2013124383A | 2013-06-24 | |||
| JP2011231377A | 2011-11-17 | |||
| JP2012012642A | 2012-01-19 | |||
| JPS545980B2 | 1979-03-23 | |||
| JPS5729211B2 | 1982-06-21 |
Other References:
See also references of EP 3418417A4
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JP)
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