Title:
HIGH STRENGTH COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME
Document Type and Number:
WIPO Patent Application WO/2018/043456
Kind Code:
A1
Abstract:
To provide: a high strength cold-rolled steel sheet which has a tensile strength of at least 980 MPa, has both high ductility and high hole-expandability, and exhibits excellent resistance welding properties; and a method for manufacturing the same. The present invention provides a high strength cold-rolled steel sheet which has a specific component composition and a steel structure comprising, by volume ratio, 35% or less ferrite, 1-10% residual austenite, 2-12% as-quenched martensite, and a total of 25-70% bainite and tempered martensite, wherein the average crystal grain size of the ferrite is 5.0 μm or less, the average crystal grain size of the residual austenite is 2.0 μm or less, the average crystal grain size of the as-quenched martensite is 3.0 μm or less, the average crystal grain size of the bainite and tempered martensite phase is 4.0 μm or less, and the average distance between particles of the as-quenched martensite is at least 1.0 μm.
Inventors:
OBATA YOSHIE (JP)
TAKASHIMA KATSUTOSHI (JP)
KOBAYASHI TAKASHI (JP)
MATSUDA HIROSHI (JP)
TAKASHIMA KATSUTOSHI (JP)
KOBAYASHI TAKASHI (JP)
MATSUDA HIROSHI (JP)
Application Number:
PCT/JP2017/030849
Publication Date:
March 08, 2018
Filing Date:
August 29, 2017
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C22C38/00; C21D9/46; C22C18/00; C22C18/04; C22C38/14; C22C38/60; C23C2/06; C25D5/26
Domestic Patent References:
| WO2014061270A1 | 2014-04-24 | |||
| WO2015151427A1 | 2015-10-08 |
Foreign References:
| JP2011001579A | 2011-01-06 | |||
| JPH08283838A | 1996-10-29 | |||
| JP2011149066A | 2011-08-04 |
Other References:
See also references of EP 3476963A4
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JP)
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