HIGH-STRENGTH COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Title:

HIGH-STRENGTH COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Document Type and Number:

WIPO Patent Application WO/2018/168618

Kind Code:

A1

Abstract:

Through the present invention, a high-strength cold-rolled steel sheet having mechanical characteristics of a tensile strength of 780 MPa or greater, a yield ratio of 70% or less, and absolute values of in-plane anisotropy of each of yield stress and tensile strength of 30 MPa or less is obtained by hot-rolling, cold-rolling, and continuously annealing a steel slug containing, in terms of mass%, 0.07-0.12% C, 0.7% or less of Si, 2.2-2.8% Mn, and a total of 0.02-0.08% Ti and Nb, to obtain a steel structure comprising a second phase composed of ferrite, tempered martensite, fresh martensite, and bainite having an area ratio of 40-80% with respect to the entire structure, the total area ratio of bainite and tempered martensite in the second phase being 50-80%, and the aspect ratio of the fresh martensite being in the range of 1.0-1.5.

Inventors:

HIRASHIMA TAKUYA (JP)
KAWAMURA KENJI (JP)
ONO YOSHIHIKO (JP)
HONDA YUMA (JP)

Application Number:

PCT/JP2018/008892

Publication Date:

September 20, 2018

Filing Date:

March 08, 2018

Export Citation:

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Assignee:

JFE STEEL CORP (JP)

International Classes:

C22C38/00; C21D9/46; C22C38/14; C22C38/38

Domestic Patent References:

WO2017038070A1	2017-03-09
WO2016072479A1	2016-05-12
WO2016194272A1	2016-12-08
WO2015080242A1	2015-06-04
WO2013047760A1	2013-04-04

Foreign References:

JP2014005514A	2014-01-16
JP2013181183A	2013-09-12
JP2007138262A	2007-06-07
JP2010070843A	2010-04-02
JP2011094230A	2011-05-12

Other References: