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/2019/131188

Kind Code:

A1

Abstract:

Provided are a high-strength cold rolled steel sheet having a tensile strength of 1320 MPa or greater and superior ductility and stretch flangeability, as well as a low failure rate for flare tests, and a method for manufacturing the same. This high-strength cold rolled steel sheet has a prescribed composition. The total surface area ratio of ferrite and bainitic ferrite is in a range of 10 – 50%, the surface area ratio for retained austenite is in the range of greater than 15% to 50%, and the surface area ratio for tempered martensite is in the range of greater than 15% to 60%. The proportion of retained austenite with an aspect ratio of 0.6 or less is 70% by surface area ratio, and of the retained austenite with an aspect ratio of 0.6 or less, the proportion present at ferrite grain boundaries with a misorientation of 40% or greater is 50% or greater by surface area ratio, with the average KAM value for the bcc phase being 1° or less.

Inventors:

TANAKA TAKAAKI (JP)
TOJI YUKI (JP)

Application Number:

PCT/JP2018/045967

Publication Date:

July 04, 2019

Filing Date:

December 13, 2018

Export Citation:

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Assignee:

JFE STEEL CORP (JP)

International Classes:

C22C38/00; C21D9/46; C22C18/00; C22C18/04; C22C38/06; C22C38/60

Domestic Patent References:

WO2016021193A1	2016-02-11
WO2016021197A1	2016-02-11
WO2016113789A1	2016-07-21
WO2016132680A1	2016-08-25
WO2016132680A1	2016-08-25
WO2016021193A1	2016-02-11

Foreign References:

JP2013237917A	2013-11-28
JP2018178248A	2018-11-15

Other References: