COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Title:

COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Document Type and Number:

WIPO Patent Application WO/2016/136810

Kind Code:

A1

Abstract:

This cold-rolled steel sheet has a predetermined chemical composition, and has a metallographic structure containing, by area fraction, 40.0% to below 60.0% of polygonal ferrite, 30.0% or more of bainitic ferrite, 10.0-25.0% of retained austenite, and 15.0% or less of martensite. In the retained austenite, the proportion of retained austenite having an aspect ratio of 2.0 or less, a major axis length of 1.0 µm or less, and a minor axis length of 1.0 µm or less is 80.0% or more. In the bainitic ferrite, the proportion of bainitic ferrite which has an aspect ratio of 1.7 or less, and in which the average crystallographic misorientation is 0.5° to below 3.0° in a region surrounded by grain boundaries having a crystallographic misorientation of 15° or more, is 80.0% or more. The connectivity D value between the martensite, the bainitic ferrite, and the retained austenite is 0.70 or less.

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Inventors:

TAKEDA KENGO (JP)
HAYASHI KUNIO (JP)
UENISHI AKIHIRO (JP)
AZUMA MASAFUMI (JP)
NOZAKI TAKAYUKI (JP)
TODA YURI (JP)

Application Number:

PCT/JP2016/055428

Publication Date:

September 01, 2016

Filing Date:

February 24, 2016

Export Citation:

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Assignee:

NIPPON STEEL & SUMITOMO METAL CORP (JP)

International Classes:

C22C38/60; C21D8/02; C21D9/46

Domestic Patent References:

WO2013125400A1

2013-08-29

Foreign References:

JP2011214081A	2011-10-27
JP2011149066A	2011-08-04
JP2007154283A	2007-06-21
JP2004292891A	2004-10-21

Other References: