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

Title:

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

Document Type and Number:

WIPO Patent Application WO/2020/145108

Kind Code:

A1

Abstract:

The purpose of the present invention is to provide: a high-strength cold-rolled steel sheet that has high strength, excellent ductility, excellent hole expandability, and excellent resistance weldability; and a production method for the high-strength cold-rolled steel sheet. This high-strength cold-rolled steel sheet has a specific composition and a steel structure that is, by volume%, 10%–70% ferrite, 1%–10% retained austenite, 10%–60% bainite, and 2%–50% martensite, the average crystal grain size of the ferrite being no more than 6.0 μm, the average crystal grain size of the retained austenite being no more than 4.0 μm, the average crystal grain size of the bainite being no more than 6.0 μm, and the average crystal grain size of the martensite being no more than 4.0 μm. The concentration ratio of the average concentration of Si to a depth of 10 μm from the surface of the high-strength cold-rolled steel sheet to the average concentration of Si throughout the high-strength cold-rolled steel sheet is, by mass ratio, greater than 1.00 but less than 1.30.

Inventors:

OBATA YOSHIE (JP)
TAKASHIMA KATSUTOSHI (JP)
YOKOTA TAKESHI (JP)

Application Number:

PCT/JP2019/050284

Publication Date:

July 16, 2020

Filing Date:

December 23, 2019

Export Citation:

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Assignee:

JFE STEEL CORP (JP)

International Classes:

C22C38/00; C21D9/46; C22C38/14; C22C38/60; C23C2/06; C23C2/28; C23C2/40; C23C8/14; C23C26/00

Domestic Patent References:

WO2018043456A1	2018-03-08
WO2017203994A1	2017-11-30

Foreign References:

JP2010059452A	2010-03-18
JP2018521222A	2018-08-02
JP2002294398A	2002-10-09

Other References: