COLD-ROLLED STEEL SHEET AND MANUFACTURING METHOD THEREOF

Title:

COLD-ROLLED STEEL SHEET AND MANUFACTURING METHOD THEREOF

Document Type and Number:

WIPO Patent Application WO/2022/190958

Kind Code:

A1

Abstract:

This cold-rolled steel sheet has a predetermined chemical composition, wherein: a metallographic structure at a t/4 position, which is located at 1/4 of the sheet thickness t from the surface in a sheet thickness direction, contains, by volume ratio, 2.0% to 8.0% of residual austenite, 80.0% to 98.0% of tempered martensite, a total of 0.0% to 15.0% of ferrite and bainite, and 0.0% to 5.0% of martensite; both in a central region and in an edge region positioned 50 mm from an edge in a width direction, a 20 µm region, which is positioned 20 µm from the surface in the sheet thickness direction, has a metallographic structure containing, by volume ratio, a total of 75.0% to 100.0% of ferrite and bainite and a total of 0.0% to 25.0% of martensite and tempered martensite; and a 75 µm region, which is positioned 75 µm from the surface in the sheet thickness direction, has a metallographic structure containing, by volume ratio, a total of 0.0% to 15.0% of ferrite and bainite.

Inventors:

NISHIO TAKUYA (JP)
AZUMA MASAFUMI (JP)
NARITA YOSHIMASA (JP)
OKURA SHINTARO (JP)

Application Number:

PCT/JP2022/008567

Publication Date:

September 15, 2022

Filing Date:

March 01, 2022

Export Citation:

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Assignee:

NIPPON STEEL CORP (JP)

International Classes:

C22C38/00; C21D9/46; C22C38/58

Domestic Patent References:

WO2019181950A1	2019-09-26
WO2020039697A1	2020-02-27
WO2015005191A1	2015-01-15
WO2021024748A1	2021-02-11

Foreign References:

JP2010215958A	2010-09-30
JPH10130782A	1998-05-19
JP2021038717A	2021-03-11
JP2009030091A	2009-02-12
JP2010215958A	2010-09-30
JP2006104532A	2006-04-20
JP6187710B2	2017-08-30
JPH0335236B2	1991-05-27

Other References: