STEEL SHEET AND MANUFACTURING METHOD THEREFOR

WIPO Patent Application WO/2024/053736

A1

This steel sheet has a base steel sheet that has a prescribed chemical composition and a galvanization layer that is formed on the surface of the base steel sheet, wherein: where the sheet thickness of the base steel sheet is t, the metallographic structure of the base steel sheet at a t/4 location, which is a location at a depth of t/4 from the surface in a cross section in the sheet thickness direction, includes at least 85% of tempered martensite, at least 7% of retained austenite, and 0-8% of at least one substance selected from ferrite, pearlite, bainite, and fresh martensite by volume; the metallographic structure in a surface region, which is the range up to a location 50 μm from the surface in the cross section in the sheet thickness direction, includes at least 30% of bainite by volume, where the remainder is at least one substance selected from ferrite, pearlite, tempered martensite, fresh martensite, and retained austenite; and prior austenite grains in the surface region have a diameter in the sheet thickness direction of no more than 10.0 μm and a tensile strength of at least 1,470 MPa.

SUZUKI YUYA (JP)
SAWADA MASAYOSHI (JP)
AZUMA MASAFUMI (JP)
TAKEDA KENGO (JP)

PCT/JP2023/032868

March 14, 2024

September 08, 2023

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NIPPON STEEL CORP (JP)

C22C38/00; C21D9/46; C22C38/60

WO2018105003A1	2018-06-14
WO2019186997A1	2019-10-03
WO2020262652A1	2020-12-30

JP6635236B1	2020-01-22
JP2020523473A	2020-08-06
KR20220019867A	2022-02-18

MATSUNUMA Yasushi et al. (JP)

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