STEEL SHEET AND MANUFACTURING METHOD THEREFOR

Title:

STEEL SHEET AND MANUFACTURING METHOD THEREFOR

Document Type and Number:

WIPO Patent Application WO/2019/187090

Kind Code:

A1

Abstract:

This steel sheet has a prescribed chemical composition, wherein a steel structure in the interior of the steel sheet contains, by volume fraction, 0–30% soft ferrite, 3–40% residual austenite, 0–30% fresh martensite, and a total of 0–10% pearlite and cementite, the remainder including hard ferrite. In the interior of the steel sheet the number percentage of residual austenite with an aspect ratio of 2.0 or greater included among all of the residual austenite is 50% or greater, a soft layer with a thickness of 1–100 μm in the thickness direction from the surface exists, of the ferrite contained in the soft layer the volume fraction of crystal grains with an aspect ratio of less than 3.0 is 50% or greater, the volume fraction of the residual austenite in the soft layer is less than 50% of the volume fraction of the residual austenite in the interior of the steel sheet, and the peak emission intensity of a wavelength representing Si appears in a range of greater than 0.2 μm from the surface and 5.0 μm or less from the surface.

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Inventors:

YOKOYAMA TAKAFUMI (JP)
SANO KOHICHI (JP)
OKAMOTO RIKI (JP)
KAWATA HIROYUKI (JP)
SAKURADA EISAKU (JP)
YAMAGUCHI YUJI (JP)
SHIOKAWA KAZUKI (JP)
NAKAHIRA YUICHI (JP)
UEDA KOHEI (JP)
NAKATA MASAHIRO (JP)
UCHIDA SATOSHI (JP)

Application Number:

PCT/JP2018/013846

Publication Date:

October 03, 2019

Filing Date:

March 30, 2018

Export Citation:

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Assignee:

NIPPON STEEL CORP (JP)

International Classes:

C22C38/00; C21D9/46; C22C38/60

Domestic Patent References:

WO2017029814A1	2017-02-23
WO2018030500A1	2018-02-15
WO2017164346A1	2017-09-28
WO2016013144A1	2016-01-28
WO2017183349A1	2017-10-26
WO2015151419A1	2015-10-08

Foreign References:

JP2017145468A	2017-08-24
JP2009108343A	2009-05-21
JP2011149066A	2011-08-04
JP2009209451A	2009-09-17
JP2017186614A	2017-10-12

Attorney, Agent or Firm:

TANAI Sumio et al. (JP)

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