	US 12,454,733 B2
	High strength member, method for manufacturing high strength member, and method for manufacturing steel sheet for high strength member
Takuya Hirashima, Tokyo (JP); and Shinjiro Kaneko, Tokyo (JP)
Assigned to JFE Steel Corporation, Tokyo (JP)
Appl. No. 17/610,483
Filed by JFE Steel Corporation, Tokyo (JP)
PCT Filed May 12, 2020, PCT No. PCT/JP2020/019021 § 371(c)(1), (2) Date Nov. 11, 2021, PCT Pub. No. WO2020/230796, PCT Pub. Date Nov. 19, 2020.
Claims priority of application No. 2019-092656 (JP), filed on May 16, 2019; and application No. 2019-121144 (JP), filed on Jun. 28, 2019.
Prior Publication US 2022/0220577 A1, Jul. 14, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C21D 9/46 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/08 (2006.01); C22C 38/14 (2006.01); C22C 38/20 (2006.01); C22C 38/22 (2006.01); C22C 38/24 (2006.01); C22C 38/26 (2006.01); C22C 38/38 (2006.01)

CPC C21D 9/46 (2013.01) [C21D 6/001 (2013.01); C21D 6/002 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/08 (2013.01); C22C 38/14 (2013.01); C22C 38/20 (2013.01); C22C 38/22 (2013.01); C22C 38/24 (2013.01); C22C 38/26 (2013.01); C22C 38/38 (2013.01); C21D 2211/002 (2013.01); C21D 2211/008 (2013.01); C21D 2221/01 (2013.01)]

5 Claims

1. A high strength member comprising a bending ridge line portion formed from a steel sheet,

wherein the steel sheet has a chemical composition containing, by mass %,

C: 0.17% or more and 0.35% or less,

Si: 0.001% or more and 1.2% or less,

Mn: 0.9% or more and 3.2% or less,

P: 0.020% or less,

S: 0.0010% or less,

Al: 0.010% or more and 0.20% or less,

N: 0.010% or less, and a balance of Fe and incidental impurities, and

a microstructure, in which a total area fraction of one or both of bainite containing carbides having an average grain size of 50 nm or less and martensite containing carbides having an average grain size of 50 nm or less is 90% or more, and

the member having

a tensile strength of 1470 MPa or higher,

a residual stress of 300 MPa or lower in an end surface of the bending ridge line portion, and

a Vickers hardness (HV) of 200 or higher and 450 or lower in the end surface of the bending ridge line portion.