	US 12,392,007 B2
	High strength steel sheet, high strength member, and methods for manufacturing the same
Takuya Hirashima, Tokyo (JP); Yu Hashimoto, Tokyo (JP); Shinjiro Kaneko, Tokyo (JP); and Yoshihiko Ono, Tokyo (JP)
Assigned to JFE Steel Corporation, Tokyo (JP)
Appl. No. 17/630,243
Filed by JFE Steel Corporation, Tokyo (JP)
PCT Filed Jul. 29, 2020, PCT No. PCT/JP2020/029050 § 371(c)(1), (2) Date Jan. 26, 2022, PCT Pub. No. WO2021/020439, PCT Pub. Date Feb. 4, 2021.
Claims priority of application No. 2019-140373 (JP), filed on Jul. 31, 2019.
Prior Publication US 2022/0282353 A1, Sep. 8, 2022
Int. Cl. C21D 9/50 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/54 (2006.01); C23C 2/02 (2006.01); C23C 2/26 (2006.01); C23C 2/28 (2006.01)

CPC C21D 9/50 (2013.01) [C21D 6/004 (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); C21D 8/0263 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/54 (2013.01); C23C 2/02 (2013.01); C23C 2/022 (2022.08); C23C 2/26 (2013.01); C23C 2/28 (2013.01); C21D 2211/001 (2013.01); C21D 2211/002 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01); C21D 2211/009 (2013.01)]

12 Claims

1. A high strength steel sheet having a tensile strength of 590 MPa or larger and a chemical composition in mass % containing:

C: 0.06% or more and 0.14% or less,

Si: 0.1% or more and 1.5% or less,

Mn: 1.4% or more and 2.2% or less,

P: 0.05% or less,

S: 0.0050% or less,

Al: 0.01% or more and 0.20% or less,

N: 0.10% or less,

Nb: 0.015% or more and 0.060% or less, and

Ti: 0.001% or more and 0.030% or less, optionally containing one or more of following (A) to (C);

(A) one of, or two or more of

Cr: 0.01% or more and 0.15% or less,

Mo: 0.01% or more and less than 0.10%, and

V: 0.001% or more and 0.065% or less,

(B) B: 0.0001% or more and less than 0.002%,

Cu: 0.001% or more and 0.2% or less, and

Ni: 0.001% or more and 0.1% or less,

contents of S, N and Ti satisfying Formula (1) below,

a balance being Fe and an inevitable impurity,

comprising, in terms of area fraction relative to an entire steel microstructure, 30% or more and 100% or less ferrite, 0% or more and 70% or less martensite, and less than 20% in total of pearlite, bainite and retained austenite, and the ferrite containing, in terms of area fraction relative to an entire microstructure, 0% or more and 10% or less non-recrystallized ferrite, with a difference between a maximum value and a minimum value of the area fraction of the non-recrystallized ferrite in a longitudinal direction of the steel sheet of 5% or below:

[% Ti]−(48/14)[% N]−(48/32)[% S]≤0, Formula (1):

in Formula (1), [% Ti] represents content (mass %) of component element Ti, [% N] represents content (mass %) of component element N, and [% S] represents content (mass %) of component element S.