	US 12,110,568 B2
	Steel sheet and member, and methods for manufacturing same
Yoichiro Matsui, Tokyo (JP); Yuka Miyamoto, Tokyo (JP); and Takeshi Yokota, Tokyo (JP)
Assigned to JFE STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/434,255
Filed by JFE STEEL CORPORATION, Tokyo (JP)
PCT Filed Feb. 28, 2020, PCT No. PCT/JP2020/008223 § 371(c)(1), (2) Date Aug. 26, 2021, PCT Pub. No. WO2020/175665, PCT Pub. Date Sep. 3, 2020.
Claims priority of application No. 2019-036104 (JP), filed on Feb. 28, 2019.
Prior Publication US 2022/0154301 A1, May 19, 2022
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 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/22 (2006.01); C22C 38/24 (2006.01); C22C 38/26 (2006.01); C22C 38/28 (2006.01); C22C 38/54 (2006.01)

CPC C21D 9/46 (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 8/0263 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/008 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/22 (2013.01); C22C 38/24 (2013.01); C22C 38/26 (2013.01); C22C 38/28 (2013.01); C22C 38/54 (2013.01); C21D 2211/004 (2013.01); C21D 2211/005 (2013.01)]

12 Claims

1. A steel sheet having a chemical composition comprising, by mass %:

C: 0.10% or more and 0.33% or less;

Si: 0.01% or more and 0.50% or less;

Mn: 0.40% or more and 1.25% or less;

P: 0.03% or less;

S: 0.01% or less;

sol. Al: 0.10% or less;

N: 0.01% or less;

Cr: 0.50% or more and 1.50% or less; and

a balance being Fe and incidental impurities,

wherein the steel sheet has a microstructure containing ferrite and carbides, a ratio of a volume of the ferrite and the carbides to a volume of an entire microstructure is 90% or more, and a ratio of a volume of proeutectoid ferrite to the volume of the entire microstructure is in a range of 20% or more and 80% or less,

a Mn concentration in the carbides is in a range of 0.10 mass % or more and 0.50 mass % or less, and

a ratio of a number of carbides with particle diameters of 1 μm or more to a total number of carbides is in a range of 30% or more and 60% or less.