US 12,173,380 B2
Steel sheet and method for producing same
Eriko Tsukamoto, Tokyo (JP); and Kengo Takeda, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 18/035,066
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Dec. 24, 2021, PCT No. PCT/JP2021/048346
§ 371(c)(1), (2) Date May 2, 2023,
PCT Pub. No. WO2022/149502, PCT Pub. Date Jul. 14, 2022.
Claims priority of application No. 2021-001682 (JP), filed on Jan. 7, 2021.
Prior Publication US 2024/0011114 A1, Jan. 11, 2024
Int. Cl. C21D 9/46 (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); C23C 2/06 (2006.01); C23C 2/40 (2006.01)
CPC C21D 9/46 (2013.01) [C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0273 (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); C23C 2/06 (2013.01); C23C 2/40 (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)] 6 Claims
OG exemplary drawing
 
1. A steel sheet comprising, as a chemical composition, by mass %:
C: 0.10% to 0.40%;
Si: 0.10% to 1.20%;
Al: 0.30% to 1.50%;
Mn: 1.0% to 4.0%;
P: 0.0200% or less;
S: 0.0200% or less;
N: 0.0200% or less;
O: 0.0200% or less;
Ni: 0% to 1.00%;
Mo: 0% to 0.50%;
Cr: 0% to 2.00%;
Ti: 0% to 0.100%;
B: 0% to 0.0100%;
Nb: 0% to 0.10%;
V: 0% to 0.50%;
Cu: 0% to 0.50%;
W: 0% to 0.10%;
Ta: 0% to 0.100%;
Co: 0% to 0.50%;
Mg: 0% to 0.050%;
Ca: 0% to 0.0500%;
Y: 0% to 0.050%;
Zr: 0% to 0.050%;
La: 0% to 0.0500%;
Ce: 0% to 0.050%;
Sn: 0% to 0.05%;
Sb: 0% to 0.050%;
As: 0% to 0.050%; and
a remainder of Fe and impurities,
wherein the steel sheet includes, as a metallographic structure,
ferrite, bainite, and pearlite in a total volume percentage of 0% or more and 50% or less,
residual austenite in a volume percentage of 3% or more and 20% or less, and
a remainder of one or two of fresh martensite and tempered martensite,
residual austenite having an aspect ratio of 3.0 or more occupies 80% or more of a total residual austenite by area ratio,
the steel sheet includes an internal oxide layer that is present from a surface of the steel sheet to a depth of at least 4.0 μm and a decarburized layer that is present from a surface of the steel sheet to a depth of 10 μm or more and 100 μm or less, and
an amount of diffusible hydrogen included in the steel sheet is 1.00 ppm or less on a mass basis.