US 12,344,911 B2
High-strength steel sheet and method for manufacturing same
Masafumi Azuma, Tokyo (JP); Eisaku Sakurada, Tokyo (JP); Genki Abukawa, Tokyo (JP); Kenichiro Otsuka, Tokyo (JP); and Takeshi Toyoda, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/430,651
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Mar. 19, 2020, PCT No. PCT/JP2020/012425
§ 371(c)(1), (2) Date Aug. 12, 2021,
PCT Pub. No. WO2020/196311, PCT Pub. Date Oct. 1, 2020.
Claims priority of application No. 2019-055469 (JP), filed on Mar. 22, 2019.
Prior Publication US 2022/0186333 A1, Jun. 16, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C21D 9/46 (2006.01); B21C 47/02 (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 38/42 (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 2/40 (2006.01); C23G 1/00 (2006.01)
CPC C21D 9/46 (2013.01) [B21C 47/02 (2013.01); C21D 8/0226 (2013.01); C21D 8/0263 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (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 2/40 (2013.01); C23G 1/00 (2013.01); C21D 2211/002 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01); C21D 2211/009 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A high-strength steel sheet, comprising,
as a chemical composition, by mass %:
C: 0.020 to 0.090%;
Si: 0.01 to 2.00%;
Mn: 1.00 to 3.00%;
Ti: 0.010 to 0.200%;
Al: 0.005 to 1.000%;
P: 0.100% or less;
S: 0.0100% or less;
N: 0.0100% or less;
Ni: 0 to 2.00%;
Cu: 0 to 2.00%;
Cr: 0 to 2.00%;
Mo: 0 to 2.00%;
Nb: 0 to 0.100%;
V: 0 to 0.100%;
W: 0 to 0.100%;
B: 0 to 0.0100%;
REM: 0 to 0.0300%;
Ca: 0 to 0.0300%;
Mg: 0 to 0.0300%; and
a remainder of Fe and impurities,
wherein 0.100≤Ti+Nb+V≤0.450 is satisfied,
a microstructure contains, by volume percentage, 95% or more of tempered martensite and bainite in total, and a remainder consists of ferrite and pearlite,
the microstructure contains 5.2×1011 pieces/mm3 or more of, per unit volume, precipitate having an equivalent circle diameter of 5.0 nm or less and containing Ti,
Hvs/Hvc which is a ratio of an average hardness Hvs at a position of a depth of 20 μm from a surface to an average hardness Hvc at a position of 0.20 to 0.50 mm from the surface is 0.85 or more,
a tensile strength is 1186 MPa or more,
a yield ratio is 0.96 or more, and
a product of the tensile strength and elongation is 12,000 MPa×% or more.