US 12,258,644 B2
High-strength galvanized steel sheet and method for manufacturing the same
Hiroshi Hasegawa, Tokyo (JP); Tatsuya Nakagaito, Tokyo (JP); and Kana Sasaki, Tokyo (JP)
Assigned to JFE Steel Corporation, Tokyo (JP)
Appl. No. 17/421,475
Filed by JFE Steel Corporation, Tokyo (JP)
PCT Filed Oct. 2, 2019, PCT No. PCT/JP2019/038832
§ 371(c)(1), (2) Date Jul. 8, 2021,
PCT Pub. No. WO2020/148948, PCT Pub. Date Jul. 23, 2020.
Claims priority of application No. 2019-006974 (JP), filed on Jan. 18, 2019.
Prior Publication US 2022/0064754 A1, Mar. 3, 2022
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 2/28 (2006.01); C23C 2/40 (2006.01)
CPC C21D 9/46 (2013.01) [C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0263 (2013.01); C21D 8/0273 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C23C 2/28 (2013.01); C23C 2/29 (2022.08); C23C 2/40 (2013.01); C21D 2201/05 (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
 
1. A high-strength galvanized steel sheet comprising a base steel sheet and a galvanized layer on a surface of the base steel sheet, wherein
the base steel sheet has a chemical composition containing, by mass %,
C: 0.12% to 0.35%,
Si: 0.5% to 3.0%,
Mn: 1.5% to 4.0%,
P: 0.100% or less (not including 0%),
S: 0.02% or less (not including 0%),
Al: 0.01% to 1.50%, with the balance being Fe and inevitable impurities, and wherein
the base steel sheet has a microstructure
in which an area fraction of martensite is 30% or less, an area fraction of pearlite is 1% or less, a total area fraction of tempered martensite and carbide-containing bainite is 30% or more and 99% or less, an area fraction of retained austenite is 1% to 20%, and a total area fraction of ferrite and non-carbide-containing bainite is 45% or less in the steel sheet microstructure in a region from a position located 300 μm from the steel sheet surface to a position located 400 μm from the steel sheet surface, and
in which an area fraction of retained austenite grains having two or more crystal orientations is 13% or more and 40% or less in all the retained austenite grains in a region from a position located 300 μm from the steel sheet surface to a position located 400 μm from the steel sheet surface, where the retained austenite grains having two or more crystal orientations are grains formed by a combination of plural austenite sub-grains having a misorientation of 15° or more.