US 12,227,851 B2
High-strength Zn—Al—Mg-based surface-coated steel sheet and method for producing same
Susumu Fujiwara, Tokyo (JP); Shinya Uesugi, Tokyo (JP); and Tomoharu Shigetomi, Tokyo (JP)
Assigned to NIPPON STEEL NISSHIN CO., LTD., Tokyo (JP)
Appl. No. 16/615,955
Filed by NIPPON STEEL NISSHIN CO., LTD., Tokyo (JP)
PCT Filed Sep. 1, 2017, PCT No. PCT/JP2017/031654
§ 371(c)(1), (2) Date Nov. 22, 2019,
PCT Pub. No. WO2018/220873, PCT Pub. Date Dec. 6, 2018.
Claims priority of application No. 2017-109575 (JP), filed on Jun. 1, 2017.
Prior Publication US 2020/0173004 A1, Jun. 4, 2020
Int. Cl. C23C 2/06 (2006.01); C21D 3/06 (2006.01); C21D 8/02 (2006.01); C22C 18/04 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/12 (2006.01); C22C 38/14 (2006.01); C22C 38/32 (2006.01); C23C 2/02 (2006.01); C23C 2/26 (2006.01); C23C 2/28 (2006.01)
CPC C23C 2/06 (2013.01) [C21D 3/06 (2013.01); C21D 8/0205 (2013.01); C22C 18/04 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/12 (2013.01); C22C 38/14 (2013.01); C22C 38/32 (2013.01); C23C 2/02 (2013.01); C23C 2/022 (2022.08); C23C 2/0222 (2022.08); C23C 2/0224 (2022.08); C23C 2/024 (2022.08); C23C 2/26 (2013.01); C23C 2/28 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A surface-coated steel sheet comprising:
a base steel sheet having a steel composition by mass of C: 0.01 to 0.20%, Si: 0.01 to 0.50%, Mn: 0.10 to 2.50%, P: 0.005 to 0.050%, B: 0.0005 to 0.010%, Ti: 0.01 to 0.20%, Nb: 0 to 0.10%, Mo: 0 to 0.50%, Cr: 0 to 0.50%, Al: 0.01 to 0.10%, and the balance of Fe and inevitable impurities; and
a Zn-Al-Mg-based coating layer disposed on a surface of the base steel sheet, the Zn-Al-Mg-based coating layer having a metal element composition ratio by mass of Al: 1.0 to 22.0%, Mg: 1.3 to 10.0%, Si: 0 to 2.0%, Ti: 0 to 0.10%, B: 0 to 0.05%, Fe: 2.0% or less, and the balance of Zn and inevitable impurities, and having cracks of which a total extension per mm2 is 3.0 to 8.0 mm measured by scanning electron microscopic observation,
the surface-coated steel sheet having a diffusible hydrogen concentration in the base steel sheet of 0.20 ppm or less and having a time until occurrence of red rust of 7000 hours or more as measured by a neutral salt spray test (salt concentration: 50g/L, temperature: 35° C., back face and edge face seal of test piece: present) according to JIS Z2371: 2015, wherein the surface-coated steel sheet has a tensile strength in a rolling direction of 590 MPa or higher and 855 MPa or less.