US 12,448,697 B2
Surface-treated steel sheet and production method therefor
Yuji Nakano, Kudamatsu (JP); Koh Yoshioka, Kudamatsu (JP); and Kazuhiko Ishihara, Kudamatsu (JP)
Assigned to TOYO KOHAN CO., LTD., Tokyo (JP)
Appl. No. 17/606,603
Filed by TOYO KOHAN CO., LTD., Tokyo (JP)
PCT Filed Apr. 27, 2020, PCT No. PCT/JP2020/017988
§ 371(c)(1), (2) Date Oct. 26, 2021,
PCT Pub. No. WO2020/222305, PCT Pub. Date Nov. 5, 2020.
Claims priority of application No. 2019-086917 (JP), filed on Apr. 27, 2019.
Prior Publication US 2022/0235482 A1, Jul. 28, 2022
Int. Cl. C25D 5/12 (2006.01); C25D 5/50 (2006.01); C25D 7/06 (2006.01); H01M 50/116 (2021.01); H01M 50/107 (2021.01)
CPC C25D 5/12 (2013.01) [C25D 5/50 (2013.01); C25D 7/0614 (2013.01); H01M 50/116 (2021.01); H01M 50/107 (2021.01)] 16 Claims
OG exemplary drawing
 
1. A surface-treated steel sheet, comprising:
a steel sheet; and
a nickel-cobalt-iron diffusion layer formed on the steel sheet as an outermost layer, wherein when intensities for Ni, Co, and Fe are consecutively measured from a surface of the nickel-cobalt-iron diffusion layer in a depth direction by radio frequency glow discharge optical emission spectrometry, and a concentration of Ni, a concentration of Co, and a concentration of Fe at each depth position of the nickel-cobalt-iron diffusion layer are determined based on the intensities for Ni, Co, and Fe,
a Co concentration gradient ΔPCo ranging from a depth position DCo_MAX to a depth position DCo_15% is 7.8% by mass/0.1 μm or more and 33% by mass/0.1 μm or less, where a depth position at which the concentration of Co is maximum is defined as DCo_MAX and a depth position which is located closer to the steel sheet than the depth position DCo_MAX and at which the concentration of Co is 15% of a maximum value is defined as DCo_15%,
a Ni content in the nickel-cobalt-iron diffusion layer is 8.5 g/m2 or less, a total content of Ni and Co contained in the nickel-cobalt-iron diffusion layer is 10.0 g/m2 or less, and
an Fe concentration PFe(DNi_0.5%) at a depth position DNi_0.5% is 20% by mass or more, where among depth positions at which an intensity for Ni in the nickel-cobalt-iron diffusion layer is 0.5% of a maximum value, a depth position located closest to the surface is defined as DNi_0.5%.