US 12,473,652 B2
Galvannealed steel sheet, electrodeposition-coated steel sheet, automotive part, method of producing electrodeposition-coated steel sheet, and method of producing galvannealed steel sheet
Shunsuke Yamamoto, Tokyo (JP); Katsutoshi Takashima, Tokyo (JP); Yusuke Okumura, Tokyo (JP); Tomomi Kanazawa, Tokyo (JP); Katsuya Hoshino, Tokyo (JP); Takashi Kawano, Tokyo (JP); Takako Yamashita, Tokyo (JP); Hiroshi Matsuda, Tokyo (JP); and Yoichi Makimizu, Tokyo (JP)
Assigned to JFE STEEL CORPORATION, Tokyo (JP)
Appl. No. 18/251,242
Filed by JFE STEEL CORPORATION, Tokyo (JP)
PCT Filed Nov. 5, 2021, PCT No. PCT/JP2021/040875
§ 371(c)(1), (2) Date May 1, 2023,
PCT Pub. No. WO2022/097737, PCT Pub. Date May 12, 2022.
Claims priority of application No. 2020-186209 (JP), filed on Nov. 6, 2020.
Prior Publication US 2023/0407484 A1, Dec. 21, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. C22C 38/02 (2006.01); B32B 15/01 (2006.01); C21D 8/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C23C 2/02 (2006.01); C23C 2/06 (2006.01); C23C 2/28 (2006.01); C23C 28/02 (2006.01); C25D 3/20 (2006.01)
CPC C23C 28/021 (2013.01) [C21D 8/0236 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (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 2/026 (2022.08); C23C 2/06 (2013.01); C23C 2/28 (2013.01); C25D 3/20 (2013.01)] 16 Claims
OG exemplary drawing
 
1. A galvannealed steel sheet comprising:
a Si-containing cold-rolled steel sheet containing Si in an amount of 0.1 mass % or more and 3.0 mass % or less;
an Fe-based electroplating layer formed on at least one surface of the Si-containing cold-rolled steel sheet;
a galvannealed layer formed on the Fe-based electroplating layer, and
a decarburized layer extending from the interface between the galvannealed layer and the Fe-based electroplating layer towards the Fe-based electroplating layer, wherein
in an intensity profile measured by glow discharge optical emission spectrometry, a value of ISi,Fe/ISi,bulk is 0.30 or more, where ISi,Fe denotes an average Si intensity in a region ranging from a position shifted from an interface between the galvannealed layer and the Fe-based electroplating layer towards the galvannealed layer, by a distance corresponding to a thickness obtained by converting an Fe content (mass %) in the galvannealed layer into a thickness (μm) as a plating layer, to an interface between the Fe-based electroplating layer and the Si-containing cold-rolled steel sheet, and ISi,bulk denotes an average Si intensity in the Si-containing cold-rolled steel sheet,
an average value of C concentration in a region ranging from 10 μm to 20 μm in the thickness direction from the interface between the galvannealed layer and the Fe-based electroplating layer towards the Fe-based electroplating layer is 0.10 mass % or less,
the number of crystal grain boundaries in the Fe-based electroplating layer that are in contact with the Si-containing cold-rolled steel sheet at the interface between the Fe-based electroplating layer and the Si-containing cold-rolled steel sheet is 10 or more per 10 μm in a sheet transverse direction in an observation field of view of the Si-containing cold-rolled steel sheet, and
a coating weight (g/m2) per surface of the Fe-based electroplating layer, denoted by C.W.Fe1, and a thickness (μm) of the decarburized layer, denoted by Ca, satisfy the following formula (1):
0.8×(C.W.Fe1)+(Cd)≥70(1).