US 12,221,701 B2
Welded member of galvanized steel sheets
Ki-Cheol Kang, Gwangyang-si (KR); Sang-Ho Uhm, Incheon (KR); Chang-Woon Jee, Gwangyang-si (KR); Yeon-Chae Jeong, Gwangyang-si (KR); and Kwang-Tai Min, Gwangyang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Filed by POSCO CO., LTD, Pohang-si (KR)
Filed on Mar. 29, 2024, as Appl. No. 18/622,583.
Application 18/622,583 is a division of application No. 17/414,231, abandoned, previously published as PCT/KR2019/018005, filed on Dec. 18, 2019.
Claims priority of application No. 10-2018-0164821 (KR), filed on Dec. 19, 2018.
Prior Publication US 2024/0240299 A1, Jul. 18, 2024
Int. Cl. C23C 2/06 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/22 (2006.01); C22C 38/24 (2006.01); C22C 38/26 (2006.01); C22C 38/32 (2006.01); C22C 38/38 (2006.01); C23C 2/02 (2006.01); C23C 2/28 (2006.01); C23C 2/40 (2006.01)
CPC C23C 2/06 (2013.01) [C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/008 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/22 (2013.01); C22C 38/24 (2013.01); C22C 38/26 (2013.01); C22C 38/32 (2013.01); C22C 38/38 (2013.01); C23C 2/02 (2013.01); C23C 2/0222 (2022.08); C23C 2/0224 (2022.08); C23C 2/024 (2022.08); C23C 2/28 (2013.01); C23C 2/40 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A welded member including:
a first steel sheet including a first base steel sheet and a first zinc-based plating layer formed on a surface of the first base steel sheet; and
a second steel sheet spot-welded on the first steel sheet and facing the first zinc-based plating layer of the first steel sheet, a first spot-welded zone being formed between the first steel sheet and the second steel sheet,
wherein a surface layer of the first base steel sheet has a decarburization ratio of 30% or more, the decarburization ratio being represented by equation 1 as below,
Decarburization ratio (%) of surface layer=(1−average carbon concentration in surface layer/bulk carbon concentration)*100 where the surface layer refers to a region of the first base steel sheet from the surface thereof to a depth of 35 μm,  [Equation 1]
wherein a shoulder portion of the first spot-welded zone includes a B-type crack having a length of 100 μm or less, and no C-type crack.