US 12,467,108 B2
High-strength steel sheet and manufacturing method thereof
Young-Roc Im, Gwangyang-si (KR); Man-Young Park, Gwangyang-si (KR); Jong-Chan Park, Gwangyang-si (KR); Eul-Yong Choi, Gwangyang-si (KR); Min-Seo Koo, Gwangyang-si (KR); Jong-Kweon Kim, Gwangyang-si (KR); and Jae-Hoon Lee, Gwangyang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 17/625,625
Filed by POSCO, Pohang-si (KR)
PCT Filed Jul. 20, 2020, PCT No. PCT/KR2020/009548
§ 371(c)(1), (2) Date Jan. 7, 2022,
PCT Pub. No. WO2021/020787, PCT Pub. Date Feb. 4, 2021.
Claims priority of application No. 10-2019-0091890 (KR), filed on Jul. 29, 2019; and application No. 10-2019-0170277 (KR), filed on Dec. 18, 2019.
Prior Publication US 2022/0259691 A1, Aug. 18, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C21D 9/46 (2006.01); B32B 15/01 (2006.01); C21D 6/00 (2006.01); C21D 8/00 (2006.01); C21D 8/02 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/54 (2006.01); C22C 38/58 (2006.01)
CPC C21D 9/46 (2013.01) [B32B 15/013 (2013.01); C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/005 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/54 (2013.01); C22C 38/58 (2013.01); C21D 2211/001 (2013.01); C21D 2211/008 (2013.01)] 13 Claims
 
1. A high-strength steel sheet comprising:
by weight percent (wt %), 0.12% to less than 0.17% of carbon (C), 0.3% to 0.8% of silicon (Si), 2.5% to 3.0% of manganese (Mn), 0.4% to 1.1% of chromium (Cr), 0.01% to 0.3% of aluminum (Al), 0.01% to 0.03% of niobium (Nb), 0.01% to 0.03% of titanium (Ti), 0.001% to 0.003% of boron (B), 0.04% or less of phosphorus (P), 0.01% or less of sulfur (S): 0.01% or less of nitrogen (N), and a balance of iron (Fe) and inevitable impurities,
wherein the contents of C, Si, and Al satisfy mathematical equation (1) below,
a microstructure of the high-strength steel sheet includes, by area fraction, more than 50% to 70% or less of tempered martensite and remaining retained austenite, fresh martensite, ferrite and bainite, and
wherein a cementite phase as a second phase is precipitated and distributed in an area fraction of 1% or more and 3% or less between the bainite laths or at the laths or grain boundaries of the tempered martensite phase,

OG Complex Work Unit Math
wherein [C], [Si] and [Al] refer to the wt % of C, Si and Al, respectively.