US 12,338,533 B2
High-strength hot-dip galvanized steel sheet with excellent formability and process for producing same
Yu-Mi Ha, Gwangyang-si (KR); and Jun-Sung Yeom, Gwangyang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 18/035,924
Filed by POSCO CO., LTD, Pohang-si (KR)
PCT Filed Oct. 27, 2021, PCT No. PCT/KR2021/015231
§ 371(c)(1), (2) Date May 8, 2023,
PCT Pub. No. WO2022/103024, PCT Pub. Date May 19, 2022.
Claims priority of application No. 10-2020-0150899 (KR), filed on Nov. 12, 2020.
Prior Publication US 2024/0011141 A1, Jan. 11, 2024
This patent is subject to a terminal disclaimer.
Int. Cl. C23C 2/40 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (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 38/16 (2006.01); C23C 2/06 (2006.01)
CPC C23C 2/40 (2013.01) [C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0273 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/004 (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 38/16 (2013.01); C23C 2/06 (2013.01); C21D 2211/005 (2013.01); Y10T 428/12799 (2015.01)] 2 Claims
OG exemplary drawing
 
1. A high-strength hot-dip galvanized steel sheet having excellent formability, the steel sheet comprising in mass %:
0.005 to 0.009% of C; 0.05% or less of Si; 0.3 to 0.8% of Mn; 0.06 to 0.09% of P; 0.01% or less of S; 0.005% or less of N; 0.1% or less of S·Al; 0.05 to 0.08% of Mo; 0.01 to 0.03% of Ti; 0.03 to 0.045% of Nb; 0.06 to 0.1% of Cu; 0.0015% or less of B; and a balance of Fe and inevitable impurities, wherein C, Ti, and Nb satisfy Relation 1,
the steel sheet has a microstructure including 95% or more of ferrite in terms of area fraction,
the ferrite has an average grain size of 15 μm or less, with ultrafine grains of 6 μm or less occupying 5 to 10% in a 1 mm×1 mm area, and
the steel sheet has a surface nanohardness value of 1 to 1.5 GPa,
0.05≤[(Nb(48/93))+(Ti(93/48))+(C(12/48))]≤0.065.  [Relation 1]