US 11,680,305 B2
High strength steel sheet having excellent high-temperature elongation characteristic, warm-pressed member, and manufacturing methods for the same
Je-Woong Lee, Gwangyang-si (KR); and Sang-Ho Han, Gwangyang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 16/470,401
Filed by POSCO, Pohang-si (KR)
PCT Filed Dec. 12, 2017, PCT No. PCT/KR2017/014582
§ 371(c)(1), (2) Date Jun. 17, 2019,
PCT Pub. No. WO2018/117523, PCT Pub. Date Jun. 28, 2018.
Claims priority of application No. 10-2016-0174960 (KR), filed on Dec. 20, 2016.
Prior Publication US 2019/0316235 A1, Oct. 17, 2019
Int. Cl. C22C 38/04 (2006.01); C21D 8/02 (2006.01); C22C 38/02 (2006.01); C22C 38/18 (2006.01)
CPC C22C 38/04 (2013.01) [C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C22C 38/02 (2013.01); C22C 38/18 (2013.01); C21D 2211/005 (2013.01); C21D 2211/009 (2013.01); C22C 2204/00 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A member, comprising:
by weight %, carbon (C): 0.4 to 0.9%, chromium (Cr): 0.01 to 1.5%, phosphorus (P): 0.03% or less (excluding 0%), sulfur (S): 0.01% or less (excluding 0%), nitrogen (N): 0.01% or less (excluding 0%), alkali-soluble aluminum (sol.Al): 0.1% or less (excluding 0%), and a balance of iron (Fe) and inevitable impurities, and including at least one among manganese (Mn): 2.1% or less (excluding 0%), and silicon (Si): 1.6% or less (excluding 0%); and
a microstructure comprising: 80% or more of pearlite and 20% or less of ferrite by area fraction, and
wherein the cementite of the pearlite has an N value of 70% or more in the following Relational Expression 2,
N(%)=Nx/(Nx+Ny)*100,  Relational Expression 2:
where Nx is a number of cementite whose major axis length is 200 nm or less, and Ny is a number of cementite whose major axis length exceeds 200 nm.