US 12,258,657 B2
Hot-rolled steel sheet having excellent impact resistance, steel pipe, member, and manufacturing methods therefor
Hwan-Goo Seong, Gwangyang-si (KR); Yeol-Rae Cho, Gwangyang-si (KR); and Seong-Beom Bae, Gwangyang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Filed by POSCO, Pohang-si (KR)
Filed on May 24, 2022, as Appl. No. 17/752,306.
Application 17/752,306 is a division of application No. 16/957,948, abandoned, previously published as PCT/KR2018/015900, filed on Dec. 14, 2018.
Claims priority of application No. 10-2017-0180183 (KR), filed on Dec. 26, 2017.
Prior Publication US 2022/0341012 A1, Oct. 27, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C22C 38/02 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C21D 8/10 (2006.01); C21D 9/08 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/50 (2006.01); C22C 38/54 (2006.01)
CPC C22C 38/54 (2013.01) [C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0257 (2013.01); C21D 8/105 (2013.01); C21D 9/08 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/50 (2013.01); C21D 2211/005 (2013.01); C21D 2211/009 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A member, comprising, by weight %:
0.35-0.55% of C,
0.7-1.5% of Mn,
0.3% or less (excluding 0%) of Si,
0.03% or less (including 0%) of P,
0.004% or less (including 0%) of S,
0.04% or less (excluding 0%) of Al,
0.3% or less (excluding 0%) of Cr,
0.3% or less (excluding 0%) of Mo,
0.1-1.0% of Ni,
0.1-1.0% of Cu,
0.006% or less (excluding 0%) of N, and
a balance of Fe and other impurities,
the alloy elements satisfying relational formulae 1-4 as below,
the member having a microstructure consists of, by volume %, one or two of 90% or more of martensite and tempered martensite, and 10% or less of retained austenite, and
the member has a tensile strength of 1876 MPa or higher,
(Mn/Si)≥3 (a weight ratio)  [Relational Formula 1]
(Ni+Cu)/(C+Mn)≥0.2 (a weight ratio)  [Relational Formula 2]
(Ni/Si)≥1 (a weight ratio)  [Relational Formula 3]
Cu+Ni≥0.976% (a weight %).  [Relational Formula 4]