US 11,939,639 B2
Ultra-high-strength hot-rolled steel sheet, 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)
Appl. No. 16/957,675
Filed by POSCO, Pohang-si (KR)
PCT Filed Dec. 13, 2018, PCT No. PCT/KR2018/015861
§ 371(c)(1), (2) Date Jun. 24, 2020,
PCT Pub. No. WO2019/132340, PCT Pub. Date Jul. 4, 2019.
Claims priority of application No. 10-2017-0179278 (KR), filed on Dec. 26, 2017.
Prior Publication US 2020/0362429 A1, Nov. 19, 2020
Int. Cl. C21D 8/02 (2006.01); C21D 9/08 (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 38/10 (2006.01); C22C 38/12 (2006.01); C22C 38/28 (2006.01); C22C 38/32 (2006.01); C23G 1/00 (2006.01)
CPC C21D 8/0226 (2013.01) [C21D 9/085 (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 38/105 (2013.01); C22C 38/12 (2013.01); C22C 38/28 (2013.01); C22C 38/32 (2013.01); C23G 1/00 (2013.01); C21D 2211/001 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01); C21D 2211/009 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A hot-rolled steel sheet for a hot press member comprising, by weight, C: 0.43 to 0.60%, Mn: 0.7 to 1.5%, Si: 0.3% or less (excluding 0%), P: 0.03% or less (including 0%), S: 0.004% or less (including 0%), Al: 0.04% or less (excluding 0%), Cr: 0.3% or less (excluding 0%), Mo: 0.3% or less (excluding 0%), Ni: 0.099 to 1.5%, Cu: 0.096 to 1.5%, Cu+Ni: 1.1% or more, Ti: 0.04% or less (excluding 0%), B: 0.005% or less (excluding 0%), N: 0.006% or less (excluding 0%), and a balance of Fe and impurities,
wherein the alloying element satisfies the following relationships 1 and 2,
the hot-rolled steel sheet includes a microstructure comprising, by volume, 7 to 30% of ferrite and 70 to 93% of pearlite, and
the hot-rolled steel sheet has a tensile strength of 710 MPa or more:
(Mn/Si)≥3 (weight ratio)   [Relationship 1]
15.8≥(Ni/Si)≥1 (weight ratio)   [Relationship 2]