Invention Grant
- Patent Title: Ultra-high-strength hot-rolled steel sheet, steel pipe, member, and manufacturing methods therefor
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Application No.: US16957675Application Date: 2018-12-13
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Publication No.: US11939639B2Publication Date: 2024-03-26
- Inventor: Hwan-Goo Seong , Yeol-Rae Cho , Seong-Beom Bae
- Applicant: POSCO
- Applicant Address: KR Pohang-si
- Assignee: POSCO CO., LTD
- Current Assignee: POSCO CO., LTD
- Current Assignee Address: KR Pohang-si
- Agency: Morgan, Lewis & Bockius LLP
- Priority: KR 20170179278 2017.12.26
- International Application: PCT/KR2018/015861 2018.12.13
- International Announcement: WO2019/132340A 2019.07.04
- Date entered country: 2020-06-24
- Main IPC: C21D8/02
- IPC: C21D8/02 ; C21D9/08 ; C21D9/46 ; C22C38/00 ; C22C38/02 ; C22C38/04 ; C22C38/06 ; C22C38/10 ; C22C38/12 ; C22C38/28 ; C22C38/32 ; C23G1/00

Abstract:
A preferable aspect of the present invention provides: an ultra-high-strength hot-rolled steel sheet containing, by weight, one or two of 0.40-0.60% 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, 0.9-1.5% of Ni, and 0.9-1.5% of Cu, 1.1% or more of Cu+Ni, 0.04% or less (excluding 0%) of Ti, 0.005% or less (excluding 0%) of B, 0.006% or less (excluding 0%) of N, and the balance Fe and other impurities, the alloy elements satisfying relational formulas 1 and 2 below, wherein a microstructure of the hot-rolled steel sheet comprises, by volume, 7% or more of ferrite and 93% or less of perlite; a steel pipe and a member each using the same; and manufacturing methods therefor. [Relational formula 1] (Mn/Si) #3 (weight ratio) [Relational formula 2] (Ni/Si) #1 (weight ratio)
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