US 12,392,019 B2
Wire rod for cold heading having excellent delayed fracture resistance characteristics, parts, and manufacturing method therefor
Byung-In Jung, Pohang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 17/783,378
Filed by POSCO CO., LTD, Pohang-si (KR)
PCT Filed Dec. 15, 2020, PCT No. PCT/KR2020/018363
§ 371(c)(1), (2) Date Jun. 8, 2022,
PCT Pub. No. WO2021/125749, PCT Pub. Date Jun. 24, 2021.
Claims priority of application No. 10-2019-0169264 (KR), filed on Dec. 17, 2019.
Prior Publication US 2023/0023191 A1, Jan. 26, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. C22C 38/46 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/44 (2006.01)
CPC C22C 38/46 (2013.01) [C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/44 (2013.01)] 3 Claims
 
1. A high-strength heat-treated part with high resistance to hydrogen-delayed fracturing, the high-strength heat-treated part having a chemical composition comprising, by wt %, C: 0.3% to 0.5%, Si: 0.01% to 0.3%, Mn: 0.3% to 1.0%, Cr: 0.5% to 1.5%, Mo: 0.5% to 1.5%, Ni: 0.5% to 2.0%, V: 0.01% to 0.4%, and a balance of Fe and other impurities, the chemical composition satisfying the relational expression 1 below,
the high-strength heat-treated part has a microstructure comprising, by area %, 5% to 20% auto-tempered martensite and a balance of lower bainite,
1.21Cr+3.94Mo+15V≥3.567  [Condition 1]
where Cr, Mo, and V respectively refer to a content thereof in wt %.