US 12,264,387 B2
Steel plate having excellent heat affected zone toughness and method for manufacturing thereof
Tae-Il So, Gwangyang-si (KR); and Sang-Deok Kang, Gwangyang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 17/298,881
Filed by POSCO, Pohang-si (KR)
PCT Filed Nov. 29, 2019, PCT No. PCT/KR2019/016740
§ 371(c)(1), (2) Date Jun. 1, 2021,
PCT Pub. No. WO2020/111874, PCT Pub. Date Jun. 4, 2020.
Claims priority of application No. 10-2018-0150705 (KR), filed on Nov. 29, 2018.
Prior Publication US 2022/0127704 A1, Apr. 28, 2022
Int. Cl. C21D 8/02 (2006.01); B23K 9/16 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/08 (2006.01); C22C 38/12 (2006.01); C22C 38/14 (2006.01)
CPC C22C 38/14 (2013.01) [B23K 9/16 (2013.01); C21D 8/0247 (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 38/08 (2013.01); C22C 38/12 (2013.01); C21D 2211/001 (2013.01); C21D 2211/002 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A steel material, comprising, by weight:
0.02 to 0.08% of carbon (C),
0.15 to 0.5% of silicon (Si),
1.2 to 1.8% of manganese (Mn),
0.008% or less, excluding 0%, of phosphorus (P),
0.003% or less, excluding 0%, of sulfur(S),
0.005 to 0.1% of aluminum (Al),
0.01 to 0.5% of nickel (Ni),
0.01 to 0.1% of molybdenum (Mo),
0.005 to 0.05% of niobium (Nb),
0.005 to 0.02% of titanium (Ti),
20 to 100 ppm of nitrogen (N), and
a balance of Fe and other unavoidable impurities,
wherein the steel material satisfies the following Relation Formula 1,
wherein a microstructure of a base metal includes 20 to 60% of an acicular ferrite phase and 40 to 80% of a bainite phase by area fraction,
wherein a microstructure of a fusion line in a heat affected zone after welding includes a ferrite phase in 5 to 20% by area and a bainite phase as a remainder, and
wherein the steel material has a thickness of 10 to 40 mm:
0.42>C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15  [Relation Formula 1]
wherein each element means a weight content.