	US 12,134,801 B2
	High strength hot rolled steel sheet having excellent elongation and method for manufacturing the same
Jin-Ho Bae, Gwangyang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 17/295,929
Filed by POSCO, Pohang-si (KR)
PCT Filed Nov. 26, 2019, PCT No. PCT/KR2019/016309 § 371(c)(1), (2) Date May 21, 2021, PCT Pub. No. WO2020/111705, PCT Pub. Date Jun. 4, 2020.
Claims priority of application No. 10-2018-0146879 (KR), filed on Nov. 26, 2018.
Prior Publication US 2022/0025476 A1, Jan. 27, 2022
Int. Cl. C21D 9/46 (2006.01); C21D 8/02 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/58 (2006.01)

CPC C21D 9/46 (2013.01) [C21D 8/0226 (2013.01); C21D 8/0263 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/58 (2013.01); C21D 2211/001 (2013.01); C21D 2211/002 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01); C21D 2211/009 (2013.01)]

6 Claims

1. A hot rolled steel sheet-having excellent elongation, comprising:

by wt %, 0.11 to 0.14% of C, 0.20 to 0.50% of Si, 1.8 to 2.0% of Mn, 0.03% or less of P, 0.02% or less of S, 0.01 to 0.04% of Nb, 0.5 to 0.8% of Cr, 0.01 to 0.03% of Ti, 0.2 to 0.4% of Cu, 0.1 to 0.4% of Ni, 0.2 to 0.4% of Mo, 0.007% or less of N, 0.001 to 0.006% of Ca, 0.01 to 0.05% of Al, a balance of Fe, and inevitable impurities,

wherein relational expressions 1 to 3 below are satisfied, and

a microstructure comprises, by area %, 88% or more of bainite, excluding 100%, 10% or less of ferrite, excluding 0%, 2% or less of pearlite, excluding 0%, and 0.8% or less of martensite-austenite constituent, inclusive of 0%,

7≤(Mo/93)/(P/31)≤16 [Relational Expression 1]

1.6≤Cr+3Mo+2Ni≤2 [Relational Expression 2]

6≤(3C/12+Mn/55)×100≤7 [Relational Expression 3]

where, in relational expressions 1 to 3, the contents of alloying elements are based on wt %.