	US 12,264,374 B2
	Hot-rolled steel sheet and method for manufacturing same
Daisuke Ito, Tokyo (JP); and Takeshi Toyoda, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/420,583
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Jan. 20, 2020, PCT No. PCT/JP2020/001756 § 371(c)(1), (2) Date Jul. 2, 2021, PCT Pub. No. WO2020/170681, PCT Pub. Date Aug. 27, 2020.
Claims priority of application No. 2019-026739 (JP), filed on Feb. 18, 2019.
Prior Publication US 2022/0106655 A1, Apr. 7, 2022
Int. Cl. C21D 8/02 (2006.01); B21C 47/02 (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 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/54 (2006.01)

CPC C21D 8/0226 (2013.01) [B21C 47/02 (2013.01); C21D 8/0263 (2013.01); C21D 9/46 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/54 (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)]

8 Claims

1. A hot-rolled steel sheet comprising chemical components containing by mass %:

C: 0.12% or more and 0.25% or less,

Si: 0.01% or more and 2.0% or less,

Mn: 0.5% or more and 3.0% or less,

P: 0.020% or less,

S: 0.010% or less,

Al: 0.001% or more and 0.10% or less,

B: 0.0005% or more and 0.0050% or less,

Cu: 0% or more and 0.50% or less,

Ni: 0% or more and 0.50% or less,

Cr: 0% or more and 0.50% or less,

Mo: 0% or more and 0.50% or less,

V: 0% or more and 0.05% or less,

Ca: 0% or more and 0.05% or less, and

REM: 0% or more and 0.01% or less, and containing one or both of:

Nb: 0.001% or more and 0.020% or less, and

Ti: 0.001% or more and 0.20% or less, and

the balance of Fe and impurities,

wherein

a metal structure at a position of ¼ sheet thickness from a surface of the sheet contains more than 90%, in area ratio, of tempered martensite,

carbides in the tempered martensite have an average grain size of 10 nm or less,

prior austenite grains have an average grain size of 14 μm to less than 40 μm,

the prior austenite grains have an aspect ratio of 3.5 or less, and

an X-ray random intensity ratio of {112}<110> orientation at a position of ½ sheet thickness from a surface is 4.0 or less.