	US 12,344,913 B2
	Hot-rolled steel sheet and manufacturing method thereof
Eisaku Sakurada, Tokyo (JP); Takashi Yasutomi, Tokyo (JP); and Genki Abukawa, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/794,672
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Apr. 21, 2021, PCT No. PCT/JP2021/016148 § 371(c)(1), (2) Date Jul. 22, 2022, PCT Pub. No. WO2021/225074, PCT Pub. Date Nov. 11, 2021.
Claims priority of application No. 2020-082656 (JP), filed on May 8, 2020.
Prior Publication US 2023/0097055 A1, Mar. 30, 2023
Int. Cl. C21D 9/46 (2006.01); C21D 8/02 (2006.01); C22C 38/06 (2006.01); C22C 38/22 (2006.01); C22C 38/24 (2006.01); C22C 38/26 (2006.01); C22C 38/28 (2006.01); C22C 38/32 (2006.01); C22C 38/34 (2006.01); C22C 38/38 (2006.01)

CPC C21D 9/46 (2013.01) [C21D 8/0226 (2013.01); C22C 38/06 (2013.01); C22C 38/22 (2013.01); C22C 38/24 (2013.01); C22C 38/26 (2013.01); C22C 38/28 (2013.01); C22C 38/32 (2013.01); C22C 38/34 (2013.01); C22C 38/38 (2013.01); C21D 2211/001 (2013.01); C21D 2211/002 (2013.01); C21D 2211/003 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)]

6 Claims

1. A hot-rolled steel sheet comprising, as a chemical composition, by mass %:

C: 0.060% to 0.170%;

Si: 0.030% to 1.700%;

Mn: 1.20% to 3.00%;

Al: 0.010% to 0.700%;

Nb: 0.005% to 0.050%;

P: 0.0800% or less;

S: 0.0100% or less;

N: 0.0050% or less;

Ti: 0% to 0.1800%;

Mo: 0% to 0.150%;

V: 0% to 0.3000%;

Cr: 0% to 0.500%;

B: 0% to 0.0030%; and

a remainder consisting of Fe and an impurity,

wherein, in metallographic structures at a ¼ position in a sheet thickness direction from a surface and at a ½ position in the sheet thickness direction from the surface, by vol %,

bainite and martensite are a total of 80.0% or more,

ferrite is 20.0% or less, and

cementite and residual austenite are a total of 0% to 10.0%,

in a metallographic structure of a region from the surface to a 100 μm position in the sheet thickness direction from the surface,

an average grain diameter of prior austenite grains is less than 30.00 μm,

a region, where a rotation angle between a normal line of the surface and a (011) pole near the normal line is 5° or less, is 0.150 or less from the surface in terms of a sheet thickness direction position standardized by a sheet thickness,

a region, where the rotation angle between the normal line of the surface and the (011) pole near the normal line becomes 20° or more, is 0.250 or more from the surface in terms of the sheet thickness direction position standardized by the sheet thickness, and

a tensile strength is 880 MPa or more.