公开(公告)号：US20250101553A1

公开(公告)日：2025-03-27

申请号：US18728338

申请日：2023-01-27

Applicant: NIPPON STEEL CORPORATION

Inventor： Hideto HIROSHIMA ,  Hiroshi SHUTO ,  Kazumasa TSUTSUI ,  Yukiko KOBAYASHI

IPC: C22C38/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14

Abstract: This hot-rolled steel sheet has a desired chemical composition and microstructure, an average sphere equivalent radius of alloy carbides in the ferrite is 0.5 nm or more and less than 5.0 nm, an average number density of the alloy carbides in the ferrite is 3.5×1016/cm3 or more, an E value that indicates periodicity of the microstructure is 10.7 or more, and an I value that indicates uniformity of the microstructure is 1.020 or more, a standard deviation of a Mn concentration is 0.60 mass % or less, and a tensile strength is 980 MPa or more.

公开(公告)号：US20230287530A1

公开(公告)日：2023-09-14

申请号：US17918903

申请日：2021-04-15

Applicant: NIPPON STEEL CORPORATION

Inventor： Yukiko KOBAYASHI ,  Jun TAKAHASHI ,  Tatsuo YOKOI ,  Riki OKAMOTO ,  Takeshi TOYODA

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14

CPC classification number: C21D8/0226 ,  C21D9/46 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008

Abstract: A high-strength hot-rolled steel sheet: having a predetermined chemical composition; having a mean dislocation density of from 1 × 1014 to 1 × 1016 m-2, and containing at least bainitic ferrite, in which a total area ratio of the bainitic ferrite and ferrite is 70% or more and less than 90%, and in which a total area ratio of martensite and retained austenite is 5% or more and 30% or less, in which, in ferrite crystal grains and in bainitic ferrite crystal grains, a mean number density of TiC precipitates is from 1 × 1017 to 5 × 1018 [precipitates/cm3], in which an amount of Ti present as a TiC precipitate precipitated in a matrix not on dislocations is 30 mass% or more of a total amount of Ti in the steel sheet, and in which a tensile strength is 850 MPa or more.

公开(公告)号：US20250092496A1

公开(公告)日：2025-03-20

申请号：US18729628

申请日：2023-03-03

Applicant: NIPPON STEEL CORPORATION

Inventor： Miyuri UMEHARA ,  Yukiko KOBAYASHI ,  Shunsuke TANIGUCHI ,  Naoki MATSUI ,  Shingo YAMASAKI ,  Yuji SAKIYAMA

IPC: C22C38/22 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/24

Abstract: A steel material according to the present disclosure consists of, by mass %, C: 0.30 to 0.50%, Si: 0.01 to 0.30%, Mn: 0.10 to 1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.01 to 0.80%, Mo: 0.70 to less than 1.50%, V: 0.01 to 0.50%, Al: 0.005 to 0.100%, and N: 0.0010 to 0.0300%, with the balance being Fe and impurities. The area fraction of hard structure is 90% or more and the Vickers hardness is 220 to 400 HV. The number density of cementite particles in the hard structure is 4.0 pieces/μm2 or more. The number ratio of cementite particles having an area of 0.0005 to 0.0100 μm2 among a plurality of the cementite particles in the hard structure is 50.0% or more. The sample standard deviation of the areas of a plurality of the cementite particles in the hard structure is 0.070 μm2 or less.