公开(公告)号：US20210180163A1

公开(公告)日：2021-06-17

申请号：US17269312

申请日：2019-06-10

Applicant: JFE Steel Corporation

Inventor： Shimpei Yoshioka ,  Yoshihiko Ono

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

Abstract: A high-strength steel sheet according to the present invention includes a specific chemical composition, and a steel structure in which a total area fraction of martensite and bainite in a position of ¼ of a sheet thickness is 95% or more and 100% or less, the balance in a case where the total area fraction is not 100% contains retained austenite, and an area fraction of ferrite in a region extending up to 10 μm in a sheet thickness direction from a surface is 10% or more and 40% or less, in which a tensile strength is 1320 MPa or more, and a Vickers hardness in a position of 15 μm in the sheet thickness direction from the surface satisfies a specified formula.

公开(公告)号：US11008635B2

公开(公告)日：2021-05-18

申请号：US16077266

申请日：2017-02-15

Applicant: JFE Steel Corporation

Inventor： Shimpei Yoshioka ,  Yoshihiko Ono ,  Yusuke Kimata ,  Hiroyuki Masuoka

IPC: C22C38/16 ,  C22C38/60 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/10 ,  C22C38/12 ,  C22C38/14 ,  C22C38/20 ,  C22C38/34 ,  C22C38/32 ,  C22C38/38 ,  C21D9/46 ,  C21D6/00 ,  C21D8/02

Abstract: Provided is a high-strength cold-rolled steel sheet has a chemical composition containing, by mass %, C: 0.10% or more and 0.6% or less, Si: 1.0% or more and 3.0% or less, Mn: more than 2.5% and 10.0% or less, P: 0.05% or less, S: 0.02% or less, Al: 0.01% or more and 1.5% or less, N: 0.005% or less, Cu: 0.05% or more and 0.50% or less, and the balance being Fe and inevitable impurities, and a tensile strength of 1180 MPa or more, in which a steel sheet surface coverage of oxides mainly containing Si is 1% or less, a steel sheet surface coverage of iron-based oxides is 40% or less, CuS/CuB is 4.0 or less, and a tensile strength is 1180 MPa or more, where CuS denotes a Cu concentration in a surface layer of a steel sheet and CuB denotes a Cu concentration in base steel.

公开(公告)号：US10982297B2

公开(公告)日：2021-04-20

申请号：US16329672

申请日：2017-09-28

Applicant: JFE STEEL CORPORATION

Inventor： Yoshihiko Ono ,  Shimpei Yoshioka ,  Nobuyuki Nakamura ,  Hiroshi Hasegawa

IPC: C23C2/06 ,  C23C2/40 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/42 ,  C22C38/46 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C22C38/44 ,  B32B15/01 ,  C21D8/02 ,  C21D9/46 ,  C21D6/00 ,  C22C38/08 ,  C22C38/16 ,  C21D8/04 ,  C22C38/60 ,  C22C38/14 ,  C22C38/12 ,  C22C38/04 ,  C21D9/52 ,  C22C38/40 ,  C22C38/18 ,  B32B15/04 ,  C22C38/28 ,  C22C38/32 ,  C22C38/22 ,  C23C30/00 ,  C23C28/00 ,  B32B15/18 ,  C22C38/20 ,  C22C38/24 ,  C22C38/26 ,  C23C28/02

Abstract: A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure including martensite and bainite. The total area fraction of the martensite and the bainite to the entirety of the microstructure is more than 90% and 100% or less. The microstructure includes inclusion clusters A and B, the content of the clusters A in the microstructure being 2 clusters/mm2 or less, and the content of the clusters B in the microstructure being 5 clusters/mm2 or less. The microstructure includes carbide particles including Fe as a main constituent which have an aspect ratio of 2.0 or less and a major axis of 0.30 μm or more and 2 μm or less. The content of the carbide particles in the microstructure is 4000 particles/mm2 or less. The microstructure includes prior γ grains having an average size of 6 to 15 μm.