公开(公告)号：US20230041990A1

公开(公告)日：2023-02-09

申请号：US17787857

申请日：2021-02-05

Applicant: NIPPON STEEL CORPORATION

Inventor： Jun ANDO ,  Teruki HAYASHIDA ,  Tatsuo YOKOI ,  Akifumi SAKAKIBARA

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08

Abstract: A hot-rolled steel sheet has, as a chemical composition, by mass %: C: 0.01% to 0.30%; Si: 0.01% to 3.00%; Mn: 0.20% to 3.00%; P: 0.030% or less; S: 0.030% or less; Al: 0.001% to 2.000%; N: 0.0100% or less; and Ni: 0.02% to 0.50%, in which among measurement points at which elemental analysis is performed at a measurement pitch of 1 μm using an EPMA in a region of 250 μm×250 μm on a surface, the percentage of measurement points having a Ni content of 0.5 mass % or more is 10% to 70%.

公开(公告)号：US20250109467A1

公开(公告)日：2025-04-03

申请号：US18711674

申请日：2022-12-22

Applicant: NIPPON STEEL CORPORATION

Inventor： Daisuke ITO ,  Akifumi SAKAKIBARA ,  Teruki HAYASHIDA ,  Tatsuo YOKOI ,  Kazuhisa KUSUMI

IPC: C22C38/58 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/28 ,  C22C38/38 ,  C22C38/42 ,  C22C38/50 ,  C22C38/54

Abstract: A hot-rolled steel sheet has a predetermined chemical composition, a microstructure at a location of ¼ of a sheet thickness and at a location of 100 μm from a surface comprising, in area %, one or more of martensite and tempered martensite: 95% or more in total, and ferrite, bainite and pearlite: 5% or less in total, and an average dislocation density at the location of 100 μm from the surface is 1.2 times or more of an average dislocation density at the location of ¼ of the sheet thickness.

公开(公告)号：US20230357908A1

公开(公告)日：2023-11-09

申请号：US18027800

申请日：2022-01-07

Applicant: NIPPON STEEL CORPORATION

Inventor： Daisuke ITO ,  Akifumi SAKAKIBARA ,  Teruki HAYASHIDA ,  Tatsuo YOKOI

IPC: C22C38/58 ,  C22C38/42 ,  C22C38/54 ,  C22C38/50 ,  C22C38/32 ,  C22C38/28 ,  C22C38/14 ,  C22C38/12 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D9/46 ,  C21D6/00 ,  C21D1/18

CPC classification number: C22C38/58 ,  C22C38/42 ,  C22C38/54 ,  C22C38/50 ,  C22C38/32 ,  C22C38/28 ,  C22C38/14 ,  C22C38/12 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/002 ,  C22C38/001 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0263 ,  C21D9/46 ,  C21D6/002 ,  C21D6/004 ,  C21D6/005 ,  C21D6/008 ,  C21D1/18 ,  C21D2211/008

Abstract: In a hot-rolled steel sheet, a microstructure contains, in area ratio, at a location at ¼ a sheet thickness, a total amount of 90% or more of one or more of martensite and tempered martensite and a total amount of 10% or less of one or more of ferrite, bainite, and pearlite, at a location of 200 μm from the surface, a total amount of 70% or more and less than 90% of one or more of martensite and tempered martensite and a total amount of more than 10% and 30% or less of one or more of ferrite, bainite, and pearlite.

公开(公告)号：US20220010396A1

公开(公告)日：2022-01-13

申请号：US17283476

申请日：2019-10-21

Applicant: NIPPON STEEL CORPORATION

Inventor： Tatsuo YOKOI ,  Teruki HAYASHIDA ,  Mutsumi SAKAKIBARA ,  Jun ANDO ,  Shinsuke KAI ,  Hiroshi SHUTO

IPC: C21D9/46 ,  B21B1/02 ,  C22C38/58 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23G1/08

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, and in a case where the thickness is denoted by t, the metallographic structure at a t/4 position from the surface contains one or both of tempered martensite and lower bainite at a volume percentage of 90% or more, the tensile strength is 980 MPa or more, and the average Ni concentration on the surface is 7.0% or more.

公开(公告)号：US20210395852A1

公开(公告)日：2021-12-23

申请号：US17285013

申请日：2019-10-21

Applicant: NIPPON STEEL CORPORATION

Inventor： Tatsuo YOKOI ,  Hiroshi SHUTO ,  Teruki HAYASHIDA ,  Jun ANDO ,  Mutsumi SAKAKIBARA

IPC: C21D9/46 ,  C22C38/58 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C23G1/08 ,  C21D8/02 ,  C21D6/00

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in which in a case where the thickness is denoted by t, a metallographic structure at a t/4 position from the surface includes, by area fraction, 77.0% to 97.0% of bainite or tempered martensite, 0% to 5.0% of ferrite, 0% to 5.0% of pearlite, 3.0% or more of residual austenite, and 0% to 10.0% of martensite, in the metallographic structure, the average grain size excluding the residual austenite is 7.0 μm or less, the average number density of iron-based carbides having a diameter of 20 nm or more is 1.0×106 carbides/mm2 or more, a tensile strength is 980 MPa or more, and an average Ni concentration on the surface is 7.0% or more.