公开(公告)号：US20220119928A1

公开(公告)日：2022-04-21

申请号：US17428239

申请日：2020-04-24

Applicant: NIPPON STEEL CORPORATION

Inventor： Yuya SUZUKI ,  Kengo TAKEDA

IPC: C22C38/58 ,  B32B15/01 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00

Abstract: The present invention relates to steel sheet realizing both formability and weldability. The steel sheet of the present invention is characterized in that at a surface layer part of a region down to 30 μm from the surface of the steel sheet in the sheet thickness direction, Si oxide grains are present in 3000 to 6000/mm2 in number density, an average of natural logarithms of the particle sizes of the Si oxide grains measured in m units is −2.0 to −1.2, the standard error of the natural logarithms of the particle sizes is 0.6 or less, and the number of Si oxide grains with deviations of the natural logarithms of the particle sizes from the average larger than 2 times the standard error is 5% or less of the total number of Si oxide grains and at a position of ½ of the thickness of the steel sheet, the number density of the Si oxide grains is 1000/mm2 or less.

公开(公告)号：US20250075283A1

公开(公告)日：2025-03-06

申请号：US18580470

申请日：2022-03-31

Applicant: NIPPON STEEL CORPORATION

Inventor： Kengo TAKEDA ,  Katsuya NAKANO

IPC: C21D9/46 ,  C21D6/00 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/10 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/30 ,  C22C38/32 ,  C22C38/38 ,  C22C38/42 ,  C22C38/44 ,  C22C38/48 ,  C22C38/50 ,  C22C38/52 ,  C22C38/54 ,  C22C38/58 ,  C22C38/60

Abstract: A steel sheet excellent in shapeability and bending strength is disclosed. The steel sheet of the present disclosure has a predetermined chemical composition, has a predetermined microstructure, has a difference of within 10.0% between a number density of precipitates in the tempered martensite at a first surface at a front side of the steel sheet and a number density of precipitates in the tempered martensite at a second surface at a back side of the steel sheet, and has a yield strength of 600 MPa or more.

公开(公告)号：US20250011905A1

公开(公告)日：2025-01-09

申请号：US18700212

申请日：2022-10-21

Applicant: NIPPON STEEL CORPORATION

Inventor： Koyo OHGA ,  Kengo TAKEDA ,  Katsuya NAKANO

IPC: C22C38/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C23C2/06

Abstract: What is claimed is a steel sheet having a predetermined chemical composition, in which a microstructure includes, by area ratio, ferrite: 5.0% or less, martensite and tempered martensite: more than 90.0% in total, and a remainder: one or two or more of bainite, pearlite, and residual austenite, when an interface where an orientation difference between adjacent martensite and tempered martensite is 15 degrees or more is defined as a prior austenite grain boundary, grain boundary binding energy EGB determined by a concentration of each alloying element on the prior austenite grain boundary is 0.50 or more, and a tensile strength is 1,500 MPa or more.

公开(公告)号：US20240327962A1

公开(公告)日：2024-10-03

申请号：US18711903

申请日：2022-11-29

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Chisato YOSHINAGA ,  Takuya KUWAYAMA ,  Kengo TAKEDA ,  Takuya MITSUNOBU ,  Seiji FURUSAKO ,  Tatsuya OBUCHI

IPC: C22C38/04 ,  C21D6/00 ,  C21D8/02 ,  C22C38/02 ,  C22C38/06 ,  C23C2/06 ,  C23C2/20 ,  C23C2/28 ,  C23C2/40

CPC classification number: C22C38/04 ,  C21D6/005 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C22C38/02 ,  C22C38/06 ,  C23C2/06 ,  C23C2/20 ,  C23C2/28 ,  C23C2/40 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/003 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/009

Abstract: Provided are a hot dip galvanized steel sheet having a predetermined chemical composition, and a steel microstructure comprising, by vol %, ferrite: 0 to 50%, tempered martensite: 1% or more, retained austenite: 5% or more, fresh martensite: 0 to 15%, total of pearlite and cementite: 0 to 5%, and balance: bainite, when measuring by GDS, a maximum value of Al concentration of an Al rich layer present at an interface of the base steel sheet and the hot dip galvanized layer is 2.0 mass % or more and an Sis/Sib right under the interface is 0.90 or less, a number density of recessed parts with a depth of more than 2 μm at the interface is 2.0/100 μm or less per interface length, and a tensile strength is 980 MPa or more, and a method for producing the same.

公开(公告)号：US20230349022A1

公开(公告)日：2023-11-02

申请号：US18025862

申请日：2021-09-28

Applicant: NIPPON STEEL CORPORATION

Inventor： Yuya SUZUKI ,  Kengo TAKEDA

IPC: C21D9/46 ,  C22C38/60 ,  C22C38/58 ,  C22C38/48 ,  C22C38/42 ,  C22C38/38 ,  C22C38/34 ,  C22C38/30 ,  C22C38/28 ,  C22C38/26 ,  C22C38/22 ,  C22C38/20 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  B22D11/00 ,  C21D8/02 ,  C21D6/00 ,  B32B15/01

CPC classification number: C21D9/46 ,  C22C38/60 ,  C22C38/58 ,  C22C38/48 ,  C22C38/42 ,  C22C38/38 ,  C22C38/34 ,  C22C38/30 ,  C22C38/28 ,  C22C38/26 ,  C22C38/22 ,  C22C38/20 ,  C22C38/14 ,  C22C38/12 ,  C22C38/105 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/008 ,  C22C38/005 ,  C22C38/002 ,  C22C38/001 ,  B22D11/001 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0278 ,  C21D6/001 ,  C21D6/002 ,  C21D6/004 ,  C21D6/005 ,  C21D6/007 ,  C21D6/008 ,  B32B15/013 ,  C21D2211/005 ,  C21D2211/009 ,  C23C2/40

Abstract: A steel sheet according to an aspect of the present invention has a predetermined chemical composition, in which a metallographic structure at a ¼ thickness portion includes, by volume percentage, a total of 50% or more of one or both of martensite and bainite and 8% or more of residual austenite, an average value of aspect ratios of prior austenite grains is 5.0 or more, number density of AlN is 3000 pieces/mm2 or more and less than 6000 pieces/mm2 at a depth position of 30 μm from a sheet surface, an internal oxidation layer in which at least a part of a crystal grain boundary is coated with an oxide is provided from the sheet surface to a depth of 5.0 μm or more, grain boundary coverage of the oxide is 60% or more in a region from the sheet surface to a depth of 5.0 μm, and a tensile strength is 980 MPa or more.

公开(公告)号：US20230193415A1

公开(公告)日：2023-06-22

申请号：US17927107

申请日：2021-08-16

Applicant: NIPPON STEEL CORPORATION

Inventor： Arisa IKEDA ,  Kengo TAKEDA

IPC: C21D9/46 ,  C22C38/60 ,  C22C38/50 ,  C22C38/48 ,  C22C38/42 ,  C22C38/38 ,  C22C38/34 ,  C22C38/30 ,  C22C38/28 ,  C22C38/26 ,  C22C38/22 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D6/00 ,  C21D8/02 ,  C25D3/44 ,  C25D5/36

CPC classification number: C21D9/46 ,  C22C38/60 ,  C22C38/50 ,  C22C38/48 ,  C22C38/42 ,  C22C38/38 ,  C22C38/34 ,  C22C38/30 ,  C22C38/28 ,  C22C38/26 ,  C22C38/22 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/105 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/008 ,  C22C38/005 ,  C22C38/002 ,  C22C38/001 ,  C21D6/001 ,  C21D6/002 ,  C21D6/004 ,  C21D6/005 ,  C21D6/007 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C25D3/44 ,  C25D5/36 ,  C21D2211/008

Abstract: In a steel sheet according to the present embodiment, a Ti content and a N content satisfy Ti−3.5×N≥0.003, at a sheet thickness ¼ position, a metallographic structure includes 90% or more of martensite in terms of volume fraction, at the sheet thickness ¼ position, a number density of TiC having a circle equivalent diameter of 1 to 500 nm is 3.5×104 particles/mm2 or more, at the sheet, thickness ¼ position, a value of a median value of a Mn concentration+3σ is 5.00% or less, and a hardness measured at the sheet thickness ¼ position is 1.30 times or more a hardness measured at a position 50 μm deep from a surface of the steel sheet.

公开(公告)号：US20230041513A1

公开(公告)日：2023-02-09

申请号：US17785367

申请日：2020-12-21

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroyuki KAWATA ,  Kengo TAKEDA ,  Katsuya NAKANO

IPC: C21D9/46 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/00 ,  C23C2/06 ,  C23C2/40 ,  C21D8/02

Abstract: A steel sheet includes a predetermined composition, in which a microstructure at a ¼ thickness position from a surface in a sheet thickness direction includes, by vol %, ferrite: 80% or more, martensite: 2% or less, and residual austenite: 2% or less, a proportion of unrecrystallized ferrite in the ferrite of 5% or less, and in the microstructure of the steel sheet stretched by 10% at the ¼ thickness position from the surface in the sheet thickness direction, a number density of voids having a maximum diameter of 1.0 μm or more is 1.0×109 pieces/m2 or less.

公开(公告)号：US20220063245A1

公开(公告)日：2022-03-03

申请号：US17415794

申请日：2020-03-16

Applicant: NIPPON STEEL CORPORATION

Inventor： Katsuya NAKANO ,  Kengo TAKEDA ,  Hiroyuki KAWATA

IPC: B32B15/01 ,  C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/58 ,  C22C38/42 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/22 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00

Abstract: High strength steel sheet improved in formability, bending load, and bendability is provided. The high strength steel sheet has a center part of sheet thickness and a surface soft part formed at one side or two sides of the center part of sheet thickness, has metal structures of the center part of sheet thickness comprised of, by area ratio, tempered martensite: 85% or more, one or more of ferrite, bainite, pearlite, and retained austenite: total of less than 15%, and as-quenched martensite: less than 5%, has metal structures of the surface soft part comprised of, by area ratio, ferrite: 65% or more, pearlite: 5% or more and less than 20%, one or more of tempered martensite, bainite, and retained austenite: total of less than 10%, and as-quenched martensite: less than 5%, has average distances of pearlite at the surface soft part of 3 μm or more, and has Vickers hardness (Hc) of the center part of sheet thickness and Vickers hardness (Hs) of the surface soft part satisfying 0.50≤Hs/Hc≤0.75.

公开(公告)号：US20200232058A1

公开(公告)日：2020-07-23

申请号：US16487009

申请日：2018-02-20

Applicant: NIPPON STEEL CORPORATION

Inventor： Kengo TAKEDA ,  Riki OKAMOTO ,  Kazuo HIKIDA ,  Katsuya NAKANO ,  Yuya SUZUKI ,  Genki ABUKAWA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/34 ,  C22C38/06 ,  C22C38/00 ,  C22C38/60 ,  C21D8/02 ,  C21D6/00

Abstract: There is provided a steel sheet including an inner layer and a hard layer formed on one or both surfaces of the inner layer, wherein each content of C and Mn in the hard layer is more than each content of C and Mn in the inner layer, a thickness of the hard layer is 20 μm or more and a total of the thickness of the hard layer is ⅖ or less of the entire sheet thickness, an average micro-Vickers hardness of the hard layer is 400 HV or more and less than 800 HV, an average micro-Vickers hardness of the inner layer is 350 HV or more and is 50 HV or more smaller than a hardness of the hard layer, and a screw dislocation density of the inner layer is 2.0×1013 m/m3 or more.

公开(公告)号：US20250146095A1

公开(公告)日：2025-05-08

申请号：US18837473

申请日：2023-02-17

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Kengo TAKEDA ,  Katsuya NAKANO ,  Taku MIYAKAWA

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

Abstract: This steel sheet includes, in mass % C: 0.15% to 0.50%, Si: 0.01% to 1.00%, Mn: 1.00% to 3.00%, P: 0% to 0.0200%, S: 0.0001% to 0.0200%, Al: 0.001% to 0.100%, and N: 0% to 0.0200%, with the remainder being Fe and impurities, in which a metallorgraphic structure has an area fraction of 0% to 10.0% of retained austenite and 0% to 5.0% of pearlite, ferrite, and bainite in total, with the remaining structure being martensite and tempered martensite, a maximum diameter of MnS predicted by extreme value statistics is 30 μm or less, a surface roughness Ra is 5 μm or less, and a surface layer has a Vickers hardness of greater than or equal to a tensile strength TS (MPa) of the steel sheet×0.25.