公开(公告)号：US20240068066A1

公开(公告)日：2024-02-29

申请号：US18280105

申请日：2022-02-22

Applicant: NIPPON STEEL CORPORATION

Inventor： Yasuaki TANAKA ,  Shohei YABU ,  Hiroshi SHUTO ,  Koutarou HAYASHI ,  Takashi YASUTOMI ,  Eisaku SAKURADA

IPC: C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C22C38/60

CPC classification number: C21D9/46 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C22C38/60

Abstract: There is provided a steel sheet having a chemical composition comprising, in mass %, C: 0.05 to 0.25%, Si: 0.2 to 2.0%, Mn: 1.2 to 3.0%, P: 0.030% or less, S: 0.050% or less, Al: 0.01 to 0.55%, N: 0.0100% or less, and Ti: 0.010 to 0.250%, with the balance: Fe and impurities, wherein a random intensity ratio of a texture in a near-surface portion of the steel sheet is 8.0 or less, and a minimum angle formed between a maximum strength orientation in a {110} pole figure of the texture and a normal direction of a rolled surface of the steel sheet is 10° or less.

公开(公告)号：US20230323496A1

公开(公告)日：2023-10-12

申请号：US18021066

申请日：2021-06-15

Applicant: NIPPON STEEL CORPORATION

Inventor： Mitsuru YOSHIDA ,  Hiroshi SHUTO ,  Kazumasa TSUTSUI ,  Koutarou HAYASHI

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14

CPC classification number: C21D8/0226 ,  C21D9/46 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C21D2211/001 ,  C21D2211/005 ,  C21D2211/009

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure, in terms of area%, residual austenite is less than 3.0%, ferrite is less than 15.0%, and pearlite is less than 5.0%, an E value that indicates periodicity of the microstructure is less than 10.7, and an I value that indicates uniformity of the microstructure is less than 1.020, a standard deviation of a Mn concentration is 0.60 mass% or less, and a tensile strength is 780 MPa or more.

公开(公告)号：US20210002741A1

公开(公告)日：2021-01-07

申请号：US17040891

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Shohei YABU ,  Koutarou HAYASHI ,  Akihiro UENISHI

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/20 ,  C22C38/32

Abstract: A steel sheet including, in mass %, C: 0.05% or more and 0.30% or less, Si: 0.05% or more and 6.00% or less, Mn: 1.50% or more and 10.00% or less, and the balance: Fe and impurities, a steel sheet structure is composed of, in area ratio, 15% or more and 80% or less of ferrite and 20% or more and 85% or less in total of a hard structure composed of any one of bainite, martensite, or retained austenite, or any combination thereof, and to a steel sheet thickness t, an area ratio of a maximum coupled ferrite region in a region from a t/2 position at the steel sheet thickness center to a position at a depth of 3t/8 from a surface is 80% or more in area ratio to a total ferrite area, and a two-dimensional isoperimetric constant of the maximum coupled ferrite region is 0.35 or less.

公开(公告)号：US20220259692A1

公开(公告)日：2022-08-18

申请号：US17765697

申请日：2020-10-12

Applicant: NIPPON STEEL CORPORATION

Inventor： Shohei YABU ,  Kunio HAYASHI ,  Koutarou HAYASHI ,  Kazumasa TSUTSUI

IPC: C21D9/46 ,  B21B3/02 ,  C21D6/00 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/24 ,  C22C38/22 ,  C22C38/16 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in which a microstructure contains, by area %, bainite: 80.0% or more, ferrite: 10.0% or less, and a remainder in the microstructure: 10.0% or less, a total density of a length L7 of a grain boundary having a crystal orientation difference of 7° and a length L68 of a grain boundary having a crystal orientation difference of 68° about a direction in the bainite is 0.35 to 0.60 μm/μm2, and a tensile strength is 780 MPa or more.

公开(公告)号：US20210164082A1

公开(公告)日：2021-06-03

申请号：US17054467

申请日：2019-07-26

Applicant: NIPPON STEEL CORPORATION

Inventor： Mai NAGANO ,  Koutarou HAYASHI ,  Akihiro UENISHI

IPC: C22C38/58 ,  C22C38/02 ,  C21D8/02 ,  C21D9/46

Abstract: What is provided is a high-strength steel sheet having a large bake hardening amount and a uniform bake hardenability is provided according to the present invention, the high-strength steel sheet comprising, by mass %: C: 0.13% to 0.40%; Si: 0.500% to 3.000%; Mn: 2.50% to 5.00%; P: 0.100% or less; S: 0.010% or less; Al: 0.001% to 2.000%; N: 0.010% or less; and a remainder consisting of Fe and impurities, wherein martensite is 95% or more in an area ratio, and residual structure is 5% or less in an area ratio, a ratio C1/C2 of an upper limit C1 (mass %) of Si concentrations to a lower limit C2 (mass %) of the Si concentrations in a cross section in a thickness direction is 1.25 or less, precipitates having a major axis of 0.05 μm or more and 1.00 μm or less and an aspect ratio of 1:3 or more are included in a number density of 30/μm2 or more, and a tensile strength is 1300 MPa or more.

公开(公告)号：US20230140358A1

公开(公告)日：2023-05-04

申请号：US17908581

申请日：2021-03-09

Applicant: NIPPON STEEL CORPORATION

Inventor： Mitsuru YOSHIDA ,  Shunsuke TANIGUCHI ,  Koutarou HAYASHI ,  Hiroshi SHUTO

IPC: C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/00 ,  C22C38/06 ,  C22C38/02 ,  C22C38/54 ,  C23C2/04

Abstract: This steel sheet has a predetermined chemical composition, Ex. C that is obtained by Ex. C = (%C) - 12 ( (%Ti*)/48 + (%V)/51 + (%Nb)/93 + (%Mo)/96 + (%W)/184} is 0.020% or less, a microstructure at a ¼ depth position of a sheet thickness from a surface contains 60% or more of ferrite, 0% to 5% of MA and a total of 0% to 5% of pearlite and cementite with a remainder of bainite in terms of area fractions, in the microstructure, the average crystal grain diameter is 10.0 µm or less, the average aspect ratio of crystal grains is 0.30 or more, the standard deviation of a Mn concentration is 0.60 mass% or less, a Ti-based carbide having a Baker-Nutting orientation relationship in the ferrite is precipitated in a semi-coherent state, and a tensile strength is 980 MPa or more.

公开(公告)号：US20230021370A1

公开(公告)日：2023-01-26

申请号：US17911974

申请日：2021-03-17

Applicant: NIPPON STEEL CORPORATION

Inventor： Takahiko KOHTAKE ,  Koutarou HAYASHI ,  Yoshihiro SUWA

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

Abstract: A steel sheet has a predetermined chemical composition containing, in mass %, C: more than 0.18% and less than 0.30%, Mn: more than 2.50% and 4.00% or less, and other elements. The steel micro-structure at a position at a depth of ¼ of the sheet thickness from the surface in an L cross section of the steel sheet is, in area %, tempered martensite: 25 to 90%, ferrite: 5% or less, retained austenite: 10 to 50%, and bainite: 5% or less. At a position at a depth of ¼ of the sheet thickness from the surface of the L cross section, the proportion of a total area of retained austenite grains having an area of 1 μm2 or more and having a grain shape circularity of 0.1 or more is less than 50% with respect to the entire area of retained austenite. The steel sheet satisfies the formula CMnγ/CMnα≥1.2.

公开(公告)号：US20220119902A1

公开(公告)日：2022-04-21

申请号：US17422406

申请日：2020-01-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroshi SHUTO ,  Koutarou HAYASHI ,  Hiroshi KAIDO ,  Akifumi SAKAKIBARA ,  Jun ANDO ,  Tetsu ASATO

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in which a metal microstructure contains, by area %, 3.0% or more of residual austenite, has a ratio L52/L7 of a length L52 of a grain boundary having a crystal orientation difference of 52° to a length L7 of a grain boundary having a crystal orientation difference of 7° about a direction of 0.10 or more and 0.18 or less, has a standard deviation of a Mn concentration of 0.60 mass % or less, and has a tensile strength of 980 MPa or more.

公开(公告)号：US20210017622A1

公开(公告)日：2021-01-21

申请号：US17043267

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Jun HAGA ,  Kohichi SANO ,  Koutarou HAYASHI ,  Kunio HAYASHI ,  Masaharu KAMEDA ,  Akihiro UENISHI ,  Hiroyuki KAWATA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/38 ,  C22C38/32 ,  C22C38/22 ,  C22C38/16 ,  C22C38/14 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D6/00 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: A hot dip galvanized steel sheet and hot dip galvannealed steel sheet improved in uniform ductility and local ductility, yield strength and tensile strength, and low temperature impact property, characterized by having a predetermined chemical composition, having a metal structure containing, by volume %, retained austenite: over 5.0% and tempered martensite: over 5.0%, having retained austenite containing C: 0.85 mass % or more, and having a ratio [C]γgb/[P]γgb of an amount of segregation of C (number of atoms/nm2): [C]γgb to an amount of segregation of P (number of atoms/nm2): [P]γgb at prior austenite grain boundaries of 4.0 or more.

公开(公告)号：US20200071801A1

公开(公告)日：2020-03-05

申请号：US16490465

申请日：2018-04-27

Applicant: NIPPON STEEL CORPORATION

Inventor： Shohei YABU ,  Koutarou HAYASHI ,  Genki ABUKAWA ,  Akihiro UENISHI

IPC: C22C38/04 ,  C22C38/06 ,  C22C38/02 ,  C21D8/02

Abstract: A high strength steel sheet containing a large amount of Mn which has bendability suitable as a material for auto part use and a method of producing the same are provided. A high strength steel sheet comprising a center part in a sheet thickness and a softened surface layer part on one surface or both surfaces of the center part in the sheet thickness, characterized in that, the center part in the sheet thickness has an average Mn concentration of greater than 4.0 mass % and less than 10.0 mass %, each softened surface layer part has a thickness of 0.1% to 30% of the sheet thickness, and the softened surface layer part has an average Mn concentration of 2.5 mass % or less, a recrystallization rate of 90% or more, and recrystallized structures with an average crystal grain size of 0.1 μm or more and 40 μm or less.