公开(公告)号：US20220389531A1

公开(公告)日：2022-12-08

申请号：US17771770

申请日：2021-01-04

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroyuki KAWATA ,  Kengo TAKEDA ,  Eriko TSUKAMOTO

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/32 ,  C22C38/28 ,  C22C38/22 ,  C22C38/16 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C22C38/08 ,  C23C2/06 ,  C23C2/40

Abstract: A steel sheet has a predetermined chemical composition, in which a microstructure in a ¼ width portion, a microstructure in a ½ width portion, and a microstructure in a ¾ width portion, include, by area %, ferrite: 80% or more, martensite: 2% or less, and residual austenite: 2% or less, in which a proportion of unrecrystallized ferrite in the ferrite is 5% to 60%, an average grain size of carbonitrides is 6.0 nm to 30.0 nm, and Expressions (2) to (5) are satisfied. ΔSF/μSF≤0.10  (2) ΔdF/μdF≤0.20  (3) ΔSUF≤20  (4) ΔdC/μdC≤0.50  (5)

公开(公告)号：US20220282351A1

公开(公告)日：2022-09-08

申请号：US17426592

申请日：2020-03-12

Applicant: NIPPON STEEL CORPORATION

Inventor： Kengo TAKEDA ,  Hiroyuki KAWATA ,  Takafumi YOKOYAMA ,  Katsuya NAKANO

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/52 ,  C22C38/54 ,  C22C38/60

Abstract: Provided are: a steel sheet having a high strength and excellent hydrogen embrittlement resistance; and a method of producing the same. The steel sheet has prescribed chemical composition and structure, in which a standard deviation σ of Mn concentration satisfies σ≥0.15 Mnave (wherein, Mnave represents an average Mn concentration) and a region with a Mn concentration of higher than (Mnave+1.3σ) has a circle-equivalent diameter of less than 10.0 μm. The method of producing the steel sheet includes: the hot rolling step that includes finish rolling a slab having a prescribed chemical composition under prescribed conditions; the step of coiling the thus obtained hot-rolled steel sheet at a coiling temperature of 450 to 700° C.; and the step of cold rolling the hot-rolled steel sheet and subsequently annealing this steel sheet at 800 to 900° C.

公开(公告)号：US20220267874A1

公开(公告)日：2022-08-25

申请号：US17601580

申请日：2020-06-26

Applicant: NIPPON STEEL CORPORATION

Inventor： Katsuya NAKANO ,  Kengo TAKEDA ,  Hiroyuki KAWATA ,  Akihiro UENISHI ,  Yuya SUZUKI

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/38 ,  C22C38/32 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: A steel sheet having a tensile strength of 1100 MPa or more and excellent in crash resistance, having a micro-structure containing tempered martensite: 95 vol. % or more, wherein in a cross section parallel to a sheet-thickness direction of the steel sheet, when a sheet thickness is denoted by t, in a 300-μm-square region centered about a t/2 point, a standard deviation of Vickers hardnesses that are measured under a load of 9.8 N at 30 points is 30 or less, wherein when a 100-μm-square region centered about a t/2 point is divided into 10×10, 100 subregions, and at a center of each of the subregions, a nano hardness is measured under a maximum load of 1 mN, out of the subregions, the number of subregions each of which makes a difference in nano hardness of 3 GPa or more from any one of eight surrounding subregions is 10 or less.

公开(公告)号：US20220186337A1

公开(公告)日：2022-06-16

申请号：US17600021

申请日：2020-04-08

Applicant: NIPPON STEEL CORPORATION

Inventor： Kohichi SANO ,  Hiroyuki KAWATA ,  Kengo TAKEDA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/18 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: This steel sheet has a predetermined chemical composition, in which the area ratio of plate martensite is 10% or more, the average grain size of prior austenite grains is 2.0 μm to 10.0 μm, the maximum diameter thereof is 20.0 μm or less, the amount of solid solution C in martensite is 0.20 mass % or less, the average carbide size is 0.25 μm or less, the crystal orientation difference between plate martensite and another martensite adjacent thereto in the same prior austenite grain is 10.0° or less, and the P concentration at grain boundaries of the prior austenite grains is 4.0 at % or less.

公开(公告)号：US20220119908A1

公开(公告)日：2022-04-21

申请号：US17427870

申请日：2020-02-06

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Hiroyuki KAWATA ,  Kunio HAYASHI ,  Yuji YAMAGUCHI ,  Satoshi UCHIDA

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/52 ,  C22C38/54 ,  C22C38/60 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23C2/40

Abstract: Provided are a hot dip galvanized steel sheet comprising a base steel sheet and a hot dip galvanized layer on at least one surface of the base metal steel sheet, wherein the base steel sheet has a predetermined chemical composition, and contains, by volume fraction, ferrite: 0% to 50%, retained austenite: 0% to 30%, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, when there are remaining structures, the remaining structures consist of bainite, a concentration of B atoms at prior austenite grain boundaries is 2.0 atm % or more, and an average effective crystal grain size is 7.0 μm or less, and a method for producing the same.

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：US20240425960A1

公开(公告)日：2024-12-26

申请号：US18685405

申请日：2021-08-27

Applicant: NIPPON STEEL CORPORATION

Inventor： Yasuhiro ITO ,  Hiroyuki KAWATA ,  Mai NAGANO ,  Satoshi HIRONAKA

IPC: C22C38/60 ,  C21D6/00 ,  C21D8/02 ,  C21D9/48 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/44 ,  C22C38/50 ,  C22C38/54 ,  C22C38/58

Abstract: The steel sheet contains, as a chemical composition, by mass %, C: 0.040% to 0.100%, Mn: 1.00% to 2.00%, Si: 0.005% to 1.500%, P: 0.100% or less, S: 0.0200% or less, Al: 0.005% to 0.700%, N: 0.0150% or less, O: 0.0100% or less, and a remainder: Fe and impurities, in which an arithmetic mean waviness Wa is in a range of 0.10 to 0.30 μm.

公开(公告)号：US20240344165A1

公开(公告)日：2024-10-17

申请号：US18681807

申请日：2021-08-27

Applicant: NIPPON STEEL CORPORATION

Inventor： Yasuhiro ITO ,  Mai NAGANO ,  Hiroyuki KAWATA ,  Satoshi HIRONAKA

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

CPC classification number: C21D9/46 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C23C2/06 ,  C23C2/40

Abstract: Adopted are a steel sheet contains, as a chemical composition, by mass %, C: 0.040% to 0.105%, Mn: 1.00% to 2.30%, Si: 0.005% to 1.500%, Al: 0.005% to 0.700%, P: 0.100% or less, S: 0.0200% or less, N: 0.0150% or less, O: 0.0100% or less, and a remainder: Fe and impurities, in which ΔC that is calculated from C20, which is a C content at a 20 μm depth position from a surface, C60, which is a C content at a 60 μm depth position from the surface, and the following expression (1) is in a range of 0.20 to 0.90 mass %/mm, and a press-formed article that is obtained by press-forming the steel sheet.








Δ
⁢
C

=


(


C
60

-

C

2
⁢
0



)

/

(
0.04
)






(
1
)

公开(公告)号：US20230047282A1

公开(公告)日：2023-02-16

申请号：US17786988

申请日：2020-12-21

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroyuki KAWATA ,  Kengo TAKEDA ,  Mai NAGANO

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/28 ,  C22C38/12 ,  C22C38/16 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: A steel sheet includes a predetermined composition satisfying Expression (1), in which the microstructure at the ¼ thickness position from the surface in the sheet thickness direction includes, by vol %, ferrite: 95% or more and a remainder of the microstructure: 5% or less, has a proportion of unrecrystallized ferrite in the ferrite of 5% or less, and a half width w and an X-ray wavelength λ at a peak of (200) plane of the ferrite satisfy Expression (2). 0.80≤{(Ti/48−N/14)+Nb/93}/(C/12)≤5.00  (1) w×λ≥0.20  (2)

公开(公告)号：US20220195556A1

公开(公告)日：2022-06-23

申请号：US17604720

申请日：2020-06-26

Applicant: NIPPON STEEL CORPORATION

Inventor： Katsuya NAKANO ,  Kengo TAKEDA ,  Hiroyuki KAWATA ,  Akihiro UENISHI

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/38 ,  C22C38/32 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: A steel sheet including a steel micro-structure containing, in volume fraction, tempered martensite: 85% or more, retained austenite: 5% or more to less than 15%, and ferrite, pearlite, bainite, and as-quenched martensite being less than 10% in total, when contents of Mn and C in the retained austenite are denoted by MnA and CA, and when contents of Mn and C in a matrix are denoted by MnM and CM, respectively, following Formulas (1) to (3) are satisfied, and the number of carbides having an equivalent circle radius of 0.1 μm or more is 100 or less in a region measuring 20000 μm2, and the steel sheet has a tensile strength of 1100 MPa or more. The steel sheet is excellent in crash resistance and formability. MnA/MnM≥1.2  (1) CA/CM≤5.0  (2) CA≤1.0  (3)