公开(公告)号：US20200325554A1

公开(公告)日：2020-10-15

申请号：US16772692

申请日：2017-12-15

Applicant: NIPPON STEEL CORPORATION

Inventor： Kengo TAKEDA ,  Kunio HAYASHI ,  Akihiro UENISHI ,  Hiroyuki KAWATA ,  Chisato YOSHINAGA ,  Yasunobu MIYAZAKI ,  Toyomitsu NAKAMURA

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

Abstract: A steel sheet having a chemical composition of the base metal including, in mass %, C: 0.17 to 0.40%, Si: 0.10 to 2.50%, Mn: 1.00 to 10.00%, P: 0.001 to 0.03%, S: 0.0001 to 0.02%, Al: 0.001 to 2.50%, N: 0.0001 to 0.010%, O: 0.0001 to 0.010%, Ti: 0 to 0.10%, Nb: 0 to 0.10%, V: 0 to 0.10%, B: 0 to 0.010%, Cr: 0 to 2.00%, Ni: 0 to 2.00%, Cu: 0 to 2.00%, Mo: 0 to 2.00%, Ca: 0 to 0.50%, Mg: 0 to 0.50%, REM: 0 to 0.50%, the balance: Fe and impurities, wherein the steel sheet has an internal oxidized layer in which at least one part of a crystal grain boundary is covered by oxides, and in which a grain boundary coverage ratio of oxides is 60% or more in a region from the surface of the base metal to a depth of 5.0 μm.

公开(公告)号：US20240182997A1

公开(公告)日：2024-06-06

申请号：US18410064

申请日：2024-01-11

Applicant: NIPPON STEEL CORPORATION

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

IPC: C21D9/46 ,  B32B15/01 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/52 ,  C22C38/54 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

CPC classification number: C21D9/46 ,  B32B15/013 ,  C21D8/0226 ,  C21D8/0263 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/52 ,  C22C38/54 ,  C22C38/60 ,  C23C2/02 ,  C23C2/0224 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/003 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/009

Abstract: A hot dip galvanized steel sheet includes 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：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：US20220154302A1

公开(公告)日：2022-05-19

申请号：US17437369

申请日：2020-03-05

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroyuki KAWATA

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/54 ,  C22C38/60 ,  C23C2/06 ,  C23C2/40 ,  B22D11/124

Abstract: This steel sheet has a predetermined chemical composition, a microstructure contains, in terms of a volume fraction, ferrite: 10% to 75%, martensite: 20% to 90%, retained austenite: 0% to 5%, bainite and bainitic ferrite in total: 0% to 50%, and pearlite: 0% to 5%, a proportion of unrecrystallized ferrite in the ferrite is 0% to 25%, cementite that is contained in the martensite satisfies a predetermined relational expression, a density of transition carbide included in the martensite is 1.0×1013 pieces/m3 or more, a density of coarse inclusion having an equivalent circle diameter of 10 μm or more is 0.50 pieces/mm2 or less, in a surface parallel to the surface at a position ¼ of the sheet thickness deep from the surface in the sheet thickness direction, a ratio of a maximum value Hvmax of Vickers hardness to a minimum value Hvmin of the Vickers hardness is 1.40 or less, and an average value of minimum distances between peaks of the Vickers hardness in a distribution map of the Vickers hardness is 1.00 mm or less.

公开(公告)号：US20220112569A1

公开(公告)日：2022-04-14

申请号：US17428715

申请日：2020-01-07

Applicant: NIPPON STEEL CORPORATION

Inventor： Masahiro KUBO ,  Hiroyuki KAWATA ,  Kenichiro OTSUKA ,  Masafumi AZUMA

IPC: C21D8/00 ,  C22C38/02 ,  C22C38/16 ,  C22C38/04

Abstract: A steel sheet includes, as a chemical composition, by mass %: C: 0.0015% to 0.0400%; Mn: 0.20% to 1.50%; P: 0.010% to 0.100%; Cr: 0.001% to 0.500%; Si: 0.200% or less; S: 0.020% or less; sol. Al: 0.200% or less; N: 0.0150% or less; Mo: 0% to 0.500%; B: 0% to 0.0100%; Nb: 0% to 0.200%; Ti: 0% to 0.200%; Ni: 0% to 0.200%; Cu: 0% to 0.100%; and a remainder including iron and impurities, in which a metallographic structure in a surface layer region includes ferrite having a volume fraction of 90% or more, and in the surface layer region, an average grain size of the ferrite is 1.0 μm to 15.0 μm, and a texture in which an XODF{001}/{111}, S as a ratio of an intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.30 or more and less than 3.50 is included.

公开(公告)号：US20220064771A1

公开(公告)日：2022-03-03

申请号：US17421317

申请日：2020-02-06

Applicant: NIPPON STEEL CORPORATION

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

IPC: C22C38/58 ,  C22C38/02 ,  C22C38/50 ,  C22C38/46 ,  C22C38/48 ,  C22C38/42 ,  C22C38/52 ,  C22C38/00 ,  C22C38/54 ,  C22C38/44 ,  C21D8/02

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: 6% to 30%, bainite: 5% or more, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, a number density of tempered martensite with a circle equivalent diameter of 5.0 μm or more is 20/1000 μm2 or less, and an area ratio of fresh martensite with a circle equivalent diameter of 2.0 μm or more after imparting 5% plastic strain is 10% or less, and a method for producing the same.

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：US20210340653A1

公开(公告)日：2021-11-04

申请号：US17312853

申请日：2018-12-11

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroyuki KAWATA ,  Eisaku SAKURADA ,  Kohichi SANO ,  Takafumi YOKOYAMA

IPC: C22C38/58 ,  C22C38/02 ,  C22C38/00 ,  C22C38/06 ,  C22C38/50 ,  C22C38/42 ,  C22C38/46 ,  C22C38/48 ,  C22C38/44 ,  C22C38/54 ,  C21D8/02 ,  C21D9/46 ,  C23C2/06 ,  C23C2/40

Abstract: A high-strength steel sheet excellent in formability, toughness and weldability has a chemical composition including: by mass %, C: 0.05 to 0.30%, Si: 2.50% or less, Mn: 0.50 to 3.50%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance consisting of Fe and inevitable impurities. The high-strength steel sheet has a microstructure in a region from ⅛t (t: sheet thickness) to ⅜t (t: sheet thickness) from a steel sheet surface, the microstructure including: by volume %, acicular ferrite (3): 20% or more, and martensite (4):10% or more, aggregated ferrite: 20% or less, residual austenite: 2.0% or less, and the martensite satisfies a formula (A), ∑ i = 1 5 ⁢ ⁢ d i a i 1.5 ≤ 10.0 ( A )

公开(公告)号：US20200024709A1

公开(公告)日：2020-01-23

申请号：US16499834

申请日：2017-03-31

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Riki OKAMOTO ,  Yuji YAMAGUCHI ,  Kazuki SHIOKAWA ,  Yuichi NAKAHIRA ,  Hiroyuki KAWATA

IPC: C22C38/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/54 ,  C22C38/60 ,  C21D8/02 ,  C21D9/46 ,  C23C2/06

Abstract: A cold-rolled steel sheet is provided that has a tensile strength of 980 MPa or more, and has a prescribed chemical composition. The microstructure is composed of, in area %, ferrite: 1 to 29%, retained austenite: 5 to 20%, martensite: less than 10%, pearlite: less than 5%, and the balance: bainite and/or tempered martensite. The total sum of the lengths of phase boundaries where ferrite comes in contact with martensite or retained austenite having a circle-equivalent radius of 1 μm or more is 100 μm or less per 1000 μm2. The cold-rolled steel sheet is excellent in workability and low-temperature toughness, and in particular is excellent in low-temperature toughness after introduction of plastic strain.

公开(公告)号：US20240247357A1

公开(公告)日：2024-07-25

申请号：US18290088

申请日：2021-05-10

Applicant: NIPPON STEEL CORPORATION

Inventor： Jun MAKI ,  Keitaro MATSUDA ,  Hiroyuki KAWATA

IPC: C23C2/40 ,  C21D6/00 ,  C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/22 ,  C22C38/38 ,  C23C2/06

CPC classification number: C23C2/40 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0278 ,  C21D9/46 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/22 ,  C22C38/38 ,  C23C2/06

Abstract: The present invention relates to a galvanized steel sheet comprising steel sheet containing C: 0.05 to 0.30%, Si: 0.01 to 3.00%, Mn: 0.80 to 3.00%, and Al: 0.010 to 2.000% and having a thickness of 0.10 to 0.95 mm, and a galvanized layer on the steel sheet, wherein a tensile strength is 550 to 1500 MPa, and, when defining a thickness of an internal oxide layer per surface of the steel sheet as “A” (μm), a thickness of a decarburized layer per surface of the steel sheet as “B” (μm), and a thickness of the steel sheet as “t” (μm), A/B: 0.01 to 0.50 and B/t: 0.001 to 0.200.