公开(公告)号：US20200283869A1

公开(公告)日：2020-09-10

申请号：US16759678

申请日：2017-11-15

Applicant: NIPPON STEEL CORPORATION

Inventor： Yuri TODA ,  Kunio HAYASHI ,  Katsuya NAKANO ,  Eisaku SAKURADA ,  Akihiro UENISHI ,  Kengo TAKEDA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/20 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23C2/06 ,  C23C2/40

Abstract: A high-strength cold-rolled steel sheet which is a steel sheet having a tensile strength of 980 MPa or more has a predetermined chemical component composition, a metallographic microstructure of the steel sheet contains, by area ratio, ferrite and granular bainite: 10% or more and 50% or less in total, one or both of upper bainite and lower bainite: 10% or more and 50% or less in total, tempered martensite: more than 0% and 30% or less, retained austenite: 5% or more, and one or more of pearlite, cementite, and martensite: 0% to 10% in total, and an area ratio of the ferrite with respect to a total area ratio of the ferrite and the granular bainite is 25% or less.

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：US20230304119A1

公开(公告)日：2023-09-28

申请号：US18020841

申请日：2021-10-15

Applicant: NIPPON STEEL CORPORATION

Inventor： Takuya KUWAYAMA ,  Kunio HAYASHI ,  Takafumi YOKOYAMA

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

CPC classification number: C21D9/46 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/001 ,  C22C38/002 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C23C2/40 ,  C23C2/06 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/009

Abstract: This steel sheet has a predetermined chemical composition, in which a microstructure at a ¼ depth position of a sheet thickness from a surface of the steel sheet contains, by volume fraction, ferrite: 0% to 50%, residual austenite: 6% to 30%, bainite: 5% to 60%, tempered martensite: 5% to 50%, fresh martensite: 0% to 10%, and pearlite: 0% to 5%, at the ¼ depth position of the sheet thickness from the surface, a number proportion of the residual austenite having an aspect ratio of 2.0 or more to an entire residual austenite is 50% or more, and a number density of inclusions and precipitates having a grain size of 1 μm or more is 30/mm2 or less, and at a 1/20 depth position of the sheet thickness from the surface, an average interval between Mn-concentrated portions in a direction perpendicular to a rolling direction is 300 μm or less, and a standard deviation of Mn concentrations in the residual austenite is 0.40% or less.

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：US20200010919A1

公开(公告)日：2020-01-09

申请号：US16487043

申请日：2018-02-20

Applicant: NIPPON STEEL CORPORATION

Inventor： Yuya SUZUKI ,  Katsuya NAKANO ,  Genki ABUKAWA ,  Kunio HAYASHI

IPC: C21D9/46 ,  C22C38/04 ,  C22C38/06 ,  C22C38/60 ,  C23C2/06 ,  C22C38/02 ,  C21D8/02

Abstract: High strength steel sheet having a tensile strength of 800 MPa or more comprising a middle part in sheet thickness and a soft surface layer arranged at one side or both sides of the middle part in sheet thickness, wherein each soft surface layer has a thickness of more than 10 μM and 30% or less of the sheet thickness, the soft surface layer has an average Vickers hardness of more than 0.60 time and 0.90 time or less the average Vickers hardness of the sheet thickness 1/2 position, and the soft surface layer has a nano-hardness standard deviation of 0.8 or less is provided.

公开(公告)号：US20220275493A1

公开(公告)日：2022-09-01

申请号：US17634229

申请日：2020-09-03

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Kazuki SHIOKAWA ,  Tatsuya OBUCHI ,  Kunio HAYASHI

IPC: C22C38/60 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/44 ,  C22C38/42 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/04 ,  C22C38/02 ,  C22C38/06 ,  C22C38/00 ,  C22C38/10 ,  C21D9/46 ,  C21D8/02

Abstract: Provided are a steel sheet having a predetermined chemical composition and having the following steel structure, and a method of manufacturing the steel sheet.
(1) In area ratio %, ferrite: 0 to 5%, martensite: 90 to 100%, a ratio of tempered martensite to total martensite: 80 to 100%, and retained austenite: 0.5 to 6.0% are contained.
(2) The number density of inclusions satisfying the maximum diameter≥3 μm is 40 inclusions/mm2 or less.
(3) When the number density of the inclusions satisfying the maximum diameter≥3 μm in each section is calculated, the number density in the section where the number density of inclusions is in the top 10% is 80 inclusions/mm2 or less.
(4) Formula (A) is satisfied. Vγ′/Vγ≥0.1  (A) Vγ: Initial retained austenite, Vγ′: Retained austenite after deep cooling at −196° C.
(5) The tensile strength is 1470 MPa or more.

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：US20200232060A1

公开(公告)日：2020-07-23

申请号：US16487030

申请日：2018-02-20

Applicant: NIPPON STEEL CORPORATION

Inventor： Katsuya NAKANO ,  Yuya SUZUKI ,  Genki ABUKAWA ,  Kunio HAYASHI

IPC: C21D9/46 ,  B32B15/01 ,  C23C2/06 ,  C23C2/40 ,  C23C2/28 ,  C21D8/02 ,  C21D6/00 ,  C22C38/38 ,  C22C38/32 ,  C22C38/22 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

Abstract: High strength steel sheet having a tensile strength of 800 MPa or more comprising a middle part in sheet thickness and a soft surface layer arranged at one side or both sides of the middle part in sheet thickness, wherein each soft surface layer has a thickness of more than 10 μm and 30% or less of the sheet thickness, the soft surface layer has an average Vickers hardness of 0.60 time or less the average Vickers hardness of the sheet thickness ½ position, and the soft surface layer has a nano-hardness standard deviation of 0.8 or less is provided.

公开(公告)号：US20200094525A1

公开(公告)日：2020-03-26

申请号：US16467295

申请日：2017-01-17

Applicant: NIPPON STEEL CORPORATION

Inventor： Genki ABUKAWA ,  Kunio HAYASHI ,  Kazuo HIKIDA ,  Kaoru KAWASAKI

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

Abstract: A steel sheet for hot stamping includes a steel structure represented by an area fraction of bainite, fresh martensite and tempered martensite: 80% or more in total, and a product of a number density (pieces/μm2) of carbides and a proportion of carbides precipitated into prior austenite grains in carbides: 0.50 or more.