公开(公告)号：US20220090247A1

公开(公告)日：2022-03-24

申请号：US17415462

申请日：2019-10-25

Applicant: JFE STEEL CORPORATION

Inventor： Shimpei YOSHIOKA ,  Yoshihiko ONO ,  Yuma HONDA ,  Nobuyuki NAKAMURA

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

Abstract: A steel sheet having a specified chemical composition and a tensile strength of 1,320 MPa or more, and methods for producing the steel sheet. The steel sheet has a specified microstructure including martensite and bainite, the total area fraction of the martensite and the bainite being 92% or more and 100% or less, the balance being one or more selected from ferrite and retained austenite. The forumulae [%Ti]+[%Nb]>0.007 and [%Ti]×[%Nb]2≤7.5×10−6 are satisfied in the chemical composition.

公开(公告)号：US20210130919A1

公开(公告)日：2021-05-06

申请号：US16762501

申请日：2018-11-07

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Takayuki FUTATSUKA ,  Kentaro SATO ,  Shimpei YOSHIOKA ,  Yoshihiko ONO ,  Yoshimasa FUNAKAWA

IPC: C21D9/46 ,  B32B15/01 ,  C21D8/02 ,  C21D6/00 ,  C22C38/58 ,  C22C38/54 ,  C22C38/52 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C22C38/60

Abstract: Disclosed is a hot-pressed steel sheet member having a tensile strength of 1780 MPa or more and excellent bending collapsibility. The hot-pressed steel sheet member includes: a specific chemical composition; a microstructure in which an average grain size of prior austenite grains is 8 μm or less, a volume fraction of martensite is 90% or more, and a solute C content is 25% or less of a total C content; and a tensile strength of 1780 MPa or more.

公开(公告)号：US20200332382A1

公开(公告)日：2020-10-22

申请号：US16754135

申请日：2018-11-07

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Takayuki FUTATSUKA ,  Kentaro SATO ,  Shimpei YOSHIOKA ,  Yoshihiko ONO ,  Yoshimasa FUNAKAWA

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/10 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/32 ,  C23C2/06 ,  C23C2/12

Abstract: Disclosed is a hot-pressed steel sheet member having a tensile strength of 1780 MPa or more and excellent bending collapsibility. The hot-pressed steel sheet member has: a specific chemical composition where a ratio of a C content in mass % to a Nb content in mass %, C/Nb, is from 22 to 100; a microstructure in which an average grain size of prior austenite grains is 8 μm or less, a volume fraction of martensite is 90% or more, and a solute C content is 25% or less of a total C content; and a tensile strength of 1780 MPa or more.

公开(公告)号：US20220056549A1

公开(公告)日：2022-02-24

申请号：US17415532

申请日：2019-10-25

Applicant: JFE STEEL CORPORATION

Inventor： Shimpei YOSHIOKA ,  Yoshihiko ONO ,  Yuma HONDA ,  Nobuyuki NAKAMURA

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C23C2/06 ,  B22D11/18

Abstract: A steel sheet having a specified chemical composition and a tensile strength of 1,320 MPa or more, and methods for producing the steel sheet. The steel sheet has a specified microstructure including martensite and bainite, the total area fraction of the martensite and the bainite being 95% or more and 100% or less, the balance being one or more selected from ferrite and retained austenite. The forumulae [% Ti]+[% Nb]>0.007 and [% Ti]×[% Nb]2≤7.5×10−6 are satisfied in the chemical composition.

公开(公告)号：US20220010397A1

公开(公告)日：2022-01-13

申请号：US17285375

申请日：2019-10-16

Applicant: JFE STEEL CORPORATION

Inventor： Yoshihiko ONO ,  Junya TOBATA ,  Hiroyuki AKIMOTO ,  Yoichiro MATSUI ,  Shinjiro KANEKO

IPC: C21D9/46 ,  C21D8/02 ,  C21D1/22 ,  C21D6/00 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/42 ,  C22C38/44 ,  C22C38/14 ,  C22C38/12 ,  C22C38/04 ,  C22C38/02 ,  C22C38/06 ,  C22C38/00

Abstract: A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure comprising ferrite: 5% or less, and at least one of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ: 95% to 100%, and retained γ: 5% to 20%. Retained γUB has a specified area percentage SγUB, retained γLB has a specified distribution number NγLB, and at least one of (i) fresh martensite has a specified equivalent circular grain diameter and aspect ratio and (ii) retained γ grains has a specified equivalent circular grain diameter and aspect ratio.

公开(公告)号：US20200270717A1

公开(公告)日：2020-08-27

申请号：US16089846

申请日：2017-01-16

Applicant: JFE STEEL CORPORATION

Inventor： Tatsuya NAKAGAITO ,  Yoshimasa FUNAKAWA ,  Yoshihiko ONO ,  Hiroshi HASEGAWA

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

Abstract: A steel sheet having excellent fatigue resistance as a material for automobile parts and a TS of 590 MPa or more, and a method for producing the same. The steel sheet having a specified chemical composition and a microstructure of 50% or more and 90% or less of martensite, 10% to 50% of ferrite and bainite in total, in terms of an area ratio, and an average concentration of solute Mn in ferrite in a region from a surface of a base steel to a depth of 0.5 μm is 60% or more relative to an average concentration of solute Mn in ferrite at a location of ¼ in the thickness of the steel sheet.

公开(公告)号：US20190112681A1

公开(公告)日：2019-04-18

申请号：US16089051

申请日：2017-01-16

Applicant: JFE STEEL CORPORATION

Inventor： Tatsuya NAKAGAITO ,  Yoshimasa FUNAKAWA ,  Yoshihiko ONO ,  Hiroshi HASEGAWA

IPC: C21D8/02 ,  C22C38/04 ,  C22C38/02 ,  C22C38/06 ,  C22C38/00 ,  C22C38/12 ,  C22C38/14 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C21D9/46

Abstract: A steel sheet having excellent fatigue resistance as a material for automobile parts and a TS of 590 MPa or more, and a method for producing the same. The steel sheet has a composition comprising, by mass %, C: 0.04% or more and 0.15% or less, Si: 0.3% or less, Mn: 1.0% or more and 2.6% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 0.1% or less, N: 0.015% or less, one or two of Ti and Nb: 0.01% or more and 0.2% or less in a total, and the balance being Fe and unavoidable impurities. The steel sheet has 50% or more of ferrite and 10% or more and 50% or less of martensite in terms of an area ratio, and a microstructure in which a standard deviation of nano-hardness is 1.50 GPa or less and tensile strength of 590 MPa or more.

公开(公告)号：US20210355559A1

公开(公告)日：2021-11-18

申请号：US17286148

申请日：2019-10-16

Applicant: JFE STEEL CORPORATION

Inventor： Yoshihiko ONO ,  Junya TOBATA ,  Hiroyuki AKIMOTO ,  Yoichiro MATSUI ,  Shinjiro KANEKO

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C21D1/20 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/44 ,  C22C38/42 ,  C22C38/14 ,  C22C38/12 ,  C22C38/60 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

Abstract: A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure comprising ferrite: 5% or less, and at least one of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ: 95% to 100% by area percentage, and retained γ: 4% to 15% by volume percentage. Retained γUB has a specified area percentage SγUB, retained γLB has a specified distribution number NγLB, and at least one of (i) fresh martensite has a specified equivalent circular grain diameter and aspect ratio and (ii) retained γ grains has a specified equivalent circular grain diameter and aspect ratio.

公开(公告)号：US20210054478A1

公开(公告)日：2021-02-25

申请号：US16964651

申请日：2019-01-24

Applicant: JFE STEEL CORPORATION

Inventor： Takuya HIRASHIMA ,  Yoshihiko ONO

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C21D1/26 ,  C22C38/06 ,  C22C38/04 ,  C22C38/00 ,  C22C38/18 ,  C22C38/12 ,  C22C38/16 ,  C22C38/08 ,  C22C38/02

Abstract: A high-ductility, high-strength steel sheet having excellent close-contact bendability and a method for producing the same. The steel sheet has a specified chemical composition and a microstructure comprising, by area percentage, 50% or more of a ferrite phase, 5% to 30% of a pearlite phase, and 15% or less in total of bainite, martensite, and retained austenite, in which the area percentage of ferrite grains each containing three or more cementite grains having an aspect ratio of 1.5 or less is 30% or less, and the number of inclusions having a particle size of 10 μm or more present in a portion extending from a surface to a ¼ thickness position is 2.0 particles/mm2 or less.

公开(公告)号：US20190194775A1

公开(公告)日：2019-06-27

申请号：US16329672

申请日：2017-09-28

Applicant: JFE STEEL CORPORATION

Inventor： Yoshihiko ONO ,  Shimpei YOSHIOKA ,  Nobuyuki NAKAMURA ,  Hiroshi HASEGAWA

IPC: C21D9/46 ,  C23C2/06 ,  C23C2/40 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/42 ,  C22C38/46 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C22C38/44 ,  B32B15/01 ,  C21D8/02 ,  C21D6/00

CPC classification number: C21D9/46 ,  B32B15/013 ,  C21D6/004 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/021 ,  C21D8/0236 ,  C21D8/0247 ,  C21D8/0405 ,  C21D8/041 ,  C21D8/0426 ,  C21D8/0436 ,  C21D8/0473 ,  C21D2211/002 ,  C21D2211/008 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54 ,  C22C38/58 ,  C22C38/60 ,  C23C2/06 ,  C23C2/40

Abstract: A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure including martensite and bainite. The total area fraction of the martensite and the bainite to the entirety of the microstructure is more than 90% and 100% or less. The microstructure includes inclusion clusters A and B, the content of the clusters A in the microstructure being 2 clusters/mm2 or less, and the content of the clusters B in the microstructure being 5 clusters/mm2 or less. The microstructure includes carbide particles including Fe as a main constituent which have an aspect ratio of 2.0 or less and a major axis of 0.30 μm or more and 2 μm or less. The content of the carbide particles in the microstructure is 4000 particles/mm2 or less. The microstructure includes prior γ grains having an average size of 6 to 15 μm.