公开(公告)号：US20240271243A1

公开(公告)日：2024-08-15

申请号：US18568407

申请日：2022-03-18

Applicant: JFE Steel Corporation

Inventor： Lingling Yang ,  Yuki Toji ,  Tomomi Kanazawa ,  Shunsuke Yamamoto

IPC: C21D9/46 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/10 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/34 ,  C22C38/38 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

CPC classification number: C21D9/46 ,  C21D1/18 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/007 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0257 ,  C21D8/0263 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/10 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/34 ,  C22C38/38 ,  C22C38/60 ,  C23C2/022 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/008 ,  C22C2202/02

Abstract: A high strength galvanized steel sheet is disclosed having a tensile strength of 1,320 MPa or more. A chemical composition of a steel sheet contains, by mass, C: 0.150 to 0.450%, Si: 0.80 to 3.00%, Mn: 2.00 to 4.00%, P: not more than 0.100%, S: not more than 0.0200%, Al: not more than 0.100%, O: not more than 0.0100%, and N: not more than 0.0100%, with a balance of Fe and inevitable impurities. An amount of diffusible hydrogen in steel is not more than 0.60 mass ppm. A total of tempered martensite and bainite is 60 to 95%, retained austenite is 5 to 30%, and retained austenite having an aspect ratio of 5.5 or higher with respect to an entire retained austenite is not more than 50%, and fresh martensite having a diameter of 2.0 μm or less is not more than 20%.

公开(公告)号：US11661642B2

公开(公告)日：2023-05-30

申请号：US17042250

申请日：2019-03-20

Applicant: JFE STEEL CORPORATION

Inventor： Kazuki Endo ,  Yoshiyasu Kawasaki ,  Yuki Toji ,  Yoshimasa Funakawa ,  Mai Aoyama

IPC: C22C38/04 ,  B21B27/10 ,  C21D6/00 ,  C21D8/02 ,  C22C33/02

CPC classification number: C22C38/04 ,  B21B27/106 ,  C21D6/005 ,  C21D8/0226 ,  C22C33/0264

Abstract: A high-strength steel sheet includes a steel structure with: ferrite being 35% to 80%, martensite being 5% to 35%, and tempered martensite being 0% to 5% in terms of area fraction; retained austenite being 8% or more in terms of volume fraction; an average grain size of: the ferrite being 6 μm or less; and the retained austenite being 3 μm or less; a value obtained by dividing an area fraction of blocky austenite by a sum of area fractions of lath-like austenite and the blocky austenite being 0.6 or more; a value obtained by dividing, by mass %, an average Mn content in the retained austenite by an average Mn content in the ferrite being 1.5 or more; and a value obtained by dividing, by mass %, an average C content in the retained austenite by an average C content in the ferrite being 3.0 or more.

公开(公告)号：US20220396847A1

公开(公告)日：2022-12-15

申请号：US17770336

申请日：2020-10-08

Applicant: JFE Steel Corporation

Inventor： Kazuki Endoh ,  Yoshiyasu Kawasaki ,  Yuki Toji

IPC: C21D9/46 ,  C22C38/02 ,  C22C38/00 ,  C22C38/06 ,  C22C38/04 ,  C21D8/02 ,  C23C2/06 ,  C23C2/40 ,  B21C47/02

Abstract: Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, tempered martensite: 3.0% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 μm or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.

公开(公告)号：US20210140023A1

公开(公告)日：2021-05-13

申请号：US16074184

申请日：2017-01-30

Applicant: JFE Steel Corporation

Inventor： Yuki Toji ,  Akio Ohmori ,  Koichi Nakashima ,  Ryo Arao ,  Katsuyuki Ichimiya ,  Kazukuni Hase

IPC: C22C38/54 ,  C22C38/00 ,  C22C38/04 ,  C22C38/46 ,  C22C38/42 ,  C22C38/48 ,  C22C38/50 ,  C22C38/06 ,  B23K35/30 ,  C22C38/44

Abstract: Provided is a steel material for high heat input welding having excellent welding heat affected zone low-temperature toughness at −55° C. in the case that the steel material is welded by high heat input welding with a heat input of more than 80 kJ/cm. The steel material may be used in low-temperature storage tanks, for example. The steel material for high heat input welding includes, in mass %, C: 0.04 to 0.09%, Si: 0.15 to 0.25%, Mn: 1.40 to 2.00%, P: 0.015% or less, S: 0.0005 to 0.0040%, Al: 0.030 to 0.080%, Ti: 0.005 to 0.025%, B: 0.0003 to 0.0020%, Ca: 0.0005 to 0.0030%, N: 0.0030 to 0.0060%, O: 0.0040% or less, Nb: 0.005% or less, and Mo: 0.005% or less, the balance being Fe and incidental impurities.

公开(公告)号：US12297543B2

公开(公告)日：2025-05-13

申请号：US17766412

申请日：2020-09-25

Applicant: JFE Steel Corporation

Inventor： Yoshiyasu Kawasaki ,  Muneka Iwasawa ,  Yuki Toji ,  Yoshimasa Funakawa

IPC: C23C2/02 ,  C21D8/02 ,  C22C38/00 ,  C22C38/04 ,  C22C38/06 ,  C23C2/28

Abstract: A high strength steel sheet has a yield-point elongation of 1.0% or greater and a tensile strength of 980 MPa or greater. The high strength steel sheet has a specific chemical composition and microstructure. The ferrite has an average grain size of 5.0 μm or less, the retained austenite has an average grain size of 2.0 μm or less, a value obtained by dividing a Mn content of the retained austenite by a Mn content of steel is 1.50 or greater, 15% or more of all retained austenite grains in the retained austenite have an aspect ratio of 3.0 or greater, and 15% or more of all the retained austenite grains in the retained austenite have an aspect ratio of less than 2.0.

公开(公告)号：US20240052464A1

公开(公告)日：2024-02-15

申请号：US17766412

申请日：2020-09-25

Applicant: JFE Steel Corporation

Inventor： Yoshiyasu Kawasaki ,  Muneka Iwasawa ,  Yuki Toji ,  Yoshimasa Funakawa

IPC: C22C38/04 ,  C22C38/00 ,  C22C38/06 ,  C21D8/02

CPC classification number: C22C38/04 ,  C22C38/001 ,  C22C38/06 ,  C21D8/0236 ,  C21D8/0273 ,  C21D8/0205 ,  C21D8/0278 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/001

Abstract: A high strength steel sheet has a yield-point elongation of 1.0% or greater and a tensile strength of 980 MPa or greater. The high strength steel sheet has a specific chemical composition and microstructure. The ferrite has an average grain size of 5.0 μm or less, the retained austenite has an average grain size of 2.0 μm or less, a value obtained by dividing a Mn content of the retained austenite by a Mn content of steel is 1.50 or greater, 15% or more of all retained austenite grains in the retained austenite have an aspect ratio of 3.0 or greater, and 15% or more of all the retained austenite grains in the retained austenite have an aspect ratio of less than 2.0.

公开(公告)号：US11788163B2

公开(公告)日：2023-10-17

申请号：US17042291

申请日：2019-03-20

Applicant: JFE STEEL CORPORATION

Inventor： Kazuki Endo ,  Yoshiyasu Kawasaki ,  Yuki Toji ,  Yoshimasa Funakawa ,  Mai Aoyama

IPC: C21D9/46 ,  C22C38/38 ,  C22C38/28 ,  C22C38/16 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C21D8/02 ,  C21D6/00 ,  C22C38/00 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

CPC classification number: C21D9/46 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/16 ,  C22C38/28 ,  C22C38/38 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C21D2211/001 ,  C21D2211/005 ,  C21D2211/008

Abstract: A high-strength steel sheet includes a steel structure with: ferrite being 35% to 80% and tempered martensite being greater than 5% and 20% or less in terms of area fraction; retained austenite being 8% or more in terms of volume fraction; an average grain size of: the ferrite being 6 μm or less; and the retained austenite being 3 μm or less; a value obtained by dividing an area fraction of blocky austenite by a sum of area fractions of lath-like austenite and the blocky austenite being 0.6 or more; a value obtained by dividing, by mass %, an average Mn content in the retained austenite by an average Mn content in the ferrite being 1.5 or more; and a value obtained by dividing, by mass %, an average C content in the retained austenite by an average C content in the ferrite being 3.0 or more.

公开(公告)号：US20220364196A1

公开(公告)日：2022-11-17

申请号：US17770118

申请日：2020-10-08

Applicant: JFE Steel Corporation

Inventor： Kazuki Endoh ,  Yoshiyasu Kawasaki ,  Yuki Toji

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

Abstract: Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, tempered martensite: 3.0% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 μm or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.

公开(公告)号：US11459647B2

公开(公告)日：2022-10-04

申请号：US16957105

申请日：2018-12-13

Applicant: JFE STEEL CORPORATION

Inventor： Takaaki Tanaka ,  Yuki Toji

IPC: C21D9/46 ,  C22C38/54 ,  C21D8/02 ,  C22C38/00 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/50 ,  C23C2/02 ,  C23C2/06 ,  C23C2/40

Abstract: Provided are a high-strength cold rolled steel sheet that has a tensile strength of 980 MPa or more, excellent ductility, and a low failure rate in a hole expanding test, and a method for manufacturing the same. A high-strength cold rolled steel sheet comprises a predetermined composition, wherein a total area ratio of ferrite and bainitic ferrite is 20% to 80%, an area ratio of retained austenite (RA) is more than 10% and 40% or less, an area ratio of tempered martensite is more than 0% and 50% or less, a ratio of RA with an aspect ratio of 0.5 or less is 75% or more, a ratio of RA with an aspect ratio of 0.5 or less in ferrite grain boundaries is 50% or more, and an average KAM value of bcc phase is 1° or less.

公开(公告)号：US11359256B2

公开(公告)日：2022-06-14

申请号：US16957104

申请日：2018-12-13

Applicant: JFE STEEL CORPORATION

Inventor： Takaaki Tanaka ,  Yuki Toji

IPC: C21D9/46 ,  B21B3/02 ,  B32B15/01 ,  C21D6/00 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/34 ,  C22C38/38 ,  C22C38/60 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: Provided are a high-strength cold-rolled steel sheet that has a tensile strength of 1320 MPa or more, excellent ductility and stretch flangeability, and a low failure rate in a hole expanding test, and a method for manufacturing the same. A high-strength cold-rolled steel sheet comprises a specific composition, wherein a total area ratio of ferrite and bainitic ferrite is 10% to 50%, an area ratio of retained austenite (RA) is more than 15% and 50% or less, an area ratio of tempered martensite is more than 15% and 60% or less, a ratio of RA with an aspect ratio of 0.6 or less is 70% or more, a ratio of RA with an aspect ratio of 0.6 or less in ferrite grain boundaries is 50% or more, and an average KAM value of bcc phase is 1° or less.