公开(公告)号：US12157923B2

公开(公告)日：2024-12-03

申请号：US17417865

申请日：2019-08-23

Applicant: JFE Steel Corporation

Inventor： Hiroshi Hasegawa ,  Hidekazu Minami ,  Tatsuya Nakagaito

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/38 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C23G1/02 ,  C21D9/00

Abstract: A high-strength hot-dip galvanized steel sheet includes a hot-dip galvanized layer on a surface of the steel sheet and has a specific component composition and a steel microstructure containing, on an area percentage basis, 90% to 100% of martensite and carbide-containing bainite in total and 0% to 10% of retained austenite, and containing prior austenite grains having an aspect ratio of 2.0 or less, in a region extending from 300 μm to 400 μm from the surface layer, in which the ratio of the average amount of C at 5 μm from the surface layer to the average amount of C at 70 μm from the surface layer is 0.2 to 0.8, and the ratio of the standard deviation of the amount of C to the average amount of C in a region extending from 300 μm to 400 μm from the surface layer is 0.40 or less.

公开(公告)号：US20240247332A1

公开(公告)日：2024-07-25

申请号：US18289606

申请日：2022-05-13

Applicant: JFE Steel Corporation

Inventor： Hiroshi Hasegawa ,  Hideyuki Kimura

IPC: C21D9/46 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/38 ,  C22C38/50 ,  C22C38/54 ,  C22C38/60

CPC classification number: C21D9/46 ,  C21D1/18 ,  C21D6/002 ,  C21D6/004 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0263 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/38 ,  C22C38/50 ,  C22C38/54 ,  C22C38/60 ,  C21D2211/002 ,  C21D2211/008

Abstract: A high-strength hot-rolled steel sheet according to the present invention has a specific chemical composition and a steel microstructure including, as main phases, 80% to 100% of martensite and bainite in terms of total area fraction. An entire area fraction of the martensite dispersed in the bainite is 2% to 20%. Among the martensite dispersed in the bainite, an area fraction of martensite each having an orientation difference of 15° or more between a crystal orientation of the martensite and a crystal orientation of at least one of bainite adjacent to the martensite is more than 50% relative to the whole martensite dispersed in the bainite. When regions surrounded by boundaries between adjacent crystals having an orientation difference of 15° or more are defined as crystal grains, an average aspect ratio of the crystal grains present in a region extending from a surface of the steel sheet to a depth of 5 μm is 2.0 or less.

公开(公告)号：US11466350B2

公开(公告)日：2022-10-11

申请号：US16969996

申请日：2019-02-06

Applicant: JFE Steel Corporation

Inventor： Hiroshi Hasegawa ,  Tatsuya Nakagaito

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

Abstract: There are provided a high-strength steel sheet excellent in strength, workability in terms of, for example, λ, and energy absorption characteristics, and a production method therefor.
The high-strength steel sheet has a specific component composition and a steel microstructure containing, on an area percent basis, 1% to 35% ferrite having an aspect ratio of 2.0 or more, 10% or less ferrite having an aspect ratio of less than 2.0, less than 5% non-recrystallized ferrite, 40% to 80% in total of bainite and martensite containing carbide, 5% to 35% in total of fresh martensite and retained austenite, and 3% to 35% retained austenite, the retained austenite having a C content of 0.40% to 0.70% by mass.

公开(公告)号：US20220090223A1

公开(公告)日：2022-03-24

申请号：US17417897

申请日：2019-08-23

Applicant: JFE Steel Corporation

Inventor： Hiroshi Hasegawa ,  Tatsuya Nakagaito ,  Yuki Takeda

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C23C2/28 ,  C23C2/40 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/22 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/60

Abstract: The high-strength hot-dip galvanized steel sheet has a specific chemical composition and the following steel microstructure. In a region extending from 300 to 400 μm from a surface layer of the steel sheet in a thickness direction of the steel sheet, the total area fraction of martensite and bainite containing carbides is 60 to 100%, and the average grain size of prior austenite is 15 μm or less. In the region extending from 300 to 400 μm from the surface layer of the steel sheet in the thickness direction of the steel sheet, the ratio of the height of a peak of P in an Auger electron spectrum at a position 5 nm or more from a prior-austenite grain boundary to the height of a peak of P in an Auger electron spectrum at the prior-austenite grain boundary is 0.20 or more.

公开(公告)号：US11136642B2

公开(公告)日：2021-10-05

申请号：US16089928

申请日：2017-01-17

Applicant: JFE STEEL CORPORATION

Inventor： Hiroshi Hasegawa ,  Yoshimasa Funakawa

IPC: C21D9/46 ,  B32B15/01 ,  C21D8/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C22C38/26 ,  C22C38/22 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/60 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/08 ,  C23C2/12 ,  C23C2/00 ,  C22C38/38 ,  C21D6/00

Abstract: A steel sheet, a plated steel sheet, and methods for producing a hot-rolled steel sheet, a cold-rolled full hard steel sheet, and a steel sheet. The steel sheet has a specified composition and a microstructure including 0 to 80% of polygonal ferrite and 20 to 100% of a total of martensite, bainite, and residual austenite in terms of an area ratio within 20 μm of the steel sheet surface. The content of Mn in martensite present within 20 μm of the steel sheet surface ([Mn]SM) and the content of Mn in a bulk ([Mn]B) satisfy [Mn]SM/[Mn]B≤1.5. At a location 300 μm from the steel sheet surface, an area ratio of the martensite is in a range of 20 to 50%.

公开(公告)号：US10590503B2

公开(公告)日：2020-03-17

申请号：US15104718

申请日：2014-12-16

Applicant: JFE STEEL CORPORATION

Inventor： Hiroshi Hasegawa ,  Shinjiro Kaneko ,  Yoichi Makimizu ,  Yoshitsugu Suzuki

IPC: C22C38/00 ,  C21D9/46 ,  C23C2/06 ,  C22C38/38 ,  C22C38/58 ,  C21D8/02 ,  C22C18/04 ,  C23C2/28 ,  C23C2/40 ,  B32B15/01 ,  C22C38/02 ,  C22C38/06 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54 ,  C23C2/02 ,  C23C2/36

Abstract: Provided are a high-strength galvanized steel sheet which can preferably be used as a material for automobile parts and a method for manufacturing the steel sheet. The steel sheet has a C content of 0.15% or less, in which an area ratio of ferrite is 10% or less, an area ratio of bainitic ferrite is 2% or more and 30% or less, an area ratio of martensite is 60% or more and 98% or less, an area ratio of retained austenite is less than 2%, an average grain diameter of martensite adjacent to bainite is 15 μm or less, a proportion of massive martensite adjacent only to bainite to the whole metallographic structure is 10% or less, and a value (ΔHv) calculated by subtracting the Vickers hardness at a position located at 20 μm from the surface of the steel sheet from the Vickers hardness at a position located at 100 μm from the surface of the steel sheet is 30 or more.

公开(公告)号：US10526676B2

公开(公告)日：2020-01-07

申请号：US15104609

申请日：2014-11-27

Applicant: JFE STEEL CORPORATION

Inventor： Hiroshi Hasegawa ,  Shinjiro Kaneko ,  Yoichi Makimizu ,  Yoshitsugu Suzuki

IPC: C22C38/00 ,  C21D9/46 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C22C38/38 ,  C22C38/58 ,  C22C18/04 ,  C21D8/02 ,  B32B15/01 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54 ,  C23C2/02 ,  C23C2/36

Abstract: Provided are a high-strength steel sheet, which is suitable as a material of automotive parts, and a method for producing the high-strength steel sheet. In the high-strength steel sheet, the C content is 0.15% or less, the area ratio of ferrite is 8% to 45%, the area ratio of martensite is 55% to 85%, the proportion of martensite grains adjacent to only ferrite grains in the entire microstructure is 15% or less, the average crystal grain sizes of ferrite and martensite are each 10 μm or less, and the area ratio of ferrite grains having a size of 10 μm or more to all the ferrite grains included in a portion of the steel sheet which extends from 20 to 100 μm below the surface thereof is less than 5%.

公开(公告)号：US10370737B2

公开(公告)日：2019-08-06

申请号：US15543271

申请日：2015-11-24

Applicant: JFE STEEL CORPORATION

Inventor： Hiroshi Hasegawa ,  Hideyuki Kimura ,  Yoshimasa Funakawa ,  Yoichi Makimizu ,  Yoshitsugu Suzuki

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/26 ,  C22C38/24 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C22C38/38 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  B32B15/01 ,  C23C30/00 ,  C23C2/12 ,  B32B15/18 ,  B32B15/04 ,  C23C2/02 ,  C22C38/58 ,  C22C38/04 ,  C21D8/04

Abstract: A high-strength galvanized steel sheet and method for producing the same. The high-strength galvanized steel sheet including a specified chemical composition and a microstructure comprising, in terms of area fraction, a tempered martensite phase: 30% or more and 73% or less, a ferrite phase: 25% or more and 68% or less, a retained austenite phase: 2% or more and 15% or less, and other phases: 10% or less (including 0%), the other phases comprising a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%), the tempered martensite phase having an average grain size of 8 μm or less, the ferrite phase having an average grain size of 5 μm or less, and the retained austenite phase having a C content less than 0.7% by mass.

公开(公告)号：US10294542B2

公开(公告)日：2019-05-21

申请号：US15305557

申请日：2015-03-18

Applicant: JFE STEEL CORPORATION

Inventor： Hideyuki Kimura ,  Koichiro Fujita ,  Hiroshi Hasegawa

IPC: C21D9/46 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C22C38/00 ,  B32B15/01 ,  C21D6/00 ,  C21D8/02 ,  C23C2/40 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/32 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C23F17/00

Abstract: A method is provided for producing a high-strength galvanized steel sheet having a microstructure that contains martensite in an area proportion of 20% or more and 60% or less and ferrite in an area proportion of 40% or more and 80% or less includes, in sequence, hot-rolling a steel slab containing a specific component composition, performing cold rolling, performing primary annealing, performing pickling, performing secondary annealing, and performing galvanizing treatment, in which in the primary annealing, heating is performed at an average heating rate of 0.1° C./sec. or more and less than 3° C./sec. in the temperature range of 600° C. to 750° C., an annealing temperature of 750° C. to 850° C. is maintained for 10 to 500 seconds, and then cooling is performed from the annealing temperature range to a cooling stop temperature of 600° C. or lower at an average cooling rate of 1 to 15° C./sec, in which in the pickling, the pickling weight loss of the steel sheet is 0.05 to 5 g/m2 in terms of Fe, in which in the secondary annealing, an annealing temperature of 750° C. to 850° C. is maintained for 10 to 500 seconds, and then cooling is performed from the annealing temperature at an average cooling rate of 1 to 15° C./s, and in which after the galvanizing treatment, cooling is performed at an average cooling rate of 5 to 100° C./sec.

公开(公告)号：US09982318B2

公开(公告)日：2018-05-29

申请号：US15405819

申请日：2017-01-13

Applicant: JFE Steel Corporation

Inventor： Shinjiro Kaneko ,  Tatsuya Nakagaito ,  Hiroshi Hasegawa ,  Yasunobu Nagataki

IPC: C21D9/46 ,  C23C2/06 ,  B32B15/01 ,  C23C2/28 ,  C23C2/40 ,  C21D8/02 ,  C21D1/34 ,  C22C18/04 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/22 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

CPC classification number: C21D9/46 ,  B32B15/013 ,  C21D1/34 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D2211/002 ,  C21D2211/008 ,  C22C18/04 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/22 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/285 ,  C23C2/40 ,  Y02P10/212

Abstract: A galvanized steel sheet has formability and crashworthiness, consists of 0.03% to 0.13% C, 1.0% to 2.0% Si, 2.4% to 3.5% Mn, 0.001% to 0.05% P, 0.0001% to 0.01% S, 0.001% to 0.1% Al, 0.0005% to 0.01% N, and 0.0003% to 0.01% B on a mass basis; and optionally contains at least one selected from the following A-C: A: at least one selected from the group consisting of 0.0005% to 0.1% Ti and 0.0005% to 0.05% Nb on a mass basis; B: at least one selected from the group consisting of 0.01% to 1.0% Mo, 0.01% to 2.0% Ni, and 0.01% to 2.0% Cu on a mass basis; and C: 0.001% to 0.005% Ca on a mass basis; the remainder being Fe and unavoidable impurities, and a microstructure containing a tempered martensitic phase and a bainitic phase such that the sum of an area fraction of the tempered martensitic phase and an area fraction of the bainitic phase is 30% or more, the area fraction of the tempered martensitic phase is 30% or more in the absence of the bainitic phase, wherein a distance of closest approach of the tempered martensitic phase is 10 μm or less and contents of C, Mn, and B satisfy (1): (% Mn)+1000×(% B)≥35×(% C)  (1).