公开(公告)号：US20220010414A1

公开(公告)日：2022-01-13

申请号：US17289951

申请日：2019-09-25

Applicant: JFE STEEL CORPORATION

Inventor： Takuya HIRASHIMA ,  Shimpei YOSHIOKA ,  Shinjiro KANEKO

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

Abstract: A high-strength member having excellent delayed fracture resistance, a method for manufacturing the high-strength member, and a method for manufacturing a steel sheet for the high-strength member. The high-strength member has a bent ridge portion obtained by using a steel sheet having a tensile strength of 1470 MPa or more, an edge surface of the bent ridge portion has a residual stress of 800 MPa or less, and a longest crack among cracks that extend from the edge surface of the bent ridge portion in a bent ridge direction D1 has a length of 10 μm or less.

公开(公告)号：US20190093190A1

公开(公告)日：2019-03-28

申请号：US16082158

申请日：2017-01-30

Applicant: JFE STEEL CORPORATION

Inventor： Fusae SHIIMORI ,  Shinjiro KANEKO ,  Yasunobu NAGATAKI

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

Abstract: A high-strength steel sheet exhibiting excellent ductility and stretch-flangeability, and a method for manufacturing such a high-strength steel sheet. The high-strength steel sheet has a chemical composition including specific proportions of components in which C/Mn is 0.08 to 0.20, the balance being iron and inevitable impurities, and includes microstructures including, in terms of area fraction relative to all the microstructures, 40% to 70% total of ferrite and bainitic ferrite, 5% to 35% martensite and 5% to 30% retained austenite. The proportion of martensite (including retained austenite) adjacent to bainitic ferrite is not less than 60% of all martensite (including retained austenite). The proportion of 4.0 GPa and smaller differences in microhardness measured at 0.5 μm intervals is not less than 70%. The proportion of microstructures with 8.0 GPa or smaller microhardness is not less than 85% of all the microstructures.

公开(公告)号：US20170204492A1

公开(公告)日：2017-07-20

申请号：US15329026

申请日：2015-07-31

Applicant: JFE STEEL CORPORATION

Inventor： Keiji UEDA ,  Shinjiro KANEKO ,  Masami IWASAKI ,  Reiko SUGIHARA ,  Takeshi YOKOTA ,  Kazuhiro SETO

IPC: C21D9/46 ,  C21D1/26 ,  C22C38/58 ,  C22C38/50 ,  C22C38/48 ,  C22C38/42 ,  C22C38/38 ,  C22C38/28 ,  C22C38/26 ,  C22C38/22 ,  C22C38/20 ,  C22C38/24 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02

CPC classification number: C21D9/46 ,  C21D1/26 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/06 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/38 ,  C22C38/42 ,  C22C38/48 ,  C22C38/50 ,  C22C38/58

Abstract: A cold-rolled steel sheet having excellent spot weldability suitable for use in vehicles, electric appliances, etc. is provided. The cold-rolled steel sheet has a steel composition containing, in mass%: C: 0.05% to 0.13%; Si: 0.05% to 2.0%; Mn: 1.5% to 4.0%; P: 0.05% or less; S: 0.005% or less; Al: 0.01% to 0.10%; Cr: 0.05% to 1.0%; Nb: 0.010% to 0.070%; Ti: 0.005% to 0.040%; and N: 0.0005% to 0.0065%, with a mass ratio Ti/N of Ti and N being 2.5 or more and 7.5 or less, and a balance being Fe and incidental impurities, wherein 70 mass % or more of Ti in steel exists as a precipitate, and 15 mass % or more of Nb in the steel exists as solute Nb, and a tensile strength is 980 MPa or more.

公开(公告)号：US20170175219A1

公开(公告)日：2017-06-22

申请号：US15327126

申请日：2015-08-05

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu KAWASAKI ,  Hiroshi MATSUDA ,  Yoshie OBATA ,  Shinjiro KANEKO ,  Takeshi YOKOTA ,  Kazuhiro SETO

IPC: C21D9/46 ,  C22C38/38 ,  C22C38/60 ,  C22C38/32 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/14 ,  C22C38/12 ,  C21D8/02 ,  C22C38/28

Abstract: Disclosed is a high-strength steel sheet having a predetermined chemical composition, satisfying the condition that Mn content divided by B content equals 2100 or less, and a steel microstructure that contains, by area, 25-80% of ferrite and bainitic ferrite in total, 3-20% of martensite, and that contains, by volume, 10% or more of retained austenite, in which the retained austenite has a mean grain size of 2 μm or less, a mean Mn content in the retained austenite in mass % is at least 1.2 times the Mn content in the steel sheet in mass %, and an aggregate of retained austenite formed by seven or more identically-oriented retained austenite grains accounts for 60% or more by area of the entire retained austenite.

公开(公告)号：US20220298594A1

公开(公告)日：2022-09-22

申请号：US17639086

申请日：2020-08-25

Applicant: JFE STEEL CORPORATION

Inventor： Takuya HIRASHIMA ,  Shimpei YOSHIOKA ,  Shinjiro KANEKO ,  Soshi YOSHIMOTO ,  Tomohiro HASHIMUKAI ,  Yoshihiko ONO

IPC: C21D9/46 ,  C22C38/38 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C21D1/18

Abstract: A steel sheet having a steel microstructure including, by area %, martensite in a range of 20% or more and 100% or less, ferrite in a range of 0% or more and 80% or less, and the balance being 5% or less. A residual stress generated at the transverse center of the steel sheet when the steel sheet is subjected to a V-bending process is 800 MPa or less. A residual stress generated at the transverse end of the steel sheet when the steel sheet is subjected to a V-bending process is 90% or more and 110% or less of the residual stress generated at the transverse center of the steel sheet. The maximum amount of warpage of the steel sheet sheared to a length of 1 m in the longitudinal direction is 15 mm or less.

公开(公告)号：US20220002827A1

公开(公告)日：2022-01-06

申请号：US17290155

申请日：2019-09-25

Applicant: JFE STEEL CORPORATION

Inventor： Takuya HIRASHIMA ,  Shimpei YOSHIOKA ,  Shinjiro KANEKO

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/60 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/24 ,  C22C38/22 ,  C22C38/20

Abstract: A high-strength steel sheet having high delayed fracture resistance and a method for manufacturing the high-strength steel sheet. The high-strength steel sheet has a specified chemical composition. Relative to the whole microstructure of the steel sheet, the total area fraction of at least one of (i) bainite containing carbide grains having an average grain size of 50 nm or less and (ii) martensite containing carbide grains having an average grain size of 50 nm or less is 90% or more. The average number of inclusions having an average grain size of 5 μm or more that are present in a section of the steel sheet perpendicular to a rolling direction is 5.0/mm2 or less.

公开(公告)号：US20190093191A1

公开(公告)日：2019-03-28

申请号：US15768894

申请日：2016-10-03

Applicant: JFE STEEL CORPORATION

Inventor： Koichi NAKAGAWA ,  Shinjiro KANEKO ,  Takeshi YOKOTA ,  Kazuhiro SETO

IPC: C21D8/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D1/18 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23C2/40

Abstract: A hot pressed member having all of: high strength of 1500 MPa or more in tensile strength TS; high ductility of 6.0% or more in uniform elongation uEl; and excellent heat treatment hardenability of increasing in yield stress YS by 150 MPa or more when subjected to heat treatment (baking finish) is provided. A hot pressed member comprises: a predetermined chemical composition (in particular, low C of 0.090% or more and less than 0.30% and high Mn of 3.5% or more and less than 11.0%); a microstructure including a martensite phase of 70.0% or more in volume fraction and a retained austenite phase of 3.0% or more and 30.0% or less in volume fraction; and a dislocation density of 1.0×1016/m2 or more.

公开(公告)号：US20180305785A1

公开(公告)日：2018-10-25

申请号：US15768905

申请日：2016-10-03

Applicant: JFE STEEL CORPORATION

Inventor： Koichi NAKAGAWA ,  Shinjiro KANEKO ,  Takeshi YOKOTA ,  Kazuhiro SETO

IPC: C21D9/46 ,  B21D22/20 ,  C21D1/18 ,  B21D22/02 ,  C22C38/60 ,  C22C38/58

CPC classification number: C21D9/46 ,  B21D22/02 ,  B21D22/022 ,  B21D22/20 ,  B21D24/00 ,  B21D53/88 ,  C21D1/18 ,  C21D9/00 ,  C21D2211/001 ,  C21D2211/005 ,  C21D2211/008 ,  C22C38/00 ,  C22C38/004 ,  C22C38/58 ,  C22C38/60

Abstract: A hot pressed member comprises: a predetermined chemical composition (in particular, low C of 0.090% or more and less than 0.30% and high Mn of 3.5% or more and less than 11.0%); a first region having: a microstructure including a martensite phase of 80.0% or more in volume fraction and a retained austenite phase of 3.0% or more and 20.0% or less in volume fraction; and a dislocation density of 1.0×1016/m2 or more; and a second region having a microstructure including a ferrite phase of 30.0% or more and 60.0% or less in volume fraction, a retained austenite phase of 10.0% or more and 70.0% or less in volume fraction, and a martensite phase of 30.0% or less in volume fraction.

公开(公告)号：US20220002832A1

公开(公告)日：2022-01-06

申请号：US17447973

申请日：2021-09-17

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu MINAMI ,  Shinjiro KANEKO

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/38 ,  C22C38/60 ,  C22C38/04 ,  C21D1/25 ,  C22C38/34 ,  C21D1/20 ,  C21D1/18 ,  C23C2/06 ,  B32B15/01 ,  C21D6/00

Abstract: A production method for a high-strength steel sheet having a tensile strength TS of 780 MPa or more is provided. The production method comprises: heating a steel slab having a predetermined chemical composition; hotrolling the steel slab; coiling the hot-rolled sheet; subjecting the hot-rolled sheet to pickling treatment; holding the hot-rolled sheet in a pre-determined temperature range for predetermined time; cold rolling the hot-rolled sheet to obtain a cold-rolled sheet; subjecting the cold-rolled sheet to first annealing treatment; cooling the cold-rolled sheet at a pre-determined average cooling rate; cooling the cold-rolled sheet to room temperature; reheating the clod-rolled sheet to perform second annealing treatment; cooling the cold-rolled sheet at a first average cooling rate; cooling the cold-rolled sheet at a second average cooling rate; reheating the cold-rolled sheet to a predetermined reheating temperature range; and holding the cold-rolled sheet in the reheating temperature range.

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.