公开(公告)号：US20230127243A1

公开(公告)日：2023-04-27

申请号：US17915739

申请日：2021-03-25

Applicant: JFE STEEL CORPORATION

Inventor： Lingling YANG ,  Yoshiyasu KAWASAKI ,  Tatsuya NAKAGAITO ,  Shotaro TERASHIMA ,  Shunsuke YAMAMOTO ,  Katsuya HOSHINO ,  Yuki TAKEDA

IPC: C21D9/46 ,  C22C38/60 ,  C22C38/38 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D6/00 ,  C21D8/02 ,  B32B15/01

Abstract: A steel sheet having a tensile strength (TS) of 1180 MPa or more, high LME resistance, and good weld fatigue properties. The steel sheet has a specific chemical composition and a specific steel microstructure. Crystal grains containing an oxide of Si and/or Mn in a region within 4.9 μm in a thickness direction from a surface of the steel sheet have an average grain size in the range of 3 to 10 μm, the lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 μm in the thickness direction from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy a specified formula.

公开(公告)号：US20220251676A1

公开(公告)日：2022-08-11

申请号：US17630504

申请日：2020-06-19

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu MINAMI ,  Takeshi YOKOTA ,  Yoshiyasu KAWASAKI ,  Shotaro TERASHIMA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/58 ,  C22C38/44 ,  C22C38/32 ,  C22C38/30 ,  C22C38/28 ,  C22C38/26 ,  C22C38/24 ,  C22C38/20 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: Provided are a high-strength hot-dip galvanized steel sheet that has a tensile strength of 1180 MPa or more and excellent ductility, stretch flangeability, bendability and LME resistance and can manufacture parts with high dimensional accuracy, and its manufacturing method. The high-strength steel sheet with a tensile strength of 1180 MPa or more has a chemical composition containing C, Si, Mn, P, S, Al and N, with [% Si], [% Mn], [% P], [% Mo] and [% Cr] satisfying a predetermined relationship and the balance being Fe and inevitable impurities, and a steel microstructure including ferrite, tempered martensite and bainite, and retained austenite, where the diffusible hydrogen amount in the steel sheet is 0.60 mass ppm or less, a thickness of softened surface layer is 5 μm or more and 150 μm or less, and a frequency of coincidence boundary in the steel sheet surface layer after a high-temperature tensile test is 0.45 or less.

公开(公告)号：US20220186334A1

公开(公告)日：2022-06-16

申请号：US17433875

申请日：2019-12-10

Applicant: JFE STEEL CORPORATION

Inventor： Kazuki ENDOH ,  Yoshiyasu KAWASAKI ,  Yuki TOJI ,  Yoshimasa FUNAKAWA ,  Mai AOYAMA

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

Abstract: An object is to provide a high strength steel sheet having a TS (tensile strength) of 980 MPa or more and excellent formability and a method for manufacturing the steel sheet.
A high strength steel sheet which is excellent in terms of formability, which is manufactured under optimized manufacturing conditions, and which has a predetermined chemical composition and a steel microstructure including, in terms of area fraction, 35% or more and 80% or less of ferrite, 5% or more and 35% or less of as-quenched martensite, 0.1% or more and less than 3.0% of tempered martensite, and 8% or more of retained austenite, in which the average grain size of the ferrite is 6 μm or less, in which the average grain size of the retained austenite is 3 μm or less, in which a value calculated by dividing the average Mn content in the retained austenite by the average Mn content in the ferrite is 1.5 or more, in which a value calculated by dividing the sum of the area fraction of as-quenched martensite having a circle-equivalent grain size of 3 μm or more and the area fraction of retained austenite having a circle-equivalent grain size of 3 μm or more by the sum of the area fraction of all the as-quenched martensite and the area fraction of all the retained austenite is less than 0.4, and in which a value calculated by dividing the area fraction of retained austenite grains adjacent to three or more ferrite grains having different crystal orientations by the area fraction of all the retained austenite is less than 0.6.

公开(公告)号：US20190276907A1

公开(公告)日：2019-09-12

申请号：US16090883

申请日：2017-03-08

Applicant: JFE STEEL CORPORATION

Inventor： Takako YAMASHITA ,  Yoshiyasu KAWASAKI ,  Takashi KOBAYASHI ,  Masayasu UENO ,  Yasunobu NAGATAKI

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

Abstract: A steel sheet having TS of 590 MPa or more and YR of 68% or more is obtained by providing a predetermined chemical composition and a predetermined steel microstructure, where an average aspect ratio of crystal grains of each phase (polygonal ferrite, martensite, and retained austenite) is 2.0 or more and 15.0 or less, wherein the polygonal ferrite has an average grain size of 6 μm or less, the martensite has an average grain size of 3 μm or less, the retained austenite has an average grain size of 3 μm or less, and a value obtained by dividing a Mn content in the retained austenite in mass % by a Mn content in the polygonal ferrite in mass % equals 2.0 or more.

公开(公告)号：US20190106760A1

公开(公告)日：2019-04-11

申请号：US16090892

申请日：2017-03-08

Applicant: JFE STEEL CORPORATION

Inventor： Takako YAMASHITA ,  Yoshiyasu KAWASAKI ,  Takashi KOBAYASHI ,  Masayasu UENO ,  Yasunobu NAGATAKI

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

Abstract: A steel sheet having TS of 980 MPa or more and YR of 68% or more is obtained by providing a predetermined chemical composition and a predetermined steel microstructure, where an average aspect ratio of crystal grains of each phase (polygonal ferrite, martensite, and retained austenite) is 2.0 or more and 20.0 or less, wherein the polygonal ferrite has an average grain size of 4 μm or less, the martensite has an average grain size of 2 μm or less, the retained austenite has an average grain size of 2 μm or less, and a value obtained by dividing a Mn content in the retained austenite in mass % by a Mn content in the polygonal ferrite in mass % equals 2.0 or more.

公开(公告)号：US20180363088A1

公开(公告)日：2018-12-20

申请号：US15735678

申请日：2016-08-10

Applicant: JFE STEEL CORPORATION

Inventor： Kenji TSUZUMI ,  Yoshiyasu KAWASAKI ,  Yuji MIKI

IPC: C21D9/46 ,  C22C38/50 ,  C22C38/58 ,  C22C38/32 ,  C22C38/26 ,  C22C38/24 ,  C22C38/22 ,  C22C38/20 ,  B22D11/00 ,  B22D11/124 ,  C21D8/02 ,  C21D6/00 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C23C2/12 ,  C23C2/28 ,  C23C2/40 ,  C23C28/02 ,  B32B15/01

Abstract: A high strength steel sheet having excellent surface quality and formability with a tensile strength of 980 MPa or more and a TS-El balance of 30000 MPa % or more is provided. A high strength steel sheet comprises: a chemical composition containing C: 0.08% to 0.30%, Si: 2.0% or less, Mn: more than 3.0% and 10.0% or less, P: 0.05% or less, S: 0.01% or less, Al: 1.5% or less, Ti: 0.010% to 0.300%, and N: 0.0020% to 0.0100% in a range satisfying 1.1≤(Ti+Mn1/2/400)/(0.01+5N)≤6.0; and a microstructure including a retained austenite phase and a ferrite phase, wherein a ratio γMn/αMn of an average Mn concentration (γMn) of the retained austenite phase to an average Mn concentration (αMn) of the ferrite phase is 1.5 or more.

公开(公告)号：US20170298482A1

公开(公告)日：2017-10-19

申请号：US15516698

申请日：2015-10-29

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu KAWASAKI ,  Hiroshi MATSUDA ,  Takeshi YOKOTA ,  Takako YAMASHITA ,  Kazuhiro SETO

IPC: C22C38/14 ,  B32B15/01 ,  C23C2/40 ,  C23C2/12 ,  C22C38/12 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C21D1/26 ,  C23F17/00 ,  B32B15/18 ,  B32B15/20 ,  C25D3/22

Abstract: Disclosed is a steel sheet having a predetermined chemical composition and a steel microstructure that contains, in area ratio, 15% or more and 55% or less of polygonal ferrite and 15% or more and 30% or less of martensite, and that contains, in volume fraction, 12% or more of retained austenite, in which the polygonal ferrite, the martensite, and the retained austenite have a mean grain size of 4 μm or less, 2 μm or less, and 2 μm or less, respectively, and each have a mean grain aspect ratio of 2.0 or less, and in which a value obtained by dividing an Mn content in the retained austenite in mass % by an Mn content in the polygonal ferrite in mass % equals 2.0 or more.

公开(公告)号：US20170218475A1

公开(公告)日：2017-08-03

申请号：US15500446

申请日：2015-08-05

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu KAWASAKI ,  Hiroshi MATSUDA ,  Takeshi YOKOTA ,  Yoshimasa FUNAKAWA ,  Kazuhiro SETO ,  Yukihiro MATSUBARA

IPC: C21D9/46 ,  C23C2/28 ,  C23C2/40 ,  C23G1/00 ,  C21D8/02 ,  C22C38/60 ,  C22C38/38 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  B32B15/01 ,  C23C2/06

CPC classification number: C21D9/46 ,  B32B15/013 ,  C21D1/26 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0247 ,  C21D8/0263 ,  C21D8/0278 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/38 ,  C22C38/60 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C23G1/00

Abstract: Disclosed is a method comprising: preparing a steel slab with a predetermined chemical composition; subjecting the steel slab to hot rolling by heating it to a temperature of 1100-1300° C., hot rolling it with a finisher delivery temperature of 800-1000° C. to form a hot-rolled steel sheet, and coiling the steel sheet at a mean coiling temperature of 200-500° C.; subjecting the steel sheet to pickling treatment; and subjecting the steel sheet to annealing by retaining the steel sheet at a temperature of 740-840° C. for 10-900 s, then cooling the steel sheet at a mean cooling rate of 5-50° C./s to a cooling stop temperature of higher than 350° C. and 550° C. or lower, and retaining the steel sheet in a temperature range of higher than 350° C. to 550° C. for 10 s or more.

公开(公告)号：US20170204491A1

公开(公告)日：2017-07-20

申请号：US15326793

申请日：2015-08-05

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu KAWASAKI ,  Hiroshi MATSUDA ,  Takeshi YOKOTA ,  Yoshimasa FUNAKAWA ,  Kazuhiro SETO ,  Yukihiro MATSUBARA

IPC: C21D9/46 ,  C21D6/00 ,  C22C38/60 ,  C22C38/38 ,  C22C38/16 ,  C23C2/06 ,  C22C38/12 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C23F17/00 ,  C21D8/02 ,  C22C38/14

CPC classification number: C21D9/46 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D8/0278 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/38 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23F17/00

Abstract: Disclosed is a method comprising: preparing a steel slab with a predetermined chemical composition; subjecting the steel slab to hot rolling by heating it to a temperature of 1100-1300° C., hot rolling it with a finisher delivery temperature of 800-1000° C. to form a hot-rolled steel sheet, and coiling the steel sheet at a mean coiling temperature of 200-500° C.; subjecting the steel sheet to pickling treatment; subjecting the steel sheet to annealing by retaining the steel sheet at a temperature of 740-840° C. for 10-900 s, and the cooling the steel sheet at a mean cooling rate of 5-30° C./s to a cooling stop temperature of 150-350° C.; and subjecting the steel sheet to reheating treatment by reheating the steel sheet to a reheating temperature of higher than 350° C. and 550° C. or lower, and retaining the steel sheet at the reheating temperature for 10 s or more.

公开(公告)号：US20250163552A1

公开(公告)日：2025-05-22

申请号：US18730452

申请日：2022-11-28

Applicant: JFE STEEL CORPORATION

Inventor： Kazuki ENDOH ,  Yoshiyasu KAWASAKI ,  Masaki TADA ,  Takuya TAKASHITA ,  Jun HORIUCHI ,  Hiroyuki MASUOKA

IPC: C22C38/04 ,  B22F10/28 ,  B33Y10/00 ,  B33Y70/00 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/08 ,  C22C38/10 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/38 ,  C22C38/60

Abstract: An additive manufacturing product that has a chemical composition containing, in mass %, C: 0.030% or more and 0.800% or less, Si: 0.01% or more and 2.50% or less, Mn: 0.10% or more and 8.00% or less, P: 0.100% or less, S: 0.0200% or less, Al: 0.100% or less, N: 0.1000% or less, and O: 0.5000% or less, with the balance being Fe and inevitable impurity. The additive manufacturing product has a steel microstructure where area fraction of pores is 0.50% or less, area fraction of martensite in a region excluding pores is 90% or more, average aspect ratio of prior austenite grains is 1.5 or more, and LHA/L, high-angle grain boundary length LHA divided by grain boundary length L with a misorientation angle of 20° or more and 50° or less, is 2.0 or more.