公开(公告)号：US20190040511A1

公开(公告)日：2019-02-07

申请号：US16072904

申请日：2017-01-26

Applicant: JFE STEEL CORPORATION

Inventor： Hiroshi HASEGAWA ,  Yoshimasa FUNAKAWA ,  Hiromi YOSHITOMI ,  Yoichi MAKIMIZU ,  Yoshitsugu SUZUKI ,  Gentaro TAKEDA ,  Yoshikazu SUZUKI ,  Yoshimasa HIMEI

IPC: C23C2/02 ,  C22C38/60 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C21D9/46 ,  C23C2/06 ,  C23C2/26 ,  C23C2/40

Abstract: A high-strength galvanized steel sheet having improved post-work impact resistance, a method for producing the high-strength galvanized steel sheet, and a high-strength member produced using the steel sheet. The high-strength galvanized steel sheet includes a steel sheet having a microstructure including ferrite and carbide-free bainite, martensite and carbide-containing bainite, and retained austenite, the total area fraction of ferrite and carbide-free bainite being 0% to 55%, the total area fraction of martensite and carbide-containing bainite being 45% to 100%, and the area fraction of retained austenite being 0% to 5%. Additionally, a galvanizing layer is disposed on the steel sheet. The density of gaps that cut across the entire thickness of the galvanizing layer in a cross section of the galvanizing layer, which is taken in the thickness direction so as to be perpendicular to the rolling direction, is 10 gaps/mm or more.

公开(公告)号：US20180030564A1

公开(公告)日：2018-02-01

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 ,  C22C38/26 ,  C22C38/24 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C21D6/00 ,  C22C38/38

CPC classification number: C21D9/46 ,  B32B15/013 ,  B32B15/04 ,  B32B15/043 ,  B32B15/18 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0463 ,  C21D8/0473 ,  C21D2211/001 ,  C21D2211/005 ,  C21D2211/008 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/24 ,  C22C38/26 ,  C22C38/38 ,  C22C38/58 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23C2/285 ,  C23C2/40 ,  C23C30/00 ,  C23C30/005 ,  Y10T428/12757 ,  Y10T428/12799 ,  Y10T428/12951 ,  Y10T428/12958 ,  Y10T428/12972

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：US20180002800A1

公开(公告)日：2018-01-04

申请号：US15543062

申请日：2015-11-24

Applicant: JFE STEEL CORPORATION

Inventor： Hiroshi HASEGAWA ,  Hideyuki KIMURA ,  Yoshimasa FUNAKAWA ,  Yoichi MAKIMIZU ,  Yoshitsugu SUZUKI

IPC: C23C2/40 ,  C22C38/04 ,  C21D9/46 ,  C22C38/02 ,  C23C2/28 ,  C22C38/06

CPC classification number: C23C2/40 ,  B32B15/013 ,  B32B15/04 ,  B32B15/043 ,  B32B15/18 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D9/46 ,  C21D2211/001 ,  C21D2211/005 ,  C21D2211/008 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/24 ,  C22C38/26 ,  C22C38/38 ,  C22C38/58 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23C2/285 ,  C23C30/00 ,  C23C30/005 ,  Y10T428/12757 ,  Y10T428/12799 ,  Y10T428/12951 ,  Y10T428/12958 ,  Y10T428/12972

Abstract: A high-strength galvanized steel sheet that includes a chemical composition containing, by mass %, C: 0.15% or more and 0.25% or less, Si: 0.50% or more and 2.5% or less, Mn: 2.3% or more and 4.0% or less, P: 0.100% or less, S: 0.02% or less, Al: 0.01% or more and 2.5% or less, and Fe and inevitable impurities. The steel sheet having a microstructure containing, by an area percentage basis, 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 20% or less, and other phases: 10% or less (including 0%), the other phases containing a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%).

公开(公告)号：US20170321297A1

公开(公告)日：2017-11-09

申请号：US15535175

申请日：2015-10-27

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Kohei HASEGAWA ,  Yoshimasa FUNAKAWA

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

CPC classification number: C21D9/46 ,  C21D1/28 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0247 ,  C21D8/0263 ,  C21D8/0273 ,  C21D8/0278 ,  C21D8/0405 ,  C21D8/0426 ,  C21D8/0436 ,  C21D8/0447 ,  C21D8/0463 ,  C21D8/0473 ,  C21D8/0478 ,  C21D9/48 ,  C21D2211/002 ,  C21D2211/008 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/58

Abstract: A high-strength cold-rolled steel sheet having a specified chemical composition and a microstructure including ferrite having an average crystal grain diameter of 2 μm or less in an amount of 10% to 25% in terms of volume fraction, retained austenite in an amount of 5% to 20% in terms of volume fraction, martensite having an average crystal grain diameter of 2 μm or less in an amount of 5% to 15% in terms of volume fraction, and the balance being a multi-phase structure including bainite and tempered martensite having an average crystal grain diameter of 5 μm or less, in which a relational expression, 0.35≦V2/V1≦0.75 (1), is satisfied, where V1 is a volume fraction of phases which are different from ferrite and V2 is a volume fraction of tempered martensite.

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：US20200172991A1

公开(公告)日：2020-06-04

申请号：US16616602

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Takashi KOBAYASHI ,  Yoshimasa FUNAKAWA ,  Seiji NAKAJIMA

IPC: C21D9/46 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/22 ,  C22C38/16 ,  C22C38/08 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C21D1/18 ,  C23C2/12 ,  C23C2/06 ,  C23C2/40 ,  B32B15/01 ,  C25D3/54 ,  C25D3/22 ,  C25D3/56 ,  B21D22/20 ,  B21K29/00

Abstract: Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing, excellent delayed fracture resistance, and high tensile shear stress after resistance spot welding by properly adjusting its chemical composition and its microstructure such that at least 20 Nb-based precipitates having a grain size of less than 0.10 μm are present on average per 100 μm2 of a cross section parallel to a thickness direction of the member, a prior austenite average grain size is 8 μm or less, an average aspect ratio of prior austenite grains is 2.5 or less, and a volume fraction of martensite is 90% or more, and such that a standard deviation of Vickers hardness measured every 200 μm on a surface of the member is 40 or less.

公开(公告)号：US20200032362A1

公开(公告)日：2020-01-30

申请号：US16073397

申请日：2017-01-26

Applicant: JFE STEEL CORPORATION

Inventor： Hiroshi HASEGAWA ,  Yoshimasa FUNAKAWA

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

Abstract: A warm-workable high-strength steel sheet having superior warm workability and residual ductility after warm working, and a method for manufacturing such steel sheets. The warm-workable high-strength steel sheet has a chemical composition including, in mass %, C: 0.05 to 0.20%, Si: not more than 3.0%, Mn: 3.5 to 8.0%, P: not more than 0.100%, S: not more than 0.02%, Al: 0.01 to 3.0% and N: not more than 0.010%, the balance being Fe and inevitable impurities. The steel sheet has a microstructure that includes, in area fractions, 10 to 60% retained austenite, 10 to 80% ferrite, 5 to 50% martensite and 0 to 5% bainite, the C content in the retained austenite being less than 0.40 mass %.

公开(公告)号：US20190112682A1

公开(公告)日：2019-04-18

申请号：US16089193

申请日：2017-03-17

Applicant: JFE STEEL CORPORATION

Inventor： Noriaki KOHSAKA ,  Yoshimasa FUNAKAWA

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

Abstract: A steel sheet having low yield ratio, tensile strength of 780 MPa or more, and good bending fatigue properties. The steel sheet includes a specific chemical composition and a steel microstructure having an area percentage of a ferrite phase of 20% or more and 80% or less and an area percentage of a martensite phase of 20% or more and 80% or less, the area percentage being determined by microstructure observation, in which a surface layer portion of the steel sheet has an average ferrite grain size of 5.0 μm or less and an inclusion density of 200 particles/mm−2 or less, and in which the steel sheet has a surface hardness of 95% or more when the steel sheet has a hardness of 100% at a position ½t, where t represents the thickness of the steel sheet, away from a surface of the steel sheet in the thickness direction.

公开(公告)号：US20190032186A1

公开(公告)日：2019-01-31

申请号：US16071581

申请日：2017-01-20

Applicant: JFE STEEL CORPORATION

Inventor： Takashi UENO ,  Hiroshi HASEGAWA ,  Yoshimasa FUNAKAWA ,  Yoshimasa HIMEI ,  Yoshikazu SUZUKI

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

Abstract: High strength steel sheets that have excellent ductility and low-temperature toughness and methods for producing such high strength steel sheets. A high strength steel sheet includes a composition containing, on a mass % basis, C: 0.05% to 0.30%, Si: 0.5% to 2.5%, Mn: 0.5% to 3.5%, P: 0.003% to 0.100%, S: 0.02% or less, Al: 0.010% to 1.5%, and N: 0.01% or less, the balance being Fe and unavoidable impurities, and a steel microstructure including a ferrite phase with an area fraction of 10% to 70%, a hard second phase with an area fraction of 30% to 90%, and a carbide that is at an interface between a ferrite phase and a hard second phase and that has an average equivalent-circle diameter of 200 nm or less.

公开(公告)号：US20180291476A1

公开(公告)日：2018-10-11

申请号：US15577989

申请日：2016-05-26

Applicant: JFE STEEL CORPORATION

Inventor： Yuma HONDA ,  Yoshimasa FUNAKAWA ,  Kozo HARADA

IPC: C21D9/46 ,  C22C38/54 ,  C22C38/48 ,  C22C38/16 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/04 ,  C21D6/00 ,  C23C2/28 ,  C23C2/40 ,  B32B15/01 ,  C25D3/22 ,  C25D5/36

Abstract: A high-strength steel sheet having high yield ratio, excellent stretch flange formability, and resistance to secondary working embrittlement. The steel sheet has a composition containing C: 0.02% to less than 0.10%, Si: less than 0.3%, Mn: less than 1.0%, P: 0.10% or less, S: 0.020% or less, Al: 0.01% to 0.10%, N: 0.010% or less, and Nb: 0.003% to less than 0.070% on a mass basis, the remainder being Fe and inevitable impurities. A steel microstructure of the steel sheet contains ferrite: 90% or more and a total of pearlite, martensite, retained austenite, and cementite: 0% to 10% on an area fraction basis, in which the average grain size of the ferrite is 15.0 μm or less, and in which the average aspect ratio of the ferrite is 1.2 or more; and a tensile strength of 500 MPa or less.