公开(公告)号：US20240318287A1

公开(公告)日：2024-09-26

申请号：US18579575

申请日：2022-03-18

Applicant: JFE STEEL CORPORATION

Inventor： Sho HIGUCHI ,  Yoshiyasu KAWASAKI ,  Tatsuya NAKAGAITO ,  Takako YAMASHITA ,  Tomomi KANAZAWA ,  Shunsuke YAMAMOTO

IPC: C22C38/04 ,  C21D6/00 ,  C21D8/02 ,  C22C38/02 ,  C22C38/06 ,  C23C2/06 ,  C23C2/28

CPC classification number: C22C38/04 ,  C21D6/005 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C22C38/02 ,  C22C38/06 ,  C23C2/06 ,  C23C2/29 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008

Abstract: A galvanized steel sheet combining high strength with excellent formability, specifically, excellent ductility, hole expansion formability, local ductility, strain hardenability, and dimensional accuracy when forming a member. The base steel sheet has a defined chemical composition and a steel microstructure as follows: ferrite area ratio: 35.0% or more and 95.0% or less, bainitic ferrite area ratio: 1.0% or more and 40.0% or less, tempered martensite area ratio: 50.0% or less (including 0%), retained austenite area ratio: 1.5% or more, fresh martensite area ratio: 20.0% or less (including 0 %), SBF+STM+2×SMA: 10.0% or more and less than 65.0%, SBF+STM: 3.0 % or more and 60.0% or less, SMA1/SMA: 0.40 or less, IDR [% Cγ]: 0.16% or more, and tensile strength: 590 MPa or more and less than 980 MPa.

公开(公告)号：US20230129828A1

公开(公告)日：2023-04-27

申请号：US17914895

申请日：2021-03-25

Applicant: JFE STEEL CORPORATION

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

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

Abstract: A steel sheet with a tensile strength (TS) of 780 MPa or more and less than 1180 MPa, a member, and a method for producing them. In a region of the steel sheet within 4.9 μm in the thickness direction, a region with a Si concentration not more than one-third of the Si concentration in the chemical composition of the steel sheet and with a Mn concentration not more than one-third of the Mn concentration in the chemical composition of the steel sheet has a thickness of 1.0 μm or more. The lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 μm 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 the following formula (1): LSi+LMn≤(TSi+TMn)/4  (1).

公开(公告)号：US20180327884A1

公开(公告)日：2018-11-15

申请号：US15779157

申请日：2016-11-08

Applicant: JFE STEEL CORPORATION

Inventor： Mai AOYAMA ,  Minoru TANAKA ,  Yoshitsugu SUZUKI ,  Yoshiyasu KAWASAKI ,  Hideyuki TAKAHASHI

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

CPC classification number: C21D9/46 ,  B32B15/013 ,  C21D1/185 ,  C21D1/76 ,  C21D6/004 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D8/0278 ,  C21D8/0463 ,  C21D8/0473 ,  C21D9/48 ,  C21D2211/001 ,  C21D2211/005 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/28 ,  C22C38/38 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/40

Abstract: A high-strength galvanized steel sheet and a method for producing the steel sheet. The steel sheet has a composition that includes C: 0.030% to 0.250%, Si: 0.01% to 3.00%, Mn: 2.00% to 10.00%, P: 0.001% to 0.100%, S: 0.0001% to 0.0200%, N: 0.0005% to 0.0100%, Ti: 0.005% to 0.200%, on a mass basis, and Fe and inevitable impurities. Additionally, the steel sheet has concentration of solute Mn at a depth of 5 μm or less from a surface of the steel sheet that is 1.50% by mass or less, and a value obtained by dividing the average mass percentage of Mn in retained austenite by the average mass percentage of Mn in ferrite is 2.0 or more.

公开(公告)号：US20180127847A9

公开(公告)日：2018-05-10

申请号：US15520236

申请日：2015-10-29

Applicant: JFE STEEL CORPORATION

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

IPC: C21D9/46 ,  C25D3/22 ,  B32B15/01 ,  C23C2/40 ,  C23C2/12 ,  C22C38/38 ,  C22C38/28 ,  C22C38/16 ,  C22C38/12 ,  C22C38/08 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23G1/00

CPC classification number: C21D9/46 ,  B32B15/012 ,  B32B2255/06 ,  B32B2255/205 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0263 ,  C21D8/0278 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/008 ,  C22C38/02 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/28 ,  C22C38/38 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23C2/40 ,  C23G1/00 ,  C25D3/22

Abstract: Disclosed is a steel sheet having a predetermined chemical composition and a steel microstructure that contains, in area ratio, 35% or more and 80% or less of polygonal ferrite and 5% or more and 25% or less of martensite, and that contains, in volume fraction, 8% or more of retained austenite, in which the polygonal ferrite, the martensite, and the retained austenite have a mean grain size of 6 μm or less, 3 μm or less, and 3 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：US20180127846A9

公开(公告)日：2018-05-10

申请号：US15517467

申请日：2015-10-29

Applicant: JFE STEEL CORPORATION

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

IPC: C21D9/46 ,  C25D3/22 ,  C21D8/02 ,  C22C38/28 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/60

CPC classification number: C21D9/46 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0278 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/28 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C25D3/22

Abstract: A high-strength steel sheet with excellent formability and high yield ratio that has TS of 590 MPa or more and YR of 68% or more is obtained by providing a predetermined chemical composition and a steel microstructure that contains, in area ratio, 35 to 80% of polygonal ferrite, 5% or more of non-recrystallized ferrite, and 5 to 25% of martensite, and that contains, in volume fraction, 8% or more of retained austenite, in which the polygonal ferrite has a mean grain size of 6 μm or less, the martensite has a mean grain size of 3 μm or less, the retained austenite has a mean grain size of 3 μm or less, and 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：US20180057916A1

公开(公告)日：2018-03-01

申请号：US15551301

申请日：2016-01-25

Applicant: JFE Steel Corporation

Inventor： Yoshie OBATA ,  Yoshiyasu KAWASAKI ,  Keiji UEDA ,  Shinjiro KANEKO ,  Takeshi YOKOTA ,  Kazuhiro SETO

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

CPC classification number: C22C38/14 ,  C21D8/0236 ,  C21D8/0268 ,  C21D9/46 ,  C21D2211/001 ,  C21D2211/004 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/009 ,  C22C38/00 ,  C22C38/001 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/16 ,  C22C38/18 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/40

Abstract: A steel having a composition containing C: more than 0.20% and 0.45% or less, Si: 0.50% to 2.50%, Mn: 2.00% or more and less than 3.50%, and one or two selected from Ti: 0.005% to 0.100% and Nb: 0.005% to 0.100% is hot-rolled and cold-rolled. The steel sheet is heated to 800° C. to 950° C. and cooled to a cooling-end temperature of 350° C. to 500° C. at a cooling rate of 5° C./s or more to form a steel sheet having a microstructure including martensite and bainite phases such that the total proportion of the martensite and bainite phases is 80% or more by volume. The steel sheet is heated to 700° C. to 840° C. and maintained at 700° C. to 840° C., cooled to a cooling-end temperature of 350° C. to 500° C. at a cooling rate of 5 to 50° C./s, and maintained within the above temperature range for 10 to 1800 s.

公开(公告)号：US20170327919A1

公开(公告)日：2017-11-16

申请号：US15520531

申请日：2015-10-29

Applicant: JFE STEEL CORPORATION

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

IPC: C21D9/46 ,  B32B15/01 ,  C23C2/40 ,  C23C2/12 ,  C23C2/06 ,  C22C38/38 ,  C22C38/28 ,  C22C38/16 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C23G1/00 ,  C21D6/00 ,  C21D8/02 ,  C25D3/22

CPC classification number: C21D9/46 ,  B32B15/012 ,  B32B15/013 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D2211/001 ,  C21D2211/005 ,  C21D2211/008 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/28 ,  C22C38/38 ,  C22C38/58 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23C2/40 ,  C23G1/00 ,  C25D3/22

Abstract: A high-strength steel sheet with excellent formability and high yield ratio that has TS of 980 MPa or more and YR of 68% or more is obtained by providing a predetermined chemical composition and a steel microstructure that contains, in area ratio, 15 to 55% of polygonal ferrite, 8% or more of non-recrystallized ferrite, and 15 to 30% of martensite, and that contains, in volume fraction, 12% or more of retained austenite, in which the polygonal ferrite has a mean grain size of 4 μm or less, the martensite has a mean grain size of 2 μm or less, the retained austenite has a mean grain size of 2 μm or less, and 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：US20170314091A1

公开(公告)日：2017-11-02

申请号：US15520236

申请日：2015-10-29

Applicant: JFE STEEL CORPORATION

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

IPC: C21D9/46 ,  B32B15/01 ,  C23C2/40 ,  C23C2/12 ,  C22C38/38 ,  C22C38/28 ,  C22C38/16 ,  C22C38/12 ,  C22C38/08 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23G1/00 ,  C25D3/22

CPC classification number: C21D9/46 ,  B32B15/012 ,  B32B2255/06 ,  B32B2255/205 ,  C21D6/001 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0263 ,  C21D8/0278 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/008 ,  C22C38/02 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/28 ,  C22C38/38 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C23C2/40 ,  C23G1/00 ,  C25D3/22

Abstract: Disclosed is a steel sheet having a predetermined chemical composition and a steel microstructure that contains, in area ratio, 35% or more and 80% or less of polygonal ferrite and 5% or more and 25% or less of martensite, and that contains, in volume fraction, 8% or more of retained austenite, in which the polygonal ferrite, the martensite, and the retained austenite have a mean grain size of 6 μm or less, 3 μm or less, and 3 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：US20170306435A1

公开(公告)日：2017-10-26

申请号：US15517467

申请日：2015-10-29

Applicant: JFE STEEL CORPORATION

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

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/28 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/60 ,  C25D3/22

CPC classification number: C21D9/46 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0278 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/28 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/12 ,  C23C2/28 ,  C25D3/22

Abstract: A high-strength steel sheet with excellent formability and high yield ratio that has TS of 590 MPa or more and YR of 68% or more is obtained by providing a predetermined chemical composition and a steel microstructure that contains, in area ratio, 35 to 80% of polygonal ferrite, 5% or more of non-recrystallized ferrite, and 5 to 25% of martensite, and that contains, in volume fraction, 8% or more of retained austenite, in which the polygonal ferrite has a mean grain size of 6 μm or less, the martensite has a mean grain size of 3 μm or less, the retained austenite has a mean grain size of 3 μm or less, and 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.