公开(公告)号：US20220275471A1

公开(公告)日：2022-09-01

申请号：US17632566

申请日：2020-07-16

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Takeshi YOKOTA

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C23G1/08

Abstract: The high-strength thin steel sheet has a chemical composition containing C, Si, Mn, P, S, Al, and N, with the balance being Fe and inevitable impurities, and a complex structure containing ferrite, tempered martensite, and bainite, where a volume fraction of a total of tempered martensite and bainite containing five or more carbides with a particle size of 0.1 μm or more and 1.0 μm or less in a grain with respect to a total of the tempered martensite and the bainite is 85% or more, and C mass % and Mn mass % in a region of 20 μm or less in a thickness direction from a surface of the steel sheet are each 20% or less with respect to C mass % and Mn mass % in a region of 100 μm or more and 200 μm or less from the surface of the steel sheet.

公开(公告)号：US20220177992A1

公开(公告)日：2022-06-09

申请号：US17437357

申请日：2020-02-13

Applicant: JFE STEEL CORPORATION

Inventor： Yoshie OBATA ,  Katsutoshi TAKASHIMA ,  Minoru TANAKA ,  Yoshiko NAKAHARA

IPC: C21D9/46 ,  B21D22/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C22C38/12 ,  C22C38/60 ,  C23C2/06 ,  C23C2/12 ,  C23C2/40 ,  C23G1/00 ,  C21D8/02 ,  B21C47/02

Abstract: A hot press member includes excellent indentation peel strength which has a tensile strength of 1780 MPa or more. A plating layer has at a surface thereof a 10-point average roughness Rzjis of 25 μm or less, and a steel sheet contains, in mass %, not less than 0.25% but less than 0.50% of C, 1.5% or less of Si, 1.1-2.4% of Mn, 0.05% or less of P, 0.005% or less of S, 0.01-0.50% of Al, 0.010% or less of N, 0.001-0.020% of Sb, 0.005-0.15% of Nb, and 0.005-0.15% of Ti, the balance being Fe and incidental impurities. The average crystal grain size of prior austenite is 7 μm or less and the volume proportion of martensite is 90% or more, within 50 μm in the thickness direction from the surface of the steel sheet excluding the plating layer.

公开(公告)号：US20210130919A1

公开(公告)日：2021-05-06

申请号：US16762501

申请日：2018-11-07

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Takayuki FUTATSUKA ,  Kentaro SATO ,  Shimpei YOSHIOKA ,  Yoshihiko ONO ,  Yoshimasa FUNAKAWA

IPC: C21D9/46 ,  B32B15/01 ,  C21D8/02 ,  C21D6/00 ,  C22C38/58 ,  C22C38/54 ,  C22C38/52 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C22C38/60

Abstract: Disclosed is a hot-pressed steel sheet member having a tensile strength of 1780 MPa or more and excellent bending collapsibility. The hot-pressed steel sheet member includes: a specific chemical composition; a microstructure in which an average grain size of prior austenite grains is 8 μm or less, a volume fraction of martensite is 90% or more, and a solute C content is 25% or less of a total C content; and a tensile strength of 1780 MPa or more.

公开(公告)号：US20200332382A1

公开(公告)日：2020-10-22

申请号：US16754135

申请日：2018-11-07

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi TAKASHIMA ,  Takayuki FUTATSUKA ,  Kentaro SATO ,  Shimpei YOSHIOKA ,  Yoshihiko ONO ,  Yoshimasa FUNAKAWA

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/10 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/32 ,  C23C2/06 ,  C23C2/12

Abstract: Disclosed is a hot-pressed steel sheet member having a tensile strength of 1780 MPa or more and excellent bending collapsibility. The hot-pressed steel sheet member has: a specific chemical composition where a ratio of a C content in mass % to a Nb content in mass %, C/Nb, is from 22 to 100; a microstructure in which an average grain size of prior austenite grains is 8 μm or less, a volume fraction of martensite is 90% or more, and a solute C content is 25% or less of a total C content; and a tensile strength of 1780 MPa or more.

公开(公告)号：US20190203315A1

公开(公告)日：2019-07-04

申请号：US16325299

申请日：2017-08-29

Applicant: JFE STEEL CORPORATION

Inventor： Yoshie OBATA ,  Katsutoshi TAKASHIMA ,  Takashi KOBAYASHI ,  Hiroshi MATSUDA

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/60 ,  C23F17/00 ,  B32B15/01

CPC classification number: C21D9/46 ,  B32B15/013 ,  C21D1/18 ,  C21D1/25 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D8/0278 ,  C21D8/0405 ,  C21D8/0426 ,  C21D8/0436 ,  C21D8/0463 ,  C21D8/0473 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C22C18/04 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/60 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C23F17/00 ,  C25D3/22

Abstract: A high-strength cold rolled steel sheet having a specified chemical composition and a method for producing the same. The steel sheet having a microstructure including, in terms of volume fraction, 35% or less of ferrite, 1% or more and 10% or less of retained austenite, 2% or more and 12% or less of as-quenched martensite, and a total of 25% to 70% of bainite and tempered martensite. The microstructure has an average crystal grain diameter of the ferrite: 5.0 μm or less, an average crystal grain diameter of the retained austenite: 2.0 μm or less, an average crystal grain diameter of the as-quenched martensite: 3.0 μtm or less, an average crystal grain diameter of the bainite and the tempered martensite phase: 4.0 μm or less, and an average intergrain distance of the as-quenched martensite of 1.0 μm or more.

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.