公开(公告)号：US20240360532A1

公开(公告)日：2024-10-31

申请号：US18681864

申请日：2022-06-21

Applicant: JFE STEEL CORPORATION

Inventor： Yuji TANAKA ,  Takeshi NISHIYAMA ,  Masanari TOMOZAWA ,  Kazuki ENDOH ,  Hidekazu MINAMI ,  Junya TOBATA ,  Yuki TOJI

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

CPC classification number: C21D9/46 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0268 ,  C21D8/0273 ,  C21D8/0278 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12

Abstract: The steel sheet comprising a chemical composition containing C, Si, Mn, P, S, Al, N, Ti, Nb, and B, with the balance being Fe and inevitable impurities, and satisfying predetermined formula, in which the total area ratio of martensite and bainite is 95% or more, the average grain size of prior austenite grains is 10 μm or less, the B concentration at a prior austenite grain boundary is 0.10% or more in mass %, a C-concentrated region is provided along a martensitic grain boundary, and the C-concentrated region has a C concentration of 4.0 times or more than the C content in the steel, and the C-concentrated region has a concentration width of 3 nm or more and 100 nm or less in a direction perpendicular to the martensitic grain boundary and a length of 100 nm or more in a direction parallel to the martensitic grain boundary.

公开(公告)号：US20220340989A1

公开(公告)日：2022-10-27

申请号：US17636714

申请日：2020-06-19

Applicant: JFE STEEL CORPORATION

Inventor： Yuji TANAKA ,  Hidekazu MINAMI ,  Naoki TAKAYAMA ,  Takako YAMASHITA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/16 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23C2/40 ,  C23C2/28

Abstract: A high-strength cold-rolled steel sheet having a high yield ratio and excellent stretch flangeability and a method for manufacturing the steel sheet. The high-strength cold-rolled steel sheet has a chemical composition including, by mass %, C: 0.10 to 0.30%, Si: 0.50 to 2.00%, Mn: 2.5 to 4.0%, P: 0.050% or less, S: 0.020% or less, Al: 0.10% or less, N: 0.01% or less, Ti: 0.100% or less, and B: 0.0003 to 0.0030%, with the balance being Fe and incidental impurities. N and Ti satisfy a specified formula, and the total area fraction of martensite and bainite is 95% or more. The number density of bainite grains having an area of 3 μm2 or more and a carbon concentration of less than 0.7C is 1200 grains/mm2 or less.

公开(公告)号：US20210381075A1

公开(公告)日：2021-12-09

申请号：US17283840

申请日：2019-08-20

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu MINAMI ,  Yuji TANAKA ,  Junya TOBATA ,  Takeshi YOKOTA

IPC: C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C23G1/00 ,  C23C2/06 ,  C23C2/12 ,  C25D3/22 ,  C25D3/44

Abstract: A high-strength steel sheet having a tensile strength of 1,180 MPa or more, and specified chemical composition. The steel sheet includes a steel structure in which an area fraction of martensite having a carbon concentration of more than 0.7×[% C] and less than 1.5×[% C] is 55% or more, an area fraction of tempered martensite having a carbon concentration of 0.7×[% C] or less is 5% or more and 40% or less, a ratio of a carbon concentration in retained austenite to a volume fraction of retained austenite is 0.05 or more and 0.40 or less, and the martensite and the tempered martensite each have an average grain size of 5.3 μm or less, where [% C] represents the content, by mass %, of compositional element C in steel.

公开(公告)号：US20200040420A1

公开(公告)日：2020-02-06

申请号：US16485083

申请日：2018-02-09

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu MINAMI ,  Fusae SHIIMORI ,  Shinjiro KANEKO ,  Takashi KOBAYASHI ,  Yuji TANAKA

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C21D1/26 ,  C22C38/24 ,  C22C38/60 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

Abstract: There is provided a high-strength steel sheet and a method for producing the same. The high-strength steel sheet has a specified chemical composition and a steel microstructure including, by area fraction, 75.0% or more tempered martensite, 1.0% or more and 20.0% or less fresh martensite, and 5.0% or more and 20.0% or less retained austenite. A hardness ratio of the fresh martensite to the tempered martensite is 1.5 or more and 3.0 or less, the ratio of the maximum KAM value in the tempered martensite in the vicinity of the heterophase interface between the tempered martensite and the fresh martensite to the average KAM value in the tempered martensite is 1.5 or more and 30.0 or less, and the average of ratios of grain sizes of prior austenite grains in the rolling direction to those in the thickness direction is 2.0 or less.

公开(公告)号：US20240368719A1

公开(公告)日：2024-11-07

申请号：US18565265

申请日：2022-03-28

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu MINAMI ,  Masayasu UENO ,  Yuki TOJI ,  Yuji TANAKA ,  Junya TOBATA ,  Kazuki ENDOH

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

Abstract: Provided is a high strength steel sheet with high stretch flangeability and high YR in the rolling direction as well as in the direction orthogonal to the rolling direction with TS of 1180 MPa or more. The high strength steel sheet has a prescribed chemical composition and steel microstructure. In particular, an average grain size of the hard phase is 5.3 μm or less, the volume fraction-carbon concentration ratio of retained austenite (γ) is 0.10 or more and 0.45 or less, and the integration degree of {112} orientation is 1.0 or more.

公开(公告)号：US20220195552A1

公开(公告)日：2022-06-23

申请号：US17593062

申请日：2020-02-21

Applicant: JFE STEEL CORPORATION

Inventor： Hidekazu MINAMI ,  Yuji TANAKA ,  Takeshi YOKOTA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/40 ,  C22C38/38 ,  C22C38/32 ,  C22C38/30 ,  C22C38/28 ,  C22C38/26 ,  C22C38/24 ,  C22C38/22 ,  C22C38/20 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: A high-strength steel sheet comprises: a chemical composition containing C, Si, Mn, P, S, Al, N, Mo, Cr, Ca, and Sb with a balance consisting of Fe and inevitable impurities, wherein [% Si], [% Mn], [% P], [% Mo], and [% Cr] satisfy a predetermined relationship; a steel microstructure that contains ferrite, hard phase, and retained austenite and in which a carbon concentration in the retained austenite is 0.55% or more and 1.10% or less, an amount of diffusible hydrogen in the steel sheet is 0.80 mass ppm or less, a surface layer softening thickness is 5 μm or more and 150 μm or less, and a corresponding grain boundary frequency in a surface layer of the steel sheet after a high-temperature tensile test is 0.45 or less; and a tensile strength of 980 MPa or more.

公开(公告)号：US20190062863A1

公开(公告)日：2019-02-28

申请号：US16075747

申请日：2017-01-12

Applicant: JFE STEEL CORPORATION

Inventor： Yuji TANAKA ,  Sarka MIKMEKOVA ,  Takako YAMASHITA ,  Yoshie OBATA

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C23C2/02 ,  C23C2/40 ,  C23C2/06 ,  B32B15/01 ,  C22C38/04 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00

Abstract: A high-strength cold rolled steel sheet has both high strength, i.e. a tensile strength of 900 MPa or more, and high workability, i.e. a total elongation of 20% or more, and also has a low yield ratio of less than 60%. The high-strength cold rolled steel sheet comprises: a predetermined chemical composition; and a steel structure having, in area ratio, ferrite: 30% to 75%, martensite: 15% to 40%, and retained austenite: 10% to 30%. In the case where a distribution of crystal grain circularity of the retained austenite is represented by a histogram with a class range of more than 0.1×(n−1) and 0.1×n or less and a class value of 0.1×n (n is an integer from 1 to 10), a mode of the crystal grain circularity of the retained austenite is 0.7 or more.

公开(公告)号：US20190048436A1

公开(公告)日：2019-02-14

申请号：US16075750

申请日：2017-01-12

Applicant: JFE STEEL CORPORATION

Inventor： Yuji TANAKA ,  Sarka MIKMEKOVA ,  Takako YAMASHITA ,  Yoshie OBATA

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/06 ,  C22C38/04 ,  C22C38/00 ,  C22C38/02

Abstract: A high-strength cold rolled steel sheet has both high strength, i.e. a tensile strength of 900 MPa or more, and high workability, i.e. a total elongation of 20% or more, and also has a high yield ratio of 60% or more. The high-strength cold rolled steel sheet comprises: a predetermined chemical composition; and a steel structure having, in area ratio, ferrite: 30% to 75%, martensite: 15% to 40%, and retained austenite: 10% to 30%. In the case where a distribution of crystal grain circularity of the retained austenite is represented by a histogram with a class range of more than 0.1×(n−1) and 0.1×n or less and a class value of 0.1×n (n is an integer from 1 to 10), a mode of the crystal grain circularity of the retained austenite is 0.6 or less.

公开(公告)号：US20170336336A1

公开(公告)日：2017-11-23

申请号：US15528330

申请日：2015-03-23

Applicant: JFE STEEL CORPORATION

Inventor： Yuji TANAKA ,  Takako YAMASHITA ,  Masayasu NAGOSHI

IPC: G01N23/225 ,  H01J37/256 ,  H01J37/18 ,  H01J37/28 ,  G01N23/207

CPC classification number: G01N23/2252 ,  G01N23/207 ,  H01J37/18 ,  H01J37/256 ,  H01J37/28 ,  H01J2237/022 ,  H01J2237/2067 ,  H01J2237/2807 ,  H01J2237/2813

Abstract: The present invention makes it possible to analyze trace carbon in a sample without the effects of contamination. In an electron probe microanalyzer, a liquid nitrogen trap and a plasma or oxygen radical generator are jointly used as a means for suppressing contamination, and two or more carbon detection units for detecting characteristic x-rays of carbon in the sample are provided.

公开(公告)号：US20230235421A1

公开(公告)日：2023-07-27

申请号：US18247073

申请日：2021-08-05

Applicant: JFE STEEL CORPORATION

Inventor： Yuji TANAKA ,  Masaki TADA ,  Yuki TOJI ,  Shinsuke KOMINE ,  Yoshie OBATA ,  Yusuke KIMATA

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C23C2/20

CPC classification number: C21D8/0268 ,  C21D9/46 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C21D8/0226 ,  C21D8/0263 ,  C23C2/20 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008

Abstract: A high-strength cold-rolled steel sheet comprises: a chemical composition that contains C, Si, Mn, P, S, N, Al, Ti, Nb, and B with a balance consisting of Fe and inevitable impurities, and satisfies [mol % N]/[mol % Ti]