公开(公告)号：US20230265548A1

公开(公告)日：2023-08-24

申请号：US18009852

申请日：2021-08-10

Applicant: NIPPON STEEL CORPORATION

Inventor： Takeshi TOYODA ,  Eisaku SAKURADA

IPC: C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/46 ,  C21D9/46 ,  C21D8/02 ,  C21D6/00

CPC classification number: C22C38/54 ,  C21D6/004 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0226 ,  C21D9/46 ,  C22C38/001 ,  C22C38/02 ,  C22C38/002 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008

Abstract: Provided is a hot rolled steel sheet having a tensile strength of 780 MPa or more, a sheet thickness of 1.2 to 4.0 mm, and a sheet width of 750 mm or more, and satisfying -15≤(λW 1 +λW2)/2-λC ≤15 (where λW1 and λW2 respectively indicate hole expansion ratios (%) at ⅛ positions of the sheet width from one end of the hot rolled steel sheet in a sheet width direction perpendicular to a rolling direction and the other end at an opposite side, and λC indicates a hole expansion ratio (%) of a sheet width center part).

公开(公告)号：US20220372588A1

公开(公告)日：2022-11-24

申请号：US17767229

申请日：2020-12-08

Applicant: NIPPON STEEL CORPORATION

Inventor： Daisuke ITO ,  Shohei YABU ,  Takeshi TOYODA

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/28 ,  C22C38/32

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a ¼ position of a sheet thickness in a sheet thickness direction from a surface, a primary phase is bainite, a secondary phase is martensite or a martensite-austenite mixed phase, an average grain size of the secondary phase is 1.5 μm or less, an average grain size of particles having grain diameters that are largest 10% or less out of all particles in the secondary phase is 2.5 μm or less, a pole density in a (110) orientation is 3.0 or less, and, in a microstructure from the surface to a 1/16 position of the sheet thickness in the sheet thickness direction from the surface, a pole density in a (110) orientation is 3.0 or less.

公开(公告)号：US20220112574A1

公开(公告)日：2022-04-14

申请号：US17429565

申请日：2020-03-19

Applicant: NIPPON STEEL CORPORATION

Inventor： Masafumi AZUMA ,  Eisaku SAKURADA ,  Genki ABUKAWA ,  Kenichiro OTSUKA ,  Takeshi TOYODA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/38 ,  C22C38/28 ,  C22C38/26 ,  C22C38/24 ,  C22C38/16 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23C2/40

Abstract: A high-strength steel sheet includes a predetermined chemical composition, a microstructure contains, by volume percentage, 80% or more of tempered martensite, and a remainder consists of ferrite and bainite, the microstructure contains 5.0×1011 pieces/mm3 or more of, per unit volume, precipitate containing Ti and having an equivalent circle diameter of 5.0 nm or less, Hvs/Hvc which is a ratio of an average hardness Hvs at a position of a depth of 20 μm from a surface to an average hardness Hvc at a position of 0.20 to 0.50 mm from the surface is 0.85 or more, and the tensile strength is 1,180 MPa or more.

公开(公告)号：US20210025019A1

公开(公告)日：2021-01-28

申请号：US16648976

申请日：2018-11-22

Applicant: NIPPON STEEL CORPORATION

Inventor： Tetsuya HIRASHIMA ,  Takeshi TOYODA

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

Abstract: Provided is a hot rolled steel sheet comprising a predetermined composition wherein the hot rolled steel sheet comprises ferrite with an average orientation difference in the same grain of 0.5 to 5.0° in 30 to 70 vol %, the ferrite and martensite in a total of 90 vol % or more, and a balance microstructure of 10 vol % or less, has an average grain size of the ferrite of 0.5 to 5.0 μm, and has an average grain size of the martensite and the balance microstructure of 1.0 to 10 μm. Provided is a method for producing a hot rolled steel sheet comprising rolling where two or more consecutive passes of rolling including a final pass are performed under conditions of a rolling temperature: A point or more and less than Ae3 point, a strain rate: 1.0 to 50/sec, and a time between passes: within 10 seconds and where a total strain amount of all passes satisfying the conditions is 1.4 to 4.0, cooling by a 20° C./sec or more average cooling rate, and coiling the steel sheet at room temperature or more and less than 300° C.

公开(公告)号：US20240384381A1

公开(公告)日：2024-11-21

申请号：US18285546

申请日：2022-04-12

Applicant: NIPPON STEEL CORPORATION

Inventor： Takeshi TOYODA ,  Hiroshi SHUTO

IPC: C22C38/38 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/22 ,  C22C38/24 ,  C22C38/28

Abstract: This hot-rolled steel sheet has a predetermined chemical composition and microstructure, in which, within regions obtained by dividing a sheet thickness cross section parallel to a rolling direction into three parts in a sheet thickness direction, when a pole density of the {001} plane of ferrite and bainite in a center region is Pi, and a pole density of the {001} plane of ferrite and bainite in a surface layer region is Ps, Pi/Ps is 1.2 to 2.0, and a tensile strength is 950 MPa or more.

公开(公告)号：US20220186333A1

公开(公告)日：2022-06-16

申请号：US17430651

申请日：2020-03-19

Applicant: NIPPON STEEL CORPORATION

Inventor： Masafumi AZUMA ,  Eisaku SAKURADA ,  Genki ABUKAWA ,  Kenichiro OTSUKA ,  Takeshi TOYODA

IPC: C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/48 ,  C22C38/50 ,  C22C38/46 ,  C22C38/54 ,  C21D8/02 ,  B21C47/02 ,  C23G1/00 ,  C23C2/40

Abstract: A high-strength steel sheet includes a predetermined chemical composition, a microstructure contains, by volume percentage, 95% or more of tempered martensite and bainite in total, and a remainder consists of ferrite and pearlite, the microstructure contains 5.0×109 pieces/mm or more of, per unit volume, precipitate having an equivalent circle diameter of 5.0 nm or less and containing Ti, Hvs/Hvc which is a ratio of an average hardness Hvs at a position of a depth of 20 μm from a surface to an average hardness Hvc at a position of 0.20 to 0.50 mm from the surface is 0.85 or more, a tensile strength is 980 MPa or more, and a product of the tensile strength and elongation is 12,000 MPa×% or more.

公开(公告)号：US20220090224A1

公开(公告)日：2022-03-24

申请号：US17420024

申请日：2019-12-24

Applicant: NIPPON STEEL CORPORATION

Inventor： Takeshi TOYODA ,  Hitoshi NIKAIDO ,  Kohei NAKADA ,  Yui YAMASHITA ,  Kazuki MATSUDA

IPC: C21D9/46 ,  C21D9/50 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/50 ,  B23K9/16 ,  C22C38/58 ,  C22C38/54 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42

Abstract: Hot-rolled steel sheet having a chemical composition including, in mass %, C: 0.02 to 0.20%, Si: 0.01 to 1.50%, Mn: 0.10 to 3.00%, P: 0.10% or less, S: 0.010% or less, Al: 0.005 to 0.100%, Ti: 0.02 to 0.20%, N: 0.001 to 0.010%, Cu: 0 to 0.50%, Ni: 0 to 0.50%, Cr: 0 to 1.00%, Mo: 0 to 0.40%, Nb: 0 to 0.060%, V: 0 to 1.00%, B: 0 to 0.0100%, Ca: 0 to 0.0050%, O: 0.0100% or less, and the balance: Fe and impurities; in which: a steel micro-structure includes, in area %, ferrite: 60 to 80%, and a total of ferrite and bainite: 90% or more; an average of the crystal grain size of ferrite and bainite is 7.0 μm or less, a standard deviation of the crystal grain size is 2.0 or less; and a standard deviation of a diameter of Ti carbo-nitrides is 10 nm or less.

公开(公告)号：US20210062289A1

公开(公告)日：2021-03-04

申请号：US17048430

申请日：2019-04-26

Applicant: NIPPON STEEL CORPORATION

Inventor： Tetsuya HIRASHIMA ,  Takeshi TOYODA

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

Abstract: In a hot-rolled steel sheet having a predetermined chemical composition and having a metallographic structure including 90 vol % or greater of martensite and 0 vol % to 10 vol % of a residual structure, the residual structure includes one or both of bainite and ferrite, the average prior austenite grain size in an L-section parallel to a rolling direction and an average prior austenite grain size in a C-section parallel to a direction orthogonal to the rolling direction are 1.0 μm to 10.0 μm the aspect ratio associated with the prior austenite grain size is 1.8 or less, the average grain size of the residual structure in the L-section and the average grain size of the residual structure in the C-section are 5.0 μm or less, and the aspect ratio associated with the average grain size of the residual structure is 2.0 or less.