公开(公告)号：US20210123122A1

公开(公告)日：2021-04-29

申请号：US17041372

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Kohichi SANO ,  Riki OKAMOTO ,  Hiroyuki KAWATA ,  Eisaku SAKURADA ,  Yuji YAMAGUCHI ,  Kazuki SHIOKAWA ,  Yuichi NAKAHIRA ,  Kohei UEDA ,  Masahiro NAKATA ,  Satoshi UCHIDA

IPC: C22C38/58 ,  C22C38/54 ,  C22C38/52 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/02 ,  C22C38/00 ,  C22C38/06 ,  C21D9/46 ,  C23C2/06 ,  C23C2/40 ,  C21D8/02 ,  C21D9/00

Abstract: This steel sheet has a predetermined chemical composition, in which a steel structure of an inside of the steel sheet contains, by volume fraction, soft ferrite: 0% to 30%, retained austenite: 3% to 40%, fresh martensite: 0% to 30%, a sum of pearlite and cementite: 0% to 10%, and a remainder includes hard ferrite, in the inside of the steel sheet, a number proportion of the retained austenite having an aspect ratio of 2.0 or more in the total retained austenite is 50% or more, a soft layer having a thickness of 1 to 100 μm from a surface in a sheet thickness direction is present, in ferrite contained in the soft layer, a volume fraction of grains having an aspect ratio of less than 3.0 is 50% or more, the volume fraction of retained austenite in the soft layer is less than 50% of the volume fraction of the retained austenite of the inside of the steel sheet, and a peak of an emission intensity at a wavelength indicating Si appears in a range of more than 0.2 μm and 5.0 μm or less from the surface.

公开(公告)号：US20210340653A1

公开(公告)日：2021-11-04

申请号：US17312853

申请日：2018-12-11

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroyuki KAWATA ,  Eisaku SAKURADA ,  Kohichi SANO ,  Takafumi YOKOYAMA

IPC: C22C38/58 ,  C22C38/02 ,  C22C38/00 ,  C22C38/06 ,  C22C38/50 ,  C22C38/42 ,  C22C38/46 ,  C22C38/48 ,  C22C38/44 ,  C22C38/54 ,  C21D8/02 ,  C21D9/46 ,  C23C2/06 ,  C23C2/40

Abstract: A high-strength steel sheet excellent in formability, toughness and weldability has a chemical composition including: by mass %, C: 0.05 to 0.30%, Si: 2.50% or less, Mn: 0.50 to 3.50%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance consisting of Fe and inevitable impurities. The high-strength steel sheet has a microstructure in a region from ⅛t (t: sheet thickness) to ⅜t (t: sheet thickness) from a steel sheet surface, the microstructure including: by volume %, acicular ferrite (3): 20% or more, and martensite (4):10% or more, aggregated ferrite: 20% or less, residual austenite: 2.0% or less, and the martensite satisfies a formula (A), ∑ i = 1 5 ⁢ ⁢ d i a i 1.5 ≤ 10.0 ( A )

公开(公告)号：US20220119909A1

公开(公告)日：2022-04-21

申请号：US17432016

申请日：2020-04-08

Applicant: NIPPON STEEL CORPORATION

Inventor： Kohichi SANO ,  Hiroyuki KAWATA

IPC: C21D9/46 ,  B32B15/01 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C22C38/54 ,  C22C38/50 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/38 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: A steel sheet of the present invention is a steel sheet having a predetermined chemical composition and containing at least ferrite, residual austenite, and/or martensite in a microstructure, and furthermore, is a steel sheet in which, in a plane parallel to a rolled surface, an average distance between centers of high Mn regions adjacent to each other is 1.00 mm or less, a density DA of the high Mn regions at a sheet width center portion and a density DB of the high Mn regions at a ¼ position from a sheet width end portion satisfy a relationship of 0.77≤DA/DB≤1.30, a ratio of an average hardness of the high Mn regions to an average hardness of the low Mn regions is 1.1 to 2.0, and a difference between an average of a top 5% and an average of a bottom 5% of Mn contents in the low Mn regions is 0.3% or more.

公开(公告)号：US20210017620A1

公开(公告)日：2021-01-21

申请号：US16982003

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Riki OKAMOTO ,  Kohichi SANO ,  Hiroyuki KAWATA ,  Kohei UEDA ,  Eisaku SAKURADA

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C23C2/06 ,  C23C2/40 ,  C22C38/18 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/60 ,  C22C38/00 ,  B32B15/01

Abstract: This steel sheet has a predetermined chemical composition, in which a steel structure of an inside of the steel sheet contains, by volume fraction, soft ferrite: 0% to 30%, retained austenite: 3% to 40%, fresh martensite: 0% to 30%, a sum of pearlite and cementite: 0% to 10%, and a remainder includes hard ferrite, a number proportion of the retained austenite having an aspect ratio of 2.0 or more in the total retained austenite is 50% or more, a soft layer having a thickness of 1 to 100 μm from a surface in a sheet thickness direction is present, in ferrite contained in the soft layer, a volume fraction of grains having an aspect ratio of 3.0 or more is 50% or more, a volume fraction of retained austenite in the soft layer is 80% or less of the volume fraction of the retained austenite in the inside of the steel sheet, and a peak of an emission intensity at a wavelength indicating Si appears in a range of more than 0.2 μm and 10.0 μm or less from the surface.

公开(公告)号：US20220127691A1

公开(公告)日：2022-04-28

申请号：US17312871

申请日：2018-12-11

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroyuki KAWATA ,  Eisaku SAKURADA ,  Kohichi SANO ,  Takafumi YOKOYAMA

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

Abstract: A high-strength steel sheet includes a chemical composition including: by mass %, C: 0.080 to 0.500%, Si: 2.50% or less, Mn: 0.50 to 5.00%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance: Fe and inevitable impurities. The high-strength steel sheet satisfying a predetermined formula has a microstructure in a region from ⅛t to ⅜t from a steel sheet surface. The microstructure includes: by volume %, 20% or more of acicular ferrite, 20% or more of an island-shaped hard structure including residual austenite, 2% to 25% of residual austenite, and 20% or less of aggregated ferrite.

公开(公告)号：US20210095356A1

公开(公告)日：2021-04-01

申请号：US16981653

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Kohichi SANO ,  Riki OKAMOTO ,  Hiroyuki KAWATA ,  Eisaku SAKURADA ,  Yuji YAMAGUCHI ,  Kazuki SHIOKAWA ,  Yuichi NAKAHIRA ,  Kohei UEDA ,  Masahiro NAKATA ,  Satoshi UCHIDA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/18 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23C2/40 ,  C23C2/28

Abstract: A steel sheet according to an aspect of the present invention has a predetermined chemical composition, in which a steel structure of an inside of the steel sheet contains, by volume fraction, soft ferrite: 0% to 30%, retained austenite: 3% to 40%, fresh martensite: 0% to 30%, a sum of pearlite and cementite: 0% to 10%, and a remainder including hard ferrite, in the inside of the steel sheet, a number proportion of the retained austenite having an aspect ratio of 2.0 or more in the total retained austenite is 50% or more, a soft layer having a thickness of 1 μm to 100 μm from the surface is present in a sheet thickness direction, among ferrite contained in the soft layer, a volume fraction of grains having an aspect ratio of less than 3.0 is 50% or more, a volume fraction of retained austenite in the soft layer is 50% or more of the volume fraction of the retained austenite of the inside of the steel sheet, and a peak of an emission intensity at a wavelength indicating Si appears in a range of more than 0.2 μm from the surface to 5 μm or less from the surface.

公开(公告)号：US20210047716A1

公开(公告)日：2021-02-18

申请号：US17043283

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Kohichi SANO ,  Hiroyuki KAWATA ,  Yuji YAMAGUCHI ,  Satoshi UCHIDA ,  Yoshinori IMAI ,  Riki OKAMOTO

IPC: C22C38/60 ,  B32B15/01 ,  C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/58 ,  C22C38/48 ,  C22C38/44 ,  C22C38/14 ,  C22C38/12 ,  C22C38/16 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/08 ,  C23C2/28 ,  C23C2/40 ,  C23C2/06

Abstract: A steel sheet includes a hot-dip galvanized layer or a galvannealed layer on a surface of the steel sheet, the steel sheet including: in mass %, C: 0.06% or more and 0.22% or less; Si: 0.50% or more and 2.00% or less; Mn: 1.50% or more and 2.80% or less; Al: 0.02% or more and 1.00% or less; P: 0.001% or more and 0.100% or less; S: 0.0005% or more and 0.0100% or less; N: 0.0005% or more and 0.0100% or less; and a balance: Fe and impurities.

公开(公告)号：US20220186337A1

公开(公告)日：2022-06-16

申请号：US17600021

申请日：2020-04-08

Applicant: NIPPON STEEL CORPORATION

Inventor： Kohichi SANO ,  Hiroyuki KAWATA ,  Kengo TAKEDA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/18 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: This steel sheet has a predetermined chemical composition, in which the area ratio of plate martensite is 10% or more, the average grain size of prior austenite grains is 2.0 μm to 10.0 μm, the maximum diameter thereof is 20.0 μm or less, the amount of solid solution C in martensite is 0.20 mass % or less, the average carbide size is 0.25 μm or less, the crystal orientation difference between plate martensite and another martensite adjacent thereto in the same prior austenite grain is 10.0° or less, and the P concentration at grain boundaries of the prior austenite grains is 4.0 at % or less.

公开(公告)号：US20210017622A1

公开(公告)日：2021-01-21

申请号：US17043267

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Jun HAGA ,  Kohichi SANO ,  Koutarou HAYASHI ,  Kunio HAYASHI ,  Masaharu KAMEDA ,  Akihiro UENISHI ,  Hiroyuki KAWATA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/38 ,  C22C38/32 ,  C22C38/22 ,  C22C38/16 ,  C22C38/14 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D6/00 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: A hot dip galvanized steel sheet and hot dip galvannealed steel sheet improved in uniform ductility and local ductility, yield strength and tensile strength, and low temperature impact property, characterized by having a predetermined chemical composition, having a metal structure containing, by volume %, retained austenite: over 5.0% and tempered martensite: over 5.0%, having retained austenite containing C: 0.85 mass % or more, and having a ratio [C]γgb/[P]γgb of an amount of segregation of C (number of atoms/nm2): [C]γgb to an amount of segregation of P (number of atoms/nm2): [P]γgb at prior austenite grain boundaries of 4.0 or more.

公开(公告)号：US20200087764A1

公开(公告)日：2020-03-19

申请号：US16466981

申请日：2016-12-05

Applicant: NIPPON STEEL CORPORATION

Inventor： Kohichi SANO ,  Riki OKAMOTO

IPC: C22C38/42 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/60 ,  C21D9/46 ,  C22C38/44 ,  C22C38/50 ,  C22C38/58

Abstract: A high-strength steel sheet has a chemical composition consisting of, in mass percent, C: 0.10 to 0.24%, Mn: 3.50 to 12.00%, Si: 0.005 to 5.00%, Al: 0.005 to 5.00%, P: 0.15% or less, S: 0.030% or less, N: 0.020% or less, O: 0.010% or less, Cr: 0 to 5.00%, Mo: 0 to 5.00%, Ni: 0 to 5.00%, Cu: 0 to 5.00%, Nb: 0 to 0.50%, Ti: 0 to 0.50%, W: 0 to 0.50%, B: 0 to 0.010%, Ca: 0 to 0.05%, Mg: 0 to 0.05%, Zr: 0 to 0.05%, REM: 0 to 0.05%, Sb: 0 to 0.50%, Sn: 0 to 0.50%, As: 0 to 0.05%, and V: 0 to 2.0%, with the balance: Fe and impurities, and a steel micro-structure at a ¼ sheet-thickness position includes, in area percent, retained austenite: 10.0 to 55.0%, high temperature tempered martensite: 30.0 to 75.0%, and low temperature tempered martensite: 15.0 to 60.0%, with the balance including fresh martensite: 0 to 10.0%, pearlite: 0 to 5.0%, and bainite: 0 to 5.0%.