公开(公告)号：US20230141963A1

公开(公告)日：2023-05-11

申请号：US17915354

申请日：2021-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Yasuaki TANAKA ,  Hitoshi NIKAIDO ,  Hiroyuki KAWATA ,  Natsuko SUGIURA

IPC: C22C38/58 ,  C22C38/50 ,  C22C38/48 ,  C22C38/42 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00

CPC classification number: C22C38/58 ,  C22C38/50 ,  C22C38/48 ,  C22C38/42 ,  C22C38/06 ,  C22C38/02 ,  C22C38/002

Abstract: There is provided a steel sheet including a chemical composition consisting of, in mass %: C: 0.03 to 0.25%, Si: 0.1 to 2.0%, Mn: 1.0 to 3.0%, P: 0.200% or less, S: 0.0500% or less, Al: 0.01 to 1.00%, N: 0.0100% or less, and Ti: 0.01 to 0.25%, with the balance: Fe and impurities, and a steel micro-structure containing, in area %: ferrite: 50 to 85%, the balance being one or more kinds selected from martensite, bainite, and retained austenite, and an intensity of γ-fiber is more than 4.0 times in terms of random intensity ratio, and an average KAM value of grains having crystal orientations that form angles within 10° from γ-fiber is 1.30° or less.

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：US20220074015A1

公开(公告)日：2022-03-10

申请号：US17419557

申请日：2020-01-07

Applicant: NIPPON STEEL CORPORATION

Inventor： Masahiro KUBO ,  Hiroyuki KAWATA ,  Masahiro SAITO ,  Kenichiro OTSUKA ,  Masafumi AZUMA

IPC: C21D9/46 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/44 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C21D1/18 ,  B32B15/01

Abstract: A steel sheet has a predetermined chemical composition, in which a metallographic structure in a surface layer region ranging from a surface to a position of 20 μm from the surface in a sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 1.0% to 15.0%, the metallographic structure in an internal region ranging from a position of more than 20 μm from the surface in the sheet thickness direction to a ¼ thickness position from the surface in the sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 5.0% to 25.0%, the volume fraction of the secondary phase in the surface layer region is less than the volume fraction of the secondary phase in the internal region, and in the surface layer region, the average grain size of the secondary phase is 0.5 μm to 4.0 μm, and a texture in which an XODF{001}/{111} as the ratio of the intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.70 to 2.50 is included.

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：US20220316020A1

公开(公告)日：2022-10-06

申请号：US17420088

申请日：2020-01-07

Applicant: NIPPON STEEL CORPORATION

Inventor： Masahiro KUBO ,  Hiroyuki KAWATA ,  Masahiro SAITO ,  Kenichiro OTSUKA ,  Masafumi AZUMA

IPC: C21D8/02 ,  C22C38/54 ,  C22C38/14 ,  C22C38/12 ,  C22C38/04

Abstract: A steel sheet has a predetermined chemical composition, in which a metallographic structure in a surface layer region ranging from a surface to a position of 20 μm from the surface in a sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 0.01% to 5.0%, a metallographic structure in an internal region ranging from a position of more than 20 μm from the surface in the sheet thickness direction to a ¼thickness position from the surface in the sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 2.0% to 10.0%, the volume fraction of the secondary phase in the surface layer region is less than the volume fraction of the secondary phase in the internal region, and in the surface layer region, an average grain size of the secondary phase is 0.01 μm to 4.0 μm, and a texture in which an XODF{001}/{111} as the ratio of the intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.60 or more and less than 2.00 is included.

公开(公告)号：US20220127709A1

公开(公告)日：2022-04-28

申请号：US17427680

申请日：2020-02-06

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Hiroyuki KAWATA ,  Kunio HAYASHI ,  Yuji YAMAGUCHI ,  Satoshi UCHIDA

IPC: C23C2/40 ,  C21D9/46 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/52 ,  C22C38/54 ,  C22C38/60 ,  C23C2/06 ,  C23C2/28

Abstract: Provided are a hot dip galvanized steel sheet comprising a base steel sheet wherein the base steel sheet has a predetermined chemical composition, and contains ferrite: 50% or less, retained austenite: 30% or less, tempered martensite: 5% or more, fresh martensite: 10% or less, and pearlite and cementite in total: 5% or less, remaining structures consist of bainite, and a number ratio of tempered martensite with a Mn concentration profile satisfying [Mn]b/[Mn]a>1.2 and [Mn]a/[Mn]

公开(公告)号：US20220090248A1

公开(公告)日：2022-03-24

申请号：US17425234

申请日：2020-02-06

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Hiroyuki KAWATA ,  Kunio HAYASHI ,  Yuji YAMAGUCHI ,  Satoshi UCHIDA

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

Abstract: Provided are a hot dip galvanized steel sheet comprising a base steel sheet wherein the base steel sheet has a predetermined composition and contains ferrite: 0% to 50%, retained austenite: 0% to 30%, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, remaining structures consist of bainite, when defining a region having a hardness of 90% or less of the hardness at a position of ¼ thickness to the base steel sheet side from an interface of the base steel sheet and a hot dip galvanized layer as a “soft layer”, there is a soft layer having a thickness of 10 μm or more at the base steel sheet side from the interface, the soft layer contains tempered martensite, and an increase rate in a thickness direction of an area % of tempered martensite from the interface to the inside of the base steel sheet inside the soft layer is 5.0%/pm or less, and a method for producing the same.

公开(公告)号：US20220001929A1

公开(公告)日：2022-01-06

申请号：US17292945

申请日：2019-11-12

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroaki KUBOTA ,  Yuri TODA ,  Hiroyuki KAWATA

IPC: B62D21/15 ,  B62D25/02 ,  B62D25/04 ,  B62D25/20

Abstract: The frame member has a flat sheet portion with a recessed portion having a pair of wall portions and a bottom portion extending between tip portions in an extending direction of the pair of wall portions, in which a Vickers hardness of a region of the flat sheet portion excluding the recessed portion is 330 Hv or more, a depth of the recessed portion is 5 mm or more, when a width of the recessed portion is L0 and a cross-sectional length of an inner peripheral wall of the recessed portion consisting of the pair of wall portions and the bottom portion is L1, a value of (L1−L0)/L0 is 0.18 or more and 2.8 or less, and a Vickers hardness of a ridgeline portion extending between the flat sheet portion and the recessed portion is 1.06 times or more and 1.20 times or less the Vickers hardness of the region of the flat sheet portion excluding the recessed portion.

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：US20210070368A1

公开(公告)日：2021-03-11

申请号：US16965922

申请日：2019-10-09

Applicant: NIPPON STEEL CORPORATION

Inventor： Yuri TODA ,  Hiroaki KUBOTA ,  Hiroyuki KAWATA ,  Daisuke MAEDA

IPC: B62D21/15

Abstract: In a frame member, the hardness of a sheet-thickness-direction central section in a portion where a softening layer is provided is greater than or equal to 400 Hv, the softening layer has hardness smaller by at least 10 Hv than the hardness of the sheet-thickness-direction central section in the portion where the softening layer is provided, the thickness of the softening layer is greater than or equal to 2% of the sheet thickness but smaller than 20% of the sheet thickness, the hardness of the softening layer at the surface is greater than or equal to 0.5 times the hardness of the sheet-thickness-direction central section but smaller than 0.9 times the hardness of the sheet-thickness-direction central section, the softening layer has a first hardness changing area and a second hardness changing area, an absolute value ΔHv1 of a change in hardness of the first hardness changing area in the sheet thickness direction is greater than an absolute value ΔHv2 of a change in hardness of the second hardness changing area in the sheet thickness direction, and R/t≤2.5 is satisfied, where R represents the bending radius of the corner section, and t represents the sheet thickness of the corner section.