公开(公告)号：US20220389545A1

公开(公告)日：2022-12-08

申请号：US17295298

申请日：2019-11-20

Applicant: NIPPON STEEL CORPORATION

Inventor： Shohei YABU ,  Kunio HAYASHI ,  Yuji YAMAGUCHI ,  Marina MORI ,  Naoki INOUE ,  Genki ABUKAWA

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

Abstract: A hot-rolled steel sheet includes, as chemical composition, C, Si, Mn, and sol.Al. In the hot-rolled steel sheet, an average of pole densities in crystal orientation group consisting of {110} to {110} in surface region is 0.5 to 3.0, a standard deviation of the pole densities in the crystal orientation group is 0.2 to 2.0, and the tensile strength is 780 to 1370 MPa.

公开(公告)号：US20220259692A1

公开(公告)日：2022-08-18

申请号：US17765697

申请日：2020-10-12

Applicant: NIPPON STEEL CORPORATION

Inventor： Shohei YABU ,  Kunio HAYASHI ,  Koutarou HAYASHI ,  Kazumasa TSUTSUI

IPC: C21D9/46 ,  B21B3/02 ,  C21D6/00 ,  C22C38/38 ,  C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/24 ,  C22C38/22 ,  C22C38/16 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in which a microstructure contains, by area %, bainite: 80.0% or more, ferrite: 10.0% or less, and a remainder in the microstructure: 10.0% or less, a total density of a length L7 of a grain boundary having a crystal orientation difference of 7° and a length L68 of a grain boundary having a crystal orientation difference of 68° about a direction in the bainite is 0.35 to 0.60 μm/μm2, and a tensile strength is 780 MPa or more.

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：US20210230712A1

公开(公告)日：2021-07-29

申请号：US17051110

申请日：2019-04-26

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Kunio HAYASHI ,  Masahiro NAKATA ,  Yuji YAMAGUCHI ,  Satoshi UCHIDA

IPC: C21D9/46 ,  C21D6/00 ,  B32B15/01 ,  C21D1/26 ,  C22C38/38 ,  C22C38/30 ,  C22C38/22 ,  C22C38/16 ,  C22C38/60 ,  C22C38/12 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/26 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: A zinc-plated steel sheet of an aspect of the present invention includes a steel sheet having a predetermined chemical composition and a zinc-plated layer. In the steel sheet, steel microstructures in a range of ⅛ thickness to ⅜ thickness, having the center at ¼ thickness from a steel sheet surface, include, by vol %, ferrite: 0% to 10%, bainite: 0% to 20%, tempered martensite: 70% or more, fresh martensite: 0% to 10%, retained austenite: 0% to 10%, and pearlite: 0% to 5%. In the zinc-plated steel sheet, the amount of hydrogen emitted when the steel sheet is heated to 200° C. from a room temperature after removal of the zinc-plated layer is 0.40 ppm or less per mass of the steel sheet, the tensile strength is 1470 MPa or more, and no cracking occurs in a U-shape bending test where a stress equivalent to 1000 MPa is applied for 24 hours.

公开(公告)号：US20210155999A1

公开(公告)日：2021-05-27

申请号：US17047663

申请日：2019-04-26

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Kunio HAYASHI ,  Masahiro NAKATA ,  Yuji YAMAGUCHI ,  Satoshi UCHIDA

IPC: C21D9/46 ,  C21D1/26 ,  C21D6/00 ,  C23C2/02 ,  C23C2/06 ,  C23C2/40 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C22C38/60 ,  B32B15/01

Abstract: A zinc-plated steel sheet of an aspect of the present invention includes a steel sheet having a predetermined chemical composition and a zinc-plated layer. In the steel sheet, steel microstructures in a range of ⅛ thickness to ⅜ thickness, having the center at ¼ thickness from a steel sheet surface, include, by vol %, ferrite: 0% to 10%, bainite: 0% to 30%, tempered martensite: 50% or more, fresh martensite: 0% to 10%, retained austenite: more than 10% and 30% or less, and pearlite: 0% to 5%. In the zinc-plated steel sheet, the amount of hydrogen emitted when the steel sheet is heated to 200° C. from room temperature after removal of the zinc-plated layer is 0.40 ppm or less per mass of the steel sheet, the tensile strength is 1470 MPa or more, and no cracking occurs in a U-shape bending test where a stress equivalent to 1000 MPa is applied for 24 hours.

公开(公告)号：US20210040588A1

公开(公告)日：2021-02-11

申请号：US16975985

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Yuri TODA ,  Eisaku SAKURADA ,  Kunio HAYASHI ,  Akihiro UENISHI

IPC: C22C38/32 ,  C22C38/28 ,  C22C38/26 ,  C22C38/24 ,  C22C38/22 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/60 ,  C23C2/06 ,  C23C2/12 ,  C23C2/40 ,  C21D9/46

Abstract: A steel sheet has a predetermined chemical composition and a metal structure represented by, in area fraction, polygonal ferrite: 40% or less, martensite: 20% or less, bainitic ferrite: 50% to 95%, and retained austenite: 5% to 50%. In area fraction, 80% or more of the bainitic ferrite is composed of bainitic ferrite grains that have an aspect ratio of 0.1 to 1.0 and have a dislocation density of 8×102 (cm/cm3) or less in a region surrounded by a grain boundary with a misorientation angle of 15° or more. In area fraction, 80% or more of the retained austenite is composed of retained austenite grains that have an aspect ratio of 0.1 to 1.0, have a major axis length of 1.0 μm to 28.0 μm, and have a minor axis length of 0.1 μm to 2.8 μm.

公开(公告)号：US20200325554A1

公开(公告)日：2020-10-15

申请号：US16772692

申请日：2017-12-15

Applicant: NIPPON STEEL CORPORATION

Inventor： Kengo TAKEDA ,  Kunio HAYASHI ,  Akihiro UENISHI ,  Hiroyuki KAWATA ,  Chisato YOSHINAGA ,  Yasunobu MIYAZAKI ,  Toyomitsu NAKAMURA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/38 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: A steel sheet having a chemical composition of the base metal including, in mass %, C: 0.17 to 0.40%, Si: 0.10 to 2.50%, Mn: 1.00 to 10.00%, P: 0.001 to 0.03%, S: 0.0001 to 0.02%, Al: 0.001 to 2.50%, N: 0.0001 to 0.010%, O: 0.0001 to 0.010%, Ti: 0 to 0.10%, Nb: 0 to 0.10%, V: 0 to 0.10%, B: 0 to 0.010%, Cr: 0 to 2.00%, Ni: 0 to 2.00%, Cu: 0 to 2.00%, Mo: 0 to 2.00%, Ca: 0 to 0.50%, Mg: 0 to 0.50%, REM: 0 to 0.50%, the balance: Fe and impurities, wherein the steel sheet has an internal oxidized layer in which at least one part of a crystal grain boundary is covered by oxides, and in which a grain boundary coverage ratio of oxides is 60% or more in a region from the surface of the base metal to a depth of 5.0 μm.