公开(公告)号：US20220145417A1

公开(公告)日：2022-05-12

申请号：US17434981

申请日：2020-03-12

Applicant: NIPPON STEEL CORPORATION

Inventor： Kengo TAKEDA ,  Hitoshi NIKAIDO ,  Hiroyuki KAWATA ,  Takafumi YOKOYAMA

IPC: C21D9/46 ,  C22C38/58 ,  C22C38/54 ,  C22C38/52 ,  C22C38/50 ,  C22C38/48 ,  C22C38/44 ,  C22C38/10 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: Provided are: a steel sheet having a high strength and excellent stretch formability; and a method of producing the same. The steel sheet has prescribed chemical composition and structure, in which the integration degree of the (111) orientation of ferrite is 3.0 or higher, and the integration degree of the (252) orientation of martensite and tempered martensite is 5.0 or lower. The method of producing the steel sheet includes: the step of continuously casting a molten steel having the prescribed chemical composition, and performing 5 to 40% rolling reduction at a temperature of 800° C. to lower than 1,200° C. in a period after the continuous casting until cooling to room temperature; the hot rolling step of performing hot rolling with a finishing temperature of 650 to 950° C.; the step of coiling the resulting hot-rolled steel sheet at a coiling temperature of 400 to 700° C.; the step of retaining the hot-rolled steel sheet at (coiling start temperature+20° C. to 100° C.) for 5 to 300 minutes; the step of cold rolling the hot-rolled steel sheet at a rolling reduction ratio of 10.0 to 90.0%; and the step of annealing the resulting cold-rolled steel sheet at 700 to 900° C.

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.