公开(公告)号：US20230399712A1

公开(公告)日：2023-12-14

申请号：US18033729

申请日：2021-08-31

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Yusuke TSUNEMI ,  Tatsuya OBUCHI ,  Akinobu MINAMI ,  Takuya KUWAYAMA

IPC: C21D9/46 ,  C22C38/58 ,  C22C38/50 ,  C22C38/42 ,  C22C38/38 ,  C22C38/28 ,  C22C38/14 ,  C22C38/12 ,  C22C38/60 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C21D1/18

CPC classification number: C21D9/46 ,  C22C38/58 ,  C22C38/50 ,  C22C38/42 ,  C22C38/38 ,  C22C38/28 ,  C22C38/14 ,  C22C38/12 ,  C22C38/60 ,  C22C38/10 ,  C22C38/08 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/008 ,  C22C38/005 ,  C22C38/002 ,  C22C38/001 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0278 ,  C21D6/001 ,  C21D6/002 ,  C21D6/004 ,  C21D6/005 ,  C21D6/007 ,  C21D6/008 ,  C21D1/18 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/003 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/009 ,  C23C2/06

Abstract: Provided are a steel sheet having a predetermined chemical composition, and a steel microstructure comprising, by vol %, ferrite: 1 to 50%, ratio of nonrecrystallized ferrite in the ferrite: 0 to 50%, tempered martensite: 1% or more, retained austenite: 5% or more, fresh martensite: 0 to 10%, total of pearlite and cementite: 0 to 5%, and balance: bainite, and, when analyzing the surface by an EPMA, an area ratio of regions with an AlS/SiS ratio of 0.2 or less is 50% or less, and a tensile strength is 980 MPa or more, and a method for producing the same.

公开(公告)号：US20220275493A1

公开(公告)日：2022-09-01

申请号：US17634229

申请日：2020-09-03

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Kazuki SHIOKAWA ,  Tatsuya OBUCHI ,  Kunio HAYASHI

IPC: C22C38/60 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/44 ,  C22C38/42 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/08 ,  C22C38/04 ,  C22C38/02 ,  C22C38/06 ,  C22C38/00 ,  C22C38/10 ,  C21D9/46 ,  C21D8/02

Abstract: Provided are a steel sheet having a predetermined chemical composition and having the following steel structure, and a method of manufacturing the steel sheet.
(1) In area ratio %, ferrite: 0 to 5%, martensite: 90 to 100%, a ratio of tempered martensite to total martensite: 80 to 100%, and retained austenite: 0.5 to 6.0% are contained.
(2) The number density of inclusions satisfying the maximum diameter≥3 μm is 40 inclusions/mm2 or less.
(3) When the number density of the inclusions satisfying the maximum diameter≥3 μm in each section is calculated, the number density in the section where the number density of inclusions is in the top 10% is 80 inclusions/mm2 or less.
(4) Formula (A) is satisfied. Vγ′/Vγ≥0.1  (A) Vγ: Initial retained austenite, Vγ′: Retained austenite after deep cooling at −196° C.
(5) The tensile strength is 1470 MPa or more.

公开(公告)号：US20240327962A1

公开(公告)日：2024-10-03

申请号：US18711903

申请日：2022-11-29

Applicant: NIPPON STEEL CORPORATION

Inventor： Takafumi YOKOYAMA ,  Chisato YOSHINAGA ,  Takuya KUWAYAMA ,  Kengo TAKEDA ,  Takuya MITSUNOBU ,  Seiji FURUSAKO ,  Tatsuya OBUCHI

IPC: C22C38/04 ,  C21D6/00 ,  C21D8/02 ,  C22C38/02 ,  C22C38/06 ,  C23C2/06 ,  C23C2/20 ,  C23C2/28 ,  C23C2/40

CPC classification number: C22C38/04 ,  C21D6/005 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C22C38/02 ,  C22C38/06 ,  C23C2/06 ,  C23C2/20 ,  C23C2/28 ,  C23C2/40 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/003 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/009

Abstract: Provided are a hot dip galvanized steel sheet having a predetermined chemical composition, and a steel microstructure comprising, by vol %, ferrite: 0 to 50%, tempered martensite: 1% or more, retained austenite: 5% or more, fresh martensite: 0 to 15%, total of pearlite and cementite: 0 to 5%, and balance: bainite, when measuring by GDS, a maximum value of Al concentration of an Al rich layer present at an interface of the base steel sheet and the hot dip galvanized layer is 2.0 mass % or more and an Sis/Sib right under the interface is 0.90 or less, a number density of recessed parts with a depth of more than 2 μm at the interface is 2.0/100 μm or less per interface length, and a tensile strength is 980 MPa or more, and a method for producing the same.