公开(公告)号：US20250144736A1

公开(公告)日：2025-05-08

申请号：US18833901

申请日：2023-02-07

Applicant: NIPPON STEEL CORPORATION

Inventor： Shinji KODAMA ,  Seiji FURUSAKO ,  Chisato YOSHINAGA ,  Takuya KUWAYAMA ,  Kengo TAKEDA ,  Takuya MITSUNOBU ,  Hironori SATO

IPC: B23K11/11 ,  B23K11/31 ,  B23K103/04

Abstract: This spot welding device is a spot welding device for performing spot welding on a plurality of steel sheets overlapping with each other by clamping the plurality of steel sheets between a pair of electrodes, and energizing the plurality of steel sheets while pressurizing the plurality of steel sheets, in which a speed at which the pair of electrodes approach each other is limited to at least 12.0 mm/s or slower during a period from start of the energization to end of the energization.

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.

公开(公告)号：US20230304119A1

公开(公告)日：2023-09-28

申请号：US18020841

申请日：2021-10-15

Applicant: NIPPON STEEL CORPORATION

Inventor： Takuya KUWAYAMA ,  Kunio HAYASHI ,  Takafumi YOKOYAMA

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

CPC classification number: C21D9/46 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/001 ,  C22C38/002 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C23C2/40 ,  C23C2/06 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/009

Abstract: This steel sheet has a predetermined chemical composition, in which a microstructure at a ¼ depth position of a sheet thickness from a surface of the steel sheet contains, by volume fraction, ferrite: 0% to 50%, residual austenite: 6% to 30%, bainite: 5% to 60%, tempered martensite: 5% to 50%, fresh martensite: 0% to 10%, and pearlite: 0% to 5%, at the ¼ depth position of the sheet thickness from the surface, a number proportion of the residual austenite having an aspect ratio of 2.0 or more to an entire residual austenite is 50% or more, and a number density of inclusions and precipitates having a grain size of 1 μm or more is 30/mm2 or less, and at a 1/20 depth position of the sheet thickness from the surface, an average interval between Mn-concentrated portions in a direction perpendicular to a rolling direction is 300 μm or less, and a standard deviation of Mn concentrations in the residual austenite is 0.40% or less.

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：US20230304112A1

公开(公告)日：2023-09-28

申请号：US18007621

申请日：2021-07-09

Applicant: NIPPON STEEL CORPORATION

Inventor： Shohei YABU ,  Kazumasa TSUTSUI ,  Takuya KUWAYAMA

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/52 ,  C22C38/54

CPC classification number: C21D8/0226 ,  C21D9/46 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/52 ,  C22C38/54 ,  C21D2211/005

Abstract: This hot rolled steel sheet has a predetermined chemical composition, in which the microstructure contains, by area%, polygonal ferrite: 2.0% or more and less than 10.0% and the remainder in the microstructure: more than 90.0% and 98.0% or less, and a correlation value that is obtained by analyzing the remainder in the microstructure in a SEM image of the microstructure is 0.82 to 0.95, and a maximum probability value is 0.0040 to 0.0200.