公开(公告)号：US20220119902A1

公开(公告)日：2022-04-21

申请号：US17422406

申请日：2020-01-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroshi SHUTO ,  Koutarou HAYASHI ,  Hiroshi KAIDO ,  Akifumi SAKAKIBARA ,  Jun ANDO ,  Tetsu ASATO

IPC: C21D8/02 ,  C21D9/46 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in which a metal microstructure contains, by area %, 3.0% or more of residual austenite, has a ratio L52/L7 of a length L52 of a grain boundary having a crystal orientation difference of 52° to a length L7 of a grain boundary having a crystal orientation difference of 7° about a direction of 0.10 or more and 0.18 or less, has a standard deviation of a Mn concentration of 0.60 mass % or less, and has a tensile strength of 980 MPa or more.

公开(公告)号：US20220081748A1

公开(公告)日：2022-03-17

申请号：US17423307

申请日：2020-01-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Koutarou HAYASHI ,  Hiroshi SHUTO ,  Kazumasa TSUTSUI ,  Hiroshi KAIDO

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

Abstract: This hot-rolled steel sheet has a predetermined chemical composition, in which a metallographic structure contains, by area %, 3.0% or more of retained austenite, has a ratio L52/L7 of a length L52 of a grain boundary having a crystal misorientation of 52° to a length L7 of a grain boundary having a crystal misorientation of 7° about a direction of more than 0.18, has a standard deviation of a Mn concentration of 0.60 mass % or less, and has a tensile strength of 1180 MPa or more.

公开(公告)号：US20210381086A1

公开(公告)日：2021-12-09

申请号：US17285428

申请日：2019-10-21

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroshi SHUTO ,  Akifumi SAKAKIBARA ,  Shinsuke KAI ,  Koutarou HAYASHI ,  Hiroshi KAIDO

IPC: C22C38/38 ,  C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/26 ,  C22C38/34 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C22C38/10 ,  C22C38/08

Abstract: This hot-rolled steel sheet has a predetermined chemical composition. The metallographic structure at a sheet thickness ¼ depth from a surface and at a center position in a sheet width direction in a sheet width cross section parallel to a rolling direction contains, by area %, 77.0% to 97.0% of bainite and tempered martensite in total, 0% to 5.0% of ferrite, 0% to 5.0% of pearlite, 3.0% or more of residual austenite, and 0% to 10.0% of martensite. The average grain size of the metallographic structure excluding the residual austenite is 7.0 μm or less. The C concentration in the residual austenite is 0.5 mass % or more. The number density of iron-based carbides having a diameter of 20 nm or more is 1.0×106 carbides/mm2 or more.