公开(公告)号：US20210115541A1

公开(公告)日：2021-04-22

申请号：US17042250

申请日：2019-03-20

Applicant: JFE STEEL CORPORATION

Inventor： Kazuki ENDO ,  Yoshiyasu KAWASAKI ,  Yuki TOJI ,  Yoshimasa FUNAKAWA ,  Mai AOYAMA

IPC: C22C38/04 ,  C22C33/02 ,  B21B27/10 ,  C21D6/00 ,  C21D8/02

Abstract: A high-strength steel sheet includes a steel structure with: ferrite being 35% to 80%, martensite being 5% to 35%, and tempered martensite being 0% to 5% in terms of area fraction; retained austenite being 8% or more in terms of volume fraction; an average grain size of: the ferrite being 6 μm or less; and the retained austenite being 3 μm or less; a value obtained by dividing an area fraction of blocky austenite by a sum of area fractions of lath-like austenite and the blocky austenite being 0.6 or more; a value obtained by dividing, by mass %, an average Mn content in the retained austenite by an average Mn content in the ferrite being 1.5 or more; and a value obtained by dividing, by mass %, an average C content in the retained austenite by an average C content in the ferrite being 3.0 or more.

公开(公告)号：US20210108282A1

公开(公告)日：2021-04-15

申请号：US17043514

申请日：2019-03-20

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu KAWASAKI ,  Kazuki ENDO ,  Yuki TOJI ,  Yoshimasa FUNAKAWA ,  Satoshi MAEDA ,  Mai AOYAMA

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  B32B15/01 ,  C23C2/02 ,  C23C2/28 ,  C23C2/40 ,  C23C2/06

Abstract: A high-strength steel includes a steel structure with: in area fraction, 60.0% to less than 90.0% of ferrite, 0% to less than 5.0% of unrecrystallized ferrite, 2.0% to 25.0% of martensite, 0% to 5.0% of carbide, and 0% to 3.0% of bainite; in volume fraction, more than 7.0% of retained austenite; in a cross-sectional view of 100 μm×100 μm, a value obtained by dividing number of retained austenite that are not adjacent to retained austenite whose crystal orientations are different by a total number of retained austenite being less than 0.80, an average crystal grain size of the ferrite being 6.0 μm or less, an average crystal grain size of the retained austenite being 3.0 μm or less, and a value obtained by dividing, by mass %, an average content of Mn in the retained austenite by an average content of Mn in steel being 1.50 or more.

公开(公告)号：US20210010101A1

公开(公告)日：2021-01-14

申请号：US17042291

申请日：2019-03-20

Applicant: JFE STEEL CORPORATION

Inventor： Kazuki ENDO ,  Yoshiyasu KAWASAKI ,  Yuki TOJI ,  Yoshimasa FUNAKAWA ,  Mai AOYAMA

IPC: C21D9/46 ,  C22C38/38 ,  C22C38/28 ,  C22C38/16 ,  C22C38/12 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: A high-strength steel sheet includes a steel structure with: ferrite being 35% to 80% and tempered martensite being greater than 5% and 20% or less in terms of area fraction; retained austenite being 8% or more in terms of volume fraction; an average grain size of: the ferrite being 6 μm or less; and the retained austenite being 3 μm or less; a value obtained by dividing an area fraction of blocky austenite by a sum of area fractions of lath-like austenite and the blocky austenite being 0.6 or more; a value obtained by dividing, by mass %, an average Mn content in the retained austenite by an average Mn content in the ferrite being 1.5 or more; and a value obtained by dividing, by mass %, an average C content in the retained austenite by an average C content in the ferrite being 3.0 or more.