公开(公告)号：US20210017622A1

公开(公告)日：2021-01-21

申请号：US17043267

申请日：2018-03-30

Applicant: NIPPON STEEL CORPORATION

Inventor： Jun HAGA ,  Kohichi SANO ,  Koutarou HAYASHI ,  Kunio HAYASHI ,  Masaharu KAMEDA ,  Akihiro UENISHI ,  Hiroyuki KAWATA

IPC: C21D9/46 ,  B32B15/01 ,  C22C38/38 ,  C22C38/32 ,  C22C38/22 ,  C22C38/16 ,  C22C38/14 ,  C22C38/08 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C21D6/00 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: A hot dip galvanized steel sheet and hot dip galvannealed steel sheet improved in uniform ductility and local ductility, yield strength and tensile strength, and low temperature impact property, characterized by having a predetermined chemical composition, having a metal structure containing, by volume %, retained austenite: over 5.0% and tempered martensite: over 5.0%, having retained austenite containing C: 0.85 mass % or more, and having a ratio [C]γgb/[P]γgb of an amount of segregation of C (number of atoms/nm2): [C]γgb to an amount of segregation of P (number of atoms/nm2): [P]γgb at prior austenite grain boundaries of 4.0 or more.