公开(公告)号：US20220090224A1

公开(公告)日：2022-03-24

申请号：US17420024

申请日：2019-12-24

Applicant: NIPPON STEEL CORPORATION

Inventor： Takeshi TOYODA ,  Hitoshi NIKAIDO ,  Kohei NAKADA ,  Yui YAMASHITA ,  Kazuki MATSUDA

IPC: C21D9/46 ,  C21D9/50 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/50 ,  B23K9/16 ,  C22C38/58 ,  C22C38/54 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42

Abstract: Hot-rolled steel sheet having a chemical composition including, in mass %, C: 0.02 to 0.20%, Si: 0.01 to 1.50%, Mn: 0.10 to 3.00%, P: 0.10% or less, S: 0.010% or less, Al: 0.005 to 0.100%, Ti: 0.02 to 0.20%, N: 0.001 to 0.010%, Cu: 0 to 0.50%, Ni: 0 to 0.50%, Cr: 0 to 1.00%, Mo: 0 to 0.40%, Nb: 0 to 0.060%, V: 0 to 1.00%, B: 0 to 0.0100%, Ca: 0 to 0.0050%, O: 0.0100% or less, and the balance: Fe and impurities; in which: a steel micro-structure includes, in area %, ferrite: 60 to 80%, and a total of ferrite and bainite: 90% or more; an average of the crystal grain size of ferrite and bainite is 7.0 μm or less, a standard deviation of the crystal grain size is 2.0 or less; and a standard deviation of a diameter of Ti carbo-nitrides is 10 nm or less.