公开(公告)号：EP3296415A4

公开(公告)日：2018-03-21

申请号：EP16830039

申请日：2016-07-20

Applicant: JFE STEEL CORP

Inventor： YAMAZAKI KAZUHIKO ,  TOYODA SHUNSUKE ,  MORIYASU NORIAKI ,  IRISA KENTARO

IPC: C22C38/00 ,  C21D8/02 ,  C21D9/46 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/40 ,  C22C38/60

CPC classification number: C21D9/46 ,  C21D8/0226 ,  C21D8/0263 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C22C38/00 ,  C22C38/001 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/40 ,  C22C38/60

Abstract: To provide a high-strength hot-rolled steel sheet that has excellent punching workability and hole expandability and has a tensile strength TS of 980 MPa or more; and a method for manufacturing the high-strength hot-rolled steel sheet. The high-strength hot-rolled steel sheet has a chemical composition containing specified amounts of C, Si, Mn, P, S, Al, N, Ti, Cr, and B, and has a microstructure including a bainite phase having an area ratio of 85% or more as a main phase, and a martensite phase or martensite-austenite constituent having an area ratio of 15% or less as a second phase, the balance being a ferrite phase, wherein the second phase has an average grain diameter of 3.0 µm or less, prior-austenite grains have an average aspect ratio of 1.3 or more and 5.0 or less, recrystallized prior-austenite grains have an area ratio of 15% or less relative to non-recrystallized prior-austenite grains, and the high-strength hot-rolled steel sheet contains 0.10% or less by mass% of precipitates having a diameter of less than 20 nm.