High-strength hot-rolled steel sheet having a tensile strength of 780 MPa or more and method for producing the same

摘要

An object of the present invention is to provide a high workability high strength hot-rolled steel sheet having excellent magnetic properties and excellent punching workability and having a tensile strength of 780 MPa or more. In mass%, C: 0.070 to 0.140%, Si: 0.10 to 1.00%, Mn: 1.00 to 1.80%, P: 0.050% or less, S: 0.0050 %: N: 0.0080% or less, Al: 0.010 to 0.100% and Ti: 0.050 to 0.150%, with the balance being composed of Fe and inevitable impurities And having a bainite structure with a volume fraction of 95% or more, 80% or more of the total precipitated carbides are dispersed in the grain boundaries of the bainitic ferrite constituting the bainite structure, and 80% of the total precipitated carbides. A high-strength hot-rolled steel sheet having a tensile strength of 780 MPa or more, wherein the average particle size is 20 to 300 nm.