| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength hot-rolled steel sheet which has both a tensile strength of 900 MPa or more and excellent workability (especially, blanking property), and a manufacturing method therefor. <P>SOLUTION: The high-strength hot rolled steel sheet whose tensile strength is 900 MPa or more and which is excellent in blanking property has a composition containing, by mass%, 0.05-0.11% C, 0.3% or less Si, less than 0.5% Mn, 0.03% or less P, 0.005% or less S, 0.1% or less Al, 0.01% or less N, 0.0005-0.005% B, 0.01-0.25% Nb, and 0.05-0.4% V, so as to satisfy [Nb]/93+[V]/51≥0.0043 (wherein [Nb] and [V] represent an amount of the respective elements contained (mass%)), with the remainder comprising Fe and unavoidable impurities, and has a structure where the area rate of the ferrite phase is 95% or more, the average crystal grain size of the ferrite phase is 10 μm or less, and the average particle size of carbide in a crystal grain of the ferrite phase is less than 10 nm. <P>COPYRIGHT: (C)2013,JPO&INPIT |
