Economical alloy die high intensity hot rolling steel sheet and its production manner

摘要

P To provide a hot-rolled steel sheet which has a strength of ≥ 540 MPa and excellent workability and is used for automotive parts or the like and to provide a method for producing the same. PSOLUTION: The low alloy type high-strength hot-rolled steel sheet having a tensile strength of 540 to 650 MPa or more has a composition comprising, by mass and 0.02 to 0.08% C, 0.01 to 1.50% Si and 0.1 to 1.5% Mn, and further comprising 0.03 to 0.06% Ti and in which Ti/C also satisfies 0.375 to 1.6, and the content of P is limited to ≤ 0.1%, the content of S is limited to ≤ 0.005%, the content of Al is limited to ≤ 0.5% and the content of N is limited to ≤ 0.009%, and the balance Fe with inevitable impurities, and the average diameter of TiC precipitates is 0.8 to 3 nm and the average number density is ≥ 1× 10SP17/SPpieces/cmSP3/SP. PCOPYRIGHT: (C)2011 and JPO& INPIT