Patent ID: 7527700

Claim:
A high strength hot rolled steel sheet consisting of 0.04 to 0.15% C, 1.5% or less Si, 0.5 to 1.6% Mn, 0.04% or less P, 0.005% or less S, 0.04% or less Al, 0.03 to 0.15% Ti, 0.03 to 0.5% Mo, by mass, and balance of Fe and inevitable impurities, and having a microstructure consisting of ferrite containing precipitates, second phase of bainite and/or martensite, and other phase, wherein some of the precipitates in the ferrite containing precipitates contain Ti—Mo compound carbides, and the mean diameter of the precipitates is 20 nm or less and the mean distance between the precipitates is 60 nm or less, the hardness of the ferrite determined by a Nano Hardness Tester is 3 to 8 Gpa, the percentage of the ferrite containing precipitates is 40 to 95%, and the percentage of the other phase is 5% or less, and the steel sheet has a tensile strength of 780 Mpa or more.