Patent ID: 9689060
Date: 2017-06-27
CPC Classifications: C21D,C22C

Claim:
1. A high-strength hot-rolled steel sheet, comprising, by mass %: C: 0.05 to 0.20%; Si: 0.5 to 1.7%; Mn: 1.0 to 2.5%; Al: 0.001 to 0.10%; V: 0.0005 to 0.10%; and one component selected from the group consisting of Ti, Nb, and mixtures thereof, in the following amounts: Ti: 0.05 to 0.20%; Nb: 0.02 to 0.20%; and mixtures thereof comprising 0.05 to 0.20% Ti and 0.02 to 0.20% Nb; with the remaining mass % comprising iron; and inevitable impurities; wherein: the steel sheet has a tensile strength of 786 MPa or more; the steel sheet has a microstructure comprising, by area ratio based on the total microstructure: ferrite: 50 to 90%; bainite: 10 to 50%; and martensite+retained austenite: less than 10%; an average particle size of precipitated carbides present in the ferrite is less than 6 nm; a total content of V, Ti, and Nb forming the precipitated carbides is 0.02% or more; and the steel sheet satisfies the following Expression 1: where element symbols in the Expression 1 correspond to mass %.