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Abstract

A quenched-tempered high-strength steel having a yield strength of 900-1000 MPa grade and a method of producing the same, with the components and amounts thereof by weight percentage being: C: 0.16-0.20%, Si: 0.10-0.30%, Mn: 0.80-1.60%, Cr: 0.20-0.70%, Mo: 0.10-0.45%, Ni: 0.10-0.50%, Nb: 0.010-0.030%, Ti: 0.010-0.030%, V: 0.010-0.050%, B: 0.0005-0.0030%, Al: 0.02-0.06%, Ca: 0.001-0.004%, N: 0.002-0.005%, P≦0.020%, S≦0.010%, O≦0.008%, and the balance of Fe and unavoidable impurities, and Ceq 0.51-0.60%, Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15; 3.7≦Ti/N≦7.0; 1.0≦Ca/S≦3.0; 0.8%≦Mo+0.8Ni+0.4Cr+6V≦1.3%. By using a process of controlling rolling, controlling cooling, and off-line quenching+tempering, a steel sheet produced according to the disclosure has a yield strength of 900-1080 MPa, a tensile strength of 950-1200 MPa, an elongation >10%, and an impact energy at −40° C. >40 J.

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