HIGH-STRENGTH HIGH-TOUGHNESS NON-QUENCHED AND TEMPERED ROUND STEEL AND PREPARATION METHOD

摘要

A high-strength high-toughness non-quenched and tempered round steel, relating to the technical field of non-quenched and tempered steel, the chemical components and mass percentages thereof being as follows: C: 0.27％–0.33％, Si: 0.40％–0.70％, Cr: 0.10％–0.30％, Mn: 1.30％–1.65％, S: 0.065％–0.100％, Al: 0.005％–0.040％, V: 0.06％–0.020％, Ti: 0.010％–0.040％, N: 0.0120%–0.0250%, the remainder being Fe and unavoidable impurities, and the manganese equivalence Mneq being: 1.70％–2.10％. In the present non-quenched and tempered steel, the low-cost free-cutting element S is increased, a dispersive distribution of sulphides and V(N, C) compounds is formed, and by means of continuous uniform cooling and rolling and temperature-controlled cooling after rolling, a high-toughness non-quenched and tempered steel bar having excellent mechanical performance is obtained, the impact energy of the rolled material reaching 190J or higher.