Low-yield-ratio high-strength steel plate and production method thereof

The invention relates to a low-yield-ratio high-strength steel plate. The low-yield-ratio high-strength steel plate comprises the following components of, in percentage by weight, 0.070%-0.10% of C, 1.60%-2.0% of Mn, 0.10%-0.40% of Si, less than or equal to 0.0050% of S, less than or equal to 0.015% of P, 0.040%-0.070% of Nb, 0.008%-0.020% of Ti, less than or equal to 0.10% of V, 0.020%-0.060% ofAlt, 0.0010%-0.0025% of B, 0.25%-0.50% of Cr, 0.10%-0.30% of Mo, and the balance Fe and inevitable impurities; and the invention further provides a production method of the low-yield-ratio high-strength steel plate. In a production process, a lath bainite structure is obtained through a TMCP process, a ferrite and tempered martensite structure with a lath structure reserved is obtained through a critical zone quenching and tempering process, the low-yield-ratio high-strength steel plate is obtained, the comprehensive cost is low, and the application to the engineering machinery industry is facilitated. 本发明涉及一种低屈强比高强度钢