890MPa-grade high-strength QP steel with low yield-tensile ratio and production method of 890MPa-grade high-strength QP steel

The invention provides an 890MPa-grade high-strength Qamp with a low yield ratio. The invention discloses P steel and a production method thereof. A thick plate comprises the following chemical components in percentage by mass: less than or equal to 0.1% of C, 0.4-0.6% of Si, 1.4-1.8% of Mn, 0.4-0.8% of Cr, 0.6-1.0% of Ni, 0.2-0.6% of Mo, 0.02-0.08% of Nb, 0.02-0.08% of V, 0.01-0.03% of Ti, 0.01-0.05% of Al, 0.8-1.5% of Cu and the balance of Fe and inevitable impurities. According to the production process, on the basis of adopting the components, controlled rolling and controlled cooling and off-line salt bath Qamp are adopted; and P, a heat treatment process is conducted, and the 890 MPa-grade high-strength steel with the thickness of 15 mm and the low yield ratio is prepared. Two-stage rolling is adopted in the controlled rolling and controlled cooling process, water cooling is conducted to 400-420 DEG C after rolling, and then air cooling is conducted to the room temperature. According to the 890MPa-grade