420MPa-grade low-alloy high-strength steel with high work hardening rate and manufacturing method thereof

The invention relates to 420MPa-grade low-alloy high-strength steel with high work hardening rate and a manufacturing method thereof, the steel comprises the following chemical components in percentage by mass: 0.08%-0.1% of C, 0.3%-0.5% of Si, 1.5%-1.7% of Mn, less than or equal to 0.018% of P, less than or equal to 0.008% of S, 0.02%-0.05% of Al, 0.1%-0.2% of Cr, 0.045%-0.065% of Nb, 0.01%-0.03% of Ti, less than or equal to 0.006% of N, and the balance of Fe and inevitable impurities, and the Nb + Ti accounts for 0.05%-0.08%. On the basis of a C-Si-Mn system, Nb and Ti are added and matched with a small amount of Cr, the solid solution strengthening and grain refining effects of the Nb and Ti are utilized, the microstructure is regulated and controlled, the yield ratio of the steel plate is reduced, and the yield ratio of the steel plate is controlled to be 0.6-0.8. 本发明涉及高加工硬化率的420MPa级低合金高强钢及制造方法，钢中化学成分按质量百分比计为：C：0.08％～0.1％，Si:0.3％～0.5％，Mn：1.5％～1.7％，P≤0.018％，S≤0.008％，Al：0.02％～0.05％，Cr：0.1％～0.2％，Nb：0.045％～0.