高韧性420MPa级桥梁钢开发及强化机制分析

通过优化合金成分、改进控轧控冷工艺等手段，成功开发出屈服强度在480~530MPa，抗拉强度在560~630MPa，延伸率在21%~25%，-20℃冲击功全部在200J以上的Q420桥梁钢.对透射电镜下的析出相及金相显微组织中的晶粒尺寸进行相关统计计算，得到各类强化贡献量数值，并对Q420桥梁钢的强化机制进行了分析.分析结果表明:在新开发的Q420桥梁钢中析出强化贡献量占全部强度的10%以下，而固溶强化量及细晶强化量分别占全部强度的54%及36%，因此确认420MPa级桥梁钢的强化机制以固溶强化、细晶强化为主.

Development and Strengthening Mechanism of 420MPa Grade Bridge Steel with High Toughness

The Q420 bridge steel with yield strength of 480~ 530MPa， tensile strength of 560~ 630MPa， elongation of 21 %~ 25% and impact strength of more than 200J at-20℃was developed by optimization of alloy composition and improvement of control rolling and control cooling process. The amount of various types of strengthening contribution was obtained through analyzing the amount of precipitation by transmission electron microscopy and the grain size of metallographic microstructure. Then the strengthening mechanism of Q420 bridge steel was studied. The results showed that the contribution of precipitation strengthening accounts for less than 10% of the total strength for Q420 bridge steel， and the contribution of solid solution strengthening and fine grain strengthening are 54% and 36%，respectively.It is confirmed that solid solution strengthening and fine grain strengthening are dominated in 420MPa grade steel.