690MPa高强韧建筑用钢的热处理与组织性能研究

Study on Heat Treatment and Microstructure and Properties of 690MPa High Strength and Toughness Construction Steel

研究了回火温度对热轧态高强韧结构钢拉伸、0℃和-20℃冲击力学性能以及显微形貌的影响,分析了回火热处理的作用机理。结果表明,当回火温度在450℃以下时,试验用钢具有较高的强塑性和冲击性能以及低屈强比,可以满足690 MPa级高强韧抗震结构钢的使用要求;随着回火温度的升高,试验用钢的组织仍然为贝氏体,只是板条贝氏体会随着回火温度的升高而发生粗化和长大,贝氏体束宽呈不断增大趋势,板条边界也逐渐模糊,并最终转化成块状组织;位错密度会随着回火温度的升高而降低,块状M/A岛状组织逐渐从连续分布演变为链条状分布于贝氏体板条之间,位错强化效果逐渐减弱。

The effects of tempering temperature on the tensile performance,0 ℃ and-20 ℃ impact mechanical properties and micromorphology of hot rolled steel were studied,and the mechanism of the heat treatment was analyzed. The results showed that when the tempering temperature was below 450 ℃,the test steel had high strength and plasticity,good impact property and low yield ratio,which could meet the requirements of 690 MPa high strength and toughness aseismatic steel;that with the increasing of tempering temperature,the structure of the steel was still bainite,but the slab bainite coarsened and grew,the width of bainite slat kept constantly increasing,the boundary of the slab got gradually blurred and eventually turned into massive tissue;that the dislocation density decreased with the rising of the tempering temperature,and the bulk M/A islands gradually evolved from continuous distribution to chain like structure distributed among bainite slates,so that the dislocation strengthening effect decreased.