The present article aims at elucidating the effect of thermo-mechanical controlled processing (TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy steels for developing superior low temperature toughness construction steel. The microstructural features were characterized by scanning electron microscope equipped with electron backscatter diffraction, and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution. The results showed that the lower finish cooling temperature could lead to a considerable increase in impact toughness for this steel. A mixed microstructure was obtained by TMCP at lower finish cooling temperature, which contained much fine lath-like bainite with dot-shaped M/A constituent and less granular bainite and bainite ferrite. In this case, this steel possesses yield and ultimate tensile strengths of ~ 885 MPa and 1089 MPa, respectively, and a total elongation of ~ 15.3%, while it has a lower yield ratio of ~ 0.81. The superior impact toughness of ~ 89 J at −20 °C was obtained, and this was resulted from the multi-phase microstructure including grain refinement, preferred grain boundaries misorientation, fine lath-like bainite with dot-shaped M/A constituent.

本文旨在阐明热机械控制加工（TMCP），特别是最终冷却温度，对开发卓越的低温韧性建筑钢的高强度低合金钢的组织和力学性能的影响。通过配备电子背散射衍射的扫描电子显微镜表征其微观结构特征，并分析与拉伸性能和冲击韧性有关的力学行为，并与微观结构演变相关联。结果表明，较低的最终冷却温度可导致该钢的冲击韧性大大提高。通过TMCP在较低的最终冷却温度下获得了混合的显微组织，含有许多细的板条状贝氏体，具有点状M / A成分，而颗粒状的贝氏体和贝氏体铁素体则较少。在这种情况下，这种钢的屈服强度和极限抗拉强度分别为〜885 MPa和1089 MPa，总伸长率为〜15.3％，而屈服比较低，约为0.81。在-20°C时获得了〜89 J的优异冲击韧性，这是由于多相组织包括晶粒细化，优选的晶界错位，具有点状M / A成分的细条状贝氏体所致。