焊缝强韧化是提升高性能桥梁钢焊接接头力学性能的关键，通过微观组织调控优化焊缝性能是实现这一目标的有效途径。 本文以 500 MPa 级高性能桥梁钢为研究对象，系统分析了其焊缝组织的典型特征，并建立了微观组织与冲击韧性之间的映射关系，为高性能桥梁钢焊缝的强韧化设计提供理论依据。 研究表明，细小而交错分布的针状铁素体组织形成“网篮组织”，增加裂纹萌生和扩展所需能量，使焊接接头的冲击韧性提高。 多边形铁素体组织则由于晶界取向差较大，易于形成晶间裂纹，降低焊接接头的裂纹萌生功。 粗大的针状铁素体组织对裂纹扩展的阻碍作用明显降低，使焊接接头的冲击韧性下降。

Strengthening and toughening welds are the keys to improving the mechanical properties of high-performance bridge steel welds. Optimizing weld performance through microstructure control is an effective way to achieve this goal. Taking 500 MPa high-performance bridge steel as the research object, the typical characteristics of its weld microstructure were systematically analysed, and a mapping relationship between microstructure and impact toughness was established, providing a theoretical basis for the strengthening and toughening design of high-performance bridge steel welds. Research has shown that the small and staggered distribution of needle-like ferrite forms a "basketweave", which increases the energy required for crack initiation and propagation and improves the impact toughness of welded joints. The polygonal ferrite structure is prone to intergranular cracks due to the large difference in grain boundary orientation, which reduces the crack initiation energy of welded joints. The hindering effect of the coarse needle-like ferrite structure on crack propagation is significantly reduced, resulting in a decrease in the impact toughness of the welded joints.