Abstract:  According to the abnormal fracture phenomenon of 87MnSi steel wire rod for bridge cable， the evolution of microstructure and mechanical properties during production processing were systematically analyzed. The results show that the microstructure of the rod is composed of pearlite and a small amount of proeutectoid ferrite， and the cementite lamellae are randomly distributed. After cold drawing， the cementite lamellae are rotated or fibrotic， and some cementite are broken and dissolved， the dissolution amount is 1.40wt.%（9.69%）. After ho-dip galvanizing， the dissolved cementite is spheroidized. In the process of cold drawing， hot-dip galvanizing and stabilization treatment， the microhardness of wire rod （329.8HV） increases （450.2HV） firstly， then decreases （447.9HV） and increases （474.8HV） finally. The cementite dissolved in the cold drawing process increases the hardness of the steel wire to 468.3HV， while the spheroidized cementite in the hot galvanizing process decreases the hardness to 439.8HV， and deteriorates tensile property. When the degree of spheroidization of cementite on the edge is obvious， the microstructure and mechanical properties of the steel wire inside and outside are greatly different， and the fracture is eventually caused by uneven force during stabilizing treatment.

Key words:  , Bridge Cable, 87MnSi Steel, Hot-dip Galvanizing, Stabilizing Treatment, Fracture, Cementite Spheroidization

摘要： 针对桥梁缆索用87MnSi钢线材的异常断裂现象，对其盘条和生产工艺过程中钢丝的微观组织和力学性能演变规律进行系统分析。结果表明，盘条组织由珠光体和少量的先共析铁素体组成，且渗碳体片层随机分布。冷拉拔后，渗碳体片层发生扭转弯曲或减薄纤维化，且部分渗碳体发生破碎溶解，溶解量为1.40%（占比9.69%）。热镀锌后，溶解的渗碳体发生球化。盘条（329.8HV）在冷拉拔-热镀锌-稳定化处理过程中的显微硬度呈现先增大（450.2HV）后减小（447.9HV）再增大（469.6HV）的变化趋势；冷拉拔过程中溶解的渗碳体使得钢丝硬度值上升至468.3HV，而热镀锌过程渗碳体的球化，导致硬度值下降至439.8HV，并恶化拉伸性能。当边部的渗碳体球化程度明显时，使得钢丝内外组织和力学性能存在较大差异，并在稳定化处理过程中因受力不均匀而导致断裂。

关键词: 桥梁缆索, 87MnSi钢, 热镀锌, 稳定化处理, 断裂, 渗碳体球化