Abstract: The production process flow sheet for hard wire coil of steel 65C (/% : 0. 62 〜0. 70C, 0. 18 ~ 0. 28Si, 0. 55 ~0. 75Mn) is 120 t converter-LF-170 mm x 170 mm costing billet-rolling by high speed mill. The fracture cause of steel 65 C during ∅6. 5 mm hot rolled coil cold-drawing to ∅1. 85 mm wire has been analyzed by optical microscope and scanning electron microscope. Test results show that the macro-feature of fracture is pencil-tip in shape, and the structure homogeneity at coil cross section is poor； the cracks originate at coarse proeutectoid ferrite and thick-lamellar cementite in center of section ； and the main causes of fracture are low sorbite percentage, existing large block proeutectoid ferrite and central carbon segregation.

Key words: Segregation5 C, Hard Wire, Hot-Rolled Coil, Cold Drawing, Pencil-Tip Shaped Fracture, Proeutectoid Ferrite, Central Segregation

摘要： 65钢(/%:0.62～0.。70C、0.18～0.28Si、0.55～O.75Mn)硬线盘条的生产流程为120 t转炉-LF-170mm×170 mm连铸-高速线材轧制。采用光学和扫描电子显微镜分析了65钢∅6.5 mm热轧盘条在冷拉至∅1.85mm过程中断裂的原因。实验结果表明,断口宏观特征为笔尖状,盘条横截面组织均匀性较差;裂纹起源于心部粗大的先共析铁素体和粗片状渗碳体,断裂的主要原因是索氏体化率低,存在大块先共析铁素体和中心碳偏析。

关键词: 65钢, 硬线, 热轧盘条, 冷拉, 笔尖状断裂, 先共析铁素体, 中心偏析