【作者】 曹文奎；

【导师】 蒋建清； 于金； 方峰；

【作者基本信息】 东南大学 ， 材料学， 2006， 硕士

【摘要】 高强度低松弛预应力钢绞线作为第三代高档建筑材料,被广泛应用于高层建筑、大跨度桥梁等现代化大型建筑。其中1860MPa级PC钢绞线是已商业化的钢绞线中强度级别最高,用量最大的品种。其生产过程是高碳盘条经7～10道次的连续冷拉拔形变而成。由于现代化大生产的连续性要求,通常采用电阻对焊的方法将不同盘卷连接起来,在生产过程中盘条电阻对焊区域常发生拉丝和绞线断裂。绞线断口分析的结果表明,焊接区表面润滑不良产生的表面缺陷,是导致发生绞线断裂现象的主要原因。采用磷化处理的方法来改善表面润滑性能,是减少表面缺陷产生的有效方法。研究了促进剂(羟胺(HAS)和La(NO3)3)对磷化过程的φ-t曲线的影响,及磷化膜的生长规律。结果表明,羟胺有明显的加速磷化腐蚀反应的作用,使磷化膜晶粒的沉积速度加快,成膜阶段的时间缩短,磷化膜晶粒细小致密;La(NO3)3参与磷化膜晶粒的形核,降低磷化膜晶粒的形核势垒,加速磷化膜晶粒的生成,使膜晶粒细小致密;当羟胺和La(NO3)3共同作用时,能综合二者的促进作用,起到良好的效果。研究了磷化工艺对磷化膜形貌的影响规律,并对其摩擦学性能进行了研究,结果表明,膜重大、晶粒细小致密的磷化膜具有较好的减摩效果,其摩擦系数为0.2左右,而相同条件下未磷化处理样品的摩擦系数约为0.7;磷化膜皂化处理后,其摩擦性能更佳,摩擦系数均在0.2以下。磷化工艺的生产试用结果表明,采用本低温快速磷化工艺对盘条焊接区进行磷化处理,能有效减轻表面裂纹的产生。更多还原

【Abstract】 As high-grade structure material, 1860MPa prestressed concrete (PC) steel strand is widely used in modern construction, such as skyscrapers, large span bridges, and so on. It was made of high-carbon steel wires after drawing deformation. The bar to bar are connected by butt resistance welding in order to keep continuous drawing. Fracture often occurrs in the weld joint of the wire during drawing and twisting.According to fracture analysis , it is found that the fractures of the stands are mainly caused by the surface deficiency in weld joints where is badly lubricated. Phosphate treatment can improve surface lubricating property. This is also an effective way to reduce surface flaws.This paper studies the influence of accelerators(HAS&La(NO3)3) onφ-t diagram and growth laws of phosphate film. The results show that HAS has a dramatic effect on accelerating the corrosion reaction of parkerizing. It makes deposition rate faster, film forming time shorter and grain finer and denser. La(NO3)3 is involved in nucleation process of phosphate film, and reduces the potential barrier for grain nucleation. Furthermore, it accelerates the grain to form and makes grain fine and dense. When both are added, they can promote each other and have better result.The influence of phosphating process on the morphology of phosphate film is also studied. Besides, the tribological property is also studied. The results indicate that the phosphate film which is heavier and composed of finer and denser grains has better antifriction effect. The friction coefficient is approximately 0.2 while on the same condition the sample is 0.7 which is unphospharized. After soap treatment, phosphate film shows better antifriction property, and friction coefficient is below 0.2.When the above phosphating process is used in weld joints during the production process of strands, it turns out to be an effective way to reduce the appearence of surface cracks.更多还原