| This paper describes the tension-tension fatigue properties of high-carbon steel wire containing around 0.6wt.% C, which is used as a stranded wire for ACSR(Aluminum Stranded Conductors Steel Reinforced) in transmission power lines. ACSR which consists of galvanized steel strand and aluminum core always experiences serious vibration by wind. Therefore, it is very important to clarify the fatigue property of core wire for ACSR to determine its lifetime and stability of power delivery. Since steel wires are produced by a wire drawing process, they possess a very long fiber-lamellar microstructure which has a very short inter-layer distance between ferrite and cementite layer. The long fiber-lamellar microstructure is expected to have a different fatigue behavior compared to conventional plate and bulk-type materials. In order to characterize the fatigue property of steel wire having the unique microstructure mentioned above, tension-tension fatigue tests were carried out on specimens drawn to various strains. The fatigue strength was 106.7㎏f/㎟ at ε=1.79, and 92.0㎏f/㎟ at ε=1.19, which showed an inverse relationship with drawing strains. The fatigue strength of a hard-drawn wire was as high as 66∼70% level of its tensile strength. This value was very high compared to that of rolled or full-annealed materials, which exhibited 40∼60% level of their tensile strength. The high fatigue strength is attributed to the very fine elongated pearlitic microstructure formed by the drawing process, which suppresses formation and growth of microcracks. A good correlationship between theoretical fatigue strength and experimental one was found, which meant that yield and tensile strength were the main factors to affect the fatigue property of the steel wire. |
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