Abstract:Medium-drawn low-oxygen copper wire is a crucial raw material for producing ultra-fine copper wire. Its characteristics including microstructure, synergy of strength and ductility, and conductivity significantly influence the production efficiency and quality of ultra-fine low-oxygen copper wire. This study investigated the optimal annealing process for medium-drawn low-oxygen copper wire by selecting different annealing voltage parameters within the range of 0~29 V for online annealing. Mechanical and electrical conductivity tests were conducted, and the microstructure of copper wires with varying degrees of annealing was characterized. The relationship between annealing voltage and the performance of medium-drawn low-oxygen copper wire was quantitatively analyzed, the impact of annealing microstructure on performance was also studied. The results indicated that an annealing voltage of 13 V was the threshold at which significant changes in performance occurred. At the voltage of 21 V, copper wire exhibited a fully recrystallized structure, optimal conductivity and elongation, with tensile strength reaching a stable value. However, excessive annealing voltage led to over annealing oxidation on copper wire surface, significant grain coarsening, and the appearance of over-burning holes, resulting in performance degradation.