Manufacturing Thermal-resistant Aluminum Alloy Wire for Overhead Line Conductor

Abstract

One of the overhead line conductor’s tasks is to ensure high electrical conductivity and high tensile strength after repeated heating to 180 oC. However, conventional aluminum conductor steel reinforced (ACSR) does not meet the above requirements (operating temperature ≤ 90 oC). To solve this problem, foreign countries have used Zr-bearing aluminum alloy, adding other alloying elements, such as Si and Fe, to manufacture thermal-resistant wire for overhead line conductors. This paper aim is to study the manufacturing process of thermal-resistant Al-Zr-Si-Fe alloy wire for overhead line conductors. Al-Zr-Si-Fe alloy was manufactured in the electric furnace and then cast in the permanent mold. Al-Zr-Si-Fe alloy billets were extruded to a diameter of 4.5-4.7 mm at 470 oC. After that, the extruded rods were cold-drawn to a diameter of 2.5 mm. The wire samples were annealed for 10 hours in an electric furnace at a temperature ranging from 350 oC to 450 oC. The as-cast Al-Zr-Si-Fe alloy microstructures show that the alloy grain morphologies are fine and equiaxed, and there are no Al3Zr crystals in the alloys. The electrical resistivity of the as-drawn Al-Zr-Si-Fe alloy wire is high because zirconium completely dissolves in an aluminum solid solution. After annealing the wire at 350 oC, the tensile strength of the wire decreases, and elongation slightly increases due to the reduction of lattice distortions. Resistivity slightly decreases because the metastable Al3Zr particle precipitation from aluminum solid solution is relatively slow at temperatures < 400 °C. At an annealing temperature of 400–450 oC, the tensile strength increases significantly, the elongation slightly decreases, and the resistivity noticeably decreases due to the precipitation of metastable Al3Zr (L12) particles. After annealing at 450 oC for 10 hours, the mechanical, electrical, and thermal-resistant properties of the wire meet the AT1 type requirements of standard IEC 62004.