Premature failure of Aluminum Core Steel Reinforced wires

During torsion test several galvanized Aluminium Core Steel Reinforced (ACSR) wires of 3.54 mm diameter (drawn from 5.5 wires) have failed after 16 twists as against the normal of about 28 twists. The premature failure is believed to be due to acid exposure prior to the galvanizing. In order to minimize the problem 0.2% Cr is added into the steel composition. The failure analysis of the sample showed that hydrogen exposure during pickling process prior to the galvanizing operation is not the proper reason for failure. Further study showed that addition of chromium into the steel composition enhances the pre mature failure life but that is also much above than the purview of present plant operating conditions. The microstructural study shows that the premature failure specimen has disaligned and broken lamellae with globular cementite which creates an array of voids. These voids hinder rotation during torsion thus leading to brittle fracture.