Stereomicroscopic Analysis of Fracture Surfaces of Cold Drawn Steel Wires

The investigation on the fractured surface of steel wires in the tensile test and torsion test has been carried out using stereomicroscopic technique. The analysis has been done on cold drawn wires subjected to different pass schedules. Investigation revealed that pass schedule having optimum true strain resulted in the best mechanical properties. Hot rolled piano wire rod having carbon percentage 0.87% has been used in the investigation. The fully pearlitic microstructure is developed during lead patenting process of wire rod at 950 ℃. The wire rod has been reduced from 7.00 mm diameter to 2.6 mm wire diameter by subjecting it to three different pass schedules. The investigation revealed that highest UTS and TS properties are achieved in pass schedule-1 and pass schedule-2 respectively in the cold drawn wire of diameter 2.60 mm. The high reduction rate per die in pass schedule-1 has a negative effect on torsion strength whereas the low reduction rate per die in pass schedule-3 has negative effect on torsion strength as well as tensile strength.