The effect of a non-circular drawing sequence on spheroidization of medium carbon steel wires

Abstract

A non-circular drawing (NCD) sequence was applied as a prior cold working to improve spheroidization in a medium carbon steel wire. To investigate the effect of the NCD sequence on spheroidization behavior of the medium carbon steel wire, numerical simulations and experiments were carried out up to the fourth pass and were compared with the results of the conventional wire drawing (WD). From the three-dimensional numerical results, it was found that the NCD sequence could impose higher and relatively more homogeneous plastic deformation on the wire than the WD process. Spheroidization annealing at subcritical temperature of 705°C for 2, 4, and 8h was applied for the specimens that were produced by the WD and NCD processes, respectively. Tension and Vickers micro-hardness tests were conducted to measure mechanical properties of the annealed specimens. The annealed specimen processed by the NCD sequence showed the reduced ultimate tensile strength and micro-hardness, and the enhanced reduction of area compared to those values for the WD process. According to upsetting test results, it was found that cold workability was also improved for the annealed specimen processed by the NCD process compared to the one produced by the WD process. Scanning electron microscopy (SEM) was employed to investigate the microstructure change and to quantitatively measure the spheroidization ratio of the annealed specimens processed by both processes. Owing to the SEM results, the spheroidization of the annealed specimens processed by the NCD sequence was improved compared to the one produced by the WD process. It can be construed from the current investigation that the NCD sequence might be helpful in improving the spheroidization of cementite and cold workability of medium carbon steel wires during the subcritical annealing.