Correlation between Microstructural Evolution and Mechanical Properties of 2000 MPa Cold-Drawn Pearlitic Steel Wires during Galvanizing Simulated Annealing

Abstract

In the present experiment, hot-dip galvanizing simulated annealing of 2000 MPa cold-drawn pearlitic steel wires was carried out at 450 °C. The effects of microstructural evolution on the mechanical properties of the as-prepared wires were analyzed through scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile test, torsion test, and Vickers hardness test. In addition, the relationship between torsion laps and microstructural evolution of cold-drawn pearlitic steel wires was investigated in detail. It was found that the torsional performance of the wires deteriorated after annealing at 450 °C for 2–5 min, and the corresponding microstructural evolution was accompanied by the partial degradation of lamellar pearlites due to the diffusion and dislocation pinning of dissolved carbon atoms in ferrites, and it is not feasible to achieve the matching of strength and torsion laps by prolonging the holding time. The deterioration in torsional performance can be attributed to the microstructural difference between the surface and the center of the annealed wires. When the proportion of non-lamellar structure between the surface and the center in each specimen exceeded 8%, the microhardness difference was found to be greater than 40 HV and the torsion lap was less than 3 circles.