Dislocation Density Evolution and Flow Stress Modelling During Cold Drawing of Low Carbon Steel Wire for Nigerian Reinforcement Applications

This study investigates dislocation density evolution and develops a physics-based flow stress model for low carbon steel wire during multi-pass cold drawing, with direct application to the optimisation of wire drawing schedules at pre-stressing wire manufacturers supplying Nigeria's pre-stressed concrete bridge and building construction sector. Cold drawing work hardens steel wire through dislocation multiplication and interaction, and accurate modelling of this process enables prediction of tensile strength and ductility at each drawing stage without extensive empirical testing. Dislocation densities are measured experimentally by X-ray line profile analysis (modified Williamson-Hall and Warren-Averbach methods) on cold-drawn wire specimens at cumulative area reductions of 0, 10, 20, 30, 40, and 55 percent. EBSD is applied to characterise texture development and subgrain formation at each reduction level. The Kocks-Mecking-Estrin (KME) dislocation density evolution model is fitted to the experimental dislocation density versus strain data, and the constitutive flow stress equation is calibrated. The model is embedded in a finite element simulation of the multi-pass drawing process implemented in DEFORM software, and predictions of die force, drawing stress, and final wire tensile strength are validated against mill production data from a cooperating facility in Lagos State. The study provides a physically grounded cold drawing process model directly applicable to Nigerian wire manufacturing. Keywords: cold drawing, dislocation density, flow stress model, low carbon steel wire, work hardening.