The Analysis and Control of Micro-Hardness Distribution During Wire Drawing

During wire drawing processes a critical parameter is the micro-hardness distribution imposed. The present numerical and experimental investigation focused on the effects of and interdependence between processing parameters such as die angle, bearing length, lubrication, and draw speed during wire drawing. The micro-hardness distribution imparted by the drawing process was selected as the focal product quality attribute. The goal of the study was to evaluate the ability to create desired hardness levels in a drawn wire product. The numerical component of the study was performed using DEFORM-2D™, a commercially available metal forming software package based on the finite element method. In addition, experimental verifications of the software predictions were completed wherever possible. Full factorial designs of the processing parameters were studied, and it was found that the final hardness distribution was primarily affected by the die angle. Interactions between the four processing parameters were negligible. Based upon this finding, it was concluded that strength and hardness variations inherent to stock wire could be detected and minimized during wire drawing through the appropriate science-based selection of die angle. This could dramatically enhance the consistency of the wide range of common metal products that are manufactured from wire stock.