Effects of die design, manufacturing and process parameters on chevron and surface cracking of copper wire during wire drawing

Abstract

The practice of copper wire drawing has faced problems regarding process, quality and manufacturing cost and satisfying world market demand of drawn wires. Of great importance to the practitioner are problems due to the interaction of process parameters during wire drawing. The present research study on the “Effects of Die Design, Manufacturing and Process Parameters on Chevron and Surface Cracking of Copper Wire during Wire Drawing” is based on multi-pass copper wire drawing studies from the industry and the application of a scientific approach using the finite element method (FEM). A 2-dimensional axisymmetric model of multi-pass copper wire drawing was developed using ABAQUS 6.14 to model and simulate the major factors contributing to and influencing the development of both internal (chevron) and surface cracks during copper wire drawing, with an emphasis on die bearing length variation. Drawn wire scanning electron micrographs were used to validate the effects of bearing length variation during copper wire drawing. Studies showed that a good selection and application of die geometrical and process parameters participating as an integral unit in copper wire drawing leads to the production of a defect-free copper wire. Models showed that, except the exit angle, all other die geometrical parameters influenced ductile damage. Studies from the simulations and drawn wire micrographs showed that the Cockroft and Latham damage criterion was not met in all the multi-pass stages for the internal centerline nodes, whereas the criterion was met during the second and third multi-pass stages for the surface nodes. The models showed that internal centreline damage is minimised when using bearing length values between 30% and 40% while surface damage is lower when using bearing lengths of 30%.