The influences of the variable speed and internal die geometry on the performance of two commercial soluble oils in the drawing process of pure copper fine wire

Gustavo Aristides Santana Martínez,Leonardo Kyo Kabayama,Oscar Rodriguez-Alabanda,Marius Tintelecan,Umberto Prisco

doi:10.1007/s00170-021-08172-2

Abstract

The cold wiredrawing process constitutes a classical-tribological system in which a stationary tribe-element (die) is in contact with a tribe-element in relative motion (wire) and both interacting with the interfacial tribe-element (lubricant). This condition is reflected in the effect of friction as a function of the drawing speed and temperature, and directly affects the wearing of the surface into the die and the final quality on the drawn wire. The aim of this work has been to determine the best conditions to process ETP-copper using two different types of oil/water emulsion lubricants. For this purpose, six different die geometries have been proposed and a set of tests have been carried out at different speeds (between 1 and 21 m/s) to determine those combinations that give a lower value in the required drawing force (Fd). The experiments allowed to know the friction coefficient (µ), the temperature profile inside the drawing die and in the lubricant and also the mean roughness (Ra) in the drawn product. The results have shown that drawing speeds above 10 m/s significantly decrease the drawing force and, as a consequence, the friction effect on the interface. The best results have been achieved in the combinations of the lower die angle (2β = 14°) with drawing speeds between 17 and 18 m/s with both types of lubricants used, obtaining the lower values of the friction coefficient between µ = 0.10–0.15 with the lubricant type D (Agip S234-60 oil at 7% concentration). It has been found that those tests carried out with dies with a smaller approach angle have generally made it possible to obtain better qualities in the final product. Additionally, FEM simulations have been done to analyse those cases with the lower values of µ, throwing values of Fd that are consistent with those measured in the experimental setting and allowing to better understand the behavior of the material as it passes through the die.

Highlights

In the production of metal wire by cold wiredrawing process the die angle (2β), the cross-sectional area reduction (r), the process speed (v), and the friction coefficient (μ) have a major influence over the required drawing force (Fd), and the lubrication regime is a key factor in the process
The best results were obtained with the use of the lubricant type LUB C and are shown in Fig. 4, where the temperature on the die (Tdie), the temperature of the lubricant into the flood chamber (Tlub), and the drawing force (Fd) are graphically represented vs. drawing speed (v), since these output parameters have been monitored in both types of different lubricating emulsion mixtures object of study
Analyzing the evolution of the stresses that are generated in the deformation zone during the wiredrawing process, Yoshida confirmed in his work that the distribution of axial and radial stresses in the deformation zone into the die affects the final dimension and straightness in the wire processed by drawing [29]

Summary

Introduction

In the production of metal wire by cold wiredrawing process the die angle (2β), the cross-sectional area reduction (r), the process speed (v), and the friction coefficient (μ) have a major influence over the required drawing force (Fd), and the lubrication regime is a key factor in the process. By the use of numerical models and methods, Chen and Huang [3] and Majzoobi et al [4] determined that 2β, Hc and the temperature profile into the die have a significant effect on the drawing process, but it is very important to consider the effect of the wire-die contact length (l) which determines the contact surface at the interface and has a direct effect on the lubrication conditions and, as a consequence, on the value of the friction coefficient μ, involved in the process Another consulted works demonstrated the feasibility of the use of FEM applied to model the wiredrawing process and focused on the improvement of the geometry of the die [13], on the analysis of the strain distribution in the wire during the process [14] or even to analyze the distribution of residual stresses accumulated in the product once it has been shaped [15], among other output variables.

Methods

Results

Conclusion