Effect of reduction ratio, inclusion size and distance between inclusions on wire breaks in Cu fine wiredrawing

The presence of an inclusion in wire makes wire breaks easy to occur even with a high reduction ratio. The investigation presented here is mainly aimed at determining the reduction ratio when size of an inclusion, application of back tension and distance between inclusions are considered. In order to investigate the effect of back tension on wire breaks, the applied back tension in a slip type continuous drawing machine is calculated quantitatively using some parameters such as diameter and peripheral speed of capstan and coiling number. The effect of an inclusion size and reduction ratio on wire breaks is investigated when quantitatively calculated back tension being 28% of drawing force is applied. The size of an inclusion varies 5, 7 and 10 μm, the reduction ratio varies 10, 13 and 16%, the distance between inclusions is set to be 0.25 and 0.5 mm, respectively. Conical dies with a half angle α of 7°, which is the value generally used in commercial production. As the FEM code, the commercially available software DEFORM-2D is used. Copper is used for fine wire drawing process that initial diameter is 1 mm and final diameter is up to 50 μm. Accumulated strain and mean stress are simultaneously calculated to obtain damage value in the multistage wiredrawing. The defects of central burst type are generated at a smaller total reduction ratio with decreasing unit reduction ratio and with increasing inclusion size. Furthermore, damage value rises because the tensile stress in deformation zone increases by applied back tension. The distance between inclusions would not affect wire breaks because the distance is expanded excessively through multistage wiredrawing.