Ductility Improvement of High Carbon Steel Wire by Alternate Wire Drawing

Abstract

High carbon steel wires, due to their high mechanical strength and high fatigue characteristics, have been widely used in industrial products such as bridge cables and steel cords for tires. To produce wires that match the requirements for those purposes, wire drawing process is used. However, after the processing, tensile strength of the wires increases, but ductility decreases due to the shear deformation near the wire surface. In this study, we examined ductility improvement methods of high carbon steel wires and as a solution we suggest a method of processing called “alternate wire drawing”. The next step was to determine the usefulness of alternate wire drawing for increasing the ductility of the wires. Firstly we studied the total equivalent strain and the change of the shape of elements for each drawn wire by FEM analysis before testing. It was determined that in the case of alternate drawn wire the deformation of the elements was small also alternate wire drawing method is inhibiting the increase of total equivalent strain on wire surface. In case of tensile testing of drawn wire, we examined the mechanical properties of each wire drawing method and compared them. By doing this test we understood that in the case of alternate drawing there is a significant increase of breaking strain and drawing rate. We also have done torsion test to confirm the ductility of conventional wire drawing and alternate wire drawing. In case of conventional wire drawing method (Total reduction 91.7%) delamination appeared, however alternate wire drawing method (Total reduction 91.7%) there was no delamination. In addition, in case of total reduction of 97.2%, alternate drawn wire increases 20% more its torsion characteristics, than conventional drawn wire. And we also studied the changes of the crystal grain of drawn wire by EBSD (Electron Back Scatter Diffraction Patterns). We found out that grain size was shrunk by conventional drawn wire due to share deformation and for alternate drawn wire we confirmed that it was possible to inhibit the grain shrinking by 15% compared to the conventional drawing method. As a conclusion we found out that, by using alternate wire drawing method it is possible to improve the ductility of high carbon steel wires with the high tensile strength.