Post Rejection Renewal of Mechanical Properties for Mild Steel Electrical Wire by Cold Multi-Pass Drawing

Steel wire is widely used for electrically conductive cables reinforcing, and the cheapest grades of mild steel are sufficient. From this point of view in the paper analyzed the strength requirements for electrical purposes steel wire, namely for the cores and armour of steel, combined steel-aluminum, and steel-copper cables. Produced by drawing wire of low-carbon S235JR steel is widely used for overhead power transmission lines, grounding connections, messenger wires, wire communication, antenna support on stretchers, etc. The necessity of the control and correction of the overheating defect at annealing after drawing in obtaining the wire of the required level of strength is shown. The basic target of the work was about the modes’ development for the steel wire grains grinding by cold plastic deformation by re-drawing. Five combination modes with cold drawing, annealing and overheating were investigated for ensuring the increase in strength indicators of the steel wire to S235JR grade requirements. An inequality is obtained for the relation between the stress equilibrium equation for the separation case of wire with sharpened end reduced area due to the indentation of the pincer claws to hold the ends of the wire. The cold drawing modes designing for overheated mild steel wire taking into account the conditions of this mathematical expression guarantee the removing of the wire end tensile breaks at both the beginning and the stable drawing stages.