Temperature modes and critical velocities during wire drawing

Abstract

Rod and wire product manufacturing is usually accompanied by residual stresses. The reason for this is both plastic deformation and potential thermoplastic deformation that occurs due to the contact frictional heating of metal surfaces. Undesirable residual stresses in the surface layers affect the accuracy and increase the probability of hardware destruction that can be observed in drawing product manufacturing. The authors of the article propose a method of determining the contact heating conditions based on the criteria of residual stress prevention. Temperature conditions causing thermoplastic deformations are determined according to thermoelasticity equations. Critical values are calculated for the temperature difference between the center and the surface of the stretched wire, at which the latter transits to a plastic state followed by residual stress formation. The limiting drawing velocities for a number of nonferrous metals (copper, zirconium, titanium) are defined. The excess of those top velocities will lead to undesirable residual stresses in the stretched product. It is proposed as a recommendation to increase the critical speed by creating hydrodynamic (fluid) friction conditions in metal products manufacturing.