THE SCIENTIFIC BASIS OF INTENSIFICATION OF CARBON WIRE DRAWING SCHEDULES

A wire manufacturing process includes wire rod structure and surface preparation (heat treatment), coating, shaping and other operations with finished wire. A key operation influencing the shape and properties is drawing using monolithic and roller dies of various structures. Drawing shows a diagram of opposite principal stresses and a symmetric diagram of principal strains characterized by high efficiency of the deformation and lower energy consumption. Tensile stress sigma(1) contributes to embrittlement during drawing, and maximum allowed value sigma(1) <= sigma(B). limits the strain rate in a pass. Forming during drawing in monolithic dies is determined by a die reduction angle, reduction per die, friction factor and strain rate. When assessing force factors, the said factors include drawing force (stress) and ultimate tensile strength of the material under study. The existing procedures are used to calculate limit single and aggregate reduction per die, die angle, force parameters and stability of the process. However, they do not factor into physical and mechanical properties of wire, its stress state in and out of a deformation zone. Using hardness coefficient distribution fields and the Lode-Nadai coefficient in a conical deformation zone and hydrostatic stress distribution fields, we developed a stress state determination procedure and a new calculation method and algorithm of drawing sequences. Curves of hydrostatic stress on the wire axis and drawing force are built for various die reduction angles and reductions for carbon steels. This procedure may be applied both for designing new and analyzing existing drawing sequences used to produce wire of the set quality at minimum manufacturing costs.