Characterization of fire-refined copper recycled from scrap

Certain properties of fire-refined copper recycled from scrap have been cha racterized. A method is presented to calculate the half-softening temperatu re and the annealing temperature that allows 30% elongation to failure, her einafter referred to as epsilon(30%) temperature, on the basis of hardness measurements. The relation between ultimate strain and ultimate elongation has been studied and is described by a mathematicale xpression that seems t o be independent of copper composition and annealing temperature. The micro structure of annealed samples reveals that recrystallization begins at half -softening temperature, and is ending at epsilon(30%) temperature, although grain growth is not observed. An optimal range of oxygen content has been found that gives the minimum epsilon(30%) temperature for each studied comp osition, and a mathematical expression with which to calculate those minimu m temperatures is developed. The influence of cold-working degree on epsilo n(30%) temperature is also described; these temperatures reach a constant m inimum value for each composition at high deformation degrees of cold-worki ng. (C) 1999 Kluwer Academic Publishers.