Research on the drawing process of Cu and CuZn wires obtained in the cryogenic conditions

Abstract

Cryogenic conditions are new and promising environment for non-conventional copper base metal forming processing. Significant increase of ultimate tensile strength of copper and selected copper alloys during cryogenic wire drawing process is observed, but knowledge about technological aspects of the process is poor. The research paper presents the analysis of components limiting of cryogenic wire drawing forces and impact of the zinc addition on macroscopic properties of the wires obtained in the single-stage cryogenic drawing process. As part of the experimental research fine copper and Cu-Zn wires with 2.5 wt% and 6.5 wt% of zinc were produced by melting of fine metals in graphite crucibles using the induction furnace and casting it into steel moulds, its drawing and annealing. The research included wire drawing process conducted both attheambient temperature and at the liquid nitrogen. Surface roughness test, mechanical properties tests (Brinell hardness, uniaxial tensile test) and physical properties test (resistivity) of wires were made. The significant effect of friction coefficient on wire drawing force under cryogenic condition was shown and the increase of the ultimate tensile test and hardness value of the Cu-Zn wires incomparison with the wires obtained at the ambient temperature has been observed.