Effect and mechanism of vacuum melting on impurity elements, pores and inclusions in pure copper

Abstract

In this paper, the pure copper melt was purified by vacuum melting technology, and the purity and three-dimensional high-precision X-ray computed tomography morphology(3D-CT) changes of pore and inclusion defects were comprehensively observed. The total amount of impurity elements decrease from 178.74 ppm to 49.04 ppm, and the removal rate of impurity elements reached 72.6 %, the purity is improved from 3N to 4N. The hydrogen (H) content is reduced from 3.2 ppm to 0.9 ppm and the oxygen (O) content is reduced from 25.5 ppm to 11.7 ppm. The H and O contents are reduced by 71.9 % and 54.1 %, and the porosity and volume fraction of inclusion defects are reduced by 65.9 % and 52.2 %, respectively. In the vacuum melting process, the impurity elements are removed by volatilization, and the generation of inclusions can be reduced at the same time; H is precipitated to form hydrogen bubbles floating up to remove; O is formed into oxide inclusions gradually floating up to the surface of the melt. Vacuum melting technology can improve the purity of pure copper and greatly reduce the pore and inclusion defects in the cast billet.