Study of ultrahigh-purity copper billets refined by vacuum melting and directional solidification
Tóm tắt
The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidification (VMDS). The precise impurity analysis of copper billets was carried out with a glow discharge mass spectrometer (GDMS). The results demonstrate that the total concentration of twenty-two impurities is decreased by 63.1wt.%–66.5 wt.%. Ag, P, S, Na, Mg, Se, Zn, In and Bi are easy to be removed due to lgP
imp - lgP
Cu > 1.5, and they can be removed effectively under the vacuum condition of 1650–1700 K for 30 min. The electrical conductivity of 5N copper is higher than that of the raw material as the impurity concentrations decrease. The segregation effect in directional solidification can be remarkable when the equilibrium distribution coefficient (k
0) value is less than 0.65 due to the strong affinity of Cu for some metallic and non-metallic impurities.
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