Thermodynamics Analysis And An Experimentdal Study Of Deleading Of Blister Copper

This study conducted a thermodynamics analysis and an experimentdal study of deleading of blister copper as to provide some suggestions to deal with the problems of excessive content of lead which would lead to water pollution and do harm to human health.Concerning the need of deleading of cast copper alloy, two kinds of research methods were carried out, they were vulcanized slagging deleading and oxidated slagging deleading, thermodynamics analysis were followde respectively. And the results showde that in the melting temperature range, the standard free energy of vulcanized deleading was a positive value and increasing with the temperature, thus the deleading process was not enabled, while as the standard free energy of oxidated deleading was a negtive value where the deleading process was enabled. Thus the method of utilizing oxidated slagging deleading was decided, in which Cu2O served as oxidant and SiO2 as slag forming materials.Combined with the module of heat of formation, two activity modeles of the Cu-Pb binary system and the Cu-Zn-Pb ternary system were set respectively, where the activity of each elements in both systems were calculated. And the results revealed that the effect of temperature on the activity was little, while the main effect was the mole percent of the elements in the fusant.A calculation of the free energy of the deleading with the help of activity data could assist the analysis of the effect factors of the deleading process. It was revealed that when the composition is fixed, the free energy is linear with the temperature and that a lower temperature facilitates the deleading process. It was also revealed that the higher the lead content is, the lower the actual free energy is, which is easier for the deleading process. In the Cu-Pb-Zn ternary system, the affinities of the elements to oxygen is ranged as, from high to low, Zn, Pb, Cu, thus Zn is the first element to be oxidated. When the temperature is definite, the higher the Zn content is, the higher the equilibrium concentration of Zn is, and the more unfavorable to the deleading is.A beforehand copper-lead alloy with a Pb percentage of 5% was melted with Cu2O according to the proportion of M(Cu₂O:MPb )= 1:1. And sampling analyses of the deleading were carried out respectively after smelting of 0.5h, 1h, 1.5h, 2h, 2.5h under the temperature of 1150℃, 1200℃, 1300℃, 1400℃. The results showed that at 1150℃, a best deleading rate and effect were achieved, which is concordant with the thermomechanical analysis.Another sampling test of the Cu55.407Zn38.405Pb2.168 alloy was conducted in which the contents of each elements were analyzed respectively after smelting of 0.5h, 1h, 1.5h, 2h, 2.5h under the temperature of 1150℃. And the results showed that the Cu content in the fusant increased as the smelting time went on, while the contents of Zn and Pb decreased,and that changing rate and degree of Cu and Zn were considerable big, while for Pb, the rate and the degree were lowest among the three elements. The explanation for these should be that there were volatilization loss for both Zn and Pb, as well as the combustible loss of Zn.