Phase equilibria of silicate slags relevant to the copper smelting/converting operations have been systemically investigated in the temperature range 1.200 to 1.300 °C and oxygen partial pressures between 10-5 and 10-9 atm. The experimental procedures include high temperature equilibration, quenching and accurate measurements of phase compositions using electron probe X-ray microanalysis (EPMA). The effects of CaO, Al2O3, MgO and PO2 on the phase equilibria of the fayalite slags have been systematically investigated.
It was found that spinel and silica are major primary phases in the composition range related to copper smelting/converting slags. In addition, olivine, diopside and pyroxene also appear at certain conditions. The presence ofup to 20 wt% CaO, and up to 10 wt% MgO and Al2O3 in the slag increases the spinel liquidus and decreases the silica liquidus. Liquidus temperatures in silica primary phase field are not sensitive to PO2; Liquidus temperatures in spinel primary phase field increase significantly with increasing PO2.