In this study, the effect of MgO on the phase equilibria of iron silicate slags in equilibrium with Fe₃O₄ spinel and matte of fixed 72 wt % Cu were identified at controlled P(SO₂) 0.3 and 0.6 atm. The experimental process includes equilibration, quenching and Electron Probe X-ray Micro Analysis (EPMA). Spinel (Fe₃O₄) substrates were applied to confirm the equilibrium was achieved in the primary phase field of spinel. It was found that the presence of MgO increases the liquidus temperature of slag under a constant SiO₂ content, i.e., more SiO₂ is required to be fluxed to keep a stable smelting temperature with MgO. The effects of CaO and MgO on the liquidus of the system were further compared and found that the influence of MgO is stronger than CaO at 1250 °C under the same weight content while opposite situation occurs at 1200 °C, which is different from the FactSage predictions. Thus, the present study provides important information not only for the industrial smelting process but also for the thermodynamic modelling.

在这项研究中，确定了MgO对Fe ₃ O ₄尖晶石和固定的72 wt％Cu的冰铜平衡下的硅酸铁矿渣的相平衡的影响，其受控P（SO ₂）为0.3和0.6 atm。实验过程包括平衡，淬灭和电子探针X射线显微分析（EPMA）。施加尖晶石（Fe ₃ O ₄）衬底以确认在尖晶石的主相场中达到平衡。发现在恒定的SiO ₂含量（即更多的SiO _2）下，MgO的存在会提高炉渣的液相线温度。为了使MgO保持稳定的熔融温度，需要将其熔化。进一步比较了CaO和MgO对系统液相线的影响，发现在相同重量下，在1250°C时MgO的影响要比CaO强，而在1200°C时则相反，这与FactSage不同预测。因此，本研究不仅为工业冶炼过程提供了重要信息，而且为热力学建模提供了重要的信息。