The solubility of Cr2O3 in calcium ferrite slags at 1573 K

Continuous converting of copper matte based on calcium ferrite slag has many attractions for the copper smelting industry. However, a serious drawback is that this slag leads to shorter furnace campaigns because it is aggressive toward the magnesia-chromia refractories that form the furnace lining. As part of an investigation into the causes of this aggressiveness with a view to devising strategies to mitigate it, the solubility of Cr2O3 in calcium ferrite slag has been determined. The standard drop-quench experimental technique was employed at a temperature of 1573 K and a relatively high oxygen partial pressure of 3.7×10−4 atm, conditions similar to those used in continuous converting. It was found that approximately 2 wt pct of Cr2O3 can dissolve in calcium ferrite slag under these conditions. The Cr2O3 solubility was found to be unaffected by the Cu2O content of the slag, but may decrease as CaO content decreases. The implications of these findings on the mechanism of attack of magnesia-chromia refractories by calcium ferrite slag are discussed.