LAUSR

Abstract In the present study, effect of CaF2–CaO–Al2O3–MgO–TiO2 slag with various TiO2 contents on the desulfurization of Inconel 718 alloy was investigated at 1773 K to provide the fundamental information for the establishment of desulfurization procedure during electroslag remelting (ESR) process. The melt-quenching method did not accurately determine the change in content of sulfur and oxygen in the nickel-based alloy with time for the present study, which uses a novel experimental apparatus. The results indicated that the final sulfur content in the nickel-based alloy increased from 7 to 9 ppm when the TiO2 content in slag of CaF2–CaO–Al2O3–MgO–TiO2 system increased from 2.17 to 10% without addition of deoxidizer. In order to further expound the desulfurization mechanism, meanwhile, the relationship between the oxygen activity at slag–metal interface and reaction time under conditions of various TiO2 in the slag was studied by coupling with the developed mass transfer model. The calculated oxygen content in bulk metal has a good corresponding relationship with the measured oxygen content in the nickel-based alloy. The oxygen activity at slag–metal interface increased up to 9.6 ppm when TiO2 content was 10% in the slag, giving rise to the decrease in desulfurization ratio in high TiO2 content. The optimal condition for simultaneously ensuring low sulfur content and maintaining oxidative elements, such as Al and Ti, uniformly from bottom to top of the ESR ingot is also discussed.