Yttrium Oxyfluorides as Refractory Material for Induction Melting of Commercially Pure Titanium

Ti and its alloys are expensive materials because of the complexities involved in their extraction from the ore, melting, and machining processes. In this study, an energy-effective approach to induction melting of commercially pure Ti using ceramic crucibles was investigated. Crucibles composed of yttrium oxyfluorides were prepared, and pure Ti was melted in a high-frequency induction furnace using the oxyfluoride crucibles. Ti with silver-like luster was obtained when a YOF/Y7O6F9 crucible was used. The Vickers hardness of the thus-obtained Ti was comparable to that of Ti before melting and the concentration of O in the Ti was 0.2%, which is within the acceptable range for pure Ti. There were no cracks in the crucible after melting Ti. When Ti was melted using Y5O4F7 or Y5O4F7/YF3 crucible, the concentration of O in melted Ti was 0.15%, while the crucible cracked after melting Ti. Consequently, YOF/Y7O6F9 is a promising refractory material for handling molten Ti.