Titanium melt interaction with the refractory oxides of some metals

Abstract

This article reviews perspectives of various refractory oxides application, including rare earth elements as fire resistance material to produce tiegels for titanium induction melting and titanium alloys. The interaction of titanium molten with calcium oxide, magnesium, zirconium, and the rare earth elements oxides: lanthanum, cerium, and yttrium were studied in theory and by testing. In order to assess the possibility of using oxides of these metals in the manufacture of refractories for Ti alloys melting, the thermodynamic calculations were performed using the Outotec HSC Chemistry 8 program. The Gibbs free energy of the reactions of interaction between titanium alloys with the listed oxides was calculated. The Gibbs energy was testified to have positive values in the high temperatures, which in theory means that they can be used as refractory materials in the smelting of titanium. The experiments of short-term interaction of titanium with the oxides of the listed elements were carried out under heating in a vacuum induction furnace. The interaction was evaluated by the change in the titanium structure after melting it in the volume of the pressed oxide powder. In the process of titanium melting with oxides of calcium and magnesium at high temperatures, an intense boiling and splashing are observed. This fact is explained by the titanium restores calcium and magnesium to the state of the metal, and the low boiling temperature of calcium and magnesium causes the release of a large amount of metal vapor. Titanium is heavily contaminated by the metals that form these oxides, and, therefore, by oxygen being in contact with La2O3, CeO2, and ZrO2. The yttrium oxide is testified to be the most resistant to the titanium melting, there is no significant contamination of the molten with yttrium and oxygen, and this increases the titanium hardness by 20%. The experiments have resulted in that it was recommended to use yttrium oxide as a refractory material.