Deoxidation of Titanium Using Mg as Deoxidant in MgCl2-YCl3 Flux

Direct Deoxidation of Ti by Mg in MgCl₂–HoCl₃ Flux

“…Compared with Ca, Y and Ho, the deoxidation capacity of Mg is low due to the weak affinity of Mg for O. For example, at 1300 K, the calculated value of the deoxidation limit of Mg/MgO equilibrium is 25000 mass ppm O, and the experimental value is 12100 mass ppm O, 5) which is much higher than that of Ca/CaO equilibrium. In order to remelt the Ti scraps with the virgin metals for producing Ti ingots, the O concentration in Ti should be reduced to the level of Ti sponge (approximately 500 mass ppm O).…”

“…Furthermore, increasing demand for Ti, particularly in the aerospace industry, has led to a growth in the amount of Ti scrap waste from the fabrication of Ti products. 5) The recycling of Ti scraps, therefore, it has become imperative for Ti industries to solve the contradiction between the high production cost of Ti and the increased amount of waste Ti.…”

“…6) The O content in Ti usually increases during the melting, casting, and machining processes because of the strong affinity of Ti for O at high temperatures. 5,7,8) The O content of Ti products is usually higher than that of Ti sponge, which will be further increased during service processes, especially when Ti products are exposed to air at elevated temperatures. Therefore, Ti scraps often contain O concentrations ranging between 2000 and 4000 mass ppm O, which is significantly higher than that in the virgin metals for producing ingots.…”

“…Ca, Y, and Ho) as deoxidants is also possible. As shown in Table 1, 5,9,14,15) Ca, Y, and Ho are candidates for use as deoxidants. For example, at 1173 K, the calculated deoxidation limit of Ca/CaO equilibrium is 320 mass ppm O, and that of Y/Y 2 O 3 and Ho/Ho 2 O 3 equilibrium are 130 mass ppm O and 260 mass ppm O, respectively.…”

“…4,43) As shown in Fig. 1(e), the formation of oxyhalides of some rare earth elements in molten halide fluxes can be Table 1 Calculated partial pressure of O 2 and the theoretical O level in ¢-Ti under various equilibrium conditions at 1173 K. 5,9,14,15) Table 2 Solubility of oxide (MO x ) in molten chloride (MCl 2 ) at different temperatures, C MOx (mol%). 31,38) Fig .…”