Study on the calciothermic reduction of titanium and rare eath metals and the recycle of calcium.

通过饱和钙蒸气直接还原二氧化钛，可以得到低氧含量的钛，因为它可以去除氧，达到能够克服氧对金属在固溶体范围内的亲和力的程度。在讨论从钛的氧化物中提炼钛时，了解氧在钛- o固溶体中的热力学稳定性是必不可少的。然而，钛中的氧具有较高的稳定性，使用固体电解质的普通气体平衡法或电动势法不适用于活度测量。因此，在这项研究中，钛金属在饱和钙蒸气和氧化钙共存的条件下，在1173和1573 K之间的封闭钢弹中进行平衡，淬火并分析氧。在1173和1573 K条件下，平衡气体浓度分别为300和900质量ppm。然后用这些数据推导出β -Ti相场中氧势、温度和组成的关系：1/2 ln(<p_(0_2)> /101325Pa)=ln(%O) + 12.1-71900 T 1173-1573 K, (%O)<0.15质量%尝试在1273 K下用饱和钙蒸气还原<TiO_2>粉末，按照<TiO_2> (s) + Ca(g) = Ti(s) + CaO(s)。还原产物的电子显微图显示，还原后的钛颗粒被固体反应产物CaO完全包围。在还原阶段，还原速率变得非常低，此时氧化物的分解几乎停止，Ti-O固溶体开始脱氧。

Titanium with low oxygen content has been expected to be obtainable by direct reduction of titanium dioxide with saturated calcium vapor, because it can remove the oxygen to the extent to which it is able to overcome the affinity of the oxygen for the metal in the solid solution range.A knowledge of the thermodynamic stability of oxygen in the Ti-O solid solution is indispensable in any discussion of the refining of titanium from its oxide. Oxygen in titanium has, however, high stability that ordinary gas equilibration or EMF method using solid electrolyte is not applicable to activity measurement. In this investigation, titanium metal was, therefore, equilibrated under coexistance of saturated calcium vapor and calcium oxide in closed bombs of steel at temperatures between 1173 and 1573 K, quenched and analysed for oxygen. The equilibrium gas concentrations were 300 and 900 mass ppm at 1173 and 1573 K, respectively. The data were then used to derive the relationship among oxygen potential, temperature and composition in the beta -Ti phase field:1/2 ln( <p_(0_2)> /101325Pa)=ln(%O) + 12.1-71900 T 1173-1573 K, (%O)<0.15 mass%Attempts were made to produce titanium by reducing <TiO_2> powders with saturated calcium vapors at 1273 K according to<TiO_2> (s) + Ca(g) = Ti(s) + CaO(s).Electron micrographs of the reduction products showed that the reduced titanium particles were completly surrounded with the solid reaction product, CaO. The reduction rate become very low at the reduction stage at which the decomposition of oxide almost ceased and the deoxidation of the Ti-O solid solution began to take place.